Method and device for reactive dyeing based on microfluidic droplet jetting

Abstract

The present application belongs to the technical field of reactive dyeing, and particularly relates to a reactive dyeing method and device based on microfluidic droplet injection. The method stores reactive dyeing liquid and sodium carbonate alkali liquid separately, mixes the two liquids on a microfluidic chip for no more than 5 minutes before injection, and obtains mixed dyeing liquid. The mixed dyeing liquid is atomized into micron-level droplets by a coaxial pneumatic nozzle, and is directionally injected and deposited on a target surface of a fabric, so that single-side dyeing is realized by controlling injection parameters. Finally, dyeing is completed by steaming and fixing. In the whole process, sodium sulfate is not needed, salt-free dyeing is realized, dyeing liquid and alkali liquid are mixed instantaneously, hydrolysis is effectively inhibited, and the fixing rate is significantly higher than that of a traditional process. The method can also set up double independent injection units to realize double-side same-color or double-side different-color dyeing.

Description

Technical Field

[0001] This invention belongs to the field of reactive dyeing technology, specifically relating to a reactive dyeing method and apparatus based on microfluidic droplet jetting. Background Technology

[0002] Traditional reactive dyeing processes mainly employ immersion dyeing and pad dyeing, typically requiring high liquor ratios, high concentrations of inorganic salts and alkalis to promote dye adsorption and fixation. These methods suffer from significant drawbacks, including high water consumption, high wastewater discharge, excessive use of sodium sulfate leading to extremely high total dissolved solids (TDS) levels in the wastewater with significant treatment challenges, dyes prone to hydrolysis under alkaline conditions resulting in low fixation rates and waste, high colored wastewater load, uneven dye liquor distribution, and poor controllability of penetration, making it difficult to meet diverse needs such as single-sided dyeing or double-sided coloring. In recent years, while improved technologies such as salt-free modified cotton, low liquor ratio dyeing, foam dyeing, and spray dyeing have emerged, numerous bottlenecks remain. For example, modified cotton is costly, foam dyeing suffers from poor uniformity due to uncontrollable foam half-life, and spray dyeing exhibits wide droplet size distribution and uncontrollable penetration. In particular, existing technologies often pre-mix dyes and alkalis during the dyeing process, causing dye hydrolysis before reaching the fibers, significantly reducing fixation efficiency.

[0003] The closest existing technologies to this invention mainly include the following categories. Inkjet printing technology uses pre-mixed reactive dye inks, which are sprayed onto the fabric through piezoelectric or hot steam nozzles. This type of technology requires pretreatment of the fabric, such as padding with alkaline solution and sizing, which prolongs the process and is time-consuming and labor-intensive. At the same time, a large amount of humectants, surfactants and other auxiliaries need to be added to the ink to meet the physical requirements of the nozzle spraying, which significantly increases the wastewater treatment load. For example, the process disclosed in patent CN116065409A uses a liquid dyeing technology that uses a large droplet piezoelectric nozzle to uniformly spray dye liquid on both sides of the fabric, which can control the total liquid content of the fabric to 10%~40% and directly perform saturated steam steaming for color fixing, achieving low liquid content dyeing. However, in this technology, the dye liquor and alkali liquor are still premixed. The embodiments explicitly state that the dye, alkali, and sodium sulfate are pre-mixed to prepare the spray dye liquor, thus making it impossible to avoid the dye hydrolyzing upon contact with the alkali before spraying. Furthermore, the droplets generated by the piezoelectric nozzles are large in volume and have a wide droplet size distribution, resulting in poor deposition and spreading on the fabric surface, making it difficult to achieve unilateral directional deposition. Airflow atomization dyeing is mostly used for loose fibers or yarns. This technology uses high-speed airflow to atomize the dye liquor and spray it onto the fibers in a rope-like motion. The lack of precise relative motion trajectory control between the atomization unit and the fabric makes it difficult to achieve unilateral directional dyeing of planar fabrics and also fails to meet the requirement of different colors on both sides. Salt-free / low-salt dyeing technology mainly involves cationic modified cotton or water / non-aqueous media dyeing; however, this modification treatment adds additional processes such as padding, drying, and washing, significantly increasing the modification cost compared to conventional processes. While non-aqueous media dyeing technology can achieve salt-free dyeing, it requires specialized dyeing equipment, has a complex media recovery system, and has high industrialization costs.

