Method for antibacterial treatment of functional textile fabric

Abstract

This invention relates to the field of textile finishing technology and discloses a method for antibacterial treatment of functional textile fabrics. The method includes immersing and pre-drying a pre-treated pure cotton fabric in a first working solution containing a multifunctional crosslinking agent; coating one side of the fabric with a second working solution containing a cationic antibacterial agent using a microfoam application method; subjecting the fabric to a temperature gradient baking process, in which the first stage triggers the vaporization of free water at 90°C to 100°C, and the second stage raises the temperature to 130°C to 140°C to complete the catalytic crosslinking reaction; finally, the fabric is washed and dried with hot air. The single-sided application of microfoam blocks direct contact between anions and cations in the working solution, preventing electrostatic complexation that could lead to demulsification and failure of the bath solution; simultaneously, the temperature gradient baking promotes the penetration of antibacterial components into the fiber interior and the formation of a covalent crosslinking network with the substrate, thus improving the wash fastness of the antibacterial treated fabric.

Description

Technical Field

[0001] This invention relates to the field of textile finishing technology, specifically to an antibacterial treatment method for functional textile fabrics. Background Technology

[0002] Pure cotton fabrics are widely used in daily life due to their excellent moisture absorption and breathability, but they can also easily become a breeding ground for microorganisms. To impart antibacterial properties to cotton fabrics, industrial processes often employ finishing techniques that add antibacterial agents. In existing antibacterial finishing systems for pure cotton fabrics, positively charged cationic antibacterial polymers and multifunctional anionic crosslinking agents are typically mixed in the same bath, and the fabric is processed using conventional padding processes.

[0003] This co-bath treatment method has certain limitations in actual production. Cationic antibacterial agents and polyvalent anionic crosslinking agents are prone to electrostatic complexation reactions in the mixed solution, which can cause polymer molecular chain segment shrinkage and a decrease in the hydrophilicity of the system. As the treatment time increases, macroscopic phase separation occurs in the working solution, and insoluble colloidal particles precipitate, causing the bath solution to demulsify and fail, affecting the stability of continuous fabric processing.

[0004] Meanwhile, conventional co-bath padding processes rely primarily on the mechanical extrusion of rollers to allow the working solution to adhere, making it difficult for larger molecular weight antibacterial components to penetrate deep into the amorphous regions within the cotton fibers. This results in most of the antibacterial agent remaining only on the fabric surface. This distribution leads to insufficient covalent bonding between the antibacterial agent and cellulose macromolecules. When the fabric undergoes washing and mechanical friction during daily use, the surface antibacterial components are easily detached, causing the fabric to lose its antibacterial sites, resulting in poor overall wash fastness and an inability to maintain long-term antibacterial function. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides an antibacterial treatment method for functional textile fabrics. This method solves the problem that in existing antibacterial finishing processes for cotton fabrics, cationic antibacterial agents and polyvalent anionic crosslinking agents easily undergo electrostatic complexation reactions in the same working bath, causing polymer molecular chain segment shrinkage and decreased hydrophilicity. This leads to macroscopic phase separation and the formation of insoluble colloidal particles, resulting in demulsification and failure of the bath solution. Simultaneously, conventional padding processes cannot promote the deep penetration of antibacterial macromolecules into the fiber interior, resulting in low covalent bonding efficiency and poor wash fastness of the fabric.

[0006] To achieve the above objectives, the present invention provides the following technical solution: an antibacterial treatment method for functional textile fabrics, comprising the following steps: The pretreated pure cotton woven plain fabric is continuously introduced into the padding tank containing the first working solution for double immersion and double padding treatment, and the fabric padding rate is controlled between 65% and 75%. The impregnated fabric is fed into an infrared pre-drying machine for controlled moisture pre-drying, and the absolute moisture content of the fabric is controlled to be between 15% and 20% when it is pre-dried. The pre-dried semi-dry fabric is fed into a foam finishing machine, and the second working liquid micro foam is coated on one side of the fabric using a slit applicator. The amount of foam applied is controlled to be between 20% and 30% of the dry weight of the fabric. The fabric is directly fed into a multi-box tenter frame for temperature gradient baking. In the first stage, the fabric is treated at 90°C to 100°C for 90 to 120 seconds to trigger free water vaporization and delay electrostatic assembly. In the second stage, the temperature is rapidly increased to 130°C to 140°C for 90 to 120 seconds to complete the eutectic catalytic crosslinking reaction. After baking, the fabric is continuously washed with warm water at 40°C to 50°C to remove free inorganic salts and unreacted substances, and finally dried with conventional hot air at 100°C to 110°C. The first working fluid contains a multifunctional crosslinking agent, a crosslinking catalyst, and industrial-grade glycerol that acts as a hydrogen bond conformation occupier or a eutectic precursor. The second working solution, the foaming mother liquor, contains cationic antibacterial agents, neutral inorganic salts that provide charge shielding, nonionic foaming agents, and foam stabilizers.

[0007] By adopting the above technical solution, the non-contact, single-sided foam application method replaces the traditional co-bath mixing and rolling, physically blocking the reverse diffusion path from the first working liquid to the second working liquid, thus preventing the contact complexation of anions and cations in the working liquid. Combined with a temperature gradient baking process and a specific reagent combination, the following reaction mechanism is achieved: In the first stage of temperature gradient baking, when the system is in the temperature range of 90℃ to 100℃, free water vaporizes, and the concentration of neutral inorganic salts increases with the evaporation of water. The charge shielding effect of ions weakens the electrostatic attraction between the cationic antibacterial agent and the negative charge on the surface of cellulose, promoting the penetration of the cationic antibacterial agent into the amorphous region inside the fiber, changing the distribution state of the antibacterial macromolecules, and achieving delayed electrostatic assembly.

[0008] In the second stage of temperature gradient baking, the system temperature rises to 130℃ to 140℃. Industrial-grade glycerol and a multifunctional crosslinking agent construct a eutectic microenvironment within the fabric, reducing the activation energy required for the crosslinking reaction. The following chemical reaction steps occur in this stage: Step 1: The multifunctional crosslinking agent undergoes a dehydration reaction under crosslinking catalyst and high temperature conditions to form an acid anhydride intermediate; Step 2: The acid anhydride intermediate undergoes an esterification reaction with the hydroxyl groups on the surface of cellulose; Step 3: The acid anhydride intermediate undergoes an acylation reaction with the terminal amino and imino groups of the cationic antibacterial agent that penetrates deep into the fiber.

[0009] Therefore, the following effects are achieved: a three-dimensional macromolecular covalently cross-linked network is formed between the cationic antibacterial agent and the cellulose matrix. This covalent network structure is stable and can resist chemical stripping and mechanical friction during the washing process. The antibacterial polymer that penetrates into the yarn can still provide contact bactericidal sites after the surface fibers of the fabric are worn, maintaining the long-term antibacterial activity of the fabric and improving the wash fastness of the antibacterial finishing.

[0010] Preferably, the first working solution is made from raw materials containing the following concentrations: 30 g / L to 50 g / L of a multifunctional crosslinking agent, 15 g / L to 25 g / L of a crosslinking catalyst, and 15 g / L to 25 g / L of industrial-grade glycerol. The multifunctional crosslinking agent is citric acid, the crosslinking catalyst is sodium hypophosphite, and the pH of the first working solution is calibrated to the range of 3.2 to 3.5 using a 10% (w / w) sodium hydroxide aqueous solution.

