A method for increasing the rate of polycondensation reaction of polyester materials

Abstract

The application discloses a method for improving the polycondensation reaction rate of polyester material. The method uses dihydric alcohol and dicarboxylic acid and derivatives thereof as raw monomers, adds aromatic unit alcohol as a third component, sequentially carries out esterification reaction, pre-polycondensation reaction and final polycondensation reaction, and adds a high-efficiency catalyst in the pre-polycondensation reaction stage. In general, the addition of unit alcohol in the reaction will end the molecular chain of esterification product, which is not conducive to the growth of polymer chain and is generally used as a chain terminator. However, the esterification product is capped by adding aromatic unit alcohol in the esterification reaction stage in the application. Since the ester exchange activity of aryl ester is greater than that of aliphatic alkyl ester, the leaving ability of the aromatic unit alcohol is stronger in the polycondensation reaction, which is more conducive to improving the polycondensation reaction rate.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials, and particularly relates to a method for increasing the polycondensation reaction rate of polyester materials. Background Technology

[0002] Polymer materials are widely used in our daily lives, and polyester materials have become an indispensable part of our daily routines. Currently, whether it is non-degradable polyester materials such as PET and PBT, or biodegradable polyester materials such as PBS, PBAT, and PES, the main production process still adopts the direct esterification method. This process has a relatively long final polycondensation time, which directly affects various properties of the polymer. Therefore, accelerating the polycondensation reaction rate is of great significance for saving production costs and improving product quality.

[0003] Patent number CN111471166A, patent title "A method for shortening the reaction time of polyester polycondensation", this method does not change other reaction parameters, but requires the addition of a certain amount of zinc compounds in the polycondensation stage, which can significantly shorten the polycondensation reaction time. However, adding zinc compounds is equivalent to increasing the amount of catalyst used. Therefore, although the effect is good, there are still problems of cost and more side reactions.

[0004] Patent number CN1552754A, entitled "A Method for Improving the Polycondensation Reaction Rate of Polyester," describes a method that accelerates the polycondensation reaction rate by adding a certain amount of multifunctional substances. While this method can accelerate the reaction rate and rapidly increase viscosity, the addition of these multifunctional substances results in a certain gel structure, which has some adverse effects on the subsequent processing of the polyester material.

[0005] Weinland DH, van der Maas K, Wang Y, et al. Overcoming the low reactivity of biobased, secondary diols in polyester synthesis[J]. Nature Communications, 2022, 13(1): 7370. A method combining molten solution and ester was proposed. High molecular weight isosorbide was obtained by end-capping the esterified product with p-cresol, a reactive phenolic solvent. However, such extensive use of toxic phenolic solvents not only affects human health but also places a significant burden on the vacuum system, increases the solvent recovery process, and is detrimental to continuous production. The strong acidity of phenolic solvents also contributes to equipment corrosion. More importantly, the catalysts currently used in the synthesis of biodegradable polyesters such as PBS, PBAT, and PES are mainly environmentally friendly titanium-based catalysts. Phenolic solvents readily react with titanium-based catalysts, resulting in low catalytic activity and a significant decrease in the polycondensation reaction rate. Summary of the Invention

[0006] The purpose of this invention is:

[0007] A method for increasing the polycondensation rate of polyester materials is provided, and this method does not change the catalyst dosage or introduce other molecular chain segments that would disrupt the crystallinity of the polyester material. This method involves adding a certain amount of aromatic monohydric alcohol, utilizing the greater transesterification reactivity of aryl esters compared to aliphatic alkyl esters, and then using a vacuum system to remove the aromatic monohydric alcohol, thereby achieving rapid molecular chain growth and increasing the polyester polycondensation rate.

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

[0009] A method for increasing the polycondensation reaction rate of polyester materials, wherein the method for increasing the polycondensation reaction rate is achieved by adding an aromatic monool as a third component in an esterification reaction using diols, dicarboxylic acids and their derivatives as raw materials.

