High-tear-resistance breathable synthetic leather and preparation method thereof
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HUASHI(FUJIAN) SCI & TECH CO LTD
- Filing Date
- 2026-04-23
- Publication Date
- 2026-05-26
- Estimated Expiration
- Not applicable · inactive patent
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Abstract
Description
Technical Field
[0001] This invention relates to the field of synthetic leather technology, and in particular to a highly tear-resistant, breathable synthetic leather and its preparation method. Background Technology
[0002] Synthetic leather, as an important alternative to natural leather, has been widely used in footwear, automotive interiors, furniture, and clothing due to its environmental friendliness, processability, and cost advantages. With the development of industry technology, existing synthetic leathers mostly adopt a multi-layered composite structure design. They use polymers such as polyurethane and polyvinyl chloride as the matrix, combined with inorganic fillers, plasticizers, and other additives, along with processes such as foaming, phase separation, coating, and curing, to achieve basic flexibility, abrasion resistance, and a certain degree of breathability. For example, some technologies improve airflow by adding porous fillers or using foaming processes to create breathable channels; others enhance the material's mechanical strength by introducing rigid inorganic fillers or crosslinking agents to meet the needs of common applications.
[0003] However, with the increasing demands on the comprehensive performance of synthetic leather in high-end applications, existing technologies are gradually revealing many limitations. Firstly, it is difficult to optimize breathability and mechanical strength in a coordinated manner. Current technologies often use simple foaming or the addition of porous fillers to improve breathability, resulting in a loose internal structure and a significant decrease in tear resistance and interlayer bonding. Conversely, increasing cross-linking density or using rigid fillers to enhance strength can easily cause pore blockage, drastically reducing breathability and creating a technical contradiction where breathability and strength are mutually exclusive. Secondly, the stability of interlayer bonding is insufficient. Existing multi-layer synthetic leathers mostly rely on adhesive bonding or simple physical interlocking, which not only poses environmental risks due to residual formaldehyde and other harmful substances but also easily leads to interlayer slippage and peeling during long-term use or repeated bending, affecting product lifespan. Third, the dynamic mechanical properties and durability need to be improved. Existing materials lack an effective stress dissipation mechanism. After repeated bending, molecular chain fatigue fracture is likely to occur, leading to material hardening and cracking. At the same time, the surface wear-resistant layer is mostly a simple coating or an unmodified filler dispersion system. The filler is not firmly bonded to the matrix and is prone to falling off after long-term friction, which aggravates surface wear.
[0004] The shortcomings of these existing technologies make it difficult for synthetic leather to fully meet the application requirements in high-end footwear materials, automotive interiors, and high-end furniture, where stringent requirements exist for breathability, comfort, mechanical stability, flexural durability, and abrasion resistance. Therefore, developing a synthetic leather technology that can simultaneously address issues such as breathability and strength, stable interlayer bonding, and excellent flexural durability and abrasion resistance has become an important direction for industry development. Summary of the Invention
[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a highly tear-resistant, breathable synthetic leather and its preparation method.
[0006] To achieve the above objectives, the present invention adopts the following technical solution: a highly tear-resistant and breathable synthetic leather, comprising, from top to bottom, a surface abrasion-resistant layer, a middle functional layer, and a bottom flexible layer;
[0007] The surface wear-resistant layer is formed by sterically hindered phase separation to create pores and then cross-linking and curing KH-560 modified nano alumina, hydroxyl-terminated IPDI-based aliphatic polyurethane, IPDI trimer, dispersant and ethyl acetate.
[0008] The intermediate functional layer is formed by dynamic hydrogen bonding crosslinking and separation of the isocyanate-terminated MDI-based aromatic polyurethane, hydroxyl-terminated ureidopyrimidinone, KH-550 modified diatomaceous earth, toughening agent and N,N-dimethylacetamide from a non-solvent-induced phase.
[0009] The bottom flexible layer is formed by microphase separation and pore creation of hydroxyl-terminated polyether modified IPDI-based flexible polyurethane, IPDI trimer, hydroxyl-terminated polybutadiene, hydrolysis stabilizer, defoamer and ethyl acetate.
[0010] The surface wear-resistant layer and the bottom flexible layer are cross-linked with the intermediate functional layer through hydroxyl and isocyanate groups and connected by multiple hydrogen bonds through hydroxyl and hydroxyl-terminated ureidopyrimidinone groups.
[0011] Preferably, the raw materials of the surface wear-resistant layer are, by weight parts: 80-90 parts of hydroxyl-terminated IPDI-based aliphatic polyurethane, 2-3 parts of IPDI trimer, 5-8 parts of KH-560 modified nano-alumina, 0.5-1 parts of dispersant, and 180-200 parts of ethyl acetate; wherein the dispersant is sodium polycarboxylate.
[0012] Preferably, the hydroxyl-terminated IPDI-based aliphatic polyurethane is polymerized from IPDI and poly(1,4-butanediol adipate), with a hydroxyl content of 3.5±0.3% and a number-average molecular weight of 1,4-butanediol adipate of 1000±50.
[0013] Preferably, the terminal hydroxyl IPDI-based aliphatic polyurethane can be synthesized by a prepolymer method known to those skilled in the art or can be purchased commercially.
[0014] Preferably, the raw materials of the intermediate functional layer are, by weight, the following: isocyanate-terminated MDI-based aromatic polyurethane: 60-70 parts, hydroxyl-terminated ureidopyrimidinone: 8-12 parts, KH-550 modified diatomaceous earth: 15-20 parts, toughening agent: 4-6 parts, and N,N-dimethylacetamide: 140-160 parts.
[0015] Preferably, the hydroxyl-terminated ureidopyrimidinone (UPy-OH) has the following structure:
[0016] The chemical reaction equation for its preparation is as follows:
[0017] .
[0018] Preferably, the method for preparing the hydroxyl-terminated ureidopyrimidinone is as follows:
[0019] 6-Methylisocytosine and HDI were dissolved in an appropriate amount of anhydrous DMSO at a molar ratio of 1:1, and the mixture was refluxed at 55°C for 2 hours under nitrogen protection. The NCO content in the system was detected by the di-n-butylamine method. When the NCO content decreased to half of the initial content, the mixture was cooled to room temperature. Ethanolamine was added to continue the reaction, and the change in NCO in the system was detected every 20 minutes by the di-n-butylamine method. The reaction was stopped when NCO in the system completely disappeared, and the mixture was allowed to stand and cool to obtain UPy-OH.
[0020] Preferably, the terminal isocyanate-terminated MDI-based aromatic polyurethane is polymerized from MDI and poly(1,4-butanediol adipate), with an NCO content of 9.0±0.5%, wherein the number average molecular weight of poly(1,4-butanediol adipate) is 1000±50.
[0021] Preferably, the terminal isocyanate-terminated MDI-based aromatic polyurethane can be synthesized by a prepolymer method known to those skilled in the art or can be purchased commercially.
[0022] Preferably, the toughening agent refers to carboxyl-terminated butadiene-acrylonitrile liquid rubber (CTBN).
