A method for the preparation of a pre-nucleated assisted low density thermoplastic elastomer foam

Abstract

This invention relates to a method for preparing prenucleation-assisted low-density thermoplastic elastomer foam. The method involves feeding thermoplastic elastomer particles into the feed port of an extrusion foaming equipment, adjusting the temperature of each temperature zone of the screw, the screw speed, and the amount of foaming agent gas added to melt the thermoplastic elastomer particles and mix them with the foaming agent gas, then extruding and foaming to obtain a prenucleated sample with pores. The first foaming vessel is pre-set to a low temperature, and the prenucleated sample is transferred to it. A first low-pressure gas is introduced, and the sample is placed under low-temperature and low-pressure conditions for a second preset saturation time, followed by depressurization. The second foaming vessel is pre-set to a high temperature, and the prenucleated sample with sufficient foaming agent gas adsorbed is transferred to it. A second low-pressure gas is introduced, and the sample is placed under high-temperature and low-pressure conditions for a third preset saturation time, followed by depressurization and foaming to obtain low-density thermoplastic elastomer foam. The foam is then cooled to stabilize its cell structure.

Description

Technical Field

[0001] This invention relates to polymer foam processing technology, and more particularly to a method for preparing prenucleation-assisted low-density thermoplastic elastomer foam. Background Technology

[0002] Polymer foam materials are a class of lightweight materials with porous structures, which have advantages such as low density, good thermal insulation and good sound absorption. Among them, thermoplastic elastomer foam materials are currently the most widely used type of polymer foam materials. They have advantages such as high mechanical strength, good resilience, softness and shock absorption, and have attracted much attention in the fields of automotive lightweighting, product packaging, sports equipment, building decoration, aerospace and protective equipment.

[0003] Traditional industrial preparation methods for thermoplastic elastomer foam materials mainly include physical foaming and chemical foaming. However, chemically foamed thermoplastic elastomer foam materials suffer from problems such as gas residue and strong odor, which restricts their development. Currently, supercritical foaming, which uses supercritical fluids such as supercritical carbon dioxide or supercritical nitrogen to replace traditional organic foaming agents, is the latest, most environmentally friendly, and safest foaming technology. It greatly overcomes the environmental hazards and safety issues caused by traditional chemical foaming agents, making it a green and environmentally friendly advanced foaming technology.

[0004] Supercritical foaming technology is currently mainly divided into three categories: injection molding foaming, extrusion foaming, and autoclave foaming. Among them, autoclave foaming is the most widely used method in industrial production of thermoplastic elastomer foams due to its outstanding advantages such as high material adaptability, good nucleation effect, high foaming ratio, easy control of the molding process, and the ability to prepare various types of products. In the autoclave foaming process, the thermoplastic elastomer preform is placed in a high-temperature autoclave, and a high-pressure supercritical gas, such as supercritical carbon dioxide, supercritical nitrogen, or a mixture of supercritical carbon dioxide and supercritical nitrogen, is introduced. After a period of time, the gas diffuses into the polymer preform and reaches saturation. The pressure is then rapidly released through manually controlled equipment to produce low-density thermoplastic elastomer foam. Finally, the foam is cooled to stabilize the cell structure, thereby realizing the preparation of low-density elastomer foam.

[0005] The current disadvantages of autoclave foaming technology are as follows:

[0006] Disadvantage 1: During the autoclaving process of thermoplastic elastomers, the time required for gas to diffuse into the elastomer material and reach saturation is usually quite long. This is because the diffusion rate of supercritical gas in thermoplastic elastomers is low, and the saturation time increases significantly with the increase of the blank thickness. This greatly restricts the preparation of thicker thermoplastic elastomer foams and severely limits the actual industrial production efficiency.

[0007] Disadvantage 2: Autoclave foaming requires high-pressure equipment. This type of equipment operates under harsh conditions and poses safety hazards such as leaks and explosions, placing high demands on the professionalism of operators and the safety of the equipment. Furthermore, high-pressure equipment consumes a large amount of energy, has extremely high requirements for equipment materials and processing, and necessitates regular maintenance and replacement of easily worn parts, resulting in high operating and maintenance costs. Summary of the Invention

[0008] (a) Technical problems to be solved

[0009] To address the aforementioned problems in the prior art, this invention provides a method for preparing prenucleation-assisted low-density thermoplastic elastomer foam, which improves production efficiency while ensuring production safety.

