High-precision control and high-fastness dyeing method for reduction dyeing of loose fiber cotton

Abstract

The invention relates to the technical field of textile dyeing processes, and discloses a loose fiber cotton reduction dyeing high-precision control and high-fastness dyeing method which comprises the following steps: S1, high-precision bath ratio control: calculating an actual bath ratio by measuring the relationship between the liquid level of a dye vat and the water volume and combining fiber volume expansion compensation; s2, dyeing uniformity is optimized, non-uniform local pressure of the fibers is reduced in a low-pressure cake making and cylinder filling mode, and the stirring frequency is adjusted in different dyeing stages through variable-frequency stirring control; s3, performing reduction dyeing and secondary reduction, namely reducing the reduced dye under an alkaline condition, slowly heating to a target temperature within a controlled temperature range so that the dye is uniformly adsorbed to the surface of the fiber, and performing secondary reduction by adopting a low-concentration reducing agent and alkali after dyeing is completed. Through a low-pressure cake making and cylinder filling mode, uniform permeation of dye liquor is achieved, local chromatic aberration is avoided, dye diffusion is matched with requirements of different stages through variable-frequency stirring control, and dyeing uniformity is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of textile dyeing technology, and in particular to a method for reducing and dyeing loose-fiber cotton with high-precision control and high-fastness. Background Art

[0002] In the textile dyeing process, uniform dye adhesion, dye fixation, and the final physical properties of the fabric are key factors in determining dyeing quality. Existing dyeing technologies utilize high-pressure drum filling, fixed-rate stirring, air oxidation fixation, and high-temperature rapid drying to improve production efficiency and ensure dyeing results. However, as the textile market's demand for high-quality dyeing continues to increase, these traditional processes are facing emerging technical bottlenecks in dyeing uniformity, dye adsorption stability, and fabric dimensional control, necessitating further optimization.

[0003] In the prior art, the high-pressure cake-filling method easily causes local compression of the fiber, which hinders the penetration of the dye solution and leads to uneven dyeing depth; the fixed-rate stirring cannot accurately match the dye diffusion requirements at different stages of dyeing, and is prone to color flowers or color differences; the air oxidation fixation is greatly affected by environmental conditions, the oxidation rate is unstable, and the fixation is uneven, resulting in decreased color fastness; although the high-temperature rapid drying and shaping method can improve production efficiency, the fabric is unevenly heated during the drying process, which can easily lead to dimensional deformation, and the hand feel becomes hard and the comfort level decreases. The above problems affect the stability of the dyeing quality and limit the scope of application of the existing process. In response to these shortcomings, the present invention proposes a more optimized dyeing process scheme, which fundamentally improves the consistency and stability of dyeing by adjusting the filling method, introducing dynamic stirring control, optimizing the fixation method, and adopting low-tension drying and shaping technology. Summary of the Invention

[0004] In response to the shortcomings of the existing technology, the present invention provides a method for high-precision control and high-fastness dyeing of loose-fiber cotton reduction dyeing. The existing technology has a single data collection method and a computing model that relies on a centralized architecture, resulting in insufficient real-time performance, weak data privacy protection capabilities, and difficulty in adapting business optimization strategies to dynamic market changes.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solutions: A method for reducing and dyeing loose fiber cotton with high precision and high fastness, comprising the following steps:

[0006] S1. High-precision bath ratio control: by measuring the relationship between the dye vat liquid level and water volume, combined with fiber volume expansion compensation, the actual bath ratio is calculated;

[0007] S2. Dyeing uniformity is optimized by adopting low-pressure cake-loading method to reduce local uneven pressure on fibers, and adjusting the stirring frequency at different stages of dyeing through variable frequency stirring control;

[0008] S3, vat dyeing and secondary reduction, reducing the vat dye under alkaline conditions and slowly heating to the target temperature within a controlled temperature range to allow the dye to be evenly adsorbed on the fiber surface. After dyeing is completed, a low concentration reducing agent and alkali are used for secondary reduction;

[0009] S4, oxidation control, adopts a staged oxidation process, firstly carries out the first stage oxidation at a lower pH value, and then carries out the second stage oxidation at a higher pH value to fully fix the dye;

[0010] S5, soaping and post-treatment, high temperature soaping is used to remove unfixed dyes, and softening agent and antistatic agent are used for post-treatment.

