A physical microcellular foaming forming process of a polymer material

Abstract

The application discloses a high polymer material physical microcellular foaming forming process, which comprises the following steps: S1. high-pressure reactor supercritical gas permeation: high polymer elastomer material particles are put into a high-pressure reactor, carbon dioxide or nitrogen or mixed gas of the two is introduced into the reactor, the pressure in the reactor is controlled to be 7-25 MPa, the temperature is 25-40 DEG C, heat preservation is carried out for 30-120 min, first rapid pressure relief is carried out, second pressure relief is carried out, and the gas in the reactor is slowly exhausted; S2. steam moulding machine foaming forming: two times of steam penetration are adopted, one-stage steam pressure is 0.01-0.02 MPa, steam time is 20-100 s, two-stage penetration steam pressure is 0.015-0.03 MPa, steam time is 30-160 s; water cooling; S3. product stabilization and ripening: the product is put into an oven for heating treatment, the temperature is set to be 25-80 DEG C, and heating treatment is carried out for 24-48 h.

Description

Technical Field

[0001] This invention relates to the field of polymer foaming technology, specifically to a physical microporous foaming molding process for polymer materials. Background Technology

[0002] Microcellular elastomers are important polymer materials with a unique microporous structure containing numerous air bubbles. Their density can be reduced by 5-98% compared to before foaming. This unique gas-solid two-phase structure endows them with many excellent properties: low density, high elasticity, excellent flexibility, and high shock absorption, sound insulation, and heat insulation properties. They are widely used in sealing, footwear, clothing, soundproofing, heat insulation, shock absorption, and fitness equipment. Microcellular elastomers include polymers such as TPU, PA, TPEE, PP, PS, PET, and PLA. Among them, TPU (Thermoplastic Polyurethanes) is a type of polymer material between rubber and plastic and is currently a hot research topic. Supercritical carbon dioxide physically microcellular foamed TPU particles are a newly developed type of foamed particle in recent years. The foaming process uses supercritical carbon dioxide as a foaming agent, resulting in products with low specific gravity, high resilience, and low compression set. Furthermore, the entire preparation process uses only carbon dioxide and high-temperature water vapor, making the manufacturing process green and environmentally friendly.

[0003] Currently, the most commonly used processes for preparing polymer foam materials are rapid decompression foaming and decompression heating foaming. The molding steps of the two foaming processes are as follows:

[0004] I. Rapid pressure relief foaming process steps:

[0005] Step 1: Supercritical Permeation Rapid Depressurization Foaming of Elastomer Particles: Elastomer particles and water are placed in a reactor, ensuring the water completely submerges the particles. The agitator inside the reactor is activated, keeping the water and particles in constant motion. Carbon dioxide or nitrogen gas is introduced into the reactor, and the temperature and pressure are increased to 10-20 MPa, with the temperature controlled at 120-160°C. During this process, the water inside the reactor prevents the particles from sticking together under high temperature and pressure. The agitator continuously stirs the material and water, both to prevent particle adhesion and to bring the particles to the water surface so that carbon dioxide gas can penetrate into the particles. This pressure, temperature, and stirring rate are maintained for 2-5 hours to allow the gas to fully penetrate the particles. Then, the pressure relief valve is opened, rapidly releasing the pressure for 2-10 seconds at a rate of 5 MPa / s. The elastomer particles are instantly ejected from the high-pressure reactor and rapidly expand.

[0006] The following problems exist in this process: (1) The material at the bottom of the vessel cannot be stirred and sinks to the bottom, which prevents carbon dioxide from fully penetrating into the interior, resulting in some particles failing to foam and expand. (2) The particles are soaked in high-pressure, high-temperature water and carbon dioxide gas for a long time, which causes the acidity inside the material to reappear. During long-term use, the acid inside the product will gradually damage the product, making it prone to damage. (3) The depressurization rate of this process is extremely fast, the depressurization sound is very loud, and there are certain safety hazards. (4) The carbon dioxide gas in this process is instantly vented and cannot be recycled.

[0007] The second step is the stabilization and maturation of the foamed granules: Freshly foamed granules, due to their numerous microporous structures and the presence of high-pressure carbon dioxide gas inside, will gradually leak out, causing the granules to shrink rapidly and deflate. Then, air gas will gradually enter the foamed granules, causing them to gradually expand and become fuller. This maturation process requires standing at 40-60℃ for 6-7 days to ensure complete gas replacement and stabilization of the foamed granules. After maturation, the foamed granules shrink by 50-70% compared to freshly foamed granules, and their specific gravity increases significantly.

