Cyclic utilization method of foamed polyurethane

Abstract

The invention discloses a cyclic utilization method of foamed polyurethane. The method comprises the following steps: S1, crushing leftover materials of the foamed polyurethane; s2, modifying the crushed foamed polyurethane leftover material with a silane surface modifier, and performing ultrasonic treatment to obtain modified powder; s3, uniformly mixing the polyurethane pre-material with a dispersing agent to obtain a mixture A; s4, adding the modified powder subjected to ultrasonic treatment into the mixture A, and uniformly mixing to obtain a mixture B; and S5, adding isocyanate into the mixture B, mixing and foaming to prepare the regenerated polyurethane. According to the invention, the waste polyurethane leftover material is used as a raw material, and the lightweight regenerated polyurethane foam with excellent mechanical properties is successfully prepared by using a method of changing the shape of the leftover material by using a physical method, further crushing by using ultrasonic waves, carrying out silane modification treatment and adding a small amount of compound to assist in changing the dispersity of the polyurethane leftover material powder in a system; waste utilization is achieved, and low-density and high-quality regenerated foam is prepared in a green and environment-friendly mode.

Description

Technical Field

[0001] The present invention relates to the technical field of polyurethane materials, in particular to a recycling method of foamed polyurethane. Background Art

[0002] Polyurethane foam has many excellent properties, such as acoustic properties, thermal insulation properties, cushioning properties, etc. For this reason, polyurethane foam is widely used and is often used as furniture padding, vehicle seat padding, refrigeration equipment insulation material, building insulation material, etc.

[0003] The production and preparation of polyurethane foam generates a large amount of waste and scrap. Traditionally, there are two methods for disposing of waste polyurethane foam: incineration and landfill. Incineration produces highly pungent, noxious gases that seriously pollute the atmosphere, while landfilling occupies a significant amount of land. Besides incineration and landfill, two main methods for recycling polyurethane foam scrap have been reported: physical and chemical. Six chemical recycling technologies can be summarized: alcoholysis, hydrolysis, alkaline hydrolysis, ammonia hydrolysis, thermal decomposition, and hydrocracking. In terms of the performance of the final product, alcoholysis, alkaline hydrolysis, and hydrolysis are preferred among chemical recycling methods. However, their disadvantages are that the reactions are carried out under high temperature and strong alkaline conditions, which require high equipment requirements, high production costs, and difficulty in industrialization. Chemical recycling methods still face challenges, such as the separation and purification of degradation products, recovery efficiency and reusability, and the suppression of toxic byproducts. Further research is needed, and the green recycling and efficient energy utilization of polyurethane foam waste are attracting increasing attention and research. Physical polyurethane recycling typically involves mechanical methods, such as solid-state shear extrusion and cryogenic grinding, to grind waste polyurethane foam into powdered particles. These particles are then incorporated into other materials or into polyurethane foam prepolymers. Incorporating these into polyurethane foam prepolymers is undoubtedly the simplest and most effective way to recycle polyurethane foam scraps. Current research has limited its use to recycling polyurethane scraps, resulting in weak functionality or a focus on improving mechanical properties while neglecting quality control. Research is still lacking on how to prevent the density of recycled polyurethane foam from increasing. Summary of the Invention

[0004] Based on the technical problems existing in the background technology, the present invention proposes a method for recycling foamed polyurethane. Using waste polyurethane scraps as raw materials, the scraps are physically changed in shape, further crushed by ultrasound, modified with silane, and a small amount of compounds are added to assist in changing the dispersion of the polyurethane scrap powder in the system. The method successfully prepares lightweight recycled polyurethane foam with excellent mechanical properties; it not only achieves waste utilization, but also achieves the green and environmentally friendly preparation of low-density, high-quality recycled foam.

[0005] The recycling method of the foamed polyurethane proposed by the present invention comprises the following steps:

[0006] S1: Crushing of polyurethane foam scraps;

[0007] S2: Modifying the crushed polyurethane foam scraps with a silane surface modifier and performing ultrasonic treatment to obtain a modified powder;

[0008] S3: uniformly mix the polyurethane dispersant to obtain a mixture A;

[0009] S4: adding the ultrasonically treated modified powder to mixture A and mixing to obtain mixture B;

[0010] S5: adding isocyanate to mixture B and mixing and foaming to obtain recycled polyurethane.

[0011] Preferably, the particle size of the crushed polyurethane foam scraps is 141.88-371.93 μm.

[0012] Preferably, the silane surface modifier contains at least one of an alkoxy group and an acetoxy group.

