Synthesis method of bio-based poly (butylene succinate)

Abstract

The invention relates to a synthetic method of bio-based poly (butylene succinate), which comprises the following steps: taking bio-based succinic acid and 1, 4-butanediol as polymeric monomers, and synthesizing the bio-based poly (butylene succinate) through esterification, pre-polycondensation and final polycondensation, during esterification, a compound catalyst is added; during final polycondensation, a stabilizer and a lubricant are added; the compound catalyst comprises a mixture of titanium organic ester, an antimony compound, silicon organic ester, hydroxycarboxylic acid and 1, 4-butanediol. According to the synthesis method provided by the invention, the hue of the product is greatly improved, meanwhile, the product with a relatively low melt index can be obtained, and the application range is relatively wide.

Description

Technical Field

[0001] The invention relates to the technical field of polymer material synthesis, and in particular to a method for synthesizing bio-based polybutylene succinate. Background Art

[0002] Polybutylene succinate (PBS) is a typical biodegradable plastic that can replace traditional plastics and is widely used in various fields of human life. It can be degraded into plastics that are harmless to the environment under natural environmental conditions. It can be converted into fertilizer, carbon dioxide and water through composting, thereby greatly reducing the impact of waste plastics on the environment. It is an effective way to achieve resource recycling and utilization.

[0003] At present, the polybutylene succinate on the market is basically obtained by polymerizing the petroleum raw materials succinic acid and butanediol. Due to the increasing depletion of petroleum resources, the production of bio-based polybutylene succinate by fermenting succinic acid from biological resources to replace the existing petroleum-based polybutylene succinate is a new direction for the development of the degradable plastic industry. However, there are still a series of problems with the polybutylene succinate synthesized using bio-based succinic acid. Due to the inherent organic acids and double-bond impurities in the bio-based raw materials, under the existing polybutylene succinate catalyst system, the reaction rate of the esterification stage of bio-based succinic acid is low, and the esterification rate of the esterification product is low. In addition, these biomass impurities are generally not resistant to high temperatures. In the final polycondensation stage of polybutylene succinate, it is very easy to yellow and cross-link, which reduces the product quality of bio-based polybutylene succinate. The resulting problems such as high product melt index and poor product color limit the application scenarios.

[0004] CN1239563A discloses a method for preparing polybutylene succinate. Succinic acid and butanediol are placed in a reaction device, wherein the molar ratio of succinic acid to butanediol is 1-3:1, and an esterification reaction is carried out at a temperature of 150-200°C under normal pressure, and then polycondensation is carried out at a temperature of 200-280°C and under reduced pressure to 10-100 Pa in the presence of a catalyst to obtain polybutylene succinate; wherein the amount of the catalyst is 0.01-5% of the molar number of succinic acid. However, this method does not optimize the color problem of the polybutylene succinate product.

[0005] CN102746493A discloses a method for preparing all-biobased polybutylene succinate (PBS), which uses biomass dimethyl succinate and 1,4-butanediol as polymerization monomers, adopts an efficient composite catalyst system, and prepares all-biobased polybutylene succinate through a two-stage polymerization process of transesterification and polycondensation. However, the process of synthesizing bio-based polybutylene succinate from biomass dimethyl succinate has limitations in large-scale application in the future because bio-based raw materials have not yet been industrialized.

[0006] CN100562537A discloses a high molecular weight polybutylene succinate and a preparation method thereof, wherein the polybutylene succinate with low cost, high molecular weight, narrow molecular weight distribution and excellent mechanical properties is prepared by melt reaction of diisocyanate with diisocyanate as chain extender, especially low molecular weight diisocyanate as prepolymer. However, the preparation method has toxicity due to the use of isocyanate chain extender, which limits the application range in the field of food packaging.

