Preparation method of scratch-resistant leather
By constructing a composite coating on the leather surface consisting of a dual dynamic covalent network, a biomimetic layered crack-resistant reinforcing phase, and a gradient modulus hardening layer, the problem of easy damage to leather is solved. This achieves a multi-mechanism synergistic effect of self-repair, crack resistance, low friction, and scratch resistance, thereby improving the overall scratch resistance of the leather.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZHEJIANG TONGTIANXING GRP CO LTD
- Filing Date
- 2026-03-18
- Publication Date
- 2026-05-12
AI Technical Summary
Existing leather products are prone to surface scratches, coating cracking, loss of gloss and structural damage during use, and their scratch resistance is poor. Traditional technologies cannot simultaneously achieve a comprehensive performance of self-repair, crack resistance, low friction and scratch resistance.
A composite coating system consisting of a dual dynamic covalent network self-healing polyurethane emulsion, a biomimetic layered crack-resistant reinforcing phase, and a gradient modulus surface hardening layer is adopted. By forming an S–S dynamic covalent network, oriented boron nitride nanosheets, and low-friction graphene quantum dots on the leather surface, combined with an ultraviolet light-induced crosslinking reaction, a multi-layer gradient structure is constructed.
It significantly improves the leather's self-healing ability, crack resistance, and scratch resistance, while maintaining its flexibility and low-friction properties, extending its service life, and preserving its natural feel.
Smart Images
Figure CN122013551A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of leather functionalization technology, and specifically to a method for preparing scratch-resistant leather. Background Technology
[0002] During daily use, leather products are subjected to scratches from hard objects, friction from particles, and bending stress, which can easily lead to quality problems such as surface scratches, coating cracking, loss of gloss, and structural damage, seriously affecting the appearance and service life of leather products.
[0003] Existing technologies for preparing scratch-resistant leather typically employ two approaches: one is to increase the coating hardness by adding high-modulus resins to enhance surface scratch resistance; the other is to add inorganic nanofillers, utilizing their reinforcing effect to prevent crack propagation. However, these technologies have significant drawbacks: There is an inherent contradiction between increased hardness and flexibility. High-hardness coatings are prone to cracking during bending, resulting in a loss of the natural feel of leather. In nanoparticle-reinforced systems, fillers tend to agglomerate, resulting in weak interfacial bonding with the matrix resin, limited reinforcing effect, and a rough coating surface. Furthermore, the coating lacks self-healing capabilities after scratches, leading to irreversible damage and insufficient durability in leather products. A single reinforcement mechanism cannot simultaneously meet the comprehensive performance requirements of scratch resistance, crack resistance, and low friction. Therefore, there is an urgent need to develop a composite coating system that integrates self-healing, crack resistance, low friction, and scratch resistance functions to address the shortcomings of traditional technologies. Summary of the Invention
[0004] The purpose of this invention is to provide a method for preparing scratch-resistant leather, so as to solve the problems of poor scratch resistance and crack resistance of existing leather.
[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: A method for preparing scratch-resistant leather specifically includes the following steps: S1: Preparation of self-healing polyurethane emulsion: Polycarbonate diol is used as the soft segment polyol and aliphatic diisocyanate is used as the hard segment raw material. The reaction is carried out under nitrogen atmosphere and 70-90℃ for 1.5-3h to obtain polyurethane prepolymer. Diamine chain extender with disulfide bond structure and chain extender monomer with vicinal diol structure are introduced into the prepolymer, and chain extension reaction is carried out at 60-80℃ for 1-2h. Then, phenylboronic acid or its derivative monomer is added, and the reaction is continued for 0.5-1h, so that S-S dynamic covalent bond network and B-O reversible borate bond network are formed in the polyurethane molecular chain at the same time. Finally, a neutralizing agent is added to adjust the pH to 7-8, and high-speed emulsification and dispersion are carried out to obtain dual dynamic self-healing waterborne polyurethane emulsion.
