Pbat-based degradable composite foamed material and one-pot one-step preparation method and application thereof

Abstract

The present application belongs to the technical field of polymer foaming material and biomass composite material, and particularly relates to a PBAT-based degradable composite foaming material and a one-pot one-step preparation method and application thereof. PBAT, biomass fibers and auxiliary reagents are first placed in a high-pressure reaction kettle or a supercritical reaction kettle, and pre-assembly of the PBAT and the biomass fibers is performed under normal pressure or low pressure; then pre-permeation is performed in an initial supercritical state, and plasticization swelling is performed by increasing temperature and pressure to a later supercritical state; finally, pressure relief is performed to obtain the PBAT-based degradable composite foaming material. The PBAT-based degradable composite foaming material prepared by the present application has fine and uniform cell structure, low cell collapse tendency, good resilience, excellent wear resistance and compression resistance, and the process flow is short, green and environmentally friendly, and the damage to the fiber aspect ratio is small, which is suitable for industrialization.

Description

Technical Field

[0001] This invention belongs to the technical field of polymer foam materials and biomass composite materials, specifically relating to a PBAT-based biodegradable composite foam material and its one-step single-reactor preparation method. This PBAT-based biodegradable composite foam material is used for shoe soles. Specifically, this invention utilizes supercritical CO2 to plasticize the surface of PBAT and the mass transfer effect on auxiliary reagents to simultaneously achieve in-situ construction and composite foaming of the PBAT / biomass fiber system interface within a single high-pressure reactor. Background Technology

[0002] Polybutylene adipate / terephthalate (PBAT) is an aliphatic-aromatic copolyester that combines flexibility and biodegradability. After foaming, PBAT can achieve lightweight, cushioning, energy absorption, and thermal insulation properties, thus showing promising applications in biodegradable shoe soles, packaging cushioning, and functional foam products. However, PBAT still suffers from problems such as insufficient melt strength, slow crystallization rate, and a relatively narrow foaming window. Direct foaming can easily lead to defects such as cell collapse, uneven cell size distribution, and insufficient product shrinkage and dimensional stability.

[0003] Regarding the supercritical foaming of PBAT bulk, existing patents have proposed using supercritical CO2 to swell PBAT and rapidly depressurize for nucleation and foaming. For example, CN119775739A discloses a supercritical foamed PHA / PBAT composite material and its preparation method and application, which uses PHA as a reinforcing agent to prepare a PBAT / PHA foam material with a high expansion ratio. However, its technical focus is mainly on the supercritical foaming process of PBAT bulk, without addressing the interfacial compatibility issues, fiber dispersion issues, and the synergistic issues of cell wall support and cell stabilization during the foaming process in the natural fiber reinforced system.

[0004] To address the issues of narrow foaming window and insufficient melt strength in PBAT, existing patents often employ modification methods such as chain extension, crosslinking, nucleation, or multi-component blending. For example, patent application CN108264736A discloses a biodegradable PBAT-based foam material and its preparation method, which uses multiple screw extruders to perform stepwise melt reactions and mixing of polymers, chain modifiers, chain extenders, crosslinking agents, nucleating agents, and foaming agents to obtain a continuously and stably foamable PBAT-based material. Patent application CN118085518A discloses a biodegradable PBAT-based foam material for footwear and its preparation method, which discloses a technical route of first granulating by twin-screw extrusion, then placing the masterbatch in an autoclave for supercritical foaming, and finally steam molding into a shoe midsole. While these methods can improve the foaming performance or footwear performance of PBAT, they still rely on pre-melt blending and granulation followed by autoclave foaming, representing a two-step or multi-step process of "blending first, then foaming."

[0005] On the other hand, existing patents concerning the composite of natural plant fibers and PBAT typically focus on fiber pre-modification and melt composite. For example, patent application CN121087783A, "Modified Bamboo Fiber, PBAT Composite Material and Plastic Article," discloses a technical solution that involves first subjecting bamboo fibers to hot-pressing in water and loading them with a blocked aziridine crosslinking agent, and then preparing a composite material with PBAT. Its focus is on improving the interfacial interaction between bamboo fibers and PBAT and the mechanical properties of the composite material. This type of solution demonstrates that there are indeed problems such as poor interfacial compatibility between natural plant fibers and PBAT, and that simple mixing can easily lead to increased brittleness and decreased strength. However, its primary goal is to obtain a dense composite material, and it does not establish a coupling relationship with the supercritical CO2 foaming process.

