Process for the synthesis of water-soluble polyesters without catalyst

Abstract

The present application relates to a method for synthesizing water-soluble polyester without catalyst, comprising the following steps: (1) batching dicarboxylic acid, dihydric alcohol and diacid salt; wherein (n1+n3):n2=(1.02-3):1, n1 is the amount of substance of dicarboxylic acid, n2 is the amount of substance of dihydric alcohol, and n3 is the amount of substance of diacid salt; (2) performing esterification reaction under inert atmosphere, the reaction temperature is 80-220 DEG C, and the reaction time is 1-20 h; (3) performing polycondensation reaction under vacuum condition, the reaction temperature is 220-300 DEG C, and the reaction time is 1-10 h. The synthesis method avoids the environmental and health risks caused by traditional catalysts, and the prepared polyester not only has good stability and performance in chemical structure, but also fully considers environmental friendliness and safety in the production process; these new polyester materials are non-toxic and harmless, and meet the concept of green economy and sustainable development.

Description

Technical Field

[0001] This invention belongs to the field of polyester synthesis technology, and specifically relates to a method for synthesizing water-soluble polyester without a catalyst. Background Technology

[0002] Synthetic polymers, due to their lightweight, low cost, excellent corrosion resistance, and durability, have become indispensable general-purpose materials in modern society, widely used in packaging, construction, transportation, electronics, and many other fields. These materials, with their good mechanical properties, chemical stability, and ease of processing, meet various industrial needs and are therefore widely used in daily life. However, most synthetic polymers are derived from petroleum-derived compounds, such as polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET). While these plastic products improve our quality of life, they also pose challenges to environmental sustainability.

[0003] Despite their significant advantages and wide applications in many fields, these synthetic materials also have significant drawbacks. First, recycling these materials is extremely difficult, primarily due to their complex chemical structures and diverse processing methods, resulting in an imperfect recycling system and high processing costs. Second, because most synthetic polymers have extremely long degradation cycles, they are not biodegradable and tend to accumulate in the environment over long periods, forming large amounts of plastic waste. Large quantities of untreated plastic waste not only occupy vast amounts of land resources but also cause serious pollution to natural ecosystems such as water, soil, and air, further posing a potential threat to wildlife and human health. Therefore, the non-degradability and difficulty in recycling synthetic polymers have become major challenges facing environmental protection and sustainable development.

[0004] Currently, while aliphatic polyesters exhibit good biodegradability, their degradation cycle is relatively long, especially under unsuitable environmental conditions (such as dry or sterile environments), making degradation difficult. Furthermore, aliphatic polyesters generally have low water solubility, being either insoluble or having very low solubility in water, thus limiting their suitability for water-based applications. This restricts their application in fields requiring water-soluble materials.

[0005] Furthermore, the synthesis of aliphatic polyesters typically relies on the introduction of metal catalysts to promote polymerization and increase the molecular weight of the polyester. However, the use of such metal catalysts can lead to metal residues, posing potential risks and hazards to human health and the environment, and limiting their application in high-end fields. As early as 1929, Carothers, a pioneer in polymer chemistry, systematically studied the direct polyesterification of dicarboxylic acids and diols without a catalyst. In polyesterification, the system could promote molecular weight increase through the autocatalytic action of the dicarboxylic acid. However, Carothers encountered significant challenges in maintaining a balanced carboxyl to hydroxyl ratio during polyesterification, which is crucial for obtaining high molecular weight polyesters. Simultaneously, the reduction of terminal carboxyl groups in the later stages of polyesterification further hindered the success of the synthesis. Subsequently, the industry adopted transesterification using excess alcohol as a synthetic method. This method facilitates achieving equimolar ratios of functional groups through the exchange of small alcohol molecules. Due to the absence of autocatalytic carboxyl groups and the high activation energy associated with transesterification, heavy metal catalysts are required to improve reaction efficiency. Generally, the process of removing metal catalyst residues from polyester requires the use of organic solvents, which not only significantly increases production costs but may also introduce solvent residue problems, thereby creating new environmental and safety hazards. Therefore, how to fundamentally eliminate toxic metal catalyst residues in polyester while maintaining the lowest possible cost remains a major challenge in current polyester synthesis. Summary of the Invention

[0006] Based on the aforementioned shortcomings and deficiencies in the prior art, one of the objectives of this invention is to at least solve one or more of the aforementioned problems in the prior art. In other words, one of the objectives of this invention is to provide a catalyst-free method for synthesizing water-soluble polyesters that meets one or more of the aforementioned requirements.

