High-functionality low-viscosity polyester polyol and step-by-step synthesis method thereof

Abstract

The invention belongs to the technical field of polyester polyol, and particularly relates to high-functionality low-viscosity polyester polyol and a step-by-step synthesis method thereof. Comprising the following steps: (1) adding dihydric alcohol, dicarboxylic acid, a catalyst and an antioxidant into a reaction kettle, heating and vacuumizing, and carrying out esterification and ester exchange reaction to prepare a polyester polyol intermediate; and (2) cooling the polyester polyol intermediate prepared in the step (1), adding polyol into the reaction kettle, and continuously carrying out ester exchange reaction to obtain the high-functionality low-viscosity polyester polyol after the reaction is finished. According to the step-by-step synthesis method, the problems that in the prior art, high-functionality polyester polyol is large in viscosity and low-viscosity products are difficult to prepare are solved, the viscosity of the high-functionality polyester polyol can be effectively reduced under the same raw material system and hydroxyl value conditions through specific raw material selection and process control, and the method is simple in process and easy to implement. The industrial production is convenient.

Description

Technical Field

[0001] The present invention belongs to the technical field of polyester polyols, and particularly relates to high functionality low viscosity polyester polyols and a stepwise synthesis method thereof. Background Art

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

[0003] The conventional preparation method of polyester polyols is to put small molecule polyacids and polyols into a reaction kettle and synthesize them by means of alcohol-acid condensation reaction. Traditional high functionality polyester polyols are usually prepared by this method, that is, directly putting high functionality small molecule polyols (or polyacids) into the reaction kettle for high temperature alcohol-acid condensation reaction. However, high functionality small molecule polyols (or polyacids) are prone to crosslinking reactions during the alcohol-acid condensation reaction; and limited by the addition amount of high functionality small molecule polyols (or polyacids), the functionality of the high functionality polyester polyols prepared by this method is relatively limited. At the same time, if the functionality is further increased (i.e., the addition amount of high functionality small molecule polyols (or polyacids) is increased), the reaction system is prone to crosslinking gel during the process, and a liquid product with fluidity cannot be obtained.

[0004] In addition, as the functionality of polyester polyols increases, the interaction between molecular chains increases, resulting in a significant increase in viscosity, which brings many problems to the processing and application of polyester polyols. For example, in the processing processes such as mixing, stirring, and conveying, more energy is required, and it is difficult to achieve uniform dispersion, thereby affecting the product quality. In order to reduce the viscosity of polyester polyols, the prior art usually adopts methods such as adding diluents or reducing the molecular weight, but these methods often sacrifice some properties of polyester polyols. For example, adding diluents will reduce the solid content of the product and affect the final properties of the product; reducing the molecular weight may lead to a decrease in the mechanical properties of the product and cannot meet the requirements of some high-performance applications.

[0005] Therefore, it is of great practical significance and broad market demand to develop a preparation method of polyester polyols with both high functionality and low viscosity. Summary of the Invention

[0006] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a stepwise synthesis method of high functionality and low viscosity polyester polyol, which solves the problems that the high functionality polyester polyol has a high viscosity and it is difficult to prepare a low viscosity product in the prior art. Through specific raw material selection and process control, under the same raw material system and hydroxyl value conditions, the viscosity of the high functionality polyester polyol can be effectively reduced, and the method has a simple process and is convenient for industrial production.

[0007] Another purpose of the present invention is to provide a high functionality and low viscosity polyester polyol.

[0008] The technical solution adopted by the present invention is as follows: The stepwise synthesis method of the high functionality and low viscosity polyester polyol includes the following steps: (1) Put a diol, a dicarboxylic acid, a catalyst and an antioxidant into a reaction kettle, heat up and evacuate under nitrogen protection and stirring conditions to carry out esterification and transesterification reactions until the acid value ≤ 5mgKOH / g to obtain a polyester polyol intermediate; (2) After cooling the polyester polyol intermediate obtained in step (1), put a polyol into the reaction kettle and continue the transesterification reaction. After the reaction is completed, cool and discharge the material to obtain a high functionality and low viscosity polyester polyol.

[0009] The diol is selected from one or more of aliphatic diols with 2 to 10 carbon atoms, preferably one or more of ethylene glycol, propylene glycol, 1,4-butanediol, diethylene glycol or neopentyl glycol.

[0010] The dicarboxylic acid is selected from one or more of aliphatic dicarboxylic acids or aromatic dicarboxylic acids with 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.

