Thermoplastic elastomer foamed film and method for producing the same

Abstract

The application discloses a thermoplastic elastomer foamed film and a preparation method thereof, and relates to the technical field of foamed materials. The preparation method of the thermoplastic elastomer foamed film comprises the following steps: preparing a modified nucleating agent; uniformly mixing the modified nucleating agent, a thermoplastic elastomer and a chain extender, and then adding the mixture into an intermediate layer extruder; adding polyethylene and a compatilizer into top layer and bottom layer extruders; adding a physical foaming agent into the intermediate layer extruder, and then jointly extruding through a die to obtain a multilayer co-extrusion foamed film; cooling the multilayer co-extrusion foamed film through a casting roller and an opened air knife, and then performing hot pressing through a back pressure roller, preheating in a heating bin, and then pulling the hot-pressed and preheated multilayer film to a stretching roller to perform stretching and setting, and finally winding to obtain the thermoplastic elastomer foamed film. The application solves the problems that the existing high-pressure fluid escapes too fast in the thermoplastic elastomer melt, the foaming ratio is low, and the cell rupture is prone to occur.

Description

Technical Field

[0001] This invention relates to the technical field of foamed materials, and more particularly to a thermoplastic elastomer foamed film and its preparation method. Background Technology

[0002] Thermoplastic elastomers possess the excellent properties of traditional cross-linked vulcanized rubber, such as high elasticity, aging resistance, and oil resistance, while also having the advantages of easy processing and wide range of processing methods found in ordinary plastics. Lightweight polymer foam materials produced by foaming thermoplastic elastomers have wide applications in aerospace, defense, energy, transportation, packaging, electrical appliances, and sporting goods.

[0003] However, the thickness requirements for foamed materials vary when applied to different products. Currently, people have higher demands for the thickness of foamed materials. Furthermore, existing thermoplastic elastomer foamed materials are prone to low foaming ratios in the production process due to rapid gas escape, and problems such as easy rupture of cell walls and difficulty in cell formation also occur. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a thermoplastic elastomer foam film and its preparation method. This invention solves the problems of excessively rapid escape of high-pressure fluid in thermoplastic elastomer melts, low foaming ratios, and easy cell rupture. Furthermore, it enables precise control of the foam film thickness to meet the needs of different products.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] In a first aspect, the present invention provides a method for preparing a thermoplastic elastomer foam film, comprising the following steps:

[0007] (1) A processing device for thermoplastic elastomer foam film is provided, the processing device including a top layer extruder, an intermediate layer extruder, a bottom layer extruder, a die head, an air knife, a casting roller, a back pressure roller, a heating chamber, and a stretching roller;

[0008] (2) Disperse diatomaceous earth in an organic solvent to obtain a mixed solution, then add silane coupling agent dropwise to the mixed solution and carry out a constant temperature stirring reflux reaction. After the reaction is complete, filter, wash and dry the product to obtain a modified nucleating agent. The mass ratio of the silane coupling agent to diatomaceous earth is (1-3):1.

[0009] (3) Add thermoplastic elastomer and chain extender to the modified nucleating agent, mix evenly to obtain a premix, and then add the premix to the intermediate layer extruder. Polyethylene and compatibilizer are added to both the top layer extruder and the bottom layer extruder.

[0010] (4) Add physical foaming agent to the intermediate layer extruder, and then extrude the materials extruded by the intermediate layer extruder, the top layer extruder and the bottom layer extruder through the die head to form a multi-layer co-extruded foam film.

[0011] (5) Then the multi-layer co-extruded foam film is passed through the casting roller and the air knife is turned on for rapid cooling. The multi-layer co-extruded foam film is then pulled to the back pressure roller for hot pressing. After that, it is preheated through the heating chamber. Then the hot-pressed and preheated multi-layer film is pulled to the stretching roller for stretching and shaping. Finally, it is wound up to obtain the thermoplastic elastomer foam film.

