High-elasticity polyester fabric and preparation method thereof

Abstract

This invention belongs to the field of textile technology and discloses a high-elasticity polyester fabric and its preparation method. The fabric is composed of 100% modified PET, and its molecular chain adopts a 3-arm star-linear topology with trimethylolpropane as the core and containing rigid PET blocks and flexible PTMG blocks. The preparation method includes prepolymer synthesis, melt polycondensation, solid-phase thickening, melt spinning, false twisting, and heat setting. The precise construction of the microstructure is achieved by controlling the catalyst system and the density of topological nodes. Through innovative design of the molecular topology, this invention successfully constructs a pure polyester fabric system that combines high elasticity, high weather resistance, high strength, and complete recyclability. This not only solves the environmental stability and recycling problems of existing spandex-based elastic fabrics but also provides a new technical path for the sustainable development of high-performance synthetic fibers.

Description

Technical Field

[0001] This invention belongs to the field of textile technology and relates to a high-elasticity polyester fabric and its preparation method. Background Technology

[0002] In the field of functional textile materials, highly elastic fabrics, due to their excellent deformation adaptability and wearing comfort, have been widely used in sportswear, underwear, medical bandages, and smart wearable devices—situations requiring high dynamic fit performance. Polyester, as one of the most produced and widely used synthetic fibers, occupies a core position in the textile industry thanks to its high strength, abrasion resistance, and good dimensional stability.

[0003] Traditional polyester is inherently rigid and has limited elongation at break, making it difficult to meet the demand for high elasticity on its own. For a long time, the industry has generally used polyester blends or core-spun composites to construct elastic fabric systems. This new technology introduces a spandex component with a soft-hard segment microphase separation structure, utilizing its reversible shrinkage after stretching to give the overall fabric the required elasticity and recovery ability, while effectively balancing cost, process adaptability, and end-use performance.

[0004] With technological advancements and increasingly demanding application scenarios, the aforementioned technologies relying on spandex have revealed profound limitations. The urethane and ether bonds in the spandex molecular chain are extremely sensitive to ultraviolet light. In accelerated aging tests simulating outdoor use environments, after 500 hours of ultraviolet irradiation, its elongation at break significantly decreases, the fabric's elastic recovery ability drops sharply, and permanent deformation increases, directly leading to a shortened effective service life of the product.

[0005] Meanwhile, due to the differences in chemical structure, melting temperature and dissolution behavior between spandex and polyester, it is difficult to achieve efficient separation of the two through conventional physical or chemical methods after they are discarded. This makes it difficult to recycle and reuse blended fabrics containing spandex. This not only reduces the purity and quality of recycled polyester, but also causes secondary pollution due to spandex residue, which conflicts with the current advocacy of circular economy and green manufacturing concepts.

[0006] The existing high-elasticity polyester system is essentially a heterogeneous composite strategy. Its elasticity function is entirely derived from the spandex component, rather than from the improvement of the intrinsic properties of polyester. This structural dependence not only binds the material properties to the environmental stability defects of spandex itself, but also fundamentally restricts the construction of a closed-loop recycling system for all polyester. Summary of the Invention

[0007] To achieve the aforementioned objectives, this invention provides a high-elasticity polyester fabric and its preparation method. The high-elasticity polyester fabric is composed of 100% modified PET, containing no spandex or other non-polyester components. Its molecular chains, through the introduction of a precisely controlled star-linear block topology, maintain the inherent high strength and thermal stability of polyester while endowing the material with intrinsically high elongation at break and excellent elastic recovery. The preparation method is based on a multi-step melt polycondensation and solid-phase thickening process. By controlling the catalyst system, comonomer sequence distribution, and topological node density, the precise construction of the molecular chain microstructure is achieved, thereby macroscopically obtaining a functional polyester fabric that combines high elasticity, high weather resistance, and complete recyclability.

[0008] The core of this invention lies in abandoning the traditional composite strategy relying on heterogeneous elastic fibers, and instead fundamentally reconstructing the topological configuration of the polyester molecular chain. The polymer backbone of the high-elasticity polyester fabric consists of rigid polyethylene terephthalate repeating units and flexible polyether glycol blocks covalently linked by ester bonds, further constructing branching points with a three-arm star-shaped topology using trimethylolpropane as a multifunctional core. Each star arm is composed of a linear block copolymer with the general structural formula: -[PET] m -[PTMG] n - where m is the number of repeating units of ethylene terephthalate, ranging from 50 to 200; n is the number of repeating units of PTMG formed by the homopolymerization of tetrahydrofuran, ranging from 10 to 50.

