Polyvinyl chloride production process based on hot water feeding

Abstract

The invention relates to the technical field of polyvinyl chloride, and discloses a polyvinyl chloride production process based on hot water feeding, which comprises the following steps: S1, raw material preparation: preparing raw materials meeting purity and quality requirements; s2, feeding water and monomers: injecting hot water at a preset temperature into a polymerization kettle, and then feeding the monomers; s3, adding a dispersing agent: adding the dispersing agent into the polymerization kettle; s4, coarse material prediction: observing and predicting the stability condition of a dispersion system in the kettle; s5, adding an initiator: adding the initiator into the polymerization kettle; s6, adding a terminating agent; s7, performing subsequent treatment; according to the invention, a hot water feeding processing technology is adopted, so that the heating period is eliminated, the purposes of shortening the PVC polymerization period and improving the production intensity of the polymerization kettle are achieved, meanwhile, heat balance is carried out on a polymerization system, and the temperature of the polymerization kettle is equal to the temperature of the polymerization reaction after the materials are added by controlling the addition amount of cold and hot deionized water.

Description

Technical Field

[0001] The invention relates to the technical field of polyvinyl chloride production, in particular to a polyvinyl chloride production process based on hot water feeding. Background Art

[0002] Polyvinyl chloride is a polymer formed by the free radical polymerization mechanism of vinyl chloride monomer in the presence of initiators such as peroxides and azo compounds or under the action of light or heat. It is the third largest synthetic polymer plastic in the world, second only to polyethylene and polypropylene. PVC occupies a very important position in the consumption structure of the construction industry. About 60% of PVC is used to produce construction materials such as profiled doors and windows and special-shaped materials.

[0003] At present, in the process of producing polyvinyl chloride, some polymerization processes adopt a room temperature water feeding process, and then introduce steam through the jacket of the polymerization kettle to increase the temperature. After reaching the predetermined reaction temperature, the polymerization reaction begins. When in use, the polymerization kettle requires a heating step, and the single kettle production cycle is long, which can easily cause the kettle wall to overheat, resulting in serious sticking to the kettle and unstable product quality. Summary of the invention

[0004] The object of the present invention is to provide a polyvinyl chloride production process based on hot water feeding to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solution: a polyvinyl chloride production process based on hot water feeding, comprising the following steps:

[0006] S1. Raw material preparation: Prepare raw materials that meet purity and quality requirements;

[0007] S2, water and monomer feeding: inject hot water of a predetermined temperature into the polymerization kettle, and then add the monomer;

[0008] S3, adding dispersant: adding dispersant into the polymerization kettle;

[0009] S4. Coarse material prediction: observe and predict the stability of the dispersed system in the kettle;

[0010] S5, adding initiator: adding the initiator into the polymerization kettle;

[0011] S6, adding terminator: after the polymerization reaction is completed, adding terminator into the polymerization reactor;

[0012] S7. Subsequent treatment: Discharging, flushing, stripping and drying of the polymerization product.

[0013] Preferably, in S1, the raw materials include vinyl chloride monomer, dispersant, deionized water, initiator and terminator, and the temperature of the hot water in S2 is 80°C to 90°C.

[0014] Preferably, in S2, water is added from the bottom of the kettle as a continuous phase, and monomers are added from the top of the kettle as a dispersed phase, and the hot water and the monomers need to be stirred to mix them evenly. In S3, the dispersants are L9-78 and LM-10HD, wherein L9-78 is the main dispersant and LM-10HD is the secondary dispersant.

[0015] Preferably, in S4, it is necessary to observe the physical properties of the dispersed system such as appearance and viscosity to preliminarily judge its stability, and a camera and a viscometer are required in S4.

[0016] Preferably, the initiator in S5 is diethylhexyl peroxydicarbonate, and in S5, cold pure water needs to be added to the hot pure water adding pipeline.

