A biobased succinic acid composition, a preparation method thereof, and a polyester prepared therefrom

Abstract

The present invention provides a bio-based succinic acid composition, a preparation method thereof, and a polyester prepared therefrom. The bio-based succinic acid composition includes bio-based succinic acid and metal ions; the mass content of metal ions in the bio-based succinic acid composition is 10 to 350 ppm. In the present invention, a bio-based succinic acid composition containing metal ions is used as a polyester raw material, and the content of metal ions in the bio-based succinic acid composition is controlled within a specific range, so that the mechanical properties and thermal retention stability of the obtained polyester are better.

Description

Technical Field

[0001] The present invention belongs to the technical field of polyester preparation, and particularly relates to a bio-based succinic acid composition, a preparation method thereof, and a polyester prepared therefrom. Background Art

[0002] Succinic acid (also known as amber acid), as a C4 compound, is widely used in industries such as medicine, pesticides, dyes, spices, paints, food, and plastics, and can also be used to synthesize organic chemicals such as 1,4-butanediol, tetrahydrofuran, γ-butyrolactone, and biodegradable materials such as polybutylene succinate (PBS), having good biological application prospects. Compared with the production of succinic acid using petroleum resources as raw materials, the production of succinic acid using biomass resources as raw materials has the advantages of renewable raw materials, low cost, less pollution, and the ability to solve environmental problems (such as the greenhouse effect), and has become a research hotspot in recent years.

[0003] The production of succinic acid using biomass resources as raw materials mostly adopts the fermentation method. For example, succinic acid is synthesized by means of microbial conversion or a combination of microbial conversion and chemical conversion methods. In microbial conversion, a decrease in pH will lead to a decrease in the metabolic activity of microorganisms and even stop their activities, resulting in a deterioration of the manufacturing yield. Therefore, a neutralizing agent is usually used to regulate the pH of the fermentation system. Then, the neutralized succinic acid fermentation broth is purified to obtain a succinic acid product with a purity greater than 99%. However, the obtained high-purity succinic acid product will also contain nitrogen elements contained in biomass resources, nitrogen elements from microorganisms or enzymes, or ammonia used in the purification process, sulfur elements, inorganic acids, organic acids, metal cations, etc.; and the aforementioned neutralizing agents include ammonia, ammonium carbonate, urea, hydroxides of alkali (earth) metals (such as NaOH, KOH, Ca(OH)2, Mg(OH)2, etc.), carbonates of alkali (earth) metals (such as Na2CO3, K2CO3, CaCO3, MgCO3), etc., which will further cause residues of nitrogen elements and metal ions in succinic acid.

[0004] When the content of metal cations in succinic acid exceeds 600 ppm, the reaction activity of succinic acid will be weakened, the product quality of the obtained polyester will deteriorate, and the thermal stability of the polyester will be poor. Especially in the case of long-term heat retention, the polyester will undergo thermal decomposition in processing equipment such as extruders or injection molding machines, resulting in a sharp decline in the performance of the molded product.

[0005] Therefore, developing a bio-based succinic acid composition that can improve the thermal stability of polyester and enable the polyester to still have a high tensile strength retention rate under long-term heat retention is an urgent problem to be solved in the field. Summary of the Invention

[0006] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a biobased succinic acid composition, a preparation method thereof, and a polyester prepared therefrom, which are used to solve the problem of poor thermal retention stability of the polyester prepared from biobased succinic acid in the existing technology.

[0007] To achieve this purpose, the present invention adopts the following technical solutions:

[0008] In the first aspect, the present invention provides a biobased succinic acid composition, which includes biobased succinic acid and metal ions; the mass content of metal ions in the biobased succinic acid composition is 10 - 350 ppm.

[0009] In the present invention, using biobased succinic acid containing metal ions as raw materials and controlling the content of metal ions in the biobased succinic acid composition within a specific range, the prepared polyester has better mechanical properties and thermal retention stability under the same reaction conditions, and a low melt index.

[0010] In the present invention, the mass content of metal ions in the biobased succinic acid composition is 10 - 350 ppm, for example, it can be 10 ppm, 20 ppm, 30 ppm, 40 ppm, 50 ppm, 60 ppm, 70 ppm, 80 ppm, 90 ppm, 100 ppm, 110 ppm, 120 ppm, 130 ppm, 140 ppm, 150 ppm, 160 ppm, 170 ppm, 180 ppm, 190 ppm, 200 ppm, 210 ppm, 220 ppm, 230 ppm, 240 ppm, 250 ppm, 260 ppm, 270 ppm, 280 ppm, 290 ppm, 300 ppm, 310 ppm, 320 ppm, 330 ppm, 340 ppm, 350 ppm or the range between any of the above values.

[0011] Preferably, the mass content of metal ions in the biobased succinic acid composition is 20 - 280 ppm, and more preferably 60 - 200 ppm.

[0012] In the present invention, when the mass content of metal ions is within the above range, the mechanical properties and thermal retention stability of the obtained polyester are better; if the metal ion content is too high, it will affect the reaction activity of succinic acid, thereby affecting the polyester properties; and obtaining biobased succinic acid with a low metal ion content is what those skilled in the art pursue. To achieve a very low (<10 ppm) metal ion content, multiple purifications and expensive purification equipment need to be invested, which is economically disadvantageous; while the biobased succinic acid composition provided by the present invention can not only not significantly increase the cost, but also obtain high-performance polyester materials.

[0013] Preferably, the metal ions include Na + , K + , Mg 2+ , Ca 2+ or a combination of any one or at least two of them.

[0014] In the present invention, the metal ions may be the metal ions remaining in the process of preparing bio - based succinic acid using biomass resources as raw materials, or metal - ion - containing compounds may be additionally added as needed.

