A method for recycling waste polyurethane materials and a method for preparing polyurethane products.

Abstract

This invention discloses a method for recycling waste polyurethane materials and a method for preparing polyurethane products, belonging to the technical field of waste polyurethane material recycling and reuse. The recycling method includes: a powder preparation stage, where waste polyurethane materials are pulverized using a pulverizing device to obtain polyurethane powder; a premix preparation stage, where the polyurethane powder is mixed with a degrading agent, catalyst, and co-solvent in a specific ratio, and then mixed uniformly using a stirring device to obtain a premix with a certain powder content; and a degradation stage, where the premix is ​​ground, extruded, and sheared using equipment with mechanical shearing and extrusion functions, the reaction process is carried out within a set temperature range, and after the reaction is completed, a degraded polyurethane mixture is obtained. In the method for preparing polyurethane products, part or all of the polyol raw material is taken from the degradation mixture. This invention achieves low reagent consumption, low temperature and short time degradation, no need for gas protection, and no generation of toxic substances such as aromatic amines. The resulting high-performance heterogeneous polyol can be directly used in the preparation of polyurethane products without any post-processing.

Description

Technical Field

[0001] This invention relates to the field of waste polyurethane material recycling technology, and in particular to a method for recycling waste polyurethane materials and a method for preparing polyurethane products. Background Technology

[0002] Polyurethane materials are widely used in building insulation, automotive interiors, furniture manufacturing, footwear materials, and packaging. Currently, the recycling methods for waste polyurethane materials are mainly divided into two categories: physical methods and chemical methods.

[0003] Physical methods include landfilling, incineration, and physical pulverization. Landfilling and incineration easily lead to heavy metal pollution in the soil, emissions of air pollutants (such as dioxins), and exacerbated greenhouse gas emissions, and completely destroy the material's reuse value. Physically pulverized materials are mostly used as fillers or raw materials for low-end products. This method is simple and easy to implement, but the added value of the products is low, making it difficult to achieve large-scale resource recycling.

[0004] Chemical degradation methods utilize degrading agents to break the covalent bonds in polyurethane molecules, converting them into low-molecular-weight compounds, thereby achieving raw material-level recycling. Chemical degradation methods mainly include hydrolysis, alcoholysis, ammonolysis, acid hydrolysis, glycolysis, alkaline hydrolysis, and thermal degradation. These degradation methods have been researched and applied to some extent, but they also have some problems. For example, hydrolysis requires harsh reaction conditions, the catalyst cannot be recycled, and wastewater treatment costs are high; alkaline hydrolysis causes significant environmental pollution and has high degradation costs; thermal degradation not only causes significant environmental pollution but also yields products with low chemical added value. Current research shows that while some methods can degrade polyurethane, there is still room for improvement in degradation conditions, product performance, and applications. For example, some methods require high temperatures, consume a lot of energy, and produce toxic and harmful substances; some degradation products cannot be directly used for reprocessing, or the performance of reprocessed products differs significantly from the original products.

[0005] Furthermore, existing technologies generally neglect the impact of pretreatment processes on degradation efficiency. Traditional methods often involve directly mixing pulverized polyurethane micropowder with a degradation agent, achieving degradation through high temperatures or a large proportion of the degradation agent, catalyst, and prolonged reaction. This lack of activation of the surface active groups of the micropowder and uniform dispersion of the degradation agent results in degradation reactions occurring only on the particle surface, making it difficult to destroy the internal cross-linked structure. Consequently, this leads to incomplete degradation and a wide molecular weight distribution of the products. Simultaneously, high temperatures easily trigger the breakage of chemical bonds other than urethane bonds, producing toxic byproducts such as aromatic amines, and damaging the residual cross-linked network of the micropowder, resulting in decreased product performance during reuse.

[0006] In summary, current waste polyurethane material recycling technologies still face multiple bottlenecks in terms of degradation efficiency, product performance, environmental friendliness, and process economics. Therefore, developing a highly efficient, environmentally friendly waste polyurethane material recycling process that can guarantee the performance of remanufactured products is of significant practical importance.

[0007] The information disclosed in this background section is only intended to enhance the understanding of the background technology of this application, and therefore may include prior art that is not known to those skilled in the art. Summary of the Invention

[0008] To address the problems of high temperature and high energy consumption, large amount of degrading agent, unstable product performance, and low replacement ratio of waste polyurethane materials in polyurethane recycled products in existing polyurethane chemical degradation technologies, this invention provides a method for recycling waste polyurethane materials and a method for preparing polyurethane products. Through an innovative process of "low-temperature mechanochemical shallow heterogeneous catalytic degradation", the degradation process achieves low reagent consumption, low temperature and short time, no need for gas protection and no generation of toxic substances such as aromatic amines. The resulting high-performance heterogeneous polyol can be directly used for the preparation of polyurethane products without any post-processing. Moreover, the prepared polyurethane products have excellent performance, with some properties improved by more than 10% compared with the original formula, thus promoting the efficient and green recycling of waste polyurethane.

[0009] To achieve the above-mentioned objectives, the present invention employs the following technical solution:

[0010] In some embodiments of this application, a method for recycling waste polyurethane materials is provided, including:

[0011] In the powder preparation stage, waste polyurethane materials are crushed using crushing equipment to obtain polyurethane powder;

[0012] In the premix preparation stage, the polyurethane powder is mixed with the degradation agent, catalyst and cosolvent in proportion, and mixed evenly by a stirring device to obtain a premix with a certain powder content.

[0013] In the degradation stage, the premixed liquid is ground, squeezed and sheared using equipment with mechanical shearing and extrusion functions. The reaction process is carried out within a set temperature range, and after the reaction is completed, a degraded mixture of polyurethane material is obtained.

[0014] The above technical solution has the following advantages or beneficial effects:

[0015] Existing methods for degrading and recycling waste polyurethane materials mostly require large amounts of degrading agents to degrade small quantities of waste polyurethane into liquid products at high temperatures. These products then undergo multi-stage distillation to remove toxic byproducts before practical application. Furthermore, these methods cannot completely replace raw materials in the production process. This invention innovatively employs a "low-temperature mechanochemical shallow heterogeneous catalytic degradation" process. Through the synergistic effect of equipment with strong mechanical shearing and extrusion capabilities and low-temperature chemical degradation, a gel polyol containing highly active polyurethane powder and free of toxic byproducts such as aromatic amines is produced. The product has a high powder content, low viscosity, and strong process applicability, achieving efficient resource recovery and utilization of waste polyurethane materials.

[0016] This invention employs a synergistic effect of mechanical force and chemical degradation, namely a shallow heterogeneous degradation process. This significantly reduces the viscosity of the alcohol-powder mixture and refines the average particle size of the micropowder, resulting in a heterogeneous degradation product with a narrow molecular weight distribution in the liquid component and high surface activity in the solid component for repolymerization. The term "heterogeneous" refers to the fact that the degradation mixture obtained by this process is a solid-liquid two-phase mixture containing incompletely degraded polyurethane micropowder particles and degradation liquid, which is significantly different from the products obtained by ordinary degradation processes. The term "shallow degradation" means that the incompletely degraded polyurethane micropowder in the degradation mixture obtained by this invention retains part of the original cross-linked network framework structure of the polyurethane micropowder while also being enriched with a large number of newly formed hydroxyl and amine groups on the surface, unlike the traditional fully degraded liquid recovery form.

[0017] The waste polyurethane material recycling method disclosed in this invention adopts a "low-temperature mechanical mechanical chemical shallow heterogeneous catalytic degradation" process: First, the scraps, waste materials and polyurethane materials aged for many years generated during the production of polyurethane products are cleaned and coarsely crushed. The coarsely crushed powder is uniformly mixed with degradation agent, catalyst and co-solvent through a stirring device to obtain a premixed liquid. Then, the premixed liquid is deeply ground, extruded and sheared in a low-temperature environment using a strong mechanical shearing and extrusion device, so that the degradation agent and catalyst are uniformly dispersed on the surface and pores of the micro powder, forming a "catalyst-micro powder-degradation agent" pre-activation system. With the control of chemical degradation modes such as alcoholysis and aminolysis, the proportion of urethane bond breaking is precisely controlled to achieve controllable shallow degradation of polyurethane micro powder.

[0018] The core advantage of this process lies in the fact that this invention uses specialized equipment with strong mechanical shearing and extrusion capabilities to process the mixture of polyurethane micropowder, degrading agent, catalyst, and cosolvent. Relying on the high shear stress and friction effect generated by mechanical force, it not only refines the particle size of the micropowder and directly destroys the cross-linked structure on the surface of the micropowder, but also simultaneously reduces the activation energy of the carbamate group chain scission degradation, increases the contact probability between the degrading agent, catalyst, and the surface of the micropowder, and forms a ternary interaction interface of "micropowder surface degradation sites - polar groups of degrading agent - active center of catalyst", providing efficient reaction sites for subsequent degradation reactions, significantly shortening the shallow degradation reaction process, and increasing the reaction rate.

[0019] Compared to traditional processes, the synergistic degradation system disclosed in this application can achieve controllable shallow degradation of polyurethane micropowder under low-temperature conditions, using approximately 4% of the degrading agent and half the catalyst of common chemical degradation processes, along with a shorter reaction time. During the degradation stage, the polyol, acting as a co-solvent, possesses both swelling regulation and reaction mediation functions. Through swelling, it increases the porosity of the micropowder, promotes the penetration of the degrading agent into the cross-linked network within the micropowder, and drives reactions such as alcoholysis and aminolysis from the particle surface inwards.

[0020] This process avoids the risks of high-temperature degradation and eliminates the generation of toxic byproducts such as aromatic amines. It overcomes the limitations of traditional degradation processes that rely on inert gas protection, allowing for stable operation in an open environment and effectively reducing process requirements and external environmental interference. The synergistic effect of mechanical and chemical degradation significantly reduces the viscosity of the alcohol-powder mixture and refines the average particle size of the micropowder, resulting in a heterogeneous degradation product with a narrow molecular weight distribution in the liquid component and high surface activity in the solid component for repolymerization. This product retains some of the original cross-linked network skeletal structure of the polyurethane micropowder while enriching the surface with a large number of newly formed active functional groups such as hydroxyl and amine groups. No separation or purification process is required, and it can directly replace polyols as raw materials for polyurethane material production. Experimental testing shows that polyurethane products prepared using the degradation mixture of this invention as raw material exhibit excellent performance, with some properties improved by more than 10% compared to the original formula. This breaks through the limitations of traditional micropowder substitution ratios, achieving green, efficient, and high-value recycling of waste polyurethane materials, and providing a new technical solution for the circular economy development of the polyurethane industry.

[0021] In summary, this invention, through a "low-temperature mechanochemical shallow heterogeneous catalytic degradation" process, overcomes the technological bottlenecks of traditional degradation processes, which rely on high temperatures, high amounts of degrading agents, low degradation efficiency, generation of toxic byproducts, complex and unstable product purification processes, and low application added value. It achieves the goal of shallow degradation of polyurethane materials under low-temperature conditions using a small amount of chemical reagents. This method is applicable to the recycling of waste polyurethane materials with different chemical structures and degrees of cross-linking. It boasts significant advantages such as simple and efficient process, no toxic byproducts, environmental friendliness, direct application of products without complex separation processes, and high application added value. Therefore, it has important practical value for promoting the circular economy development of the polyurethane industry.

[0022] In some embodiments of this application, during the premix preparation stage, the amount of the degrading agent added is determined based on the molar amount of urethane groups in the polyurethane powder and the target degradation rate; wherein, the degradation rate = (molar amount of degraded urethane groups / total molar amount of initial urethane groups) × 100%, and the amount added is calculated according to the molar reaction ratio between the polar groups and urethane in the degrading agent; the degradation rate of the urethane is 5-70%.

[0023] In some embodiments of this application, during the premix preparation stage, the co-solvent is a mixture of one or more polyols in any proportion.

[0024] In some embodiments of this application, during the premix preparation stage, the powder content of the premix is ​​<60%.

[0025] In some embodiments of this application, during the degradation stage, the reaction temperature is 60-160°C and the reaction time is 10 min-3 h.

[0026] In some embodiments of this application, during the degradation stage, the progress of the degradation reaction can be indirectly determined based on the color change or flowability change of the mixture in the reaction vessel.

[0027] In some embodiments of this application, the viscosity of the degradation mixture is less than 20,000 mPa·s after being allowed to stand and cool to room temperature.

