Preparation method of high color fastness low temperature energy-saving dyed stretch fabric

Abstract

This invention relates to the field of textile printing and dyeing technology, and discloses a method for preparing high-color-fastness, low-temperature, energy-saving dyed elastic fabric. The method includes: feeding a polyester / polyurethane interwoven elastic fabric into a dyeing machine; adding water to adjust to a first temperature; adding anhydrous sodium sulfate, sodium diisobutyl sulfosuccinate, and fatty alcohol polyoxyethylene ether in a circulating cycle; raising the temperature to a second temperature and adding propylene carbonate; subsequently adding gluconate-δ-lactone and Disperse Red 60, and circulating at a constant temperature; then raising the temperature to the highest dyeing temperature and holding; lowering the temperature to a third temperature and draining the dye liquor; refilling with water and adding fatty alcohol polyoxyethylene ether for hot water washing; and finally, rinsing with cold water and setting. This invention utilizes the low-temperature swelling effect of propylene carbonate and the slow-release acid-producing mechanism of gluconate-δ-lactone to control the highest dyeing temperature at 92–98°C, avoiding heat damage and elasticity loss of polyurethane fibers, improving dye uptake and fabric color fastness, while reducing dyeing energy consumption.

Description

Technical Field

[0001] This invention relates to the field of textile printing and dyeing technology, specifically to a method for preparing a high-color-fastness, low-temperature, energy-saving dyed elastic fabric. Background Technology

[0002] Polyester and polyurethane interwoven elastic fabrics possess both good dimensional stability and elasticity, making them widely used in textile fabrics. Polyester fibers have a compact molecular structure and high crystallinity; in conventional dyeing processes, high-temperature and high-pressure conditions of around 130°C are typically required for disperse dyes to penetrate the fiber interior and complete the dyeing process. However, the polyurethane fibers in the interwoven fabric have poor heat resistance. Under prolonged high-temperature treatment, the hard segments of its macromolecular chains are prone to thermal depolymerization and breakage, resulting in the elastic fabric losing its original elasticity.

[0003] To avoid heat damage to polyurethane fibers, dyeing temperatures are typically lowered. However, at low temperatures, the amorphous regions of polyester fibers do not expand sufficiently, resulting in a smaller internal free volume and increased resistance to the diffusion of disperse dye molecules into the fiber. This diffusion difficulty leads to a lower dye uptake rate, with more dye adhering to the fiber surface and forming floating color, reducing the fabric's wash fastness and rubbing fastness. In actual production, to improve dyeing performance at low temperatures, acids and various carrier auxiliaries are usually added directly to the dye bath. Conventional acid addition methods can cause the pH value of the dye bath to drop rapidly in a short time, disrupting the stable state of the disperse dyes and causing dye molecules to aggregate and precipitate in the liquid phase, resulting in color spots on the fabric surface. Furthermore, the excessive addition of auxiliaries increases the difficulty of subsequent wastewater treatment. Therefore, how to maintain the elasticity of polyurethane fibers at lower dyeing temperatures while ensuring the uptake rate of disperse dyes and the final color fastness of the fabric is a technical problem that the printing and dyeing industry needs to solve. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for preparing high-color-fastness, low-temperature energy-saving dyed elastic fabric. This method solves the problems of heat damage and loss of elasticity in existing polyester and polyurethane interwoven elastic fabrics during traditional high-temperature dyeing, while conventional low-temperature dyeing suffers from low disperse dye uptake and poor fabric color fastness.

[0005] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for preparing a high-color-fastness, low-temperature energy-saving dyed elastic fabric, comprising the following steps: Polyester and polyurethane interwoven elastic fabric is put into a dyeing machine, room temperature water is injected, the circulation pump is turned on, and the dye liquor temperature is adjusted to the first temperature; anhydrous sodium sulfate, sodium diisobutyl sulfosuccinate and fatty alcohol polyoxyethylene ether are added to the dyeing machine, and the first temperature is maintained for circulation. The dye bath temperature is increased to the second temperature according to the first heating rate, and propylene carbonate is added to the dyeing machine for circulation; Then gluconate-δ-lactone and Disperse Red 60 were added, and the initial pH of the staining bath was controlled between 7.0 and 7.5. The solution was then circulated at a constant temperature in the second temperature range. The dye bath temperature is increased from the second temperature to the highest dyeing temperature according to the second heating rate, and the temperature is maintained and circulated at the highest dyeing temperature. Cool down to the third temperature and drain the dye liquor; refill with cold water and heat up to the third temperature, add detergent fatty alcohol polyoxyethylene ether, and circulate at the third temperature for hot water washing; After draining, the fabric is rinsed with cold water, dehydrated, and shaped to obtain dyed elastic fabric.

[0006] By adopting the above technical solution, and through a multi-stage temperature control and batch addition of various auxiliaries, the morphological structure of polyester fibers and the chemical microenvironment of the dye liquor are altered, thereby improving dye diffusion and fixation capabilities while lowering the overall dyeing temperature. The specific reaction process and mechanism of action are as follows: In the early stages of system establishment, anhydrous sodium sulfate is added to increase the electrolyte concentration of the dye bath, thereby reducing the surface charge repulsion of the disperse dye; sodium diisobutyl sulfosuccinate acts as a penetrant to reduce the surface tension of the liquid, and works in conjunction with fatty alcohol polyoxyethylene ether to achieve the effect of leveling and dispersing. The synergistic effect of the three allows the dye liquor to penetrate into the micropores of the interwoven elastic fabric at the first temperature.

