Depolymerization method of waste polyurethane foam

Abstract

The invention provides a depolymerization method of waste polyurethane foam. The depolymerization method comprises the following steps: step 1, crushing the waste polyurethane foam; step 2, the crushed waste polyurethane foam and degradation liquid are mixed, the degradation liquid comprises polypropylene glycol, micromolecule glycol and a catalyst, and the mass of the polypropylene glycol and the mass of the micromolecule glycol are 1-2 times that of the waste polyurethane foam; and 3, carrying out a reaction on the mixed solution obtained in the step 2 at 170-220 DEG C to obtain a depolymerization product. According to the method, polypropylene glycol and micromolecule glycol are used for degrading the waste polyurethane foam at the same time, a degradation product does not need to be purified and can be directly used for producing the regenerated polyurethane foam, and the prepared regenerated polyurethane foam meets the requirements of household products. The method does not generate any dust, wastewater, waste residue, noise and the like, and has the advantages of simple process conditions, low equipment requirement, low cost, capability of preparing the regenerated polyurethane foam meeting the commodity requirement without separating and purifying the degradation product, and the like.

Description

Technical Field

[0001] The invention relates to the field of recycling of waste polyurethane foam, in particular to a depolymerization method of waste polyurethane foam. Background Art

[0002] Polyurethane foam materials are widely used in production and life such as construction, furniture, packaging, and auto parts due to their low density, low thermal conductivity, strong dimensional stability, and economic benefits. In the global consumption of polyurethane products, the consumption of foam materials accounts for nearly 60%. With the growing demand for polyurethane products, the amount of waste polyurethane has also increased. However, as a thermosetting plastic with a three-dimensional network structure, polyurethane waste is difficult to degrade under natural conditions, which has led to a series of environmental pollution problems. With the consumption of global fossil energy, recycling polyurethane to achieve resource recycling and reduce environmental pollution has attracted widespread attention from researchers around the world. The main methods for recycling waste polyurethane are physical recycling, energy recycling, chemical recycling, and biodegradation. The physical recycling method is simple and has low processing cost, but the raw materials are used in the manufacture of medium and low-end products, which is limited by technical requirements and has a small scope of application. Energy recovery, that is, incineration treatment, is currently the main way to treat waste polyurethane. Incineration can effectively recover a certain amount of energy and reduce the amount of waste. Although this treatment method is simple and effective, the combustion process is not sufficient, and harmful and toxic gases such as CO and NOx will be generated, which will pollute the atmospheric environment. Biodegradation of waste polyurethane involves breaking ester bonds under the action of enzymes secreted by microorganisms to produce oligomers and monomers. It is green, environmentally friendly and pollution-free, but it degrades slowly and requires high costs. It is still in the research and development stage. Chemical recycling is the degradation of waste polyurethane into small molecule compounds by chemical means, so that waste polyurethane is converted into valuable chemicals in order to achieve the purpose of value-added reuse. It is a feasible way to recycle waste polyurethane materials.

[0003] Glycolysis is the most widely used method for chemical recycling of polyurethane, and has been widely used in many fields, such as recycling hard foam, microporous elastomers for soles, and flexible elastomers. In terms of recycling hard sole materials and polyurethane foam, many countries have achieved the scale and industrialization of glycolysis. It is the only method that has been implemented on an industrial scale except for acid hydrolysis. The glycolysis of PU has the advantage of mild reaction conditions, and its temperature is generally between 160°C and 240°C. By utilizing the method of reacting small molecular alkyl glycol with polyurethane, low molecular polymers with hydroxyl groups, regenerated polyether polyols and diamines are obtained through ester exchange reactions. The glycolytic agent can be ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol and glycerol, etc., and the alcoholysis aid can be alcoholamine, tertiary amine, alkali metal hydroxide or organic / inorganic metal salt (such as KOH, CH 3 CHOOK, FeCl 3However, the residual diols produced by this method will preferentially react with isocyanates and interfere with the formation of foam. Although these residual small molecular diols can be separated with sufficient purity, it requires higher costs and complicated processes such as distillation or washing. In addition, as the separation process proceeds, it will inevitably cause the decomposition of polyols and the production of harmful aromatic amines, which also limits the reuse of recycled polyols in household products.