[0028] In some embodiments of this application, a method for preparing a polyurethane product is provided, wherein part or all of the polyol raw material is a degradation mixture obtained by the waste polyurethane material recycling method described above.

[0029] The above technical solution has the following advantages or beneficial effects:

[0030] The degradation mixture of the present invention does not contain toxic and harmful substances such as aromatic amines. It can be directly used in the production line to replace polyol raw materials without any post-processing. The dosage can be flexibly adjusted according to the actual production needs of the factory and the product performance indicators, thereby optimizing and improving the performance of foamed products and saving the factory about 10% of production costs.

[0031] Meanwhile, this degradation mixture exhibits low viscosity and good uniformity, demonstrating convenience in filling, transportation, storage, and use. Its applicability is also outstanding, allowing for the matching of appropriate processing technologies to different materials provided by factories and the performance requirements of the final product.

[0032] In some embodiments of this application, the preparation method includes a product reprocessing stage, in which component A and component B are mixed in a certain proportion and then the product is reprocessed; component A is a mixture of the degradation mixture and chain extender, catalyst and stabilizer, and foaming agent is added as needed; component B is isocyanate.

[0033] In some embodiments of this application, during the powder preparation stage, a pulverizing device is used to pulverize one of waste polyurethane elastomer, polyurethane flexible foam or polyurethane rigid foam to obtain polyurethane powder.

[0034] In the premix preparation stage, the polyurethane powder is mixed with the degradation agent, catalyst, and polyol (i.e. cosolvent) used to prepare other types of polyurethane materials in proportion, and mixed evenly by stirring equipment to obtain a premix with a certain powder content.

[0035] During the degradation stage, the premixed liquid is subjected to grinding, extrusion and shearing processes using equipment with mechanical shearing and extrusion functions. The reaction process is carried out within a set temperature range, and after the reaction is completed, a degradation mixture of polyurethane elastic material is obtained.

[0036] In the in-process manufacturing stage, the degradation mixture of the polyurethane material is mixed with the polyol used to prepare the corresponding polyurethane material as a polyol raw material.

[0037] In some embodiments of this application, a method for recycling waste polyurethane materials is provided, including:

[0038] In the powder preparation stage, waste polyurethane materials are crushed using crushing equipment to obtain polyurethane powder;

[0039] In the premix preparation stage, the polyurethane powder is mixed with the degradation agent and catalyst in proportion, and then mixed evenly by a stirring device to obtain a premix with a certain powder content.

[0040] In the degradation stage, the premixed liquid is ground, squeezed and sheared using equipment with mechanical shearing and extrusion functions. The reaction process is carried out within a set temperature range, and after the reaction is completed, a degraded mixture of polyurethane material is obtained.

[0041] The above technical solution has the following advantages or beneficial effects:

[0042] The "low-temperature mechanochemical shallow heterogeneous catalytic degradation" process proposed in this invention utilizes continuous strong mechanical shearing provided by equipment such as colloid mills to efficiently process the degradation material, offering the following advantages compared to existing chemical degradation processes:

[0043] This invention employs specialized equipment with strong mechanical shearing and extrusion capabilities to process a mixture of polyurethane micropowder, degrading agent, catalyst, and cosolvent. Relying on the high shear stress and frictional effect generated by mechanical force, it not only refines the micropowder particle size and directly disrupts the cross-linked structure on the micropowder surface, but also simultaneously reduces the activation energy for the chain-breaking degradation of urethane groups. This increases the contact probability between the degrading agent, catalyst, and the micropowder surface, forming a ternary interaction interface of "micropowder surface degradation sites - polar groups of the degrading agent - active centers of the catalyst." This provides highly efficient reaction sites for subsequent degradation reactions, significantly shortening the shallow degradation reaction process and increasing the reaction rate. Furthermore, compared with existing degradation processes, this process can significantly reduce the temperature threshold required for the degradation reaction, fundamentally suppressing high-temperature-induced side reactions and, in principle, eliminating the generation of toxic byproducts such as aromatic amines. This has significant practical implications for the high-value reuse of degradation products and environmental protection.

[0044] In some embodiments of this application, a method for recycling waste polyurethane materials is provided, including:

[0045] In the powder preparation stage, waste polyurethane materials are crushed using crushing equipment to obtain polyurethane powder;

[0046] In the mixed degradation stage, the polyurethane powder, degradation agent, and catalyst are added in proportion to a device with mechanical shearing and extrusion functions, and the co-solvent is added as needed. Mixing and degradation are carried out within a set temperature range to obtain a degradation mixture of polyurethane material.

[0047] The above technical solution has the following advantages or beneficial effects: The "low-temperature mechanochemical shallow heterogeneous catalytic degradation" process proposed in this invention efficiently processes the degradation material through continuous strong mechanical shearing action provided by equipment such as colloid mills, and has the following advantages compared with existing chemical degradation processes:

[0048] This invention employs specialized equipment with strong mechanical shearing and extrusion capabilities to process a mixture of polyurethane micropowder, degrading agent, catalyst, and cosolvent. Relying on the high shear stress and frictional effect generated by mechanical force, it not only refines the micropowder particle size and directly disrupts the cross-linked structure on the micropowder surface, but also simultaneously reduces the activation energy for the chain-breaking degradation of urethane groups. This increases the contact probability between the degrading agent, catalyst, and the micropowder surface, forming a ternary interaction interface of "micropowder surface degradation sites - polar groups of the degrading agent - active centers of the catalyst." This provides highly efficient reaction sites for subsequent degradation reactions, significantly shortening the shallow degradation reaction process and increasing the reaction rate. Furthermore, compared with existing degradation processes, this process can significantly reduce the temperature threshold required for the degradation reaction, fundamentally suppressing high-temperature-induced side reactions and, in principle, eliminating the generation of toxic byproducts such as aromatic amines. This has significant practical implications for the high-value reuse of degradation products and environmental protection.

[0049] In addition, equipment using mechanical shearing and extrusion functions can simultaneously achieve reactant mixing and polyurethane material degradation, reducing the initial investment cost of the production line, and can still achieve good shallow heterogeneous degradation and recycling results under appropriate process parameter settings.

[0050] Other features and advantages of the present invention will become clearer after reading the detailed embodiments of the invention in conjunction with the accompanying drawings. Attached Figure Description

[0051] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0052] Figure 1 This is a schematic diagram of a method for recycling waste polyurethane materials according to some embodiments;

[0053] Figure 2 This is a schematic diagram of a method for preparing a polyurethane article according to some embodiments;

[0054] Figure 3 This is a schematic diagram of a method for recycling waste polyurethane materials according to some other embodiments;

[0055] Figure 4 This is a schematic diagram of a method for recycling waste polyurethane materials according to some other embodiments;

[0056] Figure 5 This is a performance comparison chart of the degradation mixture from Example 1 with other products;

[0057] Figure 6This is a comparison chart of the performance of the foamed product of Example 1 with other foamed products;

[0058] Figure 7 The NMR spectrum of the aminolysis products of waste polyurethane flexible foam in Example 1 is shown below.

[0059] Figure 8 This is a performance comparison chart of the degradation mixture from Example 2 with other products;

[0060] Figure 9 This is a comparison chart of the performance of the foamed product in Example 2 with other foamed products;

[0061] Figure 10 The NMR spectrum of the alcoholysis products of waste polyurethane rigid foam in Example 2 is shown below.

[0062] Figure 11 This is a performance comparison chart of the degradation mixture of Example 3 with other products;

[0063] Figure 12 This is a comparison chart of the performance of the foamed product of Example 3 with other foamed products;

[0064] Figure 13 The NMR spectrum of the aminolysis products of waste polyurethane elastomer in Example 3 is shown below.

[0065] Figure 14 This is a performance comparison chart of the degradation mixture of Example 4 with other products;

[0066] Figure 15 This is a comparison chart of the performance of the foamed product in Example 4 with other foamed products;

[0067] Figure 16 The NMR spectrum of the aminolysis products of waste polyurethane flexible foam in Example 4 is shown below.

[0068] Figure 17 This is a performance comparison chart of the degradation mixture of Example 5 with other products;

[0069] Figure 18 This is a comparison chart of the performance of the foamed product of Example 5 with other foamed products;

[0070] Figure 19 The NMR spectrum of the aminolysis products of waste polyurethane flexible foam in Example 5 is shown below.

[0071] Figure 20 This is a performance comparison chart of the degradation mixture of Example 6 with other products;

[0072] Figure 21 This is a comparison chart of the performance of the foamed product of Example 6 with other foamed products;

[0073] Figure 22The image shows the NMR spectrum of the alcoholysis products of waste polyurethane elastomer in Example 6. Detailed Implementation

[0074] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0075] In the description of this application, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0076] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0077] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0078] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0079] The following disclosure provides many different embodiments or examples for implementing various structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, examples of various specific processes and materials are provided in this invention, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0080] In some embodiments of this application, reference is made to Figure 1 A method for recycling waste polyurethane material is provided, including a powder preparation stage. In the powder preparation stage, the waste polyurethane material is pulverized using a pulverizing device to obtain polyurethane powder. The polyurethane powder is then sealed and stored in a self-sealing bag. For example, the particle size range of the polyurethane powder is <25 mm.

[0081] The waste polyurethane material recycling method also includes a premix preparation stage. In the premix preparation stage, the polyurethane powder is mixed with a degradation agent, a catalyst, and a co-solvent in a certain proportion, and then mixed evenly using a stirring device to obtain a premix with a certain powder content.

[0082] The recycling method for waste polyurethane materials also includes a degradation stage. In this stage, the premixed liquid is ground, extruded, and sheared using equipment with mechanical shearing and extrusion capabilities. The reaction process is carried out within a set temperature range, and after the reaction is complete, a degraded polyurethane mixture is obtained. The degraded mixture is then stored in a sealed glass container.

[0083] The recycling method for waste polyurethane materials includes a powder preparation stage, a premix preparation stage, and a degradation stage, which are carried out sequentially.

[0084] Existing methods for degrading and recycling waste polyurethane materials mostly rely on high temperatures and high amounts of degrading agents, resulting in low degradation efficiency and the generation of toxic byproducts. Furthermore, the purification process for these products is complex and their performance is unstable, leading to low added value. This invention innovatively employs a "low-temperature mechanochemical shallow heterogeneous catalytic degradation" process. Through the synergistic effect of equipment with strong mechanical shearing and extrusion capabilities and low-temperature chemical degradation, it achieves the goal of shallow degradation of polyurethane materials using a small amount of chemical reagents under low-temperature conditions. This method is applicable to the recycling of waste polyurethane materials with different chemical structures and degrees of cross-linking. It boasts significant advantages such as simple and efficient process, no toxic byproducts, environmental friendliness, direct application of the product without complex separation processes, and high added value. The resulting gel polyol product containing highly active polyurethane powder has a high powder content, low viscosity, and strong process applicability, achieving efficient resource recovery and utilization of waste polyurethane materials.

[0085] This invention employs a synergistic effect of mechanical force and chemical degradation, namely a shallow heterogeneous degradation process. This significantly reduces the viscosity of the alcohol-powder mixture and refines the average particle size of the micropowder, resulting in a heterogeneous degradation product with a narrow molecular weight distribution in the liquid component and high surface activity in the solid component for repolymerization. The term "heterogeneous" refers to the fact that the degradation mixture obtained by this process is a solid-liquid two-phase mixture containing incompletely degraded polyurethane micropowder particles and degradation liquid, which is significantly different from the products obtained by ordinary degradation processes. The term "shallow degradation" means that the incompletely degraded polyurethane micropowder in the degradation mixture obtained by this invention retains part of the original cross-linked network framework structure of the polyurethane micropowder while also being enriched with a large number of newly formed hydroxyl and amine groups on the surface, unlike the traditional fully degraded liquid recovery form.

[0086] The waste polyurethane material recycling method disclosed in this invention adopts a "low-temperature mechanical mechanical chemical shallow heterogeneous catalytic degradation" process: First, the scraps, waste materials and polyurethane materials aged for many years generated during the production of polyurethane products are cleaned and coarsely crushed. The coarsely crushed powder is uniformly mixed with degradation agent, catalyst and co-solvent through a stirring device to obtain a premixed liquid. Then, the premixed liquid is deeply ground, extruded and sheared in a low-temperature environment using a strong mechanical shearing and extrusion device, so that the degradation agent and catalyst are uniformly dispersed on the surface and pores of the micro powder, forming a "catalyst-micro powder-degradation agent" pre-activation system. With the control of chemical degradation modes such as alcoholysis and aminolysis, the proportion of urethane bond breaking is precisely controlled to achieve controllable shallow degradation of polyurethane micro powder.

