Stretch resistant multi-layer pu leather material and method for producing the same

Abstract

The application provides a kind of stretchable multi-layer PU leather material and its production method, leather material includes from inside to outside anti-permeation base cloth layer, adhesive layer, PU composite film layer, microcapsule slow-release functional finishing layer;The thickness of adhesive layer is 0.15-0.25mm;PU composite film layer is made of the inner layer high crosslinking PU layer with the thickness of 0.25-0.35mm and the outer layer low crosslinking PU layer with the thickness of 0.15-0.25mm;The inner layer high crosslinking PU layer is formed by curing SiO2 modified polyurethane resin slurry, and the outer layer low crosslinking PU layer is formed by curing polyurethane resin slurry;SiO2 modified polyurethane resin slurry and polyurethane resin slurry both contain aziridine crosslinking agent;The thickness of the microcapsule slow-release functional finishing layer is 0.05-0.10mm.The leather material effectively solves the problem that traditional PU leather is easy to break after thinning, and improves the stretch resistance and antibacterial effect.

Description

Technical Field

[0001] This invention belongs to the field of functional artificial leather technology, specifically relating to a tensile-resistant multilayer PU leather material and its production method. Background Technology

[0002] PU leather is a type of artificial leather material with polyurethane (PU) as the main film-forming substance. With its soft touch, wear-resistant and scratch-resistant properties, and highly realistic leather appearance, it is widely used in car seat upholstery, high-end bag fabrics, and antibacterial clothing linings. It not only plays a decorative role but also needs to meet functional requirements such as waterproofing and antibacterial properties, making it an important material in both industrial and consumer goods sectors.

[0003] Existing PU leather exhibits several performance defects: First, insufficient tensile strength: With the trend towards lightweight and thinner products, the interlayer bonding of traditional PU leather is weak, making it prone to delamination under long-term tensile stress; simultaneously, the overall elongation at break is low, making it difficult to meet the deformation requirements of dynamic usage scenarios. Second, limited environmental friendliness: The solvent-based adhesives used in traditional PU leather production contain a large amount of volatile organic compounds, which can easily cause air pollution after emission; some fluorinated waterproofing agents, due to their long carbon chains (such as C8), have environmental durability and are restricted by international environmental regulations, while alternative materials lack sufficient waterproof durability. Third, poor long-term functionality: When antibacterial and adsorption functional ingredients are directly added to the coating layer, they are easily lost due to friction, washing, or changes in ambient temperature; the antibacterial rate can drop to below 50% within 7 days; the functional ingredients are only physically bonded to the substrate, lacking chemical bonding, and are prone to detachment after long-term use, leading to functional failure.

[0004] Existing technologies have proposed various improvement solutions to address the above problems, such as using a single high-crosslinking density PU resin, adding a small amount of bio-based plasticizer, and directly mixing antibacterial agents (such as quaternary ammonium salts) with adsorbent particles (such as activated carbon) and then coating them onto the surface.

[0005] The method of directly mixing antibacterial agents with adsorbent particles and then coating them onto a surface has the following drawbacks. On the one hand, the antibacterial agent (such as quaternary ammonium salt) is not treated with any protective measures and is directly exposed to the coating surface. During use, it dissolves rapidly due to friction, washing, or increased ambient temperature, causing the antibacterial rate to plummet from the initial 90% to below 40% within 7 days, failing to meet long-term antibacterial requirements. On the other hand, the adsorbent particles (such as activated carbon) and PU resin are only physically dispersed and mixed. Due to differences in surface energy, the particles are prone to agglomeration, which not only reduces adsorption efficiency but also creates stress concentration points within the coating layer, leading to a decrease in coating strength and easy peeling during use. In addition, the functional components lack chemical bonding with the PU film layer and are only fixed by physical interlocking. Under long-term stretching or bending, interfacial separation easily occurs between the functional layer and the substrate, further accelerating functional failure.

[0006] Therefore, there is an urgent need for a tensile-resistant multilayer PU leather material and its production method that utilizes the synergistic effects of multilayer structure optimization, environmentally friendly raw material substitution, and functional controlled-release technology. Summary of the Invention

[0007] The purpose of this invention is to provide a tensile-resistant multilayer PU leather material and its production method, which can effectively solve the problems of insufficient tensile properties, poor environmental performance, and lack of long-term functionality of traditional PU leather.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a tensile-resistant multilayer PU leather material, comprising, from the inside out, an impermeable base fabric layer, an adhesive layer, a PU composite film layer, and a microcapsule sustained-release functional coating layer; The impermeable base fabric layer is formed from a polyamide-polyester blended fabric treated with a fluorine-based waterproofing agent solution through a two-dip-two-roll process and a curing treatment. The adhesive layer has a thickness of 0.15-0.25 mm and is formed by curing the adhesive layer slurry; The total thickness of the PU composite film is 0.4-0.6 mm, consisting of an inner highly cross-linked PU layer with a thickness of 0.25-0.35 mm and an outer low-cross-linked PU layer with a thickness of 0.15-0.25 mm. The inner highly cross-linked PU layer is formed by curing SiO2-modified polyurethane resin slurry, and the outer low-cross-linked PU layer is formed by curing polyurethane resin slurry. Both the SiO2-modified polyurethane resin slurry and the polyurethane resin slurry contain aziridine cross-linking agents. The thickness of the microcapsule sustained-release functional coating layer is 0.05-0.10 mm, and it is formed by curing the functional coating layer slurry.

[0009] Furthermore, the mixing ratio of the fluorinated waterproofing agent to water in the fluorinated waterproofing agent solution is (1.5-2):1000, and the fluorinated waterproofing agent is a C6 waterproofing agent.