[0013] Preferably, the silane surface modifier is one or more of γ-aminopropyltriethoxysilane, N-β-aminoethyl-γ-aminopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-methacryloxypropyltrimethoxysilane.

[0014] Preferably, the ultrasonic treatment has a frequency range of 20-100 kHz, a time of 20-40 min, and a temperature of 20-30°C.

[0015] Preferably, the dispersant contains at least one of a hydroxyl group and a carboxyl group.

[0016] Preferably, the dispersant is one or more of polyethylene glycol, sodium fatty alcohol polyoxyethylene ether carboxylate, polyvinyl alcohol and polyvinyl butyral.

[0017] Preferably, the mass ratio of polyurethane material, isocyanate and foamed polyurethane scraps is 1:1.5-2.3:0.05-0.15.

[0018] Beneficial technical effects of the present invention:

[0019] (1) Filler particle size control and dispersion optimization: By precisely controlling the pulverization process of polyurethane scraps, the particle size distribution is uniform and within the optimal range; the ultrasonic pulverization process is adopted, and the micro-jet effect of ultrasound is utilized to further promote the dispersion uniformity of the powder, effectively avoiding the problem of pore structure differences caused by uneven particle size, thereby significantly improving the mechanical properties and structural uniformity of the recycled foam.

[0020] (2) Surface modification to enhance compatibility: Before adding the scrap powder, a high-power ultrasonic generator is used to modify the powder surface with silane. The modifier is uniformly attached to the filler surface through ultrasonic cavitation, which can effectively block polar hydroxyl groups and reduce the water absorption of the powder. At the same time, the silane modification can convert the isocyanate groups on the powder into carbamate or urea groups, inhibiting the agglomeration of the powder. A small amount of functional compounds containing hydroxyl or carboxyl groups are introduced as dispersants during the dispersion process. The hydroxyl or carboxyl groups in these compounds will form hydrogen bonds with the amino groups and a small amount of hydroxyl groups on the surface of the powder, inhibiting its premature reaction with the isocyanate groups, and synergistically promoting the effective combination of the scrap and the polyurethane matrix, significantly improving the interface compatibility and dispersibility between the filler and the matrix material, thereby reducing the apparent density of the recycled foam and improving the mechanical properties and interface bonding strength of the recycled foam.

[0021] (3) Synergistic improvement of lightweight and mechanical properties: By optimizing the addition ratio and dispersion process of scraps and combining with the introduction of a small amount of hydroxyl compounds, the problems of foaming difficulty and increased density caused by the introduction of fillers in traditional methods are solved, and the lightweight and mechanical properties of recycled foam are simultaneously improved.

[0022] (4) Green recycling and high reuse rate: The process conditions adopted by the present invention are mild and easy to operate, and the preparation of recycled foam can be completed in a relatively short time. Since no other foreign elements are introduced, the recycled polyurethane foam has good recyclability, further improving the resource utilization rate of polyurethane scraps, and effectively reducing resource waste and environmental pollution. This inventive method is more competitive in terms of environmental protection, performance optimization, process efficiency and application expansion, and is in line with the current trend of green manufacturing and sustainable development. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 SEM images of the polyurethane foam proposed in the present invention; a is Comparative Example 1, b is Example 1, c is Example 2, d is Example 3, e is Comparative Example 2, f is Comparative Example 3, g is Comparative Example 4, and h is Example 4;

[0024] Figure 2The pore size distribution diagram of the polyurethane foam proposed in the present invention; A is Comparative Example 1, B is Example 1, C is Example 2, D is Example 3, E is Comparative Example 2, F is Comparative Example 3, G is Comparative Example 4, and H is Example 4;

[0025] Figure 3 Thermogravimetric analysis diagrams of the polyurethane foams of Comparative Example 1, Example 3 and Example 4 proposed in the present invention;

[0026] Figure 4 This is a compression displacement-stress change diagram of the polyurethane foam proposed in the present invention;

[0027] Figure 5 This is the compression displacement-stress change diagram of polyurethane foam prepared with different dispersants proposed in the present invention. DETAILED DESCRIPTION

[0028] The present invention will be further explained below with reference to specific embodiments.

[0029] The performance parameter determination method of the polyurethane foam in the present invention is as follows:

[0030] (1) Apparent density: Cut the foam into 1 cubic centimeter pieces and weigh them on a tray balance, record them as m (unit: g), then the density is equal to m*10 3 Kg / m 3 .