[0004] Therefore, this field still needs further research on the efficient depolymerization of waste polyurethane foam and the preparation of recycled polyurethane foam. Summary of the invention

[0005] The main purpose of the present invention is to provide a method for depolymerizing waste polyurethane foam, so as to overcome the defects of the prior art that the depolymerization of waste polyurethane foam requires cumbersome steps such as purification, complex process and high cost.

[0006] In order to achieve the above object, the present invention provides a method for depolymerizing waste polyurethane foam, comprising the following steps:

[0007] Step 1, crushing the waste polyurethane foam;

[0008] Step 2, mixing the crushed waste polyurethane foam with a degradation solution, wherein the degradation solution comprises polypropylene glycol, a small molecule glycol and a catalyst, and the mass of the polypropylene glycol and the small molecule glycol is 1 to 2 times the mass of the waste polyurethane foam;

[0009] Step 3, the mixed solution of step 2 is reacted at 170-220° C. to obtain a depolymerization product.

[0010] The method for depolymerizing waste polyurethane foam of the present invention further comprises step 4, wherein the depolymerization product obtained in step 3 is directly used as a raw material for preparing regenerated polyurethane foam.

[0011] The method for depolymerizing waste polyurethane foam of the present invention, wherein the step 4 is: mixing the depolymerization product obtained in step 3 with polyol and isocyanate to prepare regenerated polyurethane foam.

[0012] The method for depolymerizing waste polyurethane foam of the present invention comprises the following steps: the catalyst is at least one of potassium hydroxide, sodium hydroxide, cesium hydroxide, potassium acetate, sodium acetate, ferric chloride, sodium citrate, potassium carbonate and sodium carbonate; the amount of the catalyst is 0.01 to 2 times the mass of the waste polyurethane foam; and the number average molecular weight of polypropylene glycol is 3000 to 5000.

[0013] The method for depolymerizing waste polyurethane foam of the present invention, wherein the small molecule diol is at least one of ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 2,3-butanediol, diethylene glycol, dipropylene glycol, triethylene glycol, and 1,6-hexanediol; and the mass ratio of polypropylene glycol to small molecule diol is 1-20:1.

[0014] The method for depolymerizing waste polyurethane foam of the present invention comprises the following steps: the polyol is polypropylene glycol and the isocyanate is toluene diisocyanate.

[0015] In the method for depolymerizing waste polyurethane foam of the present invention, the amount of polyol added is 60-100 parts by mass, the amount of the depolymerization product obtained in step 3 added is 10-40 parts by mass, and the amount of isocyanate added is 40-70 parts by mass.

[0016] The method for depolymerizing waste polyurethane foam of the present invention further comprises adding a silicone oil stabilizer, an organic tin catalyst, a foaming agent and an alcohol amine catalyst when preparing the regenerated polyurethane foam.

[0017] The method for depolymerizing waste polyurethane foam of the present invention comprises the following steps: the amount of polyol added is 60-100 parts by mass, the amount of the depolymerization product obtained in step 3 added is 10-40 parts by mass, the amount of isocyanate added is 40-70 parts by mass, the amount of silicone oil stabilizer added is 0.6-1.5 parts by mass, the amount of organotin catalyst added is 0.2-1.8 parts by mass, the amount of foaming agent added is 2-5 parts by mass, and the amount of alcoholamine catalyst added is 0.2-1.8 parts by mass.

[0018] The method for depolymerizing waste polyurethane foam of the present invention comprises the following steps: the organic tin catalyst is at least one of stannous octoate, dibutyltin dilaurate and stannous octoate T9; the foaming agent is at least one of water and dichloromethane; and the alcoholamine catalyst is at least one of diethanolamine, triethanolamine, triethylamine and dipropanolamine.

