Plastic production system and production method

Abstract

The invention relates to a plastic production system and method. The plastic production system comprises a first mixing device, a main pipeline and a second mixing device. The first mixing equipment is sequentially provided with a first feeding hole, a second feeding hole, a third feeding hole and a fourth feeding hole in the material flowing direction; the second feeding hole is connected with a melt feeding pipe which can be opened or closed and is used for inputting the melt of the first polymer; a third feed port and a mixed discharge port; the main pipeline comprises a first branch pipe and a second branch pipe which can be opened or closed, and the first branch pipe is connected with the third feeding hole and is used for inputting a melt of a second polymer into the third feeding hole; and the second mixing equipment is arranged at the downstream of the mixed discharge hole and the main pipeline, is connected with the mixed discharge hole through a discharge pipeline, and is connected with the main pipeline through a second branch pipe. According to the invention, the polymer is directly and continuously blended and modified, and the additive can be added in the blending process of multiple polymerization kettles to more flexibly change and improve the product performance.

Description

Technical Field

[0001] The invention relates to a plastic production system and a production method. Background Art

[0002] At present, there are few reports on the modification methods for the continuous or intermittent preparation of special engineering plastic products. Engineering plastic modification refers to the addition of various additives, changing the morphology or structure of plastics, etc., to improve or improve certain properties of engineering plastics, such as density, hardness, precision, appearance, processability, transparency, mechanical properties, electromagnetic properties, chemical properties, corrosion resistance, aging resistance, wear resistance, thermal properties, flame retardancy, barrier properties, etc. Its purpose is to meet the special requirements of material properties in specific application fields, while reducing costs and improving production efficiency. The methods of plastic modification can be roughly divided into physical methods and chemical methods. Among them, the physical method mainly improves its performance by adding substances or blending with other resins; the chemical method mainly modifies the morphology and structure through chemical reactions.

[0003] The manufacturing process of traditional engineering plastic modified products represented by patent CN114957979B relies on original granular materials as starting materials, and the modification is mainly achieved by adjusting the screw process parameters. However, since the process adopts a batch feeding method, differences between batches are difficult to avoid, which directly leads to inconsistency in product quality, specifically manifested in low physical properties. In addition, the granular raw materials used in traditional technologies must undergo a transition from solid to molten state during the modified production process, that is, a remelting process, which not only increases energy consumption and production costs, but also involves high-temperature degradation, which may damage the physical and chemical performance indicators of the product, thereby reducing product quality.

[0004] Patent application CN101016411A discloses an online modification production method for engineering plastics: a molten polymer of a certain molecular weight obtained by continuous polymerization is directly sent online to a screw extruder, an appropriate amount of additives is added according to product requirements, and the polymer is uniformly mixed and extruded by a screw extruder. This scheme is only applicable to the production and modification of molten polymers produced by continuous polymerization, and requires a screw extruder with a large processing capacity and relatively good performance, with high equipment cost and large floor space. Blending modification operations cannot be performed. At the same time, this scheme does not optimize the feeding metering device, and the material is easily accumulated and deteriorated in the pipeline after the equipment has been running for a long time, resulting in impurities in the product, and yellow spot material and black spot material appear.

[0005] Invention patent CN1035546C discloses a method and device for directly and continuously modifying a polymer melt, that is, by separating the side stream melt from the melt flow to be modified, dispersing the additives originally added to the melt in a specially designed screw extruder, and then remixing the additive melt with the melt flow to be modified. This solution is also only applicable to additive modification, and cannot be used for blending and modifying multiple polymers. This solution does not optimize the feeding metering device, and the material is also likely to remain in the pipeline during long-term operation, resulting in impurities in the product, and the appearance of yellow spot material and black spot material. Summary of the invention

[0006] The present invention provides a plastic production system and production method to solve the technical problems existing in the prior art, such as reliance on primary granular materials and difficulty in blending and modifying multiple polymers. The present invention enables direct and continuous blending and modification of polymers, and additives can be added during the blending process of multiple polymerization kettles to more flexibly change and improve product performance.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[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:

[0010] A first feed port, for adding additives;

[0011] A second feed port, the second feed port is connected to a melt feed pipe that can be opened or closed, and is used to input the melt of the first polymer;

[0012] A third feed inlet and a mixed discharge outlet;

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

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

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

[0016] Wherein, the screw extruder can be divided into 6-8 zones according to temperature; the first feed port is arranged in the first zone along the material flow direction; the second feed port is arranged in the second zone along the material flow direction; the third feed port is arranged in the third zone along the material flow direction.