[0011] Preferably, the bath ratio in S1 is controlled by establishing a mathematical relationship between the dye vat liquid level and the water volume, and is calculated in combination with fiber volume compensation.

[0012] Preferably, the pressure of the low-pressure cake-making cylinder in S2 is controlled at 0.1 MPa to 0.4 MPa.

[0013] Preferably, the frequency range of the variable frequency stirring control in S2 is 35Hz to 55Hz, wherein 35Hz to 40Hz is used in the pre-treatment stage, 40Hz to 45Hz is used in the early stage of dyeing, 50Hz to 55Hz is used in the middle stage of dyeing, and 40Hz to 45Hz is used in the late stage of dyeing.

[0014] Preferably, the heating rate during the reduction dyeing process in S3 is controlled between 1°C / min and 3°C / min, and constant temperature dyeing is performed within a temperature range of 50°C to 70°C, and the dyeing time is controlled between 30min and 70min.

[0015] Preferably, the secondary reduction in S3 uses a low concentration of reducing agent and alkali.

[0016] Preferably, the first stage of the staged oxidation in S4 uses a low concentration oxidant and performs oxidation in the pH range of 8 to 9, and the second stage uses a higher concentration oxidant and performs oxidation in the pH range of 9 to 10.

[0017] Preferably, the soaping in S5 adopts a high-temperature soaping method, the temperature is controlled between 88° C. and 96° C., and the time is controlled between 22 minutes and 28 minutes.

[0018] Preferably, the post-finishing in S5 is performed with 1% to 1.5% of a softener and 0.5% to 1% of an antistatic agent.

[0019] The present invention provides a method for reducing and dyeing loose-fiber cotton with high-precision control and high-fastness properties. It has the following beneficial effects:

[0020] 1. The present invention adopts a low-pressure cake-making and loading method to achieve the technical effect of optimizing the fiber stacking state and improving the permeability of the dye solution. Compared with the high-pressure cake-making method in the existing technology, which leads to high-density areas inside the fibers and obstructed dye penetration, it solves the problems of uneven dye solution flow and serious local color difference, making the dyeing process more uniform and ultimately improving the dyeing consistency.

[0021] 2. The present invention introduces a variable frequency stirring control strategy to achieve the technical effect of optimizing the diffusion rate of the dye solution and improving the dyeing uniformity. In the prior art, the dye solution flow rate is constant. Stirring too fast can easily lead to premature dye adhesion, while stirring too slowly can cause uneven dye distribution. The present invention adjusts the stirring frequency in stages to match the dye solution with the dye penetration requirements at different stages, solving the problems of uneven dyeing in the early stage and insufficient penetration in the middle stage, making the dyeing process more stable and controllable.

[0022] 3. The present invention adopts a step-by-step oxidation method combined with hydrogen peroxide oxidation to achieve uniformity and stability of dye fixation. Traditional air oxidation has the problems of uncontrollable rate and incomplete dye fixation, which affects the color fastness. The present invention uses gradual temperature increase oxidation combined with chemical oxidation to convert the dye under suitable conditions, completely solving the problems of uneven color fixation and serious color fading, improving wash fastness and rubbing fastness, and making the quality of the finished product more reliable.

[0023] 4. The present invention adopts staged drying and low-tension shaping technology to achieve the technical effects of fabric dimensional stability and optimized feel. Compared with the traditional high-temperature rapid drying method that easily causes fabric shrinkage, deformation, and rough feel, the present invention uses gradual temperature drying and combines low-tension shaping to ensure that the fabric maintains dimensional stability while having a softer feel, ultimately improving the comfort and appearance quality of the finished product. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A diagram showing the steps of the method of the present invention. DETAILED DESCRIPTION

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the present specification. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0026] Please see the attached Figure 1 The embodiment of the present invention provides a method for reducing and dyeing loose-fiber cotton with high precision and high fastness, comprising the following steps:

