Manufacturing method for high-strength biodegradable polyester fiber

Abstract

An object of the present invention is to provide a method for producing high-strength biodegradable polyester fibers. The present invention relates to a method for producing high-strength biodegradable polyester fibers, which involves adding an ionic copolymer polyester to a biodegradable polyester and melt-spinning the resulting fiber; the amount of the ionic copolymer polyester added is 1 to 10% of the mass of the biodegradable polyester; the ionic copolymer polyester is composed of nonionic polyester segments and sulfonate-based ionic polyester segments, with ester bonds connecting different nonionic polyester segments, different ionic polyester segments, and the nonionic polyester segments and ionic polyester segments; the nonionic polyester chain segments have 4 to 10 repeating units, and the sulfonate-based ionic polyester segments have 2 to 8 repeating units; and the ionic copolymer polyester has an intrinsic viscosity of 0.55 to 0.85 dL / g. By incorporating the ionic copolymer polyester into the biodegradable polyester, the present invention achieves continuous and stable fiber formation and significantly increases the mechanical strength of the fiber.

Description

[Technical Field]

[0001] The present invention belongs to the polyester technical field and relates to the production of biodegradable polyester fibers, and more particularly to a method for producing high-strength biodegradable polyester fibers. [Background technology]

[0002] Fiber materials are the basic raw materials in the textile industry. Technological innovation in fiber materials is constantly invigorating the textile industry. Due to its stable chemical structure and excellent mechanical properties, traditional polyester fibers are widely used in various fields, including household textiles, clothing, and industrial materials. In areas such as disposable medical and sanitary textiles, where recycling is not possible after use, the fiber materials used must have good biodegradability, which can reduce environmental pollution.

[0003] Biodegradable polyesters produced from common long-chain hydrocarbon-based dicarboxylic acids and diols include PBAT, PBST, and PBS. PBAT is a terpolymer of terephthalic acid, adipic acid, and butanediol. It has good processability, high toughness, and excellent biodegradability, breaking down into carbon dioxide, biomass, and water in soil or compost. PBAT fiber materials also have good biodegradability and a softer feel than fiber materials such as polylactic acid (PLA) and polyglycolic acid (PGA). However, the random copolymerization used in the synthesis of PBAT makes crystallization difficult, limiting the development of PBAT fiber manufacturing technology and its application as a fiber material. Therefore, using PBAT as a raw material to produce degradable fibers that meet the demands of environmental protection and sustainable development will expand its application fields and have important market significance.

[0004] Chinese Patent CN100412242C discloses a method for producing polybutylene (terephthalate-co-succinate) fiber, in which a copolymer polyester is melt-extruded to form an undrawn yarn, which is then balanced under constant temperature and humidity conditions for 5 to 13 hours and drawn to produce biodegradable polyester fiber. Chinese Patent CN113201805A discloses a method for producing PBAT fiber, in which the PBAT fiber spinning process involves cooling, bundling, oil application, drawing, and winding in that order. The cooling process employs a combination of slow and fast cooling, optimizing the PBAT spinning and cooling process. Specifically, slow cooling is used when the yarn is cooled to near its crystallization temperature, and heat treatment is performed near the PBAT crystallization temperature, allowing PBAT sufficient time to crystallize, completing the crystallization and improving the crystallinity. The improved crystallinity prevents the yarn from sticking during the bundling and winding process, improving the quality of the PBAT fiber. CN103668540B relates to PBAT fibers and their manufacturing methods, which, when the linear polyester has a high molecular weight and a uniform molecular weight distribution, can effectively improve the cooling difficulty and adhesion problems in the PBAT spinning process by simultaneously extending the cooling distance during the spinning process. CN103668541B relates to degradable fibers containing PBAT and their manufacturing methods, which are manufactured from components containing the following weight parts: polybutylene(adipate-co-terephthalate) (PBAT) with one or two of polyhydroxybutyrate, polyhydroxybutyrate-valerate, polybutylene succinate, or polylactic acid. When the linear polyester used in spinning has a high molecular weight and a uniform molecular weight distribution, the resulting fiber has good performance, and, when the cooling distance during the spinning process is extended, can effectively improve the cooling difficulty and adhesion problems in the PBAT spinning process.

[0005] Chinese Patent CN113122952A relates to PBAT fiber and its manufacturing method. The molecular chain of PBAT fiber contains butylene terephthalate segments, butylene adipate segments, and 5-sodium sulfonate-butylene isophthalate segments. The segment length controls the balance between PBAT's crystallization ability and performance, and the incorporation of SSIPA into the segments improves fiber performance. Chinese Patent CN112048058B relates to a method for manufacturing high-melting, crystalline, biodegradable copolyesters. This involves mixing an isohexitol-based polyester prepolymer, an aliphatic polyester prepolymer, and a chain extender, and then reacting them to produce a high-melting, crystalline, biodegradable copolyester. To achieve good overall performance (thermal properties, mechanical properties, and biodegradability), the terephthalic acid content in commercial PBAT and PBST-based aliphatic-aromatic copolyesters is typically 40-50 mol%. Based on ΔTm = ΔHm / ΔSm, the addition of copolymerized monomers disrupts the crystalline regularity of the PBS repeating units, lowering the crystallization enthalpy of the segments or increasing the entropy of the segments, resulting in poor crystallization ability for the PBAT and PBST biodegradable polyesters. On the other hand, in block copolymers, if each component segment is sufficiently long, each can form a crystalline region, imparting a certain degree of crystallinity to the copolymer.

[0006] Biodegradable polyesters such as PBAT, PBST, and PBS have low crystallization ability and cannot be sufficiently cooled and solidified during the air-cooling process during spinning. This leads to fibers sticking together, making continuous and stable spinning impossible, and the resulting fibers have low mechanical strength. These factors significantly limit their application. As is clear from the above-mentioned prior art, to address this issue, biodegradable polyesters are copolymerized and then the spinning process is innovated to strengthen air-cooling and extend the air-cooling area, thereby improving the fiber sticking problem. Previously reported techniques involve copolymerizing biodegradable polyesters with a high proportion of modifiers to improve the biodegradable polyester's heat resistance and crystallization ability, followed by optimizing the spinning process to obtain fibers. However, copolymerization with a high proportion of modifiers destroys the biodegradable polyester's inherent chemical structure, adversely affecting the biodegradability of the fibers. Furthermore, spinning using copolymerized biodegradable polyesters does not offer the same operational flexibility as blending and addition. One method for improving the crystallization ability of biodegradable polyesters is to control the length and sequence structure of the segments and introduce other segments during the synthesis stage of the biodegradable polyester. However, this often results in changes in the biodegradability of the synthesized copolymer polyester. In particular, aromatic heterocycles in the introduced segments significantly inhibit the biodegradability of the polyester, and if the content is greater than 50 mol%, the polymer becomes difficult to biodegrade. Summary of the Invention [Problem to be solved by the invention]

[0007] The objective of the present invention is to solve the above-mentioned problems in the prior art and provide a method for producing high-strength biodegradable polyester fibers. This invention addresses the problem that current biodegradable polyesters such as PBAT, PBST, and PBS have poor crystallization ability during melt spinning, which prevents rapid cooling and solidification, leading to adhesion of the fibers and making their applications difficult. By incorporating a certain amount of ionic copolyester into the biodegradable polyester, the crystallization ability is significantly improved, enabling continuous and stable fiber formation and significantly improving fiber strength, thereby meeting application requirements.