[0015] In the present invention, when the metal ions are the metal ions remaining in the process of preparing bio - based succinic acid using biomass resources as raw materials, the content of metal ions in succinic acid can be reduced through post - treatment, so that the content of metal ions in the final bio - based succinic acid composition is within a specific range; the methods of the post - treatment include extraction and adsorption by a cation - exchange resin column.

[0016] Preferably, the metal ions include Na + , K + , Mg 2+ and Ca 2+ .

[0017] Preferably, the mass content of Na + or K + in the bio - based succinic acid composition is ≤60 ppm, for example, it can be 5 ppm, 10 ppm, 15 ppm, 20 ppm, 25 ppm, 30 ppm, 35 ppm, 40 ppm, 45 ppm, 50 ppm, 55 ppm, 60 ppm or the range between any of the above values; more preferably, it is 2 - 50 ppm, and even more preferably, it is 5 - 30 ppm.

[0018] Preferably, the mass content of Mg 2+ in the bio - based succinic acid composition is ≤50 ppm, for example, it can be 5 ppm, 10 ppm, 15 ppm, 20 ppm, 25 ppm, 30 ppm, 35 ppm, 40 ppm, 45 ppm, 50 ppm or the range between any of the above values; more preferably, it is 5 - 40 ppm, and even more preferably, it is 10 - 30 ppm.

[0019] Preferably, the mass content of Ca 2+The mass content is ≤ 220 ppm, and for example, it can be 10 ppm, 20 ppm, 30 ppm, 40 ppm, 50 ppm, 60 ppm, 70 ppm, 80 ppm, 90 ppm, 100 ppm, 110 ppm, 120 ppm, 130 ppm, 140 ppm, 150 ppm, 160 ppm, 170 ppm, 180 ppm, 190 ppm, 200 ppm, 210 ppm, 220 ppm or a range between any of the above values; it is further preferably 20 - 170 ppm, and more preferably 70 - 130 ppm.

[0020] Preferably, under the conditions of a temperature of 25°C and a concentration of 0.1 mol / L, the pH value of the aqueous solution of the biobased succinic acid composition is ≤ 2.8, and for example, it can be 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.8, 2, 2.1, 2.2, 2.3, 2.4, 2.5 or a range between any of the above values; more preferably, the pH value is ≤ 2.6, and particularly preferably ≤ 2.4.

[0021] Generally, under the conditions of 25°C and a concentration of 0.1 mol / L, the pH value of succinic acid is 2.7. When succinic acid reacts with butanediol to synthesize aliphatic polyesters, the lower the pH value of the system, the more beneficial it is to improve the reaction activity, increase the reaction efficiency and reaction degree, thereby shortening the polymerization residence time and obtaining aliphatic polyesters with better quality indicators such as acid value and color value and better thermal stability; in the present invention, when using a neutralizing agent to regulate the pH of the fermentation system, the pH value of the aqueous solution of the biobased succinic acid composition can be reduced by regulating the addition amount of the neutralizing agent. Using the biobased succinic acid composition with such a low pH value as a raw material, polyesters with better performance can be prepared; preferably, the pH value of the aqueous solution of the biobased succinic acid composition is 2.6 or less.

[0022] In a second aspect, the present invention provides a preparation method of the biobased succinic acid composition according to the first aspect, and the preparation method includes the following steps:

[0023] (1) Using biomass resources as raw materials to prepare succinic acid stock solution;

[0024] (2) Purifying the succinic acid stock solution obtained in step (1) to obtain the biobased succinic acid composition; the purification method includes an extraction method and a cation exchange resin column adsorption method.

[0025] In the present invention, in the preparation method, through extraction and cation exchange resin column for purification, a biobased succinic acid composition with high purity and low metal ion content can be obtained.

[0026] Preferably, the content of succinic acid in the stock solution of succinic acid is 70-95 g / L, for example, it can be 70 g / L, 72 g / L, 75 g / L, 78 g / L, 80 g / L, 82 g / L, 85 g / L, 88 g / L, 90 g / L, 92 g / L, 95 g / L or the range between any of the above values.

[0027] Preferably, the extraction method includes forward cross-flow extraction and reverse cross-flow extraction.

[0028] Preferably, the extractant for the forward cross-flow extraction includes phosphate ester extractants.

[0029] Preferably, the phosphate ester extractants include at least one of diisooctyl phosphate, diethyl phosphate or triethyl phosphate.

[0030] In the present invention, based on the volume of the stock solution of succinic acid being 1 L, the mass of the extractant for the forward cross-flow extraction is 20-55 g, for example, it can be 20 g, 22 g, 24 g, 26 g, 28 g, 30 g, 32 g, 34 g, 36 g, 38 g, 40 g, 42 g, 44 g, 46 g, 48 g, 50 g, 52 g, 54 g, 55 g or the range between any of the above values, more preferably 25-45 g, and particularly preferably 30-40 g.

[0031] Preferably, the extractant for the reverse cross-flow extraction is water.

[0032] In the present invention, based on the volume of the solution containing succinic acid obtained by the forward cross-flow extraction being 1 L, the mass of the extractant for the reverse cross-flow extraction is 30-95 g, for example, it can be 30 g, 32 g, 35 g, 38 g, 40 g, 42 g, 45 g, 48 g, 50 g, 52 g, 55 g, 58 g, 60 g, 62 g, 65 g, 68 g, 70 g, 72 g, 75 g, 78 g, 80 g, 82 g, 85 g, 88 g, 90 g, 92 g, 95 g or the range between any of the above values, more preferably 40-75 g, and particularly preferably 50-70 g.

[0033] In the present invention, the number of times of the forward cross-flow extraction and the reverse cross-flow extraction are each independently ≥1 time, for example, it can be 1 time, 2 times, 3 times, 4 times, 5 times, 6 times, 7 times, 8 times or the range between any of the above values.