[0010] (II) Technical Solution

[0011] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a method for preparing pre-nucleation assisted low-density thermoplastic elastomer foam, comprising the following steps:

[0012] S0. Pre-set the temperature of the forced-air drying oven, and put the thermoplastic elastomer particles into the forced-air drying oven to dry for a first preset time using a preset drying method;

[0013] S1. The thermoplastic elastomer particles are placed into the feed port of the extrusion foaming equipment. The temperature of each temperature zone of the screw, the screw speed and the amount of foaming agent gas added are adjusted to melt the thermoplastic elastomer particles and mix the thermoplastic elastomer particles with the foaming agent gas. The foaming process is then extruded to obtain a foamed product with pores. The foamed product is defined as a prenucleation sample.

[0014] S2. Pre-set the first foaming vessel to a low temperature, the temperature range of which is -30℃ to 80℃. Transfer the pre-nucleated sample to the first foaming vessel and introduce a first low-pressure gas, the pressure range of which is 2MPa to 10MPa. Place the sample under low temperature and low pressure conditions for a second preset time to allow the pre-nucleated sample to adsorb a sufficient amount of foaming agent gas, and then release the pressure.

[0015] S3. Pre-set the second foaming vessel to a high temperature, the temperature range of which is 90℃-160℃. Transfer the pre-nucleated sample with sufficient foaming agent gas adsorbed to the second foaming vessel. Introduce a second low-pressure gas, the pressure range of which is 2MPa-10MPa. Place the sample under high temperature and low pressure conditions for a saturated third preset time. Depressurize and foam to obtain a low-density thermoplastic elastomer foam. Then cool and stabilize the cell structure of the low-density thermoplastic elastomer foam.

[0016] (III) Beneficial Effects

[0017] The beneficial effects of this invention are:

[0018] 1) This invention divides the three continuous stages of gas adsorption, cell nucleation and cell growth in the supercritical autoclave foaming process of thermoplastic elastomers into three steps: extrusion preform making, low temperature and low pressure saturation high temperature and low pressure foaming. These three steps can be carried out simultaneously, resulting in higher parallel production efficiency.

[0019] 2) In this invention, the pores in the pre-nucleated sample can act as gas storage sites when saturated at low temperature and low pressure. Compared with the traditional autoclave saturation process, the gas solubility can be greatly improved. Therefore, lower density thermoplastic elastomer foam can be prepared at the same saturation temperature, or thermoplastic elastomer foam of the desired density can be prepared at a lower saturation temperature.

[0020] 3) This invention achieves the preparation of low-density thermoplastic elastomer foam under low-pressure conditions throughout the entire process, avoiding the use of high-pressure equipment. In traditional autoclave foaming processes, the gas saturation pressure is generally greater than 12 MPa. However, in this invention, for different types of thermoplastic elastomers, the gas pressure range in the second step of low-temperature low-pressure saturation and the third step of high-temperature low-pressure saturation is 2 MPa-10 MPa, generally not exceeding 8 MPa, which greatly reduces the gas saturation pressure. Attached Figure Description

[0021] Figure 1 This is a flowchart of a method for preparing prenucleation-assisted low-density thermoplastic elastomer foam according to the present invention;

[0022] Figure 2 This is a detailed process implementation roadmap for a prenucleation-assisted low-density thermoplastic elastomer foam preparation method according to the present invention.

[0023] Figure 3 The image shows an electron microscope image of a prenucleated sheet with a porosity of 35% prepared by thermoplastic polyurethane extrusion foaming in Example 2.

[0024] Figure 4 The image shows an electron microscope image of the thermoplastic polyurethane prenuclear board in Example 2 after it was fully saturated at 50°C and 6MPa under low temperature and low pressure conditions, and then foamed at 130°C and 3MPa under high temperature and low pressure conditions. Detailed Implementation

[0025] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] Please refer to Figure 1 and Figure 2 As shown, a method for preparing prenuclear-assisted low-density thermoplastic elastomer foam includes the following steps:

[0027] S0. Pre-set the temperature of the forced-air drying oven, and put the thermoplastic elastomer particles into the forced-air drying oven to dry for a first preset time using a preset drying method;

[0028] S1. The thermoplastic elastomer particles are placed into the feed port of the extrusion foaming equipment. The temperature of each temperature zone of the screw, the screw speed and the amount of foaming agent gas added are adjusted to melt the thermoplastic elastomer particles and mix the thermoplastic elastomer particles with the foaming agent gas. The foaming process is then extruded to obtain a foamed product with pores. The foamed product is defined as a prenucleation sample.

