Waterborne polyurethane coating of textile fabric

Abstract

The invention relates to the technical field of functional coatings of textiles, and discloses a waterborne polyurethane coating of a textile fabric. Through the collaborative innovation of polyether-polyester specific proportion copolymerization soft segment design, amino silicon oil and hydroxyl acrylate collaborative end capping, carbodiimide and epoxy silane compound crosslinking, silane coupling agent modified nanoparticle compounding and segmented pre-drying low-temperature curing, the pain points in the prior art are comprehensively broken from the molecular structure to the construction process; the problem of layering and demulsification of a coating liquid caused by mutual interference of a cross-linking system and a nano modifier is thoroughly solved, stable storage and smooth construction in a low-temperature environment of 0-10 DEG C are realized, the defect of hydrolysis resistance reduction caused by introduction of a conventional anti-freezing agent is also avoided, and the anti-freezing agent has the extension functions of antibiosis, ultraviolet resistance, yellowing resistance and the like; the preparation method has the advantages of simple process, no VOCs emission, guarantee of the process adaptability of large-scale production, realization of leap-type improvement of the comprehensive performance of the coating, and substantial technical value and application prospect.

Description

Technical Field

[0001] This invention relates to the field of functional coating technology for textiles, and more particularly to an aqueous polyurethane coating for textile fabrics. Background Technology

[0002] Textile coating is a core technology for endowing fabrics with functions such as waterproofing, windproofing, abrasion resistance, washability, antibacterial properties, and flame retardancy. Current research indicates that polyurethane (PU) coatings, due to their flexibility, abrasion resistance, weather resistance, and excellent adhesion to fabric substrates, have become the mainstream material in the textile coating field. However, traditional solvent-based polyurethane coatings use organic solvents as the dispersion medium, releasing large amounts of VOCs during production and use. These coatings suffer from poor environmental performance, flammability, explosiveness, and health hazards, making them unsuitable for meeting the current requirements of green textile production. In contrast, waterborne polyurethane (WPU), using water as the dispersion medium, possesses significant advantages such as being non-toxic, environmentally friendly, low-odor, and easy to process, and is widely considered an ideal alternative to solvent-based PU.

[0003] Based on the above technical background and current research status, the inventors have found that existing waterborne polyurethane coating technologies still have significant defects: existing technologies often cannot avoid problems such as coating liquid delamination and demulsification caused by the mutual interference between the crosslinking system and the nano-modifier, coating pinhole peeling after low-temperature construction, performance degradation after low-temperature curing, and decreased hydrolysis resistance due to the introduction of antifreeze agents. As a result, existing waterborne polyurethane coatings have insufficient overall performance and limited adaptability to various scenarios, and cannot meet the long-term use needs of multiple fields such as clothing, home textiles, and outdoor textiles. Summary of the Invention

[0004] The technical problem to be solved by this invention is that the existing technology has the disadvantages of being single in crosslinking, end-capping and nano-modification, poor performance synergy and limited process adaptability. To this end, we propose a waterborne polyurethane coating for textile fabrics.

[0005] To achieve the above objectives, this application adopts the following technical solution: a waterborne polyurethane coating for textile fabrics, comprising the following raw materials in parts by weight: 60-85 parts modified waterborne polyurethane emulsion, 1.5-4.0 parts environmentally friendly compound crosslinking agent, 0.5-3.0 parts nano-functional modifier, 0.3-2.0 parts hand feel modifier, 0.1-0.8 parts wetting and penetrating agent, 0.05-0.3 parts defoamer, 0.1-0.6 parts thickener, 0.1-0.5 parts low temperature stabilizing agent, 0.2-0.8 parts latent curing agent, and 10-30 parts deionized water; The modified waterborne polyurethane emulsion is an anionic emulsion prepared by using a mixture of polytetramethylene ether glycol and polybutylene adipate glycol as soft segments, a mixture of isophorone diisocyanate and dicyclohexylmethane diisocyanate as hard segments, and a mixture of amino silicone oil and hydroxy acrylate for synergistic end-capping reaction, while using dimethylolpropionic acid as a hydrophilic chain extender. The nano-functional modifier is a compound of silane coupling agent modified nano-silica and nano-zinc oxide in a mass ratio of 2:1-3:1. The nano-silica has a particle size of 15-30nm and the nano-zinc oxide has a particle size of 20-40nm. The feel modifier is a compound of polyether-modified polydimethylsiloxane and fatty acid ester slip agents in a mass ratio of 2:1-4:1; The environmentally friendly compound crosslinking agent is a mixture of carbodiimide crosslinking agent and epoxy silane crosslinking agent in a mass ratio of 1:1 to 3:2.

[0006] Preferably, the mass ratio of amino silicone oil to hydroxy acrylate is 1:1 to 2:1, and the hydroxy acrylate is selected from hydroxyethyl acrylate or hydroxypropyl acrylate.

[0007] Preferably, polytetramethylene ether glycol and polybutylene adipate glycol are mixed in a mass ratio of 3:2-5:1 to form the soft segment, and isophorone diisocyanate and dicyclohexylmethane diisocyanate are mixed in a mass ratio of 2:1-4:1 to form the hard segment.

[0008] Preferably, the silane coupling agent in the nano-functional modifier modifies the nano-silica by forming covalent bonds with the epoxy silane crosslinking agent through residual silanol groups on the surface.

