A process and system for producing chlorinated polyethylene with constant acid concentration

Abstract

This invention relates to the field of chlorinated polyethylene production technology, and more particularly to a process for producing chlorinated polyethylene with a constant acid concentration. The process involves adding hydrochloric acid, polyethylene, and related additives to a reactor, introducing chlorine gas, and circulating the liquid within the reactor. Part of the liquid enters an acid-water mixer, while the hydrochloric acid flows through a filter to the dilute acid side, leaving the solid material on the concentrated acid side. After the hydrochloric acid flows out from the dilute acid side, fresh water is added to the concentrated acid side. This invention also provides a chlorinated polyethylene production system with a constant acid concentration, including a chlorination reactor with an acid-water mixer on one side. An automatic fresh water inlet valve is located above the acid-water mixer, and an automatic hydrochloric acid outlet valve is located at the outlet of the acid-water mixer. Therefore, this invention can maintain a constant acid concentration within the reactor throughout the entire reaction process, reducing equipment and production costs, while also minimizing pressure and temperature fluctuations within the reactor and improving product quality stability.

Description

Technical Field

[0001] This invention relates to the field of chlorinated polyethylene production technology, and in particular to a process and system for producing chlorinated polyethylene with a constant acid concentration. Background Technology

[0002] Chlorinated polyethylene is a polymer material produced by the substitution reaction of chlorine gas with polyethylene. Due to the introduction of chlorine atoms, chlorinated polyethylene has properties between rubber and plastic, and can be used as an excellent plastic modifier or as a special rubber.

[0003] The main production methods for chlorinated polyethylene include solid-phase method, solvent method, and suspension method. The suspension method is the most widely used in industrial production, where polyethylene is suspended in water or hydrochloric acid and reacted with chlorine under certain conditions. During the reaction, chlorine undergoes a substitution reaction with hydrogen atoms in polyethylene to produce hydrogen chloride, which dissolves in the solution to form hydrochloric acid. Depending on the chlorine content in the chlorinated polyethylene, approximately 0.3 to 0.45 tons of hydrogen chloride are produced for every ton of chlorinated polyethylene produced. Assuming a solid-liquid ratio of 20% in chlorinated polyethylene production, the hydrogen chloride produced will increase the hydrochloric acid content in the solution by 5% to 8%. According to chemical reaction kinetics, as the hydrochloric acid concentration increases, the forward reaction of chlorine with polyethylene substitution under the existing conditions will be less favorable, increasing the energy consumption of the reaction. This manifests as increased reaction pressure and a slower reaction rate in chlorinated polyethylene production.

[0004] Currently, the traditional suspension process for producing chlorinated polyethylene generally uses a batch process. Chlorine is passed through a closed chlorination reactor. As the amount of chlorine increases, the concentration of hydrochloric acid in the reactor continuously increases, slowing down the reaction rate. To ensure the reaction continues, the pressure inside the reactor is maintained at a high level, increasing the reaction time. This not only places higher demands on the pressure resistance of the equipment, increasing equipment costs, but also increases safety hazards. The increased reaction time reduces production efficiency and adversely affects the reduction of production costs.

[0005] In conclusion, the existing technology obviously has inconveniences and defects in practical use, so it is necessary to improve it. Summary of the Invention

[0006] To address the aforementioned shortcomings, the present invention aims to provide a process and system for producing chlorinated polyethylene with a constant acid concentration. This system can maintain a constant acid concentration within the reactor throughout the entire reaction process, reducing the adverse effects of rising acid concentration on the substitution forward reaction, improving the production efficiency of chlorinated polyethylene, reducing equipment and production costs, while also minimizing pressure and temperature fluctuations within the reactor, improving the timeliness of hydrochloric acid filtration and dilution, ensuring the accuracy of various process parameters during the production of chlorinated polyethylene, and enhancing the stability of product quality.

[0007] To achieve the above objectives, the present invention provides a process and system for producing chlorinated polyethylene with a constant acid concentration, comprising the following steps:

[0008] Step 1: Chlorine

[0009] Hydrochloric acid, polyethylene, and related additives are added to the reactor. After sealing the reactor, chlorine gas is introduced into the reactor to carry out a substitution reaction. The hydrogen chloride produced by the reaction will continuously enter the liquid, and the proportion of solids will continuously increase.