[0034] Preferably, the cation exchange resin column can adsorb Na + , K + , Mg 2+ , Ca2+ at least one of

[0035] In the present invention, the cation exchange resin is a 732-type cation exchange resin; the cation exchange resin includes, but is not limited to: Amberlite IR-120, Dowex-50; Germany: Lewatit-100; Japan: Diaion SK-1.

[0036] Preferably, the flow rate of the column loading in the cation exchange resin column adsorption method is 0.5 - 2.8 BV / h, for example, it can be 0.5 BV / h, 0.6 BV / h, 0.8 BV / h, 1 BV / h, 1.1 BV / h, 1.2 BV / h, 1.3 BV / h, 1.4 BV / h, 1.5 BV / h, 1.6 BV / h, 1.7 BV / h, 1.8 BV / h, 1.9 BV / h, 2 BV / h, 2.1 BV / h, 2.2 BV / h, 2.3 BV / h, 2.4 BV / h, 2.5 BV / h, 2.6 BV / h, 2.7 BV / h, 2.8 BV / h or the range between any of the above values; more preferably 0.8 - 2 BV / h, and even more preferably 1 - 1.3 BV / h.

[0037] In the present invention, in the cation exchange resin column adsorption method, after passing through the cation exchange resin column, it further includes a step of eluting with water.

[0038] Preferably, the mass of the water is 2 - 7 times the mass of the solution to be eluted, for example, it can be 2 times, 3 times, 4 times, 5 times, 6 times, 7 times or the range between any of the above values.

[0039] In the present invention, the solution to be eluted refers to the solution containing succinic acid before passing through the cation exchange resin.

[0040] Preferably, the biomass resources include plant resources and / or animal resources, and are preferably plant resources.

[0041] In the present invention, the plant resources refer to biomass resources that can convert the solar energy into forms such as starch or cellulose through photosynthesis and store it; the animal resources refer to biomass resources that grow and develop by preying on plants; the plant resources or animal resources also include products obtained by processing plant resources or animal resources.

[0042] In the present invention, by way of example, the plant resources include, but are not limited to, wood, rice straw, rice husk, rice bran, old rice, corn, sugarcane, cassava, corn cobs, cassava starch residue, bagasse, vegetable oil residue, buckwheat, soybeans, food waste, etc.

[0043] In the present invention, the preparation method further includes converting the biomass resource into a carbon source, and then preparing succinic acid stock solution using the carbon source as a raw material; the method for converting into a carbon source includes, but is not limited to, chemical treatment, physical treatment, biological treatment, etc.; exemplarily, the chemical treatment can employ acid treatment (such as treatment with strong acids like sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, etc.), alkali treatment, ammonia freezing and steam explosion treatment, solvent extraction treatment, supercritical fluid treatment, oxidant treatment, etc.; the physical treatment can be crushing treatment, steam explosion treatment, microwave treatment, electron beam irradiation treatment, etc.; the biological treatment can be microbial treatment, enzyme treatment, etc.

[0044] In the present invention, the carbon source exemplarily includes, but is not limited to, hexoses such as glucose, mannose, galactose, fructose, sorbose, tagatose, etc.; pentoses such as arabinose, xylose, ribose, xylulose, ribulose, etc.; disaccharides or polysaccharides such as pentosan, sucrose, starch, cellulose, etc., preferably glucose, fructose, xylose, and particularly preferably glucose.

[0045] Preferably, the method for preparing the succinic acid stock solution in step (1) includes microbial fermentation method and / or chemical conversion method, and preferably the microbial fermentation method.

[0046] In the present invention, the microorganism used in the microbial fermentation method only needs to be able to produce dicarboxylic acid, and exemplarily includes: anaerobic bacteria, facultative anaerobic bacteria, aerobic bacteria, etc.; the anaerobic bacteria can be, for example, Anaerobiospirillum genus (US5143833A); the facultative anaerobic bacteria can be, for example, Actinobacillus genus (US5504004A), Escherichia genus (US5770435A), etc.; the aerobic bacteria can be, for example, Corynebacterium genus (Japanese Patent Laid-Open No. 11-113588 or CN103183813A), and these documents are hereby incorporated by reference; preferably aerobic bacteria such as Corynebacterium genus are used.

[0047] As coryneform bacteria, microorganisms belonging to the genus Corynebacterium, the genus Brevibacterium, or the genus Arthrobacter can be mentioned. Among them, preferred microorganisms can be microorganisms belonging to the genus Corynebacterium or the genus Brevibacterium, and more preferred microorganisms can be microorganisms belonging to Corynebacterium glutamicum, Brevibacterium flavum, Brevibacterium ammoniagenes, or Brevibacterium lactofermentum.

[0048] In microbial conversion, when the pH decreases, the metabolic activity of the microorganisms decreases or the activity stops, resulting in deterioration of the production rate or death of the microorganisms. Therefore, a neutralizing agent is usually used to regulate the pH of the fermentation system. Generally, the pH in the reaction system is measured by a pH sensor, and then the pH is adjusted to a specified pH range by adding a neutralizing agent. The method of adding the neutralizing agent is not particularly limited and can be added continuously or intermittently. The pH value can be adjusted to the range where the activity of the microorganisms such as the bacteria and fungi used can be most effectively exerted. The pH value is usually 4 to 10, preferably 6 to 9.

[0049] Examples of the neutralizing agent include ammonia, ammonium carbonate, urea, hydroxides of alkali metals, hydroxides of alkaline earth metals, carbonates of alkali metals, and carbonates of alkaline earth metals; ammonia, ammonium carbonate, and urea are preferred. In addition, examples of the hydroxides of the above-mentioned alkali (earth) metals include NaOH, KOH, Ca(OH)2, Mg(OH)2, or a mixture thereof, and examples of the carbonates of the alkali (earth) metals include Na2CO3, K2CO3, CaCO3, MgCO3, or a mixture thereof.