[0011] The catalyst is a titanium-based catalyst or a tin-based catalyst, preferably stannous octoate, tetrabutyl titanate or tetraisopropyl titanate; the addition amount of the catalyst is 10 to 500 ppm of the total mass of the diol and the dicarboxylic acid.

[0012] The antioxidant is a mixture of a hindered phenol antioxidant and a phosphite antioxidant, and the mass ratio of the hindered phenol antioxidant to the phosphite antioxidant is (1 to 2):1. The hindered phenol antioxidant is preferably antioxidant 1010 or antioxidant 1076, and the phosphite antioxidant is preferably antioxidant 168 or antioxidant 626; the addition amount of the antioxidant is 1 to 5‰ of the total mass of the diol and the dicarboxylic acid.

[0013] The molar ratio of the diol to the dicarboxylic acid is (1.05 to 2.2):1; in step (1), the temperature of the esterification and transesterification reactions is 200 to 230 °C, and the reaction pressure is -0.09 to -0.1 MPa.

[0014] The functionality of the polyol is ≥3 and the number average molecular weight is ≤500 g / mol, and the amount of the polyol used is 5 to 30% of the total mass of the diol, dicarboxylic acid and polyol.

[0015] The polyol is one or more of trimethylolpropane, glycerol or pentaerythritol.

[0016] In step (2) described above, the temperature of the transesterification reaction is 180 to 200 °C, the reaction pressure is -0.06 to -0.08 MPa, and the reaction time is 4 to 6 h.

[0017] The high functionality and low viscosity polyester polyol is prepared by the above-described stepwise synthesis method of the high functionality and low viscosity polyester polyol.

[0018] The synthesis principle of the present invention is as follows: The diol and the dicarboxylic acid first undergo an esterification reaction and a transesterification reaction, and continuously polycondense to form a linear, low molecular weight polyester diol (or polyester diacid) chain. When the reaction proceeds to a certain extent, the polyester diol (or polyester diacid) chain reaches a certain molecular weight. At this time, the high functionality and low molecular weight polyol will undergo a secondary transesterification reaction with the polyester chain. During this reaction process, the ester bond in the system reacts with the high functionality polyol in a high temperature environment, and the alcohol hydroxyl group attacks the ester carbonyl group on the formed molecular chain to form a tetrahedral intermediate. Subsequently, this intermediate decomposes, resulting in the cleavage of the ester bond in the original molecular chain, and the high functionality polyol is reconnected with the polyester molecular chain, thereby realizing transesterification. This process avoids the crosslinking situation caused by the direct reaction of the high functionality and low molecular weight polyol with an excessive amount of small molecule dicarboxylic acid.

[0019] This synthesis principle is different from the traditional one-step method. In the traditional one-step method, the small molecule alcohol reacts with the dicarboxylic acid to generate active ester groups and hydroxyl groups, and these active groups continue to react with each other and form a polyester chain through continuous polycondensation, that is, the process of gradually polymerizing from monomers to form a polyester.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Low viscosity characteristic: The polyester polyol prepared by the stepwise synthesis method of the present invention has a viscosity that is 30 to 50% lower than that of the polyester polyol prepared by the traditional one-step method under the same raw material system and the same hydroxyl value conditions, which greatly improves the processing performance of the product. In the fields of coatings, adhesives, etc., it is possible to perform coating, painting and other operations more conveniently, thereby improving production efficiency; (2) High functionality advantage: The polyester polyol prepared by the present invention has a relatively high functionality, which can endow polyurethane materials with better cross-linking performance and mechanical properties, enabling it to exhibit excellent wear resistance, strength and resilience in applications such as elastomers and foam materials; (3) Simple process: The step-by-step synthesis method of the present invention has mild reaction conditions and a relatively simple operation process. It does not require special equipment and complex processes, is easy to industrialize, helps to reduce production costs, and improves the market competitiveness of products. Specific implementation mode

[0021] The present invention will be further described below in conjunction with embodiments, but it does not limit the implementation of the present invention.

[0022] Unless otherwise specified, the raw materials used in the examples and comparative examples are all conventional commercially available raw materials, and the process methods used in the examples and comparative examples are all conventional methods in the art unless otherwise specified.