[0010] Step 2: Filtering acid

[0011] Under the action of stirring in the reactor, the liquid flows in circulation. Part of the liquid enters the acid-water mixer, the hydrochloric acid flows to the dilute acid side through the filter screen, and the solid material remains on the concentrated acid side.

[0012] Step 3: Dilution and Reflux

[0013] After the hydrochloric acid flows out from the dilute acid side, fresh water is added to the concentrated acid side. As the liquid flows in circulation, it enters the reactor, keeping the acid concentration and solid-liquid ratio in the reactor constant.

[0014] The present invention also provides a chlorinated polyethylene production system with constant acid concentration, including a chlorination reactor, a chlorination port at the bottom of the chlorination reactor, a reactor circulating water jacket outside the chlorination reactor, a reactor agitator inside the chlorination reactor, an acid-water mixer connected to one side of the chlorination reactor, the side of the acid-water mixer closer to the chlorination reactor being the concentrated acid side, and the side of the acid-water mixer farther from the chlorination reactor being the dilute acid side, an automatic fresh water input valve above the acid-water mixer, and an automatic hydrochloric acid output valve at the outlet of the acid-water mixer.

[0015] According to the constant acid concentration chlorinated polyethylene production system of the present invention, an upper axial flow check valve and a lower axial flow check valve are provided between the chlorination reactor and the acid water mixer.

[0016] According to the present invention, in a constant acid concentration chlorinated polyethylene production system, the acid water mixer is provided with an acid water mixer filter screen.

[0017] According to the present invention, in a constant acid concentration chlorinated polyethylene production system, the freshwater input automatic valve is connected to a freshwater heat exchanger.

[0018] According to the constant acid concentration chlorinated polyethylene production system of the present invention, a guide tube is provided inside the chlorination reactor, and the guide tube is located outside the reactor agitator.

[0019] The purpose of this invention is to provide a process and system for producing chlorinated polyethylene with a constant acid concentration. In the production of chlorinated polyethylene, this invention solves the technical problem of the gradual increase in hydrochloric acid concentration caused by the dissolution of hydrogen chloride produced in the substitution reaction in the feed solution. This ensures that the acid concentration in the reactor remains constant throughout the reaction process, reducing the adverse effects of increased acid concentration on the forward substitution reaction, improving the production efficiency of chlorinated polyethylene, and reducing equipment and production costs. This invention also provides a chlorinated polyethylene production system with a constant acid concentration, including an acid-water mixer. When the feed solution passes through a filter screen, hydrochloric acid is filtered into the dilute acid side, while chlorinated... The chlorinated polyethylene material remains in the feed solution, preventing its loss with the acid. Simultaneously, when fresh water is added, it automatically backwashes the filter screen, reducing the tedious manual backwashing process and ensuring optimal filtration efficiency. The cylindrical agitator allows the feed solution to circulate in a preset direction, enabling efficient operation of the acid-water mixer. Furthermore, the one-way valve and automatic valve are automatically controlled by a computer program, reducing pressure and temperature fluctuations within the reactor and improving the timeliness of hydrochloric acid filtration and dilution. This ensures the accuracy of various process parameters during chlorinated polyethylene production and enhances product quality stability. In summary, the beneficial effects of this invention are: maintaining a constant acid concentration within the reactor throughout the reaction process, reducing the adverse effects of rising acid concentration on the substitution reaction, improving chlorinated polyethylene production efficiency, reducing equipment and production costs, minimizing pressure and temperature fluctuations within the reactor, improving the timeliness of hydrochloric acid filtration and dilution, ensuring the accuracy of various process parameters during chlorinated polyethylene production, and enhancing product quality stability. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the chlorinated polyethylene production system with constant acid concentration according to the present invention;

[0021] In the diagram: 1-Chlorination reactor, 2-Chlorine inlet, 3-Flow guide tube, 4-Reaction reactor circulating water jacket, 5-Reaction reactor agitator, 6-Desalinated water heat exchanger, 7-Desalinated water input automatic valve, 8-Upper axial flow check valve, 9-Acid-water mixer dilute acid side, 10-Acid-water mixer, 11-Acid-water mixer concentrated acid side, 12-Acid-water mixer filter screen, 13-Hydrochloric acid output automatic valve, 14-Lower axial flow check valve. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0023] This invention provides a process for producing chlorinated polyethylene with a constant acid concentration, comprising the following steps:

