Preparation method of waste PET alcoholysis polyester polyol
Patent Information
- Application Number
- CN202610114188.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-28
- Publication Date
- 2026-09-25
AI Technical Summary
然而，由于结构和性能稳定导致PET塑料难以回收利用，大量堆积的废弃PET塑料造成了严重的环境污染和大量的资源浪费
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Figure CN122810364A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of environmentally friendly and recyclable polymer material preparation technology, specifically relating to a method for preparing polyester polyols from waste PET alcoholysis. Background Technology
[0002] PET plastic is favored for its high strength, light weight, and good transparency, and is widely used in the packaging of beverages, food, and cosmetics. However, due to its stable structure and performance, PET plastic is difficult to recycle, and the large accumulation of waste PET plastic has caused serious environmental pollution and a significant waste of resources.
[0003] Among various recycling technologies, the ethylene glycol alcoholysis of waste PET has become the easiest recycling technology to achieve large-scale industrial degradation due to its advantages such as high safety, suitable reaction conditions, and the potential for upgrading and applying the products. Its high-value-added alcoholysis products, ethylene glycol terephthalate and its derived polyester polyols, have a dihydroxyl-terminated structure, making them potential raw materials for the preparation of polyurethane materials. Ethylene glycol alcoholysis of waste PET plastic has significant potential for industrial development.
[0004] Therefore, it is necessary to invent a method for preparing polyester polyols from waste PET alcoholysis to solve the above problems. Summary of the Invention
[0005] This invention utilizes inexpensive and commercially available ethylene glycol as the alcoholysis agent, zinc acetate as the catalyst, and adipic acid as the esterification monomer to achieve the preparation of aromatic alcoholysis polyols with tunable structure and properties while recycling waste PET bottle flakes. This invention employs various characterization methods to study the composition and thermal properties of the alcoholysis products and polyester polyols under different alcoholysis and esterification process conditions, aiming to achieve economical and efficient alcoholysis and precise controllability of the esterification process.
[0006] The present invention adopts the following technical solution: Green aromatic alcoholysis polyols are prepared by a simple one-pot process using waste PET bottle flakes, ethylene glycol, zinc acetate, and adipic acid. The reaction principle is as follows:
[0007] The specific steps are as follows: Waste PET bottle flakes were washed three times with anhydrous ethanol and then dried in a 60 °C oven for later use.
[0008] (1) When using, add waste PET bottle flakes, ethylene glycol and zinc acetate to a three-necked flask and place it in an oil bath. Heat to 220 °C and start the equipped mechanical stirring and the condenser with an oil seal. React for a certain period of time.
[0009] The amount of zinc acetate added is 0.5% of the mass of the PET bottle flakes.
[0010] (2) Then the temperature was lowered to 170 °C, and adipic acid was added for esterification and chain extension. The reaction was carried out for 60 min.
[0011] The molar ratio of adipic acid to ethylene glycol is 0.65:1.
[0012] The reaction system was reheated to 220 °C and the apparatus was changed. The spherical condenser was replaced with a straight condenser, and the reaction continued. After a certain period of time, the system was evacuated and the vacuum level was adjusted to 0.1 MPa. Finally, the reaction was completed, and a brown paste-like product was obtained, yielding an aromatic alcoholysis polyol. Attached Figure Description
[0013] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.
[0014] Figure 1 IOH and Mn in different proportions in the embodiments; Figure 2 IOH and Iα of PEO at different ratios; Figure 3 Thermal stability curves (a) and DTG curves (b) of PEO at different proportions; Figure 4 The condensation unit is equipped with a mechanical stirrer connected to an oil seal. Detailed Implementation
[0015] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.