[0023] Preferably, the raw materials of the bottom flexible layer are as follows by weight: 85-95 parts of hydroxyl-terminated polyether modified IPDI-based flexible polyurethane, 1-2 parts of IPDI trimer, 5-7 parts of hydroxyl-terminated polybutadiene, 1-2 parts of hydrolysis stabilizer, 0.3-0.5 parts of defoamer, and 180-210 parts of ethyl acetate.
[0024] Preferably, the hydroxyl content of the hydroxyl-terminated polybutadiene is 0.47-0.53 mmol / g.
[0025] Preferably, the hydroxyl-terminated polyether modified IPDI-based flexible polyurethane is polymerized from IPDI and polytetrahydrofuran diol, with a hydroxyl content of 3.2±0.5% and a number-average molecular weight of 3000-4000 for the polytetrahydrofuran diol.
[0026] Preferably, the hydroxyl-terminated polyether modified IPDI-based flexible polyurethane can be synthesized by a prepolymer method known to those skilled in the art or can be purchased commercially.
[0027] Preferably, the hydrolysis-resistant stabilizer refers to carbodiimide.
[0028] Preferably, the defoamer refers to BYK-066N.
[0029] Furthermore, the present invention also provides a method for preparing highly tear-resistant and breathable synthetic leather, comprising the following steps:
[0030] (1) Preparation of surface wear-resistant layer slurry: Add ethyl acetate to the reaction vessel, heat to 60-70℃, add hydroxyl-terminated IPDI-based aliphatic polyurethane under stirring, keep warm and stir for 20-30 min, then add IPDI trimer, continue to keep warm and stir for 15-25 min, then add KH-560 modified nano alumina and sodium polycarboxylate, disperse under stirring for 1-1.5 h to obtain surface wear-resistant layer slurry;
[0031] (2) Preparation of intermediate functional layer slurry: N,N-dimethylacetamide and KH-550 modified diatomaceous earth were added to the reaction vessel and ultrasonically dispersed for 40-50 min. The temperature was raised to 65-75℃, and isocyanate-terminated MDI-based aromatic polyurethane was added under stirring. The mixture was kept warm and stirred for 30-40 min. Then, hydroxyl-terminated ureidopyrimidinone and toughening agent were added. The mixture was kept warm and reacted for 1-2 h under stirring. The temperature was lowered to 40-45℃ and stirring was continued for 20-40 min to obtain intermediate functional layer slurry.
[0032] (3) Preparation of bottom flexible layer slurry: Add ethyl acetate to the reactor, heat to 60-70℃, add hydroxyl-terminated polyether modified IPDI-based flexible polyurethane under stirring, keep warm and stir for 20-30 min, add IPDI trimer, continue to keep warm and stir for 10-20 min, then add hydroxyl-terminated polybutadiene, anti-hydrolysis stabilizer and defoamer, stir and disperse for 40-50 min to obtain bottom flexible layer slurry;
[0033] (4) Lamination and curing: The surface wear-resistant layer slurry is uniformly coated onto the release paper, and the wet film thickness is controlled to be 0.15-0.25 mm. It is then dried in an oven at 110-120℃ for 40-50 s to obtain the surface wear-resistant layer. The intermediate functional layer slurry is uniformly coated onto the surface wear-resistant layer, and the wet film thickness is controlled to be 0.4-0.6 mm. It is then immediately immersed in deionized water at 38-42℃ for 80-90 s. After immersion, the surface water is drained, and the material is pre-dried in a forced-air oven at 70-80℃ for 10-20 s to obtain the intermediate functional layer. The bottom flexible layer slurry is uniformly coated onto the intermediate functional layer, and the wet film thickness is controlled to be 0.25-0.35 mm. It is then dried in an oven at 120-130℃ for 50-60 s to obtain the composite layer. The composite layer is then peeled off from the release paper to obtain the synthetic leather blank.
[0034] (5) Post-treatment purification: Place the synthetic leather blank in a vacuum drying oven at 70-80℃ and dry for 10-20 minutes. Then, heat-treat it in an oven at 90-100℃ for 20-40 minutes. After cooling to room temperature, immerse it in a 2-5wt% neutral detergent solution and wash for 5-10 minutes. Finally, rinse it with deionized water 3-4 times and dry it to obtain a highly tear-resistant and breathable synthetic leather product.
[0035] Preferably, the ultrasonic power in (2) is 300-500W and the frequency is 15-25kHz.
[0036] Preferably, the neutral detergent in (5) is selected from one of the nonionic surfactants of fatty alcohol polyoxyethylene ethers.
[0037] More preferably, the neutral detergent in (5) refers to Pingpingjia O-20.
[0038] Preferably, the mechanism by which the highly tear-resistant and breathable synthetic leather of the present invention exhibits high tear resistance and breathability is explained as follows:
[0039] The high tear resistance of this invention is achieved through the rigid connection of covalent bonds, the dynamic reinforcement of hydrogen bonds, the energy dissipation of elastic segments, and the structural support of inorganic fillers, which together resist tearing stress. The specific mechanism is as follows:
[0040] 1. Strong interlayer bonding through a combination of covalent and multiple hydrogen bonds prevents interfacial delamination.
[0041] Interlayer bonding is the foundation of tear resistance. This invention achieves a dual connection of "irreversible covalent bonds + reversible dynamic hydrogen bonds" through the design of functional groups between different layers, completely eliminating interlayer interface defects.
[0042] Covalent bond formation: The terminal hydroxyl groups of the surface wear-resistant layer and the bottom flexible layer undergo a urethane esterification reaction with the terminal isocyanate groups of the intermediate functional layer to form stable urethane covalent bonds. This reaction occurs throughout the entire process of lamination curing and post-treatment heat treatment. The reaction formula is as follows:
[0043] R-OH + O=C=N-R'→R-OOC-NH-R';
[0044] Among them, the surface layer of IPDI-based aliphatic polyurethane with terminal hydroxyl end and the bottom layer of IPDI-based flexible polyurethane with terminal hydroxyl end provide sufficient -OH active sites. After the intermediate functional layer of MDI-based aromatic polyurethane is grafted with UPy-OH and CTBN, the residual NCO can fully react with the interlayer -OH to form an integrated structure of "surface-intermediate-bottom layer" covalently bonded, avoiding interlayer peeling when torn.
[0045] Multiple hydrogen bond reinforcement: The hydroxyl-terminated ureidopyrimidinone (UPy-OH) molecules grafted into the intermediate functional layer contain urea groups and pyrimidine ring ketone groups, which can form two types of hydrogen bonds: one is the fourfold hydrogen bond between UPy molecules, and the other is the OH···O (UPy's C=O and -OH) and OH···N (UPy's pyrimidine ring N and -OH) hydrogen bonds formed between UPy and the surface / bottom layer residual -OH. This dynamic hydrogen bond network can undergo "dissociation-reorganization" under tearing stress, dissipating a large amount of tearing energy. At the same time, the network structure is restored after the stress is relieved. Combined with the rigid constraint of covalent bonds, it significantly improves tear resistance and toughness.