[0027] S1. High-precision bath ratio control: by measuring the relationship between the dye vat liquid level and water volume, combined with fiber volume expansion compensation, the actual bath ratio is calculated to ensure the stability of the dye solution;

[0028] In this embodiment, a mathematical relationship model between the dye vat liquid level and the water volume is first established to ensure the accuracy of the bath ratio calculation. In general, the shape of the dye vat can be approximately regarded as consisting of an upper cylinder and a lower semi-ellipsoid. In one possible implementation, assuming that the height of the upper cylinder of the dye vat is H c , with a diameter of D c , the maximum height of the lower ellipsoid is H e , the short axis is B, then the calculation of water volume corresponding to different liquid levels can be divided into two parts:

[0029] Specifically, for the cylindrical part, the water volume calculation formula is:

[0030]

[0031] Where: V c is the water volume of the cylindrical part (L); D c is the diameter of the cylinder (m); H c is the water level height of the cylindrical part (m).

[0032] For the lower semi-ellipsoid part, the water volume can be approximately calculated as:

[0033]

[0034] Where: V e is the water volume of the ellipsoid part (L); H e is the maximum height of the ellipsoid (m).

[0035] In one possible implementation, a linear relationship can be obtained between the dye vat liquid level H and the water volume V by fitting experimental data:

[0036] H=K1V+B1;

[0037] Where: K1 is the empirical fitting coefficient, which depends on the geometry of the dye vat and experimental measurement data; B1 is the offset correction value to compensate for the actual measurement error.

[0038] As an option, in order to further improve the bath ratio calculation accuracy, it is necessary to consider the problem of compensating for the volume change of the fiber in water. Generally, cotton fiber will expand in volume after absorbing water. If compensation calculation is not performed, the bath ratio calculation value will be too small, affecting the uniformity of dye distribution. In some embodiments, the volume increment of unit mass cotton fiber after absorbing water can be obtained by experimental measurement and is defined as V f , which is calculated as follows:

[0039] Vf =M f ×K2;

[0040] Where: V f M is the volume compensation amount affected by fiber water absorption (L); f is the mass of fiber in the dye vat (g); K2 is the water absorption volume compensation coefficient of unit mass of cotton fiber (L / g), which is determined by experiment.

[0041] In general, after determining the relationship between the dye vat liquid level and water volume, as well as fiber volume compensation, the actual bath ratio R is calculated as follows:

[0042]

[0043] Where: R is the actual bath ratio (L / g); V is the total amount of water added to the dye vat (L); V f Compensate the fiber volume for the amount of water (L).

[0044] In one possible implementation, to ensure the accuracy of dynamic adjustment of the bath ratio, a liquid level sensor can be used to monitor the dye vat water level in real time and dynamically calculate it based on a preset liquid level-water volume relationship. If the system detects that the bath ratio deviation exceeds a set threshold, it can automatically adjust the bath ratio by adding or draining water to ensure that the actual bath ratio remains within the set range. Alternatively, a PLC (programmable logic controller) combined with a liquid level sensor can be used for closed-loop control of the bath ratio to ensure that bath ratio fluctuations during the dyeing process are controlled within ±1.5%.

[0045] In some embodiments, the bath ratio calculation method can be optimized to meet the requirements of different dyeing processes. For example, for high-concentration dyeing processes, the fiber volume compensation coefficient K2 can be appropriately increased to accommodate higher dye concentrations. For low-concentration dyeing processes, the calculation accuracy can be further improved by adjusting the correction parameter B1 in the liquid level-water volume relationship.

[0046] The high-precision bath ratio control method described in this embodiment can ensure the stability of dye solution concentration, reduce color difference problems caused by bath ratio changes during the dyeing process, optimize dye utilization, and improve dyeing consistency and reproducibility.