[0024] Step 1: Chlorine

[0025] A certain amount of hydrochloric acid, polyethylene, and related additives are added to the reactor (the composition and proportion of raw materials for the production of chlorinated polyethylene are conventional technical means, and the selection of raw materials and additives are mature technical means. Those skilled in the art can add them according to the actual situation, which will not be elaborated here). After sealing the reactor, chlorine gas is introduced into the reactor to carry out the substitution reaction. The hydrogen chloride produced by the reaction will continuously enter the liquid, and the proportion of solids will continuously increase.

[0026] Step 2: Filtering acid

[0027] To prevent the hydrochloric acid concentration in the feed solution from continuously increasing, the feed solution is circulated in the reactor under the action of stirring. Part of the feed solution enters the acid-water mixer, the hydrochloric acid flows to the dilute acid side through the filter screen, and the solid material remains on the concentrated acid side.

[0028] Step 3: Dilution and Reflux

[0029] To prevent the liquid content in the reactor from decreasing and the hydrochloric acid concentration from increasing, a certain amount of fresh water is added to the concentrated acid side after the hydrochloric acid flows out from the dilute acid side. As the liquid content circulates, it enters the reactor, keeping the acid concentration and solid-liquid ratio in the reactor constant.

[0030] Chlorination is achieved by suspending chlorinated polyethylene powder in hydrochloric acid or water in an acidic or aqueous medium. Based on the chlorination reaction mechanism and production process conditions, chlorine atoms in chlorine gas undergo a substitution reaction with hydrogen atoms in polyethylene, simultaneously producing hydrogen chloride. The hydrogen chloride dissolves in the solution to form hydrochloric acid. As the reaction continues, the hydrochloric acid concentration gradually increases. To minimize the impact of this increased concentration on the reacting plastic and production efficiency...

[0031] See Figure 1The present invention also provides a chlorinated polyethylene production system with constant acid concentration, including a chlorination reactor 1. The bottom of the chlorination reactor 1 is provided with a chlorination port 2. The bottom chlorination method not only improves the reaction efficiency of chlorine, but also allows the hydrogen chloride generated by the substitution reaction to dissolve in the feed liquid circulating from the acid-water mixer as early as possible, so that the hydrochloric acid concentration in the feed liquid is always kept at a constant acid concentration. The chlorination reactor 1 is provided with a reactor circulating water jacket 4. The chlorination reactor 1 is provided with a reactor agitator 5. An acid-water mixer 10 is provided on one side of the chlorination reactor 1. The side of the acid-water mixer 10 closer to the chlorination reactor 1 is the concentrated acid side 11 of the acid-water mixer, and the side of the acid-water mixer 10 further away from the chlorination reactor 1 is the dilute acid side 9 of the acid-water mixer. The acid-water mixer 10 is connected to the chlorination reactor 1. A fresh water input automatic valve 7 is provided above the acid-water mixer 10, through which fresh water can be added to the acid-water mixer 10. A hydrochloric acid output automatic valve 13 is provided at the outlet end of the acid-water mixer 10.

[0032] See Figure 1 Preferably, an upper axial flow check valve 8 and a lower axial flow check valve 14 are provided between the chlorination reactor 1 and the acid water mixer 10. The purpose is to make the liquid flow in a predetermined direction. The liquid can only enter the acid water mixer 10 from the chlorination reactor 1 through the upper axial flow check valve 8, and the liquid can only enter the chlorination reactor 1 from the acid water mixer 10 through the lower axial flow check valve 14. The circulation direction of the liquid is consistent with that of the chlorination reactor 1, which is beneficial to maintaining a constant hydrochloric acid concentration.