[0006] In summary, existing technologies can be broadly categorized into three types: one is supercritical CO2 foaming of PBAT bulk material; another is shoe or general-purpose modification schemes that improve PBAT foaming performance through chain extension, nucleation, and extrusion granulation; and the third is dense composite material schemes that improve the composite performance of natural plant fibers with PBAT through pretreatment. While these three types of technologies improve the performance of PBAT-based foamed materials to a certain extent, the performance improvement is limited, and the processes are numerous and complex, making it difficult to maintain stable quality control. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a PBAT-based biodegradable composite foam material and its single-reactor one-step preparation method. This method uses PBAT as the foaming matrix and biomass fiber as the reinforcing phase. In a single high-pressure reactor, particle-fiber pre-assembly, supercritical CO2 plasticizing mass transfer, in-situ interfacial bridging, and rapid pressure relief synchronous composite foaming are completed sequentially. This solves the problems of insufficient melt strength of PBAT direct foaming, poor interfacial compatibility between biomass fiber and PBAT, and the long process and easy damage to fiber structure in traditional two-step methods. The single-reactor, one-step preparation method of PBAT-based biodegradable composite foam material of this invention does not rely on twin-screw high-shear integral melt blending. Instead, it continuously completes particle-fiber pre-assembly, in-situ bridging of the fiber / matrix interface, and rapid depressurization synchronous composite foaming in a single high-pressure reactor or supercritical reactor by utilizing the plasticizing effect of supercritical CO2 on the surface of PBAT particles and the mass transfer effect on auxiliary reagents. This allows biomass fibers to be embedded in the shallow surface layer and particle contact area of ​​PBAT particles, and an in-situ bridging layer to be formed at the particle contact interface. As a result, biomass fiber reinforcement, heterogeneous nucleation, and foam wall stabilization occur synergistically within the same process window.

[0008] The technical solution of this invention is: a one-step single-reactor preparation method for PBAT-based biodegradable composite foaming materials, comprising the following steps: (1) Place PBAT and biomass fiber in a high-pressure reactor or a supercritical reactor. Under normal or low pressure conditions, PBAT and biomass fiber are pre-assembled by turning, rolling or mechanically stirring at low speed to generate PBAT / biomass fiber pre-assembly. Furthermore, the auxiliary reagents placed in the high-pressure reactor do not come into direct contact with PBAT and biomass fibers; (2) Introduce CO2 into the high-pressure reactor or supercritical reactor to remove the air in the reactor, raise the temperature and pressure to the initial supercritical state for pre-permeation, continue to raise the temperature and pressure to the later supercritical state for plasticizing and swelling, and quickly depressurize to obtain PBAT-based biodegradable composite foam material.

[0009] Step (1): PBAT particles and biomass fibers are pre-dried, wherein the moisture content of PBAT is controlled below 0.1% and the moisture content of biomass fibers is controlled below 1%.

[0010] In step (1), the amount of PBAT added is 80-97 parts by mass, preferably 88-92 parts by mass, and more preferably 90-91 parts by mass; the amount of biomass fiber added is 3-15 parts by mass, preferably 6-10 parts by mass, and more preferably 8-9 parts by mass; the amount of auxiliary reagent added is 0.2-5 parts by mass, preferably 1-3 parts by mass, and more preferably 2-3 parts by mass.

[0011] The biomass fiber has a length of 80-400 μm, an average diameter of 10-50 μm, and an aspect ratio of 3-20; preferably, the length is 250-450 μm and the average diameter is 30-40 μm. The biomass fiber is selected from any one or any combination of biomass virgin fiber, biomass regenerated fiber, and biomass synthetic fiber. The biomass virgin fiber is selected from any one or any combination of natural plant fiber, natural animal fiber, and microbial cellulose fiber. The biomass regenerated fiber is selected from any one or any combination of regenerated cellulose fiber, regenerated protein fiber, chitin fiber, chitosan fiber, and seaweed fiber. The biomass synthetic fiber is selected from any one or any combination of polylactic acid, polycaprolactone, bio-based PTT (polypropylene terephthalate), and PHA (polyhydroxyalkanoate). Preferably, it is biomass virgin fiber, and more preferably, natural plant fiber, such as cotton fiber, bamboo fiber, or wood fiber. As one embodiment, the biomass fiber is preferably cotton fiber with a length of 250-450 μm and an average diameter of 30-40 μm.