[0010] Furthermore, the adhesive layer slurry comprises, by weight, 70-80 parts castor oil polyester polyol, 30-40 parts HDI type isocyanate prepolymer, 5-8 parts epoxidized soybean oil, 0.02-0.04 parts organic bismuth catalyst, and 2-4 parts nano-montmorillonite.

[0011] Furthermore, the weight ratio of the SiO2 modified polyurethane resin slurry and the aziridine crosslinking agent contained in the polyurethane resin slurry is (8-10):(3-5).

[0012] Furthermore, the SiO2-modified polyurethane resin slurry comprises, by weight, 80-90 parts of SiO2-modified polyurethane resin, 8-10 parts of aziridine crosslinking agent, 5-8 parts of propylene glycol methyl ether acetate, and 10-15 parts of magnesium hydroxide; the polyurethane resin slurry comprises, by weight, 85-95 parts of polyurethane, 3-5 parts of aziridine crosslinking agent, 3-6 parts of propylene glycol methyl ether acetate, and 2-5 parts of color paste.

[0013] Furthermore, the SiO2-modified polyurethane resin is prepared by in-situ polymerization, which involves grafting γ-aminopropyltriethoxysilane onto the surface of SiO2 nanoparticles with a particle size of 20-50 nm and then blending them with a polyurethane prepolymer.

[0014] Furthermore, the functional coating slurry comprises, by weight, 60-70 parts of waterborne polyurethane dispersion, 10-15 parts of nano bamboo charcoal powder, 5-8 parts of tea tree essential oil microcapsules, and 3-5 parts of nano silica.

[0015] The present invention also provides a method for producing the tensile-resistant multilayer PU leather material as described above, comprising the following steps: S1. Preparation of impermeable base fabric: The polyamide-polyester blended fabric is immersed in a fluorine-based waterproofing agent solution, treated by a two-dip and two-roll process, and then baked to obtain the impermeable base fabric. S2, Adhesive layer coating: Apply adhesive slurry to the surface of the impermeable base fabric and pre-bake at 80-90℃ for 2 minutes to form an adhesive layer; S3, PU composite film forming: First, the SiO2 modified polyurethane resin slurry is coated onto release paper and baked at 120-130℃ for 3 minutes to form an inner highly cross-linked PU layer; then, polyurethane resin slurry is coated onto the surface of the inner highly cross-linked PU layer and baked at 100-110℃ for 2 minutes to form an outer low cross-linked PU layer, thus obtaining a PU composite film. S4. Interlayer lamination: The inner highly cross-linked PU layer of the PU composite film is bonded to the adhesive layer, and after hot pressing and cooling, the release paper is peeled off to obtain a semi-finished product. S5. Microcapsule sustained-release functional coating: The functional coating slurry is coated onto the surface of the outer low cross-linked PU layer of the semi-finished product, baked at 80-90℃ for 2 minutes, and then baked at 110-120℃ for 1 minute to form a microcapsule sustained-release functional coating layer, thus obtaining the finished product.

[0016] Furthermore, in step S1, the roll residue of the polyamide-polyester blended fabric after the two-dip and two-roll process is 65%-75%.

[0017] Furthermore, in step S4, the hot pressing conditions are: hot pressing temperature of 110-120℃, pressure of 0.3-0.5MPa, and hot pressing time of 25-30 seconds.

[0018] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows: 1. In the leather material of this invention, the PU composite film layer is designed with a gradient between an inner highly cross-linked PU layer and an outer low-cross-linked PU layer. The difference in cross-linking agent content between the two layers regulates the cross-linking density of the molecular chains. The inner highly cross-linked PU layer forms a tight network structure, providing high modulus support; the outer low-cross-linked PU layer retains space for the molecular chains to move, maintaining flexibility. Simultaneously, the SiO2-modified polyurethane resin, through grafting γ-aminopropyltriethoxysilane onto the surface of nanoparticles, enhances the compatibility between SiO2 and the PU molecular chains, avoids localized stress concentration, effectively solves the problem of easy breakage after thinning traditional PU leather, and effectively improves the tensile strength of the leather material. 2. The microcapsule sustained-release coating layer in the leather material of this invention uses microcapsules to encapsulate tea tree oil. Utilizing the composite coagulation effect of polymer materials, a dense capsule wall is formed on the surface of the tea tree oil. During use, the capsule wall slowly swells and releases the tea tree oil, significantly extending the duration of action of the antibacterial components. Simultaneously, the porous structure of the nano-bamboo charcoal powder provides more adsorption sites, and the continuous phase structure of the waterborne polyurethane avoids the agglomeration of the bamboo charcoal powder, balancing the adsorption performance with the strength of the microcapsule sustained-release coating layer, thus achieving long-lasting functionality. Detailed Implementation

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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.

[0020] Example 1: A tensile-resistant multilayer PU leather material, comprising, from the inside out, an impermeable base fabric layer, an adhesive layer, a PU composite film layer, and a microcapsule sustained-release coating layer; The impermeable base fabric layer is formed from a polyamide-polyester blended fabric treated with a fluorine-based waterproofing agent solution through a two-dip-two-roll process and a curing treatment. The adhesive layer has a thickness of 0.2 mm and is formed by curing the adhesive layer slurry; The total thickness of the PU composite film is 0.5 mm, consisting of an inner highly cross-linked PU layer with a thickness of 0.3 mm and an outer low-cross-linked PU layer with a thickness of 0.2 mm. The inner highly cross-linked PU layer is formed by curing SiO2-modified polyurethane resin slurry, and the outer low-cross-linked PU layer is formed by curing polyurethane resin slurry. Both the SiO2-modified polyurethane resin slurry and the polyurethane resin slurry contain aziridine cross-linking agents. The thickness of the microcapsule sustained-release functional coating layer is 0.08 mm, and it is formed by curing the functional coating layer slurry.