[0016] This invention provides, for example Figure 1-3 The present invention discloses a method for preparing polyester polyols from the alcoholysis of waste PET. The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0017] The sources and specifications of the raw materials and reagents used in the experiment are shown in Table 1: Table 1 Experimental materials and reagents
[0018] The sources and specifications of the experimental instruments used in the experiment are shown in Table 2: Table 2 Experimental Instruments
[0019] The alcoholysis process of waste PET bottle flakes is affected by the raw material ratio and alcoholysis time. It is necessary to balance the reaction efficiency and energy loss during the alcoholysis process. Although extending the alcoholysis time can yield products with a higher degree of alcoholysis, it will increase production costs. However, if the alcoholysis time is too short, the product will contain long PET chain segments, which will affect the performance of the value-added products. Therefore, selecting an appropriate alcoholysis time is particularly important for large-scale recycling of waste PET.
[0020] Example 1 The mass ratio of reactants was fixed at PET:ethylene glycol = 1.3:1.0. Waste PET bottle flakes were washed three times with anhydrous ethanol and dried in a 60 °C oven. When needed, the waste PET bottle flakes, ethylene glycol, and 0.5 wt% PET zinc acetate were added to a three-necked flask and placed in an oil bath. The mixture was heated to 220 °C, and the equipped mechanical stirrer and oil-sealed condenser were started. The reaction was allowed to proceed for 90 minutes, and the hydroxyl value was measured.
[0021] Example 2 The mass ratio of reactants was fixed at PET:ethylene glycol = 1.3:1.0. Waste PET bottle flakes were washed three times with anhydrous ethanol and dried in a 60 °C oven. When needed, the waste PET bottle flakes, ethylene glycol, and 0.5 wt% PET zinc acetate were added to a three-necked flask and placed in an oil bath. The mixture was heated to 220 °C, and the equipped mechanical stirrer and oil-sealed condenser were started. The reaction was allowed to proceed for 110 min, and the hydroxyl value was measured.
[0022] Example 3 The mass ratio of reactants was fixed at PET:ethylene glycol = 1.3:1.0. Waste PET bottle flakes were washed three times with anhydrous ethanol and dried in a 60 °C oven. When needed, the waste PET bottle flakes, ethylene glycol, and 0.5 wt% PET zinc acetate were added to a three-necked flask and placed in an oil bath. The mixture was heated to 220 °C, and the equipped mechanical stirrer and oil-sealed condenser were started. The reaction was allowed to proceed for 130 min, and the hydroxyl value was measured.
[0023] Example 4 The mass ratio of reactants was fixed at PET:ethylene glycol = 1.3:1.0. Waste PET bottle flakes were washed three times with anhydrous ethanol and dried in a 60 °C oven. When needed, the waste PET bottle flakes, ethylene glycol, and 0.5 wt% PET zinc acetate were added to a three-necked flask and placed in an oil bath. The mixture was heated to 220 °C, and the equipped mechanical stirrer and oil-sealed condenser were started. The reaction was allowed to proceed for 150 min, and the hydroxyl value was measured.
[0024] Example 5 The mass ratio of reactants was fixed at PET:ethylene glycol = 0.9:1.0. Waste PET bottle flakes were washed three times with anhydrous ethanol and dried in a 60 °C oven. When needed, the waste PET bottle flakes, ethylene glycol, and 0.5 wt% PET zinc acetate were added to a three-necked flask and placed in an oil bath. The mixture was heated to 220 °C, and the equipped mechanical stirrer and oil-sealed condenser were started. The reaction was allowed to proceed for 90 minutes, and the hydroxyl value was measured.
[0025] Example 6 The mass ratio of reactants was fixed at PET:ethylene glycol = 1.1:1.0. Waste PET bottle flakes were washed three times with anhydrous ethanol and dried in a 60 °C oven. When needed, the waste PET bottle flakes, ethylene glycol, and 0.5 wt% PET zinc acetate were added to a three-necked flask and placed in an oil bath. The mixture was heated to 220 °C, and the equipped mechanical stirrer and oil-sealed condenser were started. The reaction was allowed to proceed for 90 minutes, and the hydroxyl value was measured.
