Process for dyeing polyester and its blended fabric after acid reduction cleaning

Abstract

This invention relates to the field of textile dyeing and finishing technology, and discloses an acidic reduction cleaning process for polyester and its blended fabrics after dyeing. In this acidic reduction cleaning process, after disperse dyeing, the residual dyeing liquor is retained without drainage. Acetic acid is directly added to adjust the pH of the system to 4.0-6.0, followed by the addition of an acidic reduction cleaning agent. The process is then carried out in situ reduction cleaning at 80-95℃ for 20-30 minutes. Subsequently, the process is completed with sodium carbonate neutralization soaping and two water rinses. Compared to traditional alkaline reduction cleaning, this invention avoids yellowing caused by a high-temperature alkaline environment, significantly improving color fastness and appearance stability. Simultaneously, it eliminates the need for initial water change, reducing the post-dyeing cleaning from 6 tanks to 4 tanks, saving 4481L of water and 50 minutes per batch, and significantly reducing the total nitrogen content of wastewater (≤5mg / L), achieving a synergistic optimization of high efficiency, energy saving, and environmental protection.

Description

Technical Field

[0001] This invention belongs to the field of textile dyeing and finishing technology, specifically relating to an acid reduction cleaning process for dyed polyester and its blended fabrics. Background Technology

[0002] Polyester and its blended fabrics are widely used in clothing, home textiles, and other fields due to their advantages such as high strength, abrasion resistance, crispness, and easy care. Disperse dyes are commonly used for dyeing polyester. After dyeing, reduction washing is necessary to remove surface dye from the fabric to improve color fastness and ensure the stability of the product's appearance. This is a key step in the dyeing and finishing process.

[0003] However, traditional reduction cleaning processes, which use "thiourea dioxide + baking soda" as the core alkaline reduction system, can remove floating color, but they also have many technical bottlenecks that severely restrict the development of the industry. 1) Poor color stability: Under a high-temperature alkaline environment of 95℃, polyester and its blended fabrics are prone to yellowing, especially light-colored and sensitive-colored fabrics, resulting in a high rework rate. 2) Imbalance between energy consumption and efficiency: The process flow is lengthy (dyeing T → water discharge → reduction cleaning → acid treatment → soda ash treatment → washing water), requiring 6 tanks of water throughout the process. Heating, heat preservation and water replacement consume a lot of electricity and steam. The total working time for a single batch of products can reach 419 minutes. The turnover rate of dyeing tanks is low, and production efficiency is limited. 3) Significant environmental pressure: The total nitrogen content of thiourea dioxide reaches 137.2 mg / L at a concentration of 2 g / L. After a large amount of high-nitrogen wastewater enters the sewage treatment system, it significantly increases the difficulty and cost of denitrification treatment, which is contrary to the national green production policy. 4) Limited room for performance improvement: Some color fastness indicators (such as wet rubbing fastness and white impact fastness) are difficult to meet the needs of mid-to-high-end fabrics.

[0004] Therefore, developing a reduction cleaning process that can solve the problem of yellowing of light, simplify the process, reduce energy consumption, meet environmental protection requirements, and improve cleaning effect has become a technical challenge that the industry urgently needs to overcome. Summary of the Invention

[0005] The purpose of this invention is to provide an acid reduction cleaning process for dyed polyester and its blended fabrics, which solves the technical problem that traditional alkaline reduction cleaning in the prior art easily causes color shift and yellowing of polyester and its blended fabrics, affecting the consistency of the appearance of the finished product.

[0006] An acid reduction cleaning process for dyed polyester and its blended fabrics, characterized by comprising the following steps: Step (1) Dyeing: Place polyester or its blended fabric in a dyeing vat and dye it using disperse dyes according to conventional processes. The dyeing process is completed at 95°C. Step (2) In-situ acidic reduction cleaning: After dyeing, retain all dyeing residue without draining the water. Adjust the pH of the system to 4.0-6.0, and then add acidic reducing cleaning agent at a dosage of 0.5-1.5% (OWF) of the fabric weight. Heat the system to 80-95℃ and keep it at this temperature for 20-30 minutes to complete the reduction cleaning. Through the above technical solutions, step (2) eliminates the cumbersome steps of discharging dye liquor, pre-washing with water, draining the liquor again, and re-preparing the reduction bath in the traditional process.

[0007] Step (3) Post-reduction treatment and washing: Drain the acidic waste liquid after reduction cleaning; inject hot water into the dyeing vat, add sodium carbonate during the heating process, and keep the temperature at 75-85℃ for 8-12 minutes. This step is used to neutralize the residual acidity and perform preliminary soaping; after draining the alkaline treatment liquid, inject clean water into the dyeing vat and treat it at 70-80℃ for 8-12 minutes; drain the liquid again, inject cold water, and rinse at room temperature to 40℃ for 8-12 minutes to remove residual auxiliaries and make the fabric pH close to neutral. Step (4) Finishing: After washing, the fabric is subjected to routine dehydration, drying and heat setting to obtain the finished product.

