A modified polymer polyol, its preparation and use

Abstract

The application discloses a modified polymer polyol and a preparation method and application thereof. The modified polymer polyol is obtained by copolymerization of a polymer polyol and a dihydroxy disulfide compound, and the molar ratio of the hydroxyl in the polymer polyol to the dihydroxy disulfide compound is 1:1. The modified polymer polyol embeds a disulfide bond (-S-S-) into a polymer chain, and the disulfide bond only serves as a depolymerization site, ensures the end group activity of the modified polymer polyol, the stability of the molecular weight and the hydroxyl value, directly reacts with isocyanate without additional end capping / modification, and does not affect the core indexes such as the mechanical property and the bonding property of the synthesized polyurethane. Through the introduction of the disulfide bond, the reduction depolymerization can be carried out in the specific way of breaking the disulfide bond, and the problems such as byproduct pollution and odor exceeding the standard caused by the traditional alcoholysis method are avoided.

Description

Technical Field

[0001] This invention relates to the field of polymer polyol modification and recycling applications, and more specifically, to a recyclable modified polymer polyol based on disulfide bonds, its preparation method, and its applications. Background Technology

[0002] Polyurethane (PU) materials, with their excellent mechanical properties, bonding strength, thermal insulation, and processing adaptability, are widely used in numerous fields such as automobile manufacturing, home appliance insulation, building energy conservation, and electronic device packaging, becoming an indispensable polymer material. However, with the rapid expansion of the polyurethane industry, the emissions of waste materials and discarded products (such as semi-rigid foam for automotive headliners, refrigerator insulation layers, and waste pipe foam) generated during its production process have surged, reaching millions of tons globally each year. Therefore, the recycling and reuse of waste polyurethane has become an urgent issue for the industry to address.

[0003] Currently, polyurethane recycling technologies are mainly divided into physical recycling methods and chemical recycling methods. Physical recycling methods are suitable for waste with low cross-linking degree and no obvious aging, but the performance of the recycled products is severely degraded, making it difficult to meet the requirements of high-end products. Chemical recycling methods break the cross-linking structures of polyurethane, such as ester bonds and urea bonds, through chemical action, degrading it into reusable oligomers or small molecule compounds, and have industrial application prospects. Among them, alcoholysis has become the most widely used chemical recycling method in industry due to its mild reaction conditions, easy separation of alcoholysis agents, and high product utilization rate. However, existing chemical recycling technologies still face several technical bottlenecks in the recovery of polymer polyols: First, the main chain structure of traditional polymer polyols is stable, and the polyurethane network formed by cross-linking with isocyanates is dense, making degradation difficult. Even with alcoholysis, incomplete degradation, large fluctuations in the hydroxyl value of the recycled polyol, and a wide molecular weight distribution can occur, affecting the performance stability of the recycled products. Second, the recycling process easily generates toxic aromatic amine byproducts such as 4,4'-diaminodiphenylmethane (MDA) and residual alcoholysis agents. These harmful substances not only affect the mechanical properties and processing safety of the recycled polyurethane but also produce irritating odors, making it difficult to meet the strict control requirements for volatile organic compounds (VOCs) and odors in the automotive and home appliance industries. Third, existing recyclable polyol preparation processes often involve cumbersome steps, catalyst residues, and numerous side reactions, making industrial scale-up difficult and production costs high, thus limiting their large-scale promotion. Summary of the Invention

[0004] The primary objective of this invention is to overcome the problems of difficult recovery of polymer polyols, easy generation of toxic byproducts in the recovery process of existing technologies, low purity of recovered products, and unstable performance, and to provide a modified polymer polyol.

[0005] Another object of the present invention is to provide a method for preparing modified polymer polyols.

[0006] Another object of the present invention is to provide a polymer polyol modified polyurethane resin.

[0007] Another object of the present invention is to provide a method for preparing the above-mentioned polymer polyol modified polyurethane resin.