[0007] In summary, it is still necessary to develop a new method for synthesizing bio-based polybutylene succinate in order to address the problem that the existing bio-based polybutylene succinate synthesis technology is difficult to obtain products with both low melt index and good hue. Summary of the invention

[0008] In view of the shortcomings of the prior art, the object of the present invention is to provide a method for synthesizing bio-based polybutylene succinate. The obtained bio-based polybutylene succinate has the characteristics of low melt index and excellent color and has a wide range of applications.

[0009] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0010] The present invention provides a method for synthesizing bio-based polybutylene succinate, which comprises the following steps:

[0011] Bio-based succinic acid and 1,4-butanediol are used as polymerization monomers, and bio-based polybutylene succinate is synthesized through esterification, pre-polycondensation and final polycondensation; during esterification, a composite catalyst is added; during final polycondensation, a stabilizer and a lubricant are added;

[0012] The composite catalyst comprises a mixture of titanium organic ester, antimony compound, silicon organic ester, hydroxycarboxylic acid and 1,4-butanediol.

[0013] The method for synthesizing bio-based polybutylene succinate provided by the present invention comprises the following steps: adding a composite catalyst in the esterification stage; the composite catalyst adopts a titanium / silicon / antimony composite system and introduces hydroxycarboxylic acid to improve the hydrolysis resistance of the catalyst and regulate the catalytic activity, thereby improving the esterification reaction efficiency of bio-based succinic acid and 1,4-butanediol, and allowing the polycondensation reaction to proceed rapidly at a lower temperature; and adding a lubricant in the final polycondensation stage improves the mass transfer and heat transfer efficiency of high-viscosity materials in this stage, which is conducive to the rapid conduction of the polycondensation reaction at a lower temperature, avoiding yellowing and cross-linking caused by biomass impurities in a high-temperature system during the synthesis of the bio-based polybutylene succinate, greatly improving the product hue, and obtaining a product with a lower melt index.

[0014] Preferably, the preparation step of the composite catalyst comprises: mixing titanium organic ester, antimony compound, silicon organic ester, hydroxycarboxylic acid and 1,4-butanediol, and reacting at 80° C. and 10 KPa for 1-2 hours.

[0015] Preferably, during the esterification, part or all of the composite catalyst is added; when part of the composite catalyst is added, the remaining amount of the composite catalyst is added during the pre-polycondensation.

[0016] Preferably, the amount of the composite catalyst added during the esterification is 50-100wt% of the total amount of the composite catalyst, for example, it can be 50wt%, 60wt%, 80wt%, 90wt% or 100wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0017] Preferably, the molar ratio of titanium organic ester to silicon organic ester in the composite catalyst is (1-10):1, the molar ratio of titanium organic ester to antimony compound is (1-10):1, the molar ratio of titanium organic ester to hydroxycarboxylic acid is 1:(1-3), and the mass ratio of 1,4-butanediol in the composite catalyst is 30-70wt%.

[0018] The molar ratio of the titanium organic ester to the silicon organic ester is (1-10):1, for example, 1:1, 3:1, 5:1, 8:1 or 10:1, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0019] The molar ratio of the titanium organic ester to the antimony compound is (1-10):1, for example, 1:1, 3:1, 5:1, 8:1 or 10:1, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0020] The molar ratio of the titanium organic ester to the hydroxycarboxylic acid is 1:(1-3), for example, 1:1, 1:1.5, 1:2, 1:2.5 or 1:3, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0021] The mass proportion of 1,4-butanediol in the composite catalyst is 30-70wt%, for example, 30wt%, 40wt%, 50wt%, 60wt% or 70wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0022] Preferably, the total amount of the composite catalyst in the bio-based polybutylene succinate is 0.008-0.015wt% based on the mass fraction of the titanium organic ester, for example, it can be 0.008wt%, 0.01wt%, 0.012wt%, 0.013wt% or 0.015wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0023] Preferably, the titanium organic ester includes titanate, and the titanate includes any one of butyl titanate, isopropyl titanate, tetraethyl titanate, bistriethanolamine diisopropyl titanate or tetraisooctyl titanate, or a combination of at least two of them. Typical but non-limiting combinations include a combination of butyl titanate and isopropyl titanate, a combination of tetraethyl titanate, bistriethanolamine diisopropyl titanate and tetraisooctyl titanate, or a combination of butyl titanate, isopropyl titanate, tetraethyl titanate, bistriethanolamine diisopropyl titanate and tetraisooctyl titanate.

