Polyurethane plastic track composite material containing DPU waste and preparation method thereof

Abstract

The invention relates to the technical field of solid waste recycling, in particular to a DPU waste-containing polyurethane plastic track composite material and a preparation method thereof, and the preparation method comprises the following steps: step (1) preparation of pretreated waste particles: preparing materials, mixing, carbonizing and carrying out microwave treatment to obtain the pretreated waste particles; (2) preparing modified waste particles: performing surface modification and grafting on the pretreated waste particles to obtain the modified waste particles; and (3) preparing the composite material, namely proportioning the modified waste particles, extruding and granulating to obtain the polyurethane plastic track composite material. Through combination of the components and the process, the performance defects of the DPU waste are improved, and efficient application of the DPU waste in a high-performance plastic track composite material is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of solid waste recycling, and in particular to a polyurethane plastic runway composite material containing DPU waste and a preparation method thereof. Background Art

[0002] With growing environmental awareness and the demand for resource reuse, the recycling and reuse of waste polymer materials has become a research hotspot. In particular, the use of DPU waste in polyurethane (PU) plastic track composites is limited by its poor activation performance, susceptibility to cracking, aging, and peeling. Therefore, how to effectively activate DPU waste and incorporate it into high-performance plastic track composites has become a pressing technical challenge.

[0003] Publication number CN110055858A discloses an environmentally friendly hybrid plastic track and its preparation method. This patent provides a modular, environmentally friendly hybrid plastic track made primarily from shoe waste. Using shoe waste instead of EPDM rubber particles as the elastic filler in the hybrid track not only achieves the required elastic properties of the plastic track, but also transforms some of the shoe waste into a reusable resource, reducing waste and the adverse environmental impact of disposal. Furthermore, the track is easy to assemble and effectively minimizes the effects of thermal expansion on the elasticity of the track. However, experiments have shown that the surface of DPU waste particles is highly inert, making it difficult to form effective chemical bonds with the polyurethane matrix. Experiments have shown that directly blending recycled DPU particles (particle size 0.1-1 mm) at an addition level greater than 15% can reduce the composite material's elongation at break from 320% to 150%, and its tensile strength by 50%. Furthermore, conventional processes employ direct blending of inorganic fillers (such as calcium carbonate and talc), but physical mixing struggles to activate the surface active groups of the waste material. Studies have shown that the shear strength of the interface between untreated DPU particles and the matrix is ​​less than 30% of that of the original material. Composite materials containing DPU waste have weakened interfaces, and microcracks expand into macro cracks under dynamic loads. Residual amine catalysts (such as triethylenediamine) in DPU waste will catalyze the hydrolysis of the matrix and accelerate the embrittlement of the material. Traditional plastic tracks break polymer chains under ultraviolet radiation, resulting in powdering. DPU waste has its molecular chains damaged during the recycling process, and its UV resistance is further reduced. Composite materials containing waste are more susceptible to oxidation due to the promotion of residual catalysts. The interface between DPU waste and the matrix is ​​prone to peeling due to water vapor penetration.

[0004] Publication number CN110819060B discloses a method for increasing the viscosity of waste ABS plastics. This patent increases the molecular weight and avoids the quality degradation caused by the reduction of molecular weight by adding hydroxyl-terminated polybutadiene (HTPB) and antioxidants to waste ABS plastics, providing a new direction for the recycling and reuse of waste plastics. However, this technical solution is mainly aimed at the modification of ABS plastics, and is not applicable to the activation of DPU waste and its application in polyurethane plastic tracks. The chemical structure of DPU waste is significantly different from that of ABS. Direct application of this method may not be able to effectively solve the performance defects of DPU waste in plastic track composite materials, such as easy cracking and peeling.

[0005] The above problems indicate that the existing polymer material recycling and reuse technology still has shortcomings in the activation treatment of DPU waste and its application in polyurethane plastic track composite materials. Summary of the Invention

[0006] In order to achieve the above-mentioned objectives, the present invention provides a polyurethane plastic track composite material containing DPU waste and a preparation method thereof, aiming to improve the performance defects of DPU waste through a specific activation treatment process and realize its efficient application in high-performance plastic track composite materials, thereby meeting the needs of environmental protection and resource recycling.

[0007] The present invention adopts the following technical solutions:

[0008] A polyurethane plastic track composite material containing DPU waste is prepared by the following steps:

[0009] By weight,

[0010] Step (1) Preparation of pretreated waste particles: 100 parts by mass of DPU waste particles crushed to a particle size of 0.1 to 1 mm are mixed evenly with 5 to 50 parts by mass of silica aerogel powder, followed by surface carbonization treatment at a treatment temperature of 150 to 350° C. for 10 to 120 minutes, followed by microwave treatment at a microwave power of 300 to 1500 W for 1 to 30 minutes, and dispersion to obtain pretreated waste particles;

[0011] Step (2) Preparation of modified waste particles: Surface modification of the pretreated waste particles is performed, followed by grafting reaction with a polyurethane monomer in the presence of a catalyst at a reaction temperature of 40 to 90° C. for a reaction time of 0.5 to 5 hours to obtain modified waste particles;

[0012] Step (3) Preparation of composite material: 100 parts by mass of modified waste particles are mixed with 20 to 200 parts by mass of plastic polyurethane base material, and the mixture is extruded and granulated to obtain a polyurethane plastic runway composite material.

