High-elasticity composite fiber heat treatment process

Abstract

The application relates to the technical field of chemical fiber post-treatment, and particularly discloses a high-elasticity composite fiber heat treatment process, which comprises the following steps: S1. fiber pretreatment: polyester-polyamide composite raw materials are immersed in a surfactant cleaning solution with a concentration of 1-2 wt%; S2. steam pre-swelling: the pretreated raw materials are placed in a 105-110 DEG C saturated steam environment for 1.5-2.5 minutes; S3. gradient heat setting: the raw materials pass through three temperature-controlled hot air zones in sequence; S4. negative pressure rapid cooling: the heat-set fibers are cooled to a fiber temperature <50 DEG C; and S5. post-treatment setting: the fibers are wound into a cylinder. The fibers can be used in the high-end textile field, have the characteristics of low oil agent residue rate and high breaking strength, and solve the problem that cleanliness and mechanical properties are difficult to coordinate in the traditional process; the product size stability and processing efficiency are improved through the wind speed gradient ratio and humidity control.

Description

Technical Field

[0001] This application relates to the field of chemical fiber post-processing technology, and more specifically, to a heat treatment process for highly elastic composite fibers. Background Technology

[0002] Post-processing of chemical fibers refers to a series of processing steps taken after the chemical fibers have completed their initial fiber formation in order to achieve the specified physical and mechanical properties and performance characteristics, spinnability and dyeability, and meet the requirements of the final use. These processes typically include, but are not limited to: stretching, heat setting, oiling and crimping, as well as cutting, web forming, twisting, drying and packaging processes depending on the variety and end use. Among these, heat treatment is an important means of post-processing of chemical fibers.

[0003] In related heat treatment processes, anionic surfactants are used for oil cleaning. However, the single polarity of anionic surfactant molecules and the insufficient penetration of sulfonic acid groups lead to a high oil residue rate. At the same time, the use of strong alkali for cleaning causes fiber swelling, resulting in a decrease in the fiber's breaking strength. Summary of the Invention

[0004] To address the issues of high oil residue and decreased tensile strength caused by the use of anionic surfactants for oil cleaning in related heat treatment processes, this application provides a heat treatment process for highly elastic composite fibers.

[0005] This application provides a heat treatment process for highly elastic composite fibers, employing the following technical solution:

[0006] A heat treatment process for highly elastic composite fibers includes the following steps:

[0007] S1. Fiber pretreatment: The polyester-nylon composite raw material is immersed in a surfactant cleaning solution with a concentration of 1-2wt%, and then drawn by the guide roller at 40-50℃ for 2-3 minutes, wherein the traction tension is controlled at 0.15-0.25cN / dtex.

[0008] S2. Steam pre-expansion: Place the pretreated raw material in a saturated steam environment at 105-110℃ for 1.5-2.5 minutes;

[0009] S3. Gradient heat setting: The raw materials are sequentially passed through three temperature-controlled hot air zones:

[0010] Zone 1: The raw materials are heat-treated at 115-125℃ for 0.8-1.2 minutes, during which the wind speed in this zone is controlled at 8-10m / s;

[0011] Second zone: The raw materials processed in the first zone are treated at 145-155℃ for 1.3 to 1.7 minutes, during which the wind speed in this zone is controlled at 12 to 15 m / s;

[0012] Third zone: The raw materials processed in the second zone are treated at 95-105℃ for 0.4-0.6 minutes, during which the wind speed in this zone is controlled at 5-8m.

[0013] S4. Negative pressure rapid cooling: Cooling the heat-set fibers to a fiber temperature <50℃ under vacuum conditions of -0.08 to -0.1 MPa and 35-45℃.

[0014] S5. Post-treatment and setting: The fiber is treated in an environment of 30-35℃ and 60%~65% relative humidity for 24±2 hours, and finally wound into a tube with a constant tension of 0.10±0.02cN / dtex.

[0015] By adopting the above technical solution, due to the use of anionic surfactant concentration control, tension gradient orientation from 0.15cN / dtex to 0.25cN / dtex, three-level temperature zone synergistic wind speed control for crystal growth, and supramolecular relaxation under a humidity environment of 62%±1%, the effects of reduced oil residue rate, increased fiber breaking strength, increased crimp permanent set rate, and increased elastic recovery rate are achieved.

[0016] Preferably, the polyester-nylon composite material has a core-sheath structure, wherein the sheath is polyester and the core is nylon.

[0017] By adopting the above technical solution, due to the use of a polyester-polyamide core-skin composite structure, dual-temperature melt temperature control, and optimized skin ratio, the interfacial bonding layer thickness is enhanced, thereby improving the peel strength and balancing the strength of polyester and the hygroscopicity of polyamide.

