Using 136m 3 Method for producing SG-8 type polyvinyl chloride resin by polymerizing kettle

Abstract

The present invention provides a method using 136m 3 The method for producing SG-8 type polyvinyl chloride resin in a polymerization kettle belongs to the technical field of polyvinyl chloride resin production, comprising: using an anti-sticking kettle agent to treat 136m 3 The anti-sticking process of the polymerization kettle is to coat the wall; the feeding process is to add the auxiliary agent, water and vinyl chloride monomer to the polymerization kettle after the wall coating; the reaction process is to add the initiator to the polymerization kettle after the feeding to initiate the polymerization reaction; and the terminator is added to the polymerization kettle to terminate the reaction and the unloading process is to discharge the SG-8 type polyvinyl chloride resin slurry in the polymerization kettle. The present invention adopts 136m for the first time 3 The polymerization kettle produces SG-8 polyvinyl chloride resin, and the transformation is carried out on the existing SG-5 polyvinyl chloride resin production equipment, which effectively improves the utilization rate of the polymerization kettle, and also improves the production intensity and production efficiency of a single kettle, and the product quality is good, thereby increasing the production capacity of SG-8 polyvinyl chloride resin and reducing production energy consumption and costs.

Description

Technical Field

[0001] The present invention relates to the technical field of polyvinyl chloride resin production, in particular to a method of using 136m 3 The invention discloses a method for producing SG-8 type polyvinyl chloride resin by using a polymerization kettle. Background Art

[0002] Polyvinyl chloride, abbreviated as PVC (Polyvinyl chloride) in English, is a polymer formed by the polymerization of vinyl chloride monomer (VCM) in the presence of peroxides, azo compounds and other initiators; or under the action of light or heat, according to the free radical polymerization mechanism. Vinyl chloride homopolymer and vinyl chloride copolymer are collectively referred to as polyvinyl chloride resin, which has high chemical stability and good plasticity. Polyvinyl chloride resin is one of the largest plastic products in the world, with low price and wide application. Polyvinyl chloride resin is a white powder with an amorphous structure, low branching degree, poor light and heat stability, and is mainly used in pipes, profiles, plates, hoses, wires and cables, films, shoes, toys, auto parts, etc. At present, there are two commonly used production methods for polyvinyl chloride, namely the carbide acetylene method and the petroleum ethylene method. The energy structure characteristics of my country's "rich in coal, poor in oil, and little gas" determine that the carbide acetylene method is the main process route for producing polyvinyl chloride.

[0003] In recent years, with the continuous optimization of polyvinyl chloride resin production process and the continuous improvement of automation, the quality and production capacity of polyvinyl chloride resin have been further improved, and the classification of products has become more refined and differentiated. The differentiation of polyvinyl chloride resin and production according to order requirements have become the general trend. Among them, SG-8 polyvinyl chloride resin has an increasingly wide range of applications and a growing demand due to its advantages of low melting and gelling temperature, short plasticizing time, good fluidity, and high product transparency.

[0004] At present, SG-8 polyvinyl chloride resin is usually produced by high temperature method or chain transfer agent method. The chain transfer agent method is rarely used because of the disadvantages of having a very bad odor in the reaction, being harmful to the human body, and being easily affected by the chain transfer agent to produce coarse materials. The high temperature method requires that the polymerization reaction temperature be kept constant (i.e., the polymerization heat release rate = the heat transfer rate of the polymerization kettle), and the polyvinyl chloride polymerization kettle is a reaction vessel used to synthesize polyvinyl chloride. The equipment structure of the polymerization kettle directly affects the quality of the polyvinyl chloride product. The existing SG-8 polyvinyl chloride resin is usually 30m 3 、70m 3 Polymerization kettle production, the maximum volume of the polymerization kettle used in production is 108m 3At the beginning of construction, most domestic manufacturers focused on the production of SG-5 polyvinyl chloride resin. Therefore, the existing polymerization reactors are often only suitable for the production of general-purpose SG-5 polyvinyl chloride resin. The product is single and the competitive advantage is not obvious. In order to improve the productivity of SG-8 polyvinyl chloride resin, 136m 3 The invention discloses a production method of SG-8 type polyvinyl chloride resin by using a polymerization kettle and its supporting technology. Summary of the invention

[0005] The present invention provides a 136m3 polyvinyl chloride resin production equipment transformed from SG-5 type polyvinyl chloride resin production equipment, which has good product quality, stable post-processing performance, and reduces production energy consumption and cost. 3 The method of producing SG-8 polyvinyl chloride resin by polymerizing kettle is used to solve the existing 136m 3 The polymerization kettle is unable to produce SG-8 polyvinyl chloride resin and the output of SG-8 polyvinyl chloride resin is lower than the demand.

[0006] To achieve the above object, the present invention provides a 136m 3 A method for producing SG-8 type polyvinyl chloride resin in a polymerization kettle, comprising: using an anti-sticking kettle agent to treat 136m 3 The anti-sticking process of the polymerization kettle is to coat the wall; the feeding process is to add the auxiliary agent, desalted water and vinyl chloride monomer to the polymerization kettle after coating; the reaction process is to add the initiator to the polymerization kettle after feeding to initiate the polymerization reaction; and the unloading process is to add the terminator to the polymerization kettle to terminate the reaction and discharge the SG-8 type polyvinyl chloride resin slurry in the polymerization kettle; the initiator is BNP and TAPP; in the feeding process, the feeding amount of desalted water is 55-57t, and the feeding amount of vinyl chloride monomer is 43-46t; 136m 3 The loading factor of the polymerization reactor is 80-85%.