[0012] The auxiliary reagents are selected from any one or any combination of isocyanates, silane coupling agents, epoxy chain extenders, and acid anhydride compatibilizers. The isocyanates are selected from any one or any combination of TDI (toluene diisocyanate), MDI (4,4'-diphenylmethane diisocyanate), HDI (hexamethylene diisocyanate), IPDI (isophorone diisocyanate), and XDI (terephthalimide diisocyanate). The silane coupling agents are selected from aminosilane coupling agents, mercaptosilane coupling agents, epoxysilane coupling agents, vinylsilane coupling agents, and methacryloyloxysilane coupling agents. The agent may be any one or any combination thereof. The epoxy chain extender is selected from any one or any combination of KL-E4300, KL-E4370, KL-E4370B, YDR-48E, YDR-68E, polyfunctional styrene-acrylate oligomers (styrene-glycidyl methacrylate copolymer), epoxy resin E-20, etc. The anhydride compatibilizer is selected from any one or any combination of maleic anhydride, polypropylene-grafted maleic anhydride, ethylene-octene copolymer-grafted maleic anhydride, ethylene propylene diene monomer (EPDM)-grafted maleic anhydride, polystyrene-grafted maleic anhydride, and polyethylene-grafted maleic anhydride. The auxiliary reagent is preferably an isocyanate, more preferably diphenylmethane-4,4'-diisocyanate (MDI).

[0013] Step (1): The pre-assembly speed is 5-60 rpm and the pre-assembly time is 5-30 min. Biomass fibers are attached to the PBAT surface by turning, rolling or low-speed mechanical stirring.

[0014] Step (2): Replace the air in the high-pressure reactor or supercritical reactor with 0.1-0.8 MPa CO2 1-5 times, preferably with 0.3-0.8 MPa CO2 3-4 times, and then discharge the air in the high-pressure reactor.

[0015] Step (2): Pre-permeation at an initial supercritical state of 35-50℃ and 2-6MPa for 10-30 min, preferably at 40-45℃ and 4-5MPa for 20-25 min. During the pre-permeation process, CO2 penetrates into the PBAT surface and produces plasticizing swelling, while simultaneously inducing auxiliary reagents to migrate to the interface between the biomass fiber and PBAT, thus completing plasticizing mass transfer.

[0016] Step (2): Plasticizing and swelling is performed in a supercritical state at 85-110℃ and 8-16MPa for 20-120 min, preferably at 95-105℃ and 10-14MPa for 40-90 min, and further preferably at 98-102℃ and 11-13MPa for 55-65 min. Under this supercritical state, the transport characteristics of CO2 enable the auxiliary reagent to bridge the interface between the polar groups on the surface of the biomass fiber and the terminal groups of the PBAT chain. This allows the biomass fiber to embed into the shallow layer of PBAT and the contact area between PBATs, forming a fiber-rich reinforcement zone on the surface of PBAT and an interfacial bridging layer between PBATs, thus completing the in-situ construction of the interface.

[0017] Step (2), rapid depressurization for 1-5 seconds. After the temperature and pressure are increased to the later supercritical state for plasticizing and swelling to reach a steady state, the high-pressure reactor or supercritical reactor is rapidly depressurized to allow CO2 dissolved in PBAT to precipitate rapidly and induce the formation of cells to obtain a fine and uniform cell structure. Biomass fibers serve as heterogeneous nucleation sites and cell wall support framework. This operation involves rapid depressurization and simultaneous composite foaming.

[0018] The present invention also provides a PBAT-based biodegradable composite foam material prepared by the above-described single-reactor one-step preparation method. The PBAT-based biodegradable composite foam material contains a continuous PBAT phase, a biomass fiber reinforcing phase located on the uninterrupted PBAT surface layer, and a bridging reinforcement layer embedded with biomass cellulose located at the contact interface between the uninterrupted PBAT phases. The biomass fiber reinforcing phase and the bridging reinforcement layer are located in the foam wall region of the PBAT-based biodegradable composite foam material.