[0021] Preparation method of the impermeable base fabric layer: A polyamide-polyester blended fabric (PA6:PET=3:7) was immersed in a fluorine-based C6 waterproofing agent solution (C6 waterproofing agent:water=1.8:1000, temperature 25℃). After a two-dip and two-nip process, the roll residue of the polyamide-polyester blended fabric was reduced to 70%. The fabric was then baked at 185℃ for 35 seconds to obtain a water-impermeable base fabric (thickness 0.3mm) that was impermeable to water within 5 minutes. Preparation method of adhesive layer slurry: Add 75 parts of castor oil polyester polyol to a planetary mixer, heat to 60℃, and stir at 300 r / min for 10 min until completely melted; slowly add 35 parts of HDI type isocyanate prepolymer, and continue stirring for 15 min to ensure full contact between the isocyanate and polyol; sequentially add 6 parts of epoxidized soybean oil (acid value ≤0.5mgKOH / g), 0.03 parts of organic bismuth catalyst (Bi content 18%), and 3 parts of nano-montmorillonite, increase the speed to 800 r / min, and stir for 30 min until the slurry is uniform and free of particles; finally, cool to 50℃ and degas under vacuum (vacuum degree -0.09MPa) for 10 min to obtain the adhesive layer slurry; Preparation method of SiO2 modified polyurethane resin: 1) Surface grafting treatment of SiO2 nanoparticles: 200g of SiO2 nanoparticles (30nm particle size) were added to 500mL of anhydrous ethanol and ultrasonically dispersed for 30min (400W power) to form a uniform dispersion; 10g of γ-aminopropyltriethoxysilane (KH-550) was added to the dispersion, and the pH was adjusted to 4 (using glacial acetic acid). The mixture was refluxed at 70℃ for 4h; after the reaction was completed, the mixture was centrifuged (8000r / min, 10min), washed 3 times with anhydrous ethanol, and vacuum dried at 60℃ for 24h to obtain SiO2 nanoparticles with surface grafted silane coupling agent (grafting rate 88%). 2) Synthesis of SiO2-modified polyurethane resin: 800g of polytetramethylene ether glycol (PTMG, molecular weight 2000) was added to a reactor and dehydrated under vacuum at 110℃ for 1h (vacuum degree -0.09MPa); the temperature was lowered to 70℃, and 200g of isophorone diisocyanate (IPDI) was added. The mixture was reacted at 60℃ for 2h (NCO content controlled at 3.5%) to obtain a PU prepolymer; 45g of SiO2 nanoparticles with surface-grafted silane coupling agent were added to the PU prepolymer and dispersed at high speed at 1500r / min for 30min to form a SiO2 / PU prepolymer mixture; 30g of chain extender 1,4-butanediol (BDO) was added and reacted at 80℃ for 1h; finally, deionized water (solid content adjusted to 62%) was added and emulsified at high speed (10000r / min, 5min) to obtain a SiO2 modified polyurethane resin.

[0022] Preparation method of SiO2 modified polyurethane resin slurry: 85 parts of SiO2-modified polyurethane resin were added to a dispersion vessel and stirred at a low speed of 500 r / min. Then, 9 parts of aziridine crosslinking agent (CX-100, 100% solid content), 7 parts of propylene glycol methyl ether acetate, and 13 parts of magnesium hydroxide (particle size 2 μm) were added in sequence. The speed was increased to 1200 r / min and stirred for 40 min until the slurry was uniform (fineness ≤20 μm) to obtain SiO2-modified polyurethane resin slurry.

[0023] Preparation method of polyurethane resin slurry: Add 90 parts of polyurethane to a dispersion vessel and stir at a low speed of 400 r / min; add 4 parts of aziridine crosslinking agent (CX-100, solid content 100%), 5 parts of propylene glycol methyl ether acetate, and 3 parts of color paste in sequence; increase the speed to 800 r / min and stir for 30 min until the slurry is uniform (fineness ≤15μm) to obtain polyurethane resin slurry.

[0024] Preparation method of functional coating slurry: 1) Preparation of tea tree oil microcapsules: Gelatin (5g) and gum arabic (5g) were dissolved in 400mL of deionized water (40℃) to form a wall material solution (concentration 2.5%); tea tree oil (6g) was added to the wall material solution and emulsified at 10000r / min for 10min to form an O / W emulsion (oil droplet size 5μm); the pH was adjusted to 4.5 with 10% acetic acid solution, the temperature was lowered to 10℃, and 5% glutaraldehyde solution (2mL) was added for curing for 30min; centrifugation (5000r / min, 5min), washing twice with deionized water, and vacuum drying at 60℃ were performed to obtain tea tree oil microcapsules (core material content 60%, average particle size 5μm); 2) Mixing: Add 65 parts of waterborne polyurethane dispersion (solid content 45%, anionic) to the dispersion vessel and stir at 300 r / min; add 12 parts of nano bamboo charcoal powder, 6 parts of tea tree essential oil microcapsules and 4 parts of nano silica (particle size 20 nm) in sequence; stir at 600 r / min for 20 min until uniform (fineness ≤10 μm) to obtain functional coating slurry.

