Full-bio-based poly (butylene succinate) as well as preparation method and application thereof

Abstract

The invention provides full-bio-based poly (butylene succinate) as well as a preparation method and application thereof. The mass content of a free P element in the full-bio-based poly (butylene succinate) is 0.1-100 ppm, and the mass content of a Cl element in the full-bio-based poly (butylene succinate) is 0.1-15 ppm. The melt index of the full-bio-based poly (butylene succinate) under the conditions of 190 DEG C and 2.16 kg is 3.0-10.0 g / 10 min, and the bio-based carbon proportion is 99.99%-100%, so that the full-bio-based poly (butylene succinate) conforms to the concepts of green, low carbon and sustainable development, and is large in molecular weight, low in impurity content, excellent in mechanical properties and appearance, and suitable for industrial production. The high-performance requirements of multiple fields such as packaging materials, food contact materials and mulching films on degradable bio-based materials can be met, and the application prospect is wide.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer materials, and particularly relates to a fully bio-based polybutylene succinate and its preparation method and application. Background Art

[0002] Polybutylene succinate (PBS) is a biodegradable polyester, and its final degradation products are CO2 and H2O, which are non-toxic and harmless. Moreover, PBS has a high heat distortion temperature and is widely used in fields such as film bags, disposable tableware, and medical and health appliances. The synthesis methods of PBS are divided into direct esterification method and transesterification method. The direct esterification method uses succinic acid and 1,4-butanediol (BDO) as raw materials to obtain the product through esterification reaction and polycondensation reaction. The transesterification method uses dimethyl succinate (DMS) and 1,4-butanediol (BDO) as raw materials to carry out transesterification reaction and polycondensation reaction. By controlling conditions such as temperature, pressure, types of additives, and reaction time, PBS resins of different qualities can be obtained.

[0003] According to different manufacturing sources, the monomer raw materials of PBS, succinic acid and 1,4-butanediol, are divided into petrochemical-based and bio-based. Petrochemical-based monomers are converted from raw materials such as coal, petroleum, and natural gas, while bio-based monomers are obtained through microbial fermentation. The production process of preparing succinic acid by microbial fermentation includes two stages. The first stage is to ferment with specific microorganisms to obtain succinic acid fermentation broth, and the second stage is to treat the succinic acid fermentation broth by some physical and chemical methods to separate impurities and extract succinic acid from the fermentation broth. Bio-based 1,4-butanediol is made from bio-based succinic acid through processes such as esterification, hydrogenation, and purification.

[0004] At present, petrochemical-based monomers are still mainly used in the industrial production of PBS because the current production cost of bio-based succinic acid is still higher than that of petrochemical-based succinic acid. However, petrochemical-based monomers rely on non-renewable resources. To achieve sustainable development and low-carbon economy, using bio-based monomers to replace petrochemical-based monomers to prepare PBS products is the main trend in the future field of polymer materials. Therefore, improving the quality of bio-based PBS, developing bio-based PBS with low impurity content, high molecular weight, good appearance and mechanical properties, is an urgent problem to be solved in this field. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a fully bio-based polybutylene succinate and its preparation method and application. The fully bio-based polybutylene succinate has a low melt index, low contents of P element and Cl element, and has the characteristics of high mechanical and mechanical properties and light color, and has broad application prospects.

[0006] To achieve this purpose, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a fully bio-based polybutylene succinate, which comprises polybutylene succinate, P element and Cl element; the mass content of free P element in the fully bio-based polybutylene succinate is 0.1-100 ppm, and the mass content of Cl element in the fully bio-based polybutylene succinate is 0.1-15 ppm; the melt index of the fully bio-based polybutylene succinate under the conditions of 190 °C and 2.16 kg is 3.0-10.0 g / 10 min.

[0008] The fully bio-based polybutylene succinate provided by the present invention is prepared from bio-based succinic acid and bio-based 1,4-butanediol, wherein the proportion of bio-based carbon is 99.99%-100%, which conforms to the concept of green, low-carbon and sustainable development; the fully bio-based polybutylene succinate has a low melt index, a large molecular weight, low contents of free P element and Cl element, light color, excellent mechanical properties and appearance, can meet the high-performance requirements of degradable bio-based materials in multiple fields such as packaging materials, food contact materials, and mulch films, and has broad application prospects.

[0009] The following are the preferred technical solutions of the present invention, but do not limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the objectives and beneficial effects of the present invention can be better achieved.

[0010] In the present invention, the fully bio-based polybutylene succinate contains optionally non-free P element. The "non-free P element" is connected to the polybutylene succinate molecule through a chemical bond. It can be understood that a phosphorus-containing compound is introduced as a raw material in the preparation process of the fully bio-based polybutylene succinate, and the phosphorus-containing compound participates in a chemical reaction, so that the P element is connected to the polybutylene succinate molecule through a chemical bond. The free P element refers to the P element other than the P element connected to the polybutylene succinate molecule through a chemical bond, that is, the free P element is the P element derived from bio-based succinic acid that is not connected to the polybutylene succinate molecule, and its mass content in the fully bio-based polybutylene succinate is 0.1-100 ppm, for example, it can be 0.15 ppm, 0.3 ppm, 0.5 ppm, 1 ppm, 2 ppm, 5 ppm, 8 ppm, 10 ppm, 20 ppm, 30 ppm, 40 ppm, 50 ppm, 60 ppm, 80 ppm or 90 ppm, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the above range. Preferably, it is 10-98 ppm, and more preferably 70-95 ppm.

[0011] The mass content of Cl element in the all-bio-based polybutylene succinate is 0.1-15 ppm, for example, it can be 0.15 ppm, 0.3 ppm, 0.5 ppm, 0.8 ppm, 1 ppm, 1.5 ppm, 2 ppm, 2.5 ppm, 3 ppm, 3.5 ppm, 4 ppm, 5 ppm, 6 ppm, 7 ppm, 8 ppm, 9 ppm, 10 ppm, 11 ppm, 12 ppm, 13 ppm or 14 ppm, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the specific point values included in the scope of the present invention are not exhaustively listed herein. Preferably, it is 1-12 ppm.

[0012] In the present invention, "ppm" represents parts per million, and 1 ppm represents one in a million.

[0013] Exemplarily, the content of free P element in the all-bio-based polybutylene succinate can be tested by phosphomolybdic acid colorimetry and standard curve method; the specific test method includes: digesting the all-bio-based polybutylene succinate to release the P to be measured into the solution; reacting the solution with molybdate and reducing it to a blue compound with a reducing agent (ascorbic acid), obtaining the absorbance by colorimetry, and substituting it into the standard working curve of P content to obtain the content of free P element in the all-bio-based polybutylene succinate.

[0014] Exemplarily, the digestion method of the all-bio-based polybutylene succinate includes: mixing the powder of the all-bio-based polybutylene succinate with an aqueous solution of potassium persulfate (mass concentration of 8.7%) and digesting at 140°C for 15 min.

[0015] Exemplarily, the mass content of Cl element in the all-bio-based polybutylene succinate can be tested by inductively coupled plasma-mass spectrometry or by ammonium thiocyanate volumetric method.

[0016] It should be noted that the testing of the mass content of Cl element and P element (except for the P element chemically bonded to the polybutylene succinate molecule) in the all-bio-based polybutylene succinate is not limited to the methods listed above.

[0017] The melt index of the fully bio-based polybutylene succinate under the conditions of 190 °C and 2.16 kg is 3.0 - 10.0 g / 10 min. For example, it can be 3.5 g / 10 min, 4.0 g / 10 min, 4.5 g / 10 min, 5.0 g / 10 min, 5.5 g / 10 min, 6.0 g / 10 min, 6.5 g / 10 min, 7.0 g / 10 min, 7.5 g / 10 min, 8.0 g / 10 min, 8.5 g / 10 min, 9.0 g / 10 min or 9.5 g / 10 min, as well as specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range. Further preferably, it is 4.0 - 6.0 g / 10 min.

[0018] Exemplarily, the melt index of the fully bio-based polybutylene succinate can be measured by a melt index instrument.

[0019] Preferably, the terminal carboxyl value of the fully bio-based polybutylene succinate is 30 - 80 mol / t. For example, it can be 32 mol / t, 35 mol / t, 38 mol / t, 40 mol / t, 42 mol / t, 45 mol / t, 48 mol / t, 50 mol / t, 52 mol / t, 55 mol / t, 58 mol / t, 60 mol / t, 62 mol / t, 65 mol / t, 68 mol / t, 70 mol / t, 72 mol / t, 75 mol / t or 78 mol / t, as well as specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range.

[0020] Exemplarily, the terminal carboxyl value of the fully bio-based polybutylene succinate can be measured according to the method in Standard FZ / T50012 - 2006.

[0021] Preferably, the melting point of the fully bio-based polybutylene succinate is 110 - 116 °C. For example, it can be 110.5 °C, 111 °C, 115.5 °C, 112 °C, 112.5 °C, 113 °C, 113.5 °C, 114 °C, 114.5 °C, 115 °C or 115.5 °C, as well as specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range.

