A continuous foaming method and continuous foaming device for polymer particles

Abstract

The invention discloses a continuous foaming method for polymer particles, comprising the following steps: S1, conveying a suspension and an isolating agent into a polymer bead foaming heating high-pressure-ultra-high-pressure container; S2, heating the suspension and the isolating agent mixture; S3, conveying polymer particles, carbon dioxide and nitrogen mixed gas into the polymer bead foaming heating high-pressure-ultra-high-pressure container successively or simultaneously; S4, the polymer particles are swollen and infiltrated by the mixed gas in the polymer bead foaming heating high-pressure-ultra-high-pressure container, and finally ejected from the foaming nozzle above, at which time the polymer particles expand and foam due to rapid pressure relief to form polymer foaming beads; S5, collecting the polymer foaming beads; The invention also discloses a continuous foaming device for polymer particles, which solves the technical problems of unstable production quality, poor uniformity and low foaming ratio of polymer foaming beads.

Description

Technical Field

[0001] The invention relates to the field of polymer particle foaming, in particular to a continuous foaming method and a continuous foaming device for polymer particles. Background Art

[0002] Polymer foam beads are a kind of bead-like material with a porous structure made by foaming a polymer matrix. They are then processed through molding equipment, using steam molding or bonding molding to make the polymer foam beads fuse with each other and be processed into foam products with a certain geometric structure. They are strong and lightweight, energy-absorbing and shock-proof, and heat-insulating. They are widely used in packaging, construction, transportation, sports equipment and other fields.

[0003] At present, polymer foam beads are mainly prepared by kettle pressure foaming and extrusion foaming. The production process of preparing polymer foam beads by kettle pressure foaming is carried out in an intermittent manner, and the control is relatively simple, but its production efficiency is low. Although the polymer foam beads prepared by the existing extrusion foaming method have the advantages of continuous molding, high production efficiency, and good automation, their production process is unstable, the pressure adjustment range is small, the temperature control system is complex, the pressure relief rate of the extrusion foaming process is small and cannot be adjusted and controlled, the foam beads have poor pore uniformity, a small foaming ratio, and a large open porosity of the foam beads. Summary of the invention

[0004] The purpose of the present invention is to overcome the above-mentioned defects in the prior art and to provide a continuous foaming method and a continuous foaming device for polymer particles to solve the technical problems of unstable production quality of polymer foam beads, poor uniformity of the pores of the foam beads, small foaming ratio and large open porosity of the foam beads.

[0005] To achieve the above object, the present invention provides a method for continuous foaming of polymer particles, comprising the following steps:

[0006] S1, conveying the suspension and the release agent mixture at a temperature of 60°C to 200°C into a polymer bead foaming and heating high-pressure-ultra-high-pressure container, and filling the polymer bead foaming and heating high-pressure-ultra-high-pressure container; wherein the density of the selected suspension is greater than the density of the polymer particles, and the relative density of the suspension is 0.5-5.0;

[0007] S2, using a heating device to uniformly heat the suspension and the release agent mixture in the high-pressure / ultra-high-pressure container for foaming the polymer beads, so that the temperature in the high-pressure / ultra-high-pressure container is uniform, and the heating temperature is 60° C. to 350° C.;

[0008] Preferably, the temperature is controlled to be 5°C to 150°C below the melting point of the polymer;

[0009] S3. After the suspension and the release agent are uniformly heated to the specified temperature, the polymer particles with a preheating temperature of 60°C to 300°C and a mixed gas of carbon dioxide and nitrogen with a temperature of 60°C to 350°C and a pressure of 0 to 50 MPa are successively or simultaneously transported to the polymer bead foaming heating high-pressure or ultra-high-pressure container; wherein the pressure of the polymer bead foaming heating high-pressure or ultra-high-pressure container can be freely adjusted with the pressure of the gas delivery system, and the pressure adjustment range is 0 to 50 MPa;