[0007] Preferably, the temperature of the desalted water is 85-95°C. In the feeding process, the water-to-oil ratio of the desalted water and the vinyl chloride monomer is adjusted to not less than 1.25, which is beneficial to increase the dispersibility of the vinyl chloride monomer, achieve the purpose of increasing the heat exchange effect and reducing the heat exchange load of the polymerization kettle, and also make the polymerization reaction easier to control. The use of hot desalted water can make the temperature of the system after the desalted water, vinyl chloride monomer and additives are mixed closer to the set reaction temperature, thereby simplifying the polymerization kettle heating link and reducing the batch production time, saving a lot of non-production time and heating energy consumption, and improving the production utilization rate of the polymerization kettle. At the same time, it can also avoid low-temperature reactions in the heating link (such as the optimal production temperature of the SG-5 type is about 56°C), reduce the amount of by-products with different polymerization degrees, more accurately control the molecular weight distribution width of the product, and improve the concentration and quality of polyvinyl chloride products.

[0008] Furthermore, the above method also includes a refining process for purifying the SG-8 polyvinyl chloride resin slurry to obtain an SG-8 polyvinyl chloride resin product; the steps of the refining process are as follows: using a stripping tower to strip the SG-8 polyvinyl chloride resin slurry, and drying the SG-8 polyvinyl chloride resin crude product obtained by stripping to obtain an SG-8 polyvinyl chloride resin product; the top temperature of the stripping tower is 103-109°C, the bottom temperature is 111-120°C, and the top pressure is 0.04-0.07MPa.

[0009] In a specific example, the stripping tower adopts an overflow weir tower, and the drying adopts a fluidized bed drying process. Stripping can greatly reduce the residual amount of vinyl chloride monomer, and at the same time facilitate the reuse of unreacted vinyl chloride monomer, which is beneficial to improve the utilization rate of vinyl chloride monomer. Fluidized bed drying can greatly improve the drying efficiency, remove water and other impurities, and obtain a powdered SG-8 type polyvinyl chloride resin product.

[0010] Furthermore, the method also includes a monomer recovery process for recovering vinyl chloride monomer, and the steps of the monomer recovery process are as follows: when the polymerization kettle is unloaded, the unreacted vinyl chloride monomer in the polymerization kettle is recovered from the top of the discharge tank, and the vinyl chloride monomer in the SG-8 type polyvinyl chloride resin slurry is recovered from the top of the stripping tower, and the recovered vinyl chloride monomer is uniformly sent to the recovery monomer storage tank for standby. Unreacted gas-phase vinyl chloride monomer is recovered during unloading, and unreacted vinyl chloride monomer is recovered again during purification by the stripping tower, which can avoid the vinyl chloride monomer remaining in the SG-8 type polyvinyl chloride resin product to affect the product quality. At the same time, the recovered vinyl chloride monomer can be sent to the polymerization kettle again to participate in production, thereby improving the utilization rate of vinyl chloride monomer, reducing resource waste, and reducing production costs.

[0011] Furthermore, in the feeding process, the vinyl chloride monomer added to the polymerization kettle includes fresh vinyl chloride monomer and recycled vinyl chloride monomer, and the feeding amount of recycled vinyl chloride monomer is 6-7 tons. In the production of SG-8 polyvinyl chloride resin, fresh vinyl chloride monomer is mixed with recycled vinyl chloride monomer, which not only saves vinyl chloride monomer resources and improves the utilization rate of vinyl chloride monomer, but also reduces the amount of gaseous vinyl chloride monomer to be treated as waste gas, which has good economic value and environmental value.

[0012] Furthermore, in the feeding process, the feeding amount of the initiator is 27-30 kg, and the weight ratio of BNP to TAPP is 1:(1.9-2.1); when the initiator is fed, BNP is prepared into a mixed solution with a mass fraction of 50%, and TAPP is prepared into a mixed solution with a mass fraction of 40%. The initiator feeding time of the present invention is placed at the end, and the temperature control and reaction are started after the initiator is added, which can shorten the time for some vinyl chloride monomers to react at low temperatures to generate by-products with different polymerization degrees, reduce the molecular weight distribution width of the target product, improve the concentration and quality of polyvinyl chloride products, and also help to reduce the number of fish eyes generated in downstream production.

[0013] Furthermore, in the feeding process, the auxiliary agents include an inefficient buffer, a dispersant I, a dispersant II and a dispersant III in the order of addition. After the inefficient buffer is added, stirring is turned on to provide a stirring environment, and the stirring speed is 90 to 95 r / min; the addition amount of the inefficient buffer is 3 to 4 kg, and the inefficient buffer is an ammonium bicarbonate solution with a mass concentration of 1%.

[0014] Further, the addition amount of dispersant I is 20-21 kg, and dispersant I is a water-soluble polyvinyl alcohol with a mass concentration of 5%; the addition amount of dispersant II is 20-21 kg, and dispersant II is cellulose with a mass concentration of 3%; the addition amount of dispersant III is 18-20 kg, and dispersant III is polyvinyl alcohol with a degree of alcoholysis of 55%. Preferably, dispersant I is 48-80 water-soluble polyvinyl alcohol purchased from Kuraray Co., Ltd. of Japan.

[0015] The selection of dispersants and the amount of addition will affect the product quality. The use of the dispersants of the present invention can avoid the problem of irregular or coarse product particles caused by inappropriate dispersants. Under the premise of ensuring the apparent density of the product, the dispersants can make the internal structure of the product resin particles loose, making it easier for the vinyl chloride monomer remaining in the product resin to be removed. Selecting polyvinyl alcohols with different alcoholysis degrees as dispersants can achieve the most economical cost-effectiveness while ensuring high-quality product quality.

