Method for degrading polyurethane through boron catalysis

Abstract

The invention discloses a method for catalyzing and degrading polyurethane by boron. The method comprises the following steps: heating polyurethane and a catalyst in tert-butyl alcohol to react; the used catalyst is substituted borane; the temperature of the heating reaction is 60-80 DEG C; according to the method disclosed by the invention, polyurethane is degraded by a substituted borane-tert-butyl alcohol catalytic system, polyol and isocyanate are recycled, and meanwhile, a substituted borane catalyst and tert-butyl alcohol can also be recycled. The degradation method provided by the invention is mild in reaction condition, simple in process, good in yield, low in energy consumption and environment-friendly, and can provide a technical basis for efficient recycling, degradation and recycling of the polyurethane plastic.

Description

Technical Field

[0001] This invention relates to the field of polymer degradation technology, and in particular to a method for boron-catalyzed degradation of polyurethane. Background Technology

[0002] Polyurethane, made from raw materials such as polyisocyanates and polyols, is an important class of polymer materials widely used in automobile manufacturing, refrigerator manufacturing, transportation, and civil engineering. In recent decades, with the continuous growth in polyurethane usage, polyurethane waste has also gradually increased, causing pollution problems. Currently, the main methods for treating polyurethane waste are landfilling or incineration, which not only waste resources but also cause environmental pollution. Therefore, how to achieve efficient degradation and recycling of polyurethane to reduce environmental pollution has become one of the major problems that the polyurethane industry needs to solve.

[0003] Chemical degradation and recycling is an ideal method for polyurethane recycling. Depending on the type of degrading agent and degradation conditions, it can be categorized into hydrolysis, alkaline hydrolysis, amino hydrolysis, and alcohol degradation. While these methods can mitigate environmental pollution to some extent, they still have some drawbacks, such as long reaction cycles, high temperatures, difficulty in separating products from the degradation system, large amounts of solvent required, complex processes, and high energy consumption. For example, Chinese patent CN202310381466.X discloses a method for degrading and recycling polyurethane using an alkaline ionic liquid and methanol as a catalytic system. This method is carried out at 60-80℃, but requires high pressure conditions, making the process quite difficult. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a boron-catalyzed method for degrading polyurethane, achieving efficient degradation of polyether polyurethane under normal pressure. The degradation products are isocyanate and polyether polyol, which are easy to separate and purify, and the catalyst can also be recycled and reused.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] This invention provides a method for boron-catalyzed degradation of polyurethane, comprising the following steps:

[0007] The polyurethane and the catalyst are reacted in tert-butanol by heating; the catalyst is a substituted borane; the temperature of the heating reaction is 60-80°C.

[0008] In some specific embodiments, the polyurethane is a granular material that has been crushed or cut into pieces; the particle size of the granular material is preferably 5 to 10 mm.

[0009] In a preferred embodiment, the heating reaction is carried out under stirring conditions;

[0010] Preferably, the heating reaction takes 3 to 5 hours.

[0011] In a preferred embodiment, the substituted borane is selected from any one of triphenylborane, tripentafluorophenylborane, tri-m-methylphenylborane, tri-p-tert-butylphenylborane, tri-p-methoxyphenylborane, and tributylborane;

[0012] Preferably, the mass of the catalyst is 1 to 3 wt% of the mass of the polyurethane.

[0013] In a preferred embodiment, the mass of the tert-butanol is 3 to 5 times the mass of the polyurethane.

[0014] In the technical solution of the present invention, the polyurethane is a polyether-type polyurethane.

[0015] In a preferred embodiment, post-processing is also included; the post-processing includes the following operations:

[0016] The solution was cooled to 30–35°C and filtered to obtain solid isocyanate. The filtrate was distilled to recover tert-butanol, and the catalyst was extracted to recover the catalyst. The remaining components were added to water and then extracted with an organic solvent, dried, and concentrated to obtain polyol.