[0026] Example 7 The mass ratio of reactants was fixed at PET:ethylene glycol = 1.3:1.0. Waste PET bottle flakes were washed three times with anhydrous ethanol and dried in a 60 °C oven. When needed, the waste PET bottle flakes, ethylene glycol, and 0.5 wt% PET zinc acetate were added to a three-necked flask and placed in an oil bath. The mixture was heated to 220 °C, and the equipped mechanical stirrer and oil-sealed condenser were started. The reaction was allowed to proceed for 90 minutes, and the hydroxyl value was measured.
[0027] Example 8 The mass ratio of reactants was fixed at PET:ethylene glycol = 1.5:1.0. Waste PET bottle flakes were washed three times with anhydrous ethanol and dried in a 60 °C oven. When ready for use, the waste PET bottle flakes, ethylene glycol, and 0.5 wt% PET zinc acetate were added to a three-necked flask and placed in an oil bath. The mixture was heated to 220 °C, and the equipped mechanical stirrer and oil-sealed condenser were started. The reaction was allowed to proceed for 90 minutes, and the hydroxyl value was measured.
[0028] Example 9 The mass ratio of reactants was fixed at PET:ethylene glycol = 1.1:1.0. Waste PET bottle flakes were washed three times with anhydrous ethanol and dried in a 60 °C oven. When needed, the waste PET bottle flakes, ethylene glycol, and 0.5 wt% PET zinc acetate were added to a three-necked flask and placed in an oil bath. The mixture was heated to 220 °C, and the equipped mechanical stirrer and oil-sealed condenser were started. The reaction was allowed to proceed for 90 min, and the hydroxyl value was measured. The temperature was then lowered to 170 °C, and oxalic acid was added at a molar ratio of ethylene glycol:oxalic acid = 1:0.65 for esterification and chain extension. The reaction was allowed to proceed for 60 min, and the acid value was measured again. Simultaneously, the reaction system was heated back to 220 °C, and the apparatus was changed. A spherical condenser was replaced with a straight condenser, and the reaction continued for 310 min. A vacuum was then applied to the system, and the vacuum level was adjusted to 0.1 MPa. Finally, the reaction was completed, yielding a brown paste-like product. The acid and hydroxyl values were measured again.
[0029] Example 10 The mass ratio of reactants was fixed at PET:ethylene glycol = 1.1:1.0. Waste PET bottle flakes were washed three times with anhydrous ethanol and dried in a 60 °C oven. When needed, the waste PET bottle flakes, ethylene glycol, and 0.5 wt% PET zinc acetate were added to a three-necked flask and placed in an oil bath. The mixture was heated to 220 °C, and the equipped mechanical stirrer and oil-sealed condenser were started. The reaction was allowed to proceed for 90 min, and the hydroxyl value was measured. The temperature was then lowered to 170 °C, and oxalic acid was added at a molar ratio of ethylene glycol:oxalic acid = 1:0.65 for esterification and chain extension. The reaction was allowed to proceed for 60 min, and the acid value was measured again. Simultaneously, the reaction system was heated back to 220 °C, and the apparatus was changed. A spherical condenser was replaced with a straight condenser, and the reaction continued for 360 min. Afterward, a vacuum was applied to the system, and the vacuum level was adjusted to 0.1 MPa. Finally, the reaction was completed, yielding a brown paste-like product. The acid and hydroxyl values were measured again.