[0022] Exemplarily, the melting point of the fully bio-based polybutylene succinate can be measured by a melting point instrument.

[0023] Preferably, the tensile strength of the all-bio-based polybutylene succinate is ≥35 MPa, and can be 35 - 40 MPa; the elongation at break is ≥180%, more preferably ≥200%, and can be 200% - 250%.

[0024] Preferably, the flexural strength of the all-bio-based polybutylene succinate is ≥28 MPa, more preferably ≥30 MPa, and can be 30 - 32 MPa.

[0025] Preferably, the absolute value of the a value of the chromaticity of the all-bio-based polybutylene succinate is ≤0.2, and the b value is ≤8. It has a light color and does not show the phenomena of turning red or yellow.

[0026] Optionally, the tensile strength and elongation at break of the all-bio-based polybutylene succinate can be obtained by testing according to the method in Standard ISO 527-2-2012; the flexural strength can be obtained by testing according to the method in Standard ISO 178-2019; the chromaticity value is obtained by injection molding the all-bio-based polybutylene succinate to be tested into a spline and testing with a color difference meter.

[0027] In a second aspect, the present invention provides a preparation method of the all-bio-based polybutylene succinate as described in the first aspect, and the preparation method includes:

[0028] Performing an esterification reaction on bio-based succinic acid and bio-based 1,4-butanediol to obtain an esterified product;

[0029] The bio-based succinic acid includes succinic acid, Cl - and PO4 3- , and the mass content of Cl - in the bio-based succinic acid is 0.1 - 50 ppm, and the mass content of PO4 3- is 0.1 - 200 ppm;

[0030] Performing a polycondensation reaction on the esterified product in the presence of a catalyst and a branching agent to obtain the all-bio-based polybutylene succinate.

[0031] The present invention uses bio-based succinic acid and bio-based 1,4-butanediol as monomers, and obtains the all-bio-based polybutylene succinate through an esterification reaction and a polycondensation reaction; wherein, the bio-based succinic acid contains a specific content of Cl - and PO4 3- , has a high purity of succinic acid and an extremely low content of inorganic salts, thereby effectively inhibiting side reactions, reducing by-products, improving the polymerization efficiency, and obtaining an all-bio-based polybutylene succinate with a low melt index, a large molecular weight, good mechanical properties and hue.

[0032] The Cl -The mass content is 0.1 - 30 ppm. For example, it can be 0.15 ppm, 0.3 ppm, 0.5 ppm, 1 ppm, 2 ppm, 5 ppm, 8 ppm, 10 ppm, 15 ppm, 20 ppm, 25 ppm or 28 ppm, as well as specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range. Further preferably, it is 0.5 - 15 ppm.

[0033] In the bio - based succinic acid, the PO4 3- The mass content is 0.1 - 200 ppm. For example, it can be 0.15 ppm, 0.3 ppm, 0.5 ppm, 1 ppm, 2 ppm, 5 ppm, 8 ppm, 10 ppm, 20 ppm, 30 ppm, 40 ppm, 50 ppm, 60 ppm, 80 ppm, 100 ppm, 120 ppm, 150 ppm, 180 ppm or 190 ppm, as well as specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range.

[0034] Preferably, the mass percentage content (purity) of succinic acid in the bio - based succinic acid ≥ 99.7%. For example, it can be 99.72%, 99.75%, 99.78%, 99.8%, 99.82%, 99.85%, 99.88%, 99.9%, 99.92%, 99.93%, 99.94%, 99.95%, 99.96%, 99.97%, 99.98%, 99.99% or 99.999%, as well as specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range.

[0035] Exemplarily, the content and purity of Cl in the bio - based succinic acid - can be tested and obtained by the method in Standard GB / T 34686 - 2017; the content of PO4 3- can be tested and obtained by the phosphomolybdic acid colorimetric method.

[0036] Preferably, the preparation method of the bio - based succinic acid comprises the following steps:

[0037] Inoculate the seed liquid of the succinic - acid - producing strain into a culture medium for fermentation to obtain a fermentation broth;

[0038] Ultrafilter the fermentation broth to obtain a permeate;

[0039] Use an extractant to perform multi - stage forward cross - flow extraction on the permeate to obtain a succinic - acid - loaded organic phase;

[0040] Use a stripping agent to perform multi-stage counter-current extraction on the succinic acid-loaded organic phase to obtain an aqueous solution of succinic acid;

[0041] The aqueous solution of succinic acid is concentrated and crystallized to obtain the bio-based succinic acid.

[0042] As a preferred technical solution of the present invention, a combined purification process including ultrafiltration, multi-stage forward cross-flow extraction, and multi-stage counter-current extraction is designed in the preparation method of the bio-based succinic acid, which effectively reduces the content of impurities such as inorganic salts in the fermentation broth, and omits steps such as the calcium salt method, ammonium salt method, ion exchange, decolorization, and electrodialysis used in traditional purification methods, avoiding the introduction of impurities, and obtaining bio-based succinic acid with high purity and low inorganic salt impurity content.

[0043] Preferably, the succinic acid-producing strain includes Escherichia coli, Actinobacillus succinogenes, or Anaerobiospirillum. The strains used in the present invention are all known strains and can be obtained through commercial channels.

[0044] Preferably, the inoculation amount of the seed liquid is 1-10%, for example, it can be 2%, 3%, 4%, 5%, 6%, 7%, 8%, or 9%, as well as specific point values between the above point values. Due to space limitations and for the sake of brevity, the present invention does not exhaustively list the specific point values included in the above range.

[0045] In the present invention, the term "inoculation amount" refers to the volume percentage of the seed liquid relative to the culture medium.

[0046] Preferably, the pH value of the fermentation is 6.0-7.5, for example, it can be 6.2, 6.5, 6.6, 6.8, 7.0, 7.2, or 7.4, as well as specific point values between the above point values. Due to space limitations and for the sake of brevity, the present invention does not exhaustively list the specific point values included in the above range.

[0047] As a preferred technical solution of the present invention, an alkaline neutralizing agent is added to the system during the fermentation to keep the pH value of the fermentation at 6.0-7.5.

[0048] Preferably, the alkaline neutralizing agent includes any one or a combination of at least two of sodium hydroxide, sodium carbonate, magnesium carbonate, magnesium chloride, calcium carbonate, and calcium chloride.

[0049] Preferably, the stirring speed of the fermentation is 100-600 r / min, for example, it can be 150 r / min, 200 r / min, 250 r / min, 300 r / min, 350 r / min, 400 r / min, 450 r / min, 500 r / min, or 550 r / min, as well as specific point values between the above point values. Due to space limitations and for the sake of brevity, the present invention does not exhaustively list the specific point values included in the above range.

[0050] Preferably, the temperature of the fermentation is 30 - 40 °C, for example, it can be 31 °C, 32 °C, 33 °C, 34 °C, 35 °C, 36 °C, 37 °C, 38 °C or 39 °C, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range.

[0051] Preferably, the time of the fermentation is 20 - 70 h, for example, it can be 22 h, 25 h, 28 h, 30 h, 32 h, 35 h, 38 h, 40 h, 42 h, 45 h, 48 h, 50 h, 52 h, 55 h, 58 h, 60 h, 62 h, 65 h or 68 h, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range.

[0052] Preferably, the fermentation includes aerobic fermentation and anaerobic fermentation carried out in sequence.

[0053] As a preferred technical solution of the present invention, aerobic fermentation is carried out first during the fermentation process. At this stage, the growth of the bacteria reaches the stationary phase, and then it enters the anaerobic fermentation stage to promote the efficient production of succinic acid and improve the succinic acid yield.

[0054] Preferably, the dissolved oxygen content of the aerobic fermentation is 20% - 50%, for example, it can be 22%, 25%, 28%, 30%, 32%, 35%, 38%, 40%, 42%, 45% or 48%, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range.

[0055] In the present invention, the term "dissolved oxygen content" refers to the volume percentage of oxygen in the fermentation system.

[0056] Preferably, the temperature of the aerobic fermentation is 33 - 40 °C, for example, it can be 34 °C, 35 °C, 36 °C, 37 °C, 38 °C or 39 °C, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range.

[0057] Preferably, the stirring speed of the aerobic fermentation is 200 - 500 r / min, for example, it can be 220 r / min, 250 r / min, 280 r / min, 300 r / min, 320 r / min, 350 r / min, 380 r / min, 400 r / min, 420 r / min, 450 r / min or 480 r / min, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range.

[0058] Preferably, the time of the aerobic fermentation is 4 - 12 h, for example, it can be 4.5 h, 5 h, 5.5 h, 6 h, 6.5 h, 7 h, 7.5 h, 8 h, 8.5 h, 9 h, 9.5 h, 10 h, 10.5 h, 11 h or 11.5 h, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the said range.

