Scheme for solving problem of gel generation in LCBR low cis rubber polymerization kettle

Abstract

The invention relates to a scheme for solving the problem of gel generation in a low cis rubber polymerization kettle, in a kettle type batch polymerization process, an inner cooling pipe is not arranged in the kettle, the height-diameter ratio of a jacket type kettle body is increased to more than three times, and the heat exchange area is increased; a catalyst and materials are directly inserted below the liquid level by adopting a static mixer, and the materials at an outlet are quickly dispersed by a stirrer to prevent local heat generation from generating gel; the inner and outer double-helical-ribbon stirrer with high material viscosity is selected, a gap smaller than 20mm is kept between the outer diameter of a helical ribbon and the kettle wall, the kettle wall can be cleaned twice when the stirrer rotates by one circle, and the heat removal effect at the kettle wall is improved; the bending strength of the square tubes can be improved by 1.27 times compared with that of round tubes, and the square tubes form a combined section frame shaft without a through shaft in the center, so that the problem of shaft sticking of a glue solution at the center shaft is solved, and the rigidity of the stirring shaft is improved; and the square tube combined frame is equivalent to a frame type paddle, so that material mixing is facilitated. In conclusion, the hanging glue in each flowing dead zone in the polymerization kettle can be eliminated, and the gel generated in the kettle is reduced.

Description

Technical Field

[0001] The invention belongs to special equipment for synthetic rubber polymerization process production, relates to a solution to the problem of gel generation in a LCBR low-cis rubber polymerization kettle, and is also suitable for polymerization reactors using intermittent polymerization processes for other highly difficult materials. Background Art

[0002] There are two production processes for LCBR low-cis polybutadiene rubber: intermittent polymerization and continuous polymerization. The domestic batch polymerization process is a kettle-type process. The polymerization kettle uses five layers of CBY-E and one layer of two blades with a 45° inclined propeller. Six groups of internal cooling tubes are used in the kettle to increase the heat exchange area. Each group has 9 vertical pipes. Each group of internal cooling tubes is fixed to the wall of the polymerization kettle with three tube clamps. The glue hanging in the kettle is mostly concentrated between the tubes of the internal cooling tube, at the tube clamps and at the root of the blades, and is distributed in a mass shape. The upper part of the kettle hangs more glue than the lower part. Due to the serious glue hanging, more gel is produced, which affects the product quality and output of LCBR. The country also introduced the Belgian FINA technology (PHILIPS patent), using a three-layer inclined propeller agitator to ensure the mixing of initiator, butadiene and solvent to avoid hot spots. In the intermittent polymerization, each kettle uses a large amount of solvent to wash the kettle wall to reduce the glue hanging on the polymerization kettle wall.

[0003] The locations where gel is produced in the LCBR low-cis polybutadiene rubber polymerization kettle are: the kettle wall between the two layers of blades, the upper blade, the inner cooling tube, the central axis and other dead zones. The main reasons for the formation of gel are: the catalyst and materials cannot directly enter below the liquid surface; the selection of stirring blades is unreasonable, and the radial flow effect is weak; during the polymerization of low-cis rubber, the viscosity of the rubber liquid increases to more than 3Pa.s as the reaction residence time increases, and the selection of the agitator for mixing high-viscosity materials with low-viscosity solvents is very important; the glue liquid stays on the stirring shaft, the kettle wall, the inner cooling tube and other dead zones for a long time, and the high heat generated locally will produce gel. Summary of the invention

[0004] The technical purpose is to solve the problem of gelation in the LCBR low-cis rubber polymerization kettle; to solve the mixing problem of the solvent viscosity of 0.05Pa.s and the viscosity of the rubber liquid rising to 3.0Pa.s after the polymerization reaction; to solve the heat exchange problem of the polymerization kettle; the problem of gelation on the liquid surface where the catalyst and materials enter; to solve the agitator selection problem; to solve the "climbing rod effect" caused by the rubber liquid hugging the central stirring shaft, and to improve the stiffness of the stirring shaft; to eliminate the flow dead zone in the polymerization kettle and other problems.