[0029] S2. Pre-set the first foaming vessel to a low temperature, the temperature range of which is -30℃ to 80℃. Transfer the pre-nucleated sample to the first foaming vessel and introduce a first low-pressure gas, the pressure range of which is 2MPa to 10MPa. Place the sample under low temperature and low pressure conditions for a second preset time to allow the pre-nucleated sample to adsorb a sufficient amount of foaming agent gas, and then release the pressure.

[0030] S3. Pre-set the second foaming vessel to a high temperature, the temperature range of which is 90℃-160℃. Transfer the pre-nucleated sample with sufficient foaming agent gas adsorbed to the second foaming vessel. Introduce a second low-pressure gas, the pressure range of which is 2MPa-10MPa. Place the sample under high temperature and low pressure conditions for a saturated third preset time. Depressurize and foam to obtain a low-density thermoplastic elastomer foam. Then cool and stabilize the cell structure of the low-density thermoplastic elastomer foam.

[0031] As can be seen from the above description, the beneficial effects of the present invention are as follows:

[0032] 1) This invention divides the three continuous stages of gas adsorption, cell nucleation and cell growth in the supercritical autoclave foaming process of thermoplastic elastomers into three steps: extrusion preform making, low temperature and low pressure saturation high temperature and low pressure foaming. These three steps can be carried out simultaneously, resulting in higher parallel production efficiency.

[0033] 2) In this invention, the pores in the pre-nucleated sample can act as gas storage sites when saturated at low temperature and low pressure. Compared with the traditional autoclave saturation process, the gas solubility can be greatly improved. Therefore, lower density thermoplastic elastomer foam can be prepared at the same saturation temperature, or thermoplastic elastomer foam of the desired density can be prepared at a lower saturation temperature.

[0034] 3) This invention achieves the preparation of low-density thermoplastic elastomer foam under low-pressure conditions throughout the entire process, avoiding the use of high-pressure equipment. In traditional autoclave foaming processes, the gas saturation pressure is generally greater than 12 MPa. However, in this invention, for different types of thermoplastic elastomers, the gas pressure range in the second step of low-temperature low-pressure saturation and the third step of high-temperature low-pressure saturation is 2 MPa-10 MPa, generally not exceeding 8 MPa, which greatly reduces the gas saturation pressure.

[0035] Furthermore, the thermoplastic elastomer particles are made of thermoplastic polyurethane, thermoplastic polyester, ethylene-vinyl acetate copolymer, polyetheramide, polybutylene terephthalate, polyolefin, acrylate and polyamide.

[0036] As can be seen from the above description, the present invention can be applied to the preparation of low-density thermoplastic elastomer foams from various materials, and has wide applicability.

[0037] Furthermore, the following is included before S1:

[0038] S0. Pre-set the temperature of the forced-air drying oven, and place the thermoplastic elastomer particles into the forced-air drying oven to dry for a first preset time using a preset drying method.

[0039] Furthermore, in S0, the drying temperature range is set to 40℃-180℃, the first preset drying time is 0.5h-12h, and the preset drying method is vacuum drying, forced air drying, or natural drying.

[0040] Furthermore, the extrusion foaming equipment in S1 is a single-screw extruder or a twin-screw extruder, the temperature of each temperature zone of the screw is 20℃-100℃ higher than the melting point of the thermoplastic elastomer material, the screw speed is 10rpm-100rpm, and the added foaming agent gas is nitrogen or carbon dioxide, and the amount of foaming agent gas added is 1wt%-10wt%.

[0041] Furthermore, the porosity of the foamed product obtained by extrusion foaming in S1 ranges from 10% to 60%.

[0042] Furthermore, the first low-pressure gas introduced in S2 is of the type of supercritical carbon dioxide, supercritical nitrogen, or a mixture of supercritical carbon dioxide and supercritical carbon dioxide.

[0043] As can be seen from the above description, a wide variety of gases can be selected as the first low-pressure gas, providing a broad range of choices.

[0044] Furthermore, the second preset duration in S2 is 0.5h-12h.

[0045] Furthermore, the second low-pressure gas introduced in S3 is supercritical carbon dioxide, supercritical nitrogen, or a mixture of supercritical carbon dioxide and supercritical carbon dioxide.

[0046] Furthermore, the third preset duration in S3 is 5min-180min.