[0087] The core advantage of this process lies in the fact that this invention uses specialized equipment with strong mechanical shearing and extrusion capabilities to process the mixture of polyurethane micropowder, degrading agent, catalyst, and cosolvent. Relying on the high shear stress and friction effect generated by mechanical force, it not only refines the particle size of the micropowder and directly destroys the cross-linked structure on the surface of the micropowder, but also simultaneously reduces the activation energy of the carbamate group chain scission degradation, increases the contact probability between the degrading agent, catalyst, and the surface of the micropowder, and forms a ternary interaction interface of "micropowder surface degradation sites - polar groups of degrading agent - active center of catalyst", providing efficient reaction sites for subsequent degradation reactions, significantly shortening the shallow degradation reaction process, and increasing the reaction rate.

[0088] Compared to traditional processes, the synergistic degradation system disclosed in this application can achieve controllable shallow degradation of polyurethane micropowder under low-temperature conditions, using approximately 4% of the degrading agent and half the catalyst of common chemical degradation processes, along with a shorter reaction time. During the degradation stage, the polyol acts as a co-solvent, possessing both swelling regulation and reaction mediation functions: it can increase the porosity of the micropowder through swelling, promoting the penetration of the degrading agent into the cross-linked network within the micropowder, and driving catalytic decomposition reactions such as alcoholysis and aminolysis from the particle surface inwards.

[0089] This process avoids the risks of high-temperature degradation and eliminates the generation of toxic byproducts such as aromatic amines. It overcomes the limitations of traditional degradation processes that rely on inert gas protection, allowing for stable operation in an open environment and effectively reducing process requirements and external environmental interference. The synergistic effect of mechanical and chemical degradation significantly reduces the viscosity of the alcohol-powder mixture and refines the average particle size of the micropowder, resulting in a heterogeneous degradation product with a narrow molecular weight distribution in the liquid component and high surface activity in the solid component for repolymerization. This product retains some of the original cross-linked network skeletal structure of the polyurethane micropowder while enriching the surface with a large number of newly formed active functional groups such as hydroxyl and amine groups. No separation or purification process is required, and it can directly replace polyols as raw materials for polyurethane material production. Experimental testing shows that polyurethane products prepared using the degradation mixture of this invention as raw material exhibit excellent performance, with some properties improved by more than 10% compared to the original formula. This breaks through the limitations of traditional micropowder substitution ratios, achieving green, efficient, and high-value recycling of waste polyurethane materials, and providing a new technical solution for the circular economy development of the polyurethane industry.

[0090] In summary, this invention, through a "low-temperature mechanochemical shallow heterogeneous catalytic degradation" process, overcomes the bottlenecks of traditional degradation processes, which rely on high temperatures, high amounts of degrading agents, low degradation efficiency, generation of toxic byproducts, complex and unstable product purification processes, and low application added value. It achieves the goal of shallow degradation of polyurethane materials under low-temperature conditions using a small amount of chemical reagents. This process is applicable to the recycling of waste polyurethane materials with different chemical structures and degrees of cross-linking. It also boasts significant advantages such as simple and efficient process, no toxic byproduct generation, environmental friendliness, direct application of products without complex separation processes, and high application added value. Therefore, it has important practical value for promoting the circular economy development of the polyurethane industry.

[0091] In some embodiments of this application, during the powder preparation stage, the waste polyurethane material is one or more combinations of polyurethane flexible foam, polyurethane rigid foam, and polyurethane elastomer.

[0092] This limitation enables efficient processing of polyurethane materials with different structural characteristics. Polyurethane flexible foam is characterized by low crosslinking density, high elasticity, and high open-cell ratio. The microparticles formed after pulverization have relatively large particle sizes, but the surface of the microparticles is rich in pores, which is conducive to the penetration of degradation agents in the subsequent premixed solution.

[0093] Rigid polyurethane foam possesses characteristics such as high crosslinking density, high rigidity, and high closed-cell rate. Due to the large number of urea-formaldehyde bonds in rigid foam, it requires higher mechanical shear strength compared to flexible foam. However, this process effectively breaks down its dense structure through the synergistic effect of "mechanical force + chemical degradation," ensuring a high degradation rate.

[0094] Polyurethane elastomers possess both a certain degree of crosslinking and elasticity. When pulverized, the micro powder exhibits good toughness and excellent compatibility with cosolvents (polyols). It can rapidly swell during the degradation stage, making it easier for urethane bonds to contact the degradation agent.

[0095] This limitation allows the process to flexibly handle various combinations of waste materials and adapt to the mixed characteristics of materials in actual recycling scenarios. When processing mixed waste materials of flexible and rigid foam, the particle size distribution of the micro powder can be controlled by adjusting the crushing parameters (such as increasing the feeding rate and compression ratio when the proportion of flexible foam is high), ensuring the uniformity of subsequent degradation reactions; when elastomers are mixed in, their non-porous and dense structure can reduce the agglomeration phenomenon during the preparation of the premix.

[0096] Furthermore, this limitation is compatible with the core process characteristics of this application. Whether it is a low-crosslinked flexible foam or a high-crosslinked rigid foam, the "low-temperature mechanochemical shallow heterogeneous catalytic degradation" process can control the degradation rate within the range of 5-70% by adjusting parameters such as shear strength and degradation agent ratio, ultimately obtaining a degradation mixture with a viscosity of less than 20000 mPa·s.

[0097] In some embodiments of this application, during the powder preparation stage, the pulverizing equipment is one or more combinations of equipment with shearing and crushing functions, such as crushers, extruders, refining mills, open mills, ball mills, air jet mills, vibratory mills, and sand mills.

[0098] In some embodiments of this application, amine compounds are used as degrading agents during the premix preparation stage. In other embodiments of this application, alcohol compounds are used as degrading agents during the premix preparation stage.

[0099] The degrading agent is one or more combinations of methanol, ethanol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, glycerol, 1,4-butanediol, 1,3-butanediol, didihydroxyol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, tetraethylenepentamine, triethylenetetramine, diethylenetriamine, ethanolamine, diethanolamine, triethanolamine, 3-propanolamine, isopropanolamine, diisopropanolamine, triisopropanolamine, succinic acid, oxalic acid, phthalic acid, and maleic acid.

[0100] In some embodiments of this application, during the premix preparation stage, the catalyst is one or more combinations of metal compounds and alkaline earth metal acetates, titanates, Lewis acids, Lewis bases, acidic ionic liquids, alkanolamines, and tertiary amine compounds.

[0101] In some embodiments of this application, the catalyst accounts for 0.01-0.5% of the mass of the polyurethane powder.

[0102] Catalysts within this ratio range can synergistically interact with the physical effects of mechanical shearing and extrusion. When the catalyst concentration is in the lower range of 0.01-0.05%, sufficient active sites are provided for the selective cleavage of carbamate bonds. Under the high shear stress caused by mechanical force, the activation energy of the degradation reaction is significantly reduced, promoting shallow degradation reactions at low temperatures. At this point, shallow degradation mainly occurs at cracks, breaks, or weak cross-linking points on the surface of the microparticles. When the catalyst concentration is in the middle range of 0.05-0.2%, its catalytic effect can more easily penetrate into the cross-linked network inside the microparticles. Utilizing the strong shearing and extrusion effect generated by mechanical force and the swelling effect of the co-solvent, the catalyst can penetrate into the pores of the microparticles, driving the degradation reaction from the surface inwards. At this point, the cleavage ratio of carbamate bonds is precisely controlled, avoiding the destruction of the original skeletal structure due to excessive degradation while ensuring that the microparticle surface is enriched with sufficient active functional groups such as hydroxyl and amino groups.

[0103] When the catalyst concentration is in the higher range of 0.2-0.5%, it is more suitable for treating waste polyurethane materials with high cross-linking degree and severe aging. Under strong mechanical shearing and extrusion, a higher proportion of catalyst can accelerate the breaking down of the cross-linking structure on the surface of the micropowder, ensuring the sufficiency of the degradation reaction.

[0104] Furthermore, the catalyst ratio range is compatible with the low-temperature process and open reaction environment of this application. Compared to traditional processes where catalysts are easily deactivated at high temperatures and require excessive addition, the synergistic effect of mechanical force and chemical catalysis in this application significantly improves the catalyst utilization efficiency, achieving efficient degradation at a ratio of 0.01-0.5%. This not only reduces reagent costs but also minimizes the adverse effects on product performance that catalyst residues may cause.

[0105] In some embodiments of this application, during the premix preparation stage, the amount of the degrading agent added is determined based on the molar amount of urethane groups in the polyurethane powder and the target degradation rate. Specifically, the degradation rate = (molar amount of degraded urethane groups / initial total molar amount of urethane groups) × 100%, and the amount added is calculated according to the molar reaction ratio between the polar groups and urethane groups in the degrading agent. For example, the reaction ratio is 1:1.

[0106] This calculation method achieves a quantitative match between the amount of degrading agent used and the target degree of degradation. Since urethane groups are key structural units in the polyurethane molecular chain, their breakage ratio directly determines the depth of the degradation reaction. By pre-measuring the total molar amount of initial urethane groups in the polyurethane powder and combining it with a preset degradation rate, the molar amount of urethane groups to be degraded can be accurately calculated. Furthermore, based on the molar reaction ratio between polar groups and urethane groups in the degrading agent, the amount of degrading agent added can be accurately determined, ensuring that the degrading agent reacts only with the target number of urethane groups. This avoids insufficient degradation due to insufficient dosage, or excessive degradation and side reactions due to excessive dosage.

[0107] This method minimizes the waste of degradation agents and reduces process costs. In traditional processes, degradation agents are often added in excess based on experience to compensate for local reagent shortages caused by uneven reactions. However, the excess not only fails to participate in the effective reaction but also increases the burden on subsequent separation and purification. In this application, the strong shear dispersion effect brought about by mechanical force allows the degradation agent to fully contact the urethane groups on the surface and inside of the polyurethane micropowder, thereby increasing the reaction rate.

[0108] This calculation method lays the foundation for maintaining the excellent performance of the degradation products. As mentioned earlier, the core of this application is to achieve controllable shallow degradation of polyurethane micropowder, which requires retaining some of the original cross-linked network skeleton and enriching surface-active functional groups. If the amount of degradation agent is too large, it will lead to excessive breakage of urethane bonds, destroying the skeleton structure of the micropowder and causing the degradation products to lose their value as high-performance raw materials; if the amount is insufficient, the number of surface-active functional groups of the micropowder will be insufficient, affecting its reactivity with other raw materials. Based on the quantitative addition of the molar reaction ratio, the breaking ratio of urethane bonds can be precisely controlled, ensuring that the ratio of solid micropowder to liquid components in the degradation products is appropriate, and that the content of active functional groups such as hydroxyl and amino groups on the surface of the micropowder is stable. The heterogeneous degradation mixture obtained in this way can be directly used in the production of polyurethane products without post-treatment, and the key properties of the products, such as tensile strength and elongation at break, are improved by more than 10% compared with the original formulation.

[0109] Furthermore, this calculation method is well-suited to the "low-temperature mechanical force synergy" system of this application. Under the high-stress environment generated by mechanical shearing and extrusion, the contact efficiency between the degrading agent and polyurethane micropowder is significantly improved. Sufficient reaction can be achieved without high-temperature conditions, avoiding the volatilization of the degrading agent due to high temperatures, further ensuring the accuracy of dosage calculations. Simultaneously, this method is applicable to different types of waste polyurethane materials (such as polyurethane flexible foam, polyurethane rigid foam, and polyurethane elastomers). By simply adjusting the calculation parameters according to the content of their urethane groups, different degradation requirements can be flexibly met, enhancing the versatility and practicality of the process.

[0110] In some embodiments of this application, the degradation rate of the carbamate is 5-70%.

[0111] A degradation rate range of 5-70% can flexibly adapt to the recycling needs of various waste polyurethane materials. When the degradation rate is in the lower range of 5-30%, it is suitable for treating waste polyurethane materials with low cross-linking degree and light aging degree (such as scraps generated during the production process). At this time, only a small number of urethane groups break, and the polyurethane micropowder can retain the original cross-linked network skeleton to the greatest extent, with only a suitable amount of active functional groups such as hydroxyl and amine groups generated on the surface. The resulting degradation products can be directly used as a reinforcing phase in the preparation of polyurethane materials to improve the mechanical properties of the products.

