A configuration system and method of low-concentration initiator for polyvinyl chloride production

Abstract

A kind of configuration system and configuration method of low concentration initiator for polyvinyl chloride production belong to the technical field of polyvinyl chloride production, mainly aiming at the automatic configuration of initiator aqueous solution with mass concentration of 1-2%.The configuration system is composed of cold pure water storage tank, hydrogen peroxide storage tank, chloroester storage tank, sodium hydroxide storage tank, dispersant (polyvinyl alcohol) storage tank, polyethylene glycol storage tank, neutralizing agent (citric acid) storage tank and initiator preparation tank;The present application is to synthesize peroxide di (2-ethylhexyl) ester initiator (EHP) by using sodium hydroxide, hydrogen peroxide and chloroester, because strong base is used in the reaction process, the system is alkaline, after the reaction is completed, the pH value needs to be adjusted to 3-6 by using neutralizing agent (citric acid), to improve the stability of EHP;Again, because EHP is insoluble in water, dispersant (polyvinyl alcohol) needs to be added during preparation, to reduce surface tension, control particle size, form EHP emulsion, and improve its catalytic effect in polyvinyl chloride production.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of polyvinyl chloride production, and particularly relates to a configuration system and method of low-concentration initiator for polyvinyl chloride production, mainly aiming at the automatic configuration of initiator aqueous solution with a mass concentration of 1-2%. BACKGROUND

[0002] The most commonly used production method of polyvinyl chloride (hereinafter referred to as PVC) at present is water phase suspension method, and the basic production principle is to gradually add deionized water and vinyl chloride monomer in a polymerization kettle, to make vinyl chloride (hereinafter referred to as VCM) suspended in water phase under the action of initiators, dispersants and the like, so that the vinyl chloride generates polymerization reaction to form polyvinyl chloride resin under specific temperature and pressure in the polymerization kettle.

[0003] The role of the initiator is to generate active free radicals through thermal decomposition, to serve as a starting point of chain initiation reaction, and to trigger the chain growth reaction of vinyl chloride monomer, so that the initiator is the most important additive in PVC production.

[0004] Traditional polyvinyl chloride manufacturers all purchase high-quality-concentration (50% or 75% concentration) initiators, store them through cold storage or low-temperature storage tanks, and need to ensure that the storage temperature is about -20 DEG C, which has the following shortcomings: (1) large equipment investment, in addition to the necessary initiator solution storage tank, investment in cold storage or refrigeration unit and the like is also needed; (2) safety risk, 50% or 75% concentration initiators usually need to be stored in an environment with a temperature of -15 to -20 DEG C, and there is a risk of decomposition and heat release when the temperature rises; (3) high cost, the cost of purchased finished initiator (peroxide) is about 50-60 yuan / tPVC. SUMMARY

[0005] The purpose of the application is to provide a configuration system and method of low-concentration initiator for polyvinyl chloride production, which principle is to synthesize di(2-ethylhexyl) peroxydicarbonate initiator (EHP) by using sodium hydroxide, hydrogen peroxide and chloroester. Since strong alkali is used in the reaction process, the system is alkaline, and after the reaction is completed, a neutralizing agent (citric acid) is used to adjust the pH value to 3-6, to control the system in an acidic environment and improve the stability of EHP. Since EHP is insoluble in water, a dispersing agent (polyvinyl alcohol) needs to be added in the preparation process to reduce the surface tension, control the particle size, form EHP emulsion, and improve the catalytic effect in polyvinyl chloride production. Since the EHP preparation link is complicated, the addition amount and addition time of each additive need to be strictly controlled, and generally the addition amount needs to be automatically adjusted through DCS program to control the initiator concentration, and the low-concentration initiator for polyvinyl chloride production is configured for the amount of a single polymerization kettle each time.

[0006] The low-concentration initiator preparation system for polyvinyl chloride production comprises a cold pure water storage tank, a hydrogen peroxide storage tank, a chloroester storage tank, a sodium hydroxide storage tank, a dispersant (polyvinyl alcohol) storage tank, a polyethylene glycol storage tank, a neutralizing agent (citric acid) storage tank and an initiator preparation tank; a cold pure water electromagnetic flowmeter, a cold pure water mass flowmeter and a cold pure water automatic regulating valve are sequentially arranged on the outlet pipeline of the cold pure water storage tank; a hydrogen peroxide electromagnetic flowmeter, a hydrogen peroxide mass flowmeter and a hydrogen peroxide automatic regulating valve are sequentially arranged on the outlet pipeline of the hydrogen peroxide storage tank; a chloroester electromagnetic flowmeter, a chloroester mass flowmeter and a chloroester automatic regulating valve are sequentially arranged on the outlet pipeline of the chloroester storage tank; a sodium hydroxide automatic regulating valve, a sodium hydroxide electromagnetic flowmeter and a sodium hydroxide mass flowmeter are sequentially arranged on the outlet pipeline of the sodium hydroxide storage tank; a dispersant automatic regulating valve, a dispersant electromagnetic flowmeter and a dispersant mass flowmeter are sequentially arranged on the outlet pipeline of the dispersant storage tank; a polyethylene glycol automatic regulating valve, a polyethylene glycol electromagnetic flowmeter and a polyethylene glycol mass flowmeter are sequentially arranged on the outlet pipeline of the polyethylene glycol storage tank; a neutralizing agent automatic regulating valve, a neutralizing agent electromagnetic flowmeter and a neutralizing agent mass flowmeter are sequentially arranged on the outlet pipeline of the neutralizing agent storage tank; a frequency conversion stirrer is arranged in the initiator preparation tank; the initiator preparation tank is a jacket structure and is provided with a jacket chilled water inlet pipeline and a jacket chilled water return pipeline.