[0010] Furthermore, the diol is an aliphatic or aromatic diol; the dicarboxylic acid is an aliphatic or aromatic dicarboxylic acid.

[0011] Furthermore, aliphatic diols are selected from C2 to C3. 10 One or more aliphatic diols; aromatic diols selected from C8 to C95. 16 A mixture of one or more aromatic diols. Aliphatic dicarboxylic acids are selected from C2 to C3. 16 Aliphatic dicarboxylic acids, C2-C 16Aliphatic dicarboxylic anhydrides or C2-C 16 A mixture of one or more aliphatic diacyl halides. Aromatic dicarboxylic acids are selected from C8 to C96. 16 Aromatic dicarboxylic acids, C8-C 16 Aromatic dicarboxylic anhydrides or C8-C 16 One or more of the aromatic diacyl halides.

[0012] Furthermore, the aromatic monool structure can be one or a mixture of two or more of the following structural formulas:

[0013]

[0014] Where R is C 1-10 Hydrocarbon group.

[0015] Furthermore, the method for increasing the polycondensation reaction rate of biodegradable polyester materials comprises the following steps:

[0016] a. Esterification reaction: Diols, dicarboxylic acids and their derivatives, and aromatic monohydric alcohols are mixed, stirred and heated to carry out the esterification reaction until no more esterified water is distilled off.

[0017] b. Pre-polymerization reaction: After adding a catalyst to the ester and stirring, the temperature is raised to the pre-polymerization reaction temperature, and small molecules are removed under low vacuum conditions.

[0018] c. Final polycondensation reaction: The small molecules are further removed under reduced pressure to a high vacuum condition to carry out the final polycondensation reaction.

[0019] Furthermore, the molar ratio of the diol to the dicarboxylic acid and its derivatives in the esterification reaction is 1.1 to 1.6:1, and the amount of aromatic monool added is preferably 1 to 44.8 wt% of the theoretical yield of the final polymer.

[0020] Furthermore, the amount of aromatic monool added in the esterification reaction is 4–10 wt% of the theoretical yield of the final polyester material. The esterification reaction temperature is 160–180 °C, and the time is 2.5–6 h.

[0021] Furthermore, in the pre-polymerization reaction stage, the catalyst is one or more titanium-based catalysts; the amount of catalyst added is calculated based on the mass of titanium element and is 50-600 ppm of the theoretical yield of the final polyester material; the low vacuum condition refers to the condition of reducing the pressure to an absolute pressure of 1000-2000 Pa; the pre-polymerization reaction temperature is 220-240℃, and the pre-polymerization reaction time is 0.5-1 h.

[0022] Furthermore, in the pre-condensation reaction stage, the titanium-based catalyst is one or more of tetraethyl titanate, tetraisopropyl titanate, or tetrabutyl titanate; the stirring time is 10-15 min.

[0023] Furthermore, the reaction temperatures for both the pre-condensation reaction and the final condensation reaction are the same, 220–240 °C; depressurization refers to reducing the pressure to an absolute pressure of 30–150 Pa within 10–20 min; and the final condensation reaction time is 2–6 h.

[0024] The beneficial effects of this invention are as follows:

[0025] This invention provides a method for increasing the polycondensation reaction rate of biodegradable polyester materials. The method is simple, low-cost, and easy to operate. Furthermore, this method does not change the amount of catalyst, thus avoiding the aggravation of side reactions and the introduction of other molecular segments that disrupt the regularity of polymer chains. This preserves the crystallinity of the polymer and has high application value. Detailed Implementation

[0026] The present invention will now be described in detail with reference to the embodiments.

