A plastic production system and production method

Abstract

The present application relates to a plastic production system and a production method. The plastic production system comprises a first mixing device, a main pipeline and a second mixing device. The first mixing device is sequentially provided with a first feeding port for adding additives, a second feeding port connected with an openable or closable melt feeding pipe for inputting a melt of a first polymer, a third feeding port and a mixing discharge port. The main pipeline comprises an openable or closable first branch pipe and a second branch pipe. The first branch pipe is connected with the third feeding port for inputting a melt of a second polymer into the third feeding port. The second mixing device is arranged downstream of the mixing discharge port and the main pipeline, and is connected with the mixing discharge port through a discharge pipeline and connected with the main pipeline through the second branch pipe. The present application enables direct and continuous polymer blending modification, and additives can be added in the blending process of multiple polymer kettles to more flexibly change and improve product performance.

Description

Technical Field

[0001] This invention relates to a plastic production system and production method. Background Technology

[0002] Currently, there are few reports on modification methods for the continuous or batch preparation of specialty engineering plastics. Engineering plastic modification refers to improving or enhancing certain properties of engineering plastics, such as density, hardness, precision, appearance, processability, transparency, mechanical properties, electromagnetic properties, chemical properties, corrosion resistance, aging resistance, abrasion resistance, thermal properties, flame retardancy, and barrier properties, by adding various additives or altering the morphology or structure of the plastic. The aim is to meet the specific performance requirements of particular applications while reducing costs and improving production efficiency. Plastic modification methods can be broadly classified into physical and chemical methods. Physical methods mainly improve performance by adding substances or blending with other resins; chemical methods mainly modify the morphology and structure through chemical reactions.

[0003] The manufacturing process of traditional modified engineering plastics, exemplified by patent CN114957979B, relies on virgin granular materials as starting materials and primarily achieves modification through adjusting screw process parameters. However, due to the batch feeding method, batch-to-batch variations are unavoidable, directly leading to inconsistencies in product quality, specifically manifested as lower physical properties. Furthermore, the granular raw materials used in traditional technologies must undergo a transformation from solid to molten state during modification, i.e., a remelting process. This not only increases energy consumption and production costs but also involves high-temperature degradation, potentially damaging the product's physicochemical properties and thus reducing product quality.

[0004] Patent application CN101016411A discloses an online modification production method for engineering plastics: molten polymer of a certain molecular weight obtained through continuous polymerization is directly fed online to a screw extruder. Appropriate additives are added according to product requirements, and the polymer is uniformly mixed and extruded through the screw extruder. This method is only suitable for modifying molten polymers produced by continuous polymerization, requiring a high-capacity, high-performance screw extruder, resulting in high equipment costs and a large footprint. It cannot perform blending modification operations. Furthermore, this method does not optimize the material feeding and metering device, leading to material accumulation and deterioration in the pipelines after long-term operation, resulting in impurities in the product, such as yellow and black spots.

[0005] Invention patent CN1035546C discloses a method and apparatus for direct and continuous modification of polymer melt. This method involves separating a sidestream melt from the melt stream to be modified, dispersing additives previously added to the melt in a specially designed screw extruder, and then remixing the additive melt aggregate with the melt stream to be modified. However, this method is only applicable to additive modification and cannot be used for blending modification of multiple polymers. Furthermore, this method does not optimize the material conveying and metering device, and during long-term operation, material residues can easily remain in the pipeline, resulting in impurities in the product and the appearance of yellow and black spots. Summary of the Invention

[0006] This invention addresses the technical problems of existing technologies, such as reliance on virgin particulate materials and difficulty in blending and modifying multiple polymers, by providing a plastic production system and method. This invention enables direct and continuous blending and modification of polymers, allowing for the addition of additives during blending processes in various polymerization reactors to more flexibly alter and enhance product performance.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a plastic production system, which includes a first mixing device, a main pipeline, and a second mixing device;

[0009] The first mixing device is provided with the following components sequentially along the material flow direction:

[0010] The first feed inlet is used to add additives;

[0011] The second feed port is connected to an openable or closable melt feed pipe for feeding the melt of the first polymer;

[0012] Third feed inlet and mixing outlet;

[0013] The main pipeline includes a first branch pipe and a second branch pipe that can be opened or closed. The first branch pipe is connected to the third inlet and is used to input the melt of the second polymer into the third inlet.

[0014] The second mixing device is located downstream of the mixing outlet and the main pipeline, and is connected to the mixing outlet via the discharge pipeline, and to the main pipeline via the second branch pipe.

[0015] In this invention, the first mixing device may be a screw extruder.

[0016] The screw extruder can be divided into 6-8 zones according to temperature; the first feed inlet is located in the first zone along the material flow direction; the second feed inlet is located in the second zone along the material flow direction; and the third feed inlet is located in the third zone along the material flow direction.

[0017] The screw diameter of the screw extruder can be 50-150 mm, for example 75 mm.

[0018] The length-to-diameter ratio of the screw in the screw extruder can be (20-50): 1, and more preferably (30-40): 1.

[0019] In this invention, the second mixing device can be a dynamic mixer or a static mixer.

[0020] In this invention, an injection valve may be provided on the discharge pipe.

[0021] The injection valve and the discharge pipe can be connected by a flange.

[0022] In this invention, the mixing outlet and the discharge pipe can be connected by a flange.

[0023] In this invention, the second branch pipe and the feed inlet of the second mixing device can be connected by a flange.

[0024] In this invention, the first branch pipe and the third feed inlet can be connected by a flange.

[0025] In this invention, the first branch pipe and the main pipe can be connected by a flange.

[0026] The flange connection can be a quick-connect flange.

[0027] In this invention, the first inlet can be connected to the additive feed pipe.

[0028] In this invention, the end of the additive feed pipe furthest from the first feed inlet can be connected to the outlet of the additive feeding device. The additive feeding device may be equipped with a metering module.

[0029] In this invention, the end of the melt feed pipe furthest from the second feed port can be connected to the outlet of the first final polymerization reactor.

[0030] In this invention, the discharge port of the first final polymerization reactor may be equipped with a first bottom valve.

[0031] Preferably, the first bottom valve is an electric top-bottom valve.

[0032] In this invention, the first bottom valve can be connected to the melt feed pipe via a flange.