[0059] Preferably, the dissolved oxygen content of the anaerobic fermentation is 0 - 0.5%, for example, it can be 0, 0.01%, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4% or 0.45%, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the said range.

[0060] Preferably, the temperature of the anaerobic fermentation is 30 - 40 °C, for example, it can be 31 °C, 32 °C, 33 °C, 34 °C, 35 °C, 36 °C, 37 °C, 38 °C or 39 °C, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the said range.

[0061] Preferably, the stirring speed of the anaerobic fermentation is 200 - 300 r / min, for example, it can be 210 r / min, 220 r / min, 230 r / min, 240 r / min, 250 r / min, 260 r / min, 270 r / min, 280 r / min or 290 r / min, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the said range.

[0062] Preferably, the time of the anaerobic fermentation is 30 - 50 h, for example, it can be 32 h, 35 h, 36 h, 38 h, 40 h, 42 h, 45 h, 46 h or 48 h, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the said range.

[0063] In the present invention, the fermentation broth is ultrafiltered to remove the bacterial cells and insoluble solid impurities, and a permeate is obtained.

[0064] Preferably, the pore size of the ultrafiltration membrane used for the ultrafiltration is 20 - 80 nm, for example, it can be 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm or 75 nm, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the said range.

[0065] Preferably, the temperature of the ultrafiltration is 40 - 60 °C, for example, it can be 42 °C, 45 °C, 48 °C, 50 °C, 52 °C, 55 °C or 58 °C, as well as the specific point values between the above point values. Due to space limitations and for the sake of brevity, the present invention does not exhaustively list the specific point values included in the range.

[0066] Preferably, the concentration multiple of the ultrafiltration is 10 - 40 times, for example, it can be 12 times, 15 times, 18 times, 20 times, 22 times, 25 times, 28 times, 30 times, 32 times, 35 times or 38 times, as well as the specific point values between the above point values. Due to space limitations and for the sake of brevity, the present invention does not exhaustively list the specific point values included in the range.

[0067] Preferably, the extractant includes a combination of a phosphoric acid ester complexing agent and a cosolvent.

[0068] Preferably, the phosphoric acid ester complexing agent has a structure shown in Formula I:

[0069]

[0070] In Formula I, R1 is selected from any one of C1 - C10 straight-chain or branched-chain alkyl groups;

[0071] In Formula I, R2 is selected from any one of H, C1 - C10 straight-chain or branched-chain alkyl groups;

[0072] In Formula I, R3 is selected from any one of C1 - C10 straight-chain or branched-chain alkyl groups, hydroxyl groups, and C1 - C10 alkoxy groups.

[0073] Among them, the C1 - C10 straight-chain or branched-chain alkyl groups can all be straight-chain or branched-chain alkyl groups of C1, C2, C3, C4, C5, C6, C7, C8, C9, C10, and exemplarily include but are not limited to: methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, 2-methylbutyl, n-pentyl, isopentyl, neopentyl, n-hexyl, neohexyl, 2-ethylhexyl, n-octyl, isooctyl, n-heptyl, n-nonyl, n-decyl, etc.

[0074] The C1 - C10 alkoxy groups can all be straight-chain or branched-chain alkoxy groups of C1, C2, C3, C4, C5, C6, C7, C8, C9, C10, and specific examples thereof can be monovalent groups obtained by connecting O to the examples of the above straight-chain or branched-chain alkyl groups.

[0075] Preferably, the phosphoric acid ester complexing agent includes any one or a combination of at least two of diisooctyl phosphate, dimethylheptyl methylphosphonate, and mono(2-ethylhexyl) 2-ethylhexyl phosphate.

[0076] Preferably, the cosolvent includes alcohol solvents, more preferably C7-C12 alcohol solvents (such as C7, C8, C9, C10, or C11, etc.), and even more preferably any one or a combination of at least two of n-heptanol, isooctanol, n-nonanol, and n-decanol.

[0077] As a preferred technical solution of the present invention, in the multi-stage forward cross-flow extraction, a phosphate ester complexing agent with the structure shown in Formula I is used. The P=O group in its molecular structure belongs to a Lewis basic polar functional group, which has stable properties, large bond energy, and strong complexing ability, and can complex with succinic acid (containing the Lewis acidic group -COOH). At the same time, an alcohol solvent is used as a cosolvent in the extractant, and it synergizes with the phosphate ester complexing agent to form a mixed extractant system, significantly improving the effect of extracting succinic acid from the permeate.

[0078] Preferably, the volume ratio of the phosphate ester complexing agent to the cosolvent is 1:(0.1-10), for example, it can be 1:0.2, 1:0.5, 1:0.8, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, or 1:10, etc.

[0079] Preferably, the volume ratio of the extractant to the permeate is (3-5):1, for example, it can be 3.2:1, 3.5:1, 3.8:1, 4:1, 4.2:1, 4.5:1, 4.8:1, etc.

[0080] Preferably, the number of stages of the multi-stage forward cross-flow extraction is 2-3 stages.

[0081] Preferably, the temperature of the multi-stage forward cross-flow extraction is 20-60°C, for example, it can be 22°C, 25°C, 28°C, 30°C, 32°C, 35°C, 38°C, 40°C, 42°C, 45°C, 48°C, 50°C, 52°C, 55°C, or 58°C, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list all the specific point values included in the range.

[0082] Preferably, the number of stages of the multi-stage reverse cross-flow extraction is 2-5 stages, for example, it can be 2 stages, 3 stages, 4 stages, or 5 stages.

[0083] Preferably, the stripping agent for the first-stage reverse cross-flow extraction is water, and the stripping agent for the 2-nth stage reverse cross-flow extraction is an alkaline salt solution; n represents an integer from 2 to 5, for example, 2, 3, 4, or 5.

[0084] As a preferred technical solution of the present invention, in the multi-stage counter-current extraction, water is used as the stripping agent in the first stage. As the stripping progresses, the succinic acid in the water increases and the pH of the system gradually decreases, thus affecting the solubility of succinic acid in water. An alkaline salt solution is used as the stripping agent in the second stage and subsequent stages, which can regulate the pH value of the solution, thereby increasing the solubility of succinic acid, promoting the stripping process, increasing the stripping yield, and obtaining high-purity bio-based succinic acid with a lower inorganic salt content.

[0085] Preferably, the alkaline salt includes any one or a combination of at least two of sodium carbonate, potassium carbonate, sodium bicarbonate, and potassium bicarbonate.

[0086] Preferably, the mass percentage content of the alkaline salt in the alkaline salt solution is 5%-10%, for example, it can be 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, or 9.5%, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range.

[0087] Preferably, the volume ratio of the stripping agent to the succinic acid-loaded organic phase is (3-5):1, for example, it can be 3.2:1, 3.5:1, 3.8:1, 4:1, 4.2:1, 4.5:1, 4.8:1, etc.

[0088] Preferably, the temperature of the multi-stage counter-current extraction is 40-80°C, for example, it can be 42°C, 45°C, 48°C, 50°C, 52°C, 55°C, 58°C, 60°C, 62°C, 65°C, 68°C, 70°C, 72°C, 75°C, or 78°C, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range.

[0089] Preferably, the temperature of the concentration is 60-80°C, for example, it can be 62°C, 65°C, 68°C, 70°C, 72°C, 75°C, or 78°C, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range.

[0090] Preferably, the concentration method includes evaporation concentration.

[0091] Preferably, the system pressure of the concentration is 10-40 kPa, for example, it can be 12 kPa, 15 kPa, 18 kPa, 20 kPa, 22 kPa, 25 kPa, 28 kPa, 30 kPa, 32 kPa, 35 kPa, or 38 kPa, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range.

[0092] Preferably, the concentration multiple is 2 - 10 times, for example, it can be 2.5 times, 3 times, 3.5 times, 4 times, 4.5 times, 5 times, 5.5 times, 6 times, 6.5 times, 7 times, 7.5 times, 8 times, 8.5 times, 9 times or 9.5 times, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the above range.

[0093] Preferably, the crystallization temperature is 10 - 30 °C, for example, it can be 12 °C, 15 °C, 18 °C, 20 °C, 22 °C, 25 °C or 28 °C, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the above range.

[0094] Preferably, the system pressure for crystallization is 60 - 80 kPa, for example, it can be 62 kPa, 65 kPa, 68 kPa, 70 kPa, 72 kPa, 75 kPa or 78 kPa, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the above range.

[0095] Preferably, after crystallization, it further includes the steps of centrifugal separation and drying.

[0096] Preferably, after crystallization, it further includes the steps of redissolution and recrystallization.

[0097] Preferably, the solvent used for redissolution includes water.

[0098] Preferably, the redissolution temperature is 40 - 80 °C, for example, it can be 42 °C, 45 °C, 48 °C, 50 °C, 52 °C, 55 °C, 58 °C, 60 °C, 62 °C, 65 °C, 68 °C, 70 °C, 72 °C, 75 °C or 78 °C, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the above range.