[0010] S4. The polymer particles are in the polymer bead foaming and heating high-pressure-ultra-high-pressure container at a temperature of 60°C to 350°C and a pressure of 0 to 50 MPa. The polymer particles will be swollen and penetrated by the mixed gas. Since the relative density of the polymer particles is smaller than that of the suspension, the polymer particles gradually move upward under the action of the suspension force, and after 5 to 60 minutes, they are finally ejected continuously from the upper foaming nozzle. The pressure relief rate of the foaming can be freely adjusted by adjusting the gap width between the foaming nozzle and the pressure regulating block arranged above the polymer bead foaming and heating high-pressure-ultra-high-pressure container to adjust the pressure in the polymer bead foaming and heating high-pressure-ultra-high-pressure container and the change of the pressure of the foaming nozzle, thereby controlling the pressure relief rate of the foaming nozzle. The adjustment range of the gap width is 0.1 to 10.0 mm. At this time, the polymer particles expand and foam due to rapid pressure relief to form polymer foaming beads.

[0011] S5. Collect the polymer foam beads sprayed from the foaming nozzle.

[0012] Preferably, the method further comprises the following steps:

[0013] S6. Wash, dry and package the collected polymer foam beads.

[0014] Preferably, the suspension is a mixed suspension of one or more of a talc suspension, a calcium carbonate suspension or a barium sulfate suspension.

[0015] Preferably, the release agent is a mixture of one or more of an aqueous soap release agent, an aqueous zinc stearate, an aqueous calcium stearate, and a soap water release agent.

[0016] Preferably, in step S4, the pressure of the polymer particles sprayed from the foaming nozzle is controlled to be 0.5-15 MPa, and the pressure relief speed is 1-10000 MPa / s.

[0017] Compared with the prior art, the method for continuous foaming of polymer particles provided by the present invention has the following beneficial effects:

[0018] (1) This method can realize high pressure continuous sealed conveying of polymer particle materials, and can ensure the continuous preparation of foamed polymer foam beads, and has the outstanding advantages of high production efficiency and low cost;

[0019] (2) Since the pressure of the high-pressure / ultra-high-pressure container for foaming and heating polymer beads in the technical solution is derived from the pressure of the mixed gas of carbon dioxide and nitrogen, the pressure of the high-pressure / ultra-high-pressure container for foaming and heating polymer beads can be freely adjusted along with the pressure adjustment of the mixed gas of carbon dioxide and nitrogen. According to the process pressure requirement, the pressure of the high-pressure / ultra-high-pressure container and the pressure change of the foaming nozzle can be freely adjusted by setting a foaming nozzle with adjustable pressure relief rate above the high-pressure / ultra-high-pressure container for foaming and heating polymer beads; the pressure adjustment range of the technical solution of the present invention is wide, and the pressure can easily reach 50 MPa. The pressure of the high-pressure / ultra-high-pressure container can be freely adjusted according to the pressure requirement. The pressure relief rate of the foaming nozzle is controlled by adjusting the pressure of the extruder and the foaming nozzle, thereby overcoming the defect that the pressure cannot be adjusted during the foaming process of the extruder; the pressure relief rate of the pressure system of the method for continuously preparing the foamed polymer foam beads can be adjusted as needed, and the precise control of the product structure of the polymer foam particles can be achieved to ensure better quality, thereby overcoming the defect that the method for continuous foaming by extrusion is unstable in process, and the pressure relief rate of the extruder in the foaming process is small and cannot be adjusted and controlled, the foaming beads have poor pore uniformity, a small foaming ratio, and a large open porosity. Therefore, the foaming process of the method has the advantages of being more stable, more reliable in control, more efficient in production, and low in cost;

[0020] (3) The technical solution adopts a heating device to heat the polymer beads for foaming and uniformly heat the high-pressure-ultra-high-pressure container as a whole, so that the temperature difference of the overall temperature of the high-pressure-ultra-high-pressure container is small, the temperature of the entire temperature system is basically consistent, and there is no temperature difference, which ensures the consistency of the foaming quality and overcomes the instability factor of the large temperature difference of the extruder foaming temperature from the melting temperature to the extrusion foaming temperature. The temperature change range of the extruder extrusion foaming process is generally from the melting temperature (about 200°C) to the foaming temperature (about 100°C), and the temperature difference changes greatly;

[0021] (4) The polymer foam beads prepared by this method have a large foaming ratio, a fine and uniform pore structure, and a closed cell rate of more than 90%, overcoming the defect of low closed cell rate of the extrusion continuous foaming method.