[0046] 2. Targeted toughening design for each layer, forming a three-level support of "wear resistance - rigidity - flexibility".
[0047] Surface wear-resistant layer: A dense network is formed by cross-linking IPDI-based aliphatic polyurethane with terminal hydroxyl groups (IPDI) as the matrix. KH-560 modified nano-alumina is uniformly dispersed in the matrix through steric hindrance. The rigid particle characteristics of the nano-alumina enhance the surface hardness. The alkoxy groups of the silane coupling agent on its surface undergo a weak condensation reaction with the hydroxyl groups of the polyurethane, forming an "inorganic particle-organic matrix" interfacial transition layer. This avoids stress concentration caused by particle shedding and enhances the surface tear resistance. The cross-linking reaction formula between IPDI trimer and polyurethane is as follows:
[0048] R-OH + (O=C=N)-R''→R-OOC-NH-R''; The cross-linked surface layer forms a "rigid particle dispersion + dense cross-linked network" structure, which can resist surface stress concentration in the initial stage of tearing;
[0049] Intermediate functional layer: As the tear-resistant core layer, it adopts a design of "rigid polyurethane matrix + dynamic hydrogen bond network + elastic toughening segments". The matrix is MDI-based aromatic polyurethane (containing a rigid benzene ring structure with high mechanical strength). The grafted UPy groups form a dynamic hydrogen bond network. The carboxyl-terminated butadiene-acrylonitrile liquid rubber (CTBN) is grafted onto the main chain through the addition reaction of the terminal carboxyl group (-COOH) with polyurethane -NCO, as shown in the following reaction formula:
[0050] NCO-R'''+HOOC-CTBN-COOH+NCO-R'''→R'''-NH-CO-CTBN-CO-NH-R'''; Butadiene elastic segments can undergo elastic deformation upon tearing, while acrylonitrile polar segments form a compatible transition layer with the matrix, dissipating tearing energy through "deformation-dissociation" and compensating for the brittle defects of aromatic polyurethanes; At the same time, the inorganic rigid skeleton of KH-550 modified diatomite can support the polyurethane matrix, preventing the matrix from excessively deforming and breaking under stress, forming a "rigid-dynamic-elastic" triple reinforcement system with the UPy hydrogen bond network and CTBN elastic segments;
[0051] The bottom flexible layer uses IPDI-based flexible polyurethane modified with hydroxyl-terminated polyether as the matrix. The soft segments of polytetrahydrofuran diol (PTMG) endow the matrix with excellent flexibility and bending resistance. Hydroxyl-terminated polybutadiene (HTPB) is grafted onto the main chain through the urethane esterification reaction of the terminal hydroxyl groups with polyurethane-NCO, forming a comb-like structure of "polyurethane hard segments - PTMG soft segments - HTPB elastic branches". The long-chain polybutadiene elastic segments of HTPB can undergo tensile deformation when torn, dispersing the stress to a wider range and avoiding fracture caused by local stress concentration. At the same time, the flexibility of the bottom layer can buffer the transmission of tear stress to the middle layer, forming a three-level stress regulation system of "flexible support - rigid load bearing - elastic dissipation".
[0052] 3. Post-processing enhances structural stability and improves tear resistance and durability.
[0053] The post-processing stages, including vacuum drying, heat treatment, and gradient cooling, further optimize the tear-resistant structure: vacuum drying at 70-80℃ removes residual solvents and trace amounts of moisture, preventing internal matrix defects caused by solvent residue; heat treatment at 90-100℃ promotes the continued cross-linking of unreacted -OH and -NCO bonds, increasing the overall cross-linking density and inducing the orderly arrangement of the UPy hydrogen bond network, enhancing the dynamic reinforcement effect; during room temperature cooling, the molecular chains slowly orient and fix, eliminating internal stress and avoiding tear sensitivity caused by stress concentration; neutral detergent cleaning only removes surface impurities without damaging the interlayer covalent bonds and hydrogen bond structure, ensuring tear resistance stability during long-term service.
[0054] The breathability of this invention stems from a continuous, interconnected channel design. By collaboratively constructing a pore size gradient through different pore-forming mechanisms, it simultaneously ensures the stability and continuity of the channels. The specific mechanism is as follows:
[0055] 1. Directional construction of a three-level porous structure
[0056] Each layer employs a targeted pore-forming method to ensure air permeability while preventing pore collapse. The specific pore-forming mechanism is as follows:
[0057] Surface wear-resistant layer: "Sterile phase separation pore-forming" is adopted; KH-560 modified nano alumina is used as rigid particles and uniformly dispersed in polyurethane slurry. The silane coupling agent on its surface improves the compatibility with the organic matrix and avoids agglomeration; during the drying and curing process at 110-120℃, the polyurethane molecular chains cross-link and shrink. Due to the steric hindrance effect, the nano alumina cannot be completely embedded in the matrix, and the space it occupies forms nanoscale pores; at the same time, the cross-linking reaction between IPDI trimer and polyurethane forms a dense network, which supports the nanopore wall structure, avoids pore closure, and finally forms a uniformly distributed breathable channel, which can block dust and other impurities from entering, while allowing gas to pass freely;
[0058] Intermediate functional layer: Pore formation is achieved using "non-solvent-induced phase separation (NIPS) + inorganic filler porous reinforcement"; N,N-dimethylacetamide in the slurry rapidly exchanges with deionized water, promoting the rapid aggregation of polyurethane molecular chains to form a continuous organic matrix, and the gaps left during the solvent-non-solvent exchange process form channels; at the same time, KH-550 modified diatomite itself has natural porosity, and its porous structure is interconnected with the channels formed by phase separation, constructing a multi-level porous structure of "diatomite native pores - phase separation induced pores"; this layer serves as the air-permeable core, and its large pore size design ensures rapid gas transmission, while the inorganic skeleton of diatomite enhances the stability of the channels and avoids channel deformation during gas transmission;
[0059] Bottom flexible layer: "Microphase separation pore formation" is adopted; the non-polar polybutadiene segments of HTPB and the polar urea hard segments of polyurethane have a large difference in compatibility. During the preparation of slurry at 60-70℃ and drying at 120-130℃, the HTPB segments spontaneously separate from the polyurethane hard segments to form a microphase region; in the later stage of drying, some low molecular weight HTPB segments slightly volatilize, and the space they occupy forms flexible channels. The pore walls are composed of polyurethane-HTPB graft copolymer, which has both flexibility and toughness and can keep the channels open when bending and stretching.
[0060] 2. Mechanism for ensuring the continuity of the channel
[0061] The continuous continuity of the three-level channels is crucial for air permeability. This invention, through component design and process control, fundamentally prevents channel blockage or breakage.
