Foaming material, preparation method, recycling method and judgment method for reprocessing

Abstract

The present invention discloses a foaming material, a preparation method, a recycling method and a method for judging reprocessability. The raw material composition of the foaming material of the present invention includes TPEE, an epoxy chain extender and a catalyst; wherein, the weight ratio of the TPEE, the epoxy chain extender and the catalyst is 100:(0.05-0.5):(0.01-0.1); the catalyst is a transesterification catalyst. The foaming material of the present invention has a dynamic crosslinked network structure, which enhances the entanglement of molecular chains, improves the viscoelasticity of the melt, and at the same time has good fluidity. It can not only maintain or even improve the original foamability of the material, but also prevent the thermal degradation of the foaming material during hot processing, and preferably maintain the original foamability and mechanical properties, so that the foaming material can be processed and foamed multiple times, having high economic benefits.

Description

Technical Field

[0001] The present invention relates to a foaming material, a preparation method, a recycling method, and a method for judging reprocessability. Background Art

[0002] Thermoplastic polyether ester elastomer (TPEE) is a block copolymer with polyester as the hard segment and polyether as the soft segment, possessing the rigidity of polyester and the elasticity of polyether, and is highly favored. Benefiting from the excellent mechanical properties, heat resistance, barrier properties, etc. of TPEE, it already has a large market scale and a rapidly growing market demand year by year. TPEE foaming material is also one of its largest downstream products. Introducing a bubble structure into the solid phase of TPEE will endow it with unique properties, such as cushioning and resilience. Therefore, TPEE foaming materials have been widely used in various fields, such as automobiles, medical devices, and sports equipment.

[0003] The increasingly expanding market demand has gradually made the recycling of TPEE foaming materials a difficult problem. Therefore, an environmentally friendly method for recycling and reusing TPEE foaming materials is urgently needed. Polyester is extremely prone to thermal degradation under high temperature and aerobic environments; during twin-screw extrusion in industry, mechanical degradation and thermal degradation also occur. Therefore, the mechanical properties of recycled polyester are poor. Currently, recycled polyester is usually used in a "downgraded" manner, that is, it is put into fields with lower performance requirements for continued use. However, ultimately, the large-scale elimination of polyester cannot be avoided, resulting in environmental pollution and waste of resources. Adding a chain extender to recycled polyester to increase the molecular weight is also a good choice, which can improve the melt strength and mechanical properties. However, this method has a high cost and poor economic benefits. TPEE containing a large number of ester bonds also has the above problems. Therefore, if the closed-loop of preparation, recycling, and reusing of TPEE foaming materials can be achieved, it is beneficial to protect the ecological environment and avoid large-scale waste of resources.

[0004] As a new type of polymer material, vitrimer combines the characteristics of thermoplastic and thermosetting polymers, and its main feature is a dynamic cross-linked network. Temperature is the simplest way to stimulate the dynamic behavior of the cross-linked network. At high temperatures, the dynamic cross-linked network of vitrimer is activated, and continuous reactions occur between the networks, endowing it with good fluidity, similar to thermoplastic polymers. In a low-temperature environment, the dynamic cross-linking is terminated, forming a permanently stable cross-linked structure, similar to thermosetting polymers. The cross-linked network can endow the polymer with good thermal stability and prevent degradation, and the polymer after thermal processing can still maintain excellent properties. However, too many cross-linked structures will also lead to poor fluidity of the polymer and prevent foaming, while vitrimer balances the relationship between the two well. If a dynamic cross-linked network is introduced into TPEE to prepare vitrimer, it can achieve reprocessing after foaming, realize a closed-loop economy of recycling, be beneficial to ecological environment protection, and have extremely high economic benefits.

[0005] Therefore, there is an urgent need to provide a foaming material, a preparation method, a recycling method, and a method for judging reprocessability to enhance the foamability of TPEE materials, avoid polymer degradation, and achieve the purpose of multiple processing and forming of TPEE materials. Summary of the Invention

[0006] In order to solve the defects of existing foaming materials, such as easy degradation under high-temperature processing, difficult recycling, and low foamability of the recycled material, the present invention provides a foaming material, a preparation method, a recycling method, and a method for judging reprocessability. The foaming material of the present invention has a dynamic cross-linked network structure, which enhances molecular chain entanglement, improves the viscoelasticity of the melt, and at the same time has good fluidity. It can not only maintain or even improve the original foamability of the material, but also prevent thermal degradation of the foaming material during thermal processing, and preferably maintain the original foamability and mechanical properties, enabling the foaming material to be processed and foamed multiple times, with high economic benefits.