[0033] See Figure 1 Preferably, the acid-water mixer 10 is equipped with an acid-water mixer filter screen 12 to prevent solid materials in the feed solution from being discharged with hydrochloric acid, thus avoiding a decrease in product recovery rate. After the feed solution passes through the acid-water mixer filter screen 12, the automatic hydrochloric acid output valve 13 is opened by the computer control system, and the hydrochloric acid is output to the hydrochloric acid storage tank. After a certain amount of hydrochloric acid is output, the automatic hydrochloric acid output valve 13 is closed, and the automatic fresh water input valve 7 is opened. Fresh water enters the feed solution after passing through the acid-water mixer filter screen 12 to replenish the discharged hydrochloric acid. At the same time, the solid materials attached to the acid-water mixer filter screen 12 can be backwashed, flushing the solid materials into the feed solution, and continuing to enter the circulating feed solution to participate in the substitution reaction. This ensures a good filtration effect of the acid-water mixer filter screen 12 and avoids some polyethylene particles not reacting completely, which would affect product quality.

[0034] See Figure 1 Preferably, the freshwater input automatic valve 7 is connected to the freshwater heat exchanger 6 to prevent fluctuations in the temperature of the liquid in the chlorination reactor 1, so that the temperature of the freshwater is consistent with the temperature of the liquid in the chlorination reactor 1.

[0035] See Figure 1Preferably, a guide tube 3 is provided inside the chlorination reactor 1, and the guide tube 3 is located outside the reactor agitator 5. Under the stirring of the reactor agitator 5, the liquid flows from bottom to top inside and outside the guide tube 3. At the same time, under the action of gravity and the guide tube 3, the solid particles in the liquid fall quickly. Therefore, the solid-liquid ratio in the liquid entering the acid water mixer 10 through the upper axial flow check valve 8 is reduced, and it is not easy to clog the acid water mixer filter screen 12.

[0036] In the acid-phase chlorinated polyethylene reaction system, chlorinated polyethylene is added to 16% hydrochloric acid. After adding additives, the temperature is raised and chlorine gas is introduced according to a predetermined program to carry out a substitution reaction. As the reaction continues, hydrogen chloride is continuously generated, causing the hydrochloric acid concentration to gradually increase. In traditional industrial production processes, the hydrochloric acid concentration will increase by 5% to 8% after the reaction is completed, and the solid-liquid ratio will increase by 5%. However, in the method and system for preparing chlorinated polyethylene with constant acid concentration and solid-liquid ratio of the present invention, by continuously removing part of the 16% hydrochloric acid and adding the same amount of fresh water, the hydrochloric acid concentration is kept constant at 16%, and the solid-liquid ratio is maintained at the initial 20%. The addition of fresh water not only keeps the hydrochloric acid concentration constant and replenishes the removed hydrochloric acid in a timely manner, but also keeps the solid-liquid ratio in the chlorination reactor 1 constant, avoiding instability in the production system.

[0037] See Figure 1 According to the chlorination reaction mechanism and production process conditions, chlorine atoms in chlorine gas undergo a substitution reaction with hydrogen atoms in polyethylene, simultaneously producing hydrogen chloride. Hydrogen chloride dissolves in the feed solution to generate hydrochloric acid. As the reaction continues, the hydrochloric acid concentration gradually increases. To reduce the impact of increased hydrochloric acid concentration on the reacting plastic and production efficiency, the feed solution in chlorination reactor 1 enters the concentrated acid side 11 of the acid-water mixer through the upper axial flow check valve 8. The hydrochloric acid passes through the filter screen 12 of the acid-water mixer and enters the dilute acid side 9 of the acid-water mixer. Solid materials remain in the concentrated acid side 11 and the filter screen 12 of the acid-water mixer. The hydrochloric acid in the dilute acid side 9 of the acid-water mixer is discharged through the hydrochloric acid outlet. The actuated valve 13 delivers the hydrochloric acid to the hydrochloric acid storage tank. Based on the chlorine flow rate, the computer control system automatically calculates the amount of hydrochloric acid produced by the reaction. The control system automatically closes the hydrochloric acid output valve 13. Then, the control system automatically opens the fresh water input valve 7 to replenish fresh water. Based on the hydrochloric acid output, the fresh water input valve 7 is automatically closed. The fresh water enters the acid-water mixer 10. From the dilute acid side 9 of the acid-water mixer, it passes through the filter screen 12 of the acid-water mixer and enters the concentrated acid side 11 of the acid-water mixer. The diluted liquid enters the chlorination reactor 1 through the lower axial flow check valve 14, thereby achieving the goal of gradually diluting the hydrochloric acid produced by the reaction and maintaining a constant hydrochloric acid concentration in the chlorination reactor 1.