[0018] Preferably, the surfactant in step S1 is sodium dodecylbenzenesulfonate and polyethylene glycol octylphenyl ether, with a mass ratio of 1:0.3-0.5.

[0019] By adopting the above technical solution, due to the compounding ratio of sodium dodecylbenzenesulfonate and polyethylene glycol octylphenyl ether, the low-temperature treatment environment, and the control of penetration time, the effects of improved decontamination efficiency and peeling efficiency are achieved, water absorption rate is reduced, secondary pollution caused by the thermal motion of molecular chains is blocked, and the density of fiber fibrillation damage is reduced.

[0020] Preferably, the wind speed control of the three temperature zones in step S3 satisfies the following relationship: the wind speed in the second zone is higher than that in the first zone, and the wind speed in the first zone is higher than that in the third zone, and the wind speed in the second zone is 1.2-1.5 times that in the first zone.

[0021] By adopting the above technical solution, due to the use of wind speed gradient ratio control, three-level temperature zone synergy and wind speed-temperature matching, it is possible to avoid excessive nylon melting delay, ensure the complete growth of polyester crystal nuclei, reduce the accumulation of internal stress in the fiber by low-speed airflow, and thus improve the fiber elasticity recovery rate.

[0022] Preferably, in step S2, the steam saturation is ≥98%, and the moisture content of the fiber after swelling is controlled at 25% to 30%.

[0023] By adopting the above technical solution, the steam partial pressure sensor is used to ensure the steam saturation in real time, and the temperature control range is adjusted and the moisture content threshold is monitored. Therefore, the latent heat release attenuation caused by insufficient saturation is avoided, the micropore density meets the requirements of subsequent processing, the hydrogen bond dissociation caused by excessive moisture content is blocked, and the fiber modulus is maintained, so as to coordinate the effects of plasticization and structural strengthening.

[0024] Preferably, the processing time of each temperature zone in the gradient heat setting in step S3 satisfies the following ratio: first zone time: second zone time: third zone time = 1:1.3-1.5:0.4-0.5.

[0025] By adopting the above technical solution, the process of polyamide melting-polyester crystallization and the conversion balance of α / β crystal form are controlled by the two-zone / one-zone time gradient ratio. Therefore, the effect of avoiding the reduction of crystal nucleus density caused by insufficient melting is achieved, ensuring the reduction of spherulite size and the stable improvement of fracture strength is obtained.

[0026] Preferably, in step S4, the fiber cooling rate is controlled at 30-35℃ / s, and ultrasonic oscillation treatment is performed during the cooling process.

[0027] By adopting the above technical solution, the use of cooling regulation combined with ultrasonic oscillation avoids the coarsening of spherulites caused by excessively low cooling rates, thereby ensuring improved fracture strength, suppressing the accumulation of freezing stress in amorphous regions caused by excessively high cooling rates, and generating microjets to destroy crystal nuclei aggregates and simultaneously remove uncrystallized oligomers, which improves the core-shell bonding strength.

[0028] Preferably, the relative humidity in step S5 is controlled at 62±1%, and the airflow velocity in the post-treatment environment is 0.5~0.8m / s.

[0029] By adopting the above technical solution, humidity control is achieved by using a sensor-linked ultrasonic humidifier, a variable frequency fan maintains uniform airflow, and humidity error is set based on the moisture absorption mutation point of polyamide. Therefore, the effects of avoiding insufficient hydrogen bond recombination caused by low humidity, stable dyeing rate, suppressing excessive free water penetration caused by excessive humidity, and maintaining high hot melt peel strength are achieved.

[0030] Preferably, in step S1, the surface roughness Ra of the guide roller is ≤0.2μm, and the distance between adjacent rollers is 1.8-2.2 times the fiber length.

[0031] By adopting the above technical solution, the surface roughness Ra of the guide roller is ensured to be Ra≤0.2μm by precision grinding, real-time monitoring by white light interferometer, and roller spacing is adjusted to 1.8-2.2 times the fiber length. Therefore, the friction coefficient caused by excessive roughness is prevented from increasing, and a low fibrillation damage density is maintained.

[0032] In summary, this application has the following beneficial effects:

[0033] 1. Because this application uses a surfactant system of sodium dodecylbenzenesulfonate and polyethylene glycol octylphenyl ether compounded by mass, the polyoxyethylene chain of polyethylene glycol octylphenyl ether penetrates the intermolecular gaps of nylon through hydrogen bonding, and works synergistically with the sulfonic acid groups of sodium dodecylbenzenesulfonate to remove oil, reduce the residual rate, and at the same time maintain the fiber water absorption rate at a low level, thereby increasing the breaking strength and achieving the effect of improving the cleanliness of the fiber interface and strengthening the mechanical properties.

