Preparation method of finishing agent for improving dry and wet rubbing color fastness performance of fabric

Abstract

The invention discloses a preparation method of a finishing agent for improving the dry and wet rubbing color fastness performance of a fabric, and belongs to the technical field of material preparation. The method comprises the following steps: firstly, adding isophorone diisocyanate and polyethylene glycol into a reactor according to a specific molar ratio to carry out prepolymerization reaction, and then sequentially carrying out operations of hydrophilic chain extension, neutralization, emulsification dispersion and the like to form a waterborne polyurethane emulsion; adding ethylene glycol diglycidyl ether, triethylamine, tetrabutylammonium bromide, KH550 modified nano silicon dioxide and the like to carry out ring-opening reaction; and finally, carrying out polycondensation and crosslinking to obtain the finishing agent. On the basis of waterborne polyurethane, a high-strength net structure is constructed through a multi-step cross-linking reaction, toxic substances such as epoxy chloropropane and the like are avoided, the dry and wet rubbing color fastness, the hand feeling, the washability and the storage stability are remarkably improved, and an innovative scheme is provided for improving the high-performance and green color fastness of the dark natural fiber fabric.

Description

Technical Field

[0001] The invention belongs to the technical field of material preparation, and in particular relates to a method for preparing a finishing agent for improving the dry and wet friction color fastness of fabrics. Background Art

[0002] Insufficient wet and dry friction color fastness is a long-standing technical challenge in the textile printing and dyeing industry. This is particularly true for dark-colored natural fibers such as cotton and linen, as well as their blends. Dyes easily detach from the fiber surface under dry or wet friction, leading to color migration, deterioration of the fabric's appearance, and the risk of dye staining. Traditional wet and dry friction color fastness finishing agents often rely on toxic substances such as aldehyde crosslinkers and epichlorohydrin. While these agents can improve color fastness, they suffer from biotoxicity and residual migratable chemicals (such as APEO), making them difficult to meet the stringent requirements of modern textiles for ecological safety and human health.

[0003] Water-based polyurethanes are widely used in existing technologies due to their environmental friendliness and excellent film-forming properties. However, pure water-based polyurethane films have limited mechanical strength and are susceptible to wear and breakage during wet and dry friction. While the introduction of nanofillers (such as SiO2) can enhance mechanical properties and alleviate wear and breakage issues, nanoparticles tend to aggregate in aqueous systems and have weak interfacial bonding with the polyurethane matrix, resulting in poor stability of the finishing agent. This can lead to inconsistent fabric finishing effects and poor color fastness enhancement.

[0004] Therefore, developing a method for preparing a finishing agent that has both high dry and wet friction color fastness and environmental friendliness has become a technical problem that the industry urgently needs to solve. Summary of the Invention

[0005] The present invention aims to provide a method for preparing a finishing agent that improves the color fastness of fabrics to dry and wet friction. By constructing a multi-crosslinked network structure and optimizing nanoparticle dispersion and interfacial bonding, the present invention solves the problems of insufficient mechanical strength of pure water-based polyurethane film layers, easy agglomeration of nanoparticles, and weak interfacial bonding in the prior art. This achieves the goal of improving the color fastness to wet friction while also being environmentally friendly.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] A method for preparing a finishing agent for improving the dry and wet friction color fastness of a fabric comprises the following steps:

[0008] S1 prepolymerization: isophorone diisocyanate and polyethylene glycol are added to the reactor in a molar ratio of NCO: OH = 1.5-2.0: 1, followed by addition of 0.01-0.05wt% catalyst and reaction at 75-85 ° C for 2-3h;

[0009] S2 hydrophilic chain extension reaction: the reaction system was cooled to 60-70 ° C, 3-6wt% of 2,2-dimethylol propionic acid was added, and the reaction was continued for 2-4h;

[0010] S3 neutralization reaction: the reaction system was cooled to 40-50 ° C, triethylamine was added and stirred for 25-50 min; wherein the molar ratio of triethylamine to 2,2-dimethylolpropionic acid was 0.9-1.1: 1;

[0011] S4 emulsification dispersion: under high-speed stirring, followed by slowly adding deionized water and a composite emulsifier dissolved in diethylenetriamine, and stirring was continued for 1-2h to form an aqueous polyurethane emulsion; wherein the amount of diethylenetriamine is 0.8-1.0 times the number of moles of the remaining NCO groups in step S1;

[0012] S5 ring-opening reaction: 1-5wt% of ethylene glycol diglycidyl ether, 0.1-0.5wt% of triethylamine, 0.1-0.3wt% of tetrabutylammonium bromide, and 0.5-1wt% of KH550 modified nano-silica were added to the aqueous polyurethane emulsion, uniformly dispersed, heated to 60-75 ° C and reacted for 4-6h;

[0013] S6. Condensation polymerization and crosslinking: Raise the temperature to 80-90°C and continue the reaction for 3-5 hours to produce an environmentally friendly wet friction color fastness improving finishing agent.

