Method for regenerating polyether polyol from polyurethane and application of polyol

Abstract

The invention discloses a method for regenerating polyether polyol from polyurethane and application of the polyol, and belongs to the field of high polymer materials. The method for regenerating polyether polyol from polyurethane comprises the following steps: pretreating waste polyurethane foam, performing alcoholysis reaction, and recovering; and adding an organic carboxylic acid modifier, carrying out a modified condensation reaction, and carrying out post-treatment to obtain the regenerated polyether polyol. The organic carboxylic acid modifier is at least one of formic acid, acetic acid, oxalic acid and benzoic acid. The method for regenerating polyether polyol from polyurethane provided by the invention can achieve the effects of effectively removing aromatic amine and being simple in process.

Description

Technical Field

[0001] The invention relates to polymer materials, in particular to a method for regenerating polyether polyol from polyurethane and application of the polyol. Background Art

[0002] Polyurethane (PU), short for polyurethane, is an emerging organic polymer material known as the "fifth plastic." Its exceptional properties have led to its widespread application across numerous sectors of the national economy. Polyurethane has a wide range of applications, including coatings, adhesives, fabric finishes, leather modifiers, flexible and rigid polyurethane foams, and elastomers. Applications include textiles, construction, aviation, shipbuilding, transportation, medicine, and electronics. Soft polyurethane, primarily a thermoplastic linear structure, offers superior stability, chemical resistance, resilience, and mechanical properties compared to PVC foam. It also exhibits lower compression set and offers excellent thermal, acoustic, seismic, and toxic properties, making it commonly used in packaging, sound insulation, and filter materials. Rigid polyurethane plastics are lightweight, offer superior sound and thermal insulation, chemical resistance, excellent electrical properties, are easy to process, and have low water absorption. They are primarily used in construction, automotive, aviation, and thermal insulation structural materials. Polyurethane elastomers, with properties intermediate between those of plastic and rubber, are oil-resistant, wear-resistant, cold-resistant, aging-resistant, hard, and elastic, and are primarily used in the footwear and medical industries.

[0003] With the rapid development of polyurethane, waste has also increased. This includes large amounts of polyurethane foam used for insulation and sofa cushions, waste PU shoe soles, and waste PU leather. Therefore, polyurethane recycling has become a major issue that the polyurethane industry urgently needs to address. Recycling and reusing waste polyurethane has practical significance in reducing environmental pollution and lowering the production cost of new products.

[0004] Landfill is a common method for treating polyurethane waste, accounting for nearly 50% of polyurethane waste. Once landfilled, the waste gradually decomposes into small molecules, which not only seriously pollutes the environment but also results in a significant waste of resources. Disposing of these wastes solely through landfill and incineration not only occupies land, but also pollutes the environment and represents a significant waste of resources. Researchers are dedicated to developing efficient polyurethane recycling technologies, primarily physical and chemical. Chemical recycling has garnered increasing attention in recent years.

[0005] Chemical recovery of polyurethane foam involves re-degrading the foam to produce a recovered liquid. Chemical recovery methods primarily include alkaline hydrolysis, aminolysis, hydrolysis, and alcoholysis. Alcoholysis offers a simple process and convenient use of the recovered liquid, making alcoholysis the predominant method in industrial chemical recovery. While alcoholysis can yield regenerated polyols, it also produces carcinogenic aromatic amines, such as 4,4'-diaminodiphenylmethane and toluenediamine. Aromatic amines are considered toxic and potentially carcinogenic, particularly to water bodies. The lower their content in the product, the better. With stricter environmental regulations and restrictions on aromatic amines in the polyurethane industry, recycled polyols cannot be used in industries such as home appliances and foam coatings. CN114106281A discloses a degradation method for recovering polyurethane. After the alcoholysis reaction, furfural and benzaldehyde are used to remove the aromatic amines. However, the relatively large amounts of these two additives increase production costs and affect the performance of the regenerated polyols. Therefore, there is a need for a new process to better remove aromatic amines. Summary of the Invention

[0006] Purpose of the invention: The purpose of the present invention is to provide a method for regenerating polyether polyol from polyurethane by effectively removing aromatic amines and having a simple process.

[0007] Another object of the present invention is to provide an application of the regenerated polyether polyol.

[0008] Technical solution: The method for removing aromatic amines from polyurethane regenerated polyether polyols of the present invention comprises the following steps:

[0009] (1) pre-treating the waste polyurethane foam and performing alcoholysis reaction to recover the waste polyurethane foam;

[0010] (2) adding an organic carboxylic acid modifier to carry out a modification condensation reaction, and obtaining a regenerated polyether polyol after post-treatment.

[0011] Preferably, the organic carboxylic acid modifier is at least one of formic acid, acetic acid, oxalic acid, and benzoic acid.

[0012] Preferably, the raw materials for the alcoholysis reaction in step (1) include waste foam particles and diethylene glycol, and the amount of the organic carboxylic acid modifier added in step (2) is 2-6% of the total mass of the waste foam particles and diethylene glycol, and more preferably 3%.