[0005] The technical solution is to solve the problem of gelation in the LCBR low-cis rubber polymerization kettle. Its structure is as follows: Figure 1As shown. In the figure: the power part (1), the kettle body with a jacket (2), the upper shaft (3), the square tube combined frame shaft (4), the inner spiral belt (5), the outer spiral belt (6), the variable diameter spiral belt (7), the lower shaft (8), the low bearing pair (9), the head cover (10), the static mixer (11) and other parts are composed, and the main pipe openings are: N1 catalyst and material inlet, N2 gas outlet, N3 glue outlet, N4 bearing solution inlet. The kettle is suitable for the intermittent operation of the polymerization reaction of low-cis rubber, and solves the heat exchange problem of the polymerization kettle. The catalyst and the material are mixed before entering the liquid surface. After entering below the liquid surface, the agitator can quickly disperse them to prevent local overheating. The spiral ribbon agitator adopts a central non-through shaft to eliminate the problem of the glue holding the central stirring shaft. Improving the stiffness of the stirring shaft can reduce the gap between the blade and the kettle wall, and eliminate the flow dead zone in the polymerization kettle.

[0006] The jacketed kettle body (2) adopts the jacket heat exchange, and no internal cooling pipe is arranged in the kettle. The ratio of height to diameter is greater than 3 to increase the heat exchange area, improve the stiffness of the stirring shaft, reduce the gap between the blade and the kettle wall, clean the accumulated glue on the kettle wall, increase the heat removal, and reduce the generation of gel.

[0007] The catalyst and the material are first mixed by a static mixer (11) before entering the liquid surface. After entering below the liquid surface, the agitator can quickly disperse them, thereby eliminating the problem of the catalyst scattering above the liquid surface or on the upper blades, and locally generating reaction heat to form a gel due to self-polymerization.

[0008] Select an internal and external double-screw ribbon agitator suitable for mixing materials with a viscosity greater than 3.0 Pa.s. Keep a gap of less than 20mm between the maximum diameter of the spiral ribbon and the kettle wall. Each revolution can remove the glue on the kettle wall twice to prevent the glue from staying on the kettle wall, which is beneficial to the heat exchange of the jacket and reduces the generation of gel.

[0009] The agitator uses a square tube combined frame shaft (4), which is composed of an upper cone sleeve (4-1), an outer cross square tube frame (4-2), an inner square tube frame (4-3), a cross rib plate (4-4), a rib plate (4-5), a lower cone sleeve and other parts. Figure 2 The stirring shaft has eliminated the center through shaft, so there is no problem of glue sticking to the shaft. Not only the overall rigidity of the stirring shaft is improved, the weld length between the spiral ribbon and the square tube is the side length of the square tube, which is simple and strong. The frame uses square tubes of the same size, which can increase the bending strength by 1.27 times compared with round tubes. The combined frame composed of square tubes is equivalent to a frame-type paddle, which is beneficial to material mixing.

[0010] An internal and external double-screw agitator is selected, which is suitable for the viscosity range from 0.05Pa.s to 3.0Pa.s. The motor is equipped with a frequency converter. When the viscosity is low, the agitator speed is fast. As the viscosity increases, the agitator speed is reduced and the Reynolds number is greater than 2000, and the kettle is in a turbulent state.

[0011] The gas evaporated by the reaction heat in the polymerization kettle is discharged through the N2 gas outlet, enters the cooler for cooling, and then enters the N4 bearing solution inlet to serve as lubrication and cooling for the bottom bearing pair (9), thereby preventing the temperature from rising and causing gelling.