[0007] The outlets of the cold pure water automatic regulating valve, the hydrogen peroxide automatic regulating valve and the chloroester automatic regulating valve are sequentially connected together through pipelines, and an automatic switch valve is arranged on the pipeline between the outlets of the cold pure water automatic regulating valve and the hydrogen peroxide automatic regulating valve.

[0008] An initiator mixer is further arranged on the outlet pipeline of the cold pure water automatic regulating valve, and the initiator mixer is a pipeline structure with an inlet, an intermediate port and an outlet and a necked middle part (the principle is the Venturi ejector principle, the local necking of the pipeline causes the flow rate to suddenly increase, and a negative pressure area is locally formed, so that the hydrogen peroxide and the chloroester can quickly and uniformly enter the initiator mixer through the intermediate port); the outlet of the cold pure water automatic regulating valve is connected with the inlet of the initiator mixer, the outlet of the chloroester automatic regulating valve is connected with the intermediate port of the initiator mixer, the outlet of the initiator mixer, the outlet of the sodium hydroxide mass flowmeter, the outlet of the dispersant mass flowmeter, the outlet of the polyethylene glycol mass flowmeter and the outlet of the neutralizing agent mass flowmeter are sequentially connected together through a cold pure water pipeline, and then connected to the initiator preparation tank.

[0009] Due to the corrosive nature of the chloroester, the chloroester storage tank and outlet pipeline need to be treated with high corrosion-resistant lining, generally using PTFE (polytetrafluoroethylene) lining, PE (polyethylene) lining or propylene oxide lining. Hydrogen peroxide and peroxide have oxidizing properties, so the hydrogen peroxide storage tank, initiator synthesis tank and corresponding pipeline need to be pickled and passivated. The addition amount of each additive needs to be strictly controlled during the initiator synthesis process, so a double flow meter of electromagnetic flow meter and mass flow meter is set to reduce the addition error.

[0010] The configuration method of the low-concentration initiator for polyvinyl chloride production according to the present application comprises the following steps:

[0011] Step 1: Open the cold pure water automatic regulating valve, control the flow rate to be 6-10 m³ / h, and the cold pure water at 25-35℃ in the cold pure water storage tank is added to the initiator mixer through the cold pure water electromagnetic flow meter, cold pure water mass flow meter and cold pure water automatic regulating valve from the inlet, and then enters the initiator preparation tank through the cold pure water pipeline from the outlet of the initiator mixer;

[0012] Step 2: When the cold pure water flow rate is stable, open the polyethylene glycol automatic regulating valve, control the flow rate to be 400-600 kg / h, and the polyethylene glycol in the polyethylene glycol storage tank is carried to the initiator preparation tank by the cold pure water in the cold pure water pipeline through the polyethylene glycol automatic regulating valve, polyethylene glycol electromagnetic flow meter and polyethylene glycol mass flow meter, and when the addition amount of polyethylene glycol reaches 10-12 kg, the polyethylene glycol automatic regulating valve is closed, and the addition of polyethylene glycol is completed;

[0013] Step 3: After the addition of polyethylene glycol is completed, the low-speed stirring of the initiator preparation tank frequency converter stirrer is started (the stirring speed is 1400-1600 rpm, and the stirrer must run during the synthesis of the initiator. The design of the stirrer is to provide sufficient mixing in the initiator preparation tank, thereby creating the best droplet size for the synthesis of the initiator);

[0014] Step 4: While the low-speed stirring of the initiator preparation tank frequency converter stirrer is started, the chloroester automatic regulating valve is opened, the flow rate is controlled to be 1600-1800 kg / h, the chloroester in the chloroester storage tank is added to the initiator mixer through the chloroester electromagnetic flow meter, chloroester mass flow meter and chloroester automatic regulating valve from the intermediate port, and then is carried to the initiator preparation tank by the cold pure water in the cold pure water pipeline from the outlet of the initiator mixer, when the addition amount of chloroester reaches 32-34 kg, the chloroester automatic regulating valve is closed, the addition of chloroester is completed, and then the high-speed stirring of the initiator preparation tank frequency converter stirrer is started (the stirring speed is 2400-2600 rpm);

