High-strength low-shrinkage polyester fiber and preparation method thereof

Abstract

The invention relates to the technical field of high-performance polyester, in particular to a high-strength low-shrinkage polyester fiber and a preparation method thereof. The defects that existing polyester fibers are poor in strength and shrinkage resistance are overcome. The preparation method comprises the following steps: mixing the modified resin, the modified nano silicon dioxide, the composite antioxidant, the composite nucleating agent and the composite lubricant, and carrying out melt spinning. Wherein the modified resin is prepared from the following raw materials: dimethyl terephthalate, isophthalic acid, ethylene glycol and isosorbide; the modified nano silicon dioxide comprises nano silicon dioxide, KH570 and silver nitrate; the composite antioxidant comprises an antioxidant 1010, an antioxidant 168 and an antioxidant 1222; the composite nucleating agent comprises sodium benzoate and nano montmorillonite; the composite lubricant is prepared from ethylene bis stearamide and pentaerythritol stearate. The prepared polyester fiber is high in strength, high in shrinkage resistance and suitable for manufacturing of outdoor equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of high-performance polyester, in particular to a high-strength and low-shrinkage polyester fiber and a preparation method thereof. Background Art

[0002] Polyester fiber is typically made from purified terephthalic acid or dimethyl terephthalate and ethylene glycol, and is produced through esterification, transesterification, and polycondensation to produce polyethylene terephthalate (PET), a fiber-forming polymer. In the traditional melt-spinning process, PET chips are melted at high temperatures, converted into a uniform melt, and then extruded through the fine holes of a spinneret under precisely controlled pressure to form a thin stream of melt. After extrusion, the melt stream is often cooled using side-blown air. The cooling air speed, temperature, and uniformity significantly affect the fiber's crystal structure and orientation. The nascent fiber has low strength after cooling and requires a stretching process. Through stretching at varying times, the macromolecular chains are oriented along the fiber's axis, increasing fiber strength. The stretched fiber also requires heat setting to eliminate internal stress and stabilize the fiber structure.

[0003] While high-performance polyester excels in many fields, such as its excellent abrasion and weather resistance, making it widely used in outdoor tents and mountaineering equipment, existing fiber production processes still lack strength and thermal shrinkage. This strength struggles to meet the demands of products like professional climbing ropes that withstand high dynamic loads. In high-temperature environments, such as when outdoor equipment is exposed to the scorching sun, the fibers can easily shrink and deform, causing dimensional changes and reducing performance and safety. Therefore, developing high-performance polyester fibers that combine high strength with low shrinkage, and thus overcome the limitations of current fiber production processes, is crucial for advancing industries like outdoor equipment.

[0004] Therefore, a high-strength, low-shrinkage polyester fiber and a preparation method thereof are proposed. Summary of the Invention

[0005] The present invention aims to provide a high-strength, low-shrinkage polyester fiber and a method for preparing the same. The fiber is prepared by mixing a modified resin, modified nano-silica, a composite antioxidant, a composite nucleating agent, and a composite lubricant, followed by melt spinning. The modified resin comprises raw materials including dimethyl terephthalate, isophthalic acid, ethylene glycol, and isosorbide; the modified nano-silica comprises nano-silica, KH570, and silver nitrate; the composite antioxidant comprises antioxidant 1010, antioxidant 168, and antioxidant 1222; the composite nucleating agent comprises sodium benzoate and nano-montmorillonite; and the composite lubricant comprises ethylene bisstearamide and pentaerythritol stearate. The polyester fiber prepared in this manner exhibits high strength and strong shrinkage resistance, making it suitable for use in the manufacture of outdoor equipment.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] In one aspect, the present invention provides a high-strength, low-shrinkage polyester fiber, specifically comprising the following components:

[0008] The polyester fiber comprises, by weight, 100 parts of modified resin, 8-12 parts of modified nano-silicon dioxide, 1.7-2.1 parts of composite antioxidant, 1.2-1.6 parts of composite nucleating agent, and 2 parts of composite lubricant;

[0009] Modified resins include dimethyl terephthalate, isophthalic acid, ethylene glycol, and isosorbide;

[0010] Modified nano-silica includes nano-silica, KH570, and silver nitrate;

[0011] Preferably, the composite antioxidant includes antioxidant 1010, antioxidant 168, and antioxidant 1222; the weight ratio of antioxidant 1010, antioxidant 168, and antioxidant 1222 in the composite antioxidant is 7:7:5.