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

[0018] The aspect ratio of the screw of the screw extruder may be (20-50):1, preferably (30-40):1.

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

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

[0021] Wherein, the injection valve and the discharge pipe can be connected by flange.

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

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

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

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

[0026] Wherein, the flange connection can adopt a quick-connect flange.

[0027] In the present invention, the first feed port can be connected to an additive feed pipe.

[0028] In the present invention, one end of the additive feeding pipe away from the first feeding port can be connected to the discharge port of the additive feeding device. The additive feeding device can be provided with a metering module.

[0029] In the present invention, one end of the melt feed pipe away from the second feed port can be connected to the discharge port of the first final polymerization reactor.

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

[0031] Wherein, the bottom valve is preferably an electric top and bottom valve.

[0032] In the present invention, the bottom valve can be connected to the melt feed pipe flange.

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

[0034] In the present invention, a metering device may be provided on the melt feeding pipe.

[0035] Wherein, the metering device is preferably a melt metering pump or a combination of a melt pump and a flow meter.

[0036] In the present invention, the inlet and the outlet of the metering device can be respectively connected to the melt feed pipe preferably through flanges.

[0037] Wherein, the flange connection can adopt a quick-connect flange.

[0038] In the present invention, the feed port of the main pipeline can be connected to the discharge port of the second final polymerization reactor.

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

[0040] Wherein, the bottom valve is preferably an electric top and bottom valve.

[0041] In the present invention, the bottom valve can be connected to the main pipeline flange.

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

[0043] Wherein, the flange connection can adopt a quick-connect flange.

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

[0045] Wherein, the metering device is preferably a melt metering pump or a combination of a melt pump and a flow meter;

[0046] In the present invention, the inlet and the outlet of the metering device can be respectively connected to the main pipeline preferably through flanges.

[0047] In the present invention, the main pipeline may be perpendicular to the ground.

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

[0049] Wherein, the cleaning outlet can be arranged between the connection between the discharge pipe and the main pipe and the second mixing device.

[0050] In a second aspect, the present invention provides a plastic production method, which uses the plastic production system as described above to control the opening or closing of the melt feed pipe and the first branch pipe to switch at least the following working conditions:

[0051] ① In the first working condition where the melt feed pipe is opened and the first branch pipe is closed, the plastic production method comprises the following steps:

[0052] Adding the additive to the first feed port, adding the first polymer melt to the second feed port, and adding the second polymer melt to the main pipeline;

[0053] The additive and the first polymer melt are uniformly mixed in the first mixing device, the obtained mixture is discharged through the mixing outlet, and then enters the second mixing device through the discharge pipe, and is uniformly mixed with the second polymer melt added to the second mixing device through the second branch pipe;

[0054] ② In the second working condition where the melt feed pipe and the first branch pipe are opened, the plastic production method comprises the following steps:

[0055] Adding the additive to the first feed port, adding the first polymer melt to the second feed port, and adding the second polymer melt to the main pipeline;

[0056] The additive, the first polymer melt and part of the second polymer melt are uniformly mixed in the first mixing device, the obtained mixture is discharged through the mixing outlet, and then enters the second mixing device through the discharge pipe, and is uniformly mixed with the remaining second polymer melt added to the second mixing device through the second branch pipe;

[0057] ③ In working condition 3, the first branch pipe is opened and the melt feed pipe is closed, the plastic production method comprises the following steps:

[0058] Adding the additive to the first feed port, and adding the second polymer melt to the main pipeline;

[0059] The additive and part of the second polymer melt are mixed uniformly in the first mixing device, and the obtained mixture is discharged through the mixing outlet, and then enters the second mixing device through the discharge pipe, and is mixed uniformly with the remaining second polymer melt added to the second mixing device through the second branch pipe.

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

[0061] In the present invention, the relative viscosity of the first polymer may be 2-2.7, such as 2.0-2.2.

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

[0063] In the present invention, the melting point of the first polymer may be 230-240°C, such as 232-238°C.

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

[0065] In the present invention, the relative viscosity of the second polymer may be 2-3.2, such as 2.5-2.7 or 2.4-2.6.

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

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

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

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

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

[0071] Wherein, the antioxidant is preferably a phosphite antioxidant or a hindered phenol antioxidant.

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

[0073] Wherein, the elastomer is preferably nylon elastomer, polyolefin elastomer or polyethylene octene co-elastomer.