[0031] (2) Expansion rate: The volume is measured by the water displacement method. When the foam is completely immersed in water, the reading V on the electronic balance is the volume of the foam. Divide V by the volume of pure polyurethane foam V0 to obtain the expansion rate of the foam. Assume that the expansion rate of pure polyurethane foam is 100%.

[0032] (3) Water absorption: Sample size is 10 mm x 10 mm x 10 mm. Dry in a 60°C oven for 24 hours, and measure the mass m0. Then soak in deionized water at room temperature for 96 hours, and measure the mass m1. Water absorption = [(m1 - m0) / m0] * 100%.

[0033] (4) Compressive strength: The electronic universal material testing machine compresses the sample at a rate of 20% of the initial thickness per minute until the sample thickness becomes 85% of the initial thickness, and the maximum compressive strength of the sample is taken.

[0034] (5) The cell surface morphology was observed using a scanning electron microscope. The instrument parameters were as follows: secondary electron resolution: 1.4 nm (1 kV, deceleration mode); 1.0 nm (15 kV), magnification: 20 to 800,000 times, acceleration voltage: 0.5 to 30 kV, and detection current: 0.3 to 22 nA.

[0035] (6) The pore size was collected and calculated using the software NanoMeasurer on the pore SEM image to obtain the pore size distribution and the average pore size of the foam. The average pore size calculation formula is dave = ∑(di*Fi), (di: pore size, Fi: frequency of occurrence).

[0036] The proportions mentioned in the present invention are all proportions to the amount of material A.

[0037] The polyurethane in the embodiments of the present invention is purchased from Chongqing Weibo New Materials Co., Ltd., and the other raw materials are also commercially available.

[0038] Example 1

[0039] Cut 2g of polyurethane foam scraps into small pieces and grind them into flocculent powder in a grinder for 90 seconds. Weigh 4.72g of the polyurethane stock and 0.236g of the powder. Add the powder to the polyurethane stock in small increments, stirring while adding. Manually stir until uniform, obtaining Mixture A. Stir Mixture A with a handheld blender at a rate of 2800 rpm for 30 seconds. Add 7.08g of isocyanate to Mixture A and stir rapidly at a rate of 2800 rpm for 20 seconds. The reaction temperature is 30°C. The foaming reaction is complete when the foam volume no longer increases and no gas is generated, yielding Regenerated Polyurethane Foam 1.

[0040] Example 2

[0041] Cut 2g of polyurethane foam scraps into small pieces and grind them into flocculent powder in a grinder for 90 seconds. Weigh 4.72g of the polyurethane stock and 0.472g of the powder. Add the powder to the polyurethane stock in small increments, stirring while adding. Manually stir until uniform, to obtain Mixture A. Stir Mixture A with a handheld blender at a rate of 2800 rpm for 30 seconds. Add 7.08g of isocyanate to Mixture A and stir rapidly at a rate of 2800 rpm for 20 seconds. The reaction temperature is 30°C. The foaming reaction is complete when the foam volume no longer increases and no gas is generated, yielding Regenerated Polyurethane Foam 2.

[0042] Example 3

[0043] Cut 2g of polyurethane foam scraps into small pieces and grind them into flocculent powder in a grinder for 90 seconds. Weigh 4.72g of the polyurethane stock and 0.708g of the powder. Add the powder to the polyurethane stock in small increments, stirring while adding. Manually stir until uniform, to obtain Mixture A. Stir Mixture A with a handheld blender at a rate of 2800 rpm for 30 seconds. Add 7.08g of isocyanate to Mixture A and stir rapidly at a rate of 2800 rpm for 20 seconds. The reaction temperature is 30°C. The foaming reaction is complete when the foam volume no longer increases and no gas is generated, yielding Regenerated Polyurethane Foam 3.

[0044] Example 4

[0045] Take 2 g of polyurethane foam scraps, cut them into small pieces, put them into a grinder and grind them into flocculent powder for 90 seconds; take 2 g of the powder into a round-bottom flask, add 0.15 g of γ-aminopropyltriethoxysilane and 100 mL of DMF and mix them evenly; perform ultrasonic treatment in an ultrasonic generator with an ultrasonic frequency of 50 kHz; filter, remove DMF by washing with deionized water multiple times; and dry at 45°C for 24 hours to obtain a modified powder.