[0013] Preferably, the process for preparing the pre-treated waste particles comprises the following steps:

[0014] Step (1-1) Mixing: 100 parts by weight of DPU waste particles with a particle size of 0.1 to 1 mm are added to a conical mixer and stirred at a low speed of 50 rpm; 5 to 50 parts of silica aerogel powder with a particle size of 1 to 100 μm are added in three batches, with an interval of 2 minutes between each batch to reduce adhesion and improve wear resistance; the speed is increased to 300 rpm, and after mixing for 15 minutes, the machine is stopped to scrape the wall to avoid dead corners, and then mixed for another 5 minutes. The filler coverage rate must be greater than 90%;

[0015] Step (1-2) Surface carbonization treatment: The mixed material is transferred to a carbonization device, and high-purity nitrogen (nitrogen content 99.99%) is introduced into the carbonization device to make the oxygen volume concentration <0.5%; during the heating stage, the temperature is raised at a rate of 10°C / minute to prevent the particles from being deformed due to thermal shock; during the holding stage, due to the difference in heat conduction efficiency caused by the difference in particle size, the carbonization temperature and holding time are determined according to the particle size. For particles with a particle size of 0.1 to 0.3 mm, the carbonization temperature is set to 150 to 200°C. The holding time is 10 to 30 minutes. For particles with a particle size of 0.3 to 0.6 mm, the carbonization temperature is set at 200 to 300°C and the holding time is 30 to 90 minutes. For particles with a particle size of 0.6 to 1.0 mm, the carbonization temperature is set at 300 to 350°C and the holding time is 90 to 120 minutes. The surface is dehydrogenated to form a micro-carbonized layer. Using high temperature to treat small-sized particles will cause the particles to melt and agglomerate. Using low temperature to treat large-sized particles will result in a low carbonized layer thickness and incomplete subsequent reactions.

[0016] Step (1-3) Microwave treatment: The surface carbonized particles are spread flat on a quartz boat with a thickness of ≤3 cm. Too thick will result in uneven microwave penetration. A rotating tray (5-10 rpm) is set in the microwave cavity to ensure uniform heating. The microwave parameters are set according to the particle size. Particles with a particle size of 0.1-0.3 mm are treated at a power of 300-600 W for 5-15 minutes, particles with a particle size of 0.3-0.6 mm are treated at a power of 600-1200 W for 10-25 minutes, and particles with a particle size of 0.6-1.0 mm are treated at a power of 1200-1500 W for 15-30 minutes. Pore development and dispersion are promoted. After the microwave is stopped, nitrogen is passed through for rapid cooling (to prevent oxidation), and the mixture is cooled to <60°C and transferred to a sealed container.

[0017] Preferably, the process for preparing the modified waste particles is as follows: in step (2), the surface modifier is at least one of a silane coupling agent, a titanate coupling agent or plasma treatment, and the specific methods of the three modification treatments are:

[0018] (1.a) Silane coupling agent treatment: Dilute the silane coupling agent (KH-550 / KH-570) with an ethanol-water (volume ratio 9:1) solution to a concentration of 2-5 wt%; place the pretreated particles in a vortex disperser, stir at a low speed of 200 rpm, spray the coupling agent solution at an atomization pressure of 0.2 MPa, raise the temperature to 70-80°C, increase the rotation speed to 1500 rpm, and react for 20 minutes.

[0019] (1.b) Titanate coupling agent treatment: Suitable for silica aerogel powder filler systems; titanate (NDZ-201) and anhydrous toluene are mixed in a volume ratio of 1:10, added to the pretreated particles, and stirred at 60°C for 30 minutes. Deionized water containing 0.5% of the titanate by weight is then added dropwise, the temperature is raised to 90°C, and the reaction is carried out for 10 minutes to form Ti-O-Si bonds;

[0020] (1.c) Plasma treatment: A normal pressure argon plasma jet was used with a power of 800 W, an argon flow rate of 15 L / min, a treatment distance of 50 mm, and a treatment time of 3 min. Plasma treatment introduced -COOH / -OH groups onto the particle surface.

[0021] In step (2), the specific process of the grafting reaction includes the following steps:

[0022] Step (2-1) Reaction System Construction: 100 parts of DPU modified particles were placed in a reactor, preheated to 40°C, 1 to 20 parts of polyurethane monomer were added, and a catalyst (dissolved in five times the mass of acetone) at a concentration of 0.1% to 5% of the mass of the polyurethane monomer was added dropwise via a metering pump, and a grafting reaction was carried out in the presence of the catalyst;

[0023] Preferably, the polyurethane monomer is a mixture of an isocyanate compound and a polyol compound, wherein the isocyanate compound includes at least one of toluene diisocyanate TDI, diphenylmethane diisocyanate MDI, and isophorone diisocyanate IPDI, and the polyol compound is a polyether polyol or a polyester polyol;

[0024] Preferably, the catalyst is an organotin or amine catalyst;

[0025] Step (2-2) controls the temperature and time for the reaction in stages: stage 1 is low-temperature anchoring, heating to 50±1°C, stirring at 200-300 rpm, and reacting for 0.5 h to allow -NCO to preferentially react with the surface active groups of the particles, and the viscosity of the system increases slightly; stage 2 is medium-temperature chain extension, heating to 70±1°C, stirring at 400 rpm, and reacting for 1.5 h to allow the polyol to react with the remaining -NCO to extend the graft chain, and a gel-like coating layer appears on the surface of the particles; stage 3 is high-temperature curing, heating to 90±1°C, stirring at 100 rpm, and reacting for 1 h to promote the unreacted -NCO to form biuret crosslinking, and the particles turn from brown to dark brown;

[0026] Step (2-3) reaction termination and post-treatment: adding a terminator, adding 1.2 times the molar number of benzoyl chloride as the catalyst at 70° C., and stirring for 20 minutes; stripping and desolventizing, treating at 80° C. and -0.08 MPa for 1 hour to remove 90% of the solvent, heating to 100° C. and treating at -0.095 MPa for 2 hours to reduce the residual monomer to <100 ppm; product separation: centrifugal filtration through a 300-mesh sieve, washing with petroleum ether after filtration, and drying the product in a fluidized bed at 80° C. for 30 minutes to obtain modified waste particles.

[0027] Preferably, the process for preparing the composite material is:

[0028] Step (3-1) Mixing: Preheat the mixing chamber to 150°C, add 100 parts of plastic polyurethane base material (thermoplastic polyurethane TPU base material), melt and plasticize for 2 minutes, and then add modified waste particles and additives; then increase the speed step by step, first stir at 30 rpm for 1 minute, gently mix to prevent particle breakage, then stir at 60 rpm for 2 minutes, moderately shear and tear the carbonized layer, and finally stir at 90 rpm for 2 minutes, high temperature and high pressure promote interface entanglement; when the power curve of the mixer tends to be stable and the fluctuation is less than 5%, stop mixing.