[0014] As some possible implementation methods of the present application, in step S1, the catalyst is a DABCO T-120 catalyst.

[0015] As some possible implementation methods of the present application, in step S4, the composite emulsifier is composed of 3-5 wt% fatty alcohol polyoxyethylene ether and 2-3 wt% alkyl glycoside.

[0016] As some possible implementation methods of the present application, in step S3, a borax-boric acid buffer solution is added to adjust the pH of the system to 8.0±0.5.

[0017] As some possible implementation methods of the present application, in step S4, 1-2 wt% amino silicone oil emulsion is added.

[0018] As some possible implementation methods of the present application, in step S4, 0.1-0.3 wt% of anionic emulsion stabilizer is further added.

[0019] As some possible implementation methods of the present application, the amino silicone oil emulsion is epoxy-modified amino silicone oil.

[0020] As some possible implementation methods of the present application, in step S5, 0.5-5 wt% of thiol PEG is added.

[0021] As some possible implementation methods of the present application, in step S5, 0.05-0.1 wt% vitamin E is added.

[0022] As some possible implementation methods of the present application, in step S6, 0.3-0.5 wt% of N,N'-disuccinimidyl carbonate is added.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The present invention is based on water-based polyurethane. In the prepolymerization reaction, isophorone diisocyanate reacts with polyethylene glycol to form a terminal-NCO polyurethane. Hydrophilic chain extension introduces carboxyl groups to impart water solubility, and neutralization and emulsification form a stable emulsion. During the ring-opening reaction, ethylene glycol diglycidyl ether covalently bonds with the polyurethane chain segment and KH550 modified SiO2 to form a "polyurethane-ethylene glycol diglycidyl ether-SiO2" triple crosslinked network, significantly enhancing the mechanical strength of the film layer (effectively resisting friction stress, reducing film damage and dye shedding), as well as enhancing dry and wet friction color fastness. The fabric treated with the finishing agent of the present invention has a wet friction color fastness of not less than grade 4.0, a dry friction color fastness of not less than grade 4.5, and a wash retention rate (100 times) of not less than 85.2%, which is significantly improved compared to the basic fabric performance. At the same time, it avoids the use of toxic substances such as aldehyde-containing crosslinking agents and epichlorohydrin, taking into account environmental friendliness and meeting the stringent requirements of modern textiles for ecological safety and human health.

[0025] 2. This invention builds upon the "polyurethane-ethylene glycol diglycidyl ether-SiO2" triple crosslinked network by adding an epoxy-modified amino silicone oil emulsion, an anionic emulsion stabilizer, and N,N'-disuccinimidyl carbonate. The epoxy-modified amino silicone oil emulsion chemically bonds into the crosslinked network, imparting softness and smoothness to the fabric; the anionic emulsion stabilizer enhances emulsion stability; and the N,N'-disuccinimidyl carbonate increases crosslink density, further improving the fabric's wet and dry rubbing color fastness, softness, and washability.

[0026] 3. This invention introduces mercapto-PEG and vitamin E during the ring-opening reaction, achieving comprehensive optimization of the finishing agent's performance. Specifically, mercapto-PEG efficiently crosslinks with the system, significantly increasing the crosslink density and significantly enhancing dry and wet rubbing color fastness. It also improves the dispersibility of nano-silica and enhances abrasion resistance. Vitamin E exerts an antioxidant effect, slowing film degradation and improving washability. DETAILED DESCRIPTION

[0027] In existing technologies, pure water-based polyurethane films have limited mechanical strength and are susceptible to wear and breakage during wet friction. While the introduction of nanofillers (such as SiO2) can enhance mechanical properties and alleviate wear and breakage issues, nanoparticles tend to aggregate in aqueous systems and have weak interfacial bonding with the polyurethane matrix, resulting in poor stability of the finishing agent. This can lead to inconsistent fabric finishing effects and issues such as improved color fastness.

