Method for removing aromatic amine in polyurethane waste foam regenerated polyol and application of regenerated polyol

Abstract

The invention discloses a method for removing aromatic amine in polyurethane waste foam regenerated polyol and application of the regenerated polyol, and the method comprises the following steps: (1) after the alcoholysis reaction of polyurethane waste foam is finished, adding a self-made auxiliary agent, and enabling the cyano group of the self-made auxiliary agent to react with the amino group of the aromatic amine; (2) carrying out reduced pressure distillation to remove excessive alcoholysis agent and small molecular byproducts; and (3) filtering to obtain regenerated polyol. According to the method, the content of aromatic amine in the regenerated polyol can be effectively reduced by adding the self-made auxiliary agent, the method only needs to add the self-made auxiliary agent into the alcoholysis reaction kettle for reaction, other purification equipment is not needed, the addition amount is small, and the regenerated polyol meets the requirements of polyol for hard foam.

Description

Technical Field

[0001] The invention belongs to the field of polyurethane foam plastic recycling, and particularly relates to a method for removing aromatic amines from polyols regenerated from waste polyurethane foams and application of the regenerated polyols. Background Art

[0002] Polyurethane plays a very important role in modern industry. With the continuous emergence of new varieties and the continuous increase in production, the development and utilization of polyurethane has attracted great attention from all countries. As early as 1849, someone synthesized isocyanate, the raw material required for the preparation of polyurethane, which laid the foundation for the industrialization of polyurethane in the future.

[0003] In the initial stage of polyurethane development, Bayer used isocyanate as raw material to prepare polyurethane through polymerization reaction, but the practical value of the obtained polyurethane was not high. It was not until the 20th century that polyurethane was gradually industrialized. my country's polyurethane industry started relatively late. It was not until 1958, when the domestic research on toluene diisocyanate (TDI) matured, that the polyurethane industry began to develop rapidly. By the 1970s, the polyurethane industry had a certain scale. In the 1980s, my country introduced production lines for TDI, diphenylmethane diisocyanate (MDI) and polyether polyols, making the polyurethane industry a large-scale industry in China.

[0004] With the further expansion of polyurethane production scale and the continuous expansion of application fields, a large amount of waste is generated in the process of polyurethane production and use. Although their stacking causes less direct pollution to the environment, due to their strong chemical inertness, they are difficult to be degraded by air or microorganisms under normal circumstances. Large-scale stacking will occupy a huge space, thus bringing great burden to life and the natural environment. Processing polyurethane material waste to make it into polyurethane production raw materials or other products can not only solve the shortage of resources and energy, but also reduce the development of primary resources and waste emissions, especially for promoting the concept of comprehensive resource utilization and sustainable development. This low-cost and high-efficiency disposal method is the most economical in the comprehensive regeneration technology of polyurethane material waste, and is very suitable for a developing country like my country with relatively scarce resources and a large population. Therefore, as an indispensable link in the field of polyurethane resource utilization, the recycling and reuse of waste polyurethane materials has a very broad prospect, and it is also a matter of great environmental, social and economic benefits.

[0005] The level of recycling and reuse of waste materials not only reflects a country's environmental protection concept, but also indirectly reflects the country's level of scientific and technological development. Some developed countries such as Japan, the United States and EU countries have begun to promote this concept to varying degrees. China has become the largest producer and consumer of polyurethane. At the same time, the recycling of polyurethane waste is imminent. Therefore, it is necessary to propose a feasible polyurethane waste recycling method that is suitable for my country's national conditions, so that my country's polyurethane industry can embark on a sustainable development path of conservation and environmental protection.

[0006] Chemical recycling of polyurethane foam can re-degrade the foam to obtain recycled liquid. Chemical recycling methods mainly include alkaline hydrolysis, amine hydrolysis, hydrolysis and alcoholysis. Alcoholysis is simple in process and convenient in application of recycled liquid. Therefore, alcoholysis is the main chemical recycling method in industry. Alcoholysis can obtain regenerated polyols, but it also produces carcinogenic aromatic amines, such as 4,4'-diaminodiphenylmethane and toluenediamine. Aromatic amines are considered toxic and may cause cancer, especially for water bodies. The less the content in the product, the better. With the strict environmental protection requirements and the restrictions on aromatic amines in the polyurethane industry, the recycled polyols cannot be used in industries such as home appliances and foam coatings. Patent CN 114106281A describes the use of furfural and benzaldehyde to remove aromatic amines after alcoholysis reaction. The use of these two additives is relatively large, which will increase production costs on the one hand and affect the index performance of regenerated polyols on the other hand. Therefore, a new process for removing aromatic amines is needed. Summary of the invention

[0007] Purpose of the invention: The first purpose of the present invention is to provide a method for removing aromatic amines from polyols regenerated from waste polyurethane foams. After the polyols are regenerated from polyurethane foams, the aromatic amines are removed and the regenerated polyols meet the requirements of rigid foams. The regeneration method is simple and does not require other purification equipment. The second purpose of the present invention is to provide the use of the regenerated polyols in the preparation of polyurethane rigid foam plastics.

