A method for recycling polyurethane foam based on acetone oxime

Abstract

The application discloses a method for recycling polyurethane foam based on acetone oxime, which comprises the following steps: (1) adding acetone oxime into polyurethane foam to carry out a degradation reaction, so as to obtain a degradation product; (2) dispersing the degradation product obtained in step (1) into acetone oxime, heating to above the melting point of acetone oxime to carry out melting, and then cooling to below the melting point of acetone oxime, so as to obtain a mixture; and (3) carrying out vacuum sublimation on the mixture obtained in step (2), so as to obtain newly generated polyurethane foam. The method provided by the application can recycle polyurethane foam waste into new foam or 3D printing products without special molecular structure design, without changing existing production equipment and without consuming any reagent.

Description

Technical Field

[0001] This invention relates to the field of polyurethane foam recycling technology, and more specifically to a method for recycling polyurethane foam based on acetone oxime. Background Technology

[0002] Polyurethane offers a high degree of freedom in structural design and a wide range of adjustable performance, and is widely used in our lives in the form of foams, adhesives, sealants, leather, coatings, fibers, and elastomers. It is reported that in 2019, the global annual production of polyurethane reached 29 million tons (https: / / plasticseurope.org / knowledge-hub / plastics-the-facts-2020 / :Plastics Europe.Plastics-the facts 2020.Available online:). Foam, as the most important product form of polyurethane, accounts for approximately 67% of polyurethane production and is widely used in cushions, mattresses, pillows, sofas, and thermal and sound insulation materials for buildings and refrigerators (Y. Deng, et al. J. Environ. Manage. 2021, 278:111527. D. Simon, et al. Waste Manage. 2018, 76:147-171). Such a large production volume is accompanied by the challenge of disposing of a large amount of waste.

[0003] To address the challenges of waste disposal, experts and scholars have conducted extensive research. Traditional physical recycling methods involve hot pressing or directly using the pulverized waste as filler; these methods are simple, but the performance and economic value of the recycled products are usually low, severely limiting their application. Traditional chemical recycling methods degrade polyurethane through processes such as alcoholysis and ammonolysis, recovering the initial raw materials; however, these methods consume large amounts of reagents and can only recover a portion of the raw material—polyol. Emerging chemical recycling methods can reconstruct reversible bonds, giving the material the ability to be reprocessed; however, these methods usually require special molecular structure design, and the form of the recycled products is generally limited to solid films (X. Wang, et al. Green Chem. 2021, 23:307-313). All these factors have prevented current recycling methods from reaching the stage of large-scale implementation. Summary of the Invention

[0004] The purpose of this invention is to provide a method for recycling polyurethane foam based on acetone oxime, which requires no special molecular structure design, no change to existing production equipment, and no consumption of any reagents, and recycles polyurethane foam waste into new foam and 3D printed products.

[0005] This invention provides the following technical solution:

[0006] A method for recycling polyurethane foam based on acetone oxime, the method comprising the following steps:

[0007] (1) Add acetone oxime to polyurethane foam to carry out degradation reaction and obtain degradation products;

[0008] (2) Disperse the degradation product obtained in step (1) into acetone oxime, heat it to above the melting point of acetone oxime to melt it, and then cool it to below the melting point of acetone oxime to obtain a mixture;

[0009] (3) The mixture obtained in step (2) is subjected to vacuum sublimation to obtain newly generated polyurethane foam.

[0010] The present invention targets the recycling of commercial polyurethane foam. On the basis of degrading and recycling polyurethane foam waste, it further utilizes it into new foam and 3D printed products through melting, cooling and vacuum sublimation.

[0011] In step (1), the amount of acetone oxime added is 0.1-100 times the mass of polyurethane foam, the degradation temperature is 50-300℃, and the degradation time is 5min-10h.

[0012] In step (1), during the degradation reaction, the urethane bonds, urea bonds, and biuret bonds in the polyurethane foam react with acetone oxime; the functional groups of the degradation products are hydroxyl, amino, urea, blocked isocyanate, etc., which are groups that can participate in the reaction and reconstruct the molecular network. The degradation products are functional oligomers and / or small molecules, and the oligomers are linear, branched, or hyperbranched macromolecules.