[0016] Furthermore, in the reaction process, the reaction temperature in the polymerization kettle is controlled to be 65-68°C, the kettle pressure is 1.15-1.23 MPa, and the reaction time is 200-280 min; and during the reaction, 2.0-2.5 m 3 Desalted water is injected at a rate of / h. When the reaction reaches 180-200min, 5-6kg of high-efficiency buffer is added to the polymerization kettle. The high-efficiency buffer is liquid alkali with a mass concentration of 2%.

[0017] Preferably, the injection amount of the seal water of the polymerization kettle is 0.95-1m 3 The maximum rate of desalted water injected during the reaction is required to be no more than 2.5 m 3 / h. Further preferably, the temperature of the desalted water injected during the reaction is 66-68°C. The polymerization reaction conversion rate in the polymerization kettle can be adjusted by the polymerization kettle shaft sealing water and the reaction injection water, and the reaction temperature can be accurately controlled within the range of 65-68°C. The reaction injection water can also greatly reduce the viscosity of the material to prevent the kettle from sticking, making the reaction rate more balanced, and ensuring that the conversion rate of the normal reaction of the polymerization kettle can be controlled at 80-85%, and the particle size of the polyvinyl chloride product is uniform.

[0018] Preferably, in the reaction process, the pH of the reaction system in the polymerization kettle is controlled to be 7 to 7.5. The addition of low-efficiency buffer and high-efficiency buffer to the reaction system of the polymerization kettle is to control the pH value of the entire reaction system. The pH of the reaction system is controlled within the range of 7 to 7.5 by the buffer, and the stability of the pH value of the reaction system is maintained, which is more conducive to the occurrence of the polymerization reaction and the generation of the target product. At the same time, the pH is controlled and adjusted, which also reduces the difficulty of treating the wastewater after production and reduces the amount of wastewater treatment agent used.

[0019] Furthermore, during the polymerization reaction, when the reaction pressure drop of the polymerization kettle reaches 0.125MPa or the maximum reaction time, a terminator is injected into the polymerization kettle to terminate the reaction; the injection amount of the terminator is 43-46kg, and the terminator is an environmentally friendly terminator. Preferably, the terminator is environmentally friendly terminator 4348 or other existing known and commonly used terminators. The terminator can quickly terminate the reaction of free radicals, ensure that the initiator completely loses its activity, terminate the polymerization reaction in time, and obtain high-quality polyvinyl chloride products with uniform molecular weight and stable molecular structure, while also having the effect of preventing aging.

[0020] Furthermore, in the unloading process, after the reaction is terminated, the top condenser is used to forcibly cool the polymerization kettle until the kettle pressure of the polymerization kettle drops below 0.7MPa, and then the unloading valve is opened to unload the SG-8 type polyvinyl chloride resin slurry into the slurry tank. After the reaction is terminated, the polymerization kettle still has a relatively high kettle pressure, and the design pressure of the slurry tank is generally 0.8MPa. If the polymerization kettle is directly unloaded, it will cause overpressure in the slurry tank, causing safety accidents caused by leakage of vinyl chloride monomer, and it is also easy to carry vinyl chloride products to the recovery monomer storage tank to cause product waste, and it is also easy to damage the unloading pump seal. Therefore, using the top condenser to forcibly cool the kettle pressure of the polymerization kettle to drop below 0.7MPa before starting the unloading procedure can reduce the risk of safety accidents caused by leakage of vinyl chloride monomer.

[0021] Furthermore, the steps of wall coating operation in the anti-sticking kettle process are:

[0022] (1) Condenser wall coating: After the anti-sticking agent is mixed with water vapor to form an anti-sticking agent atomized liquid, the top and bottom of the kettle top condenser are coated with the anti-sticking agent atomized liquid. The amount of the anti-sticking agent used in the condenser wall coating is 4-5 kg;

[0023] (2) Coating the inner wall of the reactor: Use the atomized liquid of the anti-sticking agent to coat the feed inlet, the inner wall of the polymerization reactor, the stirring device and the baffle. The amount of the anti-sticking agent used in the coating of the inner wall of the reactor is 9 to 10 kg;

[0024] (3) Post-coating flushing: High-pressure flushing water is introduced into the top condenser and the inside of the polymerization kettle for flushing, and the resulting wastewater is pumped to the wastewater tank.

[0025] Preferably, the anti-sticking agent is polyethyleneimine or other known and commonly used anti-sticking agents. Further preferably, the anti-sticking agent flow rate for forming the anti-sticking agent atomized liquid is 900-1000 L / h, and the water vapor flow rate is 1.3-1.6 t / h.

[0026] Anti-sticking agent usually has oleophobic and hydrophilic properties. When coating the wall, the anti-sticking agent is atomized by high-temperature and high-pressure steam and enters the kettle top condenser and the polymerization kettle. The atomized liquid of the anti-sticking agent can improve the uniformity of spraying and prevent the occurrence of dead corners in wall coating, thereby evenly forming a layer of oleophobic and hydrophilic film on the top and bottom of the kettle top condenser, the feed inlet, the inner wall of the polymerization kettle, the stirring device and the baffle. The step-by-step wall coating makes the wall coating more uniform, avoids dead corners during wall coating, thereby avoiding the problem of kettle sticking during the reaction process, extending the service life of the polymerization kettle, improving the utilization rate and production efficiency of the polymerization kettle, and reducing the cleaning cost of the polymerization kettle.