[0017] Preferably, the extractant used to recover the catalyst is n-hexane; in some specific embodiments, the mass of the n-hexane is 1 to 2 times that of the polyurethane.

[0018] Preferably, the organic solvent is selected from at least one of dichloromethane, ethyl acetate, and toluene.

[0019] by Figure 1 Taking the polyurethane shown as an example, the degradation mechanism in this invention is as follows:

[0020] In this invention, substituted borane is used as a catalyst, and tert-butanol is used as a solvent and alcoholysis agent to achieve the degradation of polyurethane through a heating reaction at 60–80 °C. Under the catalysis of substituted borane, the carbonyl group in the polyurethane is activated, enhancing its electrophilicity. In tert-butanol, due to the significant steric hindrance of the tert-butyl group, it cannot act as a nucleophile to attack the carbonyl carbon core. However, the amino group in the urethane structure can act as a better nucleophile to attack the carbonyl carbon core, promoting the cleavage of the ester group, thereby generating isocyanate and releasing polyol.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] (1) This invention utilizes substituted borane-tert-butanol as a catalytic system. Under the interaction of the two, the carbonyl group can be selectively activated, and the amino group in the urethane structure can be used as a nucleophile to attack the carbonyl group to achieve the degradation of polyurethane.

[0023] (2) The degradation products, isocyanates and polyols, in this invention are easy to separate and purify, and the substituted borane catalyst and tert-butanol can also be recycled and reused.

[0024] (3) The degradation method provided by the present invention has mild reaction conditions, simple process, good yield, low energy consumption and environmental protection, which can provide a technical basis for the efficient recycling and degradation of polyurethane plastics. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the polyurethane degradation mechanism of the present invention. Detailed Implementation

[0026] The following embodiments are merely some, not all, of the embodiments of the present invention. Therefore, the detailed descriptions of the embodiments provided below are not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0027] In this invention, unless otherwise specified, all equipment and raw materials are commercially available or commonly used in the industry. The methods described in the following embodiments are conventional methods in the art, unless otherwise specified.

[0028] In the following embodiments, the polyurethane material is taken from the thermal insulation board of the building wall, which is crushed or cut into small particles with a particle size of 5-10 mm; the degradation product isocyanate is characterized by NMR data, the viscosity of the degraded and regenerated polyol is characterized by a viscometer, and the hydroxyl value is characterized by a hydroxyl value determination method.

[0029] Example 1

[0030] 20g of pulverized polyurethane material and 100mL of tert-butanol were placed into a 500mL three-necked flask equipped with a mechanical stirrer. 0.2g of triphenylborane was added to the reaction flask. The mixture was heated in an oil bath to 80℃ and stirred for 5 hours. After degradation, the liquid in the flask was cooled to 30-35℃. The reaction system was observed to be a suspension. After filtration, the obtained solid isocyanate (structure shown) was obtained. Figure 1 (As shown) 2.12g; after distilling to recover tert-butanol from the obtained filtrate, the remaining sample was extracted with 40g of n-hexane to separate n-hexane, which was then concentrated to obtain triphenylborane; the remaining component was added to 60mL of pure water and 60mL of dichloromethane, separated to obtain the dichloromethane phase, dried and concentrated to obtain a polyol with a mass of 4.62g, a yield of 77%, a viscosity of 2172MPa·s, and a hydroxyl value of 363mg KOH / g.

[0031] Example 2

[0032] 20g of pulverized polyurethane material and 100mL of tert-butanol were placed into a 500mL three-necked flask equipped with a mechanical stirrer. 0.2g of tris(pentafluorophenyl)borane was added to the reaction flask. The mixture was heated in an oil bath to 80℃ and stirred for 5 hours. After degradation, the liquid in the flask was cooled to 30-35℃. The reaction system was observed to be a suspension. After filtration, the obtained solid isocyanate (structure as shown) was obtained. Figure 1 (As shown) 1.88g; after distilling to recover tert-butanol from the obtained filtrate, the remaining sample was extracted with 40g of n-hexane to separate n-hexane, which was then concentrated to obtain tri-pentafluorophenylborane; the remaining component was added to 60mL of pure water and 60mL of dichloromethane, separated to obtain the dichloromethane phase, dried and concentrated to obtain a polyol with a mass of 4.32g, a yield of 72%, a viscosity of 2156MPa·s, and a hydroxyl value of 357mg KOH / g.