[0007] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0008] A catalyst-free method for synthesizing water-soluble polyesters includes the following steps:

[0009] (1) Ingredients of dicarboxylic acid, diol and dicarboxylic acid salt; wherein, (n1+n3):n2=(1.02~3):1, n1 is the amount of substance of dicarboxylic acid, n2 is the amount of substance of diol and n3 is the amount of substance of dicarboxylic acid salt;

[0010] (2) The esterification reaction is carried out under an inert atmosphere at a temperature of 80–220°C for 1–20 h.

[0011] (3) The polycondensation reaction is carried out under vacuum conditions at a temperature of 220-300℃ and a reaction time of 1-10h.

[0012] As a preferred embodiment, the molar ratio of the dicarboxylic acid to the dicarboxylic acid salt is 0.9 to 60.

[0013] As a preferred embodiment, the structural formula of the dicarboxylic acid is:

[0014]

[0015] R1 is an aliphatic hydrocarbon, aromatic hydrocarbon, or ether with repeating unit -CH2CH2O-, -CH2CH2CH2O-, or -CH2CH2CH2CH2O- and an average molecular weight of 200 to 6000, having 1 to 36 carbon atoms.

[0016] As a preferred embodiment, the dicarboxylic acid includes malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, octanoic acid, azelaic acid, sebacic acid, undecanoic acid, dodecanoic acid, tetradecanoic acid, hexadecanoic acid, octadecanoic acid, methylmalonic acid, 2-butyloctanoic acid, 2-propylmalonic acid, 2-methylglutaric acid, 3-methylglutaric acid, 3-methyladacic acid, maleic acid, trans-butenedioic acid, itaconic acid, isopropylmalonic acid, 2,3-dibromosuccinic acid, and p-... One or more of the following: phthalic acid, isophthalic acid, phthalic acid, 5-methylisophthalic acid, phenyl succinic acid, benzyl malonic acid, furanyl dicarboxylic acid, pyridine dicarboxylic acid, cyclohexanedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, dimer acid, hydrogenated dimer acid, hydrogenated dimer oleic acid, dimer linoleic acid, dimer linolenic acid, dimer myristic acid, polyethylene glycol with carboxyl groups at both ends, polypropylene glycol with carboxyl groups at both ends, and polytetrahydrofuran with carboxyl groups at both ends.

[0017] As a preferred embodiment, the structural formula of the diol is:

[0018]

[0019] R2 is an aliphatic hydrocarbon, aromatic hydrocarbon, or ether with repeating unit -CH2CH2O-, -CH2CH2CH2O-, or -CH2CH2CH2CH2O- and an average molecular weight of 200-6000, having 2 to 36 carbon atoms.

[0020] As a preferred embodiment, the diol includes one or more of the following: ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, undecanediol, dodecanediol, tetradecanediol, terephthalic acid, isophthalic acid, ophthalic acid, furanyl alcohol, furanyl alcohol, pyridinediethanol, cyclohexanediol, catechol, resorcinol, hydroquinone, 1,3-adamantanediol, phenylethylene glycol, polyethylene glycol, polypropylene glycol, and polytetrahydrofuran.

[0021] As a preferred embodiment, the structural formula of the dicarboxylic acid salt is:

[0022]

[0023] or

[0024] X 2 -Y 2+

[0025] Wherein, R3 is an aliphatic hydrocarbon, aromatic hydrocarbon, or ether with repeating unit -CH2CH2O-, -CH2CH2CH2O-, or -CH2CH2CH2CH2O- and an average molecular weight of 200-6000, having 1-36 carbon atoms, and X- or X 2 - is an anion, Y + Or Y 2+ It is a cation.

