A process for the regeneration of polyurethane polyether polyols

Abstract

This invention discloses a method for regenerating polyurethane polyether polyol, comprising the following steps: (1) mixing waste polyurethane and alcoholysis agent in a weight ratio of 1~2.5:1, adding 0.05%~0.2% catalyst of the total mass of waste polyurethane and alcoholysis agent, replacing the reaction atmosphere with inert gas, heating to 160~200℃, and carrying out alcoholysis reaction; (2) filtering the product from step (1) to remove solids, cooling to 80~110℃, adding 1~15% glycidyl ether containing substituents based on the total mass of the filtered material, and reacting for 0.5~5 hours to obtain polyether polyol. By adding epoxy glycidyl ether modifiers, not only can the aromatic amines of the regenerated polyether polyol be effectively reduced, but the hydroxyl / ether bonds generated by the ring opening can form coordination complexes with residual metal ions in the catalyst, achieving the effect of synergistic removal of the catalyst in the system. In addition, this type of modifier can also end-cap and extend the chain with the terminal carboxyl and terminal aldehyde groups in the crude regenerated polyether, thereby achieving the effect of narrowing the molecular weight distribution and reducing the viscosity of the product.

Description

Technical Field

[0001] This invention relates to a method for preparing polymers, and more particularly to a method for regenerating polyurethane polyether polyols. Background Technology

[0002] Polyurethane semi-rigid foam combines excellent mechanical properties, cushioning, and thermal insulation, and is widely used in automotive interiors, home appliance insulation, building sealing, and rail transportation. It is one of the fastest-growing thermosetting foam varieties among polymer materials. With the continuous increase in production capacity and consumption, a large amount of production scraps, discarded products, and construction waste have accumulated. Recycling and regenerating polyurethane semi-rigid foam is beneficial for making full use of resources and reducing the pressure of waste disposal.

[0003] Chemical recycling of polyurethane foam can degrade the foam to obtain a recycled liquid. Chemical recycling methods mainly include alkaline hydrolysis, amino hydrolysis, hydrolysis, and alcoholysis. Alcoholysis is currently the route with the best industrial potential in polyurethane chemical recycling. Its principle is to use polyhydroxy small molecule compounds or oligomers to exchange with urethane bonds, "breaking down" the long chains or cross-linked polyurethane networks, transforming them into polyether diols, aliphatic diols, and some low molecular weight polyurethane diols. However, crude alcoholysis products have many defects and are difficult to meet the requirements of industrial reuse: Firstly, alcoholysis products often use amine compounds, such as diethanolamine, as catalysts. The affinity of amino groups for isocyanates is greater than that for hydroxyl groups. In subsequent reuse processes, residual catalysts can easily block the alcohol reaction and accelerate the reaction rate (CN 102504331 A), causing product self-polymerization, oxidation, cross-linking, and deterioration, leading to product stratification, increased viscosity, darkening of color, and poor storage stability. As an improvement to the amine compound approach, Lewis acids and alkali metal hydroxides, when used as catalysts for alcoholysis, leave metal ion residues that affect the polyurethane polymerization process, leading to uncontrolled foaming and curing rates.

[0004] The polyurethane molecular chain contains urea bonds, which are prone to hydrolysis or decomposition during recycling, forming toxic substances such as aromatic amines. This also easily leads to uncontrolled reaction rates during recycling. Utilizing ring-opening polymerization between epoxides and amine bonds helps reduce the amine value of the raw materials. For example, CN 113896880 A discloses a method for preparing polyether polyols from recycled rigid polyurethane foam, and CN 120390760 A discloses a method for recovering polyols. However, CN 113896880 A uses a large amount of propylene oxide and is relatively complex to operate. The method disclosed in CN 120390760 A has room for further reduction in aromatic amine content. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a method for simultaneously reducing the amine content and metal ion residue in the product of recycled polyurethane polyether polyol.