[0025] The production method of PU leather material includes the following steps: S1. Preparation of impermeable base fabric: Polyamide-polyester blended fabric (PA6:PET=3:7) is immersed in fluorine-based C6 waterproofing agent solution (C6 waterproofing agent:water=1.8:1000, temperature 25℃), and after a two-dip and two-padding process, the padding rate of the polyamide-polyester blended fabric is 70%, and it is baked at 185℃ for 35 seconds to obtain an impermeable base fabric (thickness 0.3mm) that is impermeable to water within 5 minutes. S2, Adhesive layer coating: The adhesive slurry is mixed evenly at 70℃ and coated onto the surface of the impermeable base fabric using a comma-shaped scraper. It is then pre-baked at 85℃ for 2 minutes to form an adhesive layer with a thickness of 0.2mm. S3, PU composite film forming: SiO2 modified polyurethane resin slurry is coated onto release paper (texture depth 0.1mm), and baked at 125℃ for 3min to form an inner highly cross-linked PU layer with a thickness of 0.3mm; polyurethane resin slurry is coated onto the surface of the inner highly cross-linked PU layer, and baked at 105℃ for 2min to form an outer low cross-linked PU layer with a thickness of 0.2mm, resulting in a PU composite film with a total thickness of 0.5mm; S4. Interlayer lamination: The inner highly cross-linked PU layer of the PU composite film is bonded to the adhesive layer. The mixture is hot-pressed at 120℃ and 0.5MPa for 30 seconds, and after cooling, the release paper is peeled off to obtain a semi-finished product. S5. Microcapsule sustained-release functional coating: The functional coating slurry is coated onto the surface of the outer low cross-linked PU layer of the semi-finished product using a micro-gravure roller coating process. It is first baked at 85℃ for 2 minutes, and then baked at 115℃ for 1 minute to form a microcapsule sustained-release functional coating layer with a thickness of 0.08 mm, thus obtaining the finished product.

[0026] Example 2: A tensile-resistant multilayer PU leather material, which differs from Example 1 only in that the weight ratio of the SiO2 modified polyurethane resin slurry and the aziridine crosslinking agent contained in the polyurethane resin slurry is 8:3.

[0027] Example 3: A tensile-resistant multilayer PU leather material, comprising, from the inside out, an impermeable base fabric layer, an adhesive layer, a PU composite film layer, and a microcapsule sustained-release coating layer; The impermeable base fabric layer is formed from a polyamide-polyester blended fabric treated with a fluorine-based waterproofing agent solution through a two-dip-two-roll process and a curing treatment. The adhesive layer has a thickness of 0.15 mm and is formed by curing adhesive slurry. The total thickness of the PU composite film is 0.4 mm, consisting of an inner highly cross-linked PU layer with a thickness of 0.25 mm and an outer low-cross-linked PU layer with a thickness of 0.15 mm. The inner highly cross-linked PU layer is formed by curing SiO2-modified polyurethane resin slurry, and the outer low-cross-linked PU layer is formed by curing polyurethane resin slurry. Both the SiO2-modified polyurethane resin slurry and the polyurethane resin slurry contain aziridine cross-linking agents. The thickness of the microcapsule sustained-release functional coating layer is 0.05 mm, and it is formed by curing the functional coating layer slurry.

[0028] Preparation method of the impermeable base fabric layer: A polyamide-polyester blended fabric (PA6:PET=3:7) was immersed in a fluorine-based C6 waterproofing agent solution (C6 waterproofing agent:water=1.5:1000, temperature 25℃). After a two-dip and two-nip process, the roll residue of the polyamide-polyester blended fabric was reduced to 65%. The fabric was then baked at 185℃ for 35 seconds to obtain a water-impermeable base fabric (thickness 0.3mm) that was impermeable to water within 5 minutes. Preparation method of adhesive layer slurry: Add 70 parts of castor oil polyester polyol to a planetary mixer, heat to 60℃, and stir at 300 r / min for 10 min until completely melted; slowly add 30 parts of HDI type isocyanate prepolymer, and continue stirring for 15 min to ensure full contact between the isocyanate and polyol; add 5 parts of epoxidized soybean oil (acid value ≤0.5mgKOH / g), 0.02 parts of organic bismuth catalyst (Bi content 18%), and 2 parts of nano-montmorillonite in sequence, increase the speed to 800 r / min, and stir for 30 min until the slurry is uniform and free of particles; finally, cool to 50℃ and degas under vacuum (vacuum degree -0.09MPa) for 10 min to obtain the adhesive layer slurry; Preparation method of SiO2 modified polyurethane resin: 1) Surface grafting treatment of SiO2 nanoparticles: 200g of SiO2 nanoparticles (particle size 20nm) were added to 500mL of anhydrous ethanol and ultrasonically dispersed for 30min (power 400W) to form a uniform dispersion; 10g of γ-aminopropyltriethoxysilane (KH-550) was added to the dispersion, and the pH was adjusted to 4 (using glacial acetic acid). The mixture was refluxed at 70℃ for 4h; after the reaction was completed, the mixture was centrifuged (8000r / min, 10min), washed 3 times with anhydrous ethanol, and vacuum dried at 60℃ for 24h to obtain SiO2 nanoparticles with surface grafted silane coupling agent (grafting rate 88%). 2) Synthesis of SiO2-modified polyurethane resin: 800g of polytetramethylene ether glycol (PTMG, molecular weight 2000) was added to a reactor and dehydrated under vacuum at 110℃ for 1h (vacuum degree -0.09MPa); the temperature was lowered to 70℃, and 200g of isophorone diisocyanate (IPDI) was added. The mixture was reacted at 60℃ for 2h (NCO content controlled at 3.5%) to obtain a PU prepolymer; 45g of SiO2 nanoparticles with surface-grafted silane coupling agent were added to the PU prepolymer and dispersed at high speed at 1500r / min for 30min to form a SiO2 / PU prepolymer mixture; 30g of chain extender 1,4-butanediol (BDO) was added and reacted at 80℃ for 1h; finally, deionized water (solid content adjusted to 62%) was added and emulsified at high speed (10000r / min, 5min) to obtain a SiO2 modified polyurethane resin.