[0007] The inventors of the present application found during the research and development process that introducing a cross-linked structure into TPEE is not conducive to the subsequent foaming process. Without introducing a cross-linked structure, after re-thermal processing of the TPEE foaming material, obvious degradation of TPEE will occur, specifically manifested as the color turning yellow and darkening, its foamability deteriorating, and the obtained foaming material being unable to be used again. Therefore, for those skilled in the art, the main technical difficulty lies in finding a balance point to enable TPEE to maintain its original foamability while avoiding degradation during re-thermal processing. The inventors of the present application unexpectedly discovered that by using specific types of chain extenders and catalysts and optimizing their dosages, not only can the foamability of TPEE be maintained or even enhanced, but also polymer degradation can be effectively avoided, and it can be processed and formed multiple times to prepare a foaming material.

[0008] The present invention mainly adopts the following technical solutions to solve the above technical problems:

[0009] The present invention provides a foaming material, and its raw material composition includes TPEE, an epoxy chain extender, and a catalyst;

[0010] Among them, the weight ratio of the TPEE, the epoxy chain extender, and the catalyst is 100:(0.05 - 0.5):(0.01 - 0.1);

[0011] Among them, the catalyst is a transesterification catalyst.

[0012] In the present invention, the epoxy chain extender reacts with the terminal carboxyl groups and terminal hydroxyl groups of the TPEE molecular chains, the epoxy groups of the epoxy chain extender undergo ring opening, while achieving a chain extension effect on the TPEE, a hydroxyl group is generated, and under the catalytic action of the transesterification catalyst, the hydroxyl group then undergoes a transesterification reaction with the ester bonds in the polymer system, thereby forming a dynamic crosslinked structure.

[0013] In the present invention, the weight ratio of the TPEE, the epoxy chain extender, and the catalyst is preferably 100:(0.05 - 0.5):(0.01 - 0.05), more preferably 100:(0.1 - 0.5):(0.01 - 0.05), for example, 100:0.3:0.05 or 100:0.5:0.05.

[0014] Those skilled in the art generally understand that the TPEE is a thermoplastic polyester elastomer, also known as polyester rubber, which is a linear block copolymer containing polybutylene terephthalate (PBT) polyester hard segments and aliphatic polyester or polyether soft segments.

[0015] In the present invention, the TPEE can be a conventional commercially available TPEE material in the art. Preferably, the weight average molecular weight of the TPEE is 15000 - 25000 g / mol.

[0016] In the present invention, the epoxy chain extender preferably includes one or a combination of more of KL-E series polymeric epoxy functionalized chain extenders, bisphenol A epoxy glycerol ether, isocyanuric acid trisglycidyl ester, N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane, and trimethylolpropane triglycidyl ether. For example, it is a KL-E series polymeric epoxy functionalized chain extender, trimethylolpropane triglycidyl ether, or N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane.

[0017] Among them, the KL-E series polymeric epoxy functionalized chain extender is preferably KL-E4370.

[0018] In the present invention, the epoxy equivalent of the epoxy chain extender is preferably 270 - 300 g / mol.

[0019] In the present invention, the transesterification catalyst preferably comprises an imidazole compound and / or an organozinc compound.

[0020] Among them, the imidazole compound preferably comprises one or more of 1-methylimidazole, 2-methylimidazole, and 4-methylimidazole, for example, 2-methylimidazole.

[0021] Among them, the organozinc compound preferably comprises one or more of zinc acetylacetonate, anhydrous zinc acetate, and zinc acrylate, for example, anhydrous zinc acetate.

[0022] The present invention also provides a method for preparing a foamed material, which comprises the following steps: extruding, thermoforming, and foaming the raw material composition containing the foamed material as described above to obtain the foamed material.

[0023] In the present invention, the extrusion can be carried out by a conventional method in the art, for example, extrusion using an extruder.

[0024] Among them, the extruder can use a conventional basic device in the art, for example, a twin-screw extruder.

[0025] In the present invention, the temperature of the extrusion can be 140-235°C, preferably 155-225°C, for example, 175°C, 185°C, 205°C, or 220°C.

[0026] In the present invention, the rotation speed of the extrusion can be 80-160 rpm.

[0027] In the present invention, cooling and pelletizing can also be included after the extrusion and before the thermoforming.