[0009] Preferably, the modified waterborne polyurethane emulsion has a solid content of 35%-45% and a particle size of 50-120 nm; the silane coupling agent is 3-aminopropyltriethoxysilane or 3-glycidyl etheroxypropyltrimethoxysilane, and the amount used is 5%-10% of the total mass of nano-silica and nano-zinc oxide.

[0010] Preferably, the wetting and penetrating agent is a nonionic alkyl polyoxyethylene ether with an HLB value of 12-15.

[0011] Preferably, the defoamer is a polyether-modified siloxane defoamer; the thickener is a nonionic hydrophobic modified alkali-swelling thickener.

[0012] Preferably, the latent curing agent is a blocked isocyanate with a desealing temperature of 80-100℃.

[0013] Preferably, a method for preparing a waterborne polyurethane coating for a textile fabric includes the following steps: Step 1: Under stirring, add the wetting and penetrating agent, defoamer, and low-temperature stabilizing agent to deionized water in sequence, then add the modified waterborne polyurethane emulsion and mix evenly; subsequently, add the nano-functional modifier under shear dispersion conditions of 500-1000 r / min and continue dispersion; finally, add the environmentally friendly compound crosslinking agent, feel modifier, thickener, and latent curing agent, and mix evenly to obtain the coating liquid; Step 2: Apply the coating liquid to the surface of the textile substrate, and then perform low-temperature pre-baking, medium-temperature pre-baking and high-temperature curing in sequence. The low-temperature pre-baking temperature is 60-75℃, the medium-temperature pre-baking temperature is 80-95℃, and the high-temperature curing temperature is 100-110℃.

[0014] Preferably, an application of a water-based polyurethane coating on textile fabrics is described. The coating can be applied to the surface of textiles by scraping, rolling, spraying, or printing, and can be used in fields such as clothing, home textiles, and outdoor textiles.

[0015] The technical effects and advantages of this invention are as follows: In this invention, a molecular design that synergistically caps amino silicone oil and hydroxyl acrylate introduces flexible silicone segments and reactive hydroxyl groups at the ends of the polyurethane chain, laying the foundation for low-temperature toughness and secondary crosslinking. A crosslinking strategy combining carbodiimide and epoxy silane is then employed, with the epoxy silane acting as a key bridge. One end is compatible with the siloxane segment, while the other end forms covalent bonds with the silane coupling agent-modified nanoparticles, precisely anchoring the nanofunctional phase within the crosslinking network. This fundamentally solves the storage demulsification problem caused by poor compatibility between nanoparticles and crosslinking agents. Combined with a gradient temperature rise and latent curing matching curing process, the gradual removal of moisture and precise triggering of the crosslinking reaction are achieved at low temperatures. Ultimately, this synergistic process enables the coating to exhibit excellent stability during low-temperature application and storage at 5-10℃, simultaneously achieving a high level of synergy in multiple properties such as water resistance, high adhesion, high moisture permeability, and long-lasting antibacterial and UV resistance. This successfully overcomes the long-standing technical bottlenecks of performance degradation and compatibility in low-temperature water-based systems. Attached Figure Description

[0016] The disclosure of this invention is illustrated with reference to the accompanying drawings. It should be understood that the drawings are for illustrative purposes only and are not intended to limit the scope of protection of this invention. In the drawings, the same reference numerals are used to refer to the same parts: Figure 1 This is a flow chart of the coating preparation process of the present invention; Figure 2 This is a schematic diagram comparing the basic performance of the present invention; Figure 3 This is a comparison chart of the functional extension performance of the present invention. Detailed Implementation

[0017] It is readily understood that, based on the technical solution of this invention, those skilled in the art can propose various interchangeable structural methods and implementations without altering the essential spirit of the invention. Therefore, the following detailed embodiments and accompanying drawings are merely illustrative examples of the technical solution of this invention and should not be considered as the entirety of the invention or as limitations or restrictions on the technical solution of this invention.

[0018] Example 1 Reference Figure 1-3 As shown, the present invention provides a technical solution: a water-based polyurethane coating for textile fabrics, comprising the following steps: Step 1: Preparation of modified waterborne polyurethane emulsion: Polytetramethylene ether glycol with a number average molecular weight of 1500 and polybutylene adipate glycol with a number average molecular weight of 2000 are added to a constant temperature reactor at a mass ratio of 4:1. The temperature is raised to 80℃, and vacuum dehydration is carried out for 2 hours. The purpose of this step is to remove moisture from the raw materials to avoid the reaction of moisture with isocyanate affecting the synthesis of the prepolymer. The temperature is lowered to 70℃, and a mixture of isophorone diisocyanate and dicyclohexylmethane diisocyanate at a mass ratio of 3:1 is added. The mixture is stirred at 300 r / min for 1.5 hours. The hard segment ratio of 3:1 is chosen to balance the flexibility and crosslinking density of the coating. Isophorone diisocyanate provides flexibility, while dicyclohexylmethane diisocyanate enhances mechanical strength. Dimethylolpropionic acid is added at 4.0% of the total mass of soft and hard segments, and the mixture is heated to 75℃ and reacted for 1 hour. The amount of dimethylolpropionic acid is 4.0%. To ensure the emulsion has good water solubility and stability, and to provide carboxyl sites for subsequent crosslinking, a mixture of amino silicone oil with an ammonia value of 0.45 mmol / g and hydroxyethyl acrylate at a mass ratio of 1.5:1 was added and reacted at 80℃ for 2 hours. This ratio is the optimal value for synergistic end-capping agents (1:1-2:1). Amino silicone oil reduces surface energy and improves the feel, while hydroxyethyl acrylate introduces crosslinking sites to enhance wear resistance. The two work synergistically to solve the imbalance between feel and wear resistance. The temperature was lowered to 40℃, and triethylamine was added to neutralize to pH=7.5. Deionized water was added under 1000 r / min shear and dispersed for 30 min to obtain a polyether-polyester copolymer anionic waterborne polyurethane emulsion with a solid content of 40%, a particle size of 80 nm, and a glass transition temperature of -25℃. The solid content and particle size meet the limits of 35%-45% and 50-120 nm, respectively. The glass transition temperature ensures low-temperature stability.

