High-functionality, low-viscosity polyester polyols and their stepwise synthesis methods

Abstract

This invention belongs to the field of polyester polyol technology, specifically relating to high-functionality, low-viscosity polyester polyols and their stepwise synthesis method. It includes the following steps: (1) adding a diol, a dicarboxylic acid, a catalyst, and an antioxidant into a reaction vessel, heating and evacuating to perform esterification and transesterification reactions, obtaining a polyester polyol intermediate; (2) cooling the polyester polyol intermediate obtained in step (1), adding a polyol to the reaction vessel, continuing the transesterification reaction, and obtaining a high-functionality, low-viscosity polyester polyol after the reaction is complete. The stepwise synthesis method solves the problem of high viscosity and difficulty in preparing low-viscosity products in existing high-functionality polyester polyols. Through specific raw material selection and process control, under the same raw material system and hydroxyl value conditions, the viscosity of high-functionality polyester polyols can be effectively reduced. Furthermore, this method is simple and easy to industrialize.

Description

Technical Field

[0001] This invention belongs to the field of polyester polyol technology, specifically relating to high-functionality, low-viscosity polyester polyols and their stepwise synthesis methods. Background Technology

[0002] Polyester polyols are one of the important raw materials for the production of polyurethane, and their properties have a crucial impact on the performance of polyurethane products. In many application fields, such as the preparation of high-performance polyurethane foams, elastomers, and coatings, high-functionality polyester polyols are required to impart excellent mechanical properties, heat resistance, chemical resistance, and other characteristics to the products.

[0003] The conventional method for preparing polyester polyols involves adding small-molecule polyacids and polyols to a reactor and synthesizing them through an alkyd-acid condensation reaction. This method is commonly used to prepare high-functionality polyester polyols, where high-functionality small-molecule polyols (or polyacids) are directly added to the reactor for a high-temperature alkyd-acid condensation reaction. However, high-functionality small-molecule polyols (or polyacids) are prone to cross-linking during alkyd-acid condensation; and the functionality of the high-functionality polyester polyols obtained by this method is relatively limited due to the limited amount of high-functionality small-molecule polyols (or polyacids) added. Furthermore, if the functionality is further increased (i.e., by increasing the amount of high-functionality small-molecule polyols (or polyacids) added), the reaction system is prone to cross-linking and gelation during the process, making it impossible to obtain a flowable liquid product.

[0004] Furthermore, as the functionality of polyester polyols increases, the interactions between their molecular chains strengthen, leading to a significant increase in viscosity. This presents numerous challenges to the processing and application of polyester polyols. For example, during processing such as mixing, stirring, and conveying, more energy is required, and achieving uniform dispersion is difficult, thus affecting product quality. To reduce the viscosity of polyester polyols, existing technologies typically employ methods such as adding diluents or reducing molecular weight. However, these methods often sacrifice some of the properties of the polyester polyol. For instance, adding diluents reduces the solid content of the product, affecting its final performance; reducing the molecular weight may lead to a decrease in the mechanical properties of the product, failing to meet the requirements of some high-performance applications.

[0005] Therefore, developing a method for preparing polyester polyols that combine high functionality and low viscosity is of great practical significance and has broad market demand. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a stepwise synthesis method for high-functionality, low-viscosity polyester polyols. This method solves the problem of high viscosity and difficulty in preparing low-viscosity products from high-functionality polyester polyols in existing technologies. Through specific raw material selection and process control, the viscosity of high-functionality polyester polyols can be effectively reduced under the same raw material system and hydroxyl value conditions. Furthermore, this method is simple and easy to implement for industrial production.

[0007] Another object of the present invention is to provide a high-functionality, low-viscosity polyester polyol.

[0008] The technical solution adopted in this invention is as follows:

[0009] The stepwise synthesis method of the high-functionality, low-viscosity polyester polyol includes the following steps:

[0010] (1) Diol, dicarboxylic acid, catalyst and antioxidant are added to the reaction vessel, heated and vacuumed under nitrogen protection and stirring conditions to carry out esterification and transesterification reaction until the acid value is ≤5mgKOH / g, and polyester polyol intermediate is obtained.

