Method for manufacturing high-strength biodegradable polyester fibers

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] This invention belongs to the field of polyester technology and relates to the production of biodegradable polyester fibers, and more specifically, to a method for producing high-strength biodegradable polyester fibers. [Background technology]

[0002] Textile materials are fundamental raw materials in the spinning industry. Technological innovations in textile materials constantly provide new vitality to the textile industry. Conventional polyester fibers, due to their stable chemical structure and excellent mechanical properties, are widely used in various fields such as household textiles, clothing, and industrial materials. In fields such as disposable medical and sanitary textile products, where recycling after use is not possible, it is necessary for the textile materials used to have good biodegradability, thereby reducing environmental pollution.

[0003] Biodegradable polyesters produced from dicarboxylic acids and diols based on common long-chain hydrocarbons include PBAT, PBST, and PBS. Of these, PBAT is a ternary copolymer composed of terephthalic acid, adipic acid, and butanediol. It exhibits good processability, high toughness, and excellent biodegradability, decomposing into carbon dioxide, biomass, and water under soil or composting conditions. Simultaneously, PBAT fiber materials have good biodegradability and a softer feel compared to fiber materials such as polylactic acid (PLA) and polyglycolic acid (PGA). However, because random copolymerization is employed in the synthesis process of PBAT, crystallization is difficult, which limits the development of PBAT fiber manufacturing technology and the application of PBAT as a fiber material. Therefore, producing biodegradable fibers using PBAT as a raw material that meet the requirements of environmental protection and sustainable development will expand its application fields and have significant market implications.

[0004] Chinese patent CN100412242C discloses a method for producing polybutylene (terephthalate-cosuccinate) fibers. It involves melt-extruding copolymer polyester to form undrawn yarn, balancing it under constant temperature and humidity conditions for 5 to 13 hours, and then drawing it to produce biodegradable polyester fibers. Chinese patent CN113201805A relates to a method for producing PBAT fibers. In the spinning process of PBAT fibers, the processes are carried out in the order of cooling, bundling, lubrication, drawing, and winding. The cooling process employs a combination of slow cooling and strong cooling to optimize the PBAT spinning and cooling process. Specifically, when the yarn is cooled to near its crystallization temperature, a slow cooling method is used, and a heat retention treatment is performed near the PBAT crystallization temperature to give PBAT sufficient crystallization time, completing the crystallization of PBAT and improving the degree of crystallization. By improving the degree of crystallization, the adhesion phenomenon that occurs in the bundling and winding process of PBAT fibers is avoided, and the quality of the PBAT fibers is improved. CN103668540B relates to PBAT fibers and a method for producing the same, and effectively improves cooling difficulties and adhesion problems in the PBAT spinning process by extending the cooling distance during the spinning process when the molecular weight of the linear polyester is high and uniformly distributed. CN103668541B relates to a biodegradable fiber containing PBAT and a method for producing the same, and is produced from components containing the following parts by weight: polybutylene (adipate-co-terephthalate) (PBAT) to which one or two of polyhydroxybutyric acid, polyhydroxybutyric acid-valeric acid, polybutylene succinate, or polylactic acid are introduced, and when the molecular weight of the linear polyester used for spinning is high and uniformly distributed, the performance of the resulting fiber is good, and by extending the cooling distance during the spinning process, cooling difficulties and adhesion problems in the PBAT spinning process are effectively improved.

[0005] Chinese patent CN113122952A relates to PBAT fibers and a method for producing the same. The molecular chain of the PBAT fiber contains a butylene terephthalate segment, a butylene adipate segment, and a sodium 5-sulfonate-butylene isophthalate segment. The balance between the crystallization ability and performance of PBAT is controlled by the segment length, and fiber performance is improved by introducing SSIPA into the segments. CN112048058B relates to a method for producing a high-melting-point crystalline biodegradable copolymer polyester. An isohexitol-based polyester prepolymer, an aliphatic polyester prepolymer, and a chain extender are mixed and reacted to produce a high-melting-point crystalline biodegradable copolymer polyester. To obtain good overall performance (thermal properties, mechanical properties, biodegradability), the terephthalic acid content in commercial PBAT and PBST-based aliphatic-aromatic copolymer polyesters is usually 40-50 mol%. Based on ΔTm = ΔHm / ΔSm, the addition of copolymer monomers disrupts the crystalline regularity of the PBS repeating units, reducing the crystallization enthalpy of the segments or increasing the entropy of the segments, resulting in poor crystallization ability of 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, conferring 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 blow-cooling in spinning, leading to fiber adhesion and making continuous and stable molding impossible. Furthermore, the mechanical strength of the fibers is low. These factors significantly limit their applications. As is evident from the known technologies described above, to address this problem, biodegradable polyesters are copolymerized, and then the problem of fiber adhesion is improved by enhancing blow-cooling through spinning process innovations and extending the blow-cooling area. Existing reported technologies involve copolymerizing biodegradable polyesters with a high proportion of modifying components to improve the heat resistance and crystallization performance of the biodegradable polyester, followed by optimizing spinning to obtain fibers. However, copolymerization with a high proportion of modifying components disrupts the original chemical arrangement structure of the biodegradable polyester, unfavorably affecting the biodegradability of the fibers. Additionally, spinning using copolymerized biodegradable polyesters lacks the operational flexibility of blend-addition methods. Furthermore, while there are methods to improve crystallization ability by controlling the length and arrangement structure of segments and introducing other segments during the biodegradable polyester synthesis stage, this often alters the biodegradation performance of the synthesized copolymer polyester. In particular, aromatic heterocycles in the introduced segments significantly inhibit the biodegradation performance of the polyester, and when the content is >50 mol%, the polymer becomes difficult to biodegrade. [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The object of the present invention is to solve the problems of the prior art and provide a method for producing high-strength biodegradable polyester fibers. The present invention addresses the problem that current biodegradable polyesters such as PBAT, PBST, and PBS have weak crystallization ability during melt spinning, making rapid cooling and solidification impossible, causing fibers to stick together, and consequently making their application difficult. By introducing a certain amount of ionic copolymer polyester into the biodegradable polyester, its crystallization ability is significantly improved, enabling continuous and stable fiber formation and greatly increasing fiber strength, thereby meeting application requirements.

