Continuous extrusion tubular polymer bead foaming material preparation device and method and application

Abstract

The invention provides a preparation device for a continuous extrusion tubular polymer bead foaming material. An outlet of an extruder is connected with a material inlet of a cavity of an underwater granulator; foaming gas in the gas tank and a dispersion solution in the high-pressure reaction kettle are pressurized and then enter the cavity, and a material outlet of the cavity is connected with a high-pressure pipeline; a plurality of choke stirrers are arranged in the high-pressure pipeline; the tail end of the high-pressure pipeline is connected with a control valve; and the material is sprayed out from an outlet of the control valve, depressurized and foamed. The invention also provides a preparation method of the polymer bead foaming material. According to the invention, an extrusion method and a kettle type foaming process are combined, and a pipeline with a certain length and controllable internal pressure and temperature is used as a reaction kettle, so that the impregnation of foaming gas is completed in the process of conveying materials in the pipeline. The polymer bead foaming material has the characteristics of continuity of extrusion bead foaming and high closed-cell rate of water kettle type bead foaming, and the prepared polymer bead foaming material has the advantages of high closed-cell rate, good rebound resilience, good consistency, good uniformity and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer bead foaming materials, and specifically relates to a preparation device and method of a continuously extruded tubular polymer bead foaming material, and also relates to the polymer bead foaming material prepared based on the preparation device and method. Background Art

[0002] Polymer foaming technology has made remarkable progress in recent years. Researchers have focused on the optimization and practical application of two foaming processes: extrusion and batch reaction. Extrusion is widely used in the production of various polymer foam materials due to its efficient production capacity. However, the foamed products produced by this method often have the problem of too high open porosity, which directly leads to insufficient resilience, thus limiting its use in high-performance applications. Therefore, although the extrusion method can quickly generate foamed particles, its limitations in application range have prompted researchers to pay attention to the intermittent autoclave method.

[0003] Intermittent kettle foaming technology has been warmly welcomed by the market in recent years because it can produce foamed particles with a high closed-cell rate. The significant advantage of this foaming process is that the foamed materials it produces usually have excellent resilience and can meet more diverse industrial needs. Intermittent kettle foaming technology can be further divided into dry method and water phase method. In the foaming production of crystalline polymers such as polypropylene beads, the water phase method can effectively prevent adhesion between particles. However, intermittent kettle foaming technology performs well in some aspects. As a batch production process, the intermittent nature of its production process leads to many challenges in 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 porosity in the production of continuous bead foaming and the stability problem of batch products of intermittent kettle foaming technology, the present invention proposes the idea of ​​combining the continuous bead extrusion foaming method with the intermittent kettle foaming technology, and provides a tubular foaming method that can not only continuously and stably feed, but also has the characteristics of kettle foaming, that is, to develop a preparation device and method for continuous bead foaming of polymer carbon dioxide using water as a 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 at the same time promote the technological innovation and development of related industries. Summary of the invention

[0005] One of the purposes of the present invention is to provide a device for preparing a continuously extruded tubular polymer bead foam material having a high closed cell ratio, good resilience, good consistency and uniformity.

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

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

[0008] The technical solution adopted by the present invention to achieve one of the purposes is: to provide a preparation device for continuously extruding tubular polymer bead foaming materials, comprising: an extruder, an underwater pelletizer, a high-pressure pipeline, a control valve, a gas tank, a high-pressure reactor, and a flow-blocking agitator; The extruder is provided with a feeding port, 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 a high-pressure pipeline; the end of the high-pressure pipeline is connected to a control valve, and the material is sprayed out at the outlet of the control valve, the pressure is released and foaming occurs; The gas tank is connected to the cavity through a first booster pump, and a foaming gas is provided in the gas tank; the high-pressure reactor is connected to the cavity through a second booster pump, and a dispersed solution is contained in the high-pressure reactor; the foaming gas and the dispersed solution are pressurized by the first booster pump and the second booster pump respectively and then enter the cavity; The length of the high-pressure pipeline is 50-500 meters, the reaction pressure in the high-pressure pipeline is 2-15MPa, and the reaction temperature is 135-180°C; there are multiple choke agitators, which are evenly distributed in the high-pressure pipeline and are used to control the residence time of the material in the high-pressure pipeline.