[0008] To achieve the above objectives, the present invention adopts the following technical solutions: (1) The method for producing high-strength biodegradable polyester fibers is to add an ionic copolymer polyester to biodegradable polyester and melt-spin the mixture to produce high-strength biodegradable polyester fibers.

[0009] (2) The amount of ionic copolyester added is 1-10% of the biodegradable polyester mass. Most current biodegradable polyesters (including PBAT, PBS, PBST, etc.) are unable to be sufficiently cooled and solidified during the air cooling process during spinning, resulting in adhesion between fibers, making continuous and stable molding impossible. The resulting fibers also have low mechanical strength, significantly limiting their applications. The amount of ionic copolyester added has a significant impact on the performance of the spun biodegradable polyester fiber. If the amount of ionic copolyester added is less than 1%, the ionic copolyester content in the biodegradable polyester is low, the melt cannot be effectively controlled, and the fibers are still prone to adhesion problems. If the amount of ionic copolyester added is more than 10%, the ionic copolyester content in the biodegradable polyester is excessive, significantly improving fiber spinnability and eliminating adhesion problems, but reducing the biodegradability of the spun fibers. Therefore, the ionic copolyester content in biodegradable polyester fibers must be strictly controlled.

[0010] (3) Ionic copolyesters are composed of nonionic polyester segments and sulfonate-based ionic polyester segments, and different nonionic polyester segments, different ionic polyester segments, and nonionic polyester segments and ionic polyester segments are all connected by ester bonds.

[0011] (4) The intrinsic viscosity of the ionic copolyester is 0.55 to 0.85 dl / g.

[0012] Preferred technical solutions: In the above-mentioned method for producing high-strength biodegradable polyester fibers, the biodegradable polyester is polybutylene(adipate-co-terephthalate) (PBAT), polybutylene(terephthalate-co-succinate) (PBST), polybutylene succinate (PBS), poly-3-hydroxyalkanoate (PHA), or polyε-caprolactone (PCL), and the number average molecular weight of the biodegradable polyester is 50,000 to 100,000 g / mol.

[0013] In the above-mentioned method for producing high-strength biodegradable polyester fiber, the process parameters for melt spinning are as follows: spinning temperature 220-280°C, cooling air temperature 15-20°C, relative humidity 60-85%, air pressure 20-80kPa, fiber oil adhesion rate 0.6-1.5%, heat roller GR1 speed 1000-1500m / min, heat roller GR1 temperature 60-90°C, heat roller GR2 speed 2500-3500m / min, and heat roller GR2 temperature 100-120°C.

[0014] In the manufacturing method for the high-strength biodegradable polyester fiber described above, the repeating units of the nonionic polyester segment are 4 to 10, and the repeating units of the sulfonate-based ionic polyester segment are 2 to 8. The number of repeating units of the nonionic polyester segment and the sulfonate-based ionic polyester segment has a significant impact on the structure and performance of the synthesized ionic copolymer polyester and must be controlled within this range. If the number of repeating units is below the set range, when the two substances are polymerized at a fixed mass ratio (i.e., the number of moles of both substances is fixed), the synthesized ionic copolymer polyester approaches a random copolymer polyester, resulting in significantly reduced crystallinity and adhesion during drying, making the ionic copolymer polyester unusable for spinning. If the number of repeating units is above the set range, when the two substances are polymerized at a fixed mass ratio (i.e., the number of moles of both substances is fixed), the number of repeating units of both segments is too high, resulting in excessive molecular weights, which reduces the reactivity during copolymerization. As a result, the molecular weight of the ionic copolymer polyester does not meet the spinning requirements, making it unusable.

[0015] In the method for producing the high-strength biodegradable polyester fiber described above, the ionic copolyester is produced as follows: first, a nonionic polyester and a sulfonate-based ionic polyester are synthesized by an esterification reaction, and then the nonionic polyester and the sulfonate-based ionic polyester are subjected to a polycondensation reaction to produce the ionic copolyester.

[0016] In the method for producing the high-strength biodegradable polyester fiber, the molar ratio of the nonionic polyester to the sulfonate-based ionic polyester is 2:8 to 8:2.

[0017] In the method for producing the high-strength biodegradable polyester fiber, the nonionic polyester is produced by esterifying dicarboxylic acid I and diol I, in which the molar ratio of dicarboxylic acid I to diol I is 1:1.05-1.5, the dicarboxylic acid I is terephthalic acid, isophthalic acid or adipic acid, and the diol I is ethylene glycol, propylene glycol, butanediol or pentanediol.

[0018] In the above-mentioned method for producing high-strength biodegradable polyester fibers, the catalyst used in the esterification reaction of the nonionic polyester is titanium diethylate, tetrabutyl titanate, antimony diethylate, antimony (III) acetate, or antimony (III) oxide, and the amount used is 10 to 100 ppm based on the mass of the dicarboxylic acid I.

[0019] In the above-mentioned method for producing high-strength biodegradable polyester fibers, the esterification reaction conditions for the nonionic polyester are a temperature of 150 to 250°C, a pressure of 0.01 to 0.5 MPa, and a time of 1.5 to 3.5 hours.

[0020] In the method for producing the high-strength biodegradable polyester fiber, the sulfonate-based ionic polyester is produced by a stepwise esterification reaction of dicarboxylic acid II and diol II. In the first-stage esterification reaction, the molar ratio of the number of carboxyl functional groups of the dicarboxylic acid II to the number of hydroxyl functional groups of the diol II is 1.05-1.50; in the second-stage esterification reaction, only the diol II is added, and the amount of the diol II added is 10-60% of the molar amount of the dicarboxylic acid II added in the first-stage esterification reaction; Dicarboxylic acid II is sodium 5-sulfoisophthalate or sodium 2-sulfoterephthalate; Diol II is potassium 2,5-dihydroxybenzenesulfonate, sodium N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonate, sodium 2-[(tris(hydroxymethyl)methyl)amino]-1-ethanesulfonate, or sodium 3-[N-tris(hydroxymethyl)methylamine]-2-hydroxypropanesulfonate.