[0008] The third step is steam molding: After the mold is closed, the stabilized and matured foamed granules are sucked into the mold, and high-temperature steam is introduced. The steam pressure is 0.01-0.03MPa, and the heating time is 30-120s. Cold water is introduced into the mold frame to cool it down. After cooling down to 30-50℃, the mold is opened to complete the steam molding.

[0009] Because the diameter of the foamed particles is about 4-8mm, the particles are relatively large. For some molds with more complex structures and smaller sizes, it is difficult for the particles to fill the entire mold. This results in some smaller or thinner products or products with more complex structures not being able to be formed or the molded products collapsing severely.

[0010] The fourth step is to stabilize the molded product: The prepared molded product needs to be placed in an environment of 40-60℃ for 24h-48h. This is because the foamed particles will expand after being heated by steam, and the newly formed product will gradually shrink, with a shrinkage rate of about 1%-3%.

[0011] II. Depressurization and Heating Foaming Process Steps:

[0012] Step 1: Supercritical permeation of particles: Place the elastomer particles into the reactor, introduce carbon dioxide gas into the reactor, and increase the temperature and pressure to control the temperature at 30-40℃ and the pressure at 10-20MPa. Maintain this state and let the particles permeate in the reactor for 2-5 hours to allow the carbon dioxide gas to fully permeate into the particles. Then, depressurize and empty the gas in the reactor. The depressurization rate is controlled at 0.12MPa / s. At this time, the particles are still inside the reactor and their volume has not expanded.

[0013] Step 2: Heating and foaming of elastomer particles: The elastomer particles that have completed permeation are taken out of the reactor and placed in a heating and foaming equipment for heating and foaming. The equipment temperature is controlled at 90-120℃ and the heating time is controlled at 60-120s. When the particles are heated, the supercritical fluid inside the particles instantly vaporizes and overflows, and the particles expand and foam.

[0014] This foaming process is inefficient, subsequent heating costs are high, and the uneven heating of the particles during the heating process leads to uneven foaming ratio.

[0015] Step 3: Stabilization and maturation of foamed particles: Same as rapid depressurization foaming process.

[0016] Step 4, steam molding: same as rapid depressurization foaming process.

[0017] Step 5, stabilization of the molded product: same as the rapid depressurization foaming process.

[0018] In summary, the existing technology has the following main drawbacks: (1) The processing cycle is long, taking about 9-10 days from supercritical particle infiltration, heating and foaming, stabilization and maturation of foamed particles, steam molding, and stabilization of molded products; (2) For small or complex irregularly shaped products, the large size of the foamed particles during steam molding can lead to insufficient material feeding, resulting in material shortage and product collapse in the molded products; (3) It is difficult to prepare products that require filling with functional inserts inside the product; (4) To prepare colored products, the material particles need to be mixed with a certain proportion of color powder or masterbatch before foaming the elastomer material particles and then remelted and granulated. The re-granulated particles are then foamed and molded. However, the elastomer material will be degraded by being extruded and granulated again by screw extrusion. The color powder filled inside will also cause large air bubbles and damage inside the foamed particles, which will lead to severe shrinkage of the foamed particles and molded products, and a decrease in compression set and tear strength. Summary of the Invention

[0019] The purpose of this invention is to address the above-mentioned problems by providing a physical microporous foaming molding process for polymer materials. This process can prepare foamed products with low density, high tear strength, and complex shapes and structures. Compared with traditional molding methods, the products produced by the process of this invention have a lighter specific gravity, less permanent compression deformation, and stronger tear strength.

[0020] To achieve its objective, the present invention employs the following technical solution:

[0021] A physical microporous foaming molding process for polymer materials includes the following steps:

[0022] S1. Supercritical gas permeation in a high-pressure reactor:

[0023] High-molecular elastomer material particles are placed in a high-pressure reactor. Carbon dioxide, nitrogen, or a mixture of both are introduced into the reactor. The pressure inside the reactor is controlled at 7–25 MPa, and the temperature at 25–40°C. The temperature is maintained for 30–120 minutes. After the gas inside the particles reaches saturation, the temperature inside the reactor is lowered to -10°C to 0°C and maintained for at least 1 minute. Then, a first rapid depressurization is performed: the pressure inside the reactor is rapidly reduced to 3–5 MPa at a depressurization rate of 1.5–2.5 MPa / s. Then, a second depressurization is performed to slowly empty the gas inside the reactor at a depressurization rate of 0.01–0.02 MPa / s. The material is then removed and stored at -10–0°C. The high-molecular elastomer material is selected from TPU, PA (polyamide), TPEE (thermoplastic polyester elastomer), PP (polypropylene), PS (polystyrene), PET (polyethylene terephthalate), and PLA (polylactic acid).