[0004] In summary, none of the aforementioned existing technologies combine microfluidic online instantaneous mixing with pneumatic atomization for unilateral directional deposition, nor can they maximally suppress the hydrolysis of dyes and alkali solutions. Specifically, inkjet printing and liquid dyeing both use premixed dye solutions, meaning the dye has already come into contact with the alkali agent during storage and transportation before jetting, making hydrolysis unavoidable; airflow atomization dyeing and foam dyeing cannot achieve precise droplet size control and unilateral directional deposition; salt-free / low-salt dyeing relies on fiber modification or media replacement, increasing process complexity and cost. Therefore, there is an urgent need for a reactive dyeing method and apparatus that can suppress dye hydrolysis at the source, achieve low chemical consumption, and enable precise unilateral deposition. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide a reactive dyeing method based on microfluidic droplet jetting, which solves problems such as easy hydrolysis of dyes, high salt and water consumption, and difficulty in achieving single-sided / double-sided color variation in existing technologies.

[0006] The present invention also provides its apparatus, which is scientifically and rationally designed.

[0007] The reactive dyeing method based on microfluidic droplet jetting described in this invention includes the following steps: (1) Preparation of dyeing solution and fixing alkali solution: Prepare the dyeing solution and fixing alkali solution for the reactive dye separately and store them separately; do not mix them until just before spraying. Do not add sodium sulfate throughout the dyeing process to achieve salt-free dyeing.

[0008] (2) Microfluidic online mixing: A dual-channel injection pump delivers the dye solution and alkali solution to a microfluidic chip mixing device at a set flow ratio. The online mixing is completed instantaneously within the channel using convection diffusion to obtain a mixed dyeing working solution. The online mixing is completed before spraying, and the mixing time does not exceed 5 minutes. By precisely controlling the mixing time, the dye hydrolysis rate can be minimized based on the hydrolysis kinetics of different reactive dyes.

[0009] (3) Microdroplet jetting and deposition: The mixed dyeing working solution is atomized and sprayed onto the surface of the target fabric through a nozzle, forming microdroplet deposition to achieve single-sided dyeing; (4) Steam color fixing: Fabrics deposited with mixed dye liquor are subjected to steam fixation. This involves steaming the fabric with deposited microdroplets under saturated steam conditions (100-102℃). The dye diffuses into the fiber interior and covalently bonds with the cellulose hydroxyl groups. Subsequent steps include cold water washing (20-30℃), hot water washing (60-80℃), cold water washing, and drying to obtain the dyed finished product. The process flow diagram of the reactive dye dyeing method based on microfluidic droplet jetting is shown below. Figure 7 As shown.

[0010] The color-fixing alkaline solution mentioned in step (1) is an aqueous solution of sodium carbonate.

[0011] The microfluidic chip mixing device described in step (2) has a Y-shaped or T-shaped circular channel with a channel diameter of 800-1000 μm. A T-shaped channel is preferred.

[0012] The nozzle in step (3) is a coaxial atomizing nozzle, with the mixed dyeing working solution flowing through its inner tube and compressed air flowing through its outer tube. The pressure of the compressed air is 0.05-0.15 MPa, preferably 0.1 MPa. Under the shearing action of the airflow, the mixed dye solution is broken into uniform micro-droplets and sprayed onto the surface of the cotton fabric at a certain speed.

[0013] In step (3), the distance between the nozzle and the target surface of the fabric is 5-15cm, preferably 10cm; the scanning interval is 4-7mm, preferably 6mm, and the scanning speed is 400r / min.

[0014] By controlling the distance between the nozzle and the fabric, the spray pressure, the scanning speed, and the scanning interval, microdroplets can be controllably deposited on the target surface of the fabric.

[0015] The flow rate (total liquid flow rate) of the mixed dyeing working solution in step (3) is 5-20 mL / h, preferably 10 mL / h. Too low a flow rate results in a high gas-liquid ratio, small droplet size, large specific surface area, strong evaporation of water during spraying, dye aggregation, insufficient fiber swelling, and low fixation rate. Too high a flow rate leads to excessive wetting of the fabric, increased dye penetration into non-target surfaces, and weakened single-sided deposition characteristics. At the preferred flow rate of 10 mL / h, the optimal balance of high color payoff on the target surface and no contamination on non-target surfaces can be achieved.

[0016] Experiments show that when the total liquid flow rate is 10 mL / h, the dye penetration depth is about 40-85 μm, the permeability is about 20-45%, and the K / S value of the non-target surface is <1.

[0017] The reactive dye in step (1) is selected from one or more of CI Reactive Black 5, CI Reactive Red 195, CI Reactive Red AS raw powder, CI Reactive Yellow 15, and CI Reactive Blue 49. The steam fixation time in step (4) is 3-10 min.