[0013] In step (2), the melting temperature is 60-200℃ and the cooling temperature is below 60℃.

[0014] In step (2), the mixture comprises the crystalline phase of acetone oxime and degradation products discharged from the crystalline phase of acetone oxime.

[0015] In step (2), acetone oxime is released during sublimation and can be recovered by condensation.

[0016] In step (2), after the degradation reaction is complete, the functional degradation products are dispersed in an excess of acetone oxime. The mixture is heated above the melting point of acetone oxime (60°C) to melt the entire degradation system and pour it into a mold. Then, it is cooled to below 60°C to allow the acetone oxime to crystallize; at this point, the functional polymer is expelled from the crystalline phase of the acetone oxime.

[0017] In step (3), the temperature of vacuum sublimation is 80-250℃, the time is 1min-24h, and the vacuum degree is 0.001-0.1MPa.

[0018] In step (3), the density of the newly generated polyurethane foam is 5-1200 kg / m³. 3 The porosity is 1-99%.

[0019] In step (3), the preparation of the new polyurethane foam is mainly accomplished through vacuum sublimation and its accompanying crosslinking reaction. Specifically, vacuum sublimation can obtain a porous structure, which is accompanied by the crosslinking reaction of functional degradation products: under vacuum conditions, the hydroxyl, amino, and urea bonds of the functional degradation products react with the blocked isocyanate to form urethane bonds, urea bonds, and biuret bonds, thereby reconstructing its crosslinking network. The crosslinking reaction can also support the porous structure generated by vacuum sublimation.

[0020] The method for recycling polyurethane foam based on acetone oxime further includes: melting and pouring the foam into a mold, cooling and removing the mold, and then sublimating the foam under vacuum to obtain the molded polyurethane foam.

[0021] The method for recycling polyurethane foam based on acetone oxime further includes: adding the melted polyurethane foam to a 3D printer for extrusion molding, cooling it, and then performing vacuum sublimation to obtain the molded polyurethane foam / 3D printed product.

[0022] 3D printed products possess a multi-level structure, including macroscopic morphology, oriented filaments, interconnected porous structures along the filament direction, and interconnected porous structures between the filaments. The first two can be controlled through the 3D printer; the latter two can be controlled by altering the amount of acetone oxime, degradation temperature, degradation time, and the temperature, time, and vacuum level of vacuum sublimation. This multi-level structure can endow materials with a very broad range of adjustable properties, including density, porosity, and mechanical properties.

[0023] Furthermore, the performance of the newly generated foam and 3D printed products can also be adjusted by adding additives, including isocyanates, blocked isocyanates, epoxy, acryloyl chloride, carbonates, acrylates / methacrylates, vinyl, allyl, mercapto, polyols, amines and other reagents. The additives are added before the acetone oxime is cooled in step (2).

[0024] Compared with current recycling methods, the method provided by this invention has the following advantages: (1) It is suitable for all types of polyurethane foam, does not require special molecular structure design, and does not require changes to existing production equipment; (2) It does not require the consumption of any reagents; (3) The recycled products are new foam and 3D printed products, and the performance is adjustable over a very wide range. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the degradation reaction of polyurethane foam;

[0026] Figure 2 A schematic diagram of the reaction of degradation products and acetone oxime during melting, cooling and vacuum sublimation;

[0027] Figure 3 This is a schematic diagram of the cross-linking reaction of degradation products during vacuum sublimation;

[0028] Figure 4 This is a schematic diagram of the entire process of recycling polyurethane foam.

[0029] Figure 5 This is a schematic diagram illustrating the preparation of new low-density foam from recycled shaped polyurethane foam in Example 1.

[0030] Figure 6 This is a schematic diagram illustrating the preparation of new high-density foam from recycled shaped polyurethane foam in Example 2.