[0046] Weigh 4.72g of polyurethane material, add 0.8% of the dispersant polyvinyl butyral (PVB) to the polyurethane material, and stir until uniformly mixed to obtain Mixture A. Weigh 0.708g of the modified powder and add it to Mixture A in small portions, stirring while adding. Manually stir until uniformly mixed to obtain Mixture B. Stir Mixture B using a handheld blender at a rate of 2800 rpm for 30 seconds. Add 7.08g of isocyanate to Mixture B and stir rapidly at a rate of 2800 rpm for 20 seconds. The reaction temperature is 30°C. The foaming reaction is terminated when the foam volume no longer increases and no gas is generated, yielding Regenerated Polyurethane Foam 4.

[0047] Example 5

[0048] Take 2 g of polyurethane foam scraps, cut them into small pieces, put them into a grinder and grind them into flocculent powder for 90 seconds; take 2 g of the powder into a round-bottom flask, add 0.15 g of γ-aminopropyltriethoxysilane and 100 mL of DMF and mix them evenly; perform ultrasonic treatment in an ultrasonic generator with an ultrasonic frequency of 50 kHz; filter, remove DMF by washing with deionized water multiple times; and dry at 45°C for 24 hours to obtain a modified powder.

[0049] Weigh 4.72g of polyurethane material, add 3% of a dispersant, sodium fatty alcohol polyoxyethylene ether carboxylate, to the polyurethane material, and stir until uniformly mixed to obtain Mixture A. Weigh 0.708g of modified powder and add it to Mixture A in small portions, stirring while adding. Manually stir until uniformly mixed to obtain Mixture B. Stir Mixture B using a handheld blender at a rate of 2800 rpm for 30 seconds. Add 7.08g of isocyanate to Mixture B and stir rapidly at a rate of 2800 rpm for 20 seconds. The reaction temperature is 30°C. The foaming reaction is terminated when the foam volume no longer increases and no gas is generated, yielding Regenerated Polyurethane Foam 5.

[0050] Example 6

[0051] Take 2 g of polyurethane foam scraps, cut them into small pieces, put them into a grinder and grind them into flocculent powder for 90 seconds; take 2 g of the powder into a round-bottom flask, add 0.15 g of γ-aminopropyltriethoxysilane and 100 mL of DMF and mix them evenly; perform ultrasonic treatment in an ultrasonic generator with an ultrasonic frequency of 50 kHz; filter, remove DMF by washing with deionized water multiple times; and dry at 45°C for 24 hours to obtain a modified powder.

[0052] 4.72g of polyurethane material was weighed, and 2% of the dispersant polyvinyl alcohol (PVA, solvent: DMF, mass volume ratio of PVA to DMF: 1:10) was added to the polyurethane material and stirred to obtain mixture A. 0.708g of modified powder was weighed and added to mixture A in small amounts and multiple times, stirring while adding. Mixture B was obtained by manual stirring. Mixture B was stirred using a handheld blender at a stirring rate of 2800 rpm for 30 seconds. 7.08g of isocyanate was added to mixture B and stirred rapidly at a stirring rate of 2800 rpm for 20 seconds. The reaction temperature was 30°C. The foaming reaction was terminated when the foam volume no longer increased and no gas was generated, resulting in regenerated polyurethane foam 6.

[0053] Comparative Example 1

[0054] 4.72 g of polyurethane was weighed, and 7.08 g of isocyanate was added and mixed. The mixture was stirred rapidly at a stirring rate of 2800 / min for 20 s at a reaction temperature of 30° C. A foaming reaction was performed to obtain polyurethane foam 7.

[0055] Comparative Example 2

[0056] Cut 2g of polyurethane foam scraps into small pieces and grind them into flocculent powder in a grinder for 90 seconds. Weigh 4.72g of the polyurethane stock and 0.7552g of the powder. Add the powder to the polyurethane stock in small increments, stirring while adding. Manually stir until uniformly mixed to obtain Mixture A. Stir Mixture A with a handheld blender at a rate of 2800 rpm for 30 seconds. Add 7.08g of isocyanate to Mixture A and stir rapidly at a rate of 2800 rpm for 20 seconds. The reaction temperature is 30°C. The foaming reaction is complete when the foam volume no longer increases and no gas is generated, yielding Regenerated Polyurethane Foam 8.

[0057] Comparative Example 3

[0058] 2g of polyurethane foam scraps were cut into small pieces and placed in a grinder for 60 seconds to form a flocculent powder. 4.72g of the polyurethane stock and 0.708g of the powder were weighed and added to the polyurethane stock in small portions, stirring the mixture manually until uniform. Mixture A was then stirred with a handheld blender at a rate of 2800 rpm for 30 seconds. 7.08g of isocyanate was added to the mixture and stirred rapidly at a rate of 2800 rpm for 20 seconds. The reaction temperature was 30°C. The foaming reaction was terminated when the foam volume ceased to increase and gas generation ceased, yielding recycled polyurethane foam 9.