[0024] S2. Steam molding machine for foaming:

[0025] After the steam molding machine is preheated, the mold is closed, and then the granular material obtained in step S1 is placed into the steam molding machine. Two steam penetrations are used. The steam pressure in the first stage is 0.01-0.02 MPa and the steam time is 20-100 s. The steam pressure in the second stage is 0.015-0.03 MPa and the steam time is 30-160 s. After the steam heating is completed, the mold is vented and water-cooled. After water cooling, the product is removed.

[0026] S3. Product stabilization and maturation:

[0027] The product formed in step S2 is placed in an oven for heating treatment at a temperature of 25-80℃ for 24-48 hours.

[0028] Preferably, before step S1, the polymer elastomer material particles are pretreated with an organic solvent: the polymer elastomer material particles are immersed in an organic solvent with a volume fraction concentration of 10% to 100% for 10 to 60 minutes, wherein the organic solvent is selected from methanol, ethanol, methane, ethane, and pentane.

[0029] Preferably, the volume fraction concentration of the organic solvent is greater than or equal to 30%.

[0030] Preferably, in step S1, the polymer elastomer material particles can be mixed with 0.1wt% to 5wt% of color powder before being placed in a high-pressure autoclave to prepare colored products.

[0031] Preferably, the color powder is an organic color powder.

[0032] In the above technical solution, in step S1, after the gas inside the particles reaches saturation, the temperature inside the reactor is lowered to -10℃~0℃ and maintained for 1~20min or 1~15min or 1~10min, and then the first rapid depressurization is performed.

[0033] In the above technical solution, in step S2, after the steam heating is completed, the mold is vented and water-cooled: water at 20-50°C is introduced for cooling, and the water cooling time is 60-180 seconds.

[0034] In the above technical solution, in step S1, the first rapid depressurization is performed to rapidly reduce the pressure of the vessel to 3.5-4.5 MPa, with a depressurization rate of 1.5-2.5 MPa / s.

[0035] Preferably, in step S3, the heat treatment temperature is 50–80°C.

[0036] Preferably, in step S2, the granular material obtained in step S1 is placed together with the insert into a steam molding machine to prepare an article containing the insert.

[0037] The beneficial effects of this invention are:

[0038] 1. The process of this invention does not require the introduction of water into the high-pressure reactor, while the traditional process does require the introduction of water into the high-pressure reactor:

[0039] In traditional processes, water needs to be circulated inside the high-pressure reactor to prevent the granules from sticking together and clumping under high temperature and pressure. An agitator within the reactor continuously stirs the material and water, both to prevent particle adhesion and to bring the granules to the water surface so that carbon dioxide gas can penetrate them. However, some granules inevitably remain at the bottom of the reactor, unable to be stirred to the water surface, resulting in insufficient carbon dioxide penetration. Consequently, during the foaming process, some materials exhibit low foaming ratios or fail to foam at all.

[0040] The process of this invention does not require the addition of water to the high-pressure reactor. Carbon dioxide and / or nitrogen gas are transformed into a liquid or supercritical fluid state inside the reactor under high pressure, which can fully and uniformly penetrate into the interior of the particles.

[0041] 2. The process of this invention eliminates the steps of heating and foaming with foaming equipment, and stabilizing and shaping the granules after heating and foaming:

[0042] Traditional processes first require high temperature and pressure to permeate carbon dioxide gas into the particles inside a high-pressure reactor. Then, rapid pressure relief foaming is used, or the particles are taken out and placed in a foaming equipment for heating and foaming. After the foamed particles shrink, set and stabilize, they are then molded into products in a molding machine. The entire production cycle is about 9-10 days.

[0043] The process of this invention uses low-temperature permeation in a high-pressure reactor, followed by foaming and molding using a steam molding machine. After molding, it can be stabilized and cured for 24-48 hours. The entire production cycle is about 2-3 days, which significantly shortens the production cycle.