[0047] S2. Dyeing uniformity is optimized by using a low-pressure cake-filling method to reduce uneven local pressure on the fibers, and variable frequency stirring control to adjust the stirring frequency at different stages of dyeing to improve dye penetration and uniformity;

[0048] In this embodiment, a low-pressure beating and loading method is used to reduce local compression of the fibers and improve dye liquor permeability. Generally, traditional high-pressure beating methods easily lead to the formation of high-density areas within the fibers, making it difficult for the dye liquor to penetrate evenly, thus affecting dyeing consistency. In one possible implementation, the beating and loading pressure is controlled at ≤0.4MPa. By reducing the beating pressure, the fibers maintain a relatively loose structure during the loading process, reducing the uneven dye adhesion caused by the dense packing of fibers during the dyeing process.

[0049] As an option, the dough-making method can be further optimized based on the fiber type, fiber length, and dyeing requirements. For example, in some embodiments, a layered low-pressure dough-making method can be used, where pressure is applied layer by layer in stages, with each layer slightly lower than the previous one, to ensure a balanced overall fiber density and reduce the formation of local dense areas. In addition, in another possible implementation, the dough-making time can be adjusted to allow the fibers to slowly form under low pressure, thereby reducing the impact of instantaneous high pressure on the fiber structure and improving the dye solution penetration effect.

[0050] While optimizing the loading method, this embodiment further employs variable frequency stirring control to ensure that the flow state of the dye liquor at different stages meets the dye penetration requirements. Generally, the stirring rate directly affects the diffusion rate of the dye liquor and the uniformity of dye adsorption. In one possible implementation, the stirring frequency during the dyeing process is set by stage to meet the dye penetration requirements at different stages:

[0051] Pre-treatment stage: The stirring frequency is set at 35-40Hz. This stage is mainly used for additive penetration and fiber swelling. Lower stirring intensity can reduce fiber entanglement and improve the uniform distribution of additives.

[0052] Initial stage of dyeing: The stirring frequency is adjusted to 40-45Hz. At this time, the dye has just begun to diffuse. The stirring intensity should be appropriately increased to make the dye solution quickly and evenly distributed on the fiber surface, reduce local concentration gradients, and avoid uneven dyeing.

[0053] Mid-dyeing stage: The stirring frequency is increased to 50-55Hz. During this stage, the dye enters the fiber in large quantities. High-frequency stirring can enhance the fluidity of the dye solution, increase the dye diffusion rate, and ensure that the dye can fully enter the fiber structure.

[0054] Late stage of dyeing: The stirring frequency is adjusted back to 45Hz. At this time, the dye adsorption is basically completed. Reducing the stirring intensity can reduce the color difference caused by excessive flow of the dye solution, while stabilizing the dye fixation and improving the final dyeing uniformity.

[0055] In another possible implementation, the stirring frequency can be nonlinearly adjusted based on the dye liquor viscosity, dye type, and fiber structure. For example, in some embodiments, a dynamic variable frequency control strategy can be employed. During the dyeing process, the stirring frequency is adjusted based on the real-time detection of the dye liquor viscosity or dye absorption rate to match the dye diffusion rate, thereby improving overall dyeing uniformity.

[0056] Furthermore, in some embodiments, to further optimize the dye liquor circulation pattern, a flow guide device may be provided within the dye vat to optimize the dye liquor flow path and avoid local dyeing variations caused by uneven flow velocity distribution. In one possible implementation, the flow guide device may employ an annular dye liquor distribution system, specifically, an annular nozzle disposed within the dye vat to direct the dye liquor along a fixed path, thereby reducing dye liquor short-circuiting and improving dye liquor flow velocity uniformity.

[0057] This embodiment optimizes the fiber stacking state through a low-pressure cake-making and cylinder-loading method, and combines it with a variable frequency stirring strategy to achieve precise flow control of the dye solution during the dyeing process, ensure dyeing uniformity, and improve dyeing consistency.

