Preparation device, method and application of a continuous extrusion tubular polymer bead foaming material

Abstract

The present invention provides a preparation device for continuously extruding tubular polymer bead foaming materials. The outlet of an extruder is connected to the material inlet of the cavity of an underwater pelletizer; the foaming gas in a gas tank and the dispersion solution in a high-pressure reaction kettle enter the cavity after being pressurized. The material outlet of the cavity is connected to a high-pressure pipeline; a plurality of flow-blocking stirrers are arranged in the high-pressure pipeline, and the end of the high-pressure pipeline is connected to a control valve; the material is ejected, depressurized and foamed at the outlet of the control valve. The present invention also provides a preparation method for polymer bead foaming materials. The present invention combines the extrusion method with the kettle-type foaming process, uses a pipeline with a controllable length, internal pressure and temperature as a reaction kettle, and enables the foaming gas to be impregnated during the transportation of the material in the pipeline. The present invention has the characteristics of both the continuity of extruded bead foaming and the high closed-cell rate of water kettle-type bead foaming. The prepared polymer bead foaming material has advantages such as a high closed-cell rate, good resilience, good consistency and uniformity.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer bead foaming materials, and particularly relates to a preparation device and method for continuously extruding tubular polymer bead foaming materials, and also relates to a polymer bead foaming material obtained based on the above preparation device and method. Background Art

[0002] In recent years, remarkable progress has been made in polymer foaming technology. The focus of researchers has mainly been on the optimization and practical application of two foaming processes: the extrusion method and the batch reaction method. Due to its high production capacity, the extrusion method is widely used in the production of various polymer foaming materials. However, the foamed products produced by this method often have the problem of too high open cell ratio, which directly leads to insufficient resilience, thereby limiting its use in high-performance application fields. Therefore, although the extrusion method can quickly generate foamed particles, its limitations in the application scope have prompted the intermittent autoclave method to attract the attention of researchers.

[0003] The intermittent autoclave foaming technology has recently been warmly welcomed by the market because it can produce foamed particles with a relatively high closed cell ratio. The significant advantage of this foaming process is that the foaming materials produced by it usually have excellent resilience and can meet more diverse industrial needs. The intermittent autoclave foaming technology can be further divided into dry method and aqueous phase method. In the production of crystalline polymer bead foaming such as polypropylene beads, the aqueous phase method can effectively prevent adhesion between particles. However, although the intermittent autoclave foaming technology performs well in some aspects, as a batch production process, the intermittency of its production process still faces many challenges in terms of product consistency and uniformity. Especially in the case of large-scale production, how to ensure the performance stability of each batch of products has become a key issue.

[0004] In order to overcome the problem of high open cell ratio in continuous bead foaming production and the stability problem of batch products in the intermittent autoclave foaming technology, the present invention proposes an idea of combining the continuous bead extrusion foaming method with the intermittent autoclave foaming technology, and provides a tubular foaming method that can not only continuously and stably supply materials but also has the characteristics of the autoclave foaming method, that is, to develop a preparation device and method for polymer carbon dioxide continuous bead foaming with water as the dispersion medium, which not only has important theoretical significance but also can bring significant economic benefits and technological progress in practical applications. This will provide a more robust solution for the production of polymer bead foaming materials and promote the technological innovation and development of related industries. Summary of the Invention

[0005] One object of the present invention is to provide a preparation device for continuously extruding tubular polymer bead foaming materials with a high closed cell ratio, good resilience, good consistency and uniformity of the product.

[0006] The second object of the present invention is to provide a method for preparing a continuously extruded tubular polymer bead foaming material with a high closed cell ratio, good resilience, and good consistency and uniformity.

[0007] The third object of the present invention is to provide a polymer bead foaming material with a high closed cell ratio, good resilience, and good consistency and uniformity.

[0008] The technical solution adopted by the present invention to achieve the first object is: to provide a preparation device for continuously extruded tubular polymer bead foaming material, including: an extruder, an underwater pelletizer, a high-pressure pipeline, a control valve, a gas tank, a high-pressure reaction kettle, and a flow-blocking stirrer;

[0009] The extruder is provided with a feeding port, and the outlet of the extruder is connected to the material inlet of the cavity of the underwater pelletizer; the material outlet of the cavity is connected to the high-pressure pipeline; the end of the high-pressure pipeline is connected to the control valve, and the material is ejected, depressurized, and foamed at the outlet of the control valve;

[0010] The gas tank is connected to the cavity through a first booster pump, and the gas tank is provided with a foaming gas; the high-pressure reaction kettle is connected to the cavity through a second booster pump, and the high-pressure reaction kettle is filled with a dispersion solution; the foaming gas and the dispersion solution enter the cavity after being pressurized by the first booster pump and the second booster pump respectively;

[0011] The length of the high-pressure pipeline is 50 - 500 meters, the reaction pressure in the high-pressure pipeline is 2 - 15 MPa, and the reaction temperature is 135 - 180 °C; there are multiple flow-blocking stirrers evenly distributed in the high-pressure pipeline for controlling the residence time of the material in the high-pressure pipeline.