[0011] By employing the above technical solution, citric acid can provide sufficient carboxyl reaction sites, and sodium hypophosphite enhances the catalytic efficiency of dehydration to anhydride. Maintaining the pH value within a specific acidic range helps maintain the dissociation equilibrium of the system, preventing premature cross-linking of citric acid during the padding stage and ensuring the uniform distribution and chemical stability of the primer on the fabric surface.

[0012] Preferably, the second working foaming stock solution is made from raw materials containing the following concentrations: 10 g / L to 20 g / L cationic antibacterial agent, 15 g / L to 20 g / L neutral inorganic salt, 2 g / L to 4 g / L nonionic foaming agent, and 0.5 g / L to 1.5 g / L foam stabilizer. The cationic antibacterial agent is polyhexamethylene biguanide, the neutral inorganic salt is sodium chloride, the nonionic foaming agent is alkyl polysaccharide glycoside, and the foam stabilizer is hydroxyethyl cellulose.

[0013] By employing the above technical solution, alkyl polysaccharides and hydroxyethyl cellulose form a nonionic surfactant system that will not electrostatically repel or complex with positively charged polyhexamethylene biguanide. Sodium chloride provides sodium and chloride ions to perform charge shielding, allowing the polymer chains to unwind in the liquid matrix.

[0014] Preferably, the pH value of the foaming mother liquor of the second working solution is 6.0 to 6.2; the average pore diameter of the microfoam of the second working solution is between 50 μm and 100 μm, and the foaming ratio is constant between 5 and 8 times.

[0015] By adopting the above technical solution, microfoams with specific pore size and magnification possess rheological stability and shear resistance, ensuring uniform coating and release of the second working fluid on one side of the fabric, and preventing excessive liquid penetration that could cause mixing of the agents on the front and back of the fabric.

[0016] Preferably, the preparation process of the first working solution includes: injecting 70% of the rated volume of deionized water into a mixing vessel equipped with a mechanical stirrer, setting the stirring speed to 150 rpm to 200 rpm, and slowly adding the formulated amount of multifunctional crosslinking agent, crosslinking catalyst, and industrial-grade glycerol sequentially, stirring continuously for 20 to 30 minutes until all solid components are completely dissolved in the aqueous phase to form a homogeneous transparent solution. While continuously stirring, the online pH monitor of the mixing vessel is turned on, and a 10% sodium hydroxide aqueous solution is slowly added dropwise to the system at a flow rate of 10 mL / min to 20 mL / min using a metering pump to dynamically monitor the dissociation equilibrium of the system. After stopping the addition of sodium hydroxide solution, deionized water is added to the mixing vessel to the rated volume, and stirring continues for 10 minutes to ensure uniform system concentration.

[0017] By adopting the above technical solution, the adjustment method combining dynamic monitoring and slow addition avoids local pH fluctuations, ensures that the solution is in a homogeneous and stable state, and improves the dispersion uniformity of industrial-grade glycerol as a conformational site occupier in the system.

[0018] Preferably, the preparation process of the second working solution foaming mother liquor includes: injecting 80% of the rated volume of deionized water into a mixing vessel equipped with a homogenizing emulsification shearing function; sequentially adding the formulated amount of cationic antibacterial agent and neutral inorganic salt and stirring for 15 minutes; reducing the stirring speed to 50 rpm to 80 rpm; then slowly adding the formulated amount of nonionic foaming agent and foam stabilizer and continuing to gently stir and mix for 20 minutes; adding glacial acetic acid, monovalent organic acid, or sodium hydroxide solution dropwise to the system to precisely adjust the pH value of the system; then adding deionized water to the rated volume to obtain a transparent and stable foaming mother liquor; pumping the foaming mother liquor through a closed pipeline into the stator and rotor mixing chamber of an industrial dynamic foaming machine; and simultaneously injecting constant pressure compressed air into the mixing chamber to prepare homogeneous microfoam.

[0019] By employing the above technical solutions, segmented control of stirring speed prevents the formation of large bubbles in the system due to the initial foaming agent. Monovalent organic acids or sodium hydroxide are used to adjust the pH value, avoiding the introduction of polyvalent anions into the system, preventing the precipitation of polymer macromolecules, and ensuring that the antibacterial foam liquid possesses stable foaming capabilities.

[0020] This invention provides an antibacterial treatment method for functional textile fabrics. It has the following beneficial effects: 1. This invention employs a microfoam single-sided application method to coat a second working solution containing a cationic antibacterial agent, forming a physical isolation between the second working solution and the first working solution containing a polyvalent anionic crosslinking agent during the padding process. This process changes the traditional co-bath mixing and finishing mode, avoiding direct contact between anions and cations in the liquid state and the resulting electrostatic complexation reaction, preventing the precipitation of insoluble colloidal particles, and maintaining the homogeneous and stable state of the working solution.

[0021] 2. This invention employs a two-stage temperature gradient baking process. In the first stage, during temperature-controlled vaporization, the concentration of inorganic salts increases as moisture evaporates, utilizing the charge shielding effect of ions to promote the penetration of cationic antibacterial agents into the fiber interior. In the second stage, the increased temperature triggers a cross-linking reaction, causing the antibacterial macromolecules to form a covalent network with the cellulose matrix. This structure allows the fabric to maintain its antibacterial activity after washing and rubbing, improving the wash fastness of the antibacterial finish.

[0022] 3. The present invention introduces industrial-grade glycerol into the first working solution, which, together with the multifunctional crosslinking agent, constructs a low eutectic microenvironment inside the fabric, reducing the activation energy of the crosslinking reaction. This allows the dehydration to anhydride formation and subsequent esterification and acylation reactions to be completed at 130°C to 140°C. While ensuring the effective grafting of antibacterial macromolecules, it reduces the damage to the strength of pure cotton fabrics caused by conventional high-temperature baking, thus maintaining the physical and mechanical properties of the fabric. Attached Figure Description

[0023] Figure 1 This is a comparison diagram of the heat flux curves of the differential scanning calorimeter of the present invention; Figure 2 This is a line graph showing the change in citric acid reaction conversion rate at different baking temperatures according to the present invention. Figure 3 The test results of the electrolyte of the present invention on the macroscopic effect of the penetration depth of the cationic polymer are grouped into bar charts. (a) is a comparison chart of the absolute K / S values ​​of the samples under different rubbing times, and (b) is a comparison chart of the retention rate of K / S values ​​after different rubbing times compared with the initial surface. Figure 4 This is a line graph showing the turbidity change of the second working fluid under different continuous operating times according to the present invention. Figure 5 The graphs show the changes in the antibacterial rate of fabric samples against representative test bacteria under different washing cycles according to the present invention. (a) is a graph showing the antibacterial rate test results against Escherichia coli, and (b) is a graph showing the antibacterial rate test results against Staphylococcus aureus. Figure 6 This is a bar chart comparing the apparent yellowing index (YI) of the fabric samples of the present invention under different finishing processes; Figure 7 The bar charts showing the comparison of the macroscopic bending length of the fabric samples after different process treatments are shown below. (a) is a graph showing the test results of the warp bending length of the fabric, and (b) is a graph showing the test results of the weft bending length of the fabric. Detailed Implementation

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Preparation Examples 1-2: Preparation Example 1: This preparation example provides a method for preparing a primer activation solution (first working solution), including the following steps: (1) In a conventional industrial mixing vessel equipped with a mechanical stirring device, inject 70% of the rated volume of deionized water, turn on the stirring, and set the stirring speed to 150~200 rpm; (2) Add the formula amount of multifunctional crosslinking agent (citric acid), crosslinking catalyst (sodium hypophosphite, NaH2PO2) and hydrogen bond conformation occupier / eutectic precursor (industrial grade glycerol) to the mixing tank in sequence, and stir continuously for 20 to 30 minutes until all solid components are completely dissolved in the aqueous phase to form a homogeneous transparent solution. (3) Under continuous stirring, turn on the online pH monitor of the mixing vessel, and slowly add 10% sodium hydroxide (NaOH) aqueous solution to the system at a flow rate of 10~20mL / min using a metering pump, dynamically monitor the dissociation equilibrium state of the system, until the pH value of the solution is accurately calibrated to the range of 3.2~3.5; (4) Stop adding sodium hydroxide solution, add deionized water to the mixing tank to the rated volume, and continue stirring for 10 minutes to make the system concentration uniform, thus obtaining the primer activation solution (first working solution) to be used.