[0015] Step 5: After the addition of chloroester is completed, the automatic on-off valve is opened for 8-15 seconds and then closed; during the opening of the automatic on-off valve, 25-35℃ cold pure water from the cold pure water storage tank flushes the chloroester in the pipeline and the initiator mixer; after the automatic on-off valve is closed, the hydrogen peroxide automatic regulating valve is opened, and the flow rate is controlled at 500-700 kg / h; the hydrogen peroxide in the hydrogen peroxide storage tank is added to the initiator mixer through the hydrogen peroxide electromagnetic flowmeter, the hydrogen peroxide mass flowmeter, and the hydrogen peroxide automatic regulating valve via the intermediate port, and then is taken to the initiator preparation tank by the cold pure water in the cold pure water pipeline via the outlet of the initiator mixer; when the amount of hydrogen peroxide added reaches 10-12 kg, the hydrogen peroxide automatic regulating valve is closed, and the addition of hydrogen peroxide is completed;

[0016] Step 6: 60-90 seconds after the addition of hydrogen peroxide is completed, the sodium hydroxide automatic regulating valve is opened, and the flow rate is controlled at 3-5 m³ / h; the sodium hydroxide in the sodium hydroxide storage tank is added to the cold pure water pipeline via the sodium hydroxide automatic regulating valve, the sodium hydroxide electromagnetic flowmeter, and the sodium hydroxide mass flowmeter, and is taken to the initiator preparation tank by the cold pure water; when the amount of sodium hydroxide added reaches 75-80 kg, the sodium hydroxide automatic regulating valve is closed, and the addition of sodium hydroxide is completed;

[0017] Step 7: After the addition of sodium hydroxide is completed, the cold pure water automatic regulating valve is closed, and 7-8 minutes are waited; during the closing of the cold pure water automatic regulating valve, the chloroester, the hydrogen peroxide, and the sodium hydroxide are fully reacted in the initiator preparation tank to synthesize the initiator EHP (di(2-ethylhexyl) peroxydicarbonate), and the reaction formula is as follows:

[0018] R-COCl + H2O2 + NaOH → R-CO-O-O-CO-R + NaCl + H2O, R represents a 2-ethylhexyl group;

[0019] Step 8: After the synthesis of the initiator is completed, the cold pure water automatic regulating valve is opened, and the dispersant automatic regulating valve is opened, and the flow rate is controlled at 2-4 m³ / h; the dispersant in the dispersant storage tank is added to the cold pure water pipeline via the dispersant automatic regulating valve, the dispersant electromagnetic flowmeter, and the dispersant mass flowmeter, and is taken to the initiator preparation tank by the cold pure water; at this time, the dispersant is added to control the particle size of the initiator; when the amount of dispersant added reaches 40-45 kg, the dispersant automatic regulating valve is closed, and the addition of dispersant is completed;

[0020] Step 9: After the addition of dispersant is completed, the neutralizing agent automatic regulating valve is opened, and the flow rate is controlled at 1.5-3.0 m³ / h; the neutralizing agent in the neutralizing agent storage tank is added to the cold pure water pipeline via the neutralizing agent automatic regulating valve, the neutralizing agent electromagnetic flowmeter, and the neutralizing agent mass flowmeter, and is taken to the initiator preparation tank by the cold pure water; when the amount of neutralizing agent added reaches 40-42 kg, the neutralizing agent automatic regulating valve is closed, and the addition of neutralizing agent is completed; the neutralizing agent adjusts the pH value of the initiator system to 3-6.

[0021] Step 10: When the neutralizing agent is added, continue to open the cold pure water automatic regulating valve, and when the amount of cold pure water reaches 2200-2400 kg, close the cold pure water automatic regulating valve, and control the mass concentration of the initiator in the initiator preparation tank to be 1-2%, and the initiator preparation is completed;

[0022] Step 11: After the initiator preparation is completed, the frequency conversion stirrer of the initiator preparation tank is maintained at high speed stirring (speed 2400-2600 rpm) for 4-6 minutes, and then the frequency conversion stirrer of the initiator preparation tank is maintained at low speed stirring (speed 1400-1600 rpm) for 5-10 minutes, to ensure that the initiator system is stable; during the preparation of the initiator, the initiator preparation tank jacket freezing water must be kept open, and the temperature of the initiator preparation tank is controlled at 10-25℃.

[0023] The beneficial effects of the present application are:

[0024] (1) Improve the safety performance: usually the mass concentration of the initiator for polyvinyl chloride is 45-75%, and the storage temperature needs to be about-20℃, and the decomposition risk exists at too high temperature, and the present application is to synthesize the initiator aqueous solution with a mass concentration of 1-2%, and the low-concentration initiator aqueous solution is safer to store, and does not need a low-temperature cold storage, and further freezing the jacket (7℃) can ensure safe storage, and greatly improves the safety;

[0025] (2) Reduce the cost: the cost of using low-concentration initiator to produce polyvinyl chloride is about 20 yuan / tPVC, and the cost of outsourcing finished initiator (peroxide) is about 50-60 yuan / tPVC, which greatly reduces the cost;