[0021] In the method for producing the high-strength biodegradable polyester fiber, the catalyst for the stepwise esterification reaction of the sulfonate-based ionic polyester is benzenesulfonic acid, which is added during the first-stage esterification reaction in an amount of 10 to 1000 ppm based on the mass of dicarboxylic acid II.

[0022] In the method for producing the high-strength biodegradable polyester fiber, the conditions for the first-stage esterification reaction are: temperature 220-250°C, pressure 0.05-0.5 MPa, and time 3.0-5.0 hours; and the conditions for the second-stage esterification reaction are: temperature 240-260°C, pressure 0.1-0.5 MPa, and time 0.5-1.0 hours.

[0023] In the method for producing the high-strength biodegradable polyester fiber, the polycondensation reaction of the nonionic polyester and the sulfonate-based ionic polyester is divided into a preliminary polycondensation reaction and a final polycondensation reaction. The preliminary polycondensation reaction temperature is 240-260°C, the reaction time is 0.1-1.0 hour, and the pressure is 500-1000 Pa; The final polycondensation reaction temperature is 260 to 285°C, the reaction time is 1.5 to 3.0 hours, and the pressure is 0 to 100Pa.

[0024] The above high-strength biodegradable polyester fiber In the production method, the polycondensation catalyst is tetrabutyl titanate, titanium diethylate, antimony trioxide, antimony diethylate or antimony (III) acetate, and the amount added is 50 to 500 ppm of the total mass of the sulfonate ionic polyester and the nonionic polyester.

[0025] In the method for producing the high-strength biodegradable polyester fiber, the crystallization temperature of the biodegradable polyester modified with the ionic copolymer polyester is 50 to 150°C, and the half-crystallization time t 1 / 2 The crystallization time is 1.0 to 3.0 minutes, and the crystallization enthalpy is 10 to 50 J / g.

[0026] In the above-mentioned method for producing high-strength biodegradable polyester fiber, the single filament fineness of the high-strength biodegradable polyester fiber is 1.5 to 5.0 dtex, the oil-free yarn (note: oil-free yarn refers to untreated fiber that has been subjected to a cooling and air-drying process after melt extrusion) has a number average molecular weight reduction of 500 to 2000 g / mol, the fiber breaking strength is ≥ 2.50 cN / dtex, the breaking elongation is 15.0 to 35.0%, and the elastic recovery rate under 2 to 10% tensile deformation is ≥ 90%; the biodegradation performance of the high-strength biodegradable polyester fiber is compostable biodegradation rate ≥ 60%, and disintegration rate ≥ 90%.

[0027] The principle of the present invention is as follows.

[0028] PBAT fiber materials have good biodegradability and a softer feel than fiber materials such as polylactic acid (PLA) and polyglycolic acid (PGA). However, biodegradable polyesters such as PBAT, PBST, and PBS have low crystallization ability and cannot be sufficiently cooled and solidified during the air-cooling process during spinning. This leads to adhesion between fibers, making continuous and stable molding impossible, and the resulting fibers have low mechanical strength. These factors significantly limit their applications. Previous techniques have addressed the issue of fiber adhesion by innovating the spinning process to strengthen air-cooling and extend the air-cooling area, or by controlling the length and sequence of chain segments and introducing additional chain segments during the biodegradable polyester synthesis process to improve crystallization ability. However, this often results in changes in the biodegradability of the resulting copolymer polyester. In particular, aromatic heterocycles in the introduced chain segments significantly hinder the biodegradability of the polyester, making the polymer difficult to biodegrade when their content is greater than 50 mol%.

[0029] In the present invention, an ionic copolyester is introduced into the biodegradable polyester. The ionic copolyester is composed of a sulfonate-based ionic polyester segment and a nonionic polyester segment. The nonionic polyester segment has good thermodynamic compatibility with the biodegradable polyester segment, allowing the ionic copolyester to be uniformly dispersed in the spinning melt. During the extrusion and cooling process of the biodegradable polyester melt, the ionic copolyester acts as a heterophase nucleating agent in the biodegradable polyester melt, promoting rapid crystallization of the melt under cooling conditions. At the same time, under high-speed spinning and high drawing ratios, a significant orientation process occurs in the melt, which further induces crystallization. Once a certain degree of crystallinity is reached, the adhesion phenomenon of fiber bundles is significantly reduced, allowing for continuous and stable fiber formation.

[0030] The present invention uses a copolymerization method to produce ionic copolyesters, which are composed of nonionic and ionic segments. Both segments first undergo an esterification reaction to form hydroxy-terminated oligomers with a certain degree of polymerization, and then undergo a polycondensation reaction to form a block-structured, regular copolyester. The nonionic segments are obtained by the esterification reaction of a diol and a dicarboxylic acid. By controlling the alcohol-acid molar ratio (diol excess), the oligomers are diol-terminated at the end of the esterification reaction. The present invention employs a stepwise esterification process. In the first esterification step, the number of carboxyl functional groups in the dicarboxylic acid containing sulfonate ion groups is in excess to ensure complete reaction of the alcohol monomer with sulfonate ion groups. Due to the excess carboxyl groups at the end of the first esterification step, the product is dicarboxylic acid-terminated. In the second esterification step, an excess of end-capping diol is introduced and allowed to fully react with the first-stage esterification product to form the ionic segments. Both the nonionic and ionic segments are diol-terminated oligomers that undergo a polycondensation reaction to produce the final product.

[0031] The polycondensation reaction is divided into preliminary polycondensation and final polycondensation. The preliminary polycondensation reaction is carried out under a relatively low vacuum. This is mainly because at this point, the relative molecular weights of the nonionic and ionic segments are still relatively low, and if a high vacuum were applied directly, they would be easily drawn out of the reaction system, making stable copolymerization impossible. At the end of the preliminary polycondensation reaction, the molecular weight of the product in the system has increased, and after moving on to the final polycondensation reaction step, they are not drawn out of the system even under a high vacuum, making stable polymerization possible.