[0012] Preferably, the composite nucleating agent includes sodium benzoate and nano-montmorillonite.

[0013] Preferably, the intrinsic viscosity of the modified resin is 0.66-0.70 dL / g.

[0014] Preferably, the nano-silica is fumed nano-silica, and the particle size of the fumed nano-silica is 30-50 nm.

[0015] In another aspect, the present invention provides a method for preparing high-strength, low-shrinkage polyester fiber, comprising the following steps:

[0016] S1: drying the modified PET chips to a moisture content of <50 ppm and then mixing them with modified nano-silica, a composite antioxidant, a composite nucleating agent, and a composite lubricant for 30 minutes to form a dry blend;

[0017] S2: The dry blend is melt-blended and extruded at 255°C, ejected through a spinneret with a pore size of 0.3 mm, cooled and solidified at 20°C and a wind speed of 0.5 m / s, and the spinning speed is 1200 m / min to obtain spun fibers;

[0018] S3: performing a first-stage drawing of the spun fiber at 75-85° C.; then performing a second-stage drawing at 105-115° C. with a total drawing ratio of 3.8-4.2 times to obtain a fiber tow; and heat-setting the fiber tow at 210-220° C. to obtain a heat-set fiber tow;

[0019] S5: performing a three-dimensional curling treatment on the heat-set fiber tow to obtain a curled fiber; and treating the curled fiber at a relaxation heat treatment temperature of 115° C. for 0.8 h to obtain a polyester fiber.

[0020] Preferably, the preparation method of the modified resin is as follows: 100 parts of dimethyl terephthalate, 13-17 parts of isophthalic acid, 44 parts of ethylene glycol, 10-14 parts of isosorbide, 0.05 parts of zinc acetate and 0.1 parts of trisnonylphenol phosphite are added to a reactor, reacted at 180°C for 1.5 hours to obtain an oligomer ester; 0.04 parts of antimony trioxide are added to the oligomer ester, and the mixture is reacted at 230°C and 5kPa vacuum for 1 hour for pre-polycondensation; then, the mixture is reacted at 260°C for 3 hours to obtain a molten copolyester; the molten copolyester is quenched and solidified by cooling water at 15-20°C, and sliced ​​to obtain polyester slices; the polyester slices are treated at 130°C and 100Pa vacuum conditions for 4 hours to obtain pre-crystallized slices; the pre-crystallized slices are reacted at 205°C under a nitrogen atmosphere for 12 hours for solid-phase polycondensation until the intrinsic viscosity reaches 0.66-0.70dL / g to obtain a modified resin.

[0021] Preferably, the preparation method of modified nano-silica is as follows: 10 parts of nano-silica, 5 parts of deionized water and 1-2 parts of KH570 are added to 200 parts of anhydrous ethanol, reacted at 75°C for 5 hours to obtain a suspension, an aqueous solution containing 0.3-0.34 parts of silver nitrate is added to the suspension, stirred at room temperature for 1 hour to obtain a mixed solution, 0.35 parts of L-ascorbic acid solution is added to the mixed solution, and the pH value is adjusted to 8.5 with water, stirred and reacted at room temperature for 3-4 hours, centrifuged to obtain a reaction product, and the reaction product is washed and dried to obtain modified nano-silica.

