A method for efficiently preparing high-multiple thermoplastic elastomer foams

Abstract

The application discloses a method for efficiently preparing high-ratio thermoplastic elastomer foam, which comprises the following steps: placing a thermoplastic elastomer material in a first autoclave heated to a first foaming temperature, introducing a supercritical fluid to a first foaming pressure, and then foaming after pressure relief for 4-10 hours to obtain a pre-foamed thermoplastic elastomer material with a foaming ratio of 1.2-3; then transferring the pre-foamed thermoplastic elastomer material into a second autoclave heated to a second foaming temperature, introducing a supercritical fluid to a second foaming pressure, and then foaming after pressure relief for 10-30 minutes to obtain a thermoplastic elastomer foam with a foaming ratio of 8-12. The preparation method provided by the application has the advantages of high production efficiency and stable product performance when a large amount of materials is processed, and the production energy consumption is greatly reduced; meanwhile, the thermoplastic elastomer foam prepared by the method has a high foaming ratio and low density.

Description

Technical Field

[0001] This invention relates to the field of foam material preparation technology, and in particular to a method for efficiently preparing high-ratio thermoplastic elastomer foam. Background Technology

[0002] The information disclosed in the background section of this invention is intended only to enhance the understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Thermoplastic elastomer foam materials have been widely used in sports equipment, footwear, transportation, and thermal insulation. Supercritical foaming technology uses an inert gas in a fluid state under supercritical conditions as a foaming agent. Through high temperature and pressure, the foaming gas is uniformly penetrated into the interior of polymer particles, causing the polymer volume to expand to several times its original size. This foaming technology does not use any chemical foaming agents or crosslinking agents, does not release or leave any harmful substances, is very environmentally friendly, and produces foamed products with excellent performance.

[0004] According to Fick's Law, the saturation time of a supercritical fluid is proportional to the square of its thickness. Therefore, in the preparation of thick thermoplastic elastomer foam materials (such as sheets), the saturation time of the supercritical fluid is longer. To obtain foamed parts with lower density, fewer foamed parts are produced each time, resulting in a longer production cycle.

[0005] Patent CN 115505161A (publication date: 2022.12.23) discloses a nylon molded foam material and its preparation method. The method involves first placing a nylon sheet in the foaming cavity of a primary molding die, heating it, and injecting high-pressure supercritical fluid for a predetermined time, then opening the die to release pressure. Next, it is placed in the foaming cavity of a secondary molding die, where the gas is locked under normal pressure and heating for a predetermined time before the die is opened and pressure released, resulting in the nylon molded foam material. However, the production volume of a single molding cycle is limited, and producing a large quantity still takes a long time. The secondary molding method primarily addresses the problem of holes and tears in the foamed sheet caused by the intense expansion during primary foaming, but it cannot solve the problem of long supercritical fluid saturation time and low production efficiency for thick sheets / plates.

[0006] Patent CN 110776724 B (February 25, 2022) discloses a functional elastic foam material, its preparation method, and its application. It employs supercritical nitrogen intermittent heating foaming with a saturation pressure of 16-30 MPa, a saturation temperature of 80-120℃, a saturation time of 4-8 hours, a depressurization time of 1-15 seconds, and foaming at 150-180℃ for 5-30 minutes to obtain the functional elastic foam material. This patent primarily utilizes a solvent to swell the material in the patterned area on the board, resulting in a larger foaming ratio in that area compared to the surrounding area, thus creating an embossed effect. However, this patent only provides a method for preparing embossed patterns with a height of 0.8-2.0 mm, which is unsuitable for preparing thick-sized board foams. Furthermore, the patent uses a temperature-induced foaming method with post-saturation heating foaming. If this method is used for thick board / sheet foaming, it will actually prolong the saturation time of the board / sheet, thus failing to solve the problem of low production efficiency in thick board / sheet foaming.

[0007] Therefore, how to provide a highly efficient method for preparing thermoplastic elastomer materials using supercritical fluid as a foaming agent that can produce high foaming ratios and good product consistency is an urgent problem to be solved. Summary of the Invention

[0008] In view of this, the present invention provides a method for efficiently preparing high expansion ratio thermoplastic elastomer foam. The preparation method provided by the present invention has the advantages of high production efficiency and stable product performance when the processing volume is large, which greatly reduces the production energy consumption. At the same time, the prepared thermoplastic elastomer foam has a high expansion ratio and low density.