[0032] In the present invention, the ionic copolyesters incorporated into the biodegradable polyesters generally have superior mechanical properties and thermal stability to their parent polymers. The ionic copolyesters contain abundant sulfonate ionic bonds, and the ionomers contain multiple ion pairs and ion clusters. These aggregates function as physical commissures, enhancing inter-chain interactions. When incorporated into fiber materials, the mechanical strength of the fibers can be significantly improved. This improvement in mechanical properties manifests itself in improved breaking strength during fiber tension and improved elastic recovery within a certain deformation range. At the same time, the commissures are reversible and dissociate under a certain shear force, ensuring thermoplastic processability. [Effects of the Invention]

[0033] Advantages of the present invention include: (1) This invention introduces an ionic copolyester into biodegradable polyester, and during the extrusion and cooling process of the biodegradable polyester melt, the ionic copolyester functions as a heterophase nucleating agent in the biodegradable polyester melt. At the same time, under high-speed spinning and high drawing ratio, orientation induces further crystallization, significantly reducing the adhesion phenomenon of fiber bundles that have reached a certain degree of crystallinity, thereby achieving continuous and stable fiber formation. The chemical structure of the biodegradable polyester is not changed, and no new spinning equipment is required.

[0034] (2) The ionic copolyesters introduced into the biodegradable polyesters of this invention contain abundant sulfonate ionic bonds. The multiple ion pairs and ion clusters present in the ionomers function as physical commissures, enhancing interactions between molecular chains. When incorporated into fiber materials, these aggregates significantly increase the mechanical strength of the fibers. This improvement in mechanical performance manifests itself as improved breaking strength during the fiber tension process and improved elastic recovery within a certain deformation range. DETAILED DESCRIPTION OF THE INVENTION

[0035] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as it does not deviate from the gist of the invention. Furthermore, even if a person skilled in the art is permitted to modify the present invention in various ways after reading the contents of the present invention, such modifications are also limited within the scope of the claims of the present invention as equivalent forms of the present invention.

[0036] The test method adopted in this invention is as follows: (1) Half-crystallization time t 1 / 2 : The sample is tested using a Q-20 DSC manufactured by TA Corporation, USA. Before testing, the sample is vacuum dried at 135°C for 24 hours. The test temperature is raised from 25°C to 300°C at a rate of 10°C / min in a nitrogen atmosphere, held for 3 minutes to remove the thermal history, and then cooled from 300°C to 25°C. The peak that appears during the temperature drop from 300°C to 25°C is called the cooling crystallization peak, and the temperature corresponding to the peak is the cooling crystallization temperature. The time required for the sample to crystallize from the start to completion is called the crystallization time, and the time when the crystallinity reaches 50% is called the half-crystallization time t 1 / 2 Let's say.

[0037] (2) Crystallization enthalpy: The sample is tested using a Q-20 DSC manufactured by TA Corporation, USA. Prior to testing, the sample is vacuum dried at 135°C for 24 hours. The test temperature is raised from 25°C to 300°C at a rate of 10°C / min in a nitrogen atmosphere, held for 3 minutes to remove thermal history, and then cooled from 300°C to 25°C. The peak that appears during the temperature drop from 300°C to 25°C is called the cooling crystallization peak, and the temperature corresponding to the peak is the cooling crystallization temperature. The cooling crystallization process is an exothermic process, and the total heat released by a unit mass of sample from the start to the end of crystallization is taken as the crystallization enthalpy; (3) Oil-free molecular weight: The molecular weight (number average molecular weight Mn) and molecular weight distribution index (PDI) of the polyester are measured using an Agilent 1260 Infinity II gel permeation chromatograph. 1,1,1,3,3,3-hexafluoro-2-propanol is used as the eluent, and the flow rate is 1 mL / min. For the test, the sample is dried and then dissolved in hexafluoroisopropanol to prepare a 10 mg / mL solution. The test is performed when the column temperature reaches 35 ± 1°C.

[0038] (4) Intrinsic viscosity: The intrinsic viscosity of the ionic copolyester is tested according to GB / T 14190-2017. In the following examples of the present invention, the mass ratio of phenol to 1,1,2,2-tetrachloroethane is 50:50.

[0039] (5) The molecular weight (number average molecular weight Mn and weight average molecular weight Mw) and molecular weight distribution index (PDI) of the biodegradable polyester are measured using an Agilent 1260 Infinity II gel permeation chromatograph. 1,1,1,3,3,3-hexafluoro-2-propanol is used as the eluent, and the flow rate is 1 mL / min. For the test, the sample is dried and then dissolved in hexafluoroisopropanol to prepare a 10 mg / mL solution. The test is performed when the column temperature reaches 35 ± 1°C.

[0040] (6) Breaking strength: The breaking strength test in the dry state specified in GB / T 14344-2008 "Test method for tensile properties of long chemical fibers" is adopted; (7) Breaking elongation: The breaking elongation test in the dry state specified in GB / T 14344-2008 Test method for tensile properties of chemical fibers and long fibers is used; (8) Composting biodegradability: Tested according to GB / T 19277.1-2011 Determination of the ultimate aerobic biodegradability of materials under controlled composting conditions - Carbon dioxide evolution measurement method; (9) Disintegration: Tested according to GB / T 19811-2005 Determination of Disintegration of Plastic Materials under Defined Pilot-Scale Composting Conditions.

[0041] Example 1 This is a method for producing high-strength biodegradable polyester fiber, and the specific steps are as follows: (1) Mix terephthalic acid and ethylene glycol in a molar ratio of 1:1.05, and carry out esterification reaction under conditions of 250℃ and 0.05MPa for 3.5 hours to produce nonionic polyester, in which the esterification catalyst is titanium diethylate, and the dosage is 10 ppm of the mass of terephthalic acid.

[0042] (2) Sulfonate-based ionic polyester is produced by a stepwise esterification reaction of sodium 5-sulfoisophthalate and potassium 2,5-dihydroxybenzenesulfonate. In the first step of the esterification reaction, the molar ratio of the number of carboxyl functional groups of sodium 5-sulfoisophthalate to the number of hydroxyl functional groups of potassium 2,5-dihydroxybenzenesulfonate was 1.05. In the second stage esterification reaction, potassium 2,5-dihydroxybenzenesulfonate was added in an amount of 10% of the molar amount of sodium 5-sulfoisophthalate added in the first stage, The benzenesulfonic acid used as a catalyst for the stepwise esterification reaction was added at 1000 ppm by mass of sodium 5-sulfoisophthalate during the first stage esterification reaction. The first-stage esterification reaction conditions were a temperature of 220°C, a pressure of 0.05 MPa, and a time of 3 hours, and the second-stage esterification reaction conditions were a temperature of 240°C, a pressure of 0.1 MPa, and a time of 0.5 hours.