[0033] Preferably, the first bottom valve is connected to the first elbow via a flange, and the first elbow is connected to the melt feed pipe.

[0034] In this invention, a first metering device may be provided on the melt feed pipe.

[0035] The first metering device is preferably a melt metering pump or a combination of a melt pump and a flow meter.

[0036] In this invention, the inlet and outlet of the first metering device can preferably be connected to the melt feed pipe via flanges.

[0037] The flange connection can be a quick-connect flange.

[0038] In this invention, the inlet of the main pipeline can be connected to the outlet of the second final polymerization reactor.

[0039] In this invention, the discharge port of the second final polymerization reactor may be equipped with a second bottom valve.

[0040] The second bottom valve is preferably an electric top-bottom valve.

[0041] In this invention, the second bottom valve can be connected to the main pipeline via a flange.

[0042] Preferably, the second bottom valve is connected to the second elbow via a flange, and the second elbow is connected to the main pipeline.

[0043] The flange connection can be a quick-connect flange.

[0044] In this invention, a second metering device may be provided on the main pipeline.

[0045] The second metering device is preferably a melt metering pump or a combination of a melt pump and a flow meter;

[0046] In this invention, the inlet and outlet of the second metering device can preferably be connected to the main pipeline via flanges.

[0047] In this invention, the main pipeline can be perpendicular to the ground.

[0048] In this invention, a cleaning outlet may be provided on the second branch pipe.

[0049] The cleaning outlet can be located between the connection between the discharge pipe and the main pipe and the second mixing device.

[0050] Secondly, the present invention provides a plastic production method, which employs the plastic production system described above, and controls the opening or closing of the melt feed pipe and the first branch pipe to switch between at least the following operating conditions:

[0051] ①In the first operating condition where the melt feed pipe is open and the first branch pipe is closed, the plastic production method includes the following steps:

[0052] The additive is added to the first feed inlet, the first polymer melt is added to the second feed inlet, and the second polymer melt is added to the main pipeline;

[0053] The additive and the first polymer melt are mixed evenly in the first mixing device, and the resulting mixture is discharged through the mixing outlet and then enters the second mixing device through the discharge pipe, where it is mixed evenly with the second polymer melt added to the second mixing device through the second branch pipe.

[0054] ②In the second operating condition where the melt feed pipe and the first branch pipe are open, the plastic production method includes the following steps:

[0055] The additive is added to the first feed inlet, the first polymer melt is added to the second feed inlet, and the second polymer melt is added to the main pipeline;

[0056] The additive, the first polymer melt, and a portion of the second polymer melt are mixed evenly in the first mixing device. The resulting mixture is discharged through the mixing outlet and then enters the second mixing device through the discharge pipe, where it is mixed evenly with the remaining second polymer melt added to the second mixing device through the second branch pipe.

[0057] ③ In condition three, where the first branch pipe is open and the melt feed pipe is closed, the plastic production method includes the following steps:

[0058] The additive is added to the first feed inlet, and the second polymer melt is added to the main pipeline;

[0059] The additive and a portion of the second polymer melt are mixed evenly in the first mixing device. The resulting mixture is discharged through the mixing outlet and then enters the second mixing device through the discharge pipe, where it is mixed evenly with the remaining second polymer melt added to the second mixing device through the second branch pipe.

[0060] In this invention, the first polymer may be a polyamide. Preferably, the polyamide is PA6, PA66, PA MXD6, PA MXD10, PA MXD12, PA610, PA612, PA410, or a PA66-PA610 copolymer.

[0061] In this invention, the relative viscosity of the first polymer can be 2-2.7, for example 2.0-2.2.

[0062] In this invention, the density of the first polymer at 25°C can be 1.20-1.25 g / mL, for example 1.21 g / mL.

[0063] In this invention, the melting point of the first polymer can be 230-240°C, for example 232-238°C.

[0064] In this invention, the second polymer may be a polyamide. Preferably, the polyamide is PA6, PA66, PA MXD6, PA MXD10, PA MXD12, PA610, PA612, PA410, or a PA66-PA610 copolymer.

[0065] In this invention, the relative viscosity of the second polymer can be 2-3.2, for example 2.5-2.7 or 2.4-2.6.

[0066] In this invention, the density of the second polymer at 25°C can be 1.12-1.15 g / mL.

[0067] In this invention, the melting point of the second polymer can be 210-260°C, for example 247-253°C or 217-223°C.

[0068] In this invention, the first polymer and the second polymer may be different polyamides.

[0069] In this invention, the additive may be one or more of glass fiber, antioxidant, coupling agent, lubricant, montmorillonite, elastomer and antiblocking agent, and optionally the first polymer and / or the second polymer.

[0070] Preferably, the glass fiber is a short glass fiber or a long glass fiber. The length of the short glass fiber is preferably 1-3 mm.

[0071] The antioxidant is preferably a phosphite antioxidant or a hindered phenolic antioxidant.

[0072] The coupling agent is preferably a silane coupling agent, such as KH550 or KH560.

[0073] The elastomer is preferably a nylon elastomer, a polyolefin elastomer, or a polyethylene octene co-elastomer.

[0074] The anti-blocking agent is preferably talc, diatomaceous earth, or silica.

[0075] The lubricant is preferably polyethylene wax.

[0076] Preferably, the montmorillonite is nano-montmorillonite.

[0077] In this invention, in either the first or second operating condition, the mass flow rate ratio of the additive to the first polymer melt can be (0.1-2):1, for example, 0.7:5.7, 1.5:6, or 8:5.7.

[0078] In this invention, in either working condition one or working condition two, the mass flow rate ratio of the second polymer melt introduced into the main pipeline to the first polymer melt can be (1-4):1, for example 15:5.7, 15:6 or 14.3:5.7.

[0079] In this invention, in the first operating condition, the mass flow rate of the second polymer melt introduced into the main pipeline can be greater than the mass flow rate of the first polymer melt.

[0080] In this invention, preferably, in the second operating condition, the mass flow rate of the second polymer melt introduced into the main pipeline is greater than the mass flow rate of the first polymer melt, and the mass flow rate of the first polymer melt is greater than the mass flow rate of the second polymer melt introduced into the first branch pipe.