[0023] Example 1 The step-by-step synthesis method of the high functionality and low viscosity polyester polyol includes the following steps: (1) Put 250 g of ethylene glycol, 500 g of adipic acid, 0.12 g of tetrabutyl titanate, 1.4 g of antioxidant 1010 and 0.9 g of antioxidant 168 into a reaction kettle. Under the protection of nitrogen, stir and mix evenly, heat up to 225 °C, evacuate to a vacuum pressure of -0.1 MPa, and carry out esterification and transesterification reactions until the acid value reaches 2 mgKOH / g to obtain a polyester polyol intermediate; (2) Cool the polyester polyol intermediate prepared in step (1) to 200 °C, put 150 g of trimethylolpropane into the reaction kettle, adjust the pressure in the kettle to -0.07 MPa, and continue the transesterification reaction for 5 h. Measure the hydroxyl value to be 286 mgKOH / g. After the reaction is completed, cool and discharge the material to obtain the high functionality and low viscosity polyester polyol.

[0024] Example 2 The step-by-step synthesis method of the high functionality and low viscosity polyester polyol includes the following steps: (1) Put 250 g of ethylene glycol, 500 g of adipic acid, 0.12 g of tetrabutyl titanate, 1.4 g of antioxidant 1010 and 0.9 g of antioxidant 168 into a reaction kettle. Under the protection of nitrogen, stir and mix evenly, heat up to 225 °C, evacuate to a vacuum pressure of -0.1 MPa, and carry out esterification and transesterification reactions until the acid value reaches 2 mgKOH / g to obtain a polyester polyol intermediate; (2) Cool the polyester polyol intermediate prepared in step (1) to 200 °C, add 225 g of trimethylolpropane to the reaction kettle, adjust the pressure in the kettle to -0.07 MPa, and continue the transesterification reaction for 5 h. The hydroxyl value is measured to be 368 mg KOH / g. After the reaction is completed, cool down and discharge the material to obtain a high functionality and low viscosity polyester polyol.

[0025] Example 3 The stepwise synthesis method of the high functionality and low viscosity polyester polyol includes the following steps: (1) Add 150 g of ethylene glycol, 170 g of diethylene glycol, 430 g of succinic acid, 0.12 g of tetrabutyl titanate, 2 g of antioxidant 1076, and 1.75 g of antioxidant 626 to the reaction kettle. Under the protection of nitrogen, stir and mix evenly, heat up to 230 °C, evacuate to a vacuum pressure of -0.1 MPa, and carry out the esterification and transesterification reactions until the acid value is 5 mg KOH / g to obtain a polyester polyol intermediate. (2) Cool the polyester polyol intermediate prepared in step (1) to 180 °C, add 150 g of trimethylolpropane to the reaction kettle, adjust the pressure in the kettle to -0.06 MPa, and continue the transesterification reaction for 5 h. The hydroxyl value is measured to be 272 mg KOH / g. After the reaction is completed, cool down and discharge the material to obtain a high functionality and low viscosity polyester polyol.

[0026] Example 4 The stepwise synthesis method of the high functionality and low viscosity polyester polyol includes the following steps: (1) Add 440 g of diethylene glycol, 310 g of phthalic acid, 0.375 g of tetraisopropyl titanate, 0.9 g of antioxidant 1076, and 0.9 g of antioxidant 168 to the reaction kettle. Under the protection of nitrogen, stir and mix evenly, heat up to 200 °C, evacuate to a vacuum pressure of -0.09 MPa, and carry out the esterification and transesterification reactions until the acid value is 2 mg KOH / g to obtain a polyester polyol intermediate. (2) Keep the temperature of the polyester polyol intermediate prepared in step (1) at 200 °C, add 40 g of glycerol to the reaction kettle, adjust the pressure in the kettle to -0.08 MPa, and continue the transesterification reaction for 6 h. The hydroxyl value is measured to be 371 mg KOH / g. After the reaction is completed, cool down and discharge the material to obtain a high functionality and low viscosity polyester polyol.

[0027] Example 5 The stepwise synthesis method of the high functionality and low viscosity polyester polyol includes the following steps: (1) Put 230 g of propylene glycol, 520 g of sebacic acid, 0.0075 g of stannous octoate, 1.8 g of antioxidant 1010 and 0.9 g of antioxidant 168 into the reaction kettle. Under the protection of nitrogen, stir and mix evenly, heat up to 225 °C, evacuate to a vacuum pressure of -0.1 MPa, and carry out esterification and transesterification reactions until the acid value reaches 2 mgKOH / g to obtain a polyester polyol intermediate. (2) Cool the polyester polyol intermediate obtained in step (1) to 200 °C, put 100 g of trimethylolpropane into the reaction kettle, adjust the pressure in the kettle to -0.07 MPa, and continue the transesterification reaction for 5 h. Measure the hydroxyl value to be 195 mgKOH / g. After the reaction is completed, cool and discharge the material to obtain a high-functional low-viscosity polyester polyol.