[0008] To achieve the above objectives, the technical solution employed by this invention is as follows: (1) A method for producing high-strength biodegradable polyester fibers involves adding an ionic copolymer polyester to a biodegradable polyester and melt spinning the resulting material.

[0009] (2) The amount of ionic copolymer polyester added is 1-10% of the mass of biodegradable polyester. Most current biodegradable polyesters (including PBAT, PBS, PBST, etc.) cannot be sufficiently cooled and solidified by blow cooling during spinning, causing the fibers to stick together, making continuous and stable molding impossible, and the mechanical strength of the fibers is also low. These factors severely limit their applications. The amount of ionic copolymer polyester added has a significant effect on the performance of the spun biodegradable polyester fibers. If the amount of ionic copolymer polyester added is less than 1%, the ionic copolymer polyester content in the biodegradable polyester is low, and its molten state cannot be effectively controlled, so the fibers are still prone to adhesion problems; if the amount of ionic copolymer polyester added exceeds 10%, the ionic copolymer polyester content in the biodegradable polyester becomes excessive, the spinnability of the fibers is greatly improved and adhesion problems do not occur, but the biodegradability of the spun fibers decreases. Therefore, it is necessary to strictly control the ionic copolymer polyester content in biodegradable polyester fibers.

[0010] (3) The ionic copolymer polyester is composed of a nonionic polyester segment and a sulfonate-based ionic polyester segment, and the different nonionic polyester segments, the different ionic polyester segments, and the nonionic polyester segments and ionic polyester segments are all linked by ester bonds.

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

[0012] As a preferred technical solution: In the above-described 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 poly-ε-caprolactone (PCL), and the number-average molecular weight of the biodegradable polyester is 50,000 to 100,000 g / mol.

[0013] In the above-described method for producing high-strength biodegradable polyester fibers, the melt spinning process parameters 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, heat roller GR2 temperature 100-120°C.

[0014] In the above-described method for producing high-strength biodegradable polyester fibers, 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 significantly affects the structure and performance of the synthesized ionic copolymer polyester, and therefore must be controlled within this range. If the number of repeating units falls below the set range, polymerizing both substances at a fixed mass ratio (i.e., fixed number of moles of both substances) results in a synthesized ionic copolymer polyester that approaches a random copolymer polyester, significantly reducing its crystalline properties, and causing the ionic copolymer polyester to adhere during drying, making it unusable for spinning. If the number of repeating units exceeds the set range, polymerizing both substances at a fixed mass ratio (i.e., fixed number of moles of both substances) results in an excessive number of repeating units and a high molecular weight for both segments, reducing the reaction activity during copolymerization. The molecular weight of the ionic copolymer polyester fails to meet spinning requirements, making it unsuitable for application.

[0015] In the above-mentioned method for producing high-strength biodegradable polyester fibers, the method for producing ionic copolymer polyester is as follows: First, a nonionic polyester and a sulfonate-based ionic polyester are synthesized by an esterification reaction, and then the ionic copolymer polyester is produced by a polycondensation reaction of the nonionic polyester and the sulfonate-based ionic polyester.

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

[0017] In the above-described method for producing high-strength biodegradable polyester fibers, the nonionic polyester is produced by an esterification reaction of dicarboxylic acid I and diol I, where the molar ratio of dicarboxylic acid I to diol I is 1:1.05 to 1.5, and dicarboxylic acid I is terephthalic acid, isophthalic acid, or adipic acid, and diol I is ethylene glycol, propylene glycol, butanediol, or pentanediol.