[0050] In the present invention, in step (1), using a biomass resource as a raw material, the succinic acid stock solution can be prepared by a conventional method in the art. For example, it can be prepared by referring to the method in CN118459331A.

[0051] Preferably, the purification method further includes decolorization with activated carbon and / or filtration.

[0052] Preferably, in the decolorization with activated carbon, based on the volume of the solution to be decolorized being 1 L, the mass of the activated carbon is 0.5 to 10 g, for example, it can be 0.5 g, 1 g, 2 g, 3 g, 4 g, 5 g, 5.2 g, 5.5 g, 5.8 g, 6 g, 6.2 g, 6.5 g, 6.8 g, 7 g, 7.2 g, 7.5 g, 7.8 g, 8 g, 8.5 g, 9 g, 9.5 g, 10 g, or a range between any of the above values.

[0053] In the present invention, the solution to be decolorized can be a succinic acid stock solution or a solution after other purification treatments, such as a solution after at least one purification treatment such as extraction, adsorption on a cation exchange resin column, and filtration of the succinic acid stock solution.

[0054] Preferably, the temperature for the decolorization with activated carbon is 60 to 85 °C, and the time is 30 to 65 min.

[0055] In the present invention, the filtration includes filtration using an ultrafiltration membrane; the pore size of the ultrafiltration membrane is 20 - 80 nm, for example, it can be 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm or 80 nm, or the range between any of the above values.

[0056] Preferably, the temperature of the filtration is 40 - 60 °C, for example, it can be 40 °C, 42 °C, 44 °C, 46 °C, 48 °C, 50 °C, 52 °C, 54 °C, 56 °C, 58 °C or 60 °C, or the range between any of the above values.

[0057] Preferably, after the purification, it further includes the steps of vacuum distillation and / or cooling crystallization.

[0058] In the present invention, the temperature of the vacuum distillation is 65 - 75 °C, the pressure is -0.07 - -0.1 MPa, and when the content of succinic acid is greater than 15 wt%, the distillation is stopped; the concentrated succinic acid solution is placed at a low temperature (≤8 °C) for cooling crystallization to obtain the bio - based succinic acid composition.

[0059] As a preferred technical solution of the present invention, the preparation method includes the following steps:

[0060] (1) Using biomass resources as raw materials, preparing a succinic acid stock solution with a succinic acid content of 70 - 95 g / L;

[0061] (2) Subjecting the succinic acid stock solution obtained in step (1) to forward cross - flow extraction using a phosphoric acid ester extractant to obtain a succinic acid - loaded organic phase; then, subjecting the succinic acid - loaded organic phase to reverse cross - flow extraction with water to obtain a succinic acid aqueous solution; based on the volume of the succinic acid stock solution being 1 L, the mass of the phosphoric acid ester extractant is 20 - 55 g; based on the volume of the succinic acid - loaded organic phase being 1 L, the mass of water is 30 - 95 g; the number of times of forward cross - flow extraction and reverse cross - flow extraction are each independently ≥1 time;

[0062] (3) Passing the succinic acid aqueous solution obtained in step (2) through a cation exchange resin column at a flow rate of 0.5 - 2.8 BV / h, and eluting with water having a mass 2 - 7 times that of the succinic acid aqueous solution to obtain a succinic acid effluent; the elution is carried out with water having a mass 2 - 7 times that of the succinic acid aqueous solution.

[0063] (4) The succinic acid effluent obtained in step (3) is successively subjected to decolorization with activated carbon and filtration to obtain a succinic acid filtrate; based on the volume of the succinic acid effluent being 1 L, the mass of the activated carbon is 0.5 - 10 g; the temperature for decolorization with activated carbon is 60 - 85°C, and the time is 30 - 65 min; the filtration is carried out using an ultrafiltration membrane, and the temperature for filtration is 30 - 60°C;

[0064] (5) The succinic acid filtrate obtained in step (4) is subjected to vacuum distillation and cooling crystallization to obtain the bio - based succinic acid composition.

[0065] In the present invention, the purification method further includes the calcium salt method, the electrodialysis method, etc.

[0066] In the third aspect, the present invention provides a polyester, and the raw materials for preparing the polyester include the bio - based succinic acid composition described in the first aspect.

[0067] The polyester produced using the specific bio - based succinic acid composition of the present invention as a raw material has a shorter residence time.

[0068] Preferably, the polyester comprises the following components:

[0069] Component A:

[0070] Based on the total molar amount of component A being 100 mol%, a dicarboxylic acid compound comprising the following components:

[0071] a1, 65 - 100 mol% of bio - based succinic acid and / or its ester derivatives;

[0072] a2, 0 - 35 mol% of adipic acid and / or its ester derivatives;

[0073] And component B: 1,4 - butanediol in at least an equimolar amount to component A; the bio - based succinic acid is the bio - based succinic acid composition described in the first aspect.

[0074] In the present invention, the molar ratio of component B to component A is (1 - 3):1, for example, it can be 1:1, 1.2:1, 1.5:1, 1.8:1, 2:1, 2.2:1, 2.5:1, 2.8:1, 3:1 or a range between any of the above values, and more preferably (1 - 2):1.

[0075] In the present invention, the polyester comprising the following components means that the molecular structure of the polyester contains structural units derived from component A and structural units derived from component B; the dicarboxylic acid compound comprising the following components means that in the molecular structure of the polyester, the dicarboxylic acid structural unit part contains structural units derived from component a1 and structural units derived from component a2.

[0076] In the present invention, it is 65 to 100 mol%, for example, it can be 65 mol%, 66 mol%, 68 mol%, 70 mol%, 72 mol%, 74 mol%, 76 mol%, 78 mol%, 80 mol%, 82 mol%, 84 mol%, 86 mol%, 88 mol%, 90 mol%, 92 mol%, 94 mol%, 96 mol%, 98 mol%, 100 mol% or a range between any of the above values.