[0028] Based on this, the present invention provides a method for preparing a finishing agent for improving the color fastness of fabrics to dry and wet friction, comprising the following steps:

[0029] S1 prepolymerization: isophorone diisocyanate and polyethylene glycol are added to the reactor in a molar ratio of NCO: OH = 1.5-2.0: 1, followed by addition of 0.01-0.05wt% catalyst and reaction at 75-85 ° C for 2-3h;

[0030] S2 hydrophilic chain extension reaction: the reaction system was cooled to 60-70 ° C, 3-6wt% of 2,2-dimethylol propionic acid was added, and the reaction was continued for 2-4h;

[0031] S3 neutralization reaction: the reaction system was cooled to 40-50 ° C, triethylamine was added and stirred for 25-50 min; wherein the molar ratio of triethylamine to 2,2-dimethylolpropionic acid was 0.9-1.1: 1;

[0032] S4 emulsification dispersion: under high-speed stirring, followed by slowly adding deionized water and a composite emulsifier dissolved in diethylenetriamine, and stirring was continued for 1-2h to form an aqueous polyurethane emulsion; wherein the amount of diethylenetriamine is 0.8-1.0 times the number of moles of the remaining NCO groups in step S1;

[0033] S5 ring-opening reaction: 1-5wt% of ethylene glycol diglycidyl ether, 0.1-0.5wt% of triethylamine, 0.1-0.3wt% of tetrabutylammonium bromide, and 0.5-1wt% of KH550 modified nano-silica were added to the aqueous polyurethane emulsion, uniformly dispersed, heated to 60-75 ° C and reacted for 4-6h;

[0034] S6. Condensation polymerization and crosslinking: Raise the temperature to 80-90°C and continue the reaction for 3-5 hours to produce an environmentally friendly wet friction color fastness improving finishing agent.

[0035] The present invention uses waterborne polyurethane as a matrix and constructs a composite system with multiple cross-linked networks through multi-step reactions. The core mechanism is as follows:

[0036] In step S1: isophorone diisocyanate (IPDI) and polyethylene glycol (PEG) generate a polyurethane prepolymer containing terminal -NCO through the addition reaction of -NCO and -OH, which provides active sites for subsequent cross-linking.

[0037] In step S2: 2,2-dimethylolpropionic acid (DMPA) is introduced, and its hydroxyl group reacts with -NCO, while the carboxyl group (-COOH) imparts hydrophilicity to the system, laying the foundation for emulsification and dispersion.

[0038] In steps S3-S4: triethylamine neutralizes the carboxyl group to generate a water-soluble salt, which is then stirred at high speed to form an aqueous polyurethane emulsion; diethylenetriamine (DETA) acts as a chain extender to react with the remaining -NCO to initially construct a cross-linked structure.

[0039] In steps S5-S6: the epoxy groups of ethylene glycol diglycidyl ether (EGDGE) are ring-opened and react with the hydroxyl and amino groups of the polyurethane segments to form a chemical cross-linked network; KH550-modified SiO2 is bonded to the polyurethane network through the surface amino groups (-NH2) to enhance the mechanical strength; finally, the temperature is increased to maximize the cross-linking density, forming a finishing agent with excellent dry and wet friction color fastness, strong wear resistance, and environmental protection.

[0040] In addition, after adding modified silica, the present invention can increase the roughness of the fabric film layer, enhance the bonding strength with the fabric fibers through mechanical engagement, and at the same time adsorb dyes to inhibit migration; secondly, after the SiO2 surface is modified with KH550, the amino group (-NH2) can react with the active group of polyurethane to achieve chemical bonding rather than physical blending, effectively preventing particle shedding.

[0041] Functional synergy: Nano-size effect. After the SiO2 surface is modified with KH550, the amino groups (-NH2) can react with the active groups of polyurethane, achieving chemical bonding rather than physical blending, effectively improving the interfacial bonding with the polyurethane matrix, thereby effectively alleviating the problem of easy shedding of nanoparticles.

[0042] In order to improve the catalytic performance during the prepolymerization of IPDI and PEG, as some possible embodiments of the present application, the type of catalyst is further limited, that is, in step S1, the catalyst is DABCO T-120 catalyst.

[0043] In order to further improve the problem of poor dispersibility of modified SiO2, as some feasible embodiments of the present application, the components and dosage of the composite emulsifier are further limited, that is, in step S4, the composite emulsifier is composed of 3-5wt% fatty alcohol polyoxyethylene ether (AEO-9) and 2-3wt% alkyl glycoside (APG0810).

[0044] AEO-9 prevents aggregation through steric hindrance from its polyoxyethylene chains, while its hydrophilic head group is compatible with water and its hydrophobic chain adsorbs to the SiO2 surface. APG0810, through the hydrophilic nature of its glycoside chains and the hydrophobic nature of its alkyl chains, enhances interfacial compatibility and forms a stable dispersion layer. The synergistic effect of these two agents effectively reduces surface tension and interparticle attraction, enabling uniform dispersion of the modified SiO2 and avoiding localized stress concentrations.