[0099] Preferably, the system pressure for redissolution is 5 - 30 kPa, for example, it can be 6 kPa, 8 kPa, 10 kPa, 12 kPa, 15 kPa, 18 kPa, 20 kPa, 22 kPa, 25 kPa or 28 kPa, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the above range.

[0100] Preferably, the recrystallization temperature is 10 - 30 °C, for example, it can be 12 °C, 15 °C, 18 °C, 20 °C, 22 °C, 25 °C or 28 °C, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the above range.

[0101] Preferably, the system pressure for recrystallization is 60 - 80 kPa. For example, it can be 62 kPa, 65 kPa, 68 kPa, 70 kPa, 72 kPa, 75 kPa, or 78 kPa, as well as specific point values between the above point values. Due to space limitations and for the sake of simplicity, the specific point values included in the scope of the present invention are not exhaustively listed herein.

[0102] Preferably, after recrystallization, the steps of centrifugal separation and drying are further included.

[0103] In a preferred technical solution, the preparation method of the bio - based succinic acid includes the following steps:

[0104] (S1) Inoculate the seed liquid of the succinic acid - producing strain into a culture medium for fermentation at an inoculation amount of 1 - 10% to obtain a fermentation broth;

[0105] The pH value of the fermentation is 6.0 - 7.5, including aerobic fermentation and anaerobic fermentation carried out in sequence. The dissolved oxygen amount of the aerobic fermentation is 20% - 50%, the temperature is 33 - 40 °C, the rotation speed is 200 - 600 r / min, and the time is 4 - 12 h; the dissolved oxygen amount of the anaerobic fermentation is 0 - 0.5%, the temperature is 30 - 40 °C, the rotation speed is 200 - 300 r / min, and the time is 30 - 50 h;

[0106] (S2) Ultrafilter the fermentation broth. The pore size of the ultrafiltration membrane is 20 - 80 nm, the temperature is 40 - 60 °C, and the concentration multiple is 10 - 40 times to obtain a permeate;

[0107] (S3) Use an extractant to perform multi - stage forward cross - flow extraction on the permeate to obtain a succinic acid - loaded organic phase;

[0108] The extractant includes a phosphoric acid ester complexing agent and a co - solvent with a volume ratio of 1:(0.1 - 10). The phosphoric acid ester complexing agent has the structure shown in Formula I, and the co - solvent is a C7 - C12 alcohol solvent; the volume ratio of the extractant to the permeate is (3 - 5):1;

[0109] The number of stages of the multi - stage forward cross - flow extraction is 2 - 3, and the temperature is 20 - 60 °C;

[0110] (S4) Use a stripping agent to perform multi - stage reverse cross - flow extraction on the succinic acid - loaded organic phase to obtain an aqueous succinic acid solution;

[0111] The volume ratio of the stripping agent to the succinic acid - loaded organic phase is (3 - 5):1;

[0112] The number of stages of the multi-stage countercurrent extraction is 3 - 5, and the temperature is 40 - 80 °C; the stripping agent for the first-stage countercurrent extraction is water, and the stripping agents for the 2 - n-stage countercurrent extractions are alkaline brine solutions, and the mass percentage content of the alkaline salt in the alkaline brine solution is 5% - 10%; n represents an integer from 3 to 5;

[0113] (S5) Concentrate, crystallize, centrifuge, dry, redissolve, recrystallize, centrifuge, and dry the aqueous succinic acid solution in sequence to obtain the bio-based succinic acid;

[0114] The temperature of the concentration is 60 - 80 °C, the system pressure is 10 - 40 kPa, and the concentration multiple is 2 - 10 times; the temperatures of the crystallization and recrystallization are each independently 10 - 30 °C, and the system pressures are each independently 60 - 80 kPa; the temperature of the redissolution is 40 - 80 °C, and the system pressure is 5 - 30 kPa.

[0115] In the present invention, the bio-based 1,4-butanediol can be obtained commercially or can be prepared by methods well known in the art.

[0116] Exemplarily, the bio-based 1,4-butanediol is prepared using the bio-based succinic acid as a raw material, and the specific method can refer to the preparation routes known in the prior art. For example, refer to "Green Catalytic Synthesis of 1,4-Butanediol Based on Bio-Based Succinic Acid", Li Kefan, East China Normal University.

[0117] Preferably, the purity of the bio-based 1,4-butanediol is ≥99.5%, for example, it can be 99.55%, 99.6%, 99.65%, 99.7%, 99.75%, 99.8%, 99.85%, 99.9%, 99.95%, 99.99% or 100%, as well as the specific point values between the above point values. Due to space limitations and for the sake of brevity, the present invention does not exhaustively list the specific point values included in the range.

[0118] Preferably, the chromaticity of the bio-based 1,4-butanediol is ≤10, for example, it can be 1, 2, 3, 4, 5, 6, 7, 8 or 9, etc.

[0119] Exemplarily, the chromaticity of the bio-based 1,4-butanediol can be tested by the method in Standard GB / T 3143 - 1982.

[0120] Exemplarily, the purity of the bio-based 1,4-butanediol can be tested by gas chromatography, which is a method well known in the art for testing the purity of compounds. The present invention does not limit the specific testing method of gas chromatography.

[0121] Preferably, the molar ratio of the biobased succinic acid to the biobased 1,4-butanediol is 1:(1.2 - 1.6), for example, it can be 1:1.22, 1:1.25, 1:1.28, 1:1.3, 1:1.32, 1:1.35, 1:1.38, 1:1.4, 1:1.42, 1:1.45, 1:1.48, 1:1.5, 1:1.52, 1:1.55 or 1:1.58, etc.

[0122] Preferably, the temperature of the esterification reaction is 150 - 170 °C, for example, it can be 152 °C, 154 °C, 155 °C, 156 °C, 158 °C, 170 °C, 172 °C, 174 °C, 175 °C, 176 °C or 178 °C, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the above range.

[0123] Preferably, the time of the esterification reaction is 2 - 4 h, for example, it can be 2.2 h, 2.5 h, 2.8 h, 3 h, 3.2 h, 3.5 h or 3.8 h, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the above range.

[0124] Preferably, the catalyst includes a titanate catalyst, and more preferably includes any one or a combination of at least two of tetramethyl titanate, tetraethyl titanate, tetra-isopropyl titanate, tetra-n-butyl titanate, and tetra-iso-octyl titanate.

[0125] Preferably, based on the total mass of the biobased succinic acid and the biobased 1,4-butanediol being 100%, the dosage of the catalyst is such that the mass content of Ti element is 50 - 200 ppm, for example, it can be 60 ppm, 80 ppm, 100 ppm, 120 ppm, 140 ppm, 150 ppm, 160 ppm or 180 ppm, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the above range.

[0126] Preferably, the branching agent is a polyhydroxy compound with a functionality ≥ 3 (such as 3, 4, 5, 6, etc.), and more preferably includes any one or a combination of at least two of glycerol, trimethylolpropane, pentaerythritol, and dipentaerythritol.

[0127] Preferably, based on the total mass of the bio-based succinic acid and bio-based 1,4-butanediol being 100%, the dosage of the branching agent is such that the mass content of its hydroxyl groups is 200 - 1000 ppm. For example, it can be 250 ppm, 300 ppm, 350 ppm, 400 ppm, 450 ppm, 500 ppm, 550 ppm, 600 ppm, 650 ppm, 700 ppm, 750 ppm, 800 ppm, 850 ppm, 900 ppm or 950 ppm, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the said range.

[0128] Preferably, the polycondensation reaction is carried out in the presence of a heat stabilizer.

[0129] Preferably, the heat stabilizer includes phosphate ester compounds, and more preferably includes any one or a combination of at least two of trimethyl phosphate, triethyl phosphate, isopropyl phosphate, n-butyl phosphate, isooctyl phosphate, and triphenyl phosphate.

[0130] Preferably, based on the total mass of the bio-based succinic acid and bio-based 1,4-butanediol being 100%, the dosage of the heat stabilizer is such that the mass content of P element in the heat stabilizer is 5 - 100 ppm. For example, it can be 10 ppm, 20 ppm, 30 ppm, 40 ppm, 50 ppm, 60 ppm, 70 ppm, 80 ppm or 90 ppm, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the said range.

[0131] It should be noted that the phosphate ester compounds as heat stabilizers will participate in chemical reactions, connecting the P element to the poly(butylene succinate) molecule through chemical bonds to form non-free P elements.

[0132] Preferably, the polycondensation reaction includes a prepolymerization reaction and a final polymerization reaction carried out in sequence.

[0133] Preferably, the temperature of the prepolymerization reaction is 180 - 240 °C. For example, it can be 185 °C, 190 °C, 195 °C, 200 °C, 205 °C, 210 °C, 215 °C, 220 °C, 225 °C, 230 °C or 235 °C, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the said range.