[0022] To achieve the above-mentioned purpose, the present invention also provides a polymer particle continuous foaming device, including a bead foaming system, and a polymer particle conveying system, a gas conveying system and a liquid conveying system respectively connected to the bead foaming system; the bead foaming system includes a polymer bead foaming heating high-pressure-ultra-high-pressure container, a foaming nozzle arranged above the polymer bead foaming heating high-pressure-ultra-high-pressure container, a nozzle gap pressure regulating block arranged above the foaming nozzle, a foaming bead collecting box arranged above the polymer bead foaming heating high-pressure-ultra-high-pressure container, a foaming bead discharge port arranged on one side of the foaming bead collecting box, and a pressure regulating block for the polymer bead foaming heating high-pressure-ultra-high-pressure container. A heating device for uniform heating as a whole; the polymer particle conveying system comprises a polymer particle storage tank for storing polymer particles, and a pressure conveyor connected to the polymer particle storage tank; the pressure conveyor is used to quantitatively convey polymer particles into a polymer bead foaming heating high-pressure-ultra-high-pressure container; the liquid conveying system is used to convey a suspension and a release agent mixed liquid with a temperature of 60°C to 200°C into the polymer bead foaming heating high-pressure-ultra-high-pressure container; the gas conveying system is used to convey a carbon dioxide and nitrogen mixed gas with a temperature of 60°C to 350°C and a pressure of 0 to 50MPa into the polymer bead foaming heating high-pressure-ultra-high-pressure container.

[0023] Preferably, the suspension is a mixed suspension of one or more of talcum powder suspension, calcium carbonate suspension or barium sulfate suspension; the isolation agent is a mixture of one or more of aqueous soap isolation agent, aqueous zinc stearate and aqueous calcium stearate, and soap water isolation agent.

[0024] Preferably, the liquid delivery system includes a liquid storage tank for storing a suspension and an isolating agent, a liquid high-pressure pump connected to the liquid storage tank, a liquid heater connected to the liquid high-pressure pump, and a one-way valve connected to the liquid heater, and the one-way valve is connected to the polymer bead foaming heating high-pressure-ultra-high-pressure container; the gas delivery system includes a carbon dioxide storage tank for storing carbon dioxide, a nitrogen storage tank for storing nitrogen, a first high-pressure pump connected to the carbon dioxide storage tank, a second high-pressure pump connected to the nitrogen storage tank, and a gas heater respectively connected to the first high-pressure pump and the second high-pressure pump, and the gas heater is connected to the polymer bead foaming heating high-pressure-ultra-high-pressure container or a pressure conveyor.

[0025] Preferably, the pressure conveyor is a Venturi tube, and the gas heater is connected to the pressure conveyor.

[0026] Preferably, the pressure conveyor includes a cylinder body connected to a polymer bead foaming and heating high-pressure to ultra-high-pressure container, a piston rod slidably connected in the cylinder body, and a driving cylinder for driving the piston rod to telescopically slide in the cylinder body; a polymer particle storage chamber is provided on the piston rod, and when the piston rod is in a retracted state, the polymer particle storage chamber is connected to a polymer particle storage tank, and when the piston rod is in an extended state, the polymer particle storage chamber is connected to the polymer bead foaming and heating high-pressure to ultra-high-pressure container.

[0027] Compared with the prior art, the polymer particle continuous foaming device provided by the present invention has the following beneficial effects:

[0028] (1) The device can realize high-pressure continuous sealed conveying of polymer particle materials, which can ensure the continuous preparation of foamed polymer foam beads, and has the outstanding advantages of high production efficiency and low cost;

