Efficient flame-retardant antibacterial polyurethane synthetic leather and preparation method thereof

Abstract

The invention discloses efficient flame-retardant antibacterial polyurethane synthetic leather and a preparation method thereof, and relates to the technical field of polyurethane synthetic leather, the polyurethane synthetic leather comprises a base cloth layer and a polyurethane functional layer covering the surface of the base cloth layer; the polyurethane functional layer is prepared from the following components in parts by weight: 80 to 95 parts of polyether polyol, 30 to 45 parts of diisocyanate, 5 to 10 parts of a composite flame retardant, 3 to 6 parts of a synergistic flame retardant, 0.5 to 1.5 parts of an antibacterial agent, 2 to 4 parts of a chain extender and 0.05 to 0.2 part of a catalyst. According to the efficient flame-retardant antibacterial polyurethane synthetic leather provided by the invention, the synthetic leather has excellent flame-retardant grade and good antibacterial property and mechanical property, and the preparation method disclosed by the invention is simple in process and suitable for industrial production.

Description

Technical Field

[0001] This invention relates to the field of polyurethane synthetic leather technology, and in particular to a high-efficiency flame-retardant and antibacterial polyurethane synthetic leather and its preparation method. Background Technology

[0002] Polyurethane synthetic leather is widely used in furniture, automotive interiors, footwear, and bags due to its appearance and feel resembling natural leather, as well as its advantages such as wear resistance, impact resistance, and good machinability. However, as a polymer material, polyurethane has a low limiting oxygen index (≤18%), making it flammable. When burning, it produces dense smoke and severe dripping, significantly limiting its application in specialized fields. Traditional additive flame retardants (such as aluminum hydroxide / magnesium hydroxide and unmodified hypophosphite) have poor compatibility with the polyurethane matrix, requiring large amounts to achieve high flame retardancy ratings, severely degrading the material's mechanical properties and feel. Furthermore, flame retardant and antibacterial functions are usually independent and difficult to synergize. Therefore, flame retardant modification is of great significance.

[0003] There are already various solutions for flame-retardant polyurethane leather in the prior art. For example, Chinese invention patent CN109706747A discloses a flame-retardant leather brick and its embroidery method, which uses manganese hypophosphite or modified manganese hypophosphite as a flame-retardant additive; Chinese invention patent CN110615882A discloses a polyhydroxy nitrogen-phosphorus synergistic flame retardant, a flame-retardant polyurethane hot melt adhesive and its preparation method, which are used in polyurethane hot melt adhesives to improve flame-retardant durability; Chinese invention patent CN110669461A discloses a magnetically conductive flame-retardant polyurethane pressure-sensitive adhesive and its preparation method, which uses ammonium polyphosphate flame-retardant slurry to prepare the magnetically conductive flame-retardant polyurethane pressure-sensitive adhesive. However, these existing technologies have many drawbacks: (1) Many inorganic flame retardants require a high addition amount to achieve the ideal flame retardant level, which often seriously deteriorates the mechanical properties and processing fluidity of the polyurethane matrix, resulting in the leather products becoming harder and less flexible; (2) Flame retardants are prone to agglomeration in the polyurethane matrix and have poor dispersibility, which not only affects the flame retardant efficiency but also leads to stress defects in the material, reducing mechanical strength; (3) Most flame retardant solutions only focus on flame retardant performance and do not integrate other functions such as antibacterial and anti-mildew, making it difficult to meet the application scenarios with strict requirements for hygiene performance, such as medical, infant products, and high-end home furnishings; (4) Some high-efficiency flame retardants are halogenated products, which do not conform to the global environmental protection trend, while some non-halogenated flame retardants may have problems with migration or poor hydrolysis resistance.

[0004] Aluminum hypophosphite, as an environmentally friendly inorganic phosphorus-based flame retardant, possesses high thermal stability. During combustion, it promotes char formation, and the phosphoric acid produced during combustion decomposition can coat the material surface, isolating oxygen and releasing water vapor to dilute flammable gases, thus exhibiting both flame-retardant and smoke-suppressing effects. However, its polar surface has poor compatibility with the non-polar polyurethane matrix, and direct addition can easily lead to weak interfacial bonding and performance degradation. Therefore, there is an urgent need to develop a new technology that can solve the dispersion problem of aluminum hypophosphite in polyurethane and, on this basis, achieve multifunctional integration of flame retardancy and antibacterial properties without affecting the basic physical properties of polyurethane leather. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a high-efficiency flame-retardant and antibacterial polyurethane synthetic leather and its preparation method. This invention provides a high-efficiency flame-retardant and antibacterial polyurethane synthetic leather, which possesses excellent flame retardancy, good antibacterial properties, and mechanical properties. The preparation method of this invention is simple and suitable for industrial production.