[0034] 2. In this application, a negative pressure rapid cooling process with cooling rate combined with ultrasonic oscillation is preferred. The ultrasonic cavitation effect destroys crystal nuclei aggregates larger than 5 micrometers in size, while generating microjets and inhibiting spherulite coarsening to make the spherulite size smaller, thereby improving the interlayer peel strength and controlling residual internal stress, thus achieving the effects of strengthening the skin-core interface and reducing internal stress.

[0035] 3. The method of this application promotes the recombinant hydrogen bond of polyamide by controlling the relative humidity and wind speed of the post-processing environment and adjusting the humidity window. The intensity of the characteristic peak at 3300 cm⁻¹ is verified by Fourier transform infrared spectroscopy without attenuation and the free volume fraction is stable, which improves the dyeing rate and optimizes the dimensional change rate of the garment after washing. It achieves a synergistic optimization effect of fiber moisture absorption function and dimensional stability. Attached Figure Description

[0036] Figure 1 This is a flowchart of a heat treatment process for a high-elasticity composite fiber proposed in this application. Detailed Implementation

[0037] The present application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0038] In related heat treatment processes, anionic surfactants are used for oil cleaning. However, the single polarity of anionic surfactant molecules and the insufficient penetration of sulfonic acid groups lead to a high oil residue rate. At the same time, the use of strong alkali for cleaning causes fiber swelling, resulting in a decrease in the fiber's breaking strength.

[0039] This application provides a heat treatment process for highly elastic composite fibers, including the following steps: S1. Fiber pretreatment; S2. Steam pre-expansion; S3. Gradient heat setting; S4. Negative pressure rapid cooling; S5. Post-treatment setting: winding the fibers into a cylinder.

[0040] This application employs a surfactant system composed of sodium dodecylbenzenesulfonate and polyethylene glycol octylphenyl ether in a mass ratio. The polyoxyethylene chains of polyethylene glycol octylphenyl ether penetrate the intermolecular spaces of nylon through hydrogen bonding, and work synergistically with the sulfonic acid groups of sodium dodecylbenzenesulfonate to remove oil, reduce the residual rate, and maintain the fiber water absorption rate at a low level, thereby increasing the breaking strength. This results in improved fiber interface cleanliness and enhanced mechanical properties.

[0041] Please see the appendix Figure 1 This application provides a heat treatment process for highly elastic composite fibers, including the following steps:

[0042] S1. Fiber pretreatment: The polyester-nylon composite raw material is immersed in a surfactant cleaning solution with a concentration of 1-2wt%, and then drawn by the guide roller at 40-50℃ for 2-3 minutes, wherein the traction tension is controlled at 0.15-0.25cN / dtex.

[0043] S2. Steam pre-expansion: Place the pretreated raw material in a saturated steam environment at 105-110℃ for 1.5-2.5 minutes;

[0044] S3. Gradient heat setting: The raw materials are sequentially passed through three temperature-controlled hot air zones:

[0045] Zone 1: The raw materials are heat-treated at 115-125℃ for 0.8-1.2 minutes, during which the wind speed in this zone is controlled at 8-10m / s;

[0046] Second zone: The raw materials processed in the first zone are treated at 145-155℃ for 1.3 to 1.7 minutes, during which the wind speed in this zone is controlled at 12 to 15 m / s;

[0047] Third zone: The raw materials processed in the second zone are treated at 95-105℃ for 0.4-0.6 minutes, during which the wind speed in this zone is controlled at 5-8m.

[0048] S4. Negative pressure rapid cooling: Cooling the heat-set fibers to a fiber temperature <50℃ under vacuum conditions of -0.08 to -0.1 MPa and 35-45℃.

[0049] S5. Post-treatment and setting: The fiber is treated in an environment of 30-35℃ and 60%~65% relative humidity for 24±2 hours, and finally wound into a tube with a constant tension of 0.10±0.02cN / dtex.

[0050] Specifically, in the fiber pretreatment stage, the raw material is impregnated with an aqueous solution of anionic surfactant at a mass percentage concentration of 1 wt% to 2 wt%. This concentration range has been verified by orthogonal experiments to remove spinning oil and prevent fiber swelling. Subsequently, the raw material is treated with a traction tension of 0.15 cN / dtex to 0.25 cN / dtex through a guide roller at 40°C to 50°C for 2 to 3 minutes. This tension parameter is set based on fiber breaking strength tests, which can achieve preliminary molecular chain orientation without inducing fibrillation damage. The steam pre-swelling process uses a saturated steam environment at 105°C to 110°C for 1.5 to 2.5 minutes. This temperature threshold allows the amorphous region of the fiber to soften sufficiently while the crystalline region remains stable. The treatment time is determined by differential scanning calorimetry to measure the glass transition time window. Gradient heat... The setting stage is divided into three temperature control zones: In the first zone, X-ray diffraction analysis confirms that the environmental parameters in this zone promote the rearrangement of molecular chains in the amorphous region to form a pre-crystallized network; in the second zone, accelerated heat conduction causes the nylon component to melt and induce the growth of polyester crystal nuclei, and Fourier transform infrared spectroscopy verifies that the crystallinity of the treated raw material is improved; in the third zone, a slow-speed environment eliminates internal stress and locks the supramolecular structure; negative pressure rapid cooling achieves rapid phase change locking of the fiber temperature below 50℃, and the vacuum environment avoids plastic deformation caused by moisture condensation; after post-treatment setting, the fiber moisture content is stabilized to 3.5%±0.5% and then wound with a constant tension of 0.10±0.02cN / dtex. Dynamic mechanical analysis confirms that this combination of humidity and tension can maintain a permanent setting rate of ≥92% for the crimp, while the elastic recovery rate is improved to 88.5%±1.5%.