[0011] (2) After cooling the polyester polyol intermediate obtained in step (1), add the polyol into the reactor and continue the transesterification reaction. After the reaction is completed, cool down and discharge the material to obtain a high-functionality, low-viscosity polyester polyol.

[0012] The diol is selected from one or more aliphatic diols having 2 to 10 carbon atoms, preferably one or more of ethylene glycol, propylene glycol, 1,4-butanediol, diethylene glycol, or neopentyl glycol.

[0013] The dicarboxylic acid is selected from one or more aliphatic or aromatic dicarboxylic acids having 4 to 10 carbon atoms, preferably one or more of succinic acid, glutaric acid, adipic acid, sebacic acid, terephthalic acid, isophthalic acid, or phthalic acid.

[0014] The catalyst is a titanium-based catalyst or a tin-based catalyst, preferably stannous octoate, tetrabutyl titanate, or tetraisopropyl titanate; the amount of catalyst added is 10 to 500 ppm of the total mass of the diol and dicarboxylic acid.

[0015] The antioxidant is a mixture of hindered phenolic antioxidants and phosphite antioxidants, with a mass ratio of hindered phenolic antioxidants to phosphite antioxidants of (1~2):1. The hindered phenolic antioxidant is preferably antioxidant 1010 or antioxidant 1076, and the phosphite antioxidant is preferably antioxidant 168 or antioxidant 626. The amount of antioxidant added is 1~5‰ of the total mass of the diol and dicarboxylic acid.

[0016] The molar ratio of the diol to the dicarboxylic acid is (1.05~2.2):1; in step (1), the temperature of the esterification and transesterification reaction is 200~230℃, and the reaction pressure is -0.09~-0.1MPa.

[0017] The polyol has a functionality ≥3 and a number-average molecular weight ≤500g / mol. The amount of polyol used is 5~30% of the total mass of the diol, dicarboxylic acid and polyol.

[0018] The polyol is one or more of trimethylolpropane, glycerol, or pentaerythritol.

[0019] In step (2), the temperature of the transesterification reaction is 180~200℃, the reaction pressure is -0.06~-0.08MPa, and the reaction time is 4~6h.

[0020] The high-functionality, low-viscosity polyester polyol is prepared using the stepwise synthesis method described above.

[0021] The synthesis principle of this invention is as follows:

[0022] Diols and dicarboxylic acids first undergo esterification and transesterification reactions, continuously polycondensing to form linear, low-molecular-weight polyester glycol (or polyester diacid) chains. When the reaction progresses to a certain extent, the polyester glycol (or polyester diacid) chains reach a certain molecular weight. At this point, a high-functionality, low-molecular-weight polyol undergoes a secondary transesterification reaction with the polyester chain. During this reaction, the ester bonds within the system react with the high-functionality polyol at high temperatures, and the hydroxyl groups attack the ester carbonyl groups on the already formed molecular chain, forming a tetrahedral intermediate. Subsequently, this intermediate decomposes, causing the ester bonds in the original molecular chain to break, and the high-functionality polyol reconnects with the polyester molecular chain, thus achieving transesterification. This process avoids the direct reaction between the high-functionality, low-molecular-weight polyol and an excess of small-molecule dicarboxylic acid, which could lead to cross-linking.

[0023] The principle of this synthesis differs from the traditional one-step method. In the traditional one-step method, small molecule alcohols undergo esterification with dicarboxylic acids to generate active ester groups and hydroxyl groups. These active groups continue to react with each other, forming polyester chains through continuous polycondensation, i.e., a process of gradually polymerizing from monomers to form polyesters.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] (1) Low viscosity characteristics: The polyester polyol prepared by the stepwise synthesis method of the present invention has a viscosity that is 30-50% lower than that of polyester polyol prepared by the traditional one-step method under the same raw material system and the same hydroxyl value, which greatly improves the processing performance of the product. In the fields of coatings and adhesives, it can be more convenient to carry out coating and other operations, thereby improving production efficiency;

[0026] (2) Advantage of high functionality: The polyester polyol prepared by the present invention has high functionality, which can give polyurethane materials better crosslinking performance and mechanical properties, so that they exhibit excellent wear resistance, strength and resilience in applications such as elastomers and foam materials.