[0043] (3) The nonionic polyester from step (1) and the sulfonate-based ionic polyester from step (2) are mixed in a molar ratio of 2:8, and subjected to preliminary polycondensation at 240°C and 1000 Pa for 0.1 hours, followed by final polycondensation at 260°C and 0 Pa for 0.15 hours to prepare an ionic copolymer polyester. The polycondensation catalyst is tetrabutyl titanate, and the dosage is 50 ppm of the total weight of both polyesters.

[0044] The resulting ionic copolyester is composed of nonionic polyester segments and sulfonate-based ionic polyester segments, with ester bonds linking different nonionic polyester segments, different ionic polyester segments, and the nonionic and ionic polyester segments. Furthermore, the number of repeating units of the nonionic polyester segments is 10, the number of repeating units of the ionic polyester segments is 6, and the intrinsic viscosity of the copolyester is 0.55 dL / g.

[0045] (4) The ionic copolyester from step (3) is added to PBAT (number average molecular weight 100,000 g / mol) at 1% of the PBAT mass and mixed uniformly to prepare a biodegradable polyester modified with the ionic copolyester, which is then melt-spun into a high-strength biodegradable polyester fiber. The spinning conditions are: spinning temperature 220°C, cooling air temperature 15°C, relative humidity 60%, air pressure 80 kPa, oil adhesion rate 0.6%, heat roller GR1 speed 1000 m / min, heat roller GR1 temperature 90°C, heat roller GR2 speed 2500 m / min, and heat roller GR2 temperature 100°C.

[0046] The biodegradable polyester modified with the obtained ionic copolyester had a crystallization temperature of 110°C and a half-crystallization time of t 1 / 2 It has the characteristics of crystallization enthalpy 45 J / g in 1 min.

[0047] The obtained high-strength biodegradable polyester fiber has a single yarn fineness of 1.5 dtex, an oil-free yarn number-average molecular weight reduction of 2000 g / mol, a breaking strength of 2.50 cN / dtex, a breaking elongation of 35.0%, and an elastic recovery rate of 91% under 2 to 10% tensile deformation.Its biodegradability is 60% for composting and 90% for disintegration.

[0048] Example 2 This is a method for producing high-strength biodegradable polyester fiber, and the specific steps are as follows: (1) Isophthalic acid and propylene glycol are mixed in a molar ratio of 1:1.5, and esterification is carried out for 1.5 hours under conditions of 230°C and 0.5 MPa to produce a nonionic polyester, in which the esterification catalyst is tetrabutyl titanate, and the dosage is 20 ppm of the mass of isophthalic acid.

[0049] (2) Sulfonate-based ionic polyester is produced by a stepwise esterification reaction of sodium 5-sulfoisophthalate and sodium N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonate. In the first step of the esterification reaction, the molar ratio of the number of carboxyl functional groups of sodium 5-sulfoisophthalate to the number of hydroxyl functional groups of sodium N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonate is 1.5. In the second stage esterification reaction, 60% of the molar amount of sodium 5-sulfoisophthalate added in the first stage was added with sodium N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonate; The benzenesulfonic acid used as a catalyst for the stepwise esterification reaction was added at 10 ppm by mass of sodium 5-sulfoisophthalate during the first stage esterification reaction. The conditions for the first stage esterification reaction were a temperature of 250°C, a pressure of 0.5 MPa, and a time of 4 hours, and the conditions for the second stage esterification reaction were a temperature of 250°C, a pressure of 0.2 MPa, and a time of 0.8 hours.

[0050] (3) The nonionic polyester from step (1) and the sulfonate-based ionic polyester from step (2) are mixed in a molar ratio of 8:2, and subjected to preliminary polycondensation at 260°C and 500 Pa for 1 hour, followed by final polycondensation at 285°C and 100 Pa for 3 hours to prepare an ionic copolymer polyester. The polycondensation catalyst is titanium diethylate, and the dosage is 60 ppm of the total mass of both polyesters.

[0051] The resulting ionic copolyester is composed of nonionic polyester segments and sulfonate-based ionic polyester segments, with ester bonds connecting different nonionic polyester segments, different ionic polyester segments, and the nonionic and ionic polyester segments. Furthermore, the number of repeating units of the nonionic polyester segments is 8, the number of repeating units of the ionic polyester segments is 4, and the intrinsic viscosity of the copolyester is 0.85 dL / g.

[0052] (4) The ionic copolyester from step (3) is added to PBST (number average molecular weight 750,000 g / mol) at 10% of the PBST mass and mixed uniformly to prepare a biodegradable polyester modified with the ionic copolyester, which is then melt-spun into high-strength biodegradable polyester fibers. The spinning conditions are: spinning temperature 280°C, cooling air temperature 20°C, relative humidity 85%, air pressure 20 kPa, oil adhesion rate 1.5%, heat roller GR1 speed 1500 m / min, heat roller GR1 temperature 60°C, heat roller GR2 speed 3500 m / min, and heat roller GR2 temperature 120°C.

[0053] The biodegradable polyester modified with the obtained ionic copolyester has a crystallization temperature of 150°C and a half-crystallization time of t 1 / 2 It has the characteristics of 2 min, crystallization enthalpy 50 J / g.

[0054] The obtained high-strength biodegradable polyester fiber has a single yarn fineness of 2 dtex, an oil-free yarn number-average molecular weight reduction of 1500 g / mol, a breaking strength of 2.71 cN / dtex, a breaking elongation of 29.6%, and an elastic recovery rate of 90% under 2-10% tensile deformation.Its biodegradability is 90% for composting and 95% for disintegration.

[0055] Example 3 This is a method for producing high-strength biodegradable polyester fiber, and the specific steps are as follows: (1) Adipic acid and butanediol are mixed in a molar ratio of 1:1.15, and esterification is carried out under conditions of 150°C and 0.01 MPa for 1.5 hours to produce nonionic polyester, in which the esterification catalyst is antimony diethylate, and the dosage is 100 ppm of the mass of adipic acid.