[0012] Due to the special mesoporous structure and channel structure of mesoporous materials (density approximately 2000-2500 kg / m³), 3 The porosity is approximately 80-90%, and the pore volume is approximately 0.45-0.95 cm³. 3 / g, specific surface area is approximately 10-80m² 2 Mesoporous materials ( / g) can rapidly and massively adsorb high-pressure fluids. Therefore, during polymer extrusion foaming, they effectively store high-pressure fluids by forming "cavitation" structures, preventing rapid gas diffusion and escape, thus resulting in foamed materials with excellent cell structure. When the porosity and specific surface area are lower than the aforementioned values, the "gas storage" capacity of mesoporous materials is low, and the heterogeneous nucleation energy barrier is high, making it impossible to form effective "cavitation" structures for the polymer matrix and improve heterogeneous nucleation ability. Therefore, this invention, by adding mesoporous materials as heterogeneous nucleating agents, can effectively reduce the heterogeneous nucleation energy barrier of cells, further improving cell nucleation efficiency, thereby achieving the purpose of refining cells and increasing cell density. Furthermore, by surface modification of the mesoporous materials, their dispersion behavior in the polymer matrix can be optimized, avoiding easy agglomeration, thereby achieving uniform cell nucleation and distribution, and homogenizing the cells.

[0013] This invention rapidly increases the foaming ratio of thermoplastic elastomer foam films by simultaneously providing non-foaming, fast-crystallizing solid PE layers on both the upper and lower sides of the thermoplastic elastomer to further prevent rapid gas escape. The addition of chain extenders effectively improves the melt strength of the thermoplastic elastomer and further enhances the ability of the thermoplastic elastomer matrix to restrict rapid gas escape. Simultaneously, by pre-mixing the thermoplastic elastomer raw materials and additives (modifying nucleating agents and chain extenders) and adding them to the intermediate layer extruder, and then adding PE and compatibilizers to the top and bottom layer extruders respectively, and after stable extrusion in all three extruders, a physical foaming agent is injected into the gas injection port in the middle section of the intermediate layer extruder. Subsequently, after the multi-layer co-extruded foam film is extruded from the die, it is rapidly cooled and shaped by an air knife and a low-temperature casting roller, and then drawn to a winding roller for winding, thus obtaining the thermoplastic elastomer foam film. The thermoplastic elastomer foam film material prepared by this invention has a smooth surface, good flatness, uniform cell size, and a high foaming ratio. Furthermore, by setting up casting rollers, back pressure rollers, heating chambers, and stretching rollers in cooperation, this invention facilitates precise control of the thickness of the foamed film, enabling it to be better applied to different products.

[0014] Preferably, the organic solvent in step (1) is toluene, and the silane coupling agent is APTES.

[0015] Preferably, the mass ratio of silane coupling agent to diatomaceous earth in step (1) is 2:1.

[0016] Preferably, the processing equipment for the thermoplastic elastomer foam film in step (1) includes a top layer extruder, an intermediate layer extruder, a bottom layer extruder, a die head, an air knife, a casting roller, a back pressure roller, a heating chamber, and a stretching roller.

[0017] Preferably, the top layer extruder, the middle layer extruder, and the bottom layer extruder are all single screw extruders, and the single screw extruder includes one or more air inlets.

[0018] Preferably, the intermediate layer extruder has one or more air inlets.

[0019] Preferably, the premix in step (2) includes 0.1-10 parts of modified nucleating agent, 100 parts of thermoplastic elastomer, and 0.1-1 parts of chain extender.

[0020] More preferably, the premixture in step (2) includes 1-5 parts of modified nucleating agent, 100 parts of thermoplastic elastomer, and 0.2-0.4 parts of chain extender.

[0021] Preferably, in step (2), the amount of polyethylene used is 100 parts; the amount of compatibilizer used is 1-10 parts, preferably 1-5 parts.

[0022] Preferably, the thermoplastic elastomer in step (2) is at least one of TPU, TPEE, and TPAE.

[0023] Preferably, the chain extender in step (2) is at least one of a difunctional acid derivative, isocyanate, acid anhydride, and epoxide.

[0024] Preferably, the compatibilizer in step (2) is at least one of polyethylene wax and maleic anhydride.

[0025] Preferably, the physical foaming agent in step (3) is at least one of CO2, N2, methane, propane, butane, and Freon.

[0026] Preferably, in step (4), the temperature range of the air knife blower is 0-100℃, the temperature range of the casting roller is 0-180℃, the temperature range of the back pressure roller is 0-180℃, and the temperature range of the heating chamber is 30-150℃.

[0027] More preferably, in step (4), the temperature range of the casting roller is 20-150℃, the temperature range of the back pressure roller is 50-150℃, and the temperature range of the heating chamber is 50-150℃.