[0012] Beneficial effects: A solution is adopted to solve the problem of gel generation in the LCBR low-cis rubber polymerization kettle, and the heat exchange area is increased by increasing the height-to-diameter ratio of the polymerization kettle; the inner cooling tube is eliminated and the central axis is cancelled, so that the flow dead zone in the kettle can be eliminated; the gap between the agitator blade and the kettle wall is maintained at less than 20 mm, which can prevent the glue liquid from staying on the kettle wall, which is beneficial to the heat exchange of the jacket; the square tube combined frame shaft (4) is selected to improve the overall rigidity of the agitator shaft and eliminate the problem of the glue liquid holding the shaft and not flowing. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 :General diagram of low cis polymerization reactor

[0014] In the figure: power part (1), kettle with jacket (2), upper shaft (3), square tube combined frame shaft (4), inner spiral belt (5), outer spiral belt (6), variable diameter spiral belt (7), lower shaft (8), lower bearing pair (9), head cover (10), static mixer (11). Main pipe openings: N1 catalyst and material inlet, N2 gas outlet, N3 glue liquid outlet, N4 bearing solution inlet.

[0015] Figure 2 :Square tube composite frame axis diagram

[0016] An upper cone sleeve (4-1), an outer cross square tube frame (4-2), an inner square tube frame (4-3), a cross rib plate (4-4), a rib plate (4-5), and a lower cone sleeve.

[0017] Figure 3 : General drawing of the original domestic low-cis polymerization reactor (internal data for auditors to refer to)

[0018] Figure 4 : The original domestic low-cis polymerization kettle general diagram shows the glue coating on the lower blades (internal data for auditors to compare and refer to)

[0019] Figure 5 : Glue coating on the lower part of the inner cooling pipe (internal data for auditors to refer to)

[0020] Figure 6 : Glue coating on the upper part of the inner cooling pipe (internal data for auditors to refer to)

[0021] Figure 7 : Glue coating on the upper blade (internal data for auditors to refer to) DETAILED DESCRIPTION

[0022] according to Figure 1 The structural design of LCBR low-cis rubber polymerization kettle has a height-to-diameter ratio of greater than 3, the cylindricity, ovality and straightness of the kettle are all less than 20mm, and the outer diameter runout of the agitator is less than 5mm, to ensure that the gap between the outer diameter of the ribbon paddle and the kettle wall is less than 20mm and will not hang on the kettle wall.

[0023] Select an SK type static mixer (11), with more than 8 mixing units, a distance between the outlet and the frame axis greater than 50 mm, and an outward extension when the length is greater than the distance to the frame axis.

[0024] All parts in contact with materials are polished, with a surface finish of ≤0.2um.

[0025] After the agitator is manufactured, a torque test must be performed and the torsional deformation should be ≤0.5 degrees / meter.

[0026] Low-cis rubber adopts intermittent kettle polymerization process. The polymerization temperature control range is 40-100℃, and the pressure control range is 0.05-1.0MPa. After the reaction time is 30 minutes, the rubber liquid should be sent to the mixing tank to add terminator and antioxidant to complete the termination reaction. This can ensure that the polymerization reaction of the next kettle is not affected by the residue of terminator and antioxidant.

[0027] An internal and external double-screw ribbon agitator is used, which is suitable for viscosity ranging from 0.05Pa.s to 3.0Pa.s. The motor is equipped with a frequency converter. When the viscosity is low, the agitator uses a fast speed. As the viscosity increases, the speed of the agitator is gradually reduced, but the Reynolds number must be greater than 2000 to keep the kettle in a turbulent state and allow the glue and solvent to be fully mixed.

[0028] By adopting the solution to solve the problem of gelation in the LCBR low-cis rubber polymerization kettle, the amount of gel in the polymerization kettle can be reduced to a specified minimum range.