[0074] Wherein, the anti-adhesive agent is preferably talcum powder, diatomaceous earth or silicon dioxide.

[0075] Wherein, the lubricant is preferably polyethylene wax.

[0076] Wherein, the montmorillonite is preferably nano-montmorillonite.

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

[0078] In the present invention, in the operating condition 1 or the operating condition 2, the mass flow ratio of the second polymer melt introduced into the main pipeline to the first polymer melt may be (1-4):1, for example, 15:5.7, 15:6 or 14.3:5.7.

[0079] In the present invention, in the working condition 1, the mass flow rate of the second polymer melt introduced into the main pipeline may be greater than the mass flow rate of the first polymer melt.

[0080] In the present 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 the present invention, the mass flow ratio of the first polymer melt to the second polymer melt introduced into the first branch pipe may be (0.5-3):1, for example, 5.7:3;

[0082] In the present invention, in the working condition 2 or the working condition 3, the mass flow ratio of the additive to the second polymer melt introduced through the first branch pipe may be (0.1-3):1, for example, 1.5:6, 8:3 or 8:5.7;

[0083] In the present invention, in the operating condition 2 or the operating condition 3, the mass flow ratio of the second polymer melt introduced into the main pipeline and the second polymer melt introduced into the first branch pipe can be (1.5-6):1, preferably (2-6):1, for example 21:6, 15:3 or 20.7:5.7.

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

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

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

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

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

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

[0090] In the present invention, when the first mixing device is a screw extruder, the temperature of the seventh zone along the material flow direction of the screw extruder can be 235-240°C.

[0091] In the present invention, when the first mixing device is a screw extruder, the temperature of the eighth zone along the material flow direction of the screw extruder can be 220-230°C.

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

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

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

[0095] Adding the additive to the first feed port, and adding the second polymer melt to the main pipeline;

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

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

[0098] The reagents and raw materials used in the present invention are commercially available.

[0099] The positive and progressive effects of the present invention are:

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

[0101] (2) The plastic production system of the present invention has a small overall size, reduces costs, and can be used for both intermittent and continuous production; the application field is wider, and the plastic does not necessarily need to be directly fed into a pelletizer after passing through the plastic production system, but can be fed into a solvent-based or melt-type casting machine for film production;

[0102] (3) The plastic production system of the present invention has a melt pump with a metering function, which can achieve accurate metering of the molten modified melt; the main pipeline is vertical, and gravity is used to discharge the material as much as possible to prevent accumulation at the bends of the pipe or the "dead zone"; a screen changer can be installed in the metering device to filter the polyamide melt and reduce 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, and the shaped materials generated from the unmodified polymer products can be added to the additive feeding device for remelting in the feeder and then used 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 melt pump inlet and outlet, the injection valve inlet and outlet, and the mixer inlet all use quick-connect flanges, and prefabricated spare pipes and flanges that can be replaced are prepared. When yellow and black spots are found in the product, the remaining pipes can be quickly replaced with clean spare pipes to continue production, and the remaining pipes can be calcined, cleaned, etc. and then kept in standby use;

[0105] (6) In the plastic production system of the present invention, a cleaning outlet can be provided on the second branch pipe, and a cleaning liquid can be added to the reactor to complete the cleaning, and then the nitrogen can be pressed out, and the pipe can be cleaned at the same time, and it can also be used to discharge the nitrogen purge 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 selectable raw material process indicators and range are relatively wide. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0108] As shown in the figure, the symbols are: additive feeding device 1, first final polymerization reactor 2, screw extruder 3, discharge pipe 36, second final polymerization reactor 4, mixer 5, injection valve 6, main pipeline 7, first branch pipe 73, second branch pipe 75. DETAILED DESCRIPTION

[0109] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The experimental methods in the following examples without specifying specific conditions are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0110] In the following embodiments and application examples, the basic conditions of the raw materials used are as follows:

[0111] Glass fiber, length 1-3mm, diameter 9-13μm, purchased from Hengshi Fiber Industry 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 copolymer (POE), was purchased from Dow Chemical Company of the United States, model 7467.

[0116] Anti-adhesive agent, silica, was purchased from Shunde New Materials Company, model TAISIL 100.