[0028] Preferably, in step (4), the rotational speed ratio between the stretching roller and the back pressure roller is greater than 1, and the temperature of the stretching roller is room temperature.

[0029] More preferably, the speed ratio of the stretching roller to the back pressure roller in step (4) is in the range of 1-10 times.

[0030] Preferably, the screw speed of the top extruder and the bottom extruder in step (4) is 20-30 rpm.

[0031] Secondly, the present invention also provides a thermoplastic elastomer foam film prepared by the above method.

[0032] The multilayer foamed film prepared by this invention comprises a top layer, a middle layer, and a bottom layer. The surface of the multilayer foamed film is smooth and flat, the thickness is relatively thin, and the overall density is 0.08-0.1 g / cm³. 3 The thickness is 0.8-2mm, the width is 50-55cm, the surface layer thickness is 0.1-0.15mm, and the average cell size is 100-130μm.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] This invention employs a multi-layer co-extrusion foaming process and uses modified mesoporous materials as heterogeneous nucleating agents. It connects the intermediate layer extruder, the top layer extruder, and the bottom layer extruder in parallel. By providing solid layers (top and bottom layers) with fast crystallization rates on both sides of the foamed layer (intermediate layer) and adding modified nucleating agents to the thermoplastic elastomer matrix to form "cavities," it avoids the low foaming ratio of the foamed layer due to rapid gas escape. This solves the technical problems of easy rupture of cell walls and difficulty in cell formation caused by low melt strength of thermoplastic elastomers. Attached Figure Description

[0035] Figure 1 This is a schematic diagram illustrating the processing of the thermoplastic elastomer foam film described in this invention.

[0036] Figure 2 This is a schematic diagram of the structure of the thermoplastic elastomer foam film described in this invention. Detailed Implementation

[0037] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments, but the scope of protection and implementation of the present invention are not limited thereto.

[0038] Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0039] Example 1

[0040] A thermoplastic elastomer foam film comprises a three-layer structure: a top layer, a middle layer, and a bottom layer, such as... Figure 2 As shown; the intermediate layer includes a modified nucleating agent, a thermoplastic elastomer, and a chain extender; the top / bottom layers include polyethylene and a compatibilizer. In this embodiment, the thermoplastic elastomer is TPU, the chain extender is a multifunctional epoxy chain extender, and the compatibilizer is polyethylene wax.

[0041] The processing equipment for the thermoplastic elastomer foam film of this invention includes a top layer extruder, a middle layer extruder, a bottom layer extruder, a die head, an air knife, a casting roller, a back pressure roller, a heating chamber, and a stretching roller, such as... Figure 1 As shown.

[0042] A method for preparing a thermoplastic elastomer foam film includes the following steps:

[0043] (1) Preparation of modified nucleating agent: Using a low-temperature reflux method, 5g of ground and sieved diatomaceous earth was dispersed in 30ml of dry toluene solution. After being fully dispersed, 10mL of PTES was added dropwise to the diatomaceous earth / toluene mixture from one end of a three-necked flask during constant temperature stirring and reflux. The mass ratio of silane coupling agent to diatomaceous earth was 2:1. The mixture was stirred at 90℃ (400rpm) and refluxed for 12h. After the silanization reaction, the product was filtered, washed thoroughly with toluene and ethanol (to remove solvent and excess unreacted silane coupling agent), and dried at 70℃ overnight to finally obtain the modified nucleating agent.

[0044] (2) Feeding the intermediate layer extruder: 100 parts TPU, 5 parts modified nucleating agent and 0.3 parts chain extender are premixed and mixed evenly to obtain a premix. Then the premix is ​​added to the intermediate layer extruder. When the extruder temperature reaches the preset temperature, that is, the temperature of each zone reaches 128℃ (feeding zone)-178℃-178℃-145℃-113℃-115℃-135℃ (die head)-145℃ (screen changer), the blend is put into the extruder for melt extrusion. The screw speed is 60 rpm.

[0045] (3) Top / bottom extruder feeding: 100 parts of PE and 5 parts of compatibilizer are premixed. After the extruder temperature reaches the preset temperature, that is, the temperature of each zone is 100℃ (feeding zone)-110℃-120℃-130℃-140℃-140℃-120℃ (die head), the blend is added to the extruder for melt extrusion. The screw speed is 20 rpm.