[0018] This invention reveals that different reactive dyes exhibit significant differences in their sensitivity to alkali concentration and steaming time. Microfluidic technology allows for precise adjustment of the mixing ratio and steaming conditions, resulting in a synergistic effect. The concentration and steaming time of the sodium carbonate aqueous solution are set according to the type of dye: CI Active Black 5: Sodium carbonate aqueous solution concentration 30 g / L, steaming time 3 min; CI Active Red AS Powder: Sodium carbonate aqueous solution concentration 30 g / L, steaming time 3 min; CI Reactive Red 195: Sodium carbonate aqueous solution concentration 30 g / L, steaming time 4 min; CI Active Yellow 15: Sodium carbonate aqueous solution concentration 20 g / L, steaming time 4 min; CI Reactive Blue 49: Sodium carbonate aqueous solution concentration 40 g / L, steaming time 10 min.

[0019] The method further includes performing microfluidic online mixing and microdroplet spraying and deposition on both sides of the fabric to achieve double-sided same-color or double-sided different-color dyeing. The steps to achieve double-sided dyeing mode by adjusting process parameters are as follows: When double-sided color is required, independent microfluidic droplet spraying units are set on both sides of the fabric to spray the mixed dyeing working solution separately, independently controlling the type, concentration, and flow rate of the dye, or after spraying and depositing on one side, the fabric is reversed to spray and deposit on the other side, achieving one color on each side with clear boundaries and no color mixing.

[0020] The apparatus for reactive dyeing based on microfluidic droplet jetting according to the present invention includes: at least one microfluidic chip mixing device, at least one coaxial atomizing nozzle, at least two liquid storage containers, an injection pump for controlling the liquid flow rate, a scanning platform for controlling the relative movement between the nozzle and the fabric (the fabric rotates with the roller, and after the nozzle jets for a certain period of time, the control panel operates the robotic arm equipped with the nozzle to move, so that the nozzle moves a fixed distance along the width direction), and a steaming unit.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) This invention employs a dual-channel instantaneous mixing method, where the dye and alkali solution are mixed instantaneously before atomization, with a mixing time not exceeding 5 minutes. This avoids the hydrolysis of the dye due to prolonged contact with the alkali solution caused by premixing. Experiments have shown that for CI Reactive Black 5, Reactive Yellow 15, and Reactive Blue 49, the fixation rates of the method of this invention reach 93.83%, 76.62%, and 68.81%, respectively, all higher than the 91.07%, 69.92%, and 65.08% of the traditional pad-dry-pad-steam process.

[0022] 2) This invention eliminates the need for sodium sulfate, achieving salt-free dyeing. Experiments have shown that the total dissolved solids (TDS) in wastewater is reduced by more than 80% compared to traditional processes, significantly reducing the difficulty of wastewater treatment and the environmental impact.

[0023] 3) This invention uses pneumatic atomized microdroplet single-sided deposition technology, which eliminates the need for large dyeing vats and reduces water consumption by 30%-40%; the alkali agent is directionally deposited on the target surface, reducing sodium carbonate usage by 5%-30%, which significantly saves chemicals and water resources.

[0024] 4) This invention directs dye deposition onto the target surface of the fabric, avoiding the dye waste caused by double-sided dyeing in traditional pad dyeing. Compared with traditional pad dyeing, dye consumption is reduced by 32%-57% (specifically, Reactive Yellow 15 is reduced by 57.68%, Reactive Red 195 by 55.57%, Reactive Black 5 by 43.37%, and Reactive Blue 49 by 32.71%), significantly improving dye utilization.

[0025] 5) The carbon emissions related to resource input of this invention are reduced by 35%-60% compared with traditional processes; the color of wastewater is reduced by 45%-75% and the chemical oxygen demand (COD) is reduced by 50%-70%, resulting in significant environmental benefits.

[0026] 6) Compared with inkjet printing technology, which also uses droplet coloring, this invention does not require additional fabric pretreatment processes such as sizing, saving time and effort. Furthermore, it does not require the addition of large amounts of humectants, surfactants, and other auxiliaries to the ink, reducing the use of chemicals and wastewater load.

[0027] 7) This invention can dye on demand. By calculating the required amount of dye and precisely controlling the spray volume, it avoids excessive dyeing and dye waste, and achieves nearly 100% utilization of dye.