[0027] Example 1

[0028] A method for increasing the polycondensation reaction rate of biodegradable polyester materials, the method is as follows:

[0029] In a nitrogen atmosphere, 135.6 g of succinic anhydride, 171 g of 1,4-butanediol, and 2.3 g of phenylethanol were added sequentially to a 500 mL four-necked flask equipped with a thermocouple, stirrer, and condenser. The temperature was raised to 170 °C for esterification. Esterification continued for 3 hours after the first drop of esterification water distilled from the system. Then, the vacuum system was changed, and 0.583 g of tetrabutyl titanate catalyst diluted with BDO was added to the system. The mixture was stirred at 170 °C for 10 minutes, then heated to 230 °C. Pre-polymerization was carried out under a vacuum of 2000 Pa for 1 hour, followed by final polymerization at a vacuum of 50 Pa after 15 minutes. The reaction was stopped and the product was discharged when the high vacuum time reached the specified time.

[0030] The obtained polymer was tested using a melt indexer, and the measured melt index and final polycondensation time are shown in Table 1.

[0031] Example 2

[0032] A method for increasing the polycondensation reaction rate of biodegradable polyester materials, the method is as follows:

[0033] In a nitrogen atmosphere, 135.6 g of succinic anhydride, 171 g of 1,4-butanediol, and 6.5 g of phenylethanol were added sequentially to a 500 mL four-necked flask equipped with a thermocouple, a stirrer, and a condenser. The temperature was raised to 170 °C for esterification. Esterification continued for 3 hours after the first drop of esterification water distilled from the system. Then, the vacuum system was changed, and 0.583 g of tetrabutyl titanate catalyst diluted with BDO was added to the system. The mixture was stirred at 170 °C for 10 minutes, then heated to 230 °C. Pre-polymerization was carried out under a vacuum of 2000 Pa for 1 hour, followed by final polymerization at a vacuum of 50 Pa after 15 minutes. The reaction was stopped and the product was discharged when the high vacuum time reached the specified time.

[0034] The obtained polymer was tested using a melt indexer, and the measured melt index and final polycondensation time are shown in Table 1.

[0035] Example 3

[0036] A method for increasing the polycondensation reaction rate of biodegradable polyester materials, the method is as follows:

[0037] In a nitrogen atmosphere, 135.6 g of succinic anhydride, 171 g of 1,4-butanediol, and 14.0 g of phenylethanol were added sequentially to a 500 mL four-necked flask equipped with a thermocouple, stirrer, and condenser. The temperature was raised to 170 °C for esterification. Esterification continued for 3 hours after the first drop of esterified water distilled from the system. Then, the vacuum system was changed, and 0.583 g of tetrabutyl titanate catalyst diluted with BDO was added to the system. The mixture was stirred at 170 °C for 10 minutes, then heated to 230 °C. Pre-polymerization was carried out under a vacuum of 2000 Pa for 1 hour, followed by final polymerization at a vacuum of 50 Pa after 15 minutes. The reaction was stopped and the product was discharged when the high vacuum time reached the specified time.

[0038] The obtained polymer was tested using a melt indexer, and the measured melt index and final polycondensation time are shown in Table 1.

[0039] Example 4

[0040] A method for increasing the polycondensation reaction rate of biodegradable polyester materials, the method is as follows:

[0041] In a nitrogen atmosphere, 135.6 g of succinic anhydride, 171 g of 1,4-butanediol, and 28.0 g of phenylethanol were added sequentially to a 500 mL four-necked flask equipped with a thermocouple, stirrer, and condenser. The temperature was raised to 170 °C for esterification. Esterification continued for 3 hours after the first drop of esterification water distilled from the system. Then, the vacuum system was changed, and 0.583 g of tetrabutyl titanate catalyst diluted with BDO was added to the system. The mixture was stirred at 170 °C for 10 minutes, then heated to 230 °C. Pre-polymerization was carried out under a vacuum of 2000 Pa for 1 hour, followed by final polymerization at a vacuum of 50 Pa after 15 minutes. The reaction was stopped and the product was discharged when the high vacuum time reached the specified time.

[0042] The obtained polymer was tested using a melt indexer, and the measured melt index and final polycondensation time are shown in Table 1.