[0008] The above-mentioned objective of the present invention is achieved through the following technical solution: A modified polymeric polyol, wherein the modified polymeric polyol is obtained by copolymerizing a polymeric polyol with a dihydroxy disulfide compound, wherein the molar ratio of the hydroxyl groups in the polymeric polyol to the dihydroxy disulfide compound is 1:1.

[0009] This invention utilizes a "main-chain block disulfide bond modification" route to prepare modified polymer polyols, achieving the regeneration and reuse of polyol compounds. Based on polymer polyols, this technology introduces disulfide bonds (-SS-) uniformly through a terminal hydroxyl dehydration reaction, forming a modified polymer polyol with depolymerizable sites in the main chain and retained terminal hydroxyl groups. This process does not alter the functionality or linear structure of the grafted ends of the polymer polyol. It ensures that the core indicators such as mechanical properties and adhesive properties meet application requirements when reacting with isocyanates to synthesize polyurethane. Furthermore, during recycling, a mild reduction reaction rapidly breaks down functional sites, achieving efficient recycling and regeneration of the polymer main chain. This avoids the problems of high temperature and pressure, byproduct pollution, and excessive odor associated with traditional alcoholysis methods. The method for preparing the modified polymer polyol includes the following steps: S1. Under cationic catalyst and inert atmosphere conditions, add dihydroxy disulfide compound to polymer polyol system and react until the number average molecular weight and hydroxyl value reach the theoretical range; S2. Cool down and adjust the pH of the system to terminate the reaction, and then perform post-treatment to obtain the modified polymer polyol.

[0010] Preferably, in step S1, the polymer polyol is one or more of polyester polyol, polyether polyol, polycarbonate polyol, polybutadiene polyol, or polycaprolactone polyol.

[0011] Preferably, in step S1, the number-average molecular weight Mn of the polymer polyol is 2000 to 8000.

[0012] Preferably, in step S1, the functionality of the polymer polyol is f = 2 to 4.

[0013] Preferably, in step S1, the dihydroxy disulfide compound is one or more of bis(2-hydroxyethyl) disulfide, bis(3-hydroxypropyl) disulfide, bis(4-hydroxyphenyl) disulfide, and 2,2'-dithiobis(1-propanol).

[0014] Preferably, in step S1, the molar ratio of the dihydroxy disulfide compound to the hydroxyl group in the polymer polyol is 1:1.

[0015] Preferably, in step S1, the cationic catalyst is one or more of boron trifluoride diethyl ether or its complex, boron trifluoride methyl ether or its complex, zinc chloride or aluminum trichloride.

[0016] Preferably, in step S1, the amount of the cationic catalyst is 0.1 to 0.4% of the total mass of the dihydroxydisulfide compound and the polymer polyol.

[0017] Preferably, in step S1, the reaction temperature is 110–130°C.

[0018] Preferably, in step S2, the alkali neutralizing agent is one or more of triethanolamine, diethanolamine, sodium hydroxide, sodium bicarbonate, sodium carbonate, or ammonia water.

[0019] Preferably, in step S2, the cooling temperature is 60–80°C.

[0020] More preferably, in step S2, the cooling temperature is 70-80°C.

[0021] Preferably, in step S2, the post-processing includes vacuum evacuation to remove small molecules, water washing to remove salt, and vacuum drying.

[0022] A polymer polyol-modified polyurethane resin, wherein the modified polymer polyol is reacted with diisocyanate as a polyol raw material.

[0023] Preferably, the diisocyanate is one or more of toluene diisocyanate, diphenylmethane diisocyanate, 1,6-hexane diisocyanate, isophorone diisocyanate, 1,5-naphthalene diisocyanate, and phenyldimethyl diisocyanate.

[0024] Preferably, the molar ratio of the isocyanate group in the diisocyanate to the hydroxyl group in the modified polymer polyol is 1.6 to 2.4:1.

[0025] In the preparation of the polymer polyol modified polyurethane resin, a catalyst is usually required.

[0026] Preferably, the catalyst is one or more of organotin, organoamine, or organobismuth.