[0051] See appendix Figure 1 The polyester-nylon composite material has a core-sheath structure, in which the sheath is polyester and the core is nylon;

[0052] Specifically, the polyester-nylon composite raw material is prepared using a core-sheath composite spinning process, where the sheath is polyethylene terephthalate (PET) and the core is polyamide-6. The PET melt temperature is controlled at 275°C to 280°C using a twin-screw extruder, while the polyamide-6 melt temperature is controlled at 255°C to 260°C. A precise metering pump is then used to regulate the melt flow rates of the sheath and core layers at a volumetric flow rate ratio of 2.5:1 to 3.2:1. The core-sheath structure utilizes the high-rigidity molecular chains of the polyester sheath to form an external protective layer, while the amide bonds of the polyamide in the core layer form hydrogen bonds with water molecules to achieve moisture absorption. The interface between the two layers forms an interpenetrating network structure through shear-induced orientation during melt extrusion. Scanning electron microscopy has verified that when the thickness of the interfacial bonding layer reaches 0.8 μm to 1.2 μm, it can synergistically balance fiber breaking strength and moisture regain.

[0053] See appendix Figure 1In step S1, the surfactant is sodium dodecylbenzenesulfonate and polyethylene glycol octylphenyl ether, with a mass ratio of 1:0.3-0.5.

[0054] Specifically, the mass ratio range in step S1 is determined by measuring the interfacial tension: when the ratio is higher than 1:0.3, the oil-water interfacial tension >35mN / m leads to an increase in oil residue to over 8wt%; when the ratio is lower than 1:0.5, the critical micelle concentration decreases to 0.5mmol / L, causing fiber swelling to exceed the standard by 20%; therefore, the mass ratio is selected as 1:0.3-0.5; under treatment conditions of 40-50℃, the sulfonic acid groups of sodium dodecylbenzenesulfonate bind to the hydrophobic groups of the polyester surface oil through ionic bonds, while polyethylene glycol... Octylphenyl ether's polyoxyethylene chains penetrate the intermolecular spaces of nylon through hydrogen bonding, synergistically achieving an oil removal efficiency of 95±2%. By controlling the temperature of the treatment solution to be maintained below the glass transition point, secondary pollution caused by the thermal motion of molecular chains is prevented. The total surfactant concentration is controlled at 1-2wt% based on the optimized contact angle of the raw materials: this concentration range reduces the contact angle of the polyester surface from 85° to 45±3°, while maintaining the fiber water absorption rate at <3wt%, and the treatment time of 2-3 minutes ensures that the wetting depth reaches 30±5% of the fiber diameter.

[0055] See appendix Figure 1 In step S3, the wind speed control of the three temperature zones satisfies the following relationship: the wind speed in the second zone is higher than that in the first zone, and the wind speed in the first zone is higher than that in the third zone, and the wind speed in the second zone is 1.2-1.5 times that in the first zone.

[0056] Specifically, based on the phase transition kinetics of polyester-polyamide composite fibers: when the wind speed ratio is less than 1.2 times, insufficient heat conduction rate in the second zone leads to a delay of more than 15s in the absorption of nylon melting enthalpy, resulting in incomplete growth of polyester crystal nuclei, followed by a decrease in crystallinity as measured by X-ray diffraction; when the wind speed ratio is greater than 1.5 times, the pre-orientation process of molecular chains in the first zone is excessively accelerated, and the orientation factor measured by the sound velocity method is greater than 0.92, causing an increase in the probability of brittle fracture of the fiber; the first zone can promote the deentanglement of molecular chains in the amorphous region, and at this time, every 1m / s increase in wind speed can shorten the glass transition time by 12±0.5s; while the treatment environment in the second zone can increase the melting peak temperature of polyamide by 5℃±0.5℃, thereby inducing the growth of polyester grain size to 45nm±3nm; the reduction in wind speed in the third zone can reduce the accumulation of internal stress, thereby improving the elastic recovery rate.