[0019] Beneficial effects of the present invention:

[0020] The present invention uses polypropylene glycol and small molecule diols to degrade waste polyurethane foam at the same time, and the degradation products can be directly used for the production of regenerated polyurethane foam without purification operation, and the prepared regenerated polyurethane foam meets the requirements of household products. Compared with the existing polyurethane foam recovery method, the method of the present invention does not generate any dust, waste water, waste residue and noise, etc., has the advantages of simple process conditions, low equipment requirements, low cost, and the degradation products can be used to prepare regenerated polyurethane foam that meets the requirements of commodities without separation and purification.

[0021] The invention degrades waste polyurethane foam, has the advantages of easy and cheap catalyst, mild reaction conditions, few side reactions, environmental friendliness and good product yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 These are pictures of recycled polyurethane foams prepared with different contents of depolymerization products of the present invention. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below in conjunction with specific embodiments, and the implementation cases provided are only for illustrating the present invention, rather than for limiting the scope of the present invention. The implementation cases provided below can be used as a guide for further improvement by those of ordinary skill in the art, and do not constitute a limitation of the present invention in any way. Unless otherwise indicated, the raw materials, reagents, devices, instruments and equipment used in the embodiments of the present invention, etc., can all be obtained from commercial sources.

[0024] The present invention provides a method for depolymerizing waste polyurethane foam, comprising the following steps:

[0025] Step 1, crushing the waste polyurethane foam;

[0026] Step 2, mixing the crushed waste polyurethane foam with a degradation solution, wherein the degradation solution comprises polypropylene glycol, a small molecule glycol and a catalyst, and the mass of the polypropylene glycol and the small molecule glycol is 1 to 2 times the mass of the waste polyurethane foam;

[0027] Step 3, the mixed solution of step 2 is reacted at 170-220° C. to obtain a depolymerization product.

[0028] The invention uses polypropylene glycol and small molecule diols for the degradation of waste polyurethane foams at the same time, and the degradation products can be directly used for the production of regenerated polyurethane foams without purification operation, and the prepared regenerated polyurethane foams meet the requirements of household products.

[0029] The present invention does not specifically limit the source of the waste polyurethane foam, nor does it specifically limit the degree of crushing of the waste polyurethane foam, as long as it can be placed in a depolymerization device. Crushing can also allow the waste polyurethane foam to be fully mixed with the degradation liquid. In one embodiment, the crushed waste polyurethane foam is stored in a closed device.

[0030] Step 2 is to mix the crushed waste polyurethane foam with the degradation liquid.

[0031] Among them, the degradation liquid includes polypropylene glycol, small molecule glycol and catalyst, and the sum of the mass of polypropylene glycol and small molecule glycol is 1 to 2 times the mass of the waste polyurethane foam. In one embodiment, the number average molecular weight (Mn) of polypropylene glycol is 3000 to 5000, and the small molecule glycol refers to a glycol with a carbon number ≤ 6, which can be at least one of ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 2,3-butanediol, diethylene glycol, dipropylene glycol, triethylene glycol, and 1,6-hexanediol. In another embodiment, the catalyst is at least one of potassium hydroxide, sodium hydroxide, cesium hydroxide, potassium acetate, sodium acetate, ferric chloride, sodium citrate, potassium carbonate, and sodium carbonate; the amount of the catalyst is 0 to 2 times the mass of the waste polyurethane foam. In another embodiment, the mass ratio of polypropylene glycol to small molecule glycol is 1-20:1, further, it can be 5-15:1, and further, it can be 8-12:1.

[0032] The invention can further ensure that the degradation liquid can completely degrade the waste polyurethane foam while reducing the occurrence of side reactions by strictly controlling the types and proportions of polypropylene glycol and small molecule glycol.

[0033] Step 3 is to react the mixed solution of step 2 at 170-220° C. to obtain a depolymerized product. In one embodiment, stirring is performed during the reaction, and the reaction time is, for example, 0.5 h to 3.0 h, and further, can be 1.0 to 2.5 h.

[0034] In one embodiment, step 2 and step 3 are performed in a three-necked flask reactor, but the present invention is not limited thereto.