[0007] As the dye liquor penetrates deeper into the fiber, the temperature is raised to a second temperature and propylene carbonate is added. Propylene carbonate undergoes physical penetration into the amorphous region of the polyester fiber, weakening the van der Waals forces and hydrogen bonds between the polyester macromolecular chains. This process increases the free volume within the polyester fiber, lowers the glass transition temperature, and provides diffusion channels for dye molecules to enter the fiber interior at lower temperatures.

[0008] The dyeing process is controlled by adding gluconate-δ-lactone and Disperse Red 60. Under heating conditions, gluconate-δ-lactone undergoes a hydrolytic ring-opening reaction in the dye bath to generate gluconic acid. This hydrolytic acid production process is linear, stabilizing the initial pH of the dye bath in the range of 7.0 to 7.5, and then transitioning to a weakly acidic environment. This slow-release acid production mechanism prevents a rapid decrease in dye bath acidity from causing dye aggregation and precipitation, thus maintaining the monomolecular dispersion of Disperse Red 60.

[0009] With the combined effect of the aforementioned microenvironment and physical channels, thermodynamics drives dye molecules to penetrate deep into the intermolecules of the fiber and complete fixation. The entire process maintains the maximum dyeing temperature within a specific range to prevent thermal depolymerization of the hard segments in the polyurethane chain. After cooling and draining, the emulsifying and solubilizing effect of fatty alcohol polyoxyethylene ether at a third temperature is used to peel off excess unfixed dye adhering to the fiber surface and introduce it into the aqueous phase.

[0010] Therefore, it achieves the effect of increasing the dye uptake rate of disperse dyes, avoiding thermal elasticity loss of elastic fibers, and improving the final color fastness of fabrics under conditions lower than conventional dyeing temperatures.

[0011] Preferably, the added anhydrous sodium sulfate, sodium diisobutyl sulfosuccinate, fatty alcohol polyoxyethylene ether, propylene carbonate, and glucono-δ-lactone comprise the following components in parts by weight: 5.0 to 10.0 parts of anhydrous sodium sulfate; 1.0 to 2.0 parts of sodium diisobutyl sulfosuccinate; 1.0 to 2.0 parts of fatty alcohol polyoxyethylene ether; 2.0 to 4.0 parts of propylene carbonate; and 1.0 to 2.5 parts of glucono-δ-lactone. Based on the mass of the polyester and polyurethane interwoven elastic fabric, the amount of glucono-δ-lactone added per 100g of the polyester and polyurethane interwoven elastic fabric is 1.0 to 2.0g, and the amounts of other components are calculated accordingly based on the aforementioned parts by weight ratios.

[0012] By employing the above technical solution, the solute balance system of each auxiliary agent in the dye bath liquid phase is defined. The controlled dosage of propylene carbonate ensures that the polyester fibers reach a swollen state, avoiding excessive dissolution; the quantitative dosage of gluconate-δ-lactone is related to fabric quality, ensuring that the total amount of acid produced by hydrolysis matches the buffering capacity of the dye bath itself. This maintains the stability of the dye bath system and also prevents excessive auxiliary agents from causing an increase in the chemical oxygen demand (COD) load of the wastewater.

[0013] Preferably, the first temperature is 40 to 50°C, and the cycle time at the first temperature is 5 to 10 minutes. The first heating rate is 1.0 to 1.5°C / min, the second temperature is 58 to 62°C, and the cycle time after adding propylene carbonate is 3 to 5 minutes. Subsequently, after adding the gluconate-δ-lactone and Disperse Red 60, the cycle time at the second temperature is 15 to 25 minutes. The second heating rate is 1.0 to 1.5°C / min, the maximum staining temperature is controlled within the range of 92 to 98°C, and the cycle time at the maximum staining temperature is 40 to 60 minutes.

[0014] By adopting the above technical solution, step-by-step temperature control and heating rate ensure a smooth transition of the physicochemical state of the dye bath during the dyeing process. The heating rate is controlled at 1.0 to 1.5℃ / min, allowing time for the swelling agent to penetrate into the fiber, preventing uneven coloring caused by excessively high local concentrations. The maximum dyeing temperature is controlled within the range of 92 to 98℃, which is above the critical point of the diffusion activation energy of Disperse Red 60 and below the temperature threshold for chain scission of polyurethane macromolecules, achieving compatibility between dyeing fixation and elasticity retention processes.

[0015] Preferably, the third temperature is 75 to 85°C. The amount of the detergent, fatty alcohol polyoxyethylene ether, added is 1.0 to 2.0 g per 1 L of cold water; the hot water washing time at the third temperature is 15 to 20 minutes. When initially injecting room temperature water and re-injecting cold water, 0.8 to 1.2 L of room temperature water and cold water are injected for every 100 g of the polyester and polyurethane interwoven elastic fabric, respectively.

[0016] By adopting the above technical solution, a third temperature of 75 to 85°C is set in conjunction with a specific amount of nonionic surfactant for hot water washing, achieving the desired stain removal range and removing oligomers and floating dyes, thereby improving the fabric's resistance to rubbing and soaping color fastness. By limiting the water volume in a small bath ratio, the dye distribution coefficient between the aqueous and fiber phases is increased, improving dye utilization while reducing overall heating energy consumption.