[0029] (2) With the present device, the pressure of the high-pressure / ultra-high-pressure container for foaming and heating polymer beads is derived from the pressure of the carbon dioxide and nitrogen mixed gas. Therefore, the pressure of the high-pressure / ultra-high-pressure container for foaming and heating polymer beads can be freely adjusted along with the pressure adjustment of the carbon dioxide and nitrogen mixed gas. According to the process pressure requirement, the pressure of the high-pressure / ultra-high-pressure container and the pressure change of the foaming nozzle can be freely adjusted by setting a foaming nozzle with adjustable pressure relief rate above the high-pressure / ultra-high-pressure container for foaming and heating polymer beads. The pressure adjustment range of the technical solution of the present invention is wide, and the pressure can easily reach 50 MPa. The high-pressure / ultra-high-pressure container can be freely adjusted according to the pressure requirement. The pressure of the extruder and the change of the pressure of the foaming nozzle are controlled to control the pressure relief rate of the foaming nozzle, thus overcoming the defect that the pressure cannot be adjusted during the foaming process of the extruder. The pressure relief rate of the pressure system of the device for continuously preparing foamed polymer foam beads can be adjusted as needed, which can realize the precise control of the product structure of the polymer foam particles, ensure better quality, and overcome the defect of unstable process of the method of continuous foaming by extrusion; while the pressure relief rate of the extruder in the foaming process is small and cannot be adjusted and controlled, the uniformity of the pores of the foam beads is poor, the foaming ratio is small, and the open porosity of the foam beads is large. The device has the advantages of being more stable, more reliable to control, more efficient in production, and low in cost;

[0030] (3) The technical solution adopts a heating device to heat the polymer beads for foaming and uniformly heat the high-pressure-ultra-high-pressure container as a whole, so that the temperature difference of the overall temperature of the high-pressure-ultra-high-pressure container is small, the temperature of the entire temperature system is basically consistent, and there is no temperature difference, which ensures the consistency of the foaming quality and overcomes the instability factor of the large temperature difference of the extruder foaming temperature from the melting temperature to the extrusion foaming temperature. The temperature change range of the extruder extrusion foaming process is generally from the melting temperature (about 200°C) to the foaming temperature (about 100°C), and the temperature difference changes greatly;

[0031] (4) The polymer foam beads prepared by the device have a large foaming ratio, a fine and uniform pore structure, and a closed cell rate of more than 90%, overcoming the defect of low closed cell rate of the extrusion continuous foaming method. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 It is a schematic diagram of the planar structure of a continuous foaming device for preparing low-density polymer particles by continuous foaming provided by the present invention;

[0034] Figure 2 It is a schematic diagram of the planar structure of the polymer particle conveying system provided by the present invention when the pressure conveyor is a venturi tube;

[0035] Figure 3 It is a schematic diagram of the planar structure of the polymer particle conveying system provided by the present invention when the pressure conveyor is a cylinder particle material pressure conveying device and is in a material storage state;

[0036] Figure 4 It is a schematic plan view of the structure of the polymer particle conveying system provided by the present invention when the pressure conveyor is a cylinder particle material pressure conveying device and is in a feeding state. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are 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 creative work are within the scope of protection of the present invention.

[0038] The present invention provides a continuous foaming method and a continuous foaming device for preparing low-density polymer particles by continuous foaming, such as Figure 1 As shown, it comprises a bead foaming system 1, and a polymer particle conveying system 2, a gas conveying system 3 and a liquid conveying system 4 respectively connected to the bead foaming system 1.

[0039] The bead foaming system 1 includes a polymer bead foaming heating high-pressure-ultra-high pressure container 11, a foaming nozzle 12 arranged above the polymer bead foaming heating high-pressure-ultra-high pressure container 11, a nozzle gap pressure regulating block 13 arranged above the foaming nozzle 12, a foaming bead collecting box 14 arranged above the polymer bead foaming heating high-pressure-ultra-high pressure container 11, a foaming bead discharge port 15 arranged on one side of the foaming bead collecting box 14, and a heating device. The heating device here is used to heat the material in the polymer bead foaming heating high-pressure-ultra-high pressure container 11. In this embodiment, it is preferably a heating sleeve 16 arranged on the outer wall of the polymer bead foaming heating high-pressure-ultra-high pressure container 11. The pressure of the polymer bead foaming heating high-pressure-ultra-high pressure container 11 can be freely adjusted with the pressure of the gas delivery system 3, and the pressure adjustment range is 0 to 50 MPa.

[0040] The polymer particle conveying system 2 includes a polymer particle storage tank 21 for storing polymer particles, and a pressure conveyor 22 connected to the polymer particle storage tank 21; the pressure conveyor 22 is used to quantitatively convey polymer particles into the polymer bead foaming heating high-pressure-ultra-high-pressure container 11.