[0009] The overall idea and inventive principle of the present invention are as follows: The invention provides a novel preparation device for continuously extruding tubular polymer bead foaming materials, wherein the preparation device connects an extruder, a high-pressure underwater pelletizing system and a high-pressure pipeline, and simultaneously introduces a foaming gas of 2-15MPa 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, and a control valve is arranged 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 is foamed into beads due to the sudden pressure release.

[0010] The present invention combines the extrusion method with the kettle foaming process. On the basis of the continuous material supply provided by the extrusion method, a pipeline with a certain length, controllable internal pressure and temperature is used as a reaction container, so that the material can be fully impregnated with the foaming gas during the transportation process in the pipeline. This preparation device has the characteristics of the continuity of extruded bead foaming and the high closed-cell rate of water kettle bead foaming. The prepared polymer bead foaming material has the advantages of high closed-cell rate, good resilience, good consistency and uniformity.

[0011] 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 that the gas is fully impregnated in the material, thereby improving the quality of the product. 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 50-500 meters, so that the material can be fully impregnated during the transportation process. In large-scale production, the high-pressure pipeline has the same effect as the reactor of the intermittent reactor method, while ensuring the continuity of product production. On the other hand, the pressure in the high-pressure pipeline is controlled to be 2-15MPa, so that the pressure in the high-pressure pipeline is lower than the pressure in the extruder, which is conducive 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 the different types of materials.

[0012] Furthermore, the present invention sets a plurality of flow-blocking agitators in the high-pressure pipeline to block the material in the forward flow process. The setting of the flow-blocking agitator can prolong the residence time of the material in the high-pressure pipeline, and the control of the material residence time is achieved by changing the number of flow-blocking agitators, the length of the high-pressure pipeline and the rotation speed of the flow-blocking agitator. The optimal residence time is controlled to be 30-60 minutes, so that the gas has enough time to penetrate into the material.

[0013] Preferably, the number of the flow-blocking agitators is 3-5, and the rotation speed of the flow-blocking agitator is 300-500rpm. The flow-blocking agitator 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 fluid, thereby achieving a blocking effect in the forward flow of the material.

[0014] Furthermore, the high-pressure pipeline is made of stainless steel, and the pipeline diameter is 50-500 mm. Preferably, the high-pressure pipeline diameter is 110-200 mm.

[0015] Furthermore, the compressive strength of the cavity of the underwater pelletizer 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 and the cavity.

[0016] Furthermore, the foaming gas in the gas tank includes 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 and then enters the cavity.

[0017] Furthermore, the autoclave adopts a two-stage series autoclave, which can ensure the continuous and stable supply of the dispersed solution. The solution in the autoclave is water, or a mixture of water, a surfactant and an inorganic isolating agent, and the temperature of the solution in the autoclave is 135-180°C. Specifically, the temperature of the dispersed solution is optimized and adjusted according to different types of materials.

[0018] Furthermore, the dispersed solution in the autoclave is passed into the cavity in a constant pressure or constant flow manner through a second booster pump. Preferably, the second booster pump is set to a constant flow type, and the flow of the dispersed solution can be adjusted to be constant according to the opening of the control valve.

[0019] Preferably, the dispersion solution is composed of 100 parts of water, 0.8-1.5 parts of surfactant and 3-5 parts of inorganic isolating agent by weight. The surfactant includes one or more of sodium dodecylbenzene sulfate, sodium dodecylbenzene sulfonate and Tween 80; the inorganic isolating agent includes one or more of kaolin, talc, nano calcium carbonate and clay.

[0020] Furthermore, a heating unit is provided outside the high-pressure pipeline to control the temperature of the material in the high-pressure pipeline to be within a suitable range.