[0017] Preferably, when adding cold pure water to the hot pure water adding pipeline, the hot pure water temperature value needs to be calculated, and the formula is:

[0018] c1m1(t-t1)=c2m2(t2-t)

[0019] Among them, c1 represents the specific heat capacity of cold pure water; m1 represents the mass of cold pure water; t represents the temperature of hot pure water; t1 represents the initial temperature of cold pure water; c2 represents the specific heat capacity of hot pure water; m2 represents the mass of hot pure water; t2 represents the initial temperature of hot pure water.

[0020] Preferably, in S2, temperature sensors are required to be used inside the polymerization kettle and the jacket of the polymerization kettle. In S1, when the raw materials are stored, the storage temperature of the raw materials needs to be regulated by the temperature sensors.

[0021] Preferably, in S5, the temperature rise rate needs to be controlled, wherein the temperature rise rate needs to be calculated based on the rate of adding hot pure water, the difference between the temperature in the kettle and the reaction temperature.

[0022] Preferably, the terminator in S6 is acetone thiosemicarbazone, and in S6, the terminator is added when the pressure drop of the polymerization reaction reaches 0.05-0.15 MPa.

[0023] Preferably, in S7, the polymerization product needs to be discharged from the polymerization kettle through a discharge system, and a flushing device, a stripping tower and a dryer need to be used.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention adds water and monomers at the same time, water is added from the bottom of the kettle as a continuous phase, and monomers are added from the top of the kettle as a dispersed phase, so that the monomers and water can be fully mixed. At the same time, water is added first and then the monomers are added for a while, so that the monomers can be prevented from infiltrating the kettle wall and causing the kettle sticking phenomenon. By adjusting the adding sequence of the initiator and VCM, VCM can be fully dispersed in water under the action of water, dispersant and stirring. Since there is no initiator in the system at this time, polymerization will not occur. Finally, the initiator is added at the reaction temperature and the reaction is carried out immediately, so the generation of high molecular weight PVC is avoided and the number of fish eyes is reduced. By setting the rough material prediction, in the actual production process, sometimes the dispersant metering is inaccurate or the dispersant fails. This causes the dispersion system to be unstable, resulting in the generation of coarse materials during the reaction process. If the stability of the dispersion system in the reactor can be predicted before the reaction, the generation of coarse materials can be avoided; at the same time, the processing technology of hot water feeding is adopted to eliminate the heating period, thereby achieving the purpose of shortening the PVC polymerization cycle and improving the production intensity of the polymerization reactor; a high turbidity point dispersant is used, and a dispersant system suitable for hot water feeding is selected after vinyl chloride polymerization experiments; by performing heat balance on the polymerization system and controlling the amount of cold and hot deionized water added, the temperature of the polymerization reactor is made equal to the polymerization reaction temperature when the feed is added. By analyzing the formation mechanism of PVC coarse materials, it is found that the formation of PVC coarse materials can be predicted by using the change of the stirring power of the polymerization reactor, thereby reducing the occurrence of defective products. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A method flow chart of a preferred embodiment of the polyvinyl chloride production process based on hot water feeding provided by the present invention;

[0027] Figure 2 This is a schematic diagram of the clean and hot pure water process provided by the present invention. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] See also Figure 1-2 As shown, a polyvinyl chloride production process based on hot water feeding comprises the following steps:

[0030] S1. Raw material preparation: Prepare raw materials that meet purity and quality requirements;

[0031] S2. Feeding of water and monomers: Inject hot water of a predetermined temperature into the polymerization kettle, and then add the monomers; the hot and cold water feeding process uses relatively more dispersant and takes a long time to feed, but the total time to reach the inflection point temperature is the feeding time, which is 40-50 minutes shorter than the cold water feeding, greatly increasing the output of a single kettle and preventing the monomer from wetting the kettle wall, which is beneficial to improving the anti-sticking kettle effect.