[0117] Polyamide (MXD6) is prepared by sequentially passing m-xylenediamine 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-xylenediamine and adipic acid is 25-30°C; the temperature of the amidation reaction in the amidation reactor is 135°C, the residence time is 0.5h, and the pressure is 0.3MPa; the temperature of the pre-polycondensation reaction in the prepolymerization reactor is 230°C, the pressure is 0.6MPa, and the residence time is 2h; the temperature of the final polycondensation reaction in the first final polymerization reactor 2 is 235-240°C, the pressure is -0.1MPa, and the residence time is 1.5h. MXD6: melting point 235±3°C, relative viscosity 2.1±0.1, density at 25°C is about 1.21g / mL.

[0118] PA66, prepared from hexamethylenediamine and adipic acid, can be finally obtained in the second final polymerization reactor 4, with a molecular formula (C 10 H 22 N 2 O 2 ) n , melting point 250±3℃, density 1.15g / mL at 25℃, relative viscosity 2.5-2.7.

[0119] PA6, which is obtained by polymerization of caprolactam, can be finally obtained in the second final polymerization reactor 4, and has a molecular formula (C 6 H 11 NO) n, melting point 220±3℃, density about 1.12g / mL at 25℃, relative viscosity 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, a dimensionless quantity. Reference standard: GB / T 12006.1-2009.

[0121] Example 1

[0122] A plastic production system, such as Figure 1 , comprising 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 port, a second feed port, a third feed port and a mixing outlet in sequence along the material flow direction.

[0123] In this embodiment, the discharge port of the additive feeding device 1 is connected to the first feed port of the screw extruder 3 through the additive feed pipe. The discharge port of the first final polymerization reactor 2 is connected to the second feed port of the screw extruder 3 through the melt feed pipe. The discharge port of the second final polymerization reactor 4 is connected to the feed port of the mixer 5 through the main pipeline 7 and the second branch pipe 75. The mixed discharge port of the screw extruder 3 is connected to the second branch pipe 75 through the discharge pipeline 36, and the discharge pipeline 36 is provided with an injection valve 6. The injection valve 6 is used to control the flow of the discharge pipeline 36. A part 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 pipeline 7 is connected to the third feed port of the screw extruder 3 through the first branch pipe 73.

[0124] In this embodiment, the screw extruder 3 is divided into the first zone, the second zone, the third zone, the fourth zone, the fifth zone and the sixth zone in the material flow direction according to the different temperatures. In other embodiments, there may also be a seventh zone and an eighth zone; the first feed port is arranged in the first zone; the second feed port is arranged in the second zone; the third feed port is arranged in the third zone. The discharge port of the mixer 5 is connected to the feed port of the cutter through a product pipeline. 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 strand 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 provided with a weighing module. In this embodiment, solid additives and / or solid product slices can be added to the additive feeding device 1, and the solid product slices can be shaped materials of unmodified product slices.

[0126] In this embodiment, a melt metering pump is provided on the melt feed pipe. In this embodiment, the main pipeline 7 is provided with a melt metering pump. The melt metering pump has a metering function and can achieve accurate metering of the molten polymer. In this embodiment, a screen changer is installed at the discharge port of the melt metering pump to filter the polymer melt and reduce impurities contained in the melt. In other embodiments, the melt metering pump can be replaced by a combination of an ordinary melt pump, a flow meter and a regulating valve.

[0127] In this embodiment, the discharge port of the first final polymerization reactor 2 is provided with an electric top and bottom valve, which is connected to the elbow by a quick flange, and the 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 by a quick flange. In this embodiment, the discharge port of the second final polymerization reactor 4 is provided with an electric top and bottom valve, the elbow is connected by a quick flange, and the 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 by a quick flange. In this embodiment, the main pipeline 7 is connected to the feed port of the mixer 5 by a quick flange. In this embodiment, the product pipeline is connected to the discharge port of the mixer 5 by a quick flange. In this embodiment, the injection valve 6 is connected to the discharge pipe 36 by a quick flange; the mixed discharge port of the screw extruder 3 is connected to the discharge pipe 36 by a quick flange; the second branch pipe 75 is connected to the feed port of the mixer 5 by a quick flange.

[0128] In this embodiment, the main pipeline 7 is arranged vertically, and gravity is used to discharge the material as much as possible to prevent it from accumulating at the bends of the pipe fittings or in the "dead zone". In other embodiments, the electric top and bottom valves can be replaced with other forms of bottom valves or discharge valves. In this embodiment, the pipeline flanges between the equipment can be quickly disassembled, and prefabricated spare pipelines 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 residual material pipelines to continue production, and the residual material pipelines can be calcined, cleaned, etc. and then kept in reserve.