[0008] Furthermore, in step (2), the pH value of the system is 4.0-5.0.

[0009] Furthermore, in step (2), the preferred system heating temperature is 95°C.

[0010] Furthermore, the acidic reducing cleaning agent is an acidic reducing cleaning agent with a total nitrogen content ≤ 5 mg / L at a concentration of 2 g / L.

[0011] Furthermore, the amount of acetic acid used is 0.25-0.5% (OWF) of the fabric weight.

[0012] Furthermore, the polyester blended fabrics include, but are not limited to, polyester-spandex, polyester-cotton, polyester-viscose and their multi-component blended fabrics.

[0013] Furthermore, in step (3), the amount of sodium carbonate used is 0.05-0.2% (OWF).

[0014] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: The acidic reduction cleaning process provided by this invention, through the innovative combination of a specialized acidic reduction cleaning agent and a one-bath process, produces the following significant beneficial effects compared to the traditional alkaline thiourea dioxide process, effectively solving a long-standing technical problem in the industry: 1. By changing the reducing cleaning environment from the traditional high-temperature, strong alkaline (pH>10) to a mild acidic (pH4-6), the hydrolysis, damage, and yellowing of polyester fibers and disperse dyes under high-temperature alkaline conditions are fundamentally avoided. This maximizes the preservation of the original color of the dyes, especially for light-colored, sensitive colors, and high-value-added fabrics, ensuring that the finished product has bright, stable, and consistent colors, and reducing the rework rate by more than 80%.

[0015] 2. This invention features a unique one-bath continuous dyeing-reduction process. After dyeing, there is no need to drain the dye bath or refill with water; the pH is adjusted and rinsing is completed directly in the original bath. This streamlines the traditional, lengthy 6-tank process to 4 tanks, reducing the total production time per batch from approximately 419 minutes to approximately 369 minutes, increasing efficiency by about 12% and significantly improving dye bath turnover and overall production capacity. Furthermore, the simplified process directly leads to a comprehensive reduction in water, electricity, and steam consumption, saving 0.074 yuan per pound of fabric. With a daily production of 50,000 pounds of fabric, this translates to annual cost savings of 1.332 million yuan, while simultaneously saving 82,800 tons of water per year, resulting in a significant improvement in economic benefits.

[0016] 3. In the process claimed by this invention, the total nitrogen content of the acidic reducing cleaning agent is extremely low (≤5 mg / L), far lower than that of traditional thiourea dioxide. This reduces the total nitrogen pollutant emissions in wastewater by more than 99% at the source, greatly alleviating the denitrification load and cost of end-of-pipe wastewater treatment, perfectly meeting the requirements of green and clean production.

[0017] 4. This invention simplifies the process while achieving a gentler and more thorough removal of surface dyes from fabrics through the synergistic effect of an optimized acidic reduction system and subsequent treatments. Fabrics treated with this invention exhibit key performance indicators such as washability, water immersion resistance, wet rubbing resistance, and white impact fastness that meet or exceed those of traditional alkaline processes, satisfying the stringent requirements of the mid-to-high-end market for the intrinsic quality of textiles. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram comparing the new acidic reduction cleaning process of this invention with the traditional alkaline reduction cleaning process. Detailed Implementation

[0020] The technical solutions of 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.

[0021] The acidic reducing cleaning agent used in this invention is HS-379B, purchased from Wuxi Kailai Biotechnology Co., Ltd., and its total nitrogen content (2g / L solution) is ≤5mg / L.

[0022] Example 1: Acidic reducing cleaning of Anta stretch jacquard double-sided fabric Anta stretch jacquard double-sided fabric is a multi-component blended elastic fabric, including the following components: Polyester composition: 50D / 12F semi-dull drawn textured yarn (DTY), S-twist direction; 100D / 72F semi-dull polyester yarn; 30D / 12F semi-dull drawn textured yarn (DTY), S-twist direction.

[0023] Cotton composition: 50S / 1 combed cotton, using the SIRO COMPACT process.

[0024] Spandex composition: 20D transparent spandex yarn, Z-twist direction.