[0006] In a first aspect, the present invention provides a high-efficiency flame-retardant and antibacterial polyurethane synthetic leather, wherein the polyurethane synthetic leather comprises a base fabric layer and a polyurethane functional layer covering the surface of the base fabric layer; by weight, the polyurethane functional layer comprises: 80-95 parts of polyether polyol, 30-45 parts of diisocyanate, 5-10 parts of composite flame retardant, 3-6 parts of synergistic flame retardant, 0.5-1.5 parts of antibacterial agent, 2-4 parts of chain extender, and 0.05-0.2 parts of catalyst; wherein the antibacterial agent is any one of silver-loaded mesoporous silica, zinc-loaded silica, and zinc-loaded zeolite; the chain extender is any one of 1,4-butanediol, ethylene glycol, and neopentyl glycol; the catalyst is any one of organobismuth catalyst, dibutyltin dilaurate, and organozinc catalyst; and the polyether polyol is any one of polyether polyols with a functionality of 2-4 and a molecular weight of 2000-6000.

[0007] In the above technical solution, polyether polyols constitute the long-chain soft segments of polyurethane molecules. They determine the basic flexibility, elasticity, low-temperature resistance, and hydrolysis resistance of synthetic leather.

[0008] Diisocyanates constitute the hard segments of polyurethane molecules. They react with the hydroxyl groups (-OH) of polyols and chain extenders to form urethane bonds (-NH-COO-), thereby forming a polymer. These hard segments are dispersed in the soft polyol chains, giving synthetic leather tensile strength, hardness, abrasion resistance, and heat resistance.

[0009] The composite flame retardant decomposes upon heating during combustion, generating phosphoric acid, which catalyzes the dehydration of the polyurethane matrix, forming a non-flammable carbon layer. This carbon layer covers the material surface, isolating it from oxygen and heat. The decomposition process releases water vapor, diluting flammable gases.

[0010] Synergistic flame retardants enhance the flame retardant effect and can work synergistically with composite flame retardants.

[0011] Antibacterial agents can inhibit the respiration and reproduction of microorganisms, achieving broad-spectrum, highly effective, and long-lasting antibacterial and antifungal effects.

[0012] Chain extenders primarily react with diisocyanates to extend regular hard segment structures within the polyurethane molecular chain. These hard segment regions aggregate through interactions such as hydrogen bonding, significantly improving the tensile strength, modulus, hardness, and tear strength of synthetic leather.

[0013] The catalyst selectively and efficiently catalyzes the reaction between isocyanate groups and hydroxyl groups, while minimizing the catalytic effect of side reactions. It significantly shortens reaction time and lowers reaction temperature, ensuring that the polymerization reaction proceeds rapidly, fully, and stably under the set process conditions, thereby guaranteeing a stable molecular structure and uniform performance of the final product.

[0014] Optionally, the polyether polyol is a polyoxypropylene triol with a functionality of 3 and a molecular weight of 3000-5000.

[0015] In the above technical solution, a polyether polyol with a functionality of 3 is used, which can form a three-dimensional cross-linked network structure, giving the synthetic leather good mechanical strength and resilience. A molecular weight of 3000-5000 ensures that the molecular chains are long enough, thus making the synthetic leather soft.

[0016] Optionally, the diisocyanate is 4,4'-diphenylmethane diisocyanate.

[0017] In the above technical solution, 4,4'-diphenylmethane diisocyanate contains a rigid benzene ring, which, after reacting with polyols, can form regular hard segments in the polyurethane molecular chain. This can impart higher tensile strength, tear strength, hardness, abrasion resistance, and creep resistance to synthetic leather. 4,4'-diphenylmethane diisocyanate has a highly symmetrical molecular structure. This symmetry allows the hard segments in the polyurethane chain to arrange and stack more orderly, forming a more complete microphase separation structure.

[0018] Optionally, the synergistic flame retardant is a blend of melamine polyphosphate and amino POSS in a mass ratio of 2-5:1.

[0019] In the above technical solution, melamine polyphosphate decomposes at high temperature to generate strong dehydrating acids such as polyphosphoric acid, which catalyze the dehydration of the polyurethane polymer matrix into carbon, forming the framework of the expanded carbon layer. Simultaneously, the melamine structure decomposes upon heating, releasing non-combustible gases such as nitrogen and ammonia, causing the molten carbon layer to expand and form a loose, porous insulating layer. It can also act as a foaming agent, providing gas for the expansion process.