[0017] This invention provides a method for preparing a high-color-fastness, low-temperature, energy-saving dyed elastic fabric. It has the following beneficial effects: 1. This invention introduces propylene carbonate during the first heating stage, promoting its penetration into the amorphous regions of the polyester fiber. This lowers the fiber's glass transition temperature and increases its internal free volume, providing a channel for dye molecules to diffuse at lower temperatures. This allows the maximum dyeing process temperature to be controlled below conventional high temperatures, ensuring the disperse dye uptake rate while preventing the thermal depolymerization of polyurethane segments caused by high-temperature dyeing, thus maintaining the elasticity of the interwoven elastic fabric.

[0018] 2. This invention introduces gluconic acid-δ-lactone into the dye bath, utilizing its characteristic of undergoing a hydrolytic ring-opening reaction upon heating to steadily release gluconic acid. This slow-release acid production process stabilizes the initial pH of the dye bath within the neutral to slightly alkaline range and gradually transitions to a slightly acidic state, avoiding the excessively rapid decrease in dye bath acidity caused by conventional direct acid addition. It prevents the aggregation and precipitation of disperse dyes in the liquid phase, maintains the monomolecular dispersion of the dye, and reduces the risk of color variations in fabrics during the dyeing process.

[0019] 3. In this invention, after dyeing, the solution is cooled to a specific temperature for draining, and then re-injected with fatty alcohol polyoxyethylene ether for hot water washing. This temperature range falls precisely within the staining point range of the nonionic surfactant used. Its emulsifying and solubilizing properties remove unfixed dye and oligomers adhering to the fiber surface into the aqueous phase, improving the fabric's resistance to rubbing and soaping colorfastness. Simultaneously, the use of a small liquor ratio during washing reduces process water consumption and lowers energy consumption during the heating process. Attached Figure Description

[0020] Figure 1 This is a comparison of the transmittance curves of the two aqueous solution systems of the present invention as a function of temperature. Figure 2 This is a comparison of the dynamic curves of pH value of the dye bath changing with time and temperature under two different acidification processes of the present invention. Figure 3 This is a comparison of the curves showing the change of residual propylene carbonate in the fabric with washing time under two different post-treatment washing processes of the present invention. Figure 4 Line graphs showing the spatial distribution of apparent color gain in fabrics using different dyeing systems of the present invention; Figure 5 The graph shows the change in elastic recovery rate of elastic fabrics under reciprocating stretching before and after different dyeing processes according to the present invention. Figure 6 This is a line graph showing the decay of apparent color retention rate of fabrics with different dyeing and post-treatment processes under continuous multiple washing cycles according to the present invention. Detailed Implementation

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Preparation Examples 1-3: Preparation Example 1: This preparation example provides a material combination for high color fastness, low temperature, and energy-saving dyeing, with each component weighed according to the following mass for later use: 7.5g anhydrous sodium sulfate, 1.5g sodium diisobutyl sulfosuccinate, 1.5g fatty alcohol polyoxyethylene ether, 3.0g propylene carbonate and 1.5g gluconate-δ-lactone.

[0023] Preparation Example 2: This preparation example provides a material combination for high color fastness, low temperature, and energy-saving dyeing, with each component weighed according to the following mass for later use: 5.0g anhydrous sodium sulfate, 1.0g sodium diisobutyl sulfosuccinate, 1.0g fatty alcohol polyoxyethylene ether, 2.0g propylene carbonate and 1.0g glucono-δ-lactone.

[0024] Preparation Example 3: This preparation example provides a material combination for high color fastness, low temperature, and energy-saving dyeing, with each component weighed according to the following mass for later use: 10.0g anhydrous sodium sulfate, 2.0g sodium diisobutyl sulfosuccinate, 2.0g fatty alcohol polyoxyethylene ether, 4.0g propylene carbonate and 2.5g glucono-δ-lactone.

[0025] Examples 1-4: Example 1: This embodiment provides a method for preparing a high color fastness, low temperature, energy-saving dyed elastic fabric, including the following steps: 100g of polyester / polyurethane interwoven elastic fabric was added to the dyeing machine, along with 1L of room temperature water. The circulation pump was turned on, and the dye bath temperature was adjusted to 45℃. Anhydrous sodium sulfate, sodium diisobutyl sulfosuccinate, and fatty alcohol polyoxyethylene ether from Preparation Example 1 were added, and the mixture was circulated at 45℃ for 5 minutes. The dye bath temperature was increased to 60℃ at a rate of 1.2℃ / min, and propylene carbonate from Preparation Example 1 was added. The mixture was circulated for 3 minutes, followed by the addition of gluconate-δ-lactone from Preparation Example 1 and 2.0g of Disperse Red 60. The initial pH of the dye bath was checked and found to be between 7.0 and 7.5. The mixture was circulated at 60℃ for 20 minutes. The dye bath temperature was increased from 60℃ to 95℃ at a rate of 1.2℃ / min, and the mixture was circulated at 95℃ for 50 minutes. The temperature was then lowered to 80℃, and the dye bath was drained. Refill with 1L of cold water and heat to 80℃. Add 1.5g of detergent fatty alcohol polyoxyethylene ether and circulate at 80℃ for 15 minutes for hot water washing. After draining, rinse with cold water and remove from the tank. Dehydrate and set to obtain dyed elastic fabric.