[0028] 8) This invention can achieve single-sided dyeing, double-sided same color, and double-sided different color in one step. When the double-sided color is different, the boundary is clear and there is no color mixing phenomenon, which can flexibly meet the diverse dyeing needs. Attached Figure Description

[0029] Figure 1 This is a front view of the microfluidic spray chip. Figure 2 A bottom view of the microfluidic spray chip; Figure 3 Dimensional annotations for the main view of the microfluidic spray chip; Figure 4 This is a dimensioned view of the microfluidic spray chip from a bottom perspective. Figure 5 A front view of the internal structure of a microfluidic spray chip; Figure 6 This is a side view of the internal structure of a microfluidic spray chip. The components include: 1. Liquid inlet; 2. Mixing pipe; 3. Liquid outlet; 4. Air inlet; 5. Spray needle; 6. Air outlet; 7. Shell; Figure 7 This is a process flow diagram of the reactive dyeing method based on microfluidic droplet jetting described in this invention; Figure 8 The results compare the resource consumption and wastewater pollutant load of microfluidic droplet jet (MDJ) dyeing in Examples 1-4 with that of pad-dry-steam (PDPS) dyeing in Comparative Example 1, where: (a) dye consumption; (b) water consumption; (c) Na2CO3 consumption; (d) Na2SO4 consumption; (e) carbon emissions related to resource input; (f) wastewater color; (g) total dissolved solids (TDS) in wastewater; (h) pH value of wastewater; and (i) chemical oxygen demand (COD) of wastewater. Figure 9The images shown are digital scans of the microfluidic droplet jet single-sided dyed fabrics obtained in Examples 1-4, where: (a) CI Reactive Black 5; (b) CI Reactive Red 195; (c) CI Reactive Yellow 15; (d) CI Reactive Blue 49.

[0030] Figure 10 The images show digital scans of the microfluidic droplet-jet double-sided dyed fabrics obtained in Examples 1-4, where: Front side: (a1) CI Reactive Yellow 15; (b1) CI Reactive Red 195; (c1) CI Reactive Blue 49; (d1) CI Reactive Black 5. Back side: (a2) CI Reactive Yellow 15; (b2) CI Reactive Red 195; (c2) CI Reactive Blue 49; (d2) CI Reactive Black 5.

[0031] Figure 11 The image shows a digital scan of the double-sided, differently colored fabric obtained in Example 5, where: (a) CI Reactive Red AS raw powder; (b) CI Reactive Black 5; Figure 12 The images shown are super-depth fabric images and cross-sectional views of the microfluidic droplet jet single-sided dyed fabrics obtained in Examples 1-4, wherein: super-depth fabric images: (a) CI Reactive Black 5; (b) CI Reactive Red 195; (c) CI Reactive Yellow 15; (d) CI Reactive Blue 49; cross-sectional views: (e) CI Reactive Black 5; (f) CI Reactive Red 195; (g) CI Reactive Yellow 15; (h) CI Reactive Blue 49; Figure 13 The graph shows the penetration depth and permeability data of the microfluidic droplet jet single-sided dyed fabrics obtained in Examples 1-4. Detailed Implementation

[0032] The present invention will be further described below with reference to the embodiments.

[0033] Unless otherwise specified, all raw materials used in the examples were commercially available.

[0034] The cotton fabric used in the examples and comparative examples has the following specifications: cotton fabric, plain weave 1 / 1, 40s × 40s, 112g / m². 2 The number of warp fibers is 133, and the number of weft fibers is 72.

[0035] All dyes used in the examples and comparative examples were purchased from Jinan Hailiang Dyestuff Chemical Co., Ltd.

[0036] Example 1 (CI Active Yellow 15) The aforementioned reactive dyeing method based on microfluidic droplet jetting comprises the following steps: (1) Preparation of dyeing solution and fixing alkali solution: Take 50 g / L CI Reactive Yellow 15 (monovinyl sulfone type) aqueous solution as dye solution and 20 g / L Na2CO3 aqueous solution as alkali solution, and place them in two storage containers respectively; (2) Microfluidic online mixing: The dye solution and alkali solution were injected into a microfluidic chip mixing device (T-shaped circular channel, channel diameter 0.9 mm) at flow rates of 5 mL / h and 5 mL / h respectively (total flow rate 10 mL / h) using a dual-channel injection pump. Figure 1 This is a front view of the microfluidic spray chip. Figure 2 This is a bottom view of the microfluidic spray chip. Figure 3 This is a dimensioned view of the microfluidic spray chip's main structure. Figure 4 This is a top-view dimensioned diagram of a microfluidic spray chip. Figure 5 This is a front view of the internal structure of the microfluidic spray chip. Figure 6 This is a side view of the internal structure of the microfluidic spray chip, including an inlet 1, a mixing channel 2, an outlet 3, an air inlet 4, a spray needle 5, an air outlet 6, and a housing 7. The mixing time is less than 5 minutes to obtain a mixed staining working solution. The mixing time is calculated based on a circular channel with a diameter of 0.9 mm and a length of 7.5 cm, resulting in a volume of 47.7 mm³. 3 Based on the lowest flow rate of 1 ml / h in the experiment, the mixing time before mixing and spraying is approximately 3 minutes. The actual mixing time in this embodiment is 17.172 seconds.