[0027] The present invention provides a method using 136m 3 The method of producing SG-8 type polyvinyl chloride resin by polymerization kettle has the following advantages:

[0028] 1) This invention uses 136m for the first time 3 The polymerization kettle produces SG-8 type polyvinyl chloride resin, and the conversion rate can reach more than 80%, ensuring 136m 3 The transformation of the resin production of the polymerizer has made 136m 3 The polymerization kettle can be applied to the production of SG-8 polyvinyl chloride resin, reach full production capacity and meet standards, significantly increase the production volume of SG-8 polyvinyl chloride resin, effectively improve the utilization rate and production capacity of the polymerization kettle, and transform the existing SG-5 polyvinyl chloride resin production equipment during production. The equipment transformation cost is low, which reduces the production cost of SG-8 polyvinyl chloride resin and improves the competitiveness of the enterprise.

[0029] 2) 136m is used in the present invention 3The SG-8 type polyvinyl chloride resin products produced by the polymerization kettle have stable quality and good product particle morphology. The use of new initiator formula and dispersant formula has improved the quality of polyvinyl chloride resin products. The use of anti-sticking kettle agent and step-by-step wall coating operation has improved the kettle coating effect and anti-sticking kettle effect, extended the kettle cleaning cycle, improved product quality, shortened production time, improved single kettle production intensity and production efficiency, and improved equipment utilization rate and production cycle.

[0030] 3) The production method of the present invention can be used at 136m 3 The SG-8 polyvinyl chloride resin is produced under the polymerization kettle system with good production stability. The method adjusts and optimizes the feeding procedure, shortens the auxiliary heating time by using hot desalted water, pushes the initiator feeding time to the end, shortens the time for some vinyl chloride monomers to react at low temperatures to generate by-products with different polymerization degrees, reduces the molecular weight distribution width of the polyvinyl chloride resin product, and ensures the stability of the polyvinyl chloride product quality and post-processing performance.

[0031] 4) This production method increases the volume of the production kettle when producing SG-8 polyvinyl chloride resin, and improves the production capacity of SG-8 polyvinyl chloride resin by changing the feeding method, adjusting the production process, shortening the polymerization auxiliary time, etc. The whole kettle time is 300 minutes, and the single kettle production capacity reaches 36 tons. At the same time, the production energy consumption and cost are reduced, the difficulty of sewage treatment is reduced, and it has significant economic benefits. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention is clearly and completely described below. Obviously, the described embodiments are 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 also fall within the scope of protection of the present invention.

[0033] The following examples use conventional instruments and equipment in the art. Unless otherwise specified, the test materials and reagents used in the following examples can be obtained from commercial sources, and their specifications are conventional specifications in the art. If no specific techniques or conditions are specified in the following examples, they can be carried out according to the techniques or conditions described in the literature in the art or according to the product instructions.

[0034] It should be noted that, in the present invention and the following embodiments, concentrations, ratios, etc. not otherwise specified are all weight concentrations, weight ratios, etc., "%" means weight percentage, and "parts" means parts by weight, which are common writing habits used by those skilled in the art and are therefore not described in detail in the present invention.

[0035] Due to 136m 3Polymerization kettles are mostly used to produce SG-5 type polyvinyl chloride resin. The quality of SG-8 type polyvinyl chloride resin produced by the original production method of SG-5 type polyvinyl chloride resin is unstable, the cleaning cycle is short, and the production has no cost competitive advantage. Therefore, it is decided to carry out technical innovation and transformation. In the specific transformation implementation method, 136m 3 The method for producing SG-8 type polyvinyl chloride resin by polymerizing kettle comprises the following steps:

[0036] (1) Anti-sticking process: Use anti-sticking agent to treat 136m 3 The polymerization reactor is subjected to wall coating operation; the anti-sticking agent is polyethyleneimine or other existing known and commonly used anti-sticking agents. The details are as follows:

[0037] (1.1) Condenser wall coating: After the anti-sticking agent is mixed with water vapor to form an anti-sticking agent atomized liquid, the top and bottom of the kettle top condenser are coated with the anti-sticking agent atomized liquid. The amount of anti-sticking agent used in the condenser wall coating is 4-5 kg; the anti-sticking agent flow rate to form the anti-sticking agent atomized liquid is 900-1000 L / h, and the water vapor flow rate is 1.3-1.6 t / h;

[0038] (1.2) Coating the inner wall of the reactor: Use the atomized liquid of the anti-sticking agent to coat the feed inlet, the inner wall of the polymerization reactor, the stirring device and the baffle. The amount of the anti-sticking agent used in the coating of the inner wall of the reactor is 9-10 kg;

[0039] (1.3) Post-coating flushing: Pass high-pressure flushing water into the top condenser and the inside of the polymerization kettle for flushing, and the resulting wastewater is pumped to the wastewater tank.

[0040] (2) Feeding process: add 3-4 kg of low-efficiency buffer to the wall-coated polymerization reactor, then start stirring to provide a stirring environment, and the stirring speed is 90-95 r / min; then add 20-21 kg of dispersant I, 20-21 kg of dispersant II and 18-20 kg of dispersant III in sequence, and then add 55-57 tons of desalted water and 43-46 tons of vinyl chloride monomer, 136 m 3 The loading factor of the polymerization kettle can reach 80-85%. The above-mentioned inefficient buffer is a 1% ammonium bicarbonate solution; the dispersant I is a 5% water-soluble polyvinyl alcohol (preferably 48-80 water-soluble polyvinyl alcohol from Kuraray Co., Ltd. of Japan); the dispersant II is a 3% cellulose; the dispersant III is a polyvinyl alcohol with a degree of alcoholysis of 55%. The above-mentioned vinyl chloride monomer includes 37-39t of fresh vinyl chloride monomer and 6-7t of recycled vinyl chloride monomer. The temperature of the desalted water is 85-95°C.