[0009] In a first aspect, the present invention provides a method for efficiently preparing high-ratio thermoplastic elastomer foam, comprising the following steps:

[0010] The thermoplastic elastomer material is placed in a first high-pressure autoclave heated to the first foaming temperature, and supercritical fluid is introduced to the first foaming pressure. After saturation for 4 to 10 hours, the pressure is released and foaming is carried out to obtain a pre-foamed thermoplastic elastomer material with a foaming ratio of 1.2 to 3.

[0011] The pre-foamed thermoplastic elastomer material is transferred to a second high-pressure reactor heated to the second foaming temperature. Supercritical fluid is introduced to the second foaming pressure. After saturation for 10-30 minutes, the pressure is released and foaming is carried out to obtain a thermoplastic elastomer foam with a foaming ratio of 8-12.

[0012] The volume ratio of the first high-pressure vessel to the second high-pressure vessel is 1:0.8 to 1.2, and the second foaming pressure is lower than the first foaming pressure.

[0013] Preferably, the thermoplastic elastomer material is selected from one of thermoplastic polyamide elastomers, thermoplastic polyurethane elastomers, thermoplastic polyester elastomers, and thermoplastic polyolefin elastomers.

[0014] Preferably, the first foaming temperature is T. m -50℃~T m -40℃; first foaming pressure is 8~15MPa.

[0015] Preferably, the supercritical fluid includes supercritical CO2 and / or supercritical N2.

[0016] Preferably, the second foaming temperature is T. m -30℃~T m -20℃; the second foaming pressure is 4~6MPa.

[0017] Preferably, the depressurization time for foaming after saturation for 4-10 hours is 1-5 seconds; the depressurization time for foaming after saturation for 10-30 minutes is 1-5 seconds.

[0018] Preferably, the thermoplastic elastomer material is a sheet or plate; the thickness of the sheet or plate is 8-12 mm.

[0019] Preferably, after the first batch of pre-foamed thermoplastic elastomer materials is prepared in the first autoclave, the first autoclave continues to prepare the next batch of pre-foamed thermoplastic elastomer materials.

[0020] Furthermore, during the process of preparing the next batch of pre-foamed thermoplastic elastomer material in the first autoclave, the first batch of pre-foamed thermoplastic elastomer material is transferred in multiple batches to the second autoclave heated to the second foaming temperature to prepare thermoplastic elastomer foam.

[0021] Secondly, the present invention provides a high-ratio thermoplastic elastomer foam obtained by the above-described efficient method for preparing high-ratio thermoplastic elastomer foam.

[0022] Thirdly, the present invention provides the application of the above-mentioned high-ratio thermoplastic elastomer foam in the field of thermal insulation.

[0023] Compared with the prior art, the present invention has achieved the following beneficial effects:

[0024] (1) The present invention adopts a pre-foaming molding method. The pre-foaming has a low foaming ratio, which can realize the production of a large number of pre-foamed products. The second foaming time is very short. Although the single processing volume is small and multiple preparations are required, the production time can still be greatly shortened when processing a large amount. At the same time, the pre-foaming and the second foaming process can be carried out simultaneously, which can effectively improve production efficiency.

[0025] (2) The preparation method of the present invention requires low pressure and short time for the second foaming, thus resulting in lower production energy consumption and the production of thermoplastic elastomer foam with a higher foaming ratio. In addition, the time for the second foaming of the present invention is not subject to special restrictions. That is, whether the gas remains inside the pre-foamed sample will not affect the foaming ratio and product performance of the prepared thermoplastic elastomer foam. Therefore, there is no need to use a second high-pressure reactor with a volume much larger than that of the first high-pressure reactor to ensure product stability. Attached Figure Description

[0026] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation thereof. Obviously, those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0027] Figure 1 This is a scanning electron microscope image of the PEBA foam prepared in Example 1 of the present invention;

[0028] Figure 2 This is a scanning electron microscope image of the PEBA foam prepared in Comparative Example 1 of the present invention. Detailed Implementation

[0029] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0030] This invention provides a method for efficiently preparing high-ratio thermoplastic elastomer foam, comprising the following steps:

[0031] The thermoplastic elastomer material is placed in a first high-pressure autoclave heated to the first foaming temperature, and supercritical fluid is introduced to the first foaming pressure. After saturation for 4 to 10 hours, the pressure is released and foaming is carried out to obtain a pre-foamed thermoplastic elastomer material with a foaming ratio of 1.2 to 3.