[0024] Preferably, the antimony compound includes any one of antimony trioxide, antimony acetate or antimony glycolate, or a combination of at least two of them. Typical but non-limiting combinations include a combination of antimony trioxide and antimony acetate, a combination of antimony acetate and antimony glycolate, or a combination of antimony trioxide, antimony acetate and antimony glycolate.

[0025] Preferably, the silicone organoester includes silicate, and the silicate includes any one of tetraethyl orthosilicate, methyl orthosilicate or propyl orthosilicate, or a combination of at least two of them. Typical but non-limiting combinations include a combination of tetraethyl orthosilicate and methyl orthosilicate, a combination of methyl orthosilicate and propyl orthosilicate, or a combination of tetraethyl orthosilicate, methyl orthosilicate and propyl orthosilicate.

[0026] Preferably, the hydroxycarboxylic acid comprises citric acid and / or lactic acid.

[0027] Preferably, the amount of the stabilizer is 0.01-0.1wt% of the theoretical bio-based polybutylene succinate product mass, for example, it can be 0.01wt%, 0.03wt%, 0.05wt%, 0.08wt% or 0.1wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0028] Preferably, the stabilizer comprises a phosphoric acid compound and / or a phosphorous acid compound.

[0029] Preferably, the stabilizer includes any one of phosphoric acid, trimethyl phosphate, triethyl phosphate, dimethyl phosphate, triphenyl phosphate, diphenyl phosphate, phosphorous acid, hypophosphorous acid, triphenyl phosphite or diphenyl phosphite, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of phosphoric acid and trimethyl phosphate, a combination of triethyl phosphate, dimethyl phosphate, triphenyl phosphate and diphenyl phosphate, or a combination of phosphoric acid, trimethyl phosphate, triethyl phosphate, dimethyl phosphate, triphenyl phosphate, diphenyl phosphate, phosphorous acid, hypophosphorous acid, triphenyl phosphite and diphenyl phosphite.

[0030] Preferably, the amount of the lubricant is 0.1-1wt% of the theoretical bio-based polybutylene succinate product mass, for example, it can be 0.1wt%, 0.3wt%, 0.5wt%, 0.8wt% or 1wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0031] Preferably, the lubricant comprises a stearic acid compound.

[0032] Preferably, the lubricant includes any one of stearic acid, sodium stearate, magnesium stearate or calcium stearate, or a combination of at least two of them. Typical but non-limiting combinations include a combination of stearic acid and sodium stearate, a combination of sodium stearate, magnesium stearate and calcium stearate, or a combination of stearic acid, sodium stearate, magnesium stearate and calcium stearate.

[0033] Preferably, the molar ratio of the bio-based succinic acid to 1,4-butanediol is 1:(1-2), for example, 1:1, 1:1.2, 1:1.5, 1:1.8 or 1:2, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0034] Preferably, the esterification temperature is 190-210° C., the time is 2-3 hours, and the pressure is normal pressure.

[0035] The esterification temperature is 190-210°C, for example, 190°C, 195°C, 200°C, 205°C or 210°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0036] The esterification time is 2-3 hours, for example, 2 hours, 2.2 hours, 2.5 hours, 2.8 hours or 3 hours, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0037] Preferably, the pre-condensation temperature is 220-230° C., the time is 1-3 h, and the pressure drops from normal pressure to below 1 KPa during the pre-condensation process.

[0038] The pre-polycondensation temperature is 220-230° C., for example, 220° C., 222° C., 225° C., 228° C. or 230° C., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0039] The pre-polycondensation time is 1-3 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours or 3 hours, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0040] During the pre-polycondensation process, the pressure drops from normal pressure to below 1 KPa, for example, it can be 1 KPa, 0.8 KPa, 0.5 KPa, 0.2 KPa or 0.1 KPa, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0041] Preferably, the final polycondensation temperature is 230-240° C., the time is 3-5 h, and the pressure is ≤50 Pa.