[0026] As a preferred embodiment, the dicarboxylic acid salt comprises malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, octanoic acid, azelaic acid, sebacic acid, undecanoic acid, dodecanoic acid, tetradecanoic acid, hexadecanoic acid, octadecanoic acid, methylmalonic acid, 2-butyloctanoic acid, 2-propylmalonic acid, 2-methylglutaric acid, 3-methylglutaric acid, 3-methyladacic acid, maleic acid, transbutenic acid, itaconic acid, isopropylmalonic acid, 2,3-dibromosuccinic acid, and p-phenylene oxide. Dicarboxylic acid, isophthalic acid, phthalic acid, 5-methylisophthalic acid, phenylbutyric acid, benzylmalonic acid, furanyldicarboxylic acid, pyridinedicarboxylic acid, cyclohexanedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, dimer acid, hydrogenated dimer acid, hydrogenated dimer oleic acid, dimer linoleic acid, dimer linolenic acid, dimer myristic acid, polyethylene glycol with carboxyl groups at both ends, polypropylene glycol with carboxyl groups at both ends, polytetrahydrofuran with carboxyl groups at both ends, or one or more of the following: cationic Na + K + Ca 2+ Mg 2+ Li + 、Sr 2+ NH4 + Zn 2+ And one or more of the following dicarboxylic acid salts composed of anionic carboxylates, sulfates, sulfites, nitrates, acetates, phosphates, and sulfonates.

[0027] As a preferred embodiment, in step (2), the esterification reaction is carried out at a temperature of 130–220°C for 6–10 hours.

[0028] As a preferred embodiment, in step (3), the vacuum degree is <30Pa, the temperature of the polycondensation reaction is 220-260℃, and the time is 2-8h.

[0029] Compared with the prior art, the beneficial effects of this invention are:

[0030] (1) The water-soluble polyester synthesis method without any additives or catalysts provided by the present invention abandons the traditional toxic metal catalysts and successfully synthesizes a series of high molecular weight polyester materials by using a catalyst-free polycondensation mechanism. This synthesis method avoids the environmental and health risks brought about by traditional catalysts. The polyesters obtained not only have good stability and performance in chemical structure, but also fully consider environmental friendliness and safety in the production process. These new polyester materials are non-toxic and harmless, which is in line with the concept of green economy and sustainable development.

[0031] (2) The polyester material prepared by the present invention has excellent water solubility. Compared with traditional plastics, these polyesters can be degraded more efficiently through water treatment or biodegradation after use, thereby significantly reducing persistent pollution to the environment. In addition, the water solubility of polyester also provides new possibilities for its application in multiple fields. For example, in drug delivery systems, water-soluble polyesters can achieve controlled release of drugs, improve drug bioavailability and targeting. In the field of cleaning products such as laundry detergent pods, these polyesters can dissolve quickly in water and release effective ingredients, which is in line with the development trend of modern green washing technology.

[0032] (3) Although the polyester prepared by the present invention exhibits excellent water solubility, a dynamic cross-linking structure is introduced into its molecular structure, which makes it exhibit excellent mechanical properties while maintaining good solubility. This dynamic cross-linking structure can form reversible physical cross-linking points between the molecular chains of the polyester, thereby enhancing the mechanical strength, toughness and deformation resistance of the water-soluble polyester. In addition, by adjusting the feed ratio of the reactants, the mechanical properties of the polyester, including its tensile strength, elastic modulus and elongation at break, can be effectively adjusted. Attached Figure Description

[0033] Figure 1 The tensile curves of the polyester obtained in Example 1 and Comparative Example 1 of the present invention are shown.

[0034] Figure 2 This is a comparison diagram of the swelling and dissolution of polyesters obtained in Example 1 and Comparative Example 1 of the present invention.