[0029] Step (3-2) extrusion molding: Use a conveyor belt with a surface temperature of 160°C to transfer the mixed material to the extruder to prevent secondary agglomeration caused by cooling of the material; the temperature of each extrusion temperature zone is set as follows: feeding section 120°C, gentle compression to prevent degradation; melting section 170°C, fully melt TPU; mixing section 190°C, disperse inorganic fillers; die head 185°C, stable stripping to prevent mold expansion; after stripping, pelletize in 40°C water to obtain polyurethane plastic runway composite material particles with a particle size of 1 to 10 mm, and dehydrate the obtained particles in a centrifuge at a speed of 3000 rpm for 5 minutes to control the moisture content of the material to be less than 0.1%.

[0030] The present invention's solution regenerates DPU waste through the synergy of multiple components and precise process adaptation, with silica aerogel powder serving as a key medium throughout the entire process. During the mixing stage, silica aerogel powder is gradually embedded into the surface of DPU particles. Its nanoporous structure provides a uniform heat conduction path for the subsequent carbonization process, effectively suppressing local overheating. During the carbonization process, gradient temperature control under an inert atmosphere simultaneously catalyzes the selective cracking of the aerogel surface, assisting in the formation of a homogeneous microporous structure. The microwave treatment stage leverages the aerogel's high dielectric properties to enhance energy absorption efficiency, deeply activating the carbonized layer through power parameters tailored to the particle size.

[0031] The surface modification process fully utilizes the reactivity of silanol groups on the aerogel surface: silane coupling agents are sprayed with an ethanol solution to condense with silanol groups and graft amino groups. Titanate is hydrolyzed to form Ti-O-Si bonds. Plasma treatment further introduces active groups into the aerogel interface, creating a high-density grafting anchor point. In the three-stage temperature control strategy for the grafting reaction, isocyanate preferentially bonds with the modified active sites on the aerogel to form a rigid anchoring layer. Polyol chain extension then constructs a flexible coating network on the particle surface. High-temperature crosslinking ultimately strengthens the core-shell structure.

[0032] The compounding process highlights the aerogel's bridging function: the stepped speed of internal mixing at a high temperature of 150°C makes the aerogel the physical crosslinking point between the TPU molecular chains and the carbonized layer. Low-speed mixing protects its porous structure, medium-speed shearing promotes the penetration of TPU segments into the aerogel pores, and high-speed stirring achieves molecular chain penetration and entanglement. The temperature zoning design of the extrusion process enables the aerogel to play a structural guiding role: the feeding stage is 120°C to protect its thermal stability, and the mixing stage is 190°C to utilize its high specific surface area to induce orderly dispersion of the filler. Ultimately, a quaternary synergistic reinforcement phase of carbonized layer-aerogel-grafted chain-TPU matrix is ​​formed, achieving performance optimization at high waste content.

[0033] This solution also proposes a method for preparing the above-mentioned polyurethane plastic track composite material containing DPU waste, comprising the following steps:

[0034] Step (1) Preparation of pretreated waste particles: batching, mixing, carbonizing, and microwave treatment to obtain pretreated waste particles;

[0035] Step (2) Preparation of modified waste particles: surface modification and grafting of pretreated waste particles to obtain modified waste particles;

[0036] Step (3) Preparation of composite material: Modify waste material particles, extrude and granulate to obtain polyurethane plastic track composite material.

[0037] Compared with the prior art, the present invention has the following advantages:

[0038] 1. Silica aerogel powder serves as a multifunctional medium throughout the entire process. Its nanoporous structure is embedded in the surface of DPU particles during the mixing stage, acting as a heat diffusion barrier to prevent local overheating during carbonization, and utilizing its high dielectric properties to enhance energy absorption efficiency during microwave treatment. At the same time, the active silanol groups on the aerogel surface efficiently bond with the silane / titanate coupling agent, constructing high-density anchor points for the grafting reaction. Ultimately, in the compounding stage, it becomes a physical cross-linking hub for the TPU molecular chain to penetrate the carbonized layer, achieving a three-level reinforcement of the carbonized layer-aerogel-grafted chain at the waste-matrix interface.

[0039] 2. The entire process precisely matches material properties: During the carbonization stage, temperature and time are controlled according to particle size classification, combined with nitrogen quenching to lock the microporous structure and simultaneously avoid the risk of oxidative degradation; microwave treatment deeply activates the surface through dynamic adaptation of particle size and power, forming a synergistic effect with the dielectric response of the aerogel; the three-stage temperature control strategy of the grafting reaction achieves molecular-level orderly assembly of isocyanate anchoring, polyol chain extension and high-temperature cross-linking; in the compounding process, the stepped mixing speed and extrusion temperature zoning are coordinated to first protect the particle structure and then gradually shear and fuse, so that the high-dosage waste materials form a uniformly dispersed reinforcing phase network in the TPU matrix. DETAILED DESCRIPTION

[0040] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0041] Overall embodiment

[0042] A polyurethane plastic track composite material containing DPU waste is prepared by the following steps, calculated by weight:

[0043] Step (1) pre-processing waste particles preparation;

[0044] Step (1-1) Mixing: 100 parts of DPU waste particles with a particle size of 0.1 to 1 mm were added to a conical mixer and stirred at a low speed of 50 rpm; 5 to 50 parts of silica aerogel powder with a particle size of 1 to 100 μm were added in three batches, with an interval of 2 minutes between each addition; the speed was increased to 300 rpm, and after mixing for 15 minutes, the machine was stopped to scrape the wall, and then mixed for another 5 minutes;

[0045] Step (1-2) surface carbonization treatment: the mixture is transferred into a carbonization device, and high-purity nitrogen is introduced into the carbonization device to make the oxygen volume concentration <0.5%; the temperature is increased at a rate of 10°C / minute during the heating stage; during the holding stage, due to the difference in heat conduction efficiency caused by the difference in particle size, the carbonization temperature and holding time are determined according to the particle size. For particles with a particle size of 0.1 to 0.3 mm, the carbonization temperature is set to 150 to 200°C and the holding time is 10 to 30 minutes; for particles with a particle size of 0.3 to 0.6 mm, the carbonization temperature is set to 200 to 300°C and the holding time is 30 to 90 minutes; for particles with a particle size of 0.6 to 1.0 mm, the carbonization temperature is set to 300 to 350°C and the holding time is 90 to 120 minutes;

