A high impact resistant PVC resin production device and method

Abstract

The present invention discloses a high-impact PVC resin production device and method, comprising an additive storage tank and a catalyst storage tank, wherein the additive storage tank is sequentially connected to an additive metering tank, an additive premixing tank, a buffer tank, and a polymerization kettle; the catalyst storage tank is sequentially connected to a catalyst metering tank, a buffer tank, and a polymerization kettle; the connecting pipelines of the catalyst metering tank and the buffer tank are respectively connected to a monomer storage tank and a pure water storage tank; the polymerization kettle is further connected to a polymerization kettle heating pump, which is connected to the circulating cooling water inlet and outlet of the polymerization kettle jacket; an impact modifier storage hopper is installed above the polymerization kettle, and the impact modifier storage hopper is used to store the impact modifier. The present invention can achieve the goal of improving the uniform dispersion of the impact modifier and good bonding with the PVC interface, which is relatively difficult, and the formation of a certain proportion of graft copolymers during the preparation process improves the compatibility between the components. The performance of the PVC composite material prepared by alloying in the kettle is often better than the corresponding PVC alloy prepared by melt blending of the same composition.

Description

Technical Field

[0001] The invention belongs to the technical field of PVC graft copolymer production methods, and particularly relates to a high-impact resistant PVC resin production device and a high-impact resistant PVC resin preparation method. Background Art

[0002] In recent years, the PVC processing industry has continuously adopted various physical and chemical modification methods to further improve the processing and performance of PVC resins. Physical blending modification is simple to operate and does not require changes to the existing resin production process. It is widely used in downstream PVC processing plants. However, it suffers from poor physical mixing effects and the high cost of high-performance modifiers, which results in physical modification failing to achieve a qualitative leap in the impact resistance of PVC. In recent years, there has been a lot of research on the modification of vinyl chloride suspension polymerization, mainly focusing on improving the resin's thermal stability, whiteness, impact resistance, and aging properties. To improve the compatibility between toughening modifiers and PVC, graft copolymerization has been used to obtain graft copolymerized toughened and modified PVC to improve the impact resistance of PVC. This has become a more effective approach to toughening and modifying PVC.

[0003] In recent years, with the increase in production capacity and output, competition in the PVC market has become particularly fierce. However, market competition ultimately comes down to a competition between product quality and production costs. An effective way to reduce PVC costs is to increase production capacity. To increase the capacity of polymerization units, shortening the polymerization auxiliary time is a key aspect.

[0004] Currently, the mainstream feeding method for PVC suspension polymerization involves sequentially coating the polymerization reactor, followed by adding cold pure water. Dispersants and initiators are added during this process, and monomers are added after the cold pure water is added. After monomer addition is complete, hot pure water is added. Based on the solubility characteristics and ratio of VC monomers and modifiers such as core-shell acrylic copolymers (ACR), chlorinated vinyl chloride (CPE), ethylene-vinyl acetate copolymers (EVA), acrylonitrile-butadiene-styrene copolymers (ABS), and thermoplastic polyurethane elastomers (TPU), these monomers are added during the suspension polymerization of vinyl chloride to undergo suspension graft copolymerization, modifying the molecular structure of the PVC and improving the impact resistance and processing properties of the PVC composite resin. After the polymerization reaction is complete, a defoamer is added, and the polymerization reactor is discharged. This production process can meet normal and stable production requirements, but while maintaining stable production, it is still necessary to shorten batch production time and increase the production capacity of the polymerization reactor. Summary of the Invention

[0005] The purpose of the present invention is to provide a high-impact PVC resin production device.

[0006] The present invention also aims to provide a method for preparing a high-impact PVC resin, which effectively solves the problem of low efficiency of existing PVC resin production methods.

[0007] The first technical solution adopted by the present invention is a high-impact PVC resin production device, which includes an additive storage tank and a catalyst storage tank. The additive storage tank is sequentially connected to an additive metering tank, an additive premixing tank, a buffer tank, and a polymerization kettle; the catalyst storage tank is sequentially connected to a catalyst metering tank, a buffer tank, and a polymerization kettle; the connecting pipelines of the catalyst metering tank and the buffer tank are respectively connected to a monomer storage tank and a pure water storage tank; the polymerization kettle is also connected to a polymerization kettle heating pump, which is connected to the circulating cooling water inlet and outlet of the polymerization kettle jacket;

[0008] An impact modifier storage hopper is installed above the polymerization kettle, and the impact modifier storage hopper is used to store the impact modifier.