[0020] Amino-based POSS is an organic-inorganic hybrid nanomaterial with a cage-like siloxane core structure. Its surface amino groups (-NH2) can interact with polyurethane matrices or melamine polyphosphate. During combustion, the inorganic portion (SiO2) of POSS migrates to the char surface, forming a robust siliceous protective layer. This significantly enhances the density, continuity, and mechanical strength of the char layer, making it less prone to cracking under high temperatures and flame erosion. The surface amino groups can also act as weak crosslinking points, improving the initial thermal stability of the polyurethane matrix. POSS itself also promotes the formation of a more stable char layer. This reinforced char layer effectively encapsulates the polymer, preventing combustion droplets generated during melting, and significantly contributing to achieving the UL94V-0 rating.

[0021] When the two are blended, an organic-inorganic hybrid carbon layer is formed. This carbon layer not only possesses thickness and an expanded structure, but also exhibits high strength, density, and thermal stability. It effectively isolates oxygen and external heat from the substrate, inhibits the leakage of internal combustible degradation products, and prevents molten droplets caused by material melting.

[0022] Optionally, the preparation method of the synergistic flame retardant is as follows: first, amino POSS is dispersed in an appropriate amount of anhydrous ethanol, and ultrasonically treated for 10-20 minutes to obtain a suspension. Then, this suspension is mixed with melamine polyphosphate powder at a mass ratio, and stirred at high speed at 500-700 rpm for 20-40 minutes to form a slurry. The solvent is removed by vacuum drying to obtain the blend.

[0023] In the above technical solution, the ultrasonic waves generated by the ultrasonic treatment in the liquid produce strong impact force and microjets, which can effectively suspend amino POSS in ethanol as primary particles or extremely small secondary aggregates. The -NH2 groups on the surface of amino POSS and the groups on the surface of melamine polyphosphate particles may interact more tightly through hydrogen bonds and other means, under the medium of ethanol. When the suspension is mixed with melamine polyphosphate powder under high-speed stirring, the tiny POSS particles will uniformly adhere to the surface of larger melamine polyphosphate particles with the help of the wetting and shearing forces of the liquid phase. This results in better compatibility and dispersion stability of the synergistic flame retardant in the subsequent preparation of synthetic leather, reducing the sedimentation or agglomeration of fillers caused by poor compatibility, thereby ensuring the stability and leveling properties during the preparation of synthetic leather.

[0024] Optionally, the composite flame retardant is an organic-inorganic composite aluminum hypophosphite powder.

[0025] Optionally, the preparation method of the organic-inorganic composite aluminum hypophosphite powder is as follows: aluminum sulfate is dissolved in deionized water and stirred at 75-85°C until the solution is clear, then sodium hypophosphite solution is slowly added, wherein the Al... 3+ :H2PO2− The molar ratio of the two components was 1:0.8-1.2. The mixture was reacted for 1-2 hours under microwave assistance at a power of 250-350W to obtain an inorganic aluminum hypophosphite crystal nucleus suspension. While maintaining a constant temperature, an ethanol solution of diethylphosphite and an ethanol solution of KH-550 silane coupling agent were added dropwise. The diethylphosphite reacted with Al... 3+ The molar ratio is 0.6-0.9:1, the amount of KH-550 silane coupling agent is 3-5% of the mass of aluminum sulfate, the pH is adjusted to 4.5-5.5 with acetic acid, and the reaction is carried out at a constant temperature for 2-3 hours. After the reaction is completed, the mixture is centrifuged, washed, and dried to constant weight to obtain organic-inorganic composite aluminum hypophosphite powder.

[0026] In the above technical solution, diethyl hypophosphite and KH-550 are not simply physically coated on the surface of pre-prepared aluminum hypophosphite particles, but directly participate in the reaction during the formation and growth of aluminum hypophosphite crystal nuclei. The hypophosphite ions of diethyl hypophosphite can coordinate with aluminum ions, becoming part of the crystal. The silanol groups, hydrolysis products of KH-550, can also condense with the hydroxyl groups on the surface of the crystal nuclei. This forms a strong "core-shell-bridge" chemical bond structure, making the modifier less prone to migration and detachment, achieving molecular-level hybridization of the organic and inorganic phases. This greatly improves compatibility and dispersibility in the polyurethane matrix.

[0027] The ethyl group of diethylphosphine and the amino and propyl groups of KH-550, introduced through the reaction, form an organic molecular layer on the surface of the composite flame retardant powder. This organic layer exhibits excellent compatibility with the non-polar polyurethane matrix. It effectively reduces the surface energy of nano / micro particles, preventing their agglomeration in the polyurethane slurry. It also exhibits strong adhesion to the polyurethane matrix, avoiding the degradation of mechanical properties caused by weak filler-matrix interface bonding. The introduction of diethylphosphine also provides an additional organic phosphorus source, increasing the overall phosphorus content and improving flame retardant efficiency.