Claims

1. A solution to the problem of gel formation in a LCBR low-cis rubber polymerization kettle. The main equipment of the polymerization kettle is composed of: a power part (1), a kettle body with a jacket (2), an upper shaft (3), a square tube combined frame shaft (4), an inner spiral belt (5), an outer spiral belt (6), a variable diameter spiral belt (7), a lower shaft (8), a low bearing pair (9), a head cover (10), a static mixer (11) and other parts. The kettle is suitable for the intermittent polymerization reaction of low-cis rubber, and solves the mixing problem of the solvent viscosity of 0.05 Pa.s and the viscosity of the rubber liquid rising to 3.0 Pa.s after the polymerization reaction. It solves the heat exchange problem of the polymerization kettle. Before the catalyst and the material enter the liquid surface, they are first mixed. After entering below the liquid surface, the agitator can quickly disperse them to prevent local overheating. The spiral ribbon agitator adopts a center non-through shaft to eliminate the problem of the rubber liquid hugging the center stirring shaft. Improving the stiffness of the stirring shaft can reduce the gap between the blade and the kettle wall, and eliminate the flow dead zone in the polymerization kettle.

2. According to claim 1, a solution to the problem of gel formation in a LCBR low-cis rubber polymerization kettle is characterized in that: The jacketed kettle body (2) adopts the jacket heat exchange, and no internal cooling pipe is arranged in the kettle. The ratio of height to diameter is greater than 3 to increase the heat exchange area, improve the stiffness of the stirring shaft, reduce the gap between the blade and the kettle wall, clean the accumulated glue on the kettle wall, increase the heat removal, and reduce the generation of gel.

3. The solution for solving the problem of gel generation in the LCBR low-cis rubber polymerization kettle according to claim 1, characterized in that: The catalyst and the material are first mixed by a static mixer (11) before entering the liquid surface. After entering below the liquid surface, the agitator can quickly disperse them, thereby eliminating the problem of the catalyst scattering above the liquid surface or on the upper blades, and locally generating reaction heat to form a gel due to self-polymerization.

4. The solution for solving the problem of gel generation in the LCBR low-cis rubber polymerization kettle according to claim 1, characterized in that: Select an internal and external double-screw ribbon agitator suitable for mixing materials with a viscosity greater than 3.0 Pa.s. Keep a gap of less than 20mm between the maximum diameter of the spiral ribbon and the kettle wall. Each revolution can remove the glue on the kettle wall twice to prevent the glue from staying on the kettle wall, which is beneficial to the heat exchange of the jacket and reduces the generation of gel.

5. The solution for solving the problem of gel generation in LCBR low-cis rubber polymerization kettle according to claim 1, characterized in that: The agitator adopts a square tube combined frame shaft (4), which is composed of an upper cone sleeve (4-1), an outer cross square tube frame (4-2), an inner square tube frame (4-3), a cross rib plate (4-4), a rib plate (4-5), a lower cone sleeve and other parts. The agitator shaft eliminates the central through shaft, so there is no problem of glue holding the shaft, which not only improves the overall rigidity of the agitator shaft, but also the length of the weld between the spiral belt and the square tube is the side length of the square tube, which is simple and strong. The frame adopts square tubes of the same size, which can increase the bending strength of the round tube by 1.27 times. The combined frame composed of square tubes is equivalent to a frame-type paddle, which is conducive to material mixing.

6. The solution for solving the problem of gel formation in the LCBR low-cis rubber polymerization kettle according to claim 1, characterized in that: An internal and external double-screw ribbon agitator is used, which is suitable for the viscosity range from 0.05Pa.s to 3.0Pa.s. The motor is equipped with a frequency converter. When the viscosity is low, the agitator uses a fast speed. As the viscosity increases, the speed of the agitator is gradually reduced. However, the Reynolds number must be greater than 2000 to keep the kettle in a turbulent state, so that the reactants are fully mixed and the amount of gel produced is reduced.

7. The solution for solving the problem of gel formation in the LCBR low-cis rubber polymerization kettle according to claim 1, characterized in that: The gas evaporated by the reaction heat in the polymerization kettle is discharged through the N2 gas outlet, enters the cooler for cooling, and then enters the N4 bearing solution inlet to serve as lubrication and cooling for the bottom bearing pair (9), thereby preventing the temperature from rising and causing gelling.

Images