[0009] The present invention is also characterized in that:

[0010] A monomer feeding pump is also provided on the connecting pipeline between the monomer storage tank and the buffer tank, and a pure water feeding pump is also provided on the connecting pipeline between the pure water storage tank and the buffer tank.

[0011] The impact modifier storage hopper is installed on the upper head of the polymerization kettle.

[0012] A premixed additive feeding pump is also provided on the connecting pipeline between the additive premixing tank and the buffer tank.

[0013] A flow meter a is further provided on the connecting pipe between the monomer storage tank and the buffer tank, and a flow meter b is further provided on the connecting pipe between the pure water storage tank and the buffer tank. The second technical solution adopted by the present invention is a method for preparing a high-impact PVC resin, and the specific operating steps are as follows:

[0014] Step 1: Pre-feeding operation: Measure and mix the dispersant and other additives according to the formula amount, and store them in the additive premix tank; add pure water to the pure water storage tank; add the impact modifier to the impact modifier storage hopper;

[0015] Step 2: The polymerization kettle is stirred at a low speed, and the polymerization kettle is vacuumed to deoxygenate, and the polymerization kettle is pumped to a negative pressure condition;

[0016] Step 3: Add 60% to 80% of the total formula of vinyl chloride monomer through the monomer feeding pump, stir the polymerization kettle at a low speed, and then raise the temperature of the polymerization kettle to 50-70° C. through the polymerization kettle heating pump. The impact modifier enters the polymerization kettle through the impact modifier storage hopper to swell and pulverize the vinyl chloride monomer;

[0017] Step 4: The remaining vinyl chloride monomer and catalyst are added into the operation, wherein the catalyst is pre-stored in a buffer tank through a catalyst metering tank, and the temperature of the polymerization kettle is reduced to 40-50°C through 20°C circulating cooling water configured by the utility project, and the remaining vinyl chloride monomer is added into the polymerization kettle through a monomer feeding pump. The catalyst enters the polymerization kettle along with the addition of the remaining vinyl chloride monomer to participate in the reaction;

[0018] Step 5: The polymerization kettle temperature is raised to the polymerization reaction temperature for producing PVC resin by a polymerization kettle temperature raising pump; when the polymerization kettle temperature reaches the set polymerization reaction temperature, polymerization reaction occurs, and the polymerization reaction temperature fluctuation range is maintained at ±0.2°C;

[0019] Step 6: After the polymerization reaction is completed, the polymerization pressure is reduced to 0.41-0.42 MPa, and then a terminator is added into the polymerization kettle to terminate the polymerization reaction, and the discharge and unreacted vinyl chloride monomer recovery operations are carried out.

[0020] The present invention is also characterized in that:

[0021] The invention synthesizes a high-impact PVC resin by using a swelling, pulverization and suspension graft polymerization integrated in-vessel technology. The invention comprises the following steps: adding a formulated amount of an impact modifier, a formulated amount of cold deionized water, a dispersant, a defoamer and other auxiliary agents into a polymerization kettle, starting stirring (stirring speed of 50-150 r / min), and evacuating the kettle to a negative pressure for 10 minutes; adding 60-80% of the formulated amount of vinyl chloride monomer into the kettle, adjusting the stirring speed (stirring speed of 400-600 r / min), and heating the materials in the kettle to swell and pulverize the VC of the EVA; after the swelling and pulverization is completed within 120-150 minutes, adding an initiator and the remaining vinyl chloride monomer, heating the kettle to a polymerization temperature, and carrying out a polymerization reaction; adding a terminator to terminate the discharge after the reaction is completed; and drying in an oven at 60°C for 48 hours.

[0022] The outlet pressure of the vinyl chloride monomer feeding pump shall not be lower than 1.2 MPa; and the pressure in the polymerization kettle shall be maintained at 0.8 MPa to 1.2 MPa during the polymerization reaction.