[0035] Figure 3 This is a photograph of the polyester used as the outer film of laundry detergent pods in Example 1 of the present invention. Detailed Implementation

[0036] The method for synthesizing water-soluble polyester without any additives or catalysts of the present invention mainly involves the esterification reaction of dicarboxylic acids, diols, and dicarboxylic acid salts in an inert atmosphere and the polycondensation reaction of the prepolymer under vacuum conditions, and the reaction formulas are as follows:

[0037]

[0038] Wherein, R1 is an aliphatic hydrocarbon, aromatic hydrocarbon or ether with a repeating unit of -CH2CH2O-, -CH2CH2CH2O- or -CH2CH2CH2CH2O- and an average molecular weight of 200 to 6000, having 1 to 36 carbon atoms;

[0039] R2 is an aliphatic hydrocarbon, aromatic hydrocarbon, or ether with repeating unit -CH2CH2O-, -CH2CH2CH2O-, or -CH2CH2CH2CH2O- and an average molecular weight of 200 to 6000, having 2 to 36 carbon atoms.

[0040] R3 is an aliphatic hydrocarbon, aromatic hydrocarbon, or ether with repeating unit -CH2CH2O-, -CH2CH2CH2O-, or -CH2CH2CH2CH2O- and an average molecular weight of 200 to 6000, having 1 to 36 carbon atoms.

[0041] X is a carboxylic acid, sulfuric acid, sulfurous acid, nitric acid, acetic acid, phosphoric acid, or sulfonic acid;

[0042] Y is Na, K, Ca, Mg, Li, Sr, NH4, Zn.

[0043] The aforementioned dicarboxylic acids preferably include malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, octanoic acid, azelaic acid, sebacic acid, undecanoic acid, dodecanoic acid, tetradecanoic acid, hexadecanoic acid, octadecanoic acid, methylmalonic acid, 2-butyloctanoic acid, 2-propylmalonic acid, 2-methylglutaric acid, 3-methylglutaric acid, 3-methyladacic acid, maleic acid, trans-butenedioic acid, itaconic acid, isopropylmalonic acid, 2,3-dibromosuccinic acid, and terephthalic acid. Formic acid, isophthalic acid, phthalic acid, 5-methylisophthalic acid, phenyl succinic acid, benzyl malonic acid, furanyl dicarboxylic acid, pyridine dicarboxylic acid, cyclohexanedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, dimer acid, hydrogenated dimer acid, hydrogenated dimer oleic acid, dimer linoleic acid, dimer linolenic acid, dimer myristic acid, polyethylene glycol with carboxyl groups at both ends, polypropylene glycol with carboxyl groups at both ends, and polytetrahydrofuran with carboxyl groups at both ends.

[0044] The aforementioned diols preferably include one or more of the following: ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, undecanediol, dodecanediol, tetradecanediol, terephthalic acid, isophthalic acid, o-phthalic acid, furanyl alcohol, furanyl alcohol, pyridinediethanol, cyclohexanediol, catechol, resorcinol, hydroquinone, 1,3-adamantanediol, phenylethylene glycol, polyethylene glycol, polypropylene glycol, and polytetrahydrofuran.

[0045] The aforementioned dicarboxylic acid salts preferably include malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, octanoic acid, azelaic acid, sebacic acid, undecanoic acid, dodecanoic acid, tetradecanoic acid, hexadecanoic acid, octadecanoic acid, methylmalonic acid, 2-butyloctanoic acid, 2-propylmalonic acid, 2-methylglutaric acid, 3-methylglutaric acid, 3-methyladacic acid, maleic acid, trans-butenedioic acid, itaconic acid, isopropylmalonic acid, 2,3-dibromosuccinic acid, and terephthalic acid. One or more of the following: isophthalic acid, phthalic acid, 5-methylisophthalic acid, phenyl succinic acid, benzyl malonic acid, furanyl dicarboxylic acid, pyridine dicarboxylic acid, cyclohexanedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, dimer acid, hydrogenated dimer acid, hydrogenated dimer oleic acid, dimer linoleic acid, dimer linolenic acid, dimer myristic acid, polyethylene glycol with carboxyl groups at both ends, polypropylene glycol with carboxyl groups at both ends, and polytetrahydrofuran with carboxyl groups at both ends; positive ion Na + K + Ca 2+ Mg 2+ Li + 、Sr 2+ NH4 + Zn 2+ And one or more of the following dicarboxylic acid salts composed of anionic carboxylates, sulfates, sulfites, nitrates, acetates, phosphates, and sulfonates.