[0043] Example 5

[0044] A method for increasing the polycondensation reaction rate of biodegradable polyester materials, the method is as follows:

[0045] In a nitrogen atmosphere, 135.6 g of succinic anhydride, 171 g of 1,4-butanediol, and 14.0 g of 4-methylbenzyl alcohol were added sequentially to a 500 mL four-necked flask equipped with a thermocouple, stirrer, and condenser. The temperature was raised to 170 °C for esterification. Esterification continued for 3 hours after the first drop of esterification water distilled from the system. Then, the vacuum system was changed, and 0.583 g of tetrabutyl titanate catalyst diluted with BDO was added to the system. The mixture was stirred at 170 °C for 10 minutes, then heated to 230 °C. Pre-polymerization was carried out under a vacuum of 2000 Pa for 1 hour, followed by final polymerization at a vacuum of 50 Pa after 15 minutes. The reaction was stopped and the product was discharged when the high vacuum time reached the specified time.

[0046] The obtained polymer was tested using a melt indexer, and the measured melt index and final polycondensation time are shown in Table 1.

[0047] Comparative Example 1

[0048] The method for synthesizing a biodegradable polyester without monohydric alcohol end caps is as follows:

[0049] In a nitrogen atmosphere, 135.6 g of succinic anhydride and 171 g of 1,4-butanediol were added sequentially to a 500 mL four-necked flask equipped with a thermocouple, stirrer, and condenser. The temperature was raised to 170 °C for esterification. Esterification continued for 3 hours after the first drop of esterification water distilled from the system. Then, the vacuum system was changed, and 0.583 g of tetrabutyl titanate catalyst diluted with BDO was added to the system. The mixture was stirred at 170 °C for 10 minutes, then heated to 230 °C. Pre-polymerization was carried out under a vacuum of 2000 Pa for 1 hour, followed by final polymerization at a vacuum of 50 Pa after 15 minutes. The reaction was stopped and the product was discharged when the high vacuum time reached the specified time.

[0050] The obtained polymer was tested using a melt indexer, and the measured melt index and final polycondensation time are shown in Table 1.

[0051] Comparative Example 2

[0052] The method for synthesizing aromatic monool-terminated biodegradable polyesters is as follows:

[0053] In a nitrogen atmosphere, 135.6 g of succinic anhydride, 171 g of 1,4-butanediol, and 0.7 g of phenylethanol were added sequentially to a 500 mL four-necked flask equipped with a thermocouple, stirrer, and condenser. The temperature was raised to 170 °C for esterification. Esterification continued for 3 hours after the first drop of esterification water distilled from the system. Then, the vacuum system was changed, and 0.583 g of tetrabutyl titanate catalyst diluted with BDO was added to the system. The mixture was stirred at 170 °C for 10 minutes, then heated to 230 °C. Pre-polymerization was carried out under a vacuum of 2000 Pa for 1 hour, followed by final polymerization at a vacuum of 50 Pa after 15 minutes. The reaction was stopped and the product was discharged when the high vacuum time reached the specified time.

[0054] The obtained polymer was tested using a melt indexer, and the measured melt index and final polycondensation time are shown in Table 1.

[0055] Comparative Example 3

[0056] The method for synthesizing alicyclic monool-terminated biodegradable polyesters is as follows:

[0057] In a nitrogen atmosphere, 135.6 g of succinic anhydride, 171 g of 1,4-butanediol, and 13.1 g of cyclohexylmethanol were added sequentially to a 500 mL four-necked flask equipped with a thermocouple, stirrer, and condenser. The temperature was raised to 170 °C for esterification. Esterification continued for 3 hours after the first drop of esterification water distilled from the system. Then, the vacuum system was changed, and 0.583 g of tetrabutyl titanate catalyst diluted with BDO was added to the system. The mixture was stirred at 170 °C for 10 minutes, then heated to 230 °C. Pre-polymerization was carried out under a vacuum of 2000 Pa for 1 hour, followed by final polymerization at a vacuum of 50 Pa after 15 minutes. The reaction was stopped and the product was discharged when the high vacuum time reached the specified time.

[0058] The obtained polymer was tested using a melt indexer, and the measured melt index and final polycondensation time are shown in Table 1.