[0046] (4) After the material co-extrusion is stable, open the air inlet valve of the middle layer extruder and introduce physical foaming agent (10MPa). The physical foaming agent is butane. Then observe the air inlet pressure valve and the die pressure valve. After the pressure is stable, extrude the material from the middle layer extruder, the top layer extruder and the bottom layer extruder through the die to extrude the material together to form a multi-layer co-extruded foam film.

[0047] (5) Then the multi-layer co-extruded foamed film is passed through the casting roller and the air knife is turned on for rapid cooling. The multi-layer co-extruded foamed film is pulled to the back pressure roller for hot pressing. Then it is preheated through the heating chamber. Then the hot-pressed and preheated multi-layer film is pulled to the stretching roller for stretching and shaping. Finally, it is wound up to obtain the thermoplastic elastomer foamed film. The air knife blowing temperature is 100℃, the casting roller temperature is 180℃, the back pressure roller temperature is 180℃, and the heating chamber temperature is 150℃.

[0048] The TPU foam film prepared in this embodiment has a smooth and clean surface and an overall density of 0.08 g / cm³. 3The thickness is 1±0.2mm, the width is 50cm, the surface layer thickness is 0.1mm, the foam layer has uniform pores with an average pore size of about 100μm, and the foam layer has good adhesion to the surface layer (top / bottom layer).

[0049] Example 2

[0050] A thermoplastic elastomer foam film comprises a three-layer structure: a top layer, a middle layer, and a bottom layer, such as... Figure 2 As shown; the intermediate layer includes a modified nucleating agent, a thermoplastic elastomer, and a chain extender; the top / bottom layers include polyethylene and a compatibilizer. In this embodiment, the thermoplastic elastomer is TPU, the chain extender is a multifunctional epoxy chain extender, and the compatibilizer is polyethylene wax.

[0051] The processing equipment for the thermoplastic elastomer foam film of this invention includes a top layer extruder, a middle layer extruder, a bottom layer extruder, a die head, an air knife, a casting roller, a back pressure roller, a heating chamber, and a stretching roller, such as... Figure 1 As shown.

[0052] A method for preparing a thermoplastic elastomer foam film includes the following steps:

[0053] (1) Preparation of modified nucleating agent: Using a low-temperature reflux method, 5g of ground and sieved diatomaceous earth was dispersed in 30ml of dry toluene solution. After being fully dispersed, 10mL of PTES was added dropwise to the diatomaceous earth / toluene mixture from one end of a three-necked flask during constant temperature stirring and reflux. The mass ratio of silane coupling agent to diatomaceous earth was 2:1. The mixture was stirred at 90℃ (400rpm) and refluxed for 12h. After the silanization reaction, the product was filtered, washed thoroughly with toluene and ethanol (to remove solvent and excess unreacted silane coupling agent), and dried at 70℃ overnight to finally obtain the modified nucleating agent.

[0054] (2) Feeding the intermediate layer extruder: 100 parts TPU, 5 parts modified nucleating agent and 0.3 parts chain extender are premixed and mixed evenly to obtain a premix. Then the premix is ​​added to the intermediate layer extruder. When the extruder temperature reaches the preset temperature, that is, the temperature of each zone reaches 128℃ (feeding zone)-178℃-178℃-145℃-113℃-115℃-135℃ (die head)-145℃ (screen changer), the blend is put into the extruder for melt extrusion. The screw speed is 60 rpm.

[0055] (3) Top / bottom extruder feeding: 100 parts of PE and 5 parts of compatibilizer are premixed. After the extruder temperature reaches the preset temperature, that is, the temperature of each zone is 100℃ (feeding zone)-110℃-120℃-130℃-140℃-140℃-120℃ (die head), the blend is added to the extruder for melt extrusion. The screw speed is 30 rpm.

[0056] (4) After the material co-extrusion stabilizes, open the air inlet valve of the middle layer extruder and introduce physical foaming agent (12MPa). The physical foaming agent is butane. Then observe the air inlet pressure valve and the die pressure valve. After the pressure stabilizes, extrude the material from the middle layer extruder, the top layer extruder and the bottom layer extruder through the die to extrude the material together to form a multi-layer co-extruded foam film.

[0057] (5) Then the multi-layer co-extruded foamed film is passed through the casting roller and the air knife is turned on for rapid cooling. The multi-layer co-extruded foamed film is pulled to the back pressure roller for hot pressing. Then it is preheated through the heating chamber. Then the hot-pressed and preheated multi-layer film is pulled to the stretching roller for stretching and shaping. Finally, it is wound up to obtain the thermoplastic elastomer foamed film. The air knife blowing temperature is 100℃, the casting roller temperature is 180℃, the back pressure roller temperature is 180℃, and the heating chamber temperature is 150℃.