[0022] Preferably, the spinneret is a circular spinneret.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. In the present invention, methacrylate-functionalized nanosilica enhances the interfacial bonding and dispersibility between the filler and the polyester matrix, while the loaded nanosilver provides antibacterial function. This strong interfacial bonding synergizes with the segment rigidity of isosorbide to form effective physical anchoring points, restricting molecular chain motion. Combined with optimized spinning and heat-setting processes, this improves the fiber's strength, antibacterial properties, and thermal dimensional stability, effectively reducing dry heat shrinkage.

[0025] 2. In the present invention, by introducing isophthalic acid and isosorbide for copolymerization modification, the regularity of the polyester molecular chain is destroyed to optimize crystallization behavior and enhance the toughness of the matrix itself; the rigid structure of isosorbide further enhances the chain segment stiffness and glass transition temperature, which helps to reduce shrinkage; this matrix modification synergistically acts with the external toughening and physical anchoring effect of the functional nanofiller to enhance fiber strength and reduce shrinkage.

[0026] 3. In the present invention, a 0.3 mm circular spinneret is used to ensure that the cross-section of the nascent fiber is uniform and the initial orientation is low, providing the necessary foundation for subsequent high-multiple uniform stretching; the melt composition characteristics formed by the various solid fillers in the fiber raw material and their dispersion in the modified resin are spun through a specific spinneret, so that the subsequent high-multiple stretching process to improve strength and the high-temperature heat setting process to reduce shrinkage and stabilize the structure can be effectively implemented, thereby improving the strength of the fiber and reducing the dry heat shrinkage rate.

[0027] 4. In the present invention, through the synergistic effect of strict raw material drying and a high-efficiency antioxidant system, the hydrolysis and thermal oxidative degradation of polyester during high-temperature processing are effectively prevented, thereby maintaining the structural integrity of the polymer matrix; on this stable matrix, the nucleating agent in the composite additive is able to effectively guide and optimize the crystallization behavior, forming a more regular and fine crystal structure, which is an important microscopic foundation for achieving the ultimate low dry heat shrinkage and high dimensional stability of the fiber. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of the antibacterial rate of Escherichia coli in Examples 1-4 of the present invention and Comparative Examples 1-4. DETAILED DESCRIPTION

[0029] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0030] See also Figure 1 The present invention provides a high-strength, low-shrinkage polyester fiber and a preparation method thereof. The technical solution is as follows:

[0031] Example 1

[0032] Preparation of modified resin

[0033] 100 parts of dimethyl terephthalate, 15 parts of isophthalic acid, 44 parts of ethylene glycol, 12 parts of isosorbide, 0.05 parts of zinc acetate and 0.10 parts of trinonylphenol phosphite were added to a reactor and reacted at 180°C for 1.5 hours to obtain an oligomer ester; 0.04 parts of antimony trioxide were added to the oligomer ester and reacted at 230°C and 5kPa vacuum for 1 hour for pre-polycondensation; then, the reaction was carried out at 260°C for 3 hours to obtain a molten copolyester; the molten copolyester was quenched and solidified by cooling water at 15°C and sliced ​​to obtain polyester slices; the polyester slices were treated at 130°C and 100Pa vacuum for 4 hours to obtain pre-crystallized slices; the pre-crystallized slices were reacted at 205°C under a nitrogen atmosphere for 12 hours for solid-phase polycondensation until the intrinsic viscosity reached 0.66dL / g to obtain a modified resin.

[0034] Preparation of modified nano-silica

[0035] 10 parts of fumed nano-silica with a particle size of 30 nm, 5 parts of deionized water and 1 part of KH570 were added to 200 parts of anhydrous ethanol, and the mixture was reacted at 75° C. for 5 hours to obtain a suspension. An aqueous solution containing 0.24 parts of silver nitrate was added to the suspension, and the mixture was stirred at room temperature for 1 hour to obtain a mixed solution. A solution containing 0.35 parts of L-ascorbic acid was added to the mixed solution, and the pH was adjusted to 8.5 with 25% concentrated ammonia water. The mixture was stirred and reacted at room temperature for 3 hours, and the reaction product was obtained by centrifugation. The reaction product was washed and dried to obtain modified nano-silica.