[0047] Example 1

[0048] Please refer to Figure 1 and Figure 2 As shown, a method for preparing prenuclear-assisted low-density thermoplastic elastomer foam includes the following steps:

[0049] S0. Pre-set the temperature of the forced-air drying oven, and place the thermoplastic elastomer particles into the forced-air drying oven to dry for a first preset time using a preset drying method.

[0050] In S0, the drying temperature range is set to 40℃-180℃, the first preset drying time is 0.5h-12h, and the preset drying method is vacuum drying, forced air drying, or natural drying. Preferably, the drying temperature range is 60℃-160℃, the drying time is 1h-6h, and the drying method is forced air drying or vacuum drying.

[0051] S1. The thermoplastic elastomer particles are placed into the feed port of the extrusion foaming equipment. The temperature of each temperature zone of the screw, the screw speed and the amount of foaming agent gas added are adjusted to melt the thermoplastic elastomer particles and mix the thermoplastic elastomer particles with the foaming agent gas. The foaming process is then extruded to obtain a foamed product with pores. The foamed product is defined as a prenucleation sample.

[0052] S2. Pre-set the first foaming vessel to a low temperature, the temperature range of which is -30℃ to 80℃. Transfer the pre-nucleated sample to the first foaming vessel and introduce a first low-pressure gas, the pressure range of which is 2MPa-10MPa, preferably 3MPa-8MPa. Place the sample under low temperature and low pressure conditions for a second preset saturation time to allow the pre-nucleated sample to adsorb sufficient foaming agent gas, and then release the pressure.

[0053] S3. Pre-set the second foaming vessel to a high temperature, the temperature range of which is 90℃-160℃, preferably 100℃-150℃. Transfer the pre-nucleated sample with sufficient foaming agent gas adsorbed to the second foaming vessel, and introduce a second low-pressure gas, the pressure range of which is 2MPa-10MPa, preferably 3MPa-8MPa. Place the sample under high temperature and low pressure conditions for a saturated third preset time, then depressurize and foam to obtain a low-density thermoplastic elastomer foam, and then cool and stabilize the cell structure of the low-density thermoplastic elastomer foam.

[0054] In this embodiment, the thermoplastic elastomer particles are made of thermoplastic polyurethane (TPU), thermoplastic polyester (TPEE), ethylene-vinyl acetate copolymer (EVA), polyetheramide (PEBA), polybutylene terephthalate (PBAT), polyolefin (POE), acrylate (ACM), and polyamide (TPAE).

[0055] Preferably, the thermoplastic elastomer particles are made of thermoplastic polyurethane (TPU), thermoplastic polyester (TPEE), ethylene-vinyl acetate copolymer (EVA), polyetheramide (PEBA), or polybutylene terephthalate (PBAT).

[0056] In this embodiment, the extrusion foaming equipment in S1 is a single-screw extruder or a twin-screw extruder. The temperature of each temperature zone of the screw is 20°C-100°C higher than the melting point of the thermoplastic elastomer material. The screw speed is 10rpm-100rpm. The added foaming agent gas is nitrogen or carbon dioxide, and the amount of foaming agent gas added is 1wt%-10wt%.

[0057] Preferably, the screw speed is 20 rpm to 80 rpm, and the amount of foaming agent gas added is 1 wt% to 6 wt%.

[0058] In this embodiment, the porosity of the foamed product obtained by extrusion foaming in S1 ranges from 10% to 60%, and preferably from 20% to 50%.

[0059] In this embodiment, the pre-nucleation sample in S1 is granular or plate-shaped, preferably plate-shaped, with a thickness greater than 5 mm.

[0060] In this embodiment, the first low-pressure gas introduced in S2 is supercritical carbon dioxide, supercritical nitrogen, or a mixture of supercritical carbon dioxide and supercritical carbon dioxide. Preferably, the first low-pressure gas is a mixture of supercritical carbon dioxide and supercritical carbon dioxide.

[0061] In this embodiment, the second preset duration in S2 is 0.5h-12h, and preferably, the time range of the second preset duration is 1h-6h.

[0062] In this embodiment, the second low-pressure gas introduced in S3 is supercritical carbon dioxide, supercritical nitrogen, or a mixture of supercritical carbon dioxide and supercritical carbon dioxide, preferably a mixture of supercritical carbon dioxide and supercritical carbon dioxide.

