A process for the preparation of polybutylene succinate

Abstract

The application discloses a preparation method of polybutylene succinate. The method comprises the following steps: 1) controlling the raw material 1,4-butanediol to contain 2-methoxytetrahydrofuran and 4-[(tetrahydro-2-furanyl)oxy]-1-butanol with a total amount of 0.01-0.5wt%, and the mass ratio of 2-methoxytetrahydrofuran and 4-[(tetrahydro-2-furanyl)oxy]-1-butanol is (0.3-5):1; 2) using the above 1,4-butanediol as the raw material, and making the 1,4-butanediol and succinic acid to occur esterification polycondensation reaction in the presence of a catalyst to generate polybutylene succinate. The application improves the molecular weight and distribution of PBS products, and improves the mechanical properties and thermal properties.

Description

Technical Field

[0001] This invention relates to the preparation of a polymer material, and more particularly to a method for preparing polybutylene succinate. Background Technology

[0002] Polybutylene succinate (PBS) is a copolymer of succinic acid and butanediol, exhibiting excellent biodegradability and strong application potential in food contact materials such as disposable lunch boxes and straws. However, PBS has not yet achieved large-scale application, partly due to its relatively high raw material cost compared to traditional polyolefin materials, and partly due to its lower processing temperature, resulting in PBS with lower molecular weight, lower viscosity, and mechanical properties that cannot be compared to general-purpose plastics. Furthermore, applications such as disposable lunch boxes and straws require PBS materials to possess excellent heat distortion temperatures.

[0003] Therefore, improving the molecular weight, mechanical properties, and thermal stability of PBS is an urgent problem to be solved.

[0004] Patent CN1424339A discloses a method for preparing PBS using benzenesulfonic acid, tin oxide, antimony trioxide, cadmium acetate, titanate, or any mixture of two or more thereof as a catalyst, but the highest molecular weight of the product is only 137,000, and the heat distortion temperature (HDT) of the product has not been improved.

[0005] Patent CN101935391B discloses a method for preparing high molecular weight aliphatic polyesters. This method uses aliphatic diacid diesters and aliphatic diols as raw materials for melt polycondensation, which can obtain aliphatic polyesters with a weight-average molecular weight of 50,000-250,000 and a molecular weight distribution coefficient of 1.9-2.2. However, the disadvantages of this method are long reaction time, low catalyst activity, and wide molecular weight distribution of polyester, which will reduce its heat distortion temperature and affect the application of the product in the catering industry. Summary of the Invention

[0006] To address the above technical problems, this invention proposes a method for preparing polybutylene succinate.

[0007] A method for preparing polybutylene succinate includes the following steps:

[0008] 1) Control the total content of 2-methoxytetrahydrofuran and 4-[(tetrahydro-2-furanyl)oxy]-1-butanol in the raw material 1,4-butanediol to be 0.01-0.5 wt%, and the mass ratio of 2-methoxytetrahydrofuran to 4-[(tetrahydro-2-furanyl)oxy]-1-butanol to be (0.3-5):1;

[0009] 2) Using the above-mentioned 1,4-butanediol as a raw material, it undergoes an esterification and polycondensation reaction with succinic acid in the presence of a catalyst to generate polybutylene succinate.

[0010] As a preferred embodiment of the present invention, in step 1), the raw material 1,4-butanediol is controlled to contain a total amount of 0.02-0.25 wt% of 2-methoxytetrahydrofuran and 4-[(tetrahydro-2-furanyl)oxy]-1-butanol, and the mass ratio of 2-methoxytetrahydrofuran to 4-[(tetrahydro-2-furanyl)oxy]-1-butanol is (1-3):1.

[0011] In this invention, the methods for controlling the content and ratio of 2-methoxytetrahydrofuran and 4-[(tetrahydro-2-furanyl)oxy]-1-butanol (TOBO) in the raw material 1,4-butanediol can be either direct addition or pretreatment of the raw material 1,4-butanediol by reactive distillation to convert the unavoidable impurity 4-[(tetrahydro-2-furanyl)oxy]-1-butanol into 2-methoxytetrahydrofuran that meets the specified conditions. Alternatively, a combination of the above two control methods can be used. These methods can be easily adjusted by those skilled in the art based on the information disclosed in this invention, and therefore do not constitute any limitation on this invention.