[0026] (3) The feeding sequence of various materials for synthesizing the initiator is an important factor, and the chloroester, hydrogen peroxide and sodium hydroxide are added in turn, and in the adding process, the chloroester and hydrogen peroxide need to be prevented from reacting in advance in the pipeline, so after the chloroester is added, the pipeline needs to be washed with cold pure water before adding hydrogen peroxide;

[0027] (4) The temperature affects the yield of the synthesized initiator, and usually the temperature of the synthesis system is controlled at 10-25℃ (synthesis in water); too low synthesis temperature will cause slow formation of the initiator, relatively small amount of generation, i.e. relatively low yield; too high synthesis system temperature will cause partial decomposition of CatC and CatD, accelerate the decomposition rate of the generated initiator, and directly reduce the effective yield; therefore, the temperature is very important for the synthesis of the initiator. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 The configuration system structure diagram of the low-concentration initiator for polyvinyl chloride production described in the present application. DETAILED DESCRIPTION

[0029] Example 1:

[0030] like Figure 1 As shown, the names of each part are: Cold pure water storage tank 1, Cold pure water electromagnetic flow meter 2, Cold pure water mass flow meter 3, Cold pure water automatic regulating valve 4, Hydrogen peroxide storage tank 5, Hydrogen peroxide electromagnetic flow meter 6, Hydrogen peroxide mass flow meter 7, Hydrogen peroxide automatic regulating valve 8, Chlorinated ester storage tank 9, Chlorinated ester electromagnetic flow meter 10, Chlorinated ester mass flow meter 11, Chlorinated ester automatic regulating valve 12, Automatic on / off valve 13, Initiator mixer 14, Sodium hydroxide storage tank 15, Sodium hydroxide electromagnetic flow meter 16, Sodium hydroxide mass flow meter 17, Sodium hydroxide automatic regulating valve 18, Dispersant storage tank Tank 19, Dispersant electromagnetic flowmeter; 20, Dispersant mass flowmeter; 21, Dispersant automatic regulating valve; 22, Polyethylene glycol storage tank; 23, Polyethylene glycol electromagnetic flowmeter; 24, Polyethylene glycol mass flowmeter; 25, Polyethylene glycol automatic regulating valve; 26, Neutralizing agent storage tank; 27, Neutralizing agent electromagnetic flowmeter; 28, Neutralizing agent mass flowmeter; 29, Neutralizing agent automatic regulating valve; 30, Initiator preparation tank with variable frequency stirrer; 31, Initiator preparation tank; 32, Initiator preparation tank jacketed chilled water inlet pipeline; 33, Initiator preparation tank jacketed chilled water return pipeline; 34, Cold pure water pipeline; 35.

[0031] The low-concentration initiator preparation system for polyvinyl chloride production comprises a cold pure water storage tank 1, a hydrogen peroxide storage tank 5, a chloroester storage tank 9, a sodium hydroxide storage tank 15, a dispersant (polyvinyl alcohol) storage tank 19, a polyethylene glycol storage tank 23, a neutralizing agent (citric acid) storage tank 27 and an initiator preparation tank 32; a cold pure water electromagnetic flowmeter 2, a cold pure water mass flowmeter 3 and a cold pure water automatic regulating valve 4 are sequentially arranged on an outlet pipeline of the cold pure water storage tank 1, a hydrogen peroxide electromagnetic flowmeter 6, a hydrogen peroxide mass flowmeter 7 and a hydrogen peroxide automatic regulating valve 8 are sequentially arranged on an outlet pipeline of the hydrogen peroxide storage tank 5, a chloroester electromagnetic flowmeter 10, a chloroester mass flowmeter 11 and a chloroester automatic regulating valve 12 are sequentially arranged on an outlet pipeline of the chloroester storage tank 9, a sodium hydroxide automatic regulating valve 16, a sodium hydroxide electromagnetic flowmeter 17 and a sodium hydroxide mass flowmeter 18 are sequentially arranged on an outlet pipeline of the sodium hydroxide storage tank 15, a dispersant automatic regulating valve 20, a dispersant electromagnetic flowmeter 21 and a dispersant mass flowmeter 22 are sequentially arranged on an outlet pipeline of the dispersant storage tank 19, a polyethylene glycol automatic regulating valve 24, a polyethylene glycol electromagnetic flowmeter 25 and a polyethylene glycol mass flowmeter 26 are sequentially arranged on an outlet pipeline of the polyethylene glycol storage tank 23, a neutralizing agent automatic regulating valve 28, a neutralizing agent electromagnetic flowmeter 29 and a neutralizing agent mass flowmeter 30 are sequentially arranged on an outlet pipeline of the neutralizing agent storage tank 27, and a variable-frequency agitator 31 of the initiator preparation tank 32 is arranged in the initiator preparation tank 32; the initiator preparation tank 32 is of a jacket structure and is provided with a jacketed chilled water inlet pipeline 33 and a jacketed chilled water return pipeline 34.