[0028] Among them, the pelletizing can generally be understood as granulation by those skilled in the art. Preferably, the pelletizing can be carried out by a conventional method in the art.

[0029] Among them, the cooling can be carried out by a conventional method in the art.

[0030] Among them, the temperature of the cooling can be selected according to the actual situation, preferably 30-50°C, for example, 40°C.

[0031] In the present invention, the thermoforming can be carried out by a conventional method in the art. Preferably, the thermoforming includes heating injection and cooling molding. Among them, the cooling molding is also called shaping.

[0032] Among them, the temperature of the heating injection is 180-235°C.

[0033] Among them, the temperature of the cooling molding is 40-50°C.

[0034] In a preferred embodiment of the present invention, the thermoforming includes the following steps: the raw material composition of the foaming material is filled into a specific mold with the process parameters of a storage pressure of 50 to 80 kPa, an injection pressure of 70 to 80 kPa, an injection speed of 50 to 55 cm 3 / s, a nozzle temperature of 180 to 235 °C, and an injection time of 5 to 6 s. The setting temperature is controlled at 40 to 50 °C, and the setting time is 250 to 300 s.

[0035] In the present invention, the temperature of the foaming can be 185 to 195 °C, such as 190 °C or 193 °C.

[0036] In the present invention, the pressure of the foaming can be 10 to 15 Mpa, such as 13 MPa.

[0037] In the present invention, the time of the foaming can be 60 to 90 min, such as 70 min.

[0038] In the present invention, the foaming agent used for the foaming can be a conventional foaming agent in the art, preferably a supercritical foaming agent, more preferably supercritical carbon dioxide and / or supercritical nitrogen, such as supercritical nitrogen.

[0039] In the present invention, the foaming can be carried out by a conventional method in the art. Preferably, the foaming includes the following steps: heating the sample obtained after the thermoforming to the foaming temperature, and adding the foaming agent at the foaming temperature.

[0040] In a specific embodiment of the present invention, the foaming includes the following steps: placing the sample obtained after the thermoforming in the mold cavity of a foaming kettle for heating, injecting the foaming agent simultaneously in the heat preservation state, and releasing the pressure after the foaming reaction under a certain pressure.

[0041] The present invention also provides a foaming material prepared by using the preparation method of the foaming material.

[0042] The present invention also provides a foaming material, which includes a polymer in which repeating units A are connected by ester bonds; the repeating unit A includes a TPEE structural unit and an epoxy chain extender structural unit.

[0043] The present invention also provides a method for recycling the foaming material, which includes the following steps: sequentially crushing, pelletizing, and thermoforming the foaming material.

[0044] In the present invention, the step of pelletizing is as described above.

[0045] In the present invention, the step of thermoforming is as described above.

[0046] The present invention also provides a method for judging the reprocessability of the foaming material, which comprises the following steps:

[0047] S1. Crush the foaming material into particles, and obtain TPEE particles after extrusion and air cooling granulation; wherein, the foaming ratio of the foaming material is r0;

[0048] S2. Thermoform the TPEE particle sample obtained in step S1 and then foam it to obtain a reprocessed foaming material, and measure the foaming ratio, denoted as r1;

[0049] S3. Repeat step S1 and step S2, and record the foaming ratios of the reprocessed foaming materials each time, denoted as r2, r3, r4... ri, where i is an integer;

[0050] S4. Judge whether it can be reprocessed based on the value of ri / r0.

[0051] In the present invention, in step S1, the crushing preferably comprises the following steps: freezing the foaming material with liquid nitrogen and then crushing it into uniform particles.

[0052] In step S1, the extrusion and the cooling are as described above.

[0053] In step S2, the thermoforming and the foaming are as described above.

[0054] On the basis of conforming to the common knowledge in the art, the above preferred conditions can be combined arbitrarily to obtain various preferred examples of the present invention.

[0055] The reagents and raw materials used in the present invention are all commercially available.