[0027] (3) Simple process: The stepwise synthesis method of the present invention has mild reaction conditions and relatively simple operation process. It does not require special equipment and complex processes, and is easy to industrialize. It is conducive to reducing production costs and improving the market competitiveness of products. Detailed Implementation

[0028] The present invention will be further described below with reference to the embodiments, but these embodiments do not limit the implementation of the present invention.

[0029] Unless otherwise specified, the raw materials used in the examples and comparative examples are all commercially available materials, and the process methods used in the examples and comparative examples are all conventional methods in the art.

[0030] Example 1

[0031] The stepwise synthesis method of the high-functionality, low-viscosity polyester polyol includes the following steps:

[0032] (1) 250g of ethylene glycol, 500g of adipic acid, 0.12g of tetrabutyl titanate, 1.4g of antioxidant 1010 and 0.9g of antioxidant 168 were added to the reaction vessel. Under nitrogen protection, the mixture was stirred and mixed evenly, heated to 225℃, and vacuumed to a vacuum pressure of -0.1MPa to carry out esterification and transesterification reactions until the acid value was 2mgKOH / g, thus obtaining a polyester polyol intermediate.

[0033] (2) Cool the polyester polyol intermediate obtained in step (1) to 200°C, add 150g of trimethylolpropane to the reactor, adjust the pressure inside the reactor to -0.07MPa, continue the transesterification reaction for 5h, and measure the hydroxyl value to be 286mgKOH / g. After the reaction is completed, cool down and discharge the material to obtain a high-functionality, low-viscosity polyester polyol.

[0034] Example 2

[0035] The stepwise synthesis method of the high-functionality, low-viscosity polyester polyol includes the following steps:

[0036] (1) 250g of ethylene glycol, 500g of adipic acid, 0.12g of tetrabutyl titanate, 1.4g of antioxidant 1010 and 0.9g of antioxidant 168 were added to the reaction vessel. Under nitrogen protection, the mixture was stirred and mixed evenly, heated to 225℃, and vacuumed to a vacuum pressure of -0.1MPa to carry out esterification and transesterification reactions until the acid value was 2mgKOH / g, thus obtaining a polyester polyol intermediate.

[0037] (2) Cool the polyester polyol intermediate obtained in step (1) to 200°C, add 225g of trimethylolpropane to the reactor, adjust the pressure inside the reactor to -0.07MPa, continue the transesterification reaction for 5h, and measure the hydroxyl value to be 368mgKOH / g. After the reaction is completed, cool down and discharge the material to obtain a high-functionality, low-viscosity polyester polyol.

[0038] Example 3

[0039] The stepwise synthesis method of the high-functionality, low-viscosity polyester polyol includes the following steps:

[0040] (1) 150g of ethylene glycol, 170g of diethylene glycol, 430g of succinic acid, 0.12g of tetrabutyl titanate, 2g of antioxidant 1076 and 1.75g ​​of antioxidant 626 were put into a reaction vessel. Under nitrogen protection, the mixture was stirred and mixed evenly, heated to 230℃, and vacuumed to a vacuum pressure of -0.1MPa to carry out esterification and transesterification reactions until the acid value was 5mgKOH / g, thus obtaining a polyester polyol intermediate.

[0041] (2) Cool the polyester polyol intermediate obtained in step (1) to 180°C, add 150g of trimethylolpropane to the reactor, adjust the pressure inside the reactor to -0.06MPa, continue the transesterification reaction for 5h, and measure the hydroxyl value to be 272mgKOH / g. After the reaction is completed, cool down and discharge the material to obtain a high-functionality, low-viscosity polyester polyol.