[0018] In the above-described method for producing high-strength biodegradable polyester fibers, the catalyst used in the esterification reaction of 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 by mass of dicarboxylic acid.

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

[0020] In the above method for producing high-strength biodegradable polyester fibers, sulfonate-based ion polyester is produced by a stepwise esterification reaction of dicarboxylic acid II and diol II. The molar ratio of the number of carboxyl functional groups of dicarboxylic acid II to the number of hydroxy functional groups of diol II added in the first-stage esterification reaction is 1.05 to 1.50; in the second-stage esterification reaction, only diol II is added, and the addition amount is 10 to 60% of the molar amount of dicarboxylic acid II added in the first-stage esterification reaction; Dicarboxylic acid II is sodium 5-sulfoisophthalate or sodium 2-sulphoterephthalate; 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 above high-strength biodegradable polyester fiber, the catalyst for the stepwise esterification reaction of the sulfonate-based ion polyester is benzenesulfonic acid, which is added during the first-stage esterification reaction, and the usage amount is 10 to 1000 ppm of the mass of dicarboxylic acid II.

[0022] In the method for producing the above high-strength biodegradable polyester fiber, the conditions for the first-stage esterification reaction are: temperature 220 to 250 °C, pressure 0.05 to 0.5 MPa, time 3.0 to 5.0 hr; the conditions for the second-stage esterification reaction are: temperature 240 to 260 °C, pressure 0.1 to 0.5 MPa, time 0.5 to 1. hr.

[0023] In the method for producing the above high-strength biodegradable polyester fiber, the polycondensation reaction of the non-ionic polyester and the sulfonate-based ion polyester is divided into a preliminary polycondensation reaction and a final polycondensation reaction. Among them, The temperature of the preliminary polycondensation reaction is 240 to 260 °C, the reaction time is 0.1 to 1.0 hour, 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.

[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 addition amount is 50 to 500 ppm of the total mass of the sulfonate ion polyester and the nonionic polyester.

[0025] In the production method of the above 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 is 1.0 to 3.0 minutes, and the crystallization enthalpy is 10 to 50 J / g.

[0026] In the production method of the above high-strength biodegradable polyester fiber, the fineness of the single filament of the high-strength biodegradable polyester fiber is 1.5 to 5.0 dtex, the number average molecular weight reduction of the oil-free yarn (Note: The oil-free yarn refers to the fiber without oil treatment after passing through the cooling air drying process after melt extrusion) is 500 to 2000 g / mol, the breaking strength of the fiber 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 that the compost biodegradation rate is ≥60% and the disintegration degree is ≥90%.

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

[0028] PBAT fiber materials have good biodegradability and are softer to the touch 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 blow-cooling in spinning and molding, causing fibers to stick together, making continuous and stable molding impossible, and resulting in low mechanical strength of the fibers. These factors severely limit their applications. Conventional techniques improve the problem of fiber adhesion by strengthening blow-cooling through spinning process innovations and extending the blow-cooling area, or by controlling the length and arrangement structure of chain segments and introducing other chain segments during the biodegradable polyester synthesis stage to improve crystallization ability. However, this often changes the biodegradability of the synthesized copolymer polyester, and in particular, aromatic heterocycles in the introduced chain segments significantly inhibit the biodegradability of the polyester, making the polymer difficult to biodegrade when the content is >50 mol%.

[0029] In this invention, an ionic copolymer polyester is introduced into a biodegradable polyester. The ionic copolymer polyester is composed of a sulfonate-based ionic polyester segment and a nonionic polyester segment. Since the nonionic polyester segment has good thermodynamic compatibility with the biodegradable polyester segment, the ionic copolymer polyester is uniformly dispersed in the spun melt. In the extrusion cooling process of the biodegradable polyester melt, the ionic copolymer polyester functions as a heterogeneous nucleation 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-magnification stretching, a significant orientation process occurs in the melt, and this orientation further induces crystallization. Once a certain degree of crystallization is reached, the adhesion phenomenon of fiber bundles is significantly reduced, and continuous and stable shaping of the fibers is achieved.

[0030] This invention provides a method for producing an ionic copolymer polyester by copolymerization, the copolymer polyester being composed of a nonionic segment and an ionic segment. Both segments first undergo an esterification reaction to form a hydroxy-terminated oligomer with a certain degree of low polymerization, and then both segments undergo a polycondensation reaction to form a copolymer polyester with a block-like ordered structure. The nonionic segment is obtained by the esterification reaction of a diol and a dicarboxylic acid, and by controlling the alcohol-acid molar ratio (diol excess), it is achieved that the oligomer has a diol terminus at the end of the esterification reaction. This invention is designed for stepwise esterification. In the first-step esterification, the number of carboxyl functional groups in the dicarboxylic acid containing a sulfonate ionic group is made excess to ensure that the alcohol monomer having a sulfonate ionic group reacts completely. Since there is an excess of carboxyl groups at the end of the first-step esterification reaction, the product has a dicarboxylic acid terminus. In the second-step esterification reaction, an excess amount of end-canceling diol is introduced and reacted thoroughly with the first-step esterification product to form an ionic segment. Both the nonionic and ionic segments are diol-terminated oligomers, and the final product is produced by polycondensation of these segments.