[0057] See appendix Figure 1 In step S2, the steam saturation is ≥98%, and the moisture content of the fiber after swelling is controlled at 25% to 30%.

[0058] Specifically, in step S2, the steam saturation is monitored in real time by a steam partial pressure sensor to ensure that the saturated steam ambient temperature is controlled between 105℃ and 110℃. Under these conditions, the moisture content of the fiber after swelling can be adjusted to 25wt% to 30wt%. Based on the principle of nucleation thermodynamics, when the saturation is below 98%, the release of the latent heat of vapor phase change decreases, resulting in insufficient plasticization of the amorphous region of the fiber. Wide-angle X-ray scattering detection shows that the micropore formation density is ≤120 / μm², which cannot meet the requirements of subsequent fiber processing. If the moisture content is higher than 30wt%, the degree of hydrogen bond dissociation between polyamide molecular chains reaches 45%±3%, which in turn causes the fiber modulus to decrease to 2.8cN / dtex±0.2cN / dtex.

[0059] See appendix Figure 1 In step S3, the processing time for each temperature zone of gradient heat setting satisfies the following ratio: first zone time: second zone time: third zone time = 1:1.3-1.5:0.4-0.5.

[0060] Specifically, based on the crystallization kinetics of polyester-polyamide composite fibers, the following settings are made: if the ratio of zone two to zone one is less than 1.3, then insufficient polyamide melting will result in a polyester nucleus density ≤ 1.8 × 10¹. 5 If the number of crystals per cm³ is insufficient, coarse spherulites will form during the subsequent cooling step S4 due to insufficient supercooling, resulting in a decrease in fiber breaking strength. If the ratio of zone 2 to zone 1 is greater than 1.5, the proportion of α crystals is greater than 55%, and the β→α crystal form transformation is excessive, leading to an increase in the elastic modulus during the winding process in step S5. This results in a loom breakage rate of ≥15 times / 10,000 wefts during the textile processing of the fiber, thereby affecting the performance of the fiber product.

[0061] See appendix Figure 1 In step S4, the fiber cooling rate is controlled at 30-35℃ / s, and ultrasonic oscillation is performed during the cooling process.

[0062] Specifically, in step S4, the fiber cooling rate is controlled within the range of 30℃ / s to 35℃ / s. This rate is achieved by adjusting the vacuum level and the cooling airflow temperature in tandem. When the cooling rate is below 30℃ / s, the excessively high migration rate of the polyester molecular chains leads to excessively large spherulite size, which in turn causes a decrease in fiber breaking strength. When the rate is above 35℃ / s, the glass transition window time decreases, which in turn causes the accumulation of freezing stress in the amorphous region. Meanwhile, the simultaneously applied ultrasonic oscillation treatment uses a frequency of 40kHz±1kHz and an amplitude of 50μm±5μm, and generates a cavitation effect to produce microjets in the cooling medium, which promotes the collapse of microbubbles on the fiber surface to destroy crystal nuclei aggregates larger than 5μm, while eliminating the residue of non-crystalline oligomers on the fiber surface.

[0063] See appendix Figure 1 In step S5, the relative humidity is controlled at 62±1%, and the airflow velocity in the post-treatment environment is 0.5~0.8m / s.

[0064] Specifically, in step S5, the relative humidity of the environment is achieved through the linkage of a dew point sensor and an ultrasonic humidifier; a variable frequency fan ensures uniform airflow to maintain airflow speed; based on the moisture absorption mutation point of polyamide-polyester composite fiber: when the humidity is below 61%, the hydrogen bond recombination between polyamide molecular chains is insufficient, and the orientation factor measured by the sound velocity method is ≤0.78, resulting in a decrease in dyeing rate during subsequent fiber processing; when the humidity is above 63%, the penetration depth of free water molecules is higher than 10μm, causing the fiber diameter to swell beyond the limit, resulting in a decrease in the peel strength of the fiber during hot melting.

[0065] See appendix Figure 1 In step S1, the surface roughness Ra of the guide roller is ≤0.2μm, and the distance between adjacent rollers is 1.8-2.2 times the fiber length.

[0066] Specifically, in step S1, the surface roughness of the guide roller is ensured by precision grinding and online detection by a white light interferometer. When the roughness is higher than 0.2 μm, the surface friction coefficient of the fiber increases, and atomic force microscopy shows that the fibrillation damage density is higher than 15 sites / mm, which leads to an increase in the breakage rate of heat setting in the subsequent step S3. When the spacing is less than 1.8 times the fiber length, the fiber vibration frequency is higher than 120 Hz, causing resonance and making the winding tension fluctuation CV value in step S5 higher than 8%. When the spacing is greater than 2.2 times, the fluid peeling eddy current intensity decreases, resulting in uneven wetting of the treatment liquid and affecting the dyeing of the fiber.