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

[0009] (1) After the alcoholysis reaction of the waste polyurethane foam is completed, a self-made auxiliary agent of the general formula (I) is added to react the cyano group of the self-made auxiliary agent with the amine group of the aromatic amine;

[0010] (2) removing excess alcoholysis agent and small molecular by-products by vacuum distillation;

[0011] (3) filtering to obtain regenerated polyol;

[0012] The structural formula of the self-made auxiliary agent is as follows:

[0013]

[0014] Among them, R is C1~C5.

[0015] The reaction process of the cyano group of the homemade additive and the amine group of the aromatic amine is as follows:

[0016]

[0017] If TDI is directly added to the recycled polyol, the viscosity of the product will increase and the hydroxyl value will decrease. Therefore, TDI modified with monohydric alcohol is used. However, the modified TDI has a smaller effect on the viscosity of the product due to its reduced functionality.

[0018] Preferably, in step (1), the temperature at which the cyano group of the preparation auxiliary agent reacts with the amine group of the aromatic amine is 70-80°C.

[0019] Preferably, the amount of the homemade auxiliary agent added is 2-6% of the total mass of the material after the alcoholysis reaction. If the amount added is less than 2%, the effect is not obvious, and if the amount added exceeds 6%, the content of the aromatic amine will basically not be reduced, and the cost will be increased.

[0020] Preferably, in step (2), the temperature of the reduced pressure distillation is 110-130°C.

[0021] Preferably, the preparation method of the self-made auxiliary agent comprises the following steps: monohydric alcohol and toluene diisocyanate (TDI) react under the protection of inert gas, and the cyano group reacts with the alcohol hydroxyl group to obtain the self-made auxiliary agent. The synthesis route is as follows:

[0022]

[0023] Preferably, the reaction temperature is 50-70° C., and the reaction time is 3-6 hours.

[0024] Preferably, the molar ratio of the monohydric alcohol to TDI is 1 to 1.15:1.

[0025] Preferably, the monohydric alcohol is methanol, ethanol, n-propanol or n-butanol.

[0026] Preferably, the alcoholysis reaction comprises the following steps:

[0027] (1) collecting and cleaning the waste polyurethane foam, drying and crushing the waste polyurethane foam to obtain waste polyurethane foam particles;

[0028] (2) adding the waste foam particles, diethylene glycol and potassium hydroxide into a reaction kettle, mixing them evenly, and replacing them with nitrogen;

[0029] (3) Raise the temperature under a continuous nitrogen flow atmosphere and react at 170-200° C. for 3-5 hours.

[0030] The invention discloses an application of polyol regenerated from waste polyurethane foam in the preparation of polyurethane rigid foam plastics.

[0031] Beneficial effects: Compared with the prior art, the present invention has the following advantages: (1) This method only requires adding a homemade auxiliary agent to the alcoholysis reactor for reaction, without the need for other purification equipment, and the amount added is small, and the regenerated polyol meets the requirements of polyol for rigid foam; (2) The hydroxyl value of the modified regenerated polyol is between 320 and 450 mg KOH / g, the acid value is between 0.1 and 1.5 mg KOH / g, and the aromatic amine content in the regenerated polyol is less than 1 ppm. DETAILED DESCRIPTION

[0032] The present invention is further described below in conjunction with specific embodiments.

[0033] The method for removing aromatic amines from polyols regenerated from waste polyurethane foams of the present invention comprises the following steps:

[0034] (1) collecting and cleaning the waste polyurethane foam, drying and crushing the waste polyurethane foam to obtain waste polyurethane foam particles;

[0035] (2) adding the waste foam particles, diethylene glycol and potassium hydroxide into a reaction kettle and mixing them evenly, and replacing the atmosphere with nitrogen three times;

[0036] (3) heating the reaction under a continuous nitrogen flow atmosphere;

[0037] (4) Cooling and adding homemade auxiliary agent M to react;

[0038] (5) removing excess alcoholysis agent and small molecular by-products by distillation at elevated temperature and reduced pressure;

[0039] (6) Filter to obtain regenerated polyol S.

[0040] The preparation steps of modified additive M1 are as follows:

[0041] ① Add methanol and TDI into the reaction bottle at a molar ratio of 1.15:1;

[0042] ② Raise the temperature to 55°C under nitrogen protection, stir and react for 3 hours to obtain modified additive M1.

[0043] The preparation steps of modified additive M2 are as follows:

[0044] ① Add ethanol and TDI into the reaction bottle at a molar ratio of 1.10:1;

[0045] ② Raise the temperature to 60°C under nitrogen protection, stir and react for 4 hours to obtain modified additive M2.

[0046] The preparation steps of modified additive M3 are as follows:

[0047] ① Add n-propanol and TDI into the reaction bottle at a molar ratio of 1.05:1;

[0048] ② Raise the temperature to 65°C under nitrogen protection, stir and react for 5 hours to obtain modified additive M3.