[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, and ethylene glycol cleaning liquid can be added to the reactor to complete the cleaning, and the nitrogen can be pressed out to complete the cleaning of the bottom valve, the discharge pipeline, the melt metering pump, the injection valve and other pipe fittings at the same time, and it can also be used for the discharge of nitrogen purge gas.

[0130] Example 2

[0131] A control method for a plastic production system, using the plastic production system in Example 1, the polymer melt of the first final polymerization reactor 2 can be mixed with the additive of the additive feeding device 1, and after being melt-mixed by the screw extruder 3, a molten modified melt is prepared. The polymer melt of the second final polymerization reactor 4 is input to the mixer 5 after being pressurized by the melt metering pump in the main pipeline 7. The polymer melt of the second final polymerization reactor 4 can also be added to the screw extruder 3 through the first branch pipe 73. Generally speaking, it can be divided into the following working conditions:

[0132] Working condition 1, the specific operation is as follows: open the additive feed pipe, melt feed pipe, main pipeline 7 and discharge pipeline 36, and close the first branch pipe 73. The first polymer melt of the first final polymerization reactor 2 is mixed with the additive of the additive feeding device 1, and is melt-mixed by the screw extruder 3 to form a molten modified melt; then, the second polymer melt in the second final polymerization reactor 4 is mixed with the modified melt flowing out of the discharge pipeline 36 in the mixer 5.

[0133] Working condition 2, 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, part of the second polymer melt in the second final polymerization reactor 4 and the additive of the additive feeding device 1 are mixed, and melt-mixed by the screw extruder 3 to form a molten modified melt; then, the remaining second polymer melt in the second final polymerization reactor 4 is mixed with the modified melt flowing out of the discharge pipe 36 in the mixer 5.

[0134] Working condition three, the specific operation is as follows: open the additive feed pipe, the main pipeline 7, the discharge pipe 36 and the first branch pipe 73, and close the melt feed pipe. No material is discharged from the first final polymerization reactor 2. Part of the second polymer melt in the second final polymerization reactor 4 is mixed with the additive of the additive feeding device 1, and after being melt-mixed by the screw extruder 3, a molten modified melt is prepared; then, the remaining second polymer melt in the second final polymerization reactor 4 is mixed with the modified melt flowing out of the discharge pipe 36 in the mixer 5.

[0135] Working 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 evenly mixed with the second polymer melt added to the mixer 5 through the second branch pipe 75.

[0136] Working condition 5, the specific operation is as follows: open the main pipeline 7, close the additive feed pipe, the melt feed pipe, the 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 were first mixed evenly in a mixer to form an additive, 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 via a melt metering pump at a rate of 5.7 kg / min. The additives are added from the first zone and the polyamide (MXD6) is added from the second zone.

[0140] The screw extruder 3 has a processing capacity of more than 830 kg / h, a screw diameter of 75 mm, a screw aspect ratio of 40:1, and the temperature of each zone is: 220° C. in the first zone, 235° C. in the second zone, 250° C. in the third zone, 265° C. in the fourth zone, 280° C. in the fifth zone, and 290° C. in the sixth zone. The speed is set to 600 rpm for melt blending and extrusion. The vacuum degree is -0.07 MPa. The additive and the molten polyamide (MXD6) are mixed in the screw extruder 3 to form a modified melt.

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

[0142] The mixed product is sent to an underwater pelletizer for slicing, and the resulting product is cylindrical.

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

[0144] 28.8 kg of coupling agent KH560, 47.7 kg of polyethylene octene co-elastomer, 4.5 kg of lubricant polyethylene wax, 4.5 kg of antioxidant 1098, and 4.5 kg of anti-blocking agent silica are first mixed evenly in a mixer to form an additive, which is 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 via a melt metering pump at a rate of 6 kg / min. The additives are added from the first zone and the polyamide (MXD6) is added from the second zone.

[0146] The screw extruder 3 has a processing capacity of more than 450kg / h, a screw diameter of 65mm, an aspect ratio of 35:1, and the temperature of each zone is: 240°C in the first zone, 240°C in the second zone, 240°C in the third zone, 250°C in the fourth zone, 260°C in the fifth zone, 250°C in the sixth zone, 240°C in the seventh zone, and 230°C in the eighth zone. The speed is set to 550rpm for melt blending and extrusion. The vacuum degree is -0.07MPa. The additive and the molten polyamide (MXD6) are mixed in the screw extruder 3 to form a modified melt.

[0147] The PA6 product 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 speed of 15 kg / min via a melt metering pump.

[0148] The mixed product is sent to an underwater pelletizer for slicing, and the resulting product is cylindrical.