[0029] Preparation method of SiO2 modified polyurethane resin slurry: Add 80 parts of SiO2-modified polyurethane resin to a dispersion vessel and stir at a low speed of 500 r / min; then add 8 parts of aziridine crosslinking agent (CX-100, solid content 100%), 5 parts of propylene glycol methyl ether acetate, and 10 parts of magnesium hydroxide (particle size 2 μm); increase the speed to 1200 r / min and stir for 40 min until the slurry is uniform (fineness ≤20 μm) to obtain SiO2-modified polyurethane resin slurry.

[0030] Preparation method of polyurethane resin slurry: Add 85 parts of polyurethane to a dispersion vessel and stir at a low speed of 400 r / min; add 3 parts of aziridine crosslinking agent (CX-100, solid content 100%), 3 parts of propylene glycol methyl ether acetate, and 2 parts of color paste in sequence; increase the speed to 800 r / min and stir for 30 min until the slurry is uniform (fineness ≤15μm) to obtain polyurethane resin slurry.

[0031] Preparation method of functional coating slurry: 1) Preparation of tea tree oil microcapsules: Gelatin (5g) and gum arabic (5g) were dissolved in 400mL of deionized water (40℃) to form a wall material solution (concentration 2.5%); tea tree oil (6g) was added to the wall material solution and emulsified at 10000r / min for 10min to form an O / W emulsion (oil droplet size 5μm); the pH was adjusted to 4.5 with 10% acetic acid solution, the temperature was lowered to 10℃, and 5% glutaraldehyde solution (2mL) was added for curing for 30min; centrifugation (5000r / min, 5min), washing twice with deionized water, and vacuum drying at 60℃ were performed to obtain tea tree oil microcapsules (core material content 60%, average particle size 5μm); 2) Mixing: Add 60 parts of waterborne polyurethane dispersion (solid content 45%, anionic) to the dispersion vessel and stir at 300 r / min; add 10 parts of nano bamboo charcoal powder, 5 parts of tea tree essential oil microcapsules and 3 parts of nano silica (particle size 20 nm) in sequence; stir at 600 r / min for 20 min until uniform (fineness ≤10 μm) to obtain functional coating slurry.

[0032] The production method of PU leather material includes the following steps: S1. Preparation of impermeable base fabric: Polyamide-polyester blended fabric (PA6:PET=3:7) is immersed in fluorine-based C6 waterproofing agent solution (C6 waterproofing agent:water=1.5:1000, temperature 25℃), and after a two-dip and two-padding process, the padding rate of the polyamide-polyester blended fabric is 65%. It is then baked at 185℃ for 35 seconds to obtain an impermeable base fabric (thickness 0.3mm) that is impermeable to water within 5 minutes. S2, Adhesive layer coating: The adhesive slurry is mixed evenly at 70℃ and coated onto the surface of the impermeable base fabric using a comma-shaped scraper. It is then pre-baked at 80℃ for 2 minutes to form an adhesive layer with a thickness of 0.15mm. S3, PU composite film forming: SiO2 modified polyurethane resin slurry is coated onto release paper (texture depth 0.1mm), and baked at 120℃ for 3min to form an inner highly cross-linked PU layer with a thickness of 0.25mm; polyurethane resin slurry is coated onto the surface of the inner highly cross-linked PU layer, and baked at 100℃ for 2min to form an outer low cross-linked PU layer with a thickness of 0.15mm, resulting in a PU composite film with a total thickness of 0.4mm; S4. Interlayer lamination: The inner highly cross-linked PU layer of the PU composite film is bonded to the adhesive layer. The mixture is hot-pressed at 110℃ and 0.3MPa for 25 seconds, and after cooling, the release paper is peeled off to obtain a semi-finished product. S5. Microcapsule sustained-release functional coating: The functional coating slurry is coated onto the surface of the outer low cross-linked PU layer of the semi-finished product using a micro-gravure roller coating process. It is first baked at 80℃ for 2 minutes, and then baked at 110℃ for 1 minute to form a microcapsule sustained-release functional coating layer with a thickness of 0.05 mm, thus obtaining the finished product.

[0033] Example 4: A tensile-resistant multilayer PU leather material, comprising, from the inside out, an impermeable base fabric layer, an adhesive layer, a PU composite film layer, and a microcapsule sustained-release coating layer; The impermeable base fabric layer is formed from a polyamide-polyester blended fabric treated with a fluorine-based waterproofing agent solution through a two-dip-two-roll process and a curing treatment. The adhesive layer has a thickness of 0.25 mm and is formed by curing the adhesive layer slurry; The total thickness of the PU composite film is 0.6 mm, consisting of an inner highly cross-linked PU layer with a thickness of 0.35 mm and an outer low-cross-linked PU layer with a thickness of 0.25 mm. The inner highly cross-linked PU layer is formed by curing SiO2-modified polyurethane resin slurry, and the outer low-cross-linked PU layer is formed by curing polyurethane resin slurry. Both the SiO2-modified polyurethane resin slurry and the polyurethane resin slurry contain aziridine cross-linking agents. The thickness of the microcapsule sustained-release functional coating layer is 0.10 mm, and it is formed by curing the functional coating layer slurry.