[0006] S2: Construction of the biomimetic layered crack-resistant reinforcing phase: Hexagonal boron nitride nanosheets were placed in a sodium hydroxide solution and heated in a water bath at 80-90℃ for 2-4 hours to perform surface hydroxylation treatment. After washing and drying, they were ready for use. The modified boron nitride nanosheets were added to the emulsion obtained in step S1 and dispersed for 20-40 minutes under the action of a high-shear emulsifier (speed 6000-10000 r / min) to make the boron nitride nanosheets oriented along the shear direction, forming a layered orientation structure parallel to the coating surface. At the same time, graphene quantum dots were added and ultrasonically dispersed for 10-20 minutes to make the quantum dots adsorbed in the interface region of boron nitride layers, forming a low-friction synergistic reinforcing composite phase.
[0007] S3: Formation of the composite coating The composite emulsion obtained in step S2 is uniformly applied to the surface of animal leather that has undergone impregnation, softening, tanning and retanning by roller coating process. The roller coating amount is 15-30g / m². The coated leather is placed in an oven at 50-70℃ and dried for 1-2 hours to cure and form a flexible self-healing composite layer.
[0008] S4: Construction of the gradient modulus surface hardening layer: Prepare a hardening liquid containing silane coupling agent, silica sol and photoinitiator, and uniformly coat it on the surface of the composite layer with a coating amount of 2-5 g / m²; irradiate with ultraviolet light (wavelength 365 nm, energy density 800-1200 mJ / cm²) for 5-15 s to induce sol-gel reaction, so that the crosslinking density of the coating layer decreases from the surface to the inside to form a gradient structure in the thickness direction, and finally construct a gradient modulus structure with a continuous transition between the high modulus siloxane crosslinked layer on the surface and the flexible polyurethane layer at the bottom.
[0009] The present invention also discloses a scratch-resistant leather prepared by the above method, the surface composite coating of which has a multi-mechanism synergistic function of dynamic covalent network self-healing, layered biomimetic structure crack resistance, low friction synergistic scratch resistance, and surface gradient hardening anti-scratch.
[0010] The present invention has the following beneficial effects: Dual dynamic covalent network self-repair: The reversible breakage and recombination of S–S bonds and B–O bonds enable the self-closure of microcracks at room temperature and have the ability to cyclically repair, effectively extending the service life of leather. Biomimetic layered structure for crack prevention: Directionally arranged boron nitride nanosheets form a "brick wall" barrier that can effectively block crack propagation and significantly improve the coating's scratch and crack resistance. Low friction and scratch resistance: Graphene quantum dots reduce the interfacial friction coefficient, disperse scratch stress, reduce surface wear, and maintain the smoothness of the leather surface; Gradient modulus scratch resistance: The high-modulus siloxane layer on the surface provides scratch resistance, while the flexible polyurethane layer at the bottom absorbs impact energy, preventing the coating from becoming brittle and balancing hardness and flexibility. Synergistic effect of multiple mechanisms: self-repair, crack resistance, low friction and gradient hardening functions work together to maintain stable scratch resistance of leather in long-term use without losing its natural feel. Attached Figure Description
[0011] Figure 1 The following is a detailed step diagram of the present invention. Detailed Implementation
[0012] To make the technical solution, innovations, and beneficial effects of this invention more intuitive and clear, this section defines the core structural framework of the product through exemplary embodiments, provides precise process parameters in conjunction with specific embodiments, highlights the necessity of key technical features with comparative examples, and quantitatively verifies product performance through experimental examples, thus comprehensively explaining the preparation method of the scratch-resistant leather of this invention. The key terms used in this implementation are defined as follows:
[0013] Dual dynamic covalent network: refers to the reversible cross-linking network in the polyurethane molecular chain composed of S–S dynamic covalent bonds and B–O reversible borate ester bonds, which is the core source of the coating's self-healing performance; Biomimetic layered crack-resistant reinforcing phase: refers to the “sheet-dot” synergistic reinforcing structure formed by hexagonal boron nitride nanosheets oriented under high shear field after hydroxylation modification and graphene quantum dots adsorbed on the sheet interface; Gradient modulus structure: refers to a siloxane-polyurethane composite structure in which the crosslinking density decreases from the surface to the interior in the coating thickness direction, achieving a continuous transition between high hardness of the surface layer and high flexibility of the underlying layer.