[0041] (3) Reaction process: 27-30 kg of initiator is added to the polymerization kettle after the addition to initiate the polymerization reaction. The polymerization reaction is carried out for 200-280 min under the conditions of controlling the reaction temperature in the polymerization kettle to 65-68° C., the kettle pressure to 1.15-1.23 MPa, and the pH to 7-7.5. During the reaction, 2.0-2.5 m 3 / h rate of injection of desalted water at a temperature of 66-68°C, when the reaction reaches 180-200min, add 5-6kg of high-efficiency buffer to the polymerization kettle. The above-mentioned initiator is BNP and TAPP with a weight ratio of 1: (1.9-2.1); when adding materials, BNP is prepared into a mixed solution with a mass fraction of 50%, and TAPP is prepared into a mixed solution with a mass fraction of 40%. The high-efficiency buffer is a liquid caustic soda with a mass concentration of 2%.

[0042] (4) Unloading process: When the reaction pressure drop of the polymerization kettle reaches 0.125 MPa or the maximum reaction time, 43-46 kg of terminator is injected into the polymerization kettle to terminate the reaction; after the reaction is terminated, the polymerization kettle is forcibly cooled using the kettle top condenser until the kettle pressure of the polymerization kettle drops below 0.7 MPa, and then the unloading valve is opened to unload the SG-8 type polyvinyl chloride resin slurry into the slurry tank. The above terminator is an environmentally friendly terminator (preferably environmentally friendly terminator 4348).

[0043] (5) Refining process: stripping the SG-8 polyvinyl chloride resin slurry with a stripping tower, and drying the SG-8 polyvinyl chloride resin crude product obtained by stripping to obtain the SG-8 polyvinyl chloride resin product. The top temperature of the stripping tower is 103-109°C, the bottom temperature is 111-120°C, and the top pressure is 0.04-0.07MPa. The stripping tower adopts an overflow weir plate tower, and the drying adopts a fluidized bed drying process.

[0044] (6) Monomer recovery process: When the polymerization kettle is unloaded, the unreacted vinyl chloride monomer in the polymerization kettle is recovered from the top of the discharge tank, and then the vinyl chloride monomer in the SG-8 type polyvinyl chloride resin slurry is recovered from the top of the stripping tower. The recovered vinyl chloride monomer is uniformly sent to the recovery monomer storage tank for standby use.

[0045] The present invention is further described in detail below in conjunction with the examples. However, it should be understood that the examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

[0046] Embodiment 1:

[0047] One uses 136m 3 The method for producing SG-8 type polyvinyl chloride resin by polymerizing kettle comprises the following steps:

[0048] (1) Anti-sticking process: Use anti-sticking agent-polyethyleneimine to produce 136m3 The polymerization kettle performs wall coating operation; more specific steps are as follows:

[0049] (1.1) Condenser wall coating: After the anti-sticking agent is mixed with water vapor to form an anti-sticking agent atomized liquid, the top and bottom of the kettle top condenser are coated with the anti-sticking agent atomized liquid. The amount of anti-sticking agent used in the condenser wall coating is 4 kg; the anti-sticking agent flow rate to form the anti-sticking agent atomized liquid is 900 L / h, and the water vapor flow rate is 1.3 t / h;

[0050] (1.2) Coating the inner wall of the reactor: Use the atomized liquid of the anti-sticking agent to coat the feed inlet, the inner wall of the polymerization reactor, the stirring device and the baffle. The amount of the anti-sticking agent used in the coating of the inner wall of the reactor is 9 kg;

[0051] (1.3) Post-coating flushing: Pass high-pressure flushing water into the top condenser and the inside of the polymerization kettle for flushing, and the resulting wastewater is pumped to the wastewater tank.

[0052] (2) Feeding process: add 3kg of low-efficiency buffer to the polymerizer after wall coating, then start stirring to provide a stirring environment, and the stirring speed is 90r / min; then add 20kg of dispersant I, 20kg of dispersant II and 18kg of dispersant III in order, and then add 55t of desalted water and 43t of vinyl chloride monomer. The above-mentioned low-efficiency buffer is a 1% mass concentration of ammonium bicarbonate solution; dispersant I is a 5% mass concentration of water-soluble polyvinyl alcohol (48-80 water-soluble polyvinyl alcohol of Kuraray Co., Ltd. of Japan); dispersant II is cellulose with a mass concentration of 3%; dispersant III is polyvinyl alcohol with a degree of alcoholysis of 55%. The above-mentioned vinyl chloride monomer includes 37t of fresh vinyl chloride monomer and 6t of recycled vinyl chloride monomer. The temperature of the desalted water is 85℃.

[0053] (3) Reaction process: 27 kg of initiator was added to the polymerization kettle after the addition to initiate the polymerization reaction. The polymerization reaction was carried out for 220 min under the conditions of controlling the reaction temperature in the polymerization kettle to 66° C., the kettle pressure to 1.15 MPa, and the pH to 7. During the reaction, 2.0 m 3 / h rate of injection of desalted water at a temperature of 66 ° C, when the reaction reaches 180 minutes, add 5 kg of high-efficiency buffer to the polymerization kettle. The above-mentioned initiator is BNP and TAPP with a weight ratio of 1:1.9; when adding materials, BNP is prepared into a mixed solution with a mass fraction of 50%, and TAPP is prepared into a mixed solution with a mass fraction of 40%. The high-efficiency buffer is liquid alkali with a mass concentration of 2%.