[0037] (3) Microdroplet jetting and deposition (single-sided): The mixed dyeing working solution enters the inner tube (inner diameter 1.5 mm) of the coaxial atomizing nozzle, and 0.1 MPa compressed air is introduced into the outer tube. The distance between the nozzle and the cotton fabric is 10 cm. The collecting roller rotates at 400 rpm, the scanning speed is 400 r / min, and the scanning interval is 6 mm.

[0038] (4) Steam color fixing: After spraying, the fabric was steamed in saturated steam at 100-102℃ for 4 minutes, then washed sequentially with 25℃ cold water and 70℃ hot water for 5 minutes each, and then dried. The K / S value of the target surface of the dyed fabric was measured to be 11.80, and the K / S value of the non-target surface was 0.53. The dye penetration depth was approximately 80.74 μm, the penetration rate was approximately 35.6%, the fixation rate was 76.62%, and the dye consumption was reduced by 57.68% compared with the traditional pad-dry-steam process.

[0039] Using the same process and a single nozzle, dye one side and then dye the other side to achieve double-sided dyeing with the same color, resulting in double-sided fabric with the same color.

[0040] Example 2 (CI Reactive Blue 49) Same as Example 1, except that: 50 g / L CI Reactive Blue 49 (single chlorotriazine) aqueous solution was used as the dyeing solution, 40 g / L Na2CO3 aqueous solution was used as the alkali solution, and the fabric was steamed in saturated steam at 100-102℃ for 10 min.

[0041] The measured K / S value of the dyed fabric was 8.32 on the target surface and 0.67 on the non-target surface. The fixation rate was 68.81%, the penetration depth was 77.45μm, the penetration rate was 37.4%, and the dye consumption was reduced by 32.71% compared with the traditional pad-drying and pad-steaming process.

[0042] Using the same process and a single nozzle, dye one side and then dye the other side to achieve double-sided dyeing with the same color, resulting in double-sided fabric with the same color.

[0043] Example 3 (CI Reactive Red 195) Same as Example 1, except that: 70 g / L CI Reactive Red 195 (1 vinyl sulfone and 1 monochlorotriazine) aqueous solution was used as the dyeing solution, 30 g / L Na2CO3 aqueous solution was used as the alkali solution, and the fabric was steamed in saturated steam at 100-102℃ for 4 min.

[0044] The measured K / S value of the target surface of the dyed fabric was 12.25, the K / S value of the non-target surface was 0.63, the fixation rate was 52.56%, the penetration depth was 41.79μm, the penetration rate was 20.6%, and the dye consumption was reduced by 55.57% compared with the traditional pad-drying and pad-steaming process.

[0045] Using the same process and a single nozzle, dye one side and then dye the other side to achieve double-sided dyeing (dye concentration of 50g / L for both sides) to obtain double-sided fabric with the same color.

[0046] Example 4 (CI Reactive Black 5) Same as Example 1, except that: 100 g / L CI Reactive Black 5 (2 vinyl sulfone groups) aqueous solution was used as dyeing solution, 30 g / L Na2CO3 aqueous solution was used as alkali solution, and the fabric was steamed in saturated steam at 100-102℃ for 3 min.

[0047] The measured K / S value of the target surface of the dyed fabric was 21.10, the K / S value of the non-target surface was 0.95, the fixation rate was 93.83%, the penetration depth was 80.86μm, the penetration rate was 42.9%, and the dye consumption was reduced by 43.37% compared with the traditional pad-drying and pad-steaming process.

[0048] Using the same process and a single nozzle, dye one side and then dye the other side to achieve double-sided dyeing (dye concentration of 50g / L for both sides) to obtain double-sided fabric with the same color.

[0049] Example 5 (CI Reactive Red AS Powder and CI Reactive Black 5) Same as Example 1, except that the front side uses a 50 g / L CI Reactive Red AS raw powder aqueous solution as the dye liquor and a 30 g / L Na2CO3 aqueous solution as the alkali solution. The reverse side uses a 50 g / L CI Reactive Black 5 aqueous solution as the dye liquor and a 30 g / L Na2CO3 aqueous solution as the alkali solution. The fabric is steamed in saturated steam at 100-102℃ for 3 min.