[0012] As a specific example of reactive distillation, one could perform reactive distillation by mixing 1,4-butanediol containing 4-[(tetrahydro-2-furanyl)oxy]-1-butanol with methanol. The catalyst used could be, for example, a solid acid catalyst, preferably one or more of molecular sieves, cationic resins, and solid superacids, more preferably Rohm and Haas Amberlite 35 and / or Dandong Mingzhu DA330 cationic resins. The degree of reaction should be controlled to ensure that the contents of 2-methoxytetrahydrofuran and 4-[(tetrahydro-2-furanyl)oxy]-1-butanol in 1,4-butanediol are within the aforementioned limits. In certain special cases, such as when the TOBO content in 1,4-butanediol is too low, an appropriate amount of TOBO can be added.

[0013] In their long-term research on the correlation between PBS performance and production conditions, the inventors discovered that controlling the content of the monohydroxy impurity TOBO in the raw materials is beneficial to increasing the molecular weight of PBS to a certain extent. Simultaneously, introducing a certain amount of 2-methoxytetrahydrofuran further promotes the increase in PBS molecular weight, presumably because it decomposes under polycondensation conditions to generate reactive substances that can act as chain extenders. Therefore, this invention preferably uses reactive distillation conditions to convert a certain amount of TOBO to 2-methoxytetrahydrofuran by adding methanol, thereby increasing the product molecular weight from the source during the polymer synthesis stage. However, further research revealed that the TOBO content in 1,4-butanediol cannot be too low; otherwise, the mechanical properties and thermal stability of the PBS material will be compromised. In particular, it was found that when the total amount of TOBO and 2-methoxytetrahydrofuran in 1,4-butanediol is controlled between 0.01 wt% and 0.5 wt%, and the mass ratio of 2-methoxytetrahydrofuran to TOBO is between 0.3:1 and 5:1, the mechanical properties and thermal stability of the product are significantly improved, thus completing this invention.

[0014] As a preferred embodiment of the present invention, the molar ratio of succinic acid and 1,4-butanediol is 1:(1.1-1.5), preferably 1:(1.1-1.3).

[0015] As a preferred embodiment of the present invention, the catalyst includes a main catalyst and an auxiliary agent, wherein the main catalyst is a titanate ester and the auxiliary agent is a phosphorus-containing compound;

[0016] Preferably, the main catalyst is one or more of tetrabutyl titanate, tetraisopropyl titanate, tetraethyl titanate, and tetramethyl titanate.

[0017] Preferably, the adjuvant is one or more of trimethyl phosphate, triethyl phosphate, and triphenyl phosphate.

[0018] As a preferred embodiment of the present invention, the amount of the main catalyst is 50 to 300 ppm, calculated as the sum of the mass of metallic titanium relative to the raw materials succinic acid and 1,4-butanediol.

[0019] Preferably, the amount of the additive is 10-100 ppm, calculated as the sum of the mass of phosphorus relative to the raw materials succinic acid and 1,4-butanediol.

[0020] As a preferred embodiment of the present invention, the reaction process is divided into two stages: esterification reaction and polycondensation reaction; wherein, the esterification reaction temperature is 180-250℃, and the reaction endpoint is defined as the water content of the by-product reaching more than 95% of the theoretical water production.

[0021] The polycondensation reaction is first evacuated to 1000-30000 PaA for 10-60 minutes, then evacuated to below 100 PaA, and heated to 220-260℃ for 60-200 minutes.

[0022] This invention has found that controlling the content of 2-methoxytetrahydrofuran and TOBO in 1,4-butanediol raw materials within a certain range, and adjusting the ratio of 2-methoxytetrahydrofuran and TOBO, can improve the molecular weight and distribution of PBS products, as well as their mechanical and thermal properties. Detailed Implementation

[0023] The present invention will be further illustrated below with specific embodiments. These embodiments are merely illustrative and do not limit the scope of the invention.

[0024] The sources of the reagents and raw materials used in the embodiments and comparative examples of this invention are shown in Table 1 below. Unless otherwise specified, the other reagents and raw materials are all commercially available products.

[0025] Table 1. Information on the main raw materials used in the examples.

[0026] Trimethyl phosphate Aladdin 98％ BDO Xinjiang Meike, Dalian Chemical Industrial grade Tetrabutyl titanate Aladdin 98％ Succinic acid Shandong Feiyang Chemical Superior quality DA330 Dandong Pearl -- Amberlite35 Rohm and Haas -- methanol Aladdin AR TOBO Kamel 97％

[0027] In this invention, the content of 1,4-butanediol and its components TOBO and 2-methoxytetrahydrofuran in the raw material is determined by gas chromatography. The gas chromatography analysis is performed as follows: 30m DB-WAX, ID.: 0.32mm, FD.: 0.25μm; 50-230℃, 3℃ / min, nitrogen flow rate: 30mL / min, hydrogen flow rate: 40mL / min, air flow rate: 400mL / min; injection volume: 0.2μL.