[0046] The above-mentioned ingredients include dicarboxylic acid, diol, and dicarboxylic acid salt; wherein (n1+n3):n2 = (1.02~3):1, n1 is the amount of substance of dicarboxylic acid, n2 is the amount of substance of diol, and n3 is the amount of substance of dicarboxylic acid salt; the molar ratio of dicarboxylic acid to dicarboxylic acid salt is 0.9~60; by limiting the molar ratio of dicarboxylic acid, diol, and dicarboxylic acid salt to the above range, this invention can ensure that the prepared polyester has good water solubility and mechanical properties.

[0047] The esterification reaction described above is carried out under an inert atmosphere, preferably argon. When introducing argon, the present invention does not strictly limit the gas flow rate; a flow rate commonly used by those skilled in the art can be used. The preferred temperature range for the esterification reaction is 80–220°C, more preferably 130–200°C; the preferred reaction time is 1–20 hours, more preferably 6–10 hours. These temperature and time ranges are designed to ensure that the diacid and diol can react fully, promoting efficient esterification.

[0048] Furthermore, the esterification reaction described above is preferably carried out under stirring conditions to improve the uniformity and rate of the reaction. The stirring speed is preferably >100 rpm, more preferably 200–400 rpm. Appropriate stirring helps to enhance the mixing and contact of the reactants, thereby promoting the reaction.

[0049] The polycondensation reaction described above is carried out under vacuum conditions, preferably with a vacuum level of <150 Pa, more preferably <30 Pa. By introducing argon gas and establishing a vacuum negative pressure environment, this invention helps to separate the water byproduct generated during the reaction from the polymerization system, promoting the forward polymerization reaction. Under vacuum conditions, the polycondensation reaction temperature is preferably 200–300°C, more preferably 220–260°C; the reaction time is preferably 1–10 hours, more preferably 2–8 hours. By precisely controlling the reaction temperature and time, this invention ensures the complete progress of the reaction, thereby obtaining polyester materials with high molecular weight and excellent properties.

[0050] Similarly, the polycondensation reaction is preferably carried out under stirring conditions, with a stirring speed preferably >100 rpm, more preferably 200-400 rpm. Appropriate stirring can effectively improve the efficiency of the reaction, ensure the full mixing and uniform distribution of the reactants during the reaction process, thereby promoting the smooth progress of the polycondensation reaction.

[0051] The technical solution of the present invention will be further explained and illustrated below through specific embodiments.

[0052] Example 1:

[0053] 1.845 kg of succinic acid (SA), 1 kg of ethylene glycol (EG), and 0.432 kg of sodium isophthalic acid-5-sulfonate (5-SSIPA) (mol ratio of SA:EG:5-SSIPA = 0.97:1:0.1) were sequentially added to a reactor. Simultaneously, an inert argon gas flow was introduced into the reactor to protect the reactants from oxidation. Under normal pressure, the temperature was gradually increased to 200°C for esterification, with the stirring speed maintained above 200 r / min for 9 hours, yielding a carboxyl-terminated prepolymer. After esterification, an oil pump was connected to the reactor to lower the vacuum of the polymerization system to below 100 Pa. The temperature was then raised to 250°C for transesterification, continuing the reaction for 6 hours. Under high temperature and reduced pressure, the dicarboxylic acid was continuously extracted from the polymerization system through sublimation, causing the viscosity to continuously increase, resulting in the final product, a water-soluble polyester.