[0046] Step (1-3) Microwave treatment: The surface carbonized particles are spread flat on a quartz boat with a thickness of ≤3 cm; a rotating tray (5-10 rpm) is set in the microwave cavity to ensure uniform heating; microwave parameters are set according to the particle size: particles with a particle size of 0.1-0.3 mm are treated at a power of 300-600 W for 5-15 minutes, particles with a particle size of 0.3-0.6 mm are treated at a power of 600-1200 W for 10-25 minutes, and particles with a particle size of 0.6-1.0 mm are treated at a power of 1200-1500 W for 15-30 minutes; after stopping the microwave, nitrogen is passed through to quench the particles, and the particles are cooled to <60° C. and transferred to a sealed container;

[0047] Step (2) preparing modified waste particles;

[0048] Step (2-1) Surface modification: Surface modification can be performed using three different techniques:

[0049] (1.a) Silane coupling agent treatment: Dilute the silane coupling agent (KH-550 / KH-570) with an ethanol-water (volume ratio 9:1) solution to a concentration of 2-5 wt%; place the pretreated particles in a vortex disperser, stir at a low speed of 200 rpm, spray the coupling agent solution at an atomization pressure of 0.2 MPa, raise the temperature to 70-80°C, increase the rotation speed to 1500 rpm, and react for 20 minutes.

[0050] (1.b) Titanate coupling agent treatment: Suitable for silica aerogel powder filler systems; titanate (NDZ-201) and anhydrous toluene are mixed in a volume ratio of 1:10, added to the pretreated particles, and stirred at 60°C for 30 minutes. Deionized water containing 0.5% of the titanate by weight is then added dropwise, the temperature is raised to 90°C, and the reaction is carried out for 10 minutes to form Ti-O-Si bonds;

[0051] (1.c) Plasma treatment: A normal pressure argon plasma jet was used with a power of 800 W, an argon flow rate of 15 L / min, a treatment distance of 50 mm, and a treatment time of 3 min. Plasma treatment introduced -COOH / -OH groups onto the particle surface.

[0052] Step (2-2) Grafting reaction: The grafting reaction process is divided into the following steps;

[0053] (2.a) Reaction system construction: 100 parts of DPU modified particles were placed in a reactor, preheated to 40°C, and 1 to 20 parts of a polyurethane monomer: a mixture of an isocyanate compound (at least one of TDI, MDI, and IPDI) and a polyol compound (polyether polyol or polyester polyol) were added. A catalyst (organotin or amine catalyst) at a concentration of 0.1% to 5% by weight of the polyurethane monomer (dissolved in five times the mass of acetone) was added dropwise via a metering pump, and a grafting reaction was carried out in the presence of the catalyst.

[0054] (2.b) The reaction is carried out in stages by controlling the temperature and time: Stage 1: low-temperature anchoring, heating to 50±1°C, stirring at 200-300 rpm, and reacting for 0.5 h to allow the -NCO to preferentially react with the surface active groups of the particles, resulting in a slight increase in the viscosity of the system; Stage 2: medium-temperature chain extension, heating to 70±1°C, stirring at 400 rpm, and reacting for 1.5 h to allow the polyol to react with the remaining -NCO to extend the grafted chain, forming a gel-like coating on the particle surface; Stage 3: high-temperature curing, heating to 90°C±1, stirring at 100 rpm, and reacting for 1 h to promote the unreacted -NCO to form biuret crosslinks, resulting in the particles turning from brown to dark brown;

[0055] (2.c) Reaction termination and post-treatment: Add a terminator, add 1.2 times the molar number of benzoyl chloride as the catalyst dropwise at 70°C, and stir for 20 minutes; carry out stripping and desolventizing at 80°C and -0.08 MPa for 1 hour to remove 90% of the solvent, then heat to 100°C and treat at -0.095 MPa for 2 hours to reduce the residual monomer to <100 ppm; separate the products: centrifuge through a 300-mesh sieve, wash with petroleum ether after filtration, and dry the products in a fluidized bed at 80°C for 30 minutes to obtain modified waste particles.

[0056] Step (3) Preparation of composite materials.

[0057] Step (3-1) Mixing: Preheat the mixing chamber to 150°C, add 100 parts of TPU base material, melt and plasticize for 2 minutes, and then add the modified waste particles and additives; then increase the speed step by step, first stir at 30 rpm for 1 minute, gently mix to prevent the particles from breaking, then stir at 60 rpm for 2 minutes, moderately shear and tear the carbonized layer, and finally stir at 90 rpm for 2 minutes, high temperature and high pressure promote interface entanglement; when the power curve of the mixer tends to be stable and the fluctuation is less than 5%, stop mixing.

[0058] Step (3-2) extrusion molding: Use a conveyor belt with a surface temperature of 160°C to transfer the mixed material to the extruder to prevent secondary agglomeration caused by cooling of the material; the temperature of each extrusion temperature zone is set as follows: feeding section 120°C, gentle compression to prevent degradation; melting section 170°C, fully melt TPU; mixing section 190°C, disperse inorganic fillers; die head 185°C, stable stripping to prevent mold expansion; after stripping, pelletize in 40°C water to obtain polyurethane plastic runway composite material particles with a particle size of 1 to 10 mm, and dehydrate the obtained particles in a centrifuge at a speed of 3000 rpm for 5 minutes to control the moisture content of the material to be less than 0.1%.