[0028] Example 6 The step-by-step synthesis method of the high-functional low-viscosity polyester polyol includes the following steps: (1) Put 300 g of 1,4-butanediol, 450 g of adipic acid, 0.12 g of tetrabutyl titanate, 0.5 g of antioxidant 1010 and 0.25 g of antioxidant 168 into the reaction kettle. Under the protection of nitrogen, stir and mix evenly, heat up to 225 °C, evacuate to a vacuum pressure of -0.1 MPa, and carry out esterification and transesterification reactions until the acid value reaches 2 mgKOH / g to obtain a polyester polyol intermediate. (2) Cool the polyester polyol intermediate obtained in step (1) to 200 °C, put 150 g of trimethylolpropane into the reaction kettle, adjust the pressure in the kettle to -0.08 MPa, and continue the transesterification reaction for 4 h. Measure the hydroxyl value to be 246 mgKOH / g. After the reaction is completed, cool and discharge the material to obtain a high-functional low-viscosity polyester polyol.

[0029] Comparative Example 1 Put 250 g of ethylene glycol, 500 g of adipic acid, 150 g of trimethylolpropane, 0.12 g of tetrabutyl titanate, 1.4 g of antioxidant 1010 and 0.9 g of antioxidant 168 into the reaction kettle. Under the protection of nitrogen, stir and mix evenly, heat up to 225 °C, evacuate to a vacuum pressure of -0.1 MPa, and carry out esterification and transesterification reactions. Measure the hydroxyl value to be 286 mgKOH / g. After the reaction is completed, cool and discharge the material to obtain a polyester polyol.

[0030] Comparative Example 2 250 g of ethylene glycol, 500 g of adipic acid, 225 g of trimethylolpropane, 0.12 g of tetrabutyl titanate, 1.4 g of antioxidant 1010 and 0.9 g of antioxidant 168 were put into a reaction kettle. Under the protection of nitrogen, they were stirred and mixed evenly, heated to 225 °C, and evacuated to a vacuum pressure of -0.1 MPa for esterification and transesterification reactions. Gelation occurred during the reaction process.

[0031] The polyester polyols prepared in Examples 1-6 and Comparative Examples 1-2 were subjected to performance tests. The test methods are as follows: Hydroxyl value: Tested with reference to HG / T 2709-2022; Acid value: Tested with reference to HG / T 2708-1995; Viscosity: Tested using a rotational viscometer; The test results are shown in Table 1.

[0032] Table 1 Performance test results

[0033] It can be seen from the data in Table 1 that the polyester polyol prepared by the stepwise synthesis method of the present invention has a lower viscosity under the same raw material system and the same hydroxyl value compared with the polyester polyol prepared by the traditional one-step method; while the polyester polyol prepared by the one-step method has a higher viscosity, which indicates that a greater degree of crosslinking occurred during the one-step synthesis process. And when the proportion of polyol in the raw material system is relatively high, crosslinking gelation is likely to occur during the reaction process of the polyester polyol prepared by the one-step method.

Claims

1. A stepwise synthesis method of a highly functional low-viscosity polyester polyol, characterized in that, It includes the following steps: (1) Put diol, dicarboxylic acid, catalyst and antioxidant into a reaction kettle, heat up and evacuate to carry out esterification and transesterification reactions to obtain a polyester polyol intermediate; (2) After cooling the polyester polyol intermediate obtained in step (1), put polyol into the reaction kettle and continue the transesterification reaction. After the reaction ends, a high functionality and low viscosity polyester polyol is obtained.

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

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

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

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

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

7. The stepwise synthesis method of the high functionality and low viscosity polyester polyol according to claim 1, characterized in that, The functionality of the polyol ≥ 3 and the number average molecular weight ≤ 500 g / mol, and the dosage of the polyol is 5 to 30% of the total mass of the diol, the dicarboxylic acid and the polyol.

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

10. A high functionality and low viscosity polyester polyol, characterized in that, It is prepared by using the stepwise synthesis method of the high functionality and low viscosity polyester polyol described in any one of claims 1-9.

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