[0054] (4) Unloading process: When the reaction pressure drop of the polymerization kettle reaches 0.125 MPa or the maximum reaction time, 43 kg of terminator is injected into the polymerization kettle to terminate the reaction; after the reaction is terminated, the polymerization kettle is forcibly cooled using the kettle top condenser until the kettle pressure of the polymerization kettle drops below 0.7 MPa, then the unloading valve is opened to unload the SG-8 type polyvinyl chloride resin slurry into the slurry tank. The terminator mentioned above is the environmentally friendly terminator 4348.

[0055] (5) Refining process: stripping the SG-8 polyvinyl chloride resin slurry in a stripping tower, and drying the SG-8 polyvinyl chloride resin crude product obtained by stripping to obtain the SG-8 polyvinyl chloride resin product. The top temperature of the stripping tower is 103°C, the bottom temperature is 111°C, and the top pressure is 0.04MPa. The stripping tower adopts an overflow weir plate tower, and the drying adopts a fluidized bed drying process.

[0056] (6) Monomer recovery process: When the polymerization kettle is unloaded, the unreacted vinyl chloride monomer in the polymerization kettle is recovered from the top of the discharge tank, and then the vinyl chloride monomer in the SG-8 type polyvinyl chloride resin slurry is recovered from the top of the stripping tower. The recovered vinyl chloride monomer is uniformly sent to the recovery monomer storage tank for standby use.

[0057] Embodiment 2:

[0058] One uses 136m 3 The method for producing SG-8 type polyvinyl chloride resin in a polymerization reactor, the remaining steps and experimental parameters are the same as those in Example 1, the only difference is:

[0059] In step (1), the amount of anti-sticking agent used for condenser wall coating is 5 kg; the amount of anti-sticking agent used in the wall coating inside the kettle is 10 kg; the anti-sticking agent flow rate to form the anti-sticking agent atomized liquid is 1000 L / h, and the water vapor flow rate is 1.6 t / h.

[0060] In step (2), 4 kg of low-efficiency buffer is added to the wall-coated polymerization reactor, and the stirring speed of the stirring environment is 95 r / min; then 21 kg of dispersant I, 21 kg of dispersant II and 20 kg of dispersant III are added in sequence, and then 57 tons of desalted water and 46 tons of vinyl chloride monomer are added. The above vinyl chloride monomer includes 39 tons of fresh vinyl chloride monomer and 7 tons of recycled vinyl chloride monomer. The temperature of the desalted water is 95°C.

[0061] In step (3), 30 kg of initiator was added to the polymerization kettle after the addition to initiate the polymerization reaction. The polymerization reaction was carried out for 280 min under the conditions of controlling the reaction temperature in the polymerization kettle to 68 ° C, the kettle pressure to 1.23 MPa, and the pH to 7.5. During the reaction, 2.5 m 3Desalted water at 68°C was injected at a rate of / h. When the reaction reached 200 minutes, 6 kg of high-efficiency buffer was added to the polymerization kettle. The above-mentioned initiators were BNP and TAPP at a weight ratio of 1:2.1.

[0062] In step (4), the injection amount of the terminator is 46 kg.

[0063] In step (5), the top temperature of the stripping tower is 109° C., the bottom temperature is 120° C., and the top pressure is 0.07 MPa.

[0064] Embodiment 3:

[0065] One uses 136m 3 The method for producing SG-8 type polyvinyl chloride resin in a polymerization reactor, the remaining steps and experimental parameters are the same as those in Example 1, the only difference is:

[0066] In step (1), the amount of anti-sticking agent used for condenser wall coating is 4 kg; the amount of anti-sticking agent used in the wall coating inside the kettle is 10 kg; the anti-sticking agent flow rate to form the anti-sticking agent atomized liquid is 1000 L / h, and the water vapor flow rate is 1.5 t / h.

[0067] In step (2), 3 kg of low-efficiency buffer is added to the wall-coated polymerization reactor, and the stirring speed of the stirring environment is 91 r / min; then 20 kg of dispersant I, 20 kg of dispersant II and 18 kg of dispersant III are added in sequence, and then 56 tons of desalted water and 43 tons of vinyl chloride monomer are added. The above vinyl chloride monomer includes 37 tons of fresh vinyl chloride monomer and 6 tons of recycled vinyl chloride monomer. The temperature of the desalted water is 90°C.

[0068] In step (3), 28 kg of initiator was added to the polymerization kettle after the addition to initiate the polymerization reaction. The polymerization reaction was carried out for 280 min under the conditions of controlling the reaction temperature in the polymerization kettle to 67.8 ° C, the kettle pressure to 1.20 MPa, and the pH to 7.5. During the reaction, 2.5 m 3 / h injection of desalted water at a temperature of 67°C, and when the reaction reaches 180 minutes, 5 kg of high-efficiency buffer is added to the polymerization kettle. The above-mentioned initiators are BNP and TAPP in a weight ratio of 1:2.

[0069] In step (4), the injection amount of the terminator is 45 kg.

[0070] In step (5), the top temperature of the stripping tower is 106° C., the bottom temperature is 115° C., and the top pressure is 0.05 MPa.

[0071] Comparative Example 1:

[0072] One uses 136m 3The method for producing SG-8 type polyvinyl chloride resin in a polymerization reactor, the remaining steps and experimental parameters are the same as those in Example 3, the only difference is that step (1) does not adopt a step-by-step wall coating operation, specifically as follows:

[0073] Step (1) Anti-sticking process: After the anti-sticking agent is mixed with water vapor to form an anti-sticking agent atomized liquid, the top and bottom of the kettle top condenser, the feed inlet of the polymerization kettle, the inner wall of the polymerization kettle, the stirring device and the baffle are coated at the same time. The amount of the anti-sticking agent is 14 kg; the anti-sticking agent flow rate of the anti-sticking agent atomized liquid is 900 L / h, and the water vapor flow rate is 1.3 t / h; after the anti-sticking agent atomized liquid is sprayed, high-pressure flushing water is introduced into the kettle top condenser and the inside of the polymerization kettle for flushing, and the resulting waste water is pumped to the wastewater tank.