[0032] The outlets of the cold pure water automatic regulating valve 4, the hydrogen peroxide automatic regulating valve 8 and the chloroester automatic regulating valve 12 are sequentially connected together through pipelines, and an automatic switch valve 13 is arranged on a pipeline between the outlets of the cold pure water automatic regulating valve 4 and the hydrogen peroxide automatic regulating valve 8.

[0033] An initiator mixer 14 is further arranged on an outlet pipeline of the cold pure water automatic regulating valve 4, the initiator mixer 14 is of a pipeline structure with an inlet, an intermediate port and an outlet and a necked middle part (the principle is that of a Venturi ejector, after the pipeline is partially necked, the flow rate suddenly increases, a negative pressure area is formed locally, and the hydrogen peroxide and the chloroester can quickly and uniformly enter the initiator mixer through the intermediate port); the outlet of the cold pure water automatic regulating valve 4 is connected with the inlet of the initiator mixer 14, the outlet of the chloroester automatic regulating valve 12 is connected with the intermediate port of the initiator mixer 14, the outlet of the initiator mixer 14, the outlet of the sodium hydroxide mass flowmeter 18, the outlet of the dispersant mass flowmeter 22, the outlet of the polyethylene glycol mass flowmeter 26 and the outlet of the neutralizing agent mass flowmeter 30 are sequentially connected together through a cold pure water pipeline 35, and then connected to the initiator preparation tank 32.

[0034] Example 2:

[0035] A method for preparing a low-concentration initiator for polyvinyl chloride production using the low-concentration initiator preparation system for polyvinyl chloride production described in Example 1, the steps of which are as follows:

[0036] Step 1: Open the cold pure water automatic regulating valve 4, control the flow rate to be 8 m³ / h, and the 30°C cold pure water in the cold pure water storage tank 1 is added to the initiator mixer 14 through the cold pure water electromagnetic flowmeter 2, the cold pure water mass flowmeter 3, and the cold pure water automatic regulating valve 4, and then enters the initiator preparation tank 32 after passing through the initiator mixer 14;

[0037] Step 2: When the cold pure water flow rate is stable, open the polyethylene glycol automatic regulating valve 24, control the flow rate to be 500 kg / h, and the polyethylene glycol in the polyethylene glycol storage tank 23 is brought to the initiator preparation tank 32 by the cold pure water through the polyethylene glycol automatic regulating valve 24, the polyethylene glycol electromagnetic flowmeter 25, and the polyethylene glycol mass flowmeter 26, and when the polyethylene glycol addition amount reaches 11 kg, the polyethylene glycol automatic regulating valve 24 is closed, and the polyethylene glycol addition is completed;

[0038] Step 3: After the polyethylene glycol addition is completed, the initiator preparation tank variable frequency stirrer 31 is maintained at a low speed (rotating speed of 1500 rpm), and the stirrer must be operated during the initiator synthesis. The stirrer is designed to provide sufficient mixing in the initiator preparation tank 32, thereby creating the best droplet size for the synthesis of the initiator;

[0039] Step 4: At the same time as starting the initiator preparation tank variable frequency stirrer 31 at a low speed, open the chloroester automatic regulating valve 12, control the flow rate to be 1700 kg / h, and the chloroester in the chloroester storage tank 9 is added to the initiator mixer 14 through the chloroester electromagnetic flowmeter 10, the chloroester mass flowmeter 11, and the chloroester automatic regulating valve 12, and is brought to the initiator preparation tank 32 by the cold pure water, and when the chloroester addition amount reaches 33 kg, the chloroester automatic regulating valve 12 is closed, the chloroester addition is completed, and then the initiator preparation tank variable frequency stirrer 31 is maintained at a high speed (rotating speed of 2500 rpm);

[0040] Step 5: After the addition of chloroester is completed, open the automatic on-off valve 13 for 10 seconds and then close it; during the opening of the automatic on-off valve 13, 30°C cold pure water from the cold pure water storage tank 1 flushes the pipeline and the chloroester in the initiator mixer 14; after the automatic on-off valve 13 is closed, open the automatic regulating valve 8 of hydrogen peroxide, and control the flow rate to be 600 kg / h; the hydrogen peroxide in the hydrogen peroxide storage tank 5 enters the pipeline through the hydrogen peroxide electromagnetic flowmeter 6, the hydrogen peroxide mass flowmeter 7, and the automatic regulating valve 8 of hydrogen peroxide, and then enters the initiator mixer 14 through the intermediate port; the hydrogen peroxide is then taken to the initiator preparation tank 32 by the cold pure water in the cold pure water pipeline 35 through the outlet of the initiator mixer 14; when the amount of hydrogen peroxide added reaches 11 kg, close the automatic regulating valve 8 of hydrogen peroxide, and the addition of hydrogen peroxide is completed.