[0049] The preparation steps of modified additive M4 are as follows:

[0050] ① Add n-butanol and TDI into the reaction bottle at a molar ratio of 1.05:1;

[0051] ② Raise the temperature to 70°C under nitrogen protection, stir and react for 6 hours to obtain modified additive M4.

[0052] Examples 1 to 5 and Comparative Example 1 were carried out according to the above steps. The specific conditions are shown in Table 1. The performance data of the obtained regenerated polyols are shown in Table 2.

[0053] Table 1 Mass ratio of raw materials and reaction conditions in the preparation of regenerated polyols in Examples 1 to 5 and Comparative Example 1

[0054]

[0055] The regenerated polyols prepared in Examples 1 to 5 were applied to the polyurethane rigid foaming formulation, as shown in Table 2.

[0056] Table 2 Recycled polyols to prepare polyurethane rigid foam formula

[0057]

[0058]

[0059] The acid value (GB / T12008.5-2010), hydroxyl value (GB / T12008.3-2009), viscosity (GB / T 12008.7-2010), aromatic amine content (GB / T17592-2011) of the regenerated polyols obtained in Examples 1 to 5 and the compressive strength (GB / T 8813-2008) of the polyurethane rigid foams obtained therefrom were tested. The test results are shown in Table 3.

[0060] Table 3 Performance data of regenerated polyols and rigid foams prepared from Examples 1 to 5 and Comparative Example 1

[0061]

[0062] From the hydroxyl value, viscosity, and aromatic amine parameters of the recycled polyol in Table 3, it can be seen that the hydroxyl value of the modified recycled polyol is between 320 and 450 mg KOH / g, the acid value is between 0.1 and 1.5 mg KOH / g, and the aromatic amine content is less than 1 ppm, which meets the requirements of polyols for rigid foams. From the performance data of recycled polyols and polyurethane rigid foams in Table 2, it can be seen that by adding homemade additives, the aromatic amine content in the recycled polyol can be effectively reduced without affecting the performance of the polyurethane rigid foam, meeting the application requirements of polyurethane rigid foams while reducing the harm of recycled polyols to humans and the environment.

Claims

1. A method for removing aromatic amines from polyurethane waste foam regeneration polyol, characterized in that: The following steps are involved: (1) After the alcoholysis reaction of the waste polyurethane foam is completed, a self-made auxiliary agent of the general formula (I) is added to react the cyano group of the self-made auxiliary agent with the amine group of the aromatic amine; (2) removing excess alcoholysis agent and small molecular by-products by vacuum distillation; (3) filtering to obtain regenerated polyol; The structural formula of the self-made auxiliary agent is as follows: Among them, R is C1~C5.

2. The method for removing aromatic amines from polyurethane waste foam regeneration polyol according to claim 1, characterized in that: The temperature at which the cyano group of the self-made auxiliary agent reacts with the amine group of the aromatic amine is 70-80°C.

3. The method for removing aromatic amines from polyurethane waste foam regeneration polyol according to claim 1, characterized in that: The added amount of the self-made auxiliary agent is 2-6% of the total mass of the material after the alcoholysis reaction.

4. The method for removing aromatic amines from polyurethane waste foam regeneration polyol according to claim 1, characterized in that: The preparation method of the self-made auxiliary agent comprises the following steps: monohydric alcohol and toluene diisocyanate react with cyano group and alcohol hydroxyl group under the protection of inert gas to obtain the self-made auxiliary agent.

5. The method for removing aromatic amines from polyurethane waste foam regeneration polyol according to claim 4, characterized in that: The reaction temperature is 50-70° C., and the reaction time is 3-6 hours.

6. The method for removing aromatic amines from polyurethane waste foam regeneration polyol according to claim 4, characterized in that: The molar ratio of the monohydric alcohol to toluene diisocyanate is 1-1.15:

1.

7. The method for removing aromatic amines from polyurethane waste foam regeneration polyol according to claim 4, characterized in that: The monohydric alcohol is methanol, ethanol, n-propanol or n-butanol.

8. The method for removing aromatic amines from polyols regenerated from waste polyurethane foams according to claim 1, characterized in that: The alcoholysis reaction comprises the following steps: (1) collecting and cleaning the waste polyurethane foam, drying and crushing the waste polyurethane foam to obtain waste polyurethane foam particles; (2) adding the waste foam particles, diethylene glycol and potassium hydroxide into a reaction kettle, mixing them evenly, and replacing them with nitrogen; (3) Raise the temperature under a continuous nitrogen flow atmosphere and react at 170-200° C. for 3-5 hours.

9. The method for removing aromatic amines from polyurethane waste foam regeneration polyol according to claim 1, characterized in that: In step (2), the temperature of the reduced pressure distillation is 110-130°C.

10. Use of the polyol regenerated from waste polyurethane foam according to any one of claims 1 to 9 in the preparation of polyurethane rigid foam plastics.

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