[0036] S1: 100 parts of modified resin are dried to a moisture content of <50 ppm, and then mixed with 6 parts of modified nano-silica, 1.7 parts of composite antioxidant, 1.2 parts of composite nucleating agent, and 2 parts of composite lubricant for 30 minutes to obtain a dry blend;

[0037] The composite antioxidant includes antioxidant 1010, antioxidant 168, and antioxidant 1222; the weight ratio of antioxidant 1010, antioxidant 168, and antioxidant 1222 in the composite antioxidant is 7:7:5.

[0038] The composite nucleating agent is sodium benzoate and nano-montmorillonite; the weight ratio of sodium benzoate to nano-montmorillonite is 1:1;

[0039] The composite lubricant is ethylene bisstearamide and pentaerythritol stearate; the weight ratio of ethylene bisstearamide and pentaerythritol stearate is 1:1.

[0040] S2: The dry blend is melt-blended and extruded at 255°C, ejected through a circular spinneret with a pore size of 0.3 mm, cooled and solidified at 20°C and a wind speed of 0.5 m / s, and the spinning speed is 1200 m / min to obtain spun fibers;

[0041] S3: performing a first-stage drawing of the spun fiber at 75° C.; then performing a second-stage drawing at 105° C. with a total drawing ratio of 3.8 times to obtain a fiber tow; and heat-setting the fiber tow at 215° C. to obtain a heat-set fiber tow;

[0042] S5: The heat-set fiber tow is three-dimensionally curled under the conditions of preheating at 100°C, main pressure of 170 kPa, and back pressure of 195 kPa to obtain curled fiber; the curled fiber is relaxed and heat-treated at 118°C for 0.75h to obtain polyester fiber.

[0043] The difference between Example 2 and Example 1 is that, in the preparation process of modified nano-silica, the amount of KH570 used is 1.5 parts, the amount of silver nitrate used is 0.32 parts, and the stirring reaction time is 3.5 hours; when preparing polyester fiber, the amount of modified nano-silica added is 10 parts, the amount of composite antioxidant added is 1.9 parts, and the amount of composite nucleating agent added is 1.4 parts.

[0044] The difference between Example 3 and Example 1 is that, in the process of preparing modified nano-silica, the amount of KH570 used is 2 parts, the amount of silver nitrate used is 0.34 parts, and the stirring reaction time is 4 hours; when preparing polyester fiber, the amount of modified nano-silica added is 12 parts, the amount of composite antioxidant added is 2.1 parts, and the amount of composite nucleating agent added is 1.6 parts.

[0045] The difference between Example 4 and Example 2 is that in the preparation process of the modified resin, the amount of isophthalic acid used is 15 parts and the amount of isosorbide used is 12 parts; the specific viscosity of the modified resin is 0.68 dL / g; and the particle size of the fumed nano-silica is 40 nm.

[0046] The difference between Example 5 and Example 2 is that in the preparation process of the modified resin, the amount of isophthalic acid used is 17 parts and the amount of isosorbide used is 14 parts; the specific viscosity of the modified resin is 0.70 dL / g; and the particle size of the fumed nano-silica is 50 nm.

[0047] The difference between Example 6 and Example 4 is that the first-stage drawing temperature is 80°C, the second-stage drawing temperature is 110°C, the total drawing ratio is 4.0 times, and the heat setting temperature is 215°C.

[0048] The difference between Example 7 and Example 4 is that the first-stage drawing temperature is 85°C, the second-stage drawing temperature is 115°C, the total drawing ratio is 4.2 times, and the heat setting temperature is 220°C.

[0049] The only difference between Comparative Example 1 and Example 1 is that in the polyester fiber preparation process, fumed nano-silica is used instead of modified nano-silica.