[0056] (2) Sulfonate-based ionic polyester is produced by a stepwise esterification reaction of sodium 5-sulfoisophthalate and sodium 2-[(tris(hydroxymethyl)methyl)amino]-1-ethanesulfonate. In the first-stage esterification reaction, the molar ratio of the number of carboxyl functional groups of sodium 5-sulfoisophthalate to the number of hydroxyl functional groups of sodium 2-[(tris(hydroxymethyl)methyl)amino]-1-ethanesulfonate was 1.1, In the second stage esterification reaction, 20% of the molar amount of sodium 5-sulfoisophthalate added in the first stage was added with sodium 2-[(tris(hydroxymethyl)methyl)amino]-1-ethanesulfonate, The benzenesulfonic acid used as a catalyst for the stepwise esterification reaction was added at 100 ppm by mass of sodium 5-sulfoisophthalate during the first stage esterification reaction. The conditions for the first stage esterification reaction were a temperature of 230°C, a pressure of 0.1 MPa, and a time of 5 hours, and the conditions for the second stage esterification reaction were a temperature of 260°C, a pressure of 0.3 MPa, and a time of 0.8 hours.

[0057] (3) The nonionic polyester from step (1) and the sulfonate-based ionic polyester from step (2) are mixed in a molar ratio of 5:5, and subjected to preliminary polycondensation at 250°C and 800 Pa for 0.2 hours, followed by final polycondensation at 265°C and 10 Pa for 2 hours to prepare an ionic copolymer polyester. The polycondensation catalyst is antimony trioxide, and the dosage is 500 ppm of the total weight of both polyesters.

[0058] The resulting ionic copolyester is composed of nonionic polyester segments and sulfonate-based ionic polyester segments, and different nonionic polyester segments, different ionic polyester segments, and nonionic polyester segments and ionic polyester segments are all connected by ester bonds. Furthermore, the number of repeating units of the nonionic polyester segments is 4, the number of repeating units of the ionic polyester segments is 2, and the intrinsic viscosity of the copolyester is 0.75 dL / g.

[0059] (4) The ionic copolyester from step (3) is added to PBS (number average molecular weight 50,000 g / mol) at 10% of the PBS mass and mixed uniformly to prepare a biodegradable polyester modified with the ionic copolyester, which is then melt-spun into high-strength biodegradable polyester fiber. The spinning conditions are: spinning temperature 240°C, cooling air temperature 16°C, relative humidity 65%, air pressure 70 kPa, oil adhesion rate 0.8%, heat roller GR1 speed 1200 m / min, heat roller GR1 temperature 85°C, heat roller GR2 speed 2800 m / min, and heat roller GR2 temperature 105°C.

[0060] The biodegradable polyester modified with the obtained ionic copolyester has a crystallization temperature of 80°C and a half-crystallization time of t 1 / 2 It has the characteristics of crystallization enthalpy of 50 J / g in 3 min.

[0061] The obtained high-strength biodegradable polyester fiber has a single yarn fineness of 2.5 dtex, an oil-free yarn number-average molecular weight reduction of 1200 g / mol, a breaking strength of 2.83 cN / dtex, a breaking elongation of 27.7%, and an elastic recovery rate of 90% under 2-10% tensile deformation.Its biodegradability is 80% for composting and 92% for disintegration.

[0062] Example 4 This is a method for producing high-strength biodegradable polyester fiber, and the specific steps are as follows: (1) Mix terephthalic acid and pentanediol in a molar ratio of 1:1.25, and carry out esterification reaction under conditions of 220℃ and 0.1MPa for 2.5 hours to produce nonionic polyester, in which the esterification reaction catalyst is antimony diethylate, and the dosage is 80 ppm of the mass of terephthalic acid.

[0063] (2) Sulfonate-based ionic polyester is produced by a stepwise esterification reaction of sodium 2-sulfoterephthalate and sodium 3-[N-tris(hydroxymethyl)methylamine]-2-hydroxypropanesulfonate. In the first-stage esterification reaction, the molar ratio of the number of carboxyl functional groups of sodium 2-sulfoterephthalate to the number of hydroxyl functional groups of sodium 3-[N-tris(hydroxymethyl)methylamine]-2-hydroxypropanesulfonate was 1.2. In the second stage esterification reaction, 30% of the molar amount of sodium 2-sulfoterephthalate added in the first stage was added with 3-[N-tris(hydroxymethyl)methylamine]-2-hydroxypropanesulfonate; The benzenesulfonic acid used as a catalyst for the stepwise esterification reaction was added at 800 ppm by mass of sodium 2-sulfoterephthalate during the first stage esterification reaction. The conditions for the first stage esterification reaction were a temperature of 240°C, a pressure of 0.4 MPa, and a time of 3 hours, and the conditions for the second stage esterification reaction were a temperature of 245°C, a pressure of 0.4 MPa, and a time of 0.5 hours.

[0064] (3) The nonionic polyester from step (1) and the sulfonate-based ionic polyester from step (2) are mixed in a molar ratio of 3:7, and subjected to preliminary polycondensation at 245°C and 600 Pa for 0.8 hours, followed by final polycondensation at 280°C and 80 Pa for 2.5 hours to prepare an ionic copolymer polyester. The polycondensation catalyst is antimony diethylate, and the dosage is 400 ppm of the total weight of both polyesters.

[0065] The resulting ionic copolyester is composed of nonionic polyester segments and sulfonate-based ionic polyester segments, and different nonionic polyester segments, different ionic polyester segments, and nonionic polyester segments and ionic polyester segments are all connected by ester bonds. Furthermore, the number of repeating units of the nonionic polyester segments is 6, the number of repeating units of the ionic polyester segments is 3, and the intrinsic viscosity of the copolyester is 0.60 dL / g.

[0066] (4) The ionic copolyester from step (3) is added to PHA (number average molecular weight 85,000 g / mol) at 8% of the PHA mass and mixed uniformly to prepare a biodegradable polyester modified with the ionic copolyester, which is then melt-spun into a high-strength biodegradable polyester fiber. The spinning conditions are: spinning temperature 270°C, cooling air temperature 18°C, relative humidity 80%, air pressure 30 kPa, oil adhesion rate 1.2%, heat roller GR1 speed 1400 m / min, heat roller GR1 temperature 70°C, heat roller GR2 speed 3200 m / min, and heat roller GR2 temperature 115°C.

[0067] The biodegradable polyester modified with the obtained ionic copolyester has a crystallization temperature of 70°C and a half-crystallization time of t 1 / 2 It has the characteristics of 2.5 min and crystallization enthalpy of 35 J / g.

[0068] The obtained high-strength biodegradable polyester fiber has a single yarn fineness of 3 dtex, an oil-free yarn number-average molecular weight reduction of 1000 g / mol, a breaking strength of 2.92 cN / dtex, a breaking elongation of 20.3%, and an elastic recovery rate of 90.7% under 2-10% tensile deformation. Its biodegradability is 75% for composting and 93% for disintegration.