[0059] Example 1

[0060] A polyurethane plastic track composite material containing DPU waste is prepared by the following steps, calculated by weight:

[0061] Step (1) pre-processing waste particles preparation;

[0062] Step (1-1) Mixing: 100 parts of DPU waste particles with a particle size of 0.5 mm were added to a conical mixer and stirred at a low speed of 50 rpm; 20 parts of silica aerogel powder with a particle size of 10 μm were added in three batches, with an interval of 2 minutes between each addition; the speed was increased to 300 rpm, and after mixing for 15 minutes, the mixer was stopped to scrape the wall, and then mixed for another 5 minutes;

[0063] Step (1-2) Surface carbonization treatment: The mixed material is transferred to a carbonization device, and high-purity nitrogen is introduced into the carbonization device to make the oxygen volume concentration less than 0.5%; the temperature is increased at a rate of 10°C / min during the heating stage; during the holding stage, the carbonization temperature is set to 250°C for 60 minutes;

[0064] Step (1-3) Microwave treatment: The carbonized particles were spread on a quartz boat with a thickness of ≤3 cm; a rotating tray (5-10 rpm) was set in the microwave cavity to ensure uniform heating; the particles were treated at 800 W for 15 minutes; after the microwave was stopped, nitrogen was passed through to quench the particles until the temperature was less than 60° C. and the particles were transferred to a sealed container;

[0065] Step (2) preparing modified waste particles;

[0066] Step (2-1) Surface modification treatment: Silane coupling agent treatment: The silane coupling agent KH-550 was diluted with an ethanol-water (volume ratio 9:1) solution to a concentration of 3 wt%; the pretreated particles were placed in a vortex disperser, stirred at a low speed of 200 rpm, sprayed with the coupling agent solution at an atomization pressure of 0.2 MPa, heated to 80°C, increased the speed to 1500 rpm, and reacted for 20 minutes.

[0067] Step (2-2) Grafting reaction: The grafting reaction process is divided into the following steps;

[0068] (2.a) Reaction system construction: 100 parts of DPU modified particles were placed in a reactor, preheated to 40°C, and a polyurethane monomer consisting of 4 parts of MDI and 5.2 parts of polyether polyol was added. DBTDL (0.4% by weight of the polyurethane monomer) was added dropwise via a metering pump, and a grafting reaction was carried out in the presence of a catalyst.

[0069] (2.b) The reaction was carried out in stages with controlled temperature and time: stage 1: low-temperature anchoring, heating to 50°C, stirring at 250 rpm, and reaction for 0.5 h; stage 2: medium-temperature chain extension, heating to 70°C, stirring at 400 rpm, and reaction for 1.5 h; stage 3: high-temperature curing, heating to 90°C, stirring at 100 rpm, and reaction for 1 h;

[0070] (2.c) Reaction termination and post-treatment: Add a terminator, add 1.2 times the molar number of benzoyl chloride as the catalyst dropwise at 70°C, and stir for 20 minutes; carry out stripping and desolventizing at 80°C and -0.08 MPa for 1 hour to remove 90% of the solvent, then heat to 100°C and treat at -0.095 MPa for 2 hours to reduce the residual monomer to <100 ppm; separate the products: centrifuge through a 300-mesh sieve, wash with petroleum ether after filtration, and dry the products in a fluidized bed at 80°C for 30 minutes to obtain modified waste particles.

[0071] Step (3) Preparation of composite materials.

[0072] Step (3-1) Mixing: Preheat the mixing chamber to 150°C, add 100 parts of TPU base material, melt and plasticize for 2 minutes, and then add 100 parts of modified waste particles; then increase the speed step by step, first stir at 30 rpm for 1 minute, then stir at 60 rpm for 2 minutes, and finally stir at 90 rpm for 2 minutes; when the power curve of the mixer tends to be stable and the fluctuation is less than 5%, stop mixing.

[0073] Step (3-2) extrusion molding: Use a conveyor belt with a surface temperature of 160°C to transfer the mixed material to the extruder to prevent secondary agglomeration caused by cooling of the material; the temperature of each extrusion temperature zone is set as follows: feeding section 120°C, gentle compression to prevent degradation; melting section 170°C, fully melt TPU; mixing section 190°C, disperse inorganic fillers; die head 185°C, stable stripping to prevent mold expansion; after stripping, pelletize in 40°C water to obtain polyurethane plastic runway composite material particles with a particle size of 3 mm, and dehydrate the obtained particles in a centrifuge at a speed of 3000 rpm for 5 minutes to control the moisture content of the material to be less than 0.1%.

[0074] Example 2

[0075] A polyurethane plastic track composite material containing DPU waste is prepared by the following steps, calculated by weight:

[0076] Step (1) pre-processing waste particles preparation;

[0077] Step (1-1) Mixing: 100 parts of DPU waste particles with a particle size of 0.1 mm were added to a conical mixer and stirred at a low speed of 50 rpm; a total of 5 parts of silica aerogel powder with a particle size of 1 μm were added in 3 times, with an interval of 2 minutes between each addition; the speed was increased to 300 rpm, and after mixing for 15 minutes, the mixer was stopped to scrape the wall, and then mixed for another 5 minutes;

[0078] Step (1-2) Surface carbonization treatment: The mixed material is transferred to a carbonization device, and high-purity nitrogen is introduced into the carbonization device to make the oxygen volume concentration less than 0.5%; the temperature is increased at a rate of 10°C / min during the heating stage; during the holding stage, the carbonization temperature is set to 180°C for 30 minutes;

[0079] Step (1-3) Microwave treatment: The carbonized particles were spread flat on a quartz boat with a thickness of ≤3 cm; a rotating tray (5-10 rpm) was set in the microwave cavity to ensure uniform heating; the particles were treated at 400 W for 10 minutes; after the microwave was stopped, nitrogen was passed through to rapidly cool the particles to <60°C and then transferred to a sealed container;

[0080] Step (2) preparing modified waste particles;

[0081] Step (2-1) Surface modification treatment: Plasma treatment: using an atmospheric pressure argon plasma jet apparatus, setting the power to 800 W, the argon flow rate to 15 L / min, the treatment distance to 50 mm, and the treatment time to 3 min;

[0082] Step (2-2) Grafting reaction: The grafting reaction process is divided into the following steps;

[0083] (2.a) Reaction system construction: 100 parts of DPU modified particles were placed in a reactor, preheated to 40°C, and a polyurethane monomer consisting of 2 parts of IPDI and 2.4 parts of polyether polyol was added. Dabco T-12 (0.2% by weight of the polyurethane monomer) was added dropwise via a metering pump, and a grafting reaction was carried out in the presence of a catalyst.