[0026] Example 2: This embodiment provides a method for preparing a high color fastness, low temperature, energy-saving dyed elastic fabric, including the following steps: 83.3g of polyester and polyurethane interwoven elastic fabric was added to the dyeing machine, along with 1L of room temperature water. The circulation pump was turned on, and the dye bath temperature was adjusted to 40℃. Anhydrous sodium sulfate, sodium diisobutyl sulfosuccinate, and fatty alcohol polyoxyethylene ether from Preparation Example 2 were added, and the mixture was circulated at 40℃ for 10 minutes. The dye bath temperature was increased to 58℃ at a rate of 1.5℃ / min, and propylene carbonate from Preparation Example 2 was added. The mixture was circulated for 5 minutes, followed by the addition of gluconate-δ-lactone from Preparation Example 2 and 0.5g of Disperse Red 60. The initial pH of the dye bath was checked and found to be between 7.0 and 7.5. The mixture was circulated at 58℃ for 15 minutes. The dye bath temperature was increased from 58℃ to 92℃ at a rate of 1.5℃ / min, and the mixture was circulated at 92℃ for 40 minutes. The temperature was then lowered to 75℃, and the dye bath was drained. Refill with 1L of cold water and heat to 75℃. Add 1.0g of detergent fatty alcohol polyoxyethylene ether and circulate at 75℃ for 20 minutes for hot water washing. After draining, rinse with cold water and remove from the tank. Dehydrate and set to obtain dyed elastic fabric.

[0027] Example 3: This embodiment provides a method for preparing a high color fastness, low temperature, energy-saving dyed elastic fabric, including the following steps: 125g of polyester and polyurethane interwoven elastic fabric was added to the dyeing machine, along with 1L of room temperature water. The circulation pump was turned on, and the dye bath temperature was adjusted to 50°C. Anhydrous sodium sulfate, sodium diisobutyl sulfosuccinate, and fatty alcohol polyoxyethylene ether from Preparation Example 3 were added, and the mixture was circulated at 50°C for 5 minutes. The dye bath temperature was increased to 62°C at a rate of 1.0°C / min, and propylene carbonate from Preparation Example 3 was added. The mixture was circulated for 3 minutes, followed by the addition of gluconate-δ-lactone from Preparation Example 3 and 5.0g of Disperse Red 60. The initial pH of the dye bath was checked and found to be between 7.0 and 7.5. The mixture was circulated at 62°C for 25 minutes. The dye bath temperature was increased from 62°C to 98°C at a rate of 1.0°C / min, and the mixture was circulated at 98°C for 60 minutes. The temperature was then lowered to 85°C, and the dye bath was drained. Refill with 1L of cold water and heat to 85℃. Add 2.0g of detergent fatty alcohol polyoxyethylene ether and circulate at 85℃ for 15 minutes for hot water washing. After draining, rinse with cold water and remove from the tank. Dehydrate and set to obtain dyed elastic fabric.

[0028] Example 4: This embodiment provides a method for preparing a high color fastness, low temperature, energy-saving dyed elastic fabric, including the following steps: 100g of polyester / polyurethane interwoven elastic fabric was added to the dyeing machine, along with 1L of room temperature water. The circulation pump was turned on, and the dye bath temperature was adjusted to 45℃. Anhydrous sodium sulfate, sodium diisobutyl sulfosuccinate, and fatty alcohol polyoxyethylene ether from Preparation Example 1 were added, and the mixture was circulated at 45℃ for 5 minutes. The dye bath temperature was increased to 60℃ at a rate of 1.2℃ / min, and propylene carbonate from Preparation Example 1 was added. The mixture was circulated for 3 minutes, followed by the addition of gluconate-δ-lactone from Preparation Example 1 and 1.0g of Disperse Red 60. The initial pH of the dye bath was checked and found to be between 7.0 and 7.5. The mixture was circulated at 60℃ for 20 minutes. The dye bath temperature was increased from 60℃ to 95℃ at a rate of 1.2℃ / min, and the mixture was circulated at 95℃ for 45 minutes. The temperature was then lowered to 80℃, and the dye bath was drained. Refill with 1L of cold water and heat to 80℃. Add 1.5g of detergent fatty alcohol polyoxyethylene ether and circulate at 80℃ for 15 minutes for hot water washing. After draining, rinse with cold water and remove from the tank. Dehydrate and set to obtain dyed elastic fabric.

[0029] Comparative Examples 1-5: Comparative Example 1: Compared with Example 1, the difference is that the traditional homogeneous high temperature and high pressure dyeing method is used. The anhydrous sodium sulfate, sodium diisobutyl sulfosuccinate, fatty alcohol polyoxyethylene ether, propylene carbonate and gluconate-δ-lactone in Example 1 are not added. Instead, glacial acetic acid is directly added to adjust the pH value to 4.5 and the maximum dyeing temperature is increased to 130°C for heat preservation. All other aspects are the same.

[0030] Comparative Example 2: Compared with Example 1, the difference is that the anhydrous sodium sulfate, fatty alcohol polyoxyethylene ether and gluconate-δ-lactone in Preparation Example 1 were not added, propylene carbonate was replaced with an equal amount of the traditional carrier methyl salicylate, and glacial acetic acid was added directly to adjust the pH to 4.5 before the start of the 60°C isothermal stage. All other aspects are the same.

[0031] Comparative Example 3: The difference between Example 1 and Example 2 is that anhydrous sodium sulfate was not added in Example 1, but all other aspects are the same.

[0032] Comparative Example 4: Compared with Example 1, the difference is that no gluconate-δ-lactone was added in Preparation Example 1, while in Example 1, glacial acetic acid was added directly before the 60°C isothermal cycling to instantly adjust the pH of the dye bath to 4.5. All other aspects are the same.

[0033] Comparative Example 5: Compared with Example 1, the difference is that after the post-treatment stage is cooled to 80°C, the steps of draining the dye liquor and re-injecting cold water are omitted. Instead, the detergent fatty alcohol polyoxyethylene ether is directly added to the original dye liquor for washing. All other steps are the same.