[0006] Technical solution: The method for regenerating polyurethane polyether polyols according to the present invention includes the following steps:

[0007] (1) Mix waste polyurethane and alcoholysis agent in a weight ratio of 1~2.5:1, add 0.05%~0.2% catalyst of the total mass of waste polyurethane and alcoholysis agent, replace the reaction atmosphere with inert gas, heat to 160~200℃, and carry out alcoholysis reaction; the alcoholysis agent is an oligomer and a fatty alcohol containing 2~3 hydroxyl groups, and the catalyst is at least one of sodium hydroxide, potassium hydroxide, potassium carbonate, potassium acetate, potassium methoxide, potassium ethoxide, potassium tert-butoxide, and cesium hydroxide;

[0008] (2) Filtration step (1) product, remove solids, cool to 80~110℃, add 1~15% of glycidyl ether containing substituents based on the total mass of the filtered material, react for 0.5~5 hours to obtain polyether polyol, wherein the glycidyl ether containing substituents is at least one of alkyl glycidyl ether, phenyl glycidyl ether, and aryl glycidyl ether.

[0009] Preferably, the mass ratio of waste polyurethane to alcoholysis agent is 1.5 to 2:1, and the catalyst addition ratio is 0.08% to 0.15%.

[0010] Preferably, the oligomer is at least one selected from polyethylene glycol, polypropylene glycol, and polyether polyol, with a number average molecular weight of 250-1000, and the fatty alcohol containing 2-3 hydroxyl groups is at least one selected from ethylene glycol, propylene glycol, butylene glycol, 1,6-hexanediol, diethylene glycol, triethylene glycol, dipropylene glycol, and tripropylene glycol. More preferably, the oligomer has a number average molecular weight of 250-500.

[0011] Preferably, the mass ratio of oligomer to fatty alcohol with 2-3 hydroxyl groups is 1.2-4:1. The proportion of oligomer added is related to its molecular weight; when the molecular weight of the oligomer is low, the proportion of oligomer added can be increased. More preferably, the mass ratio of oligomer to fatty alcohol with 2-3 hydroxyl groups is 1.5-3:1. Most preferably, the mass ratio is 1.8-2.5:1.

[0012] Preferably, the alcoholysis reaction lasts for 2 to 6 hours. More preferably, the alcoholysis reaction temperature is 165 to 200°C, and the duration is 2.5 to 5.5 hours.

[0013] Preferably, in step (2), the temperature is lowered to 80~105℃. If dehydration is not performed before alcoholysis, further increasing the temperature can easily trigger the hydrolysis and self-polymerization of glycidyl ether, reducing the amine removal effect. More preferably, the temperature is lowered to 80~100℃.

[0014] Preferably, in step (2), the alkyl substituent of the alkyl glycidyl ether has a length of 3 to 12 carbons. More preferably, the alkyl substituent of the alkyl glycidyl ether has a length of 4 to 10 carbons. The length can be 4, 5, 6, 7, or 8 carbons. If the carbon substituent is too long, it increases steric hindrance and reduces the reactivity. Most preferably, the glycidyl ether containing the substituent is at least one of butyl glycidyl ether, phenyl glycidyl ether, octyl glycidyl ether, and lauryl glycidyl ether.

[0015] Preferably, the amount of glycidyl ether containing the substituent is 2-12%. More preferably, the amount of glycidyl ether containing the substituent is 2-9%. Most preferably, the amount of glycidyl ether containing the substituent is 2.5-6.5%.

[0016] Preferably, in step (2), the glycidyl ether containing the substituent is added dropwise for 20-80 minutes. More preferably, the dropwise addition time is 30-60 minutes. The dropwise addition time is determined according to the amount of material added. The reaction process is exothermic, and dropwise addition can prevent overheating and avoid the reduction of the amine removal effect due to the hydrolysis and self-polymerization of epoxy groups. As the amount of material added increases, the dropwise addition time can be appropriately extended. More preferably, in step (2), after the dropwise addition is completed, the reaction continues for 1-3 hours. The reactivity is as follows: phenyl glycidyl ether > octyl, butyl > lauryl. For modifiers with high reactivity, the reaction time should be appropriately shortened.

[0017] Preferably, the post-treatment method is as follows: vacuum distillation to remove low-boiling-point substances, and filtration to remove solids; the vacuum distillation temperature is 110~130℃, and the vacuum degree is -0.095~-0.099MPa. The post-treatment temperature is controlled to avoid darkening of the product color.

[0018] Preferably, the inert gas is nitrogen or argon.