[0032] S3, adding dispersant: adding dispersant into the polymerization kettle;

[0033] S4. Coarse material prediction: observe and predict the stability of the dispersed system in the kettle. By observing and testing the situation in the kettle, it is possible to avoid explosion or coarse material in the product caused by dispersant failure or inaccurate flow meter;

[0034] S5, adding initiator: adding the initiator into the polymerization kettle;

[0035] S6, adding terminator: after the polymerization reaction is completed, adding terminator into the polymerization reactor;

[0036] S7. Subsequent treatment: Discharging, flushing, stripping and drying of the polymerization product.

[0037] refer to Figure 1 and Figure 2 As shown, in S1, the raw materials include vinyl chloride monomer, dispersant, deionized water, initiator and terminator, and the temperature of the hot water in S2 is 80°C to 90°C.

[0038] In the S2, water is added from the bottom of the kettle as a continuous phase, and the monomer is added from the top of the kettle as a dispersed phase. At the same time, the hot water and the monomer need to be stirred to make them evenly mixed. In the S3, the dispersants are L9-78 and LM-10HD, among which L9-78 is the main dispersant and LM-10HD is the secondary dispersant. The use of hot water as a continuous phase added from the bottom of the kettle helps to provide a stable reaction temperature environment. The monomer is added from the top of the kettle as a dispersed phase, which is conducive to achieving a better dispersion effect. At the same time, the stirring operation ensures that the hot water and the monomer are fully mixed, which promotes the uniformity and efficiency of the reaction. At the same time, L9-78 is used as the main dispersant and LM-10HD is used as the secondary dispersant, which can effectively control the particle size, distribution and stability, and improve the quality and performance of the polymer product.

[0039] In the S4, it is necessary to observe the appearance and physical properties such as viscosity of the dispersed system to preliminarily judge its stability. A camera and a viscometer are required in the S4. By observing the appearance of the dispersed system and measuring physical properties such as viscosity, the stability of the system can be preliminarily judged in real time and quickly to ensure the smooth progress of the production process.

[0040] The initiator in S5 is diethylhexyl peroxydicarbonate. In S5, cold pure water needs to be added to the hot pure water adding pipeline, and cold pure water needs to be added to the hot pure water adding pipeline. The temperature is controlled by an accurate calculation formula to ensure that the temperature does not over-adjust.

[0041] When adding cold pure water to the hot pure water adding pipeline, the hot pure water temperature value needs to be calculated, and the formula is:

[0042] c1m1(t-t1)=c2m2(t2-t)

[0043] Among them, c1 represents the specific heat capacity of cold pure water; m1 represents the mass of cold pure water; t represents the temperature of hot pure water; t1 represents the initial temperature of cold pure water; c2 represents the specific heat capacity of hot pure water; m2 represents the mass of hot pure water; t2 represents the initial temperature of hot pure water.

[0044] In the S2, temperature sensors are required in the polymerization kettle and inside the polymerization kettle jacket. In the S1, when storing raw materials, the storage temperature of the raw materials needs to be regulated by temperature sensors. The use of temperature sensors in the polymerization kettle, inside the polymerization kettle jacket and during the raw material storage process can monitor and regulate the temperature in real time, ensure the stability and controllability of the reaction conditions, and thus improve the quality of the product and the safety of production.

[0045] In S5, it is necessary to control the temperature rise rate, wherein the temperature rise rate needs to be calculated based on the rate of adding hot pure water, the difference between the temperature in the kettle and the reaction temperature. Calculating and controlling the temperature rise rate based on factors such as the rate of adding hot pure water, the difference between the temperature in the kettle and the reaction temperature helps to achieve a smooth reaction process and avoid product quality problems and safety hazards caused by excessive temperature fluctuations.

[0046] The terminator in S6 is acetone thiosemicarbazone. In S6, when the pressure drop of the polymerization reaction reaches 0.05-0.15 MPa, the terminator is added. When the pressure drop of the polymerization reaction reaches a specific range, the terminator is added, which can accurately control the reaction endpoint, prevent excessive polymerization or side reactions, and ensure the quality and stability of the product.