[0026] Preparation Example 2: This preparation example provides a method for preparing an antibacterial foam liquid (second working solution), including the following steps: (1) In another mixing vessel equipped with homogenization emulsification shearing function, inject 80% of the rated volume of deionized water and turn on the stirring device; (2) Add the cationic antibacterial agent (polyhexamethylene biguanide, PHMB aqueous solution) and neutral inorganic salt (sodium chloride, NaCl) in sequence, stir for 15 minutes to allow the polymer chains to fully extend and the ionic strength regulator to be evenly distributed in the system; (3) Reduce the stirring speed to 50-80 rpm, then slowly add the amount of nonionic foaming agent (alkyl polyglycoside, APG, concentration of 2-4 g / L) and foam stabilizer (hydroxyethylcellulose, HEC, concentration of 0.5-1.5 g / L) in the formula, and continue to gently stir and mix for 20 minutes; APG, as a nonionic surfactant, will not form an electrostatic complex with PHMB; (4) Add very dilute glacial acetic acid or monovalent organic acid (such as acetic acid) / sodium hydroxide solution to the system to precisely adjust and stabilize the pH value of the system in the range of 6.0~6.2, so as to avoid the introduction of polyvalent anions and the precipitation of polymer. Then add deionized water to the rated volume to obtain a transparent and stable foaming mother liquor. (5) The above foaming mother liquor is pumped into the stator and rotor mixing chamber of the industrial dynamic foaming machine through a closed pipeline, while constant pressure compressed air is injected into the mixing chamber. The gas-liquid ratio of the liquid flow rate and the compressed air intake is precisely adjusted through the control panel of the foaming machine. Under the action of mechanical shearing, a homogeneous microfoam with an average pore diameter of 50~100μm and a constant foaming ratio of 5~8 times is prepared, which is the antibacterial foam liquid (second working liquid) to be directly applied.

[0027] Examples 1-3: Example 1: This example provides an antibacterial treatment method for functional textile fabrics, including the following steps: (1) Preparation of primer activation solution: Following the method of preparation example 1, 30 g / L of citric acid, 15 g / L of sodium hypophosphite (NaH2PO2) and 15 g / L of glycerol were added sequentially to deionized water. After stirring and dissolving, the pH value was titrated to 3.2 using a 10% NaOH solution to obtain the first working solution. (2) Base coating padding: The pretreated pure cotton woven plain fabric is continuously introduced into the padding tank containing the first working liquid for double dip and double padding treatment. The mechanical pressure of the padding rollers is adjusted to control the fabric's padding rate at 65%. (3) Moisture-controlled pre-drying: The impregnated fabric is fed into the infrared pre-drying machine in a flat width, and the exhaust temperature and machine speed are controlled to keep the absolute moisture content of the fabric at 15% when it is pre-dried; (4) Preparation of antibacterial foaming liquid: Following the method in Preparation Example 2, 10 g / L of polyhexamethylene biguanide (PHMB), 15 g / L of sodium chloride (NaCl), 2 g / L of alkyl polyglucoside (APG), and 0.5 g / L of hydroxyethyl cellulose (HEC) were added sequentially to deionized water. After stirring evenly, the pH of the system was finely adjusted to 6.0 using a dilute acetic acid / sodium hydroxide solution to obtain the foaming mother liquor. The foaming mother liquor was pumped into a dynamic foaming machine, and compressed air was injected to prepare homogeneous microfoam (second working liquid) with a foaming ratio of 5 times. (5) Foam application on one side: The semi-dry fabric obtained in step (3) is fed into a foam finishing machine. A slit applicator is used to evenly coat the microfoam on one side of the fabric. The control system is controlled to make the amount of foam applied 20% of the dry weight of the fabric. (6) Temperature gradient baking: The fabric is directly fed into a multi-box tenter frame. In the first stage, it is treated at 90°C for 90 seconds to trigger free water vaporization and delay electrostatic assembly. In the second stage, the temperature is rapidly increased to 130°C and baked for 90 seconds to complete the eutectic catalytic crosslinking reaction. (7) Finishing: After baking, the fabric is continuously washed with warm water at 40°C to remove free inorganic salts and unreacted substances, and finally dried with conventional hot air at 100°C.

[0028] Example 2: This example provides an antibacterial treatment method for functional textile fabrics, including the following steps: (1) Preparation of primer activation solution: Following the method of preparation example 1, 40 g / L of citric acid, 20 g / L of sodium hypophosphite (NaH2PO2) and 20 g / L of glycerol were added sequentially to deionized water. After stirring and dissolving, the pH value was titrated to 3.35 using a 10% NaOH solution to obtain the first working solution. (2) Base coating padding: The pretreated pure cotton woven plain fabric is continuously introduced into the padding tank containing the first working liquid for double dip and double padding treatment. The mechanical pressure of the padding rollers is adjusted to control the fabric's padding rate at 70%. (3) Moisture-controlled pre-drying: The impregnated fabric is fed into the infrared pre-drying machine in a flat width, and the exhaust temperature and machine speed are controlled to keep the absolute moisture content of the fabric at 17.5% when it is pre-dried; (4) Preparation of antibacterial foaming liquid: Following the method in Preparation Example 2, 15 g / L of polyhexamethylene biguanide (PHMB), 17.5 g / L of sodium chloride (NaCl), 3 g / L of alkyl polyglucoside (APG), and 1.0 g / L of hydroxyethyl cellulose (HEC) were added sequentially to deionized water. After stirring evenly, the pH of the system was finely adjusted to 6.1 using a dilute acetic acid / sodium hydroxide solution to obtain the foaming mother liquor. The foaming mother liquor was pumped into a dynamic foaming machine, and compressed air was injected to prepare homogeneous microfoam with a foaming ratio of 6.5 times (second working liquid). (5) Foam application on one side: The semi-dry fabric obtained in step (3) is fed into a foam finishing machine. A slit applicator is used to evenly coat the microfoam on one side of the fabric. The control system is set so that the amount of foam applied is 25% of the dry weight of the fabric. (6) Temperature gradient baking: The fabric is directly fed into a multi-box tenter frame. In the first stage, it is treated at 95°C for 105 seconds to trigger free water vaporization and delay electrostatic assembly. In the second stage, the temperature is rapidly increased to 135°C and baked for 105 seconds to complete the eutectic catalytic crosslinking reaction. (7) Finishing: After baking, the fabric is continuously washed with warm water at 45°C to remove free inorganic salts and unreacted substances, and finally dried with conventional hot air at 105°C.

