Chlorinated polyethylene acid-water combination method production process

Abstract

The invention relates to a chlorinated polyethylene acid-water combination method production process, which comprises: (1) preparing materials: preparing a hydrochloric acid solution, adding a dispersant and a composite auxiliary agent, adding high density polyethylene, stirring and mixing to form a reaction slurry, and (2) carrying out a chlorination reaction: introducing liquid chlorine in three reaction stages, the three reaction stages are respectively a low-temperature stage, a medium-temperature stage and a high-temperature stage, (3) deacidifying for the first time, (4) deacidifying for the second time, (5) neutralizing, (6) adding water and mixing, and finally dehydrating and drying to obtain the finished product chlorinated polyethylene acid. According to the production process, an acid phase method is firstly adopted to carry out chlorination reaction, the chlorination reaction is respectively carried out in three stages of a low-temperature stage, a medium-temperature stage and a high-temperature stage, and then a neutralization process of an aqueous phase method is adopted subsequently, so that the produced CPE product not only can ensure higher tensile strength, but also can ensure higher elongation at break.

Description

Technical Field

[0001] The invention relates to a production method of chlorinated polyethylene, in particular to a production process of chlorinated polyethylene by acid-water combination method. Background Art

[0002] Chlorinated polyethylene (CPE), as an important thermoplastic elastomer material, has a unique chemical structure and physical properties that make it show a wide range of application prospects in many industrial fields. In the field of plastic processing, CPE is known for its excellent weather resistance, ozone resistance and chemical corrosion resistance. In addition, CPE also has good processing properties. It can be molded through various processes such as injection molding, extrusion, and calendering to meet the production needs of different products. In the field of environmental protection, CPE is widely used in fireproof materials and flame-retardant cables due to its good flame retardancy and low smoke and non-toxic properties.

[0003] The main methods for preparing chlorinated polyethylene are the acid phase method and the water phase method. The problems of these two methods are as follows: 1. The disadvantage of the acid phase method for producing CPE is that the product enters the drying system in an acidic state, and the CPE cannot be fully expanded, and the elongation at break is generally low, which can only reach 700-750%. 2. The disadvantage of the water phase method for producing CPE is that since the water phase method reacts at a low temperature, the activity of the reaction system is too poor, and PE basically does not react with chlorine. Therefore, the tensile strength of the CPE produced is generally low, at 8-9MPa.

[0004] Among the currently disclosed patent documents, Chinese invention patent 201510664364.4 discloses a method for preparing chlorinated polyethylene in an acidic medium. This method is intended to overcome the problem that the by-product hydrochloric acid neutralization process in the existing aqueous suspension chlorination method for preparing chlorinated polyolefins is energy-consuming and time-consuming and cannot be recycled. It does not mention how to solve the problems of insufficient tensile strength of CPE produced by the aqueous phase method and low elongation at break of CPE produced by the acid phase method. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a chlorinated polyethylene acid water combination production process, the production process first adopts an acid phase method to carry out a chlorination reaction, the chlorination reaction is carried out in three stages: a low temperature stage, a medium temperature stage and a high temperature stage, and then a water phase method is used for a neutralization process, and the CPE product produced can ensure both a high tensile strength and a high elongation at break.