[0069] Example 5 This is a method for producing high-strength biodegradable polyester fiber, and the specific steps are as follows: (1) Isophthalic acid and ethylene glycol are mixed in a molar ratio of 1:1.35, and esterification is carried out for 3 hours under conditions of 240°C and 0.3 MPa to produce nonionic polyester, in which the esterification catalyst is antimony(III) oxide, and the dosage is 90 ppm of the mass of isophthalic acid.

[0070] (2) Sulfonate-based ionic polyester is produced by a stepwise esterification reaction of sodium 2-sulfoterephthalate and potassium 2,5-dihydroxybenzenesulfonate. In the first step of the esterification reaction, the molar ratio of the number of carboxyl functional groups of sodium 2-sulfoterephthalate to the number of hydroxyl functional groups of potassium 2,5-dihydroxybenzenesulfonate was 1.3. In the second stage esterification reaction, potassium 2,5-dihydroxybenzenesulfonate was added in an amount of 40% of the molar amount of sodium 2-sulfoterephthalate added in the first stage, The benzenesulfonic acid used as a catalyst for the stepwise esterification reaction was added at 300 ppm by mass of sodium 2-sulfoterephthalate during the first stage esterification reaction. The first stage esterification reaction conditions were a temperature of 235°C, a pressure of 0.2 MPa, and a time of 4 hours, and the second stage esterification reaction conditions were a temperature of 255°C, a pressure of 0.35 MPa, and a time of 0.8 hours.

[0071] (3) The nonionic polyester from step (1) and the sulfonate-based ionic polyester from step (2) are mixed in a molar ratio of 4:6, and subjected to preliminary polycondensation at 250°C and 900 Pa for 0.5 hours, followed by final polycondensation at 270°C and 30 Pa for 2 hours to prepare an ionic copolymer polyester. The polycondensation catalyst is antimony(III) acetate, and the dosage is 200 ppm of the total weight of both polyesters.

[0072] The resulting ionic copolyester is composed of nonionic polyester segments and sulfonate-based ionic polyester segments, and different nonionic polyester segments, different ionic polyester segments, and nonionic and ionic polyester segments are all connected by ester bonds. Furthermore, the number of repeating units of the nonionic polyester segments is 9, the number of repeating units of the ionic polyester segments is 8, and the intrinsic viscosity of the copolyester is 0.72 dL / g.

[0073] (4) The ionic copolyester from step (3) is added to PCL (number average molecular weight 90,000 g / mol) at 3% of the PCL mass and mixed uniformly to prepare a biodegradable polyester modified with the ionic copolyester, which is then melt-spun into a high-strength biodegradable polyester fiber. The spinning conditions are: spinning temperature 260°C, cooling air temperature 17°C, relative humidity 70%, air pressure 60 kPa, oil adhesion rate 1%, heat roller GR1 speed 1200 m / min, heat roller GR1 temperature 80°C, heat roller GR2 speed 2900 m / min, and heat roller GR2 temperature 115°C.

[0074] The biodegradable polyester modified with the obtained ionic copolyester has a crystallization temperature of 50°C and a half-crystallization time of t 1 / 2 It has the characteristics of 2.8 min and crystallization enthalpy of 30 J / g.

[0075] The obtained high-strength biodegradable polyester fiber has a single yarn fineness of 4 dtex, an oil-free yarn number-average molecular weight reduction of 500 g / mol, a breaking strength of 3.0 cN / dtex, a breaking elongation of 15.0%, and an elastic recovery rate of 90.6% under 2 to 10% tensile deformation.Its biodegradability is 70% for composting and 91% for disintegration.

[0076] Example 6 This is a method for producing high-strength biodegradable polyester fiber, and the specific steps are as follows: (1) Adipic acid and propylene glycol are mixed in a molar ratio of 1:1.4, and esterification is carried out under conditions of 180°C and 0.4 MPa for 2 hours to produce nonionic polyester, in which the esterification catalyst is titanium diethylate, and the dosage is 30 ppm of the mass of adipic acid.

[0077] (2) Sulfonate-based ionic polyester is produced by a stepwise esterification reaction of sodium 2-sulfoterephthalate and sodium N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonate. In the first step of the esterification reaction, the molar ratio of the number of carboxyl functional groups of sodium 2-sulfoterephthalate to the number of hydroxyl functional groups of sodium N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonate was 1.4. In the second stage esterification reaction, 50% of the molar amount of sodium 2-sulfoterephthalate added in the first stage was added with sodium N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonate; The benzenesulfonic acid used as a catalyst for the stepwise esterification reaction was added at 500 ppm by mass of sodium 2-sulfoterephthalate during the first stage esterification reaction. The conditions for the first stage esterification reaction were a temperature of 225°C, a pressure of 0.3 MPa, and a time of 5 hours, and the conditions for the second stage esterification reaction were a temperature of 240°C, a pressure of 0.5 MPa, and a time of 1 hour.

[0078] (3) The nonionic polyester from step (1) and the sulfonate-based ionic polyester from step (2) are mixed in a molar ratio of 6:4, and subjected to preliminary polycondensation at 255°C and 700 Pa for 0.6 hours, followed by final polycondensation at 275°C and 50 Pa for 2.5 hours to prepare an ionic copolymer polyester. The polycondensation catalyst is tetrabutyl titanate, and the dosage is 80 ppm of the total weight of both polyesters.

[0079] The resulting ionic copolyester is composed of nonionic polyester segments and sulfonate-based ionic polyester segments, and different nonionic polyester segments, different ionic polyester segments, and nonionic polyester segments and ionic polyester segments are all connected by ester bonds. Furthermore, the number of repeating units of the nonionic polyester segments is 5, the number of repeating units of the ionic polyester segments is 5, and the intrinsic viscosity of the copolyester is 0.81 dL / g.

[0080] (4) The ionic copolyester from step (3) was added to PBAT (number average molecular weight 95,000 g / mol) at 5% of the PBAT mass and mixed uniformly to prepare a biodegradable polyester modified with the ionic copolyester. This was then melt-spun into a high-strength biodegradable polyester fiber. The spinning conditions were: spinning temperature 250°C, cooling air temperature 19°C, relative humidity 75%, air pressure 50 kPa, oil adhesion rate 0.9%, heat roller GR1 speed 1300 m / min, heat roller GR1 temperature 75°C, heat roller GR2 speed 3000 m / min, and heat roller GR2 temperature 108°C.

[0081] The biodegradable polyester modified with the obtained ionic copolyester has a crystallization temperature of 100°C and a half-crystallization time of t 1 / 2 It has the characteristics of 1.5 min, crystallization enthalpy 40 J / g.