[0027] Preferably, the catalyst content is 0.1 to 0.5% of the total mass of diisocyanate and modified polymer polyol.

[0028] The preparation method of the above-mentioned polymer polyol modified polyurethane resin includes the following steps: placing the modified polymer polyol, diisocyanate and catalyst in a reactor, reacting until the isocyanate reaches the theoretical value, and obtaining the polyurethane resin.

[0029] Specifically, the preparation method of the polymer polyol modified polyurethane resin includes the following steps: placing the modified polymer polyol, diisocyanate and catalyst in a reactor, heating to 60-80°C (preferably 65°C), and maintaining the temperature until the isocyanate reaches the theoretical value to obtain the urethane resin.

[0030] The present invention also claims protection for the method for recovering the above-mentioned modified polymer polyol.

[0031] The method for recovering the modified polymer polyol involves reacting the polymer polyol-modified polyurethane resin with a depolymerizing agent capable of depolymerizing SS bonds, followed by post-treatment to obtain the recycled polymer polyol.

[0032] More specifically, the method for recovering the modified polymer polyol includes the following steps: placing the polyurethane resin at room temperature until it is completely moisture-cured, and after pretreatment, gradually adding a depolymerizing agent and solvent capable of depolymerizing SS bonds, heating to 50-65°C (preferably 55°C) and holding the reaction until the particulate matter is completely dissolved, then slowly adding an oxidizing agent, and waiting until the mercapto infrared peak completely disappears, and then obtaining the regenerated polyether polyol through post-treatment.

[0033] Preferably, the pretreatment involves crushing the material into uniform particles of 5-10 mm using a pulverizer.

[0034] Preferably, the depolymerizing agent is one or more of dithiothreitol, thiourea, sodium dithionite, dithioerythritol, and β-mercaptoethanol.

[0035] Preferably, the depolymerizing agent content is 6-12% of the mass of the polyurethane resin.

[0036] Preferably, the solvent is a mixed solvent of ethanol and deionized water in a mass ratio of 2 to 5:1.

[0037] Preferably, the mass ratio of the mixed solvent to the polyurethane resin is 10 to 15:1.

[0038] Preferably, the oxidant is one or more selected from hydrogen peroxide, tert-butyl hydroperoxide, sodium persulfate, and potassium persulfate.

[0039] Preferably, the post-processing method involves extraction and separation with ethyl acetate, washing with water to remove salt, and drying under reduced pressure to remove solvent.

[0040] Compared with the prior art, the beneficial effects of the present invention are: The modified polymer polyol of the present invention uniformly embeds disulfide bonds (-SS-) into the polymer chain through a terminal hydroxyl dehydration reaction, and the disulfide bonds only serve as "depolymerization sites", ensuring the end group activity, molecular weight and hydroxyl value stability of the modified polymer polyol. It can react directly with isocyanate without additional end capping / modification, and does not affect the core indicators such as mechanical properties and adhesive properties of the synthesized polyurethane. By introducing disulfide bonds, reductive depolymerization can be achieved through specific disulfide bond cleavage, avoiding the problems of byproduct pollution and excessive odor associated with traditional alcoholysis methods. Furthermore, reductive depolymerization offers advantages such as mild conditions, high safety, and high purity of the depolymerization products, making it more environmentally friendly. The modified polymer polyol of this invention achieves the full-process technical goal of "controllable modification - usable synthesis - efficient regeneration," providing a novel technical path for the resource recycling of waste polyurethane, possessing significant industrial value and environmental significance. Detailed Implementation

[0041] To more clearly and completely describe the technical solution of the present invention, the present invention is further described in detail below through specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention. Various changes can be made within the scope of the claims of the present invention. The raw materials used in the following embodiments and comparative examples are all industrial grade. Please refer to Table 1 for the material source description.

[0042] Table 1 Material Source Description

[0043] Example 1 This embodiment provides a method for preparing modified polymer polyols and polyurethane resins, and a method for recovering modified polymer polyols.