[0019] Beneficial Effects: Compared with the prior art, the present invention has the following advantages: 1. The present invention uses alkali metal compounds as catalysts to improve the degree of alcoholysis and reduce the influence of amine groups on the catalyst. Glycidyl ethers containing phenyl, alkyl, or aryl substituents are used as modifiers. The amino and epoxy groups formed during the alcoholysis process undergo addition and ring-opening, which significantly reduces the amine value of the product. The carboxyl hydroxyl groups of the ring-opening product and the recycled polyether are capped and extended, narrowing the molecular weight distribution of the recycled polyether polyol. At the same time, the hydroxyl / ether bonds generated by ring opening can coordinate and complex with residual metal ions in the catalyst to remove metal ions from the system. When the recycled product is reused, the foaming rate is effectively slowed down, avoiding premature hardening and foam collapse; 2. The amount of modifier added is reduced, the reaction temperature is lowered, the conditions are milder, and energy consumption is reduced; 3. The alcoholysis reaction process does not require pre-dehydration, and the post-treatment is simple. Detailed Implementation

[0020] The present invention will be further described below with reference to specific embodiments. The raw material, polyether polyol CHE-303, was provided by Changhua Chemical, with a molecular weight of 300, and was prepared from glycerol and propylene oxide (PO).

[0021] Example 1

[0022] (1) After collecting the polyurethane waste foam, clean it, dry it and crush it to obtain polyurethane waste foam particles.

[0023] (2) Mix waste foam particles, CHE-303 and propylene glycol in a reactor at a mass ratio of 1.7:0.7:0.3, add 0.1% potassium hydroxide of the total material mass, mix evenly, and replace with nitrogen 3 times;

[0024] (3) Heat to 170°C under a continuous nitrogen atmosphere and react for 5 hours. After the reaction is complete, filter to remove the solid.

[0025] (4) Under a nitrogen atmosphere, the material obtained in step (3) is cooled to 90°C, and 3% butyl glycidyl ether modifier is added based on its total mass. After 30 min of addition, the reaction is carried out for 3 hours.

[0026] (5) Purification by vacuum distillation at -0.095MPa while maintaining 110℃;

[0027] (6) Filter to obtain recycled polyether polyol S1.

[0028] Example 2

[0029] (1) After collecting the polyurethane waste foam, clean it, dry it and crush it to obtain polyurethane waste foam particles.

[0030] (2) Add the waste foam particles, CHE-303, propylene glycol, and potassium hydroxide into the reactor and mix them evenly. The feeding ratio is the same as in Example 1. Nitrogen gas is purged 3 times.

[0031] (3) Heat to 200°C under a continuous nitrogen atmosphere and react for 3 hours. After the reaction is complete, filter to remove the solid.

[0032] (4) Under a nitrogen atmosphere, the material obtained in step (3) is cooled to 90°C, and 3% phenyl glycidyl ether modifier is added. After 30 min of addition, the reaction is carried out for 1 hour.

[0033] (5) Purification by vacuum distillation at 110℃ and -0.099MPa;

[0034] (6) Filter to obtain recycled polyether polyol S2.

[0035] Example 3

[0036] (1) After collecting the polyurethane waste foam, clean it, dry it and crush it to obtain polyurethane waste foam particles.

[0037] (2) Add the waste foam particles, CHE-303, propylene glycol, and potassium hydroxide into the reactor and mix them evenly. The feeding ratio is the same as in Example 1. Nitrogen gas is purged 3 times.

[0038] (3) Heat to 180°C under a continuous nitrogen atmosphere and react for 4 hours. After the reaction is complete, filter to remove the solid.

[0039] (4) Under a nitrogen atmosphere, cool down to 100°C, add 5% octyl glycidyl ether modifier, and after 30 min of dropwise addition, react for 2 hours;

[0040] (5) Purification by vacuum distillation at -0.095MPa while maintaining 130℃;

[0041] (6) Filter to obtain recycled polyether polyol S3.

[0042] Example 4

[0043] (1) After collecting the polyurethane waste foam, clean it, dry it and crush it to obtain polyurethane waste foam particles.

[0044] (2) Add the waste foam particles, CHE-303, propylene glycol, and potassium hydroxide into the reactor and mix them evenly. The feeding ratio is the same as in Example 1. Nitrogen gas is purged 3 times.

[0045] (3) Heat to 180°C under a continuous nitrogen atmosphere and react for 4 hours. After the reaction is complete, filter to remove the solid.