[0063] In this embodiment, the third preset duration in S3 is 5 min to 180 min, preferably, the time range of the third preset duration is 10 min to 60 min.

[0064] In this embodiment, the cooling method for stabilizing the cell structure of the low-density thermoplastic elastomer foam in step S3 is liquid cooling, air cooling, and air cooling, with air cooling and liquid cooling being preferred.

[0065] Example 2

[0066] Reference Figure 3 and Figure 4 As shown, the prenucleation-assisted low-density thermoplastic elastomer foam preparation method in Implementation 1 is applied to a specific case:

[0067] The raw material for the thermoplastic elastomer granules is thermoplastic polyurethane (TPU) granules, model XR-93A, with a density of 1.05 g / cm3, a hardness of 93A, and a melting point of 138℃. The manufacturer is Huafeng Chemical. The process flow based on this invention is as follows:

[0068] The first step is to pre-set the temperature of the drying oven to 100℃, put the thermoplastic polyurethane granules into the drying oven, and dry them for 3 hours to completely dry the moisture in the granules.

[0069] The second step involves feeding thermoplastic polyurethane granules into the feed hopper of an extrusion foaming machine. The temperatures of each zone are adjusted: the feed zone temperature is 50℃, the screw section temperatures are 190℃-200℃-200℃-200℃-200℃-190℃, the die head temperature is 210℃, and the mold temperature is 50℃. The gas addition rate is adjusted to 2wt%. Extrusion foaming yields a 10mm thick pre-nucleated board with a density of 0.68g / cm³ and a porosity of 35%. An electron micrograph of this pre-nucleated board is shown below. Figure 3 As shown.

[0070] The third step involves setting the temperature of the low-temperature foaming kettle to 50°C, placing the pre-nucleated board into the foaming kettle, introducing carbon dioxide gas at a pressure of 6 MPa, and allowing it to stand for 6 hours to allow the pre-nucleated board to adsorb sufficient carbon dioxide gas. Then, the pressure is manually released to obtain the pre-nucleated board that has adsorbed sufficient carbon dioxide gas.

[0071] Fourthly, the temperature of another high-temperature foaming reactor is pre-set to 130℃. The pre-nucleated board with sufficient adsorption of carbon dioxide gas is transferred to this reactor, and carbon dioxide gas at a pressure of 3 MPa is introduced. After 30 minutes, the pressure is rapidly released, and foaming is performed to obtain low-density thermoplastic polyurethane elastomer foam with a density of 0.085 g / cm³. The foam is then cooled to stabilize the cell structure. After seven days, its density stabilizes at 0.094 g / cm³. The electron micrograph of this pre-nucleated board is shown below. Figure 4 As shown.

[0072] Example 3

[0073] One of the prenucleation-assisted low-density thermoplastic elastomer foam preparation methods from Implementation 1 is applied to another specific case:

[0074] The raw material for thermoplastic elastomer granules is thermoplastic polyester elastomer (TPEE) granules, with the following specifications: ECO4056B has a density of 1.15 g / cm³, a hardness of 43D, and a melting point of 152°C. It is manufactured by Celanese. The process flow based on this invention is as follows:

[0075] The first step is to pre-set the temperature of the drying oven to 120℃, put the thermoplastic polyester elastomer granules into the drying oven, and dry them for 2 hours to completely dry the moisture in the granules.

[0076] The second step involves feeding thermoplastic polyester elastomer granules into the feed hopper of an extrusion foaming machine. The temperatures of each zone of the extrusion foaming machine are adjusted: the feed zone temperature is 60℃, the screw section temperatures are 180℃-210℃-220℃-220℃-210℃-200℃, the die head temperature is 220℃, and the mold temperature is 60℃. The gas addition amount is adjusted to 1.4wt%. The extrusion foaming process yields a pre-nucleated board with a thickness of 10mm, a density of 0.7g / cm³, and a porosity of 40%.

[0077] The third step involves setting the temperature of the low-temperature foaming kettle to 50°C, placing the pre-nucleated board into the foaming kettle, introducing carbon dioxide at a pressure of 6 MPa, and letting it sit for 6 hours to allow the pre-nucleated board to adsorb sufficient carbon dioxide gas. Then, the pressure is manually controlled to release the pressure, resulting in a pre-nucleated board that has adsorbed sufficient carbon dioxide gas.