[0013] Preferably, the modification condensation reaction temperature is 170-200°C, more preferably 180°C.

[0014] Preferably, the modification condensation reaction time is 1-3 hours, more preferably 2 hours.

[0015] Preferably, the post-treatment includes vacuum distillation; the vacuum distillation temperature is 100-120°C, more preferably 120°C.

[0016] Preferably, the waste polyurethane foam includes one of polyurethane soft foam, polyurethane semi-rigid foam and polyurethane rigid foam.

[0017] The use of the regenerated polyether polyol of the present invention in the preparation of polyurethane rigid foam comprises the following steps:

[0018] (1) Adding the obtained recycled polyether polyol to material A of the polyurethane rigid foam formula to prepare a first mixed material.

[0019] (2) The first mixed material and material B M20S are mixed evenly and then foamed to prepare polyurethane rigid foam.

[0020] Principle of the Invention: This invention aims to provide a method for effectively removing aromatic amines produced during the regeneration of polyether polyols from waste polyurethane foam. Aromatic amines are produced during the alcoholysis recovery of waste polyurethane foam. Adding an organic carboxylic acid modifier allows it to undergo a condensation reaction with the amino groups in the aromatic amines, effectively removing the aromatic amines. The condensation reaction mechanism is as follows:

[0021]

[0022] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) This method only requires the addition of an organic carboxylic acid modifier in the alcoholysis reactor, without the need for other purification equipment, and the amount added is small; (2) The viscosity of the modified regenerated polyether polyol is between 5000-10000 mPa.s, the hydroxyl value is between 500-600 mg KOH / g, the acid value is between 0.1-2.0 mg KOH / g, and the aromatic amine content in the regenerated polyol is less than 1 ppm; (3) The compressive strength of the polyurethane rigid foam prepared by the regenerated polyol obtained by this method is above 240 kPa, which meets the requirements of polyether polyol for rigid foam and reduces the harm of the regenerated polyol to humans and the environment. DETAILED DESCRIPTION

[0023] The technical solution of the present invention will be further described below in conjunction with embodiments.

[0024] Example 1

[0025] The method for regenerating polyether polyol from polyurethane of the present invention comprises the following steps:

[0026] (1) The polyurethane waste foam from PIR foam cutting scraps was collected, cleaned, dried and crushed to obtain polyurethane waste foam particles; 600 g of the waste foam particles, 400 g of diethylene glycol and 5 g of potassium hydroxide were added to a reactor and mixed evenly, replaced with nitrogen three times, and heated to 180°C under a continuous nitrogen flow atmosphere for alcoholysis reaction for 4 h.

[0027] (2) 30 g of formic acid was added as an organic carboxylic acid modifier, and the reaction was carried out at 180° C. for 1 h. The reaction was then distilled under reduced pressure at 120° C. to remove excess alcoholysis agent and small molecular by-products, and the regenerated polyether polyol was obtained by filtration.

[0028] The use of the regenerated polyether polyol of the present invention in the preparation of polyurethane rigid foam comprises the following steps:

[0029] (1) Adding the obtained recycled polyether polyol to material A of the polyurethane rigid foam formula to prepare a first mixed material; material A includes polyether polyol, silicone oil, catalyst, water, and flame retardant; wherein the mass proportion of the recycled polyether polyol is 20% of material A.

[0030] (2) The first mixed material and material B M20S were mixed evenly in a mass ratio of 1:1.07 and then foamed to prepare polyurethane rigid foam.

[0031] Example 2

[0032] The similarities between this embodiment and embodiment 1 are not repeated here, and the differences are as follows:

[0033] In the method for regenerating polyether polyol from polyurethane of the present invention, 30g of formic acid in step (2) is replaced by 24g of acetic acid; the reaction temperature and time in step (2) are 170°C and 2h, respectively.

[0034] Example 3

[0035] The similarities between this embodiment and embodiment 1 are not repeated here, and the differences are as follows:

[0036] In the method for regenerating polyether polyol from polyurethane of the present invention, 30g of formic acid in step (2) is replaced by 40g of oxalic acid; the reaction temperature and time in step (2) are 200°C and 3h, respectively.

[0037] Example 4

[0038] The similarities between this embodiment and embodiment 1 are not repeated here, and the differences are as follows:

[0039] In the method for regenerating polyether polyol from polyurethane of the present invention, 30g of formic acid in step (2) is replaced by 48g of benzoic acid; the reaction temperature and time in step (2) are 185°C and 2h, respectively.

[0040] Example 5

[0041] The similarities between this embodiment and embodiment 1 are not repeated here, and the differences are as follows:

[0042] In the method for regenerating polyether polyol from polyurethane of the present invention, 30g of formic acid in step (2) is replaced by 24g of formic acid; and the reaction time in step (2) is 3h.