[0023] Before the pre-feeding operation in step 1, the polymerization kettle coating operation must be completed. The coating operation is: using the coating liquid to be injected into the polymerization kettle through the injection valve on the top of the polymerization kettle, and through the dual action of steam and high-speed stirring of the polymerization kettle, the coating liquid is evenly sprayed on the kettle wall to prevent the polymerization kettle from sticking.

[0024] The impact modifier includes any one of core-shell acrylic copolymer, chlorinated vinyl chloride, ethylene-vinyl acetate copolymer, acrylonitrile-butadiene-styrene copolymer, and thermoplastic polyurethane elastomer, preferably ethylene-vinyl acetate copolymer, with a mass ratio of 5% to 20%.

[0025] The dispersant and other additives in step 1 are pre-mixed during the polymerization reaction of the previous batch. After the previous batch is discharged, the premix can be added to the reactor for reaction, eliminating the need for individual additions and saving production time for the current batch. The dispersant is polyvinyl alcohol (PVA) at a mass ratio of 0.2-0.5%.

[0026] The low-speed stirring rate in step 2 and step 3 is 50 r / min to 150 r / min; the catalyst in step 4 is one of tert-butyl peroxide neodecanoate and isopropyl peroxide neodecanoate, or a combination thereof;

[0027] The initiators are tert-butyl peroxydecanoate and cumyl peroxydecanoate. The initiators are used alone or in combination, and the mass ratio thereof is 0.2% to 0.5%.

[0028] The swelling pulverization method is to use VC to swell the impact modifier in the presence of a dispersant aqueous solution, and then pulverize the modifier through mechanical stirring. It has the advantages of simple equipment and convenient operation, and can realize the integration of pulverization and polymerization processes.

[0029] The polymerization reaction temperature is 57° C. to 68° C., and the reaction pressure is 0.86 MPa to 0.87 MPa.

[0030] Step 4: The catalyst is pre-charged into the buffer tank with the aid of low-pressure nitrogen.

[0031] The present invention adopts an integrated in-vessel technology of swelling and pulverizing an impact modifier (such as EVA, ACR, CPE, TPU, and ABS) having both impact modification and processing modification functions to synthesize an impact modifier / PVC alloy resin. The impact modifier is swollen and pulverized by vinyl chloride monomer, and the vinyl chloride monomer is easily polymerized in the gaps between impact modifier particles to form a network structure. The graft copolymer has good physical properties, but it is difficult to achieve uniform dispersion of the modifier and good interface bonding with the PVC resin. In addition, the formation of a certain proportion of graft copolymer during the preparation process improves the compatibility between components. The performance of the PVC material prepared by in-vessel alloying is often superior to that of the corresponding PVC alloy prepared by melt blending of the same composition.

[0032] The beneficial effects of the present invention are: the process device of the present invention

[0033] 1. The present invention can achieve uniform dispersion of the impact modifier and good interface bonding with PVC, which is difficult to achieve. In addition, a certain proportion of graft copolymer is formed during the preparation process, which improves the compatibility between the components. The performance of the PVC composite material prepared by in-vessel alloying is often better than that of the corresponding PVC alloy prepared by melt blending of the same composition.

[0034] 2. The use of swelling pulverization-suspension grafting polymerization integrated in-vessel technology can achieve excellent impact modification effect while reducing the amount of impact modifier used, and the resulting PVC resin has high impact strength.

[0035] 3. The pre-feeding system for dispersants and other additives is the core of the feeding process of the present invention. The pre-feeding system pre-disposes the additives during the polymerization reaction of the previous batch, which does not occupy the production time of the current batch, thus minimizing the feeding time of the current batch.

[0036] 4. The method for producing high-impact PVC alloys of the present invention has simple process control, which can be achieved by switching valves between pipelines. Daily maintenance is convenient and does not require excessive manpower and material resources.

[0037] 5. The process provided by the present invention is simple in design and easy to implement, especially it can be combined with existing VC suspension polymerization production equipment and related enterprises.

[0038] 6. The present invention is a process technology improvement. The high impact resistant PVC alloy production process not only increases product output, but also simplifies and optimizes product quality and ensures customer usage needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 The present invention is a schematic structural diagram of a high impact resistant PVC resin production device.