[0034] Test Examples 1-6: Test Example 1: Two test solutions were prepared for comparison. The first solution simulated the pure additive system by measuring a certain amount of room temperature water, adding only 1.5 g / L of fatty alcohol polyoxyethylene ether, and stirring until completely dissolved. The second solution simulated the salting-out system of this invention by adding an additional 7.5 g / L of anhydrous sodium sulfate to an aqueous solution containing 1.5 g / L of fatty alcohol polyoxyethylene ether and stirring until dissolved.

[0035] Start the UV-Vis spectrophotometer with a programmed temperature rise module to preheat the instrument, and set the measurement wavelength to 500 nm. Take appropriate amounts of the two prepared solutions and inject them into two quartz cuvettes respectively, and place them in the sample cell.

[0036] The instrument's temperature control program was set with an initial temperature of 40℃, and the temperature was linearly increased to 70℃ at a rate of 1℃ / min. During the heating process, the instrument automatically collected and recorded the transmittance values ​​of the sample at each specific temperature node, and the temperature at which microphase separation of the system occurred was defined by the point of sudden drop in transmittance.

[0037] Table 1. Test data on the transmittance of pure fatty alcohol polyoxyethylene ether aqueous solution and sodium sulfate-containing aqueous solution as a function of temperature. Figure 1 The horizontal axis represents temperature, and the vertical axis represents light transmittance. In the figure, the solid lines marked with hollow circles represent pure fatty alcohol polyoxyethylene ether aqueous solutions without the addition of anhydrous sodium sulfate; this system corresponds to the test object in Comparative Example 3 of this scheme. The dashed lines marked with solid squares represent fatty alcohol polyoxyethylene ether aqueous solutions with the addition of anhydrous sodium sulfate; this system corresponds to the test object in Example 1 of this scheme.

[0038] Summary: Based on Table 1 and Figure 1 According to the data, the transmittance of the pure additive system remained above 96% before heating to 60℃, indicating that the polyoxyethylene segments formed a hydrated layer in water, and the solution remained homogeneous. Above 62℃, the transmittance decreased rapidly. The salting-out system containing anhydrous sodium sulfate began to show a decrease in transmittance in the 54℃ to 56℃ range, and the sample became turbid. This is because the Hofmeister effect generated by sulfate ions disrupted the hydrated layer around the polyoxyethylene chains, leading to a decrease in the hydrophilicity of the surfactant and precipitation. The addition of anhydrous sodium sulfate lowered the cloud point to below 60℃. This allowed the system to form condensed droplets during the 60℃ isothermal stage, aiding in the enrichment of the polar swelling agent.

[0039] Test Example 2: Two sets of simulated dye baths were prepared for dynamic pH monitoring. The first set simulated a conventional acidification process, adding anhydrous sodium sulfate, sodium diisobutyl sulfosuccinate, fatty alcohol polyoxyethylene ether, and Disperse Red 60 dye in the amounts specified in Example 1 to 1 liter of room temperature water, without adding gluconate-δ-lactone. The second set simulated the process of this invention, with the exact same formulation as the first set, but with the addition of 1.5 grams of gluconate-δ-lactone. No fabric was added to either set of dye baths to eliminate the slight buffering interference of the fibers on the pH value.

[0040] Two sets of simulated dye baths were placed in jacketed reactors equipped with a programmed temperature control module, and high-temperature resistant industrial-grade online pH electrodes were inserted into the reactors. The stirring device was turned on, and the reactor temperature was raised to 60°C.

[0041] The start of the 60℃ incubation period was recorded as min 0. At this moment, glacial acetic acid was added to the first set of dye baths to adjust the pH value to approximately 4.5. Both sets of dye baths were kept at 60℃ for 20 minutes, and then heated at a rate of 1.2℃ / min until the temperature reached 95℃ after 50 minutes. During this period, the actual temperature and real-time pH value of the dye baths were recorded every 5 minutes using a data acquisition terminal.

[0042] Table 2. Test data on the dynamic changes of pH value during the programmed temperature rise process for the instantaneous acid addition system and the in-situ acid release system. Figure 2 The horizontal axis represents the running time, and the vertical axis represents the measured pH value of the dye bath. The dotted lines marked with hollow diamonds represent the instantaneous acid addition system where glacial acetic acid is added directly in the initial stage; this system corresponds to the test object in Comparative Example 4 of this scheme. The dashed lines marked with solid triangles represent the in-situ acid release system where gluconate-δ-lactone is added; this system corresponds to the test object in Example 1 of this scheme. The vertical dashed line in the figure (located at 20 min on the horizontal axis) marks the time division between the isothermal stage and the heating stage.

[0043] Summary: From Table 2 and Figure 2It is known that the pH value of the instantaneous acidification system drops directly to around 4.5 at 0 min. This abrupt acidification disrupts the electrostatic double layer surrounding the dye particles. At 60℃, the dye's diffusion ability is weak, and the weakened electrostatic repulsion leads to dye particle aggregation and precipitation, easily producing color spots and tar-like substances. In the example system, the pH value gradually decreases within the first 20 min of constant temperature at 60℃, maintaining a near-neutral state. This ensures the dispersion stability of the dye at low temperatures and prevents dye precipitation. After 20 min, as the dye bath temperature increases, lactone hydrolysis accelerates, and the pH value decreases smoothly. This continuous acid release mechanism gradually transforms the dye bath into a weakly acidic state. Combined with the expansion of the free volume of polyester fibers, this allows for slow dye uptake, reducing the risk of uneven coloring and improving the level dyeing effect.