[0041] Step 6: After the addition of hydrogen peroxide is completed for 75 seconds, open the automatic regulating valve 16 of sodium hydroxide, and control the flow rate to be 4 m³ / h; the sodium hydroxide in the sodium hydroxide storage tank 15 enters the cold pure water pipeline through the automatic regulating valve 16 of sodium hydroxide, the electromagnetic flowmeter 17, and the sodium hydroxide mass flowmeter 18, and is taken to the initiator preparation tank 32 by the cold pure water; when the amount of sodium hydroxide added reaches 78 kg, close the automatic regulating valve 16 of sodium hydroxide, and the addition of sodium hydroxide is completed.

[0042] Step 7: After the addition of sodium hydroxide is completed, close the automatic regulating valve 4 of cold pure water and wait for 7 minutes; during this period, the chloroester, hydrogen peroxide, and sodium hydroxide are fully reacted in the initiator preparation tank 32 to synthesize the initiator EHP (di(2-ethylhexyl) peroxydicarbonate);

[0043] Step 8: After the synthesis of the initiator is completed, open the automatic regulating valve 4 of cold pure water and open the automatic regulating valve 20 of dispersant, and control the flow rate to be 3 m³ / h; the dispersant in the dispersant storage tank 19 enters the cold pure water pipeline through the automatic regulating valve 20 of dispersant, the dispersant electromagnetic flowmeter 21, and the dispersant mass flowmeter 22, and is taken to the initiator preparation tank 32 by the cold pure water; the addition of dispersant controls the particle size of the initiator; when the amount of dispersant added reaches 42 kg, close the automatic regulating valve 20 of dispersant, and the addition of dispersant is completed.

[0044] Step 9: After the addition of dispersant is completed, continue to open the automatic regulating valve 28 of neutralizing agent, and control the flow rate to be 2.0 m³ / h; the neutralizing agent in the neutralizing agent storage tank 27 enters the cold pure water pipeline through the automatic regulating valve 28 of neutralizing agent, the neutralizing agent electromagnetic flowmeter 29, and the neutralizing agent mass flowmeter 30, and is taken to the initiator preparation tank 32 by the cold pure water; when the amount of neutralizing agent added reaches 41 kg, close the automatic regulating valve 28 of neutralizing agent, and the addition of neutralizing agent is completed; the pH value of the initiator system synthesized is adjusted to 6.0 by the neutralizing agent;

[0045] Step 10: When the neutralizing agent is added, open the cold pure water automatic regulating valve 4, and when the amount of the cold pure water reaches 2300 kg, close the cold pure water automatic regulating valve 4, so that the mass concentration of the initiator in the initiator preparation tank 32 is 1.5%, and the preparation of the initiator is completed;

[0046] Step 11: After the preparation of the initiator is completed, the frequency conversion stirrer 31 of the initiator preparation tank is maintained at high speed stirring (rotation speed 2500 rpm) for 5 minutes, and then the frequency conversion stirrer 31 of the initiator preparation tank is maintained at low speed stirring (rotation speed 1500 rpm) for a period of time to ensure that the initiator system is stable; during the preparation of the initiator, the jacketed freezing water of the initiator preparation tank 32 must be kept open, and the temperature is controlled at 18℃.

[0047] The related index parameters of the prepared initiator are shown in Table 1.

[0048] Table 1: Related index parameters of EHP initiator synthesized according to the above initiator synthesis method

[0049]

[0050] The active oxygen content is an important parameter for measuring the initiation ability of the EHP initiator, the higher the active oxygen content, the stronger the initiation effect, and the active oxygen content is related to the amount of each additive added during the preparation of the initiator. The hydrolysis rate of the EHP initiator is high, and acidic substances are easily produced by hydrolysis in actual application. In order to reduce the hydrolysis of EHP, it needs to be stored in an acidic environment by adding a weak acid to control the pH value of the system to be acidic. The particle size of the EHP initiator is generally controlled below 10 μm, which helps to ensure the uniform dispersion and efficient distribution of EHP in the polymerization reaction, improve the product quality and production efficiency, and ensure its effectiveness and stability in the production of polyvinyl chloride. The chloride ion content is an important index for measuring the impurity content of EHP, which should not be higher than 0.05%, i.e. 5000 mg / L. As can be seen from the data in Table 1, the initiator prepared by the present application has good performance.

[0051] The low-concentration initiator prepared by the present application can replace the original high-concentration initiator purchased from outside in the normal use of the polyvinyl chloride polymerization reaction, thereby solving the disadvantages of the high-concentration initiator, such as the need for low-temperature storage, high cost, etc., and having the same initiation effect and the quality of the final polyvinyl chloride product.