[0012] The general idea and invention principle of the present invention are as follows:

[0013] The present invention provides a novel preparation device for continuously extruded tubular polymer bead foaming material. This preparation device connects an extruder, a high-pressure underwater pelletizing system with a high-pressure pipeline, and at the same time, a foaming gas of 2 - 15 MPa is introduced into the high-pressure pipeline. During the transportation of the mixed material in the cavity of the underwater pelletizer in the high-pressure pipeline, under certain temperature and pressure conditions, the foaming gas will continuously diffuse and enter the granular polymer. A control valve is set at the end of the high-pressure pipeline to control the continuous ejection of the material. When the control valve is opened, the polymer melt containing the foaming gas in the high-pressure pipeline foams into beads due to sudden depressurization.

[0014] The present invention combines the extrusion method with the kettle foaming process. On the basis that the extrusion method provides continuous material for granulation, a pipeline with a controllable length, internal pressure and temperature is used as a reaction vessel, so that the foaming gas is fully impregnated during the transportation of the material in the pipeline. This preparation device has the characteristics of the continuity of extrusion bead foaming and the high closed-cell rate of water kettle bead foaming. The polymer bead foaming material prepared has the advantages of high closed-cell rate, good resilience, good consistency and uniformity.

[0015] In the present invention, the residence time, external pressure and temperature of the particles to be foamed in the high-pressure pipeline are necessary conditions to ensure the full impregnation of gas in the material and thus improve the product quality. On the one hand, the present invention designs the length and internal pressure of the high-pressure pipeline, and sets the length of the high-pressure pipeline to be 50 - 500 meters, which can make the material be fully impregnated during transportation. During large-scale production, the high-pressure pipeline has the same effect as the reaction kettle of the batch kettle method, and at the same time ensures the continuity of product production. On the other hand, the pressure in the high-pressure pipeline is controlled to be 2 - 15 MPa, so that the pressure in the high-pressure pipeline is lower than the pressure in the extruder, which is beneficial to the smooth extrusion of the material. Preferably, the length of the high-pressure pipeline is 300 - 500 meters, the pressure in the high-pressure pipeline is 2 - 10 MPa, and the reaction temperature in the high-pressure pipeline is 135 - 180 °C. The specific reaction pressure and reaction temperature are optimized and adjusted according to different material types.

[0016] Furthermore, the present invention is provided with a plurality of flow-blocking stirrers in the high-pressure pipeline, which are used to block the forward flow of the material. The setting of the flow-blocking stirrers can extend the residence time of the material in the high-pressure pipeline. By changing the number of flow-blocking stirrers, the length of the high-pressure pipeline and the rotation speed of the flow-blocking stirrers, the residence time of the material can be controlled, and the optimal residence time is controlled within 30 - 60 minutes to facilitate sufficient time for the gas to impregnate into the material.

[0017] Preferably, the number of the flow-blocking stirrers is 3 - 5, and the rotation speed of the flow-blocking stirrers is 300 - 500 rpm. The flow-blocking stirrer is driven by a motor to drive the stirring shaft, and the stirring shaft is equipped with blades. When the stirring shaft rotates, the blades play a role in pushing back the flow of the fluid, thereby realizing the blocking effect during the forward flow of the material.

[0018] Furthermore, the high-pressure pipeline is made of stainless steel, and the pipeline diameter is 50 - 500 mm. Preferably, the diameter of the high-pressure pipeline is 110 - 200 mm.

[0019] Furthermore, the pressure resistance of the cavity of the underwater pelletizer is not less than 15 MPa; the transmission rod connecting the motor of the underwater pelletizer and the cutting knife is magnetically sealed with the cavity.

[0020] Further, the foaming gas in the gas tank includes one or a combination of two of carbon dioxide and nitrogen; the foaming gas enters the cavity after being pressurized by the first booster pump to 2-15 MPa.

[0021] Further, the high-pressure reactor adopts two-stage series-connected high-pressure reactors, which can ensure the continuous and stable supply of the dispersion solution. The solution in the high-pressure reactor is water, or a mixed solution composed of water, a surfactant, and an inorganic isolating agent. The temperature of the solution in the reactor is 135-180 °C. Specifically, the temperature of the dispersion solution is optimized and adjusted according to different types of materials.