[0031] Polycondensation reactions are divided into pre-polycondensation and final polycondensation. The pre-polycondensation reaction is carried out under relatively low vacuum. This is mainly because, at this stage, the relative molecular weights of the nonionic and ionic segments are still relatively low, and if a high vacuum is applied directly, they are easily abstracted out of the reaction system, preventing stable copolymerization. By the end of the pre-polycondensation reaction, the molecular weight of the products in system has increased, and after moving to the final polycondensation reaction, they are not abstracted out of the system even under high vacuum, enabling stable polymerization.

[0032] In this invention, the ionic copolymer polyester introduced into the biodegradable polyester generally exhibits superior mechanical properties and thermal stability compared to its parent polymer. The ionic copolymer polyester contains abundant sulfonate ionic bonds, and the ionomer contains multiple ion pairs and ion clusters. These aggregates function as physical linkage points, enhancing intermolecular chain interactions. When introduced into a fiber material, this significantly improves the fiber's mechanical strength. This improvement in mechanical properties manifests as increased tear strength during tensile stress and improved elastic recovery within a certain deformation range. Simultaneously, these linkages are reversible, and dissociation occurs under a certain shear force, thus ensuring thermoplastic processability. [Effects of the Invention]

[0033] The advantages of the present invention include, (1) The present invention introduces an ionic copolymer polyester into a biodegradable polyester, and during the extrusion and cooling process of the biodegradable polyester molten material, the ionic copolymer polyester functions as a heterogeneous nucleating agent in the biodegradable polyester molten material. Simultaneously, under high-speed spinning and high-magnification stretching conditions, the orientation further induces crystallization, and the adhesion phenomenon of fiber bundles that have reached a certain degree of crystallinity is significantly reduced, thereby achieving continuous and stable fiber formation. This invention does not require altering the chemical structure of the biodegradable polyester or adding new spinning equipment.

[0034] (2) The ionic copolymer polyester introduced into the biodegradable polyester in the present invention contains abundant sulfonate ionic bonds. The multiple ion pairs and ion clusters present in the ionomer function as physical intersection points, enhancing intermolecular chain interactions, and when introduced into a fiber material, the mechanical strength of the fiber can be significantly increased. This improvement in mechanical performance manifests as an improvement in the tear strength during the tensile process of the fiber and an improvement in the elastic recovery rate within a certain deformation range. [Modes for carrying out 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 exceed the gist of the invention. Furthermore, while engineers in the art who have read the contents of the present invention may be permitted to modify it in various ways, such modifications are still limited to the claims of the present invention as equivalent forms of the present invention.

[0036] The test method employed in this invention is as follows: (1) Semicrystal 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 in a nitrogen atmosphere at a heating rate of 10°C / min, held for 3 minutes to remove thermal history, and then cooled from 300°C to 25°C. The peak that appears during the cooling process from 300°C to 25°C is called the cooling crystallization peak, and the temperature corresponding to this peak is defined as the cooling crystallization temperature. The time required for the sample to crystallize from the start to completion is defined as the crystallization time, and the time when the degree of crystallinity reaches 50% is defined as the semi-crystallization time t 1 / 2 Let's assume that.

[0037] (2) Crystallization Enthalpy: The sample is tested using a Q-20 DSC manufactured by TA, Inc., 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 in a nitrogen atmosphere at a heating rate of 10°C / min, held for 3 minutes to remove thermal history, and then cooled from 300°C to 25°C. The peak that appears during the cooling process from 300°C to 25°C is called the cooling crystallization peak, and the temperature corresponding to this peak is defined as the cooling crystallization temperature. The cooling crystallization process is an exothermic process, and the total amount of heat released by a unit mass of the sample from the start to the end of crystallization is defined as the crystallization enthalpy; (3) Molecular weight of oil-free yarn: The molecular weight (number-average molecular weight Mn) and molecular weight distribution coefficient (PDI) of 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 set to 1 mL / min. Before testing, 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 copolymer polyester is tested based on GB / T 14190-2017. In the following embodiment of the present invention, the test is performed with a mass ratio of phenol to 1,1,2,2-tetrachloroethane of 50:50.