[0034] Preparation method of the impermeable base fabric layer: A polyamide-polyester blended fabric (PA6:PET=3:7) was immersed in a fluorine-based C6 waterproofing agent solution (C6 waterproofing agent:water=2:1000, temperature 25℃). After a two-dip and two-padding process, the padding rate of the polyamide-polyester blended fabric was reduced to 75%. The fabric was then baked at 185℃ for 35 seconds to obtain a water-impermeable base fabric (thickness 0.3mm) that is impermeable to water within 5 minutes.

[0035] Preparation method of adhesive layer slurry: Add 80 parts of castor oil polyester polyol to a planetary mixer, heat to 60℃, and stir at 300 r / min for 10 min until completely melted; slowly add 40 parts of HDI type isocyanate prepolymer, and continue stirring for 15 min to ensure full contact between isocyanate and polyol; add 8 parts of epoxidized soybean oil (acid value ≤0.5mgKOH / g), 0.04 parts of organic bismuth catalyst (Bi content 18%), and 4 parts of nano-montmorillonite in sequence, increase the speed to 800 r / min, and stir for 30 min until the slurry is uniform and free of particles; finally, cool to 50℃ and degas under vacuum (vacuum degree -0.09MPa) for 10 min to obtain the adhesive layer slurry.

[0036] Preparation method of SiO2 modified polyurethane resin: 1) Surface grafting treatment of SiO2 nanoparticles: 200g of SiO2 nanoparticles (50nm particle size) were added to 500mL of anhydrous ethanol and ultrasonically dispersed for 30min (400W power) to form a uniform dispersion; 10g of γ-aminopropyltriethoxysilane (KH-550) was added to the dispersion, and the pH was adjusted to 4 (using glacial acetic acid). The mixture was refluxed at 70℃ for 4h; after the reaction was completed, the mixture was centrifuged (8000r / min, 10min), washed 3 times with anhydrous ethanol, and vacuum dried at 60℃ for 24h to obtain SiO2 nanoparticles with surface grafted silane coupling agent (grafting rate 88%). 2) Synthesis of SiO2-modified polyurethane resin: 800g of polytetramethylene ether glycol (PTMG, molecular weight 2000) was added to a reactor and dehydrated under vacuum at 110℃ for 1h (vacuum degree -0.09MPa); the temperature was lowered to 70℃, and 200g of isophorone diisocyanate (IPDI) was added. The mixture was reacted at 60℃ for 2h (NCO content controlled at 3.5%) to obtain a PU prepolymer; 45g of SiO2 nanoparticles with surface-grafted silane coupling agent were added to the PU prepolymer and dispersed at high speed at 1500r / min for 30min to form a SiO2 / PU prepolymer mixture; 30g of chain extender 1,4-butanediol (BDO) was added and reacted at 80℃ for 1h; finally, deionized water (solid content adjusted to 62%) was added and emulsified at high speed (10000r / min, 5min) to obtain a SiO2 modified polyurethane resin.

[0037] Preparation method of SiO2 modified polyurethane resin slurry: 90 parts of SiO2-modified polyurethane resin were added to a dispersion vessel and stirred at a low speed of 500 r / min. Then, 10 parts of aziridine crosslinking agent (CX-100, 100% solid content), 8 parts of propylene glycol methyl ether acetate, and 15 parts of magnesium hydroxide (particle size 2 μm) were added in sequence. The speed was increased to 1200 r / min and stirred for 40 min until the slurry was uniform (fineness ≤20 μm) to obtain SiO2-modified polyurethane resin slurry.

[0038] Preparation method of polyurethane resin slurry: Add 95 parts of polyurethane to a dispersion vessel and stir at a low speed of 400 r / min; add 5 parts of aziridine crosslinking agent (CX-100, solid content 100%), 6 parts of propylene glycol methyl ether acetate, and 5 parts of color paste in sequence; increase the speed to 800 r / min and stir for 30 min until the slurry is uniform (fineness ≤15μm) to obtain polyurethane resin slurry.

[0039] Preparation method of functional coating slurry: 1) Preparation of tea tree oil microcapsules: Gelatin (5g) and gum arabic (5g) were dissolved in 400mL of deionized water (40℃) to form a wall material solution (concentration 2.5%); tea tree oil (6g) was added to the wall material solution and emulsified at 10000r / min for 10min to form an O / W emulsion (oil droplet size 5μm); the pH was adjusted to 4.5 with 10% acetic acid solution, the temperature was lowered to 10℃, and 5% glutaraldehyde solution (2mL) was added for curing for 30min; centrifugation (5000r / min, 5min), washing twice with deionized water, and vacuum drying at 60℃ were performed to obtain tea tree oil microcapsules (core material content 60%, average particle size 5μm); 2) Mixing: Add 70 parts of waterborne polyurethane dispersion (solid content 45%, anionic) to the dispersion vessel and stir at 300 r / min; add 15 parts of nano bamboo charcoal powder, 8 parts of tea tree essential oil microcapsules and 5 parts of nano silica (particle size 20 nm) in sequence; stir at 600 r / min for 20 min until uniform (fineness ≤10 μm) to obtain functional coating slurry.