[0050] Non-preferred embodiment 6 Similar to Example 2, except that: with 20 g / L Na2CO3 aqueous solution and steaming for 4 min, the fixation rate of CI Reactive Blue 49 decreased to 57.3%, demonstrating the necessity of optimizing parameters for different dyes.

[0051] Non-preferred embodiment 7 Similar to Example 1, the difference lies in the total liquid flow rate being 1 ml / h and the spraying time being 10 times that of Example 1, ensuring the same amount of dye applied per unit area. The fixation rate is 70.75%, the K / S value on the target surface is 11.09, and the K / S value on the non-target surface is 0.3. It is evident that the low flow rate (1 mL / h) leads to insufficient liquid input, insufficient dye quantity, and low fixation rate. By controlling the spraying time, the amount of dye applied per unit area of ​​the fabric is ensured to be the same. However, at low flow rates, the gas-liquid ratio is high, the droplet size is small, the specific surface area is large, and the evaporation of water during the spraying process is strong. This results in two issues: firstly, a sharp increase in dye concentration within the droplets, forming large-diameter dye aggregates; secondly, the reduction in water content leads to insufficient wetting and swelling of the fibers, preventing the opening of the pores inside the fibers, causing dye aggregates to accumulate on the surface, resulting in a decrease in dye fixation rate during subsequent steaming.

[0052] Non-preferred embodiment 8 Similar to Example 1, the difference is that the total liquid flow rate is 30 ml / h, the spraying time is 1 / 3 of that in Example 1, ensuring that the amount of dye applied per unit area is consistent, the fixation rate is 77.01%, the K / S value of the target surface is 9.91, and that of the non-target surface is 0.74. It can be seen that the excessive flow rate (30 mL / h) leads to excessive penetration of the fabric, increased dye penetration to the non-target surface, and weakened single-sided deposition characteristics.

[0053] Comparative Example 1 Traditional rolling, drying, and steaming processes: CI Active Yellow 15 A two-dip, two-roller method was used. First, the sample was dipped in a 40 g / L CI Reactive Yellow 15 solution at a rolling mill pressure of 2 kg and a rotation speed of 3 r / min, with a roll-off rate of 70 ± 3%. Then, the sample was dipped in a fixing solution composed of a 20 g / L Na₂CO₃ solution and an 80 g / L Na₂SO₄ solution at a rolling mill pressure of 2 kg and a rotation speed of 3 r / min, with a roll-off rate of 70 ± 3%. The sample was then steamed under saturated steam at atmospheric pressure for 4 min, and washed with water as in Example 1.

[0054] CI Reactive Blue 49 A two-dip, two-roller method was used. First, the sample was dipped in a 30 g / L CI Reactive Blue 49 solution at a rolling mill pressure of 2 kg and a rotation speed of 3 r / min, with a roll-off rate of 70 ± 3%. Then, the sample was dipped in a fixing solution composed of a 30 g / L Na₂CO₃ solution and a 100 g / L Na₂SO₄ solution at the same rolling mill pressure of 2 kg and a rotation speed of 3 r / min, with a roll-off rate of 70 ± 3%. The sample was then steamed under saturated steam at atmospheric pressure for 11 min, and washed with water as in Example 1.

[0055] CI Active Red 195 A two-dip, two-rolling method was adopted. First, the sample was dipped in a 30 g / L CI Reactive Red 195 solution at a rolling mill pressure of 2 kg and a rotation speed of 3 r / min, with a roll-off rate of 70 ± 3%. Then, the sample was dipped in a fixing solution composed of a 20 g / L Na2CO3 solution and a 100 g / L Na2SO4 solution at a rolling mill pressure of 2 kg and a rotation speed of 3 r / min, with a roll-off rate of 70 ± 3%. The sample was then steamed under saturated steam at atmospheric pressure for 5 min, and washed with water as in Example 1.

[0056] CI Active Black 5 A two-dip, two-rolling method was adopted. First, the sample was dipped in a 50 g / L CI Reactive Black 5 solution at a rolling mill pressure of 2 kg and a rotation speed of 3 r / min, with a roll-out rate of 70 ± 3%. Then, the sample was dipped in a fixing solution composed of a 20 g / L Na2CO3 solution and a 100 g / L Na2SO4 solution at a rolling mill pressure of 2 kg and a rotation speed of 3 r / min, with a roll-out rate of 70 ± 3%. The sample was then steamed under saturated steam at atmospheric pressure for 5 min, and washed with water as in Example 1.

[0057] Taking a single-sided target surface as an example, under the same K / S value, the resources consumed by dyeing the same size fabric with the pad dyeing process and the wastewater load generated by washing the same amount of cotton fabric are compared. The carbon emission comparison is only related to resource consumption (the carbon emission of the resources required to dye 1000kg of cotton fabric is compared).