[0025] The acid reduction cleaning process of this embodiment (cylinder number JA2509779A trial) includes the following steps: Step (1) Dyeing: Place polyester or its blended fabric in a dyeing vat and dye it using disperse dyes according to conventional processes. The dyeing process is completed at 95°C. Step (2) In-situ acidic reduction cleaning: After dyeing, retain all dyeing residue without draining. Lower the dye bath temperature to 75°C, add acetic acid (HAC), adjust the pH of the system to 4.3, and then add acidic reduction cleaning agent HS-379B at a dosage of 1% (OWF) of the fabric weight. Reheat the dye bath to 95°C and keep it at this temperature for 30 minutes to complete the reduction cleaning. Step (3) Post-reduction treatment and washing: Drain the acidic waste liquid after reduction cleaning; inject hot water into the dyeing vat, add 0.15% (OWF) sodium carbonate during the heating process, heat to 80℃ and keep warm for 10 minutes. This step is used to neutralize the residual acidity and perform preliminary soaping; after draining the alkaline treatment liquid, inject clean water into the dyeing vat and treat at 75℃ for 10 minutes; drain the liquid again, inject cold water, and rinse at room temperature for 10 minutes to remove residual auxiliaries and make the fabric pH close to neutral. Step (4) Finishing: After washing, the fabric is subjected to routine dehydration, drying and heat setting to obtain the finished product.

[0026] The Anta jacquard double-sided fabric in this embodiment has also undergone traditional cleaning processes (cylinder number JA2507462A, normal cleaning), including the following steps: After the disperse dye dyeing process ends at 95°C, the high-temperature dyeing residue is completely drained. Then, sufficient cold water is injected into the main tank for dilution and the temperature is raised to 70°C. At this temperature, sodium carbonate and thiourea dioxide are added sequentially from the auxiliary tank to prepare an alkaline reducing working solution. The system is then heated to 95°C and held for 30 minutes to complete the reduction cleaning. After cleaning, the system is cooled to 75°C and the waste liquid is drained. Cold water is then injected again, and acetic acid is added for neutralization for 10 minutes before draining again. Next, hot water is injected again, and sodium carbonate is added from the auxiliary tank for alkaline post-treatment at 80°C for 10 minutes. After treatment, the temperature is lowered to 75°C before draining. Finally, water is injected again for a final cleaning for 10 minutes before draining, completing all processes.

[0027] Example 2: Restoration and cleaning of Anta stretch jacquard rib fabric Anta stretch jacquard ribbed fabric includes the following components: Polyester composition: 75D / 36F semi-dull polyester textured yarn (DTY), processed with heavy intermingled yarn, S-twist direction; 30D / 12F semi-dull polyester textured yarn (DTY), S-twist direction.

[0028] Cotton composition: 70S / 1 combed cotton, using the SIRO COMPACT process; 40S / 1 combed cotton, using the SIRO COMPACT process.

[0029] Spandex component: 20D transparent spandex yarn.

[0030] The reduction cleaning process in this embodiment is the same as in Embodiment 1 (cylinder number JA2508831A trial).

[0031] The Anta stretch jacquard rib fabric in this embodiment was also cleaned using a traditional cleaning process (cylinder number JA2508833A, normal), the same as in Embodiment 1.

[0032] Example 3: Restoration cleaning of Jordan jacquard rib fabric Jordan jacquard rib fabric, comprising the following components: Cotton composition: 16S / 1 combed cotton yarn, using the SIRO COMPACT process.

[0033] Polyester composition: 132D / 54F fully dull wool-like polyester yarn, processed with light intermingled yarn; 75D / 24F semi-dull polyester textured yarn (DTY), S-twist direction.

[0034] The reduction cleaning process in this embodiment is the same as in Embodiment 1 (cylinder number JA2502332A trial).

[0035] The Jordan jacquard rib fabric in this embodiment was also cleaned using a traditional cleaning process (cylinder number JA2502330A, normal), the same as in embodiment 1.

[0036] The test results are shown in Tables 1 and 2: Table 1: Wash fastness under different processes

[0037] Table 2: Water fastness and rubbing fastness under different processes

[0038] Environmental benefits analysis and cost savings: (1) Comparison of energy consumption and environmental benefits (taking 988 lb fabric as an example) is shown in Table 3: Table 3

[0039] (2) Cost savings are shown in Table 4: Table 4

[0040] Note: The cost savings per pound of fabric (0.074 yuan / pound) fully cover the increase in auxiliary agent costs (0.017 yuan / pound), resulting in a net reduction in unit cost.

[0041] Based on the data comparison of Examples 1-3 (trial processes) and traditional processes in Tables 1 and 2, the polyester and its blended fabrics prepared by the acid reduction cleaning process provided by the present invention exhibit excellent comprehensive performance, specifically high color fastness, strong anti-pollution properties, and outstanding production efficiency and environmental benefits.