[0044] 3. In this invention, the material entering the mold of the steam molding machine is a non-foamed polymer with a small particle size. This allows it to fit into the smaller mold space, preventing material shortages and easily producing complex and small-sized products. Traditional processes use foamed granular material for molding. The large particle size of the foamed granules necessitates filling the mold with more foamed granules to ensure a full and complete product, increasing the density of the molded product. This invention, however, produces lighter products.

[0045] 4. For some colored products, the process of this invention involves mixing the polymer material with a certain proportion of color powder before gas permeation, and then placing the mixture in a high-pressure reactor for permeation treatment. During this process, supercritical fluid can allow some of the color powder to penetrate into the interior of the polymer material. The granular material is then removed and placed into a mold of a steam molding machine. High-pressure, high-temperature steam is introduced into the mold, causing the material to foam and expand. Simultaneously, the surface of the material melts, fusing the color powder on the surface together. The foamed and expanded granules are then pressed and bonded together to obtain the colored molded product. Traditional processes for preparing colored products require first melting and granulating polymer materials with color powder and masterbatch in a screw extruder to produce colored polymer particles, followed by foaming and molding. This process significantly degrades the properties of the polymer material after shearing by the screw. Secondary granulation introduces air, creating tiny bubbles within the polymer material. During foaming, these bubbles expand further, causing severe damage within the particles. After molding, the damaged particles and degraded material properties lead to severe shrinkage, poor compression set, and significantly reduced tear strength and abrasion resistance. Therefore, the process of this invention can produce colored products with superior performance.

[0046] 5. The process of this invention can produce products containing inserts, which is impossible with traditional processes.

[0047] In this invention, in-situ treated polymer particles and functional inserts are placed together in a mold, and then high-temperature steam is introduced into the mold. During the molding process, the inserts are formed inside the product. Because the polymer particles expand and foam in the mold in this invention, a large compressive force is generated between the particles and between the particles and the inserts during the foaming process, and the inserts are firmly compressed and fixed in the middle of the product. However, in traditional molding processes, if inserts are placed in the molding mold, the connection between the foamed particles and the inserts is not strong due to the lack of a particle foaming and expansion process in the molding mold, resulting in the problem of loose inserts in the molded product. Detailed Implementation

[0048] The present invention will be further described below with reference to embodiments, but these embodiments are not intended to limit the scope of the invention.

[0049] Unless otherwise specified, the experimental methods in the following examples are conventional methods; the reagents and materials used are conventional reagents and materials, and are commercially available, unless otherwise specified.

[0050] The physical microporous foaming molding process for polymer materials of the present invention is carried out according to the following steps:

[0051] Step 1, Organic solvent pretreatment:

[0052] Polymer elastomer particles are immersed in an organic solvent (selected from ethanol, methanol, methane, ethane, or pentane) with a concentration of 10%-100% for 0-60 minutes. After immersion in the organic solvent, the elastomer particles swell. During supercritical carbon dioxide permeation, carbon dioxide gas and fillers more easily penetrate into the particles, reducing osmosis pressure, shortening permeation time, and improving permeation efficiency. The number of nuclei formed during foaming increases, resulting in foamed polymer materials with low density, thin particle skin, low hardness, and large internal bubble pore size.

[0053] The second step is supercritical gas permeation in a high-pressure reactor:

[0054] After the first step of organic solvent treatment, the polymer elastomer material particles are placed in a high-pressure reactor, and carbon dioxide, nitrogen, or a mixture of both are introduced into the reactor. The pressure inside the reactor is controlled at 7–25 MPa, and the temperature at 25–40 °C. At this time, the carbon dioxide is in a liquid or supercritical fluid state, and the polymer elastomer material particles are immersed in the fluid carbon dioxide for 30–120 minutes. After the carbon dioxide inside the granules reaches saturation, the carbon dioxide and polymer elastomer material inside the reactor are cooled to -10℃ to 0℃ (this temperature reduction prevents the granules from foaming and expanding during depressurization and also prevents the rapid overflow of carbon dioxide from inside the granules). Once the set temperature is reached, it is maintained for 1-10 minutes, followed by rapid depressurization to quickly reduce the reactor pressure to 4 MPa at a rate of 1.5-2.5 MPa / s (this rapid pressure drop causes numerous bubble nuclei to form inside the TPU granules). Then, a second depressurization (at a rate of 0.01-0.02 MPa / s) slowly empties the gas from the reactor. The material is then removed and placed in the cooling hopper of the molding machine for later use. The hopper temperature is set to -10℃ to 0℃ (low-temperature storage prevents the granules from expanding due to external heat). Alternatively, the 4 MPa pressure inside the reactor can be used to transport the material to the molding machine's hopper via a high-pressure pipeline. In this step, two depressurizations are used. The first depressurization is rapid, which causes a large number of bubble nuclei to form inside the elastomer material particles. The second depressurization is slow, which can prevent the particles from expanding and growing.