[0045] In order to further improve the protonation of modified SiO2 (-NH3 + ), as some feasible embodiments of the present application, an improved component is introduced in step S3, that is, in step S3, a borax-boric acid buffer pair is added to adjust the pH of the system to 8.0±0.5.

[0046] In order to effectively improve the roughness caused by borax microcrystals, as some embodiments of the present application, an improving component is added during the preparation, that is, in step S4, 1-2 wt% amino silicone oil emulsion is added. Amino silicone oil improves the feel through long-chain lubrication, thereby improving the roughness caused by borax.

[0047] In order to effectively improve the problem of emulsion demulsification caused by the charge difference between amino silicone oil emulsion (cationic type) and polyurethane (anionic type), as some feasible embodiments of the present application, an improvement component is added during preparation, that is, in step S4, 0.1-0.3wt% anionic emulsion stabilizer is also added. Anionic emulsion stabilizer can neutralize the interfacial charge of amino silicone oil emulsion, effectively improve the problem of emulsion demulsification caused by the charge difference between amino silicone oil emulsion and polyurethane (anionic type), significantly improve the storage stability of emulsion, avoid stratification, and ensure that the finishing agent is evenly applied to the fabric. In addition, the added anionic emulsion stabilizer can synergistically stabilize the emulsion particles with the composite emulsifier and improve the storage stability of the emulsion.

[0048] The amino group in the amino silicone oil: ① competes with the cross-linking agent (such as EGDGE) in the finishing agent for reaction sites, weakening the density of the cross-linked network; ② the amino group also absorbs moisture to form a weak interface layer, causing the finishing agent film layer to easily fall off during wet friction, etc., resulting in a decrease in the wet friction color fastness of the fabric. In order to effectively improve the problem of decreased wet friction color fastness after the introduction of amino silicone oil emulsion, as some feasible embodiments of the present application, the type of amino silicone oil emulsion is further limited, that is, the amino silicone oil emulsion is an epoxy-modified amino silicone oil.

[0049] The epoxy group can react with the hydroxyl and carboxyl groups of polyurethane, embed into the cross-linking network, and improve the cross-linking density; the hydroxyl group (-OH) generated after the epoxy group ring opening forms a hydrophobic layer with the siloxane chain (-Si-O-Si-) of the amino silicone oil, reducing moisture adsorption and effectively improving the problem of reduced wet friction color fastness.

[0050] In addition, the covalent bonding of epoxy groups with EGDGE and polyurethane segments (rather than physical adsorption of amino groups) can firmly embed amino silicone oil into the cross-linked network, avoid physical adsorption and shedding, and improve the stability of the film layer.

[0051] The long-chain structure of amino silicone oil hinders the cross-linking reaction between the polyurethane molecular chain and EGDGE through steric hindrance, resulting in a decrease in the cross-linking density of the film layer, insufficient mechanical strength, weakened adhesion of the finishing agent to the fiber, poor durability and other technical problems. Based on this, as some feasible implementation methods of the present application, in step S6, 0.3-0.5wt% N,N'-disuccinimidyl carbonate is added. N,N'-disuccinimidyl carbonate can force the amino group of amino silicone oil to participate in cross-linking, eliminate the long-chain steric hindrance effect, and enhance the integrity of the film layer. In addition, N,N'-disuccinimidyl carbonate can react with the carboxyl group of polyurethane to form ureide bonds, replacing the easily hydrolyzed ether bonds and improving alkaline stability.

[0052] Although KH550-SiO2 can improve stability through amino cross-linking, the nanoparticles may still fall off due to local stress concentration. Based on this, as some feasible implementation methods of the present application, in step S5, 0.5-5wt% thiol PEG is added. The thiol group reacts with the hydroxyl group on the surface of SiO2 to form an -Si-OS- bond. The chemical anchoring effect is better than that of simple amino bonding. At the same time, the long PEG chain further stabilizes the particles through the steric effect, which can effectively improve the problem of SiO2 shedding. In addition, the long PEG chain wraps around SiO2, reduces the surface energy of the particles and reduces agglomeration. At the same time, the elastic buffer layer formed can relieve mechanical friction stress and effectively prevent SiO2 from directly contacting the skin and causing biological toxicity.

[0053] To effectively address the technical issue of sulfhydryl groups (-SH) being easily oxidized to disulfide bonds (-SS-) in air, as some possible implementations of the present application, 0.05-0.1 wt% vitamin E is added in step S5. Vitamin E, as an antioxidant, can effectively prevent the oxidation of sulfhydryl groups to disulfide bonds, which can lead to uncontrolled cross-linking or decreased dispersibility, effectively ensuring the dispersion and stable cross-linking function of the sulfhydryl PEG.