[0032] The pre-foamed thermoplastic elastomer material is transferred to a second high-pressure reactor heated to the second foaming temperature. Supercritical fluid is introduced to the second foaming pressure. After saturation for 10-30 minutes, the pressure is released and foaming is carried out to obtain a thermoplastic elastomer foam with a foaming ratio of 8-12.

[0033] The volume ratio of the first high-pressure vessel to the second high-pressure vessel is 1:0.8 to 1.2, and the second foaming pressure is lower than the first foaming pressure.

[0034] Current technologies for preparing thermoplastic elastomer foams generally employ a single-stage foaming method. Traditional methods involve foaming in the same equipment, resulting in long saturation times and low production efficiency. Even intermittent two-stage foaming is essentially a single-stage process, employing a method of saturating the sample with supercritical fluid, followed by depressurization and rapid transfer of the pre-saturated sample containing the supercritical fluid to a high-temperature, atmospheric-pressure foaming device. This method requires strict control of the sample transfer time to ensure consistent residual gas levels within the same batch of products, thereby producing thermoplastic elastomer foams with stable quality.

[0035] This invention employs a two-stage foaming method. First, a pre-foamed thermoplastic elastomer is prepared in a first autoclave, with the foaming ratio controlled at 1.2 to 3 times. This is to ensure that a large quantity of pre-foamed samples can be prepared in the first autoclave at once. Furthermore, the pre-foamed samples exhibit more pronounced microphase separation, which is beneficial for increasing the supercritical fluid diffusion rate. Simultaneously, the pre-foamed cell structure provides more unobstructed channels for supercritical fluid diffusion. Therefore, the pre-foaming process significantly reduces the saturation time of the supercritical fluid, improving production efficiency. At the same time, the pre-foaming process alters the condensed-state structure of the material, improving its viscoelastic properties and increasing the number of foaming nucleation sites. The pre-foaming-driven foaming process significantly improves the final foaming ratio and cell density of the sample, solving the bottleneck problem of high-efficiency, high-ratio foaming of thick thermoplastic elastomers.

[0036] Then, the present invention can prepare thermoplastic elastomer foam with a foaming ratio of 8 to 10 times by a second foaming (formal foaming) with low pressure and a very short time.

[0037] The second foaming (formal foaming) process of the present invention does not require consideration of the placement time of the pre-foamed sample, and the presence of supercritical fluid inside will not affect the product quality. Therefore, even if the sample quantity for each formal foaming is small and multiple batches of foaming are required, the stability of product quality can still be maintained.

[0038] The volume ratio of the first autoclave and the second autoclave of the present invention is 1:0.8 to 1.2, and more preferably 1:1. If the volume of the second autoclave is too small, the number of samples processed at one time will be greatly reduced, and it will be difficult to effectively improve production efficiency. If the volume of the second autoclave is too large, it will increase the investment in equipment costs and result in poor economic efficiency.

[0039] The present invention does not impose any special restrictions on the thermoplastic elastomer material, and commonly used thermoplastic elastomer materials in the art can be used. The present invention preferably selects one of thermoplastic polyamide elastomers (such as polyether block amide elastomers, nylon 12 elastomers), thermoplastic polyurethane elastomers, thermoplastic polyester elastomers, and thermoplastic polyolefin elastomers.

[0040] The first foaming temperature of this invention is T m -50℃~T m -40℃, first foaming pressure is 8~15MPa. The first foaming temperature is set in the low-temperature range of the material's foaming temperature window. Materials in the low-temperature range have higher strength and can suppress excessive cell growth, resulting in a lower foaming ratio. m It is the melting point of the thermoplastic elastomer.

[0041] In this invention, the supercritical fluid includes supercritical CO2 and / or supercritical N2.

[0042] In this invention, the second foaming temperature is T. m -30℃~T m -20℃; the second foaming pressure is 4-6 MPa. The second foaming temperature is adjusted according to the actual required foam density. The second foaming temperature in this invention is lower than the foaming temperature in the traditional pressure-induced supercritical foaming process. Due to the control of the material structure by the pre-foaming process, the required foam density can be obtained with a relatively small formal foaming pressure.

[0043] In this invention, the depressurization time for foaming after saturation for 4–10 hours is 1–5 seconds, and the depressurization time for foaming after saturation for 10–30 minutes is also 1–5 seconds. Both the pre-foaming and formal foaming processes are pressure-induced foaming processes, thus requiring a high depressurization rate, generally controlled within the range of 1–5 seconds.

[0044] The thermoplastic elastomer material of the present invention is a sheet or plate, and the thickness of the sheet or plate is preferably 8 to 12 mm.