[0062] Ingredient compatibility: KH-560 modified nano-alumina and KH-550 modified diatomaceous earth react with the epoxy and amino groups of silane coupling agent and the hydroxyl and isocyanate groups of polyurethane to achieve interfacial bonding between "inorganic filler and organic matrix", avoiding pore blockage caused by filler agglomeration; the acrylonitrile polar segments of CTBN and the elastic segments of HTPB form interfacial transition layers with the intermediate and bottom polyurethane matrices, respectively, to prevent elastic segments from agglomerating and blocking pores;
[0063] Processing for impurity removal and clogging prevention: After the intermediate layer phase separation, pre-drying at 70-80℃ for 10-20s can quickly remove surface free water, preventing the water from reacting with the residual -NCO in the intermediate layer to generate urea bonds and carbon dioxide, thus preventing pore blockage caused by bubble formation; vacuum drying in the post-treatment stage can thoroughly remove residual solvent, preventing solvent residue from solidifying and sealing the pores; ultrasonic cleaning with 2-5wt% leveling agent and O-20 neutral detergent dissolves only the residual sodium polycarboxylate dispersant and trace amounts of unreacted small molecules on the surface, without damaging the pore wall structure, ensuring clean and unobstructed pores;
[0064] Structural stability support: The anti-hydrolysis stabilizer carbodiimide can inhibit the hydrolytic aging of polyurethane, avoiding matrix embrittlement and pore collapse caused by hydrolysis; the bottom defoamer BYK-066N can eliminate air entrained during slurry preparation, preventing irregular large pores formed by residual bubbles from destroying the pore size gradient and ensuring the uniformity of gas transmission.
[0065] 3. Synergistic protection of breathability and tear resistance
[0066] The tertiary porous structure and the tear-resistant system are not independent but mutually supportive: the inorganic fillers (nano-alumina, diatomaceous earth) act as pore-forming agents to construct pores and as rigid reinforcements to enhance the matrix strength; the elastic segments (CTBN, HTPB) create pores through microphase separation and dissipate tear energy through elastic deformation; the strong bonding of interlayer covalent bonds and hydrogen bonds ensures tear resistance while preventing pore breakage caused by interlayer peeling. Ultimately, this achieves a synergistic effect between "high permeability" and "high tear resistance," rather than mutual constraint.
[0067] Compared with the prior art, the beneficial effects of the present invention are:
[0068] 1. This invention effectively addresses the industry pain point of traditional synthetic leather—the difficulty of balancing breathability and strength—through the synergistic design of a dynamic hydrogen bond network, elastic segment toughening, and a three-layer porous structure. While constructing gas transport channels, it also enhances the stability of the material's internal structure. This achieves efficient air circulation, providing a breathable and comfortable experience similar to natural leather, while simultaneously improving mechanical strength through the dual effects of covalent bonds and physical cross-linking. It avoids the strength reduction caused by porous structures, meeting the stringent comprehensive performance requirements of high-end applications.
[0069] 2. This invention, through the synergistic effect of cross-layer covalent bonding, hydrogen bond reinforcement, and interface anchoring, eliminates the environmental hazards and weak bonding problems associated with traditional adhesive bonding, constructing a dense and tough interlayer bonding system. The materials in each layer form an integrated structure through functional group reactions, effectively resisting interlayer peeling forces and the risk of slippage during long-term use. This avoids problems such as delamination and detachment during use, significantly extending product lifespan and making it suitable for long-term stress scenarios such as automotive interiors and high-end shoe materials.
[0070] 3. This invention relies on a dynamic flexible structure design to give the material excellent fatigue resistance. The dynamic hydrogen bond network can dissociate and reconstruct during repeated bending, while the elastic segments buffer stress through deformation, preventing molecular chain fatigue fracture. At the same time, the strong interlayer bonding force and uniformly dispersed filler effectively reduce local stress concentration, allowing the material to maintain structural integrity after long-term repeated bending. It has the soft touch of natural leather, while breaking through the limitations of traditional synthetic leather that is prone to cracking and hardening when bent, making it suitable for more flexible application scenarios.
[0071] 4. This invention enhances wear resistance through a dual design of rigid surface support and strong interfacial bonding. The modified inorganic filler forms a uniform rigid skeleton on the surface, resisting mechanical wear, while a silane coupling agent forms a chemical bond with the substrate, preventing filler detachment during friction and thus reducing wear. The cross-linked structure of the surface further strengthens wear protection, ensuring the material maintains a smooth surface during long-term use, reducing quality loss caused by wear, balancing durability and appearance retention, and lowering maintenance costs. Detailed Implementation
[0072] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with existing known technologies. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.
[0073] Preparation example: The specific preparation method of hydroxyl-terminated ureidopyrimidinone includes the following steps:
[0074] 1 mol of 6-methylisocytosine and 1 mol of HDI were dissolved in 1000 mL of anhydrous DMSO, and the mixture was refluxed at 55 °C for 2 h under nitrogen protection. The NCO content in the system was detected by the di-n-butylamine method. When the NCO content decreased to half of the initial content, the mixture was cooled to room temperature. 1.1 mol of ethanolamine was added to continue the reaction, and the change in NCO content in the system was detected every 20 min by the di-n-butylamine method. The reaction was stopped when NCO in the system completely disappeared, and the mixture was allowed to stand and cool to obtain a hydroxyl-terminated ureidinidone.
[0075] Example 1: A specific method for preparing a highly tear-resistant and breathable synthetic leather, comprising the following steps:
[0076] (1) Preparation of surface wear-resistant layer slurry: Add 1.8 kg of ethyl acetate to the reactor, heat to 60 °C, and add 800 g of hydroxyl-terminated IPDI-based aliphatic polyurethane (polymerized from IPDI and poly(1,4-butanediol adipate), hydroxyl content: 3.5 ± 0.3%, of which the number average molecular weight of poly(1,4-butanediol adipate) is 1000 ± 50) under stirring. Keep warm and stir for 20 min, then add 20 g of IPDI trimer, keep warm and stir for 15 min, then add 50 g of KH-560 modified nano alumina and 5 g of sodium polycarboxylate, and disperse under stirring for 1 h to obtain surface wear-resistant layer slurry;
[0077] (2) Preparation of intermediate functional layer slurry: 1.4 kg N,N-dimethylacetamide and 150 g KH-550 modified diatomaceous earth were added to the reactor. The mixture was ultrasonically dispersed for 40 min at a power of 300 W and a frequency of 15 kHz. The temperature was raised to 65 °C. 600 g of isocyanate-terminated MDI-based aromatic polyurethane (polymerized from MDI and poly(1,4-butanediol adipate), NCO content: 9.0 ± 0.5%, of which the number average molecular weight of poly(1,4-butanediol adipate) was 1000 ± 50) was added under stirring. The mixture was kept warm and stirred for 30 min. Then 80 g of hydroxyl-terminated ureidopyrimidinone and 40 g of carboxyl-terminated butadiene-acrylonitrile liquid rubber were added. The mixture was kept warm and stirred for 1 h. The temperature was lowered to 40 °C and stirred for another 20 min to obtain the intermediate functional layer slurry.