[0014] All raw materials used in this embodiment are commercially available industrial-grade raw materials. Unless otherwise specified, the reagent purity is analytical grade. All performance tests are performed in accordance with national standards or industry-standard methods, and the testing equipment is conventional laboratory instruments. Example line implementation Example 1: Construction of a Basic Scratch-Resistant Leather Structure
[0015] This exemplary embodiment constructs a basic scratch-resistant leather with a three-layer core structure, clearly defining the functional positioning and material composition of each layer, and providing a framework reference for specific fabrication: Dual-dynamic self-healing polyurethane matrix layer: using polycarbonate diol as the soft segment and aliphatic diisocyanate as the hard segment, introducing diamine chain extenders containing disulfide bonds and chain extenders containing o-diols, and adding phenylboronic acid monomers to construct a dual-dynamic covalent network, giving the coating room temperature self-healing ability. Bionic layered crack-resistant reinforcement layer: Hydroxylated hexagonal boron nitride nanosheets are orientedly dispersed in polyurethane emulsion. The sheets are arranged parallel to the leather surface to form a "brick wall" crack-resistant barrier. Graphene quantum dots are adsorbed at the sheet interface to reduce the interfacial friction coefficient during the scratching process. Gradient modulus surface hardening layer: Using silane coupling agent and silica sol as the main raw materials, a sol-gel reaction induced by ultraviolet light is used to form a siloxane hardening layer with crosslinking density decreasing from the surface to the inside, which takes into account both surface scratch resistance and coating flexibility.
[0016] Exemplary Example 2: Construction of Upgraded Scratch-Resistant Leather This exemplary embodiment, based on Exemplary Embodiment 1, introduces four upgraded technologies to construct high-performance scratch-resistant leather and improve the overall performance of the coating: Self-healing system upgrade: Hydrogen bond donor-acceptor structural units are added to the dual dynamic covalent network to form a triple synergistic self-healing system of "dynamic covalent bonds + reversible hydrogen bonds" to accelerate the microcrack closure rate; Enhanced structure upgrade: Polyimide nanofibers are added to the boron nitride nanosheet system to construct a stress-response-enhancing structure; at the same time, the graphene quantum dots are modified with carboxyl groups to form interfacial hydrogen bonds with polyurethane segments to construct lubrication microdomains. Gradient structure upgrade: Adjust the crosslinking density distribution of the gradient modulus structure to an exponentially decreasing form to avoid interfacial stress concentration caused by linear decrease; Surface function upgrade: Adding silicon-fluorine hybrid polysiloxane to the hardening liquid reduces the surface energy of the coating, giving the coating anti-fouling function and indirectly improving scratch resistance. Example 1: Preparation of Basic Scratch-Resistant Leather
[0017] S1: Preparation of Dual-Dynamic Self-Healing Polyurethane Emulsion 100g of polycarbonate diol (number average molecular weight 2000) and 50g of isophorone diisocyanate were added to a dry four-necked flask. The mixture was heated to 85℃ under a nitrogen atmosphere and stirred for 2 hours to obtain a polyurethane prepolymer. 8g of a diamine chain extender containing disulfide bonds (accounting for 12wt% of the total chain extender) and 5g of a chain extender monomer containing o-diol were added to the prepolymer. The mixture was heated to 70℃ and stirred for another 1.5 hours to extend the chain. 1.2g of phenylboronic acid monomer (accounting for 1.5wt% of the polyurethane solid content) was added and reacted for 40 minutes. Triethylamine was added to neutralize to pH 7.5, and the mixture was emulsified for 5 minutes in a high-speed emulsifier at 12000 r / min. Deionized water was added to adjust the solid content to 30wt% to obtain a dual-dynamic self-healing waterborne polyurethane emulsion.