[0084] (2.b) The reaction was carried out in stages with controlled temperature and time: stage 1: low-temperature anchoring, heating to 50°C, stirring at 250 rpm, and reaction for 0.5 h; stage 2: medium-temperature chain extension, heating to 70°C, stirring at 400 rpm, and reaction for 1.5 h; stage 3: high-temperature curing, heating to 90°C, stirring at 100 rpm, and reaction for 1 h;

[0085] (2.c) Reaction termination and post-treatment: Add a terminator, add 1.2 times the molar number of benzoyl chloride as the catalyst dropwise at 70°C, and stir for 20 minutes; carry out stripping and desolventizing at 80°C and -0.08 MPa for 1 hour to remove 90% of the solvent, then heat to 100°C and treat at -0.095 MPa for 2 hours to reduce the residual monomer to <100 ppm; separate the products: centrifuge through a 300-mesh sieve, wash with petroleum ether after filtration, and dry the products in a fluidized bed at 80°C for 30 minutes to obtain modified waste particles.

[0086] Step (3) Preparation of composite materials.

[0087] Step (3-1) Mixing: Preheat the mixing chamber to 150°C, add 100 parts of TPU base material, melt and plasticize for 2 minutes, and then add 100 parts of modified waste particles; then increase the speed step by step, first stir at 30 rpm for 1 minute, then stir at 60 rpm for 2 minutes, and finally stir at 90 rpm for 2 minutes; when the power curve of the mixer tends to be stable and the fluctuation is less than 5%, stop mixing.

[0088] Step (3-2) extrusion molding: Use a conveyor belt with a surface temperature of 160°C to transfer the mixed material to the extruder to prevent secondary agglomeration caused by cooling of the material; the temperature of each extrusion temperature zone is set as follows: feeding section 120°C, gentle compression to prevent degradation; melting section 170°C, fully melt TPU; mixing section 190°C, disperse inorganic fillers; die head 185°C, stable stripping to prevent mold expansion; after stripping, pelletize in 40°C water to obtain polyurethane plastic runway composite material particles with a particle size of 1 mm, and dehydrate the obtained particles in a centrifuge at a speed of 3000 rpm for 5 minutes to control the moisture content of the material to be less than 0.1%.

[0089] Example 3

[0090] A polyurethane plastic track composite material containing DPU waste is prepared by the following steps, calculated by weight:

[0091] Step (1) pre-processing waste particles preparation;

[0092] Step (1-1) Mixing: 100 parts of DPU waste particles with a particle size of 1.0 mm were added to a conical mixer and stirred at a low speed of 50 rpm; a total of 50 parts of silica aerogel powder with a particle size of 80 μm were added in three portions, with an interval of 2 minutes between each addition; the speed was increased to 300 rpm, and after mixing for 15 minutes, the mixer was stopped to scrape the wall, and then mixed for another 5 minutes;

[0093] Step (1-2) Surface carbonization treatment: The mixed material is transferred to a carbonization device, and high-purity nitrogen is introduced into the carbonization device to make the oxygen volume concentration less than 0.5%; the temperature is increased at a rate of 10°C / min during the heating stage; during the holding stage, the carbonization temperature is set to 320°C for 120 minutes;

[0094] Step (1-3) Microwave treatment: The carbonized particles were spread flat on a quartz boat with a thickness of ≤3 cm; a rotating tray (5-10 rpm) was set in the microwave cavity to ensure uniform heating; the particles were treated at a power of 1400 W for 25 minutes; after the microwave was stopped, nitrogen was passed through to rapidly cool the particles to <60°C and then transferred to a sealed container;

[0095] Step (2) preparing modified waste particles;

[0096] Step (2-1) Surface modification treatment: Titanate coupling agent treatment: Titanate (NDZ-201) and anhydrous toluene were mixed in a volume ratio of 1:10, added to the pretreated particles, and stirred at 60°C for 30 minutes; deionized water with a concentration of 0.5% by weight of the titanate was added dropwise, the temperature was raised to 90°C, and the reaction was carried out for 10 minutes to form Ti-O-Si bonds;

[0097] Step (2-2) Grafting reaction: The grafting reaction process is divided into the following steps;

[0098] (2.a) Reaction system construction: 100 parts of DPU modified particles were placed in a reactor, preheated to 40°C, and a polyurethane monomer consisting of 6 parts of TDI and 7.8 parts of polyester polyol was added. DBTDL (0.8% by weight of the polyurethane monomer) was added dropwise via a metering pump, and a grafting reaction was carried out in the presence of a catalyst;

[0099] (2.b) The reaction was carried out in stages with controlled temperature and time: stage 1: low-temperature anchoring, heating to 50°C, stirring at 250 rpm, and reaction for 0.5 h; stage 2: medium-temperature chain extension, heating to 70°C, stirring at 400 rpm, and reaction for 2 h; stage 3: high-temperature curing, heating to 90°C, stirring at 100 rpm, and reaction for 1 h;

[0100] (2.c) Reaction termination and post-treatment: Add a terminator, add 1.2 times the molar number of benzoyl chloride as the catalyst dropwise at 70°C, and stir for 20 minutes; carry out stripping and desolventizing at 80°C and -0.08 MPa for 1 hour to remove 90% of the solvent, then heat to 100°C and treat at -0.095 MPa for 2 hours to reduce the residual monomer to <100 ppm; separate the products: centrifuge through a 300-mesh sieve, wash with petroleum ether after filtration, and dry the products in a fluidized bed at 80°C for 30 minutes to obtain modified waste particles.

[0101] Step (3) Preparation of composite materials.

[0102] Step (3-1) Mixing: Preheat the mixing chamber to 150°C, add 100 parts of TPU base material, melt and plasticize for 2 minutes, and then add 200 parts of modified waste particles; then increase the speed step by step, first stir at 30 rpm for 1 minute, then stir at 60 rpm for 2 minutes, and finally stir at 90 rpm for 2 minutes; when the power curve of the mixer tends to be stable and the fluctuation is less than 5%, stop mixing.