[0019] Step 2: Fabric pretreatment: For polyester fabric with a weight of 150 g / m², use a degreasing solution with a concentration of 3 g / L, and a deionized water:nonionic degreasing agent ratio of 99.7:0.3. The degreasing temperature is 70℃ and the time is 25 min. These parameters are the conventional optimal values ​​within the concentration range of 99.8:0.2-99.5:0.5 and the temperature range of 60-80℃. This can thoroughly remove industrial oil stains from the polyester surface and avoid degreasing agent residue. Rinse twice, dry at 90℃ for 20 min until the moisture content is 2%, and cool for later use. The moisture content of 2% meets the limit of ≤3%, ensuring uniform emulsification of the subsequent coating liquid.

[0020] Step 3: Prepare the coating liquid using the following steps. Raw materials: 15 parts deionized water, 0.3 parts nonionic alkyl polyoxyethylene ether with an HLB value of 14, 0.1 parts polyether-modified siloxane defoamer, 0.3 parts propylene glycol monomethyl ether, stir at 300 rpm for 15 minutes. 15 parts deionized water corresponds to a conventional dosage of 10-30 parts. The nonionic alkyl polyoxyethylene ether with an HLB value of 14 meets the limit of 12-15, ensuring a good wetting effect on polyester fabrics. Step 31: Add 70 parts of the above modified waterborne polyurethane emulsion, stir at 200 r / min for 20 min. The amount of 70 parts of emulsion is in the range of 60-85 parts, which is suitable for the coating thickness requirements of conventional clothing fabrics. Step 32: Add 1.5 parts of nano-functional modifier (3-aminopropyltriethoxysilane modified nano-silica: nano-zinc oxide = 2.5:1, nano-silica particle size 20nm, nano-zinc oxide particle size 30nm, 3-aminopropyltriethoxysilane dosage is 8% of the total mass of nanoparticles), shear at 800r / min for 30min. The 2.5:1 mixing ratio is the optimal value between 2:1 and 3:1. The 8% dosage of 3-aminopropyltriethoxysilane is within the range of 5% to 10%, which effectively solves the problem of nanoparticle aggregation and improves compatibility with emulsion. Step 33: Add 2.5 parts of environmentally friendly compound crosslinking agent (carbodiimide crosslinking agent: 3-glycidyl etheroxypropyltrimethoxysilane = 2:1), 0.5 parts of blocked isocyanate with a desealing temperature of 90℃, stir for 25 minutes. The 2:1 compounding ratio is the optimal value between 1:1 and 3:2. The carbodiimide crosslinking agent and 3-glycidyl etheroxypropyltrimethoxysilane work synergistically to achieve hydrolysis resistance and strong adhesion. The desealing temperature of 90℃ for the blocked isocyanate is within the 80-100℃ limit, ensuring desealing and crosslinking during pre-baking. Step 34: Add 1.0 part of feel modifier (polyether modified polydimethylsiloxane: fatty acid ester slip agent = 3:1), 0.3 parts of nonionic hydrophobic modified alkali-swelling thickener, stir for 20 min, filter through 120 mesh, viscosity 5000 mPa·s. The 3:1 feel modifier ratio is the optimal value between 2:1 and 4:1. The amount of nonionic hydrophobic modified alkali-swelling thickener is 0.3 parts, which is within the range of 0.1-0.6 parts. The viscosity of 5000 mPa·s is within the limit of 3000-8000 mPa·s and is suitable for roller coating process.

[0021] Step 4: Coating application: Use roller coating method, coating amount 20g / m², coating speed 5m / min, temperature 25℃. The coating amount of 20g / m² is in the range of 10-50g / m², which is suitable for the functional requirements of conventional clothing fabrics. Roller coating method is highly efficient and suitable for mass production.

[0022] Step 5: Pre-baking and curing: Pre-baking is carried out in stages, with 65℃ / 8min and 85℃ / 5min performed sequentially. The curing temperature is 105℃ / 12min. After cooling to room temperature, the pre-baking parameters are within the range of 60-75℃ and 80-95℃ to avoid rapid evaporation of moisture that could lead to pinholes. The curing temperature of 105℃ is within the range of 100-110℃ to ensure sufficient cross-linking without damaging the fabric.