[0056] The positive and progressive effects of the present invention are as follows:

[0057] The present invention introduces a dynamic crosslinking network into the foaming material, enhances the molecular chain entanglement, and improves the viscoelasticity of the melt. Although it is a crosslinked structure, its dynamic characteristics ensure that it has good fluidity. It can not only maintain or even improve the original foamability of the material, but also prevent the thermal degradation of the foaming material during hot processing, and preferably maintain the original foamability and mechanical properties, enabling the foaming material to be processed and foamed multiple times, solving the problem of recycling of foaming materials from the source and having extremely high economic benefits. The present invention also realizes the continuous preparation of elastomer-like vitreous materials, filling the technical gap in the preparation of vitreous materials in the field of elastomers. Brief Description of the Drawings

[0058] Figure 1 It shows the change of the foaming ratio of the foaming materials prepared in Examples 1-5 and Comparative Examples 1-6 with the number of processing times. Detailed Description of the Embodiments

[0059] The present invention will be further described below by way of examples, but the present invention is not limited to the scope of the described examples. For the experimental methods without specific conditions in the following examples, they are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0060] The TPEE particles in Examples 1-5 and Comparative Examples 1-6 of the present invention were purchased from Sinopec Yizheng Chemical Fiber Co., Ltd., with the grade TX636;

[0061] The chain extender KL-E4370 was purchased from Shanxi Research Institute of Chemical Industry Co., Ltd.;

[0062] N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane was purchased from Shanghai Macklin Biochemical Co., Ltd.;

[0063] The epoxy chain extender trimethylolpropane triglycidyl ether was purchased from Shanghai Debio Biotechnology Co., Ltd.;

[0064] 2-methylimidazole was purchased from Shanghai Macklin Biochemical Co., Ltd.;

[0065] Zinc acetylacetonate was purchased from Shanghai Macklin Biochemical Co., Ltd.;

[0066] Anhydrous zinc acetate was purchased from Shanghai Macklin Biochemical Co., Ltd.

[0067] The preparation steps of the foamed materials in Examples 1-5 and Comparative Examples 1-6 are as follows. The dosages, specific types and foaming conditions of the TPEE particles, epoxy chain extender and catalyst are shown in Table 1:

[0068] (1) Mixing and extrusion: The TPEE particles, chain extender and catalyst were uniformly mixed and then fed into a twin-screw for reactive extrusion. The temperatures of each temperature zone of the extruder were: 155 °C, 185 °C, 205 °C, 220 °C, 225 °C, 225 °C, 225 °C, and the extrusion speed was 120 rpm. The extruded polymer material was cooled by air at 40 °C and then pelletized to obtain the TPEE material;

[0069] (2) Thermoforming: The TPEE material obtained in step (1) was filled into a specific mold with the process parameters of a storage pressure of 80 kPa, an injection pressure of 70 kPa, an injection speed of 50 cm 3 / s, a nozzle temperature of 225 °C, and an injection time of 5 s. The shaping temperature was controlled at 45 °C and the shaping time was 300 s.

[0070] (3) Foaming: The sample prepared in step (2) was placed in a foaming kettle, heated to the foaming temperature, and at the same time supercritical nitrogen was injected as the foaming agent. Under a certain foaming pressure, after foaming for a certain time (as shown in Table 1 below), the pressure was released to obtain the TPEE foamed material, and the foaming ratio was measured and denoted as Rv1 ;

[0071] (4) Immerse the foamed sample prepared in step (3) in liquid nitrogen for freezing, crush it into uniform particles, and then perform thermoforming at 215 °C;

[0072] (5) Repeat steps (2) to (4) 5 times, record the foaming ratio each time, denoted as r i,i＝1,2,3,4,5 , and investigate the reprocessability.

[0073] Table 1

[0074]

[0075]

[0076] Effect Example 1

[0077] Use the buoyancy method to test the foaming ratio of the foamed materials prepared in Examples 1 to 5 and Comparative Examples 1 to 6. The specific steps are as follows: (1) Weigh the mass of the foamed material sample in air, denoted as a; (2) Immerse the above sample in water, and the reading of the electronic balance under the wire mesh is denoted as b. The density of water is denoted as ρ water , and the density of the sample before foaming is denoted as ρ s . Therefore, the foaming ratio R v1 and r i,i＝1,2,3,4,5 can be calculated by the following formula:

[0078]

[0079] The results are shown in Table 2.

[0080] Table 2

[0081]

[0082] From Table 2 and Figure 1 it can be seen that:

[0083] The initial foaming ratio of the foamed material prepared in Example 1 is 9 times. After repeating steps (2) to (4) three times, the foaming ratio decreases to 8 times. After repeating steps (2) and (4) five times, the material can still maintain at 8 times, having excellent reprocessing foaming performance.

[0084] The initial foaming ratio of the foamed material prepared in Example 2 is 12 times. After repeating steps (2) to (4) five times, the foaming ratio only decreases to 11 times, having excellent reprocessing foaming performance.