[0042] A comparison of Examples 1-3 with the conventional process (normal) shows that: Fabrics treated with the acidic reduction cleaning process of this invention (trial version) show superior or equivalent performance to traditional alkaline processes (normal) in several key color fastness indicators. Particularly in wet rubbing fastness and staining fastness to acetate, nylon, and other interlinings, the process of this invention generally exhibits an improvement of 0.5-1 grades (e.g., wet rubbing fastness improved from grade 2-3 to grade 3 in Example 1, and water fastness to acetate staining improved from grade 4 to grade 4-5 in Example 3). This demonstrates that the acidic reduction system used in this invention, while efficiently removing floating dye, acts more gently on fibers and dyes, avoiding the damage to the fabric's color and surface condition caused by traditional alkaline high-temperature environments, thus achieving a comprehensive improvement in color fastness.

[0043] A comparison of energy consumption and cost data in Tables 3 and 4 shows that: While ensuring or even improving product quality, the process of this invention achieves significant energy conservation, emission reduction, and economic benefits. Specifically, the total processing time is reduced by 50 minutes, 4481 liters of water are saved per batch, and the overall energy cost per pound of fabric is reduced by 0.091 yuan. Although the cost of the special auxiliary agent HS-379B increases slightly, this is completely offset by the significantly reduced water, electricity, and gas consumption, ultimately resulting in a net reduction of 0.074 yuan in the overall processing cost per pound of fabric. This demonstrates that this invention, through its innovative one-bath process, not only simplifies operation but also fundamentally reduces high-energy-consuming processes, directly translating process optimization into quantifiable economic advantages.

[0044] A comparison of the environmental issues mentioned in the background section with the characteristics of the additives in this invention (total nitrogen ≤ 5 mg / L) shows that: This invention solves the high pollution problem of traditional thiourea dioxide processes at the source. The total nitrogen in the wastewater from traditional processes is as high as 137.2 mg / L, while the total nitrogen content of the HS-379B additive used in the new process is extremely low (≤5 mg / L). Combined with the wastewater reduction brought about by process simplification, the total nitrogen load of the overall wastewater is reduced by more than 99%.

[0045] In summary, this invention, through the synergistic innovation of an acidic reduction system and a one-bath process, successfully breaks the traditional dilemma of balancing quality, efficiency, cost, and environmental protection in alkaline reduction cleaning, achieving synergistic optimization of quality improvement, efficiency enhancement, cost reduction, and emission reduction, and providing an effective technical path for the high-quality and sustainable development of the polyester dyeing and finishing industry.

[0046] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

[0047] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. An acidic reduction cleaning process for dyed polyester and its blended fabrics, characterized in that, Includes the following steps: Step (1) Dyeing: Place polyester or its blended fabric in a dyeing vat and dye it with disperse dye. The dyeing process is completed at 95°C. Step (2) In-situ acidic reduction cleaning: After dyeing, retain all the dyeing residue, do not drain the water, lower the temperature of the dye bath, add acetic acid to adjust the pH of the system to 4.0-6.0, add acidic reducing cleaning agent, then raise the temperature of the system and keep it warm to complete the reduction cleaning; Step (3) Post-treatment and washing: Drain the acidic waste liquid, inject hot water, add sodium carbonate during the heating process, heat up and keep warm; after draining, inject clean water to wash; drain again, inject cold water to rinse at room temperature to 40°C; Step (4) Finishing: Dehydrate, dry and heat set the fabric to obtain the finished product.

2. The acidic reduction cleaning process according to claim 1, characterized in that, In step (2), the dye bath temperature is reduced to 75-80℃.

3. The acidic reduction cleaning process according to claim 1, characterized in that, In step (2), the pH value of the system is adjusted to 4.0-5.

0.

4. The acidic reduction cleaning process according to claim 1, characterized in that, In step (2), the system is heated to 80-95℃.

5. The acidic reduction cleaning process according to claim 1, characterized in that, In step (2), the heat preservation time is 20-30 minutes.

6. The acidic reduction cleaning process according to claim 1, characterized in that, In step (2), the amount of acidic reducing cleaning agent used is 0.5-1.5% (OWF) of the fabric weight.

7. The acidic reduction cleaning process according to claim 1, characterized in that, In step (2), the acidic reducing cleaning agent is an acidic reducing cleaning agent with a total nitrogen content ≤5mg / L at a concentration of 2g / L.

8. The acidic reduction cleaning process according to claim 1, characterized in that, In step (2), the amount of acetic acid used is 0.25%-0.5% (OWF) of the fabric weight.

9. The acidic reduction cleaning process according to claim 1, characterized in that, The polyester or its blended fabrics include polyester-spandex fabrics, polyester-cotton fabrics, polyester-viscose fabrics, or multi-component blended fabrics.

10. The acidic reduction cleaning process according to claim 1, characterized in that, In step (3), the amount of sodium carbonate used is 0.05-0.2% (OWF); the heating and holding conditions are: heating temperature is 75-85℃, holding time is 8-12min; the water rinsing conditions are: rinsing at 70-80℃ for 8-12min; rinsing time is 8-12min.

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