[0134] Preferably, the pressure of the prepolymerization reaction is 1 - 5 kPa, for example, it can be 1.5 kPa, 2 kPa, 2.5 kPa, 3 kPa, 3.5 kPa, 4 kPa or 4.5 kPa, as well as the specific values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific values included in the range.

[0135] Preferably, the time of the prepolymerization reaction is 1 - 3 h, for example, it can be 1.2 h, 1.5 h, 1.8 h, 2 h, 2.2 h, 2.5 h or 2.8 h, as well as the specific values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific values included in the range.

[0136] Preferably, the temperature of the final polymerization reaction is 220 - 260 °C, for example, it can be 222 °C, 225 °C, 228 °C, 230 °C, 232 °C, 235 °C, 238 °C, 240 °C, 242 °C, 245 °C, 248 °C, 250 °C, 252 °C, 255 °C or 258 °C, as well as the specific values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific values included in the range.

[0137] Preferably, the pressure of the final polymerization reaction is 20 - 100 Pa, for example, it can be 25 Pa, 30 Pa, 35 Pa, 40 Pa, 45 Pa, 50 Pa, 55 Pa, 60 Pa, 65 Pa, 70 Pa, 75 Pa, 80 Pa, 85 Pa, 90 Pa or 95 Pa, as well as the specific values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific values included in the range.

[0138] Preferably, the time of the final polymerization reaction is 2 - 6 h, for example, it can be 2.2 h, 2.5 h, 2.8 h, 3 h, 3.2 h, 3.5 h, 3.8 h, 4 h, 4.2 h, 4.5 h, 4.8 h, 5 h, 5.2 h, 5.5 h or 5.8 h, as well as the specific values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific values included in the range.

[0139] Preferably, after the final polymerization reaction, it further includes the step of extrusion granulation.

[0140] As a preferred technical solution of the present invention, the preparation method of the all - bio - based polybutylene succinate includes the following steps:

[0141] (1) Mix biobased succinic acid and biobased 1,4 - butanediol in a molar ratio of 1:(1.2 - 1.6), and carry out an esterification reaction at 150 - 170 °C for 2 - 4 h to obtain an esterified product;

[0142] (2) Place the esterified product, titanate catalyst, polyol branching agent, and phosphate ester heat stabilizer obtained in step (1) in a reaction device, and react at 180 - 240 °C and 1 - 5 kPa for 1 - 3 h to obtain a prepolymer;

[0143] Based on the total mass of the bio - based succinic acid and bio - based 1,4 - butanediol being 100%, the dosage of the titanate catalyst is such that the mass content of Ti element is 50 - 200 ppm, the dosage of the polyol branching agent is such that the mass content of its hydroxyl group is 200 - 1000 ppm, and the dosage of the phosphate ester heat stabilizer is such that the mass content of P element in the phosphate ester heat stabilizer is 5 - 100 ppm;

[0144] (3) React the prepolymer obtained in step (2) at 220 - 260 °C and 20 - 100 Pa for 2 - 6 h, and extrude and pelletize to obtain the all - bio - based poly(butylene succinate).

[0145] In a third aspect, the present invention provides an application of the all - bio - based poly(butylene succinate) as described in the first aspect in packaging materials, food - contact materials, or agricultural mulch films.

[0146] Compared with the prior art, the present invention has the following beneficial effects:

[0147] (1) In the all - bio - based poly(butylene succinate) provided by the present invention, the proportion of bio - based carbon is 99.99% - 100%, which can be naturally biodegradable, conforms to the concept of green, low - carbon and sustainable development, and significantly reduces carbon emissions; the all - bio - based poly(butylene succinate) has a low melt index, a large molecular weight, low contents of free P element and Cl element, a light color, and has higher tensile strength, high elongation at break, high flexural strength and high flexural modulus, showing excellent performance in mechanical properties and appearance, and can meet the high - performance requirements of biodegradable bio - based materials in multiple fields such as packaging materials, food - contact materials, and agricultural mulch films, with broad application prospects.

[0148] (2) In the preparation method provided by the present invention, bio - based succinic acid and bio - based 1,4 - butanediol are used as monomers, and the bio - based succinic acid contains a specific content of Cl - and PO4 3- , the succinic acid has high purity and extremely low inorganic salt content, thus effectively inhibiting side reactions, reducing by - products, improving the polymerization efficiency, and obtaining an all - bio - based poly(butylene succinate) with a low melt index, a large molecular weight, high mechanical properties and good hue. Specific Embodiments

[0149] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0150] As used herein, the terms "comprising", "including", "having", "containing" or any other variation thereof are intended to cover non-exclusive inclusion. For example, a composition, step, method, article or apparatus containing the listed elements is not necessarily limited to those elements, but may also include other elements not expressly listed or elements inherent to such composition, step, method, article or apparatus.

[0151] In the present invention, features defined with "first", "second" may explicitly or implicitly include one or more of such features, which are used to distinguish and describe features, without order or importance. In the description of the present invention, unless otherwise specified, "a plurality of" means two or more.

[0152] In the following specific embodiments of the present invention, each component for preparing the culture medium and various reagents for the purification treatment of the filtrate are commercially available chemicals; the succinic acid-producing strain is the commercially available Actinobacillus succinogenes. The specific information of some materials is as follows:

[0153] (1) Seed culture medium, the components are as follows: glucose 15 g / L, yeast extract 6 g / L, corn steep liquor dry powder 5 g / L, NaHCO3 1 g / L, NaH2PO4 1 g / L, K2HPO4 1 g / L, and the solvent is water.

[0154] (2) Fermentation culture medium, the components are as follows: glucose 100 g / L, yeast extract 20 g / L, urea 10 g / L, dipotassium hydrogen phosphate 5 g / L, potassium dihydrogen phosphate 5 g / L, magnesium sulfate 2 g / L, vitamin B1 2 g / L, and the solvent is water.

[0155] In the following specific embodiments of the present invention, the content (purity) of succinic acid and the content of Cl - in the bio-based succinic acid can be tested and obtained by the method in GB / T 34686-2017; the content of PO4 3- is tested and obtained by the phosphomolybdic acid colorimetric method, and the specific steps are as follows:

[0156] ① 10% ascorbic acid solution: Dissolve 10 g of ascorbic acid in water, transfer it to a volumetric flask and make up to 100 mL, and keep it for use after making up the volume;

[0157] ② Molybdate solution: Weigh 13 g of ammonium molybdate into a beaker, add 100 mL of water to dissolve it; weigh 0.35 g of potassium antimonyl tartrate, add 100 mL of water to dissolve it; slowly add the ammonium molybdate solution to the beaker containing 300 mL of sulfuric acid solution while stirring, then add the potassium antimonyl tartrate solution and mix evenly, transfer the mixed solution to a brown glass bottle and store it in a cool place;

[0158] ③Phosphate stock solution: Dry potassium dihydrogen phosphate at 100 °C for 2 hours, place it in a desiccator and let it stand overnight; weigh 0.2197 g of potassium dihydrogen phosphate, dissolve it in water and transfer it to a 1000 mL volumetric flask, add 5 mL of sulfuric acid solution, and make up the volume to make the phosphorus concentration in this solution 50 μg / mL.

[0159] ④Phosphate standard solution: Measure 10 mL of the phosphate stock solution into a 250 mL volumetric flask, add water to make up the volume, so that the phosphorus concentration in this solution is 2 μg / mL.

[0160] ⑤Drawing of the standard curve: Accurately pipette 0 mL, 0.5 mL, 1.0 mL, 3.0 mL, 5.0 mL, 10.0 mL and 15.0 mL of the phosphate standard solution into 50 mL stoppered colorimetric tubes respectively with a pipette, add water to the scale line, add 1 mL of 10% ascorbic acid solution to each colorimetric tube, mix well, add 2 mL of molybdate solution after 30 s and mix well thoroughly, let it stand for 15 min, then measure the absorbance at a wavelength of 700 nm with the blank solution as the reference, and draw the standard curve;

[0161] ⑥Sample determination: Accurately weigh 10.0 g of the succinic acid sample to be measured into a beaker, dissolve it in water, transfer it to a 100 mL volumetric flask, make up the volume, pipette 0.1 mL of the sample solution into a colorimetric tube with a pipette, and dilute it with water to the scale. Add 1 mL of 10% ascorbic acid solution to the colorimetric tube, mix well, add 2 mL of molybdate solution after 30 s and mix well thoroughly, let it stand for 15 min, then measure the absorbance at a wavelength of 700 nm with the blank solution as the reference, substitute it into the standard curve to obtain the PO4 3- content.

[0162] Preparation Example 1

[0163] Preparation method of biobased succinic acid A1, comprising the following steps:

[0164] (1) Preparation of the seed solution:

[0165] Inoculate a single colony of Actinobacillus succinogenes on the plate into the sterilized seed medium, and culture it in an incubator at 34 °C for 10 h to obtain the seed solution.