[0022] Further, the dispersion solution in the high-pressure reactor enters the cavity through the second booster pump in a constant pressure type or a constant flow type. Preferably, the second booster pump is set to the constant flow type, and the flow rate of the dispersion solution can be adjusted according to the opening degree of the control valve to balance the inflow and outflow.

[0023] Preferably, the dispersion solution is composed of 100 parts by weight of water, 0.8-1.5 parts of surfactant, and 3-5 parts of inorganic isolating agent. The surfactant includes one or a combination of more of sodium dodecylbenzenesulfonate, sodium dodecylbenzenesulfonate, and Tween 80; the inorganic isolating agent includes one or a combination of more of kaolin, talc powder, nano calcium carbonate, and clay.

[0024] Further, a heating unit is provided outside the high-pressure pipeline to control the temperature of the material in the high-pressure pipeline within a suitable range.

[0025] Further, the control valve is a needle valve or a ball valve. The opening degree of the control valve is related to the amount and pressure of the material in the high-pressure pipeline. When the control valve is opened, the mixed material sprays out from the outlet of the control valve. When the pressure in the high-pressure pipeline drops, the first booster pump automatically starts to replenish the pressure of the high-pressure pipeline to ensure that the reaction pressure in the high-pressure pipeline is constant and maintain the consistency and stability of the product. During the pressure relief process of opening the control valve, the polymer particles immediately complete the foaming process.

[0026] The technical solution adopted to achieve the second object of the present invention is: to provide a method for preparing a continuous extrusion tubular polymer bead foamed material using the preparation device according to the first object of the present invention, including the following steps:

[0027] S1. The polymer material and the nucleating agent enter the extruder through the feeding port, are plasticized by the screw, and are extruded from the head of the underwater pelletizer to obtain granular polymers;

[0028] S2. The foaming gas in the gas tank enters the cavity after being pressurized by the first booster pump to 2-15 MPa; the dispersion solution in the high-pressure reactor enters the cavity after being pressurized by the second booster pump;

[0029] S3. The granular polymer, foaming gas and dispersion solution form a mixed material in the cavity, enter the high-pressure pipeline under pressure, and are conveyed forward along the high-pressure pipeline. When the pressure in the pipeline reaches the target value, the control valve is opened;

[0030] S4. During the forward conveyance of the mixed material along the high-pressure pipeline, under the action of multiple flow-blocking stirrers, the flow rate of the mixed material slows down, and the foaming gas fully impregnates the granular polymer in the pipeline;

[0031] S5. After the mixed material reaches the control valve at the end of the high-pressure pipeline, it is ejected to release pressure, and the polymer immediately foams to obtain a polymer bead foaming material.

[0032] Further, in step S1, the polymer includes one or a combination of more of polypropylene, polyethylene, polylactic acid, polyphenylene ether, and thermoplastic polyurethane; the nucleating agent includes one or a combination of more of kaolin, talcum powder, zinc borate, polytetrafluoroethylene, nano calcium carbonate, and clay.

[0033] Further, in step S1, the particle size of the granular polymer is 0.5 - 3 mm.

[0034] Further, in step S5, while the mixed material is ejected to release pressure, the first booster pump is started to supplement the pressure in the high-pressure pipeline.

[0035] The technical solution adopted to achieve the third object of the present invention is: to provide a polymer bead foaming material prepared by the preparation device according to the first object of the present invention or the preparation method according to the second object of the present invention.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] (1) The preparation device for continuously extruding tubular polymer bead foaming material provided by the present invention combines the extrusion method with the kettle foaming process. On the basis of the extrusion method providing continuous material supply for granulation, a pipeline with a certain length, controllable internal pressure and temperature is used as a reaction kettle, and multiple flow-blocking stirrers are arranged in the high-pressure pipeline to control the residence time of the material in the high-pressure pipeline, so that the foaming gas is fully impregnated during the conveyance of the material in the pipeline. This preparation device combines the continuity of extrusion bead foaming and the high closed-cell rate of water kettle bead foaming. The polymer bead foaming material prepared has the advantages of high closed-cell rate, good resilience, good consistency and uniformity.

[0038] (2) The preparation method of a continuous extrusion tubular polymer bead foaming material provided by the present invention uses a polymer as the matrix, a gas such as carbon dioxide as the foaming agent, and water as the dispersion medium, and obtains polymer foamed beads through a preparation device and method combining an extruder and a pipeline. The preparation method provided by the present invention is applicable to the extrusion foaming of a variety of different polymers, has a simple preparation process flow, is easy to control, the obtained polymer bead foaming material has stable quality, and has broad popularization and application prospects. Description of the Drawings

[0039] Figure 1 It is a schematic structural diagram of a preparation device for a continuous extrusion tubular polymer bead foaming material provided by the present invention;

[0040] Among them, 1 - extruder; 2 - feeding port; 3 - underwater pelletizer; 4 - underwater pelletizer cavity; 5 - high-pressure pipeline; 6 - control valve; 7 - gas tank; 8 - first booster pump; 9 - high-pressure reaction kettle; 10 - second booster pump; 11 - flow-blocking stirrer. Specific Embodiments

[0041] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0042] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0043] As Figure 1 shown, the embodiment of the present invention provides a preparation device for a continuous extrusion tubular polymer bead foaming material, including: an extruder 1, an underwater pelletizer 3, a high-pressure pipeline 5, a control valve 6, a gas tank 7, a high-pressure reaction kettle 9, and a flow-blocking stirrer 11.