[0040] The production method of PU leather material includes the following steps: S1. Preparation of impermeable base fabric: Polyamide-polyester blended fabric (PA6:PET=3:7) is immersed in fluorine-based C6 waterproofing agent solution (C6 waterproofing agent:water=1.5:1000, temperature 25℃), and after a two-dip and two-padding process, the padding rate of the polyamide-polyester blended fabric is 65%. It is then baked at 185℃ for 35 seconds to obtain an impermeable base fabric (thickness 0.3mm) that is impermeable to water within 5 minutes. S2, Adhesive layer coating: The adhesive slurry is mixed evenly at 70℃ and coated onto the surface of the impermeable base fabric using a comma-shaped scraper. It is then pre-baked at 90℃ for 2 minutes to form an adhesive layer with a thickness of 0.25mm. S3, PU composite film forming: SiO2 modified polyurethane resin slurry is coated onto release paper (texture depth 0.1mm), and baked at 130℃ for 3min to form an inner highly cross-linked PU layer with a thickness of 0.35mm; polyurethane resin slurry is coated onto the surface of the inner highly cross-linked PU layer, and baked at 110℃ for 2min to form an outer low cross-linked PU layer with a thickness of 0.25mm, resulting in a PU composite film with a total thickness of 0.6mm; S4. Interlayer lamination: The inner highly cross-linked PU layer of the PU composite film is bonded to the adhesive layer. The mixture is hot-pressed at 120℃ and 0.5MPa for 30 seconds, and after cooling, the release paper is peeled off to obtain a semi-finished product. S5. Microcapsule sustained-release functional coating: The functional coating slurry is coated onto the surface of the outer low cross-linked PU layer of the semi-finished product using a micro-gravure roller coating process. It is first baked at 90℃ for 2 minutes, and then baked at 120℃ for 1 minute to form a microcapsule sustained-release functional coating layer with a thickness of 0.10 mm, thus obtaining the finished product.

[0041] Comparative Example 1: The difference between this comparative example and Example 1 is that the amount of aziridine crosslinking agent contained in the SiO2 modified polyurethane resin slurry and the polyurethane resin slurry is 6 parts each (without gradient design).

[0042] Comparative Example 2: The difference between this comparative example and Example 1 is that the SiO2 nanoparticles in the SiO2-modified polyurethane resin slurry were not surface-grafted with γ-aminopropyltriethoxysilane (directly blended with the PU prepolymer). In other words, the preparation method of the SiO2-modified polyurethane resin used in this comparative example is as follows: 800g of polytetramethylene ether glycol (PTMG, molecular weight 2000) is added to a reaction vessel and vacuum dehydrated at 110℃ for 1 hour (vacuum degree -0.09MPa); the temperature is then lowered to 70℃, and 200g of isophorone diisocyanate (IP) is added. DI), reacted at 60℃ for 2h (NCO content controlled at 3.5%) to obtain PU prepolymer; SiO2 nanoparticles (45g) were added to the PU prepolymer and dispersed at 1500r / min for 30min to form SiO2 / PU prepolymer mixture; chain extender 1,4-butanediol (BDO, 30g) was added and reacted at 80℃ for 1h; finally, deionized water (solid content adjusted to 62%) was added and emulsified at high speed (10000r / min, 5min) to obtain SiO2 modified polyurethane resin.

[0043] Comparative Example 3: The difference between this comparative example and Example 1 is that tea tree oil was directly added to the functional coating slurry (without microcapsule encapsulation). That is, the preparation method of the functional coating slurry used in this comparative example is as follows: 65 parts of aqueous polyurethane dispersion (solid content 45%, anionic type) were added to the dispersion vessel and stirred at 300 r / min; 12 parts of nano bamboo charcoal powder, 6 parts of tea tree oil, and 4 parts of nano silica (particle size 20 nm) were added in sequence; and the mixture was stirred at 600 r / min for 20 min until uniform (fineness ≤ 10 μm) to obtain the functional coating slurry.

[0044] The properties of the leather materials prepared in Examples 1-4 and Comparative Examples 1-3 were tested in this invention, and the results are shown in Table 1: Table 1 Performance Test Results

[0045] The performance test results above show that the elongation at break of Examples 1-4 all exceeded 410%, the antibacterial rate after 7 days was ≥83%, the adsorption capacity per unit area was ≥0.81 mg / cm², and the peel strength of the functional coating layer was ≥1.7 N / cm, demonstrating a synergistic improvement in tensile strength and long-lasting functionality. Among them, Example 1 showed the most outstanding comprehensive performance (elongation at break 420%, antibacterial rate 85%, adsorption capacity 0.85 mg / cm², peel strength 1.8 N / cm), mainly because it adopted the optimal crosslinking agent gradient (9:4) and microcapsule core material content (60%), achieving the best balance between molecular chain crosslinking density and nanoparticle dispersion.

[0046] The elongation at break of Comparative Example 1 was only 350%, significantly lower than that of Example 1. This is because the lack of gradient design resulted in an excessively high overall crosslinking density in the PU composite film, limiting the space for molecular chain movement and preventing the absorption of tensile stress through the outer low-crosslinked PU layer. This verifies the crucial role of the gradient crosslinking structure in improving tensile properties.

[0047] The peel strength of the functional coating layer in Comparative Example 2 was only 1.2 N / cm, far lower than the 1.8 N / cm in Example 1. Unmodified SiO2 showed poor compatibility with PU resin, and the nanoparticles easily agglomerated to form stress concentration points, leading to a decrease in the internal bonding strength of the functional coating layer. This demonstrates that SiO2 surface grafting modification can effectively enhance the bonding between nanoparticles and the resin interface.