[0074] Comparative Example 2:

[0075] One uses 136m 3 The method for producing SG-8 type polyvinyl chloride resin in a polymerization reactor, the remaining steps and experimental parameters are the same as those in Example 3, the only difference is that: 136 m SG-5 type polyvinyl chloride resin is used in step (2) 3 The dispersant system produced by the polymerization reactor is as follows:

[0076] In step (2), 30 kg of dispersant I, 8 kg of dispersant II and 12 kg of dispersant III are added in order, wherein dispersant I is a water-soluble polyvinyl alcohol with a mass concentration of 5% (48-80 water-soluble polyvinyl alcohol produced by Kuraray Co., Ltd. of Japan); dispersant II is cellulose with a mass concentration of 3%; and dispersant III is polyvinyl alcohol with a degree of alcoholysis of 45%.

[0077] Comparative Example 3:

[0078] One uses 136m 3 The method for producing SG-8 type polyvinyl chloride resin in a polymerization reactor, the remaining steps and experimental parameters are the same as those in Example 3, the only difference is that: 136 m SG-5 type polyvinyl chloride resin is used in step (2) 3 The initiator system for polymerization reactor production is as follows:

[0079] In step (3), 31.5 kg of initiator is added to the polymerization kettle after the addition to initiate the polymerization reaction. The initiator is CNP50 and EHP50 in a weight ratio of 1:4.

[0080] Comparative Example 4:

[0081] One uses 136m 3 The method for producing SG-8 type polyvinyl chloride resin in a polymerization reactor, the remaining steps and experimental parameters are the same as those in Example 3, the only difference is that the desalted water in step (2) is fed with cold feed, specifically as follows:

[0082] In step (2), 56t of desalted water having a temperature of 45°C is added.

[0083] Test Example 1:

[0084] SG-8 polyvinyl chloride resin quality test: Take the SG-8 polyvinyl chloride resin produced in Example 1 to Example 3 as the test sample, and test it according to the method specified in GB / T5761-2018. Each test sample of each example is set with 3 parallels, and the average value is taken. The results are shown in Table 1.

[0085] Table 1

[0086]

[0087] From the results in Table 1, it can be seen that the present invention uses 136m 3 The quality of the SG-8 polyvinyl chloride resin product produced by the polymerization kettle meets the requirements of the SG-8 superior product in the provisions of GB / T5761-2018 suspension method general-purpose polyvinyl chloride resin. The sieve residue of the polyvinyl chloride product with a 250μm sieve hole is less than 1%, and the sieve residue of the 63μm sieve hole is greater than 99%, indicating that the molecular weight distribution of the polyvinyl chloride resin product obtained by the production method of the present invention is concentrated and has good stability, ensuring the quality of the polyvinyl chloride product and the stability of post-processing performance.

[0088] Test Example 2:

[0089] Effects of different methods on the quality of polyvinyl chloride resin products: The SG-8 polyvinyl chloride resin products produced in Example 3 and Comparative Examples 1-4 were taken as test samples, and the number of fish eyes, aging whiteness and polymerization kettle operation cycle of the test samples were detected, and the molecular weight distribution width of the test samples was compared to obtain the results shown in Tables 2 and 3. Each group of test samples was set up with 3 parallels, and the average value was taken.

[0090] Table 2

[0091] <![CDATA[Number of fish eyes / piece / 400 cm 2 > Operation cycle / month Aging whiteness / % Example 3 13 12 75.7 Comparative Example 1 32 3 63.5 Comparative Example 2 21 10 72.6 Comparative Example 3 23 11 70.3 Comparative Example 4 34 9 65.8

[0092] Table 3 Comparison of molecular weight distribution

[0093]

[0094] It can be seen from the results of Table 2 and Table 3 that, compared with the production methods in Comparative Examples 1 to 4, the production method of the present invention has a reasonable ratio of initiator and dispersant, and adopts hot desalted water feeding and step-by-step wall coating operations, so that the sticking phenomenon of the polymerization kettle is weakened, the operation cycle of the polymerization kettle is extended, the number of fisheyes in the polyvinyl chloride resin product is significantly reduced, and the aging whiteness is also improved. The quality of the obtained polyvinyl chloride resin product is higher, and the molecular weight distribution width of the polyvinyl chloride resin product is smaller, the molecular weight distribution is concentrated, the product particle morphology is uniform, the product stability and particle morphology are better, and the product quality and post-processing performance are stable.