[0040] In the figure, 1. additive storage tank, 2. additive metering tank, 3. additive premixing tank, 4. premixed additive feeding pump, 5. catalyst storage tank, 6. catalyst metering tank, 7. monomer storage tank, 8. monomer feeding pump, 9. pure water storage tank, 10. pure water feeding pump, 11. buffer tank, 12. impact modifier storage hopper, 13. polymerization kettle, 14. polymerization kettle heating pump, 15. flow meter a, 16. flow meter b. DETAILED DESCRIPTION

[0041] The present invention provides a high impact resistant PVC resin production device, the specific structure is as follows Figure 1As shown, it includes an additive storage tank 1 and a catalyst storage tank 5, the additive storage tank 1 is connected to the additive metering tank 2, the additive premixing tank 3, the buffer tank 11, and the polymerization kettle 13 in sequence; the catalyst storage tank 5 is connected to the catalyst metering tank 6, the buffer tank 11 and the polymerization kettle 13 in sequence; the connecting pipelines of the catalyst metering tank 6 and the buffer tank 11 are also connected to the monomer storage tank 7 and the pure water storage tank 9 respectively; the polymerization kettle 13 is also connected to the polymerization kettle heating pump 14, and the polymerization kettle heating pump 14 is connected to the circulating cooling water inlet and outlet of the jacket of the polymerization kettle 13; the additive premixing tank 3 is a stirring device with a metering device such as an electronic scale installed on the tank body, and its stirring mechanism and internal circulation mechanism work simultaneously under the control of the electrical controller. Using this method to stir two or more liquids can shorten the mixing time and make the raw materials mixed more evenly, and is used to mix the various additives evenly and then send them into the buffer tank 11.

[0042] Both the additive metering tank 2 and the catalyst metering tank 6 are equipped with weighing equipment, such as scales and liquid level gauges, to measure additives and catalysts during the production process, playing a crucial role in controlling material flow. An impact modifier storage hopper 12 is mounted above the polymerization kettle 13 to store the impact modifier.

[0043] A monomer feeding pump 8 is further provided on the connecting pipeline between the monomer storage tank 7 and the buffer tank 11 , and a pure water feeding pump 10 is further provided on the connecting pipeline between the pure water storage tank 9 and the buffer tank 11 .

[0044] The impact modifier storage hopper 12 is installed on the upper end of the polymerization kettle.

[0045] A premixed additive feeding pump 4 is also provided on the connecting pipeline between the additive premixing tank 3 and the buffer tank 11 .

[0046] A flow meter a15 is further provided on the connecting pipeline between the monomer storage tank 7 and the buffer tank 11 , and a flow meter b16 is further provided on the connecting pipeline between the pure water storage tank 9 and the buffer tank 11 .

[0047] Automatic control valves are installed in the operations of adding pure water, vinyl chloride monomer, impact modifier, catalyst, dispersant and other additives, and are controlled by DCS program to implement automatic operation and control.

[0048] Dispersants and other additives are set up with corresponding storage tanks, and the number of storage tanks is set accordingly according to the different models and types of additives. After the concentration of these additives is measured, they are measured in the additive metering tank according to the requirements of the polymerization production process formula and then transported to the additive premixing tank. During the addition of pure water, the premixed additive feeding pump is turned on, and water and mixed additives enter the polymerization kettle together.

[0049] The vinyl chloride monomer is added in two steps. The vinyl chloride monomer accounting for about 60% to 80% of the total vinyl chloride monomer is added in the early stage to facilitate the swelling and powdering of the impact modifier and improve the grafting rate of the PVC alloy.

[0050] The outlet pressure of the vinyl chloride monomer feeding pump shall not be lower than 1.2Mpa.

[0051] During the polymerization reaction, the system pressure was maintained at 0.8 MPa to 1.2 MPa.

[0052] The present invention will be further described below with reference to specific embodiments.

[0053] Example 1

[0054] A high-impact PVC resin comprises, by weight, 100 parts of vinyl chloride monomer, 0.3 parts of dispersant, 7.5 parts of EVA, 0.34 parts of initiator, and 0.75 parts of defoamer.