[0019] The PBAT-based biodegradable composite foam material prepared by the single-reactor one-step preparation method of the present invention is used for the preparation of shoe sole products, cushioning products, elastic products, foam products, or packaging products. The applications of the cushioning products, elastic products, or foam products include, but are not limited to, packaging.

[0020] The present invention also provides a shoe sole product, cushioning product, elastic product, foam product, or packaging product containing the PBAT-based biodegradable composite foam material prepared by the single-reactor one-step preparation method of the present invention described above.

[0021] The present invention also provides a method for preparing shoe sole products, the steps of which include: maturing the PBAT-based biodegradable composite foam material obtained by the single-pot one-step preparation method of the present invention, and then performing steam molding, hot pressing or in-mold fusion molding to obtain shoe sole products.

[0022] When using steam membrane molding, the steam pressure is 0.2-0.6 MPa, preferably 0.4-0.5 MPa; the heating time is 30-120 s, preferably 60-70 s; the cooling time is 60-180 s, preferably 120-130 s; and the drying and setting temperature is 40-70℃, preferably 50-55℃.

[0023] The single-reactor, one-step preparation method of PBAT-based biodegradable composite foam material provided by this invention differs from the traditional process of integral melt blending followed by foaming. Instead of relying on continuous high shear in an extruder to achieve homogeneous dispersion of PBAT and fibers, a particle-fiber pre-assembled system is first formed in a high-pressure reactor or supercritical reactor. Then, by utilizing the plasticizing effect of supercritical CO2 on the surface of PBAT particles and the mass transfer effect on auxiliary reagents, biomass fibers are embedded in the shallow surface layer of PBAT particles and the contact area between PBAT particles, forming a bridging reinforcement layer at the interface between PBAT particles. Subsequently, rapid depressurization and synchronous composite foaming are completed in the same reactor.

[0024] In this invention, supercritical CO2 serves not only as a green physical foaming agent but also as a plasticizing medium on the surface of PBAT particles and a mass transfer medium for the migration of auxiliary reagents to the interface. Biomass fibers not only act as reinforcing fillers but also further function as heterogeneous nucleation centers and a supporting framework for the bubble walls during rapid pressure relief. The interfacial bridging layer not only improves the bonding strength between the fibers and PBAT but also inhibits cell coalescence and collapse. These multiple effects occur consecutively within the same process window, thus constituting a synergistic technical approach rather than a simple material additive process.

[0025] Compared with the prior art, the present invention has at least the following beneficial effects: (1) Pre-assembly, interface bridging and foaming are integrated through a single high-pressure reactor or supercritical reactor, which shortens the process flow and reduces process energy consumption; (2) Avoid excessive damage to the aspect ratio and surface structure of biomass fibers caused by the high shear of twin screws, which is more conducive to preserving the fiber reinforcement effect; (3) By constructing a fiber-rich reinforcement zone on the surface of PBAT particles and an interfacial bridging layer between PBAT particles, fiber reinforcement, heterogeneous nucleation and bubble wall stabilization occur synergistically, which can simultaneously improve the resilience, abrasion resistance and compression resistance of shoe sole products. (4) It is based on PBAT and biomass fiber, which is green, environmentally friendly and biodegradable, and is suitable for preparing lightweight and low-carbon sports shoe sole materials.

[0026] The PBAT-based biodegradable composite foam particles prepared by this invention have the characteristics of fine and uniform cell structure, low tendency to collapse, good resilience, and excellent abrasion resistance and compression resistance. They can be used in fully biodegradable sports shoe soles, cushioning components, and lightweight elastic products. The process of this invention is short, environmentally friendly, and causes minimal damage to the fiber aspect ratio, making it suitable for industrial scale-up. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the single-reactor one-step in-situ composite foaming technology route of the present invention.

[0028] Figure 2 This is a schematic diagram of the in-situ composite structure of the particle surface layer inside the high-pressure reactor in this invention.