[0042] The final polycondensation temperature is 230-240° C., for example, 230° C., 232° C., 235° C., 238° C. or 240° C., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0043] The final polycondensation time is 3-5 hours, for example, 3 hours, 3.5 hours, 4 hours, 4.5 hours or 5 hours, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0044] The final polycondensation pressure is ≤50Pa, for example, it can be 50Pa, 40Pa, 30Pa, 20Pa or 10Pa, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0045] As a preferred technical solution of the synthesis method of the present invention, the synthesis method comprises the following steps:

[0046] Bio-based succinic acid and 1,4-butanediol are mixed in a molar ratio of 1:(1-2), a composite catalyst is added, the amount of which is 50-100wt% of the total amount of the composite catalyst, and then the temperature is raised to 190-210°C and esterified at normal pressure for 2-3h;

[0047] The preparation steps of the composite catalyst include: mixing titanium organic ester, antimony compound, silicon organic ester, hydroxycarboxylic acid and 1,4-butanediol, and reacting at 80° C. and 10KPa for 1-2 hours; the molar ratio of titanium organic ester to silicon organic ester in the composite catalyst is (1-10):1, the molar ratio of titanium organic ester to antimony compound is (1-10):1, the molar ratio of titanium organic ester to hydroxycarboxylic acid is 1:(1-3), and the mass fraction of 1,4-butanediol in the composite catalyst is 30-70wt%; the total amount of the composite catalyst in bio-based polybutylene succinate is 0.008-0.015wt% based on the mass fraction of titanium organic ester;

[0048] Then, the remaining amount of the composite catalyst is added and pre-condensed at 220-230° C. for 1-3 hours, during which the pressure drops from normal pressure to below 1 KPa; then, a stabilizer and a lubricant are added, wherein the amount of the stabilizer is 0.01-0.1wt% of the mass of the theoretical bio-based polybutylene succinate product, and the amount of the lubricant is 0.1-1wt% of the mass of the theoretical bio-based polybutylene succinate product; and the final polycondensation is carried out at 230-240° C. and a pressure of ≤50Pa for 3-5 hours to obtain the bio-based polybutylene succinate.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] (1) The method for synthesizing bio-based polybutylene succinate provided by the present invention includes adding a composite catalyst in the esterification stage. The composite catalyst adopts a titanium / silicon / antimony composite system and introduces hydroxycarboxylic acid to improve the hydrolysis resistance of the catalyst and regulate the catalytic activity, thereby improving the esterification reaction efficiency of bio-based succinic acid and 1,4-butanediol, and allowing the polycondensation reaction to proceed rapidly at a lower temperature. By adding a lubricant in the final polycondensation stage, the mass transfer and heat transfer efficiency of high-viscosity materials in this stage is improved, which is conducive to the rapid progress of the polycondensation reaction at a lower temperature, avoiding yellowing and cross-linking caused by biomass impurities in a high-temperature system during the synthesis of bio-based polybutylene succinate, greatly improving the product hue, and obtaining a product with a lower melt index. The melt index MFR of the copolyester is 1-5g / 10min, the end carboxyl content of the copolyester is less than 15mol / t, and the b value of the copolyester is less than 5.