[0021] Furthermore, the control valve is a needle valve or a ball valve. The opening 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 is ejected from the outlet of the control valve. When the pressure in the high-pressure pipeline drops, the first booster pump is automatically started 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 opening and pressure release process of the control valve, the polymer particles immediately complete the foaming process.

[0022] The technical solution adopted by the present invention to achieve the second purpose is: to provide a method for preparing a continuously extruded tubular polymer bead foam material according to the preparation device described in one of the purposes of the present invention, comprising the following steps: S1, polymer material and nucleating agent enter the extruder through the feed port, are plasticized by the screw and extruded from the head of the underwater pelletizer to obtain granular polymer; S2, the foaming gas in the gas tank is pressurized to 2-15MPa by the first booster pump and then enters the cavity; the dispersed solution in the high-pressure reactor is pressurized by the second booster pump and then enters the cavity; S3, the granular polymer, the foaming gas and the dispersed solution form a mixed material in the cavity, enter the high-pressure pipeline under the action of pressure, and are transported forward along the high-pressure pipeline. When the pressure in the pipeline reaches the target value, the control valve is opened; S4, during the process of the mixed material being transported forward along the high-pressure pipeline, the flow rate of the mixed material is slowed down under the action of multiple flow-blocking agitators, so that the foaming gas fully impregnates the granular polymer in the pipeline; S5. After the mixed material reaches the control valve at the end of the high-pressure pipeline, it is ejected to release the pressure, and the polymer foams immediately to obtain a polymer bead foaming material.

[0023] Furthermore, in step S1, the polymer includes a combination of one or more of polypropylene, polyethylene, polylactic acid, polyphenylene ether, and thermoplastic polyurethane; the nucleating agent includes a combination of one or more of kaolin, talc, zinc borate, polytetrafluoroethylene, nano-calcium carbonate, and clay.

[0024] Furthermore, in step S1, the particle size of the granular polymer is 0.5-3 mm.

[0025] Furthermore, in step S5, while the mixed material is sprayed out to release the pressure, the first booster pump is started to supplement the pressure in the high-pressure pipeline.

[0026] The technical solution adopted by the present invention to achieve the third purpose is: to provide a polymer bead foam material, which is prepared by the preparation device according to one of the purposes of the present invention or the preparation method according to the second purpose of the present invention.

[0027] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention provides a preparation device for a continuous extrusion tubular polymer bead foam material, which combines an extrusion method with a kettle foaming process. On the basis of providing continuous material supply by the extrusion method, a pipeline of a certain length, with controllable internal pressure and temperature is used as a reactor, and a plurality of flow-blocking agitators are arranged in the high-pressure pipeline to control the residence time of the material in the high-pressure pipeline, so that the material can be fully impregnated with the foaming gas during the transportation process 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 obtained polymer bead foam material has the advantages of high closed-cell rate, good resilience, good consistency and uniformity.

[0028] (2) The present invention provides a method for preparing a continuously extruded tubular polymer bead foam material, which uses a polymer as a matrix, a gas such as carbon dioxide as a foaming agent, and water as a dispersion medium, and prepares polymer foam beads through a preparation device and method combining an extruder and a pipeline. The preparation method provided by the present invention is suitable for extrusion foaming of a variety of different polymers, has a simple preparation process, is easy to control, and the quality of the prepared polymer bead foam material is stable, which has broad promotion and application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1A schematic structural diagram of a device for preparing a continuously extruded tubular polymer bead foaming material provided by the present invention; 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 reactor; 10-second booster pump; 11-choked agitator. DETAILED DESCRIPTION

[0030] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0031] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0032] like Figure 1 As shown, an embodiment of the present invention provides a preparation device for continuously extruding tubular polymer bead foaming materials, comprising: 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 choke agitator 11.