[0047] In S7, the polymerization product needs to be discharged from the polymerization kettle through a discharge system, and a flushing device, a stripping tower and a dryer need to be used to ensure effective separation and purification of the product while also meeting environmental protection and safety requirements.

[0048] Embodiment 1

[0049] Comparison between cold water feeding and hot water feeding under the traditional feeding sequence.

[0050] Experimental conditions: 6-liter kettle, VCM reaction at 53°C for 360 minutes.

[0051] Feeding order:

[0052] 1. Add water; 2. Add dispersion; 3. Add initiator; 4. Add monomer

[0053] The experimental results are shown in the table

[0054] Effects of adding cold and hot water on PVC fisheye

[0055] Feeding method <![CDATA[Fish-eye number (dm 2 )]]> Cold water feeding 2 Hot water feeding 50

[0056] Embodiment 2

[0057] Comparison of adding VCM monomer at different water temperatures in the traditional feeding sequence

[0058] Experimental conditions: 6-liter small kettle, reaction at 53°C for 360 minutes.

[0059] Adding order:

[0060] 1. Add water; 2. Add dispersant; 3. Add initiator; 4. Add monomer

[0061] The experimental results are shown in the table

[0062] Effect of adding water of different temperatures on PVC fisheye

[0063]

[0064] Embodiment 3

[0065] Two addition sequences were used:

[0066] A: 1. Add water; 2. Add dispersant; 3. Add initiator; 4. Add monomer

[0067] B: 1. Add water (hot); 2. Add VCM; 3. Add dispersant; 4. Add initiator. Two adding methods are compared in the experiment.

[0068] Experimental conditions: 6-liter kettle, VCM reaction at 53°C for 360 min.

[0069] The experimental results are shown in the table

[0070] Effects of two adding sequences on PVC fisheye

[0071] Feeding method <![CDATA[Fish-eye number (dm 2 )]]> A 50 B 1

[0072] It is known from the above embodiments that by feeding hot water, the order of adding materials is 1. adding water (hot); 2. adding VCM; 3. adding dispersant; 4. adding initiator, which can reduce the number of fish eyes and improve the production efficiency of polyvinyl chloride.

[0073] Working principle: First, prepare the raw materials that meet the purity and quality requirements, including vinyl chloride monomer, dispersant, deionized water, initiator and terminator, etc., and then add hot water of a predetermined temperature (80℃~90℃) as a continuous phase from the bottom of the polymerization kettle, and at the same time, add the monomer as a dispersed phase from the top of the kettle, which helps to provide a stable reaction temperature environment and promote the uniform dispersion of the monomer in the hot water. The stirring operation further ensures the full mixing of the hot water and the monomer, and improves the uniformity and efficiency of the reaction. In addition, compared with cold water feeding, hot water feeding can significantly shorten the total time to reach the inflection point temperature, increase the single kettle output, and prevent the monomer from infiltrating the kettle wall, which is beneficial to the anti-sticking effect. After the monomer and hot water are evenly mixed, the main dispersant L9-78 and the secondary dispersant LM-10HD are added to the inside of the polymerization kettle, and they work together on the system to effectively control the particle size, distribution and stability, thereby improving the quality and performance of the polymerization product. Through equipment such as cameras and viscometers, the physical properties of the dispersed system in the kettle, such as appearance and viscosity, can be measured. The quality is observed and measured to preliminarily determine the stability of the system. This step helps to promptly discover and deal with problems such as dispersant failure or flow meter inaccuracy, avoid explosion or product coarse material, and ensure the smooth progress of the production process. After the system is stable, the initiator is added to the polymerization kettle to initiate the polymerization reaction of vinyl chloride monomer. At the same time, cold pure water is added to the hot pure water addition pipeline, and the temperature is controlled by an accurate calculation formula to ensure that the reaction is carried out within a suitable temperature range. In addition, the temperature rise rate needs to be calculated and controlled based on factors such as the hot pure water addition rate, the difference between the kettle temperature and the reaction temperature, so as to achieve a smooth reaction process. When the polymerization reaction pressure drop reaches 0.05-0.15MPa, the terminator is added to the polymerization kettle to quickly and effectively terminate the polymerization reaction, prevent excessive polymerization or side reactions, and ensure the quality and stability of the product. The polymerization product is then discharged from the polymerization kettle through the discharge system, and the product is subsequently treated using equipment such as a flushing device, a stripping tower and a dryer.