[0029] Example 3: This example provides an antibacterial treatment method for functional textile fabrics, including the following steps: (1) Preparation of primer activation solution: Following the method of Preparation Example 1, 50 g / L of citric acid, 25 g / L of sodium hypophosphite (NaH2PO2) and 25 g / L of glycerol were added sequentially to deionized water. After stirring and dissolving, the pH value was titrated to 3.5 using a 10% NaOH solution to obtain the first working solution. (2) Base coating and padding: The pretreated pure cotton woven plain fabric is continuously introduced into the padding tank containing the first working liquid for double dip and double padding treatment. The mechanical pressure of the padding rollers is adjusted to control the fabric's padding rate at 75%. (3) Moisture-controlled pre-drying: The impregnated fabric is fed into the infrared pre-drying machine in a flat width, and the exhaust temperature and machine speed are controlled to keep the absolute moisture content of the fabric at 20% when it is pre-dried; (4) Preparation of antibacterial foaming liquid: Following the method in Preparation Example 2, 20 g / L of polyhexamethylene biguanide (PHMB), 20 g / L of sodium chloride (NaCl), 4 g / L of alkyl polyglucoside (APG), and 1.5 g / L of hydroxyethyl cellulose (HEC) were added sequentially to deionized water. After stirring evenly, the pH of the system was finely adjusted to 6.2 using a dilute acetic acid / sodium hydroxide solution to obtain the foaming mother liquor. The foaming mother liquor was pumped into a dynamic foaming machine, and compressed air was injected to prepare homogeneous microfoam with a foaming ratio of 8 times (second working liquid). (5) Foam application on one side: The semi-dry fabric obtained in step (3) is fed into a foam finishing machine. A slit applicator is used to evenly coat the microfoam on one side of the fabric. The control system is set so that the amount of foam applied is 30% of the dry weight of the fabric. (6) Temperature gradient baking: The fabric is directly fed into a multi-box tenter frame. In the first stage, it is treated at 100°C for 120 seconds to trigger free water vaporization and delay electrostatic assembly. In the second stage, the temperature is rapidly increased to 140°C and baked for 120 seconds to complete the eutectic catalytic crosslinking reaction. (7) Finishing: After baking, the fabric is continuously washed with warm water at 50°C to remove free inorganic salts and unreacted substances, and finally dried with conventional hot air at 110°C.

[0030] Comparative Examples 1-5: Comparative Example 1: Compared with Example 2, the difference lies in the use of a conventional one-bath padding and high-temperature baking process: The first working solution and all effective components (excluding foaming agent and foam stabilizer) of the foaming mother liquor are mixed in the same bath to prepare a single working solution for single padding treatment (the padding rate is controlled at 70%). After pre-drying, steps (4) and (5) are not performed. The solution is directly put into the tenter frame and baked in a single stage at 160°C for 105 seconds. The rest are the same.

[0031] Comparative Example 2: The difference from Example 2 is that a non-contact foam application method is not used in step (5): Instead, the unfoamed mother liquor prepared in step (4) is used directly as the second working liquid tank liquid, and the semi-dry fabric obtained in step (3) is immersed in it for a conventional second immersion and padding treatment (the pressure of the rollers is adjusted to increase the liquid content of the fabric by an additional 25%), and the rest are the same.

[0032] Comparative Example 3: Compared with Example 2, the difference is that glycerol is not added when preparing the primer activation solution in step (1), but all other steps are the same.

[0033] Comparative Example 4: Compared with Example 2, the difference is that in step (4) when preparing the antibacterial foam liquid, sodium chloride (NaCl) is not added as an ionic strength regulator, while the rest are the same.

[0034] Comparative Example 5: Compared with Example 2, the difference is that the two-stage temperature gradient design was eliminated in the baking process of step (6): after the fabric completes the foam application, it does not undergo the first stage treatment at 95°C, but directly enters the high temperature zone of the setting machine and is subjected to a single-stage rapid baking at 135°C for 105 seconds. The rest are the same.

[0035] Test Examples 1-6: Test Example 1: Verification Test on the Reduction of Crosslinking Activation Energy in a Eutectic Microenvironment Take 50 mL of the first working solution prepared in Example 2 and 50 mL of the first working solution prepared in Comparative Example 3 for later use.

[0036] Cut several pieces of degreased pure cotton standard white cloth with a size of 10cm×10cm, immerse them in the two working solutions mentioned above, and adjust the roller pressure of the laboratory setting machine to control the roll residue rate of both groups of samples at 70%.

[0037] The soaked fabric samples were laid flat in a mesh belt infrared oven, the exhaust temperature was controlled, and the samples were taken out and weighed at regular intervals to ensure that the absolute moisture content of the samples was within the range of 17.5%, thus obtaining semi-dry samples for the experimental group and semi-dry samples for the control group.

[0038] Approximately 5 mg of fiber was cut from two groups of semi-dry samples and placed into an aluminum crucible of the differential scanning calorimeter, which was then pressed into a tablet and sealed. Under a nitrogen atmosphere with a flow rate of 50 mL / min, the temperature was scanned from 30 °C to 220 °C at a heating rate of 10 °C / min. The heat flux as a function of temperature was obtained, and the onset and peak temperatures of the endothermic peak were recorded.

[0039] Five pieces of each of the two semi-dry samples prepared above were placed in precision forced-air drying ovens with set temperatures of 120℃, 130℃, 135℃, 140℃ and 160℃ respectively and baked for 105 seconds.

[0040] Take out the roasted samples and place them in Erlenmeyer flasks with stoppers containing 100 mL of deionized water at 50 °C. Place them in a constant temperature water bath shaker and ultrasonically extract for 30 minutes to wash away the free citric acid and glycerol that have not undergone covalent bonding.

[0041] Pipette 50 mL of the extract into a titration vessel, add 3 drops of phenolphthalein indicator, and titrate with a 0.0512 mol / L sodium hydroxide standard solution until the solution turns a faint pink color that does not fade within half a minute. Record the volume of sodium hydroxide solution consumed.

[0042] The conversion rate of citric acid at different baking temperatures was calculated based on the difference between the initial citric acid content of the blank cloth sample and the residual citric acid in the extract.

[0043] Table 1. Conversion rate of citric acid and DSC thermal analysis parameters at different baking temperatures

[0044] Based on the data in Table 1, combined with Figure 1 A comparison of heat flux curves from differential scanning calorimetry (DSC) (the horizontal axis represents the test temperature, and the vertical axis represents the heat flux; the black dashed line represents the control group without glycerol, and the black solid line represents the experimental group with glycerol). In the control group without glycerol, the DSC endothermic peak onset temperature of citric acid was as high as 151.2℃. Combined with... Figure 2Line graph showing the change in citric acid reaction conversion rate at different baking temperatures (the horizontal axis represents the set constant baking temperature, and the vertical axis represents the crosslinking reaction conversion rate calculated by titration; the black dashed line with hollow square markings represents the control group, and the black solid line with solid circle markings represents the experimental group). The control group showed a lower reaction conversion rate in the low temperature range of 120℃ to 135℃, with a conversion rate of only 13.5% at 135℃, and reaching a conventional industrial crosslinking level of 67.4% at 160℃.