[0081] In this invention, the mass flow rate ratio of the first polymer melt to the second polymer melt introduced through the first branch pipe can be (0.5-3):1, for example 5.7:3;

[0082] In this invention, in the second or third working condition, the mass flow rate ratio of the additive to the second polymer melt introduced through the first branch pipe can be (0.1-3):1, for example 1.5:6, 8:3 or 8:5.7;

[0083] In this invention, in the second or third working condition, the mass flow rate ratio of the second polymer melt entering the main pipeline to the second polymer melt entering the first branch pipeline can be (1.5-6):1, preferably (2-6):1, for example 21:6, 15:3 or 20.7:5.7.

[0084] In this invention, when the first mixing device is a screw extruder, the temperature of the first zone along the material flow direction on the screw extruder can be 220-240℃.

[0085] In this invention, when the first mixing device is a screw extruder, the temperature of the second zone along the material flow direction on the screw extruder can be 235-240℃.

[0086] In this invention, when the first mixing device is a screw extruder, the temperature of the third zone along the material flow direction on the screw extruder can be 240-250℃.

[0087] In this invention, when the first mixing device is a screw extruder, the temperature of the fourth zone along the material flow direction on the screw extruder can be 250-265℃.

[0088] In this invention, when the first mixing device is a screw extruder, the temperature of the fifth zone along the material flow direction on the screw extruder can be 260-280℃.

[0089] In this invention, when the first mixing device is a screw extruder, the temperature of the sixth zone along the material flow direction on the screw extruder can be 250-290℃.

[0090] In this invention, when the first mixing device is a screw extruder, the temperature of the 7th zone along the material flow direction on the screw extruder can be 235-240℃.

[0091] In this invention, when the first mixing device is a screw extruder, the temperature of the 8th zone along the material flow direction on the screw extruder can be 220-230℃.

[0092] In this invention, when the first mixing device is a screw extruder, the speed of the screw extruder can be 300-900 rpm, preferably 550-600 rpm.

[0093] In this invention, when the first mixing device is a screw extruder, the vacuum degree of the screw extruder can be 0.05-0.09 MPa, preferably 0.05-0.07 MPa.

[0094] In this invention, the plastic production method may further include a fourth condition where the melt feed pipe and the first branch pipe are closed, comprising the following steps:

[0095] The additive is added to the first feed inlet, and the second polymer melt is added to the main pipeline;

[0096] The additive is discharged through the mixing outlet and then enters the second mixing device through the discharge pipe, where it is mixed evenly with the second polymer melt added to the second mixing device through the second branch pipe.

[0097] Without violating common sense in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0098] The reagents and raw materials used in this invention are all commercially available.

[0099] The positive and progressive effects of this invention are as follows:

[0100] (1) The plastic production system of the present invention can flexibly adjust the use of relevant pipelines and valves, and can quickly and conveniently obtain the required modified products and blended products, reducing unqualified products; it is possible to produce various types of engineering plastic products on a single production line at the same time.

[0101] (2) The plastic production system of the present invention has a small overall size, which reduces costs and can be used for both intermittent and continuous production. It has a wider range of applications. After passing through the plastic production system, the plastic does not necessarily go directly into the pelletizer. It can go into the solvent-based or melt-casting machine to make films.

[0102] (3) In the plastic production system of the present invention, the melt pump has a metering function, which can realize accurate metering of the molten modified melt; the main pipeline is vertical, and the material is discharged as much as possible by gravity, preventing it from accumulating at pipe bends or "dead zones"; a screen changer can be installed in the metering device to filter the polyamide melt and reduce the impurities contained in the melt.

[0103] (4) In the plastic production system of the present invention, unqualified polymer chips can be added to the additive feeding device for recycling. The irregular material generated in the unmodified polymer product is fed into the additive feeding device and remelted in the feeder for the production of blended modified products.

[0104] (5) In the plastic production system of the present invention, the pipes and flanges between the equipment can be quickly disassembled. For example, the top and bottom valve outlets of the reactor, the inlet and outlet of the melt pump, the inlet and outlet of the injection valve and the inlet of the mixer are all made of quick-connect flanges. At the same time, prefabricated spare pipes and flanges that can be replaced are prepared. When yellow and black spots are found in the product, clean spare pipes can be used to quickly replace the material residue pipes to continue production. The material residue pipes can be reused after being calcined, cleaned and other treatments.

[0105] (6) In the plastic production system of the present invention, a cleaning outlet can be provided in the second branch pipe. The cleaning liquid can be added to the reactor to complete the cleaning, and then expelled by nitrogen gas. At the same time, the pipe fittings can be cleaned, and it can also be used as the discharge of nitrogen purging gas.

[0106] (7) The plastic production method of the present invention can realize the switching operation of blending and modifying two polymer melts and modifying a single melt with additives, and the range of selectable raw materials, process indicators and ranges are relatively wide. Attached Figure Description

[0107] Figure 1 This is a schematic diagram of the plastic production system in Example 1;

[0108] The numbers in the diagram indicate: 1. Additive feeding device; 2. First final polymerization reactor; 3. Screw extruder; 36. Discharge pipe; 4. Second final polymerization reactor; 5. Mixer; 6. Injection valve; 7. Main pipe; 73. First branch pipe; 75. Second branch pipe. Detailed Implementation

[0109] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0110] The basic information about the raw materials used in the following embodiments and application examples is as follows:

[0111] Fiberglass, 1-3 mm in length and 9-13 μm in diameter, was purchased from Hengshi Fiber Base Co., Ltd. of Zhenshi Group.

[0112] Antioxidant, model 1098;

[0113] Coupling agent, model KH560;

[0114] Lubricant, polyethylene wax, purchased from Honeywell, model A-C6A.

[0115] The elastomer, polyethylene octene co-elastomer (POE), was purchased from Dow Chemical Company, USA, model number 7467.

[0116] Anti-blocking agent, silica, purchased from Shunde New Materials Co., Ltd., model TAISIL 100.

[0117] Polyamide (MXD6) is prepared by sequentially passing m-phenylenediamine and adipic acid in a mass ratio of 100:110.53 through an amidation reactor, a prepolymerization reactor, and a first final polymerization reactor 2. The feed temperature of m-phenylenediamine and adipic acid is 25-30℃. The amidation reaction in the amidation reactor is at 135℃, with a residence time of 0.5 h and a pressure of 0.3 MPa. The prepolymerization reaction in the prepolymerization reactor is at 230℃, with a pressure of 0.6 MPa and a residence time of 2 h. The final polymerization reaction in the first final polymerization reactor 2 is at 235-240℃, with a pressure of -0.1 MPa and a residence time of 1.5 h. MXD6 has a melting point of 235±3℃, a relative viscosity of 2.1±0.1, and a density of approximately 1.21 g / mL at 25℃.