[0044] (1) Preparation of modified polymer polyols 100 parts of polyether triol were placed in a reactor and heated to 120°C. 9.26 parts of bis(2-hydroxyethyl) disulfide and 0.22 parts of boron trifluoride ethyl ether were added, wherein the molar ratio of the hydroxyl groups in the polyether triol to the bis(2-hydroxyethyl) disulfide was 1:1. The reaction was carried out under nitrogen protection until the number average molecular weight and hydroxyl value reached the theoretical range. Then the temperature was lowered to 80°C, and triethanolamine was added to adjust the pH to 7-8 to terminate the reaction. Small molecules were removed by vacuum evacuation, the mixture was washed with water to remove salt, and dried under vacuum to obtain the modified polymer polyol.

[0045] (2) Preparation of polyurethane resin 100 parts of the above-mentioned modified polymer polyol, 15.95 parts of diphenylmethane diisocyanate and 0.12 parts of dibutyltin dilaurate were placed in a reactor, heated to 65°C, and kept at this temperature until the isocyanate content was 2.64% to obtain polyurethane resin.

[0046] (3) Recovery of polymer polyols The above polyurethane resin was cured at room temperature for 7 days and then crushed into uniform particles of 5-10 mm using a pulverizer. 100 parts of the particles were then placed in a reactor, and 10 parts of dithiothreitol and 1320 parts of a mixed solvent (ethanol to deionized water in a mass ratio of 3:1) were added. The temperature was raised to 55°C and the reaction was maintained until the particles were completely dissolved. Then, 10 parts of hydrogen peroxide were slowly added. After the mercapto infrared peak disappeared completely, ethyl acetate was added for extraction and separation, followed by water washing to remove salt and vacuum drying to remove the solvent, thus obtaining the regenerated polymer polyol.

[0047] Example 2 This embodiment provides a method for preparing modified polymer polyols and polyurethane resins, and a method for recovering modified polymer polyols.

[0048] (1) Preparation of modified polymer polyols 100 parts of polyester diol were placed in a reactor and heated to 120°C. 8.23 ​​parts of bis(2-hydroxyethyl) disulfide and 0.23 parts of boron trifluoride ethyl ether were added, wherein the molar ratio of hydroxyl groups in the polyester diol to bis(2-hydroxyethyl) disulfide was 1:1. The reaction was carried out under nitrogen protection until the number average molecular weight and hydroxyl value reached the theoretical range. Then the temperature was lowered to 80°C, and triethanolamine was added to adjust the pH to 7-8 to terminate the reaction. Small molecules were removed by vacuum evacuation, the product was washed with water to remove salt, and dried under vacuum to obtain the modified polymer polyol.

[0049] (2) Preparation of polyurethane resin 100 parts of the above-mentioned modified polymer polyol, 19.8 parts of diphenylmethane diisocyanate and 0.12 parts of dibutyltin dilaurate were placed in a reactor, heated to 65°C, and kept at this temperature until the isocyanate content was 2.45% to obtain polyurethane resin.

[0050] (3) Recovery of polymer polyols The above polyurethane resin was cured at room temperature for 7 days and then crushed into uniform particles of 5-10 mm using a pulverizer. 100 parts of the particles were then placed in a reactor, and 10 parts of dithiothreitol and 1320 parts of a mixed solvent (ethanol to deionized water in a mass ratio of 3:1) were added. The temperature was raised to 55°C and the reaction was maintained until the particles were completely dissolved. Then, 10 parts of hydrogen peroxide were slowly added. After the mercapto infrared peak disappeared completely, ethyl acetate was added for extraction and separation, followed by water washing to remove salt and vacuum drying to remove the solvent, thus obtaining the regenerated polymer polyol.

[0051] Example 3 This embodiment provides a method for preparing modified polymer polyols and polyurethane resins, and a method for recovering modified polymer polyols.