[0045] After the addition of glycerol, the thermodynamic properties of the system changed in the experimental group. The onset temperature of the DSC endothermic peak decreased to 114.6℃, and the peak temperature advanced to 128.3℃. The curve shows that due to the formation of a eutectic microenvironment, the endothermic peak of the crosslinking reaction shifted to the low-temperature region. The conversion rate of the experimental group reached 71.6% under the baking condition of 135℃, which is the same as the reaction level of the control group under the condition of 160℃, showing that the conversion rate of the experimental group was improved compared with that of the control group in the low-temperature range of 130℃ to 140℃.

[0046] After pure citric acid loses moisture during pre-drying, it readily crystallizes and precipitates on the fiber surface due to hydrogen bonding. The solid state restricts molecular mobility, requiring a high thermodynamic activation energy to form the five-membered cyclic anhydride intermediate needed for the reaction. Glycerol, acting as both a hydrogen bond donor and acceptor, constructs a eutectic microenvironment with citric acid during moisture evaporation. The hydroxyl groups of glycerol insert into and disrupt the rigid hydrogen bond network between citric acid molecules, preventing crystallization and maintaining the reaction system in a fluid, supercooled liquid phase after dehydration.

[0047] The liquid medium increases the collision frequency of reactant molecules and reduces mass transfer resistance, thus lowering the apparent activation energy of citric acid dehydration and cyclization. During baking, as the temperature increases, the electrostatically assembled polyhexamethylene biguanide and the hydroxyl groups on the cellulose substrate surface undergo nucleophilic substitution to replace the occupied glycerol, completing the covalent bonding of the macromolecular network. Test data quantify the compensating effect of the eutectic system on reaction kinetics and verify the feasibility of achieving crosslinking at 135℃ using this method.

[0048] Test Example 2: Macroscopic optical verification of the penetration depth (shielding effect) of electrolyte (NaCl) on cationic polymers Three fabric samples prepared in Example 2 and three fabric samples prepared in Comparative Example 4 were selected and cut into standard test samples with a size of 15cm×15cm.

[0049] Prepare a 0.5% (w / w) solution of Acid Red 18 and adjust the pH of the solution to 4.5 using glacial acetic acid.

[0050] Immerse the test sample in the dye solution and shake it in a 60°C water bath for 45 minutes, maintaining a liquor ratio of 1:30. Remove the sample and wash it continuously with deionized water until the washing solution is colorless. Air dry at room temperature.

[0051] The initial surface K / S value of the stained samples was determined using a benchtop spectrophotometer under a D65 standard light source. Five test points were randomly selected from different regions of each sample to collect data, and the arithmetic mean was calculated.

[0052] The test sample with the initial measurement completed was fixed on the test platform of the Martindale abrasion tester, fitted with a standard wool friction cloth, and the total number of friction cycles was set under a constant loading pressure of 9 kPa.

[0053] Stop the instrument after 500 and 1000 cycles respectively, remove the test sample, and use a soft brush to remove the free fiber debris from the surface.

[0054] The wear center area of ​​the test sample surface was measured again using a spectrophotometer. The K / S value after friction was recorded, and its retention rate relative to the initial surface K / S value was calculated.

[0055] Table 2. K / S values ​​and retention rates of samples under different rubbing cycles

[0056] According to Table 2 and Figure 3 , Figure 3 In (a), the horizontal axis corresponds to the initial state of the sample and the test stages after 500 and 1000 Martindale friction peels of the surface fibers. The vertical axis represents the measured K / S value. The light gray bars represent the control group without NaCl, and the dark gray bars represent the experimental group with NaCl. In the control group without NaCl, the initial surface K / S value of the sample was 13.82. After 500 and 1000 friction peels of the surface fibers, the K / S values ​​decreased to 6.17 and 2.51, respectively, showing the decrease in dye color depth in the control group during the friction peel process.

[0057] The retention rate after 1000 rubs was only 18.1%. The initial surface K / S value of the experimental group with added NaCl was 9.46, and after 500 and 1000 rubs under the same conditions, the K / S values ​​remained at 8.85 and 8.12, respectively. Figure 3 (b) The horizontal axis represents the set friction stage, and the vertical axis represents the relative retention rate percentage. The light gray and dark gray bars correspond to the control group and the experimental group, respectively. The retention rate of the experimental group after 1000 frictions reached 85.8%. Through the difference in relative values, the charge shielding effect of NaCl was quantitatively verified to promote the polymer to enter the amorphous region inside the fiber and avoid single enrichment on the surface of the fabric.

[0058] Polyhexamethylene biguanide (PHB) is a multivalent cationic polymer, while Acid Red 18 is an anionic dye. The two bind electrostatically to produce color, and the macroscopic K / S value is positively correlated with the concentration of the cationic polymer in the local area. The control group showed a higher initial K / S value and poor abrasion resistance, indicating that the polymer was retained and accumulated on the fabric surface. Without the addition of inorganic salts, PHB carries a positive charge. When it comes into contact with the negatively charged cotton fiber substrate, electrostatic attraction occurs at the interface. This electrostatic assembly leads to the deposition of polymer chains on the fiber surface, forming a macromolecular barrier layer. The steric hindrance effect hinders the diffusion of the remaining polymer molecules in the working fluid into the fiber's internal pores, resulting in electrostatic lock-in.

[0059] The experimental system contained sodium and chloride ions at varying concentrations. These ions formed an ionic atmosphere around the polyvalent cation centers of the polymer and the anionic centers on the fiber surface, reducing the electrostatic attraction between opposite charges and shortening the Debye length. This charge shielding effect inhibited the instantaneous adsorption of the polymer to the fiber surface, allowing polymer molecules more diffusion time in the aqueous phase. Under the influence of concentration gradient and capillary effect, these molecules penetrated into the yarn interior and the amorphous region of the fiber. When the fabric entered the pre-drying stage, moisture evaporation altered the ionic strength of the system, changed the solubility of the salt, and removed the shielding effect. The polymer molecules that had penetrated into the interior then underwent electrostatic and hydrogen bonding assembly with the cellulose and citric acid network of the primer, providing a distribution for subsequent covalent crosslinking. The data confirmed that the charge shielding environment constructed by sodium chloride altered the mass transfer kinetics of cationic macromolecules in the porous substrate.

[0060] Test Example 3: Stability Test of Working Fluid in Continuous Processing Prepare a 500-meter-long pure cotton woven fabric, and use the first working solution of Example 2 for padding treatment. Adjust the roller pressure to maintain the padding rate at 70%, and pre-dry it in a hot air drying room until the absolute moisture content of the fabric is about 15%, and then wind it up for later use.

[0061] The second working fluid prepared in Comparative Example 5 was injected into the padding tank at the front of the setting machine; at the same time, the second working fluid prepared in Example 2 was injected into the working fluid storage tank of the foam generation system, and the foaming ratio was adjusted to 1:5.

[0062] The continuous experimental setup was started, and the pretreated semi-dry fabric was continuously passed through the two application devices at a traction speed of 15 m / min. Comparative Example 5 used a conventional two-roll padding method; Example 2 used a closed-loop doctor blade foam system for single-sided coating.

[0063] During continuous fabric operation, based on the actual liquid carrying capacity of the fabric, an automatic liquid replenishment system continuously replenishes the padding tank or storage tank with fresh second working liquid of the same concentration to maintain the operating liquid level or reserve within the set dynamic balance range.

[0064] When the equipment runs continuously for 0 min, 15 min, 30 min, 60 min, 120 min and 180 min, a sampler is used to collect 50 mL working fluid samples from 5 cm below the liquid surface of the impregnation tank in Comparative Example 5 and from the liquid outlet valve of the storage tank in Example 2.