[0112] When the degradation rate is in the moderate range of 30-50%, it is suitable for recycling most general-purpose waste polyurethane materials (such as waste furniture foam and automotive interior parts). Within this range, the proportion of urethane groups broken is moderate, which ensures that the surface of the micropowder is enriched with sufficient active functional groups to ensure its reactivity compatibility with virgin materials, while retaining some cross-linked skeleton structure to maintain mechanical support. The solid micropowder and liquid components in the degradation products form a stable heterogeneous system, which can replace part of the polyol in the production of polyurethane foam. The compressive strength, resilience, and other properties of the finished product are equal to or even improved with the original formula.

[0113] When the degradation rate is in the higher range of 50-70%, it is suitable for treating waste polyurethane materials with high cross-linking degree and high hardness (such as rigid insulation boards and shoe sole waste). The higher degradation rate can effectively break the cross-linking network of polyurethane micropowder, further refine the particle size of the micropowder, significantly improve its dispersibility and reactivity in new materials, and have better compatibility with the substrate, making subsequent applications convenient.

[0114] This degradation rate range is well-suited to the characteristics of the "low-temperature mechanochemical shallow heterogeneous catalytic degradation" process. Under the strong shear force of mechanical force, the degrading agent can uniformly penetrate into the interior of the micropowder, making it easier to control the cleavage reaction of the carbamate groups within the range of 5-70%, avoiding the problems of local over-degradation or under-degradation caused by uneven reaction in traditional processes. At the same time, the low-temperature environment can inhibit the occurrence of side reactions, ensuring the stability of the degradation rate and providing a reliable process guarantee for industrial production.

[0115] In some embodiments of this application, during the premix preparation stage, the co-solvent is a mixture of one or more polyols in any proportion.

[0116] For example, the cosolvent is one or more polyols with a molecular weight of 100-4000 in any proportion, and its hydroxyl value is between 25-600 mg KOH / g.

[0117] Polyols, acting as co-solvents, can specifically target the cross-linked network of polyurethane micropowders. Polyurethane and polyols exhibit good compatibility; during the premixing stage, polyols can penetrate the pores and cross-linked network of the polyurethane micropowders through permeation, causing moderate swelling. This swelling increases the specific surface area of ​​the micropowders, loosening their internal cross-linked structure and providing channels for the diffusion of subsequent degradation agents and catalysts into the micropowder interior.

[0118] The addition of polyols can effectively improve the uniformity of the premix. When the amount of degrading agent and catalyst is limited, direct mixing of polyurethane micropowder with the degrading agent and catalyst easily leads to paste-like agglomeration, resulting in uneven dispersion of the degrading agent and catalyst. Polyols, with their moderate viscosity, can serve as a dispersion medium for polyurethane micropowder, forming a stable suspension system under the action of stirring equipment. When two or more polyols are used in combination, the viscosity and dispersion effect of the premix can be further optimized by adjusting the proportion of different molecular weights.

[0119] The physicochemical properties of polyols are well-suited to the low-temperature mechanochemical shallow heterogeneous catalytic degradation process. They exhibit good fluidity within the low-temperature range, reducing the flow resistance of the premixed liquid in mechanical shearing equipment and minimizing energy consumption during mechanical action. Simultaneously, polyols possess excellent thermal stability, preventing degradation under low-temperature reaction conditions and avoiding the introduction of impurities that could affect product performance. Furthermore, polyols are commonly used raw materials in the preparation of polyurethane products. When used as a co-solvent to maintain their original properties within the degradation products, they can directly participate in subsequent polyurethane synthesis reactions without additional separation and purification, simplifying process steps and reducing production costs.

[0120] In some embodiments of this application, during the premix preparation stage, the powder content of the premix is ​​<60%.

[0121] A powder content range of <60% allows for efficient contact between polyurethane micropowder and degrading agents / catalysts. When the powder content is in the lower range of <20%, the proportion of liquid components (degrading agents, co-solvents, etc.) in the premix is ​​high, allowing the polyurethane micropowder to be fully dispersed in the liquid phase. Each micropowder particle can be coated with sufficient degrading agent and catalyst. Under mechanical shearing, the surface of the micropowder is subjected to uniform stress, and the degrading agent can quickly penetrate into the particle interior, making it suitable for processing polyurethane micropowders with larger particle sizes or higher degrees of cross-linking.

[0122] When the powder content is in the moderate range of 20-40%, the premixed liquid forms a suspension system with a balanced solid-liquid ratio, possessing both fluidity and reactivity. At this point, appropriate gaps exist between the microparticles, allowing the stress generated by mechanical shearing to be effectively transferred to the surface of each particle, while the liquid phase component still ensures a sufficient supply of the degradation agent. This range is suitable for the recycling of most general-purpose waste polyurethane materials (such as flexible foam and automotive interior waste), increasing the material throughput per unit volume while avoiding agglomeration problems caused by excessive microparticles.

[0123] When the powder content is in the higher range of 40-60%, the viscosity of the premix increases, but it can still maintain a good mixing state under the strong force of the mechanical shearing equipment. A higher powder content can increase the single-batch processing capacity of waste polyurethane materials, significantly improving production efficiency, and is suitable for processing micro-powders with small particle sizes or low cross-linking degrees. At this level, the collision frequency between micro-powders increases, and the strong shearing and extrusion effect generated by mechanical force is stronger, which can accelerate the destruction of the cross-linked structure on the surface of the micro-powder and promote the degradation reaction. Simultaneously, a higher powder content can reduce the amount of liquid components used, lower production costs, and the resulting degradation products have a high proportion of solid micro-powder, making them suitable for the production of polyurethane products with less stringent mechanical performance requirements.

[0124] A powder content range of <60% is well-suited to the equipment characteristics of the "low-temperature mechanochemical shallow heterogeneous catalytic degradation" process. This process utilizes equipment with strong mechanical shearing and extrusion capabilities, enabling it to adapt to premixed liquids of varying viscosities. When the powder content is low, the shearing force of the equipment effectively disperses the microparticles, preventing sedimentation; when the powder content is high, the extrusion and grinding action of the equipment breaks up microparticle agglomerates, ensuring uniform reaction. If the powder content exceeds 60%, the viscosity of the premixed liquid will increase sharply, leading to uneven microparticle dispersion, incomplete degradation reaction, and even equipment blockage.

[0125] In some embodiments of this application, during the premix preparation stage, the equipment with mechanical shearing and extrusion functions is one or more combinations of a refining mill, planetary ball mill, colloid mill, extruder, grinding mill, pulping mill, kneader, homogenizer, and high-shear mixing emulsifier.

[0126] In some embodiments of this application, during the degradation stage, the reaction temperature is 60-160°C and the reaction time is 10 min-3 h. This invention uses a water-cooling device to keep the reaction process in a low-temperature environment.

[0127] The selective cleavage of urethane bonds can be achieved within the temperature range of 60-160℃, while avoiding excessive degradation and the formation of toxic byproducts. When the reaction temperature is in the lower range of 60-100℃, it is suitable for waste polyurethane materials that are highly sensitive to heat (such as automotive interior foam containing easily decomposable additives). At this temperature, the shearing and compressive forces of mechanical forces become the main driving force for the degradation reaction. Combined with the active catalysis of the catalyst, the controlled cleavage of urethane bonds can be achieved at low temperatures, effectively inhibiting the formation of toxic byproducts such as aromatic amines.

[0128] When the reaction temperature is in the higher range of 100-160℃, it is suitable for treating waste polyurethane materials with a high degree of cross-linking and a dense structure (such as rigid insulation boards). The increase in temperature can enhance the molecular motion rate, promote the penetration of the degradation agent into the cross-linked network inside the micropowder, and form a synergistic effect with the shearing action of mechanical force, accelerating the breaking of urethane bonds.

[0129] The reaction time of 10 min to 3 h is adapted to the synergistic effects of temperature, mechanical force, and catalyst. In the low-temperature range of 60-100℃, the reaction time is typically controlled at 1.5-3 h to compensate for the insufficient reaction rate at low temperatures. In the higher temperature range of 100-160℃, the reaction time can be shortened to 10 min to 1.5 h, utilizing the accelerated reaction effect brought about by the increased temperature to improve production efficiency.

[0130] This temperature and time range, combined with a water-cooling device, significantly reduces energy consumption and environmental risks. Compared to traditional processes requiring temperatures above 160°C and inert gas protection, the 60-160°C reaction temperature of this application reduces energy consumption and eliminates the need for gas protection, simplifying the process. Furthermore, the 10-minute to 3-hour reaction time is far shorter than the 4-8 hours of traditional processes, significantly increasing the equipment's throughput per unit time and reducing production costs.

[0131] In some embodiments of this application, during the degradation stage, the progress of the degradation reaction is indirectly determined based on the color change or flowability change of the mixture in the reactor.

[0132] The color change of the mixture is clearly correlated with the degree of urethane bond breakage. Initially, the premixed solution formed by the polyurethane micropowder, degradation agent, and co-solvent is mostly a white or light yellow suspension. As the degradation reaction proceeds, the small molecular fragments generated by the breakage of urethane bonds and the surface-active functional groups (such as hydroxyl and amino groups) alter the optical properties of the system. This color change is quantifiable, for example, by colorimetry, and shows a linear correlation with the degradation rate measured by high-performance liquid chromatography (HPLC), providing operators with a basis for indirectly judging the reaction progress without the need for complex instruments.

[0133] The changes in the flowability of the mixture are directly related to the evolution of the system viscosity and the particle size of the microparticles, reflecting the uniformity of the degradation reaction. The initial premix has poor flowability due to variations in powder content. Under the synergistic effect of mechanical shearing and chemical degradation, the particle size of the microparticles gradually decreases, and the interaction between surface-active functional groups and liquid components strengthens. The system viscosity initially decreases and then stabilizes. When the degradation rate reaches the target value, the viscosity tends to stabilize, and the flowability remains uniform. Changes in flowability can be quickly determined by measuring the flow rate.

[0134] This assessment method does not rely on sophisticated testing instruments and is suitable for continuous industrial production scenarios. In traditional processes, the degradation process requires sampling for molecular weight determination or chemical analysis, which is not only time-consuming but also causes disturbance to the reaction system due to sampling. In contrast, the color and flowability observation of this application can be performed directly through the reaction vessel window or sampling port, and the reaction status can be fed back in real time. For example, if a color change lags behind the expected time or the flowability suddenly deteriorates, the mechanical shear rate can be adjusted promptly or a small amount of degradation agent can be added to ensure the reaction proceeds along the preset path and reduce batch-to-batch variations.

[0135] Furthermore, this technical solution is compatible with the characteristics of the "low-temperature mechanochemical shallow heterogeneous catalytic degradation" process described in this application. At reaction temperatures of 60-160℃, the color change of the mixture is not affected by carbonization caused by high temperatures (because the temperature is below the degradation threshold of polyurethane), and the temperature stability maintained by the water-cooling device ensures the repeatability of color and flowability changes. Simultaneously, the uniform mixing state generated by mechanical shearing ensures consistent color and flowability distribution within the degradation reaction equipment, avoiding misjudgments caused by localized deviations.

[0136] In some embodiments of this application, the viscosity of the degradation mixture is less than 20,000 mPa·s after being allowed to stand and cool to room temperature (e.g., 25°C).

[0137] The viscosity range below 20,000 mPa·s reflects the shallow heterogeneous degradation state of polyurethane micropowder. If the viscosity is higher than 20,000 mPa·s, it indicates that the micropowder particle size is too large, the micropowder content is too high, or the surface-active functional groups are insufficient, leading to poor compatibility between the solid and liquid phases, poor flowability, and subsequent processing defects such as uneven mixing and bubbles. The viscosity range below 20,000 mPa·s corresponds to a 5-70% degradation rate of urethane esters. This range retains some of the original cross-linked backbone while ensuring good interaction between the surface-enriched hydroxyl and amine groups and the liquid components, guaranteeing a stable heterogeneous state.