[0058] Resource consumption was calculated based on fabric samples of the same size. For microfluidic droplet jet dyeing, the amounts of reactive dye solution and sodium carbonate solution used were calculated based on liquid flow rate, jetting time, solution density, and solute mass fraction. Na₂CO₃ consumption and water consumption were calculated as follows: M2=Q2T ρ2W2(1) Mw=Q1Tρ1(1-W1) + Q2Tρ2(1-W2) (2) In the formula, M2 and M w Q1 and Q2 represent the consumption of Na2CO3 and water, respectively; Q1 and Q2 are the flow rates of the reactive dye solution and the Na2CO3 solution, respectively; T is the spraying time; ρ1 and ρ2 are the solution densities; W1 and W2 are the mass fractions of the reactive dye and Na2CO3, respectively.

[0059] For microfluidic droplet jet staining and pad-dry-steam staining, the method for calculating dye consumption is as follows: M1=5C1V1N1-C2V2N2(3) In the formula, M1 is the mass of dye consumed; C1 and C2 are the dye concentrations corresponding to absorbances A1 and A2, respectively; V1 and V2 are the original volumes of the test solution used to determine A1 and A2, respectively. A1 and A2 are absorbances, and N1 and N2 are the dilution factors of the test solution.

[0060] For pad-drying and pad-steaming dyeing, the consumption of sodium carbonate, sodium sulfate, and water is calculated based on the weight of the fabric before and after padding, the mass fraction of each component in the dye liquor, and the mass fraction of each component in the fixing solution.

[0061] m d =m1-m0(4) m g =m3-m2(5) m5=m g ×w2(6) m6=m g ×w3(7) m w =m d ×(1-w1)+m g ×(1-w2-w3)(8) In the formula, m d and m g These represent the mass of dye liquor and the mass of fixing liquor retained on the fabric during the dye liquor padding and fixing liquor padding processes, respectively; m0, m1, m2, and m3 represent the fabric mass before dye liquor padding, after dye liquor padding, after dye liquor padding and drying, and after subsequent fixing liquor padding, respectively; m5, m6, and m w The numbers represent the masses of Na2CO3, Na2SO4, and water consumed, respectively; w1, w2, and w3 represent the mass fractions of dye in the dyeing solution, Na2CO3 in the fixing solution, and Na2SO4 in the fixing solution, respectively.

[0062] Resource-related carbon emissions for microfluidic droplet jet dyeing and conventional pad-dry / pad-steam dyeing were calculated using the emission factor method. This method follows product carbon footprint and life cycle assessment. The functional unit is defined as the dyeing of 1000 kg of cotton fabric. This calculation represents a portion of the carbon footprint of the dyeing process, as it only includes emissions related to resource consumption.

[0063] The comparison results of microfluidic droplet jet (MDJ) staining and comparative example 1 (PDPS) staining in terms of resource consumption and wastewater pollutant load are as follows: Figure 8 As shown, (a) dye consumption; (b) water consumption; (c) Na2CO3 consumption; (d) Na2SO4 consumption; (e) carbon emissions related to resource input; (f) wastewater color; (g) total dissolved solids (TDS) of wastewater; (h) pH value of wastewater; and (i) chemical oxygen demand (COD) of wastewater.

[0064] Digital scan images of the microfluidic droplet jet-dyed fabrics obtained in Examples 1-4 are shown below. Figure 9 As shown, (a) CI Reactive Black 5; (b) CI Reactive Red 195; (c) CI Reactive Yellow 15; (d) CI Reactive Blue 49.

[0065] Digital scan images of the microfluidic droplet jet double-sided dyed fabrics obtained in Examples 1-4 are shown below. Figure 10 As shown, the front side: (a1) CI Reactive Yellow 15; (b1) CI Reactive Red 195; (c1) CI Reactive Blue 49; (d1) CI Reactive Black 5. The back side: (a2) CI Reactive Yellow 15; (b2) CI Reactive Red 195; (c2) CI Reactive Blue 49; (d2) CI Reactive Black 5.

[0066] The digital scan image of the double-sided colorless fabric obtained in Example 5 is shown below. Figure 11 As shown, (a) CI Reactive Red AS raw powder; (b) CI Reactive Black 5. The colors on both sides are clear and there is no bleed-through.