[0054] Testing showed that the water-soluble polyester obtained in this embodiment can be completely dissolved in deionized water, with an intrinsic viscosity of 0.787 dL / g, a tensile strength of 20.84 MPa, and an elongation at break of 789%.

[0055] Example 2:

[0056] The difference between this embodiment and Embodiment 1 is that:

[0057] Simply replace succinic acid with glutaric acid. Glutaric acid 2.064 kg, ethylene glycol 1 kg, sodium isophthalic acid-5-sulfonate 0.432 kg, the mol ratio of the three is glutaric acid: ethylene glycol: sodium isophthalic acid-5-sulfonate = 0.97:1:0.1;

[0058] Everything else is the same as in Example 1;

[0059] Testing showed that the water-soluble polyester obtained in this embodiment can be completely dissolved in deionized water.

[0060] Example 3:

[0061] The difference between this embodiment and Embodiment 1 is that:

[0062] Ethylene glycol is replaced with butanediol. Succinic acid 0.707 kg, butanediol 1 kg, sodium isophthalic acid-5-sulfonate 0.165 kg, the mol ratio of the three is succinic acid:butanediol:sodium isophthalic acid-5-sulfonate = 0.97:1:0.1;

[0063] Everything else is the same as in Example 1;

[0064] Testing showed that the water-soluble polyester obtained in this embodiment can be completely dissolved in deionized water.

[0065] Example 4:

[0066] The difference between this embodiment and Embodiment 1 is that:

[0067] The mol ratios of succinic acid and sodium isophthalic acid-5-sulfonate are different. The mol ratios are: succinic acid 1.94 kg, ethylene glycol 1 kg, sodium isophthalic acid-5-sulfonate 0.216 kg, and succinic acid : ethylene glycol : sodium isophthalic acid-5-sulfonate = 1.02 : 1 : 0.05.

[0068] Everything else is the same as in Example 1;

[0069] Testing showed that the water-soluble polyester obtained in this embodiment can be completely dissolved in deionized water, with an intrinsic viscosity of 0.773 dL / g, a tensile strength of 31.09 MPa, and an elongation at break of 619%.

[0070] Example 5:

[0071] The difference between this embodiment and Embodiment 1 is that:

[0072] The mol ratios of succinic acid and sodium isophthalic acid-5-sulfonate are different. The mol ratios are: succinic acid 1.75 kg, ethylene glycol 1 kg, sodium isophthalic acid-5-sulfonate 0.648 kg, which is succinic acid : ethylene glycol : sodium isophthalic acid-5-sulfonate = 0.92 : 1 : 0.15.

[0073] Everything else is the same as in Example 1;

[0074] Testing showed that the water-soluble polyester obtained in this embodiment can be completely dissolved in deionized water, with an intrinsic viscosity of 0.790 dL / g, a tensile strength of 24.23 MPa, and an elongation at break of 516%.

[0075] Example 6:

[0076] The difference between this embodiment and Embodiment 1 is that:

[0077] The mol ratios of succinic acid and sodium isophthalic acid-5-sulfonate are different. The mol ratios of succinic acid 1.65 kg, ethylene glycol 1 kg, and sodium isophthalic acid-5-sulfonate 0.864 kg are succinic acid : ethylene glycol : sodium isophthalic acid-5-sulfonate = 0.87 : 1 : 0.2.

[0078] Everything else is the same as in Example 1;

[0079] Testing showed that the water-soluble polyester obtained in this embodiment can be completely dissolved in deionized water, with an intrinsic viscosity of 0.827 dL / g, a tensile strength of 26.46 MPa, and an elongation at break of 55%.

[0080] Example 7:

[0081] The difference between this embodiment and Embodiment 1 is that:

[0082] The mol ratios of succinic acid and sodium isophthalic acid-5-sulfonate are different. The mol ratios of succinic acid 1.56 kg, ethylene glycol 1 kg, and sodium isophthalic acid-5-sulfonate 1.08 kg are succinic acid : ethylene glycol : sodium isophthalic acid-5-sulfonate = 0.82 : 1 : 0.25.