[0138] This viscosity range facilitates the direct application of degradation mixtures. The production of polyurethane products (such as foams, elastomers, and adhesives) has specific requirements for raw material viscosity. Excessively high viscosity negatively impacts production processes and product quality, increases transport difficulty, reduces mixing efficiency, and can even damage equipment. Viscosities below 20,000 mPa·s at room temperature meet the needs of most polyurethane molding processes without the need for additional diluents or thickeners.

[0139] Room temperature viscosity can serve as a key indicator for assessing the consistency of degradation reactions. In the "low-temperature mechanochemical shallow heterogeneous catalytic degradation" process, minute fluctuations in parameters such as reaction temperature, time, and mechanical shear rate can affect the degradation effect, and the measurement of room temperature viscosity can directly reflect the cumulative effect of these fluctuations.

[0140] In some embodiments of this application, reference is made to Figure 2 The present invention provides a method for preparing polyurethane products, wherein part or all of the polyol raw material is obtained by the degradation mixture obtained by the waste polyurethane material recycling method described above.

[0141] The degradation mixture of the present invention does not contain toxic and harmful substances such as aromatic amines. It can be directly used in the production line to replace polyol raw materials without any post-processing. The dosage can be flexibly adjusted according to the actual production needs of the factory and the product performance indicators, thereby optimizing and improving the performance of foamed products and saving the factory about 10% of production costs.

[0142] Meanwhile, this degradation mixture exhibits low viscosity and good uniformity, demonstrating convenience in filling, transportation, storage, and use. Its applicability is also outstanding, allowing for the matching of appropriate processing technologies to different materials provided by factories and the performance requirements of the final product.

[0143] This method utilizes the characteristic that the degradation mixture does not contain toxic or harmful substances such as aromatic amines, eliminating the cumbersome post-processing steps of multi-stage distillation and purification required by traditional recovery methods. In traditional processes, recovered polyol raw materials may contain toxic byproducts, necessitating significant investment in equipment and costs for purification treatment (such as distillation column separation and activated carbon adsorption). However, the degradation mixture of this application eliminates the generation of toxic substances during the "low-temperature mechanochemical shallow heterogeneous catalytic degradation" process, and can be directly used in production lines to replace polyol raw materials. For example, in a polyurethane foam production line, the degradation mixture can be directly injected into the production mixing device through the existing raw material conveying pipeline without requiring equipment modification.

[0144] This method allows for flexible adjustment of the amount of degradation mixture according to the actual needs of the factory, thereby reducing costs while optimizing product performance.

[0145] The low viscosity (below 20,000 mPa·s) and good uniformity of the degradation mixture give it operational advantages throughout the entire process. In the filling stage, its flowability is close to that of the original polyol, allowing for quantitative filling using the same metering pump with no significant difference in filling efficiency. In transportation and storage, the low viscosity reduces the risk of pipeline blockage. In use, the degradation mixture exhibits excellent mixing uniformity with isocyanates, catalysts, and other components, and there are no instances of excessive or delayed localized reactions during product manufacturing.

[0146] In some embodiments of this application, the preparation method includes a product reprocessing stage, in which component A and component B are mixed in a certain proportion and then the product is reprocessed; component A is a mixture of the degradation mixture and chain extender, catalyst and stabilizer, and foaming agent is added as needed; component B is isocyanate.

[0147] For example, component A and component B are mixed in a high-speed mixer at a mass ratio of 0.5-1:1-2, and then the mixture is poured into a mold or allowed to foam freely to re-prepare polyurethane material. The chain extender is 0.1-30 parts, the foaming agent (if needed) is 5-35 parts, the catalyst is 0.1-10 parts, and the stabilizer is 0.1-10 parts.

[0148] In some embodiments of this application, reference is made to Figure 2 The preparation method of polyurethane products includes a powder preparation stage. In the powder preparation stage, waste polyurethane material is pulverized using pulverizing equipment to obtain polyurethane powder. The polyurethane powder is then sealed and stored in a resealable bag.

[0149] The preparation method of polyurethane products also includes a premix preparation stage. In the premix preparation stage, the polyurethane powder is mixed with a degradation agent, a catalyst, and a cosolvent in a certain proportion, and then mixed evenly using a stirring device to obtain a premix with a certain powder content.

[0150] The preparation method of polyurethane products also includes a degradation stage. In the degradation stage, the premixed liquid is ground, extruded, and sheared using equipment with mechanical shearing and extrusion capabilities. The reaction process is carried out within a set temperature range, and after the reaction is completed, a degraded polyurethane material mixture is obtained. The degraded mixture is then stored in a sealed glass container.

[0151] The preparation method of polyurethane products also includes a product reprocessing stage. In the product reprocessing stage, part or all of the polyol raw materials are used as a degradation mixture. The degradation mixture is mixed with chain extender, catalyst, stabilizer, and foaming agent (if necessary) as component A, and isocyanate as component B. Component A and component B are mixed in proportion and then the product is reprocessed.

[0152] In some other embodiments of this application, the method for preparing the polyurethane article includes:

[0153] In the powder preparation stage, one of the following is pulverized using a pulverizing device to obtain polyurethane powder: waste polyurethane elastomer, polyurethane flexible foam, or polyurethane rigid foam.

[0154] In the premix preparation stage, the polyurethane powder is mixed with the degradation agent, catalyst, and polyol (i.e. cosolvent) used to prepare other types of polyurethane materials in proportion, and mixed evenly by stirring equipment to obtain a premix with a certain powder content.

[0155] During the degradation stage, the premixed liquid is ground, squeezed and sheared using equipment with mechanical shearing and extrusion functions. The reaction process is carried out within a set temperature range, and after the reaction is completed, a degraded mixture of polyurethane elastomer is obtained.

[0156] In the in-process manufacturing stage, the degradation mixture of the polyurethane material is mixed with the polyol used to prepare the polyurethane material to serve as a polyol raw material.

[0157] In this embodiment, a polyurethane product is prepared by combining a degradation mixture of polyurethane material with polyol raw materials used to prepare other types of polyurethane materials. Through cross-category application experiments, this technical solution further verifies the universality of the shallow degradation process and the application potential of the degradation products.

[0158] This method confirms the good compatibility of different types of polyurethane waste in the degradation process. Polyurethane elastomers have high crosslinking density, toughness, and elasticity; polyurethane flexible foam has low crosslinking density, high elasticity, and high open-cell ratio; while polyurethane rigid foam has high crosslinking density, high rigidity, and high closed-cell ratio. When the polyurethane material degradation mixture is mixed with the polyol used to prepare other types of polyurethane materials, no additional adjustment of the premix preparation parameters (such as stirring rate and mixing time) is required to form a uniform and stable system, indicating that the degradation process of this invention has broad adaptability to polyurethane materials with different chemical structures. The introduction of other types of polyurethane material degradation mixtures can have a targeted optimization effect on the performance of the target product. For example, when the polyurethane elastomer material degradation mixture is mixed with the polyol used to prepare polyurethane flexible foam to produce polyurethane flexible foam, the rigid crosslinked skeleton micropowder retained in the elastomer degradation mixture can be uniformly dispersed in the flexible foam matrix as a reinforcing phase, significantly improving the mechanical properties of the product. This performance improvement breaks through the bottleneck of declining mechanical properties of traditional flexible foam recycled products and expands the application scenarios of flexible foam (such as high-end furniture, automotive seats, and other fields with high strength requirements). When polyurethane elastomer material degradation mixture is mixed with polyols used to produce rigid polyurethane foam, the flexible segments in the elastomer degradation mixture can improve the brittleness of the rigid foam and enhance its dimensional stability, solving the problem that traditional rigid foam recycled products cannot achieve both strength and toughness.

[0159] This method significantly enhances the industrialization potential of waste polyurethane recycling. In traditional recycling processes, different types of waste, such as elastomers, flexible foams, and rigid foams, need to be processed separately, resulting in limited raw material sources and high processing costs. This invention, through cross-category application experiments, demonstrates that elastomer degradation products can be directly mixed with other types of polyurethane raw materials, achieving mixed recycling and synergistic utilization of waste materials and reducing waste sorting costs. Simultaneously, the improved performance of recycled products increases their added value.

[0160] In some embodiments of this application, the chain extender is one or more of alcohols, diamines, alkanolamines, acid anhydrides, and trimethylolpropane.

[0161] The foaming agent is one or more of the following: alkanes, cyclopentanes, chlorofluorocarbons, N,N-azobisisobutyronitrile, antimony trioxide, dicyandiamide, dimethyl ether, water, and azodicarbonamide.

[0162] The catalyst is one or more of the following: amine compounds, tin compounds, ether compounds, acetates, inorganic strong bases, inorganic chlorides, azines, tertiary amine compounds, bismuth compounds, and dilaurates.

[0163] The stabilizer is one or more of the following: silicone oil, tertiary amine compounds and methylsiloxane compounds, hindered phenolic compounds, hindered amine compounds, benzotriazole compounds, and phosphite compounds.

[0164] The isocyanate is one or a combination of toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone isocyanate, dicyclohexylmethane diisocyanate, terephthalic diisocyanate, naphthalene-1,5-diisocyanate, and polyphenyl polymethylene polyisocyanate. The isocyanate index is 0.8-2.

[0165] In some embodiments of this application, the viscosity of the degradation reaction system and degradation products was measured at 25°C using a Brookfield ModelDV-II+ rotational viscometer.

[0166] The determination of hydroxyl value of polyurethane degradation products shall be performed in accordance with the national standard GB12008.3-89.

[0167] The molecular weight of degradation products was determined by gel permeation chromatography, using tetrahydrofuran (THF) as the mobile phase and polystyrene as the standard. A Waters 150C gel permeation chromatograph was used to determine the molecular weight of each product.

[0168] The content of aromatic amines in the degradation products was characterized by nuclear magnetic resonance spectroscopy (NMR) using a Bruker AVANCE NEO 600MHz instrument with deuterated dimethyl sulfoxide (DMSO-d6) as the solvent, and the tests were performed at room temperature. The shifts of other chemical components in the products relative to the residual peak of DMSO-d6 are expressed in ppm. The ppm values ​​of aromatic amine products ranged from 7.0 to 5.0.

[0169] Example 1 (Recycling of Waste Polyurethane Flexible Foam)

[0170] (1) Shallow degradation of polyurethane micropowder

[0171] After removing impurities from the surface of waste polyurethane flexible foam, it is coarsely crushed in a pulverizer to obtain polyurethane powder. 900g of the coarsely crushed powder, 2100g of polyether polyol with a molecular weight of 3000 and a hydroxyl value of 56mgKOH / g, 32.125g of tetraethylenepentamine as a degradation agent, and 0.625g of potassium hydroxide as a catalyst are weighed and added to a high-speed stirrer for mixing to obtain a degradation premix. Subsequently, the degradation premix is ​​subjected to deep grinding, extrusion, and shearing treatment using equipment with strong mechanical shearing and extrusion capabilities. Simultaneously, the equipment's water cooling device is adjusted to maintain the reaction at 135℃. After 1 hour of reaction, a significant change in the color and fluidity of the mixture is observed. The discharge port is opened, and the degradation mixture is poured into a beaker and allowed to stand. The equipment is then turned off, and the temperature is allowed to drop to room temperature to obtain the degradation mixture. A comparison of the performance of this degradation mixture with other products is provided below. Figure 5 As shown.

[0172] (2) Preparation of re-foamed products

[0173] Weigh 50 parts of the degradation mixture, 7.5 parts of polyether polyol with a molecular weight of 3000 and a hydroxyl value of 56 mgKOH / g, 42.5 parts of polyether polyol with a molecular weight of 3000 and a hydroxyl value of 30 mgKOH / g, 0.24 parts of chain extender, 3.3 parts of foaming agent, 0.18 parts of catalyst, 1.33 parts of stabilizer, and 5.67 parts of foaming aid. Add these to a beaker and mix evenly. The resulting mixture is designated as component A. Weigh 44.6 parts of isocyanate as component B. Mix component A and component B and stir rapidly in a high-speed stirrer for 6-10 seconds. Quickly pour the mixture into a mold and let it stand for 24 hours to obtain the polyurethane re-foamed product. The performance comparison of the foamed product in this example with other foamed products is as follows: Figure 6 As shown.

[0174] refer to Figure 5 The degradation mixture of this invention has a viscosity of 1350 mPa·s after performance testing. This product characteristic gives it good fluidity during transportation and mixing, and makes it highly practical for processing.