[0042] Example 4

[0043] The stepwise synthesis method of the high-functionality, low-viscosity polyester polyol includes the following steps:

[0044] (1) 440g of diethylene glycol, 310g of phthalic acid, 0.375g of tetraisopropyl titanate, 0.9g of antioxidant 1076 and 0.9g of antioxidant 168 were added to the reaction vessel. Under nitrogen protection, the mixture was stirred and mixed evenly, heated to 200℃, and vacuumed to a vacuum pressure of -0.09MPa to carry out esterification and transesterification reactions until the acid value was 2mgKOH / g, thus obtaining a polyester polyol intermediate.

[0045] (2) The temperature of the polyester polyol intermediate obtained in step (1) was maintained at 200℃. 40g of glycerol was added to the reactor, the pressure inside the reactor was adjusted to -0.08MPa, and the transesterification reaction was continued for 6h. The hydroxyl value was measured to be 371mgKOH / g. The reaction was completed, the temperature was lowered and the material was discharged to obtain a high-functionality, low-viscosity polyester polyol.

[0046] Example 5

[0047] The stepwise synthesis method of the high-functionality, low-viscosity polyester polyol includes the following steps:

[0048] (1) 230g of propylene glycol, 520g of sebacic acid, 0.0075g of stannous octoate, 1.8g of antioxidant 1010 and 0.9g of antioxidant 168 were added to a reaction vessel. Under nitrogen protection, the mixture was stirred and mixed evenly, heated to 225℃, and vacuumed to a vacuum pressure of -0.1MPa to carry out esterification and transesterification reactions until the acid value was 2mgKOH / g, thus obtaining a polyester polyol intermediate.

[0049] (2) Cool the polyester polyol intermediate obtained in step (1) to 200°C, add 100g of trimethylolpropane to the reactor, adjust the pressure inside the reactor to -0.07MPa, continue the transesterification reaction for 5h, and measure the hydroxyl value to be 195mgKOH / g. After the reaction is completed, cool down and discharge the material to obtain a high-functionality, low-viscosity polyester polyol.

[0050] Example 6

[0051] The stepwise synthesis method of the high-functionality, low-viscosity polyester polyol includes the following steps:

[0052] (1) 300g of 1,4-butanediol, 450g of adipic acid, 0.12g of tetrabutyl titanate, 0.5g of antioxidant 1010 and 0.25g of antioxidant 168 were added to the reaction vessel. Under nitrogen protection, the mixture was stirred and mixed evenly, heated to 225℃, and vacuumed to a vacuum pressure of -0.1MPa to carry out esterification and transesterification reactions until the acid value was 2mgKOH / g, thus obtaining a polyester polyol intermediate.

[0053] (2) Cool the polyester polyol intermediate obtained in step (1) to 200°C, add 150g of trimethylolpropane to the reactor, adjust the pressure inside the reactor to -0.08MPa, and continue the transesterification reaction for 4h. The hydroxyl value is measured to be 246mgKOH / g. After the reaction is completed, cool down and discharge the material to obtain a high-functionality, low-viscosity polyester polyol.

[0054] Comparative Example 1

[0055] 250g of ethylene glycol, 500g of adipic acid, 150g of trimethylolpropane, 0.12g of tetrabutyl titanate, 1.4g of antioxidant 1010, and 0.9g of antioxidant 168 were added to a reaction vessel. Under nitrogen protection, the mixture was stirred and mixed evenly, heated to 225℃, and evacuated to a vacuum pressure of -0.1MPa to carry out esterification and transesterification reactions. The hydroxyl value was measured to be 286mgKOH / g. After the reaction was completed, the mixture was cooled and discharged to obtain polyester polyol.