[0078] (3) Preparation of the bottom flexible layer slurry: Add 1.8 kg of ethyl acetate to the reactor, heat to 60 °C, and add 850 g of hydroxyl-terminated polyether modified IPDI-based flexible polyurethane (polymerized from IPDI and polytetrahydrofuran diol, with hydroxyl content of 3.2 ± 0.5% and number average molecular weight of polytetrahydrofuran diol of 3000) while stirring. Keep the temperature and stir for 20 min, add 10 g of IPDI trimer, continue to keep the temperature and stir for 10 min, and then add 50 g of hydroxyl-terminated polybutadiene (hydroxyl content of 0.47 mmol / g), 10 g of carbodiimide and 3 g of BYK-066N. Stir and disperse for 40 min to obtain the bottom flexible layer slurry.
[0079] (4) Lamination and curing: The surface wear-resistant layer slurry is uniformly coated onto the release paper, and the wet film thickness is controlled to be 0.15 mm. It is then placed in a 110℃ oven and dried for 40 s to obtain the surface wear-resistant layer. The intermediate functional layer slurry is uniformly coated onto the surface wear-resistant layer, and the wet film thickness is controlled to be 0.4 mm. It is then immediately immersed in deionized water at 38℃ for 80 s, removed, and the surface water is drained. It is then placed in a 70℃ forced-air oven for pre-drying for 10 s to obtain the intermediate functional layer. The bottom flexible layer slurry is uniformly coated onto the intermediate functional layer, and the wet film thickness is controlled to be 0.25 mm. It is then placed in a 120℃ oven and dried for 50 s to obtain the composite layer. The composite layer is peeled off from the release paper to obtain the synthetic leather blank.
[0080] (5) Post-treatment purification: The synthetic leather blank is placed in a vacuum drying oven at 70℃ for 10 min, then sent to a 90℃ oven for heat treatment for 20 min, then cooled to room temperature, and then immersed in a 2wt% solution of Pingpingjia O-20 for 5 min. Finally, it is rinsed three times with deionized water and dried to obtain a high tear-resistant breathable synthetic leather product.
[0081] Example 2: A specific method for preparing a highly tear-resistant and breathable synthetic leather, comprising the following steps:
[0082] (1) Preparation of surface wear-resistant layer slurry: Add 1.9 kg of ethyl acetate to the reactor, heat to 65 °C, and add 850 g of hydroxyl-terminated IPDI-based aliphatic polyurethane (polymerized from IPDI and poly(1,4-butanediol adipate), hydroxyl content: 3.5 ± 0.3%, of which the number average molecular weight of poly(1,4-butanediol adipate) is 1000 ± 50) under stirring. Keep warm and stir for 25 min, then add 25 g of IPDI trimer, keep warm and stir for 20 min, then add 65 g of KH-560 modified nano alumina and 8 g of sodium polycarboxylate, and disperse under stirring for 1.2 h to obtain surface wear-resistant layer slurry;
[0083] (2) Preparation of intermediate functional layer slurry: 1.5 kg N,N-dimethylacetamide and 180 g KH-550 modified diatomaceous earth were added to the reactor. The mixture was ultrasonically dispersed for 45 min at a power of 400 W and a frequency of 20 kHz. The temperature was raised to 70 °C. 650 g of isocyanate-terminated MDI-based aromatic polyurethane (polymerized from MDI and poly(1,4-butanediol adipate), NCO content: 9.0 ± 0.5%, of which the number average molecular weight of poly(1,4-butanediol adipate) was 1000 ± 50) was added under stirring. The mixture was kept warm and stirred for 35 min. Then 100 g of hydroxyl-terminated ureidopyrimidinone and 50 g of carboxyl-terminated butadiene-acrylonitrile liquid rubber were added. The mixture was kept warm and stirred for 1.5 h. The temperature was lowered to 42 °C and stirred for another 30 min to obtain the intermediate functional layer slurry.
[0084] (3) Preparation of the bottom flexible layer slurry: Add 2 kg of ethyl acetate to the reactor, heat to 65 °C, add 900 g of hydroxyl-terminated polyether modified IPDI-based flexible polyurethane (polymerized from IPDI and polytetrahydrofuran diol, hydroxyl content: 3.2 ± 0.5%, of which the number average molecular weight of polytetrahydrofuran diol is 3500) under stirring, keep warm and stir for 25 min, add 15 g of IPDI trimer, continue to keep warm and stir for 15 min, then add 60 g of hydroxyl-terminated polybutadiene (hydroxyl content is 0.50 mmol / g), 15 g of carbodiimide and 4 g of BYK-066N, stir and disperse for 45 min to obtain the bottom flexible layer slurry;
[0085] (4) Lamination and curing: The surface wear-resistant layer slurry is uniformly coated on the release paper, and the wet film thickness is controlled to be 0.20 mm. It is then placed in an oven at 115℃ and dried for 45 s to obtain the surface wear-resistant layer. The intermediate functional layer slurry is uniformly coated on the surface wear-resistant layer, and the wet film thickness is controlled to be 0.5 mm. It is then immediately immersed in deionized water at 40℃ for 85 s. After soaking, it is taken out, the surface water is drained, and it is placed in a forced-air oven at 75℃ for pre-drying for 15 s to obtain the intermediate functional layer. The bottom flexible layer slurry is uniformly coated on the intermediate functional layer, and the wet film thickness is controlled to be 0.30 mm. It is then placed in an oven at 125℃ and dried for 55 s to obtain the composite layer. The composite layer is peeled off from the release paper to obtain the synthetic leather blank.
[0086] (5) Post-treatment purification: The synthetic leather blank is placed in a vacuum drying oven at 75°C and dried for 15 min. Then it is placed in a 95°C oven for heat treatment for 30 min. After cooling to room temperature, it is immersed in a 3wt% solution of Pingpingjia O-20 and washed for 8 min. Finally, it is rinsed three times with deionized water and dried to obtain a high tear-resistant breathable synthetic leather product.
[0087] Example 3: A specific method for preparing a highly tear-resistant and breathable synthetic leather, comprising the following steps:
[0088] (1) Preparation of surface wear-resistant layer slurry: Add 2kg of ethyl acetate to the reactor, heat to 70℃, add 900g of hydroxyl-terminated IPDI-based aliphatic polyurethane (polymerized from IPDI and poly(1,4-butanediol adipate), hydroxyl content: 3.5±0.3%, of which the number average molecular weight of poly(1,4-butanediol adipate) is 1000±50) under stirring, keep warm and stir for 30min, then add 30g of IPDI trimer, keep warm and stir for 25min, then add 80g of KH-560 modified nano alumina and 10g of sodium polycarboxylate, disperse under stirring for 1.5h to obtain surface wear-resistant layer slurry;
[0089] (2) Preparation of intermediate functional layer slurry: 1.6 kg N,N-dimethylacetamide and 200 g KH-550 modified diatomaceous earth were added to the reactor. The mixture was ultrasonically dispersed for 50 min at a power of 500 W and a frequency of 25 kHz. The temperature was raised to 75 °C. 700 g of isocyanate-terminated MDI-based aromatic polyurethane was added under stirring. The mixture was kept warm and stirred for 40 min. Then 120 g of hydroxyl-terminated ureidopyrimidinone and 60 g of carboxyl-terminated butadiene-acrylonitrile liquid rubber were added. The mixture was kept warm and stirred for 2 h. The temperature was lowered to 45 °C and stirred for another 40 min to obtain the intermediate functional layer slurry.