[0050] The only difference between Comparative Example 2 and Example 1 is that in the preparation process of modified nano-silica, nano-silica treated with KH570 is used without subsequent silver loading treatment.

[0051] The only difference between Comparative Example 3 and Example 1 is that during the preparation of the modified nano-silica, silver loading treatment is performed and KH570 is not used to treat the nano-silica.

[0052] The only difference between Comparative Example 4 and Example 1 is that in the preparation process of modified nano-silica, nano-silica produced by precipitation method is used instead of nano-silica produced by gas phase method.

[0053] The only difference between Comparative Example 5 and Example 1 is that isophthalic acid and isosorbide are not added during the preparation of the modified resin.

[0054] The only difference between Comparative Example 6 and Example 1 is that isosorbide is not added during the preparation of the modified resin.

[0055] The only difference between Comparative Example 7 and Example 1 is that isophthalic acid is not added during the preparation of the modified resin.

[0056] The only difference between Comparative Example 8 and Example 1 is that the shape of the spinneret is triangular.

[0057] The only difference between Comparative Example 9 and Example 1 is that the aperture of the spinneret is 0.5 mm.

[0058] The only difference between Comparative Example 10 and Example 1 is that the total draft ratio is 3 times.

[0059] The only difference between Comparative Example 11 and Example 1 is that the intrinsic viscosity of the modified resin is 0.6 dL / g.

[0060] The only difference between Comparative Example 12 and Example 1 is that no composite nucleating agent is added.

[0061] The only difference between Comparative Example 13 and Example 1 is that no composite antioxidant is added.

[0062] The only difference between Comparative Example 14 and Example 1 is that in the composite antioxidant, the weight ratio of antioxidant 1010, antioxidant 168, and antioxidant 1222 is 1:1:1.

[0063] The only difference between Comparative Example 15 and Example 1 is that a composite antioxidant is prepared by using antioxidant 168 and antioxidant 1222 in a weight ratio of 1:1.

[0064] Test Example 1

[0065] Test object: The polyester fibers prepared in Examples 1-3 and Comparative Examples 1-4 were made into fabrics and then washed 30 times.

[0066] Test method: Refer to GB / T 20944.3-2008, "Evaluation of Antimicrobial Properties of Textiles - Part 3: Oscillation Method," and use Escherichia coli ATCC 29522 as the bacterial strain. The final test results are shown in Table 1.

[0067] Table 1 Antibacterial performance test results

[0068]

[0069]

[0070] Through Table 1 and Figure 1 As can be seen, the fumed nanosilica used in Comparative Example 1, which had not undergone surface chemical bonding modification, lacked functional groups on its surface that could interact well with the polyester matrix. This resulted in weak interfacial bonding between the inorganic filler and the organic matrix, leading to poor compatibility. This hindered the secure deposition and efficient loading of nanosilver particles on the silica carrier surface. During repeated washing, the loosely bound antimicrobial components were lost in large quantities from the interface, resulting in a decrease in the fiber's long-term antimicrobial performance. Consequently, the antibacterial rate against E. coli decreased after 30 washes. Although methacrylate groups were introduced onto the nanosilica surface in Comparative Example 2 through KH570 treatment, enhancing interfacial compatibility with the polyester matrix, the silver nitrate treatment and subsequent reduction steps were omitted during the preparation process. This means that the final nanofiller did not form nanosilver particles with antimicrobial activity. Therefore, the resulting fiber material itself lacked the chemical basis to kill or inhibit bacterial growth and reproduction, lacked effective inhibitory ability against E. coli before and after washing, and had an extremely low antibacterial rate. In Comparative Example 3, the nanosilica surface was not pretreated with KH570 and silver was directly loaded. The silica surface lacks the introduced methacrylate groups, which cannot effectively improve its interfacial affinity with the hydrophobic polyester matrix. This results in poor dispersibility and easy agglomeration of the silver-loaded silica particles during melt blending, and weak interfacial bonding with the polyester matrix. Weak interfacial bonding makes the loaded nanosilver particles easy to fall off during water washing, resulting in poor antibacterial durability and reduced antibacterial rate. At the same time, the agglomerated particles form stress concentration points, which reduce the mechanical properties of the material, that is, the tensile strength and elongation at break decrease; and this poor dispersion and weak interface cannot form an effective physical anchoring network to limit the movement of polyester molecular segments, resulting in an increase in dry heat shrinkage.