[0018] S2: Construction of the biomimetic layered crack-resistant reinforcing phase. Take 3g of hexagonal boron nitride nanosheets (500nm in diameter and 10nm in thickness), add 100mL of 10wt% sodium hydroxide solution, heat in a water bath at 85℃ for 3h for hydroxylation treatment, wash until neutral, and then vacuum dry. Add the modified boron nitride nanosheets to the emulsion obtained in step S1, and disperse in a high-shear emulsifier at 8000r / min for 30min to orient the nanosheets along the shear direction. Add 1g of graphene quantum dots (5nm in diameter), and ultrasonically disperse for 15min to obtain a composite emulsion.
[0019] S3: Formation of the composite coating: Take the top layer of cowhide that has been treated by liming, softening, tanning and retanning, and cut it into test pieces of 20cm×20cm; roll the composite emulsion obtained in step S2 onto the surface of the leather test piece, with a roll coating amount of 20g / m²; place it in a 60℃ oven to dry for 1.5h, and cure to form a flexible self-healing composite layer with a thickness of 25μm.
[0020] S4: Construction of Gradient Modulus Surface Hardening Layer Preparation of Hardening Solution: 15g silane coupling agent KH550, 30g silica sol (solid content 30wt%), and 2g photoinitiator 2-hydroxy-2-methyl-1-phenyl-1-propanone were mixed evenly; the hardening solution was roller-coated onto the surface of the composite layer at a coating amount of 3g / m²; ultraviolet light with a wavelength of 365nm and an energy density of 1000mJ / cm² was used to irradiate for 10s to induce a sol-gel reaction, forming a gradient modulus hardening layer with a thickness of 2μm, thus obtaining basic scratch-resistant leather. Example 2: Preparation of upgraded scratch-resistant leather
[0021] S1: Preparation of Triple Synergistic Self-Healing Polyurethane Emulsion. 100g of polycarbonate diol and 50g of isophorone diisocyanate were reacted at 85℃ for 2h under a nitrogen atmosphere to prepare a prepolymer; 8g of diamine chain extender containing disulfide bonds and 5g of chain extender monomer containing vicinal diol were added, along with 4g of hydrogen bond donor-acceptor structural unit, and the chain extension reaction was carried out at 70℃ for 1.5h; 1.2g of phenylboronic acid monomer was added, and the reaction was carried out for 40min; after neutralization and emulsification, the solid content was adjusted to 30wt% to obtain the triple synergistic self-healing waterborne polyurethane emulsion.
[0022] S2: Construction of stress-responsive biomimetic layered reinforcing phase. Take 3g of hydroxylated hexagonal boron nitride nanosheets and 0.5g of polyimide nanofibers, add them to the emulsion obtained in step S1, and disperse at 8000r / min under high shear for 30min; add 1g of carboxyl-modified graphene quantum dots, and disperse ultrasonically for 15min to obtain a stress-responsive composite emulsion.
[0023] S3: The formation of the composite coating is the same as step 3 in Example 1, forming a flexible self-healing composite layer with a thickness of 25 μm.