[0118] PA66, prepared from hexamethylenediamine and adipic acid, can ultimately be obtained in the second final polymerization reactor 4, with the molecular formula (C... 10 H 22 N2O2) n Melting point 250±3℃, density 1.15 g / mL at 25℃, relative viscosity 2.5-2.7.

[0119] PA6, polymerized from caprolactam, can ultimately be obtained in the second final polymerization reactor 4, with the molecular formula (C6H). 11 NO) nIt has a melting point of 220±3℃, a density of about 1.12 g / mL at 25℃, and a relative viscosity of 2.5±0.1.

[0120] Relative viscosity: The ratio of the viscosity of a polymer solution to the viscosity of a pure solvent at the same temperature; it is a dimensionless quantity. Reference standard: GB / T 12006.1-2009.

[0121] Example 1

[0122] A plastic production system, such as Figure 1 It includes an additive feeding device 1, a first final polymerization reactor 2, a screw extruder 3, a second final polymerization reactor 4, and a mixer 5. The screw extruder 3 is provided with a first feed inlet, a second feed inlet, a third feed inlet, and a mixing outlet in sequence along the material flow direction.

[0123] In this embodiment, the outlet of the additive feeding device 1 is connected to the first inlet of the screw extruder 3 via an additive feed pipe. The outlet of the first final polymerization reactor 2 is connected to the second inlet of the screw extruder 3 via a melt feed pipe. The outlet of the second final polymerization reactor 4 is connected to the inlet of the mixer 5 via a main pipe 7 and a second branch pipe 75. The mixing outlet of the screw extruder 3 is connected to the second branch pipe 75 via an outlet pipe 36. An injection valve 6 is provided on the outlet pipe 36 to control the flow in the outlet pipe 36. A portion of the injection valve 6 may be installed on the second branch pipe 75, but it does not control the second branch pipe 75. The main pipe 7 is connected to the third inlet of the screw extruder 3 via a first branch pipe 73.

[0124] In this embodiment, the screw extruder 3 is divided into six zones sequentially along the material flow direction according to different temperatures. In other embodiments, there may also be a seventh and eighth zone. The first feed inlet is located in the first zone; the second feed inlet is located in the second zone; and the third feed inlet is located in the third zone. The discharge port of the mixer 5 is connected to the feed port of the cutter through a product pipe. In this embodiment, the mixer 5 is a static mixer. In other embodiments, the mixer 5 is a dynamic mixer. In this embodiment, the cutter is an underwater strip pelletizer. In other embodiments, the cutter is a dry-cut pelletizer or a casting machine.

[0125] In this embodiment, the additive feeding device 1 is equipped with a weighing module. In this embodiment, solid additives and / or solid product slices can be added to the additive feeding device 1. The solid product slices can be irregularly shaped materials that are not modified product slices.

[0126] In this embodiment, a melt metering pump (i.e., the first metering device) is installed on the melt feed pipe. In this embodiment, a melt metering pump (i.e., the second metering device) is installed on the main pipe 7. The melt metering pump has a metering function, enabling accurate metering of the molten polymer. In this embodiment, a screen changer is installed at the outlet of the melt metering pump to filter the polymer melt and reduce impurities in the melt. In other embodiments, the melt metering pump can be replaced by a combination of a conventional melt pump, a flow meter, and a regulating valve.

[0127] In this embodiment, the discharge port of the first final polymerization reactor 2 is equipped with an electric top and bottom valve (i.e., the first bottom valve), which is connected to the first elbow via a quick-connect flange. The first elbow is connected to the melt feed pipe. In this embodiment, the inlet and outlet of the melt metering pump on the melt feed pipe are connected to the melt feed pipe via quick-connect flanges. In this embodiment, the discharge port of the second final polymerization reactor 4 is equipped with an electric top and bottom valve (i.e., the second bottom valve), which is connected to the second elbow via a quick-connect flange. The second elbow is connected to the main pipeline 7. In this embodiment, the inlet and outlet of the melt metering pump on the main pipeline 7 are connected to the main pipeline 7 via quick-connect flanges. In this embodiment, the main pipeline 7 is connected to the feed port of the mixer 5 via a quick-connect flange. In this embodiment, the product pipeline is connected to the discharge port of the mixer 5 via a quick-connect flange. In this embodiment, the injection valve 6 is connected to the discharge pipeline 36 via a quick-connect flange; the mixing discharge port of the screw extruder 3 is connected to the discharge pipeline 36 via a quick-connect flange; and the second branch pipe 75 is connected to the feed port of the mixer 5 via a quick-connect flange.

[0128] In this embodiment, the main pipe 7 is vertically arranged, utilizing gravity to discharge materials as much as possible and prevent accumulation at pipe bends or "dead zones." In other embodiments, the electric top and bottom valves can be replaced with other types of bottom valves or discharge valves. In this embodiment, the flanges connecting the pipes between devices can be quickly disassembled, and prefabricated spare pipes and flanges are available for replacement. When yellow or black spots are found in the product, clean spare pipes can be quickly used to replace the pipes with residual material to continue production. The pipes with residual material can be reused after calcination, cleaning, and other treatments.

[0129] In this embodiment, a cleaning outlet can be provided on the second branch pipe 75, between the connection between the discharge pipe 36 and the second branch pipe 75 and the mixer 5. Ethylene glycol cleaning solution can be added to the reactor to complete the cleaning, and nitrogen gas can be used to pressurize and discharge the nitrogen purging gas. At the same time, it can clean the second bottom valve, discharge pipe, melt metering pump and injection valve and other pipe fittings.