[0046] (4) Under a nitrogen atmosphere, the temperature was lowered to 100°C, and 5% lauryl glycidyl ether modifier was added. After the addition was completed in 45 min, the reaction was carried out for 2 hours.

[0047] (5) Purification by vacuum distillation at -0.095MPa while maintaining 110℃;

[0048] (6) Filter to obtain recycled polyether polyol S4.

[0049] Example 5 This example is similar to Example 2, except that the amount of phenyl glycidyl ether modifier added is 6%.

[0050] (1) After collecting the polyurethane waste foam, clean it, dry it and crush it to obtain polyurethane waste foam particles.

[0051] (2) Add the waste foam particles, CHE-303, propylene glycol, and potassium hydroxide into the reactor and mix them evenly. The feeding ratio is the same as in Example 1. Nitrogen gas is purged 3 times.

[0052] (3) Heat to 200°C under a continuous nitrogen atmosphere and react for 3 hours. After the reaction is complete, filter to remove the solid.

[0053] (4) Under a nitrogen atmosphere, the temperature was lowered to 90°C, and 6% phenyl glycidyl ether modifier was added. After the addition was completed in 45 min, the reaction was carried out for 1 hour.

[0054] (5) Purification by vacuum distillation at 110℃ and -0.099MPa;

[0055] (6) Filter to obtain recycled polyether polyol S5.

[0056] The difference between Comparative Example 1 and Example 1 is that no glycidyl ether modifier was added. The specific steps are as follows:

[0057] (1) After collecting the polyurethane waste foam, clean it, dry it and crush it to obtain polyurethane waste foam particles.

[0058] (2) Add the waste foam particles, CHE-303, propylene glycol, and potassium hydroxide into the reactor and mix them evenly. Then, replace the mixture with nitrogen three times.

[0059] (3) The temperature was raised to 180°C and reacted for 4 hours under a continuous nitrogen atmosphere;

[0060] (4) Purification by vacuum distillation at 110℃ and -0.095MPa;

[0061] (5) Filter to obtain recycled polyether polyol S6.

[0062] The difference between Comparative Example 2 and Example 4 is that the temperature in step (4) is 110°C. The specific steps are as follows:

[0063] (1) After collecting the polyurethane waste foam, clean it, dry it and crush it to obtain polyurethane waste foam particles.

[0064] (2) Add the waste foam particles, CHE-303, propylene glycol, and potassium hydroxide into the reactor and mix them evenly. Then, replace the mixture with nitrogen three times.

[0065] (3) The temperature was raised to 180°C under a continuous nitrogen atmosphere, and the reaction was carried out for 4 hours;

[0066] (4) Cool down to 110℃, add 5% lauryl glycidyl ether modifier, and react for 2 hours after the addition is completed in 45 min;

[0067] (5) Purification by vacuum distillation at -0.095MPa while maintaining 110℃;

[0068] (6) Filter to obtain recycled polyether polyol S7.

[0069] The difference between Comparative Example 3 and Comparative Example 2 is that zinc chloride is used instead of potassium hydroxide as the catalyst. The specific steps are as follows:

[0070] (1) After collecting the polyurethane waste foam, clean it, dry it and crush it to obtain polyurethane waste foam particles.

[0071] (2) Add the waste foam particles, CHE-303, propylene glycol, and zinc chloride into the reactor and mix them evenly. Then, replace the mixture with nitrogen three times.

[0072] (3) Heat to 200°C under a continuous nitrogen atmosphere and react for 3 hours;

[0073] (4) Cool down to 90°C, add 3% phenyl glycidyl ether modifier, and react for 1 hour after the addition is completed in 30 min;

[0074] (5) Purification by vacuum distillation at -0.095MPa while maintaining 110℃;

[0075] (6) Filter to obtain recycled polyether polyol S8.

[0076] The difference between Comparative Example 4 and Example 4 is that an equal amount of trimethylolpropane glycidyl ether was used instead of lauryl glycidyl ether as a modifier.

[0077] The acid value (GB / T12008.5-2010), hydroxyl value (GB / T12008.3-2009), viscosity (GB / T 12008.7-2010), aromatic amine (GB / T17592-2011), and determination of sodium and potassium (GB / T 12008.4-2009 (Appendix A) - Plastic polyether polyols Part 4: Determination of sodium and potassium) of the recycled polyols prepared in the examples and comparative examples were tested, and the test results are shown in Table 1.