[0166] (2) Preparation of the fermentation broth:

[0167] Add the fermentation medium to a 5 L fermenter, inoculate the seed solution obtained in step (1) into the fermentation medium at an inoculation amount of 10%, carry out aerobic fermentation and anaerobic fermentation in sequence, monitor the pH value during the whole fermentation process, and control the pH value at 6.5 by introducing a sodium carbonate solution (mass concentration 5%); obtain the fermentation broth;

[0168] Among them, the dissolved oxygen content in the aerobic fermentation is 40%, the stirring speed is 300 rpm, the temperature is 35 °C, and the time is 12 h;

[0169] The dissolved oxygen content in the anaerobic fermentation is 0.3%, the temperature is 33 °C, the rotation speed is 200 r / min, and the time is 50 h.

[0170] (3) Ultrafiltration is carried out on the fermentation broth obtained in step (2) using a 50-nm pore size ultrafiltration membrane. The temperature of ultrafiltration is 50 °C, and the concentration multiple is 25 times to obtain a permeate;

[0171] (4) Multistage forward cross-flow extraction is carried out on the permeate using an extractant. The extractant is a mixture of dimethylheptyl methylphosphonate and n-heptanol, and the volume ratio of the two is 1:1; the volume ratio of the extractant to the permeate is 4:1; the number of stages of the multistage forward cross-flow extraction is 3, and the temperature is 40 °C to obtain a succinic acid-loaded organic phase;

[0172] (5) Multistage reverse cross-flow extraction is carried out on the succinic acid-loaded organic phase obtained in step (4). The volume ratio of the succinic acid-loaded organic phase to the stripping agent is 1:4. The temperature of the multistage reverse cross-flow extraction is 70 °C, and the number of stages is 4. The stripping agent in the first stage is water, and the stripping agents in the 2nd - 4th stages are aqueous sodium carbonate solutions with a mass concentration of 6% to obtain a succinic acid aqueous solution;

[0173] (6) The succinic acid aqueous solution obtained in step (5) is evaporated and concentrated at a temperature of 70 °C, a system pressure of 25 kPa, and a concentration multiple of 5 times;

[0174] After concentration, cooling crystallization is carried out at 20 °C and a system pressure of 70 kPa, followed by centrifugal separation and drying at 85 °C to obtain crude crystals;

[0175] The crude crystals are redissolved in water at 75 °C and a system pressure of 25 kPa, and recrystallized at 25 °C and a system pressure of 65 kPa, followed by centrifugal separation and drying at 85 °C to obtain bio-based succinic acid A1, and its component information is shown in Table 1.

[0176] Preparation Example 2

[0177] A preparation method of bio-based succinic acid A2. First, the same method as in Preparation Example 1 is used to obtain a fermentation broth, and then the fermentation broth is processed according to the following method:

[0178] (1) Ultrafiltration is carried out on the fermentation broth using a 30-nm pore size ultrafiltration membrane. The temperature of ultrafiltration is 45 °C, and the concentration multiple is 35 times to obtain a permeate;

[0179] (2) The permeate is subjected to multi-stage forward cross-flow extraction with an extractant, which is a mixture of diisooctyl phosphate and isooctanol with a volume ratio of 1:8; the volume ratio of the extractant to the permeate is 5:1; the number of stages of the multi-stage forward cross-flow extraction is 2, the temperature is 60 °C, and a succinic acid-loaded organic phase is obtained;

[0180] (3) The succinic acid-loaded organic phase obtained in step (2) is subjected to multi-stage reverse cross-flow extraction. The volume ratio of the succinic acid-loaded organic phase to the stripping agent is 1:5. The temperature of the multi-stage reverse cross-flow extraction is 50 °C, and the number of stages is 5. The stripping agent for the first stage is water, and the stripping agents for the 2nd - 5th stages are aqueous sodium carbonate solutions with a mass concentration of 10%, and a succinic acid aqueous solution is obtained;

[0181] (4) The succinic acid aqueous solution obtained in step (3) is evaporated and concentrated at a temperature of 70 °C, a system pressure of 25 kPa, and a concentration multiple of 5 times;

[0182] After concentration, it is cooled and crystallized at 20 °C and a system pressure of 70 kPa, then centrifuged and dried at 85 °C to obtain crude crystals;

[0183] The crude crystals are redissolved in water at 75 °C and a system pressure of 25 kPa, and recrystallized at 25 °C and a system pressure of 65 kPa, then centrifuged and dried at 85 °C to obtain bio-based succinic acid A2, and its component information is shown in Table 1.

[0184] Preparation Example 3

[0185] A preparation method of bio-based succinic acid A3. First, a fermentation broth is obtained by the same method as in Preparation Example 1, and then the fermentation broth is treated as follows:

[0186] (1) The fermentation broth is ultrafiltered with a 40-nm pore size ultrafiltration membrane. The temperature of ultrafiltration is 55 °C, and the concentration multiple is 30 times to obtain a permeate;

[0187] (2) The permeate is subjected to multi-stage forward cross-flow extraction with an extractant, which is a mixture of 2-ethylhexyl phosphoric acid mono(2-ethylhexyl) ester and n-nonanol with a volume ratio of 1:5; the volume ratio of the extractant to the permeate is 4:1; the number of stages of the multi-stage forward cross-flow extraction is 2, the temperature is 50 °C, and a succinic acid-loaded organic phase is obtained;

[0188] (3) The succinic acid-loaded organic phase obtained in step (2) is subjected to multi-stage reverse cross-flow extraction. The volume ratio of the succinic acid-loaded organic phase to the stripping agent is 1:3. The temperature of the multi-stage reverse cross-flow extraction is 60 °C, and the number of stages is 4. The stripping agent for the first stage is water, and the stripping agents for the 2nd - 5th stages are aqueous sodium bicarbonate solutions with a mass concentration of 8%, and a succinic acid aqueous solution is obtained;

[0189] (4) Evaporate and concentrate the aqueous solution of succinic acid obtained in step (3) at a temperature of 60 °C, a system pressure of 30 kPa, and a concentration multiple of 6 times;

[0190] After concentration, perform cooling crystallization at 25 °C and a system pressure of 65 kPa, then perform centrifugal separation and drying at 85 °C to obtain crude crystals;

[0191] Redissolve the crude crystals in water at 70 °C and a system pressure of 20 kPa, perform recrystallization at 20 °C and a system pressure of 68 kPa, then perform centrifugal separation and drying at 85 °C to obtain biobased succinic acid A3, and its component information is shown in Table 1.

[0192] Preparation Example 4

[0193] A method for preparing biobased succinic acid A4, which is only different from Preparation Example 1 in that the extractant for multi-stage forward cross-flow extraction in step (4) is dimethylheptyl methylphosphonate, and other materials, dosages, steps, and process parameters are the same as those in Preparation Example 1, and the component information of the obtained biobased succinic acid A4 is shown in Table 1.

[0194] Preparation Example 5

[0195] A method for preparing biobased succinic acid A5, which is only different from Preparation Example 1 in that the extractant for multi-stage forward cross-flow extraction in step (4) is n-heptanol, and other materials, dosages, steps, and process parameters are the same as those in Preparation Example 1, and the component information of the obtained biobased succinic acid A5 is shown in Table 1.

[0196] Preparation Example 6

[0197] A method for preparing biobased succinic acid A6, which is only different from Preparation Example 1 in that n-hexanol of equal mass is used to replace n-heptanol in step (4), and other materials, dosages, steps, and process parameters are the same as those in Preparation Example 1, and the component information of the obtained biobased succinic acid A6 is shown in Table 1.

[0198] Preparation Example 7

[0199] A method for preparing biobased succinic acid A7, which is only different from Preparation Example 1 in that the stripping agent for multi-stage reverse cross-flow extraction in step (5) is water, and other materials, dosages, steps, and process parameters are the same as those in Preparation Example 1, and the component information of the obtained biobased succinic acid A7 is shown in Table 1.

[0200] Table 1

[0201]

[0202] In the following specific embodiments of the present invention, the bio-based 1,4-butanediol is a commercially available product (purchased from Liaoning Jinfa Biological Materials Co., Ltd.); the chromaticity and purity of the bio-based 1,4-butanediol are tested. The testing method for chromaticity is GB / T 3143-1982, and the measured chromaticity is 4; the purity is tested by gas chromatography using a gas chromatograph (Agilent 7820A), and the testing conditions are as follows:

[0203] Chromatographic column: DB-WAX fused silica capillary column. By plotting the standard working curve, according to the peak area of the quantitative ion of 1,4-butanediol in the sample solution, the purity of 1,4-butanediol in the test solution can be determined to be 99.72%.

[0204] The following are exemplary examples of the all-bio-based polybutylene succinate and its preparation method according to the present invention. In the following specific embodiments of the present invention, the information of the bio-based succinic acid and the bio-based 1,4-butanediol is shown in Table 1; the reagents for which the preparation method is not specified are all conventional commercially available chemicals.