[0023] Step 6: Post-processing: Dust removal using 0.4MPa high-pressure airflow, calendering, defect repair, and trimming. The dust removal pressure is within the range of 0.3-0.5MPa, and the calendering parameters meet the limits to optimize the coating feel and smoothness.

[0024] Step 7: Test results: Resistant to 55 washes, adhesion grade 0, moisture permeability 8100g / (m²·24h), hand feel 9.2 points, no delamination after 6 months of storage at 5℃, E. coli inhibition rate 95%, UPF=32, yellowing resistance grade 1.

[0025] This embodiment achieves an optimal balance of various properties through the synergistic effects of end-capping, compound cross-linking, and modified nanoparticles, fully meeting the usage requirements of conventional clothing fabrics. It highlights the multi-synergistic technical advantages of this invention. Compared with the prior art, the number of washes, adhesion, and moisture permeability are significantly improved, and the low-temperature storage stability is excellent.

[0026] Example 2 Step 1: Preparation of modified waterborne polyurethane emulsion: Polytetramethylene ether glycol with a number average molecular weight of 2000 and polybutylene adipate glycol with a number average molecular weight of 2500 are mixed at a mass ratio of 5:1. This ratio is the upper limit of 3:2-5:1, focusing on improving hydrolysis resistance and adapting to outdoor textiles that are exposed to rain for extended periods. Isophorone diisocyanate and dicyclohexylmethane diisocyanate are mixed at a mass ratio of 4:1. A 4:1 ratio of hard segments enhances crosslinking density, improving coating strength and abrasion resistance. Dimethylolpropionic acid accounts for 4.5%, which is relatively high within the range of 3.5%-5.0%, ensuring the stability of the emulsion in complex outdoor environments. 85 The reaction was carried out at ℃ for 3.5 hours to ensure sufficient synthesis of the prepolymer. Amino silicone oil with an ammonia value of 0.6 mmol / g was compounded with hydroxyethyl acrylate at a mass ratio of 2:1 for end-capping. The 2:1 end-capping ratio focuses on a soft hand feel. The dosage of 4.0% is within the range of 2.0%-4.5% to enhance the end-capping effect. The reaction was carried out at 75℃ for 2.5 hours to obtain a polyether-polyester copolymer anionic waterborne polyurethane emulsion with a solid content of 45%, a particle size of 100 nm, and a glass transition temperature of -20℃. The solid content of 45% is relatively high within the range of 35%-45%, which is suitable for the thick coating requirements of outdoor textiles. The particle size of 100 nm meets the 50-120 nm limit.

[0027] Step 2: Fabric Pretreatment: Use polyester tent fabric with a weight of 150g / m², degreasing solution concentration of 5g / L, deionized water: non-ionic degreasing agent = 99.5:0.5, which is the upper limit of the concentration range of 99.8:0.2-99.5:0.5, to thoroughly remove industrial oil stains from the polyester surface, 80℃ / 30min, which is the upper limit of degreasing temperature and time, to enhance the degreasing effect, rinse twice, dry at 100℃ / 15min to a moisture content of 1%, which is lower than the limit of ≤3%, to further ensure the adhesion between the coating liquid and the fabric.

[0028] Step 3: Prepare the coating liquid using the following steps. 10 parts deionized water (lower limit of 10-30 parts) is suitable for high-solids coating liquids; 0.5 parts of nonionic alkyl polyoxyethylene ether with an HLB value of 14 (relatively high range of 0.1-0.8 parts) enhances penetration into heavy tent fabrics; 0.2 parts of polyether-modified siloxane defoamer (range of 0.05-0.3 parts) meets the defoaming requirements of high-viscosity coating liquids; and 0.4 parts of propylene glycol monomethyl ether (range of 0.1-0.5 parts) enhances outdoor low-foaming properties. Storage stability under warm conditions: Adding 80 parts of the above-mentioned modified waterborne polyurethane emulsion, within the range of 60-85 parts, is relatively high and suitable for thick coating requirements. Adding 2.5 parts of nano-functional modifier, 3-aminopropyltriethoxysilane-modified nano-silica: nano-zinc oxide = 3:1, nano-silica particle size 30nm, nano-zinc oxide particle size 40nm, the amount of 3-aminopropyltriethoxysilane is 10% of the total mass of nanoparticles, and the 3:1 mixing ratio is 2:1. The upper limit of -3:1 focuses on improving abrasion resistance. The dosage of 3-aminopropyltriethoxysilane is 10%, within the range of 5%-10%, maximizing the compatibility between nanoparticles and the emulsion. 3.5 parts of an environmentally friendly compound crosslinking agent (carbodiimide crosslinking agent: 3-glycidyl ether propyltrimethoxysilane = 3:2) are added, within the range of 1.5-4.0 parts. The 3:2 compounding ratio emphasizes hydrolysis resistance, making it suitable for humid outdoor environments. The sealing temperature is 90℃. 0.8 parts of type Isocyanate, within the range of 0.2-0.8 parts, increases crosslinking density; 0.5 parts of feel modifier (polyether modified polydimethylsiloxane: fatty acid ester slip agent = 2:1), within the range of 0.3-2.0 parts, the 2:1 ratio focuses on abrasion resistance, suitable for outdoor use needs; 0.5 parts of nonionic hydrophobic modified alkali swelling thickener, within the range of 0.1-0.6 parts, adjusts viscosity to 7000 mPa·s, suitable for scraping coating process.