[0028] The good dispersion of composite flame retardants means that they can function uniformly and efficiently within the material during combustion. This effectively solves the problems of poor dispersibility and weak interfacial bonding of inorganic flame retardants in organic polymer matrices.

[0029] Secondly, the present invention provides a method for preparing highly efficient flame-retardant and antibacterial polyurethane synthetic leather, the method comprising the following steps: (1) Add polyether polyol, composite flame retardant, synergistic flame retardant and antibacterial agent to the reaction vessel, stir and disperse at 600-700 r / min for 25-35 min, then add chain extender and catalyst, and dehydrate under vacuum at 55-75℃ for 1-2 h. (2) Cool down to 35-45℃, add diisocyanate under nitrogen protection, and then heat up to 60-80℃ to carry out the reaction. Monitor the intensity of the NCO characteristic peak online with FTIR until its content reaches more than 99% of the theoretical calculation value to obtain flame-retardant and antibacterial polyurethane slurry. (3) The flame-retardant polyurethane slurry is coated onto the surface of the base fabric by roller coating, and then placed in an oven to cure at 105-110℃ for 8-12 minutes, and then cured at 130-140℃ for 2-4 hours. After embossing and surface treatment, the high-efficiency flame-retardant and antibacterial polyurethane synthetic leather is obtained.

[0030] In the above technical solution, in step (1), before adding the highly reactive diisocyanate, the flame retardant, antibacterial agent, and high-viscosity liquid polyether polyol are mixed and subjected to high-speed shear stirring. Utilizing the viscous resistance of the polyether polyol, the secondary agglomerates of the filler are broken up by strong mechanical shear force, achieving primary and uniform dispersion of the filler in the matrix. Adding the filler first and then the catalyst last can avoid premature polymerization reaction caused by the catalyst. If the catalyst is added first, the viscosity of the system will rise rapidly, causing the subsequent filler to fail to disperse uniformly and form agglomerates, which is detrimental to the uniformity of the product's mechanical properties and functions.

[0031] In step (2), the dehydrated mixture is cooled to 35-45℃ before diisocyanate is added. This ensures that the highly reactive diisocyanate mixes thoroughly and uniformly with the polyols and chain extenders in the system, preventing gelation or unevenness caused by localized rapid reactions. Nitrogen, as an inert gas, eliminates oxygen, preventing the polyurethane from being oxidized, yellowed, and degraded at high temperatures. This ensures that no more moisture is absorbed during the reaction. Online FTIR monitoring, by monitoring the decrease in peak intensity in real time, can accurately determine when the reaction reaches the preset endpoint, ensuring that the polyurethane molecular chains grow to the expected molecular weight, thereby guaranteeing optimal final mechanical properties. This prevents excessive branching and crosslinking due to over-reaction, which could lead to excessive slurry viscosity or gelation, affecting subsequent coating processes.

[0032] Thirdly, the application of the high-efficiency flame-retardant and antibacterial polyurethane synthetic leather prepared by the present invention or by a method for preparing high-efficiency flame-retardant and antibacterial polyurethane synthetic leather in the medical industry, food packaging industry, and infant product industry.

[0033] In summary, the present invention has at least one of the following beneficial technical effects: 1. By adding composite flame retardants, organic acids undergo in-situ polymerization and co-precipitation reactions with aluminum hypophosphite, which greatly improves its dispersibility and compatibility in the polyurethane matrix, enabling it to play a more effective flame retardant role. This forms a "core-shell-bridge" composite flame retardant and a PN-Si ternary synergistic system, significantly improving the flame retardant efficiency. This allows the product's limiting oxygen index (LOI) to reach over 33%, and vertical burning to achieve UL94V-0 rating.

[0034] 2. By adding antibacterial agents, synthetic leather is endowed with long-lasting antibacterial and antifungal properties, which broadens its application prospects in fields such as medical and health care and food packaging.

[0035] 3. The composite hybrid structure solves the problem of filler agglomeration. The "pre-dispersion-synchronous polymerization" process ensures the uniformity and stability of product quality. The flame retardant used is halogen-free and environmentally friendly. The preparation process releases no toxic substances, which is in line with the trend of green manufacturing. The preparation method has a clear process flow, mild conditions, good compatibility with existing polyurethane synthetic leather production processes, and is easy to realize large-scale industrial production. Detailed Implementation

[0036] The present invention will be further described in detail below with reference to the embodiments.