[0083] Everything else is the same as in Example 1;

[0084] Testing showed that the water-soluble polyester obtained in this embodiment can be completely dissolved in deionized water, and its intrinsic viscosity is 0.842 dL / g.

[0085] Example 8:

[0086] The difference between this embodiment and Embodiment 1 is that:

[0087] The mol ratios of succinic acid and sodium isophthalic acid-5-sulfonate are different. The mol ratios are: succinic acid 1.465 kg, ethylene glycol 1 kg, and sodium isophthalic acid-5-sulfonate 1.296 kg, which is succinic acid : ethylene glycol : sodium isophthalic acid-5-sulfonate = 0.77 : 1 : 0.3.

[0088] Everything else is the same as in Example 1;

[0089] Testing showed that the water-soluble polyester obtained in this embodiment can be completely dissolved in deionized water, and its intrinsic viscosity is 0.870 dL / g.

[0090] Comparative Example 1:

[0091] The difference between this comparative example and Example 1 is that:

[0092] Without adding sodium isophthalic acid-5-sulfonate, 2.036 kg of succinic acid and 1 kg of ethylene glycol were used, with a mol ratio of succinic acid:ethylene glycol = 1.07:1.

[0093] Everything else is the same as in Example 1;

[0094] The polyester obtained in this comparative example was found to be completely insoluble in deionized water, with an intrinsic viscosity of 0.574 dL / g, a tensile strength of 33.52 MPa, and an elongation at break of 322%.

[0095] Comparative Example 2:

[0096] The difference between this comparative example and Example 1 is that:

[0097] Sodium isophthalic acid-5-sulfonate replaces isophthalic acid. 1.845 kg of succinic acid, 1 kg of ethylene glycol, and 0.268 kg of isophthalic acid are used. The mol ratio of the three is succinic acid: ethylene glycol: isophthalic acid = 0.97:1:0.1.

[0098] Everything else is the same as in Example 1;

[0099] Tests showed that the polyester obtained in this comparative example was completely insoluble in deionized water.

[0100] Comparative Example 3:

[0101] The difference between this comparative example and Example 1 is that:

[0102] Sodium isophthalic acid-5-sulfonate is replaced with sodium benzenesulfonate. The composition is 2.036 kg of succinic acid, 1 kg of ethylene glycol, and 0.29 kg of sodium benzenesulfonate. The mol ratio of the three components is succinic acid: ethylene glycol: sodium benzenesulfonate = 1.07:1:0.1.

[0103] Everything else is the same as in Example 1;

[0104] Tests showed that the polyester obtained in this comparative example was completely insoluble in deionized water.

[0105] Comparative Example 4:

[0106] The difference between this comparative example and Example 1 is that:

[0107] The acid-alcohol ratios were different; in Example 1, the acid was in excess, while in Comparative Example 4, the alcohol was in excess.

[0108] 1.619 kg of succinic acid, 1 kg of ethylene glycol, and 0.379 kg of sodium isophthalic acid-5-sulfonate have a mol ratio of succinic acid: ethylene glycol: sodium isophthalic acid-5-sulfonate = 0.97: 1.14: 0.1.

[0109] Testing revealed that although the polyester obtained in this comparative example could dissolve in deionized water, the excessive amount of alcohol and the lack of a catalyst during the reaction resulted in low esterification efficiency and incomplete reaction, leading to a relatively low molecular weight of the obtained polyester. Furthermore, the lower molecular weight directly affected the polyester's chain structure and degree of crosslinking, resulting in poor mechanical properties, particularly in tensile strength and elongation at break, significantly limiting its applications.