[0041] The liquid delivery system 4 is used to deliver the suspension and the isolation agent mixture at a temperature of 60°C to 200°C to the polymer bead foaming heating high-pressure-ultra-high-pressure container 11. Specifically, in this embodiment, the liquid delivery system 4 includes a liquid storage tank 41 for storing the suspension and the isolation agent, a liquid high-pressure pump 42 connected to the liquid storage tank 41, a liquid heater 43 connected to the liquid high-pressure pump 42, and a one-way valve 44 connected to the liquid heater 43, and the one-way valve 44 is connected to the polymer bead foaming heating high-pressure-ultra-high-pressure container 11. In addition, the suspension here is a mixed suspension of one or more of talcum powder suspension, calcium carbonate suspension or barium sulfate suspension; the isolation agent here is a mixture of one or more of aqueous soap isolation agent, aqueous zinc stearate and aqueous calcium stearate, and soap water isolation agent. The relative density of the suspension is 0.5-5.0.

[0042] The gas delivery system 3 is used to deliver a mixed gas of carbon dioxide and nitrogen at a temperature of 60°C to 350°C and a pressure of 0 to 50 MPa to the polymer bead foaming heating high-pressure-ultra-high-pressure container 11. Specifically, in this embodiment, the gas delivery system 3 includes a carbon dioxide storage tank 31 for storing carbon dioxide, a nitrogen storage tank 32 for storing nitrogen, a first high-pressure pump 33 connected to the carbon dioxide storage tank 31, a second high-pressure pump 34 connected to the nitrogen storage tank 32, and a gas heater 35 connected to the first high-pressure pump 33 and the second high-pressure pump 34, respectively, and the gas heater 35 is connected to the polymer bead foaming heating high-pressure-ultra-high-pressure container 11 or the pressure conveyor 22.

[0043] The working principle of the device for continuously preparing foamed polymer foam beads is as follows: first, the suspension and the isolation agent in the liquid storage tank 41 are transported to the liquid heater 43 for heating by a liquid high-pressure pump 42 (the pressure is 0-50 MPa, and the pressure is selected according to the permeability of the gas to the polymer) at a temperature of 60-200°C, and then the suspension and the isolation agent are transported to the polymer bead foaming heating high-pressure-ultra-high-pressure container 11 through a one-way valve 44, so that the suspension and the isolation agent fill the entire polymer bead foaming heating high-pressure-ultra-high-pressure container 11, and at the same time, the heating sleeve 16 is used to heat the suspension in the polymer bead foaming heating high-pressure-ultra-high-pressure container 11. The suspension and the isolation agent are heated at a temperature of 60 to 350°C (the temperature is determined according to the melting temperature of the polymer. The general process temperature parameter is taken to be below the melting point of the polymer. Preferably, the temperature is controlled at 5 to 150°C below the melting point of the polymer. Different polymers have different melting points). After reaching the required temperature, the first high-pressure pump 33 (with a pressure of 0 to 50 MPa) quantitatively transports the carbon dioxide in the carbon dioxide storage tank 31 to the gas heater 35 (heating temperature is 60 to 350°C). At the same time, the second high-pressure pump 34 (with a pressure of 0 to 50 MPa) quantitatively transports the nitrogen in the nitrogen storage tank 32 to the gas heater 35. The polymer particles preheated to 60-350°C in the polymer particle storage tank 21 are then conveyed to the polymer bead foaming heating high-pressure-ultra-high-pressure container 11 in sequence or together with the heated high-pressure mixed gas (pressure of 0-50 MPa) through the pressure conveyor 22. At this time, since the polymer beads are subjected to the 60-350°C temperature and 0-50 MPa pressure in the polymer bead foaming heating high-pressure-ultra-high-pressure container 11, the polymer particles will be swollen and penetrated by the mixed gas. At the same time, since the relative density of the polymer particles is smaller than that of the suspension, the polymer The particles gradually drift upward under the action of the suspension force, and reach the foaming nozzle 12 after a period of time (5 to 60 minutes), and then are quickly and continuously ejected through the gap between the nozzle gap pressure regulating block 13 and the foaming nozzle 12. The polymer particles expand and foam due to the rapid pressure relief to form polymer foaming beads. The pressure at the foaming nozzle 12 is controlled to be 0.5 to 15 MPa, and the pressure relief rate is 1 to 10000 MPa / s. Finally, the polymer foaming beads are collected by the foaming bead collection box 14 and then discharged from the foaming bead discharge port 15. The foaming beads are then washed, dried, and packaged, thereby realizing a complete continuous foaming method for preparing foaming beads.