[0059] Comparative Example 4

[0060] 2g of polyurethane foam scraps were cut into small pieces and placed in a grinder for 120 seconds to form a flocculent powder. 4.72g of the polyurethane stock and 0.708g of the powder were weighed and added to the polyurethane stock in small increments, stirring the mixture manually until uniformly mixed to obtain Mixture A. Mixture A was stirred with a handheld blender at a rate of 2800 rpm for 30 seconds. 7.08g of isocyanate was added to Mixture A and stirred rapidly at a rate of 2800 rpm for 20 seconds. The reaction temperature was 30°C. The foaming reaction was terminated when the foam volume ceased to increase and gas generation ceased, yielding Regenerated Polyurethane Foam 10.

[0061] Comparative Example 5

[0062] Take 2 g of polyurethane foam scraps, cut them into small pieces, put them into a grinder and grind them into flocculent powder for 90 seconds; take 2 g of the powder into a round-bottom flask, add 0.15 g of γ-aminopropyltriethoxysilane and 100 mL of DMF and mix them evenly; perform ultrasonic treatment in an ultrasonic generator with an ultrasonic frequency of 50 kHz; filter, remove DMF by washing with deionized water multiple times; and dry at 45°C for 24 hours to obtain a modified powder.

[0063] Weigh 4.72g of polyurethane material and 0.708g of modified powder. Add the powder to the polyurethane material in small increments, stirring while adding. Manually stir until uniformly mixed to obtain Mixture A. Stir Mixture A using a handheld blender at a rate of 2800 rpm for 30 seconds. Add 7.08g of isocyanate to Mixture A and stir rapidly at a rate of 2800 rpm for 20 seconds. The reaction temperature is 30°C. The foaming reaction is complete when the foam volume no longer increases and no gas is generated, yielding regenerated polyurethane foam 11.

[0064] Comparative Example 6

[0065] 2g of polyurethane foam scraps were cut into small pieces and placed in a grinder for 90 seconds to pulverize into flocculent powder. 4.72g of polyurethane material was weighed, 0.8% of the dispersant polyvinyl butyral (PVB) was added to the polyurethane material, and stirred evenly to obtain Mixture A. 0.708g of powder was weighed and added to Mixture A in small amounts and multiple times, stirring while adding. Mixture B was manually stirred to obtain Mixture B. Mixture B was stirred using a handheld blender at a stirring rate of 2800 rpm for 30 seconds. 7.08g of isocyanate was added to Mixture B and mixed rapidly at a stirring rate of 2800 rpm for 20 seconds. The reaction temperature was 30°C. When the foam volume no longer increased and no gas was generated, the foaming reaction was completed, and regenerated polyurethane foam 12 was obtained.

[0066] The properties of the polyurethane foams prepared in Examples 1-6 and Comparative Examples 1-6 were measured, and the results are shown in Table 1. The foaming rate of Comparative Example 1 is 100%, and the foaming rates of Examples 1-6 and Comparative Examples 2-6 are relative to the foaming rate of Comparative Example 1.

[0067] Table 1 Polyurethane foam performance test results

[0068]

[0069] As shown in Table 1, the expansion ratios of polyurethane foams in Examples 1-3 and Comparative Example 2 are lower than the expansion ratios of polyurethane foams in Comparative Example 1, and along with the increase of the amount of polyurethane scrap, the foaming effect is worse. The expansion ratios of polyurethane foams in Examples 4-6 are higher than the expansion ratios of polyurethane foams in Example 3, and are higher than or equal to the polyurethane foam expansion ratio in Comparative Example 1, which has shown that adding a dispersant composite modification after the silane-modified powder is conducive to foaming. The regenerated polyurethane foam prepared in the present invention contains a higher content of polyurethane foam scrap, effectively achieving waste utilization of scrap, solving the problem of foaming difficulty, and making scrap play the effect of reinforcing the polyurethane foam, improving compression strength. From the results of Comparative Examples 5, 6, Example 3, and 4, it can be seen that only silane modification of the powder greatly reduces the apparent density of the foam, but also greatly reduces the compressive strength of the foam; adding only a dispersant reduces the apparent density of the foam, but the apparent density reduction is not obvious, and the compressive strength is enhanced; the foam obtained by adding a dispersant after modifying the powder not only greatly reduces the apparent density, but also further improves the compressive performance, and the foaming effect of recycling is the best. From the results of Example 4, Example 5, and Example 6, it can be seen that different dispersants have different catalytic effects on the foaming effect, among which polyvinyl alcohol has the best foaming effect, and the other two are less effective, but all have a good effect on polyurethane foaming. Among them, the compressive strength of polyvinyl butyral foaming is the best. From Comparative Example 2, it can be seen that although the compressive strength of the polyurethane foam scraps is increased, the foaming rate is greatly reduced, and its apparent density increases, which illustrates that adding a dispersant after silane modification of the powder is conducive to reducing the apparent density of the foam. The apparent density of the polyurethane foam in Example 3 is lower than that in Comparative Example 3 and Comparative Example 4. It can be seen that when the particle size of the polyurethane scrap powder is reduced to a certain extent, the apparent density of the foam will increase, thereby increasing the weight of the foam, and the compressive strength will be relatively reduced, and the overall foaming effect will deteriorate.