Claims

1. A system for preparing a low-concentration initiator for polyvinyl chloride production, characterized in that: The configuration system consists of a cold pure water storage tank (1), a hydrogen peroxide storage tank (5), a chlorinated ester storage tank (9), a sodium hydroxide storage tank (15), a dispersant storage tank (19), a polyethylene glycol storage tank (23), a neutralizer storage tank (27), and an initiator preparation tank (32). A cold pure water electromagnetic flow meter (2), a cold pure water mass flow meter (3), and a cold pure water automatic regulating valve (4) are sequentially installed on the outlet pipeline of the cold pure water storage tank (1). A hydrogen peroxide electromagnetic flow meter (6), a hydrogen peroxide mass flow meter (7), and a hydrogen peroxide automatic regulating valve (8) are sequentially installed on the outlet pipeline of the hydrogen peroxide storage tank (5). A chlorinated ester electromagnetic flow meter (10) is sequentially installed on the outlet pipeline of the chlorinated ester storage tank (9). The sodium hydroxide storage tank (15) is equipped with a sodium hydroxide mass flow meter (16), a sodium hydroxide electromagnetic flow meter (17), and a sodium hydroxide mass flow meter (18) in sequence on the outlet pipeline of the sodium hydroxide storage tank (19). The dispersant storage tank (19) is equipped with a dispersant automatic regulating valve (20), a dispersant electromagnetic flow meter (21), and a dispersant mass flow meter (22) in sequence on the outlet pipeline of the polyethylene glycol storage tank (23). The polyethylene glycol storage tank (24), a polyethylene glycol electromagnetic flow meter (25), and a polyethylene glycol mass flow meter (26) in sequence are installed on the outlet pipeline of the neutralizing agent storage tank (27). The upper part is equipped with an automatic regulating valve (28) for neutralizing agent, an electromagnetic flow meter (29) for neutralizing agent, and a mass flow meter (30) for neutralizing agent. An initiator preparation tank variable frequency stirrer (31) is installed in the initiator preparation tank (32). The initiator preparation tank (32) has a jacketed structure and is equipped with a jacketed chilled water inlet pipeline (33) and a jacketed chilled water return pipeline (34). The outlets of the automatic regulating valves (4), (8), and (12) for cold pure water, hydrogen peroxide, and chlorinated ester are connected sequentially via pipelines. An automatic switching valve (13) is installed on the pipeline between the outlets of the automatic regulating valves (4) and (8). The automatic regulating valve (4) for cold pure water... An initiator mixer (14) is installed on the outlet pipeline. The initiator mixer (14) is a pipeline structure with an inlet, a middle port and an outlet and a middle neck. The outlet of the cold pure water automatic regulating valve (4) is connected to the inlet of the initiator mixer (14), and the outlet of the chlorinated ester automatic regulating valve (12) is connected to the middle port of the initiator mixer (14). The outlet of the initiator mixer (14), the outlet of the sodium hydroxide mass flow meter (18), the outlet of the dispersant mass flow meter (22), the outlet of the polyethylene glycol mass flow meter (26) and the outlet of the neutralizer mass flow meter (30) are connected together in sequence through the cold pure water pipeline (35) and then connected to the initiator preparation tank (32).

2. The preparation system for a low-concentration initiator for polyvinyl chloride production as described in claim 1, characterized in that: The dispersant is polyvinyl alcohol, and the neutralizer is citric acid.