[0030] Example 11 The mass ratio of reactants was fixed at PET:ethylene glycol = 1.1:1.0. Waste PET bottle flakes were washed three times with anhydrous ethanol and dried in a 60 °C oven. When needed, the waste PET bottle flakes, ethylene glycol, and 0.5 wt% PET zinc acetate were added to a three-necked flask and placed in an oil bath. The mixture was heated to 220 °C, and the equipped mechanical stirrer and oil-sealed condenser were started. The reaction was allowed to proceed for 90 min, and the hydroxyl value was measured. The temperature was then lowered to 170 °C, and oxalic acid was added at a molar ratio of ethylene glycol:oxalic acid = 1:0.65 for esterification and chain extension. The reaction was allowed to proceed for 60 min, and the acid value was measured again. Simultaneously, the reaction system was heated back to 220 °C, and the apparatus was changed. A straight condenser was replaced with a spherical condenser, and the reaction continued. After 310 min, a vacuum was applied to the system, and the vacuum level was adjusted to 0.1 MPa. Finally, the reaction was completed, yielding a brown paste-like product. The sample was washed three times with 250 mL of anhydrous ethanol, then placed in an oven at 40 °C and vacuumed for 12 h to remove the ethanol. After removal, the hydroxyl value, acid value and molecular weight of the sample were re-determined.
[0031] Example 12 The mass ratio of reactants was fixed at PET:ethylene glycol = 1.1:1.0. Waste PET bottle flakes were washed three times with anhydrous ethanol and dried in a 60 °C oven. When needed, the waste PET bottle flakes, ethylene glycol, and 0.5 wt% PET zinc acetate were added to a three-necked flask and placed in an oil bath. The mixture was heated to 220 °C, and the equipped mechanical stirrer and oil-sealed condenser were started. The reaction was allowed to proceed for 90 min, and the hydroxyl value was measured. The temperature was then lowered to 170 °C, and oxalic acid was added at a molar ratio of ethylene glycol:oxalic acid = 1:0.65 for esterification and chain extension. The reaction was allowed to proceed for 60 min, and the acid value was measured again. Simultaneously, the reaction system was heated back to 220 °C, and the apparatus was changed. A straight condenser was replaced with a spherical condenser, and the reaction continued for 360 min. Afterward, a vacuum was applied to the system, and the vacuum level was adjusted to 0.1 MPa. After the final reaction, a brown paste-like product was obtained. The sample was washed three times with 250 mL of anhydrous ethanol, and then placed in an oven at 40 °C under vacuum for 12 h to remove the ethanol. After removal, the hydroxyl value, acid value and molecular weight of the sample were re-determined.
[0032] Performance tests were conducted on Examples 1-12: Gel permeation chromatography (GPC) test: The molecular weights of GLY and PEO were determined using a GPC equipped with an RI detector and an MG100 column. Tetrahydrofuran was used as the solvent for both GLY and PEO, with a concentration of 2.5 mg / mL and a concentration of 1.0 mg / mL, respectively.
[0033] Determination of hydroxyl value of waste PET alcoholysis products The hydroxyl value (IOH) of the alcoholysis product was determined according to the acetic anhydride-perchloric acid-ethyl acetate acetylation method in HG / T2709-2022. An appropriate amount of the sample to be tested was weighed into an Erlenmeyer flask containing 20 mL of ethyl acetate. 5 mL of acetylation reagent was added, and the mixture was allowed to stand at room temperature for 5 min. 2 mL of distilled water was added, and the mixture was shaken well. Then, 10 mL of pyridine-water solution was added, and the mixture was shaken well. After standing for 5 min, the mixture was titrated with 0.5 mol / L NaOH aqueous solution (preparation and standardization refer to GB / T 601-2016). Phenolphthalein-ethanol solution was used as an indicator to indicate the endpoint. A blank experiment was also performed.
[0034] The formula for calculating IOH is as follows: (2-1) In the formula: V0—The volume of NaOH standard titrant consumed in the blank titration, in mL; V1—The volume of NaOH standard titrant consumed in titrating the sample, in mL; C1—The actual concentration of the NaOH standard titrant, in mol / L; m1—mass of the sample to be tested, in grams; Determination of acid value of waste PET alcoholysis products The acid value Iα of the alcoholysis product was determined according to HG / T2708-1995. Weigh an appropriate amount of sample into an Erlenmeyer flask, add 30 mL of toluene-ethanol mixture, and after the sample dissolves, add 10 drops of phenolphthalein-ethanol indicator solution. Titrate with 0.1 mol / L KOH-ethanol standard solution (preparation and standardization refer to GB / T 601-2016), and perform a blank experiment simultaneously.