[0052] (1) Preparation of modified polymer polyols 100 parts of hydroxyl-terminated polybutadiene were placed in a reactor and heated to 120°C. 7.71 parts of bis(2-hydroxyethyl) disulfide and 0.24 parts of boron trifluoride ethyl ether were added, wherein the molar ratio of hydroxyl groups in the hydroxyl-terminated polybutadiene to bis(2-hydroxyethyl) disulfide was 1:1. The reaction was carried out under nitrogen protection until the number average molecular weight and hydroxyl value reached the theoretical range. Then the temperature was lowered to 80°C, and triethanolamine was added to adjust the pH to 7-8 to terminate the reaction. The modified polymer polyol was obtained by vacuum evacuation to remove small molecules, washing with water to remove salt, and vacuum drying.

[0053] (2) Preparation of polyurethane resin 100 parts of the above-mentioned modified polymer polyol, 10.53 parts of diphenylmethane diisocyanate and 0.12 parts of dibutyltin dilaurate were placed in a reactor, heated to 65°C, and kept at this temperature until the isocyanate content was 2.88% to obtain polyurethane resin.

[0054] (3) Recovery of polymer polyols The above polyurethane resin was cured at room temperature for 7 days and then crushed into uniform particles of 5-10 mm using a pulverizer. 100 parts of the particles were then placed in a reactor, and 10 parts of dithiothreitol and 1320 parts of a mixed solvent (ethanol to deionized water in a mass ratio of 3:1) were added. The temperature was raised to 55°C and the reaction was maintained until the particles were completely dissolved. Then, 10 parts of hydrogen peroxide were slowly added. After the mercapto infrared peak disappeared completely, ethyl acetate was added for extraction and separation, followed by water washing to remove salt and vacuum drying to remove the solvent, thus obtaining the regenerated polymer polyol.

[0055] Example 4 This embodiment provides a method for preparing modified polymer polyols and polyurethane resins, and a method for recovering modified polymer polyols.

[0056] (1) Preparation of modified polymer polyols 100 parts of polyether triol were placed in a reactor and heated to 120°C. 15.02 parts of bis(4-hydroxyphenyl) disulfide and 0.23 parts of boron trifluoride ethyl ether were added, wherein the molar ratio of hydroxyl groups in the polyether triol to bis(4-hydroxyphenyl) disulfide was 1:1. The reaction was carried out under nitrogen protection until the number average molecular weight and hydroxyl value reached the theoretical range. Then the temperature was lowered to 80°C, and triethanolamine was added to adjust the pH to 7-8 to terminate the reaction. Small molecules were removed by vacuum evacuation, the mixture was washed with water to remove salt, and dried under vacuum to obtain the modified polymer polyol.

[0057] (2) Preparation of polyurethane resin 100 parts of the above-mentioned modified polymer polyol, 15.14 parts of diphenylmethane diisocyanate and 0.12 parts of dibutyltin dilaurate were placed in a reactor, heated to 65°C, and kept at this temperature until the isocyanate content reached 2.48%, thus obtaining polyurethane resin.

[0058] (3) Recovery of polymer polyols The above polyurethane resin was cured at room temperature for 7 days and then crushed into uniform particles of 5-10 mm using a pulverizer. 100 parts of the particles were then placed in a reactor, and 10 parts of dithiothreitol and 1320 parts of a mixed solvent (ethanol to deionized water in a mass ratio of 3:1) were added. The temperature was raised to 55°C and the reaction was maintained until the particles were completely dissolved. Then, 10 parts of hydrogen peroxide were slowly added. After the mercapto infrared peak disappeared completely, ethyl acetate was added for extraction and separation, followed by water washing to remove salt and vacuum drying to remove the solvent, thus obtaining the regenerated polymer polyol.

[0059] Example 5 This embodiment provides a method for preparing modified polymer polyols and polyurethane resins, and a method for recovering modified polymer polyols.