[0058] The TPU foam film prepared in this embodiment has a smooth and clean surface and an overall density of 0.1 g / cm³. 3 The thickness is 1.3±0.2mm, the width is 55cm, the surface layer thickness is 0.2mm, the foam layer has uniform pores with an average pore size of about 130μm, and the foam layer has good adhesion to the surface layer (top / bottom layer).

[0059] Comparative Example 1

[0060] The difference from Example 1 is that the screw speed in step (3) is 10 rpm, while the other steps are the same as in Example 1.

[0061] The density of the TPU foam film prepared in this comparative example is 0.07 g / cm³. 3 The thickness is 1.1±0.1mm, and the surface layer thickness is approximately 0.05mm.

[0062] Compared with the product obtained in Example 1, it can be seen that due to the reduced extrusion amount of the surface layer (top / bottom solid layer), the surface layer's ability to restrict the rapid escape of gas decreases. Although the product density is reduced, the product surface is not smooth and is accompanied by surface cracks and wrinkles, affecting the product's appearance.

[0063] Comparative Example 2

[0064] The difference from Example 1 is that the screw speed in step (3) is 40 rpm, while the other steps are the same as in Example 1.

[0065] The density of the TPU foam film prepared in this comparative example is 0.8 g / cm³. 3 The thickness is 1.5±0.1mm, and the surface layer thickness is approximately 0.4mm.

[0066] Compared with the product obtained in Example 1, it can be seen that the excessive extrusion of the surface layer (top / bottom solid layer) leads to a thicker skin layer, which further increases the cooling time of the foam layer, thereby inducing the phenomenon of cell wall rupture and collapse, ultimately resulting in a rapid increase in the overall density of the product.

[0067] Comparative Example 3

[0068] The difference from Example 1 is that no modified nucleating agent was added in step (2), while the other steps are the same as in Example 1.

[0069] The density of the TPU foam film prepared in this comparative example is 0.8 g / cm³. 3 The thickness is 1±0.1mm.

[0070] Compared with the product obtained in Example 1, it can be seen that because no mesoporous nucleating agent was added during the TPU extrusion process, the TPU matrix's ability to prevent rapid gas escape was reduced. This made it extremely prone to cell wall rupture when the physical foaming agent was injected, resulting in a large amount of gas escape and a density of only 0.8 g / cm³. 3 .

[0071] Comparative Example 4

[0072] The difference from Example 1 is that no chain extender was added in step (2), while the other steps are the same as in Example 1.

[0073] The density of the TPU foam film prepared in this comparative example is 0.8 g / cm³. 3 The thickness is 1.3±0.1mm.

[0074] Compared with the product obtained in Example 1, it can be seen that because no chain extender was added during the TPU extrusion process, the melt strength of the TPU matrix was too low. This made it extremely prone to cell wall rupture when the physical foaming agent was injected, resulting in a large amount of gas escape and cell aggregation, with a density of only 0.8 g / cm³. 3 about.

[0075] Comparative Example 5

[0076] The difference from Example 1 is that in step (3), TPU of equal mass is used instead of PE, while the other steps are the same as in Example 1.

[0077] The density of the TPU foam film prepared in this comparative example is 0.4 g / cm³. 3 The thickness is 2±0.1mm.

[0078] Compared with the product obtained in Example 1, it can be seen that although the surface material (top / bottom solid layer) was replaced with TPU, the TPU crystallization rate was slow during rapid cooling, which caused the high-pressure fluid to break through the surface layer, ultimately resulting in the surface layer becoming uneven due to cracking.

[0079] Comparative Example 6

[0080] The difference from Example 1 is that in step (3), PP of equal mass is used instead of PE, while the other steps are the same as in Example 1.

[0081] The density of the multilayer film prepared in this comparative example is 0.9 g / cm³. 3 .

[0082] Compared with the product obtained in Example 1, although the surface layer (top / bottom solid layer) material was replaced with PP, the processing temperature (die temperature) of PP is 20°C higher than that of PE. After co-extrusion of the three layers, the cooling time of the middle foamed layer is longer, meaning a longer foaming time. This leads to a large number of ruptures in the cell walls, and after further hot pressing with back pressure rollers, the cells almost completely collapse, resulting in a density as high as 0.9 g / cm³. 3 .