[0006] The technical solution to solve the above technical problems is: a chlorinated polyethylene acid water combination production process, the raw materials are mixed by weight: 12-16 parts of high-density polyethylene, 68-73 parts of 12-18wt% hydrochloric acid solution, 0.03-0.08 parts of dispersant, 0.03-0.08 parts of composite additives, and 13-18 parts of liquid chlorine; The production steps include: (1) Preparation: Prepare a 12-18 wt% hydrochloric acid solution, add a dispersant and a composite additive, and then add high-density polyethylene and stir and mix to form a reaction slurry; (2) Chlorination reaction: It is divided into three reaction stages to control the amount of chlorine. Liquid chlorine is introduced continuously. The three reaction stages are low temperature stage, medium temperature stage and high temperature stage. Low temperature stage: raise the temperature of the reaction slurry to 72-76°C, start to continuously introduce liquid chlorine into the reaction slurry, and continue to heat the reaction slurry with an external heat source. When the reaction slurry is heated to 87-90°C, the amount of chlorine introduced is required to be 9-10% of the total amount of liquid chlorine. Medium temperature section: The reaction slurry is heated to 120-126°C mainly by the heat generated by the chlorination reaction. The whole heating process is divided into 3-5 small sections to control the chlorine flow rate. The difference in the chlorine flow rate of each small section is 0-0.5% of the total amount of liquid chlorine. When the chlorine flow rate of each small section reaches the target value, the reaction slurry temperature is required to increase by 9-11°C. The total chlorine flow rate of the medium temperature section is 58-62% of the total amount of liquid chlorine. High temperature section: In the first high temperature section, 9-10% of the total amount of liquid chlorine is introduced into the reaction slurry, and the temperature of the reaction slurry is controlled at 127-128°C; in the second high temperature section, the remaining liquid chlorine is introduced into the reaction slurry, and the temperature of the reaction slurry is controlled at 129-131°C; (3) First deacidification: After the reaction is completed, the material is cooled to below or equal to 90°C for deacidification to obtain concentrated hydrochloric acid and solid material; (4) Second deacidification: Add water or dilute acid to the solid material to mix and soak it, and then stir to form a slurry. The slurry is deacidified to obtain dilute hydrochloric acid and solid material. (5) Neutralization: Add water to the solid material to form a slurry, and then add alkali to the slurry for neutralization, so that the slurry becomes neutral or weakly alkaline. The pH value of the slurry is required to be controlled between 7 and 8; (6) After neutralization, the slurry is freed from alkaline water, water is added and mixed, and finally the chlorinated polyethylene is obtained after dehydration and drying.

[0007] Furthermore, the concentrated hydrochloric acid obtained in step (3) and the dilute hydrochloric acid obtained in step (4) are returned to step (1) for preparing a hydrochloric acid solution.

[0008] Furthermore, the dispersant in step (1) is silicon dioxide.

[0009] Furthermore, the base in step (5) is sodium hydroxide or calcium carbonate.

[0010] Furthermore, in step (3), a filter is used for deacidification, and in step (4), a centrifuge is used for deacidification.

[0011] The invention combines the acid phase method and the water phase method, firstly adopts the acid phase method to carry out the chlorination reaction, and then adopts the water phase method for neutralization. The key technical point is that the temperature of the chlorination reaction is mainly divided into three stages: a low temperature stage, a medium temperature stage and a high temperature stage. The temperature should be controlled to increase according to the corresponding chlorine flow rate so that the chlorination reaction can be carried out more reasonably. The produced CPE has a higher fracture growth rate than the CPE produced by the acid phase method, and has a higher tensile strength than the CPE produced by the water phase method.

[0012] The technical features of the chlorinated poly(ethylene glycol) acid water-combination production process of the present invention are further described below in conjunction with the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a schematic diagram of the test report of chlorinated polyethylene prepared in Example 1. DETAILED DESCRIPTION Example 1

[0014] A chlorinated polyethylene acid water combination production process, the weight ratio of raw materials is: high-density polyethylene 14% (3500kg), 15wt% hydrochloric acid solution 70%, dispersant 0.05%, composite auxiliary agent 0.05%, liquid chlorine 15.9%.

[0015] The production steps include: (1) Mix the ingredients in a 30 cubic meter rubber-lined kettle: Mix the concentrated hydrochloric acid (about 22wt%) and the dilute hydrochloric acid (about 5wt%) produced in the production process to prepare a 15wt% hydrochloric acid solution, add dispersant silica and composite additives, and then add high-density polyethylene and stir to form a reaction slurry.

[0016] (2) The reaction slurry is pumped into a 30-cubic-meter enamel reactor for chlorination reaction: the chlorine flow rate and speed are controlled in three reaction stages. Each temperature stage has different requirements for the control of the chlorine flow rate. Liquid chlorine is continuously introduced. The three reaction stages are low-temperature stage, medium-temperature stage and high-temperature stage. Controlling the quality of chlorine introduced into the reaction at each temperature stage is the key to controlling the quality of chlorinated polyethylene.