[0037] All materials used in the following examples are available for purchase on the market.

[0038] Example 1: A high-efficiency flame-retardant and antibacterial polyurethane synthetic leather and its preparation method.

[0039] The polyurethane synthetic leather comprises a base fabric layer and a polyurethane functional layer covering the surface of the base fabric layer. By weight, the polyurethane functional layer comprises: 80 parts polyether polyol, 30 parts isophorone diisocyanate, 5 parts organic-inorganic composite aluminum hypophosphite powder, 3 parts synergistic flame retardant, 0.5 parts zinc-supported zeolite, 2 parts neopentyl glycol, and 0.05 parts organic zinc catalyst. The synergistic flame retardant is a blend of melamine polyphosphate and amino POSS in a mass ratio of 2:1. The polyether polyol is polypropylene glycol with a functionality of 4 and a molecular weight of 6000.

[0040] The preparation method includes the following steps: S1. Preparation of organic-inorganic composite aluminum hypophosphite powder: Dissolve aluminum sulfate in deionized water and stir at 80°C until the solution is clear. Then slowly add sodium hypophosphite solution. 3+ :H2PO 2− The molar ratio of the two compounds was 1:0.8, and the reaction was carried out for 1.5 h under microwave assistance at a power of 300 W to obtain an inorganic aluminum hypophosphite crystal nucleus suspension. While maintaining a constant temperature, an ethanol solution of diethylphosphite and an ethanol solution of KH-550 silane coupling agent were added dropwise. The diethylphosphite reacted with Al... 3+The molar ratio was 0.6:1, the amount of KH-550 silane coupling agent was 3% of the mass of aluminum sulfate, the pH was adjusted to 4.5-5.5 with acetic acid, and the reaction was carried out at a constant temperature for 2.5 h. After the reaction was completed, the mixture was centrifuged, washed, and dried to constant weight to obtain organic-inorganic composite aluminum hypophosphite powder.

[0041] S2. Preparation of synergistic flame retardant: Amino POSS is first dispersed in an appropriate amount of anhydrous ethanol and ultrasonically treated for 15 min to obtain a suspension. Then, this suspension is mixed with melamine polyphosphate powder at a mass ratio and stirred at a high speed of 600 rpm for 30 min to form a slurry. The solvent is removed by vacuum drying to obtain the blend.

[0042] S3. Mixing of substances: Add polyether polyol, composite flame retardant, synergistic flame retardant and antibacterial agent to the reaction vessel, stir and disperse at 650 r / min for 30 min, then add chain extender and catalyst, and dehydrate under vacuum at 65℃ for 1.5 h.

[0043] S4. Preparation of flame-retardant and antibacterial polyurethane slurry: Cool down to 40℃, add diisocyanate under nitrogen protection, then heat up to 70℃ for reaction, monitor the intensity of NCO characteristic peaks online with FTIR until its content reaches more than 99% of the theoretically calculated value, and obtain flame-retardant and antibacterial polyurethane slurry.

[0044] S5. Coating and Surface Treatment: The flame-retardant polyurethane slurry is coated onto the surface of the base fabric by roller coating, and then placed in an oven to cure at 105°C for 10 minutes, followed by curing at 135°C for 3 hours. After embossing and surface treatment, the high-efficiency flame-retardant and antibacterial polyurethane synthetic leather #1 is obtained.

[0045] Example 2: A high-efficiency flame-retardant and antibacterial polyurethane synthetic leather and its preparation method.

[0046] The polyurethane synthetic leather comprises a base fabric layer and a polyurethane functional layer covering the surface of the base fabric layer. By weight, the polyurethane functional layer comprises: 95 parts polyether polyol, 45 parts phthalimide diisocyanate, 10 parts organic-inorganic composite aluminum hypophosphite powder, 6 parts synergistic flame retardant, 1.5 parts zinc-loaded silica, 4 parts ethylene glycol, and 0.2 parts dibutyltin dilaurate. The synergistic flame retardant is a blend of melamine polyphosphate and amino POSS in a mass ratio of 5:1. The polyether polyol is polypropylene tetraol with a functionality of 2 and a molecular weight of 2000.