[0009] The star-shaped arms are fixed at three, and each arm is connected to the same trimethylolpropane core via ester bonds, forming a spatially symmetrical radial configuration. This topology causes the molecular chains to be coiled and entangled in the absence of external forces. During stretching, the flexible PTMG blocks preferentially undergo conformational transformation and extension, absorbing strain energy. When the external force is removed, the entropic elastic driving force provided by the rigid PET blocks causes the molecular chains to spontaneously retract to the initial coiled configuration, thereby achieving high elastic recovery on a macroscopic scale.

[0010] In a preferred embodiment of the present invention, the method for preparing the high-elasticity polyester fabric includes the following steps:

[0011] Step 1: Prepolymer Synthesis. Purified terephthalic acid, ethylene glycol, PTMG (number average molecular weight 1000 g / mol), and trimethylolpropane were added to an esterification reactor in a molar ratio of 1.00:1.20:0.15:0.05. The esterification reaction was carried out under nitrogen protection at 220°C to 240°C and atmospheric pressure for 2.5 hours, until the water content reached more than 95% of the theoretical value, yielding a hydroxyl-terminated oligomer melt. The PTMG had a hydroxyl value of 112 mg KOH / g and a water content of less than 0.05%; the trimethylolpropane had a melting point of 58°C to 60°C.

[0012] Step 2: Melt Polycondensation. The above-mentioned oligomer melt was transferred to a polycondensation reactor, and a catalyst system was added. The catalyst system consisted of antimony acetate and tetrabutyl titanate in a mass ratio of 3:1, with a total addition amount of 250 ppm of the theoretical polymer yield. The polycondensation reaction was carried out at 275°C to 285°C and the absolute pressure was gradually reduced to 50 Pa for 2.0 hours. During the reaction, the reaction endpoint was controlled by online viscosity monitoring. The reaction was terminated when the intrinsic viscosity of the melt reached 0.60 dL / g to 0.65 dL / g, yielding star-shaped to linear block copolyester chips. The terminal carboxyl group content of the chips was less than 25 mol / t, and the diethylene glycol content was less than 1.2 wt%.

[0013] Step 3: Solid-phase viscosity enhancement. After washing and drying, the obtained chips are subjected to solid-phase polycondensation at 160℃ under a nitrogen atmosphere for 8 hours, which increases the intrinsic viscosity to 0.85 dL / g to 1.10 dL / g, while reducing the end carboxyl content to below 15 mol / t, to ensure the thermal stability and spinnability of the subsequent spinning process.

[0014] Step 4: Melt spinning. The thickened chips are melted at 285℃ to 295℃ and precisely fed to the spinning assembly via a metering pump. The filaments are extruded through a circular spinneret (0.30mm orifice, 3:1 aspect ratio), cooled by side blowing (22℃, 0.5m / s), oiled, and then wound at a high speed of 3200m / min to obtain pre-oriented yarn. The pressure of the spinning assembly is stabilized between 12MPa and 15MPa.

[0015] Step 5: False Twist Texture Processing. The pre-oriented yarn bundle is false-twist textured in a heating chamber (180℃) at second roller speeds of 800 m / min, first roller speeds of 780 m / min, and third roller speeds of 820 m / min. The twist is set to 2800 T / m, and the overfeed rate is 2.5%. The final product is a high-elasticity polyester DTY yarn. The DTY yarn has a breaking strength higher than 3.0 cN / dtex, a breaking elongation of 85% to 110%, and a boiling water shrinkage rate of 4.0% to 6.0%.

[0016] Step 6: Weaving and Heat Setting. Using the aforementioned DTY yarn as both warp and weft, the fabric is woven on a circular knitting machine with a weft plain knit structure at a gauge of 28 needles / inch to obtain the greige fabric. The greige fabric is then heat-set at 190°C under relaxed tension for 60 seconds, allowing the molecular chains to rearrange their conformation under stress-free conditions, locking in a highly elastic network structure. The fabric weight after heat setting is 180 g / m². 2 The thickness is 0.45mm.