[0044] The extruder 1 is provided with a feeding port 2, and the outlet of the extruder 1 is connected to the material inlet of the cavity 4 of the underwater pelletizer 3; the pressure resistance of the cavity 4 is not less than 15 MPa; the transmission rod connecting the motor of the underwater pelletizer 3 and the cutting knife is magnetically sealed with the cavity 4; the material outlet of the cavity 4 is connected to the high-pressure pipeline 5.

[0045] The gas cylinder 7 is connected to the cavity 4 through the first booster pump 8, and a foaming gas is provided in the gas cylinder 7; the foaming gas includes one or a combination of two of carbon dioxide and nitrogen; the foaming gas is pressurized to 2-15 MPa by the first booster pump 8 and then enters the cavity 4. The high-pressure reactor 9 is connected to the cavity 4 through the second booster pump 10, and a dispersion solution is contained in the high-pressure reactor 9; the high-pressure reactor 9 adopts a two-stage series high-pressure reactor; the dispersion solution in the high-pressure reactor 9 is water, or a mixed solution composed of water, a surfactant, and an inorganic isolating agent, and the temperature of the dispersion solution is 135-180 °C.

[0046] The length of the high-pressure pipeline 5 is 50-500 meters. A heating unit is provided outside the high-pressure pipeline 5 to control the temperature of the material in the high-pressure pipeline 5; the reaction pressure in the high-pressure pipeline 5 is 2-15 MPa, and the reaction temperature is 135-180 °C. 3-5 flow-blocking stirrers 11 are arranged in the high-pressure pipeline 5, the rotation speed of the flow-blocking stirrers 11 is 300-500 rpm, and the flow-blocking stirrers 11 control the residence time of the material in the high-pressure pipeline 5 to 30-60 minutes to facilitate sufficient time for the gas to impregnate into the material. The end of the high-pressure pipeline 5 is connected to a control valve 6, and the material is ejected, depressurized, and foamed at the outlet of the control valve 6; the control valve 6 is a needle valve or a ball valve.

[0047] The present invention will be further described below in conjunction with specific embodiments, but it is not a limitation of the present invention.

[0048] Example 1

[0049] This example provides a method for preparing a polypropylene bead foaming material based on the Figure 1 shown preparation device, including the following steps:

[0050] Step 1: 100 parts of polypropylene and 0.5 part of polytetrafluoroethylene are mixed and added to the feeding port 2 of the single-screw extruder 1. The five-section temperatures of the single-screw extruder are respectively controlled at 180 °C, 185 °C, 190 °C, 195 °C, 195 °C, and the head temperature is 190 °C. The head pressure is 8 MPa, and the rotation speed of the underwater pelletizer is 150 revolutions per minute. Granular polymers with a particle diameter of 1.0 mm are cut out underwater.

[0051] Step 2: 100 parts of water, 3 parts of kaolin, and 1 part of sodium dodecylbenzenesulfonate are added to the high-pressure reactor 9. The temperature in the high-pressure reactor 9 is heated to 150 °C, and the rotation speed is 300 revolutions per minute. The mixed aqueous solution is pumped into the underwater pelletizer cavity 4 through the second booster pump 10 to prevent the polypropylene particles cut out underwater from sticking. At the same time, the first booster pump 8 of the foaming gas carbon dioxide is turned on, and the pressure in the pipe is controlled at 2.5 MPa.

[0052] Step 3: The granular polymer, the foaming gas and the dispersion solution form a mixed material in the cavity 4, enter the high-pressure pipeline 5 under the action of pressure, and are transported forward along the high-pressure pipeline 5; the temperature of the high-pressure pipeline 5 is controlled at 150 °C throughout the process, and the pipe length is 300 meters.

[0053] Step 4: There are 5 flow-blocking stirrers 11 evenly distributed in the high-pressure pipeline 5, and the rotation speed of the flow-blocking stirrers 11 is 300 revolutions per minute. During the forward transportation of the mixed material along the high-pressure pipeline 5, under the action of the 5 flow-blocking stirrers 11, the flow rate of the mixed material slows down, and the foaming gas fully impregnates the granular polymer in the high-pressure pipeline 5.