[0047] The preparation method includes the following steps: S1. Preparation of organic-inorganic composite aluminum hypophosphite powder: Dissolve aluminum sulfate in deionized water and stir at 80°C until the solution is clear. Then slowly add sodium hypophosphite solution. 3+ :H2PO2− The molar ratio of the two compounds was 1:1.2, and the reaction was carried out for 1.5 h under microwave assistance at a power of 300 W to obtain an inorganic aluminum hypophosphite crystal nucleus suspension. While maintaining a constant temperature, an ethanol solution of diethylphosphite and an ethanol solution of KH-550 silane coupling agent were added dropwise. The diethylphosphite reacted with Al... 3+ The molar ratio was 0.9:1, the amount of KH-550 silane coupling agent was 5% of the mass of aluminum sulfate, the pH was adjusted to 4.5-5.5 with acetic acid, and the reaction was carried out at a constant temperature for 2.5 h. After the reaction was completed, the mixture was centrifuged, washed, and dried to constant weight to obtain organic-inorganic composite aluminum hypophosphite powder.

[0048] S2. Preparation of synergistic flame retardant: Amino POSS is first dispersed in an appropriate amount of anhydrous ethanol and ultrasonically treated for 15 min to obtain a suspension. Then, this suspension is mixed with melamine polyphosphate powder at a mass ratio and stirred at a high speed of 600 rpm for 30 min to form a slurry. The solvent is removed by vacuum drying to obtain the blend.

[0049] S3. Mixing of substances: Add polyether polyol, composite flame retardant, synergistic flame retardant and antibacterial agent to the reaction vessel, stir and disperse at 650 r / min for 30 min, then add chain extender and catalyst, and dehydrate under vacuum at 65℃ for 1.5 h.

[0050] S4. Preparation of flame-retardant and antibacterial polyurethane slurry: Cool down to 40℃, add diisocyanate under nitrogen protection, then heat up to 70℃ for reaction, monitor the intensity of NCO characteristic peaks online with FTIR until its content reaches more than 99% of the theoretically calculated value, and obtain flame-retardant and antibacterial polyurethane slurry.

[0051] S5. Coating and Surface Treatment: The flame-retardant polyurethane slurry is coated onto the surface of the base fabric by roller coating, and then placed in an oven to cure at 105°C for 10 minutes, followed by curing at 135°C for 3 hours. After embossing and surface treatment, the high-efficiency flame-retardant and antibacterial polyurethane synthetic leather #2 is obtained.

[0052] Example 3: A high-efficiency flame-retardant and antibacterial polyurethane synthetic leather and its preparation method.

[0053] The polyurethane synthetic leather comprises a base fabric layer and a polyurethane functional layer covering the surface of the base fabric layer. By weight, the polyurethane functional layer comprises: 90 parts polyether polyol, 38 parts toluene diisocyanate, 8 parts organic-inorganic composite aluminum hypophosphite powder, 4 parts synergistic flame retardant, 1.0 part silver-loaded mesoporous silica, 3 parts 1,4-butanediol, and 0.1 parts organic bismuth catalyst. The synergistic flame retardant is a blend of melamine polyphosphate and amino POSS in a mass ratio of 3:1. The polyether polyol is polypropylene hexaol with a functionality of 3 and a molecular weight of 4000.

[0054] The preparation method includes the following steps: S1. Preparation of organic-inorganic composite aluminum hypophosphite powder: Dissolve aluminum sulfate in deionized water and stir at 80°C until the solution is clear. Then slowly add sodium hypophosphite solution. 3+ :H2PO 2− The molar ratio of the two compounds was 1:1.0, and the reaction was carried out for 1.5 h under microwave assistance at a power of 300 W to obtain an inorganic aluminum hypophosphite crystal nucleus suspension. While maintaining a constant temperature, an ethanol solution of diethylphosphite and an ethanol solution of KH-550 silane coupling agent were added dropwise. The diethylphosphite reacted with Al... 3+ The molar ratio was 0.8:1, the amount of KH-550 silane coupling agent was 4% of the mass of aluminum sulfate, the pH was adjusted to 4.5-5.5 with acetic acid, and the reaction was carried out at a constant temperature for 2.5 h. After the reaction was completed, the mixture was centrifuged, washed, and dried to constant weight to obtain organic-inorganic composite aluminum hypophosphite powder.

[0055] S2. Preparation of synergistic flame retardant: Amino POSS is first dispersed in an appropriate amount of anhydrous ethanol and ultrasonically treated for 15 min to obtain a suspension. Then, this suspension is mixed with melamine polyphosphate powder at a mass ratio and stirred at a high speed of 600 rpm for 30 min to form a slurry. The solvent is removed by vacuum drying to obtain the blend.

[0056] S3. Mixing of substances: Add polyether polyol, composite flame retardant, synergistic flame retardant and antibacterial agent to the reaction vessel, stir and disperse at 650 r / min for 30 min, then add chain extender and catalyst, and dehydrate under vacuum at 65℃ for 1.5 h.