[0090] (3) Preparation of the bottom flexible layer slurry: Add 2.1 kg of ethyl acetate to the reactor, heat to 70 °C, and add 950 g of hydroxyl-terminated polyether modified IPDI-based flexible polyurethane (polymerized from IPDI and polytetrahydrofuran diol, with hydroxyl content of 3.2 ± 0.5% and number average molecular weight of polytetrahydrofuran diol of 4000) while stirring. Keep the temperature and stir for 30 min, add 20 g of IPDI trimer, continue to keep the temperature and stir for 20 min, and then add 70 g of hydroxyl-terminated polybutadiene (hydroxyl content of 0.53 mmol / g), 20 g of carbodiimide and 5 g of BYK-066N. Stir and disperse for 50 min to obtain the bottom flexible layer slurry.
[0091] (4) Lamination and curing: The surface wear-resistant layer slurry is uniformly coated on the release paper, and the wet film thickness is controlled to be 0.25 mm. It is then placed in a 120℃ oven and dried for 50 s to obtain the surface wear-resistant layer. The intermediate functional layer slurry is uniformly coated on the surface wear-resistant layer, and the wet film thickness is controlled to be 0.6 mm. It is then immediately immersed in deionized water at 42℃ for 90 s, removed, and the surface water is drained. It is then placed in a forced-air oven at 80℃ for 20 s to pre-dry to obtain the intermediate functional layer. The bottom flexible layer slurry is uniformly coated on the intermediate functional layer, and the wet film thickness is controlled to be 0.35 mm. It is then placed in a 130℃ oven and dried for 60 s to obtain the composite layer. The composite layer is peeled off from the release paper to obtain the synthetic leather blank.
[0092] (5) Post-treatment purification: The synthetic leather blank is placed in a vacuum drying oven at 80°C for 20 min, then sent to a 100°C oven for heat treatment for 40 min, then cooled to room temperature, and then immersed in a 5wt% solution of Pingpingjia O-20 for 10 min. Finally, it is rinsed 4 times with deionized water and dried to obtain a high tear-resistant breathable synthetic leather product.
[0093] Comparative Example 1: The difference between Comparative Example 1 and Example 2 is that the hydroxyl-terminated ureidinidone prepared according to the preparation example is replaced with ureidinidone, whose chemical structure is as follows:
[0094] .
[0095] Comparative Example 2: The difference between Comparative Example 2 and Example 2 is that the hydroxyl-terminated ureidopyrimidinone prepared according to the preparation example is not added.
[0096] Comparative Example 3: The difference between Comparative Example 3 and Example 2 is that no carboxyl-terminated liquid nitrile rubber is added.
[0097] Comparative Example 4: The difference between Comparative Example 4 and Example 2 is that KH-560 modified nano alumina and KH-550 modified diatomaceous earth are replaced with nano alumina and diatomaceous earth.
[0098] Comparative Example 5: The difference between Comparative Example 5 and Example 2 is that the hydroxyl-terminated polybutadiene is replaced with polybutadiene, Average Mn≈2600.
[0099] Performance testing:
[0100] 1. Tear Strength Test: Referring to the national standard GB / T 16578.1-2008 "Determination of Tear Resistance of Plastic Films and Sheets Part 1: Trouser Tear Test", 10 trouser-shaped samples were cut from the synthetic leather products of Examples 1-3 and each comparative example. The sample dimensions were 150 mm in length, 25 mm in width, and 75 mm in leg length. A 10 mm long slit was pre-cut in the middle of the sample to ensure a consistent tear initiation position. The samples were mounted on a tensile testing machine, with the test speed set to 500 mm / min, ambient temperature 23℃, and relative humidity 50%. After starting the equipment, the maximum force value during the tearing process was recorded. The average value of 10 samples for each sample was taken as the tear strength. The experimental results are shown in Table 1.
[0101] 2. Air permeability test: Referring to the national standard GB / T 10655.2-2003 "Determination of air permeability of textile materials", five circular samples with a diameter of 120 mm were randomly cut from the synthetic leather prepared in Examples 1-3 and Comparative Examples 1-5. Before the test, the samples were equilibrated in an environment of 23℃ and 50% relative humidity for 24 hours. An air permeability tester was used, and the test area was set to 20 cm². 2 The test pressure was 200 Pa. The instrument automatically measured the volume of air passing through the sample per unit time and calculated the average air permeability of each sample. The experimental results are shown in Table 1.
[0102] 3. Interlayer peel strength test: Referring to the national standard GB / T 2791-1995 "Test method for peel strength of adhesives - flexible materials to flexible materials", strip samples with a width of 20 mm and a length of 150 mm were cut from the synthetic leather prepared in Examples 1-3 and Comparative Examples 1-5. Using a blade, a 50 mm long initial peel end was gently cut along the interface between the surface layer and the middle layer or the middle layer and the bottom layer to ensure that the peeling only occurred at the target interface. The two ends of the sample were fixed on the upper and lower clamps of the tensile testing machine, respectively. The peeling speed was set to 100 mm / min and the ambient temperature was 23℃. During the test, the force value change during the peeling process was recorded. The average force value within the peeling length range of 50-100 mm was taken as the interlayer peel strength. The experimental results are shown in Table 1.
[0103] 4. Bending resistance test: Referring to the national standard GB / T 3903.1-2017 "Bending resistance of footwear upper, lining and insole materials", 50mm×100mm samples were cut from the synthetic leather prepared in Examples 1-3 and Comparative Examples 1-5. After equilibration in an environment of 23℃ and 50% relative humidity for 24 hours, the samples were fixed on the bending resistance tester. The bending angle was set to 180° and the bending frequency was 200 times / min. During the bending process, the sample was ensured to be subjected to uniform force and without local compression. The machine was stopped after every 1000 bends to observe whether cracks, delamination or micropore collapse appeared on the sample surface and cross-section. The number of bends when the sample first cracked was recorded. If there were no cracks after 50,000 bends, it was recorded as 50,000 bends. The experimental results are shown in Table 1.
[0104] 5. Surface abrasion resistance test: A Taber abrasion tester was used, referring to the national standard GB / T 20244-2006 "Determination of abrasion resistance of rubber or plastic coated fabrics". Circular samples with a diameter of 100 mm were cut from the surface of the synthetic leather prepared in Examples 1-3 and Comparative Examples 1-5. Before the test, the initial mass of the sample was weighed using an electronic balance with an accuracy of 0.1 mg. The grinding wheel model was set to H-18, the test load was 1000 g, the grinding wheel speed was 60 r / min, and the total abrasion revolutions were 1000 revolutions. During the test, the grinding wheel was kept in uniform contact with the sample surface to avoid excessive local wear. After the test, the residual abrasion debris on the sample surface was wiped with anhydrous ethanol, and the sample was weighed again after drying. The mass loss of the sample was calculated. The experimental results are shown in Table 1.