[0029] Step 4: Coating application: Use the scraper method, with a coating amount of 40g / m², which is slightly higher in the range of 10-50g / m² to form a thick coating and improve outdoor durability; the speed is 2m / min, which is suitable for the scraper method and the need for a thick coating; the temperature is 25℃, which is the normal construction temperature.

[0030] Step 5: Pre-baking and curing: Use 70℃ / 5min and 90℃ / 3min for pre-baking to meet the moisture removal requirements of thick coatings. 110℃ / 8min is the upper limit of curing temperature and the lower limit of time, which improves production efficiency while ensuring sufficient cross-linking.

[0031] Step 6: Post-processing: 0.5MPa high-pressure airflow dust removal, which is the upper limit of pressure, to thoroughly remove impurities from the surface of outdoor fabrics, and shape and finish (95℃ / 4min) to meet the dimensional stability requirements of outdoor textiles.

[0032] Step 7: Test results: Water wash resistance 60 times, adhesion grade 0, moisture permeability 7900g / (m²·24h), dry rubbing color fastness grade 5, hand feel 8.8 points, no delamination after 6 months of storage at 10℃, E. coli inhibition rate 96%, UPF=35, yellowing resistance grade 1.

[0033] This embodiment optimizes the raw material ratio and process parameters to meet the usage requirements of outdoor textiles, focusing on improving washability, abrasion resistance, and UV resistance. Through high-solids-content emulsion, thick coating, and enhanced cross-linking design, it meets the long-term use requirements of complex outdoor environments. Compared with existing technologies, the number of washes is increased to 60, and the UV resistance UPF value reaches 35, which is significantly better than conventional outdoor coatings. It also has excellent low-temperature storage stability, solving the pain points of easy aging and insufficient durability of outdoor textile coatings.

[0034] Example 3 Step 1: Preparation of modified waterborne polyurethane emulsion: Polytetramethylene ether glycol with a number average molecular weight of 1000 and polybutylene adipate glycol with a number average molecular weight of 1500 are mixed at a mass ratio of 3:2, which is the lower limit of 3:2-5:1, focusing on improving flexibility and adapting to lightweight nylon fabrics. Isophorone diisocyanate and dicyclohexylmethane diisocyanate are mixed at a mass ratio of 2:1, which is the lower limit of the hard segment ratio, maximizing the improvement of flexibility. The proportion of dimethylolpropionic acid is 3.5%, which is the lower limit of 3.5%-5.0%, avoiding excessive hydrophilicity of the emulsion leading to a decrease in wash resistance. The reaction is carried out at 75℃ for 2.5 hours. The synthesis of a suitable lightweight emulsion requires... The desired solution is to compound and end-cap an amino silicone oil with an ammonia value of 0.3 mmol / g and hydroxypropyl acrylate at a mass ratio of 1:1 (2.0% of the product). The 1:1 end-capping ratio is the lower limit of 1:1-2:1, balancing feel and abrasion resistance. The 2.0% dosage is also a lower limit to avoid excessive coating thickness affecting the breathability of lightweight fabrics. The mixture is reacted at 65℃ for 1.5 hours to obtain a polyether-polyester copolymer anionic waterborne polyurethane emulsion with a solid content of 35%, a particle size of 60 nm, and a glass transition temperature of -30℃. The 35% solid content is the lower limit, suitable for lightweight coatings. The -30℃ glass transition temperature meets the -35℃--15℃ limit, ensuring stability during low-temperature application.

[0035] Step 2: Fabric pretreatment: For nylon fabric with a weight of 110 g / m², use an oil remover concentration of 2 g / L, with a deionized water:nonionic oil remover ratio of 99.8:0.2 (the lower limit of the concentration range of 99.8:0.2-99.5:0.5) to avoid residual oil remover damaging the nylon fibers. Rinse at 60℃ for 20 min (the lower limit of degreasing temperature and time) to protect the elasticity of the nylon fibers. Rinse 3 times (the lower limit of more than 23 times) to thoroughly remove the oil remover. Dry at 80℃ for 25 min until the moisture content is 2.5%. Low-temperature slow drying protects the nylon fibers. A moisture content of 2.5% meets the ≤3% limit.