[0071] Test Example 2

[0072] Test objects: polyester fibers prepared in Examples 1-7 and Comparative Examples 4-15.

[0073] Test Method: The breaking strength, elongation at break, and dry heat shrinkage of polyester fibers were tested according to GB / T14464-2017. The final test results are shown in Table 2.

[0074] Table 2 Strength and shrinkage test results

[0075]

[0076]

[0077] As can be seen from Table 2, in Comparative Example 4, precipitated nano-silica was used instead of fumed nano-silica. Due to its large particle size and poor dispersibility, it easily formed agglomerates in the polyester matrix. These agglomerates act as structural defects and stress concentration points, reducing the fiber's breaking strength and elongation at break. At the same time, the unevenly dispersed particles cannot form an effective physical anchoring network to limit the movement of molecular chains, resulting in a decrease in the thermal stability of the fiber and an increase in dry heat shrinkage.

[0078] Comparative Examples 5-7 explore the impact of comonomers on resin properties. In Comparative Example 5, isophthalic acid and isosorbide are not used at all for copolymerization modification, so that the polyester molecular chain is highly regular, with high crystallinity but poor toughness, reduced elongation at break, and poor thermal stability causing dry heat shrinkage to increase significantly. Comparative Example 6 lacks isosorbide alone, which loses the segment rigidity introduced and the partial restraint on the molecular chain movement, resulting in a decrease in toughness and thermal stability, a decrease in elongation at break, and an increase in dry heat shrinkage. Comparative Example 7 lacks isophthalic acid alone, which weakens the destruction of the molecular chain regularity, affects the final crystalline structure and amorphous region characteristics, and also causes the internal toughening effect and thermal stability to decrease, manifested as a decrease in elongation at break and an increase in dry heat shrinkage. This shows that the synergistic effect of isophthalic acid and isosorbide is crucial for achieving internal toughening and reducing dry heat shrinkage.

[0079] Comparative Examples 8-11 focus on the effects of spinning and stretching process parameters on fiber structure and properties. In Comparative Example 8, the use of an irregular triangular spinneret resulted in an uneven structure of the nascent fibers, causing stress concentration and reducing the strength, elongation, and thermal stability of the final fibers. In Comparative Example 9, the use of a larger spinneret aperture changed the thickness and initial orientation of the nascent fibers, affecting the subsequent stretching effect, resulting in a decrease in the final orientation, a decrease in strength, and an increase in thermal shrinkage. In Comparative Example 10, reducing the total draft ratio resulted in a serious lack of molecular chain orientation, a significant decrease in strength, and although the elongation increased, the structure was extremely unstable, and the dry heat shrinkage increased sharply. In Comparative Example 11, the use of a resin with a lower intrinsic viscosity, i.e., a lower molecular weight, resulted in reduced entanglement between molecular chains, a decrease in the strength, elongation, and thermal deformation resistance of the fibers, and an increase in dry heat shrinkage. These changes in process parameters deviated from the optimal conditions for forming a uniform, highly oriented, and stable supramolecular structure, ultimately compromising the mechanical properties and dimensional stability of the fibers.