[0065] After shaking the extracted liquid sample well, transfer it to a standard glass cuvette and place it in a benchtop turbidity meter. Measure the turbidity value at room temperature. Read the data three times for each sample and calculate the arithmetic mean. The unit of measurement is NTU.

[0066] Table 3. Turbidity changes of the second working fluid under different continuous operating times

[0067] Based on the data in Table 3, combined with Figure 4 Line graph showing the turbidity change of the second working fluid under different continuous operating times (the horizontal axis represents the continuous processing time of the equipment, and the vertical axis represents the turbidity value; the black dashed line with hollow square marks represents the control group, and the black solid line with solid circle marks represents the experimental group). In the control group using the double-bath immersion method, the initial turbidity of the second working fluid was 2.1 NTU.

[0068] As the continuous processing time progressed, the turbidity of the liquid in the rolling tank showed an upward trend. After 60 minutes of operation, the turbidity reached 114.8 NTU, and by 180 minutes it had risen to 412.9 NTU. At this point, the liquid appeared macroscopically milky and turbid with the precipitation of flocculent material. The figure shows that during the 3-hour continuous processing test, the turbidity of the control group's liquid exhibited a non-linear increase and demulsification occurred. In the experimental group using the foam application method, the initial turbidity of the second working liquid was 2.3 NTU. During the 180-minute continuous application process, the turbidity of the working liquid in the storage tank fluctuated between 2.2 and 3.1 NTU without change. The turbidity of the experimental group's working liquid remained at a low level, and no flocculation occurred.

[0069] In the two-bath padding process, semi-dry fabric carrying components of the first working solution is directly immersed in the second bath. Liquid-phase contact triggers concentration gradient-driven mass transfer, causing uncrosslinked citric acid molecules on the fabric surface and within its pores to desorb and diffuse into the second bath solution. In aqueous solution, citric acid dissociates into polyvalent anionic carboxyl groups, which electrostatically attract the free polyvalent cationic polyhexamethylene biguanide in the second working solution, resulting in a polyelectrolyte complexation reaction. Due to this complexation reaction, polymer molecules lose their hydrophilicity and aggregate and precipitate. This not only produces a large number of insoluble particles, causing turbidity in the bath solution, but also ultimately leads to system demulsification failure.

[0070] The single-sided foam application method utilizes gas to expand the working fluid, and the applicator evenly coats the foam onto one side of the fabric surface. Under mechanical pressure and capillary force, the foam ruptures, and the liquid film penetrates into the fiber interior, preventing large-area liquid-phase contact between the fabric and the working fluid master bath. This non-contact application method blocks the backflow of citric acid from the first bath into the second bath master bath, avoiding contact between anions and cations in the working fluid. Turbidity test results show that changing the application method avoids the problems of reverse desorption between components and polyelectrolyte demulsification, ensuring the thermodynamic stability of the processing fluid and meeting the process requirements of continuous industrial production.

[0071] Test Example 4: Antibacterial Properties and Wash Fastness Test Untreated blank pure cotton fabric, the antibacterial fabric prepared in Comparative Example 1, and the antibacterial fabric prepared in Example 2 were cut and subjected to accelerated washing using a washing machine conforming to GB / T 3921 and an AATCC standard reference detergent. A single washing cycle was set to be equivalent to 5 regular household washes, and dried samples were obtained corresponding to 0, 20, and 50 equivalent household washing cycles, respectively.

[0072] Fabric samples from each washing stage were cut into pieces of approximately 5mm × 5mm. 0.75g of each piece was accurately weighed and placed into a 250mL Erlenmeyer flask with a stopper, and then subjected to high-temperature and high-pressure sterilization.

[0073] Prepare concentrations of 1.0 × 10⁻⁶. 5 CFU / mL up to 3.0 × 10⁻⁶ 5 Inoculation suspensions of Escherichia coli (ATCC 25922) and Staphylococcus aureus (ATCC 6538) at CFU / mL.

[0074] Add 50 mL of the above inoculum suspension to each Erlenmeyer flask containing the fabric sample. Fix the flask on a constant temperature water bath shaker and incubate at 37°C with continuous shaking at 150 r / min for 24 hours.

[0075] Remove the suspension after shaking culture and perform serial dilutions using physiological saline. Take 1 mL of the sample solution at each dilution and inoculate it into a nutrient agar dish.

[0076] Invert the petri dishes and incubate them in a biochemical incubator at 37°C for 24 to 48 hours. Use a colony counter to record the number of viable colonies generated in each petri dish, multiply by the corresponding dilution factor, and calculate the viable bacterial concentration in each suspension.

[0077] Based on the difference in viable bacteria concentration between the blank pure cotton base fabric group and each experimental group, the antibacterial rate of different samples against the two test bacteria under each washing cycle was calculated.

[0078] Table 4. Antibacterial rate test results of samples after different washing cycles

[0079] Based on the data in Table 4, combined with Figure 5 Line graph showing the change in the antibacterial rate of fabric samples against representative test species after different washing cycles ( Figure 5 (a) shows the results of the inhibition rate test against Escherichia coli. Figure 5 (b) Results of the antibacterial rate test against Staphylococcus aureus. The horizontal axis of both sub-graphs represents the number of routine household washes, and the vertical axis represents the antibacterial rate calculated by viable cell counting. The black dashed lines marked with hollow squares in the graphs represent the control group prepared using the conventional padding method, and the black solid lines marked with solid circles represent the experimental group prepared using deep penetration combined with in-situ cross-linking finishing. In the blank control group without antibacterial treatment, the antibacterial rate at each washing stage was 0.

[0080] The fabric of Comparative Example 1, prepared using the conventional padding method, achieved initial antibacterial rates of 98.7% and 99.2% against *Escherichia coli* and *Staphylococcus aureus*, respectively, before washing. With increasing washing cycles, the antibacterial performance of Comparative Example 1 decreased. After 50 standard washes, the antibacterial rates against the two test bacteria dropped to 32.1% and 45.8%, respectively. After multiple standard washes, the antibacterial curve of the control group showed a decreasing trend. The fabric of Example 2, treated with this method, initially achieved antibacterial rates of 99.8% and 99.9%, respectively. After 20 and 50 standard washes, the antibacterial rates against *Escherichia coli* remained at 98.2% and 95.6%, and against *Staphylococcus aureus* at 99.1% and 97.3%. The antibacterial curves of the experimental group remained close to 100% throughout the washing cycle, verifying that the cross-linking mechanism of this method imparts wash fastness to the antibacterial finishing.

[0081] In conventional padding processes, polyhexamethylene biguanide adheres to the fabric surface via intermolecular van der Waals forces and hydrogen bonds with cellulose groups. During washing, the mechanical shearing force of the water flow and the emulsifying effect of surfactants in the detergent disrupt this adhesion, causing the water-soluble antibacterial macromolecules to detach from the fiber surface.

[0082] In Example 2, the charge-shielding effect of sodium chloride was utilized to promote the penetration of polyhexamethylene biguanide into the amorphous regions within the fiber, optimizing the distribution of the antibacterial macromolecules. Simultaneously, the eutectic microenvironment formed by glycerol and citric acid lowered the activation energy of the crosslinking reaction. Under baking conditions at 135°C, citric acid first dehydrated to form an anhydride intermediate, which then underwent esterification with the hydroxyl groups on the cellulose surface and acylation with the terminal amino and imino groups of polyhexamethylene biguanide deep within the fiber.