[0070] Depend on Figure 1 SEM images of foam and Figure 2 The cell distribution diagram shows that as the amount of polyurethane foam scrap increases, the average pore size decreases. When the scrap reaches a certain level, the average pore size actually increases, indicating cell rupture. Powder particle size also affects cell size distribution. Powder particles that are too large or too small will cause cell rupture, resulting in large pores. Without dispersant, the pore size of foam is primarily distributed in a small area and fluctuates widely. However, with dispersant, the range of pore size variation is reduced, resulting in a more uniform pore size.

[0071] Figure 3It can be seen from the thermogravimetric analysis diagram and the thermogravimetric parameters in Table 2 (Comparative Example 1, Example 3 and Example 4) that the addition of polyurethane scraps will cause the temperature corresponding to 5% weight loss of the foam material to decrease, and the addition of dispersant can greatly increase the temperatures corresponding to 5% and 50% weight loss of the material, that is, the addition of dispersant effectively enhances the thermal stability of the foam.

[0072] Table 2 Thermogravimetric parameters of polyurethane foam

[0073]

[0074] Figure 4 From the compressive stress-displacement diagram, it can be seen that the compressive strength of the foams with different amounts of polyurethane scraps is greater than that of pure polyurethane foam, indicating that the recycled polyurethane foam prepared by this method has good compressive resistance. Figure 5 The compressive stress-displacement diagram shows that different dispersants also have different effects on the compressive performance.

[0075] Although the embodiments of the present application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the present application. The scope of the present application is defined by the appended claims and their equivalents, and all should be included in the scope of protection of the present application.

Claims

1. A method for recycling polyurethane foam, characterized in that: The steps are as follows: S1: Crushing of polyurethane foam scraps; S2: Modifying the crushed polyurethane foam scraps with a silane surface modifier and performing ultrasonic treatment to obtain a modified powder; S3: uniformly mixing the polyurethane material and the dispersant to obtain a mixture A; S4: adding the ultrasonically treated modified powder to mixture A and mixing to obtain mixture B; S5: adding isocyanate to mixture B and mixing and foaming to obtain recycled polyurethane.

2. The method for recycling polyurethane foam according to claim 1, wherein: The particle size of the crushed polyurethane foam scraps is 141.88-371.93 μm.

3. The recycling method of polyurethane foam according to claim 1, characterized in that: The silane surface modifier contains at least one of an alkoxy group and an acetoxy group.

4. The method for recycling polyurethane foam according to claim 3, wherein: The silane surface modifier is one or more of γ-aminopropyltriethoxysilane, N-β-aminoethyl-γ-aminopropyltrimethoxysilane, γ-glycidyloxypropyltrimethoxysilane and γ-methacryloxypropyltrimethoxysilane.

5. The method for recycling polyurethane foam according to claim 1, wherein: The frequency range of ultrasonic treatment is 20-100 kHz, the time is 20-40 min, and the temperature is 20-30°C.

6. The method for recycling polyurethane foam according to claim 1, wherein: The dispersant contains at least one of a hydroxyl group and a carboxyl group.

7. The method for recycling polyurethane foam according to claim 6, wherein: The dispersant is one or more of polyethylene glycol, sodium fatty alcohol polyoxyethylene ether carboxylate, polyvinyl alcohol and polyvinyl butyral.

8. The method for recycling polyurethane foam according to claim 1, wherein: The mass ratio of polyurethane material, isocyanate and foamed polyurethane scraps is 1:1.5-2.3:0.05-0.15.

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