[0205] In the following specific embodiments of the present invention, the testing methods for the various properties of the all-bio-based polybutylene succinate are as follows:

[0206] (1) Mass content of free P element: Measured by phosphomolybdic acid colorimetry and standard curve method. The specific steps are as follows: ① Mix potassium persulfate and water evenly to prepare a 50 g / L potassium persulfate solution; ② Mix ascorbic acid and water evenly to prepare an ascorbic acid solution with a mass concentration of 10%; ③ Dissolve 13 g of ammonium molybdate and 0.35 g of potassium antimonyl tartrate in 300 mL of sulfuric acid, then add potassium antimonyl tartrate solution and mix evenly. Transfer the mixed solution to a brown glass bottle and store it in a cool place; ④ Phosphorus standard solution: Weigh 50 mg of potassium dihydrogen phosphate and dissolve it in pure water, and make up the volume to 1000 mL. ⑤ Digestion treatment of PBS: Grind the PBS particles to be measured into powder, add it to a 15 mL digestion tube, add 2.5 mL of potassium persulfate solution to completely immerse the powder, tighten the sealing cap, and put the digestion tube into a digestion device set at 140 °C for 15 min to carry out digestion work at a fixed time and temperature; ⑥ Color development and measurement: Take out the digestion tube, wait for the liquid in the tube to cool to room temperature, add 0.6 mL of ascorbic acid solution to the digestion tube, mix well, add 1.2 mL of molybdate solution after 30 s, mix well, and after standing for 15 min, use a spectrophotometer to measure the absorbance at a wavelength of 700 nm with a blank solution as a reference; ⑦ Take 7 digestion tubes and add 0.00, 0.25 mL, 0.50 mL, 1.50 mL, 2.50 mL, 5.00 mL, 7.50 mL of phosphorus standard solution respectively, and add water to 15 mL. Carry out color development and absorbance measurement according to step ⑥. After deducting the absorbance of the blank test, plot the standard working curve with the corresponding P content; Substitute the absorbance obtained in step ⑥ into the standard working curve to obtain the content of free P element in PBS.

[0207] (2) Mass content of Cl element: Measured by inductively coupled plasma-mass spectrometry (ICP-MS). The specific steps are as follows: ① Digestion treatment of PBS: Grind the PBS particles to be measured into powder, add it to a digestion tube, add nitric acid solution (the volume ratio of nitric acid to water is 1:3) to completely immerse the PBS powder, and carry out heating digestion on a digestion instrument until the sample is completely dissolved to form a transparent digestion solution; ② Cool the digestion solution to room temperature, dilute it with water to obtain a sample solution, and then introduce it into an ICP instrument for element analysis. The ICP ionizes the atoms or molecules in the sample into ions, and separates and detects them through a mass spectrometer to obtain the signal intensity of the Cl element, and obtain the Cl content according to the built-in software of the instrument.

[0208] (3) Terminal carboxyl value: Measured according to the method in Standard FZ / T 50012-2006.

[0209] (4) Melt index: Measured by a melt index instrument under the test conditions of 190 °C and 2.16 kg.

[0210] (5) Tensile strength and elongation at break: Tested according to the method in Standard ISO 527-2-2012 under the test condition of 50 mm / min.

[0211] (6) Flexural strength: Tested according to the method in Standard ISO 178-2019 under the test condition of 2 mm / min.

[0212] (7) Hue: The fully bio-based polybutylene succinate to be tested is injection-molded into a spline and tested by a color difference meter to obtain L, a, and b values respectively; among them, L represents black and white brightness, 0 is black, and 100 is white; a represents red and green values, a < 0 represents green, a = 0 represents neutral, and a > 0 represents red; b represents yellow and blue values, b < 0 represents blue, b = 0 represents neutral, and b > 0 represents yellow.

[0213] Example 1

[0214] A fully bio-based polybutylene succinate (fully bio-based PBS) and its preparation method, the preparation method comprising the following steps:

[0215] (1) Mix bio-based succinic acid A1 and bio-based 1,4-butanediol at a molar ratio of 1:1.2 and carry out an esterification reaction at 150 °C for 4 h to obtain an esterified product;

[0216] (2) Place the esterified product obtained in step (1), a catalyst (tetra-n-butyl titanate), a branching agent (glycerol), and a heat stabilizer (n-butyl phosphate) in a prepolymerization reactor and react at 240 °C and 2 kPa for 1 h to obtain a prepolymer;

[0217] Based on the total mass of the bio-based succinic acid and bio-based 1,4-butanediol being 100%, the dosage of the catalyst is such that the mass content of Ti element is 80 ppm, the dosage of the branching agent is such that the mass content of its hydroxyl group is 800 ppm, and the dosage of the heat stabilizer is such that the mass content of P element in the heat stabilizer is 20 ppm;

[0218] (3) Transfer the prepolymer obtained in step (2) to a final polymerization reactor and react at 220 °C and 60 Pa for 6 h, and then extrude and pelletize to obtain the fully bio-based PBS, and its specific components and test data are shown in Table 2.

[0219] Example 2

[0220] A fully bio-based PBS and its preparation method, the preparation method comprising the following steps:

[0221] (1) Mix bio-based succinic acid A2 and bio-based 1,4-butanediol at a molar ratio of 1:1.4 and carry out an esterification reaction at 160 °C for 3 h to obtain an esterified product;

[0222] (2) Place the esterified product obtained in step (1), a catalyst (tetramethyl titanate), a branching agent (pentaerythritol), and a heat stabilizer (triphenyl phosphate) in a prepolymerization reactor, and react at 210 °C and 3 kPa for 2 h to obtain a prepolymer;

[0223] Based on the total mass of the bio-based succinic acid and bio-based 1,4-butanediol being 100%, the dosage of the catalyst is such that the mass content of Ti element is 98 ppm, the dosage of the branching agent is such that the mass content of hydroxyl group is 650 ppm, and the dosage of the heat stabilizer is such that the mass content of P element in the heat stabilizer is 30 ppm;

[0224] (3) Transfer the prepolymer obtained in step (2) to a final polymerization reactor, react at 240 °C and 20 Pa for 4 h, and then extrude and pelletize to obtain the all-bio-based PBS. Its specific components and test data are shown in Table 2.

[0225] Example 3

[0226] An all-bio-based PBS and its preparation method. The preparation method includes the following steps:

[0227] (1) Mix bio-based succinic acid A3 and bio-based 1,4-butanediol at a molar ratio of 1:1.6, and carry out an esterification reaction at 170 °C for 2 h to obtain an esterified product;

[0228] (2) Place the esterified product obtained in step (1), a catalyst (tetraisopropyl titanate), a branching agent (dipentaerythritol), and a heat stabilizer (triethyl phosphate) in a prepolymerization reactor, and react at 180 °C and 5 kPa for 3 h to obtain a prepolymer;

[0229] Based on the total mass of the bio-based succinic acid and bio-based 1,4-butanediol being 100%, the dosage of the catalyst is such that the mass content of Ti element is 120 ppm, the dosage of the branching agent is such that the mass content of hydroxyl group is 950 ppm, and the dosage of the heat stabilizer is such that the mass content of P element in the heat stabilizer is 40 ppm;

[0230] (3) Transfer the prepolymer obtained in step (2) to a final polymerization reactor, react at 260 °C and 80 Pa for 2 h, and then extrude and pelletize to obtain the all-bio-based PBS. Its specific components and test data are shown in Table 2.

[0231] Example 4

[0232] An all-bio-based PBS and its preparation method. The preparation method includes the following steps:

[0233] (1) Mix biobased succinic acid A1 and biobased 1,4-butanediol at a molar ratio of 1:1.5, and carry out an esterification reaction at 160 °C for 3 h to obtain an esterified product;

[0234] (2) Place the esterified product obtained in step (1), a catalyst (tetraisopropyl titanate), a branching agent (pentaerythritol), and a heat stabilizer (triethyl phosphate) in a prepolymerization reactor, and react at 200 °C and 3 kPa for 1.5 h to obtain a prepolymer;

[0235] Based on the total mass of the biobased succinic acid and biobased 1,4-butanediol being 100%, the amount of the catalyst used is such that the mass content of Ti element is 80 ppm, the amount of the branching agent used is such that the mass content of hydroxyl group is 600 ppm, and the amount of the heat stabilizer used is such that the mass content of P element in the heat stabilizer is 60 ppm;

[0236] (3) Transfer the prepolymer obtained in step (2) to a final polymerization reactor, react at 235 °C and 40 Pa for 4 h, and extrude and pelletize to obtain the all-biobased PBS. Its specific components and test data are shown in Table 4.

[0237] Comparative Example 1

[0238] An all-biobased PBS and its preparation method. The difference between the preparation method and that of Example 1 is only that biobased succinic acid A1 is replaced with an equimolar amount of biobased succinic acid A4; the types, amounts, and process steps of other materials are the same as those in Example 1, and an all-biobased PBS is obtained. The specific information is shown in Table 2.