[0033] 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 15MPa; a magnetic seal is adopted between the transmission rod connecting the motor and the cutter of the underwater pelletizer 3 and the cavity 4; the material outlet of the cavity 4 is connected to the high-pressure pipeline 5.

[0034] The gas tank 7 is connected to the cavity 4 through the first booster pump 8, and a foaming gas is provided in the gas tank 7; the foaming gas includes one or a combination of carbon dioxide and nitrogen; the foaming gas is pressurized to 2-15MPa by the first booster pump 8 and 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 mixture of water, a surfactant and an inorganic isolation agent, and the temperature of the dispersion solution is 135-180°C.

[0035] 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 2-15MPa, and the reaction temperature is 135-180°C. 3-5 flow-blocking agitators 11 are provided in the high-pressure pipeline 5. The rotation speed of the flow-blocking agitator 11 is 300-500rpm. The flow-blocking agitator 11 controls the residence time of the material in the high-pressure pipeline 5 to 30-60 minutes, so that the gas has enough time to be impregnated into the material. The end of the high-pressure pipeline 5 is connected to the control valve 6, and the material is sprayed out, depressurized and foamed at the outlet of the control valve 6; the control valve 6 is a needle valve or a ball valve.

[0036] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited thereto.

[0037] Example 1 This embodiment provides a Figure 1 The method for preparing the polypropylene bead foamed material of the preparation device shown comprises the following steps: Step 1: 100 parts of polypropylene and 0.5 parts of polytetrafluoroethylene are mixed and added to the feed port 2 of the single screw extruder 1. The five-stage temperature of the single screw extruder is controlled at 180°C, 185°C, 190°C, 195°C, 195°C, and the head temperature is 190°C. The head pressure is 8MPa, and the speed of the underwater pelletizer is 150 rpm. The granular polymer with a particle diameter of 1.0 mm is cut out underwater.

[0038] Step 2: 100 parts of water, 3 parts of kaolin, and 1 part of sodium dodecylbenzene sulfonate are added to the autoclave 9, the autoclave 9 is heated to 150°C, the speed is 300 rpm, and the mixed aqueous solution is pumped into the underwater pelletizer cavity 4 through the second booster pump 10 to prevent the underwater cut polypropylene particles from sticking. At the same time, the first booster pump 8 for foaming gas carbon dioxide is turned on to control the pressure in the tube to be 2.5 MPa.

[0039] Step 3: The granular polymer, foaming gas and dispersed solution form a mixed material in the cavity 4, 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 process, and the pipe length is 300 meters.

[0040] Step 4: Five choke agitators 11 are evenly distributed in the high-pressure pipeline 5. The rotation speed of the choke agitator 11 is 300 rpm. When the mixed material is transported forward along the high-pressure pipeline 5, the flow rate of the mixed material is slowed down under the action of the five choke agitators 11, thereby completing the full impregnation of the granular polymer in the high-pressure pipeline 5 by the foaming gas.

[0041] Step 5: Open the control valve 6 at the end of the high-pressure pipeline 5. If the pressure in the high-pressure pipeline 5 drops, the first booster pump 8 automatically starts to ensure that the pressure in the pipeline 5 is constant at 2.5 MPa. The mixed material is sprayed out from the control valve 6 to release the pressure, and the polymer foams immediately to obtain a density of 0.063 g / cm 3 Polypropylene bead foam material.

[0042] Example 2 This embodiment provides a Figure 1 The method for preparing the polylactic acid bead foamed material of the preparation device shown comprises the following steps: Step 1: 100 parts of polylactic acid and 0.5 parts of talcum powder are mixed and added to the feed port 2 of the conical twin-screw extruder 1. The three-stage temperatures 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 10MPa, and the speed of the underwater pelletizer is 180 rpm. The granular polymer with a particle diameter of 1.2mm is cut out underwater.