[0059] Comparative Example 4

[0060] The method for synthesizing alicyclic monool-terminated biodegradable polyesters is as follows:

[0061] In a nitrogen atmosphere, 135.6 g of succinic anhydride, 171 g of 1,4-butanediol, and 11.5 g of cyclohexanol were added sequentially to a 500 mL four-necked flask equipped with a thermocouple, stirrer, and condenser. The temperature was raised to 170 °C for esterification. Esterification continued for 3 hours after the first drop of esterification water distilled from the system. Then, the vacuum system was changed, and 0.583 g of tetrabutyl titanate catalyst diluted with BDO was added to the system. The mixture was stirred at 170 °C for 10 minutes, then heated to 230 °C. Pre-polymerization was carried out under a vacuum of 2000 Pa for 1 hour, followed by final polymerization at a vacuum of 50 Pa after 15 minutes. The reaction was stopped and the product was discharged when the high vacuum time reached the specified time.

[0062] The obtained polymer was tested using a melt indexer, and the measured melt index and final polycondensation time are shown in Table 1.

[0063] Comparative Example 5

[0064] The method for synthesizing aliphatic unit alcohol-terminated biodegradable polyesters is as follows:

[0065] In a nitrogen atmosphere, 135.6 g of succinic anhydride, 171 g of 1,4-butanediol, and 11.7 g of n-hexanol were added sequentially to a 500 mL four-necked flask equipped with a thermocouple, stirrer, and condenser. The temperature was raised to 170 °C for esterification. Esterification continued for 3 hours after the first drop of esterification water distilled from the system. Then, the vacuum system was changed, and 0.583 g of tetrabutyl titanate catalyst diluted with BDO was added to the system. The mixture was stirred at 170 °C for 10 minutes, then heated to 230 °C. Pre-polymerization was carried out under a vacuum of 2000 Pa for 1 hour, followed by final polymerization at a vacuum of 50 Pa after 15 minutes. The reaction was stopped and the product was discharged when the high vacuum time reached the specified time.

[0066] The obtained polymer was tested using a melt indexer, and the measured melt index and final polycondensation time are shown in Table 1.

[0067] Table 1

[0068] Example High vacuum time <![CDATA[MVR / cm 3 / 10min]]> Example 1 4h 30min 61.485 Example 2 4h 30min 26.631 Example 3 4h 30min 14.773 Example 4 4h 30min 6.834 Example 5 4h 30min 18.416 Comparative Example 1 4h 30min 84.209 Comparative Example 2 4h 30min 82.806 Comparative Example 3 4h 30min 55.539 Comparative Example 4 4h 30min 378.613 Comparative Example 5 4h 30min 329.279

[0069] As shown in Table 1, compared with Comparative Example 1, Examples 1 to 4 of the present invention show that the addition of aromatic monohydric alcohols has a more significant effect on improving the reaction rate of polycondensation. Furthermore, it can be seen that different amounts of aromatic monohydric alcohols have different effects on the polycondensation rate. Comparing Comparative Example 1 with Comparative Example 2, it can be found that when the amount of aromatic monohydric alcohol added is small, the polycondensation rate does not change significantly. Comparing Comparative Examples 4 and 5 with Comparative Example 1, it is clear that the polycondensation rate decreases significantly when aliphatic and alicyclic monohydric alcohols are used for end-capping. Comparing Example 5 with Comparative Example 1, it is found that aromatic monohydric alcohols with similar structures have a good effect on improving the polycondensation rate. Comparative Example 3 shows that although using alicyclic monohydric alcohols with similar structures to end-cap the ester can also improve the polycondensation rate to some extent, the lack of a benzene ring structure results in a relatively weaker electronic effect and a weaker group leaving ability compared to aromatic monohydric alcohols, thus the improvement in the polycondensation rate is relatively weak. This method involves adding a certain amount of aromatic monohydric alcohol, taking advantage of the fact that aryl esters have greater transesterification activity than aliphatic alkyl esters, and then using a vacuum system to remove the aromatic monohydric alcohol, thereby achieving rapid molecular chain growth and increasing the polyester polycondensation rate.