[0085] The initial foaming ratio of the foamed material prepared in Example 3 is 10 times. After repeating steps (2) to (4) five times, the foaming ratio also only decreases to 9 times, having excellent reprocessing foaming performance.

[0086] The initial foaming ratio of the foaming material prepared in Example 4 is 13 times, and it can still be maintained at 13 times after repeating steps (2) to (4) five times, having excellent reprocessing foaming performance.

[0087] The initial foaming ratio of the foaming material prepared in Example 5 is 10 times, and the foaming ratio only decreases to 9 times after repeating steps (2) to (4) five times, having excellent reprocessing foaming performance.

[0088] The foaming materials prepared in Comparative Example 1 and Comparative Example 4 only added chain extenders, and the initial foaming ratio was 9 times. The foaming ratio decreased to 4 times after repeating steps (2) to (4) five times.

[0089] The TPEE in Comparative Example 2 is a pure material, and the initial foaming ratio of the foaming material is 4 times. The foaming ratio continuously decreases after repeating steps (2) to (4) five times, and it cannot be foamed during the fourth processing.

[0090] The initial foaming ratio of the foaming material in Comparative Example 3 is only 2 times. The main reason is that the crosslinked structure generated by excessive chain extenders and catalysts hinders the growth of foam cells.

[0091] The foaming material in Comparative Example 4 did not add a catalyst, and its initial foaming ratio was 6 times. The foaming ratio decreased to 3 times after repeating steps (2) to (4) five times.

[0092] The foaming material prepared in Comparative Example 5 added an oxazoline-based chain extender, and the initial foaming ratio was 5 times. The foaming ratio decreased to 2 times after repeating steps (2) to (4) five times.

[0093] The foaming material prepared in Comparative Example 6 used KL-4370 epoxy chain extender and iron acetate catalyst, and its initial foaming ratio was 8 times. The foaming ratio decreased to 3 times after repeating steps (2) to (4) five times.

[0094] There is a correlation between the internal structure of the foaming material and its foaming ratio. Generally, if the foaming ratio remains unchanged, it indicates that the viscoelasticity of the material melt before foaming has not been changed, and thus the microstructure of the foaming material will not be changed.

[0095] During the recycling process of the foaming material, a twin-screw is usually used for reprocessing. During this process, the foaming material will undergo thermal degradation and mechanical degradation, thereby reducing the foaming performance of the material. The main reason for the decrease in the foaming ratio in Comparative Examples 1 to 2 and Comparative Examples 4 to 6 of the present invention is due to the thermal degradation and mechanical degradation of the foaming material during the twin-screw processing. By comparison, it can be seen that the foaming materials prepared in Examples 1 to 5 of the present invention still maintain a good foaming ratio during the twin-screw processing. It can be seen that the foaming materials prepared in Examples 1 to 5 have excellent reprocessing foaming performance.

[0096] When the temperature is lower than its thermoforming initial temperature, the foaming material of the present invention presents a solid state and has no fluidity. When the temperature is higher than the thermoforming initial temperature, the dynamic cross-linked structure of the foaming material of the present invention endows it with fluidity. Therefore, only thermocompression molding needs to be carried out to realize the recycling of the foaming material.

[0097] Compared with the results of Comparative Examples 1-6, the implementation effects of Examples 1-5 are better. The better performance of the foaming materials prepared in Examples 1-5 is mainly due to the dynamic cross-linked structure in the foaming materials. This dynamic cross-linked structure can not only endow the foaming materials with good foamability, greatly weaken the negative impacts of thermal degradation and mechanical degradation on polyester during the processing and forming process, realize the closed-loop economy of the reprocessing and foaming process of the foaming materials, and completely solve the recycling problem of the foaming materials from the source. The main reason for the poor foaming performance of the foaming material prepared in Comparative Example 6 is that iron acetate cannot effectively catalyze the transesterification reaction and cannot form a dynamic cross-linked structure.

[0098] The above-described embodiments are only preferred embodiments of the present invention, which are convenient for those skilled in the art to understand and use the present invention. Obviously, any person skilled in the art can make a little modification or change to this embodiment without creative labor and apply it to other embodiments. Therefore, the present invention is not limited to the above embodiments, and any equal change, simple modification and modification made within the scope of the present invention still belong to the scope covered by the present invention.