[0055] The preparation process is as follows:

[0056] (1) Add EVA, cold deionized water, dispersant, vinyl alcohol, defoamer and other additives into the polymerization kettle;

[0057] (2) Stirring was started (stirring speed was 80 r / min), and the kettle was evacuated to negative pressure for 10 min;

[0058] (3) Add 80% vinyl chloride monomer into the kettle and adjust the stirring speed (the stirring speed is 400-600 r / min);

[0059] (4) The temperature of the contents in the kettle was raised to 57°C to allow the VC in the EVA to swell and pulverize. The swelling and pulverization time was 120 min.

[0060] (5) Add initiator (cumyl peroxide) and the remaining 20% ​​of the formula amount of vinyl chloride monomer, and heat the kettle to 57° C. to carry out polymerization reaction;

[0061] (6) After the reaction is completed, a terminator is added to stop the discharge; and the high-impact PVC resin is dried in an oven at 60° C. for 48 hours.

[0062] Example 2

[0063] A high-impact PVC resin comprises, by weight, 100 parts of vinyl chloride monomer, 0.3 parts of dispersant, 7.5 parts of EVA, 0.21 parts of initiator, and 0.75 parts of defoamer.

[0064] The preparation process is as follows:

[0065] (1) Add EVA, cold deionized water, dispersant, vinyl alcohol, defoamer and other additives into the polymerization kettle;

[0066] (2) Start stirring (stirring speed is 50-150 r / min), and evacuate the kettle to negative pressure for 10 min;

[0067] (3) Add 80% vinyl chloride monomer into the kettle and adjust the stirring speed (the stirring speed is 400-600 r / min);

[0068] (4) The material in the kettle is heated to 57°C to swell and pulverize the VC of EVA. The swelling and pulverization time is 120 to 150 minutes.

[0069] (5) Add initiator (cumyl peroxide) and the remaining 20% ​​of the formula amount of vinyl chloride monomer, and heat the kettle to 57° C. to carry out polymerization reaction;

[0070] (6) After the reaction is completed, a terminator is added to stop the discharge; and the high-impact PVC resin is dried in an oven at 60° C. for 48 hours.

[0071] Table 1: Mass proportions of high impact PVC resin raw materials prepared in Example

[0072]

[0073] Table 2 Physical and chemical properties and impact strength tests of the high-impact PVC resin of the present invention

[0074]

[0075] Among them, the comparative example in Table 2 is a resin without EVA. It can be seen from Table 2 that the strength and density of the resin without EVA are relatively low.

[0076] The above content is a further detailed description of the patent of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific embodiments of the patent of the present invention are limited to this. For ordinary technicians in the technical field to which the patent of the present invention belongs, they can make several simple deductions or substitutions without departing from the concept of the present invention, which should be regarded as belonging to the patent of the present invention and the scope of patent protection shall be determined by the submitted claims.

Claims

1. A method for preparing a high impact resistant PVC resin, characterized in that: A high impact PVC resin production device is used, and the specific operation steps are as follows: Step 1: Pre-feeding operation: Measure and mix the dispersant and other additives according to the formula amount, and store them in the additive pre-mixing tank; add pure water to the pure water storage tank; add the impact modifier to the impact modifier storage hopper; The dispersant and other additives in step 1 are pre-configured during the polymerization reaction of the previous batch. After the previous batch is discharged, the premix can be added to the kettle for reaction, eliminating the step of adding materials one by one and not taking up the production time of this batch. Step 2: The polymerization kettle is stirred at a low speed, and the polymerization kettle is vacuumed to deoxygenate, and the polymerization kettle is pumped to a negative pressure condition; Step 3: Add 60% to 80% of the total formula of vinyl chloride monomer through the monomer feeding pump, stir the polymerization kettle at a low speed, and then raise the temperature of the polymerization kettle to 50-70°C through the polymerization kettle heating pump. The impact modifier enters the polymerization kettle through the impact modifier storage hopper to swell and pulverize the vinyl chloride monomer; Step 4: The remaining vinyl chloride monomer and catalyst are added into the operation, wherein the catalyst is pre-stored in a buffer tank through a catalyst metering tank, and the temperature of the polymerization kettle is reduced to 40-50°C through 20°C circulating cooling water configured by the utility project, and the remaining vinyl chloride monomer is added into the polymerization kettle through a monomer feeding pump. The catalyst enters the polymerization kettle along with the addition of the remaining vinyl chloride monomer to participate in the reaction; Step 5: The polymerization kettle temperature is raised to 57-68°C, a polymerization reaction temperature for producing PVC resin, by a polymerization kettle temperature raising pump; the reaction pressure is 0.86Mpa-0.87Mpa, and when the polymerization kettle temperature reaches the set polymerization reaction temperature, polymerization reaction occurs, and the polymerization reaction temperature fluctuation range is maintained at ±0.2°C; Step 6: After the polymerization reaction is completed, the polymerization pressure is reduced to 0.41-0.42 MPa, and then a terminator is added into the polymerization kettle to terminate the polymerization reaction, and the discharge and unreacted vinyl chloride monomer recovery operations are carried out.