[0067] Example 1

[0068] This embodiment provides a heat treatment process for highly elastic composite fibers, wherein the fiber raw material has a core-sheath structure, the sheath is polyethylene terephthalate, and the core is polyamide-6; and the surfactant ratio is: sodium dodecylbenzenesulfonate: polyethylene glycol octylphenyl ether = 1:0.3;

[0069] The above-mentioned heat treatment process for high-elasticity composite fibers:

[0070] S1. Fiber pretreatment: The polyester-nylon composite raw material is immersed in a surfactant cleaning solution with a concentration of 1.5wt%, and then drawn by the guide roller at 45℃ for 2.5min, with the traction tension controlled at 0.20cN / dtex.

[0071] S2. Steam pre-expansion: The pretreated raw material is placed in a saturated steam environment at 108℃ for 2.0 min;

[0072] S3. Gradient heat setting: First zone: The raw material is heat-treated at 120℃ for 1.0 min, and the air velocity is controlled at 9 m / s;

[0073] Zone 2: Raw materials are processed at 150℃ for 1.4 minutes, with the wind speed controlled at 13.5m / s;

[0074] Zone 3: Raw materials are processed at 100℃ for 0.5 minutes, with the wind speed controlled at 6m / s;

[0075] S4. Negative pressure rapid cooling: Cooling to fiber temperature <50℃ under vacuum conditions of -0.09MPa and 38℃, wherein the cooling rate is controlled at 32℃ / s;

[0076] S5. Post-processing and shaping: Treat in an environment of 32℃ and 62% relative humidity for 24 hours, and finally wind into a cylinder with a constant tension of 0.10cN / dtex.

[0077] Example 2

[0078] This embodiment provides a heat treatment process for highly elastic composite fibers, wherein the fiber raw material has a core-sheath structure, the sheath is polyethylene terephthalate, and the core is polyamide-6; and the surfactant ratio is: sodium dodecylbenzenesulfonate: polyethylene glycol octylphenyl ether = 1:0.35.

[0079] The above-mentioned heat treatment process for high-elasticity composite fibers:

[0080] S1. Fiber pretreatment: The polyester-nylon composite raw material is immersed in a surfactant cleaning solution with a concentration of 1.2wt%, and then drawn by the guide roller at 48℃ for 2.2min, with the traction tension controlled at 0.18cN / dtex.

[0081] S2. Steam pre-expansion: The pretreated raw material is placed in a saturated steam environment at 106℃ for 1.8 min;

[0082] S3. Gradient thermal setting:

[0083] Zone 1: The raw materials are heat-treated at 118℃ for 0.9 minutes, with the wind speed controlled at 8.5m / s;

[0084] Zone 2: Raw materials are processed at 148℃ for 1.35 minutes with the wind speed controlled at 12.2m / s;

[0085] Zone 3: Raw materials are processed at 98℃ for 0.45 minutes, with the wind speed controlled at 5.5m / s;

[0086] S4. Negative pressure rapid cooling: Cooling to fiber temperature <50℃ under vacuum conditions of -0.085MPa and 40℃, wherein the cooling rate is controlled at 31℃ / s;

[0087] S5. Post-processing and shaping: Treat in an environment of 33℃ and 63% relative humidity for 24 hours, and finally wind into a cylinder with a constant tension of 0.10cN / dtex.

[0088] Example 3

[0089] This embodiment provides a heat treatment process for highly elastic composite fibers, wherein the fiber raw material has a core-sheath structure, the sheath is polyethylene terephthalate, and the core is polyamide-6; and the surfactant ratio is: sodium dodecylbenzenesulfonate: polyethylene glycol octylphenyl ether = 1:0.5.

[0090] The above-mentioned heat treatment process for high-elasticity composite fibers:

[0091] S1. Fiber pretreatment: The polyester-nylon composite raw material is immersed in a surfactant cleaning solution with a concentration of 2wt%, and then traction-treated by the guide roller at 42℃ for 2.8min, with the traction tension controlled at 0.22cN / dtex;

[0092] S2. Steam pre-expansion: The pretreated raw material is placed in a saturated steam environment at 109℃ for 2.3 min;

[0093] S3. Gradient thermal setting:

[0094] Zone 1: The raw materials are heat-treated at 122℃ for 1.1 minutes, with the wind speed controlled at 9.8m / s;

[0095] Zone 2: Raw materials are processed at 152℃ for 1.65 minutes, with the wind speed controlled at 14.8m / s;

[0096] Zone 3: Raw materials are processed at 102℃ for 0.55 minutes, with the wind speed controlled at 7.5m / s;

[0097] S4. Negative pressure rapid cooling: Cooling to fiber temperature <50℃ under vacuum conditions of -0.095MPa and 36℃, wherein the cooling rate is controlled at 34℃ / s;

[0098] S5. Post-processing and shaping: Treat in an environment of 34℃ and 64% relative humidity for 24 hours, and finally wind into a cylinder with a constant tension of 0.10cN / dtex.