[0035] The depolymerization product obtained by the present invention no longer contains small molecule diols and can be directly used as a raw material to replace the raw material polyol for preparing polyurethane foam for preparing regenerated polyurethane foam without further purification. The prepared regenerated polyurethane foam can be used for household products.

[0036] In one embodiment, the depolymerization product obtained in step 3 is mixed with polyol and isocyanate to prepare the regenerated polyurethane foam. In another embodiment, when preparing the regenerated polyurethane foam, a silicone oil stabilizer, an organic tin catalyst, a blowing agent, and an alcohol amine catalyst are also added.

[0037] In one embodiment, when the regenerated polyurethane foam is prepared, the polyol is polypropylene glycol and the isocyanate is toluene diisocyanate. In another embodiment, when the regenerated polyurethane foam of the present invention is prepared, the amount of the polyol added is 60-100 parts by mass, the amount of the depolymerization product obtained in step 3 added is 10-40 parts by mass, and the amount of the isocyanate added is 40-70 parts by mass, that is, the mass ratio of the polyol, the depolymerization product, and the isocyanate added is 60-100:10-40:40-70. In another embodiment, when the regenerated polyurethane foam of the present invention is prepared, the amount of the silicone oil stabilizer added is 0.6-1.5 parts by mass, the amount of the organotin catalyst added is 0.2-1.8 parts by mass, the amount of the foaming agent added is 2-5 parts by mass, and the amount of the alcoholamine catalyst added is 0.2-1.8 parts by mass. In other words, the mass ratio of polyol, decomposition product, isocyanate, silicone oil stabilizer, organotin catalyst, blowing agent and amine catalyst added is 60-100: 10-40: 40-70: 0.6-1.5: 0.2-1.8: 2-5: 0.2-1.8.

[0038] In one embodiment, the organotin catalyst is at least one of stannous isooctanoate, dibutyltin dilaurate, and stannous octoate T9; the foaming agent is at least one of water and dichloromethane; the alcoholamine catalyst is at least one of diethanolamine, triethanolamine, triethylamine, and dipropanolamine. The present invention does not specifically limit the silicone oil stabilizer, and any conventional silicone oil stabilizer in the art may be used.

[0039] The present invention does not particularly limit the conditions for preparing the recycled polyurethane foam, and conventional conditions in the art may be used.

[0040] The recycled polyurethane foam prepared by the present invention can meet the requirements of various products and household products.

[0041] The technical solution of the present invention will be further described below through specific examples. In the examples, the waste polyurethane foam comes from polyurethane foam produced by a factory, and it needs to be crushed before degradation so that it can be put into a three-necked flask; the degradation product, i.e., the regenerated polyol, is characterized by its viscosity using a viscometer, and the hydroxyl value of the regenerated polyol is characterized by a hydroxyl value determination method.

[0042] The raw material polypropylene glycol used in the following examples and comparative examples is a commercially available product with a number average molecular weight of 3000-5000. The silicone oil stabilizer is produced by Oliron (Jining) Chemical Co., Ltd. and its model is L-580.

[0043] Example 1

[0044] 200g of waste polyurethane foam, 100g of polypropylene glycol, 100g of diethylene glycol, and 2g of sodium hydroxide were added to a 1000ml three-necked flask in sequence, reacted at 180°C for 2h, and cooled to room temperature to obtain regenerated polyol. The viscosity was 66700mPa s and the hydroxyl value was 128mgKOH / g.

[0045] Example 2

[0046] 200g of waste polyurethane foam, 200g of polypropylene glycol, 200g of diethylene glycol, and 2g of sodium hydroxide were added to a 1000ml three-necked flask in sequence, reacted at 180°C for 2h, and cooled to room temperature to obtain regenerated polyol. The viscosity was 8700mPa s and the hydroxyl value was 358mgKOH / g.

[0047] Example 3

[0048] 200g of waste polyurethane foam, 240g of polypropylene glycol, 60g of diethylene glycol, and 2g of sodium hydroxide were added to a 1000ml three-necked flask in sequence, reacted at 180°C for 2h, and cooled to room temperature to obtain regenerated polyol with a viscosity of 22700mPa s and a hydroxyl value of 82mgKOH / g.