Claims

1. A foaming material, characterized in that, Its raw material composition includes TPEE, an epoxy chain extender, and a catalyst; Among them, the weight ratio of the TPEE, the epoxy chain extender, and the catalyst is 100:(0.05 - 0.5):(0.01 - 0.1); Among them, the catalyst is a transesterification catalyst; The epoxy chain extender includes one or more of KL-E series polymeric epoxy-functionalized chain extenders, bisphenol A epoxy glycidyl ether, isocyanuric acid triglycidyl ester, N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane, and trimethylolpropane triglycidyl ether.

2. The foamed material according to claim 1, wherein, The weight ratio of the TPEE, the epoxy chain extender, and the catalyst is 100:(0.05 - 0.5):(0.01 - 0.05); And / or, the weight-average molecular weight of the TPEE is 15000 - 25000 g / mol; And / or, the epoxy chain extender is a KL-E series polymeric epoxy-functionalized chain extender, trimethylolpropane triglycidyl ether, or N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane; And / or, the transesterification catalyst includes imidazole compounds and / or organozinc compounds.

3. The foamed material according to claim 2, characterized in that, The weight ratio of the TPEE, the epoxy chain extender, and the catalyst is 100:(0.1 - 0.5):(0.01 - 0.05).

4. The foamed material according to claim 2, characterized in that, The weight ratio of the TPEE, the epoxy chain extender, and the catalyst is 100:0.3:0.05 or 100:0.5:0.

05.

5. The foamed material according to claim 2, characterized in that, The KL-E series polymeric epoxy-functionalized chain extender is KL-E4370; And / or, the epoxy equivalent of the epoxy chain extender is 270 - 300 g / mol; And / or, the imidazole compounds include one or more of 1-methylimidazole, 2-methylimidazole, and 4-methylimidazole; And / or, the organozinc compounds include one or more of zinc acetylacetonate, anhydrous zinc acetate, and zinc acrylate.

6. A preparation method of a foaming material, characterized in that, It includes the following steps: Extruding, thermoforming, and foaming the raw material composition containing the foaming material as described in any one of claims 1 - 5 can obtain the foaming material.

7. The preparation method of the foamed material according to claim 6, characterized in that, The temperature of the extrusion is 140 - 235 °C; And / or, the rotation speed of the extrusion is 80 - 160 rpm; And / or, cooling and pelletizing are also included after the extrusion and before the thermoforming; And / or, the temperature of the foaming is 185 - 195 °C; And / or, the pressure of the foaming is 10 - 15 Mpa; And / or, the time of the foaming is 60 - 90 min; And / or, the foaming agent used for the foaming is supercritical carbon dioxide and / or supercritical nitrogen; And / or, the thermoforming includes heating injection and cooling forming.

8. The method for preparing the foamed material according to claim 7, characterized in that, The temperature of the extrusion is 155 - 225 °C.

9. The method for preparing the foamed material according to claim 7, wherein The temperature of the extrusion is 175 °C, 185 °C, 205 °C, or 220 °C.

10. The preparation method of the foamed material according to claim 7, characterized in that, The foaming agent used for the foaming is supercritical nitrogen.

11. The preparation method of the foamed material according to claim 7, characterized in that, The temperature of the cooling is 30 - 50 °C; And / or, the foaming includes the following steps: After heating the sample obtained after the thermoforming to the foaming temperature, adding the foaming agent at the foaming temperature; And / or, the temperature of the heat injection is 180 to 235 °C; And / or, the temperature of the cooling and forming is 40 to 50 °C.

12. A foaming material, characterized in that, It is prepared by using the preparation method of the foaming material according to any one of claims 6 to 11.

13. A method for recycling the foamed material according to any one of claims 1 to 5 and 12, characterized in that, It includes the following steps: successively crushing, pelletizing and thermoforming the foaming material.

14. A method for judging the reprocessability of a foaming material according to any one of claims 1 to 5 and 12, characterized in that, It includes the following steps: S1. Crushing the foaming material into particles, and obtaining TPEE particles by air-cooling pelletizing after extrusion; wherein, the foaming ratio of the foaming material is r0; S2. Thermoforming the TPEE particle sample obtained in step S1 and then foaming to obtain a reprocessed foaming material, measuring the foaming ratio, denoted as r1; S3. Repeating step S1 and step S2, and recording the foaming ratios of the reprocessed foaming material each time, denoted as r2, r3, r4... ri, where i is an integer greater than or equal to 1; S4. Judging whether it can be reprocessed based on the value of ri / r0.

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