[0099] Comparative Example 1

[0100] This comparative example provides a composite fiber heat treatment process, wherein the mass ratio of surfactant is: sodium dodecylbenzenesulfonate: polyethylene glycol octylphenyl ether = 1:0.2, and the other parameters are the same as in Example 1.

[0101] The heat treatment process for the composite fibers described above is the same as in Example 1.

[0102] Comparative Example 2

[0103] This comparative example provides a composite fiber heat treatment process, wherein the reagent parameters are the same as in Example 1:

[0104] The above-mentioned composite fiber heat treatment process:

[0105] The S4 cooling rate was changed to 15℃ / s, and the other steps were the same as in Example 1.

[0106] Comparative Example 3

[0107] This comparative example provides a composite fiber heat treatment process, wherein the reagent parameters are the same as in Example 1:

[0108] The above-mentioned composite fiber heat treatment process:

[0109] The relative humidity of S5 was changed to 36%, and the other parameters were the same as in Example 1.

[0110] Comparative Example 4

[0111] This comparative example provides a composite fiber heat treatment process, wherein the reagent parameters are the same as in Example 1:

[0112] The above-mentioned composite fiber heat treatment process:

[0113] Replace sodium dodecylbenzenesulfonate with an equal amount of sodium dodecyl sulfate.

[0114] Performance testing

[0115] Sample preparation:

[0116] Fiber samples from Examples 1-3 and Comparative Examples 1-4 were used to prepare test strips according to GB / T14337 standard: the sample length was controlled to be 50cm, and the samples were treated at 20℃ / 65%RH for 24 hours to maintain humidity balance, with 30 strips prepared for each sample.

[0117] Testing methods and procedures:

[0118] Physical and mechanical property testing

[0119] Test item: The elastic recovery rate of the test sample is tested according to GB / T14344-2008.

[0120] Testing instrument: Electronic universal testing machine.

[0121] Steps: Cut the effective length of each sample fiber to 250mm, pre-tension 0.05cN / dtex; set the stretching rate to 500mm / min, stretch to 5% elongation and hold for 60 seconds, unload and let stand for 180 seconds, calculate the recovery rate, repeat each group of samples 3 times and take the average value.

[0122] Thermal stability test

[0123] Test item: Dry heat shrinkage rate.

[0124] Testing instrument: heat shrink apparatus.

[0125] Procedure: Take 100cm of fiber and suspend it in a 180℃ oven. At the same time, apply a pre-tension of 0.05cN / dtex to the sample. After treatment for 30 minutes, cool the sample and measure the change in sample length.

[0126] Surface morphology and structure analysis

[0127] Test item: Surface defects of the sample.

[0128] Testing instrument: Scanning electron microscope.

[0129] Steps: The sample was fractured by liquid nitrogen, then gold sputtered onto the sample, and the interface bonding of the cross section was observed. At the same time, the distribution of surface grooves and cracks was observed under 5000x magnification.

[0130] Performance Comparison Table:

[0131] Group Elastic recovery rate (%) Dry heat shrinkage rate (%) Surface defects Example 1 92.3±0.8 5.2±0.3 The surface is smooth with no obvious cracks; the cross-sectional interface is tightly bonded. Example 2 93.1±0.6 4.8±0.2 A few microgrooves, no cracks; uniform interfacial bonding. Example 3 91.5±0.9 5.5±0.4 Minor grooves, no cracks; good interface bonding. Comparative Example 1 85.2±1.2 7.6±0.5 Multiple microcracks; localized delamination at the interface. Comparative Example 2 88.4±0.7 6.3±0.4 Surface roughness, deeper grooves; weakened interfacial bonding Comparative Example 3 82.6±1.1 8.9±0.6 Significant cracks; obvious interface delamination Comparative Example 4 79.8±1.4 9.7±0.7 Dense cracks; severe interface separation

[0132] Example Conclusion:

[0133] Combining Examples 1-3 and Comparative Example 1 with the performance comparison table, it can be seen that when the proportion of polyethylene glycol octylphenyl ether in the surfactant ratio is reduced to 1:0.2, the elastic recovery rate of the fiber decreases, the dry heat shrinkage rate increases, and local peeling and microcracks appear at the interface. This indicates that insufficient polyethylene glycol octylphenyl ether ratio leads to a weakened surfactant cleaning effect, which in turn affects the skin-core layer bonding strength and thermal stability.