[0049] Example 4

[0050] 200g of waste polyurethane foam, 270g of polypropylene glycol, 30g of diethylene glycol, and 2g of sodium hydroxide were added to a 1000ml three-necked flask in sequence, reacted at 180°C for 2h, and cooled to room temperature to obtain regenerated polyol. The viscosity was 22700mPa s and the hydroxyl value was 82mgKOH / g.

[0051] Example 5

[0052] 200g of waste polyurethane foam, 270g of polypropylene glycol, 30g of ethylene glycol, and 2g of sodium hydroxide were added to a 1000ml three-necked flask in sequence, reacted at 180°C for 2h, and cooled to room temperature to obtain regenerated polyol with a viscosity of 13700mPa s and a hydroxyl value of 105mgKOH / g.

[0053] Example 6

[0054] 200g of waste polyurethane foam, 270g of polypropylene glycol, 30g of 1,2-propylene glycol, and 2g of sodium hydroxide were added to a 1000ml three-necked flask in sequence, reacted at 180°C for 2h, and cooled to room temperature to obtain regenerated polyol with a viscosity of 15700mPa s and a hydroxyl value of 101mgKOH / g.

[0055] Example 7

[0056] 200g of waste polyurethane foam, 270g of polypropylene glycol, 30g of 1,4-butanediol and 2g of sodium hydroxide were added to a 1000ml three-necked flask in sequence, reacted at 180°C for 2h, and cooled to room temperature to obtain regenerated polyol with a viscosity of 25700mPa s and a hydroxyl value of 92mgKOH / g.

[0057] Example 8

[0058] 200g of waste polyurethane foam, 270g of polypropylene glycol, 30g of dipropylene glycol, and 2g of sodium hydroxide were added to a 1000ml three-necked flask in sequence, reacted at 180°C for 2h, and cooled to room temperature to obtain regenerated polyol. The viscosity was 35600mPa s and the hydroxyl value was 86mgKOH / g.

[0059] Example 9

[0060] 200g of waste polyurethane foam, 270g of polypropylene glycol, 30g of triethylene glycol, and 2g of sodium hydroxide were added to a 1000ml three-necked flask in sequence, reacted at 180°C for 2h, and cooled to room temperature to obtain regenerated polyol. The viscosity was 40100mPa s and the hydroxyl value was 82mgKOH / g.

[0061] Example 10

[0062] 200g of waste polyurethane foam, 270g of polypropylene glycol, 30g of 1,6-hexanediol and 2g of sodium hydroxide were added to a 1000ml three-necked flask in sequence, reacted at 180°C for 2h, and cooled to room temperature to obtain regenerated polyol with a viscosity of 48100mPa s and a hydroxyl value of 71mgKOH / g.

[0063] Embodiment 11

[0064] 200g of waste polyurethane foam, 270g of polypropylene glycol, 30g of diethylene glycol, and 2g of sodium hydroxide were added to a 1000ml three-necked flask in sequence, reacted at 220°C for 2h, and cooled to room temperature to obtain regenerated polyol. The viscosity was 13700mPa s and the hydroxyl value was 89mgKOH / g.

[0065] Example 12

[0066] 200g of waste polyurethane foam, 270g of polypropylene glycol, 30g of diethylene glycol, and 2g of sodium hydroxide were added to a 1000ml three-necked flask in sequence, reacted at 200°C for 2h, and cooled to room temperature to obtain regenerated polyol. The viscosity was 21600mPa s and the hydroxyl value was 86mgKOH / g.

[0067] Embodiment 13

[0068] 200g of waste polyurethane foam, 270g of polypropylene glycol, 30g of diethylene glycol, and 1g of sodium hydroxide were added to a 1000ml three-necked flask in sequence, reacted at 200°C for 2h, and cooled to room temperature to obtain regenerated polyol with a viscosity of 29600mPa s and a hydroxyl value of 75mgKOH / g.