[0058] S3, vat dyeing and secondary reduction, reducing the vat dye under alkaline conditions and slowly heating it to the target temperature within a controlled temperature range to allow the dye to be evenly adsorbed on the fiber surface. After dyeing is completed, a low concentration of reducing agent and alkali are used for secondary reduction to remove the leuco body and improve the color fastness;

[0059] In the present embodiment, the dye is first subjected to a reduction treatment so that it is in a reduced state so that it can better enter the interior of the cotton fiber. Specifically, the reduction process of dyeing is carried out under an alkaline environment. Usually, the reduction reaction is promoted by adding a reducing agent (such as hydrosulfite) and an alkaline substance (such as caustic soda). The temperature and time of the reduction process have a direct impact on the dyeing effect. In this embodiment, the concentration of the reducing agent added is usually 15g / L to 20g / L, and the concentration of caustic soda is 10g / L to 15g / L. The temperature is controlled between 40°C and 45°C, and the reaction time is usually set to 20 to 30 minutes. By controlling these parameters, it can be ensured that the dye is fully reduced and can smoothly penetrate into the fiber.

[0060] Generally, increasing the temperature accelerates the reaction rate. However, excessively high temperatures can accelerate the decomposition of the reducing agent, causing the reaction to be too rapid. This can lead to the dye agglomerating on the fiber surface, making it difficult to distribute evenly. Therefore, in some embodiments, to better control the reaction rate, the temperature increase rate is typically set at 1°C / min to 3°C / min. This temperature increase rate ensures uniform dye adsorption while preventing uneven dye distribution caused by excessively rapid temperature increases.

[0061] Alternatively, after reaching 40°C, a constant-temperature dyeing process can be performed, maintaining the reaction temperature between 40°C and 45°C. The constant-temperature dyeing process is typically set for 20 to 30 minutes. This ensures sufficient dye reduction, improving dyeing stability and uniformity.

[0062] In another possible implementation, the temperature increase rate can be adjusted based on the actual dye type and dyeing requirements. For example, during the reduction process of certain special dyes, which may require a longer reaction time, the temperature increase rate can be appropriately reduced to avoid dye loss due to excessive temperatures. In this case, the temperature increase rate can be controlled between 0.5°C / min and 1°C / min, which allows for a smoother reduction reaction.

[0063] The next step is secondary reduction to remove any incompletely reduced leucoforms. Alternatively, this reduction typically uses a low concentration of reducing agent and a low concentration of alkaline. Specifically, the reducing agent concentration for the secondary reduction is 3g / L to 4g / L, and the caustic soda concentration is 0.6g / L to 0.8g / L. The temperature is controlled between 40°C and 50°C, and the reaction time is typically 12 to 18 minutes.

[0064] The secondary reduction reaction further treats any remaining dye residue that hasn't been fully reduced, improving the dye's color fastness. The dyeing effect is now more stable, with dry and wet rubbing fastness reaching levels above 4.5, meeting high-quality dyeing requirements.

[0065] Overall, this embodiment ensures uniform distribution and strong adhesion of the dye to the fiber by precisely controlling various vat dyeing parameters (such as reducing agent concentration, temperature, and time). A rational secondary reduction process further improves color fastness and prevents incomplete dye reduction, resulting in more stable and long-lasting color fastness.

[0066] S4, oxidation control, adopts a staged oxidation process, firstly carries out the first stage oxidation at a lower pH value, and then carries out the second stage oxidation at a higher pH value, so that the dye is fully fixed and the washing resistance and rubbing resistance are improved;

[0067] In this embodiment, a step-by-step oxidation process is used to control the uniformity of the oxidation reaction. Generally, the oxidation process can be completed through air oxidation or chemical oxidation. In one possible implementation, the oxidation process uses a step-by-step temperature increase, that is, the initial temperature is controlled at 25°C to 30°C, then gradually increased to 50°C to 55°C, and the oxidation time is set at 15 to 25 minutes. This method can effectively prevent excessive oxidation of the dye and improve color fixation uniformity.

[0068] Alternatively, hydrogen peroxide oxidation can be used. This involves adding a 1% to 2% H2O2 solution during the oxidation process, allowing the dye to be stably converted to a fixed state under appropriate oxidation conditions. Specifically, controlling the solution pH between 8.5 and 9.0 and the oxidation time between 20 and 30 minutes can improve the stability of the dye-fiber bond.

[0069] In some embodiments, oxygen bubbling can be used to further improve oxidation uniformity. This method controls the oxygen flow rate (2-4 L / min) to make the oxidation reaction more uniform, reduce areas of insufficient oxidation, and improve the fastness of the final dyeing.