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

[0040] (6) Breaking strength: The breaking strength test in a dry state as specified in "GB / T 14344-2008 Test Method for Tensile Properties of Chemical Fibers Long Fibers" shall be adopted; (7) Breaking elongation: The breaking elongation measurement test in a dry state specified in "GB / T 14344-2008 Test Method for Tensile Properties of Chemical Fibers Long Fibers" shall be adopted; (8) Biodegradation rate of compost: Tested according to "GB / T 19277.1-2011 Measurement of the ultimate aerobic biodegradation capacity of materials under controlled composting conditions: Method for measuring carbon dioxide emissions"; (9) Degree of disintegration: Tested according to "GB / T 19811-2005 Measurement of the degree of disintegration of plastic materials under defined pilot-scale composting conditions".

[0041] Example 1 The method for producing high-strength biodegradable polyester fibers is as follows: (1) Terephthalic acid and ethylene glycol are mixed in a molar ratio of 1:1.05, and an esterification reaction is carried out over 3.5 hours under conditions of 250°C and 0.05 MPa to produce a nonionic polyester. In this reaction, titanium diethylate is used as the esterification catalyst, and the amount is 10 ppm of the mass of terephthalic acid.

[0042] (2) A sulfonate-based ionic polyester is produced by a stepwise esterification reaction of sodium 5-sulfoisophthalate and potassium 2,5-dihydroxybenzenesulfonate. In the first-step esterification reaction, the molar ratio of the number of carboxyl functional groups in sodium 5-sulfoisophthalate to the number of hydroxyl functional groups in potassium 2,5-dihydroxybenzenesulfonate is set to 1.05. In the second-step esterification reaction, potassium 2,5-dihydroxybenzenesulfonate is added at an amount equivalent to 10% of the molar amount of sodium 5-sulfisophthalate added in the first step. As a catalyst for the stepwise esterification reaction, benzenesulfonic acid is added at 1000 ppm by mass of sodium 5-sulfisophthalate during the first step of the esterification reaction. The conditions for the first stage esterification reaction are a temperature of 220°C, a pressure of 0.05 MPa, and a time of 3 hours. The conditions for the second stage esterification reaction are 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 a preliminary polycondensation is carried out over 0.1 hours under conditions of 240°C and 1000 Pa, followed by a final polycondensation over 0.15 hours under conditions of 260°C and 0 Pa to prepare an ionic copolymer polyester. In this process, tetrabutyl titanate is used as the polycondensation catalyst, and the amount is 50 ppm of the total mass of both polyesters.

[0044] The resulting ionic copolymer polyester is composed of nonionic polyester segments and sulfonate-based ionic polyester segments, and the nonionic polyester segments, the ionic polyester segments, and the nonionic polyester segments are all linked by ester bonds. Furthermore, the nonionic polyester segments have 10 repeating units, the ionic polyester segments have 6 repeating units, and the intrinsic viscosity of the copolymer polyester is 0.55 dl / g.

[0045] (4) The ionic copolymer polyester from step (3) is added to PBAT (number average molecular weight 100,000 g / mol) at a concentration of 1% of the PBAT mass and uniformly mixed to prepare a biodegradable polyester modified with the ionic copolymer polyester. High-strength biodegradable polyester fibers are then produced by melt spinning. The spinning conditions are as follows: 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 copolymer polyester has a crystallization temperature of 110°C and a semi-crystallization time t 1 / 2 It has the characteristics of a crystallization enthalpy of 45 J / g at 1 min.

[0047] The obtained high-strength biodegradable polyester fiber had a single filament fineness of 1.5 dtex, an oil-free 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 2-10% tensile deformation. Its biodegradability was 60% for composting and 90% for disintegration.

[0048] Example 2 The method for producing high-strength biodegradable polyester fibers is as follows: (1) Isophthalic acid and propylene glycol are mixed in a molar ratio of 1:1.5, and an esterification reaction is carried out over 1.5 hours under conditions of 230°C and 0.5 MPa to produce a nonionic polyester. In this reaction, tetrabutyl titanate is used as the esterification catalyst, and the amount is 20 ppm of the mass of isophthalic acid.

[0049] (2) A 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 esterification reaction, the molar ratio of the number of carboxyl functional groups in sodium 5-sulfoisophthalate to the number of hydroxyl functional groups in sodium N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonate is set to 1.5. In the second esterification reaction, sodium N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonate is added at an amount equivalent to 60% of the molar amount of sodium 5-sulfisophthalate added in the first step. As a catalyst for the stepwise esterification reaction, benzenesulfonic acid is added at 10 ppm by mass of sodium 5-sulfoisophthalate during the first step of the esterification reaction. The conditions for the first stage esterification reaction are a temperature of 250°C, a pressure of 0.5 MPa, and a time of 4 hours. The conditions for the second stage esterification reaction are 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 a preliminary polycondensation is performed over 1 hour under conditions of 260°C and 500 Pa, followed by a final polycondensation over 3 hours under conditions of 285°C and 100 Pa to prepare an ionic copolymer polyester. In this process, titanium diethylate is used as the polycondensation catalyst, and the amount is 60 ppm of the total mass of both polyesters.