[0043] Example 6

[0044] The similarities between this embodiment and embodiment 1 are not repeated here, and the differences are as follows:

[0045] In the method for regenerating polyether polyol from polyurethane of the present invention, 30 g of formic acid in step (2) is replaced with 22 g of formic acid.

[0046] Comparative Example 1

[0047] The similarities between this comparative example and Example 1 are not repeated here, except that:

[0048] In the method for regenerating polyether polyol from polyurethane of the present invention, step (2) is removed, that is, no modifier is added.

[0049] Comparative Example 2

[0050] The similarities between this comparative example and Example 1 are not repeated here, except that:

[0051] In the method for regenerating polyether polyol from polyurethane of the present invention, the amount of formic acid added in step (2) is 10 g.

[0052] Comparative Example 3

[0053] The similarities between this comparative example and Example 1 are not repeated here, except that:

[0054] In the method for regenerating polyether polyol from polyurethane of the present invention, the amount of formic acid added in step (2) is 70g.

[0055] The properties of the regenerated polyether polyols obtained in the examples and comparative examples were tested, including acid value, hydroxyl value, viscosity, and aromatic amine content. The specific testing methods are as follows.

[0056] Acid value: tested according to GB / T12008.5-2010.

[0057] Hydroxyl value: tested according to GB / T 12008.3-2009.

[0058] Viscosity: tested according to GB / T 12008.7-2010.

[0059] Aromatic amine content: tested according to GB / T17592-2011.

[0060] Polyurethane rigid foams were prepared using the resulting recycled polyether polyol, and their compressive strength was tested according to GB / T 8813-2008. The compressive strengths of the polyurethane rigid foams prepared in Comparative Examples 1-3 and Examples 1-6 were 250 kPa, 255 kPa, 243 kPa, 263 kPa, 258 kPa, 260 kPa, 253 kPa, 251 kPa, and 267 kPa, respectively.

[0061] The test results are shown in Table 1.

[0062] Table 1 Test results of recycled polyether polyols obtained in each experiment

[0063]

[0064] According to the data in Table 1, the aromatic amine content in the regenerated polyether polyol modified by a certain amount of organic carboxylic acid modifier is less than 1ppm (Examples 1-6). This is because after the alcoholysis reaction is completed, carboxylic acid substances are added, and the carboxyl group in the carboxylic acid and the amino group in the aromatic amine undergo condensation reaction at high temperature, thereby achieving the purpose of removing aromatic amine. The hydroxyl value of the modified regenerated polyether polyol is between 500-600mgKOH / g, the acid value is between 0.1-2.0mgKOH / g, and the compressive strength of the polyurethane rigid foam obtained therefrom is above 240kPa. This performance meets the requirements of polyether polyol for rigid foam, reduces the harm of regenerated polyol to humans and the environment, and can be normally used in the preparation of polyurethane rigid foam products. When the addition amount of the organic carboxylic acid modifier is too low or not added (Comparative Examples 1-2), the aromatic amine content in the regenerated polyether polyol is large; when the addition amount is too high, although the aromatic amine content in the regenerated polyether polyol is less than 1ppm, its acid value is large and cannot meet the requirements, and excessive raw material consumption will increase costs.

Claims

1. A method for regenerating polyether polyol from polyurethane, characterized in that: The following steps are involved: (1) pre-treating the waste polyurethane foam and performing alcoholysis reaction to recover the waste polyurethane foam; (2) adding an organic carboxylic acid modifier to carry out a modification condensation reaction, and obtaining a regenerated polyether polyol after post-treatment.

2. The method for regenerating polyether polyol from polyurethane according to claim 1, wherein The organic carboxylic acid modifier is at least one of formic acid, acetic acid, oxalic acid and benzoic acid.

3. The method for regenerating polyether polyol from polyurethane according to claim 1, wherein The organic carboxylic acid modifier is formic acid.

4. The method for regenerating polyether polyol from polyurethane according to claim 1, wherein The raw materials for the alcoholysis reaction in step (1) include waste foam particles and diethylene glycol, and the amount of the organic carboxylic acid modifier added in step (2) is 2-6% of the total mass of the waste foam particles and diethylene glycol.

5. The method for regenerating polyether polyol from polyurethane according to claim 4, wherein: The amount of the organic carboxylic acid modifier added is 3% of the total mass of the waste foam particles and diethylene glycol.

6. The method for regenerating polyether polyol from polyurethane according to claim 1, wherein: The modification condensation reaction temperature is 170-200°C.

7. The method for regenerating polyether polyol from polyurethane according to claim 1, wherein The modification condensation reaction time is 1-3 hours.

8. The method for regenerating polyether polyol from polyurethane according to claim 1, wherein The post-treatment includes distillation under reduced pressure.

9. The method for regenerating polyether polyol from polyurethane according to claim 8, characterized in that: The reduced pressure distillation temperature is 100-120°C.

10. Use of the regenerated polyether polyol according to claim 1 in the preparation of polyurethane rigid foam.

Images