[0057] S4. Preparation of flame-retardant and antibacterial polyurethane slurry: Cool down to 40℃, add diisocyanate under nitrogen protection, then heat up to 70℃ for reaction, monitor the intensity of NCO characteristic peaks online with FTIR until its content reaches more than 99% of the theoretically calculated value, and obtain flame-retardant and antibacterial polyurethane slurry.

[0058] S5. Coating and Surface Treatment: The flame-retardant polyurethane slurry is coated onto the surface of the base fabric by roller coating, and then placed in an oven to cure at 105°C for 10 minutes, followed by curing at 135°C for 3 hours. After embossing and surface treatment, the high-efficiency flame-retardant and antibacterial polyurethane synthetic leather #3 is obtained.

[0059] Example 4: A high-efficiency flame-retardant and antibacterial polyurethane synthetic leather and its preparation method.

[0060] The polyurethane synthetic leather comprises a base fabric layer and a polyurethane functional layer covering the surface of the base fabric layer. By weight, the polyurethane functional layer comprises: 90 parts polyether polyol, 38 parts toluene diisocyanate, 8 parts organic-inorganic composite aluminum hypophosphite powder, 4 parts synergistic flame retardant, 1.0 part silver-loaded mesoporous silica, 3 parts 1,4-butanediol, and 0.1 parts organic bismuth catalyst. The synergistic flame retardant is a blend of melamine polyphosphate and amino POSS in a mass ratio of 3:1. The polyether polyol is polypropylene triol with a functionality of 3 and a molecular weight of 4000.

[0061] The preparation method in this embodiment is the same as that in Example 3.

[0062] Example 5: A high-efficiency flame-retardant and antibacterial polyurethane synthetic leather and its preparation method.

[0063] The polyurethane synthetic leather comprises a base fabric layer and a polyurethane functional layer covering the surface of the base fabric layer. By weight, the polyurethane functional layer comprises: 90 parts polyether polyol, 38 parts 4,4'-diphenylmethane diisocyanate, 8 parts organic-inorganic composite aluminum hypophosphite powder, 4 parts synergistic flame retardant, 1.0 part silver-loaded mesoporous silica, 3 parts 1,4-butanediol, and 0.1 parts organic bismuth catalyst. The synergistic flame retardant is a blend of melamine polyphosphate and amino POSS in a mass ratio of 3:1. The polyether polyol is polypropylene triol with a functionality of 3 and a molecular weight of 4000.

[0064] The preparation method in this embodiment is the same as that in Example 3.

[0065] Comparative Example 1: This comparative example provides a comparative high-efficiency flame-retardant and antibacterial polyurethane synthetic leather D1, which is the same as the high-efficiency flame-retardant and antibacterial polyurethane synthetic leather and its preparation method in Example 5, except that no antibacterial agent is added.

[0066] Comparative Example 2: This comparative example provides a comparative high-efficiency flame-retardant and antibacterial polyurethane synthetic leather D1, which is the same as the high-efficiency flame-retardant and antibacterial polyurethane synthetic leather and its preparation method in Example 5, except that an equal amount of ordinary aluminum hypophosphite is used to replace the composite flame retardant.

[0067] Comparative Example 3: This comparative example provides a comparative high-efficiency flame-retardant and antibacterial polyurethane synthetic leather D1, which is the same as the high-efficiency flame-retardant and antibacterial polyurethane synthetic leather and its preparation method in Example 5, except that: no synergistic flame retardant is added, and the amount of composite flame retardant is increased to 12 parts.

[0068] The high-efficiency flame-retardant and antibacterial polyurethane synthetic leathers #1-#5 of Examples 1-5 and the comparative high-efficiency flame-retardant and antibacterial polyurethane synthetic leathers D1-D3 of Comparative Examples 1-3 were tested in terms of LOI (GB / T2406.2-2009), flame retardancy (ANSI / UL94-2013), tensile strength (GB / T1040.5-2008), elongation at break (GB / T1040.5-2008), peel strength (GB / T2791-1995), and antibacterial rate (GB / T31402-2015). The test results are shown in Table 1.

[0069] Table 1 As can be seen from the test data obtained in Examples 1-3 in Table 1, especially the test data of Example 3, the polyurethane synthetic leather prepared by the present invention exhibits excellent comprehensive performance.

[0070] Compared to Example 3, Example 4 uses polypropylene triol with a functionality of 3 and a molecular weight of 4000 as the polyether polyol, resulting in highly efficient flame-retardant and antibacterial polyurethane synthetic leather #4 with superior properties. This is because using a polyether polyol with a functionality of 3 allows for the formation of a three-dimensional cross-linked network structure, giving the synthetic leather good mechanical strength and resilience. A molecular weight of 3000-5000 ensures sufficiently long molecular chains, resulting in a soft synthetic leather.