[0060] (1) Preparation of modified polymer polyols 100 parts of polyether triol were placed in a reactor and heated to 120°C. 9.26 parts of bis(2-hydroxyethyl) disulfide and 0.22 parts of boron trifluoride ethyl ether were added, wherein the molar ratio of the hydroxyl groups in the polyether triol to the bis(2-hydroxyethyl) disulfide was 1:1. The reaction was carried out under nitrogen protection until the number average molecular weight and hydroxyl value reached the theoretical range. Then the temperature was lowered to 80°C, and triethanolamine was added to adjust the pH to 7-8 to terminate the reaction. Small molecules were removed by vacuum evacuation, the mixture was washed with water to remove salt, and dried under vacuum to obtain the modified polymer polyol.

[0061] (2) Preparation of polyurethane resin 100 parts of the above-mentioned modified polymer polyol, 15.95 parts of diphenylmethane diisocyanate and 0.12 parts of dibutyltin dilaurate were placed in a reactor, heated to 65°C, and kept at this temperature until the isocyanate content was 2.64% to obtain polyurethane resin.

[0062] (3) Recovery of polymer polyols The above polyurethane resin was cured at room temperature for 7 days and then crushed into uniform particles of 5-10 mm using a pulverizer. 100 parts of the particles were then placed in a reactor, and 10 parts of thiourea and 1320 parts of a mixed solvent (ethanol to deionized water in a mass ratio of 3:1) were added. The temperature was raised to 55°C and the reaction was maintained until the particles were completely dissolved. Then, 10 parts of hydrogen peroxide were slowly added. After the mercapto infrared peak disappeared completely, ethyl acetate was added for extraction and separation, followed by water washing to remove salt and vacuum drying to remove the solvent, thus obtaining the regenerated polymer polyol.

[0063] Example 6 This embodiment provides a method for preparing modified polymer polyols and polyurethane resins, and a method for recovering modified polymer polyols.

[0064] (1) Preparation of modified polymer polyols 100 parts of polyether triol were placed in a reactor and heated to 120°C. 9.26 parts of bis(2-hydroxyethyl) disulfide and 0.22 parts of boron trifluoride ethyl ether were added, wherein the molar ratio of the hydroxyl groups in the polyether triol to the bis(2-hydroxyethyl) disulfide was 1:1. The reaction was carried out under nitrogen protection until the number average molecular weight and hydroxyl value reached the theoretical range. Then the temperature was lowered to 80°C, and triethanolamine was added to adjust the pH to 7-8 to terminate the reaction. Small molecules were removed by vacuum evacuation, the mixture was washed with water to remove salt, and dried under vacuum to obtain the modified polymer polyol.

[0065] (2) Preparation of polyurethane resin 100 parts of the above-mentioned modified polymer polyol, 15.95 parts of diphenylmethane diisocyanate and 0.12 parts of dibutyltin dilaurate were placed in a reactor, heated to 65°C, and kept at this temperature until the isocyanate content was 2.64% to obtain polyurethane resin.

[0066] (3) Recovery of polymer polyols The above polyurethane resin was cured at room temperature for 7 days and then pulverized into uniform particles of 5-10 mm using a pulverizer. 100 parts of the particles were then placed in a reactor, and 10 parts of sodium dithionite and 1320 parts of a mixed solvent (ethanol to deionized water in a mass ratio of 3:1) were added. The temperature was raised to 55°C and the reaction was maintained until the particles were completely dissolved. Then, 10 parts of hydrogen peroxide were slowly added. After the mercapto infrared peak completely disappeared, ethyl acetate was added for extraction and separation, followed by water washing to remove salt and vacuum drying to remove the solvent, thus obtaining the regenerated polymer polyol.

[0067] Comparative Example 1 This comparative example provides a method for preparing polyurethane resin and a method for recovering polymer polyols.

[0068] (1) Preparation of polyurethane resin 100 parts of polyether triol, 17.25 parts of diphenylmethane diisocyanate and 0.12 parts of dibutyltin dilaurate were placed in a reactor, heated to 65°C, and kept at this temperature until the isocyanate content reached 2.79%, thus obtaining polyurethane resin.