[0031] Figure 7 A schematic diagram illustrating the fabrication of 3D printed products using recycled polyurethane foam.

[0032] Figure 8 This is a schematic diagram illustrating the preparation of 3D printed products using recycled high-resilience polyurethane foam, as shown in Example 3. Detailed Implementation

[0033] The technical principle of the method for recycling polyurethane foam based on acetone oxime provided by this invention is as follows: Figures 1-3 The diagrams shown illustrate the degradation reaction of polyurethane foam, the melting, cooling, and vacuum sublimation of the degradation products and acetone oxime, and the crosslinking reaction of the degradation products during vacuum sublimation. The preparation process of the method for recycling polyurethane foam based on acetone oxime provided by this invention is as follows: Figure 4 As shown, the method provided by this invention does not require special molecular structure design, nor does it require changes to existing production equipment, and it does not require the consumption of any reagents, thus enabling the recycled product to be transformed into a new foam or 3D printed product.

[0034] The present invention will be further illustrated below with reference to specific embodiments. It should be noted that these embodiments are only used to enhance the understanding of the present invention and are not intended to limit the scope of the present invention.

[0035] Example 1: Recycling shaped polyurethane foam into new low-density foam

[0036] Raw material: Shaped polyurethane foam, density 60 kg / m³ 3 The product was provided by Yongyi Furniture Co., Ltd.; acetone oxime was purchased from McLean.

[0037] Degradation of shaped polyurethane foam: 10g of shaped polyurethane foam was pulverized and vacuum dried at 150°C for 5 min. Then, the vacuum valve was closed and acetone oxime (400g) was added. After heating at 150°C for 20 min, the shaped polyurethane foam was completely liquefied into a homogeneous solution.

[0038] Preparation of new foam: The degradation products were heated to 80°C to melt them and poured into a mold. Then, the mixture was cooled at room temperature for 10 minutes to allow the acetone oxime to crystallize into a solid. Afterward, the mold was removed, and the foam was sublimated at 130°C and a vacuum of 0.099 MPa for 2 hours to obtain new foam. Furthermore, the released acetone oxime was recovered by condensation during the sublimation process.

[0039] Performance characterization: The density of the newly formed low-density foam is 24 kg / m³. 3 The compressive modulus is 14 kPa. The compressive strength at 80% strain is 32 kPa. The morphology of shaped polyurethane foam and nascent low-density foam is as follows: Figure 5 As shown.

[0040] Example 2: Recycling shaped polyurethane foam into new high-density foam

[0041] Raw material: Shaped polyurethane foam, density 60 kg / m³ 3 The product was provided by Yongyi Furniture Co., Ltd.; acetone oxime was purchased from McLean.

[0042] Degradation of shaped polyurethane foam: 10g of shaped polyurethane foam was pulverized and vacuum dried at 150°C for 5 min. Then, the vacuum valve was closed and acetone oxime (20g) was added. After heating at 150°C for 120 min, the shaped polyurethane foam was completely liquefied into a homogeneous solution.

[0043] Preparation of new foam: The degradation products were heated to 80°C to melt them and poured into a mold. Then, the mixture was cooled at room temperature for 10 minutes to allow the acetone oxime to crystallize into a solid. Afterward, the mold was removed, and the foam was sublimated at 130°C and a vacuum of 0.099 MPa for 0.5 hours to obtain new foam. Furthermore, the released acetone oxime was recovered by condensation during the sublimation process.

[0044] Performance characterization: The density of the newly formed high-density foam is 352 kg / m³. 3 The compressive modulus is 208 kPa. The compressive strength at 80% strain is 2.26 MPa. The morphology of the shaped polyurethane foam and the nascent high-density foam are as follows: Figure 6 As shown.

[0045] Example 3: Recycling high-resilience polyurethane foam into 3D printed products

[0046] The preparation of 3D printed products is as follows: Figure 7 As shown, the degradation system is heated and melted (60-200℃), and then extruded under the control of a 3D printer. The extruded material rapidly crystallizes to form solid filaments. Following the 3D printer's program settings, the extruded filaments accumulate layer by layer, thus forming the corresponding morphology. Afterwards, vacuum sublimation (such as...) is performed. Figure 2 and Figure 3 (as shown), thus completing the curing process.