[0130] Example 2

[0131] A control method for a plastic production system, using the plastic production system of Example 1, wherein the polymer melt in the first final polymerization reactor 2 can be mixed with the additives in the additive feeding device 1, and after being melted and mixed by the screw extruder 3, a molten modified melt is produced. The polymer melt in the second final polymerization reactor 4 is pressurized by the melt metering pump (i.e., the second metering device) in the main pipeline 7 and then fed into the mixer 5. The polymer melt in the second final polymerization reactor 4 can also be added to the screw extruder 3 through the first branch pipe 73. In general, the following operating conditions can be distinguished:

[0132] Operating condition one, the specific operation is as follows: Open the additive feed pipe, melt feed pipe, main pipe 7 and discharge pipe 36, and close the first branch pipe 73. The first polymer melt in the first final polymerization reactor 2 is mixed with the additive from the additive feeding device 1, and after being melted and mixed by the screw extruder 3, a molten modified melt is produced; then, the second polymer melt in the second final polymerization reactor 4 is mixed with the modified melt flowing out from the discharge pipe 36 in the mixer 5.

[0133] Operating condition two, the specific operation is as follows: Open the additive feed pipe, melt feed pipe, main pipe 7, discharge pipe 36 and first branch pipe 73. The first polymer melt in the first final polymerization reactor 2 and part of the second polymer melt in the second final polymerization reactor 4 are mixed with the additive from the additive feeding device 1, and after being melted and mixed by the screw extruder 3, a molten modified melt is produced; then, the remaining second polymer melt in the second final polymerization reactor 4 is mixed with the modified melt flowing out from the discharge pipe 36 in the mixer 5.

[0134] Operating condition three, the specific operation is as follows: Open the additive feed pipe, main pipe 7, discharge pipe 36 and first branch pipe 73, and close the melt feed pipe. The first final polymerization reactor 2 does not discharge. Part of the second polymer melt in the second final polymerization reactor 4 is mixed with the additive from the additive feeding device 1, and after being melted and mixed by the screw extruder 3, a molten modified melt is produced; then, the remaining second polymer melt in the second final polymerization reactor 4 is mixed with the modified melt flowing out from the discharge pipe 36 in the mixer 5.

[0135] Operating condition four, the specific operation is as follows: the melt feed pipe and the first branch pipe 73 are closed, the additive is added to the first feed port, and the second polymer melt is added to the main pipe 7; the additive is discharged through the mixing outlet, and then enters the mixer 5 through the discharge pipe 36, and is mixed evenly with the second polymer melt added to the mixer 5 through the second branch pipe 75.

[0136] Operating condition 5, the specific operation is as follows: Open the main pipe 7, and close the additive feed pipe, melt feed pipe, discharge pipe 36 and the first branch pipe 73. The polymer melt in the second final polymerization reactor 4 is directly sent to the pelletizer.

[0137] Application Example 1: Working Condition 1 in Example 2

[0138] 457 kg of short glass fiber, 2.4 kg of antioxidant 1098, 15.4 kg of coupling agent KH560, and 5.2 kg of lubricant polyethylene wax are first mixed evenly in a mixer to form an additive, which is then added to the additive feeding device 1 and fed into the screw extruder 3 at a speed of 8 kg / min.

[0139] The polyamide (MXD6) discharged from the first final polymerization reactor 2 is fed into the screw extruder 3 at a rate of 5.7 kg / min via a melt metering pump (i.e., the first metering device). The additives are added from the first zone, and the polyamide (MXD6) is added from the second zone.

[0140] Screw extruder 3 has a processing capacity of over 830 kg / h, a screw diameter of 75 mm, and a length-to-diameter ratio of 40:1. The temperatures in each zone are: Zone 1 220℃, Zone 2 235℃, Zone 3 250℃, Zone 4 265℃, Zone 5 280℃, and Zone 6 290℃. The speed is set at 600 rpm for melt blending extrusion. The vacuum level is -0.07 MPa. Additives and molten polyamide (MXD6) are mixed in screw extruder 3 to form a modified melt.

[0141] PA66 obtained in the second final polymerization reactor 4 is discharged at a rate of 15 kg / min via a melt metering pump (i.e., the second metering device) and mixed with the modified melt flowing out from the discharge pipe 36 in the mixer 5.

[0142] The resulting mixed product was sent to an underwater pelletizer for slicing, and the resulting product was cylindrical with a diameter of φ3.0×3.0 mm ±5%.

[0143] Application Example 2: Working Condition 1 in Example 2

[0144] The coupling agent KH560, 28.8 kg, polyethylene octene co-elastomer, 47.7 kg, lubricant polyethylene wax, 4.5 kg, antioxidant 1098, 4.5 kg, and anti-blocking agent silica, 4.5 kg, are first mixed evenly in a mixer to form an additive. This additive is then added to the additive feeding device 1 and fed into the screw extruder 3 at a speed of 1.5 kg / min.

[0145] The polyamide (MXD6) discharged from the first final polymerization reactor 2 is fed into the screw extruder 3 at a rate of 6 kg / min via a melt metering pump (i.e., the first metering device). Additives are added from the first zone, and polyamide (MXD6) is added from the second zone.

[0146] Screw extruder 3 has a processing capacity of over 450 kg / h, a screw diameter of 65 mm, and a length-to-diameter ratio of 35:1. The temperatures of each zone are: Zone 1 240℃, Zone 2 240℃, Zone 3 240℃, Zone 4 250℃, Zone 5 260℃, Zone 6 250℃, Zone 7 240℃, and Zone 8 230℃. The speed is set at 550 rpm for melt blending extrusion. The vacuum degree is -0.07 MPa. Additives and molten polyamide (MXD6) are mixed in screw extruder 3 to form a modified melt.

[0147] The PA6 product obtained in the second final polymerization reactor 4 is mixed in the mixer 5 with the modified melt flowing out from the discharge pipe 36 at a rate of 15 kg / min by a melt metering pump (i.e., the second metering device).

[0148] The resulting mixed product was sent to an underwater pelletizer for slicing, and the resulting product was cylindrical with a diameter of φ3.0×3.0 mm ±5%.

[0149] Application Example 3: Working Condition 2 in Example 2

[0150] The difference from Application Example 1 is that a portion of the PA66 obtained in the second final polymerization reactor 4 enters the screw extruder 3 at a rate of 3 kg / min through the first branch pipe 73, where it is mixed with additives and molten polyamide (MXD6) to form a modified melt. The additives are added from the first zone, the polyamide (MXD6) is added from the second zone, and the PA66 from the first branch pipe 73 is added from the third zone.