[0070] It should be noted that the descriptions of these embodiments are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described above can be combined with each other as long as they do not conflict with each other. In addition, the above are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

Claims

1. A method for increasing the polycondensation reaction rate of polyester materials, characterized in that, The method for increasing the polycondensation reaction rate is achieved by adding an aromatic monohydric alcohol as a third component to an esterification reaction using diols, dicarboxylic acids, and their derivatives as raw materials; the amount of aromatic monohydric alcohol added is 1-44.8 wt% of the theoretical yield of the final polymer. Aromatic monools have structures that are one or more of the following structural formulas: ， Where R is C 1-2 Hydrocarbon group.

2. The method for increasing the polycondensation reaction rate of polyester materials as described in claim 1, characterized in that, The diol is an aliphatic or aromatic diol; the dicarboxylic acid is an aliphatic or aromatic dicarboxylic acid.

3. The method for increasing the polycondensation reaction rate of polyester materials as described in claim 1, characterized in that, Aliphatic diols are selected from C2~C2. 10 One or more aliphatic diols; aromatic diols selected from C8~C6. 16 One or more aromatic diols; aliphatic dicarboxylic acids selected from C2~C3. 16 Aliphatic dicarboxylic acids, C2~C 16 Aliphatic dicarboxylic anhydrides or C2~C 16 One or more aliphatic diacyl halides; aromatic dicarboxylic acids selected from C8~C6. 16 Aromatic dicarboxylic acids, C8~C 16 Aromatic dicarboxylic anhydrides or C8~C 16 One or more of the aromatic diacyl halides.

4. A method for increasing the polycondensation reaction rate of polyester materials as described in any one of claims 1-3, characterized in that, The specific steps are as follows: a. Esterification reaction: Diols, dicarboxylic acids and their derivatives, and aromatic monohydric alcohols are mixed and stirred. Heat the mixture to carry out the esterification reaction until no more esterified water distills out; b. Pre-polymerization reaction: After adding a catalyst to the ester and stirring, the temperature is raised to the pre-polymerization reaction temperature, and small molecules are removed under low vacuum conditions. c. Final polycondensation reaction: The small molecules are further removed under reduced pressure to a high vacuum condition to carry out the final polycondensation reaction.

5. The method for increasing the polycondensation reaction rate of polyester materials according to claim 4, characterized in that, The molar ratio of the diol to the dicarboxylic acid and its derivatives in the esterification reaction is 1.1 to 1.6:

1.

6. The method for increasing the polycondensation reaction rate of polyester materials according to claim 4, characterized in that, The amount of aromatic monool added in the esterification reaction is 4~10wt% of the theoretical yield of the final polyester material; the temperature of the esterification reaction is 160~180℃ and the time is 2.5~6h.

7. The method for increasing the polycondensation reaction rate of polyester materials according to claim 4, characterized in that, In the pre-polymerization reaction stage, the catalyst is one or more titanium-based catalysts; the amount of catalyst added is calculated based on the mass of titanium element and is 50~600ppm of the theoretical yield of the final polyester material; low vacuum conditions refer to the conditions where the pressure is reduced to an absolute pressure of 1000~2000Pa; the pre-polymerization reaction temperature is 220~240℃, and the pre-polymerization reaction time is 0.5~1h.

8. The method for increasing the polycondensation reaction rate of polyester materials according to claim 4, characterized in that... During the pre-condensation reaction stage, the titanium-based catalyst is one or more of tetraethyl titanate, tetraisopropyl titanate, or tetrabutyl titanate; the stirring time is 10-15 min.

9. The method for increasing the polycondensation reaction rate of polyester materials according to claim 4, characterized in that, The reaction temperatures for both the pre-condensation reaction and the final condensation reaction are the same, 220~240℃; decompression refers to reducing the pressure to an absolute pressure of 30~150Pa within 10~20min; the final condensation reaction time is 2~6h.

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