[0017] Low temperature section: Raise the temperature of the reaction slurry to 75°C, and start to continuously introduce liquid chlorine into the reaction slurry. At the same time, use an external heat source (steam) to continue heating the reaction slurry. When the reaction slurry is heated to 89-90°C, the amount of chlorine introduced is required to be 10% of the total amount of liquid chlorine. The pressure in the low temperature section is controlled below 0.5MPa.

[0018] The reaction characteristics of this stage are: before 90°C, because the temperature in the kettle has not reached the activation temperature of the chlorination reaction, the liquid chlorine reacts slowly, and steam needs to be introduced to increase the temperature and assist in improving the reaction activity. At this temperature stage, due to the slow chlorination reaction rate, if the amount of chlorine introduced is too large, the chlorine reaction is incomplete, and the excess liquid chlorine will be vaporized, which will cause the pressure in the kettle to increase, which is not conducive to safe operation. In addition, if there is too much chlorination in the low-temperature stage, the tensile strength of the product will increase, but at the same time, the elongation at break will decrease. Therefore, the amount of chlorine passed at this stage must be controlled within a reasonable range, and can be adjusted appropriately according to the analysis results of the product.

[0019] Medium temperature section: The reaction slurry is heated to 126°C mainly by the heat generated by the chlorination reaction. The whole heating process is divided into 4 small sections to control the chlorine flow rate. The chlorine flow rate in each section is the same. When the chlorine flow rate in each section reaches the target value, the reaction slurry temperature is required to increase by 9°C. The total chlorine flow rate in the medium temperature section is 60% of the total liquid chlorine. The specific operation of the medium temperature section is: by controlling the chlorine flow rate, the larger the chlorine flow in each section, the higher the temperature of the reaction slurry, and the relationship is linear; that is, when the temperature of the reaction slurry rises from 90°C to 99°C in the first section, the chlorine flow is 15% of the total amount of liquid chlorine; when the temperature of the reaction slurry rises from 99°C to 108°C in the second section, the chlorine flow is 15% of the total amount of liquid chlorine; when the temperature of the reaction slurry rises from 108°C to 117°C in the third section, the chlorine flow is 15% of the total amount of liquid chlorine; when the temperature of the reaction slurry rises from 117°C to 126°C in the fourth section, the chlorine flow is 15% of the total amount of liquid chlorine, and the pressure in the medium temperature section is controlled below 0.5MPa. To control the temperature to rise according to the corresponding chlorine flow, if there is a deviation, it needs to be adjusted by cooling water or steam.

[0020] The reaction characteristics of this stage are: the chlorination reaction has been activated, the reaction speed is fast, the reaction releases a lot of heat, and the temperature needs to be controlled by cooling water. The chlorine flow rate in this stage must be guaranteed to be about 60% of the total chlorine flow rate, and fine-tuned according to the product analysis results. The chlorination reaction in this stage mainly occurs on the surface of polyethylene. The amount of chlorine flow affects the crystallinity of the CPE rubber body and the tensile strength and hardness of CPE. If the tensile strength of the product is insufficient, the chlorine flow rate in this stage can be appropriately increased. If the tensile strength is too high, the chlorine flow rate in this stage can be appropriately reduced. This stage is a small section of 9°C, and the chlorine flow rate in each small section is kept uniform.

[0021] High temperature section: In the first high temperature section, 10% of the total amount of liquid chlorine is introduced into the reaction slurry, and the temperature of the reaction slurry is controlled at 127-128°C; in this stage, the chlorination reaction begins to enter the interior of the polyethylene, destroying the crystallization of the polyethylene. This stage is a transitional stage, and it is not advisable to introduce too much chlorine, so that the reaction can enter the second high temperature section as soon as possible. In the second high temperature section, the remaining liquid chlorine is introduced into the reaction slurry, and the reaction slurry is controlled at 129-130°C. The reaction temperature in this stage is close to the melting point of polyethylene (135°C for high-density polyethylene (HDPE)). At this time, the reaction takes place in the crystallization area of ​​polyethylene, destroying the crystallization of polyethylene, making the chlorination reaction more uniform, and the overall chlorination reaction more complete. Increasing the reaction temperature in this stage can increase the elongation at break of the product. The pressure in the high temperature section is controlled below 0.5MPa.