[0033] Example 3

[0034] 20g of pulverized old polyurethane material and 100mL of tert-butanol were placed into a 500mL three-necked flask equipped with a mechanical stirrer. 0.2g of tri-m-methylphenylborane was added to the reaction flask, and the mixture was heated in an oil bath to 80℃ and stirred for 5 hours. After degradation, the liquid in the flask was cooled to 30-35℃, and the reaction system was observed to be a suspension. After filtration, the obtained solid isocyanate (structure as shown) was obtained. Figure 1 (As shown) 1.96g; after distilling and recovering tert-butanol from the obtained filtrate, the remaining sample was extracted with 40g of n-hexane to separate n-hexane, which was then concentrated to obtain tri-m-methylphenylborane. The remaining components were added to 60mL of pure water and 60mL of dichloromethane, and the dichloromethane phase was separated, dried, and concentrated to obtain a polyol with a mass of 4.38g, a yield of 73%, a viscosity of 2148MPa·s, and a hydroxyl value of 350mg KOH / g.

[0035] Example 4

[0036] 20g of pulverized polyurethane material and 100mL of tert-butanol were placed into a 500mL three-necked flask equipped with a mechanical stirrer. 0.2g of tri-p-tert-butylphenylborane was added to the reaction flask. The flask was heated in an oil bath to 80℃ and stirred for 5 hours. After degradation, the liquid in the flask was cooled to 30-35℃. The reaction system was observed to be a suspension. After filtration, the obtained solid isocyanate (structure as shown) was obtained. Figure 1 (As shown) 1.95g; after distilling to recover tert-butanol from the obtained filtrate, the remaining sample was extracted with 40g of n-hexane to separate n-hexane, which was then concentrated to obtain tri-p-tert-butylphenylborane. The remaining component was added to 60mL of pure water and 60mL of dichloromethane, and the dichloromethane phase was separated, dried, and concentrated to obtain a polyol with a mass of 4.18g, a yield of 70%, a viscosity of 2132MPa·s, and a hydroxyl value of 342mg KOH / g.

[0037] Example 5

[0038] 20g of pulverized polyurethane material and 100mL of tert-butanol were placed into a 500mL three-necked flask equipped with a mechanical stirrer. 0.2g of tri-p-methoxyphenylborane was added to the reaction flask. The flask was heated in an oil bath to 80°C and stirred for 5 hours. After degradation, the liquid in the flask was cooled to 30-35°C. The reaction system was observed to be a suspension. After filtration, the obtained solid isocyanate (structure as shown) was obtained. Figure 1 (As shown) 2.06 g; after distilling to recover tert-butanol from the obtained filtrate, the remaining sample was extracted with 40 g of n-hexane to separate n-hexane, which was then concentrated to obtain tri-p-methoxyphenylborane; the remaining component was added to 60 mL of pure water and 60 mL of dichloromethane, separated to obtain the dichloromethane phase, dried and concentrated to obtain a polyol with a mass of 4.58 g, a yield of 76%, a viscosity of 2184 MPa·s, and a hydroxyl value of 364 mg KOH / g.

[0039] Example 6

[0040] 20g of pulverized polyurethane material and 100mL of tert-butanol were placed into a 500mL three-necked flask equipped with a mechanical stirrer. 0.2g of tributylborane was added to the reaction flask. The flask was heated to 80℃ in an oil bath and stirred for 5 hours. After degradation, the liquid in the flask was cooled to 30-35℃. The reaction system was observed to be a suspension. After filtration, the obtained solid isocyanate (structure as shown) was obtained. Figure 1 (As shown) 2.14 g; after distilling to recover tert-butanol from the obtained filtrate, the remaining sample was extracted with 40 g of n-hexane to separate n-hexane, which was then concentrated to obtain tributylborane; the remaining component was added to 60 mL of pure water and 60 mL of dichloromethane, separated to obtain the dichloromethane phase, dried and concentrated to obtain a polyol with a mass of 4.02 g, a yield of 67%, a viscosity of 2124 MPa·s, and a hydroxyl value of 320 mg KOH / g.