[0110] In addition, the mechanical properties of the water-soluble polyester and PES obtained in Example 1 and Comparative Example 1 were tested using a universal testing machine. The tensile curves obtained from the tests are shown below. Figure 1 As shown in the analysis of the tensile curves, the polyester in Comparative Example 1 exhibits typical crystalline characteristics, with a relatively clear yield point and relatively low elongation. This indicates that it is mainly composed of a semi-crystalline phase and has high structural rigidity. However, after adding the dibasic acid salt, the tensile curve clearly exhibits the characteristics of an elastomer, specifically a relatively flat stress-strain relationship and greater elongation. This indicates that the introduction of the dibasic acid salt leads to the formation of cross-linked structures between polymer segments. The formation of cross-linking points effectively enhances the three-dimensional structural stability of the polymer network and significantly improves its elastic properties, thereby improving the material's flexibility and deformability.

[0111] Tensile strength: Measured according to the method specified in ISO 527-2 Plastics Tensile Properties Test Method, wherein the tensile rate is 50 mm / min;

[0112] Elongation at break: Measured according to the method specified in ISO 527-2 Test Method for Tensile Properties of Plastics, where the tensile rate is 50 mm / min;

[0113] A dissolution and swelling experiment was conducted using chloroform solvent to compare Example 1 and Comparative Example 1. The results are as follows: Figure 2As shown in the figure. The results indicate that Comparative Example 1 is completely soluble in chloroform, while Example 1 can only swell but not dissolve in chloroform. Furthermore, Example 1 can be melt-processed into dumbbell-shaped strips at high temperatures, indicating that Example 1 has a cross-linked structure at low temperatures and exhibits thermoplasticity at high temperatures due to the breaking of ionic bonds. This further verifies that while Example 1 has good water solubility, its cross-linked structure also provides it with good mechanical properties.

[0114] Given its excellent water solubility, this material shows broad application potential in the field of laundry detergent pods. Specifically, it can be used as the outermost film of laundry detergent pods to ensure rapid dissolution upon contact with water, thereby effectively releasing the cleaning ingredients. Figure 3 As shown, using this material as the outer film ensures that laundry pods dissolve quickly during use and exhibits good water solubility and environmental friendliness. This application not only improves washing performance but also optimizes the ease of use and environmental friendliness of laundry pods. Therefore, this material has significant practical application value in the production of laundry pods.

[0115] Given that there are numerous embodiments of the present invention, and the raw materials, dosages, and process parameters involved can all be selected within a limited range according to actual needs, and the experimental data for each embodiment are extensive and numerous, it is not suitable to list and describe them one by one here. However, the content to be verified and the final conclusions obtained in each embodiment are similar. Therefore, the verification content of each embodiment will not be described one by one here.

[0116] The above description is merely a detailed explanation of preferred embodiments and principles of the present invention. For those skilled in the art, there may be changes in specific implementation methods based on the ideas provided by the present invention, and these changes should also be considered within the scope of protection of the present invention.

Claims

1. A method for synthesizing water-soluble polyester without a catalyst, characterized in that, Includes the following steps: (1) Ingredients of dicarboxylic acids, diols, and dicarboxylic acid salts; among which, ( n 1+ n 3): n 2 = (1.02~3):1, n 1 represents the amount of substance of a dicarboxylic acid. n 2 represents the amount of substance of the diol. n 3 represents the amount of substance of the dicarboxylic acid salt; the molar ratio of the dicarboxylic acid to the dicarboxylic acid salt is 0.9 to 60. The dicarboxylic acid is succinic acid or glutaric acid, the dicarboxylate is sodium isophthalic acid-5-sulfonate, and the diol includes one or more of ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, undecanediol, dodecanediol, tetradecanediol, polyethylene glycol, polypropylene glycol, and polytetrahydrofuran. (2) The esterification reaction is carried out under an inert atmosphere at a temperature of 80-220℃ for 1-20h. (3) The polycondensation reaction is carried out under vacuum conditions. The temperature of the polycondensation reaction is 200-300℃ and the time is 1-10h.

2. The method according to claim 1, characterized in that, In step (2), the esterification reaction is carried out at a temperature of 130–220°C for 6–10 hours.

3. The method according to claim 1, characterized in that, In step (3), the vacuum degree is <30Pa, the temperature of the polycondensation reaction is 220-260℃, and the time is 2-8h.

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