[0017] In another preferred embodiment of the present invention, the number-average molecular weight of PTMG can be adjusted to 650 g / mol or 2000 g / mol, and correspondingly, its molar ratio in the copolymer system can be adjusted to 0.20 or 0.10, respectively, to adapt to application scenarios with different elastic modulus requirements. When the molecular weight of PTMG is 650 g / mol, the resulting fabric has a higher initial modulus, making it suitable for sports compression garments that require rapid deformation response; when the molecular weight of PTMG is 2000 g / mol, the proportion of flexible blocks increases, resulting in a softer fabric feel, making it suitable for underwear or medical dressings.

[0018] Regardless of the variant, the molar proportion of trimethylolpropane is strictly controlled between 4% and 6% of the molar amount of purified terephthalic acid to ensure the integrity and uniformity of the star-shaped topology. If the proportion of trimethylolpropane is less than 4%, the branching degree is insufficient, and an effective elastic network cannot be formed; if it is more than 6%, it is prone to gelation or deterioration of melt flowability, affecting the continuity of spinning.

[0019] In the catalyst system, the synergistic effect of antimony acetate and tetrabutyl titanate is crucial. When antimony acetate is used alone, the polycondensation rate is slow and the PTMG blocks are prone to ether bond breakage; using titanium-based catalysts alone easily triggers side reactions, leading to a yellowing color. The 3:1 ratio of the two significantly improves the polycondensation efficiency and effectively inhibits the thermal oxidative degradation of PTMG at high temperatures, ensuring the structural integrity of the flexible blocks. The catalyst is not added during the esterification stage but is injected only once at the initial stage of polycondensation to avoid premature deactivation in the high-temperature esterification environment.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. This invention achieves intrinsic high elasticity in a pure polyester system for the first time, completely eliminating dependence on spandex. The resulting fabric contains no non-polyester components, fundamentally solving the UV aging sensitivity problem caused by spandex. After 500 hours of accelerated UV aging, the elasticity recovery rate is over 88%, far superior to spandex-blended fabrics (usually below 70%), significantly extending the product's outdoor service life.

[0022] 2. Since the fabric is composed of a single chemical component, it can be 100% chemically recycled after disposal through conventional alkaline hydrolysis or alcoholysis processes. The recycled monomers have high purity and can be directly used for the polymerization of new polyester, constructing a closed-loop recycling system. There is no spandex residue pollution during the recycling process, which meets the requirements of green manufacturing and circular economy.

[0023] 3. This invention constructs an endogenous elastic mechanism at the molecular level through a star-shaped-linear block topology design. The flexible PTMG blocks provide large deformation capacity, while the rigid PET blocks and star-shaped nodes together form a physical cross-linking network, ensuring high resilience. This structure avoids the dilemma of strength-elasticity mutual constraint in traditional copolymer modification, achieving an elongation at break of 110% while maintaining a breaking strength above 3.0 cN / dtex, meeting the mechanical requirements of functional textiles.

[0024] 4. The preparation method described is compatible with existing polyester production equipment and processes. Only the raw material formulation and catalyst system need optimization; no new specialized equipment is required, resulting in low barriers to industrialization and controllable costs. The produced DTY yarn can be directly used in conventional knitting or weaving equipment, exhibiting excellent weaving performance.

[0025] 5. By adjusting the molecular weight of PTMG and the ratio of trimethylolpropane, the elastic modulus, initial modulus, and hand feel of the fabric can be adjusted within a wide range to meet the differentiated needs of various application scenarios such as sportswear, underwear, and medical bandages, thus expanding the functional boundaries of pure polyester materials.

[0026] 6. Through innovative design of molecular topology, a pure polyester fabric system with high elasticity, high weather resistance, high strength and complete recyclability was successfully constructed. This not only solves the environmental stability and recycling problems of existing spandex-based elastic fabrics, but also provides a new technical path for the sustainable development of high-performance synthetic fibers. Detailed Implementation

[0027] This invention discloses a high-elasticity polyester fabric and its preparation method. The technical solution is entirely based on a 100% modified PET system, without introducing spandex or other non-polyester components. This fabric achieves intrinsically high elongation at break and excellent elastic recovery by designing a star-shaped-linear block topology at the molecular chain level, while maintaining the inherent high strength, thermal stability, and processability of polyester. The star-shaped structure uses trimethylolpropane as a trifunctional core, connecting three linear arms composed of rigid polyethylene terephthalate repeating units and flexible PTMG blocks, forming a spatially symmetrical radial configuration. Macroscopically, this microstructure manifests as follows: under no external force, the molecular chains are coiled and entangled; under tension, the flexible PTMG blocks preferentially extend to absorb strain energy; after the external force is removed, the entropic elastic driving force provided by the rigid PET blocks causes the chain segments to spontaneously retract, achieving high elastic recovery.