[0078] The fourth step involves pre-setting the temperature of another high-temperature foaming vessel to 135°C, transferring the pre-nucleated board with sufficient carbon dioxide gas adsorption to this foaming vessel, introducing carbon dioxide gas at a pressure of 3 MPa, and allowing it to stand for 30 minutes. Then, the pressure is rapidly released to foam low-density thermoplastic polyester elastomer foam with a density of 0.082 g / cm3. The foam is then cooled to stabilize the cell structure, and after seven days, its density stabilizes at 0.09 g / cm3.

[0079] Example 4

[0080] The method for preparing prenucleation-assisted low-density thermoplastic elastomer foam from Implementation 1 is applied to another specific case:

[0081] The raw material for thermoplastic elastomer granules is polyetheramide elastomer (PEBA) granules, model number: 4533SP01, with a density of 1.01 g / cm³ and a hardness of 45D, is manufactured by Arkema. The process flow based on this invention is as follows:

[0082] The first step is to pre-set the temperature of the drying oven to 120℃, put the polyether amide elastomer particles into the drying oven, and dry them for 2 hours to completely dry the moisture in the particles.

[0083] The second step involves feeding polyetheramide elastomer granules into the feed hopper of an extrusion foaming machine. The temperatures of each zone of the extrusion foaming machine are adjusted: the feed zone temperature is 70℃, the screw section temperatures are 190℃-210℃-220℃-220℃-210℃-200℃, the die head temperature is 220℃, and the mold temperature is 60℃. The gas addition amount is adjusted to 1.6wt%. The extrusion foaming process yields a pre-nucleated board with a thickness of 10mm, a density of 0.65g / cm³, and a porosity of 35%.

[0084] The third step involves setting the temperature of the low-temperature foaming kettle to 50°C, placing the pre-nucleated board into the foaming kettle, introducing carbon dioxide at a pressure of 6 MPa, and letting it sit for 6 hours to allow the pre-nucleated board to adsorb sufficient carbon dioxide gas. Then, the pressure is manually controlled to release the pressure, resulting in a pre-nucleated board that has adsorbed sufficient carbon dioxide gas.

[0085] The fourth step involves setting the temperature of another high-temperature foaming vessel to 130°C, transferring the pre-nucleated board with sufficient carbon dioxide gas adsorption to the foaming vessel, introducing carbon dioxide gas at a pressure of 3 MPa, and allowing it to stand for 30 minutes. Then, the pressure is rapidly released to foam low-density polyether amide elastomer foam with a density of 0.085 g / cm3. The foam is then cooled to stabilize the cell structure, and after seven days, its density stabilizes at 0.097 g / cm3.

[0086] Example 5

[0087] The prenucleation-assisted low-density thermoplastic elastomer foam preparation method from Implementation 1 is applied to another specific case:

[0088] The raw material for thermoplastic elastomer granules is polybutylene terephthalate (PBAT) granules, model number: F Blend C1200, with a density of 1.25 g / cm3 and a melt flow index of 2.7 g / 10 min (190℃@2.16 kg), is manufactured by BASF. The process flow based on this invention is as follows:

[0089] The first step is to pre-set the temperature of the drying oven to 100℃, put the polybutylene terephthalate (PET) granules into the drying oven, and dry them for 3 hours to completely dry the moisture in the granules.

[0090] The second step involves feeding polybutylene terephthalate (PET) granules into the feed hopper of an extrusion foaming machine. The temperatures of each zone of the extrusion foaming machine are adjusted: the feed zone temperature is 60℃, the screw section temperatures are 190℃-200℃-200℃-200℃-200℃-190℃, the die head temperature is 210℃, and the mold temperature is 70℃. The gas addition amount is adjusted to 1.4wt%. The extrusion foaming process yields a pre-nucleated board with a thickness of 10mm, a density of 0.75g / cm³, and a porosity of 40%.

[0091] The third step involves setting the temperature of the low-temperature foaming kettle to 50°C, placing the pre-nucleated board into the foaming kettle, introducing carbon dioxide at a pressure of 6 MPa, and letting it sit for 6 hours to allow the pre-nucleated board to adsorb sufficient carbon dioxide gas. Then, the pressure is manually controlled to release the pressure, resulting in a pre-nucleated board that has adsorbed sufficient carbon dioxide gas.