[0056] Comparative Example 2

[0057] 250g of ethylene glycol, 500g of adipic acid, 225g of trimethylolpropane, 0.12g of tetrabutyl titanate, 1.4g of antioxidant 1010 and 0.9g of antioxidant 168 were added to a reaction vessel. Under nitrogen protection, the mixture was stirred and mixed evenly, heated to 225℃, and evacuated to a vacuum pressure of -0.1MPa to carry out esterification and transesterification reactions. Gelation occurred during the reaction.

[0058] The polyester polyols obtained in Examples 1-6 and Comparative Examples 1-2 were subjected to performance tests, and the test methods are as follows:

[0059] Hydroxyl value: Tested according to HG / T 2709-2022;

[0060] Acid value: Tested according to HG / T 2708-1995;

[0061] Viscosity: Tested using a rotational viscometer;

[0062] The test results are shown in Table 1.

[0063] Table 1 Performance Test Results

[0064]

[0065] As shown in Table 1, the polyester polyol prepared by the stepwise synthesis method of this invention has a lower viscosity compared to the polyester polyol prepared by the traditional one-step method, under the same raw material system and the same hydroxyl value; while the polyester polyol prepared by the one-step method has a higher viscosity. This indicates that a greater degree of crosslinking occurs during the one-step synthesis process. Furthermore, when the proportion of polyol in the raw material system is high, crosslinking gelation is more likely to occur during the reaction process of the polyester polyol prepared by the one-step method.

Claims

1. A stepwise synthesis method for a high-functionality, low-viscosity polyester polyol, characterized in that, Includes the following steps: (1) Diol, dicarboxylic acid, catalyst and antioxidant are added to the reaction vessel, heated and vacuumed to carry out esterification and transesterification reaction to obtain polyester polyol intermediate; (2) After cooling the polyester polyol intermediate obtained in step (1), add the polyol to the reaction vessel and continue the transesterification reaction. After the reaction is completed, a high-functionality, low-viscosity polyester polyol is obtained; wherein the functionality of the polyol is ≥3 and the number-average molecular weight is ≤500g / mol.

2. The stepwise synthesis method of high-functionality, low-viscosity polyester polyol according to claim 1, characterized in that, The diol is selected from one or more aliphatic diols having 2 to 10 carbon atoms.

3. The stepwise synthesis method of high-functionality, low-viscosity polyester polyol according to claim 1, characterized in that, The dicarboxylic acid is selected from one or more aliphatic or aromatic dicarboxylic acids having 4 to 10 carbon atoms.

4. The stepwise synthesis method of high-functionality, low-viscosity polyester polyol according to claim 1, characterized in that, The catalyst is a titanium-based catalyst or a tin-based catalyst; the amount of catalyst added is 10 to 500 ppm of the total mass of the diol and dicarboxylic acid.

5. The stepwise synthesis method of high-functionality, low-viscosity polyester polyol according to claim 1, characterized in that, The antioxidant is a mixture of hindered phenolic antioxidants and phosphite antioxidants, and the amount of antioxidant added is 1 to 5‰ of the total mass of the diol and dicarboxylic acid.

6. The stepwise synthesis method of high-functionality, low-viscosity polyester polyol according to claim 1, characterized in that, The molar ratio of the diol to the dicarboxylic acid is (1.05~2.2):1; in step (1), the temperature of the esterification and transesterification reaction is 200~230℃, and the reaction pressure is -0.09~-0.1MPa; the reaction is carried out until the acid value is ≤5mgKOH / g, and the polyester polyol intermediate is obtained.

7. The stepwise synthesis method of high-functionality, low-viscosity polyester polyol according to claim 1, characterized in that, The amount of polyol used is 5-30% of the total mass of diol, dicarboxylic acid and polyol.

8. The stepwise synthesis method of high-functionality, low-viscosity polyester polyol according to claim 1, characterized in that, The polyol is one or more of trimethylolpropane, glycerol, or pentaerythritol.

9. The stepwise synthesis method of high-functionality, low-viscosity polyester polyol according to claim 1, characterized in that, In step (2), the temperature of the transesterification reaction is 180~200℃, the reaction pressure is -0.06~-0.08MPa, and the reaction time is 4~6h.

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