[0134] Combining Examples 1-3 and Comparative Example 2 with the performance comparison table, it can be seen that when the cooling rate is reduced to 15℃ / s, the fiber elastic recovery rate decreases, the dry heat shrinkage rate increases, the surface roughness intensifies, and the interfacial bonding weakens. This indicates that rapid cooling is key to maintaining the relaxed state of the molecular chains in the amorphous region of the fiber and inhibiting structural shrinkage, while slow cooling exacerbates the accumulation of residual thermal stress.

[0135] Combining Examples 1-3 and Comparative Example 3 with the performance comparison table, it can be seen that when the post-treatment setting humidity is reduced to 36%, the fiber elastic recovery rate decreases, the dry heat shrinkage rate increases, and the interface delamination and surface cracks increase significantly. This demonstrates that a high humidity environment promotes molecular chain rearrangement through the plasticizing effect of water molecules, while low humidity leads to insufficient release of internal stress, causing structural defects.

[0136] Combining Examples 1-3 and Comparative Example 4 with the performance comparison table, it can be seen that after replacing sodium dodecylbenzenesulfonate with sodium dodecyl sulfate, the elastic recovery rate dropped to 79.8%, the dry heat shrinkage rate increased to 9.7%, and severe interface separation occurred. This indicates that the benzene ring structure of sodium dodecylbenzenesulfonate has a directional adsorption effect on the PET / PA6 interface, and its molecular configuration can improve the compatibility of the composite fiber.

[0137] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A heat treatment process for highly elastic composite fibers, characterized in that, Includes the following steps: S1. Fiber pretreatment: The polyester-nylon composite raw material is immersed in a surfactant cleaning solution with a concentration of 1-2wt%, and then drawn by the guide roller at 40-50℃ for 2-3 minutes, wherein the traction tension is controlled at 0.15-0.25cN / dtex. S2, Steam pre-expansion: Place the pretreated raw material in a saturated steam environment at 105-110℃ for 1.5-2.5 minutes; S3, Gradient Heat Setting: The raw materials are sequentially passed through three temperature-controlled hot air zones: Zone 1: The raw materials are heat-treated at 115-125℃ for 0.8-1.2 minutes, during which the wind speed in this zone is controlled at 8-10m / s; Second zone: The raw materials processed in the first zone are treated at 145-155℃ for 1.3 to 1.7 minutes, during which the wind speed in this zone is controlled at 12 to 15 m / s; Third zone: The raw materials processed in the second zone are treated at 95-105℃ for 0.4-0.6 minutes, during which the wind speed in this zone is controlled at 5-8m. S4. Negative pressure rapid cooling: Cooling the heat-set fibers to a fiber temperature <50℃ under vacuum conditions of -0.08 to -0.1 MPa and 35-45℃. S5. Post-treatment and setting: The fiber is treated in an environment of 30-35℃ and 60%~65% relative humidity for 24±2 hours, and finally wound into a tube with a constant tension of 0.10±0.02cN / dtex.

2. The heat treatment process for high-elasticity composite fibers according to claim 1, characterized in that, The polyester-nylon composite material has a core-sheath structure, wherein the sheath is polyester and the core is nylon.

3. The heat treatment process for high-elasticity composite fibers according to claim 1, characterized in that, The surfactant mentioned in step S1 is sodium dodecylbenzenesulfonate and polyethylene glycol octylphenyl ether, with a mass ratio of 1:0.3-0.

5.

4. The heat treatment process for high-elasticity composite fibers according to claim 1, characterized in that, In step S3, the wind speed control of the three temperature zones satisfies the following relationship: the wind speed in the second zone is higher than that in the first zone, and the wind speed in the first zone is higher than that in the third zone, and the wind speed in the second zone is 1.2-1.5 times that in the first zone.

5. The heat treatment process for high-elasticity composite fibers according to claim 1, characterized in that, In step S2, the steam saturation is ≥98%, and the moisture content of the fiber after swelling is controlled at 25% to 30%.

6. The heat treatment process for high-elasticity composite fibers according to claim 1, characterized in that, In step S3, the processing time for each temperature zone of gradient heat setting satisfies the following ratio: first zone time: second zone time: third zone time = 1:1.3-1.5:0.4-0.

5.

7. The heat treatment process for high-elasticity composite fibers according to claim 1, characterized in that, In step S4, the fiber cooling rate is controlled at 30-35℃ / s, and ultrasonic oscillation is performed during the cooling process.

8. The heat treatment process for high-elasticity composite fibers according to claim 1, characterized in that, In step S5, the relative humidity is controlled at 62±1%, and the airflow velocity in the post-treatment environment is 0.5~0.8m / s.

9. The heat treatment process for high-elasticity composite fibers according to claim 1, characterized in that, In step S1, the surface roughness Ra of the guide roller is ≤0.2μm, and the distance between adjacent rollers is 1.8-2.2 times the fiber length.

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