[0054] Next, the preparation method of the finishing agent of the present invention is described in detail.

[0055] Example 1

[0056] S1. Prepolymerization: Isophorone diisocyanate and polyethylene glycol-1000 were added to a reactor at a molar ratio of NCO:OH = 1.6:1, followed by the addition of 0.03 wt% DABCO T-120 catalyst (the catalyst was previously diluted with acetone to a 5 wt% solution) and the reaction was carried out at 80°C, stirring at 400 rpm under a nitrogen atmosphere for 2.5 h.

[0057] S2 hydrophilic chain extension reaction: the reaction system was cooled to 65 ° C, 5wt% of 2,2-dimethylol propionic acid was added, and the reaction was stirred at a speed of 500rpm for 3h;

[0058] S3. Neutralization reaction: The reaction system was cooled to 45 ° C, triethylamine was added and stirred (800 rpm) for 30 min, and then 0.1M

[0059] Borax-boric acid buffer solution, the pH of the system is stabilized to 8.0±0.5 by stirring; wherein the molar ratio of triethylamine to 2,2-dimethylolpropionic acid is 1:1;

[0060] S4. Emulsification and dispersion: Under high-speed stirring (1000 rpm), deionized water containing diethylenetriamine, 4 wt% fatty alcohol polyoxyethylene ether and 2.5 wt% alkyl glycoside were slowly added sequentially, and stirring was continued (1300 rpm) for 1.5 h to form an aqueous polyurethane emulsion; wherein the amount of diethylenetriamine is 1.0 times the number of moles of the remaining NCO groups in step S1;

[0061] S5. Ring-opening reaction: 4 wt% of ethylene glycol diglycidyl ether, 0.3 wt% of triethylamine, and 0.2 wt% of tetrabutylammonium bromide were added to the aqueous polyurethane emulsion in sequence, and stirred at 60°C (600 rpm) for 1 h; then 1 wt% of KH550 modified nano-silica was added, stirred (600 rpm) for 30 min, and then the temperature was raised to 70°C and the stirring was continued (600 rpm) for 4 h.

[0062] S6. Condensation crosslinking: The temperature was raised to 82°C and the mixture was stirred (500-600 rpm) under a nitrogen atmosphere for 4 hours to obtain an environmentally friendly wet friction color fastness improving finishing agent.

[0063] The preparation method of KH550 modified nano-silica is as follows (other preparation methods in the prior art may also be used):

[0064] A. Add 3 g of dry nano-SiO2 (particle size 30-50 nm) to 150 mL of anhydrous ethanol-water mixture (ethanol: water = 7:3, volume ratio) and ultrasonically disperse for 30 minutes to obtain a SiO2 suspension.

[0065] 3 mL of KH550 was added to 100 mL of anhydrous ethanol-water mixture (ethanol: water = 8:2, volume ratio), 1-2 drops of glacial acetic acid were added dropwise, the pH was adjusted to 4, and magnetic stirring was performed at room temperature for 30 min to obtain a KH550 hydrolyzed solution.

[0066] B. Slowly drip the KH550 hydrolysis solution into the SiO2 suspension. After the addition is complete, heat it to 75°C and reflux with stirring for 3 hours. After the reaction is completed, cool it to room temperature, centrifuge, wash, and vacuum dry at 60-80°C to constant weight to obtain KH550 modified nano-silica.

[0067] Example 2

[0068] On the basis of Example 1, steps S4 and S6 are adjusted, and the steps after adjustment are as follows:

[0069] S4. Emulsification and dispersion: Under high-speed stirring (1000 rpm), deionized water containing diethylenetriamine, 4 wt% fatty alcohol polyoxyethylene ether and 2.5 wt% alkyl glucoside were slowly added in sequence, and after stirring (1300 rpm) for 30 min, 0.3 wt% sodium dodecylbenzenesulfonate was added. After continuing to stir (1000 rpm) for 15 min, 1.5 wt% epoxy-modified amino silicone oil emulsion was added, and then stirred (800 rpm) for 50 min to form an aqueous polyurethane emulsion.

[0070] Among them, the mass dosage of diethylenetriamine is 1.0 times of the excess NCO;

[0071] S6. Condensation crosslinking: The temperature was raised to 82°C, and 0.4 wt% N,N'-disuccinimidyl carbonate (previously prepared as a 20 wt% solution in acetone) was added. The mixture was then stirred (500 rpm) under a nitrogen atmosphere for 4 h to produce an environmentally friendly wet rubbing color fastness-enhancing finishing agent.

[0072] The remaining steps are the same as in Example 1.