[0024] S4: Construction of the exponentially decreasing gradient hardening layer. Preparation of hardening solution: 15g of silane coupling agent KH550, 30g of silica sol, 2g of photoinitiator, and 3g of silane-fluorine hybrid polysiloxane, mixed evenly; coating amount 3g / m²; UV irradiation for 10s to induce the formation of a gradient hardening layer with a crosslinking density decreasing exponential, with a thickness of 2μm, to obtain upgraded scratch-resistant leather. Comparative Example Comparative Example 1: Preparation of a single dynamic covalent network leather
[0025] The difference from Example 1 is that: in step S1, no phenylboronic acid monomer is added, and only an S–S single dynamic covalent network is constructed by a chain extender containing disulfide bonds. The remaining steps and parameters are the same as in Example 1. Comparative Example 2: Preparation of Boron Nitride Leather with No Orientation
[0026] The difference from Example 1 is that the boron nitride nanosheets in step S2 were not hydroxylated and were dispersed by ordinary stirring (500 r / min), and did not form a directional arrangement structure. The remaining steps and parameters are the same as in Example 1. Comparative Example 3: Preparation of Leather with No Gradient Hardening Layer
[0027] The difference from Example 1 is that step S4 is omitted, only the flexible self-healing composite layer is retained, and the remaining steps and parameters are the same as in Example 1. Test case Experimental Objective
[0028] The superiority of the scratch-resistant leather prepared in the embodiments of the present invention in three core indicators: scratch resistance, self-healing performance, and flexibility is verified. Test methods
[0029] Scratch resistance test: Refer to GB / T39507-2020 "Determination of abrasion resistance of leather physical and mechanical tests", use Taber abrasion tester, abrasion wheel model CS-10, load 500g, and record the number of abrasions when the coating shows obvious damage; Self-healing performance test: A 100μm wide and 15μm deep scratch was made on the leather surface with a blade. After being left at room temperature for 24 hours, the remaining width of the scratch was measured using an optical microscope. The self-healing efficiency was calculated using the following formula:
[0030] Flexibility test: Refer to QB / T2711-2005 "Determination of flexural strength of leather physical and mechanical tests", use a bending tester, bend angle 120°, bend frequency 100 times / min, and record the number of bends when the coating cracks. Test results
[0031] Group Scratch and abrasion resistance (number of times) Self-repair efficiency (%) Number of bends in flexibility (times) Example 1 2800 95 15000 Example 2 3100 98 16000 Comparative Example 1 1200 62 13000 Comparative Example 2 1500 94 8000 Comparative Example 3 800 95 12000 Results Analysis
[0032] The dual-dynamic covalent network is the core of self-healing and scratch resistance: Comparing Example 1 and Comparative Example 1, Comparative Example 1, lacking reversible B–O borate ester bonds, only has a single dynamic network, resulting in a decrease in self-healing efficiency from 95% to 62% and a 57% reduction in scratch resistance. This indicates that the synergistic effect of S–S bonds and B–O bonds can significantly enhance the reversible recombination ability of the network, achieving efficient closure of microcracks.
[0033] The orientation of boron nitride layers determines the crack resistance stability of the coating: Comparing Example 1 and Comparative Example 2, the boron nitride nanosheets in Comparative Example 2 are not oriented and cannot form a continuous "brick wall" crack-resistant barrier. The number of flexible bending cycles decreased from 15,000 to 8,000, a reduction of 47%. This proves that the oriented layered structure can effectively deflect the crack propagation path and improve the coating's resistance to bending cracking.
[0034] The gradient hardening layer significantly improves the surface's scratch resistance: Compared with Comparative Example 3, Comparative Example 3, lacking a gradient hardening layer, saw its scratch resistance decrease from 2800 cycles to 800 cycles, a reduction of 71%. This indicates that the high-modulus siloxane cross-linked surface layer can directly resist scratches from hard objects, which is key to improving the scratch resistance of leather surfaces.
[0035] Multi-mechanism synergistic upgrades achieve a leap in performance: After introducing a triple self-healing system, stress-response enhancement structure, and silicon-fluorine hybrid anti-fouling components, Example 2 shows that the number of scratches, self-healing efficiency, and flexibility are all superior to Example 1, with increases of 10.7%, 3.2%, and 6.7%, respectively. This verifies the synergistic effect of multiple upgrade technologies, which can further improve the overall performance of leather.