[0028] The technical solution of the present invention will be described in detail below with reference to specific embodiments and comparative examples, so as to ensure that those skilled in the art can fully understand and implement the present invention.

[0029] Example 1: The molar amount of trimethylolpropane was 5% of purified terephthalic acid; the number-average molecular weight of PTMG was 1000 g / mol, and the molar ratio was 0.15; the intrinsic viscosity of modified PET was 0.95 dL / g, and the melting point was 250℃; the melt spinning temperature was 290℃, and the spinneret orifice diameter was 0.30 mm; the false twist texturing heating box temperature was 180℃, and the twist was 2800 T / m; the heat setting temperature was 190℃, and the time was 60 seconds; the fabric weight was 180 g / m². 2 ;

[0030] Preparation process: Esterification reaction at 230℃ under nitrogen protection; antimony acetate and tetrabutyl titanate are compounded in a 3:1 ratio as polycondensation catalysts, with an addition amount of 250ppm; solid phase thickening at 160℃ for 8 hours; pre-oriented yarn winding speed of 3200m / min; weft plain knitting (28 needles / inch).

[0031] Example 2: The molar amount of trimethylolpropane was 4% of purified terephthalic acid, and the remaining molecular parameters and processing technology were the same as in Example 1;

[0032] Preparation process: Same as in Example 1.

[0033] Example 3: The molar amount of trimethylolpropane was 6% of purified terephthalic acid, and the remaining molecular parameters and processing technology were the same as in Example 1;

[0034] Preparation process: Same as in Example 1.

[0035] Example 4: PTMG number-average molecular weight 650 g / mol, molar ratio 0.20; other molecular parameters and processing technology are the same as in Example 1;

[0036] Preparation process: Same as in Example 1.

[0037] Example 5: PTMG number-average molecular weight 2000 g / mol, molar ratio 0.10; other molecular parameters and processing technology are the same as in Example 1;

[0038] Preparation process: Same as in Example 1.

[0039] Example 6: Melt spinning temperature 285℃, other molecular parameters and processing technology are the same as in Example 1;

[0040] Preparation process: Same as in Example 1.

[0041] Example 7: Melt spinning temperature 295℃, other molecular parameters and processing technology are the same as in Example 1;

[0042] Preparation process: Same as in Example 1.

[0043] Example 8: Heat setting temperature 180℃, time 70 seconds; other molecular parameters and processing technology are the same as in Example 1;

[0044] Preparation process: Same as in Example 1.

[0045] Comparative Example 1: Conventional PET and spandex were blended at a ratio of 90:10; no star-shaped-linear patchwork structure; weaving and finishing processes were the same as in Example 1;

[0046] Preparation process: conventional melt spinning and blending, without modified PET synthesis steps.

[0047] Comparative Example 2: No trimethylolpropane was added, and the PET had no star-shaped structure; the PTMG molar ratio was 0.15, and the remaining processing technology was the same as in Example 1;

[0048] Preparation process: No star-shaped topology modification, only conventional PET and PTMG copolymerization, the rest is the same as in Example 1.

[0049] Test method:

[0050] Elastic and mechanical property testing: tensile testing machine is used to test elongation at break and fracture strength; elastic recovery rate under 300% tensile strain is tested; glass transition temperature is tested through dynamic mechanical analysis.

[0051] Weather resistance test: Conduct a 500-hour ultraviolet aging test to monitor the elastic recovery rate retention rate; test the boiling water shrinkage rate.

[0052] Structural and processing performance testing: The distance between the star arms was analyzed by small-angle X-ray scattering; the microstructure of the fabric was observed; and the spinnability and weaving formability during the weaving process were tested.

[0053] Test data comparison table 1:

[0054]

[0055] Test data comparison table 2:

[0056]

[0057] Examples 1-8 constructed a star-linear block structure using trimethylolpropane, exhibiting an elongation at break ≥85% and a 300% tensile recovery ≥92%, which is far superior to Comparative Example 2 without a star structure. Although Comparative Example 1 had a high elongation at break, its elasticity decreased significantly after UV aging, confirming that the star structure is the key to achieving high elasticity in pure polyester.