[0043] Step 2: 100 parts of water, 4 parts of kaolin, and 1.5 parts of sodium dodecylbenzene sulfonate are added to a high-pressure reactor 9, the reactor temperature is heated to 145°C, the speed is 250 rpm, and the mixed aqueous solution is pumped into the underwater pelletizer cavity 4 through the second booster pump 10 to prevent the polylactic acid particles cut underwater from sticking. At the same time, the first booster pump 8 for foaming gas carbon dioxide is turned on to control the pressure in the tube to 3MPa.

[0044] Step 3: The granular polymer, foaming gas and dispersed solution form a mixed material in the cavity 4, 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 145°C throughout the process, and the pipe length is 500 meters.

[0045] Step 4: Three choke agitators 11 are evenly distributed in the high-pressure pipeline 5. The rotation speed of the choke agitator 11 is 300 rpm. When the mixed material is transported forward along the high-pressure pipeline 5, the flow rate of the mixed material is slowed down under the action of the three choke agitators 11, thereby completing the full impregnation of the granular polymer in the high-pressure pipeline 5 by the foaming gas.

[0046] Step 5: Open the control valve 6 at the end of the high-pressure pipeline 5. If the pressure in the high-pressure pipeline 5 drops, the first booster pump 8 automatically starts to ensure that the pressure in the pipeline 5 is constant at 3 MPa. The mixed material is sprayed out from the control valve 6 to release the pressure, and the polymer foams immediately to obtain a density of 0.085 g / cm 3 Polylactic acid bead foam material.

[0047] Example 3 This embodiment provides a Figure 1The method for preparing the polyphenylene ether polystyrene copolymer bead foamed material of the preparation device shown comprises the following steps: Step 1: 70 parts of polyphenylene ether, 30 parts of polystyrene and 0.5 parts of kaolin are mixed and added to the feed port 2 of the parallel twin-screw extruder 1. The temperatures of the 10 sections of the parallel twin-screw extruder are respectively controlled at 200°C, 205°C, 210°C, 210°C, 210°C, 210°C, 210°C, 210°C, 210°C, 210°C, and 210°C. The die temperature is 200°C. The die pressure is 8MPa, and the speed of the underwater pelletizer is 300 rpm. Granular polymer with a particle diameter of 0.9mm is cut out underwater.

[0048] Step 2: 100 parts of water, 5 parts of kaolin, and 0.8 parts of sodium dodecylbenzene sulfonate are added to the autoclave 9, the autoclave 9 is heated to 175°C, the speed is 200 rpm, and the mixed aqueous solution is pumped into the underwater pelletizer cavity 4 through the second booster pump 10 to prevent the underwater cut polyphenylene ether particles from sticking. At the same time, the first carbon dioxide booster pump 8 is turned on to control the pressure in the pipe to be 4.0 MPa.

[0049] Step 3: The granular polymer, foaming gas and dispersed solution form a mixed material in the cavity 4, 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 process, and the pipe length is 400 meters.

[0050] Step 4: There are four choke agitators 11 evenly distributed in the high-pressure pipeline 5. The rotation speed of the choke agitator 11 is 500 rpm. When the mixed material is transported forward along the high-pressure pipeline 5, the flow rate of the mixed material is slowed down under the action of the four choke agitators 11, thereby completing the full impregnation of the granular polymer in the high-pressure pipeline 5 by the foaming gas.

[0051] Step 5: Open the control valve 6 at the end of the high-pressure pipeline 5. If the pressure in the high-pressure pipeline 5 drops, the first booster pump 8 automatically starts to ensure that the pressure in the pipeline 5 is constant at 4.0 MPa. The mixed material is ejected from the control valve 6 to release the pressure, and the polymer foams immediately to obtain a density of 0.102 g / cm 3 Polyphenylene ether polystyrene copolymer bead foam material.

[0052] Example 4 This embodiment provides a Figure 1 The preparation method of the thermoplastic polyurethane TPU bead foaming material of the preparation device shown comprises the following steps: Step 1: 100 parts of thermoplastic polyurethane TPU and 1.0 part of nano calcium carbonate are mixed and added to the feed port 2 of the single screw extruder 1. The five-stage temperature of the single screw extruder is controlled at 150°C, 160°C, 170°C, 180°C, 180°C, and the head temperature is 180°C. The head pressure is 8MPa, and the speed of the underwater pelletizer is 200 rpm. The granular polymer with a particle diameter of 1.8mm is cut out underwater.