[0067] The ultra-depth fabric images and cross-sectional views of the microfluidic droplet jet single-sided dyed fabrics obtained in Examples 1-4 are shown below. Figure 12As shown, the ultra-depth fabric diagrams are as follows: (a) CI Reactive Black 5; (b) CI Reactive Red 195; (c) CI Reactive Yellow 15; (d) CI Reactive Blue 49; and the cross-sectional diagrams are as follows: (e) CI Reactive Black 5; (f) CI Reactive Red 195; (g) CI Reactive Yellow 15; and (h) CI Reactive Blue 49. As can be seen from the figures, the single-sided dyed fabric obtained by the method described in this invention exhibits no contamination on the non-target side, uniform dyeing on the target side, and achieves high colorfastness. The penetration depth and permeability data of the microfluidic droplet jet single-sided dyed fabrics obtained in Examples 1-4 are shown in the figures below. Figure 13 As shown, through Figure 12 Microscopic images of the fabric cross-section were obtained, and the penetration depth of the dye into the fabric and the total fabric thickness were determined using ImageJ software. The penetration rate was calculated as the ratio of the penetration depth to the fabric thickness, and the error bars represent the data deviation from multiple parallel tests.

Claims

1. A reactive dyeing method based on microfluidic droplet jetting, characterized in that, Includes the following steps: (1) Preparation of dyeing solution and fixing alkali solution: Prepare the dyeing solution and fixing alkali solution for reactive dyes separately, and store them separately; (2) Microfluidic online mixing: The dyeing solution and the fixing alkali solution are delivered into the microfluidic chip mixing device, and online mixing is completed instantaneously in the channel by convection diffusion to obtain a mixed dyeing working solution. The online mixing is completed before spraying and the mixing time does not exceed 5 minutes. (3) Microdroplet jetting and deposition: The mixed dyeing working solution is atomized and sprayed onto the surface of the target fabric through a nozzle, forming micro-droplet deposition to achieve single-sided dyeing. (4) Steam color fixing: Steam fixation is performed on fabrics with deposited mixed dye liquor.

2. The reactive dyeing method based on microfluidic droplet jetting according to claim 1, characterized in that, The color-fixing alkaline solution mentioned in step (1) is an aqueous solution of sodium carbonate.

3. The reactive dyeing method based on microfluidic droplet jetting according to claim 1, characterized in that, The microfluidic chip mixing device described in step (2) has a Y-shaped or T-shaped channel with a channel diameter of 800-1000μm.

4. The reactive dyeing method based on microfluidic droplet jetting according to claim 1, characterized in that, The nozzle in step (3) is a coaxial atomizing nozzle, with the inner tube of which is filled with mixed dyeing working solution and the outer tube filled with compressed air. The pressure of the compressed air is 0.05-0.15 MPa.

5. The reactive dyeing method based on microfluidic droplet jetting according to claim 1, characterized in that, In step (3), the distance between the nozzle and the target surface of the fabric is 5-15cm, and the scanning interval is 4-7mm.

6. The reactive dyeing method based on microfluidic droplet jetting according to claim 1, characterized in that, The flow rate of the mixed staining working solution in step (3) is 5-20 mL / h.

7. The reactive dyeing method based on microfluidic droplet jetting according to claim 2, characterized in that, The reactive dye in step (1) is selected from one or more of CI Reactive Black 5, CI Reactive Red 195, CI Reactive Red AS raw powder, CI Reactive Yellow 15, and CI Reactive Blue 49. The steam fixation time in step (4) is 3-10 min.

8. The reactive dyeing method based on microfluidic droplet jetting according to claim 7, characterized in that, The concentration and steaming time of the sodium carbonate aqueous solution are set according to the type of dye: CI Active Black 5: Sodium carbonate aqueous solution concentration 30 g / L, steaming time 3 min; CI Active Red AS Powder: Sodium carbonate aqueous solution concentration 30 g / L, steaming time 3 min; CI Reactive Red 195: Sodium carbonate aqueous solution concentration 30 g / L, steaming time 4 min; CI Active Yellow 15: Sodium carbonate aqueous solution concentration 20 g / L, steaming time 4 min; CI Reactive Blue 49: Sodium carbonate aqueous solution concentration 40 g / L, steaming time 10 min.

9. The reactive dyeing method based on microfluidic droplet jetting according to claim 1, characterized in that, The method also includes performing microfluidic online mixing and microdroplet spraying and deposition on both sides of the fabric to achieve double-sided same-color or double-sided different-color dyeing.

10. An apparatus for a reactive dyeing method based on microfluidic droplet jetting as described in any one of claims 1-9, characterized in that, include: The device includes at least one microfluidic chip mixing device, at least one coaxial atomizing nozzle, at least two liquid storage containers, an injection pump for controlling the liquid flow rate, a scanning platform for controlling the relative motion between the nozzle and the fabric, and a steaming unit.

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