[0175] The hydroxyl value of this product is 43.1 mgKOH / g, which is close to that of the original polyether polyol. A higher hydroxyl value means that the product has more active hydroxyl groups, which is conducive to the formation of a more stable cross-linked network structure in subsequent product applications and improves product performance.

[0176] The product's molecular weight is slightly higher than that of the original polyether polyol, while the particle size is stable in the micron range (D90: 143μm). This micron-sized particle size distribution ensures good suspension stability of the powder in the polyol (forming a stable gel state) and avoids sedimentation. At the same time, it is fine enough not to affect mixing and conveying, and is uniformly dispersed in the final foam to act as an effective reinforcing phase and active site. All product indicators are within the range of requirements for use as a raw material for polyurethane flexible foam.

[0177] Furthermore, measurements have shown that the degradation products obtained using the process of this invention do not contain toxic byproducts such as aromatic amines. There is no need for complex and costly purification steps (such as distillation, adsorption, and extraction). The products can be directly and safely used in the production of subsequent products, significantly simplifying the process, reducing costs, and improving safety.

[0178] Furthermore, TEM analysis of the micropowder revealed the visible morphology of the particles, showing that they maintained a certain cross-linked structure and were not completely broken. This is something that is difficult to achieve with simple physical pulverization or deep chemical degradation processes, and it is the key to improving the performance of foam products in subsequent applications.

[0179] Furthermore, experimental verification shows that, under the same process conditions, samples obtained solely through strong mechanical shearing cannot effectively achieve shallow and controllable breakage of polyurethane molecular chains in the mixture, nor can they form stable, low-viscosity, and highly active heterogeneous polyol products. This indicates that the synergistic effect of the mechanochemical process, chemical degradation agent, and catalyst of this invention is an indispensable key to achieving low-temperature controllable shallow degradation and high surface activation, effectively demonstrating the innovation, practicality, and efficiency of the recycling process route of this invention.

[0180] refer to Figure 6 In Application Example 1, the foaming time, gel time, and non-sticky time during the foaming process were highly consistent with those of the conventional raw material system, which were 7s, 44s, and 95s, respectively. This indicates that the product has strong process applicability and does not require major adjustments to existing foaming production lines or formulation processes. It can directly replace or partially replace the basic polyol.

[0181] Regarding the physical properties of the foamed product, the density of the foamed product prepared from the product in Example 1 is 24.5 kg / m³. 3 The size is slightly larger than that of flexible foam products prepared using the original polyether polyol. This is because the highly active polyurethane powder contained in this product is evenly dispersed in the foam matrix during the foaming process, forming a denser cell structure.

[0182] Furthermore, the hardness of the product in Example 1 is slightly higher than that of the flexible foam product prepared using the original polyether polyol, the resilience is slightly improved, and the air permeability does not change much.

[0183] Regarding compression set, the compression set of the product in Example 1 was 4.5%, which is much lower than that of the flexible foam product prepared using the original polyether polyol, with an improvement of more than 40%. This proves that this high-performance heterogeneous polyol not only has the same properties as the original polyether polyol in the application process, but also contains highly active polyurethane powder rich in active groups, which can act as reactive sites during the foaming process, promote the uniform distribution of the cross-linked network inside the foam matrix, improve the uniformity of the cells, and thus improve the overall structural uniformity and mechanical property stability of the foam.

[0184] The NMR spectrum of the amine hydrolysis products of waste polyurethane flexible foam in Example 1 is shown below. Figure 7 As shown.

[0185] Example 2 (Recycling of Waste Rigid Polyurethane Foam)

[0186] (1) Shallow degradation of polyurethane micropowder

[0187] After removing impurities from the surface of waste polyurethane rigid foam, it is coarsely crushed in a pulverizer to obtain polyurethane powder. 900g of the coarsely crushed powder, 2100g of polyether polyol with a molecular weight of 336 and a hydroxyl value of 500mgKOH / g, 8.8g of triethylene glycol as a degradation agent, and 0.625g of potassium hydroxide as a catalyst are weighed and added to a high-speed stirrer for mixing to obtain a degradation premix. The degradation premix is ​​then subjected to deep grinding, extrusion, and shearing treatment using equipment with strong mechanical shearing and extrusion capabilities. Simultaneously, the water cooling device of the equipment is adjusted to ensure the reaction proceeds at 140℃. After 2 hours of reaction, a significant change in the color and fluidity of the mixture is observed. The discharge port is opened, and the degradation mixture is poured into a beaker and allowed to stand. The equipment is then shut off, and the temperature is allowed to drop to room temperature to obtain the degradation mixture. A comparison of the performance of this degradation mixture with other products is provided below. Figure 8 As shown.

[0188] (2) Preparation of re-foamed products

[0189] Weigh 50 parts of the degradation mixture, 50 parts of polyether polyol with a molecular weight of 336 and a hydroxyl value of 500 mgKOH / g, 0.02 parts of chain extender, 0.5 parts of foaming agent, 0.16 parts of catalyst, 3.26 parts of stabilizer, and 16.2 parts of foaming aid. Add these to a beaker and mix thoroughly. The resulting mixture is designated as component A. Weigh 104.5 parts of isocyanate as component B. Mix component A and component B and stir rapidly in a high-speed stirrer for 4-8 seconds. Quickly pour the mixture into a mold and let it stand for 24 hours to obtain the polyurethane re-foamed product. The performance comparison of the foamed product in this example with other foamed products is as follows: Figure 9 As shown.

[0190] refer to Figure 8The degradation mixture of the present invention was tested for performance. The hydroxyl value of the product in Example 2 was 466.4 mg KOH / g, which was slightly lower than the original polyether polyol's 500.0 mg KOH / g, but still at a high level, which was sufficient to meet the requirements of the foaming reaction for active groups.

[0191] Its viscosity remains below 20,000 mPa·s, its molecular weight is slightly higher than that of the original polyether polyol, and its particle size is stable in the micron range (D90: 45 μm). This micron-sized particle size distribution ensures good suspension stability of the powder in the polyol (forming a stable gel state) and avoids sedimentation. At the same time, it is fine enough not to affect mixing and conveying, and is uniformly dispersed in the final foam to act as an effective reinforcing phase and active site. All product indicators are within the range of requirements for raw materials for polyurethane rigid foam.

[0192] Similar to Example 1, the degradation mixture in Example 2 also does not contain toxic byproducts such as aromatic amines. It eliminates the need for complex and costly purification steps (such as distillation, adsorption, and extraction), and the product can be directly and safely used in subsequent product manufacturing without requiring significant adjustments to existing foaming production lines or formulation processes. It can directly or partially replace the base polyol, significantly simplifying the process, reducing costs, and improving safety.

[0193] refer to Figure 9 The compressive strength of the foamed product prepared using the degradation mixture from Example 2 was 0.205 MPa, which was higher than that of the original formulation product, indicating a significant improvement in its pressure resistance. This is because the incompletely degraded polyurethane microparticles in the product acted as active crosslinking sites during the foaming process, promoting the densification of the foam matrix structure and thus enhancing the compressive strength of the product.

[0194] Thermal conductivity is an important indicator for measuring thermal insulation performance. The thermal conductivity of the foamed product in Example 2 is 19.07 mW / (mK), lower than the 21.92 mW / (mK) of the original formulation, indicating superior thermal insulation performance. This is attributed to the synergistic effect of the excellent thermal insulation properties of the polyurethane micropowder particles and the formation of the cell structure, which effectively inhibits heat transfer pathways. Furthermore, the product density is 35.2 kg / m³. 3 Its density is close to that of the original formula product, and it meets the performance requirements of the original polyether polyol foamed product.

[0195] Regarding dimensional stability, the dimensional stability of the foamed product in Example 2 was 0.10%, an improvement of approximately 16.7% compared to the original formulation. This indicates that the product exhibits less dimensional change and greater structural stability under the influence of environmental factors such as temperature variations. This is attributed to the incompletely degraded polyurethane microparticles contained in the high-performance heterogeneous degradation products of this invention. These microparticles are rich in active groups on their surface, and their small particle size and high dispersion uniformity allow them to act as active crosslinking sites during the foaming process. On the one hand, this promotes foaming uniformity and avoids uneven cell size or pore defects caused by local reaction rate differences. On the other hand, it enhances the overall structural density of the foam matrix, thereby effectively optimizing the uniformity and stability of the overall foam structure.

[0196] The NMR spectrum of the alcoholysis products of waste polyurethane rigid foam in Example 2 is shown below. Figure 10 As shown.

[0197] Example 3 (Waste Polyurethane Elastomer)

[0198] (1) Shallow degradation of polyurethane micropowder

[0199] After removing surface impurities from waste polyurethane elastomer, it is coarsely crushed in a pulverizer to obtain polyurethane powder. 900g of the coarsely crushed powder, 2100g of polyether polyol with a molecular weight of 3500 and a hydroxyl value of 120mgKOH / g, 32.125g of tetraethylenepentamine as a degradation agent, and 0.625g of potassium hydroxide as a catalyst are weighed and added to a high-speed stirrer for mixing to obtain a degradation premix. Subsequently, the degradation premix is ​​subjected to deep grinding, extrusion, and shearing treatment using equipment with strong mechanical shearing and extrusion capabilities. Simultaneously, the equipment's water cooling device is adjusted to maintain the reaction at 135℃. After 2 hours of reaction, a significant change in the color and fluidity of the mixture is observed. The discharge port is opened, and the degradation mixture is poured into a beaker and allowed to stand. The equipment is then shut off, and the temperature is allowed to drop to room temperature to obtain the degradation mixture. A comparison of the performance of this degradation mixture with other products is provided below. Figure 11 As shown.

[0200] (2) Preparation of re-foamed products

[0201] Weigh 50 parts of the degradation mixture, 50 parts of a polyether polyol with a molecular weight of 3500 and a hydroxyl value of 120 mgKOH / g, 0.44 parts of a chain extender, 0.25 parts of a catalyst, and 2.14 parts of a stabilizer. Add these to a beaker and mix thoroughly. The resulting mixture is designated as component A. Weigh 44.6 parts of isocyanate as component B. Mix component A and component B and stir rapidly in a high-speed stirrer for 6-10 seconds. Quickly pour the mixture into a mold and let it stand for 24 hours to obtain the polyurethane re-foamed product. The performance comparison of the foamed product in this example with other foamed products is as follows: Figure 12 As shown.

[0202] refer to Figure 11 The degradation mixture of Example 3 was tested and found to have a hydroxyl value of 113.3 mg KOH / g, which is slightly lower than the original polyether polyol's 120.0 mg KOH / g, but still meets the requirements for foaming reaction and provides sufficient active groups for the formation of a stable cross-linked structure.

[0203] Its viscosity remains below 20,000 mPa·s, its molecular weight is slightly higher than that of the original polyether polyol, and its particle size is stable in the micron range (D90: 75 μm). This micron-sized particle size distribution ensures good suspension stability of the powder in the polyol (forming a stable gel state) and avoids sedimentation. At the same time, it is fine enough not to affect mixing and transportation, and is uniformly dispersed in the final foam to act as an effective reinforcing phase and active site. All product indicators are within the range of requirements for raw materials used in the preparation of polyurethane elastomers.

[0204] This product also does not contain toxic byproducts such as aromatic amines, and does not require complex and costly purification steps (such as distillation, adsorption, and extraction). The product can be directly and safely used in the production of subsequent products without requiring major adjustments to existing foaming production lines or formulation processes. It can directly replace or partially replace base polyols, significantly simplifying the process, reducing costs, and improving safety.

[0205] refer to Figure 12 The foamed product prepared using the degradation mixture from Example 3 had a density of 973 kg / m³. 3 970kg / m of the original formula product 3 The very close ratio indicates that the product performs well in density adaptability and can meet the density requirements of relevant applications.

[0206] The hardness of the re-foamed product is 79 ILD, which is higher than that of the original formula product, indicating that it has a certain improvement in hardness performance.

[0207] In terms of mechanical properties, the tensile strength of the re-foamed product is 4.93 MPa, which is higher than that of the original formula product; the tear strength is 30.1 kN / m, which is 17% higher than that of the original formula product. This is mainly because the large number of active groups retained on the surface of the heterogeneous micro-powder particles contained in the degradation product of this invention can participate in the construction of cross-linking network as cross-linking points. Through chemical bonding with the matrix components, the interface is strengthened, making the cross-linking network more dense and uniform, reducing weak links. At the same time, the high strength characteristics of the micro-powder particles themselves can bear part of the load. The micron-sized and uniformly dispersed particles have a large specific surface area, which increases the contact interface area with the matrix, can uniformly disperse stress, fill micro-voids, form physical support points, limit excessive slippage of molecular chains and absorb some energy. In addition, the micro-powder particles have similar chemical structures and good compatibility with the matrix, thereby achieving a comprehensive improvement in the performance of the re-foamed product.