[0069] (2) Recovery of polymer polyols The above polyurethane resin was cured at room temperature for 7 days and then crushed into uniform particles of 5-10 mm using a pulverizer. 100 parts of the particles were then placed in a reactor and 1320 parts of mixed solvent (ethanol to deionized water in a mass ratio of 3:1) were added. The temperature was raised to 55°C, and ethyl acetate was added for extraction and separation. The mixture was washed with water to remove salt and dried under reduced pressure to remove the solvent, thus obtaining the regenerated polymer polyol.

[0070] Comparative Example 2 This comparative example provides a method for preparing polyurethane resin and a method for recovering polymer polyols.

[0071] (1) Preparation of polyurethane resin 100 parts of polyether triol, 17.25 parts of diphenylmethane diisocyanate and 0.12 parts of dibutyltin dilaurate were placed in a reactor, heated to 65°C, and kept at this temperature until the isocyanate content reached 2.79%, thus obtaining polyurethane resin.

[0072] (2) Recovery of polymer polyols The above polyurethane resin was cured at room temperature for 7 days and then crushed into uniform particles of 5-10 mm using a pulverizer. 100 parts of the particles were then placed in a reactor, and 7 parts of sodium hydroxide and 1070 parts of mixed solvent (ethylene glycol to deionized water in a mass ratio of 3:1) were added. The temperature was raised to 170°C and the reaction was maintained until the particles were completely dissolved. Ethyl acetate was added for extraction and separation, followed by washing with water to remove salt and drying under reduced pressure to remove the solvent, thus obtaining the regenerated polymer polyol.

[0073] The hydroxyl-terminated modified polyether polyols and their regenerated polyether polyols prepared in Examples 1-6 and Comparative Examples 1-2 were tested for hydroxyl value, acid value, viscosity, and aromatic amine content. The specific test methods are as follows: (1) Hydroxyl value: determined in accordance with GB / T12008.3-2009 Plastics Polyether Polyols Part 3: Determination of Hydroxyl Value.

[0074] (2) Acid value: determined in accordance with GB / T12008.5-2010 Plastics Polyether Polyols Part 5: Determination of Acid Value.

[0075] (3) Viscosity: determined in accordance with GB / T12008.7-2010 Plastics Polyether Polyols Part 7: Determination of Viscosity.

[0076] (4) Aromatic amines: determined according to GB / T 45277-2025 Determination of the content of nine primary aromatic amines in toys by gas chromatography-mass spectrometry.

[0077] (5) Number average molecular weight: According to GB / T 27843-2011 Determination of low molecular weight components of polymers in chemicals by gel permeation chromatography The hydroxyl-terminated modified polyether polyols and their regenerated polyether polyols prepared in Examples 1-5 and Comparative Examples 1-2 were tested for hydroxyl value, acid value, viscosity, aromatic amine content, and number-average molecular weight. The results are shown in Table 2 below.

[0078] Table 2. Determination of the recovery index of the modified polymer polyols prepared in Examples 1-6 and Comparative Examples 1-2.

[0079] Note: The viscosity test temperature in Example 2 was 80°C, and the other test temperatures were 23°C.

[0080] As shown in Table 2, the test results of Examples 1-6 indicate that the hydroxyl value after modification in Examples 1-6 decreased slightly compared to the value before modification, while the molecular weight increased slightly. This indicates that disulfide bonds were introduced at the ends of the polyether molecular chains. At the same time, precise control of the reaction ratio ensured the retention of the terminal hydroxyl structure and did not affect the crosslinking reactivity with isocyanate. After regeneration, the hydroxyl value rebounded significantly to near the value before modification, and the number-average molecular weight was also close to that of the original product. The depolymerization process only specifically broke the disulfide bonds without destroying the polymer backbone, achieving precise restoration of the molecular structure. As shown in Examples 1-6, polyether, polyester, and hydroxyl-terminated polybutadiene polyols all achieved efficient performance restoration after modification and regeneration, demonstrating strong compatibility among polyols with different structures. Comparative Example 1, a polyurethane resin prepared from unmodified polyether triol, showed insoluble particles after reduction and depolymerization treatment. This was mainly because it did not introduce disulfide bond depolymerization sites, and the depolymerizing agent could not break the crosslinking network of the polyurethane, resulting in incomplete degradation. This indicates that block modification of disulfide bonds is the core prerequisite for achieving efficient depolymerization of polyurethane.