[0029] Figure 3 The infrared spectrum of cotton fiber modified with MDI is shown.

[0030] Figure 4 The image shows a scanning electron microscope image of the foamed particles prepared in Example 1.

[0031] Figure 5 Scanning electron microscope image of the foamed particles prepared for Comparative Example 1.

[0032] Figure 6 Scanning electron microscope image of the foamed particles prepared for Comparative Example 2. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described below in conjunction with the accompanying drawings and embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of this invention. Conventional adjustments made by those skilled in the art to process parameters, raw material types, and proportions without departing from the concept of this invention should fall within the scope of protection of this invention.

[0034] The PBAT used in this invention preferably has a molecular weight of 40,000-60,000, a hardness of 35D-65D, and a melt index of 1-10 g / 10 min. The biomass fiber used is preferably a natural plant fiber, selected from one or more of cotton fiber, bamboo fiber, and wood fiber, preferably with a length of 80-400 μm and an average diameter of 10-50 μm. The auxiliary reagents used can be selected from at least one of isocyanates, silane coupling agents, epoxy chain extenders, and acid anhydride compatibilizers, depending on the type of interfacial interaction.

[0035] Example 1 90 parts by weight of PBAT, 8 parts by weight of cotton fiber, and 2 parts by weight of MDI were selected as raw materials. PBAT and cotton fiber were dried separately, with PBAT being vacuum dried at 60℃ for 6 h and cotton fiber being vacuum dried at 80℃ for 8 h.

[0036] Dried PBAT, cotton fibers, and MDI are simultaneously added to a high-pressure reactor equipped with a low-speed agitation mechanism. Specifically, a cylindrical container with an open top is placed in the high-pressure reactor, and MDI is added to the bottom of the reactor. The dried PBAT and cotton fibers are placed in the cylindrical container. The container prevents PBAT and cotton fibers from directly contacting MDI. The stirring rod or blade of the agitation mechanism enters the cylindrical container through the top opening to carry out mixing. The upper part of the cylindrical container wall has holes to ensure that CO2 enters the cylindrical container. Alternatively, a container with an opening is placed in the high-pressure reactor, and MDI is added to this container. The dried PBAT and cotton fibers are placed in the high-pressure reactor. The container prevents MDI from directly contacting PBAT and cotton fibers. The mixture is agitated at 20 rpm for 15 minutes under normal pressure, allowing the cotton fibers to adhere to the surface of the PBAT particles to form a particle-fiber pre-assembly. The structure in the high-pressure reactor that achieves mixing of PBAT and cotton fibers without direct contact with MDI is not described in detail here. The air inside the reactor was then replaced three times with 0.3 MPa CO2, followed by pre-permeation at 40℃ and 4 MPa for 20 min. The temperature and pressure were then increased to 100℃ and 12 MPa and held for 60 min to allow CO2 to plasticize the surface of the PBAT particles and induce MDI to migrate to the cotton fiber / PBAT interface, forming a bridging layer. After the pressure holding period, the pressure was rapidly released within 2 seconds to obtain PBAT / cotton fiber composite foamed particles. Scanning electron micrographs of the foamed particles are shown below. Figure 4 As shown.

[0037] After PBAT / cotton fiber composite foam particles were cured for 12 h, they were placed in a shoe sole mold, heated under 0.4 MPa steam for 60 s, cooled for 120 s, and dried at 55℃ for 2 h to obtain a shoe sole sample.

[0038] Example 2 The operation of this embodiment is the same as that of Embodiment 1, except that the biomass fiber used is bamboo fiber, and by mass, PBAT is 92 parts, bamboo fiber is 6 parts, and silane coupling agent (KH560) is 2 parts. The pre-assembly conditions of the high-pressure reactor are: 15 rpm agitation for 20 min. The pre-permeation conditions are: 45℃, 5 MPa pre-permeation for 15 min. The supercritical treatment conditions are: 102℃, 13 MPa pressure holding for 50 min; the depressurization time is 3 s.