[0208] The NMR spectrum of the aminolysis products of waste polyurethane elastomer in Example 3 is shown below. Figure 13 As shown.

[0209] Example 4 (Recycling of Waste Polyurethane Flexible Foam)

[0210] The difference between Example 4 and Example 1 is that the degradation agent used is different.

[0211] (1) Shallow degradation of polyurethane micropowder

[0212] After removing impurities from the surface of waste polyurethane flexible foam, it is coarsely crushed in a pulverizer to obtain polyurethane powder. 900g of the coarsely crushed powder, 2100g of polyether polyol with a molecular weight of 3000 and a hydroxyl value of 56mgKOH / g, 29.125g of diethylenetriamine as a degradation agent, and 0.625g of potassium hydroxide as a catalyst are weighed and added to a high-speed stirrer for mixing to obtain a degradation premix. Subsequently, the degradation premix is ​​subjected to deep grinding, extrusion, and shearing treatment using equipment with strong mechanical shearing and extrusion capabilities. Simultaneously, the equipment's water cooling device is adjusted to maintain the reaction at 135℃. After 30 minutes of reaction, a significant change in the color and fluidity of the mixture is observed. The discharge port is opened, and the degradation mixture is poured into a beaker and allowed to stand. The equipment is then turned off, and the temperature is allowed to drop to room temperature to obtain the degradation mixture. A comparison of the performance of this degradation mixture with other products is provided below. Figure 14 As shown.

[0213] (2) Preparation of re-foamed products

[0214] Weigh 50 parts of the degradation mixture, 7.5 parts of polyether polyol with a molecular weight of 3000 and a hydroxyl value of 56 mgKOH / g, 42.5 parts of polyether polyol with a molecular weight of 3000 and a hydroxyl value of 30 mgKOH / g, 0.22 parts of chain extender, 3.2 parts of foaming agent, 0.16 parts of catalyst, 1.33 parts of stabilizer, and 5.67 parts of foaming aid. Add these to a beaker and mix evenly. The resulting mixture is designated as component A. Weigh 44.83 parts of isocyanate as component B. Mix component A and component B and stir rapidly in a high-speed stirrer for 6-10 seconds. Quickly pour the mixture into a mold and let it stand for 24 hours to obtain the polyurethane re-foamed product. The performance comparison of the foamed product in this example with other foamed products is as follows: Figure 15 As shown.

[0215] refer to Figure 14 The degradation mixture of Example 4 was tested and found to have a viscosity of 1400 mPa·s, which ensured its stability during mixing and transportation, while avoiding the increased process difficulty caused by high viscosity.

[0216] The hydroxyl value is 43.7 mgKOH / g, which is slightly lower than that of polyether polyols, indicating that it retains high reactivity and can meet the crosslinking requirements with isocyanates during the foaming process.

[0217] With a molecular weight of 3868 g / mol, which is slightly higher than the original polyether polyol, it lays the foundation for improving the mechanical properties of subsequent foamed products.

[0218] The product has a stable particle size in the micrometer range (D90: 136μm). This micrometer-sized particle size distribution ensures good suspension stability of the powder in polyols (forming a stable gel state) and avoids sedimentation. At the same time, it is fine enough not to affect mixing and transport, and is uniformly dispersed in the final foam to act as an effective reinforcing phase and active site.

[0219] This product is identical to the original polyether polyol, and no toxic byproducts such as aromatic amines were detected. It does not require complex and costly purification steps (such as distillation, adsorption, and extraction). The product can be directly and safely used in the production of subsequent products, which significantly simplifies the process, reduces costs, and improves safety.

[0220] TEM analysis of the microparticles revealed their surface morphology, showing a certain degree of cross-linking and incomplete breakage—a characteristic difficult to achieve with simple physical pulverization or deep chemical degradation processes. This is crucial for improving the performance of foam products in subsequent applications. Furthermore, experimental verification showed that, under the same process conditions, samples obtained solely through strong mechanical shearing could not effectively achieve shallow, controllable breakage of polyurethane molecular chains in the mixture, nor could they form stable, low-viscosity, and highly active heterogeneous polyol products. This demonstrates that the synergistic effect of the mechanochemical process, chemical degradation agents, and catalysts in this invention is indispensable for achieving low-temperature, controllable shallow degradation and high surface activation, effectively confirming the innovation, practicality, and efficiency of the recycling process route of this invention.

[0221] refer to Figure 15 The foaming time of the foamed product prepared by applying the degradation mixture of Example 4 was 7s, the gel time was 45s, and the non-sticky time was 94s, which was highly consistent with the conventional raw material system. This indicates that it is highly compatible with the existing foaming process and does not require major adjustments to the existing foaming production line or formulation process. It can directly replace or partially replace the basic polyol.

[0222] Example 4: The density of the re-foamed product is 24.8 kg / m³. 3The air permeability did not change significantly, but increased slightly compared to the flexible foam products prepared using the original polyether polyol. The hardness (20.9 ILD) and resilience (35.6%) showed no significant changes, and the compression set was 3.5%, which was much lower than that of the flexible foam products prepared using the original polyether polyol, with an improvement of more than 40%. This proves that this high-performance heterogeneous polyol not only has the same properties as the original polyether polyol in the application process, but also contains highly active polyurethane powder rich in active groups, which can act as reactive sites during the foaming process, promote the uniform distribution of the cross-linked network inside the foam matrix, improve the uniformity of the cells, and thus improve the overall structural uniformity and mechanical property stability of the foam.

[0223] The NMR spectrum of the amine hydrolysis products of waste polyurethane flexible foam in Example 4 is shown below. Figure 16 As shown.

[0224] Example 5 (Recycling of Waste Polyurethane Flexible Foam)

[0225] The difference between Example 5 and Example 1 is that the degradation agent used is different.

[0226] (1) Shallow degradation of polyurethane micropowder

[0227] After removing impurities from the surface of waste polyurethane flexible foam, it is coarsely crushed in a pulverizer to obtain polyurethane powder. 900g of the coarsely crushed powder, 2100g of polyether polyol with a molecular weight of 3000 and a hydroxyl value of 56mgKOH / g, 15g of diethylene glycol as a degradation agent, and 0.625g of potassium hydroxide as a catalyst are weighed and added to a high-speed stirrer for mixing to obtain a degradation premix. The degradation premix is ​​then subjected to deep grinding, extrusion, and shearing treatment using equipment with strong mechanical shearing and extrusion capabilities. Simultaneously, the water cooling device is adjusted to maintain the reaction at 140℃. After 15 minutes of reaction, a significant change in the color and fluidity of the mixture is observed. The discharge port is opened, and the degradation mixture is poured into a beaker and allowed to stand. The equipment is then turned off, and the temperature is allowed to drop to room temperature to obtain the degradation mixture. A comparison of the performance of this degradation mixture with other products is provided below. Figure 17 As shown.

[0228] (2) Preparation of re-foamed products

[0229] Weigh 50 parts of the degradation mixture, 7.5 parts of polyether polyol with a molecular weight of 3000 and a hydroxyl value of 56 mgKOH / g, 42.5 parts of polyether polyol with a molecular weight of 3000 and a hydroxyl value of 30 mgKOH / g, 0.23 parts of chain extender, 3.2 parts of foaming agent, 0.17 parts of catalyst, 1.45 parts of stabilizer, and 5.67 parts of foaming aid. Add these to a beaker and mix evenly. The resulting mixture is designated as component A. Weigh 44.7 parts of isocyanate as component B. Mix component A and component B and stir rapidly in a high-speed stirrer for 6-10 seconds. Quickly pour the mixture into a mold and let it stand for 24 hours to obtain the polyurethane re-foamed product. The performance comparison of the foamed product in this example with other foamed products is as follows: Figure 18 As shown.

[0230] refer to Figure 17 The degradation product of Example 5, after performance testing, showed a viscosity of 1380 mPa·s, ensuring its ease of subsequent storage, transportation, and production line application. The hydroxyl value was 43.4 mgKOH / g, consistent with Example 4, further verifying the process stability. The average molecular weight was 3873 g / mol, higher than the original polyether polyol. The particle size was stable in the micrometer range (D90: 141 μm). This micrometer-scale particle size distribution ensures good suspension stability of the powder in the polyol (forming a stable gel state), avoiding sedimentation; it is also fine enough not to affect mixing and transportation, and is uniformly dispersed in the final foam to act as an effective reinforcing phase and active site.

[0231] The product in Example 5 also does not contain toxic byproducts such as aromatic amines, eliminating the need for complex and costly purification steps (such as distillation, adsorption, and extraction). The product can be directly and safely used in subsequent product manufacturing, significantly simplifying the process, reducing costs, and improving safety. TEM analysis of the micropowder clearly shows the particle morphology, revealing a certain degree of cross-linking and a partially broken state. This is difficult to achieve with simple physical pulverization or deep chemical degradation processes and is key to improving the performance of foam products in subsequent applications. Furthermore, experimental verification shows that under the same process conditions, samples obtained solely through strong mechanical shearing cannot effectively achieve shallow, controllable breakage of polyurethane molecular chains in the mixture, nor can they form stable, low-viscosity, and highly active heterogeneous polyol products. This indicates that the synergistic effect of the mechanochemical and chemical degradation agents / catalysts of this invention is indispensable for achieving low-temperature controllable shallow degradation and high surface activation, effectively demonstrating the innovation, practicality, and efficiency of the recycling process route of this invention.

[0232] refer to Figure 18The foamed product prepared using the degradation mixture in Example 5 exhibited a foaming time of 7 seconds to achieve milky white color, a gel time of 44 seconds, and a non-sticky time of 96 seconds. These times are highly consistent with conventional raw material systems, demonstrating strong process applicability. No major adjustments to existing foaming production lines or formulation processes are required, and it can directly replace or partially replace the base polyol. After curing the prepared foamed product, relevant performance tests were conducted. The density of the obtained foamed product was slightly higher than that of the previous one (24.3 kg / m³). 3 The air permeability remained relatively stable, while the hardness (21.2 ILD) and resilience (35.8%) were slightly better than the original formulation. The compressibility of the foamed product in Example 5 was 4.0%, significantly lower than that of the flexible foam product prepared using the original polyether polyol, representing an increase of over 40%. This indicates that the highly active polyurethane powder in the product is rich in active groups, which can act as reactive sites during the foaming process, promoting the uniform distribution of the cross-linked network within the foam matrix, improving cell uniformity, and thus enhancing the overall structural uniformity and mechanical stability of the foam.

[0233] The NMR spectrum of the amine hydrolysis products of waste polyurethane flexible foam in Example 5 is shown below. Figure 19 As shown.

[0234] Example 6 (Using degraded waste polyurethane elastomer for the re-foaming production of polyurethane flexible foam)

[0235] To further verify the universality of the shallow degradation process of this invention and the cross-category application potential of the degradation products, this embodiment innovatively conducts a cross-application experiment: high-performance polyols prepared from waste polyurethane elastomers through shallow heterogeneous degradation are applied to the re-foaming production of polyurethane flexible foam. This experiment aims to explore the compatibility of different types of polyurethane waste (e.g., elastomers with flexible and rigid foams) in the degradation process, as well as the regulatory effect of degradation products on the performance of target products when applied across categories. This further clarifies the technical advantages of the recycling process of this invention in broadening raw material sources and increasing the added value of recycled products, providing more comprehensive experimental evidence for the large-scale, high-value recycling of waste polyurethane materials.

[0236] (1) Shallow degradation of polyurethane micropowder

[0237] After removing surface impurities from waste polyurethane elastomers, the material is coarsely crushed in a pulverizer to obtain polyurethane powder. 900g of the coarsely crushed powder, 2100g of polyether polyol with a molecular weight of 3000 and a hydroxyl value of 56mgKOH / g, 15g of diethylene glycol as a degradation agent, and 0.625g of potassium hydroxide as a catalyst are weighed and added to a high-speed stirrer for mixing to obtain a degradation premix. The degradation premix is ​​then subjected to deep grinding, extrusion, and shearing treatment using equipment with strong mechanical shearing and extrusion capabilities. Simultaneously, the water cooling device is adjusted to maintain the reaction at 140℃. After 2 hours of reaction, a significant change in the color and fluidity of the mixture is observed. The discharge port is opened, and the degradation mixture is poured into a beaker and allowed to stand. The equipment is then shut off, and the temperature is allowed to drop to room temperature to obtain the degradation mixture. A comparison of the performance of this degradation mixture with other products is provided below. Figure 20 As shown.