[0151] The remaining PA66 obtained in the second final polymerization reactor 4 is mixed with the modified melt flowing out from the discharge pipe 36 in the mixer 5 at a rate of 12 kg / min.

[0152] The PA66 discharged through the first branch pipe 73 can be premixed with MXD6 and additives in the screw extruder 3, so that when mixed in the mixer 5, the additives and MXD6 are better distributed in the PA66 main material, resulting in better overall material performance.

[0153] Application Example 4: Working Condition 3 in Example 2

[0154] The difference from Application Example 1 is that the first final polymerization reactor 2 does not produce output, and a portion of the PA66 obtained in the second final polymerization reactor 4 enters the screw extruder 3 through the first branch pipe 73 at a rate of 5.7 kg / min, where it is mixed with additives to form a modified melt.

[0155] By adjusting the melt metering pump (i.e. the second metering device), the remaining PA66 after being diverted through the first branch pipe 73 in the main pipeline 7 is still discharged at a rate of 15 kg / min and mixed evenly by the mixer 5.

[0156] Application Example 5: Working Condition 5 in Example 2

[0157] Additive feeding device 1 and first final polymerization reactor 2 do not produce output. The PA66 obtained in the second final polymerization reactor 4 is discharged at a rate of 15 kg / min via melt metering pump (i.e., second metering device) and sent to underwater pelletizer for slicing. The resulting product is cylindrical φ3.0×3.0 mm±5%.

[0158] Application Example 6: Working Condition 1 in Example 2

[0159] The difference from Application Example 1 is that the additive feeding device 1 also adds 40 kg of the product produced in Application Example 5, which is pelleted and does not meet the size requirements, to the screw extruder 3 at a rate of 0.7 kg / min.

[0160] PA66 obtained in the second final polymerization reactor 4 is discharged at a rate of 14.3 kg / min via a melt metering pump (i.e., the second metering device) and mixed with the modified melt flowing out from the discharge pipe 36 in the mixer 5.

[0161] Application Example 7: Working Condition 3 in Example 2

[0162] The difference from Application Example 2 is that the first final polymerization reactor 2 does not produce output, and a portion of the PA6 obtained in the second final polymerization reactor 4 enters the screw extruder 3 through the first branch pipe 73 at a speed of 6 kg / min, where it is mixed with additives to form a modified melt.

[0163] By adjusting the melt metering pump (i.e. the second metering device), the remaining PA6 after being diverted through the first branch pipe 73 in the main pipeline 7 is still discharged at a rate of 15 kg / min and mixed evenly by the mixer 5.

[0164] In the above application examples 1-7, after running for a period of time or a certain batch, generally 1 to 2 weeks, ethylene glycol is added to the first final polymerization reactor 2 and the second final polymerization reactor 4 for cleaning. The cleaning is discharged through the cleaning outlet on the main pipeline 7. The pipeline connecting the equipment and the flange are quickly disassembled through quick-connect flanges. After being quickly replaced with clean spare pipe fittings, production continues. The pipelines with material residue are calcined and cleaned at a high temperature of above 330°C and then reused.

[0165] Comparative Application Example 1

[0166] 457 kg of short glass fiber, 2.4 kg of antioxidant 1098, 15.4 kg of coupling agent KH560, and 5.2 kg of lubricant polyethylene wax, 900 kg of PA66, and 342 kg of MXD6 were added to a mixer and stirred for 10 min at 85°C and a stirring speed of 250 r / min to obtain a mixture.

[0167] The mixture is fed into a twin-screw extruder via an automatic feeding device for mixing and extrusion. The twin-screw extruder has a processing capacity of over 1725 kg / h. The mixture is then cooled and granulated by a subsequent pelletizer.

[0168] Comparative Application Example 2

[0169] The coupling agent KH560, 28.8 kg, polyethylene octene elastomer, 47.7 kg, lubricant polyethylene wax, 4.5 kg, antioxidant 1098, 4.5 kg, anti-blocking agent silica, MXD6, 360 kg, and PA6, 900 kg are mixed in a mixer. The mixture is then fed into a twin-screw extruder through an automatic feeding device for mixing and extrusion. After that, it is cooled and granulated by a subsequent pelletizer. The twin-screw extruder has a processing capacity of over 1350 kg / h.

[0170] Comparative application example 2-1

[0171] The difference from Comparative Application Example 2 is that the mixture (PA6, MXD6 and additives other than the first two) is added to the twin-screw extruder for extrusion by controlling a certain feeding speed of 22.5 kg / min through an automatic feeding device. The twin-screw extruder has a processing capacity of over 1350 kg / h.

[0172] Comparative Application Example 3

[0173] The difference from Application Example 1 is that the pipeline between the equipment is only connected by ordinary flanges, without a screen changer, without a cleaning outlet in the second branch pipe 75, and without cleaning, disassembly, calcination or other operations. After two weeks of production, yellow and black spots were found in the product.

[0174] Comparative Application Example 4

[0175] The difference from Application Example 1 is that the pipeline between the equipment is only connected by ordinary flanges, without screen changers, without cleaning outlets in the second branch pipe 75, and without cleaning, disassembly, calcination and other operations. After four weeks of production, yellow and black spots were found in the product.

[0176] Effect Example

[0177] 1. Test objects: Plastic products obtained from Application Examples 1-7 and Comparative Application Examples 1-4.

[0178] 2. Testing Method:

[0179] (1) Tensile strength: Tested according to the test standard ASTM D638;

[0180] (2) Bending strength: tested according to ASTM / D790;

[0181] (3) Elongation at break: The elongation at break shall be tested in accordance with ISO 527-2 / 50;

[0182] (4) Melt flow index: Tested according to ASTM D1238;

[0183] (5) Notched impact strength of cantilever beam: tested according to ASTM / D256;

[0184] (6) Colorimetric: The difference was obtained directly from the polymer slices without processing using the x-rite Ci7600.

[0185] (7) Water absorption rate: tested according to ISO 62.

[0186] (8) Oxygen permeability: Tested according to ASTM D3985.

[0187] 3. The test results are shown in the table below:

[0188]

[0189]

[0190] By comparing Application Example 1 and Application Example 2 with Comparative Application Example 1 and Comparative Application Example 2, it can be seen that the present invention can achieve continuous online blending modification of two polymer melts and additives.