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

[0150] The difference from Application Example 1 is that part of the PA66 obtained in the second final polymerization reactor 4 enters the screw extruder 3 through the first branch pipe 73 at a speed of 3 kg / min, and is mixed with the additive and the molten polyamide (MXD6) in the screw extruder 3 to form a modified melt. The additive is added from the first zone, the polyamide (MXD6) is added from the second zone, and the PA66 of 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 pre-mixed 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, thereby making the overall performance of the material more excellent.

[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 discharge, and part of the PA66 obtained in the second final polymerization reactor 4 enters the screw extruder 3 through the first branch pipe 73 at a speed of 5.7 kg / min, and is mixed with the additive in the screw extruder 3 to form a modified melt.

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

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

[0157] The additive feeding device 1 and the first final polymerization reactor 2 do not produce and discharge materials. The PA66 obtained in the second final polymerization reactor 4 is discharged at a speed of 15 kg / min through a melt metering pump and sent to an underwater pelletizer for slicing. The obtained product is cylindrical.

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

[0159] The difference from Application Example 1 is that the product produced in Application Example 5 is also added to the additive feeding device 1, and after pelletizing, 40 kg of non-conforming shaped materials are added to the screw extruder 3 at a speed of 0.7 kg / min.

[0160] The PA66 obtained in the second final polymerization reactor 4 is discharged through a melt metering pump at a rate of 14.3 kg / min 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 discharge, and part 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, and is mixed with the additive in the screw extruder 3 to form a modified melt.

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

[0164] For 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, and discharged through the cleaning outlet on the main pipeline 7, and the pipelines and flanges between the equipment are quickly disassembled through the quick-connect flanges, and clean spare pipes are quickly replaced and production is continued. The pipelines with residual materials are calcined and cleaned at a high temperature of more than 330°C and then kept in reserve.

[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, 5.2 kg of lubricant polyethylene wax, 900 kg of PA66, and 342 kg of MXD6 were added into a mixer, and stirred at 85° C. and a stirring speed of 250 r / min for 10 min to obtain a mixture.

[0167] The mixed material is added to the twin-screw extruder through an automatic feeding device for mixed extrusion. Extruder The processing capacity is above 1725kg / h, and then it is cooled and granulated through the subsequent pelletizer.

[0168] Comparative Application Example 2

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

[0170] Comparative Application Example 2-1

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

[0172] Comparative Application Example 3

[0173] The difference from Application Example 1 is that the pipelines between the equipment are connected only by ordinary flanges, no screen changer is provided, no cleaning outlet is provided on the second branch pipe 75, and no cleaning, disassembly, calcination and other operations are performed. Two weeks after 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 pipelines between the equipment are connected only by ordinary flanges, no screen changer is provided, no cleaning outlet is provided on the second branch pipe 75, and no cleaning, disassembly, calcination and other operations are performed. Four weeks after production, yellow and black spots were found in the product.

[0176] Effect Example

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

[0178] 2. Test method:

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

[0180] (2) Flexural strength: tested in accordance with ASTM / D790;

[0181] (3) Elongation at break: Tested according to ISO 527-2 / 50;

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

[0183] (5) Izod notched impact strength: tested in accordance with ASTM / D256;

[0184] (6) Chroma: The polymer slices were not processed and directly measured by X-rite Ci7600 for difference test;

[0185] (7) Water absorption: tested in accordance with ISO 62.

[0186] (8) Oxygen transmission rate: tested in accordance with ASTM D3985.

[0187] 3. Test results are shown in the following table:

[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 and 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 premixes the polymer and the additive through the first branch pipe to achieve better distribution of the components in the product, improve the overall performance of the material, and obtain a product with higher tensile strength and flexural strength and lower water absorption.

[0192] It can be seen from Application Examples 1-5 that the present invention can achieve flexible production of a variety of modified products and unmodified products.

[0193] Through the analysis of Application Example 6, it can be seen that the present invention can realize the recycling and reuse of special-shaped materials and achieve performance indicators close to those of the original production process.

[0194]

[0195] Through the comparison between Application Example 1 and Comparative Application Examples 3-4, the present invention can reduce the impurities contained in the product and effectively improve the chromaticity index of the product.