[0051] The resulting 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 nonionic polyester segments to ionic polyester segments. Furthermore, the nonionic polyester segments have 8 repeating units, the ionic polyester segments have 4 repeating units, and the intrinsic viscosity of the copolymer polyester is 0.85 dl / g.

[0052] (4) The ionic copolymer polyester from step (3) is added to PBST (number average molecular weight 750,000 g / mol) at a concentration of 10% of the mass of PBST and uniformly mixed to prepare a biodegradable polyester modified with the ionic copolymer polyester. High-strength biodegradable polyester fibers are then produced by melt spinning. The spinning conditions are as follows: 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 copolymer polyester has a crystallization temperature of 150°C and a semi-crystallization time t 1 / 2 It has the characteristics of crystallization enthalpy of 50 J / g in 2 min.

[0054] The obtained high-strength biodegradable polyester fiber had a single-filament fineness of 2 dtex, an oil-free 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 was 90% for composting and 95% for disintegration.

[0055] Example 3 The method for producing high-strength biodegradable polyester fibers is as follows: (1) Adipic acid and butanediol are mixed in a molar ratio of 1:1.15, and an esterification reaction is carried out over 1.5 hours under conditions of 150°C and 0.01 MPa to produce a nonionic polyester. In this reaction, antimony dietilate is used as the esterification catalyst, and the amount is 100 ppm of the mass of adipic acid.

[0056] (2) A 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-step esterification reaction, the molar ratio of the number of carboxyl functional groups in sodium 5-sulfoisophthalate to the number of hydroxyl functional groups in sodium 2-[(tris(hydroxymethyl)methyl)amino]-1-ethanesulfonate] is set to 1.1. In the second esterification reaction, 20% of the molar amount of sodium 5-sulfisophthalate added in the first step is added to sodium 2-[(tris(hydroxymethyl)methyl)amino]-1-ethanesulfonate. As a catalyst for the stepwise esterification reaction, benzenesulfonic acid is added at 100 ppm by mass of sodium 5-sulfoizophthalate during the first step of the esterification reaction. The conditions for the first stage esterification reaction are a temperature of 230°C, a pressure of 0.1 MPa, and a time of 5 hours. The conditions for the second stage esterification reaction are 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 a preliminary polycondensation is performed over 0.2 hours under conditions of 250°C and 800 Pa, followed by a final polycondensation over 2 hours under conditions of 265°C and 10 Pa to prepare an ionic copolymer polyester. In this process, antimony trioxide is used as the polycondensation catalyst, and the amount is 500 ppm of the total mass of both polyesters.

[0058] The resulting 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 nonionic polyester segments to ionic polyester segments. Furthermore, the nonionic polyester segments have 4 repeating units, the ionic polyester segments have 2 repeating units, and the intrinsic viscosity of the copolymer polyester is 0.75 dl / g.

[0059] (4) The ionic copolymer polyester 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 copolymer polyester, and high-strength biodegradable polyester fibers are produced by melt spinning. The spinning conditions are as follows: 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, heat roller GR2 temperature 105°C.

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

[0061] The obtained high-strength biodegradable polyester fiber had a single filament fineness of 2.5 dtex, an oil-free 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 was 80% for composting and 92% for disintegration.

[0062] Example 4 The method for producing high-strength biodegradable polyester fibers is as follows: (1) Terephthalic acid and pentanediol are mixed in a molar ratio of 1:1.25, and an esterification reaction is carried out over 2.5 hours under conditions of 220°C and 0.1 MPa to produce a nonionic polyester. In this reaction, antimony diethylate is used as the esterification catalyst, and the amount is 80 ppm of the mass of terephthalic acid.

[0063] (2) A 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-step esterification reaction, the molar ratio of the number of carboxyl functional groups in sodium 2-sulfoterephthalate to the number of hydroxyl functional groups in sodium 3-[N-tris(hydroxymethyl)methylamine]-2-hydroxypropanesulfonate is set to 1.2. In the second esterification reaction, 30% of the molar amount of 2-sulfoterephthalate sodium added in the first step is added to 3-[N-tris(hydroxymethyl)methylamine]-2-hydroxypropanesulfonate sodium. As a catalyst for the stepwise esterification reaction, benzenesulfonic acid is added at 800 ppm by mass of 2-sulfoterephthalate-sodium during the first step of the esterification reaction. The conditions for the first stage esterification reaction are a temperature of 240°C, a pressure of 0.4 MPa, and a time of 3 hours. The conditions for the second stage esterification reaction are 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 preliminary polycondensation is carried out over 0.8 hours under conditions of 245°C and 600 Pa, followed by final polycondensation over 2.5 hours under conditions of 280°C and 80 Pa to prepare an ionic copolymer polyester. In this process, antimony dietilate is used as the polycondensation catalyst, and the amount is 400 ppm of the total mass of both polyesters.