[0022] (3) First deacidification: After the reaction is completed, the slurry is sent to the waiting kettle for cooling. After the material is cooled to 90°C, it is sent to the belt filter for deacidification to obtain concentrated hydrochloric acid (about 22wt%) and solid material. The solid material enters the next process. The concentrated hydrochloric acid removed is returned to the batching process in step (1) for acid preparation and recycling.

[0023] (4) Second deacidification: water is added to the solid material in the transfer kettle (the amount of water added is suitable for the slurry formed to be easy to pump) for mixing and infiltration to reduce the acidity. After stirring, a slurry is formed in the transfer kettle again. The slurry is deacidified by a centrifugal centrifuge to obtain dilute hydrochloric acid (about 5wt%) and solid material; the solid material is sent to the neutralization kettle for neutralization reaction. The dilute acid returns to the batching process of step (1) for acid preparation and recycling.

[0024] (5) Neutralization: Add water to the solid material (the amount of water added should be such that the formed slurry is easy to be transported by a pump) to mix and form a slurry, and then add alkali (30wt% sodium hydroxide solution) to the slurry for neutralization, so that the slurry becomes neutral or weakly alkaline. The pH value of the slurry after neutralization is controlled at 7-8.

[0025] (6) The neutralized slurry is sent to a belt filter to remove alkaline water. Then it enters the slurry tank, where water is added (the amount of water added is appropriate to make the slurry easy to pump) and mixed. The slurry in the slurry tank is sent to a finished product centrifuge for dehydration. The solid material after dehydration in the finished product centrifuge enters a dryer for drying to obtain the finished chlorinated polyethylene.

[0026] The elongation at break of the finished product of chlorinated poly(ethylene glycol) produced in Example 1 is 846%, and the tensile strength (tensile strength) is 12.1 MPa. For specific test results, please refer to Figure 1 Test report shown. Example 2

[0027] A chlorinated polyethylene acid water combination production process, the weight ratio of raw materials is: high-density polyethylene 15% (3500kg), 15wt% hydrochloric acid solution 68%, dispersant 0.04%, composite auxiliary agent 0.04%, liquid chlorine 16.92%.

[0028] The production steps include: (1) Mix the ingredients in a 30 cubic meter rubber-lined kettle: Mix the concentrated hydrochloric acid (about 22wt%) and the dilute hydrochloric acid (about 5wt%) produced in the production process to prepare a 15wt% hydrochloric acid solution, add dispersant silica and composite additives, and then add high-density polyethylene and stir to form a reaction slurry.

[0029] (2) The reaction slurry is pumped into a 30-cubic-meter enamel reactor for chlorination reaction: the chlorine flow rate and speed are controlled in three reaction stages. Liquid chlorine is continuously introduced, and the three reaction stages are low-temperature stage, medium-temperature stage and high-temperature stage. Controlling the quality of chlorine introduced into the reaction at each temperature stage is the key to controlling the quality of chlorinated polyethylene.

[0030] Low temperature section: Raise the temperature of the reaction slurry to 75°C, and start to continuously introduce liquid chlorine into the reaction slurry. At the same time, use an external heat source (steam) to continue heating the reaction slurry. When the reaction slurry is heated to 89-90°C, the amount of chlorine introduced is 9% of the total amount of liquid chlorine. The pressure in the low temperature section is controlled below 0.5MPa.