[0073] Example 3

[0074] On the basis of Example 2, step S5 is adjusted, and the steps after adjustment are as follows:

[0075] S5. Ring-opening reaction: 4 wt% of ethylene glycol diglycidyl ether, 0.3 wt% of triethylamine, and 0.2 wt% of tetrabutylammonium bromide were added to the aqueous polyurethane emulsion in sequence, and the mixture was stirred (600 rpm) at 60°C for 1 h; then 3 wt% of thiol PEG (molecular weight 1000) was added, the temperature was raised to 65°C, and the mixture was stirred (800 rpm) for 1 h; then 1 wt% of KH550 modified nano-silica was added, the mixture was stirred (600 rpm) for 30 min, and the temperature was raised to 70°C for 2 h; then 0.06 wt% of vitamin E (vitamin E was prepared into a 2 wt% solution with propylene glycol in advance) was added, and the reaction was continued for 0.5 h; finally, the temperature was raised to 75°C and kept warm for 1 h to complete the ring-opening reaction.

[0076] The remaining steps are the same as in Example 2.

[0077] The preparation method of the thiol PEG is as follows (other preparation methods in the prior art may also be used):

[0078] A. Dissolve 10 g of monomethoxypolyethylene glycol (Mw = 1000) in 50 mL of anhydrous N,N-dimethylformamide, add 3.0 g of p-toluenesulfonyl chloride, slowly add 2.1 mL of triethylamine dropwise, and stir in an ice bath for 2 h. Then, filter to remove the precipitate, pour the filtrate into 500 mL of ice water, and a white solid will precipitate. Centrifuge, wash, and vacuum dry to obtain the intermediate.

[0079] Dissolve 1.0 g of mercaptoethanol in 20 mL of deionized water, add 0.52 g of NaOH, and stir until dissolved to obtain a sodium mercaptoethanol solution.

[0080] B. The intermediate was dissolved in 50 mL of anhydrous N,N-dimethylformamide, sodium mercaptoethanol solution was added, and then 1.8 g of K2CO3 was added. The temperature was raised to 65°C and refluxed with stirring for 10 h. After cooling, the pH was adjusted to neutral with 1 mol / L HCl, and the product was poured into 500 mL of acetone to precipitate. The product was then centrifuged and washed, and the crude product was dissolved in 50 mL of deionized water and loaded into a dialysis bag with a molecular weight cutoff of 500. It was dialyzed for 24 h (the water was changed 3 times), and vacuum dried (40°C, 0.05 MPa) to constant weight to obtain thiol PEG.

[0081] Comparative Example 1

[0082] Compared with Example 1, no modified silica was added, and the remaining steps and parameters were the same as Example 1.

[0083] Comparative Example 2

[0084] Compared with Example 1, the modified silica was replaced with silica, and the remaining steps and parameters were the same as those in Example 1.

[0085] Experimental example

[0086] 1. Dry and wet rubbing color fastness, hand feel score and wash resistance retention rate.

[0087] (1) Experimental materials: 100% cotton dark denim (weight 280g / m 2 , dyed with reactive dyes, initial dry rubbing color fastness 3.2 level, wet rubbing color fastness 2.5 level).

[0088] (2) Finishing process (finishing agent concentration: 30 g / L).

[0089] Double dip and double rolling (rolling rate 70%) → pre-baking (80℃×3min) → baking (150℃×3min)

[0090] (3)Performance testing methods.

[0091] ① Color fastness to dry and wet rubbing (test standard: ISO 105-X12:2016).

[0092] Evaluation: Use a gray scale (1-5, 5 is the best) to record the color fastness to dry and wet rubbing.

[0093] ② Feel rating.

[0094] Evaluation method: Tactile evaluation by a 10-person professional panel;

[0095] Scoring standard: 1-5 points (1 = stiff, 5 = soft and smooth);

[0096] Indicators: Average values of smoothness, softness, and fullness.

[0097] ③ Washability (color fastness retention after 100 washes).

[0098] Washing conditions: ISO 105-C06:2010 (A1S procedure, 40°C, 5g / L standard detergent);

[0099] Calculation method:

[0100]

[0101] (4) Experimental results (as shown in Table 1).

[0102] Table 1:

[0103]

[0104] As shown in Table 1, the fabrics treated with the finishing agents prepared in Examples 1-3 had a dry rubbing color fastness of ≥4.5, a wet rubbing color fastness of ≥4.0, a hand feel score of ≥3.5, and a 100-wash retention rate of ≥85.2%, significantly superior to Comparative Examples 1-2. In particular, Example 3, by constructing a multi-component synergistic cross-linking network (thiol PEG efficient cross-linking, amino silicone oil flexibility modification, and KH550 nano-silica reinforcement), breaks through the bottleneck of insufficient mechanical properties and wash resistance of traditional water-based polyurethane finishing agents, significantly improving the dry and wet rubbing color fastness of the fabric to above 4.8 and a wash retention rate exceeding 95%, while also imparting a soft hand to the fabric. Furthermore, environmentally friendly raw materials are used throughout the process, providing an innovative solution for high-performance, green color fastness improvement of dark natural fiber fabrics.