[0036] Step 3: Prepare the coating liquid using the following steps. 25 parts deionized water (upper limit of 10-30 parts) is suitable for low-solids coating liquids and improves breathability; 0.8 parts nonionic alkyl polyoxyethylene ether with an HLB value of 14 (upper limit of 0.1-0.8 parts) improves the wetting effect on smooth nylon fabrics; 0.1 parts polyether-modified siloxane defoamer is suitable for low-viscosity coating liquids; 0.5 parts propylene glycol monomethyl ether (upper limit of 0.1-0.5 parts) maximizes low-temperature storage and construction stability; adding 60 parts... The above-mentioned modified waterborne polyurethane emulsion has a lower limit of 6085 parts, suitable for thin coatings. It incorporates 1.0 part of a nano-functional modifier, with a 3-glycidyl etheroxypropyltrimethoxysilane-modified nano-silica:nano-zinc oxide ratio of 2:1. The nano-silica particle size is 15 nm, and the nano-zinc oxide particle size is 20 nm. The amount of 3-glycidyl etheroxypropyltrimethoxysilane is 5% of the total mass of the nanoparticles. The 2:1 ratio balances wear resistance and antibacterial properties. The nanoparticle size is relatively small. To avoid affecting the feel of lightweight fabrics, 5% of 3-glycidyl etheroxypropyltrimethoxysilane is the minimum recommended dosage. This ensures compatibility while avoiding excessive cost. Adding 1.5 parts of an environmentally friendly compound crosslinking agent (carbodiimide crosslinking agent: 3-glycidyl etheroxypropyltrimethoxysilane = 1:1) is the minimum recommended dosage of 1.5-4.0 parts. The 1:1 ratio balances hydrolysis resistance and adhesion, meeting the needs of lightweight fabrics. 0.2 parts of a blocked isocyanate with a desealing temperature of 90℃ are also included. The lower limit is 0.2-0.8 parts to avoid excessive cross-linking that could cause the fabric to stiffen. 1.5 parts of hand feel modifier are added. The ratio of polyether-modified polydimethylsiloxane to fatty acid ester slip agent is 4:1, which is the median value of 0.3-2.0 parts. The 4:1 ratio emphasizes a soft hand feel, suitable for the needs of clothing fabrics. 0.1 parts of nonionic hydrophobic modified alkali swelling thickener is the lower limit of 0.1-0.6 parts, which adjusts the viscosity to 3000 mPa·s, suitable for roller coating and lightweight fabrics.

[0037] Step 4: Coating Application: Use roller coating method with a coating amount of 10g / m², which is the lower limit of 10-50g / m², suitable for thin fabrics. The speed is 2.5m / min, which is lower than the conventional construction speed, suitable for low temperature environments. The temperature is 5℃, which meets the 5-10℃ limit for low temperature construction. The coating roller is preheated to 18℃ to avoid sudden changes in the viscosity of the coating liquid and solve the defects of low temperature construction.

[0038] Step 5: Pre-baking and curing: 75℃ / 7min; 95℃ / 4min. The pre-baking temperature and time are higher than the conventional parameters to meet the moisture removal requirements of low-temperature construction. 100℃ / 15min is the lower limit of the curing temperature and the upper limit of the time to ensure sufficient cross-linking at low temperature.

[0039] Step 6: Post-processing: 0.3MPa high-pressure airflow dust removal, which is the lower limit of pressure to avoid damaging the thin fabric; calendering, low temperature and low pressure, to protect the nylon fibers and thin coating.

[0040] Step 7: Test results: Resistant to 50 washes, adhesion grade 0, moisture permeability 8300g / (m²·24h), no delamination after 6 months of storage at 0℃, E. coli inhibition rate 94%, UPF=30, yellowing resistance grade 1.

[0041] This embodiment addresses the low-temperature application requirements of lightweight nylon garment fabrics by optimizing parameters and emphasizing flexibility, breathability, and low-temperature application stability. Through designs such as low-solids emulsion, thin coating, and low-temperature adaptability processes, it meets the usage requirements of high-end garment fabrics. Compared with existing technologies, there is no pinhole peeling after low-temperature application, and the moisture permeability reaches 8300g / (m²·24h). It solves the pain points of difficult low-temperature application of lightweight fabrics and the difficulty in balancing breathability and washability. At the same time, it has antibacterial and UV protection functions, expanding its application scenarios.

[0042] Compare with Example 1 Compared with Example 1, the distinguishing feature is that hydroxyethyl acrylate is omitted in the synthesis of the modified waterborne polyurethane emulsion, and only an equal amount of amino silicone oil is used for end capping. The amount used is still 3.0% of the total monomer mass. The other raw materials, ratios and processes remain unchanged. The purpose of this control sample is to verify the necessity of synergistic end capping of amino silicone oil and hydroxy acrylate, and to compare the performance differences between single end capping and synergistic end capping.

[0043] Performance test results: Resistant to 35 washes, adhesion grade 2, moisture permeability 7500g / (m²·24h), no delamination after 6 months of storage at 5℃, E. coli inhibition rate 85%, UPF=25, yellowing resistance grade 2.

[0044] The control sample lacked crosslinking active sites for hydroxyethyl acrylate, resulting in insufficient crosslinking density in the coating. Consequently, the number of washes decreased from 55 to 35, the adhesion dropped from grade 0 to grade 2, and the abrasion resistance and structural stability significantly decreased. Furthermore, although a single amino silicone oil end-capping agent could ensure a certain feel, it could not form an effective synergy with the compound crosslinking agent. The moisture permeability, antibacterial properties, and UV resistance were all lower than those of Example 1. This fully demonstrates the necessity of a synergistic end-capping agent compounded in a 1:1 to 2:1 ratio, highlighting the non-obvious nature of this technical feature of the present invention, which cannot be replaced by simply using a single end-capping agent.

[0045] Compare with Example 2 Compared with Example 1, the distinguishing feature is that 3-glycidyl etheroxypropyltrimethoxysilane is removed from the coating liquid, and only 2.5 parts of carbodiimide crosslinking agent are used. The other raw materials, ratios and processes remain unchanged. The purpose of this control sample is to verify the necessity of compound crosslinking of carbodiimide crosslinking agent and epoxy silane crosslinking agent, and to compare the performance differences between single crosslinking and compound crosslinking.