[0054] Step 5: Open the control valve 6 at the end of the high-pressure pipeline 5. At this time, if the pressure in the high-pressure pipeline 5 drops, the first booster pump 8 will automatically start to ensure that the pressure in the pipeline 5 remains constant at 2.5 MPa. The mixed material is ejected from the control valve 6 to release pressure, and the polymer immediately foams to obtain polypropylene bead foaming material with a density of 0.063 g / cm 3 ³.

[0055] Example 2

[0056] This example provides a preparation method of polylactic acid bead foaming material based on the Figure 1 shown preparation device, including the following steps:

[0057] Step 1: 100 parts of polylactic acid and 0.5 part of talcum powder are mixed and added to the feeding port 2 of the conical twin-screw extruder 1. The temperatures of the three sections of the conical twin-screw extruder are controlled at 195 °C, 190 °C, and 190 °C respectively, and the head temperature is 190 °C. The head pressure is 10 MPa, and the rotation speed of the underwater pelletizer is 180 revolutions per minute. Granular polymer with a particle diameter of 1.2 mm is cut out underwater.

[0058] Step 2: Add 100 parts of water, 4 parts of kaolin, and 1.5 parts of sodium dodecylbenzenesulfonate to the high-pressure reaction kettle 9. The temperature of the reaction kettle is heated to 145 °C, and the rotation speed is 250 revolutions per minute. The mixed aqueous solution is pumped into the cavity 4 of the underwater pelletizer by the second booster pump 10 to prevent the polylactic acid particles cut out underwater from sticking. At the same time, turn on the first booster pump 8 for the foaming gas carbon dioxide, and control the pressure in the pipe to be 3 MPa.

[0059] Step 3: The granular polymer, the foaming gas and the dispersion solution form a mixed material in the cavity 4, enter the high-pressure pipeline 5 under the action of pressure, and are transported forward along the high-pressure pipeline 5; the temperature of the high-pressure pipeline 5 is controlled at 145 °C throughout the process, and the pipe length is 500 meters.

[0060] Step 4: There are 3 flow-blocking stirrers 11 evenly distributed in the high-pressure pipeline 5. The rotational speed of the flow-blocking stirrers 11 is 300 revolutions per minute. During the forward transportation of the mixed material along the high-pressure pipeline 5, under the action of the 3 flow-blocking stirrers 11, the flow rate of the mixed material slows down, and the foaming gas fully impregnates the granular polymer in the high-pressure pipeline 5.

[0061] Step 5: Open the control valve 6 at the end of the high-pressure pipeline 5. At this time, if the pressure in the high-pressure pipeline 5 drops, the first booster pump 8 will automatically start to ensure that the pressure in the pipeline 5 remains constant at 3 MPa. The mixed material is ejected from the control valve 6 to release pressure, and the polymer immediately foams to obtain a polylactic acid bead foaming material with a density of 0.085 g / cm 3 ³.

[0062] Example 3

[0063] This example provides a preparation method of a polyphenylene ether-polystyrene copolymer bead foaming material based on the Figure 1 shown preparation device, including the following steps:

[0064] Step 1: 70 parts of polyphenylene ether, 30 parts of polystyrene, and 0.5 part of kaolin are mixed and added to the feeding port 2 of the parallel twin-screw extruder 1. The temperatures of the 10 sections of the parallel twin-screw extruder 1 are respectively controlled at 200 °C, 205 °C, 210 °C, 210 °C, 210 °C, 210 °C, 210 °C, 210 °C, 210 °C, and the head temperature is 200 °C. The head pressure is 8 MPa, and the rotational speed of the underwater pelletizer is 300 revolutions per minute. Granular polymers with a particle diameter of 0.9 mm are cut out underwater.

[0065] Step 2: 100 parts of water, 5 parts of kaolin, and 0.8 part of sodium dodecylbenzenesulfonate are added to the high-pressure reaction kettle 9. The temperature in the high-pressure reaction kettle 9 is heated to 175 °C, and the rotational speed is 200 revolutions per minute. The mixed aqueous solution is pumped into the cavity 4 of the underwater pelletizer by the second booster pump 10 to prevent the polyphenylene ether particles cut out underwater from sticking. At the same time, turn on the carbon dioxide first booster pump 8 and control the pressure in the pipe to be 4.0 MPa.

[0066] Step 3: The granular polymer, the foaming gas, and the dispersion solution form a mixed material in the cavity 4 and enter the high-pressure pipeline 5 under pressure and are transported forward along the high-pressure pipeline 5; the temperature of the high-pressure pipeline 5 is controlled at 175 °C throughout the whole process, and the pipe length is 400 meters.