[0103] Step (3-2) extrusion molding: Use a conveyor belt with a surface temperature of 160°C to transfer the mixed material to the extruder to prevent secondary agglomeration caused by cooling of the material; the temperature of each extrusion temperature zone is set as follows: feeding section 120°C, gentle compression to prevent degradation; melting section 170°C, fully melt TPU; mixing section 190°C, disperse inorganic fillers; die head 185°C, stable stripping to prevent mold expansion; after stripping, pelletize in 40°C water to obtain polyurethane plastic runway composite material particles with a particle size of 10 mm, and the obtained particles are dehydrated in a centrifuge at a speed of 3000 rpm for 5 minutes to control the moisture content of the material to be less than 0.1%.

[0104] Comparative Example 1

[0105] The difference from Example 1 is that no inorganic filler is added during the pretreatment mixing.

[0106] Comparative Example 2

[0107] The difference from Example 1 is that during the carbonization treatment, only air is introduced instead of high-purity nitrogen, and the oxygen volume concentration is about 20%.

[0108] Comparative Example 3

[0109] The difference from Example 1 is that the particle size of the DPU particles is 0.2 mm, the carbonization temperature is 280° C., and the holding time is 20 min.

[0110] Comparative Example 4

[0111] The difference from Example 1 is that the particle size of the DPU particles is 0.8 mm, the carbonization temperature is 180° C., and the holding time is 100 min.

[0112] Comparative Example 5

[0113] The difference from Example 1 is that the particle size of the DPU waste does not match the microwave frequency, and the treatment is carried out at a power of 1400 W for 25 minutes.

[0114] Comparative Example 6

[0115] The difference from Example 1 is that the DPU waste is only carbonized and not subjected to microwave treatment after carbonization.

[0116] Comparative Example 7

[0117] The difference from Example 1 is that the DPU waste is not subjected to carbonization treatment but is directly subjected to microwave treatment.

[0118] Comparative Example 8

[0119] The difference from Example 1 is that no surface modification treatment is performed in step 2.

[0120] Comparative Example 9

[0121] The difference from Example 1 is that no banburying is performed in step 3.

[0122] Comparative Example 10

[0123] The difference from Example 1 is that the particle size of the DPU waste does not match the microwave frequency, and the treatment is carried out at a power of 400 W for 10 minutes.

[0124] Comparative Example 11

[0125] The difference from Example 1 is that in step (1-1) mixing, the added filler is calcium carbonate.

[0126] Performance testing:

[0127] Tensile strength: Tested in accordance with the method specified in GB / T 10654.

[0128] Elongation at break: Tested in accordance with the method specified in GB / T 10654.

[0129] Impact absorption: Tested in accordance with the method specified in GB / T 36246.

[0130] TVOC emission: Tested in accordance with the method specified in GB / T 36246.

[0131] The test results are shown in Table 1.

[0132] Table 1 Performance test results of the embodiments and comparative examples

[0133]

[0134]

[0135] The embodiment achieves performance improvement through multi-dimensional collaborative design: first, the high specific surface area and porous structure of silica aerogel powder effectively adsorb residual pollutants in DPU waste during the pretreatment stage, reducing subsequent TVOC release; second, the abundant hydroxyl groups on the aerogel surface form hydrogen bonds with the silane coupling agent, which enhances the interfacial bonding between the waste particles and the modifier, and promotes the grafting reaction to generate stable chemical bonds; third, the low thermal conductivity of the aerogel delays the aging of the matrix, while its nano-network structure expands the pores through the "micro-explosion effect" during microwave treatment, releasing more active sites and strengthening the π-π conjugation effect with the polyurethane matrix; finally, the lightweight characteristics and rigid support of the aerogel balance the toughness and strength of the material, and comprehensively improve the tensile strength, elongation at break and impact absorption performance.