[0045] In this invention, after the first batch of pre-foamed thermoplastic elastomer material is prepared in the first autoclave, the first autoclave continues to prepare the next batch of pre-foamed thermoplastic elastomer material. During the process of preparing the next batch of pre-foamed thermoplastic elastomer material in the first autoclave, the first batch of pre-foamed thermoplastic elastomer material is transferred in multiple stages to a second autoclave heated to the second foaming temperature to prepare thermoplastic elastomer foam. In this invention, the operation of the first and second autoclaves can be carried out simultaneously without mutual interference. The overall production efficiency is determined by the pre-foaming step, which has a longer saturation time. However, in this step, due to the lower foaming ratio, a larger quantity is processed in an autoclave of a fixed volume, thus significantly improving production efficiency.

[0046] The present invention also provides thermoplastic elastomer foam obtained by the above-described method for efficiently preparing high-ratio thermoplastic elastomer foam.

[0047] The present invention also provides the application of the above-mentioned thermoplastic elastomer foam in the field of thermal insulation.

[0048] The technical solution of the present invention will be further described below with reference to specific embodiments. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased on the market.

[0049] Example 1

[0050] This embodiment provides a method for efficiently preparing high-expansion polyether block amide (PEBA) foam, comprising the following steps:

[0051] PEBA disc sample dimensions: diameter 50mm, thickness 10mm.

[0052] The autoclave temperature was set to 100℃. After the temperature stabilized, the PEBA sample was placed in the first autoclave. Supercritical CO2 was introduced into the autoclave, and the pressure was set to 10MPa. After saturation for 10 hours, the pressure was released and foaming was performed. The foaming ratio of the foamed parts was measured to be approximately 1.5 times using the water displacement method. 60 pre-foamed products can be prepared at one time.

[0053] The second autoclave was set to 110℃. After the temperature stabilized, the pre-foamed PEBA sample was placed inside. Supercritical CO2 was introduced into the autoclave, and the pressure was set to 5MPa. After saturation for 15 minutes, the pressure was released for foaming. The foaming ratio of the foamed parts was measured using the water displacement method and was approximately 10 times. The resulting 60 pre-foamed products were added to the second autoclave in seven batches. The second foaming time totaled 1.75 hours, and the total production time for the 60 pre-foamed products was 11.75 hours. During the operation of the second autoclave, the first autoclave simultaneously underwent pre-foaming.

[0054] Figure 1 Scanning electron microscope (SEM) image of the PEBA foam prepared in this embodiment.

[0055] Example 2

[0056] This embodiment provides a method for efficiently preparing high-ratio thermoplastic polyurethane (TPU) foam, comprising the following steps:

[0057] TPU plate sample dimensions: length 60mm, width 60mm, thickness 9mm.

[0058] The autoclave temperature was set to 105℃. After the temperature stabilized, the TPU sample was placed in the first autoclave. Supercritical CO2 was introduced into the autoclave, and the pressure was set to 10MPa. After saturation for 9 hours, the pressure was released and foaming was performed. The foaming ratio of the foamed parts was measured to be approximately 2 times using the water displacement method. 45 pre-foamed products can be prepared at one time.

[0059] The second autoclave was set to 115℃. After the temperature stabilized, the pre-foamed TPU sample was placed inside. Supercritical CO2 was introduced into the autoclave, and the pressure was set to 5MPa. After saturation for 15 minutes, the pressure was released for foaming. The foaming ratio of the foamed parts was measured using the water displacement method and was approximately 12 times. The resulting 45 pre-foamed products were added to the second autoclave in 8 batches. The second foaming time totaled 2 hours, and the total production time for the 45 pre-foamed products was 11 hours. During the operation of the second autoclave, the first autoclave simultaneously underwent pre-foaming.

[0060] Example 3

[0061] This embodiment provides a method for efficiently preparing high-ratio thermoplastic polyester elastomer (TPEE) foam, comprising the following steps:

[0062] TPEE disc sample dimensions: diameter 50mm, thickness 9.5mm.

[0063] The autoclave temperature was set to 100℃. After the temperature stabilized, the TPEE sample was placed in the first autoclave. Supercritical CO2 was introduced into the autoclave, and the pressure was set to 15MPa. After saturation for 10 hours, the pressure was released and foaming was performed. The foaming ratio of the foamed parts was measured to be approximately 2.5 times using the water displacement method. 36 pre-foamed products can be prepared at one time.