[0080] Comparative Examples 12-15 focus on the role of nucleating agents and antioxidants in the composite additives. In Comparative Example 12, without the addition of a composite nucleating agent, the polyester crystallization process lacks effective guidance, resulting in an inadequately fine and uniform crystal structure and poor thermal stability, leading to a significant increase in dry heat shrinkage. In Comparative Example 13, without the addition of a composite antioxidant, the polyester undergoes severe thermal oxidative degradation during high-temperature processing. Molecular chain breakage leads to a sharp decrease in strength and elongation, and structural damage results in extremely high dry heat shrinkage. In Comparative Example 14, changing the composite antioxidant ratio to a non-optimized 1:1:1 ratio or removing one of the components, antioxidant 1222, as in Comparative Example 15, both disrupt the original synergistic protective effect of the three antioxidants and reduce the overall efficiency of the system in inhibiting thermal oxidative degradation. This results in slightly poorer polymer molecular weight retention, a slight decrease in mechanical properties, weakened thermal stability, and a corresponding increase in dry heat shrinkage. This demonstrates that an optimized composite nucleating agent and a specific ratio of three-component composite antioxidants are essential for controlling fiber microstructure and maintaining polymer stability during processing.

[0081] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A high-strength, low-shrinkage polyester fiber, characterized by: The polyester fiber comprises modified resin, modified nano-silica, composite antioxidant, composite nucleating agent and composite lubricant; the modified resin comprises dimethyl terephthalate, isophthalic acid, ethylene glycol and isosorbide; the modified nano-silica comprises nano-silica, KH570 and silver nitrate.

2. The high-strength, low-shrinkage polyester fiber according to claim 1, characterized in that: The composite nucleating agent comprises sodium benzoate and nano-montmorillonite.

3. The high-strength, low-shrinkage polyester fiber according to claim 1, characterized in that: The composite antioxidant includes antioxidant 1010, antioxidant 168, and antioxidant 1222.

4. A method for preparing the high-strength, low-shrinkage polyester fiber according to claim 1, characterized in that: Here are the steps: S1: drying the modified PET chips to a moisture content of <50 ppm and then mixing them with modified nano-silica, a composite antioxidant, a composite nucleating agent, and a composite lubricant to form a dry blend; S2: melt-blending and extruding the dry blend, spinning through a spinneret, cooling and solidifying, and spinning to obtain spun fibers; S3: performing a first-stage drawing of the as-spun fiber at 75-85° C.; then performing a second-stage drawing at 105-115° C., with a total drawing ratio of 3.8-4.2 times, to obtain a fiber tow; and heat-setting the fiber tow at 210-220° C. to obtain a heat-set fiber tow; S5: performing a three-dimensional crimping treatment on the heat-set fiber tow to obtain crimped fibers; and performing a relaxation heat treatment on the crimped fibers to obtain the polyester fibers.

5. The method for preparing high-strength, low-shrinkage polyester fiber according to claim 4, characterized in that: The modified resin is prepared by adding dimethyl terephthalate, isophthalic acid, ethylene glycol, isosorbide, zinc acetate and trinonylphenol phosphite into a reactor for reaction to obtain an oligomer ester; adding antimony trioxide to the oligomer ester for pre-polycondensation, and then heating the reaction to obtain a molten copolyester; quenching and solidifying the molten copolyester with cooling water, and slicing to obtain polyester chips; subjecting the polyester chips to a constant temperature treatment to obtain pre-crystallized chips; heating the pre-crystallized chips under a nitrogen atmosphere and then subjecting them to a constant temperature treatment again for solid-phase polycondensation until the intrinsic viscosity reaches 0.66-0.70 dL / g to obtain the modified resin.

6. The method for preparing high-strength, low-shrinkage polyester fiber according to claim 4, characterized in that: The preparation method of the modified nano-silica comprises: adding nano-silica, deionized water and KH570 to anhydrous ethanol for reaction to obtain a suspension, adding an aqueous solution of silver nitrate to the suspension, stirring to obtain a mixed solution, adding an L-ascorbic acid solution to the mixed solution, adjusting the pH value, stirring for reaction, centrifuging to obtain a reaction product, washing the reaction product, and drying to obtain the modified nano-silica.

7. The method for preparing high-strength, low-shrinkage polyester fiber according to claim 4, characterized in that: The spinneret is a circular spinneret.

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