[0051] (2) The method for synthesizing bio-based polybutylene succinate provided by the present invention can further expand the application scope of bio-based polybutylene succinate in the field of food packaging because no chain extender is used. DETAILED DESCRIPTION

[0052] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0053] Example 1

[0054] This embodiment provides a method for synthesizing bio-based polybutylene succinate, the method comprising the following steps:

[0055] Bio-based succinic acid and 1,4-butanediol were mixed in a molar ratio of 1:1.5, and a composite catalyst was added in an amount of 100wt% of the total amount of the composite catalyst, and then the temperature was raised to 200°C and esterified at normal pressure for 2.5h;

[0056] The preparation steps of the composite catalyst include: mixing butyl titanate, antimony acetate, tetraethyl orthosilicate, citric acid and 1,4-butanediol, and reacting at 80° C. and 10 KPa for 2 hours; the molar ratio of butyl titanate to tetraethyl orthosilicate in the composite catalyst is 5:1, the molar ratio of butyl titanate to antimony acetate is 2:1, the molar ratio of butyl titanate to citric acid is 1:2, and the mass proportion of 1,4-butanediol in the composite catalyst is 50wt%; the total amount of the composite catalyst in bio-based polybutylene succinate is 0.01wt% based on the mass fraction of butyl titanate;

[0057] Then, pre-condensation is carried out at 225°C for 2 hours, and the pressure drops from normal pressure to 1 KPa during the pre-condensation process; then, trimethyl phosphate and calcium stearate are added, the amount of trimethyl phosphate is 0.05wt% of the theoretical bio-based polybutylene succinate product mass, and the amount of calcium stearate is 0.5wt% of the theoretical bio-based polybutylene succinate product mass; at 235°C and a pressure of 50Pa, final condensation is carried out for 4 hours to obtain the bio-based polybutylene succinate.

[0058] Example 2

[0059] This embodiment provides a method for synthesizing bio-based polybutylene succinate, the method comprising the following steps:

[0060] Bio-based succinic acid and 1,4-butanediol were mixed in a molar ratio of 1:1, a composite catalyst was added in an amount of 80wt% of the total amount of the composite catalyst, and then the temperature was raised to 190°C and esterified at normal pressure for 3h;

[0061] The preparation steps of the composite catalyst include: mixing isopropyl titanate, antimony trioxide, methyl orthosilicate, lactic acid and 1,4-butanediol, and reacting at 80° C. and 10 KPa for 1 hour; the molar ratio of isopropyl titanate to methyl orthosilicate in the composite catalyst is 1:1, the molar ratio of isopropyl titanate to antimony trioxide is 10:1, the molar ratio of isopropyl titanate to lactic acid is 1:1, and the mass fraction of 1,4-butanediol in the composite catalyst is 30wt%; the total amount of the composite catalyst in bio-based polybutylene succinate is 0.008wt% based on the mass fraction of isopropyl titanate;

[0062] Then, the remaining amount of the composite catalyst is added and pre-condensed at 220°C for 3 hours, during which the pressure drops from normal pressure to 1 KPa; then, triphenyl phosphate and sodium stearate are added, the amount of triphenyl phosphate is 0.01wt% of the theoretical bio-based polybutylene succinate product mass, and the amount of sodium stearate is 0.1wt% of the theoretical bio-based polybutylene succinate product mass; at 230°C and a pressure of 50Pa, final condensation is carried out for 5 hours to obtain the bio-based polybutylene succinate.

[0063] Example 3

[0064] This embodiment provides a method for synthesizing bio-based polybutylene succinate, the method comprising the following steps:

[0065] Bio-based succinic acid and 1,4-butanediol were mixed in a molar ratio of 1:2, a composite catalyst was added in an amount of 50wt% of the total amount of the composite catalyst, and then the temperature was raised to 210°C and esterified at normal pressure for 2h;

[0066] The preparation steps of the composite catalyst include: mixing tetraethyl titanate, antimony ethylene glycol, propyl orthosilicate, citric acid and 1,4-butanediol, and reacting at 80° C. and 10 KPa for 2 hours; the molar ratio of tetraethyl titanate to propyl orthosilicate in the composite catalyst is 10:1, the molar ratio of tetraethyl titanate to antimony ethylene glycol is 1:1, the molar ratio of tetraethyl titanate to citric acid is 1:3, and the mass proportion of 1,4-butanediol in the composite catalyst is 70wt%; the total amount of the composite catalyst in bio-based polybutylene succinate is 0.015wt% based on the mass fraction of tetraethyl titanate;

[0067] Then, the remaining amount of the composite catalyst is added and pre-condensed at 230°C for 1 hour, during which the pressure drops from normal pressure to 1 KPa; then, triphenyl phosphite and magnesium stearate are added, wherein the amount of triphenyl phosphite is 0.1wt% of the theoretical mass of the bio-based polybutylene succinate product, and the amount of magnesium stearate is 1wt% of the theoretical mass of the bio-based polybutylene succinate product; and finally polycondensed at 240°C and a pressure of 50Pa for 3 hours to obtain the bio-based polybutylene succinate.