[0238] (2) Preparation of re-foamed products

[0239] Weigh 50 parts of the degradation mixture, 7.5 parts of polyether polyol with a molecular weight of 3000 and a hydroxyl value of 56 mgKOH / g, 42.5 parts of polyether polyol with a molecular weight of 3000 and a hydroxyl value of 30 mgKOH / g, 0.22 parts of chain extender, 3.3 parts of foaming agent, 0.18 parts of catalyst, 1.33 parts of stabilizer, and 5.67 parts of foaming aid. Add these to a beaker and mix evenly. The resulting mixture is designated as component A. Weigh 44.2 parts of isocyanate as component B. Mix component A and component B and stir rapidly in a high-speed stirrer for 6-10 seconds. Quickly pour the mixture into a mold and let it stand for 24 hours to obtain the polyurethane re-foamed product. The performance comparison of the foamed product in this example with other foamed products is as follows: Figure 21 As shown.

[0240] refer to Figure 20 The degradation product of Example 6, after performance testing, had a hydroxyl value of 42.8 mg KOH / g, slightly lower than the original polyether polyol's 56 mg KOH / g, but still sufficient to meet the requirements of the foaming reaction, providing enough active groups for the formation of a stable cross-linked structure. Its viscosity was 1320 mPa·s, slightly higher than the original polyether polyol, while its molecular weight was close to that of the original polyether polyol. The particle size was stable in the micrometer range (D90: 78 μm). This micrometer-scale particle size distribution ensured good suspension stability of the powder in the polyol (forming a stable gel state) and prevented sedimentation; at the same time, it was fine enough not to affect mixing and transport, and was uniformly dispersed in the final foam to act as an effective reinforcing phase and active site.

[0241] The product obtained in Example 6 also does not contain toxic byproducts such as aromatic amines, eliminating the need for complex and costly purification steps (such as distillation, adsorption, and extraction). The product can be directly and safely used in subsequent product manufacturing, significantly simplifying the process, reducing costs, and improving safety. TEM analysis of the micropowder clearly shows the particle morphology, revealing a certain degree of cross-linking and a partially broken state—something difficult to achieve with simple physical pulverization or deep chemical degradation processes, and crucial for improving the performance of foam products in subsequent applications. Furthermore, experimental verification shows that under the same process conditions, samples obtained solely through strong mechanical shearing cannot effectively achieve shallow, controllable breakage of polyurethane molecular chains in the mixture, nor can they form stable, low-viscosity, and highly active heterogeneous polyol products. This demonstrates that the synergistic effect of the mechanochemical and chemical degradation agents / catalysts of this invention is indispensable for achieving low-temperature, controllable shallow degradation and high surface activation, effectively confirming the innovation, practicality, and efficiency of the recovery process route of this invention.

[0242] refer to Figure 21 The foamed product prepared using the degradation mixture in Example 6 exhibited a foaming time of 7.5 s to milky white, a gel time of 46 s, and a non-sticky time of 99 s, which is highly consistent with the conventional raw material system. This demonstrates strong process applicability and requires no major adjustments to existing foaming production lines or formulation processes. It can directly replace or partially replace the base polyol. After the prepared foamed product underwent curing, relevant performance tests were performed. The density of the obtained foamed product was slightly higher than that of the previous one (25.5 kg / m³). 3 The air permeability remained largely unchanged, while the hardness (22.3 ILD) increased by 11.5% and the resilience (38.7%) increased by 10.6%, both significantly better than the original formula flexible foam products. The compressibility was 2.83%, far lower than the flexible foam products prepared using the original polyether polyol, representing an improvement of more than 40%. This result stems from two aspects: firstly, the elastomer powder itself has excellent mechanical properties and retains a high-strength structure after shallow degradation, serving as a reinforcing phase to enhance the deformation resistance of the flexible foam; secondly, its surface-active groups can form a denser cross-linked network with the flexible foam matrix, and combined with the uniform dispersion effect of fine particle size, further optimizes the stability of the cell structure.

[0243] The NMR spectrum of the alcoholysis products of waste polyurethane elastomer in Example 6 is shown below. Figure 22 As shown.

[0244] In some embodiments of this application, reference is made to Figure 3 A method for recycling waste polyurethane materials is provided, including a powder preparation stage. In the powder preparation stage, the waste polyurethane material is pulverized using a pulverizing device to obtain polyurethane powder.

[0245] The waste polyurethane material recycling method also includes a premix preparation stage. In the premix preparation stage, the polyurethane powder is mixed with a degradation agent and a catalyst in a certain proportion, and then mixed evenly using a stirring device to obtain a premix with a certain powder content.

[0246] The recycling method for waste polyurethane materials also includes a degradation stage. In this stage, the premixed liquid is ground, extruded, and sheared using equipment with mechanical shearing and extrusion capabilities. The reaction process is carried out within a set temperature range, and after the reaction is complete, a degraded mixture of polyurethane materials is obtained.

[0247] The recycling method for waste polyurethane materials includes a powder preparation stage, a premix preparation stage, and a degradation stage, which are performed sequentially. Because this recycling method does not contain a co-solvent, a relatively large amount of degradation agent is added during recycling, which improves the degradation effect. Therefore, the particle size range of the polyurethane powder can be appropriately increased, for example, to <30mm.

[0248] The waste polyurethane recycling process described in this invention has advantages over existing chemical degradation and recycling methods by not adding polyols as co-solvents during the degradation process. In this invention patent, the introduction of polyols as co-solvents during the degradation stage has achieved preliminary results. It is worth noting that even without adding polyols as co-solvents, the "low-temperature mechanochemical shallow heterogeneous catalytic degradation" process proposed in this invention, through the continuous strong mechanical shearing action provided by equipment such as colloid mills, efficiently processes the degradation material, and still possesses significant technical advantages over existing chemical degradation processes, specifically in the following aspects:

[0249] This invention utilizes specialized equipment with strong mechanical shearing and extrusion capabilities to process a mixture of polyurethane micropowder, degrading agent, catalyst, and cosolvent. Relying on the high shear stress and frictional effect generated by mechanical force, it not only refines the micropowder particle size and directly disrupts the cross-linked structure on the micropowder surface, but also simultaneously reduces the activation energy for the chain scission degradation of urethane groups. This increases the contact probability between the degrading agent, catalyst, and the micropowder surface, forming a ternary interaction interface of "micropowder surface degradation sites - polar groups of the degrading agent - active centers of the catalyst." This provides highly efficient reaction sites for subsequent degradation reactions, significantly shortening the shallow degradation reaction process and increasing the reaction rate. Compared with existing degradation processes, this process can significantly reduce the temperature threshold required for the degradation reaction, fundamentally inhibiting high-temperature-induced side reactions and, in principle, eliminating the generation of toxic byproducts such as aromatic amines. This has significant practical implications for the high-value reuse of degradation products and environmental protection.

[0250] In some embodiments of this application, reference is made to Figure 4 A method for recycling waste polyurethane materials is provided, comprising:

[0251] In the powder preparation stage, waste polyurethane materials are crushed using crushing equipment to obtain polyurethane powder;

[0252] In the mixed degradation stage, the polyurethane powder, degradation agent, and catalyst are added in proportion to a device with mechanical shearing and extrusion functions, and the co-solvent is added as needed. Mixing and degradation are carried out within a set temperature range to obtain a degradation mixture of polyurethane material.

[0253] The above technical solution has the following advantages or beneficial effects: The "low-temperature mechanochemical shallow heterogeneous catalytic degradation" process proposed in this invention efficiently processes the degradation material through continuous strong mechanical shearing action provided by equipment such as colloid mills, and has the following advantages compared with existing chemical degradation processes:

[0254] This invention employs specialized equipment with strong mechanical shearing and extrusion capabilities to process a mixture of polyurethane micropowder, degrading agent, catalyst, and cosolvent. Relying on the high shear stress and frictional effect generated by mechanical force, it not only refines the micropowder particle size and directly disrupts the cross-linked structure on the micropowder surface, but also simultaneously reduces the activation energy for the chain-breaking degradation of urethane groups. This increases the contact probability between the degrading agent, catalyst, and the micropowder surface, forming a ternary interaction interface of "micropowder surface degradation sites - polar groups of the degrading agent - active centers of the catalyst." This provides highly efficient reaction sites for subsequent degradation reactions, significantly shortening the shallow degradation reaction process and increasing the reaction rate. Furthermore, compared with existing degradation processes, this process can significantly reduce the temperature threshold required for the degradation reaction, fundamentally suppressing high-temperature-induced side reactions and, in principle, eliminating the generation of toxic byproducts such as aromatic amines. This has significant practical implications for the high-value reuse of degradation products and environmental protection.

[0255] In addition, equipment using mechanical shearing and extrusion functions can simultaneously achieve reactant mixing and polyurethane material degradation, reducing the initial investment cost of the production line, and can still achieve good shallow heterogeneous degradation and recycling results under appropriate process parameter settings.

[0256] In some embodiments of this application, a method for preparing a polyurethane product is provided, wherein part or all of the polyol raw material is the degradation mixture obtained by the waste polyurethane material recycling method in the above embodiments.

[0257] The preparation method includes a product reprocessing stage, in which component A and component B are mixed in a certain proportion and then the product is reprocessed; component A is a mixture of the degradation mixture and chain extender, catalyst and stabilizer, and foaming agent is added as needed; component B is isocyanate.

[0258] In the description of the above embodiments, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0259] The above are merely specific embodiments 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 method for recycling waste polyurethane material, characterized by, It includes: Powder preparation stage: using a pulverizing device to pulverize waste polyurethane materials to obtain polyurethane powder; Premixed liquid preparation stage: mixing the polyurethane powder with a degradation agent, a catalyst, and a co-solvent in proportion, and mixing evenly through a stirring device to obtain a premixed liquid with a certain powder content; Degradation stage: using a device with mechanical shear and extrusion functions to grind, extrude, and shear the premixed liquid. The reaction process is carried out within a set temperature range, the reaction temperature is 60 - 160 °C, the reaction time is 10 min - 3 h. After the reaction is completed, a degradation mixture of polyurethane materials is obtained, achieving shallow heterogeneous degradation of polyurethane powder. The obtained degradation mixture is a solid-liquid two-phase mixture containing solid incompletely degraded polyurethane micropowder particles and a degradation liquid; The viscosity of the degradation mixture is less than 20000 mPa·s; The degradation mixture does not contain aromatic amine substances and can be directly used to replace polyol raw materials in the production line without any post-treatment process; Among them, in the premixed liquid preparation stage, the addition amount of the degradation agent is calculated and determined based on the molar amount of urethane groups in the polyurethane powder and the target degradation rate. The degradation rate = (molar amount of degraded urethane groups / total molar amount of initial urethane groups) × 100%. The addition amount is calculated according to the molar reaction ratio of polar groups in the degradation agent to urethane, and the degradation rate of urethane is 5 - 70%; 2. The method for recycling waste polyurethane materials according to claim 1, wherein In the premixed liquid preparation stage, the co-solvent is one or a mixture of two or more of polyols in any proportion.

3. The method for recycling waste polyurethane materials according to claim 1, wherein In the premixed liquid preparation stage, the powder content of the premixed liquid < 60%.

4. The method for recycling waste polyurethane materials according to claim 1, wherein In the degradation stage, the progress of the degradation reaction is indirectly judged according to the color change or fluidity change of the mixture in the reaction kettle.

5. A process for the production of a polyurethane article, characterized in that, Part or all of the polyol raw materials are replaced by the degradation mixture obtained by the method for recycling waste polyurethane materials according to any one of claims 1 to 4.

6. The method for preparing a polyurethane product according to claim 5, wherein The preparation method includes a product reproduction stage, mixing component A and component B in proportion and then carrying out product reproduction; Component A is a mixture of the degradation mixture, a chain extender, a catalyst, and a stabilizer, and a blowing agent is added as needed; Component B is an isocyanate.

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