[0070] In this embodiment, after oxidation, multiple soaping steps are performed to remove unfixed dye and residual auxiliaries. Typically, the soaping solution is an alkaline solution containing a surfactant to ensure a stable bond between the dye and the fiber, free from residual impurities. In one possible implementation, the soaping solution comprises 2-4 g / L Na2CO3 and 1-2 g / L nonionic surfactant. The washing temperature is controlled between 60°C and 75°C, and the washing time is 20 to 30 minutes.

[0071] To improve soaping efficiency, in some embodiments, a gradual soaping process can be employed. Specifically, a preliminary soaping process is performed at 40°C to 50°C to remove surface color, followed by a deep wash at 70°C to 75°C to ensure complete dye fixation.

[0072] Alternatively, ultrasound-assisted soaping can be introduced during the soaping process. In one possible implementation, the ultrasound frequency is set at 20-40 kHz and the power range is 200-400 W. This method effectively increases the removal rate of unfixed dyes while reducing the impact of the washing process on fiber strength.

[0073] Furthermore, in some embodiments, to further reduce water consumption and improve soaping efficiency, a high-efficiency circulating filtration system can be employed. By installing a 0.2-0.5 μm microfiltration membrane, free dyes can be effectively removed, improving dye liquor cleanliness while reducing water consumption and enhancing the environmental friendliness of the overall dyeing process.

[0074] This example optimizes the oxidation and soaping processes to ensure stable dye fixation while removing any unfixed dye, improving dyeing uniformity and fastness. By rationally controlling the oxidation method and combining precise soaping parameters, the dyed fabric achieves high levels of wash and rubbing fastness, ensuring stable and reliable final dyeing quality.

[0075] S5, soaping and post-treatment, using high temperature soaping to remove unfixed dyes, and finishing with softeners and antistatic agents to improve the fiber feel and enhance the quality of the final product;

[0076] In this embodiment, a staged drying method is used to avoid stress concentration caused by uneven moisture evaporation within the fabric. Generally, excessively high temperatures or rapid drying rates can cause shrinkage or discoloration on the fabric surface, affecting the final quality. In one possible implementation, the fabric drying temperature is initially set at 60°C to 80°C to gradually remove moisture from the fabric, followed by a temperature increase to 100°C to 120°C for final drying. Drying time is typically controlled between 8 and 15 minutes to ensure simultaneous evaporation of moisture from the fabric interior and surface.

[0077] Alternatively, in some embodiments, hot air circulation drying can be employed, using forced hot air convection to achieve more uniform drying of fabrics. Specifically, the hot air velocity is set between 2.5 and 4.0 m / s, and an intermittent circulation mode is employed, where the hot air flow direction is periodically alternating, minimizing local temperature differences and improving drying uniformity.

[0078] In another possible implementation, far-infrared drying technology can be combined to use far-infrared radiation energy to directly act on fabrics to improve water evaporation efficiency. Generally, the far-infrared wavelength range is set at 3-8μm, and the power density is controlled at 0.5-1.2kW / m 2 , which can effectively reduce the problem of fabric deformation during the drying process and improve dimensional stability.

[0079] In this embodiment, after drying, the fabric requires a setting treatment to improve dimensional stability and enhance the final feel. Generally, controlling the setting temperature is crucial: too high a setting temperature may damage the fibers, while too low a setting temperature may result in insufficient setting. In one possible implementation, the setting temperature is set between 150°C and 180°C for 30 to 60 seconds to ensure a stable fabric structure and minimize dimensional changes during subsequent washing or use.

[0080] Alternatively, in some embodiments, a wet heat setting process can be employed. This involves appropriately increasing the fabric's humidity before setting to reduce residual stress within the fibers and improve softness after setting. Specifically, the fabric can be sprayed with humidifiers at a rate of 5-10% (mass ratio) before entering the setting machine, followed by setting to improve the fabric's resilience.

[0081] In another possible implementation, to further optimize the fabric's feel, a softening finish can be used. Typically, silicone softeners or cationic softeners can be used, with a concentration of 0.5-1.5 g / L. These softeners are applied simultaneously during the shaping process to enhance the fabric's smoothness and skin-friendliness.