[0068] Example 4

[0069] This embodiment provides a method for synthesizing bio-based polybutylene succinate, which is different from Example 1 in that, except that the total amount of the composite catalyst in the bio-based polybutylene succinate is adjusted to 0.005wt% based on the mass fraction of tetraethyl titanate, the rest is the same as Example 1.

[0070] Example 5

[0071] This embodiment provides a method for synthesizing bio-based polybutylene succinate, which is different from Example 1 in that, except that the total amount of the composite catalyst in the bio-based polybutylene succinate is adjusted to 0.02 wt % based on the mass fraction of tetraethyl titanate, the rest is the same as Example 1.

[0072] Example 6

[0073] This embodiment provides a method for synthesizing bio-based polybutylene succinate, which is different from Example 1 in that, except that the molar ratio of butyl titanate to tetraethyl orthosilicate in the composite catalyst is adjusted to 0.5:1, and the molar ratio of butyl titanate to antimony acetate is adjusted to 0.5:1, the rest is the same as Example 1.

[0074] Example 7

[0075] This embodiment provides a method for synthesizing bio-based polybutylene succinate, which is different from Example 1 in that, except that the molar ratio of butyl titanate to tetraethyl orthosilicate in the composite catalyst is adjusted to 11:1, and the molar ratio of butyl titanate to antimony acetate is adjusted to 11:1, the rest is the same as Example 1.

[0076] Comparative Example 1

[0077] This comparative example provides a method for synthesizing bio-based polybutylene succinate, which is different from Example 1 in that, except for replacing the mass of the composite catalyst with butyl titanate, the rest is the same as Example 1.

[0078] Comparative Example 2

[0079] This comparative example provides a method for synthesizing bio-based polybutylene succinate, which is different from Example 1 in that citric acid is not added to the composite catalyst, and the rest is the same as Example 1.

[0080] Comparative Example 3

[0081] This comparative example provides a method for synthesizing bio-based polybutylene succinate, which differs from Example 1 in that there is no pre-polycondensation step, and the rest is the same as Example 1.

[0082] Comparative Example 4

[0083] This comparative example provides a method for synthesizing bio-based polybutylene succinate, which is different from Example 1 in that calcium stearate is not added during the final polycondensation, and the rest is the same as Example 1.

[0084] Bio-based polybutylene succinate was synthesized by the synthesis methods provided in Examples 1-7 and Comparative Examples 1-4, and the melt index of the copolyester was tested according to Method A in GB / T 3682-2000. The test conditions were D (temperature: 190° C., load: 2.16 kg). The results are shown in Table 1.

[0085] The terminal carboxyl content of the copolyester was measured according to FZ / T50012-2006 "Determination of terminal carboxyl content in polyester by titration analysis", phenol and chloroform were mixed as solvents in a volume ratio of 2:3, and the results are shown in Table 1;

[0086] The b value of the copolyester was measured by HunterLab Ultrascan VIS spectrophotometer. The results are shown in Table 1.