[0036] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for preparing scratch-resistant leather, characterized in that, Includes the following steps: S1: Preparation of self-healing polyurethane emulsion: Polyurethane prepolymer was prepared by reacting polycarbonate diol as soft segment polyol and aliphatic diisocyanate as hard segment raw material. A diamine chain extender containing disulfide bond structure and a chain extender monomer containing vicinal diol structure were introduced to carry out chain extension reaction. Phenylboronic acid or its derivative monomer was added to the system to form S–S dynamic covalent bond network and B–O reversible borate bond network in the obtained polyurethane molecular chain. After neutralization and emulsification, a dual dynamic self-healing waterborne polyurethane emulsion was obtained. S2: Construction of the biomimetic layered crack-resistant reinforcing phase: Hexagonal boron nitride nanosheets are surface-hydroxylated and then added to the emulsion obtained in step S1. Under the action of a high shear field, the boron nitride nanosheets are oriented along the shear direction to form a layered orientation structure parallel to the coating surface. At the same time, graphene quantum dots are added to adsorb onto the boron nitride layer interface region to form a low-friction synergistic reinforcing composite phase. S3: Formation of composite coating: The composite emulsion obtained in step S2 is roller-coated onto the surface of animal leather that has undergone impregnation, softening, tanning and retanning treatments, and then dried and cured to form a flexible self-healing composite layer; S4: Construction of gradient modulus surface hardening layer: Apply a hardening liquid containing silane coupling agent, silica sol and photoinitiator to the surface of the composite layer, and induce sol-gel reaction by ultraviolet irradiation to form a crosslinking density decreasing from the surface to the inside in the coating thickness direction, thus constructing a gradient modulus structure with a continuous transition between the high modulus siloxane crosslinked layer on the surface and the flexible polyurethane layer at the bottom.
2. The method for preparing scratch-resistant leather according to claim 1, characterized in that, In step S1, the dual dynamic network composed of the S–S dynamic covalent bond network and the B–O reversible borate ester bond network further includes hydrogen bond donor-acceptor structural units, which enable the polyurethane molecular chains to form a multi-hydrogen bond physical cross-linking network, thereby constituting a triple synergistic self-healing system of "dynamic covalent bond + reversible hydrogen bond".
3. The method for preparing scratch-resistant leather according to claim 1, characterized in that, In step S2, the boron nitride nanosheets and polyimide nanofibers coexist. When subjected to external force, the nanofibers align along the stress direction to form a stress-response-enhanced structure.
4. The method for preparing scratch-resistant leather according to claim 1, characterized in that, In step S2, the graphene quantum dots are further modified with surface carboxyl or hydroxyl groups to form interfacial hydrogen bonds with polyurethane segments, thereby constructing lubricating micro-regions that can undergo interfacial slippage during the scraping process.
5. The method for preparing scratch-resistant leather according to claim 1, characterized in that, In the gradient modulus structure formed in step S4, the siloxane crosslinking density decreases exponentially along the thickness direction.
6. The method for preparing scratch-resistant leather according to claim 1, characterized in that, The hardening solution in step S4 further contains a small amount of silicon-fluorine hybrid polysiloxane side chain structural units, which reduces the surface energy of the coating.
7. The method for preparing scratch-resistant leather according to claim 1, characterized in that, In step S2, the boron nitride sheets form a multi-level stacked structure in the coating thickness direction, with the interlayer spacing exhibiting a gradient distribution from micrometer to nanometer level, thus constructing a multi-level crack deflection path.
8. The method for preparing scratch-resistant leather according to claim 1, characterized in that, The composite coating incorporates trace amounts of photothermal responsive components, causing the coating to locally increase in temperature under light or frictional heating conditions, thereby promoting the recombination rate of the dual dynamic covalent network.
9. The method for preparing scratch-resistant leather according to claim 1, characterized in that, The preferred technical parameters for steps S1-S4 are as follows: disulfide bond chain extender accounts for 5–20 wt% of the total chain extender; phenylboronic acid monomer dosage is 0.5–3 wt% of the polyurethane solid content; polyurethane emulsion solid content is 25–40 wt%; hexagonal boron nitride nanosheets have a size of 200–800 nm and a thickness of 1–20 nm, and are added at a dosage of 1–6 wt% of the resin solid content; graphene quantum dot particle size is 2–10 nm; composite coating thickness is 10–40 μm; surface siloxane hardened layer thickness is 0.5–5 μm; surface layer modulus is 2–8 times that of the bottom layer.