[0082] In some embodiments, a low-tension setting method can be employed, whereby tension is appropriately reduced during the setting process to minimize deformation caused by fabric stretching. Specifically, controlling the tension during the setting process to 1.5-3.0 cN / dtex effectively reduces mechanical stress on the fabric and improves the dimensional stability of the final product.

[0083] This example optimizes the drying and setting processes to ensure that the dyed fabric has higher dimensional stability and color fastness, while maintaining an appropriate feel and elasticity. By rationally controlling temperature, humidity, and tension parameters, combined with advanced heat treatment technology, the fabric's overall performance in the final application is optimized.

[0084] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for reducing and dyeing loose-fiber cotton with high precision and high fastness, characterized in that: The following steps are involved: S1. High-precision bath ratio control: by measuring the relationship between the dye vat liquid level and water volume, combined with fiber volume expansion compensation, the actual bath ratio is calculated; S2. Dyeing uniformity is optimized by adopting low-pressure cake-loading method to reduce local uneven pressure on fibers, and adjusting the stirring frequency at different stages of dyeing through variable frequency stirring control; S3, vat dyeing and secondary reduction, reducing the vat dye under alkaline conditions and slowly heating to the target temperature within a controlled temperature range to allow the dye to be evenly adsorbed on the fiber surface. After dyeing is completed, a low concentration reducing agent and alkali are used for secondary reduction; S4, oxidation control, adopts a staged oxidation process, firstly carries out the first stage oxidation at a lower pH value, and then carries out the second stage oxidation at a higher pH value to fully fix the dye; S5, soaping and post-treatment, high temperature soaping is used to remove unfixed dyes, and softening agent and antistatic agent are used for post-treatment.

2. The method for reducing and dyeing loose-fiber cotton with high precision and high fastness according to claim 1, characterized in that: The bath ratio in S1 is controlled by establishing a mathematical relationship between the dye vat liquid level and the water volume, and is calculated in combination with fiber volume compensation.

3. The method for reducing and dyeing loose-fiber cotton with high precision and high fastness according to claim 1, characterized in that: The pressure of the low-pressure cake-making cylinder in S2 is controlled at 0.1 MPa to 0.4 MPa.

4. The method for reducing and dyeing loose-fiber cotton with high-precision control and high-fastness according to claim 1, characterized in that: The frequency range of the variable frequency stirring control in S2 is 35Hz to 55Hz, wherein the pre-treatment stage adopts 35Hz to 40Hz, the early dyeing stage adopts 40Hz to 45Hz, the middle dyeing stage adopts 50Hz to 55Hz, and the late dyeing stage adopts 40Hz to 45Hz.

5. The method for reducing and dyeing loose-fiber cotton with high precision and high fastness according to claim 1, characterized in that: The heating rate during the reduction dyeing process in S3 is controlled between 1°C / min and 3°C / min, and constant temperature dyeing is performed within a temperature range of 50°C to 70°C, with a dyeing time controlled between 30min and 70min.

6. The method for reducing and dyeing loose-fiber cotton with high-precision control and high-fastness according to claim 1, characterized in that: The secondary reduction in S3 uses a low concentration of reducing agent and alkali.

7. The method for reducing and dyeing loose-fiber cotton with high precision and high fastness according to claim 1, characterized in that: The first stage of the staged oxidation in S4 uses a low concentration oxidant and is oxidized in the range of pH 8 to 9, and the second stage uses a higher concentration oxidant and is oxidized in the range of pH 9 to 10.

8. The method for reducing and dyeing loose-fiber cotton with high precision and high fastness according to claim 1, characterized in that: The soap washing in S5 adopts a high-temperature soap washing method, the temperature is controlled between 88° C. and 96° C., and the time is controlled between 22 minutes and 28 minutes.

9. The method for reducing and dyeing loose-fiber cotton with high precision and high fastness according to claim 1, characterized in that: The S5 finishing is performed with 1% to 1.5% of a softener and 0.5% to 1% of an antistatic agent.

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