[0087] Table 1

[0088]

[0089]

[0090] It can be seen from Table 1 that the synthesis method provided by the present invention can produce bio-based polybutylene succinate with lower melt index, lower terminal carboxyl group and lower b value;

[0091] By comparing Example 1 with Examples 4 and 5, it can be seen that if the total amount of the composite catalyst added is too low, the reaction efficiency in the polycondensation stage will be low, the product melt index will be high, and the terminal carboxyl value will be high. If the total amount of the composite catalyst added is too high, the reaction in the polycondensation stage will be too fast, the side reaction will be difficult to control, the product b value will increase, and the terminal carboxyl group will also increase. By comparing Example 1 with Examples 6 and 7, it can be seen that in the composite catalyst, the ratio of titanium / silicon / antimony needs to be controlled within a reasonable range. If the titanium content is too high, the product b value will increase and the hue will deteriorate. If the titanium content is too low, the product melt index will be high, and it is difficult to meet the use requirements. By comparing Example 1 with Comparative Example 1, it can be seen that the ratio of titanium / silicon / antimony in the composite catalyst needs to be controlled within a reasonable range. By using the composite catalyst provided by the present invention, under the same reaction process, a product with significantly lower melt index, low terminal carboxyl group and low b value can be prepared; from the comparison between Example 1 and Comparative Example 2, it can be seen that if hydroxycarboxylic acid is not added to the composite catalyst, the melt index of the product will increase, which is difficult to meet the use requirements; from the comparison between Example 1 and Comparative Example 3, it can be seen that if there is no pre-condensation step, the melt index and terminal carboxyl group of the product will increase significantly, which is difficult to meet the use requirements; from the comparison between Example 1 and Comparative Example 4, it can be seen that if a lubricant is added during the final condensation, the melt index of the product is significantly reduced while the terminal carboxyl group and the b value are basically the same, and the extrusion grade level is reached.

[0092] In summary, the synthesis method of bio-based polybutylene succinate provided by the present invention, namely, adding a composite catalyst in the esterification stage, the composite catalyst adopts a titanium / silicon / antimony composite system and introduces hydroxycarboxylic acid to improve the hydrolysis resistance of the catalyst and regulate the catalytic activity, thereby improving the esterification reaction efficiency of bio-based succinic acid and 1,4-butanediol, and allowing the polycondensation reaction to proceed rapidly at a lower temperature; by adding a lubricant in the final polycondensation stage, the mass transfer and heat transfer efficiency of high-viscosity materials in this stage is improved, which is conducive to the rapid progress of the polycondensation reaction at a lower temperature, avoiding yellowing and cross-linking caused by biomass impurities in a high-temperature system during the synthesis of bio-based polybutylene succinate, greatly improving the product hue, and obtaining a product with a lower melt index, the melt index MFR of the copolyester is 1-5g / 10min, the end carboxyl content of the copolyester is less than 15mol / t, and the b value of the copolyester is less than 5.

[0093] The method for synthesizing bio-based polybutylene succinate provided by the invention can further expand the application scope of bio-based polybutylene succinate in the field of food packaging because no chain extender is used.

[0094] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for synthesizing bio-based polybutylene succinate, characterized in that: The synthesis method comprises the following steps: Bio-based succinic acid and 1,4-butanediol are used as polymerization monomers, and bio-based polybutylene succinate is synthesized through esterification, pre-polycondensation and final polycondensation; during esterification, a composite catalyst is added; during final polycondensation, a stabilizer and a lubricant are added; The composite catalyst comprises a mixture of titanium organic ester, antimony compound, silicon organic ester, hydroxycarboxylic acid and 1,4-butanediol.

2. The synthesis method according to claim 1, characterized in that During the esterification, part or all of the composite catalyst is added; when part of the composite catalyst is added, the remaining amount of the composite catalyst is added during the pre-polycondensation; Preferably, the amount of the composite catalyst added during the esterification is 50-100 wt % of the total amount of the composite catalyst.

3. The synthesis method according to claim 1 or 2, characterized in that The molar ratio of titanium organic ester to silicon organic ester in the composite catalyst is (1-10):1, the molar ratio of titanium organic ester to antimony compound is (1-10):1, the molar ratio of titanium organic ester to hydroxycarboxylic acid is 1:(1-3), and the mass ratio of 1,4-butanediol in the composite catalyst is 30-70wt%.