3. A method for preparing a low-concentration initiator for polyvinyl chloride (PVC) production, comprising preparing the low-concentration initiator using the low-concentration initiator preparation system for PVC production as described in claim 1 or 2, characterized in that: The steps for this configuration method are as follows. Step 1: Open the automatic regulating valve (4) for cold pure water and control the flow rate to 6~10m³ / h. The cold pure water in the cold pure water storage tank (1) is added to the initiator mixer (14) through the inlet of the cold pure water electromagnetic flow meter (2), the cold pure water mass flow meter (3) and the automatic regulating valve (4). Then, the cold pure water enters the initiator preparation tank (32) through the cold pure water pipeline (35) from the outlet of the initiator mixer (14). Step 2: After the cold pure water flow rate stabilizes, open the polyethylene glycol automatic regulating valve (24) and control the flow rate to 400~600 kg / h. The polyethylene glycol in the polyethylene glycol storage tank (23) is carried by the cold pure water in the cold pure water pipeline (35) to the initiator preparation tank (32) through the polyethylene glycol automatic regulating valve (24), polyethylene glycol electromagnetic flow meter (25), and polyethylene glycol mass flow meter (26). When the amount of polyethylene glycol added reaches 10~12 kg, close the polyethylene glycol automatic regulating valve (24) and the addition of polyethylene glycol is completed. Step 3: After the polyethylene glycol is added, turn on the frequency converter (31) of the initiator preparation tank to stir at low speed; Step 4: While the initiator preparation tank is being stirred at low speed by the frequency converter agitator (31), the chlorinated ester automatic regulating valve (12) is opened to control the flow rate at 1600~1800 kg / h. The chlorinated ester in the chlorinated ester storage tank (9) is added to the initiator mixer (14) through the intermediate port via the chlorinated ester electromagnetic flow meter (10), the chlorinated ester mass flow meter (11), and the chlorinated ester automatic regulating valve (12). Then, the chlorinated ester is carried to the initiator preparation tank (32) by the cold pure water in the cold pure water pipeline (35) through the outlet of the initiator mixer (14). When the amount of chlorinated ester added reaches 32~34 kg, the chlorinated ester automatic regulating valve (12) is closed, and the addition of chlorinated ester is completed. Then, the frequency converter agitator (31) of the initiator preparation tank is turned on to stir at high speed. Step 5: After the chlorinated ester is added, open the automatic switch valve (13) and close it after 8-15 seconds. During the opening of the automatic switch valve (13), cold pure water from the cold pure water storage tank (1) flushes the chlorinated ester in the pipeline and the initiator mixer (14). After the automatic switch valve (13) is closed, open the hydrogen peroxide automatic regulating valve (8) and control the flow rate to 500-700 kg / h. The hydrogen peroxide in the hydrogen peroxide storage tank (5) is added to the initiator mixer (14) through the intermediate port via the hydrogen peroxide electromagnetic flow meter (6), hydrogen peroxide mass flow meter (7), and hydrogen peroxide automatic regulating valve (8). Then, it is carried to the initiator preparation tank (32) by the cold pure water in the cold pure water pipeline (35) through the outlet of the initiator mixer (14). When the amount of hydrogen peroxide added reaches 10-12 kg, close the hydrogen peroxide automatic regulating valve (8). The addition of hydrogen peroxide is complete. Step 6: After 60-90 seconds of hydrogen peroxide addition, open the sodium hydroxide automatic regulating valve (16) and control the flow rate to 3-5 m³ / h. Sodium hydroxide in the sodium hydroxide storage tank (15) is added to the cold pure water pipeline (35) through the sodium hydroxide automatic regulating valve (16), sodium hydroxide electromagnetic flow meter (17), and sodium hydroxide mass flow meter (18). The cold pure water carries the sodium hydroxide to the initiator preparation tank (32). When the amount of sodium hydroxide added reaches 75-80 kg, close the sodium hydroxide automatic regulating valve (16). The addition of sodium hydroxide is complete. Step 7: After the sodium hydroxide is added, close the automatic regulating valve (4) for cold pure water and wait for 7-8 minutes. During the period when the automatic regulating valve (4) for cold pure water is closed, the chlorinated ester, hydrogen peroxide and sodium hydroxide react fully in the initiator preparation tank (32) to synthesize the initiator di(2-ethylhexyl) peroxide dicarbonate. The reaction formula is R-COCl+H2O2+NaOH→R-CO-OO-CO-R+NaCl+H2O, where R represents the 2-ethylhexyl group. Step 8: After the initiator synthesis is completed, open the cold pure water automatic regulating valve (4) and the dispersant automatic regulating valve (20) to control the flow rate to 2~4 m³ / h. The dispersant in the dispersant storage tank (19) is added to the cold pure water pipeline (35) through the dispersant automatic regulating valve (20), the dispersant electromagnetic flow meter (21), and the dispersant mass flow meter (22) and is carried to the initiator preparation tank (32) by the cold pure water. When the amount of dispersant added reaches 40~45 kg, close the dispersant automatic regulating valve (20) and the dispersant addition is completed. Step 9: After the dispersant is added, open the neutralizer automatic regulating valve (28) and control the flow rate to 1.5~3.0 m³ / h. The neutralizer in the neutralizer storage tank (27) is added to the cold pure water pipeline (35) through the neutralizer automatic regulating valve (28), the neutralizer electromagnetic flow meter (29), and the neutralizer mass flow meter (30). The cold pure water carries the neutralizer to the initiator preparation tank (32). When the amount of neutralizer added reaches 40~42 kg, close the neutralizer automatic regulating valve (28). The addition of neutralizer is complete. The neutralizer will adjust the pH value of the synthesis initiator system to 2~5. Step 10: After the neutralizer is added, continue to open the cold pure water automatic regulating valve (4). When the amount of cold pure water added reaches 2200~2400kg, close the cold pure water automatic regulating valve (4) and control the mass concentration of the initiator in the initiator preparation tank (32) to 1~2%. The initiator preparation is complete. Step 11: After the initiator is prepared, keep the initiator preparation tank variable frequency stirrer (31) at high speed for 4 to 6 minutes, and then keep the initiator preparation tank variable frequency stirrer (31) at low speed for 5 to 10 minutes to ensure the stability of the initiator system; during the initiator preparation process, keep the jacket chilled water of the initiator preparation tank (32) open throughout the process.

4. The method for preparing a low-concentration initiator for polyvinyl chloride production as described in claim 3, characterized in that: The low-speed stirring speed of the variable frequency stirrer (31) in the initiator preparation tank is 1400~1600 rpm, and the high-speed stirring speed is 2400~2600 rpm.

5. The method for preparing a low-concentration initiator for polyvinyl chloride production as described in claim 3, characterized in that: The temperature of the cold pure water in the cold pure water storage tank (1) is 25~35℃.

6. The method for preparing a low-concentration initiator for polyvinyl chloride production as described in claim 3, characterized in that: During the preparation of the initiator, the jacketed chilled water of the initiator preparation tank (32) is kept open throughout the process, and the temperature of the initiator preparation tank (32) is controlled at 10~25℃.

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