[0196] In summary, the present invention provides a method for online modification of a special engineering plastic melt prepared by a continuous or intermittent reactor. The engineering plastic melt continuously or intermittently produced from the reactor can be transported to a molding device via 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 a variety of 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: A first feed port, for adding additives; A second feed port, the second feed port is connected to a melt feed pipe that can be opened or closed, and is used to input the melt of the first polymer; A third feed inlet and a mixed discharge outlet; The main pipeline includes a first branch pipe and a second branch pipe that can be opened or closed, and the first branch pipe is connected to the third feed port and is used to input the melt of the second polymer into the third feed port; The second mixing device is arranged downstream of the mixing outlet and the main pipeline, and is connected to the mixing outlet through a discharge pipeline, and is connected to the main pipeline through the second branch pipe.

2. The plastic production system according to claim 1, characterized in that: The first mixing device is a screw extruder; The screw extruder is divided into 6-8 zones according to temperature; the first feed port is arranged in the first zone along the material flow direction; the second feed port is arranged in the second zone along the material flow direction; the third feed port is arranged in the third zone along the material flow direction; The screw diameter of the screw extruder is 50-150 mm, for example 75 mm; The aspect ratio of the screw of the screw extruder is (20-50):1, preferably (30-40):1; The second mixing device is a dynamic mixer or a static mixer; The discharge pipe is provided with an injection valve; the injection valve is connected to the discharge pipe by a flange; The mixing outlet is connected to the discharge pipe 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 feed inlet by a flange; The first branch pipe is connected to the main pipe by a flange; The flange connection adopts a quick-connect flange.

3. The plastic production system according to claim 1, characterized in that: The first feed port is connected to the additive feed pipe; One end of the additive feeding pipe away from the first feeding port is connected to the discharge port of the additive feeding device; The additive feeding device is provided with a metering module.

4. The plastic production system according to claim 1, characterized in that: One end of the melt feed pipe away from the second feed port is connected to the discharge port of the first final polymerization reactor; The discharge port of the first final polymerization reactor is provided with a bottom valve; the bottom valve is preferably an electric top and bottom valve; The bottom valve is flange-connected to the melt feed pipe; preferably, the bottom valve is flange-connected to an elbow, and the elbow is connected to the melt feed pipe; The melt feed pipe is provided with a metering device; the metering device is preferably a melt metering pump or a combination of a melt pump and a flow meter; The inlet and outlet of the metering device are preferably connected to the melt feed pipe respectively through flanges; The flange connection adopts a quick-connect flange.

5. The plastic production system according to claim 1, characterized in that: The feed port of the main pipeline is connected to the discharge port of the second final polymerization reactor; The discharge port of the second final polymerization reactor is provided with a bottom valve; the bottom valve is preferably an electric top and bottom valve; The bottom valve is connected to the main pipeline flange; preferably, the bottom valve is connected to the elbow flange, and the elbow is connected to the main pipeline; the flange connection adopts a quick-connect flange; The main pipeline is provided with a metering device; the metering device is preferably a melt metering pump or a combination of a melt pump and a flow meter; The inlet and outlet of the metering device are preferably connected to the main pipeline respectively through flanges; The main pipeline is perpendicular to the ground; The second branch pipe is provided with a cleaning outlet; the cleaning outlet is arranged between the connection between the discharge pipe and the main pipe and the second mixing device.

6. A plastic production method, characterized in that: The plastic production system according to any one of claims 1 to 5 is used to control the opening or closing of the melt feed pipe and the first branch pipe, and to switch at least the following working conditions: ① In the first working condition where the melt feed pipe is opened and the first branch pipe is closed, the plastic production method comprises the following steps: Adding the additive to the first feed port, adding the first polymer melt to the second feed port, and adding the second polymer melt to the main pipeline; The additive and the first polymer melt are uniformly mixed in the first mixing device, the obtained mixture is discharged through the mixing outlet, and then enters the second mixing device through the discharge pipe, and is uniformly mixed with the second polymer melt added to the second mixing device through the second branch pipe; ② In the second working condition where the melt feed pipe and the first branch pipe are opened, the plastic production method comprises the following steps: Adding the additive to the first feed port, adding the first polymer melt to the second feed port, and adding the second polymer melt to the main pipeline; The additive, the first polymer melt and part of the second polymer melt are uniformly mixed in the first mixing device, the obtained mixture is discharged through the mixing outlet, and then enters the second mixing device through the discharge pipe, and is uniformly mixed with the remaining second polymer melt added to the second mixing device through the second branch pipe; ③ In working condition 3, the first branch pipe is opened and the melt feed pipe is closed, the plastic production method comprises the following steps: Adding the additive to the first feed port, and adding the second polymer melt to the main pipeline; The additive and part of the second polymer melt are mixed uniformly in the first mixing device, and the obtained mixture is discharged through the mixing outlet, and then enters the second mixing device through the discharge pipe, and is mixed uniformly with the remaining second polymer melt added to the second mixing device through the second branch pipe.