[0055] For colored products, in this step, TPU needs to be mixed evenly with 0.1wt% to 5wt% (the mass ratio of color powder to elastomer material), and then placed in an autoclave for the aforementioned operation. During the process of supercritical carbon dioxide penetrating into the particle, a certain proportion of color powder will migrate into the particle.

[0056] The third step is foam molding using a steam compression molding machine:

[0057] The foaming process is performed using a steam compression molding machine with a clamping pressure greater than 100t. After preheating, the mold is closed. The particle feed rate is determined based on the mold cavity size, and the particles are then fed into the mold via a quantitative feeding system (allowing precise control of the feed weight to ensure uniformity of the molded product weight). Simultaneously, depending on the material requirements, auxiliary water is selectively switched on and off during the feeding process (water replenishment helps auxiliary materials enter the mold better, especially for molds with complex structures and thin dimensions). After feeding, steam is introduced, with the initial steam pressure ranging from 0.01 to 0. At the first stage, the steam pressure is 0.02 MPa and the steam time is 20–100 s. During this time, the particles slowly expand and foam, gradually filling the cavity. The surface of the particles slightly melts, and the particles initially adhere to each other. In the second stage, the steam pressure is 0.015–0.03 MPa and the steam time is 30–160 s. During this time, the particles soften, extend, and deform, further filling the corners of the cavity, and the particles completely adhere to each other. After the steam heating is completed, the mold is vented and enters the water cooling stage. Water at 20–50°C is introduced for cooling, and the water cooling time is 60–180 s. After the water cooling is completed, the mold frame is drained and vented, the mold is opened, and the particle steam molding is completed.

[0058] Because high-temperature steam foaming and molding are performed within the mold, a thick, molten skin forms on the surface of both the granules and the molded product after the high-temperature steam heating. This skin increases the strength of the product and each foamed granule that makes up the product. After foaming and molding, the high-pressure gas inside the product escapes outwards, resulting in minimal shrinkage. The pressure within the internal air bubbles is significantly lower than the external pressure, causing external gas to rapidly enter the granules. Within a short period of about 24 hours, the internal and external gas exchange is completed and stabilized. Furthermore, the product shrinkage rate is low, around 0.5% to 1.5%, resulting in ultra-lightweight products with a specific gravity as low as 0.01 g / cm³. 3 However, in traditional foaming processes, as the gas inside the granules escapes, the foamed granules collapse. Then, external gas slowly enters the granules. Because the complete collapse of the foamed granules does not create a significant pressure difference, the gas exchange rate between the inside and outside of the granules is slow, requiring 6-7 days to fully stabilize. Furthermore, the material shrinks significantly, with foamed granules shrinking by 50%-70%. The density of the stabilized foamed granules is 0.15-0.18 g / cm³. 3 After steam molding, the granules are further compressed, resulting in a final product with a relatively high specific gravity of 0.2–0.25 g / cm³. 3 about.

[0059] The fourth step is to remove the product and let it stand for 24 to 48 hours for stabilization and maturation.

[0060] The foamed and molded product from the third step is placed in an oven for heat treatment at 25–80℃ for 24–48 hours. This heat treatment process promotes gas exchange between the internal gases and air, achieving a stable state. After the gas exchange is complete, the product's properties are fully stable. The shrinkage rate is approximately 0.5–1.5%, and the density stabilizes at 0.12 g / cm³. 3 about.

[0061] The products listed in Tables 1-3 are prepared using the process described above of the present invention (the specific process parameters for each step are shown in Tables 1-3):

[0062] Table 1

[0063]

[0064]

[0065] Table 1 lists the following specifications for TPU materials: oval TPU granules with a major and minor axis of 0.5-4 mm, polyether type, and a hardness of 70-90A; PA granules with an oval shape, a particle size of 0.4-5 mm, and a hardness of 30-50D; TPEE granules with an oval shape, a particle size of 0.4-5 mm, and a hardness of 30-50D; PP granules with an oval shape, a particle size of 0.4-5 mm, and a hardness of 20-60D; PET granules with an oval shape, a particle size of 0.4-5 mm, and a hardness of 20-60D; and PLA granules with an oval shape, a particle size of 0.4-5 mm, and a hardness of 60-90A. All these raw materials were obtained commercially. Commercially available organic pigments were used.