[0082] The obtained high-strength biodegradable polyester fiber has a single yarn fineness of 2 dtex, an oil-free yarn number-average molecular weight reduction of 1800 g / mol, a breaking strength of 2.64 cN / dtex, a breaking elongation of 32.9%, and an elastic recovery rate of 90.2% under 2-10% tensile deformation. Its biodegradability is 85% for composting and 94% for disintegration.

Claims

1. High-strength biodegradable polyester fibers are obtained by adding an ionic copolymer polyester to biodegradable polyester and melt-spinning the resulting fibers. The biodegradable polyester is polybutylene(adipate-co-terephthalate) (PBAT), polybutylene(terephthalate-co-succinate) (PBST), polybutylene succinate (PBS), poly-3-hydroxyalkanoate (P3HB) or poly-ε-caprolactone (PCL); the amount of the ionic copolyester added is 1 to 10% by mass of the biodegradable polyester; The ionic copolyester is composed of a nonionic polyester segment and a sulfonate-based ionic polyester segment, and different nonionic polyester segments, different ionic polyester segments, and the nonionic polyester segment and the ionic polyester segment are all linked by ester bonds; The intrinsic viscosity of the ionic copolyester is 0.55 to 0.85 dl / g, The nonionic polyester segment has 4 to 10 repeating units, and the sulfonate-based ionic polyester segment has 2 to 8 repeating units, The method for producing the ionic copolymer polyester comprises first synthesizing a nonionic polyester and a sulfonate-based ionic polyester by an esterification reaction, and then subjecting the nonionic polyester and the sulfonate-based ionic polyester to a polycondensation reaction to produce the ionic copolymer polyester; The sulfonate-based ionic polyester is produced by a stepwise esterification reaction of dicarboxylic acid II and diol II, in which the molar ratio of the number of carboxyl functional groups of dicarboxylic acid II added in the first esterification reaction to the number of hydroxyl functional groups of diol II is 1.05 to 1.50, and in the second esterification reaction, only diol II is added, and its amount is 10 to 60% of the molar amount of dicarboxylic acid II added in the first esterification reaction, the dicarboxylic acid II is sodium 5-sulfoisophthalate or sodium 2-sulfoterephthalate, and the diol II is potassium 2,5-dihydroxybenzenesulfonate, sodium N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonate, sodium 2-[(tris(hydroxymethyl)methyl)amino]-1-ethanesulfonate or sodium 3-[N-tris(hydroxymethyl)methylamine]-2-hydroxypropanesulfonate, The obtained high-strength biodegradable polyester fiber has the following characteristics: a single yarn fineness of 1.5 to 5.0 dtex, an oil-free yarn number-average molecular weight reduction of 500 to 2000 g / mol, a breaking strength of ≥ 2.50 cN / dtex, a breaking elongation of 15.0 to 35.0%, an elastic recovery rate under 2 to 10% tensile deformation of ≥ 90%, and a compostable biodegradability rate of ≥ 60% and a disintegration rate of ≥ 90%. A method for producing high-strength biodegradable polyester fibers.

2. 2. The method for producing high-strength biodegradable polyester fibers according to claim 1, wherein the number average molecular weight of the biodegradable polyester is 50,000 to 100,000 g / mol.

3. 2. The method for producing a high-strength biodegradable polyester fiber according to claim 1, wherein the melt spinning process parameters are a spinning temperature of 220 to 280°C, a cooling air temperature of 15 to 20°C, a relative humidity of 60 to 85%, an air pressure of 20 to 80 kPa, a fiber oil adhesion rate of 0.6 to 1.5%, a heat roller GR1 speed of 1000 to 1500 m / min, a heat roller GR1 temperature of 60 to 90°C, a heat roller GR2 speed of 2500 to 3500 m / min, and a heat roller GR2 temperature of 100 to 120°C.

4. 2. The method for producing high-strength biodegradable polyester fibers according to claim 1, wherein the molar ratio of the nonionic polyester to the sulfonate-based ionic polyester is 2:8 to 8:

2.

5. The nonionic polyester is prepared by the esterification reaction of dicarboxylic acid I and diol I, in which the molar ratio of dicarboxylic acid I to diol I is 1:1.05-1.5, the dicarboxylic acid I is terephthalic acid, isophthalic acid or adipic acid, and the diol I is ethylene glycol, propylene glycol, butanediol or pentanediol. The method for producing high-strength biodegradable polyester fibers according to claim 1.

6. The catalyst for the esterification reaction of the nonionic polyester is titanium glycolate, tetrabutyl titanate, antimony glycolate, antimony (III) acetate or antimony (III) oxide, and the amount used is 10 to 100 ppm based on the mass of the dicarboxylic acid I. The method for producing high-strength biodegradable polyester fibers according to claim 5.

7. The esterification reaction conditions for the nonionic polyester are a temperature of 150 to 250°C, a pressure of 0.01 to 0.5 MPa, and a time of 1.5 to 3.5 hours. The method for producing high-strength biodegradable polyester fibers according to claim 5.

8. The catalyst in the stepwise esterification reaction of the sulfonate-based ionic polyester is benzenesulfonic acid, which is added in the first step of the esterification reaction, in an amount of 10 to 1000 ppm based on the mass of the dicarboxylic acid II. The method for producing high-strength biodegradable polyester fibers according to claim 1.

9. The conditions for the first stage esterification reaction are a temperature of 220 to 250°C, a pressure of 0.05 to 0.5 MPa, and a time of 3.0 to 5.0 hours, and the conditions for the second stage esterification reaction are a temperature of 240 to 260°C, a pressure of 0.1 to 0.5 MPa, and a time of 0.5 to 1.0 hours. The method for producing high-strength biodegradable polyester fibers according to claim 1.

10. The polycondensation reaction between nonionic polyester and sulfonate-based ionic polyester is divided into a preliminary polycondensation reaction and a final polycondensation reaction. The temperature of the preliminary polycondensation reaction is 240 to 260°C, the reaction time is 0.1 to 1.0 h, and the pressure is 500 to 1000 Pa. The temperature of the final polycondensation reaction is 260 to 285°C, the reaction time is 1.5 to 3.0 hours, and the pressure is 0 to 100 Pa. The method for producing high-strength biodegradable polyester fibers according to claim 1.

11. The polycondensation catalyst is tetrabutyl titanate, titanium glycolate, antimony trioxide, antimony glycolate or antimony (III) acetate, and the amount added is 50 to 500 ppm of the total mass of the sulfonate ionic polyester and the nonionic polyester. The method for producing high-strength biodegradable polyester fibers according to claim 10.

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