[0035] The formula for calculating Iα is as follows: (2-2) In the formula: V''——The volume of KOH-ethanol standard titrant consumed in titrating the sample, in mL; V' — The volume of KOH-ethanol standard titrant consumed in the blank titration, in mL; C2—The actual concentration of the KOH-ethanol standard titration solution, in mol / L; m2—mass of the sample to be tested, in grams; Thermal characterization of waste PET alcoholysis products Thermogravimetric analysis (TG) was used to test the structure of the GLY product and the thermal stability of PEO. The test was conducted in an N2 atmosphere with a heating rate of 10 °C / min and a temperature range of 40-600 °C.
[0036] Performance tests were conducted on Examples 1-4. The degree of alcoholysis of waste PET bottle flakes was characterized by IOH and gel permeation chromatography, as shown in Table 3. The IOH content of the products in the examples increased slightly with increasing alcoholysis time. GPC results showed a slight decrease in the number-average molecular weight (Mn) and weight-average molecular weight (Mw) of the examples. The polydispersity index (PDI) first increased and then decreased from Examples 1 to 4, indicating that the molecular weight distribution of the products in the examples was more concentrated when alcoholysis reached 150 min.
[0037] Based on the above analysis, after 90 min of alcoholysis, extending the time has little effect on improving the degree of alcoholysis. Therefore, subsequent process exploration will be based on an alcoholysis time of 90 min.
[0038] Performance tests were conducted on Examples 5-8: The IOH values of the examples at different proportions were determined by titration. The titration results showed that the IOH values for Examples 5-8 were 308.2, 325.6, 309.8, and 268.9 mg NaOH / g, respectively. Figure 1 As the mass of the flasks continues to increase, the IOH decreases.
[0039] The molecular weights of the four examples were characterized. The Mn values of Examples 5-8 were 435, 402, 458, and 471 g / mol, respectively, consistent with the trend of IOH. Based on the above results, the alcoholysis efficiency was highest and the number of alcoholysis polyols in the product was greatest under the condition of mPET:mEG = 1.1:1.0.
[0040] The IOH and Iα of alcoholysis polyols are important indicators for optimizing synthesis conditions and evaluating reactivity, such as... Figure 3 The IOH and Iα values of the four groups of alcoholysis polyols obtained in the examples are shown. With increasing waste PET flakes, the IOH and Iα values of the alcoholysis polyols showed a trend of first decreasing and then increasing. Example 6 exhibited the lowest IOH and Iα values, at 19.6 mg NaOH / g and 1.1 mg KOH / g, respectively, indicating that Example 6 had the lowest remaining amounts of hydroxyl and carboxyl groups. Based on the inverse relationship between IOH and molecular weight, the lowest IOH value in Example 6 indicates the highest theoretical molecular weight, which is consistent with the GPC results of the alcoholysis polyols mentioned earlier. In conclusion, the alcoholysis products exhibit a higher esterification rate under the condition of mPET:mEG = 1.1:1.0.
[0041] TG and DTG curves of different embodiments are as follows Figure 3As shown in (a), the heat resistance of the samples was evaluated by the temperature (Td5%) at which the sample mass loss was 5%. The thermal stability from highest to lowest is that of Examples 7, 6, 8, and 5, with corresponding Td5% of 336.3 °C, 333.3 °C, 331.8 °C, and 328.7 °C, respectively. This may be because the thermal stability of PEO is affected by both molecular weight and the number of benzene rings in the molecular chain. 1.5PEO has a lower molecular weight, which weakens its thermal stability; therefore, 1.5PEO is less than 1.3PEO and 1.1PEO. However, compared to 0.9PEO with a similar molecular weight, the benzene rings in 1.5PEO have a stronger effect on improving thermal stability, so its thermal stability is higher than that of 0.9PEO. Similarly, the thermal stability of 1.3PEO is higher than that of 1.1PEO.