[0239] Comparative Example 2

[0240] An all-biobased PBS and its preparation method. The difference between the preparation method and that of Example 1 is only that biobased succinic acid A1 is replaced with an equimolar amount of biobased succinic acid A5; the types, amounts, and process steps of other materials are the same as those in Example 1, and an all-biobased PBS is obtained. The specific information is shown in Table 2.

[0241] Comparative Example 3

[0242] An all-biobased PBS and its preparation method. The difference between the preparation method and that of Example 1 is only that biobased succinic acid A1 is replaced with an equimolar amount of biobased succinic acid A6; the types, amounts, and process steps of other materials are the same as those in Example 1, and an all-biobased PBS is obtained. The specific information is shown in Table 2.

[0243] Comparative Example 4

[0244] A fully bio - based PBS and its preparation method. The difference between the preparation method and that of Example 1 is only that the bio - based succinic acid A1 is replaced with an equimolar amount of bio - based succinic acid A7; the types, dosages, and process steps of other materials are the same as those in Example 1, and a fully bio - based PBS is obtained. The specific information is shown in Table 2.

[0245] Table 2

[0246]

[0247] According to the data in Table 2, it can be known that the fully bio - based PBS provided by the present invention is prepared using bio - based succinic acid and bio - based 1,4 - butanediol as monomers. The proportion of bio - based carbon is approximately equal to 100%. It has a low melt index, low contents of free P element and Cl element, a high molecular weight, and low impurity content. Its tensile strength is 38 - 38.5 MPa, the elongation at break is 222% - 235%, the flexural strength is 30 - 32 MPa, the absolute value of chromaticity a value ≤ 0.2, and the b value is 6 - 7.4. There is no red - or yellow - discoloration phenomenon. It has the characteristics of high mechanical and mechanical properties and good hue, and can meet the high - performance requirements such as high strength and high durability of degradable bio - based materials in fields such as packaging materials like film bags and food - contact materials.

[0248] The contents of Cl - and PO4 3- in the succinic acid monomers used in Comparative Examples 1 - 4 are on the high side, resulting in more side reactions during the preparation process, a high content of by - products. Thus, the contents of free P element and Cl element in the obtained fully bio - based PBS are high, the melt index is high, the molecular weight is relatively low, the product color deepens, and there are problems of red - and / or yellow - discoloration. Furthermore, the mechanical and mechanical properties such as tensile fracture strength, flexural strength, and toughness of the material are reduced to varying degrees, affecting the tensile, compressive, and impact resistance properties of the product, and it is not suitable for application fields with high - strength and durability requirements.

[0249] The applicant declares that the present invention uses the above - mentioned examples to illustrate the fully bio - based polybutylene succinate of the present invention, its preparation method, and its application. However, the present invention is not limited to the above - mentioned examples, that is, it does not mean that the present invention must rely on the above - mentioned examples to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent replacement of each raw material of the product of the present invention, the addition of auxiliary components, and the selection of specific methods, etc., all fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A fully bio-based polybutylene succinate, characterized in that, The all-bio-based polybutylene succinate comprises polybutylene succinate, P element and Cl element; The mass content of free P element in the all-bio-based polybutylene succinate is 0.1 - 100 ppm, and the mass content of Cl element in the all-bio-based polybutylene succinate is 0.1 - 15 ppm; The melt index of the all-bio-based polybutylene succinate under the conditions of 190 °C and 2.16 kg is 3.0 - 10.0 g / 10 min.

2. The poly(butylene succinate) based entirely on biological materials according to claim 1, wherein The mass content of free P element in the all-bio-based polybutylene succinate is 10 - 98 ppm; Preferably, the mass content of Cl element in the all-bio-based polybutylene succinate is 1 - 12 ppm; Preferably, the melt index of the all-bio-based polybutylene succinate under the conditions of 190 °C and 2.16 kg is 4.0 - 6.0 g / 10 min.

3. The poly(butylene succinate) based entirely on biological substances according to claim 1, characterized in that, The terminal carboxyl value of the all-bio-based polybutylene succinate is 30 - 80 mol / t.

4. A method for preparing a fully bio-based polybutylene succinate according to any one of claims 1-3, characterized in that, The preparation method comprises: Performing an esterification reaction on bio-based succinic acid and bio-based 1,4-butanediol to obtain an esterified product; The bio-based succinic acid includes succinic acid, Cl - and PO4 3- , and the mass content of Cl - in the bio-based succinic acid is 0.1 - 30 ppm, and the mass content of PO4 3- is 0.1 - 200 ppm; Performing a polycondensation reaction on the esterified product in the presence of a catalyst and a branching agent to obtain the all-bio-based polybutylene succinate.

5. The preparation method according to claim 4, wherein, The preparation method of the bio-based succinic acid comprises the following steps: Inoculating the seed liquid of the succinic acid-producing strain into a culture medium for fermentation to obtain a fermentation broth; Ultrafiltering the fermentation broth to obtain a permeate; Performing multi-stage forward cross-flow extraction on the permeate with an extractant to obtain a succinic acid-loaded organic phase; Performing multi-stage reverse cross-flow extraction on the succinic acid-loaded organic phase with a stripping agent to obtain an aqueous succinic acid solution; Concentrating and crystallizing the aqueous succinic acid solution to obtain the bio-based succinic acid.

6. The preparation method according to claim 5, characterized in that, The extractant comprises a combination of a phosphoric acid ester complexing agent and a co-solvent; Preferably, the phosphoric acid ester complexing agent comprises any one or a combination of at least two of diisooctyl phosphate, dimethylheptyl methylphosphonate, and mono(2-ethylhexyl) 2-ethylhexyl phosphate; Preferably, the co-solvent comprises an alcohol solvent, and more preferably any one or a combination of at least two of n-heptanol, isooctanol, n-nonanol, and n-decanol; Preferably, the volume ratio of the phosphoric acid ester complexing agent to the co-solvent is 1:(0.1 - 10); Preferably, the volume ratio of the extractant to the permeate is (3 - 5):1; Preferably, the number of stages of the multi-stage forward cross-flow extraction is 2 - 3 stages; Preferably, the temperature of the multi-stage forward cross-flow extraction is 20 - 60 °C; Preferably, the number of stages of the multi-stage reverse cross-flow extraction is 2 - 5 stages; Preferably, the stripping agent for the first-stage reverse cross-flow extraction is water, and the stripping agents for the 2 - nth stage reverse cross-flow extraction are alkaline salt aqueous solutions; n represents an integer from 2 to 5; Preferably, the alkaline salt comprises any one or a combination of at least two of sodium carbonate, potassium carbonate, sodium bicarbonate, and potassium bicarbonate; Preferably, the mass percentage content of the alkaline salt in the alkaline salt aqueous solution is 5% - 10%; Preferably, the volume ratio of the stripping agent to the succinic acid-loaded organic phase is (3 - 5):1; Preferably, the temperature of the multi-stage counter-current extraction is 40 - 80 °C.

7. The preparation method according to claim 4, wherein The molar ratio of the bio-based succinic acid to the bio-based 1,4-butanediol is 1:(1.2 - 1.6); Preferably, the temperature of the esterification reaction is 150 - 170 °C, and the time is 2 - 4 h.

8. The preparation method according to claim 4, characterized in that, The catalyst includes any one or a combination of at least two of tetramethyl titanate, tetraethyl titanate, tetraisopropyl titanate, tetrabutyl titanate, and triisooctyl titanate; Preferably, based on the total mass of the bio-based succinic acid and the bio-based 1,4-butanediol being 100%, the dosage of the catalyst is such that the mass content of Ti element is 50 - 200 ppm; Preferably, the branching agent includes any one or a combination of at least two of glycerol, trimethylolpropane, pentaerythritol, and dipentaerythritol; Preferably, based on the total mass of the bio-based succinic acid and the bio-based 1,4-butanediol being 100%, the dosage of the branching agent is such that the mass content of its hydroxyl group is 200 - 1000 ppm; Preferably, the polycondensation reaction is carried out in the presence of a heat stabilizer; Preferably, the heat stabilizer includes any one or a combination of at least two of trimethyl phosphate, triethyl phosphate, isopropyl phosphate, n-butyl phosphate, isooctyl phosphate, and triphenyl phosphate; Preferably, based on the total mass of the bio-based succinic acid and the bio-based 1,4-butanediol being 100%, the dosage of the heat stabilizer is such that the mass content of P element in the heat stabilizer is 5 - 100 ppm.

9. The preparation method according to claim 4, characterized in that The polycondensation reaction includes a prepolymerization reaction and a final polymerization reaction carried out in sequence; Preferably, the temperature of the prepolymerization reaction is 180 - 240 °C, the pressure is 1 - 5 kPa, and the time is 1 - 3 h; Preferably, the temperature of the final polymerization reaction is 220 - 260 °C, the pressure is 20 - 100 Pa, and the time is 2 - 6 h.

10. Use of a fully bio-based polybutylene succinate according to any one of claims 1 - 3 in packaging materials, food contact materials, or agricultural films.

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