[0044] As a preferred example, Figure 2As shown, the pressure conveyor 22 can be a venturi tube. The working principle of the venturi tube is that the cylinder body first contracts and then gradually expands, and the pressure difference between the cross section of its inlet and the smallest cross section is used to convey the polymer particles in the polymer particle storage tank 21 to the polymer bead foaming heating high-pressure-ultra-high-pressure container 11 for pressurization, heating and gas penetration, so as to achieve the purpose of high-pressure pressure continuous sealing conveying of polymer particle materials, so as to continuously prepare foamed polymer foam beads. In this technical solution, the gas heater 35 is directly connected to the venturi tube.

[0045] In addition, if Figure 3 and Figure 4 As shown, the pressure conveyor 22 can also be a cylinder particle material pressure conveying device, which includes a cylinder body 221 connected to the polymer bead foaming and heating high-pressure-ultra-high-pressure container 11, a piston rod 222 slidably connected in the cylinder body 221, and a driving cylinder 223 for driving the piston rod 222 to slide telescopically in the cylinder body 221; a polymer particle storage chamber 2221 is provided on the piston rod 222, and when the piston rod 222 is in a retracted state, the polymer particle storage chamber 2221 is connected to the polymer particle storage tank 21, and when the piston rod 222 is in an extended state, the polymer particle storage chamber 2221 is connected to the polymer bead foaming and heating high-pressure-ultra-high-pressure container 11. In this technical solution, the gas heater 35 is directly connected to the interior of the polymer bead foaming heating high-pressure-ultra-high-pressure container 11, and its working principle is as follows: the piston rod 222 is located below the polymer particle storage tank 21, and the polymer particle storage cavity 2221 is connected to the discharge port of the polymer particle storage tank 21. The polymer particles fall freely into the polymer particle storage cavity 2221 under the action of gravity. Figure 3 The pressure conveyor 22 is in the storage state; then the driving cylinder 223 pushes the piston rod 222 forward, at which time the polymer particle storage chamber 2221 is connected to the polymer bead foaming and heating high-pressure-ultra-high-pressure container 11, and finally the polymer particles are released into the polymer bead foaming and heating high-pressure-ultra-high-pressure container 11, as shown in FIG. Figure 4 This is the feeding state of the pressure conveyor 22. The reciprocating motion of the piston rod 222 is driven by the driving cylinder 223, so as to achieve the purpose of continuously sealing and conveying the polymer particle material under high pressure, so as to continuously prepare the foamed polymer foam beads.

[0046] In summary, the adoption of this technical solution can realize high-pressure continuous sealed conveying of polymer particulate materials, can ensure continuous preparation of foamed polymer foam beads, and has the outstanding advantages of high production efficiency and low cost. Moreover, in this technical solution, the pressure of the polymer bead foaming and heating high-pressure-ultra-high-pressure container 11 is derived from the pressure of the carbon dioxide and nitrogen mixed gas in the gas delivery system 3. Therefore, the pressure of the polymer bead foaming and heating high-pressure-ultra-high-pressure container 11 can be freely adjusted along with the pressure adjustment of the carbon dioxide and nitrogen mixed gas. According to the process pressure requirements, the pressure of the polymer bead foaming and heating high-pressure-ultra-high-pressure container 11 and the pressure of the foaming nozzle 12 can be freely adjusted by setting a foaming nozzle 12 with adjustable pressure relief rate above the polymer bead foaming and heating high-pressure-ultra-high-pressure container 11. The adjustment range is controlled at a pressure of 0 to 50 MPa. The pressure adjustment range of the technical solution of the present invention is wide, and the pressure can easily reach 50 MPa. It can be adjusted according to the pressure requirements. It is necessary to freely adjust the changes in the pressure of the high-pressure-ultra-high-pressure container 11 for foaming the polymer beads and the pressure of the foaming nozzle 12, so as to control the pressure relief rate of the foaming nozzle 12 and overcome the defect that the pressure cannot be adjusted during the foaming process of the extruder. The pressure relief rate of the pressure system of the technical scheme for continuously preparing foamed polymer foam beads can be adjusted as needed, which can achieve precise control of the product structure of the polymer foam particles, ensure better quality, and overcome the defect of unstable process of the extrusion continuous foaming method; while the pressure relief rate of the extruder extrusion foaming process is small and cannot be adjusted and controlled, the foaming beads have poor pore uniformity, a small foaming ratio, and a large open porosity. The technical scheme has the advantages of being more stable, more reliable to control, more efficient in production, and low in cost.