[0046] Performance test results: Resistant to 30 washes, adhesion grade 2, moisture permeability 5800g / (m²·24h), no delamination after 72h storage at 5℃, E. coli inhibition rate 82%, UPF=23, yellowing resistance grade 2.

[0047] The control sample lacked 3-glycidyl etheroxypropyltrimethoxysilane, which prevented it from forming covalent bonds with the fabric fibers, resulting in an adhesion grade drop from 0 to 2. Furthermore, while a single carbodiimide crosslinking agent could improve hydrolysis resistance, the single crosslinking system failed to effectively bind with the nanoparticles, leading to a loose coating structure. The number of washes decreased from 55 to 30, and the moisture permeability dropped from 8100 g / (m²·24h) to 5800 g / (m²·24h). The overall performance was significantly inferior to Example 1, demonstrating the necessity of using a 1:1 to 3:2 combination of crosslinking agents. The synergistic effect of the two crosslinking agents simultaneously solves both hydrolysis resistance and strong adhesion issues, a feat impossible with existing single crosslinking agent technologies.

[0048] Compare with Example 3 Compared with Example 1, the distinguishing feature is that the nanofunctional modifier is unmodified nano-silica and nano-zinc oxide in a compounding ratio of 2.5:1. All other raw materials, ratios and processes remain unchanged. The purpose of this control sample is to verify the necessity of modifying nanoparticles with silane coupling agents and to compare the effects of modified and unmodified nanoparticles on performance.

[0049] Performance test results: Resistant to 25 washes, adhesion grade 3, moisture permeability 6200g / (m²·24h), delamination after 24h storage at 5℃, E. coli inhibition rate 80%, UPF=22, yellowing resistance grade 3.

[0050] The control sample, due to the lack of 3-aminopropyltriethoxysilane modification of the nanoparticles, exhibited a significant difference in surface polarity compared to the polyurethane emulsion, leading to severe agglomeration. The coating solution delaminated after 24 hours of storage at 5°C, exhibiting extremely poor stability. Furthermore, the unmodified nanoparticles could not form effective chemical bonds with the emulsion and crosslinking agent, resulting in numerous internal defects in the coating. The number of washes decreased to 25, the adhesion dropped to grade 3, and the antibacterial and UV resistance properties also significantly declined. This fully demonstrates the necessity of silane coupling agent modification, which solves the compatibility problem between the nanoparticles and the system—a feat unattainable with unmodified nanoparticle technology.

[0051] Compare with Example 4 Compared with Example 1, the distinguishing feature is that the coating is directly cured at 105°C for 20 minutes, and the segmented pre-baking is cancelled. All other raw materials, proportions and processes remain unchanged. The purpose of this control sample is to verify the necessity of the segmented pre-baking process and to compare the performance differences between segmented curing and direct curing.

[0052] Performance test results: Resistant to 20 washes, adhesion grade 3, moisture permeability 5500g / (m²·24h), pinholes on the coating surface 4 / cm², no delamination after 6 months of storage at 5℃, E. coli inhibition rate 83%, UPF=24, yellowing resistance grade 3.

[0053] Because the segmented pre-baking was omitted, the moisture in the wet film evaporated rapidly, resulting in a large number of pinholes on the coating surface. The residual moisture inside vaporized during the curing process, further damaging the coating structure. At the same time, direct high-temperature curing led to uneven cross-linking reaction, stress concentration inside the coating, a decrease in the number of water washes to 20, an adhesion level to 3, and a significant decrease in moisture permeability. The overall performance was inferior to that of Example 1, proving the necessity of the segmented pre-baking and low-temperature curing process. This process design avoids the problems of residual moisture and uneven cross-linking, which cannot be achieved by the direct curing process, demonstrating the innovation of the process design.

[0054] Compare with Example 5 Compared with Example 1, the distinguishing feature is that, in the synthesis of the modified waterborne polyurethane emulsion, the mixture of polytetramethylene ether glycol and polybutylene adipate glycol is not used. Instead, only polybutylene adipate glycol of equal mass, which is consistent with the total mass of the two soft segments in Example 1, is used as a single soft segment. All other raw materials, ratios, and processes remain unchanged. This control sample aims to verify the necessity of copolymerizing polyether and polyester in a ratio of 3:2-5:1 in this invention to solve the contradiction between low-temperature film-forming properties and hydrolysis resistance, and to clarify that a single type of soft segment cannot meet the dual performance requirements.

[0055] This control sample used only a single soft segment of polybutylene adipate diol. Although it maintained a certain degree of water resistance under conventional construction at 25°C, the glass transition temperature rose to -10°C, resulting in a significant decrease in low-temperature flexibility. Slight cracking occurred when bending at -20°C. Under low-temperature construction at 5°C, due to the increased crystallinity and insufficient flexibility of the soft segment, the coating film-forming properties were poor, resulting in a large number of pinholes. The adhesion and water resistance were significantly worse than in Example 1. This fully demonstrates that the soft segment design of this invention, which uses polytetramethylene ether diol and polybutylene adipate diol in a ratio of 3:2-5:1, is not a conventional single soft segment selection or simple ratio adjustment. Rather, it is a key and non-obvious molecular structure optimization to address the industry contradiction of not being able to simultaneously achieve low-temperature toughness and long-term hydrolysis resistance. Only this specific copolymerization ratio can simultaneously meet the comprehensive performance requirements of both conventional and low-temperature construction scenarios.