[0067] Step 4: There are 4 flow-blocking stirrers 11 evenly distributed in the high-pressure pipeline 5. The rotational speed of the flow-blocking stirrers 11 is 500 revolutions per minute. During the forward transportation of the mixed material along the high-pressure pipeline 5, under the action of the 4 flow-blocking stirrers 11, the flow rate of the mixed material slows down, and the foaming gas fully impregnates the granular polymer in the high-pressure pipeline 5.

[0068] Step 5: Open the control valve 6 at the end of the high-pressure pipeline 5. At this time, if the pressure in the high-pressure pipeline 5 drops, the first booster pump 8 will automatically start to ensure that the pressure in the pipeline 5 remains constant at 4.0 MPa. The mixed material is ejected from the control valve 6 to release pressure, and the polymer immediately foams to obtain polyphenylene ether-polystyrene copolymer bead foaming material with a density of 0.102 g / cm 3 .

[0069] Example 4

[0070] This example provides a preparation method of thermoplastic polyurethane TPU bead foaming material based on the Figure 1 shown preparation device, including the following steps:

[0071] Step 1: 100 parts of thermoplastic polyurethane TPU and 1.0 part of nano calcium carbonate are mixed and added to the feeding port 2 of the single-screw extruder 1. The five sections of the single-screw extruder are respectively controlled at 150 °C, 160 °C, 170 °C, 180 °C, 180 °C, and the head temperature is 180 °C. The head pressure is 8 MPa, and the speed of the underwater pelletizer is 200 revolutions per minute. Granular polymer with a particle diameter of 1.8 mm is cut out underwater.

[0072] Step 2: Only 100 parts of water are added to the high-pressure reactor 9, the temperature is heated to 135 °C, the speed is 200 revolutions per minute, and the mixed aqueous solution is pumped into the cavity 4 of the underwater pelletizer by the second booster pump 10. At the same time, the first booster pump 8 for the gas of nitrogen and carbon dioxide with a ratio of 1:1 is turned on, and the pipe surface pressure is controlled at 10 MPa.

[0073] Step 3: The granular polymer, foaming gas and dispersion solution form a mixed material in the cavity 4 and enter the high-pressure pipeline 5 under pressure and are transported forward along the high-pressure pipeline 5; the temperature of the high-pressure pipeline 5 is controlled at 135 °C throughout the whole process, and the pipe length is 400 meters.

[0074] Step 4: There are 5 flow-blocking stirrers 11 evenly distributed in the high-pressure pipeline 5, and the speed of the flow-blocking stirrers 11 is 300 revolutions per minute. During the forward transportation of the mixed material along the high-pressure pipeline 5, under the action of the 5 flow-blocking stirrers 11, the flow rate of the mixed material slows down, and the foaming gas fully impregnates the granular polymer in the high-pressure pipeline 5.

[0075] Step 5: Open the control valve 6 at the end of the high-pressure pipeline 5. At this time, if the pressure in the high-pressure pipeline 5 drops, the first booster pump 8 will automatically start to ensure that the pressure in the pipeline 5 remains constant at 10 MPa. The mixed material is ejected from the control valve 6 to release pressure, and the polymer immediately foams to obtain thermoplastic polyurethane TPU bead foaming material with a density of 0.1 g / cm 3 .

[0076] Comparative Example 1

[0077] This comparative example provides a method for preparing a polypropylene bead foaming material. The main difference from Example 1 is that in the preparation device used in the preparation method, the length of the high-pressure pipeline is 50 meters, and there is no flow-blocking stirrer installed in the high-pressure pipeline. The preparation method includes the following steps:

[0078] Step 1: 100 parts of polypropylene and 0.5 part of polytetrafluoroethylene are mixed and added to the feeding port 2 of the single-screw extruder 1. The five-section temperatures of the single-screw extruder are controlled at 180°C, 185°C, 190°C, 195°C, 195°C respectively, and the head temperature is 190°C. The head pressure is 8 MPa, and the rotational speed of the underwater pelletizer is 150 revolutions per minute. Granular polymers with a particle diameter of 1.0 mm are cut out underwater.

[0079] Step 2: 100 parts of water, 3 parts of kaolin, and 1 part of sodium dodecylbenzenesulfonate are added to the high-pressure reactor 9. The temperature in the high-pressure reactor 9 is heated to 150°C, and the rotational speed is 300 revolutions per minute. The mixed aqueous solution is pumped into the cavity 4 of the underwater pelletizer through the second booster pump 10 to prevent the polypropylene particles cut out underwater from sticking. At the same time, the first booster pump 8 for the foaming gas carbon dioxide is turned on, and the pressure in the pipe is controlled at 2.5 MPa.

[0080] Step 3: The granular polymer, the foaming gas, and the dispersion solution form a mixed material in the cavity 4 and enter the high-pressure pipeline 5 under pressure and are transported forward along the high-pressure pipeline 5; the temperature of the high-pressure pipeline 5 is controlled at 150°C throughout the whole process, and the pipe length is 50 meters.