[0191] By comparing Application Example 1 and Application Example 3, it can be seen that the present invention can improve the distribution of each component in the product by premixing the polymer and additives through the first branch pipe, thereby improving the overall performance of the material and resulting in a product with higher tensile strength, flexural strength and lower water absorption.

[0192] As can be seen from Application Examples 1-5, the present invention can realize the flexible production of various modified and unmodified products.

[0193] Analysis of Example 6 shows that the present invention can realize the recycling and reuse of irregularly shaped materials, achieving performance indicators close to those of the original production process.

[0194]

[0195] By comparing Application Example 1 with Comparative Application Examples 3-4, the present invention can reduce impurities in the product and effectively improve the product's color index.

[0196] In summary, the present invention provides a method for online modification of special engineering plastic melts produced by continuous or intermittent reactors. The engineering plastic melts produced continuously or intermittently from the reactor can be transported to molding equipment through a special feeding and metering system to complete online continuous processing. At the same time, functional additives such as auxiliaries and fillers can be added as needed to achieve online mixing, thereby preparing various modified engineering plastic products.

Claims

1. A plastic production system, characterized in that, It includes a first mixing device, a main pipeline, and a second mixing device; The first mixing device is provided with the following components sequentially along the material flow direction: The first feed inlet is used to add additives; The second feed port is connected to an openable or closable melt feed pipe for feeding the melt of the first polymer; Third feed inlet and mixing outlet; The main pipeline includes a first branch pipe and a second branch pipe that can be opened or closed. The first branch pipe is connected to the third inlet and is used to input the melt of the second polymer into the third inlet. The second mixing device is located downstream of the mixing outlet and the main pipeline, and is connected to the mixing outlet via the discharge pipeline, and to the main pipeline via the second branch pipe; The first mixing device is a screw extruder; the screw extruder is divided into 6-8 zones according to temperature; the first feed inlet is located in the first zone along the material flow direction; the second feed inlet is located in the second zone along the material flow direction; and the third feed inlet is located in the third zone along the material flow direction. The end of the melt feed pipe furthest from the second feed port is connected to the outlet of the first final polymerization reactor; The discharge port of the first final polymerization reactor is equipped with a first bottom valve; The inlet of the main pipeline is connected to the outlet of the second final polymerization reactor; The discharge port of the second final polymerization reactor is equipped with a second bottom valve; An injection valve is provided on the discharge pipe, and the injection valve is used to control the flow in the discharge pipe.

2. The plastic production system according to claim 1, characterized in that, The screw diameter of the screw extruder is 50-150 mm; The length-to-diameter ratio of the screw in the screw extruder is (20-50): 1; The second mixing device is a dynamic mixer or a static mixer; The injection valve and the discharge pipe are connected by a flange. The mixing outlet and the discharge pipe are connected by a flange. The second branch pipe is connected to the feed inlet of the second mixing device by a flange; The first branch pipe is connected to the third inlet by a flange; The first branch pipe is connected to the main pipe by a flange.

3. The plastic production system according to claim 2, characterized in that, The screw diameter of the screw extruder is 75 mm; The length-to-diameter ratio of the screw in the screw extruder is (30-40): 1; The flange connection uses a quick-connect flange.

4. The plastic production system according to claim 1, characterized in that, The first inlet is connected to the additive feed pipe; The end of the additive feed pipe away from the first feed inlet is connected to the outlet of the additive feeding device; The additive feeding device is equipped with a metering module.

5. The plastic production system according to claim 1, characterized in that, The first bottom valve is connected to the melt feed pipe via a flange; The melt feed pipe is equipped with a first metering device.

6. The plastic production system according to claim 5, characterized in that, The first bottom valve is an electrically operated top-bottom valve; The first bottom valve is connected to the first elbow via a flange, and the first elbow is connected to the melt feed pipe; The first metering device is a melt metering pump or a combination of a melt pump and a flow meter; The inlet and outlet of the first metering device are respectively connected to the melt feed pipe via flanges.

7. The plastic production system according to claim 6, characterized in that, The flange connection uses a quick-connect flange.

8. The plastic production system according to claim 1, characterized in that, The second bottom valve is an electrically operated top-bottom valve; The second bottom valve is connected to the main pipeline via a flange; A second metering device is installed on the main pipeline; The main pipeline is perpendicular to the ground; The second branch pipe is provided with a cleaning outlet; the cleaning outlet is located between the connection between the discharge pipe and the main pipe and the second mixing device.

9. The plastic production system according to claim 8, characterized in that, The second bottom valve is connected to the second elbow via a flange, and the second elbow is connected to the main pipeline; The second metering device is a melt metering pump or a combination of a melt pump and a flow meter; The inlet and outlet of the second metering device are connected to the main pipeline via flanges.

10. A method for producing plastics, characterized in that, It employs a plastic production system as described in any one of claims 1-9, controlling the opening and closing of the melt feed pipe and the first branch pipe to switch between at least the following operating conditions: ①In the first operating condition where the melt feed pipe is open and the first branch pipe is closed, the plastic production method includes the following steps: The additive is added to the first feed inlet, the first polymer melt is added to the second feed inlet, and the second polymer melt is added to the main pipeline; The additive and the first polymer melt are mixed evenly in the first mixing device, and the resulting mixture is discharged through the mixing outlet and then enters the second mixing device through the discharge pipe, where it is mixed evenly with the second polymer melt added to the second mixing device through the second branch pipe. ②In the second operating condition where the melt feed pipe and the first branch pipe are open, the plastic production method includes the following steps: The additive is added to the first feed inlet, the first polymer melt is added to the second feed inlet, and the second polymer melt is added to the main pipeline; The additive, the first polymer melt, and a portion of the second polymer melt are mixed evenly in the first mixing device. The resulting mixture is discharged through the mixing outlet and then enters the second mixing device through the discharge pipe, where it is mixed evenly with the remaining second polymer melt added to the second mixing device through the second branch pipe. ③ In condition three, where the first branch pipe is open and the melt feed pipe is closed, the plastic production method includes the following steps: The additive is added to the first feed inlet, and the second polymer melt is added to the main pipeline; The additive and a portion of the second polymer melt are mixed evenly in the first mixing device. The resulting mixture is discharged through the mixing outlet and then enters the second mixing device through the discharge pipe, where it is mixed evenly with the remaining second polymer melt added to the second mixing device through the second branch pipe.