[0105] Table 1 Performance Test Results
[0106]
[0107] Data Analysis:
[0108] As can be seen from the performance test data in Table 1, the synthetic leather prepared by the technical solution of the present invention in Examples 1-3 all show significant advantages in terms of tear resistance, breathability, interlayer peel strength, flexural durability and abrasion resistance, and are comprehensively superior to the comparative products. Among them, the comprehensive performance of Example 2 is the most outstanding.
[0109] The high tear resistance of Example 2 stems from the synergistic effect of multiple processes: covalent crosslinking, dynamic hydrogen bond network, elastic segment toughening, and modified filler reinforcement. The terminal hydroxyl group UPy (UPy-OH) can form a quadruple hydrogen bond dimer, constructing dynamic physical crosslinking points. Under stress, the hydrogen bonds preferentially dissociate to absorb energy, delaying crack propagation. After the external force disappears, they can be reconstructed. Simultaneously, its terminal hydroxyl group can form covalent bonds with the polyurethane matrix, achieving a synergistic effect of chemical and physical crosslinking. Carboxylated nitrile rubber (CTBN), as an elastic segment, has its carboxyl functional groups chemically crosslinked with the polyurethane, forming an interpenetrating network structure. The flexible segments can disperse stress through elastic deformation, avoiding brittle fracture caused by stress concentration. The inorganic fillers modified with KH-560 and KH-550 form stable chemical bonds with the polyurethane matrix through the "molecular bridging" effect of the silane coupling agent. The uniformly dispersed filler particles can hinder crack penetration, further enhancing strength.
[0110] The superior air permeability of Example 2 is due to the use of modified nano-alumina in the surface layer, which forms uniform nanopores through the steric hindrance effect; the middle layer forms multi-level interconnected pores under the control of KH-550 modified diatomaceous earth by non-solvent-induced phase separation; and the bottom layer of hydroxyl-terminated polybutadiene (HTPB) undergoes microphase separation with polyurethane to form flexible interconnected pores. Together, the three form a continuous gas transport channel.
[0111] The interlayer peel strength in Example 2 depends on the synergistic effect of interlayer chemical bonding, hydrogen bonding reinforcement, and interfacial compatibility. The terminal hydroxyl groups of UPy-OH can react with the active groups of the intermediate polyurethane layer to form covalent bonds, while its urea structure can form hydrogen bonds with molecules in each layer, further strengthening the interlayer interaction; the inorganic filler modified with silane coupling agent forms interfacial anchoring points between layers, reducing interlayer slippage; the elastic segments of CTBN improve the compatibility between layers and avoid interfacial stress concentration.
[0112] Example 2's excellent bending durability stems from the material's "dynamic flexible structure" design. The dynamic hydrogen bond network constructed by UPy-OH can repeatedly dissociate and reconstruct during bending, absorbing bending stress and preventing fatigue fracture of molecular chains. The flexible segments provided by CTBN and HTPB can enhance the flexibility and slippage ability of molecular chains, reducing rigid damage during bending. The strong interlayer bonding prevents interlayer delamination during bending, while the uniformly dispersed modified filler reduces local stress concentration.
[0113] The low mass loss in Example 2 is mainly due to the "rigid support + strong interface bonding" characteristics of the surface layer. KH-560 modified nano-alumina has high hardness and forms a rigid support skeleton on the surface after uniform dispersion, which can resist mechanical wear during friction. The modification of the silane coupling agent enables the nano-alumina to form a chemical bond with the polyurethane substrate, avoiding the aggravated wear caused by the shedding of filler particles during friction.
[0114] In comparison, Comparative Example 1 uses non-carboxyl-terminated UPy instead of UPy-OH. Although its terminal isocyanate groups can react with the surface and bottom hydroxyl groups, they cannot form an effective bond with the isocyanate groups of the intermediate polyurethane layer. The dispersion degree in the intermediate layer is not high, and the mechanical properties are uneven. At the same time, the UPy molecule lacks a urea group, which reduces the density of the hydrogen bond network and significantly reduces the dynamic stress dissipation capacity. Compared with Example 2, the integrity of chemical crosslinking and the synergy of physical crosslinking are both impaired, resulting in a significant decrease in tear strength, interlaminar peel strength and flexural durability. The air permeability is also reduced due to the slight blockage of pores caused by the agglomeration of UPy due to uneven dispersion.
[0115] Comparative Example 2 contains no UPy-OH and lacks the support of a dynamic quadruple hydrogen bond network. It relies solely on the covalent crosslinking of the polyurethane matrix, resulting in enhanced structural rigidity but insufficient toughness. Lacking the dynamic dissociation and reconstruction mechanism of hydrogen bonds, stress cannot be effectively dissipated, and cracks easily propagate rapidly, leading to a significant reduction in tear strength and bending cycles. The interlayer bonding relies solely on a single covalent bond, lacking hydrogen bond reinforcement, resulting in a significant decrease in peel strength. Although its pore structure is not directly affected and its air permeability is similar to that of Example 2, its overall performance is significantly inferior to that of Example 2 due to the absence of the core dynamic crosslinking network.
[0116] In Comparative Example 3, without the addition of CTBN elastic segments, the intermediate polyurethane matrix lacked a flexible cross-linked network and relied solely on rigid covalent bonds and hydrogen bonds for support, increasing the material's brittleness. The absence of CTBN resulted in insufficient stress dispersion, preventing damage buffering through elastic deformation during bending, leading to a significant decrease in tear strength and bending durability. Simultaneously, the improvement effect of CTBN on interlayer compatibility disappeared. Although the decrease in interlayer peel strength was relatively small, the overall synergy of mechanical properties was impaired, and the comprehensive performance was far inferior to that of Example 2.
[0117] Comparative Example 4 uses unmodified inorganic fillers. The fillers that have not been treated with KH-560 and KH-550 lack active groups on their surface and cannot form chemical bonds with the polyurethane substrate. They can only be dispersed by physical mixing, which easily leads to agglomeration. Agglomerated fillers not only form stress concentration points inside the material, reducing tear resistance and bending performance, but also severely block the pores of the surface and intermediate layers, resulting in a sharp decline in air permeability. At the same time, the unfixed fillers are easy to fall off during friction, which aggravates surface wear and significantly increases mass loss. All performance characteristics are significantly different from those of Example 2.
[0118] Comparative Example 5 uses polybutadiene instead of HTPB. Because polybutadiene lacks hydroxyl groups, it cannot form chemical grafts with the polyurethane matrix through hydroxy-isocyanate group reaction, and is only in a physical blend state. This results in the inability to form effective microphase separation channels in the bottom layer, and the air permeability is greatly reduced. At the same time, the ungrafted polybutadiene is unevenly dispersed, the flexibility of the bottom layer and the interfacial bonding force are reduced, and interlayer slippage and structural damage are easily generated during bending. The number of bending times is significantly reduced, and the tear resistance and interlayer peel strength are also negatively affected by the instability of the bottom layer structure. The overall performance is inferior to that of Example 2.
[0119] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.