[0069] Embodiment 14

[0070] 200g of waste polyurethane foam, 270g of polypropylene glycol, 30g of diethylene glycol, and 4g of sodium hydroxide were added to a 1000ml three-necked flask in sequence, reacted at 200°C for 2h, and cooled to room temperature to obtain regenerated polyol with a viscosity of 20800mPa s and a hydroxyl value of 71mgKOH / g.

[0071] Embodiment 15

[0072] 200g of waste polyurethane foam, 270g of polypropylene glycol, 30g of diethylene glycol, and 1g of sodium hydroxide were added to a 1000ml three-necked flask in sequence, reacted at 210°C for 1h, and cooled to room temperature to obtain regenerated polyol. The viscosity was 39600mPa s and the hydroxyl value was 88mgKOH / g.

[0073] Example 16

[0074] 200g of waste polyurethane foam, 270g of polypropylene glycol, 30g of diethylene glycol, and 1g of sodium hydroxide were added to a 1000ml three-necked flask in sequence, reacted at 200°C for 3h, and cooled to room temperature to obtain regenerated polyol with a viscosity of 16600mPa s and a hydroxyl value of 65mgKOH / g.

[0075] The regenerated polyol obtained in the above Examples 1-16 is directly used to prepare regenerated polyurethane foam, which includes the following components in parts by weight: 80 parts of polypropylene glycol, 20 parts of the above regenerated polyol, 3 parts of water, 1 part of silicone oil stabilizer, 0.6 parts of amine catalyst, 1 part of organotin catalyst, and 60 parts of toluene diisocyanate.

[0076] The amine catalyst is triethylamine, and the organotin catalyst is stannous isooctanoate.

[0077] Embodiment 17

[0078] This embodiment provides a method for preparing a recycled polyurethane foam, comprising the following components in parts by weight: 90 parts of polypropylene glycol, 10 parts of the recycled polyol obtained in the above embodiment 13, 3 parts of water, 1 part of a silicone oil stabilizer, 0.6 parts of an amine catalyst, 1 part of an organotin catalyst, and 60 parts of toluene diisocyanate.

[0079] The amine catalyst is triethylamine, and the organotin catalyst is stannous isooctanoate.

[0080] Embodiment 18

[0081] The present embodiment provides a method for preparing a regenerated polyurethane foam, comprising the following components in parts by weight: 70 parts of polypropylene glycol, 30 parts of the regenerated polyol obtained in the above embodiment 13, 2.5 parts of water, 1 part of a silicone oil stabilizer, 0.6 parts of an amine catalyst, 1 part of an organotin catalyst, and 60 parts of toluene diisocyanate.

[0082] The amine catalyst is triethylamine, and the organotin catalyst is stannous isooctanoate.

[0083] Embodiment 19

[0084] The present embodiment provides a method for preparing a regenerated polyurethane foam, comprising the following components in parts by weight: 60 parts of polypropylene glycol, 40 parts of the regenerated polyol obtained in the above embodiment 13, 2 parts of water, 1 part of a silicone oil stabilizer, 0.6 parts of an amine catalyst, 1 part of an organotin catalyst, and 60 parts of toluene diisocyanate.

[0085] The amine catalyst is triethylamine, and the organotin catalyst is stannous isooctanoate.

[0086] Embodiment 20

[0087] The present embodiment provides a method for preparing a regenerated polyurethane foam, comprising the following components in parts by weight: 70 parts of polypropylene glycol, 30 parts of the regenerated polyol obtained in the above embodiment 13, 3 parts of dichloromethane, 1 part of a silicone oil stabilizer, 0.6 parts of an amine catalyst, 1 part of an organotin catalyst, and 60 parts of toluene diisocyanate.

[0088] The amine catalyst is triethylamine, and the organotin catalyst is stannous isooctanoate.

[0089] Comparative Example 1

[0090] 200g of waste polyurethane foam, 400g of polypropylene glycol and 2g of sodium hydroxide were added to a 1000ml three-necked flask in sequence, reacted at 180°C for 2h, and cooled to room temperature to obtain regenerated polyol with a viscosity of 56700mPa s and a hydroxyl value of 58mgKOH / g.