[0039] Example 3 The operation of this embodiment is the same as that of Embodiment 1, except that the biomass fiber used is wood fiber, and by mass, PBAT is 88 parts, wood fiber is 10 parts, and epoxy chain extender (polyfunctional styrene-acrylate oligomer) is 2 parts. The pre-assembly conditions of the high-pressure reactor are 25 rpm agitation for 10 min. The pre-permeation conditions are 38℃ and 3 MPa for 25 min. The supercritical treatment conditions are 98℃ and 11 MPa pressure holding for 70 min; the depressurization time is 2 s.

[0040] Example 4 The operation of this embodiment is the same as that of Embodiment 1, except that a cotton / bamboo fiber composite reinforcement system is used, with 90 parts by weight of PBAT, 4 parts of cotton fiber, 4 parts of bamboo fiber, 1 part of MDI, and 1 part of silane coupling agent. The pre-assembly conditions are: 20 rpm agitation for 20 min; pre-permeation conditions are: 40℃, 4 MPa pre-permeation for 20 min; supercritical treatment conditions are: 105℃, 14 MPa pressure holding for 45 min; and depressurization time is 2 s.

[0041] Comparative Example 1 90 parts by weight of PBAT and 8 parts by weight of cotton fiber were mixed using conventional high-speed (1000 rpm) mixing and then directly placed in a high-pressure reactor for foaming. The air inside the reactor was replaced three times with 0.3 MPa CO2. The temperature and pressure were increased to 100℃ and maintained at 12 MPa for 2 hours, followed by rapid depressurization within 2 seconds. No auxiliary reagents were added, and no pre-permeation or in-situ interface construction steps were performed; foaming proceeded directly. Scanning electron micrographs of the foamed particles are shown below. Figure 5 As shown.

[0042] Comparative Example 2 The traditional two-step method was adopted: First, 90 parts by weight of PBAT, 8 parts by weight of cotton fiber, and 2 parts by weight of MDI were melt-blended and granulated in a twin-screw extruder. Then, the resulting granules were placed in a high-pressure reactor, and the air inside the reactor was replaced three times with 0.3 MPa CO2. The reactor was then heated and pressurized to 100℃ and maintained at 12 MPa for 2 hours, followed by rapid depressurization within 2 seconds. The scanning electron microscope image of the foamed particles is shown below. Figure 6 As shown.

[0043] The foamed particles were frozen in liquid nitrogen for 4 hours to induce brittle fracture. The fracture surface was then sputter-coated with gold to increase its conductivity. The results were obtained by scanning electron microscopy (SEM).

[0044] According to the ASTM D792 test standard, the density of the sample before and after foaming was measured, and the foaming ratio of the sample was calculated using the following formula ( ): ,in This refers to the density of the sample before foaming; the sample before foaming refers to the sample before supercritical CO2 treatment. This refers to the density of the foamed sample.

[0045] The average cell diameter (D) and cell density of the foam were calculated using ImageJ image processing software. Average cell diameter (D) and cell density ( Calculate according to the following formula: ,in The diameter in the SEM image is The number of bubbles; Where n refers to the number of bubbles in the SEM image, and A refers to the area of ​​each SEM image. This refers to the correction factor.

[0046] The resilience of the foamed sample was tested according to the GB / T6670-2008 test standard. Five different parts of the foamed sample were tested, and the average value was taken as the experimental result.

[0047] The compressive properties of the foamed samples were tested according to the GB / T8813-2020 test standard. The foamed samples were made into cubes with a thickness of 10 mm and compressed at a rate of 5 mm / min using an electronic universal testing machine to obtain the compressive modulus and compressive strength of the foamed samples.

[0048] When observing the cross-sectional morphology of the composite foamed particles obtained in the above embodiments, such as Figure 4-6 As shown, the samples prepared by the method of the present invention exhibit more uniform cell size and less bubble co-occurrence, and the supporting effect of biomass fibers can be observed in the cell wall region. Furthermore, compared to Comparative Example 1, which did not involve in-situ interface construction, the shoe sole samples of the present invention show significant improvements in resilience, compression recovery, and abrasion resistance. Compared to the traditional two-step method in Comparative Example 2, the method of the present invention maintains better structural stability while reducing the damage to the fiber aspect ratio caused by high shear, and also has a shorter process flow.