[0047] In addition, the technical solution adopts a heating device to uniformly heat the entire high-pressure-ultra-high-pressure container 11 for foaming the polymer beads. The heating device, such as the heating sleeve 16, makes the temperature difference of the overall temperature of the high-pressure-ultra-high-pressure container 11 for foaming the polymer beads less, and the temperature of the entire temperature system remains basically consistent without temperature difference, thereby ensuring the consistency of the foaming quality and overcoming the unstable factor of the large temperature difference of the extruder foaming temperature from the melting temperature to the extrusion foaming temperature. The temperature change range of the extruder extrusion foaming process generally needs to be cooled from the melting temperature (about 200°C) to the foaming temperature (about 100°C), and the temperature difference changes greatly.

[0048] Finally, the polymer foamed bead product prepared by the technical solution has a large foaming ratio, a fine and uniform pore structure, and a closed cell rate of more than 90%, overcoming the defect of low closed cell rate of the extrusion continuous foaming method.

[0049] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for continuous foaming of polymer particles, characterized in that: The following steps are involved: S1, conveying the suspension and the release agent mixture at a temperature of 60°C to 200°C into a polymer bead foaming and heating high-pressure-ultra-high-pressure container, and filling the polymer bead foaming and heating high-pressure-ultra-high-pressure container; The density of the selected suspension is greater than the density of the polymer particles, and the relative density of the suspension is 0.5-5.0; S2. Using a heating device to uniformly heat the suspension and the release agent mixture in the high-pressure / ultra-high-pressure container for foaming the polymer beads, so that the temperature in the high-pressure / ultra-high-pressure container is uniform and the heating temperature is 60°C to 350°C; and the temperature is controlled to be 5°C to 150°C below the melting point of the polymer; S3. After the suspension and the release agent are uniformly heated to the specified temperature, the polymer particles preheated at 60°C to 300°C and the mixed gas of carbon dioxide and nitrogen at 60°C to 350°C are successively or simultaneously transported to the polymer bead foaming heating high-pressure or ultra-high-pressure container; wherein the pressure of the polymer bead foaming heating high-pressure or ultra-high-pressure container can be freely adjusted according to the pressure of the gas delivery system, and the pressure adjustment range is 0 to 50 MPa; S4. The polymer particles are in the polymer bead foaming and heating high-pressure-ultra-high-pressure container at a temperature of 60°C to 350°C and a pressure of 0 to 50 MPa. The polymer particles will be swollen and penetrated by the mixed gas. Since the relative density of the polymer particles is smaller than that of the suspension, the polymer particles gradually move upward under the action of the suspension force. After 5 to 60 minutes, they are finally ejected continuously from the foaming nozzle above. The pressure relief rate of foaming can be freely adjusted by adjusting the gap width between the foaming nozzle and the pressure regulating block above the polymer bead foaming and heating high-pressure-ultra-high-pressure container and the change of the pressure of the foaming nozzle, thereby controlling the pressure relief rate of the foaming nozzle. The adjustment range of the gap width is 0.1 to 10.0 mm. At this time, the polymer particles expand and foam due to rapid pressure relief to form polymer foaming beads. S5. Collect the polymer foam beads sprayed from the foaming nozzle.

2. A method for continuous foaming of polymer particles according to claim 1, characterized in that: The following steps are also included: S6. Wash, dry and package the collected polymer foam beads.

3. A method for continuous foaming of polymer particles according to claim 1, characterized in that: The suspension is a mixed suspension of one or more of a talcum powder suspension, a calcium carbonate suspension or a barium sulfate suspension.

4. A method for continuous foaming of polymer particles according to claim 1, characterized in that: The release agent is a mixture of one or more of an aqueous soap release agent, an aqueous zinc stearate, an aqueous calcium stearate, and a soap water release agent.