[0078] Table 1. Index data of regenerated polyether polyols prepared in Examples 1-5 and Comparative Examples 1-4

[0079]

[0080] As can be seen from Table 1, the hydroxyl value, viscosity, and aromatic amine parameters of the recycled polyether polyols obtained in Examples 1-5 are between 400 and 500 mg KOH / g, the acid value is between 0.1 and 2.0 mg KOH / g, the aromatic amine content is less than 500 ppm, and the metal ion content is less than 25 ppm. Compared with Comparative Example 1, these parameters are effectively improved, which helps to enhance the foaming performance of the product. Comparative Example 2 added a modifier, but the reaction temperature was higher, resulting in an increase in the S7 amine content of the recycled polyether polyol. This may be because the high temperature caused the glycidyl ether to self-hydrolyze and polymerize. Comparative Example 3 changed the catalyst, resulting in poor catalytic effect and higher product viscosity and hydroxyl value. Comparative Example 4 changed the type of modifier. Compared with Comparative Example 2, the aromatic amine content of the recycled polyether polyol decreased, but the viscosity increased significantly. This may be because the modifier continued to react with the recycled polyether, resulting in excessively high product viscosity.

Claims

1. A method for regenerating polyurethane polyether polyols, characterized in that, Includes the following steps: (1) Mix waste polyurethane and alcoholysis agent in a weight ratio of 1~2.5:1, add 0.05%~0.2% catalyst of the total mass of waste polyurethane and alcoholysis agent, replace the reaction atmosphere with inert gas, heat to 160~200℃, and carry out alcoholysis reaction; the alcoholysis agent is an oligomer and a fatty alcohol containing 2~3 hydroxyl groups, and the catalyst is at least one of sodium hydroxide, potassium hydroxide, potassium carbonate, potassium acetate, potassium methoxide, potassium ethoxide, potassium tert-butoxide, and cesium hydroxide; (2) Filtration step (1) product, remove solids, cool to 80~110℃, add 1~15% of glycidyl ether containing substituents based on the total mass of the filtered material, react for 0.5~5 hours to obtain polyether polyol, wherein the glycidyl ether containing substituents is at least one of alkyl glycidyl ether, phenyl glycidyl ether, and aryl glycidyl ether.

2. The method for regenerating polyurethane polyether polyols according to claim 1, characterized in that, The oligomer is at least one of polyethylene glycol and polypropylene glycol, with a number average molecular weight of 250-1000, and the fatty alcohol containing 2-3 hydroxyl groups is at least one of ethylene glycol, propylene glycol, butanediol, 1,6-hexanediol, diethylene glycol, triethylene glycol, dipropylene glycol, and tripropylene glycol.

3. The method for regenerating polyurethane polyether polyols according to claim 2, characterized in that, The mass ratio of oligomers to fatty alcohols with 2-3 hydroxyl groups is 1.2-4:

1.

4. The method for regenerating polyurethane polyether polyols according to claim 1, characterized in that, The alcoholysis reaction lasts for 2 to 6 hours.

5. The method for regenerating polyurethane polyether polyols according to claim 1, characterized in that, In step (2), the temperature is reduced to 80~105℃.

6. The method for regenerating polyurethane polyether polyols according to claim 1, characterized in that, In step (2), the alkyl substituent of the alkyl glycidyl ether has a length of 3 to 12 carbons.

7. The method for regenerating polyurethane polyether polyols according to claim 1, characterized in that, The amount of glycidyl ether containing substituents added is 2-12%.

8. The method for regenerating polyurethane polyether polyols according to claim 1, characterized in that, In step (2), the glycidyl ether containing substituents is added by dropping, and the dropping time is 20 to 80 minutes.

9. The method for regenerating polyurethane polyether polyols according to claim 1, characterized in that, The post-processing method is as follows: low-boiling-point substances are removed by vacuum distillation, and solids are removed by filtration; the vacuum distillation temperature is 110~130℃, and the vacuum degree is -0.095~-0.099MPa.

10. The method for regenerating polyurethane polyether polyols according to claim 1, characterized in that, The inert gas is nitrogen or argon.

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