[0041] Example 7

[0042] 20g of pulverized polyurethane material and 100mL of tert-butanol were placed into a 500mL three-necked flask equipped with a mechanical stirrer. 0.4g of triphenylborane was added to the reaction flask. The flask was heated in an oil bath to 80°C and stirred for 5 hours. After degradation, the liquid in the flask was cooled to 30-35°C. The reaction system was observed to be a suspension. After filtration, the obtained solid isocyanate (structure as shown) was obtained. Figure 1(As shown) 2.35g; after distilling to recover tert-butanol from the obtained filtrate, the remaining sample was extracted with 40g of n-hexane to separate n-hexane, which was then concentrated to obtain triphenylborane; the remaining component was added to 60mL of pure water and 60mL of dichloromethane, separated to obtain the dichloromethane phase, dried and concentrated to obtain a polyol with a mass of 4.72g, a yield of 79%, a viscosity of 2104MPa·s, and a hydroxyl value of 354mgKOH / g.

[0043] Example 8

[0044] 20g of pulverized polyurethane material and 100mL of tert-butanol were placed into a 500mL three-necked flask equipped with a mechanical stirrer. 0.6g of triphenylborane was added to the reaction flask. The flask was heated in an oil bath to 80°C and stirred for 5 hours. After degradation, the liquid in the flask was cooled to 30-35°C. The reaction system was observed to be a suspension. After filtration, the obtained solid isocyanate (structure as shown) was obtained. Figure 1 (As shown) 2.48 g; after distilling to recover tert-butanol from the obtained filtrate, the remaining sample was extracted with 40 g of n-hexane to separate n-hexane, which was then concentrated to obtain triphenylborane; the remaining component was added to 60 mL of pure water and 60 mL of dichloromethane, separated to obtain the dichloromethane phase, dried and concentrated to obtain a polyol with a mass of 4.96 g, a yield of 83%, a viscosity of 2080 MPa·s, and a hydroxyl value of 305 mg KOH / g.

[0045] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for boron-catalyzed degradation of polyurethane, characterized in that, Includes the following steps: The polyurethane and the catalyst are reacted in tert-butanol by heating; the catalyst is a substituted borane; the temperature of the heating reaction is 60-80°C.

2. The method according to claim 1, characterized in that, The heating reaction is carried out under stirring conditions.

3. The method according to claim 1, characterized in that, The heating reaction takes 3 to 5 hours.

4. The method according to claim 1, characterized in that, The substituted borane is selected from any one of triphenylborane, tripentafluorophenylborane, tri-m-methylphenylborane, tri-p-tert-butylphenylborane, tri-p-methoxyphenylborane, and tributylborane.

5. The method according to claim 1, characterized in that, The mass of the catalyst is 1 to 3 wt% of the mass of the polyurethane.

6. The method according to claim 1, characterized in that, The mass of the tert-butanol is 3 to 5 times the mass of the polyurethane.

7. The method according to claim 1, characterized in that, The polyurethane is a polyether-type polyurethane.

8. The method according to claim 1, characterized in that, It also includes post-processing; The post-processing includes the following operations: cooling to 30-35°C, filtering to obtain solid isocyanate; recovering tert-butanol from the filtrate by distillation, recovering the catalyst by extraction, and adding water to the remaining components for organic solvent extraction, drying, and concentration to obtain polyol.

9. The method according to claim 8, characterized in that, The extractant used to recover the catalyst is n-hexane.

10. The method according to claim 8, characterized in that, The organic solvent is selected from at least one of dichloromethane, ethyl acetate, and toluene.

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