[0058] With the increase in the molar ratio of trimethylolpropane (Examples 2→1→3), the elongation at break is improved due to the increased branching degree promoting molecular chain entanglement; the molecular weight of PTMG increases (Examples 4→1→5), resulting in enhanced flexibility and improved elongation at break, but the recovery rate decreases slightly; the spinning and setting temperatures are within the optimized range, and the performance is stable.

[0059] Examples 1-8 showed a UV aging recovery rate of ≥88%, which was significantly better than Comparative Example 1 (68%), and the samples were fully recyclable. Comparative Example 1 was difficult to recycle and had poor weather resistance due to the presence of spandex, thus demonstrating the environmental and weather resistance advantages of the pure polyester system.

[0060] Examples 1-8 show a fracture strength ≥3.0 cN / dtex, balancing elasticity and strength; Comparative Example 2 has high strength but extremely poor elasticity, while Comparative Example 1 has good elasticity but insufficient strength and weather resistance, confirming that the process of the present invention can achieve a synergistic effect of elasticity, strength and weather resistance.

[0061] Examples 1-8 exhibit good spinnability and weaving properties, are compatible with existing polyester production equipment, and have a wide range of parameter adjustments to suit various needs such as sportswear and underwear.

[0062] The high-elasticity polyester fabric of this invention achieves high elasticity and high weather resistance in a pure polyester system through a star-shaped-linear block topology design, solving the recycling and aging problems of spandex blended fabrics. Different parameter combinations can meet performance requirements and are suitable for diverse textile scenarios.

[0063] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-elasticity polyester fabric, composed of 100% modified PET, free of spandex or other non-polyester components, characterized in that, The modified PET has a star-linear block topology with trimethylolpropane as a trifunctional core, connecting three linear block copolymer arms; the molar amount of trimethylolpropane is 4% to 6% of the molar amount of purified terephthalic acid; The linear block copolymer arms each have the general structural formula -[PET] m -[PTMG] n - where PET is a repeating unit of polyethylene terephthalate, PTMG is a repeating unit of polytetramethylene ether glycol, m is 50 to 200, and n is 10 to 50; the molar ratio of PTMG in the copolymer system is 0.10-0.

20.

2. A method for preparing the high-elasticity polyester fabric as described in claim 1, characterized in that... Includes the following steps: S10: Purified terephthalic acid, ethylene glycol, PTMG and trimethylolpropane are added to an esterification reactor in a molar ratio of 1.00:1.20:0.10–0.20:0.04–0.06 and the esterification reaction is carried out at 220°C to 240°C under nitrogen protection to obtain an oligomer melt with hydroxyl-terminated ends. S20: The oligomer melt is transferred to a polycondensation reactor, and a catalyst system composed of antimony acetate and tetrabutyl titanate in a mass ratio of 3:1 is added. The total amount added is 250 ppm of the theoretical polymer yield. The catalyst system is injected all at once in the early stage of polycondensation and is not added in the esterification stage. Polycondensation is carried out at 275°C to 285°C and the absolute pressure is gradually reduced to 50 Pa for 2.0 hours to obtain chips with an intrinsic viscosity of 0.60 dL / g to 0.65 dL / g. S30: The slices are subjected to solid-phase thickening at 160°C under a nitrogen atmosphere for 8 hours to increase the intrinsic viscosity to 0.85 dL / g to 1.10 dL / g; S40: The thickened chips are melt-spun at 285℃ to 295℃, extruded through a circular spinneret, cooled by side blowing, oiled, and wound into pre-oriented yarn at 3200m / min. The pressure of the spinning assembly is 12MPa to 15MPa. S50: Pre-oriented yarn is processed by false twisting, with a heating box temperature of 180℃, a twist of 2800T / m, and an overfeed rate of 2.5%, to produce high-elasticity polyester DTY yarn; S60: The fabric is woven from the DTY yarn and heat-set at 190°C under relaxed tension for 60 seconds to obtain the finished fabric.

3. The preparation method according to claim 2, characterized in that, In step S50, the first roller speed is 780 m / min, the second roller speed is 800 m / min, and the third roller speed is 820 m / min.

4. The preparation method according to claim 2, characterized in that, In step S60, the weft plain knitting structure is used to knit on a 28-needle / inch circular knitting machine.

5. The preparation method according to claim 2, characterized in that, The moisture content of the PTMG is less than 0.05%.

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