[0064] The second autoclave was set to 110℃. After the temperature stabilized, the pre-foamed TPEE sample was placed inside. Supercritical CO2 was introduced into the autoclave, and the pressure was set to 6MPa. After saturation for 20 minutes, the pressure was released for foaming. The foaming ratio of the foamed parts was measured using the water displacement method and was approximately 15 times. The resulting 36 pre-foamed products were added to the second autoclave in 6 batches, with a total foaming time of 2 hours. During the operation of the second autoclave, the first autoclave simultaneously underwent pre-foaming.

[0065] Comparative Example 1

[0066] PEBA disc sample dimensions: diameter 50mm, thickness 10mm.

[0067] The autoclave temperature was set to 120℃. After the temperature stabilized, PEBA disc samples were placed in the autoclave, and supercritical CO2 was introduced into the autoclave. The pressure was set to 10 MPa, and after saturation for 10 hours, the pressure was released for foaming. The expansion ratio of the foamed parts was measured to be approximately 6 times using the water displacement method. Fifteen foamed products could be prepared each time. The total production time for 60 PEBA foam samples was 40 hours.

[0068] Figure 2 Scanning electron microscope image of the PEBA foam prepared for this comparative example.

[0069] from Figure 1 and Figure 2The SEM image comparison revealed that the foaming temperature and pressure in Example 1 were significantly lower than those in the traditional method. However, due to the pre-foaming effect, the foam cell size was larger, the foam expansion ratio was significantly improved, and the saturation time was greatly reduced. Typically, during depressurization foaming, a decrease in temperature and pressure leads to a decrease in the expansion ratio, but the product of Example 1 achieved a higher expansion ratio under low temperature and low pressure. Furthermore, Example 1 prepared 60 PEBA foam samples in a total time of 11.75 hours, far less than the 40 hours of Comparative Example 1, demonstrating a significant increase in production rate.

[0070] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for efficiently preparing high-ratio thermoplastic elastomer foam, characterized in that, Includes the following steps: The thermoplastic elastomer material is placed in a first high-pressure autoclave heated to the first foaming temperature, and supercritical fluid is introduced to the first foaming pressure. After saturation for 4 to 10 hours, the pressure is released and foaming is carried out to obtain a pre-foamed thermoplastic elastomer material with a foaming ratio of 1.2 to 3. The pre-foamed thermoplastic elastomer material is transferred to a second high-pressure reactor heated to the second foaming temperature. Supercritical fluid is introduced to the second foaming pressure. After saturation for 10-20 minutes, the pressure is released and foaming is carried out to obtain a thermoplastic elastomer foam with a foaming ratio of 8-12. The volume ratio of the first high-pressure vessel to the second high-pressure vessel is 1:0.8~1.2, and the second foaming pressure is less than the first foaming pressure.

2. The method as described in claim 1, characterized in that, The thermoplastic elastomer material is selected from one of thermoplastic polyamide elastomers, thermoplastic polyurethane elastomers, thermoplastic polyester elastomers, and thermoplastic polyolefin elastomers.

3. The method as described in claim 1, characterized in that, The first foaming temperature is T m -50 o C~T m -40 o C; The first foaming pressure is 8~15MPa.

4. The method as described in claim 1, characterized in that, The supercritical fluid includes supercritical CO2 and / or supercritical N2.

5. The method as described in claim 1, characterized in that, The second foaming temperature is T m -30 o C~T m -20 o C; The second foaming pressure is 4~6MPa.

6. The method as described in claim 1, characterized in that, The depressurization time for foaming after saturation for 4-10 hours is 1-5 seconds; the depressurization time for foaming after saturation for 10-20 minutes is 1-5 seconds.

7. The method as described in claim 1, characterized in that, The thermoplastic elastomer material is a sheet or plate; the thickness of the sheet or plate is 8~12mm.

8. The method as described in claim 1, characterized in that, After the first batch of pre-foamed thermoplastic elastomer material is prepared in the first high-pressure reactor, the first high-pressure reactor continues to prepare the next batch of pre-foamed thermoplastic elastomer material. During the process of the first high-pressure reactor continuing to prepare the next batch of pre-foamed thermoplastic elastomer material, the first batch of pre-foamed thermoplastic elastomer material is transferred in multiple times to the second high-pressure reactor heated to the second foaming temperature to prepare thermoplastic elastomer foam.

9. The high-ratio thermoplastic elastomer foam obtained by the efficient method for preparing high-ratio thermoplastic elastomer foam according to any one of claims 1 to 8.

10. The application of the high-ratio thermoplastic elastomer foam as described in claim 9 in the field of thermal insulation.

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