[0044] Test Example 3: Example 1 and Comparative Example 5, where the dyeing process was completed and the dye bath temperature had dropped to 80°C, were selected as test subjects. The core difference between the two is that in Example 1, the old solution was drained and 1 liter of cold water was added to reheat the solution to 80°C for washing, while in Comparative Example 5, no draining was performed and detergent was added directly to the original brine dye bath for washing.

[0045] The washing process at 80℃ officially begins at 0 min. Subsequently, at 5 min, 10 min, 15 min, and 20 min, small samples of elastic fabric are quickly cut from both dyeing machines. The removed fabric samples are immediately immersed in an ice-water bath to completely block the diffusion and transfer of internal chemical substances, and then placed in a vacuum freeze dryer to freeze dry to constant weight.

[0046] Accurately weigh 2.00 g of freeze-dried fabric samples at each time point and place them in the extraction tube of a Soxhlet extractor. Use chromatographically pure acetone as the extraction solvent and continuously reflux for 4 hours on a heating mantle to fully extract the propylene carbonate remaining inside the fiber into the flask.

[0047] The extract was concentrated to a specific volume using a rotary evaporator, and the content of propylene carbonate in the extract was quantitatively determined by internal standard method using a gas chromatograph equipped with a flame ionization detector (FID). The number of milligrams of residual propylene carbonate per 100 grams of fabric was then calculated.

[0048] Table 3. Test data on the change of residual propylene carbonate in fabrics with washing time in the alternating bath water injection system and the original bath direct washing system. Figure 3The horizontal axis represents washing time, and the vertical axis represents residual propylene carbonate. Solid lines marked with hollow hexagonal stars represent the bath-changing and refilling water system where the dye liquor is drained and refilled with cold water; this system corresponds to the test subject in Example 1 of this scheme. Dashed lines marked with solid pentagrams represent the original bath washing system where the dye liquor is not drained and the washing is done directly in the old liquor; this system corresponds to the test subject in Comparative Example 5 of this scheme.

[0049] Summary: From Table 3 and Figure 3 The changes in residual washing concentration indicate that the dye bath environment affects the removal efficiency of polar small molecules. At 0 min, the propylene carbonate content in the fabrics from both processes exceeded 310 mg / 100g, indicating that the solvent had penetrated into the fiber interior during the dyeing stage. The residual concentration in the original bath washing system decreased less within 20 min, ultimately still reaching 235.4 mg / 100g of propylene carbonate. Due to the incomplete drainage of the waste liquid, the salting-out effect persisted, and the phase transition temperature of fatty alcohol polyoxyethylene ether was below 80℃, making it difficult for the condensed phase on the fiber surface to disintegrate, thus hindering the washing out of propylene carbonate.

[0050] The residual solvent in the fabric during the wash cycle rapidly decreased within the first 5 minutes, reaching extremely low levels after 15 minutes. The cloud point of the fatty alcohol polyoxyethylene ether rose again and exceeded the washing temperature, causing the condensed phase on the fiber surface to redissolve in the water. Acrylic carbonate subsequently dissolved into the washing liquid. As the solvent was extracted, the free volume within the fibers decreased, pores closed, and the dye was fixed inside the fibers. This reduced surface floating dye and improved the fabric's colorfastness to washing. Test Example 4: Fabric samples after dyeing and drying in Examples 1, 1, 3, and 4 were collected as test subjects. Example 1 represents the comprehensive system of this invention, Comparative Example 1 represents the traditional 130℃ high-temperature and high-pressure system, Comparative Example 3 represents a system lacking a salting-out coagulation mechanism, and Comparative Example 4 represents an instantaneous acid-addition system lacking a smooth acid release mechanism.

[0051] Each fabric sample was folded flat to an opaque thickness, and five spatially evenly distributed test points were randomly selected on the fabric surface. The reflectance at the maximum absorption wavelength was measured at each point, and the result was automatically converted into apparent color gain (K / S value) by the instrument's built-in software according to the Kubelka-Munk equation.

[0052] The colorimetric coordinates of five test points of the same sample were extracted, and the absolute value of the maximum color difference between them was calculated. This was used as a quantitative basis for evaluating the uniformity and color variation of the fabric surface.

[0053] Table 4. Apparent color gain (K / S value) and maximum color difference test data of fabrics at various test points under different dyeing systems Figure 4The horizontal axis represents the randomly selected test point number on the fabric surface, and the vertical axis represents the K / S value measured at that point. In the figure, solid lines marked with a solid lower triangle represent Example 1, dashed lines marked with an asterisk represent Comparative Example 1, dotted lines marked with a cross represent Comparative Example 3, and dotted lines marked with a plus sign represent Comparative Example 4. The absolute height of each line reflects the dyeing depth of the fabric, while the degree of curvature and undulation of the lines visually represents the uniformity of color in different areas of the fabric surface.

[0054] Summary: From Table 4 and Figure 4 It is evident that different processes result in varying dyeing effects on polyester fibers. Comparative Example 3 exhibits a lower dye yield, with a K / S value around 8, leading to a lighter fabric color. This is due to the lack of inorganic salts, which prevents the fatty alcohol polyoxyethylene ether from undergoing phase separation. The propylene carbonate, dispersed in water, cannot aggregate and swell on the fiber surface, hindering dye penetration into the fiber.