[0136] Compared with Example 1, Comparative Example 1 (no filler): lacks the physical support and interface reinforcement of aerogel or calcium carbonate, and the DPU waste particles rely solely on their own surface modification for bonding, resulting in weak interface forces and significantly reduced mechanical properties and impact absorption. At the same time, the porous adsorption without fillers increases the amount of pollutants remaining and TVOC increases. Comparative Example 2 (air carbonization): The high oxygen content leads to insufficient oxidation of the carbonized layer, and the graphene-like structure (sp 2Hybrid carbon is underdeveloped, resulting in weak π-π conjugation with the polyurethane matrix; the residual amount of unpyrolyzed pollutants is high, leading to a surge in TVOC; the oxidizing environment may also damage the molecular chain, weakening mechanical properties. Comparative Example 3 (small particle size + high temperature and short time carbonization): DPU particles that are too small (0.2mm) are prone to overburning and agglomeration at 280°C, forming a hard shell on the surface that hinders the exposure of grafting sites; a short holding time (20 minutes) results in a thin carbonized layer with few active sites, weak interfacial bonding, and reduced mechanical properties and impact absorption; small particles with a high specific surface area adsorb pollutants but do not completely pyrolyze, resulting in high TVOC. Comparative Example 4 (large particle size + low temperature and long time carbonization): DPU particles that are too large (0.8mm) at 180°C have insufficient heat conduction, uneven internal carbonization (charred on the outside and tender on the inside), few surface active groups, and inadequate grafting reaction; a long holding time (100 minutes) results in a loose carbon layer, reduced adsorption capacity, and still high TVOC; large particles are difficult to disperse and prone to agglomeration, reducing material uniformity. Comparative Example 5 (Microwave Parameter Mismatch): 1400W high power was used to treat small-diameter (0.2mm) DPU particles. Local microwave energy overload caused pyrolysis / combustion of the carbon layer, structural damage (cracks / holes), and a reduction in active sites. Long-term microwave treatment (25 minutes) exacerbated the damage, weakened the interface bonding, and reduced mechanical properties and impact absorption. After the carbon layer was destroyed, the pollutant adsorption capacity decreased, but incomplete pyrolysis caused pollutants to release more TVOC. Comparative Example 6 (Carbonization Only, No Microwave): The carbonized layer did not effectively expand due to the lack of the microwave "micro-explosion effect", resulting in low porosity, few active sites, and limited grafting reaction. The dense carbon layer hindered the penetration of the modifier, weak interface bonding, low mechanical properties and impact absorption. The carbon layer did not expand, leaving more pollutants and a higher TVOC. Comparative Example 7 (direct microwave treatment without carbonization): The original DPU surface is inert (more non-polar groups), and there is no chemical bonding with the modifier. The grafting reaction relies solely on physical adsorption, and the bonding force is extremely weak. Microwaves only soften the surface but cannot form graphene-like or active sites. The mechanical properties (tensile strength, elongation at break) are extremely low. The original pollutants are not pyrolyzed, and TVOC is the highest. Comparative Example 8 (no surface modification): The coupling agent modification is omitted, the DPU surface active groups are not chemically bonded to the modifier, and the grafting reaction is weak. The carbonized layer sp 2The π-π conjugation between hybrid carbon and polyurethane is not enhanced, the interface bonding force is significantly reduced, and the mechanical properties and impact absorption are greatly reduced; the unmodified surface affects the pore expansion of the carbon layer, the adsorption of pollutants is weak, and the TVOC is high. Comparative Example 9 (no banburying): the modified particles are simply mixed with TPU, without high shear dispersion and interface entanglement, and the particles are easy to agglomerate; the interface does not have the dual effect of "physical entanglement + chemical bonding", and the mechanical properties and impact absorption are significantly reduced; uneven dispersion leads to local stress concentration, further reducing performance. Comparative Example 10 (microwave parameter mismatch): 400W low power is used to treat small particle size (0.2mm) DPU particles, the microwave energy absorption is insufficient, the carbon layer pore expansion effect is poor (low porosity), and there are few active sites; the treatment time is too short (10min), the pollutants are not fully removed, the residual amount is high, and the TVOC is high; insufficient pore expansion makes it difficult for the modifier to penetrate into the carbon layer, the interface bonding is weak, and the mechanical properties and impact absorption are low. Comparative Example 11 (filler is calcium carbonate): Calcium carbonate is a solid particle with an inert surface (few hydroxyl groups), and its interfacial bonding with DPU or modifier is weaker than that of aerogel; it has no porous structure and weak ability to adsorb pollutants, and its TVOC is slightly higher; it has weak interfacial bonding with DPU, and is prone to friction and agglomeration during mixing / microwave mixing, which reduces the uniformity of the material, and its mechanical properties and impact absorption are slightly lower than those of Example 1.

Claims

1. A polyurethane plastic track composite material containing DPU waste, characterized in that: By weight, it is prepared by the following steps: By weight, Step (1) Preparation of pretreated waste particles: 100 parts by mass of DPU waste particles crushed to a particle size of 0.1 to 1 mm are mixed evenly with 5 to 50 parts by mass of silica aerogel powder, followed by surface carbonization treatment at a treatment temperature of 150 to 350° C. for 10 to 120 minutes, followed by microwave treatment at a microwave power of 300 to 1500 W for 1 to 30 minutes, and dispersion to obtain pretreated waste particles; Step (2) Preparation of modified waste particles: Surface modification of the pretreated waste particles is performed, followed by grafting reaction with a polyurethane monomer in the presence of a catalyst at a reaction temperature of 40 to 90° C. for a reaction time of 0.5 to 5 hours to obtain modified waste particles; Step (3) Preparation of composite material: 100 parts by mass of modified waste particles are mixed with 20 to 200 parts by mass of plastic polyurethane base material, and the mixture is extruded and granulated to obtain a polyurethane plastic runway composite material.

2. The polyurethane plastic track composite material containing DPU waste according to claim 1, characterized in that: The silica aerogel powder in step (1) has a particle size of 1 to 100 μm.

3. The polyurethane plastic track composite material containing DPU waste according to claim 1, characterized in that: The surface carbonization treatment in step (1) is carried out in an inert atmosphere or a vacuum environment, and the oxygen volume concentration is less than 0.5%.

4. The polyurethane plastic track composite material containing DPU waste according to claim 1, characterized in that: The surface modification treatment in step (2) is performed by using at least one of a silane coupling agent, a titanate coupling agent or plasma treatment.

5. The polyurethane plastic track composite material containing DPU waste according to claim 1, characterized in that: The polyurethane monomer in step (2) is a mixture of an isocyanate compound and a polyol compound, wherein the isocyanate compound includes at least one of toluene diisocyanate, diphenylmethane diisocyanate, and isophorone diisocyanate, and the polyol compound is a polyether polyol or a polyester polyol.

6. The polyurethane plastic track composite material containing DPU waste according to claim 1, characterized in that: The amount of polyurethane monomer added in step (2) is 1% to 20% of the mass of the polyurethane waste particles.

7. The polyurethane plastic track composite material containing DPU waste according to claim 1, characterized in that: The catalyst in step (2) is an organic tin catalyst or an amine catalyst, and its usage is 0.1% to 5% of the mass of the polyurethane monomer.

8. The polyurethane plastic track composite material containing DPU waste according to claim 1, characterized in that: The plastic polyurethane base material in step (3) is thermoplastic polyurethane or polyurethane prepolymer.

9. The polyurethane plastic track composite material containing DPU waste according to claim 1, characterized in that: The extrusion temperature in step (3) is 120-200° C., and the granulation particle size is 1-10 mm.

10. A method for preparing a polyurethane plastic track composite material containing DPU waste according to any one of claims 1 to 9, characterized in that: The following steps are involved: Step (1) Preparation of pretreated waste particles: batching, mixing, carbonizing, and microwave treatment to obtain pretreated waste particles; Step (2) Preparation of modified waste particles: surface modification and grafting of pretreated waste particles to obtain modified waste particles; Step (3) Preparation of composite material: Modify waste material particles, extrude and granulate to obtain polyurethane plastic track composite material.

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