[0056] To more intuitively and systematically compare the core performance differences of the technical solutions of this invention, the embodiments, and various comparative examples, and to clarify the impact of each technical feature on the final effect, the core performance test data of all samples are summarized in the table below.

[0057] The technical scope of this invention is not limited to the content described above. Those skilled in the art can make various modifications and variations to the above embodiments without departing from the technical concept of this invention, and all such modifications and variations should fall within the protection scope of this invention.

Claims

1. A waterborne polyurethane coating for textile fabrics, characterized in that, The raw materials include the following parts by weight: 60-85 parts modified waterborne polyurethane emulsion, 1.5-4.0 parts environmentally friendly compound crosslinking agent, 0.5-3.0 parts nano-functional modifier, 0.3-2.0 parts feel modifier, 0.1-0.8 parts wetting and penetrating agent, 0.05-0.3 parts defoamer, 0.1-0.6 parts thickener, 0.1-0.5 parts low-temperature stabilizing agent, 0.2-0.8 parts latent curing agent, and 10-30 parts deionized water; The modified waterborne polyurethane emulsion is an anionic emulsion prepared by using a mixture of polytetramethylene ether glycol and polybutylene adipate glycol as soft segments, a mixture of isophorone diisocyanate and dicyclohexylmethane diisocyanate as hard segments, and a mixture of amino silicone oil and hydroxy acrylate for synergistic end-capping reaction, while using dimethylolpropionic acid as a hydrophilic chain extender. The nanofunctional modifier is a compound of silane coupling agent modified nano silica and nano zinc oxide in a mass ratio of 2:1-3:1, with nano silica having a particle size of 15-30 nm and nano zinc oxide having a particle size of 20-40 nm. The feel modifier is a compound of polyether-modified polydimethylsiloxane and fatty acid ester slip agent in a mass ratio of 2:1-4:1; The environmentally friendly compound crosslinking agent is a mixture of carbodiimide crosslinking agent and epoxy silane crosslinking agent in a mass ratio of 1:1 to 3:

2.

2. The waterborne polyurethane coating for textile fabrics according to claim 1, characterized in that: The mass ratio of amino silicone oil to hydroxy acrylate is 1:1 to 2:1, and the hydroxy acrylate is selected from hydroxyethyl acrylate or hydroxypropyl acrylate.

3. The waterborne polyurethane coating for textile fabrics according to claim 1, characterized in that: The polytetramethylene ether glycol and polybutylene adipate glycol are mixed in a mass ratio of 3:2-5:1 to form the soft segment, and the isophorone diisocyanate and dicyclohexylmethane diisocyanate are mixed in a mass ratio of 2:1-4:1 to form the hard segment.

4. The waterborne polyurethane coating for textile fabrics according to claim 1, characterized in that: The silane coupling agent in the nanofunctional modifier modifies nano-silica by forming covalent bonds with the epoxy silane crosslinking agent through residual silanol groups on the surface.

5. The waterborne polyurethane coating for textile fabrics according to claim 1, characterized in that: The modified waterborne polyurethane emulsion has a solid content of 35%-45% and a particle size of 50-120 nm; the silane coupling agent is 3-aminopropyltriethoxysilane or 3-glycidyl etheroxypropyltrimethoxysilane, and the amount used is 5%-10% of the total mass of nano-silica and nano-zinc oxide.

6. The waterborne polyurethane coating for textile fabrics according to claim 1, characterized in that: The wetting and penetrating agent is a nonionic alkyl polyoxyethylene ether with an HLB value of 12-15.

7. The waterborne polyurethane coating for textile fabrics according to claim 1, characterized in that: The defoamer is a polyether-modified siloxane defoamer; the thickener is a nonionic hydrophobic modified alkali-swelling thickener.

8. The waterborne polyurethane coating for textile fabrics according to claim 1, characterized in that: The latent curing agent is a blocked isocyanate with a desealing temperature of 80-100℃.

9. A method for preparing an aqueous polyurethane coating for a textile fabric according to any one of claims 1-8, characterized in that, Includes the following steps: S1: Under stirring, the wetting and penetrating agent, defoamer, and low-temperature stabilizing agent are added sequentially to deionized water, followed by the modified waterborne polyurethane emulsion and mixed evenly; then, the nano-functional modifier is added under shear dispersion conditions of 500-1000 r / min and continuously dispersed; finally, the environmentally friendly compound crosslinking agent, feel modifier, thickener, and latent curing agent are added and mixed evenly to obtain the coating liquid; S2: The coating liquid is applied to the surface of the textile substrate, and then low-temperature pre-baking, medium-temperature pre-baking and high-temperature curing are performed in sequence, wherein the low-temperature pre-baking temperature is 60-75℃, the medium-temperature pre-baking temperature is 80-95℃, and the high-temperature curing temperature is 100-110℃.

10. The application of a waterborne polyurethane coating on a textile fabric according to any one of claims 1-9, characterized in that, The coating can be applied to the surface of textiles by scraping, rolling, spraying or printing, and can be used in clothing, home textiles, outdoor textiles and other fields.

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