[0055] The color yield of Comparative Example 4, which involved instantaneous acid addition, fluctuated significantly, with a maximum color difference of 5.46, and spots of varying shades appeared on the fabric surface. Glacial acetic acid caused fluctuations in the pH of the dye bath, weakening the electrostatic repulsion of dye particles and causing them to aggregate and deposit on the fabric surface, resulting in color spots and tar stains. In Example 1, gluconate-δ-lactone slowly released acid, which, combined with coagulation, allowed for stable dye penetration. Its K / S value remained above 18.4, the curve was stable, and the leveling properties were good. Its actual color depth was slightly higher than that of Comparative Example 1, which was dyed at 130℃. This indicates that this method overcame the difficulties of low-temperature dyeing, controlled the reaction process, and achieved the effect of conventional high-temperature dyeing using a 95℃ process.

[0056] Test Example 5: A representative spandex / polyester interwoven elastic fabric was selected as the object for mechanical performance evaluation. The experimental groups were divided into three groups: blank raw fabric without any dyeing or heat treatment, fabric of Example 1 dyed using the 95℃ process of this invention, and fabric of Comparative Example 1 dyed using the conventional 130℃ high temperature and high pressure process.

[0057] In a standard test environment with constant temperature and humidity (temperature 20℃, relative humidity 65%), the above three materials were cut into rectangular test strips with a width of 50 mm and a length of 200 mm along the weft direction containing spandex filaments. Five parallel samples were prepared for each group to ensure the validity of the data.

[0058] The prepared specimen is clamped at both ends in the upper and lower clamps of the universal tensile testing machine. The effective spacing length is set to 100 mm, and the running speed of the crosshead for tension and rebound is uniformly set to 300 mm / min.

[0059] The program is initiated to perform a constant elongation reciprocating cycle test. The testing machine stretches the specimen to a specified elongation of 30% and then quickly returns it to the initial position. The instrument automatically records the residual deformation of the specimen after unloading, and then continues to execute until five complete tensile-springback cycles are completed. The accompanying software calculates and outputs the dynamic elastic recovery rate for each cycle based on the difference in effective length before and after each cycle.

[0060] Table 5. Test data of elastic recovery rate of elastic fabrics under different dyeing heat histories and constant elongation cycles Figure 5 The horizontal axis represents the number of cycles of constant elongation stretching, and the vertical axis represents the elastic recovery rate of the fabric in the corresponding cycle. In the figure, the solid lines marked with a solid right triangle represent the blank raw fabric without any treatment, the dashed lines marked with a hollow left triangle represent the test objects of Example 1 dyed using the 95℃ process of this invention, and the dotted lines marked with a solid square represent the test objects of Comparative Example 1 dyed using the conventional 130℃ process.

[0061] Summary: Table 5 shows the impact of different processing temperatures on the elastic structure of spandex. After five cycles of 30% constant elongation, the elastic recovery rate of the blank fabric remained above 90%. Comparative Example 1, processed at 130℃, showed a decline in mechanical properties; the recovery rate dropped to 83.54% after the first stretch and subsequently fell below 70%. This is because prolonged high temperatures damage the internal structure of spandex, making the fabric prone to loosening and deformation during use.

[0062] The elastic recovery rate of Example 1 is similar to that of the blank fabric, with minimal deformation after repeated stretching. This is attributed to the mechanism of this method. Anhydrous sodium sulfate promotes the enrichment and swelling of propylene carbonate on the fiber surface, opening up the free volume of the polyester at 95°C, allowing the dye to penetrate. Because the dyeing temperature is controlled below the damage temperature of spandex, this process avoids high-temperature damage to the elastic yarn, maintaining the fabric's elasticity and shape retention while ensuring dyeing depth.

[0063] Test Example 6: Fabrics from Example 1, Comparative Example 1, and Comparative Example 5, after being dyed and dried, were selected as test subjects for the durability of color fastness to washing. In this evaluation, Example 1 represents the complete system of the present invention that underwent a water-filled phase change washing process, Comparative Example 1 represents a conventional 130°C high-temperature and high-pressure dyeing system, and Comparative Example 5 represents a system that, although dyed at a low temperature of 95°C, did not drain the old liquor during the post-treatment stage and was directly washed.

[0064] Each obtained tissue sample was cut into a standard specimen measuring 40 mm by 100 mm, and then sewn together with a DW-type multifiber lining fabric of the same size along the short side to prepare a combined specimen for water washing test.

[0065] Prepare a washing solution conforming to ISO 105-C06 standard, containing 4 grams of ECE standard detergent and 1 gram of anhydrous sodium carbonate per liter. Place the sewn composite sample along with 10 stainless steel beads into the stainless steel washing tank of the wash fastness tester, pour in the standard washing solution preheated to 60°C, and set the liquor ratio to 1:50.

[0066] The testing machine was started for continuous mechanical stirring and heating washing, with a single washing cycle set to 30 minutes. After the 5th, 10th, 15th, and 20th washing cycles, portions of the samples were removed, thoroughly rinsed with cold water, and hung to air dry. The apparent color gain (K / S value) of each sample before and after washing was measured using a spectrophotometer. By calculating the ratio of the K / S value after washing to that before washing, the apparent color retention rate under different washing cycles was obtained.

[0067] Table 6. Test data on apparent color retention of fabrics of different systems under continuous multiple washing cycles. Figure 6 The horizontal axis represents the number of washing cycles, and the vertical axis represents the apparent color retention rate of the fabric (%). In the figure, the dotted lines marked with hollow circles represent the test subjects of Comparative Example 1 (i.e., the 130℃ high-temperature system in the illustration) which uses traditional 130℃ high-temperature and high-pressure dyeing; the solid lines marked with solid circles represent the test subjects of Example 1 (i.e., the phase change washing system in the illustration) which uses the present invention for 95℃ dyeing supplemented with bath-changing water injection phase change washing; and the dotted lines marked with crosses represent the test subjects of Comparative Example 5 (i.e., the original bath washing system in the illustration) which is dyed at 95℃ but does not undergo phase change washing.