4. The synthesis method according to any one of claims 1 to 3, characterized in that The total amount of the composite catalyst in the bio-based polybutylene succinate is 0.008-0.015 wt % based on the mass fraction of the titanium organic ester.

5. The synthesis method according to any one of claims 1 to 4, characterized in that The titanium organic ester includes any one of butyl titanate, isopropyl titanate, tetraethyl titanate, bistriethanolamine diisopropyl titanate or tetraisooctyl titanate, or a combination of at least two thereof; Preferably, the antimony compound comprises any one of antimony trioxide, antimony acetate or antimony glycolate, or a combination of at least two thereof; Preferably, the silicone organic ester includes any one of ethyl orthosilicate, methyl orthosilicate or propyl orthosilicate, or a combination of at least two thereof; Preferably, the hydroxycarboxylic acid comprises citric acid and / or lactic acid.

6. The synthesis method according to any one of claims 1 to 5, characterized in that The amount of the stabilizer is 0.01-0.1wt% of the theoretical bio-based polybutylene succinate product mass; Preferably, the stabilizer comprises a phosphoric acid compound and / or a phosphorous acid compound; Preferably, the stabilizer includes any one of phosphoric acid, trimethyl phosphate, triethyl phosphate, dimethyl phosphate, triphenyl phosphate, diphenyl phosphate, phosphorous acid, hypophosphorous acid, triphenyl phosphite or diphenyl phosphite, or a combination of at least two thereof.

7. The synthesis method according to any one of claims 1 to 6, characterized in that The amount of the lubricant is 0.1-1wt% of the theoretical bio-based polybutylene succinate product mass; Preferably, the lubricant comprises a stearic acid compound; Preferably, the lubricant includes any one of stearic acid, sodium stearate, magnesium stearate or calcium stearate, or a combination of at least two thereof.

8. The synthesis method according to any one of claims 1 to 7, characterized in that The molar ratio of the bio-based succinic acid to 1,4-butanediol is 1:(1-2).

9. The synthesis method according to any one of claims 1 to 8, characterized in that The esterification temperature is 190-210°C, the time is 2-3h, and the pressure is normal pressure; Preferably, the pre-condensation temperature is 220-230°C, the time is 1-3h, and the pressure during the pre-condensation process drops from normal pressure to below 1KPa; Preferably, the final polycondensation temperature is 230-240° C., the time is 3-5 h, and the pressure is ≤50 Pa.

10. The synthesis method according to claim 1, characterized in that The synthesis method comprises the following steps: Bio-based succinic acid and 1,4-butanediol are mixed in a molar ratio of 1:(1-2), a composite catalyst is added, the amount of which is 50-100wt% of the total amount of the composite catalyst, and then the temperature is raised to 190-210°C and esterified at normal pressure for 2-3h; The composite catalyst comprises a mixture of titanium organic ester, antimony compound, silicon organic ester, hydroxycarboxylic acid and 1,4-butanediol, wherein the molar ratio of titanium organic ester to silicon organic ester in the composite catalyst is (1-10):1, the molar ratio of titanium organic ester to antimony compound is (1-10):1, the molar ratio of titanium organic ester to hydroxycarboxylic acid is 1:(1-3), and the mass fraction of 1,4-butanediol in the composite catalyst is 30-70wt%; the total amount of the composite catalyst in bio-based polybutylene succinate is 0.008-0.015wt% based on the mass fraction of titanium organic ester; Then, the remaining amount of the composite catalyst is added and pre-condensed at 220-230° C. for 1-3 hours, during which the pressure drops from normal pressure to below 1 KPa; then, a stabilizer and a lubricant are added, wherein the amount of the stabilizer is 0.01-0.1wt% of the mass of the theoretical bio-based polybutylene succinate product, and the amount of the lubricant is 0.1-1wt% of the mass of the theoretical bio-based polybutylene succinate product; and the final polycondensation is carried out at 230-240° C. and a pressure of ≤50Pa for 3-5 hours to obtain the bio-based polybutylene succinate.

Images