[0092] The fourth step involves pre-setting the temperature of another high-temperature foaming vessel to 130°C, transferring the pre-nucleated board material with sufficient carbon dioxide gas adsorption to this foaming vessel, introducing carbon dioxide gas at a pressure of 3 MPa, and allowing it to stand for 30 minutes. Then, the pressure is rapidly released to foam low-density polybutylene terephthalate (PET) foam with a density of 0.096 g / cm3. The foam is then cooled to stabilize the cell structure, and after seven days, its density stabilizes at 0.103 g / cm3.

[0093] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Those skilled in the art will recognize that the present invention can have many variations and improvements. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0094] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent modifications made based on the content of the present invention's specification and drawings, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for preparing prenucleation-assisted low-density thermoplastic elastomer foam, characterized in that, Includes the following steps: S1. The thermoplastic elastomer particles are placed into the feed port of the extrusion foaming equipment. The temperature of each temperature zone of the screw, the screw speed and the amount of foaming agent gas added are adjusted to melt the thermoplastic elastomer particles and mix the thermoplastic elastomer particles with the foaming agent gas. The foaming process is then extruded to obtain a foamed product with pores. The foamed product is defined as a prenucleation sample. S2. Pre-set the first foaming vessel to a low temperature, the temperature range of which is -30℃ to 80℃. Transfer the pre-nucleated sample to the first foaming vessel and introduce a first low-pressure gas, the pressure range of which is 2MPa to 10MPa. Place the sample under low temperature and low pressure conditions for a second preset time to allow the pre-nucleated sample to adsorb a sufficient amount of foaming agent gas, and then release the pressure. S3. Pre-set the second foaming vessel to a high temperature, the temperature range of which is 90℃-160℃. Transfer the pre-nucleated sample with sufficient foaming agent gas adsorbed to the second foaming vessel. Introduce a second low-pressure gas, the pressure range of which is 2MPa-10MPa. Place the sample under high temperature and low pressure conditions for a saturated third preset time. Depressurize and foam to obtain a low-density thermoplastic elastomer foam. Then cool and stabilize the cell structure of the low-density thermoplastic elastomer foam.

2. The method for preparing prenucleation-assisted low-density thermoplastic elastomer foam according to claim 1, characterized in that, The thermoplastic elastomer particles are made of materials including thermoplastic polyurethane, thermoplastic polyester, ethylene-vinyl acetate copolymer, polyetheramide, polybutylene terephthalate, polyolefin, acrylate and polyamide.

3. The method for preparing prenucleation-assisted low-density thermoplastic elastomer foam according to claim 1, characterized in that, Before S1, the following also applies: S0. Pre-set the temperature of the forced-air drying oven, and place the thermoplastic elastomer particles into the forced-air drying oven to dry for a first preset time using a preset drying method.

4. The method for preparing prenucleation-assisted low-density thermoplastic elastomer foam according to claim 3, characterized in that, The drying temperature range in S0 is set to 40℃-180℃, the first preset drying time is 0.5h-12h, and the preset drying method is vacuum drying, forced air drying, or natural drying.

5. The method for preparing prenucleation-assisted low-density thermoplastic elastomer foam according to claim 1, characterized in that, The extrusion foaming equipment in S1 is a single-screw extruder or a twin-screw extruder. The temperature of each temperature zone of the screw is 20°C-100°C higher than the melting point of the thermoplastic elastomer material. The screw speed is 10rpm-100rpm. The added foaming agent gas is nitrogen or carbon dioxide, and the amount of foaming agent gas added is 1wt%-10wt%.

6. The method for preparing prenucleation-assisted low-density thermoplastic elastomer foam according to claim 1, characterized in that, The porosity of the foamed product obtained by extrusion foaming in S1 ranges from 10% to 60%.

7. The method for preparing prenucleation-assisted low-density thermoplastic elastomer foam according to claim 1, characterized in that, The first low-pressure gas introduced in S2 is supercritical carbon dioxide, supercritical nitrogen, or a mixture of supercritical carbon dioxide and supercritical carbon dioxide.

8. The method for preparing prenucleation-assisted low-density thermoplastic elastomer foam according to claim 1, characterized in that, The second preset duration in S2 is 0.5h-12h.

9. The method for preparing prenucleation-assisted low-density thermoplastic elastomer foam according to claim 1, characterized in that, The second low-pressure gas introduced in S3 is supercritical carbon dioxide, supercritical nitrogen, or a mixture of supercritical carbon dioxide and supercritical carbon dioxide.

10. The method for preparing prenucleation-assisted low-density thermoplastic elastomer foam according to claim 1, characterized in that, The third preset duration in S3 is 5 min to 180 min.

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