[0047] Specifically, in this embodiment:

[0048] Raw material: High-resilience polyurethane foam, density 35kg / m³ 3 The product was provided by Yongyi Furniture Co., Ltd.; acetone oxime was purchased from McLean.

[0049] Degradation of high-resilience polyurethane foam: 10g of high-resilience polyurethane foam was pulverized and vacuum dried at 150°C for 5 min. Then, the vacuum valve was closed, and 200g of acetone oxime was added. After heating at 150°C for 30 min, the shaped polyurethane foam was completely liquefied into a homogeneous solution.

[0050] Preparation of 3D printed products: The degradation products were heated to 65°C to melt them, and then 3D printed. Then, the products were sublimated at 150°C and a vacuum of 0.099 MPa for 1 hour to obtain new 3D printed products. Furthermore, during the sublimation process, the released acetone oxime was recovered through condensation. The morphology of the high-resilience polyurethane foam and the newly formed 3D printed products is as follows. Figure 8 As shown.

[0051] Recyclability: Following the method described in this embodiment, the newly generated 3D printed product is degraded and recycled again to make a new 3D printed product.

Claims

1. A method for recycling polyurethane foam based on acetone oxime, characterized in that, The method includes the following steps: (1) Acetone oxime was added to polyurethane foam to carry out a degradation reaction, and degradation products were obtained; (2) Disperse the degradation product obtained in step (1) into acetone oxime, heat it to above the melting point of acetone oxime to melt it, and then cool it to below the melting point of acetone oxime to obtain a mixture; (3) The mixture obtained in step (2) is subjected to vacuum sublimation to obtain newly generated polyurethane foam.

2. The method for recycling polyurethane foam based on acetone oxime according to claim 1, characterized in that, In step (1), the amount of acetone oxime added is 0.1-100 times the mass of polyurethane foam, the degradation temperature is 50-300℃, and the degradation time is 5min-10h.

3. The method for recycling polyurethane foam based on acetone oxime according to claim 1, characterized in that, In step (1), the functional groups of the degradation product are hydroxyl, amino, urea, and blocked isocyanate.

4. The method for recycling polyurethane foam based on acetone oxime according to claim 1, characterized in that, In step (2), the melting temperature is 60-200℃ and the cooling temperature is below 60℃.

5. The method for recycling polyurethane foam based on acetone oxime according to claim 1, characterized in that, In step (2), the mixture comprises the crystalline phase of acetone oxime and degradation products discharged from the crystalline phase of acetone oxime.

6. The method for recycling polyurethane foam based on acetone oxime according to claim 1, characterized in that, In step (2), an additive is added during melting, the additive being selected from cyanate esters, blocked isocyanates, epoxy, acryloyl chloride, carbonates, acrylates / methacrylates, vinyl, allyl, mercapto, polyols, and amines.

7. The method for recycling polyurethane foam based on acetone oxime according to claim 1, characterized in that, In step (3), the temperature of vacuum sublimation is 80-250℃, the time is 1min-24h, and the vacuum degree is 0.001-0.1MPa.

8. The method for recycling polyurethane foam based on acetone oxime according to claim 1, characterized in that, In step (3), the density of the newly generated polyurethane foam is 5-1200 kg / m³. 3 The porosity is 1-99%.

9. The method for recycling polyurethane foam based on acetone oxime according to any one of claims 1-8, characterized in that, After melting, the polyurethane foam is poured into a mold, cooled, and then removed from the mold. After vacuum sublimation, the molded polyurethane foam is obtained.

10. The method for recycling polyurethane foam based on acetone oxime according to any one of claims 1-8, characterized in that, After melting, the material is added to a 3D printer for extrusion molding. After cooling, it undergoes vacuum sublimation to obtain the molded polyurethane foam.

Images