[0077] In the present invention, it is 0 to 35 mol%, for example, it can be 0 mol%, 2 mol%, 4 mol%, 6 mol%, 8 mol%, 10 mol%, 12 mol%, 14 mol%, 16 mol%, 18 mol%, 20 mol%, 22 mol%, 24 mol%, 26 mol%, 28 mol%, 30 mol%, 32 mol%, 34 mol%, 35 mol% or a range between any of the above values.

[0078] Preferably, based on the total molar amount of component A being 100 mol%, a dicarboxylic acid compound comprising the following components:

[0079] a1, 72 to 82 mol% of a biobased succinic acid and / or an ester derivative thereof;

[0080] a2, 18 to 28 mol% of adipic acid and / or an ester derivative thereof.

[0081] In the present invention, the ester derivative of succinic acid includes alkyl succinates. Exemplarily, the alkyl succinate can be at least one of dimethyl succinate, diethyl succinate, di-n-propyl succinate, di-isopropyl succinate, di-n-butyl succinate, di-isobutyl succinate, di-tert-butyl succinate, di-n-pentyl succinate, di-isopentyl succinate, di-n-hexyl succinate; the alkyl succinate can be an alkyl ester formed from succinic acid or an alkyl ester formed from succinic anhydride. Preferably, dimethyl succinate formed from succinic anhydride is used.

[0082] In the present invention, the ester derivative of adipic acid includes alkyl adipates. Exemplarily, the alkyl adipate can be at least one of dimethyl adipate, diethyl adipate, di-n-propyl adipate, di-isopropyl adipate, di-n-butyl adipate, di-isobutyl adipate, di-tert-butyl adipate, di-n-pentyl adipate, di-isopentyl adipate, di-n-hexyl adipate; the alkyl adipate can be an alkyl ester formed from adipic acid or an alkyl ester formed from adipic anhydride.

[0083] In the present invention, the derivative of dicarboxylic acid or its ester can be used alone or in the form of a mixture of two or more kinds.

[0084] In the present invention, according to Standard ISO 1133-2-2012, at 190 °C and 2.16 kg, the melt index of the polyester ≤ 8.0 g / 10 min, and more preferably the melt index is 3-7.0 g / 10 min.

[0085] Preferably, the initial tensile strength of the polyester ≥ 22 MPa, and more preferably the initial tensile strength ≥ 37 MPa.

[0086] Preferably, under the condition of heat retention at 180 °C for 10 min, the tensile strength retention rate of the polyester > 70%, more preferably the tensile strength retention rate > 82%, and particularly preferably the tensile strength retention rate > 86%.

[0087] In the present invention, the polyester can be prepared by conventional technical methods in the art. Exemplarily, the method includes the following steps:

[0088] Esterify component A and component B at a temperature of 140-220 °C and a pressure of 0.5-2 bar for 1-6 h to obtain an esterification product; subject the esterification product to a pre-polycondensation reaction at a temperature of 220-270 °C and a pressure of 0.1-1 bar for 40-120 min to obtain a pre-polycondensation product; then subject the pre-polycondensation product to a polycondensation reaction at a temperature of 230-280 °C and a pressure of 1-5 mbar for 120-180 min, slice and dry to obtain the polyester.

[0089] In the present invention, the raw materials for the esterification reaction further include a crosslinking agent, and the crosslinking agent includes at least one of tartaric acid, citric acid, malic acid, trimethylolpropane, trimethylolethane, pentaerythritol, polyether triol, glycerol, 1,3,5-benzenetricarboxylic acid, 1,2,4-benzenetricarboxylic acid, 1,2,4-benzenetricarboxylic anhydride, 1,2,4,5-benzenetetracarboxylic acid or pyromellitic dianhydride; based on the mass of the polyester finished product being 100 wt%, the mass percentage content of the crosslinking agent is 0.05-1 wt%.

[0090] In the present invention, a catalyst is also included in the pre-polycondensation reaction; the catalyst can be a tin compound, an antimony compound, a cobalt compound, a lead compound, a zinc compound, an aluminum compound or a titanium compound, more preferably a zinc compound, an aluminum compound or a titanium compound, and most preferably a titanium compound; the titanium compound can be tetrabutyl titanate or tetraisopropyl titanate; the total mass of the catalyst is 0.001-1 wt% of the mass of the polycondensation product.

[0091] The polyester described in the present invention also has biodegradability.

[0092] For the purposes of the present invention, a substance or a mixture of substances is characterized as "biodegradable" if it shows a percentage degree of biodegradation, as defined in DIN EN 13432, of at least 90%.

[0093] Biodegradation generally results in the breakdown of the polyester or polyester blend within a reasonable period of time. Degradation can occur via enzymatic, hydrolytic or oxidative pathways and / or, by exposure to electromagnetic radiation such as ultraviolet radiation, most often by exposure to microorganisms such as bacteria, yeasts, fungi or algae. Biodegradability can be quantified by mixing the polyester with compost and storing it for a specific period of time. For example, according to DIN EN 13432, during the composting process, CO2-free air is introduced into the mature compost and the compost is subjected to a specific temperature course. Here, biodegradability is defined as the percentage degree of biodegradation expressed as the ratio of the net amount of CO2 released by the sample (after deducting the amount of CO2 released by the compost without the sample) to the maximum amount of CO2 that the sample could release (calculated based on the carbon content of the sample).

[0094] Additionally, other methods for determining biodegradability are described in ASTM D5338 and ASTM D6400.

[0095] The numerical range described in the present invention not only includes the point values listed above, but also includes any point values between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values included in the range.