[0038] This invention provides a constant acid concentration process for producing chlorinated polyethylene. In the production of chlorinated polyethylene, it solves the technical problem of the gradual increase in hydrochloric acid concentration caused by the dissolution of hydrogen chloride generated in the substitution reaction in the feed solution. This ensures that the acid concentration in the reactor remains constant throughout the reaction process, reducing the adverse effects of increased acid concentration on the forward substitution reaction, improving the production efficiency of chlorinated polyethylene, and reducing equipment and production costs. This invention also provides a constant acid concentration chlorinated polyethylene production system, including an acid-water mixer. When the feed solution passes through a filter screen, hydrochloric acid is filtered into the dilute acid side, and chlorinated polyethylene... The olefin material remains in the feed solution, preventing the chlorinated polyethylene from being lost with the acid. Simultaneously, when adding fresh water, the fresh water automatically backwashes the filter screen, reducing the tedious process of manual backwashing and ensuring the filter's filtration efficiency remains optimal. The cylindrical agitator allows the feed solution to circulate in a preset direction, enabling the acid-water mixer to operate efficiently. Furthermore, the one-way valve and automatic valve are automatically controlled by a computer program, reducing pressure and temperature fluctuations within the reactor and improving the timeliness of hydrochloric acid filtration and dilution. This ensures the accuracy of various process parameters during chlorinated polyethylene production and improves product quality stability. In summary, the beneficial effects of this invention are: maintaining a constant acid concentration within the reactor throughout the reaction process, reducing the adverse effects of rising acid concentration on the substitution forward reaction, improving chlorinated polyethylene production efficiency, reducing equipment and production costs, minimizing pressure and temperature fluctuations within the reactor, improving the timeliness of hydrochloric acid filtration and dilution, ensuring the accuracy of various process parameters during chlorinated polyethylene production, and improving product quality stability.

[0039] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the appended claims.

Claims

1. A process for the production of chlorinated polyethylene with constant acid concentration, characterized in that, It comprises the following steps: Step one: chlorine passing In the reaction kettle, hydrochloric acid, polyethylene and related additives are added. After the reaction kettle is closed, chlorine is passed into the reaction kettle to carry out substitution reaction. The hydrogen chloride produced in the reaction will continuously enter the feed liquid, and the solid content will continuously increase; Step two: acid filtration Under the action of the reaction kettle stirrer, the feed liquid circulates in the kettle. Part of the feed liquid enters the acid-water mixer. The hydrochloric acid flows to the dilute acid side through the filter screen, and the solid material remains in the concentrated acid side; Step three: dilution reflux After the hydrochloric acid in the dilute acid side flows out, fresh water is added to the concentrated acid side. With the circulation of the feed liquid into the reaction kettle, the acid concentration and solid-liquid ratio in the reaction kettle are kept constant.

2. A constant acid concentration chlorinated polyethylene production system characterized by, The chlorine reaction kettle is provided with a chlorine passing port at the bottom end. The outside of the chlorine reaction kettle is provided with a reaction kettle circulating water jacket. The chlorine reaction kettle is provided with a reaction kettle stirrer inside. One side of the chlorine reaction kettle is connected with an acid-water mixer; The acid-water mixer is provided with a concentrated acid side close to the chlorine reaction kettle. The acid-water mixer is provided with a dilute acid side away from the chlorine reaction kettle; The top of the acid-water mixer is provided with a fresh water input automatic valve. The outlet end of the acid-water mixer is provided with a hydrochloric acid output automatic valve; The chlorine reaction kettle and the acid-water mixer are provided with an upper axial flow check valve and a lower axial flow check valve. The acid-water mixer is provided with an acid-water mixer filter screen. The chlorine reaction kettle is provided with a flow guide cylinder outside the reaction kettle stirrer.

3. The constant acid concentration chlorinated polyethylene production system according to claim 2, characterized by, The fresh water input automatic valve is connected with a fresh water heat exchanger.

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