[0083] Comparative Example 7

[0084] The difference from Example 1 is that in step (2), calcium carbonate with an equal mass of spherical, non-porous structure is used to replace the modified nucleating agent, while the other steps are the same as in Example 1.

[0085] Compared with the product obtained in Example 1, it can be seen that in this comparative example, due to the absence of modified mesoporous diatomaceous earth as a nucleating agent, the heterogeneous nucleation efficiency and gas storage capacity within the body are reduced, resulting in an overall density of 0.1 g / cm³ for the prepared TPU foam film. 3 The thickness was 1±0.2 mm, the cortex (solid layer) thickness was 0.1 mm, and the average pore size was approximately 150 μm, higher than the 100 μm of the sample in Example 1. After one day of storage, due to pore shrinkage, numerous wrinkles appeared on the pore walls, and the density rebounded to 0.6 g / cm³. 3 It has no commercial value.

[0086] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a thermoplastic elastomer foam film, characterized in that, Includes the following steps: (1) A processing device for thermoplastic elastomer foam film is provided, the processing device including a top layer extruder, an intermediate layer extruder, a bottom layer extruder, a die head, an air knife, a casting roller, a back pressure roller, a heating chamber, and a stretching roller; (2) Disperse diatomaceous earth in an organic solvent to obtain a mixed solution, then add silane coupling agent dropwise to the mixed solution and carry out a constant temperature stirring reflux reaction. After the reaction is complete, filter, wash and dry the product to obtain a modified nucleating agent. The mass ratio of the silane coupling agent to diatomaceous earth is 2:

1. (3) Add thermoplastic elastomer and chain extender to the modified nucleating agent, mix evenly to obtain a premix, and then add the premix to the intermediate layer extruder. Polyethylene and compatibilizer are added to both the top layer extruder and the bottom layer extruder. The thermoplastic elastomer is TPU. The screw speed is 20 rpm or 30 rpm. (4) Add physical foaming agent to the intermediate layer extruder, and then extrude the materials extruded by the intermediate layer extruder, the top layer extruder and the bottom layer extruder through the die head to form a multi-layer co-extruded foam film. (5) Then the multi-layer co-extruded foam film is passed through the casting roller and the air knife is turned on for rapid cooling. The multi-layer co-extruded foam film is then pulled to the back pressure roller for hot pressing. After that, it is preheated through the heating chamber. Then the hot-pressed and preheated multi-layer film is pulled to the stretching roller for stretching and shaping. Finally, it is wound up to obtain the thermoplastic elastomer foam film.

2. The method for preparing the thermoplastic elastomer foam film as described in claim 1, characterized in that, In step (2), the organic solvent is toluene and the silane coupling agent is APTES.

3. The method for preparing the thermoplastic elastomer foam film as described in claim 1, characterized in that, The premixture in step (3) includes 0.1-10 parts of modified nucleating agent, 100 parts of thermoplastic elastomer, and 0.1-1 parts of chain extender.

4. The method for preparing the thermoplastic elastomer foam film as described in claim 1, characterized in that, In step (3), the amount of polyethylene used is 100 parts; the amount of compatibilizer used is 1-10 parts.

5. The method for preparing the thermoplastic elastomer foam film as described in claim 1, characterized in that, Step (3) includes at least one of the following: The chain extender is at least one of a difunctional acid derivative, isocyanate, acid anhydride, and epoxide. The compatibilizer is at least one of polyethylene wax and maleic anhydride.

6. The method for preparing the thermoplastic elastomer foam film as described in claim 1, characterized in that, The physical foaming agent in step (4) is at least one of CO2, N2, methane, propane, butane, and Freon.

7. The method for preparing the thermoplastic elastomer foam film as described in claim 1, characterized in that, In step (5), the temperature range of the air knife blower is 0-100℃, the temperature range of the casting roller is 0-180℃, the temperature range of the back pressure roller is 0-180℃, and the temperature range of the heating chamber is 30-150℃.

8. The method for preparing the thermoplastic elastomer foam film as described in claim 1, characterized in that, In step (5), the speed ratio between the stretching roller and the back pressure roller is greater than 1.

9. The thermoplastic elastomer foam film prepared by the method for preparing thermoplastic elastomer foam film according to any one of claims 1-8.

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