[0096] Compared with the prior art, the present invention has the following beneficial effects:

[0097] The bio-based succinic acid composition provided by the present invention contains a specific content of metal ions, so that the polyester prepared using the bio-based succinic acid composition as a raw material has better mechanical properties and thermal stability, still has a high strength retention rate after being treated at high temperature for a period of time, and has low cost. DETAILED DESCRIPTION

[0098] 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.

[0099] If not otherwise specified, the raw materials used in the present invention are as follows:

[0100] 1,4-Butanediol: purchased from Xinjiang Meike Chemical Co., Ltd., with a purity of 99.7%;

[0101] Glycerin: Purchased from Aladdin;

[0102] Adipic acid: Purchased from Chongqing Huafeng Chemical Co., Ltd.;

[0103] Tetrabutyl titanate: Purchased from Jianyi Chemical Import and Export Co., Ltd.;

[0104] 732 cation exchange resin: Purchased from Tianjin Xijinna Environmental Protection Materials Technology Co., Ltd.

[0105] In the present invention, in the preparation method, the concentration of succinic acid in the obtained succinic acid stock solution, succinic acid aqueous solution, and succinic acid filtrate is tested by liquid chromatography, and the specific test method refers to the method disclosed in CN118459331A.

[0106] Example 1

[0107] This example provides a bio-based succinic acid composition, including bio-based succinic acid and metal ions; the content of the bio-based succinic acid, the composition and content of the metal ions are shown in Table 1, and the balance in the composition is water and other impurity acids remaining in the process of preparing the succinic acid composition.

[0108] This example provides a preparation method of a bio-based succinic acid composition, specifically including the following steps:

[0109] (1) Using biomass resources as raw materials, a succinic acid stock solution with a succinic acid content of 78 g / L is prepared. The specific preparation method can be carried out by conventional methods in the art. For example, it can be prepared with reference to the method in CN118459331A;

[0110] (2) After filtering the succinic acid stock solution obtained in step (1), taking the volume of the succinic acid stock solution as 1 L, adding 32 g of diisooctyl phosphate for 5-stage forward cross-flow extraction to obtain a succinic acid-loaded organic phase; then, taking the volume of the succinic acid-loaded organic phase as 1 L, using 65 g of deionized water for 5-stage reverse cross-flow extraction of the succinic acid-loaded organic phase to obtain a succinic acid aqueous solution;

[0111] (3) Pass the succinic acid aqueous solution obtained in step (2) through a cation exchange resin column at a flow rate of 1 BV / h, and elute with water with a mass 6 times that of the succinic acid aqueous solution to obtain a succinic acid effluent;

[0112] (4) Decolorize the succinic acid effluent obtained in step (3) with activated carbon at 75°C for 60 min. Taking the volume of the succinic acid effluent as 1 L, the mass of the activated carbon is 8 g (i.e., the mass of the activated carbon is 8 g / L); then filter at 50°C using an ultrafiltration membrane with a pore size of 40 nm to obtain a succinic acid filtrate;

[0113] (5) Subject the succinic acid filtrate obtained in step (4) to vacuum distillation, with the distillation temperature controlled at 70 °C and the pressure at -0.07 to -0.1 MPa. Stop distillation when the content of succinic acid is greater than 15 wt%. Place the concentrated succinic acid solution at a low temperature (4 °C) for cooling crystallization to obtain white succinic acid crystals, thus obtaining the bio-based succinic acid composition.

[0114] Examples 2 to 6, Comparative Examples 1 to 6

[0115] Examples 2 to 6 and Comparative Examples 1 to 6 respectively provide a bio-based succinic acid composition, whose composition and process parameters are shown in Tables 1 and 2. Among them, in the preparation method, steps (1) and (5) are the same as those in Example 1; the values corresponding to the types of the forward extractant in step (2) in Tables 1 and 2 are the mass (unit: g) of the forward extractant based on 1 L of the volume of the succinic acid stock solution; the value corresponding to deionized water is the mass (unit: g) of deionized water based on 1 L of the volume of the succinic acid-loaded organic phase; the amount of water used for elution in step (3) is the mass multiple of the succinic acid aqueous solution.

[0116] Among them, in Tables 1 and 2, " / " indicates that the component is not contained or the step is not carried out.

[0117] Example 7

[0118] This example provides a bio-based succinic acid composition, whose composition is shown in Table 1; the difference between the preparation method and that of Example 1 is only that the succinic acid stock solution is an aqueous solution of the bio-based succinic acid composition provided by Comparative Example 1 with an equal volume, and the other step parameters are the same as those in Example 1.

[0119] In the present invention, the pH value of the bio-based succinic acid composition is determined by the following method: Weigh 1.1800 ± 0.0020 g of the bio-based succinic acid composition, add it to 80 mL of deionized water, stir until completely dissolved, transfer it to a 100 mL volumetric flask, add deionized water to the calibration line of the volumetric flask to obtain a 0.1 mol / L bio-based succinic acid composition solution, measure the pH value of the bio-based succinic acid composition solution using a pH meter, perform parallel tests twice, take the average value, and retain three decimal places.

[0120] The content test of metal cations in the succinic acid composition refers to US EPA Method 3052:1996 and is analyzed by ICP-OES. It is measured according to the following procedure: Weigh about 0.1 g of the bio-based succinic acid composition, add 5 mL of nitric acid to completely immerse the bio-based succinic acid composition, then drop in 1.0 mL of hydrogen peroxide and react for 2 min. Seal it in a microwave digestion tank and digest it at 210 °C for 3 hours. After cooling to room temperature, filter it using a 0.45 μm filter membrane and dilute it to 50 mL with distilled water, and then test it by ICP-OES.

[0121] In the present invention, the test of the mass of biobased succinic acid in the biobased succinic acid composition is carried out with reference to the method for the determination of succinic acid content in Part 4.3 of GB / T 34686-2017.