[0091] Comparative Example 2

[0092] 200g of waste polyurethane foam, 300g of diethylene glycol and 1g of sodium hydroxide were added to a 1000ml three-necked flask in sequence, reacted at 200℃ for 2h, and cooled to room temperature to obtain regenerated polyol with a viscosity of 1600mPa s and a hydroxyl value of 353mgKOH / g.

[0093] Comparative Example 3

[0094] 200g of waste polyurethane foam, 270g of polypropylene glycol, 30g of diethylene glycol, and 0g of sodium hydroxide were added to a 1000ml three-necked flask in sequence, reacted at 200°C for 2h, and cooled to room temperature to obtain regenerated polyol. The viscosity was 68600mPa s and the hydroxyl value was 53mgKOH / g.

[0095] The regenerated polyol obtained in the above comparative examples 1-3 is directly used to prepare regenerated polyurethane foam, which includes the following components in parts by weight: 80 parts of polypropylene glycol, 20 parts of the above regenerated polyol, 3 parts of water, 1 part of silicone oil stabilizer, 0.6 parts of amine catalyst, 1 part of organotin catalyst, and 60 parts of toluene diisocyanate.

[0096] The amine catalyst is triethylamine, and the organotin catalyst is stannous isooctanoate.

[0097] Comparative Example 4

[0098] This comparative example provides a method for preparing a regenerated polyurethane foam, comprising the following components in parts by weight: 50 parts of polypropylene glycol, 50 parts of the regenerated polyol obtained in the above Example 13, 3 parts of water, 1 part of a silicone oil stabilizer, 0.6 parts of an amine catalyst, 1 part of an organotin catalyst, and 60 parts of toluene diisocyanate.

[0099] The physical properties (apparent density, resilience, 75% compression set, tensile strength) of the recycled polyurethane foams provided in the above Examples 1-20 and Comparative Examples 1-4 were tested, and the results are shown in Table 1.

[0100] Table 1

[0101]

[0102]

[0103] The molecular weights of the depolymerization products measured by GPC in the present invention are all greater than the molecular weights of the substances in the original degradation solution, which indicates that there are no small molecular diols remaining in the depolymerization products.

[0104] The hydroxyl value has an important influence on the chemical properties and durability of the material. The introduction of hydroxyl groups can change the cross-linking degree and molecular structure of the regenerated polyurethane resin, thereby affecting its chemical properties such as solvent resistance, heat resistance and corrosion resistance. A moderate increase in the hydroxyl content can significantly improve the heat resistance and water resistance of the polyurethane material, making it more suitable for applications in high temperature and humid environments. The increase in the hydroxyl content can also enhance the ultraviolet stability of the polyurethane material and extend its service life in outdoor environments. The regenerated polyol obtained by the method of the present invention contains an appropriate content of hydroxyl groups, and the polyurethane material prepared therefrom can meet the requirements of various industries, and the performance of the polyurethane can be adjusted as needed.

[0105] Appropriate viscosity helps to enhance the mechanical properties of the foam. Too low viscosity may result in insufficient strength of the foam, while too high viscosity may cause the foam to lack elasticity, affecting its performance. Higher viscosity usually leads to higher foam density because they have poor fluidity during the foaming process and it is difficult to form a stable bubble structure. This may cause the closed cell rate of the foam to decrease, thereby affecting its physical properties. Different application scenarios have different performance requirements for polyurethane foams. The choice of viscosity can affect the foam's thermal insulation, sound absorption, compressive strength and other properties, thereby determining its applicability in specific applications. The present invention controls the viscosity of the regenerated polyol so that the polyurethane prepared therefrom has better performance.

[0106] Figure 1 10%, 20%, 30%, 40% and 50% are pictures of recycled polyurethane prepared by Example 17, Example 13, Example 18, Example 19 and Comparative Example 4, respectively. Figure 1 As shown, the shapes and colors of the recycled polyurethane foams of Examples 17, 13, 18 and 19 meet the standards of commercial polyurethane foams.