7. The plastic production method according to claim 6, characterized in that: It meets at least one of the following conditions: ① The first polymer is polyamide; the polyamide is preferably PA6, PA66, PA MXD6, PA MXD10, PAMXD12, PA610, PA612, PA410 or PA66-PA610 copolymer; ② The relative viscosity of the first polymer is 2-2.7, for example, 2.0-2.2; ③ The density of the first polymer at 25° C. is 1.20-1.25 g / mL, for example 1.21 g / mL; ④ The melting point of the first polymer is 230-240°C, for example 232-238°C; ⑤ The second polymer is polyamide; the polyamide is preferably PA6, PA66, PA MXD6, PAMXD10, PAMXD12, PA610, PA612, PA410 or PA66-PA610 copolymer; ⑥ The relative viscosity of the second polymer is 2-3.2, such as 2.5-2.7 or 2.4-2.6; 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°C, for example 247-253°C or 217-223°C; ⑨The 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 anti-blocking agent, and optionally the first polymer and / or the second polymer; The glass fiber is preferably short glass fiber or long glass fiber; the length of the short glass fiber is preferably 1-3 mm; The antioxidant is preferably a phosphite antioxidant or a hindered phenol antioxidant; The coupling agent is preferably a silane coupling agent, such as KH550 or KH560; The elastomer is preferably a nylon elastomer, a polyolefin elastomer or a polyethylene-octene co-elastomer; The anti-adhesive agent is preferably talc, diatomaceous earth or silicon dioxide; The lubricant is preferably polyethylene wax; The montmorillonite is preferably nano-montmorillonite.

8. The plastic production method according to claim 6, characterized in that: It meets at least one of the following conditions: ① In the working condition 1 or the working condition 2, the mass flow ratio of the additive to the first polymer melt is (0.1-2):1, for example, 0.7:5.7, 1.5:6 or 8:5.7; ② In the working condition 1 or the working condition 2, the mass flow ratio of the second polymer melt introduced into the main pipeline to the first polymer melt is (1-4):1, for example, 15:5.7, 15:6 or 14.3:5.7; ③ In the working condition 1, 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 working condition, the mass flow rate of the second polymer melt introduced into the main pipe 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; preferably, the mass flow rate ratio of the first polymer melt to the second polymer melt introduced into the first branch pipe is (0.5-3):1, for example, 5.7:3; ⑤ In the working condition 2 or the working condition 3, the mass flow ratio of the additive to the second polymer melt introduced into the first branch pipe is (0.1-3):1, for example, 1.5:6, 8:3 or 8:5.7; ⑥ In the operating condition 2 or the operating condition 3, the mass flow ratio of the second polymer melt introduced into the main pipeline to the second polymer melt introduced into the first branch pipe is (1.5-6):1, preferably (2-6):1, for example 21:6, 15:3 or 20.7:5.

7.

9. The plastic production method according to claim 6, 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 of the screw extruder is 220-240°C; ② The temperature of the second zone along the material flow direction of the screw extruder is 235-240°C; ③ The temperature of the third zone along the material flow direction of the screw extruder is 240-250°C; ④ The temperature of the fourth zone along the material flow direction of the screw extruder is 250-265°C; ⑤ The temperature of the fifth zone along the material flow direction of the screw extruder is 260-280°C; ⑥ The temperature of the sixth zone along the material flow direction of the screw extruder is 250-290°C; ⑦ The temperature of the seventh zone along the material flow direction of the screw extruder is 235-240°C; ⑧ The temperature of the 8th zone along the material flow direction of the screw extruder is 220-230°C; ⑨ The speed of the screw extruder is 300-900rpm, preferably 550-600rpm; ⑩ The vacuum degree of the screw extruder is 0.05-0.09MPa, preferably 0.05-0.07MPa.

10. The plastic production method according to claim 6, characterized in that: The plastic production method further includes a fourth working condition in which the melt feed pipe and the first branch pipe are closed, comprising the following steps: Adding the additive to the first feed port, and adding the second polymer melt to the main pipeline; The additive is discharged from the mixing outlet, and then enters the second mixing device through the discharge pipe, and is evenly mixed with the second polymer melt added to the second mixing device through the second branch pipe.

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