11. The plastic production method according to claim 10, characterized in that, It satisfies at least one of the following conditions: ①The first polymer is polyamide; ② The relative viscosity of the first polymer is 2-2.7; ③ The density of the first polymer at 25°C is 1.20-1.25 g / mL; ④ The melting point of the first polymer is 230-240℃; ⑤ The second polymer is polyamide; ⑥ The relative viscosity of the second polymer is 2-3.2; ⑦ The density of the second polymer at 25°C is 1.12-1.15 g / mL; ⑧ The melting point of the second polymer is 210-260℃; ⑨ The first polymer and the second polymer are different polyamides; ⑩ The additive is one or more of glass fiber, antioxidant, coupling agent, lubricant, montmorillonite, elastomer and antiblocking agent, and optionally the first polymer and / or the second polymer.

12. The plastic production method according to claim 11, characterized in that, It satisfies at least one of the following conditions: ① In the first polymer, the polyamide is PA6, PA66, PA MXD6, PA MXD10, PA MXD12, PA610, PA612, PA410 or a PA66-PA610 copolymer; ② The relative viscosity of the first polymer is 2.0-2.2; ③ The density of the first polymer at 25°C is 1.21 g / mL; ④ The melting point of the first polymer is 232-238℃; ⑤ In the second polymer, the polyamide is PA6, PA66, PA MXD6, PA MXD10, PA MXD12, PA610, PA612, PA410 or a PA66-PA610 copolymer; ⑥ The relative viscosity of the second polymer is 2.5-2.7 or 2.4-2.6; ⑦ The melting point of the second polymer is 247-253℃ or 217-223℃; ⑧ The glass fiber is short glass fiber or long glass fiber; the length of the short glass fiber is 1-3 mm; The antioxidant is a phosphite antioxidant or a hindered phenolic antioxidant; The coupling agent is a silane coupling agent; The elastomer is a nylon elastomer, a polyolefin elastomer, or a polyethylene octene co-elastomer; The anti-blocking agent is talc, diatomaceous earth, or silica. The lubricant is polyethylene wax; The montmorillonite mentioned is nano-montmorillonite.

13. The plastic production method according to claim 12, characterized in that, The coupling agent is KH550 or KH560.

14. The plastic production method according to claim 10, characterized in that, It satisfies at least one of the following conditions: ① In either working condition one or working condition two, the mass flow rate ratio of the additive to the first polymer melt is (0.1-2):1; ② In either working condition one or working condition two, the mass flow rate ratio of the second polymer melt introduced into the main pipeline to the first polymer melt is (1-4):1; ③ In the first operating condition, the mass flow rate of the second polymer melt introduced into the main pipeline is greater than the mass flow rate of the first polymer melt; ④ In the second operating condition, the mass flow rate of the second polymer melt flowing into the main pipeline is greater than the mass flow rate of the first polymer melt, and the mass flow rate of the first polymer melt is greater than the mass flow rate of the second polymer melt flowing into the first branch pipe; the mass flow rate ratio of the first polymer melt to the second polymer melt flowing into the first branch pipe is (0.5-3):

1. ⑤ In either the second or third operating condition, the mass flow rate ratio of the additive to the second polymer melt introduced through the first branch pipe is (0.1-3):1; ⑥ In either working condition two or working condition three, the mass flow rate ratio of the second polymer melt entering the main pipeline to the second polymer melt entering the first branch pipeline is (1.5-6):

1.

15. The plastic production method according to claim 14, characterized in that, It satisfies at least one of the following conditions: ① In either working condition one or working condition two, the mass flow ratio of the additive to the first polymer melt is 0.7:5.7, 1.5:6, or 8:5.7; ② In either working condition one or working condition two, the mass flow ratio of the second polymer melt to the first polymer melt introduced into the main pipeline is 15:5.7, 15:6, or 14.3:5.7; ③ In the second operating condition, the mass flow ratio of the first polymer melt to the second polymer melt introduced through the first branch pipe is 5.7:3; ④ In the second or third operating condition, the mass flow ratio of the additive to the second polymer melt introduced through the first branch pipe is 1.5:6, 8:3, or 8:5.7; ⑤ In either working condition two or working condition three, the mass flow rate ratio of the second polymer melt entering the main pipeline to the second polymer melt entering the first branch pipeline is (2-6):

1.

16. The plastic production method according to claim 15, characterized in that, In either the second or third operating condition, the mass flow ratio of the second polymer melt entering the main pipeline to the second polymer melt entering the first branch pipeline is 21:6, 15:3, or 20.7:5.

7.

17. The plastic production method according to claim 10, characterized in that, When the first mixing device is a screw extruder, it satisfies at least one of the following conditions: ① The temperature of the first zone along the material flow direction on the screw extruder is 220-240℃; ② The temperature of the second zone along the material flow direction on the screw extruder is 235-240℃; ③ The temperature of the third zone along the material flow direction on the screw extruder is 240-250℃; ④ The temperature of the fourth zone along the material flow direction on the screw extruder is 250-265℃; ⑤ The temperature of the fifth zone along the material flow direction on the screw extruder is 260-280℃; ⑥ The temperature of the 6th zone along the material flow direction on the screw extruder is 250-290℃; ⑦ The temperature of the 7th zone along the material flow direction on the screw extruder is 235-240℃; ⑧ The temperature of the 8th zone along the material flow direction on the screw extruder is 220-230℃; ⑨ The screw extruder has a rotational speed of 300-900 rpm; ⑩ The vacuum degree of the screw extruder is 0.05-0.09 MPa.

18. The plastic production method according to claim 17, characterized in that, When the first mixing device is a screw extruder, it satisfies at least one of the following conditions: ① The screw extruder has a rotational speed of 550-600 rpm; ②The vacuum degree of the screw extruder is 0.05-0.07 MPa.

19. The plastic production method according to claim 10, characterized in that, The plastic production method also includes a fourth condition where the melt feed pipe and the first branch pipe are closed, which includes the following steps: The additive is added to the first feed inlet, and the second polymer melt is added to the main pipeline; The additive is discharged through the mixing outlet and then enters the second mixing device through the discharge pipe, where it is mixed evenly with the second polymer melt added to the second mixing device through the second branch pipe.

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