[0122] Table 1

[0123]

[0124] Table 2

[0125]

[0126] ND represents that the content of the relevant element is not detected.

[0127] Application Example 1

[0128] This application example provides a polyester. The raw materials for preparing the polyester include 350 kg of 1,4-butanediol, 327 kg of succinic acid, 1.8 kg of glycerol and 0.38 kg of tetrabutyl titanate; the succinic acid is the biobased succinic acid composition provided in Example 1.

[0129] The method for preparing the polyester includes the following steps:

[0130] S1: Physically mix succinic acid, 1,4-butanediol and glycerol. After the mixing is completed, transfer the obtained mixture to an esterification reactor, and carry out an esterification reaction at a temperature of 170°C and a pressure of 1.0 bar for 4 h to obtain an esterification product;

[0131] S2: Transfer the esterification product obtained in step S1 to a vertical reactor with stirring, add 0.38 kg of tetrabutyl titanate, and carry out a pre-polycondensation reaction on the reaction mixture at 250°C and a reactor internal pressure of 0.3 bar for 70 min to obtain a pre-polycondensation product;

[0132] S3: Transfer the prepolymer product obtained in step S2 to a horizontal reactor with stirring, and carry out a polycondensation reaction at a temperature of 253°C and a pressure of 2.5 mbar for 160 min, slice and dry to obtain the polyester.

[0133] Application Examples 2-7

[0134] Application Examples 2-7 respectively provide a polyester, the difference from Application Example 1 is only that the succinic acid is the biobased succinic acid composition provided in Examples 2-7 respectively, and other raw materials, dosages and preparation methods are the same as those in Application Example 1.

[0135] Application Example 8

[0136] Application Example 8 provides a polyester, which is different from Application Example 1 in that the total molar amount of dibasic acids remains unchanged, including 75 mol% of succinic acid and 25 mol% of adipic acid. The raw materials for preparing the polyester further include 350 kg of 1,4-butanediol, 2.8 kg of glycerol, and 0.52 kg of tetrabutyl titanate. The method for preparing the polyester includes the following steps:

[0137] S1: Physically mix succinic acid, adipic acid, 1,4-butanediol, and glycerol. After mixing is completed, transfer the obtained mixture to an esterification reactor and carry out an esterification reaction at a temperature of 200 °C and a pressure of 1.5 bar for 3 h to obtain an esterification product;

[0138] S2: Transfer the esterification product obtained in step S1 to a vertical reactor with stirring, add tetrabutyl titanate, and carry out a pre-polycondensation reaction on the reaction mixture at 240 °C and a reactor internal pressure of 0.5 bar for 100 min to obtain a pre-polycondensation product;

[0139] S3: Transfer the prepolymer product obtained in step S2 to a horizontal reactor with stirring, and carry out a polycondensation reaction at a temperature of 248 °C and a pressure of 4 mbar for 130 min, slice, and dry to obtain the polyester.

[0140] Application Example 9

[0141] Application Example 9 provides a polyester, which is different from Application Example 1 in that the total molar amount of dibasic acids remains unchanged, including 66 mol% of succinic acid and 34 mol% of adipic acid. The raw materials for preparing the polyester further include 350 kg of 1,4-butanediol, 3.8 kg of glycerol, and 0.58 kg of tetrabutyl titanate. The method for preparing the polyester includes the following steps:

[0142] S1: Physically mix succinic acid, adipic acid, 1,4-butanediol, and glycerol. After mixing is completed, transfer the obtained mixture to an esterification reactor and carry out an esterification reaction at a temperature of 210 °C and a pressure of 1.8 bar for 2 h to obtain an esterification product;

[0143] S2: Transfer the esterification product obtained in step S1 to a vertical reactor with stirring, add tetrabutyl titanate, and carry out a pre-polycondensation reaction on the reaction mixture at 260 °C and a reactor internal pressure of 0.8 bar for 80 min to obtain a pre-polycondensation product;

[0144] S3: Transfer the prepolymer product obtained in step S2 to a horizontal reactor with stirring, and carry out a polycondensation reaction at a temperature of 252 °C and a pressure of 3.5 mbar for 150 min, slice, and dry to obtain the polyester.

[0145] Comparative Application Examples 1-6

[0146] Comparative Application Examples 1-6 provide a polyester, which is only different from Application Example 1 in that the succinic acid is respectively the bio-based succinic acid composition provided in Comparative Examples 1-6, and other raw materials, dosages and preparation methods are the same as those in Application Example 1.

[0147] Performance Test

[0148] (1)Melt Index: Test the melt indexes of the polyesters provided in Application Examples 1-9 and Comparative Application Examples 1-6; the test conditions are 190 °C and 2.16 kg, and the reference standard is ISO 1133-2-2012;

[0149] (2)Inject the polyesters provided in Application Examples 1-9 and Comparative Application Examples 1-6 into mechanical splines. The temperatures of the first, second, third, and fourth sections of the injection molding machine are 180 °C, 180 °C, 180 °C, and 180 °C in sequence; according to the standard ISO 527-2-2012, test the initial tensile strength (denoted as L0) of the splines and the tensile strength of the splines after being hot-retained in the injection molding machine cavity at 180 °C for 10 min and then injected into mechanical splines (denoted as L1), and calculate the tensile strength retention rate (ΔL), ΔL = L1 / L0×100%; among them, the test conditions for the tensile strength are: the ambient temperature is 23±2 °C, and the tensile rate is 50 mm / min.

[0150] The specific test results are shown in Table 3.

[0151] Table 3

[0152]

[0153] As can be seen from Table 3, using the bio-based succinic acid composition containing a specific content of metal ions provided by the present invention as a raw material, the prepared polyester has excellent mechanical properties and thermal retention stability. At the same time, the melt index is relatively low; the melt index of the polyester ≤ 8.0 g / 10 min; the initial tensile strength ≥ 22.1 MPa, and after being hot-retained at 180 °C for 10 min, the tensile strength retention rate ≥ 70.2%.