[0048] Comparative Example 3 showed an antibacterial rate of only 40% after 7 days, with an adsorption capacity of only 0.30 mg / cm². 2 Tea tree oil, when directly exposed to the surface, is rapidly lost due to volatilization and dissolution; the nano-bamboo charcoal powder does not form a continuous phase structure with the water-based polyurethane, and the adsorption efficiency is significantly reduced after particle aggregation, verifying that microcapsule encapsulation can effectively improve antibacterial effects and enhance the long-lasting function.

Claims

1. A tensile-resistant multilayer PU leather material, characterized in that, From the inside out, it includes an impermeable base fabric layer, an adhesive layer, a PU composite membrane layer, and a microcapsule sustained-release coating layer; The impermeable base fabric layer is formed from a polyamide-polyester blended fabric treated with a fluorine-based waterproofing agent solution through a two-dip-two-roll process and a curing treatment. The adhesive layer has a thickness of 0.15-0.25 mm and is formed by curing the adhesive layer slurry; The total thickness of the PU composite film is 0.4-0.6 mm, consisting of an inner highly cross-linked PU layer with a thickness of 0.25-0.35 mm and an outer low-cross-linked PU layer with a thickness of 0.15-0.25 mm. The inner highly cross-linked PU layer is formed by curing SiO2-modified polyurethane resin slurry, and the outer low-cross-linked PU layer is formed by curing polyurethane resin slurry. Both the SiO2-modified polyurethane resin slurry and the polyurethane resin slurry contain aziridine cross-linking agents. The thickness of the microcapsule sustained-release functional coating layer is 0.05-0.10 mm, and it is formed by curing the functional coating layer slurry.

2. The tensile-resistant multilayer PU leather material according to claim 1, characterized in that, The mixing ratio of the fluorinated waterproofing agent to water in the fluorinated waterproofing agent solution is (1.5-2):1000, and the fluorinated waterproofing agent is a C6 waterproofing agent.

3. The tensile-resistant multilayer PU leather material according to claim 1, characterized in that, The adhesive layer slurry comprises, by weight, 70-80 parts castor oil polyester polyol, 30-40 parts HDI type isocyanate prepolymer, 5-8 parts epoxidized soybean oil, 0.02-0.04 parts organic bismuth catalyst, and 2-4 parts nano-montmorillonite.

4. The tensile-resistant multilayer PU leather material according to claim 1, characterized in that, The weight ratio of the SiO2 modified polyurethane resin slurry and the aziridine crosslinking agent contained in the polyurethane resin slurry is (8-10):(3-5).

5. The tensile-resistant multilayer PU leather material according to claim 1, characterized in that, The SiO2-modified polyurethane resin slurry comprises, by weight, 80-90 parts of SiO2-modified polyurethane resin, 8-10 parts of aziridine crosslinking agent, 5-8 parts of propylene glycol methyl ether acetate, and 10-15 parts of magnesium hydroxide; the polyurethane resin slurry comprises, by weight, 85-95 parts of polyurethane, 3-5 parts of aziridine crosslinking agent, 3-6 parts of propylene glycol methyl ether acetate, and 2-5 parts of color paste.

6. The tensile-resistant multilayer PU leather material according to claim 5, characterized in that, SiO2-modified polyurethane resin is prepared by in-situ polymerization, which involves grafting γ-aminopropyltriethoxysilane onto the surface of SiO2 nanoparticles with a particle size of 20-50 nm and then blending them with polyurethane prepolymer.

7. The tensile-resistant multilayer PU leather material according to claim 1, characterized in that, The functional coating slurry comprises, by weight, 60-70 parts of waterborne polyurethane dispersion, 10-15 parts of nano bamboo charcoal powder, 5-8 parts of tea tree essential oil microcapsules, and 3-5 parts of nano silica.

8. A method for producing a tensile-resistant multilayer PU leather material, used to produce the tensile-resistant multilayer PU leather material as described in any one of claims 1-7, characterized in that, Includes the following steps: S1. Preparation of impermeable base fabric: The polyamide-polyester blended fabric is immersed in a fluorine-based waterproofing agent solution, treated by a two-dip and two-roll process, and then baked to obtain the impermeable base fabric. S2, Adhesive layer coating: Apply adhesive slurry to the surface of the impermeable base fabric and pre-bake at 80-90℃ for 2 minutes to form an adhesive layer; S3, PU composite film forming: First, the SiO2 modified polyurethane resin slurry is coated onto release paper and baked at 120-130℃ for 3 minutes to form an inner highly cross-linked PU layer; then, polyurethane resin slurry is coated onto the surface of the inner highly cross-linked PU layer and baked at 100-110℃ for 2 minutes to form an outer low cross-linked PU layer, thus obtaining a PU composite film. S4. Interlayer lamination: The inner highly cross-linked PU layer of the PU composite film is bonded to the adhesive layer, and after hot pressing and cooling, the release paper is peeled off to obtain a semi-finished product. S5. Microcapsule sustained-release functional coating: The functional coating slurry is coated onto the surface of the outer low cross-linked PU layer of the semi-finished product, baked at 80-90℃ for 2 minutes, and then baked at 110-120℃ for 1 minute to form a microcapsule sustained-release functional coating layer, thus obtaining the finished product.

9. The method for producing a tensile-resistant multilayer PU leather material according to claim 8, characterized in that, In step S1, the roll residue of the polyamide-polyester blended fabric after the two-dip and two-roll process is 65%-75%.

10. A method for producing a tensile-resistant multilayer PU leather material according to claim 8, characterized in that, In step S4, the hot pressing conditions are: hot pressing temperature of 110-120℃, pressure of 0.3-0.5MPa, and hot pressing time of 25-30 seconds.

Images