[0028] In this invention, the basic physical properties of the resin are tested by the following methods:

[0029] a) Relative molecular mass: The relative molecular mass of the polymer was determined using Waters gel chromatography with chloroform as the mobile phase, an elution rate of 1 mL / min, and a temperature of 40 °C. The standard sample was narrowly distributed polystyrene.

[0030] b) Mechanical properties: Tensile strength and elongation at break were determined using an Instron 5966 universal testing machine (refer to ISO 527 method).

[0031] c) Heat distortion temperature: Measured using a Huasheng HDT / V-1103 heat distortion and Vicat softening point temperature measuring instrument.

[0032] The following Examples 1-5 and Comparative Examples 1-3 are used to provide 1,4-butanediol (BDO) for the production of PBS:

[0033] Example 1

[0034] A 50cm long distillation column was filled with 3*3θ ring packing and 20ml of Dandong Mingzhu DA330 resin. The reactive distillation conditions were: reboiler temperature controlled at 150℃, reflux ratio of 3:1, and atmospheric pressure. Commercially available industrial-grade BDO (0.04wt% TOBO content) was continuously fed into the reactive distillation column from the top at a feed rate of 60g / h. Methanol was fed from the reboiler at a feed rate of 30g / h. After reaction in the distillation column, excess methanol was collected from the top, and BDO-1 was obtained from the reboiler, containing 0.02wt% TOBO and 0.01wt% 2-methoxytetrahydrofuran.

[0035] Example 2

[0036] A 50cm long distillation column was filled with 3*3θ ring packing and 20ml of Dandong Mingzhu DA330 resin. The reactive distillation conditions were: reboiler temperature controlled at 145℃, reflux ratio of 5:1, and atmospheric pressure. Commercially available industrial-grade BDO (0.14wt% TOBO content) was continuously fed into the reactive distillation column from the top at a feed rate of 40g / h. Methanol was fed from the reboiler at a feed rate of 60g / h. After reaction in the distillation column, excess methanol was collected from the top, and BDO-2 was obtained from the reboiler, containing 0.04wt% TOBO and 0.07wt% 2-methoxytetrahydrofuran.

[0037] Example 3

[0038] A 50cm long distillation column was filled with 3*3θ ring packing and 20ml of Dandong Mingzhu DA330 resin. The reactive distillation conditions were: reboiler temperature controlled at 155℃, reflux ratio of 5:1, and atmospheric pressure. TOBO was added to commercially available industrial-grade BDO (0.14wt% TOBO content) to bring the TOBO content in the BDO reactive distillate to 0.29wt%. This BDO (0.29wt% TOBO content) was continuously fed into the reactive distillation column from the top at a feed rate of 60g / h. Methanol was fed from the reboiler at a feed rate of 60g / h. After reaction in the distillation column, excess methanol was collected from the top, and BDO-3 was obtained from the reboiler, containing 0.11wt% TOBO and 0.12wt% 2-methoxytetrahydrofuran.

[0039] Example 4

[0040] A 50cm long distillation column was filled with 3*3θ ring packing and 20ml of Dandong Mingzhu DA330 resin. The reactive distillation conditions were: reboiler temperature controlled at 155℃, reflux ratio of 5:1, and atmospheric pressure. TOBO was added to commercially available industrial-grade BDO (0.14wt% TOBO content) to bring the TOBO content in the BDO reactive distillate to 0.59wt%. The BDO was continuously fed into the reactive distillation column from the top at a feed rate of 40g / h. Methanol was fed from the reboiler at a feed rate of 60g / h. After reaction in the distillation column, excess methanol was collected from the top, and BDO-4 was obtained from the reboiler, containing 0.15wt% TOBO and 0.27wt% 2-methoxytetrahydrofuran.

[0041] Comparative Example 1

[0042] Purchased industrial-grade BDO (0.14 wt% TOBO content) was purified by distillation under the following conditions: 50 trays, reflux ratio 20:1, reboiler temperature 148°C, and pressure 2 kPaA. The purified BDO product BDO-5 with a TOBO content of 0.005 wt% was obtained from the top of the column.

[0043] Comparative Example 2

[0044] Purchased industrial-grade BDO (0.14wt% TOBO content) was used directly as raw material and labeled as BDO-6.