[0074] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0075] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A polyvinyl chloride production process based on hot water feeding, characterized in that: The following steps are involved: S1. Raw material preparation: Prepare raw materials that meet purity and quality requirements; S2, water and monomer feeding: inject hot water of a predetermined temperature into the polymerization kettle, and then add the monomer; S3, adding dispersant: adding dispersant into the polymerization kettle; S4. Coarse material prediction: observe and predict the stability of the dispersed system in the kettle; S5, adding initiator: adding the initiator into the polymerization kettle; S6, adding terminator: after the polymerization reaction is completed, adding terminator into the polymerization reactor; S7. Subsequent treatment: Discharging, flushing, stripping and drying of the polymerization product.

2. A polyvinyl chloride production process based on hot water feeding according to claim 1, characterized in that: In the S1, the raw materials include vinyl chloride monomer, dispersant, deionized water, initiator and terminator, etc., and the temperature of the hot water in the S2 is 80°C to 90°C.

3. A polyvinyl chloride production process based on hot water feeding according to claim 1, characterized in that: In the S2, water is added from the bottom of the kettle as a continuous phase, and the monomer is added from the top of the kettle as a dispersed phase. At the same time, the hot water and the monomer need to be stirred to make them evenly mixed. In the S3, the dispersants are L9-78 and LM-10HD, among which L9-78 is the main dispersant and LM-10HD is the secondary dispersant.

4. A polyvinyl chloride production process based on hot water feeding according to claim 1, characterized in that: In the S4, it is necessary to observe the physical properties of the dispersed system, such as appearance and viscosity, and preliminarily judge its stability. A camera and a viscometer are required in the S4.

5. The polyvinyl chloride production process based on hot water feeding according to claim 1, characterized in that: The initiator in S5 is diethylhexyl peroxydicarbonate. In S5, cold pure water needs to be added to the hot pure water adding pipeline.

6. A polyvinyl chloride production process based on hot water feeding according to claim 5, characterized in that: When adding cold pure water to the hot pure water adding pipeline, the hot pure water temperature value needs to be calculated, and the formula is: c1m1(t-t1)=c2m2(t2-t) Among them, c1 represents the specific heat capacity of cold pure water; m1 represents the mass of cold pure water; t represents the temperature of hot pure water; t1 represents the initial temperature of cold pure water; c2 represents the specific heat capacity of hot pure water; m2 represents the mass of hot pure water; t2 represents the initial temperature of hot pure water.

7. The polyvinyl chloride production process based on hot water feeding according to claim 1, characterized in that: In the above S2, temperature sensors are required inside the polymerization kettle and the jacket of the polymerization kettle. In the above S1, when the raw materials are stored, the storage temperature of the raw materials needs to be regulated by the temperature sensors.

8. The polyvinyl chloride production process based on hot water feeding according to claim 1, characterized in that: In S5, the temperature rise rate needs to be controlled, wherein the temperature rise rate needs to be calculated based on the speed of adding hot pure water, the difference between the temperature in the kettle and the reaction temperature.

9. The polyvinyl chloride production process based on hot water feeding according to claim 1, characterized in that: The terminator in S6 is acetone thiosemicarbazone. In S6, when the pressure drop of the polymerization reaction reaches 0.05-0.15 MPa, the terminator is added.

10. The polyvinyl chloride production process based on hot water feeding according to claim 1, characterized in that: In S7, the polymerization product needs to be discharged from the polymerization kettle through a discharge system, and a flushing device, a stripping tower and a dryer need to be used.

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