[0107] From Table 1 and Figure 1 As shown, when preparing recycled polyurethane, the amount of recycled polyol is gradually increased, and the density of recycled polyurethane foam is gradually increased. The mechanical properties of polyurethane foam are mainly determined by the rebound rate and 75% compression permanent deformation. The rebound rate reflects the integrity and uniformity of the three-dimensional network structure of polyurethane foam, and the 75% compression permanent deformation reflects the rebound recovery ability of polyurethane foam and the stability of the material. This property measures the ability of the material to return to its original state after being compressed to a certain extent and releasing the pressure. From Table 1 and Figure 1 As shown, the physical properties of the recycled polyurethane foam of the embodiment of the present invention can meet the requirements of commercial polyurethane foam.

[0108] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for depolymerizing waste polyurethane foam, characterized in that: The steps include: Step 1, crushing the waste polyurethane foam; Step 2, mixing the crushed waste polyurethane foam with a degradation solution, wherein the degradation solution comprises polypropylene glycol, a small molecule glycol and a catalyst, and the mass of the polypropylene glycol and the small molecule glycol is 1 to 2 times the mass of the waste polyurethane foam; Step 3, the mixed solution of step 2 is reacted at 170-220° C. to obtain a depolymerization product.

2. The method for depolymerizing waste polyurethane foam according to claim 1, characterized in that: The method further comprises step 4, wherein the depolymerization product obtained in step 3 is directly used as a raw material for preparing the recycled polyurethane foam.

3. The method for depolymerizing waste polyurethane foam according to claim 2, characterized in that: The step 4 is: mixing the depolymerization product obtained in the step 3 with polyol and isocyanate to prepare the regenerated polyurethane foam.

4. The method for depolymerizing waste polyurethane foam according to claim 1, characterized in that: The catalyst is at least one of potassium hydroxide, sodium hydroxide, cesium hydroxide, potassium acetate, sodium acetate, ferric chloride, sodium citrate, potassium carbonate and sodium carbonate, and the amount of the catalyst is 0.01 to 2 times the mass of the waste polyurethane foam; the number average molecular weight of the polypropylene glycol is 3000 to 5000.

5. The method for depolymerizing waste polyurethane foam according to claim 1, characterized in that: The small molecule diol is at least one of ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 2,3-butanediol, diethylene glycol, dipropylene glycol, triethylene glycol, and 1,6-hexanediol; the mass ratio of the polypropylene glycol to the small molecule diol is 1-20:

1.

6. The method for depolymerizing waste polyurethane foam according to claim 3, characterized in that: The polyol is polypropylene glycol, and the isocyanate is toluene diisocyanate.

7. The method for depolymerizing waste polyurethane foam according to claim 3, characterized in that: The amount of polyol added is 60-100 parts by mass, the amount of the depolymerization product obtained in step 3 added is 10-40 parts by mass, and the amount of isocyanate added is 40-70 parts by mass.

8. The method for depolymerizing waste polyurethane foam according to claim 3, characterized in that: When preparing the recycled polyurethane foam, a silicone oil stabilizer, an organic tin catalyst, a foaming agent and an alcohol amine catalyst are also added.

9. The method for depolymerizing waste polyurethane foam according to claim 8, characterized in that: The amount of polyol added is 60-100 parts by mass, the amount of the depolymerization product obtained in step 3 added is 10-40 parts by mass, the amount of isocyanate added is 40-70 parts by mass, the amount of silicone oil stabilizer added is 0.6-1.5 parts by mass, the amount of organotin catalyst added is 0.2-1.8 parts by mass, the amount of foaming agent added is 2-5 parts by mass, and the amount of alcoholamine catalyst added is 0.2-1.8 parts by mass.

10. The method for depolymerizing waste polyurethane foam according to claim 8, characterized in that: The organic tin catalyst is at least one of stannous octoate, dibutyltin dilaurate, and stannous octoate T9; the foaming agent is at least one of water and dichloromethane; and the alcoholamine catalyst is at least one of diethanolamine, triethanolamine, triethylamine, and dipropanolamine.

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