2. The method for preparing a high impact resistant PVC resin according to claim 1, wherein: The high-impact PVC resin production device comprises an additive storage tank (1) and a catalyst storage tank (5), wherein the additive storage tank (1) is sequentially connected to an additive metering tank (2), an additive premixing tank (3), a buffer tank (11), and a polymerization kettle (13); the catalyst storage tank (5) is sequentially connected to a catalyst metering tank (6), a buffer tank (11), and a polymerization kettle (13); and the connecting pipelines of the catalyst metering tank (6) and the buffer tank (11) are further connected to a monomer storage tank (7) and a pure water storage tank (9), respectively. An impact modifier storage hopper (12) is installed above the polymerization kettle (13), and the impact modifier storage hopper (12) is used to store the impact modifier; the impact modifier storage hopper (12) is installed on the upper head of the polymerization kettle; A premixed additive feeding pump (4) is also provided on the connecting pipeline between the additive premixing tank (3) and the buffer tank (11); A monomer feeding pump (8) is further provided on the connecting pipeline between the monomer storage tank (7) and the buffer tank (11), and a pure water feeding pump (10) is further provided on the connecting pipeline between the pure water storage tank (9) and the buffer tank (11); The polymerization kettle (13) is also connected to a polymerization kettle temperature-raising pump (14), and the polymerization kettle temperature-raising pump (14) is connected to the inlet and outlet of the jacket circulating cooling water of the polymerization kettle (13); A flow meter a (15) is further provided on the connecting pipeline between the monomer storage tank (7) and the buffer tank (11), and a flow meter b (16) is further provided on the connecting pipeline between the pure water storage tank (9) and the buffer tank (11).

3. The method for preparing a high impact resistant PVC resin according to claim 1, wherein: The outlet pressure of the vinyl chloride monomer feeding pump shall not be lower than 1.2 MPa; and the pressure in the polymerization kettle shall be maintained at 0.8 MPa to 1.2 MPa during the polymerization reaction.

4. The method for preparing a high impact resistant PVC resin according to claim 1, wherein: Before the pre-feeding operation in step 1, the polymerization kettle coating operation must be completed. The coating operation is: using the coating liquid to be injected into the polymerization kettle through the injection valve on the top of the polymerization kettle, and through the dual action of steam and high-speed stirring of the polymerization kettle, the coating liquid is evenly sprayed on the kettle wall to prevent the polymerization kettle from sticking.

5. The method for preparing a high impact resistant PVC resin according to claim 1, wherein: The impact modifier includes any one of core-shell acrylic ester copolymer, chlorinated vinyl chloride, ethylene-vinyl acetate copolymer, acrylonitrile-butadiene-styrene copolymer, and thermoplastic polyurethane elastomer; and the dispersant is polyvinyl alcohol dispersant.

6. The method for preparing a high impact resistant PVC resin according to claim 2, wherein: The low-speed stirring rate in step 2 and step 3 is 50 r / min to 150 r / min; the catalyst in step 4 is one of tert-butyl peroxide neodecanoate and isopropyl peroxide neodecanoate, or a combination thereof; in step 4, the catalyst is pre-added into the buffer tank (11) with the aid of low-pressure nitrogen.

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