5. The method for continuous foaming of polymer particles according to claim 1, characterized in that: In step S4, the pressure of the polymer particles sprayed from the foaming nozzle is controlled to be 0.5-15 MPa, and the pressure relief speed is 1-10000 MPa / s.

6. A polymer particle continuous foaming device for use in a polymer particle continuous foaming method according to any one of claims 1 to 5, comprising a bead foaming system (1), and a polymer particle conveying system (2), a gas conveying system (3) and a liquid conveying system (4) respectively connected to the bead foaming system (1), characterized in that: The bead foaming system (1) comprises a polymer bead foaming heating high-pressure / ultra-high-pressure container (11), a foaming nozzle (12) with an adjustable pressure relief rate arranged above the polymer bead foaming heating high-pressure / ultra-high-pressure container (11), a nozzle gap pressure regulating block (13) arranged above the foaming nozzle (12), a foaming bead collecting box (14) arranged above the polymer bead foaming heating high-pressure / ultra-high-pressure container (11), a foaming bead discharge port (15) arranged on one side of the foaming bead collecting box (14), and a heating device for uniformly heating the entire polymer bead foaming heating high-pressure / ultra-high-pressure container (11); The polymer particle conveying system (2) comprises a polymer particle storage tank (21) for storing polymer particles, and a pressure conveyor (22) connected to the polymer particle storage tank (21); the pressure conveyor (22) is used to quantitatively convey polymer particles into the polymer bead foaming heating high-pressure / ultra-high-pressure container (11); The liquid delivery system (4) is used to deliver a suspension and a release agent mixed liquid at a temperature of 60°C to 200°C into a polymer bead foaming heating high pressure / ultra-high pressure container (11); the gas delivery system (3) is used to deliver a carbon dioxide and nitrogen mixed gas at a temperature of 60°C to 350°C and a pressure of 0 to 50 MPa into the polymer bead foaming heating high pressure / ultra-high pressure container (11).

7. A polymer particle continuous foaming device according to claim 6, characterized in that: The suspension is a mixed suspension of one or more of talcum powder suspension, calcium carbonate suspension or barium sulfate suspension; the isolation agent is a mixture of one or more of aqueous soap isolation agents, aqueous zinc stearate, aqueous calcium stearate and soap water isolation agents.

8. A polymer particle continuous foaming device according to claim 6, characterized in that: The liquid delivery system (4) comprises a liquid storage tank (41) for storing a suspension and an isolating agent, a liquid high-pressure pump (42) connected to the liquid storage tank (41), a liquid heater (43) connected to the liquid high-pressure pump (42), and a one-way valve (44) connected to the liquid heater (43), wherein the one-way valve (44) is connected to a polymer bead foaming heating high-pressure / ultra-high-pressure container (11); The gas delivery system (3) comprises a carbon dioxide storage tank (31) for storing carbon dioxide, a nitrogen storage tank (32) for storing nitrogen, a first high-pressure pump (33) connected to the carbon dioxide storage tank (31), a second high-pressure pump (34) connected to the nitrogen storage tank (32), and a gas heater (35) respectively connected to the first high-pressure pump (33) and the second high-pressure pump (34), wherein the gas heater (35) is connected to a polymer bead foaming heating high-pressure / ultra-high-pressure container (11) or a pressure conveyor (22).

9. A polymer particle continuous foaming device according to claim 8, characterized in that: The pressure conveyor (22) is a Venturi tube, and the gas heater (35) is connected to the pressure conveyor (22).

10. The polymer particle continuous foaming device according to claim 6, characterized in that: The pressure conveyor (22) comprises a cylinder body (221) connected to a polymer bead foaming and heating high-pressure / ultra-high-pressure container (11), a piston rod (222) slidably connected to the cylinder body (221), and a driving cylinder (223) for driving the piston rod (222) to slide and retract in the cylinder body (221); a polymer particle storage chamber (2221) is provided on the piston rod (222); when the piston rod (222) is in a retracted state, the polymer particle storage chamber (2221) is connected to a polymer particle storage tank (21); when the piston rod (222) is in an extended state, the polymer particle storage chamber (2221) is connected to the interior of the polymer bead foaming and heating high-pressure / ultra-high-pressure container (11).

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