[0031] Medium temperature section: The reaction slurry is heated to 123°C mainly by the heat generated by the chlorination reaction. The whole heating process is divided into 3 small sections to control the amount of chlorine. The amount of chlorine in each section is the same. When the amount of chlorine in each section reaches the target value, the temperature of the reaction slurry is required to rise by 9°C. The total amount of chlorine in the medium temperature section is 60% of the total amount of liquid chlorine. The specific operation of the medium temperature section is: by controlling the chlorine flow rate, the larger the amount of chlorine in each section, the higher the slurry temperature, and the relationship is linear; that is, in the first section, when the temperature of the reaction slurry is heated from 90°C to 101°C, the amount of chlorine is 20% of the total amount of liquid chlorine, in the second section, when the temperature of the reaction slurry is heated from 101°C to 112°C, the amount of chlorine is 20% of the total amount of liquid chlorine, and in the third section, when the temperature of the reaction slurry is heated from 112°C to 123°C, the amount of chlorine is 20% of the total amount of liquid chlorine. The pressure in the medium temperature section is controlled below 0.5MPa. The temperature should be controlled to rise according to the corresponding chlorine flow rate. If there is any deviation, it needs to be adjusted by adding water or steam.

[0032] High temperature section: In the first high temperature section, 9% of the total amount of liquid chlorine is introduced into the reaction slurry, and the temperature of the reaction slurry is controlled at 127-128°C; in the second high temperature section, the remaining liquid chlorine is introduced into the reaction slurry, and the reaction slurry is controlled at 129-130°C. The pressure of the high temperature section is controlled below 0.5MPa.

[0033] (3) First deacidification: After the reaction is completed, the slurry is sent to the waiting kettle for cooling. After the material is cooled to 80°C, it is sent to the belt filter for deacidification to obtain concentrated hydrochloric acid (about 22wt%) and solid material. The solid material enters the next process. The concentrated hydrochloric acid removed is returned to the batching process in step (1) for acid preparation and recycling.

[0034] (4) Second deacidification: water is added to the solid material in the transfer kettle (the amount of water added is suitable for the slurry formed to be easy to pump) for mixing and infiltration to reduce the acidity. After stirring, a slurry is formed in the transfer kettle again. The slurry is deacidified by a centrifugal centrifuge to obtain dilute hydrochloric acid (about 5wt%) and solid material; the solid material is sent to the neutralization kettle for neutralization reaction. The dilute acid returns to the batching process of step (1) for acid preparation and recycling.

[0035] (5) Neutralization: Add water to the solid material (the amount of water added should be such that the formed slurry is easy to be transported by a pump) to mix and form a slurry. Then add alkali (30wt% sodium hydroxide solution) to the slurry for neutralization, so that the slurry becomes neutral or weakly alkaline. The pH value of the slurry after neutralization is controlled at 7.5.

[0036] (6) The neutralized slurry is sent to a belt filter to remove alkaline water. Then it enters the slurry tank, where water is added (the amount of water added is appropriate to make the slurry easy to pump) and mixed. The slurry in the slurry tank is sent to a finished product centrifuge for dehydration. The solid material after dehydration in the finished product centrifuge enters a dryer for drying to obtain the finished chlorinated polyethylene.

[0037] The elongation at break of the finished chlorinated poly(ethylene) acid produced in Example 2 is 834%, and the tensile strength (tensile strength) is 13 MPa.

[0038] In each embodiment of the present invention, the dispersant used is a solid dispersant (hydrophobic silica) sold by Zibo Yongwei Industry and Trade Co., Ltd., and the composite auxiliary agent is a composite auxiliary agent (containing polyvinyl pyrrolidone) for CPE production sold by Zibo Yongwei Industry and Trade Co., Ltd.

[0039] In each embodiment of the present invention, in step (4), hydrochloric acid with a concentration of 3 to 6 wt % may be added to the solid material in the transfer kettle for mixing to form a slurry.

[0040] Comparative Example 1: Steps (1), (3), (4), (5) and (6) are the same as those of Example 1, except that in step (2), the reaction slurry is directly heated to 120° C., and then all the liquid chlorine is introduced to carry out the chlorination reaction. The temperature of the reaction process is controlled at 110 to 120° C., and the pressure is controlled to be below 0.5 MPa.

[0041] Comparative Example 2: Steps (1), (3), (4), (5) and (6) are the same as those of Example 1, except that in step (2), the reaction slurry is directly heated to 60° C., and then all the liquid chlorine is introduced to carry out the chlorination reaction. The temperature of the reaction process is controlled at 60 to 120° C., and the pressure is controlled to be below 0.5 MPa.

[0042] Comparative table of properties of the finished chlorinated polyethylene produced by the examples of the present invention and the comparative examples.