[0105] The details of Examples 1-3 and Comparative Examples 1-2 are as follows:

[0106] In Example 1, isophorone diisocyanate and polyethylene glycol-1000 are first reacted through a prepolymerization reaction to form a prepolymer containing active NCO terminal groups. 2,2-Dimethylolpropionic acid is then added for hydrophilic chain extension, and triethylamine is then neutralized to form a stable waterborne polyurethane emulsion system. Ethylene glycol diglycidyl ether then undergoes a ring-opening reaction and crosslinks with other active groups. KH550-modified nanosilica is chemically embedded in the network structure, enhancing the film's wear resistance and hardness, effectively improving the fabric's wet and dry rubbing color fastness and washability, while also improving its feel.

[0107] Example 2 is based on Example 1, and sodium dodecylbenzenesulfonate and epoxy-modified amino silicone oil emulsion are added in the emulsification and dispersion stage. The former improves the stability of the emulsion, and the amino silicone oil in the latter is chemically bonded to the cross-linking network, giving the fabric soft and smooth properties and improving the feel; N,N'-disuccinimidyl carbonate is added during polycondensation cross-linking, and the catalytic reaction increases the cross-linking density, further improving the wash resistance, and the dry and wet friction color fastness is also improved due to the synergistic effect of the system.

[0108] Example 3, based on Example 2, introduces mercapto PEG and vitamin E during the ring-opening reaction. Mercapto PEG and ethylene glycol diglycidyl ether efficiently crosslink, significantly increasing the crosslink density and wet rubbing color fastness. Vitamin E exerts an antioxidant effect, delaying film aging and degradation, and improving wash resistance retention. Its structure also interacts with polyurethane, improving the dispersibility of nanosilica and synergistically enhancing wear resistance, achieving comprehensive optimization of various properties.

[0109] Compared with Example 1, Comparative Example 1 does not add modified silica. The cross-linked network of the system is loose due to the lack of rigid nanoparticle filling. During the friction and washing process, the film layer is easily worn and damaged, and the dye molecules are easily detached, resulting in a significant decrease in dry and wet friction color fastness and wash resistance. In addition, the hand feel is also poor due to the lack of the synergistic effect of nano-silica.

[0110] In Comparative Example 2, modified silica is replaced by silica. Unmodified silica is easy to agglomerate in the system and has weak interfacial bonding with the polyurethane matrix. During friction, the agglomerated particles easily become stress concentration points, causing damage to the film layer. They are also easy to fall off from the film layer during washing, destroying the integrity of the film layer, resulting in reduced dry and wet friction color fastness and washability of the fabric, and the feel score is also low.

[0111] 2. Storage stability test of finishing agent.

[0112] (1) Appearance observation.

[0113] Operation: Put the finishing agent into a transparent glass bottle, seal it and store it at room temperature (25℃) and accelerated aging conditions (50℃).

[0114] Detection time points: day 0, day 7, day 14, day 30.

[0115] Judging criteria:

[0116] Acceptable: The solution / emulsion is uniform, without precipitation, stratification or discoloration.

[0117] Unqualified: turbidity, flocs, oil-water separation or obvious color change.

[0118] (2) Viscosity change test.

[0119] Instrument: Viscometer.

[0120] Procedure: Take an appropriate amount of finishing agent and measure the initial viscosity at a constant temperature of 25°C. After storage for a specified number of days, repeat the measurement / evaluation of the viscosity change.

[0121] Judging criteria:

[0122] Stable: No significant change in viscosity (flow state remains the same as the initial state).

[0123] Unstable: The viscosity becomes significantly thicker (stringy) or thinner (watery).

[0124] (4) Stratification rate assessment.

[0125] Operation: Pour the finishing agent into a 10mL centrifuge tube, let it stand for a specified number of days under the corresponding storage conditions, centrifuge at 3000rpm for 10min, and then read the volume of the precipitate.

[0126] Calculation formula: stratification rate (%) = (precipitation volume / total emulsion volume) × 100%

[0127] Result judgment: It is generally believed that when the delamination rate is ≤1%, the system stability is good; when the delamination rate is between 1%-5%, the stability is average; when the delamination rate is greater than 5%, the system stability is judged to be unqualified.