[0095] It should be noted that in the present invention, the detailed steps of some operations are not described in detail, but belong to the prior art known to those skilled in the art, so they will not be repeated here. In addition, in the present invention, all features such as values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are only for simplicity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be deemed to have covered and specifically disclosed all possible secondary ranges and individual values ​​(including integers and fractions) within the range.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. In the present invention, not all possible combinations of the various technical features in the various embodiments or embodiments are described. As long as there is no contradiction in the combination of these technical features, the various technical features in the various embodiments or embodiments can be arbitrarily combined, and all possible combinations should be considered to be within the scope of this specification. Although the present invention has been described in detail with reference to the aforementioned embodiments, a person of ordinary skill in the art should understand that the technical solutions described in the aforementioned embodiments can still be modified, or some or all of the technical features can be replaced by equivalents, and these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. One uses 136m 3 The method for producing SG-8 type polyvinyl chloride resin by polymerizing kettle is characterized in that: include: Use anti-sticking agent to treat 136m 3 Anti-sticking process of polymerizing kettle for wall coating operation; A feeding step of adding an auxiliary agent, desalted water and vinyl chloride monomer to the polymerization kettle after wall coating; a reaction step of adding an initiator to the polymerization kettle after feeding to initiate polymerization reaction; and a discharging step of adding a terminator to the polymerization kettle to terminate the reaction and discharging the SG-8 type polyvinyl chloride resin slurry in the polymerization kettle; The initiators are BNP and TAPP; in the feeding process, the amount of desalted water added is 55-57t, the temperature of the desalted water is 85-95°C, and the amount of vinyl chloride monomer added is 43-46t; the 136m 3 The loading factor of the polymerization reactor is 80-85%; In the feeding process, the feeding amount of the initiator is 27-30 kg, and the weight ratio of the BNP to the TAPP is 1:(1.9-2.1); when the initiator is added, the BNP is prepared into a mixed solution with a mass fraction of 50%, and the TAPP is prepared into a mixed solution with a mass fraction of 40%; In the feeding process, the auxiliary agents include low-efficiency buffer, dispersant I, dispersant II and dispersant III in the order of addition. After the low-efficiency buffer is added, stirring is started to provide a stirring environment, and the stirring speed is 90-95 r / min; The addition amount of the low-efficiency buffer is 3-4 kg, and the low-efficiency buffer is an ammonium bicarbonate solution with a mass concentration of 1%; The addition amount of the dispersant I is 20-21 kg, and the dispersant I is a water-soluble polyvinyl alcohol with a mass concentration of 5%; The amount of dispersant II added is 20-21 kg, and dispersant II is cellulose with a mass concentration of 3%; The amount of dispersant III added is 18-20 kg, and dispersant III is polyvinyl alcohol with an alcoholysis degree of 55%; In the reaction process, the reaction temperature in the polymerization kettle is controlled to be 65-68°C, the kettle pressure is 1.15-1.23 MPa, and the reaction time is 200-280 min; and during the reaction, 2.0-2.5 m 3 / h injecting desalted water at a rate of 180 to 200 minutes into the reaction, adding 5 to 6 kg of a high-efficiency buffer into the polymerization kettle, wherein the high-efficiency buffer is a liquid caustic soda with a mass concentration of 2%; The steps of wall coating operation in the anti-sticking kettle process are: (1) Condenser wall coating: After the anti-sticking agent is mixed with water vapor to form an anti-sticking agent atomized liquid, the top and bottom of the kettle top condenser are coated with the anti-sticking agent atomized liquid. The amount of the anti-sticking agent used in the condenser wall coating is 4-5 kg; (2) Coating the inner wall of the reactor: Use the atomized liquid of the anti-sticking agent to coat the feed inlet, the inner wall of the polymerization reactor, the stirring device and the baffle. The amount of the anti-sticking agent used in the coating of the inner wall of the reactor is 9 to 10 kg; (3) Post-coating flushing: High-pressure flushing water is introduced into the top condenser and the inside of the polymerization kettle for flushing, and the resulting wastewater is pumped to the wastewater tank.

2. The method of claim 1 using 136m 3 The method for producing SG-8 type polyvinyl chloride resin by polymerizing kettle is characterized in that: The method further comprises a refining step of purifying the SG-8 type polyvinyl chloride resin slurry to obtain a SG-8 type polyvinyl chloride resin product; The refining process comprises the following steps: stripping the SG-8 polyvinyl chloride resin slurry by using a stripping tower, and drying the SG-8 polyvinyl chloride resin crude product obtained by stripping to obtain a SG-8 polyvinyl chloride resin product; The top temperature of the stripping tower is 103-109° C., the bottom temperature is 111-120° C., and the top pressure is 0.04-0.07 MPa.

3. The method of claim 2 using 136m 3 The method for producing SG-8 type polyvinyl chloride resin by polymerizing kettle is characterized in that: The method also includes a monomer recovery process for recovering vinyl chloride monomer, and the steps of the monomer recovery process are as follows: when the polymerization kettle is unloaded, the unreacted vinyl chloride monomer in the polymerization kettle is recovered from the top of the discharge tank, and then the vinyl chloride monomer in the SG-8 type polyvinyl chloride resin slurry is recovered from the top of the stripping tower, and the recovered vinyl chloride monomer is uniformly sent to a recovery monomer storage tank for standby use.

4. The method of claim 3 using 136m 3 The method for producing SG-8 type polyvinyl chloride resin by polymerizing kettle is characterized in that: In the feeding process, the vinyl chloride monomer added to the polymerization kettle includes fresh vinyl chloride monomer and recycled vinyl chloride monomer, and the feeding amount of the recycled vinyl chloride monomer is 6-7t.

5. The method of claim 1 using 136m 3 The method for producing SG-8 type polyvinyl chloride resin by polymerizing kettle is characterized in that: During the polymerization reaction, when the reaction pressure drop of the polymerization kettle reaches 0.125MPa or the maximum reaction time, a terminator is injected into the polymerization kettle to terminate the reaction; the injection amount of the terminator is 43-46kg, and the terminator is an environmentally friendly terminator.

6. The method of using 136m according to any one of claims 1 to 5 3 The method for producing SG-8 type polyvinyl chloride resin by polymerizing kettle is characterized in that: In the unloading process, after the reaction is terminated, the top condenser is used to forcibly cool the polymerization kettle until the kettle pressure of the polymerization kettle drops below 0.7 MPa, and then the unloading valve is opened to unload the SG-8 type polyvinyl chloride resin slurry into the slurry tank.

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