[0042] from Figure 3 (b) From this perspective, all four PEO groups exhibit two decomposition peaks. Based on molecular structure analysis, these peaks should correspond to the decomposition peaks of the ester bonds formed by the reaction of the remaining EG and AA in GLY (around 367 °C) and the decomposition peaks of the ester bonds formed by the reaction of the alcoholysis polyol and AA (around 422 °C), respectively. In conclusion, when designing PEOs, a reaction ratio of 1.1:1.0 should be selected to achieve a higher degree of esterification and relatively better heat resistance in the product.
[0043] Performance tests were conducted on Examples 9-12: Based on the preferred use of 1.1PEO for subsequent synthesis, its molecular weight and purity were controlled to obtain 1.1PEO-310 and 1.1PEO-360 with lower molecular weights, along with their corresponding purified samples 1.1PEO-310W and 1.1PEO-360W. According to the parameters of the controlled 1.1PEO samples in Table 4, reducing the esterification and vacuum polycondensation time can lower the molecular weight while maintaining the product's Iα at a relatively low value.
[0044] The purified sample showed a decrease in both IOH and Iα, indicating the presence of unreacted polyols and adipic acid impurities in PEO. Therefore, purifying PEO is an important measure to ensure the quality of subsequent products. The slight increase in PDI in the product may be due to the high viscosity of PEO, resulting in incomplete removal of anhydrous ethanol. Since the raw materials need to be dehydrated again before PU synthesis, the remaining anhydrous ethanol will not affect PU synthesis.
[0045] By regulating the esterification process, the applicability of PEO can be significantly improved, meeting diverse market demands.
[0046] IOH and molecular weight of examples under different alcoholysis times
[0047] Table 3 1.1 PEO sample parameters after adjustment
[0048] Table 4 The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.
Claims
1. An aromatic alcoholysis polyol, characterized in that, The general structural formula of the aromatic alcoholysis polyol is: ； Where n > 20, x > 20.
2. A method for the green preparation of aromatic alcoholysis polyols from waste PET, characterized in that: The preparation method steps are as follows: 1) Add waste PET bottle flakes, ethylene glycol and zinc acetate to a three-necked flask and place it in an oil bath. Heat the flask and start the equipped condenser. React for a certain period of time. Then cool the system and add adipic acid to carry out esterification and chain extension reaction for a certain period of time. 2) Reheat the reaction system and change the apparatus to carry out the polycondensation reaction. After a certain period of time, start to evacuate the system. When the reaction ends, the brown paste-like product is obtained, which is the aromatic alcoholysis polyol.
3. The preparation method according to claim 2, characterized in that: Step 1) The amount of zinc acetate added is 0.5% of the mass of the PET bottle flakes, and the molar ratio of adipic acid to ethylene glycol is 0.65:
1.
4. The preparation method according to claim 2, characterized in that: Step 1) The heating temperature is 220℃, the esterification reaction temperature is 170℃, and the reaction time is 60min.
5. The preparation method according to claim 2, characterized in that: Step 2) The replacement device is to replace the spherical condenser with a straight condenser.
6. The preparation method according to claim 2, characterized in that: Step 2) The polycondensation reaction temperature is 220℃; Vacuuming: Turn on the vacuum pump and adjust the vacuum level to 0.1 MPa for purification.
7. A green aromatic alcoholysis polyol prepared by the method according to any one of claims 1-6.
8. The application of a waste PET alcoholysis polyester polyol prepared by the method according to any one of claims 1-6 in the preparation of polyurethane.
9. The application according to claim 8, characterized in that, The polyurethane is used in flexible electronic devices, including wearable devices, sensors, and triboelectric nanogenerators.