[0081] Step 4: Open the control valve 6 at the end of the high-pressure pipeline 5. At this time, if the pressure in the high-pressure pipeline 5 drops, the first booster pump 8 will be automatically started to ensure that the pressure in the pipeline 5 is kept constant at 2.5 MPa. The mixed material is ejected from the control valve 6 to release pressure, and the polymer immediately foams to obtain a polypropylene bead foaming material with a density of 0.88 g / cm 3 ³.

[0082] Comparative Example 2

[0083] This comparative example provides a method for preparing a polypropylene bead foaming material. The main difference from Example 1 is that in the preparation device used in this comparative example, the extruder does not work continuously, and the high-pressure pipeline is used to simulate the batch kettle method. The preparation method includes the following steps:

[0084] Step 1: Before starting the extruder 1, open the control valve 6 at the end of the high-pressure pipeline 5. 100 parts of polypropylene and 0.5 parts of polytetrafluoroethylene are mixed and added to the feeding port 2 of the single-screw extruder 1. The temperatures of the five sections of the single-screw extruder are controlled at 180°C, 185°C, 190°C, 195°C, and 195°C respectively, and the head temperature is 190°C. The head pressure is 8 MPa, and the rotational speed of the underwater pelletizer is 150 revolutions per minute. Granular polymers with a particle diameter of 1.0 mm are cut out underwater.

[0085] Step 2: Add 100 parts of water, 3 parts of kaolin, and 1 part of sodium dodecylbenzenesulfonate to the high-pressure reactor 9. Heat the temperature in the high-pressure reactor 9 to 150°C and the rotational speed to 300 revolutions per minute. The mixed aqueous solution is pumped into the cavity 4 of the underwater pelletizer through the second booster pump 10 to prevent the polypropylene particles cut out underwater from sticking. At the same time, turn on the first booster pump 8 for the foaming gas carbon dioxide. The granular polymer, the foaming gas, and the dispersion solution form a mixed material in the cavity 4 and enter the high-pressure pipeline 5 under pressure and are transported forward along the high-pressure pipeline 5; the temperature of the high-pressure pipeline 5 is controlled at 150°C throughout the whole process, the pipe length is 300 meters, and there are 5 flow-blocking stirrers 11 evenly distributed along the high-pressure pipeline, with a rotational speed of 300 revolutions per minute. After the particles are ejected from the control valve 6 at the end of the opened high-pressure pipeline 5, close the control valve 6 at the end of the high-pressure pipeline 5 and turn off the extruder 1.

[0086] Step 3: Control the pressure inside the pipe to be 2.5 MPa, and after heat preservation at 150°C for 30 minutes, if the pressure inside the high-pressure pipeline 5 drops when the control valve 6 at the end of the opened high-pressure pipeline 5 is opened, the first booster pump 8 will automatically start to ensure that the pressure inside the pipeline 5 remains constant at 2.5 MPa until the particles are sprayed out. At the same time, the second booster pump 10 will also automatically start to continuously pump the mixed liquid into the cavity 4 of the underwater pelletizer. When the mixed material is ejected from the control valve 6, the polymer will immediately foam to obtain polypropylene bead foaming material with a density of 0.072 g / cm 3 ³.

[0087] The main parameters, reaction conditions, and test results of the products involved in the examples and comparative examples of the present invention are shown in Tables 1 - 3 below:

[0088] Table 1

[0089]

[0090] Table 2

[0091]

[0092] Table 3

[0093]

[0094] As can be seen from Table 3 above,

[0095] In Examples 1-4 of the present invention, by combining the extrusion method with the kettle foaming process, a pipeline with controllable length, internal pressure and temperature is used as a reaction kettle, and a plurality of flow-blocking stirrers are arranged in the high-pressure pipeline to control the residence time of the material in the high-pressure pipeline, so that the foaming gas is fully impregnated during the transportation of the material in the pipeline. The prepared polymer bead foaming material has the advantages of high closed-cell rate, good resilience, good consistency and uniformity.

[0096] Compared with Example 1, in Comparative Example 1, the length of the high-pressure pipeline is shorter and no flow-blocking stirrer is installed, and the foaming ratio of the plastic particles is small. Compared with Example 1, in Comparative Example 2, the extruder does not work continuously, and the high-pressure pipeline is used to simulate the batch kettle method, and the prepared foamed product has the defect of poor batch uniformity.

[0097] The above are only the preferred embodiments of the present invention, and do not limit the implementation manners and protection scope of the present invention. For those skilled in the art, it should be realized that all the equivalent replacements and obvious changes made by using the content of the specification of the present invention should be included in the protection scope of the present invention.