[0083] Through the aforementioned covalent bonding, a robust three-dimensional macromolecular cross-linked network is constructed between polyhexamethylene biguanide and the cellulose matrix. This three-dimensional macromolecular cross-linked network effectively resists chemical stripping and mechanical friction during washing. Furthermore, the antibacterial polymer, penetrating into the yarn, continues to provide contact-based bactericidal sites even after the surface fibers of the fabric are worn away, maintaining the fabric's long-lasting antibacterial activity. Test results confirm that this mechanism, combining deep penetration and covalent cross-linking, enhances the wash fastness of the antibacterial finishing on the fabric.

[0084] Test Example 5: Fabric Apparent Yellowing Index (YI) Test Untreated blank pure cotton woven fabric, fabric prepared by conventional high-temperature crosslinking process (Comparative Example 2), and fabric prepared by low eutectic crosslinking process (Example 2) were selected and placed in a constant temperature and humidity environment of 20°C and 65% for 24 hours to adjust humidity.

[0085] Cut various conditioned fabric samples into test pieces measuring 10cm × 10cm, and prepare 3 parallel samples for each group.

[0086] Each test piece was folded into a four-layer structure to eliminate background interference caused by light transmission through a single layer of fabric to the measurement results of the optical sensor.

[0087] Turn on the benchtop colorimetric spectrophotometer and warm it up for 30 minutes. Then, use the standard black box and standard white plate provided with the instrument to perform the calibration procedure in sequence.

[0088] Set the instrument measurement parameters, the light source to D65 standard light source, the observer angle to 10° field of view, and the measurement mode to exclude specular reflection light.

[0089] Place the folded test piece flat over the test hole of the instrument, lower the pressure hammer to fix it, and perform the measurement operation. The instrument's built-in software will automatically calculate the yellowing index (YI) according to the ASTM E313 standard.

[0090] Multiple random tests were performed on the surface of each group of samples to obtain 5 valid test data, and the arithmetic mean of each group was calculated.

[0091] Table 5. Results of Apparent Yellowing Index (YI) Test for Fabric Samples

[0092] Based on the data in Table 5, combined with Figure 6A bar chart comparing the apparent yellowing index (YI) of fabric samples under different finishing processes is presented (the horizontal axis represents different test fabric groups, in order: untreated blank pure cotton base fabric, control group fabric treated with conventional 170℃ high-temperature crosslinking process, and experimental fabric treated with 135℃ low-eutectic crosslinking process; the vertical axis represents the apparent yellowing index; the height of the bars reflects the arithmetic mean of each group of samples; the black vertical line segment at the top of the bar is an error bar, representing the standard deviation distribution of 5 repeated measurements; light gray, medium gray, and dark gray bars correspond to the three groups, respectively). The average apparent yellowing index (YI) of the untreated blank pure cotton fabric was 2.18, exhibiting the natural optical state of cellulose. The control group fabric prepared using conventional processes showed an average yellowing index of 15.82, exhibiting a yellowish appearance, indicating that the yellowing phenomenon in the control group was caused by high-temperature baking.

[0093] The yellowing index of the experimental tissues treated with this method fluctuated between 3.12 and 4.25, with an arithmetic mean of 3.72, which was slightly higher than that of the blank base fabric. This confirms that the low-temperature crosslinking mechanism mediated by the eutectic microenvironment used in this method can maintain the yellowing index of the experimental tissues at a low level and achieve the preservation of the whiteness of the finished fabric.

[0094] In traditional polycarboxylic acid crosslinking finishing, baking conditions of 160℃ to 180℃ are required to drive the esterification reaction to achieve the desired degree of crosslinking. Under thermal stress, citric acid is prone to dehydration, generating byproducts such as aconitic acid containing conjugated double bonds; cellulose macromolecules are also prone to thermal oxidative degradation at high temperatures. Optically, these changes in chemical structure manifest as absorption of ultraviolet and short-wave visible light, leading to yellowing of the fabric.

[0095] In the experimental system, glycerol and citric acid constructed a eutectic solvent microenvironment through intermolecular hydrogen bonds. This eutectic system altered the molecular dynamics of the reactants, lowering the activation energy of the crosslinking reaction. The catalytic effect facilitated the completion of the three-dimensional network crosslinking reaction under a baking condition of 135℃, circumventing the high-temperature heat treatment range of traditional processes. The lower baking temperature inhibited the pathway of citric acid conversion to aconitine, a chromogenic byproduct, thus preventing thermo-oxidative aging of cotton fibers. Test data confirmed that the low-temperature crosslinking mechanism mediated by the eutectic microenvironment blocked the generation of chromogenic groups, achieving covalent fixation of the polymeric antibacterial agent while preserving the initial whiteness of the fabric, resolving the technical contradiction between wash fastness and fabric yellowing in traditional finishing processes.

[0096] Test Example 6: Macroscopic Hand Feel and Softness Test of Fabrics Unprocessed blank pure cotton woven fabric, fabric prepared by conventional citric acid crosslinking padding process (control group), and fabric prepared by the low eutectic crosslinking combined with foam single-sided application process of this scheme (experimental group) were selected and conditioned for 24 hours at constant temperature and humidity of 20℃ and 65% relative humidity.

[0097] Using a special sampling template, rectangular test strips with dimensions of 25mm × 200mm are cut along the warp and weft directions of the fabric, and 5 parallel samples are prepared for each group in each direction.

[0098] Turn on the automatic fabric stiffness tester and set the inclination angle of the test platform to the standard 41.5°.

[0099] Lay the test strip flat on a horizontal workbench, making the longitudinal direction of the strip parallel to the direction of the tester's movement, and place a metal pressure plate on top of the strip.

[0100] The test program is started, and the instrument push plate slowly pushes the specimen out of the edge of the worktable at a constant speed of 1.5 mm / s.

[0101] The suspended part of the spline gradually droops due to its own weight. When the front end of the spline droops and touches the infrared detection beam on the inclined plane, the push plate automatically stops, and the instrument records the sliding length of the spline extending out of the worktable.

[0102] Divide the recorded sliding length by 2 to obtain the bending length of a single measurement. Collect data from 5 independent tests each in the warp and weft directions, and calculate the arithmetic mean for each.

[0103] Table 6. Bending length test results of fabric samples

[0104] Based on the data in Table 6, combined with Figure 7 Bar chart comparing the macroscopic bending length of fabric samples after different processing techniques ( Figure 7 (a) shows the results of the warp bending length test of the fabric. Figure 7 (b) shows the test results of the weft bending length of the fabric; the horizontal axis of both sub-graphs represents different test groups, namely, the untreated blank pure cotton base fabric group, the control group using the conventional citric acid crosslinking padding process, and the experimental group using the low eutectic crosslinking combined with foam single-sided application process of this scheme; the vertical axis represents the bending length measured and calculated by the automatic fabric stiffness tester. The larger the value, the higher the bending stiffness of the fabric and the stiffer the hand feel; the light gray, medium gray and dark gray bars correspond to the arithmetic mean of the above three groups, respectively. The black vertical line segment at the top of the bar is the error bar, which represents the standard deviation dispersion of 5 independent test data in the same direction. The average bending lengths of the blank pure cotton fabric in the warp and weft directions are 2.21 cm and 1.83 cm, respectively.