[0154] It can be seen from the comparative application examples that when the bio-based succinic acid composition provided by the present invention is not used as a raw material, the mechanical properties and thermal retention stability of the obtained polyester are poor.

[0155] The above specific embodiments have further elaborated on the purpose, technical solutions and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention should be included within the protection scope of the present invention.

Claims

1. A biobased succinic acid composition, characterized in that, The bio-based succinic acid composition comprises bio-based succinic acid and metal ions; The total mass content of metal ions in the bio-based succinic acid composition is 50 - 350 ppm; The metal ions include Na + , K + , Mg 2+ and Ca 2+ ; The mass content of Na + or K + in the bio-based succinic acid composition is ≤ 60 ppm; The mass content of Mg in the bio-based succinic acid composition 2+ is ≤ 50 ppm; The mass content of Ca in the bio-based succinic acid composition 2+ is ≤ 220 ppm.

2. The biobased succinic acid composition according to claim 1, wherein The total mass content of metal ions in the bio-based succinic acid composition is 50 - 280 ppm.

3. The biobased succinic acid composition according to claim 1, wherein Under the conditions of a temperature of 25°C and a concentration of 0.1 mol / L, the pH value of the aqueous solution of the bio-based succinic acid composition is ≤ 2.

8.

4. A method for preparing a bio-based succinic acid composition according to any one of claims 1 to 3, characterized in that, The preparation method comprises the following steps: (1) Using biomass resources as raw materials to prepare a succinic acid stock solution; (2) Purifying the succinic acid stock solution obtained in step (1) to obtain the bio-based succinic acid composition; The purification method comprises an extraction method and a cation exchange resin column adsorption method.

5. The preparation method according to claim 4, characterized in that, The content of succinic acid in the succinic acid stock solution is 70 - 95 g / L; The extraction method comprises forward cross-flow extraction and reverse cross-flow extraction; The extractant for the forward cross-flow extraction comprises a phosphoric acid ester extractant; The phosphoric acid ester extractant comprises at least one of diisooctyl phosphate, diethyl phosphate or triethyl phosphate; Based on the volume of the succinic acid stock solution being 1 L, the mass of the extractant for the forward cross-flow extraction is 20 - 55 g; The extractant for the reverse cross-flow extraction is water; Based on the volume of the solution containing succinic acid obtained by the forward cross-flow extraction being 1 L, the mass of the extractant for the reverse cross-flow extraction is 30 - 95 g; The number of times of the forward cross-flow extraction and the reverse cross-flow extraction are each independently ≥ 1 time; The cation exchange resin column can adsorb at least one of Na + , K + , Mg 2+ , Ca 2+ ; The loading flow rate of the cation exchange resin column adsorption method is 0.5 - 2.8 BV / h; In the cation exchange resin column adsorption method, after passing through the cation exchange resin column, it further comprises a step of eluting with water; The mass of the water is 2 - 7 times the mass of the solution to be eluted.

6. The preparation method according to claim 4, characterized in that, The biomass resources include plant resources and / or animal resources; The method for preparing the succinic acid stock solution in step (1) comprises a microbial fermentation method and / or a chemical conversion method; The purification method further comprises activated carbon decolorization and / or filtration; In the activated carbon decolorization, based on the volume of the solution to be decolorized being 1 L, the mass of the activated carbon is 0.5 - 10 g; The temperature of the activated carbon decolorization is 60 - 85°C, and the time is 30 - 65 min; After the purification, it further comprises a step of vacuum distillation and / or cooling crystallization.

7. The preparation method according to claim 4, characterized in that, The preparation method comprises the following steps: (1) Using biomass resources as raw materials to prepare a succinic acid stock solution with a succinic acid content of 70 - 95 g / L; (2) Subjecting the succinic acid stock solution obtained in step (1) to forward cross-flow extraction with a phosphoric acid ester extractant to obtain a succinic acid-loaded organic phase; then, subjecting the succinic acid-loaded organic phase to reverse cross-flow extraction with water to obtain an aqueous succinic acid solution; based on the volume of the succinic acid stock solution being 1 L, the mass of the phosphoric acid ester extractant is 20 - 55 g; based on the volume of the succinic acid-loaded organic phase being 1 L, the mass of the water is 30 - 95 g; the number of times of the forward cross-flow extraction and the reverse cross-flow extraction are each independently ≥ 1 time; (3) Pass the aqueous succinic acid solution obtained in step (2) through a cation exchange resin column at a flow rate of 0.5 - 2.8 BV / h, and elute with water having a mass 2 - 7 times that of the aqueous succinic acid solution to obtain a succinic acid effluent; (4) Successively subject the succinic acid effluent obtained in step (3) to decolorization with activated carbon and filtration to obtain a succinic acid filtrate; based on 1 L of the volume of the succinic acid effluent, the mass of the activated carbon is 0.5 - 10 g; (5) Subject the succinic acid filtrate obtained in step (4) to vacuum distillation and cooling crystallization to obtain the bio - based succinic acid composition.

8. A polyester, characterized in that, The raw materials for preparing the polyester include the bio - based succinic acid composition according to any one of claims 1 - 3.

9. The polyester according to claim 8, wherein The polyester comprises the following components: Component A: Based on the total molar amount of Component A being 100 mol%, a dicarboxylic acid compound comprising the following components: a1, 65 - 100 mol% of bio - based succinic acid and / or its ester derivatives, a2, 0 - 35 mol% of adipic acid and / or its ester derivatives; and Component B: 1,4 - butanediol in an amount at least equimolar to Component A.

10. The polyester according to claim 8, characterized in that, Under the condition of heat retention at 180 °C for 10 min, the tensile strength retention rate of the polyester > 70%.

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