[0043] Production process Elongation at break % Tensile strength MPa Example 1 846 12.1 Example 2 834 13 Comparative Example 1 726 9.5 Comparative Example 2 713 8.9

[0044] As can be seen from the above table, the elongation at break and tensile strength (tensile strength) of the finished chlorinated polyethylene produced in Example 1-2 are higher than those in Comparative Example 1-2, indicating that the chlorination reaction in step (2) of the present application is carried out in three stages: low temperature stage, medium temperature stage and high temperature stage respectively. The temperature should be controlled to increase according to the corresponding chlorine flow rate so that the chlorination reaction can proceed more reasonably, which can significantly improve the elongation at break and tensile strength of the chlorinated polyethylene.

Claims

1. A chlorinated polyvinyl acid water combination production process, characterized in that: The weight ratio of each raw material is: 12-16 parts of high-density polyethylene, 68-73 parts of 12-18wt% hydrochloric acid solution, 0.03-0.08 parts of dispersant, 0.03-0.08 parts of composite auxiliary agent, and 13-18 parts of liquid chlorine; The production steps include: (1) Preparation: Prepare a 12-18 wt% hydrochloric acid solution, add a dispersant and a composite additive, and then add high-density polyethylene and stir and mix to form a reaction slurry; (2) Chlorination reaction: It is divided into three reaction stages to control the amount of chlorine. Liquid chlorine is introduced continuously. The three reaction stages are low temperature stage, medium temperature stage and high temperature stage. Low temperature stage: raise the temperature of the reaction slurry to 72-76°C, start to continuously introduce liquid chlorine into the reaction slurry, and continue to heat the reaction slurry with an external heat source. When the reaction slurry is heated to 87-90°C, the amount of chlorine introduced is required to be 9-10% of the total amount of liquid chlorine. Medium temperature section: The reaction slurry is heated to 120-126°C mainly by the heat generated by the chlorination reaction. The whole heating process is divided into 3-5 small sections to control the chlorine flow rate. The difference in the chlorine flow rate of each small section is 0-0.5% of the total amount of liquid chlorine. When the chlorine flow rate of each small section reaches the target value, the reaction slurry temperature is required to increase by 9-11°C. The total chlorine flow rate of the medium temperature section is 58-62% of the total amount of liquid chlorine. High temperature section: In the first high temperature section, 9-10% of the total amount of liquid chlorine is introduced into the reaction slurry, and the temperature of the reaction slurry is controlled at 127-128°C; in the second high temperature section, the remaining liquid chlorine is introduced into the reaction slurry, and the temperature of the reaction slurry is controlled at 129-131°C; (3) First deacidification: After the reaction is completed, the material is cooled to below or equal to 90°C for deacidification to obtain concentrated hydrochloric acid and solid material; (4) Second deacidification: Add water or dilute acid to the solid material to mix and soak it, and then stir to form a slurry. The slurry is deacidified to obtain dilute hydrochloric acid and solid material. (5) Neutralization: Add water to the solid material to form a slurry, and then add alkali to the slurry for neutralization, so that the slurry becomes neutral or weakly alkaline. The pH value of the slurry is required to be controlled between 7 and 8; (6) After neutralization, the slurry is freed from alkaline water, water is added and mixed, and finally the chlorinated polyethylene is obtained after dehydration and drying.

2. The chlorinated polyvinyl alcohol water combination production process according to claim 1, characterized in that: The concentrated hydrochloric acid obtained in step (3) and the dilute hydrochloric acid obtained in step (4) are returned to step (1) for preparing a hydrochloric acid solution.

3. The chlorinated polyvinyl alcohol water combination production process according to claim 1 or 2, characterized in that: The dispersant in step (1) is silicon dioxide.

4. The chlorinated polyvinyl alcohol water combination production process according to claim 1 or 2, characterized in that: The alkali in step (5) is sodium hydroxide or calcium carbonate.

5. The chlorinated polyvinyl alcohol water combination production process according to claim 1 or 2, characterized in that: In step (3), a filter is used for deacidification, and in step (4), a centrifuge is used for deacidification.

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