[0065] The resulting 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 nonionic polyester segments to ionic polyester segments. Furthermore, the nonionic polyester segments have 6 repeating units, the ionic polyester segments have 3 repeating units, and the intrinsic viscosity of the copolymer polyester is 0.60 dl / g.

[0066] (4) A biodegradable polyester modified with ionic copolymer polyester is prepared by adding the ionic copolymer polyester from step (3) to PHA (number average molecular weight 85,000 g / mol) at an amount of 8% of the PHA mass and mixing it uniformly. High-strength biodegradable polyester fibers are then produced by melt spinning. The spinning conditions are as follows: 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 copolymer polyester has a crystallization temperature of 70°C and a semi-crystallization time t 1 / 2 It exhibits characteristics of a crystallization enthalpy of 35 J / g and a crystallization time of 2.5 min.

[0068] The obtained high-strength biodegradable polyester fiber had a single-filament fineness of 3 dtex, an oil-free 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 was 75% for composting and 93% for disintegration.

[0069] Example 5 The method for producing high-strength biodegradable polyester fibers is as follows: (1) Isophthalic acid and ethylene glycol are mixed in a molar ratio of 1:1.35, and an esterification reaction is carried out over 3 hours under conditions of 240°C and 0.3 MPa to produce a nonionic polyester. In this reaction, antimony(III) oxide is used as the esterification catalyst, and the amount is 90 ppm of the mass of isophthalic acid.

[0070] (2) A sulfonate-based ionic polyester is produced by a stepwise esterification reaction of sodium 2-sulfoterephthalate and potassium 2,5-dihydroxybenzenesulfonate. In the first-step esterification reaction, the molar ratio of the number of carboxyl functional groups in sodium 2-sulfoterephthalate to the number of hydroxyl functional groups in potassium 2,5-dihydroxybenzenesulfonate is set to 1.3. In the second-step esterification reaction, potassium 2,5-dihydroxybenzenesulfonate is added in an amount equivalent to 40% of the molar amount of sodium 2-sulfoterephthalate added in the first step. As a catalyst for the stepwise esterification reaction, benzenesulfonic acid was added at 300 ppm by mass of 2-sulfoterephthalate-sodium during the first step of the esterification reaction. The conditions for the first stage esterification reaction are a temperature of 235°C, a pressure of 0.2 MPa, and a time of 4 hours. The conditions for the second stage esterification reaction are 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 a preliminary polycondensation is performed over 0.5 hours under conditions of 250°C and 900 Pa, followed by a final polycondensation over 2 hours under conditions of 270°C and 30 Pa to prepare an ionic copolymer polyester. In this process, antimony(III) acetate is used as the polycondensation catalyst, and the amount is 200 ppm of the total mass of both polyesters.

[0072] The resulting ionic copolymer polyester is composed of nonionic polyester segments and sulfonate-based ionic polyester segments, and the nonionic polyester segments, the ionic polyester segments, and the nonionic polyester segments are all linked by ester bonds. Furthermore, the nonionic polyester segments have 9 repeating units, the ionic polyester segments have 8 repeating units, and the intrinsic viscosity of the copolymer polyester is 0.72 dl / g.

[0073] (4) The ionic copolymer polyester from step (3) is added to PCL (number average molecular weight 90,000 g / mol) at a concentration of 3% of the PCL mass and uniformly mixed to prepare a biodegradable polyester modified with the ionic copolymer polyester. High-strength biodegradable polyester fibers are then produced by melt spinning. The spinning conditions are as follows: 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 copolymer polyester has a crystallization temperature of 50°C and a semi-crystallization time t 1 / 2 It has a crystallization enthalpy of 30 J / g and a reaction time of 2.8 min.

[0075] The obtained high-strength biodegradable polyester fiber had a single filament fineness of 4 dtex, an oil-free 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 2-10% tensile deformation. Its biodegradability was 70% for composting and 91% for disintegration.

[0076] Example 6 The method for producing high-strength biodegradable polyester fibers is as follows: (1) Adipic acid and propylene glycol are mixed in a molar ratio of 1:1.4, and an esterification reaction is carried out over 2 hours under conditions of 180°C and 0.4 MPa to produce a nonionic polyester. In this reaction, titanium diethylate is used as the esterification catalyst, and the amount is 30 ppm of the mass of adipic acid.

[0077] (2) A 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 esterification reaction, the molar ratio of the number of carboxyl functional groups in sodium 2-sulfoterephthalate to the number of hydroxyl functional groups in sodium N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonate is set to 1.4. In the second esterification reaction, sodium N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonate is added in an amount equivalent to 50% of the molar amount of sodium 2-sulfoterephthalate added in the first step. As a catalyst for the stepwise esterification reaction, benzenesulfonic acid is added at 500 ppm by mass of 2-sulfoterephthalate-sodium during the first step of the esterification reaction. The conditions for the first stage of esterification reaction are a temperature of 225°C, a pressure of 0.3 MPa, and a time of 5 hours. The conditions for the second stage of esterification reaction are 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 a preliminary polycondensation is carried out over 0.6 hours under conditions of 255°C and 700 Pa, followed by a final polycondensation over 2.5 hours under conditions of 275°C and 50 Pa to prepare an ionic copolymer polyester. In this process, tetrabutyl titanate is used as the polycondensation catalyst, and the amount is 80 ppm of the total mass of both polyesters.