[0128] (5) Test results (as shown in Table 2).

[0129] Table 2:

[0130]

[0131]

[0132] As shown in Table 2, Example 1 maintains system stability thanks to the crosslinking network formed by ethylene glycol diglycidyl ether and the reinforcing effect of KH550-modified nanosilica. Example 2, based on Example 1, enhances stability by using sodium dodecylbenzenesulfonate and an epoxy-modified aminosilicone oil emulsion, but structural changes still occur at high temperatures, leading to increased viscosity and some stratification. Example 3 achieves high stability at both room and high temperatures by relying on the efficient crosslinking of thiol PEG and the synergistic antioxidant effect of vitamin E. However, Comparative Example 1 lacks nanosilica reinforcement, resulting in a loose crosslinking network and particle aggregation. Comparative Example 2 uses unmodified silica, resulting in turbidity and stratification of the system due to aggregates and weak interfacial bonding. Both exhibit significant instability during storage. This shows that a reasonable crosslinking system construction, effective dispersion enhancement, and antioxidant protection are key factors in improving the storage stability of finishing agents.

Claims

1. A method for preparing a finishing agent for improving the color fastness of fabrics to dry and wet friction, characterized in that: The steps include: S1 prepolymerization: isophorone diisocyanate and polyethylene glycol are added to the reactor in a molar ratio of NCO: OH = 1.5-2.0: 1, followed by addition of 0.01-0.05wt% catalyst and reaction at 75-85 ° C for 2-3h; S2 hydrophilic chain extension reaction: the reaction system was cooled to 60-70 ° C, 3-6wt% of 2,2-dimethylol propionic acid was added, and the reaction was continued for 2-4h; S3 neutralization reaction: the reaction system was cooled to 40-50 ° C, triethylamine was added and stirred for 25-50 min; wherein the molar ratio of triethylamine to 2,2-dimethylolpropionic acid was 0.9-1.1: 1; S4 emulsification dispersion: under high-speed stirring, followed by slowly adding deionized water and a composite emulsifier dissolved in diethylenetriamine, and stirring was continued for 1-2h to form an aqueous polyurethane emulsion; wherein the amount of diethylenetriamine is 0.8-1.0 times the number of moles of the remaining NCO groups in step S1; S5 ring-opening reaction: 1-5wt% of ethylene glycol diglycidyl ether, 0.1-0.5wt% of triethylamine, 0.1-0.3wt% of tetrabutylammonium bromide, and 0.5-1wt% of KH550 modified nano-silica were added to the aqueous polyurethane emulsion, uniformly dispersed, heated to 60-75 ° C and reacted for 4-6h; S6. Condensation polymerization and crosslinking: Raise the temperature to 80-90°C and continue the reaction for 3-5 hours to produce an environmentally friendly wet friction color fastness improving finishing agent.

2. The method for preparing a finishing agent for improving the color fastness of fabric to dry and wet friction according to claim 1, characterized in that: In step S1, the catalyst is DABCO T-120 catalyst.

3. The method for preparing a finishing agent for improving the color fastness of fabrics to dry and wet friction according to claim 1, characterized in that: In step S4, the composite emulsifier is composed of 3-5 wt% of fatty alcohol polyoxyethylene ether and 2-3 wt% of alkyl glycoside.

4. The method for preparing a finishing agent for improving the color fastness of fabrics to dry and wet friction according to claim 1, characterized in that: In step S3, a borax-boric acid buffer solution is added to adjust the pH of the system to 8.0±0.

5.

5. The method for preparing a finishing agent for improving the color fastness of fabrics to dry and wet friction according to claim 4, characterized in that: In step S4, 1-2 wt% amino silicone oil emulsion is added.

6. The method for preparing a finishing agent for improving the color fastness of fabrics to dry and wet friction according to claim 5, characterized in that: In step S4, 0.1-0.3 wt% of anionic emulsion stabilizer is also added.

7. The method for preparing a finishing agent for improving the color fastness of fabrics to dry and wet friction according to claim 5, characterized in that: The amino silicone oil emulsion is epoxy-modified amino silicone oil.

8. The method for preparing a finishing agent for improving the color fastness of fabrics to dry and wet friction according to claim 5, characterized in that: In step S6, 0.3-0.5 wt% of N,N'-disuccinimidyl carbonate is added.

9. The method for preparing a finishing agent for improving the color fastness of fabrics to dry and wet friction according to claim 1, characterized in that: In step S5, 0.5-5 wt% of thiol PEG is added.

10. The method for preparing a finishing agent for improving the color fastness of fabrics to dry and wet friction according to claim 9, characterized in that: In step S5, 0.05-0.1 wt % vitamin E is added.

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