[0049] Table 1. Comparison of process effects between the examples and comparative examples. In addition, infrared spectroscopy was performed on the cotton fibers treated with MDI in Example 1. The results showed that the infrared spectrum was measured at 1620 cm⁻¹. -1A distinct new characteristic peak was observed nearby, which belongs to the stretching vibration peak of the carbonyl group (C=O) in the generated urethane bond (-NHCOO-), indicating successful surface modification. Scanning electron microscopy tests were performed on the foamed particles of Example 1, Comparative Example 1, and Comparative Example 2. The results showed that the particles of Example 1 had better interfacial bonding and uniform pores after foaming, while the particles of Comparative Examples 1 and 2 had poorer interfacial bonding, with collapsed pores and uneven distribution.

[0050] The present invention can also use anhydride compatibilizers to modify the surface of biomass fibers, achieving the same or similar effects as isocyanates, silane coupling agents, and epoxy chain extenders. For example, maleic anhydride, as an anhydride compatibilizer, can undergo esterification with the hydroxyl groups on the fiber surface to modify the surface of biomass fibers.

[0051] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A one-pot one-step process for the preparation of PBAT-based degradable composite foamed material, characterized by the steps of include: (1) Place PBAT and biomass fiber in a high-pressure reactor or a supercritical reactor. Under normal pressure, PBAT and biomass fiber are pre-assembled by turning, rolling or mechanically stirring at low speed to generate PBAT / biomass fiber pre-assembly. Furthermore, the auxiliary reagents placed in the high-pressure reactor or supercritical reactor do not come into direct contact with PBAT and biomass fibers. The auxiliary reagents are selected from any one or any combination of isocyanates, silane coupling agents, and epoxy chain extenders. The biomass fiber has a length of 80-400 μm, an average diameter of 10-50 μm, and an aspect ratio of 3-20. (2) Introduce CO2 into the high-pressure reactor or supercritical reactor to remove the air in the reactor, raise the temperature and pressure to the initial supercritical state for pre-permeation, continue to raise the temperature and pressure to the later supercritical state for plasticizing and swelling, and quickly depressurize to obtain PBAT-based biodegradable composite foam material. Pre-permeation at 35-50℃ and 2-6 MPa under initial supercritical conditions for 10-30 minutes; Plasticizing and swelling were carried out by maintaining the late supercritical state at 85-110℃ and 8-16 MPa for 20-120 minutes. Rapid depressurization in 1-5 seconds; During the pre-permeation process, CO2 penetrates into the surface of PBAT and produces a plasticizing and swelling effect. At the same time, it induces auxiliary reagents to migrate to the interface between biomass fibers and PBAT, thus completing plasticizing mass transfer.

2. The one-pot one-step process according to claim 1, characterized in that, In step (1), the amount of PBAT added is 80-97 parts by mass, the amount of biomass fiber added is 3-15 parts by mass, and the amount of auxiliary reagent added is 0.2-5 parts by mass.

3. A PBAT-based degradable composite foamed material, characterized in that, The single-reactor one-step preparation method described in claim 1 or 2 produces a PBAT continuous phase, a biomass fiber reinforcing phase located on the uninterrupted PBAT surface layer, and a bridging reinforcement layer embedded with biomass cellulose located at the contact interface between the uninterrupted PBAT layers, wherein the biomass fiber reinforcing phase and the bridging reinforcement layer are located in the cell wall region of the PBAT-based biodegradable composite foam material.

4. The use of the PBAT-based biodegradable composite foam material as described in claim 3 for preparing shoe sole products or packaging products.

5. The use of the PBAT-based biodegradable composite foam material as described in claim 3 for preparing cushioning products.

6. A sole article or a packaging article, characterized by The invention contains a PBAT-based biodegradable composite foam material as described in claim 3.

7. A cushioning article characterized by, The invention contains a PBAT-based biodegradable composite foam material as described in claim 3.

8. A method for preparing a shoe sole product, characterized in that the steps include... include: After the PBAT-based biodegradable composite foam material described in claim 3 is cured, it is subjected to steam molding, hot pressing, or in-mold fusion molding to obtain shoe sole products.

9. The production method according to claim 8, characterized by, When using steam membrane molding, the steam pressure is 0.2-0.6 MPa, the heating time is 30-120 s, the cooling time is 60-180 s, and the drying and setting temperature is 40-70℃.

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