[0066] Table 2

[0067]

[0068] Table 3

[0069]

[0070] The relevant properties of the prepared products were tested according to the reference method in Table 4:

[0071] Table 4

[0072]

[0073]

[0074] The test results are shown in Table 5:

[0075] Table 5

[0076]

[0077] As shown in Table 5, compared with foamed products prepared by conventional processes, the foamed products prepared by the process of this invention have a lighter specific gravity, lower compression set, stronger tear strength, and a significantly shorter production cycle. The products in Examples 8 and 9, due to their use of PP and PET as raw materials, exhibit lower flexural strength compared to products made from other materials.

Claims

1. A physical microporous foaming molding process for polymer materials, characterized in that, Includes the following steps: S1. Supercritical gas permeation in a high-pressure reactor: Polymer elastomer material particles are placed in a high-pressure reactor. Carbon dioxide, nitrogen, or a mixture of both are introduced into the reactor. The pressure inside the reactor is controlled at 7~25 MPa, and the temperature at 25~40℃. The temperature is maintained for 30~120 minutes. After the gas inside the particles reaches saturation, the temperature inside the reactor is lowered to -10℃~0℃ and maintained for more than 1 minute. Then, a first rapid depressurization is performed: the pressure inside the reactor is rapidly reduced to 3~5 MPa at a depressurization rate of 1.5~2.5 MPa / s. Then, a second depressurization is performed to slowly empty the gas inside the reactor at a depressurization rate of 0.01-0.02 MPa / s. The material is then removed and stored at -10~0℃. The polymer elastomer material is selected from TPU, PA, TPEE, PP, PS, PET, and PLA. S2. Steam molding machine for foaming: After the steam molding machine is preheated, the mold is closed, and then the granular material obtained in step S1 is placed into the steam molding machine. Two steam penetrations are used. The steam pressure in the first stage is 0.01~0.02MPa and the steam time is 20~100s. The steam pressure in the second stage is 0.015~0.03MPa and the steam time is 30~160s. After the steam heating is completed, the mold is vented and water-cooled. After water cooling, the product is removed. S3. Product stabilization and maturation: The product formed in step S2 is placed in an oven for heat treatment at a temperature of 25~80℃ for 24h~48h.

2. The physical microporous foaming molding process for polymer materials according to claim 1, characterized in that: Before proceeding to step S1, the polymer elastomer material particles are pretreated with an organic solvent: the polymer elastomer material particles are immersed in an organic solvent with a volume fraction concentration of 10% to 100% for 10 to 60 minutes. The organic solvent is selected from methanol, ethanol, methane, ethane, and pentane.

3. The physical microporous foaming molding process for polymer materials according to claim 2, characterized in that: The volume fraction concentration of the organic solvent is greater than or equal to 30%.

4. The physical microporous foaming molding process for polymer materials according to claim 1, characterized in that: In step S1, the polymer elastomer material particles are mixed with 0.1wt%~5wt% of color powder and then placed in an autoclave to prepare colored products.

5. The physical microporous foaming molding process for polymer materials according to claim 4, characterized in that: The pigment is an organic pigment.

6. The physical microporous foaming molding process for polymer materials according to claim 1, characterized in that: In step S1, after the gas inside the particles reaches saturation, the temperature inside the reactor is lowered to -10℃~0℃ and maintained for 1~20 minutes, and then the first rapid depressurization is performed.

7. The physical microporous foaming molding process for polymer materials according to claim 1, characterized in that: In step S2, after the steam heating is completed, the mold is vented and water-cooled: water at 20~50℃ is introduced for cooling, and the water cooling time is 60~180s.

8. The physical microporous foaming molding process for polymer materials according to claim 1, characterized in that: In step S1, the first rapid depressurization involves rapidly reducing the pressure in the vessel to 3.5~4.5 MPa at a rate of 1.5~2.5 MPa / s.

9. The physical microporous foaming molding process for polymer materials according to claim 1, characterized in that: In step S3, the heat treatment temperature is 50~80℃.

10. The physical microporous foaming molding process for polymer materials according to claim 1, characterized in that: In step S2, the granular material obtained in step S1 is placed together with the insert into a steam molding machine to prepare an article containing the insert.

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