[0068] Summary: Table 6 and Figure 6 The data reflects the impact of different treatment processes on the wash resistance of the fabric. Comparative Example 5, which did not use water-changing washing, saw its color retention rate drop to 85.7% after 5 washes and to 57.1% after 20 washes, with the washing liquid becoming cloudy. This fading is due to residual propylene carbonate lowering the glass transition temperature of the fibers. During washing at 60°C, the fiber pores easily open, allowing internal dyes to leach into the water under the action of the detergent.

[0069] After 20 rounds of washing, Example 1 maintained a color retention rate of 91.5%, close to that of Comparative Example 1 (93.4%) dyed at 130°C. This verifies the effectiveness of the water-changing washing process. Replacing the dye with cold water lowers the salt concentration, raises the cloud point of the fatty alcohol polyoxyethylene ether, and causes propylene carbonate to dissolve into the water. As the solvent is washed away, the fiber pores close, fixing the dye that entered the fiber at 95°C, cutting off the dye migration path, and improving color fastness.

Claims

1. A method for preparing a high-colorfastness, low-temperature energy-saving dyed elastic fabric, characterized in that, Includes the following steps: Add the polyester and polyurethane interwoven elastic fabric into the dyeing machine, inject room temperature water, turn on the circulation pump, and adjust the dye liquor temperature to the first temperature. Anhydrous sodium sulfate, sodium diisobutyl sulfosuccinate and fatty alcohol polyoxyethylene ether are added to the dyeing machine, and the machine is kept at the first temperature and circulated. The dye bath temperature is increased to the second temperature according to the first heating rate, and propylene carbonate is added to the dyeing machine for circulation; Then gluconate-δ-lactone and Disperse Red 60 were added, and the initial pH of the staining bath was controlled between 7.0 and 7.

5. The solution was then circulated at a constant temperature in the second temperature range. The dye bath temperature is increased from the second temperature to the highest dyeing temperature according to the second heating rate, and the temperature is maintained and circulated at the highest dyeing temperature. Cool to the third temperature and drain the dye solution. Refill with cold water and heat to the third temperature, add detergent fatty alcohol polyoxyethylene ether, and circulate at the third temperature for hot water washing; After draining, the fabric is rinsed with cold water, dehydrated, and shaped to obtain dyed elastic fabric.

2. The method for preparing high color fastness, low-temperature energy-saving dyed elastic fabric according to claim 1, characterized in that, The mass ratio of anhydrous sodium sulfate, sodium diisobutyl sulfosuccinate, fatty alcohol polyoxyethylene ether, propylene carbonate, and glucono-δ-lactone added is as follows: (5.0～10.0):(1.0～2.0):(1.0～2.0):(2.0～4.0):(1.0～2.5)。 3. The method for preparing high color fastness, low-temperature energy-saving dyed elastic fabric according to claim 2, characterized in that, Based on 100g of the polyester and polyurethane interwoven elastic fabric, the amounts of each component added are as follows: Anhydrous sodium sulfate: 5.0–10.0 g; Sodium diisobutyl sulfosuccinate: 1.0–2.0 g; Fatty alcohol polyoxyethylene ether: 1.0~2.0g; Propylene carbonate: 2.0–4.0 g; Glucono-δ-lactone: 1.0~2.0g.

4. The method for preparing high color fastness, low temperature, energy-saving dyed elastic fabric according to claim 1, characterized in that, The first temperature is 40-50℃, and the cycle time is maintained at the first temperature for 5-10 minutes.

5. The method for preparing high color fastness, low temperature, energy-saving dyed elastic fabric according to claim 1, characterized in that, The first heating rate is 1.0–1.5 °C / min, the second temperature is 58–62 °C, and the circulation time after adding propylene carbonate is 3–5 min.

6. The method for preparing high color fastness, low temperature, energy-saving dyed elastic fabric according to claim 1, characterized in that, Subsequently, after adding the gluconate-δ-lactone and Disperse Red 60, the initial pH of the staining bath was controlled between 7.0 and 7.5, and the constant temperature cycling time at the second temperature was 15 to 25 minutes.

7. The method for preparing high color fastness, low temperature, energy-saving dyed elastic fabric according to claim 1, characterized in that, The second heating rate is 1.0 to 1.5 °C / min, the maximum staining temperature is controlled within the range of 92 to 98 °C, and the holding time at the maximum staining temperature is 40 to 60 min.

8. The method for preparing high color fastness, low temperature, energy-saving dyed elastic fabric according to claim 1, characterized in that, The third temperature is 75–85°C.

9. The method for preparing high color fastness, low temperature, energy-saving dyed elastic fabric according to claim 1, characterized in that, The dosage of the detergent fatty alcohol polyoxyethylene ether is 1.0-2.0g per 1L of cold water; The hot water washing cycle is performed at the third temperature for 15 to 20 minutes.

10. The method for preparing high color fastness, low temperature, energy-saving dyed elastic fabric according to claim 1, characterized in that, When initially injecting room temperature water and re-injecting cold water, each 100g of the polyester and polyurethane interwoven elastic fabric is injected with 0.8 to 1.2L of room temperature water and cold water, respectively.

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