[0045] Comparative Example 3

[0046] A 50cm long distillation column was filled with 3*3θ ring packing and 20ml of Dandong Mingzhu DA330 resin. The reactive distillation conditions were: reboiler temperature controlled at 155℃, reflux ratio of 5:1, and atmospheric pressure. Commercially available industrial-grade BDO (0.14wt% TOBO content) was continuously fed into the reactive distillation column from the top at a feed rate of 10g / h. Methanol was fed from the reboiler at a feed rate of 60g / h. After reaction in the distillation column, excess methanol was collected from the top, and BDO-7 was obtained from the reboiler, containing 0.01wt% TOBO and 0.08wt% 2-methoxytetrahydrofuran.

[0047] Examples 5-9 and Comparative Examples 4-6 below were used to prepare different PBS resins:

[0048] Example 5

[0049] 10 mol of succinic acid, 15 mol of BDO-1, 3.67 g of tetrabutyl titanate, and 0.78 g of trimethyl phosphate were added to a 5L polyester reactor. The reactor was kept at atmospheric pressure, and the mixture was stirred at a constant speed of 100 rpm. The temperature was raised to 150℃ to initiate the reaction, and then gradually increased to 250℃ over 1 hour. Esterification was completed when the amount of water distilled from the reactor reached 95% of the theoretical output. The reactor was then gradually evacuated to 15000 PaA for 50 minutes, then gradually evacuated to 90 PaA. The temperature was raised to 220℃ and maintained for 200 minutes to carry out a polycondensation reaction, yielding a polymer melt. This melt was then water-cooled and pelletized to obtain the resin product. Product specifications are shown in Table 1 below.

[0050] Example 6

[0051] 10 mol of succinic acid, 13 mol of BDO-2, 1.83 g of tetrabutyl titanate, and 0.23 g of trimethyl phosphate were added to a 5L polyester reactor. The reactor was kept at atmospheric pressure, and the mixture was stirred at a constant speed of 100 rpm. The temperature was raised to 150℃ to initiate the reaction, and then gradually increased to 250℃ over 1 hour. The esterification process was completed when the amount of water distilled from the reactor reached 95% of the theoretical output. The reactor was then gradually evacuated to 5000 PaA for 30 minutes, then gradually evacuated to 80 PaA. The temperature was raised to 245℃ and maintained for 150 minutes to carry out a polycondensation reaction, yielding a polymer melt. This melt was then water-cooled and pelletized to obtain the resin product. The product specifications are shown in Table 1 below.

[0052] Example 7

[0053] 10 mol of succinic acid, 12 mol of BDO-3, 1.83 g of tetrabutyl titanate, and 0.23 g of trimethyl phosphate were added to a 5L polyester reactor. The reactor was kept at atmospheric pressure, and the mixture was stirred at a constant speed of 100 rpm. The temperature was raised to 150℃ to initiate the reaction, and then gradually increased to 240℃ over 1 hour. The esterification process was completed when the amount of water distilled from the reactor reached 95% of the theoretical output. The reactor was then gradually evacuated to 4000 PaA for 30 minutes, then gradually evacuated to 90 PaA. The temperature was raised to 250℃ and maintained for 150 minutes to carry out a polycondensation reaction, yielding a polymer melt. This melt was then water-cooled and pelletized to obtain the resin product. The product specifications are shown in Table 1 below.

[0054] Example 8

[0055] 10 mol of succinic acid, 11 mol of BDO-3, 1.83 g of tetrabutyl titanate, and 0.46 g of trimethyl phosphate were added to a 5L polyester reactor. The reactor was kept at atmospheric pressure, and the mixture was stirred at a constant speed of 100 rpm. The temperature was raised to 150℃ to initiate the reaction. The temperature was gradually increased to 240℃ over 1 hour. Esterification was completed when the amount of water distilled from the reactor reached 95% of the theoretical output. The reactor was then gradually evacuated to 6000 PaA for 30 minutes, then gradually evacuated to 90 PaA. The temperature was raised to 250℃ and maintained for 100 minutes to carry out polycondensation. The resulting polymer melt was water-cooled and pelletized to obtain the product. Product specifications are shown in Table 1 below.

[0056] Example 9

[0057] 10 mol of succinic acid, 12 mol of BDO-4, 1.83 g of tetrabutyl titanate, and 0.23 g of trimethyl phosphate were added to a 5L polyester reactor. The reactor was kept at atmospheric pressure, and the mixture was stirred at a constant speed of 100 rpm. The temperature was raised to 150℃ to initiate the reaction. The temperature was gradually increased to 240℃ over 1 hour. Esterification was completed when the amount of water distilled from the reactor reached 95% of the theoretical output. The reactor was then gradually evacuated to 4000 PaA for 30 minutes, then gradually evacuated to 90 PaA. The temperature was raised to 250℃ and maintained for 150 minutes to induce polycondensation, yielding a polymer melt. This melt was then water-cooled and pelletized to obtain the product. Product specifications are shown in Table 1 below.