[0053] 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 rpm, and the mixed aqueous solution is pumped into the underwater pelletizer cavity 4 through the second booster pump 10. At the same time, the first booster pump 8 with a nitrogen and carbon dioxide ratio of 1:1 is turned on to control the pipe surface pressure to 10 MPa.

[0054] Step 3: The granular polymer, foaming gas and dispersed solution form a mixed material in the cavity 4, 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 process, and the pipe length is 400 meters.

[0055] Step 4: Five choke agitators 11 are evenly distributed in the high-pressure pipeline 5. The rotation speed of the choke agitator 11 is 300 rpm. When the mixed material is transported forward along the high-pressure pipeline 5, the flow rate of the mixed material is slowed down under the action of the five choke agitators 11, thereby completing the full impregnation of the granular polymer in the high-pressure pipeline 5 by the foaming gas.

[0056] Step 5: Open the control valve 6 at the end of the high-pressure pipeline 5. If the pressure in the high-pressure pipeline 5 drops, the first booster pump 8 automatically starts to ensure that the pressure in the pipeline 5 is constant at 10 MPa. The mixed material is ejected from the control valve 6 to release the pressure, and the polymer foams immediately to obtain a density of 0.1 g / cm 3 Thermoplastic polyurethane TPU bead foaming material.

[0057] Comparative Example 1 This comparative example provides a method for preparing a polypropylene bead foam material, which is mainly different from Example 1 in that the length of the high-pressure pipeline in the preparation device used in the preparation method is 50 meters, and no flow-blocking agitator is installed in the high-pressure pipeline. The preparation method comprises the following steps: Step 1: 100 parts of polypropylene and 0.5 parts of polytetrafluoroethylene are mixed and added to the feed port 2 of the single screw extruder 1. The five-stage temperature of the single screw extruder is controlled at 180°C, 185°C, 190°C, 195°C, 195°C, and the head temperature is 190°C. The head pressure is 8MPa, and the speed of the underwater pelletizer is 150 rpm. The granular polymer with a particle diameter of 1.0 mm is cut out underwater.

[0058] Step 2: 100 parts of water, 3 parts of kaolin, and 1 part of sodium dodecylbenzene sulfonate are added to the autoclave 9, the autoclave 9 is heated to 150°C, the speed is 300 rpm, and the mixed aqueous solution is pumped into the underwater pelletizer cavity 4 through the second booster pump 10 to prevent the underwater cut polypropylene particles from sticking. At the same time, the first booster pump 8 for foaming gas carbon dioxide is turned on to control the pressure in the tube to be 2.5 MPa.

[0059] Step 3: The granular polymer, foaming gas and dispersed solution form a mixed material in the cavity 4, 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 process, and the pipe length is 50 meters.

[0060] Step 4: Open the control valve 6 at the end of the high-pressure pipeline 5. If the pressure in the high-pressure pipeline 5 drops, the first booster pump 8 automatically starts to ensure that the pressure in the pipeline 5 is constant at 2.5 MPa. The mixed material is sprayed out from the control valve 6 to release the pressure, and the polymer foams immediately to obtain a density of 0.88 g / cm 3 Polypropylene bead foam material.

[0061] Comparative Example 2 This comparative example provides a method for preparing a polypropylene bead foam material. The main difference from Example 1 is that in the preparation device used in this comparative example, the extruder works discontinuously, and the high-pressure pipeline is used to simulate the intermittent autoclave method. The preparation method comprises the following steps: Step 1: Before starting the extruder 1, the control valve 6 at the end of the high-pressure pipe 5 is opened. 100 parts of polypropylene and 0.5 parts of polytetrafluoroethylene are mixed and added to the feed port 2 of the single-screw extruder 1. The five-stage temperature of the single-screw extruder is 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 8MPa, and the speed of the underwater pelletizer is 150 rpm. Granular polymer with a particle diameter of 1.0mm is cut out underwater.