[0079] The obtained ionic copolymerized polyester is composed of a non-ionic polyester segment and a sulfonate-based ionic polyester segment, and all of the different non-ionic polyester segments, different ionic polyester segments, and between the non-ionic polyester segment and the ionic polyester segment are linked by ester bonds. Moreover, the number of repeating units of the non-ionic polyester segment is 5, the number of repeating units of the ionic polyester segment is 5, and the intrinsic viscosity of the copolymerized polyester is 0.81 dl / g.

[0080] (4) Add the ionic copolymerized polyester in step (3) to PBAT (number average molecular weight 95000 g / mol) at 5% of the PBAT mass and mix uniformly to prepare a biodegradable polyester modified with the ionic copolymerized polyester, and then produce high-strength biodegradable polyester fibers by melt spinning. Among them, the spinning conditions are: 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, heat roller GR2 temperature 108 °C.

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

[0082] The obtained high-strength biodegradable polyester fiber has a single-filament fineness of 2 dtex, a decrease in the number average molecular weight of the oil-free yarn of 1800 g / mol, a breaking strength of 2.64 cN / dtex, an elongation at break of 32.9%, and an elastic recovery rate under 2-10% tensile deformation of 90.2%. As for its biodegradation performance, the composting biodegradation rate is 85% and the disintegration degree is 94%.

Claims

1. By adding an ionic copolymer polyester to biodegradable polyester and melt spinning it, a high-strength biodegradable polyester fiber is obtained, and among these, Biodegradable polyesters include 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 ionic copolymer polyester added is 1 to 10% of the mass of the biodegradable polyester. Ionic copolymer polyester is composed of nonionic polyester segments and sulfonate-based ionic polyester segments, and the nonionic polyester segments, the ionic polyester segments, and the nonionic polyester segments are all linked by ester bonds. The intrinsic viscosity of ionic copolymer polyester is 0.55 to 0.85 dl / g. 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 method for producing an ionic copolymer polyester involves first synthesizing a nonionic polyester and a sulfonate-based ionic polyester separately by esterification reactions, and then polycondensing the nonionic polyester and the sulfonate-based ionic polyester to produce the ionic copolymer polyester. Sulfonate-based ionic polyesters are 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 dicarboxylic acid II to the number of hydroxyl functional groups of diol II added is 1.05 to 1.

50. In the second-stage esterification reaction, only diol II is added, and the amount added is 10 to 60% of the molar amount of dicarboxylic acid II added in the first-stage esterification reaction. Dicarboxylic acid II is sodium 5-sulfoisophthalate or sodium 2-sulfoterephthalate, and 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 fibers have a single filament fineness of 1.5 to 5.0 dtex, an oil-free 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 of ≥90% under 2 to 10% tensile deformation, and biodegradability with a composting biodegradation rate of ≥60% and a degree of disintegration of ≥90%. A method for producing high-strength biodegradable polyester fibers, characterized by the following:

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

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

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

2.

5. Nonionic polyesters are produced by the esterification reaction of dicarboxylic acid I and diol I, where the molar ratio of dicarboxylic acid I to diol I is 1:1.05 to 1.5, and dicarboxylic acid I is terephthalic acid, isophthalic acid, or adipic acid, and diol I is ethylene glycol, propylene glycol, butanediol, or pentanediol. A method for producing high-strength biodegradable polyester fibers according to feature 1.

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

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

8. The catalyst in the stepwise esterification reaction of sulfonate-based ionic polyesters is benzenesulfonic acid, which is added during the first-step esterification reaction, and its amount used is 10 to 1000 ppm relative to the mass of dicarboxylic acid II. A method for producing high-strength biodegradable polyester fibers according to feature 1.

9. The conditions for the first-stage esterification reaction are a temperature of 220–250°C, a pressure of 0.05–0.5 MPa, and a time of 3.0–5.0 hours. The conditions for the second-stage esterification reaction are a temperature of 240–260°C, a pressure of 0.1–0.5 MPa, and a time of 0.5–1.0 hour. A method for producing high-strength biodegradable polyester fibers according to feature 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 for the preliminary polycondensation reaction is 240–260°C, the reaction time is 0.1–1.0 h, and the pressure is 500–1000 Pa. The temperature for the final polycondensation reaction is 260–285°C, the reaction time is 1.5–3.0 hours, and the pressure is 0–100 Pa. A method for producing high-strength biodegradable polyester fibers according to feature 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 nonionic polyester. A method for producing high-strength biodegradable polyester fibers according to the feature described in 10.