[0058] Comparative Example 4

[0059] PBS was prepared using essentially the same method as in Example 6, except that BDO-1 was replaced with BDO-5. The product specifications of the resulting resin are shown in Table 1 below.

[0060] Comparative Example 5

[0061] PBS was prepared using essentially the same method as in Example 7, except that BDO-1 was replaced with BDO-6. The product specifications of the resulting resin are shown in Table 1 below.

[0062] Comparative Example 6

[0063] PBS was prepared using essentially the same method as in Example 8, except that BDO-1 was replaced with BDO-7. The product specifications of the resulting resin are shown in Table 2 below.

[0064] Table 2. Product Specifications of PBS Resin

[0065] Example 5 <![CDATA[13.2*10 5 ]]> 1.95 36.0 191 95.1 Example 6 <![CDATA[13.9*10 5 ]]> 1.92 36.4 198 95.5 Example 7 <![CDATA[14.1*10 5 ]]> 1.90 36.3 194 95.6 Example 8 <![CDATA[13.8*10 5 ]]> 1.94 35.9 196 95.3 Comparative Example 4 <![CDATA[114.4*10 5 ]]> 2.32 31.8 134 89.5 Comparative Example 5 <![CDATA[8.8*10 5 ]]> 2.43 32.5 164 92.6 Comparative Example 6 <![CDATA[10.9*10 5 ]]> 2.28 32.2 141 91.3

[0066] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing polybutylene succinate, characterized in that, Includes the following steps: 1) Control the total content of 2-methoxytetrahydrofuran and 4-[(tetrahydro-2-furanyl)oxy]-1-butanol in the raw material 1,4-butanediol to be 0.01-0.5 wt%, and the mass ratio of 2-methoxytetrahydrofuran to 4-[(tetrahydro-2-furanyl)oxy]-1-butanol to be (0.3-1.8):1; 2) Using the above-mentioned 1,4-butanediol as a raw material, it undergoes an esterification and polycondensation reaction with succinic acid in the presence of a catalyst to generate polybutylene succinate.

2. The method for preparing polybutylene succinate according to claim 1, characterized in that, In step 1), the raw material 1,4-butanediol is controlled to contain a total amount of 0.02-0.25 wt% of 2-methoxytetrahydrofuran and 4-[(tetrahydro-2-furanyl)oxy]-1-butanol, and the mass ratio of 2-methoxytetrahydrofuran to 4-[(tetrahydro-2-furanyl)oxy]-1-butanol is (1-3):

1.

3. The method for preparing polybutylene succinate according to claim 1 or 2, characterized in that, The molar ratio of succinic acid to 1,4-butanediol is 1:(1.1-1.5).

4. The method for preparing polybutylene succinate according to claim 3, characterized in that, The molar ratio of succinic acid to 1,4-butanediol is 1:(1.1-1.3).

5. The method for preparing polybutylene succinate according to claim 3, characterized in that, The catalyst includes a main catalyst and an auxiliary agent, wherein the main catalyst is a titanate ester and the auxiliary agent is a phosphorus-containing compound.

6. The method for preparing polybutylene succinate according to claim 5, characterized in that, The main catalyst is one or more of tetrabutyl titanate, tetraisopropyl titanate, tetraethyl titanate, and tetramethyl titanate.

7. The method for preparing polybutylene succinate according to claim 5, characterized in that, The adjuvant is one or more of trimethyl phosphate, triethyl phosphate, and triphenyl phosphate.

8. The method for preparing polybutylene succinate according to claim 5, characterized in that, The amount of the main catalyst used is 50 to 300 ppm, calculated as the sum of the mass of metallic titanium relative to the raw materials succinic acid and 1,4-butanediol.

9. The method for preparing polybutylene succinate according to claim 8, characterized in that, The amount of the additive is 10-100 ppm, calculated based on the sum of the mass of phosphorus relative to the raw materials succinic acid and 1,4-butanediol.

10. The method for preparing polybutylene succinate according to claim 1 or 2, characterized in that, The reaction process is divided into two stages: esterification and polycondensation. The esterification reaction temperature is 180-250℃, and the reaction endpoint is defined as the water content of the by-product reaching more than 95% of the theoretical water production. The polycondensation reaction is first evacuated to 1000-30000 PaA for 10-60 minutes, then evacuated to below 100 PaA, and heated to 220-260℃ for 60-200 minutes.