Claims
1. A highly tear-resistant and breathable synthetic leather, characterized in that, From top to bottom, the layers are: a surface wear-resistant layer, a middle functional layer, and a bottom flexible layer. The surface wear-resistant layer is formed by sterically hindered phase separation to create pores and then cross-linking and curing KH-560 modified nano alumina, hydroxyl-terminated IPDI-based aliphatic polyurethane, IPDI trimer, dispersant and ethyl acetate. The intermediate functional layer is formed by dynamic hydrogen bonding crosslinking and separation of the isocyanate-terminated MDI-based aromatic polyurethane, hydroxyl-terminated ureidopyrimidinone, KH-550 modified diatomaceous earth, toughening agent and N,N-dimethylacetamide from a non-solvent-induced phase. The bottom flexible layer is formed by microphase separation and pore creation of hydroxyl-terminated polyether modified IPDI-based flexible polyurethane, IPDI trimer, hydroxyl-terminated polybutadiene, hydrolysis stabilizer, defoamer and ethyl acetate. The surface wear-resistant layer and the bottom flexible layer are cross-linked with the intermediate functional layer through hydroxyl and isocyanate groups and connected by multiple hydrogen bonds through hydroxyl and hydroxyl-terminated ureidopyrimidinone groups. The hydroxyl-terminated IPDI-based aliphatic polyurethane is polymerized from IPDI and poly(1,4-butanediol adipate), with a hydroxyl content of 3.5±0.3% and a number-average molecular weight of 1,4-butanediol adipate of 1000±50. The terminal isocyanate-based MDI-based aromatic polyurethane is polymerized from MDI and poly(1,4-butanediol adipate), with an NCO content of 9.0±0.5% and a number-average molecular weight of 1,4-butanediol adipate of 1000±50.
2. The highly tear-resistant and breathable synthetic leather according to claim 1, characterized in that, The raw materials of the surface wear-resistant layer are as follows by weight: 80-90 parts of hydroxyl-terminated IPDI-based aliphatic polyurethane, 2-3 parts of IPDI trimer, 5-8 parts of KH-560 modified nano alumina, 0.5-1 parts of dispersant, and 180-200 parts of ethyl acetate; wherein the dispersant is sodium polycarboxylate.
3. The highly tear-resistant and breathable synthetic leather according to claim 1, characterized in that, The raw materials of the intermediate functional layer are as follows by weight: isocyanate-terminated MDI-based aromatic polyurethane: 60-70 parts, hydroxyl-terminated ureidopyrimidinone: 8-12 parts, KH-550 modified diatomaceous earth: 15-20 parts, toughening agent: 4-6 parts, N,N-dimethylacetamide: 140-160 parts.
4. The highly tear-resistant and breathable synthetic leather according to claim 1, characterized in that, The toughening agent refers to carboxyl-terminated butadiene-nitrile liquid rubber.
5. The highly tear-resistant and breathable synthetic leather according to claim 1, characterized in that, The raw materials of the bottom flexible layer are as follows by weight: 85-95 parts of IPDI-based flexible polyurethane modified with hydroxyl-terminated polyether, 1-2 parts of IPDI trimer, 5-7 parts of hydroxyl-terminated polybutadiene, 1-2 parts of hydrolysis stabilizer, 0.3-0.5 parts of defoamer, and 180-210 parts of ethyl acetate.
6. The highly tear-resistant and breathable synthetic leather according to claim 1, characterized in that, The hydroxyl-terminated polyether modified IPDI-based flexible polyurethane is polymerized from IPDI and polytetrahydrofuran diol, with a hydroxyl content of 3.2±0.5%, wherein the number average molecular weight of polytetrahydrofuran diol is 3000-4000; the hydrolysis stabilizer refers to carbodiimide; and the defoamer refers to BYK-066N.
7. The method for preparing highly tear-resistant and breathable synthetic leather according to any one of claims 1-6, characterized in that, Includes the following steps: (1) Preparation of surface wear-resistant layer slurry: Add ethyl acetate to the reaction vessel, heat to 60-70℃, add hydroxyl-terminated IPDI-based aliphatic polyurethane under stirring, keep warm and stir for 20-30 min, then add IPDI trimer, continue to keep warm and stir for 15-25 min, then add KH-560 modified nano alumina and sodium polycarboxylate, disperse under stirring for 1-1.5 h to obtain surface wear-resistant layer slurry; (2) Preparation of intermediate functional layer slurry: N,N-dimethylacetamide and KH-550 modified diatomaceous earth were added to the reaction vessel and ultrasonically dispersed for 40-50 min. The temperature was raised to 65-75℃, and isocyanate-terminated MDI-based aromatic polyurethane was added under stirring. The mixture was kept warm and stirred for 30-40 min. Then, hydroxyl-terminated ureidopyrimidinone and toughening agent were added. The mixture was kept warm and reacted for 1-2 h under stirring. The temperature was lowered to 40-45℃ and stirring was continued for 20-40 min to obtain intermediate functional layer slurry. (3) Preparation of bottom flexible layer slurry: Add ethyl acetate to the reactor, heat to 60-70℃, add hydroxyl-terminated polyether modified IPDI-based flexible polyurethane under stirring, keep warm and stir for 20-30 min, add IPDI trimer, continue to keep warm and stir for 10-20 min, then add hydroxyl-terminated polybutadiene, anti-hydrolysis stabilizer and defoamer, stir and disperse for 40-50 min to obtain bottom flexible layer slurry; (4) Lamination and curing: The surface wear-resistant layer slurry is uniformly coated onto the release paper, and the wet film thickness is controlled to be 0.15-0.25 mm. It is then dried in an oven at 110-120℃ for 40-50 s to obtain the surface wear-resistant layer. The intermediate functional layer slurry is uniformly coated onto the surface wear-resistant layer, and the wet film thickness is controlled to be 0.4-0.6 mm. It is then immediately immersed in deionized water at 38-42℃ for 80-90 s. After immersion, the surface water is drained, and the material is pre-dried in a forced-air oven at 70-80℃ for 10-20 s to obtain the intermediate functional layer. The bottom flexible layer slurry is uniformly coated onto the intermediate functional layer, and the wet film thickness is controlled to be 0.25-0.35 mm. It is then dried in an oven at 120-130℃ for 50-60 s to obtain the composite layer. The composite layer is then peeled off from the release paper to obtain the synthetic leather blank. (5) Post-treatment purification: Place the synthetic leather blank in a vacuum drying oven at 70-80℃ and dry for 10-20 minutes. Then, heat-treat it in an oven at 90-100℃ for 20-40 minutes. After cooling to room temperature, immerse it in a 2-5wt% neutral detergent solution and wash for 5-10 minutes. Finally, rinse it with deionized water 3-4 times and dry it to obtain a highly tear-resistant and breathable synthetic leather product.
8. The method for preparing highly tear-resistant and breathable synthetic leather according to claim 7, characterized in that, The ultrasonic power in (2) is 300-500W and the frequency is 15-25kHz.
9. The method for preparing highly tear-resistant and breathable synthetic leather according to claim 7, characterized in that, The neutral detergent in (5) is selected from one of the nonionic surfactants of fatty alcohol polyoxyethylene ethers.