[0105] In the control group fabric treated with conventional crosslinking, the warp and weft flexural lengths increased to 4.47 cm and 3.85 cm, respectively. The required sliding length for the test strip to sag increased, indicating greater fabric bending stiffness. This demonstrates that conventional crosslinking treatment leads to increased flexural length and a stiffer hand feel. The experimental fabric prepared using this proposed process exhibited warp flexural lengths between 2.58 cm and 2.86 cm, and weft flexural lengths between 2.12 cm and 2.45 cm, with arithmetic mean values ​​of 2.73 cm and 2.28 cm, respectively. The flexural lengths remained at a relatively low level, close to that of the blank fabric.

[0106] In polycarboxylic acid crosslinking finishing, crosslinking agent molecules react with the hydroxyl groups in the amorphous regions of cellulose, forming covalent bonds that bridge adjacent macromolecular chains. This three-dimensional network structure restricts the relative slippage between cellulose macromolecular chains, increasing the fiber's flexural modulus and leading to fabric stiffening. In conventional padding methods, the working solution is more widely distributed on the fabric surface, and the solute easily migrates to the surface during drying and baking, forming a continuous resin film on the yarn surface, increasing the frictional resistance between yarns.

[0107] In this scheme, the single-sided foam application method controls the liquid supply, reducing solute accumulation and film formation on the fabric surface. The eutectic system composed of glycerol and citric acid lowers the reaction activation energy, while some glycerol molecules that do not participate in network crosslinking remain inside the fiber. Glycerol contains hydroxyl groups, and its molecular chain segments are flexible, acting as a plasticizer between cellulose macromolecules and increasing the free volume of the crosslinked network. The charge shielding effect of sodium chloride promotes the penetration of the antibacterial agent into the fiber interior, reducing the degree of macromolecular aggregation on the fiber surface.

[0108] Test data confirms that this solution, by introducing a eutectic plasticizing system and a non-contact foaming process, quantifies the impact of the internal plasticizing mechanism and the non-contact foaming process on the mechanical properties of the fabric, alleviates the increase in fabric rigidity caused by covalent cross-linking, and preserves the original bending flexibility of cotton fabric.

Claims

1. A method for antibacterial treatment of functional textile fabrics, characterized in that, Includes the following steps: The pre-treated pure cotton woven plain fabric is continuously introduced into an impregnation tank containing the first working liquid for double impregnation and double padding treatment, and the padding rate of the pure cotton woven plain fabric is controlled between 65% and 75%. The impregnated pure cotton woven plain fabric is fed into an infrared pre-drying machine for controlled moisture pre-drying, and the absolute moisture content of the pure cotton woven plain fabric is controlled to be between 15% and 20% when it is pre-dried. The semi-dry pure cotton woven plain fabric obtained by pre-drying is fed into a foam finishing machine. The micro foam of the second working liquid is coated on one side of the pure cotton woven plain fabric using a slit applicator. The amount of foam applied is controlled to be between 20% and 30% of the dry weight of the pure cotton woven plain fabric. The pure cotton woven plain fabric is directly fed into a multi-box tenter frame for temperature gradient baking. In the first stage, the fabric is treated at 90°C to 100°C for 90 to 120 seconds to trigger free water vaporization and delay electrostatic assembly. In the second stage, the temperature is rapidly increased to 130°C to 140°C for 90 to 120 seconds to complete the eutectic catalytic crosslinking reaction. The baked pure cotton woven plain fabric is washed continuously with warm water at 40°C to 50°C to remove free inorganic salts and unreacted substances, and finally dried with conventional hot air at 100°C to 110°C. The first working fluid contains a multifunctional crosslinking agent, a crosslinking catalyst, and industrial-grade glycerol that acts as a hydrogen bond conformation occupier or a eutectic precursor; The foaming stock solution of the second working solution contains a cationic antibacterial agent, a neutral inorganic salt that provides charge shielding, a nonionic foaming agent, and a foam stabilizer.

2. The antibacterial treatment method for functional textile fabrics according to claim 1, characterized in that, The first working fluid is made from raw materials containing the following concentrations: The multifunctional crosslinking agent is 30 g / L to 50 g / L, the crosslinking catalyst is 15 g / L to 25 g / L, and the industrial-grade glycerol is 15 g / L to 25 g / L.

3. The antibacterial treatment method for functional textile fabrics according to claim 2, characterized in that, The multifunctional crosslinking agent is citric acid, the crosslinking catalyst is sodium hypophosphite, and the pH value of the first working solution is standardized to the range of 3.2 to 3.5 by a 10% sodium hydroxide aqueous solution.

4. The antibacterial treatment method for functional textile fabrics according to claim 1, characterized in that, The foaming mother liquor is made from raw materials containing the following concentrations: The cationic antibacterial agent is 10 g / L to 20 g / L, the neutral inorganic salt is 15 g / L to 20 g / L, the nonionic foaming agent is 2 g / L to 4 g / L, and the foam stabilizer is 0.5 g / L to 1.5 g / L.

5. The antibacterial treatment method for functional textile fabrics according to claim 4, characterized in that, The cationic antibacterial agent is polyhexamethylene biguanide, the neutral inorganic salt is sodium chloride, the nonionic foaming agent is alkyl polysaccharide glycoside, and the foam stabilizer is hydroxyethyl cellulose.

6. The antibacterial treatment method for functional textile fabrics according to claim 1, characterized in that, The pH value of the foaming mother liquor is 6.0 to 6.2; The average pore diameter of the microfoam is between 50 μm and 100 μm, and the foaming ratio is constant between 5 and 8 times.

7. The antibacterial treatment method for functional textile fabrics according to claim 1, characterized in that, The preparation process of the first working solution includes: Inject 70% of the rated volume of deionized water into a mixing vessel equipped with a mechanical stirrer. Set the stirring speed to 150 rpm to 200 rpm. Slowly add the multifunctional crosslinking agent, the crosslinking catalyst, and the industrial-grade glycerol in sequence and continue stirring for 20 to 30 minutes until all solid components are completely dissolved in the aqueous phase to form a homogeneous transparent solution.

8. The antibacterial treatment method for functional textile fabrics according to claim 7, characterized in that, The preparation process of the first working solution further includes: With continuous stirring, turn on the online pH monitor of the mixing vessel, and slowly add a 10% sodium hydroxide aqueous solution to the system at a flow rate of 10 mL / min to 20 mL / min using a metering pump. Dynamically monitor the dissociation equilibrium of the system. After stopping the addition of the sodium hydroxide aqueous solution, add deionized water to the mixing vessel to the rated volume and continue stirring for 10 minutes to make the system concentration uniform.

9. The antibacterial treatment method for functional textile fabrics according to claim 1, characterized in that, The preparation process of the foaming mother liquor includes: Inject 80% of the rated volume of deionized water into a mixing vessel equipped with a homogenizing emulsification shearing function. Then, add the cationic antibacterial agent and the neutral inorganic salt in the prescribed amounts and stir for 15 minutes. Reduce the stirring speed to 50 to 80 rpm, and then slowly add the nonionic foaming agent and the foam stabilizer in the prescribed amounts and continue to gently stir and mix for 20 minutes.

10. The method for antibacterial treatment of functional textile fabrics according to claim 9, characterized in that, The preparation process of the foaming mother liquor also includes: The pH value of the system is precisely adjusted by adding glacial acetic acid, monovalent organic acid, or sodium hydroxide solution to the system. Then, deionized water is added to the rated volume to obtain the transparent and stable foaming mother liquor. The foaming mother liquor is pumped into the stator and rotor mixing chamber of the industrial dynamic foaming machine through a closed pipeline. At the same time, constant pressure compressed air is injected into the mixing chamber to prepare the microfoam.

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