Claims

1. A preparation device for continuously extruding tubular polymer bead foaming material, characterized in that: include: An extruder (1), an underwater pelletizer (3), a high-pressure pipeline (5), a control valve (6), a gas tank (7), a high-pressure reactor (9), and a flow-reducing agitator (11); The extruder (1) is provided with a feed port (2); the outlet of the extruder (1) is connected to the material inlet of the cavity (4) of the underwater pelletizer (3); the material outlet of the cavity (4) is connected to a high-pressure pipeline (5); the end of the high-pressure pipeline (5) is connected to a control valve (6), and the material is continuously sprayed out, depressurized and foamed at the outlet of the control valve (6); The gas tank (7) is connected to the cavity (4) via a first booster pump (8), and a foaming gas is provided in the gas tank (7); the high-pressure reactor (9) is connected to the cavity (4) via a second booster pump (10), and a dispersed solution is contained in the high-pressure reactor (9); the foaming gas and the dispersed solution are pressurized by the first booster pump (8) and the second booster pump (10) respectively and then enter the cavity (4); The length of the high-pressure pipeline (5) is 300-500 meters, the reaction pressure in the high-pressure pipeline (5) is 2-15 MPa, and the reaction temperature is 135-180° C.; The number of the flow-blocking agitators (11) is 3 to 5 and they are evenly distributed in the high-pressure pipeline (5). The rotation speed of the flow-blocking agitators (11) is 300 to 500 rpm. The flow-blocking agitator (11) is driven by a motor to drive a stirring shaft, and a paddle is installed on the stirring shaft. When the stirring shaft rotates, the paddle has a reverse thrust effect on the flow of the material, and has a blocking effect when the material flows forward, so that the residence time of the material in the high-pressure pipeline (5) is controlled to be 30 to 60 minutes.

2. The preparation device according to claim 1, characterized in that: The pressure resistance of the cavity (4) of the underwater pelletizer (3) is not less than 15 MPa; a magnetic seal is adopted between the transmission rod connecting the motor and the cutter of the underwater pelletizer (3) and the cavity (4).

3. The preparation device according to claim 1, characterized in that: The foaming gas in the gas tank (7) comprises one of carbon dioxide and nitrogen or a combination of the two; the foaming gas is pressurized to 2-15 MPa by a first booster pump (8) and then enters the cavity (4).

4. The preparation device according to claim 1, characterized in that: The high-pressure reactor (9) is a two-stage series high-pressure reactor; the dispersion solution in the high-pressure reactor (9) is water, or a mixture of water, a surfactant and an inorganic isolation agent, and the temperature of the dispersion solution is 135-180°C.

5. The preparation device according to claim 1, characterized in that: The high-pressure pipeline (5) is provided with a heating unit outside thereof, which is used to control the temperature of the material in the high-pressure pipeline (5); and the control valve (6) is a needle valve or a ball valve.

6. A method for preparing a continuously extruded tubular polymer bead foam material according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1, polymer material and nucleating agent enter the extruder (1) through the feed port (2), are plasticized by the screw, and are extruded from the head of the underwater pelletizer (3) to obtain granular polymer; S2, the foaming gas in the gas tank (7) is pressurized to 2-15 MPa by the first booster pump (8) and then enters the cavity (4); the dispersed solution in the high-pressure reactor (9) is pressurized by the second booster pump (10) and then enters the cavity (4); S3, the granular polymer, the foaming gas and the dispersed solution form a mixed material in the cavity (4), enter the high-pressure pipeline (5) under the action of pressure, and are transported forward along the high-pressure pipeline (5). When the pressure in the pipeline reaches the target value, the control valve (6) is opened; S4, during the process of the mixed material being transported forward along the high-pressure pipeline (5), the flow rate of the mixed material is slowed down under the action of the plurality of flow-blocking stirrers (11), so that the foaming gas fully impregnates the granular polymer in the high-pressure pipeline (5); S5. After the mixed material reaches the control valve (6) at the end of the high-pressure pipeline (5), it is ejected to release the pressure, and the polymer foams immediately to obtain a polymer bead foaming material.

7. The preparation method according to claim 6, characterized in that: In step S1, the polymer includes one or more combinations of polypropylene, polyethylene, polylactic acid, polyphenylene ether, and thermoplastic polyurethane; the nucleating agent includes one or more combinations of kaolin, talc, zinc borate, polytetrafluoroethylene, nano calcium carbonate, and clay.

8. The preparation method according to claim 6, characterized in that: In step S1, the particle size of the granular polymer is 0.5-3 mm.

9. A polymer bead foam material, characterized in that: The method is prepared by the preparation device according to any one of claims 1 to 5 or the preparation method according to any one of claims 6 to 8.

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