[0062] Step 2: 100 parts of water, 3 parts of kaolin, and 1 part of sodium dodecylbenzene sulfonate are added to the autoclave 9, the autoclave 9 is heated to 150°C, the speed is 300 rpm, and the mixed aqueous solution is pumped into the underwater pelletizer cavity 4 through the second booster pump 10 to prevent the underwater cut polypropylene particles from sticking. At the same time, the first booster pump 8 of the foaming gas carbon dioxide is turned on. 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 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, the pipe length is 300 meters, and there are 5 flow-blocking stirrers 11 evenly distributed along the high-pressure pipeline, and the speed is 300 rpm. After the particles are ejected from the control valve 6 at the end of the opened high-pressure pipeline 5, the control valve 6 at the end of the high-pressure pipeline 5 is closed, and the extruder 1 is closed.

[0063] Step 3: Control the pressure in the pipe to 2.5MPa, and keep it at 150°C for 30 minutes, then open the control valve 6 at the end of the high-pressure pipe 5. If the pressure in the high-pressure pipe 5 drops, the first booster pump 8 will automatically start to ensure that the pressure in the pipe 5 is constant at 2.5MPa until the particles are sprayed. At the same time, the second booster pump 10 will also automatically start to continuously pump the mixed liquid into the underwater pelletizer cavity 4. When the mixed material is sprayed out from the control valve 6, the polymer will foam and obtain a density of 0.072g / cm 3 Polypropylene bead foam material.

[0064] The main parameters, reaction conditions and test results of the products involved in the embodiments and comparative examples of the present invention are shown in Tables 1-3 below: Table 1

[0065] Table 2

[0066] Table 3

[0067] It can be seen from Table 3 above that Embodiments 1-4 of the present invention combine the extrusion method with the kettle foaming process, use a pipeline of a certain length with controllable internal pressure and temperature as a reactor, and set a plurality of resistant agitators in the high-pressure pipeline to control the residence time of the material in the high-pressure pipeline, so that the material can be fully impregnated with the foaming gas during the transportation process in the pipeline. The obtained polymer bead foaming material has the advantages of high closed cell rate, good resilience, good consistency and uniformity.

[0068] Compared with Example 1, the length of the high-pressure pipeline in Comparative Example 1 is shorter and no flow-blocking agitator is installed, so the foaming ratio of the plastic particles is small. Compared with Example 1, the extruder in Comparative Example 2 works discontinuously, and the high-pressure pipeline is used to simulate the intermittent kettle method, so the foamed product obtained has the defect of poor batch uniformity.

[0069] The above are only preferred embodiments of the present invention, and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the contents 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); the material is sprayed out at the outlet of the control valve (6), the pressure is released and foaming occurs; 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 50-500 meters, the reaction pressure in the high-pressure pipeline (5) is 2-15 MPa, and the reaction temperature is 135-180° C.; there are a plurality of flow-blocking agitators (11) evenly distributed in the high-pressure pipeline (5) for controlling the residence time of the material in the high-pressure pipeline (5).

2. The preparation device according to claim 1, characterized in that: The number of the baffle agitators (11) is 3-5, and the rotation speed of the baffle agitators (11) is 300-500 rpm.

3. 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).

4. 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).

5. 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.

6. 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.

7. A method for preparing a continuously extruded tubular polymer bead foam material according to any one of claims 1 to 6, 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.

8. The preparation method according to claim 7, 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.

9. The preparation method according to claim 7, characterized in that: In step S1, the particle size of the granular polymer is 0.5-3 mm.

10. A polymer bead foam material, characterized in that: The method is prepared by the preparation device according to any one of claims 1 to 6 or the preparation method according to any one of claims 7 to 9.

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