[0081] In Examples 1-6, no aromatic amines were detected before modification, after modification, and after regeneration. This indicates that the reduction depolymerization process only breaks disulfide bonds and does not attack the urea bonds and urethane bonds of polyurethane. This avoids the generation of aromatic amines through isocyanate decomposition caused by high temperature, eliminating the generation of toxic byproducts from the source. It fully meets the strict control requirements for volatile organic compounds and odors in high-end fields, and has significant environmental advantages. Comparative Example 2 uses the traditional alcoholysis method, which reduces urea bonds and urethane bonds to hydroxyl groups through alkaline depolymerization. After depolymerization, there are more byproducts and the purity is slightly lower, resulting in a relatively small hydroxyl value. At the same time, it generates toxic byproduct aromatic amines, which is not conducive to environmental protection and the concept of green chemistry.

[0082] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A modified polymer polyol, characterized in that, The modified polymer polyol is obtained by copolymerizing the polymer polyol with a dihydroxy disulfide compound, wherein the molar ratio of the hydroxyl groups in the polymer polyol to the dihydroxy disulfide compound is 1:

1.

2. The method for preparing the modified polymer polyol according to claim 1, characterized in that, Includes the following steps: S1. Under cationic catalyst and inert atmosphere conditions, add dihydroxy disulfide compound to polymer polyol system and react until the number average molecular weight and hydroxyl value reach the theoretical range. S2. Cool down and adjust the pH of the system to terminate the reaction, and then perform post-treatment to obtain the modified polymer polyol.

3. The preparation method according to claim 2, characterized in that, The polymer polyol mentioned in step S1 is one or more of polyester polyol, polyether polyol, polycarbonate polyol, polybutadiene polyol, or polycaprolactone polyol.

4. The preparation method according to claim 2, characterized in that, The cationic catalyst in step S1 is one or more of boron trifluoride diethyl ether or its complex, boron trifluoride methyl ether or its complex, zinc chloride or aluminum trichloride.

5. The preparation method according to claim 2, characterized in that, The dihydroxy disulfide compound in step S1 is one or more of bis(2-hydroxyethyl) disulfide, bis(3-hydroxypropyl) disulfide, bis(4-hydroxyphenyl) disulfide, or 2,2'-dithiobis(1-propanol).

6. A polymer polyol-modified polyurethane resin, characterized in that, It is prepared by reacting the modified polymer polyol described in any one of claims 1 to 5 with diisocyanate.

7. The polymer polyol-modified polyurethane resin according to claim 6, characterized in that, The diisocyanate is one or more of toluene diisocyanate, diphenylmethane diisocyanate, 1,6-hexane diisocyanate, isophorone diisocyanate, 1,5-naphthalene diisocyanate, or phenyldimethyl diisocyanate.

8. The polymer polyol-modified polyurethane resin according to claim 6, characterized in that, The molar ratio of the isocyanate group in the diisocyanate to the hydroxyl group in the modified polymer polyol is 1.6 to 2.4:

1.

9. A method for recovering polymer polyols, characterized in that, The process includes the following steps: reacting the polymer polyol modified polyurethane resin according to any one of claims 6 to 8 with a depolymerizing agent capable of depolymerizing SS bonds, followed by post-treatment to obtain a recycled polymer polyol.

10. The method for recovering polymer polyols according to claim 9, characterized in that, The depolymerizing agent is one or more of dithiothreitol, thiourea, sodium dithionite, dithioerythritol, or β-mercaptoethanol.

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