[0071] Compared to Example 4, Example 5 uses 4,4'-diphenylmethane diisocyanate as the diisocyanate, resulting in highly efficient flame-retardant and antibacterial polyurethane synthetic leather #5 with superior properties. This is because 4,4'-diphenylmethane diisocyanate contains rigid benzene rings, which, after reacting with polyols, can form regular hard segments in the polyurethane molecular chain. This imparts higher tensile strength, tear strength, hardness, abrasion resistance, and creep resistance to the synthetic leather. 4,4'-diphenylmethane diisocyanate has a highly symmetrical molecular structure. This symmetry allows the hard segments in the polyurethane chain to arrange and stack more orderly, forming a more complete microphase separation structure.

[0072] Compared to Example 5, Comparative Example 1, which did not contain any antibacterial agent, showed significantly lower performance in all aspects compared to the high-efficiency flame-retardant and antibacterial polyurethane synthetic leather D1 obtained from Example 5. This is because silver-loaded mesoporous silica endows the synthetic leather with strong and long-lasting broad-spectrum antibacterial capabilities, meeting the hygiene requirements of specific application areas.

[0073] Compared to Example 5, Comparative Example 2, which used an equal amount of ordinary aluminum hypophosphite to replace the composite flame retardant, showed significantly lower performance in all aspects of the comparative high-efficiency flame-retardant and antibacterial polyurethane synthetic leather D2 compared to Example 5's high-efficiency flame-retardant and antibacterial polyurethane synthetic leather #5. This is because the composite flame retardant prepared in this invention has a significantly better flame-retardant effect than ordinary aluminum hypophosphite. The organic groups introduced on its surface and the KH-550 modification improve its compatibility with the polyurethane matrix, resulting in more uniform dispersion and thus a more efficient flame-retardant effect. The LOI value is higher than 30%, and the vertical burning reaches V-0 level, indicating the good dispersibility of the organic-inorganic composite aluminum hypophosphite and the synergistic effect of the phosphorus-nitrogen-silicon ternary synergistic system.

[0074] Compared to Example 5, Comparative Example 3, without the addition of a synergistic flame retardant and with the amount of composite flame retardant increased to 12 parts, showed significantly lower performance of the comparative high-efficiency flame-retardant and antibacterial polyurethane synthetic leather D3 compared to Example 5's high-efficiency flame-retardant and antibacterial polyurethane synthetic leather #5. This is because melamine polyphosphate decomposes at high temperatures to generate strong dehydrating acids such as polyphosphoric acid, catalyzing the dehydration of the polyurethane polymer matrix into carbon, forming the framework of the expanded carbon layer. Simultaneously, the melamine structure decomposes upon heating, releasing non-combustible gases such as nitrogen and ammonia, causing the molten carbon layer to expand and form a loose, porous insulation layer. It can also act as a foaming agent, providing gas for the expansion process. Amino POSS is an organic-inorganic hybrid nanomaterial with a cage-like siloxane core structure; its surface amino groups (-NH2) can interact with the polyurethane matrix or melamine polyphosphate. During combustion, the inorganic portion (SiO2) of POSS migrates to the surface of the char layer, forming a robust siliceous protective layer. This significantly enhances the density, continuity, and mechanical strength of the char layer, making it less prone to cracking under high temperatures and flame erosion. The amino groups on the surface act as weak crosslinking points, improving the initial thermal stability of the polyurethane matrix. POSS itself also promotes the formation of a more stable char layer. The reinforced char layer effectively encapsulates the polymer, preventing combustion droplets generated during melting, thus greatly contributing to achieving the UL94V-0 rating. When blended, the two form an organic-inorganic hybrid char layer. This char layer not only possesses thickness and an expanded structure but also exhibits high strength, density, and thermal stability. It effectively isolates oxygen and external heat from the substrate, inhibits the overflow of internal combustible degradation products, and prevents droplets generated during material melting.

[0075] The above are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A high efficiency flame retardant antibacterial polyurethane synthetic leather and a preparation method thereof, characterized in that, The polyurethane synthetic leather comprises a base cloth layer and a polyurethane functional layer covering the surface of the base cloth layer; the polyurethane functional layer comprises, in terms of weight fractions, 80-95 parts of polyether polyol, 30-45 parts of diisocyanate, 5-10 parts of composite flame retardant, 3-6 parts of synergistic flame retardant, 0.5-1.5 parts of antibacterial agent, 2-4 parts of chain extender, and 0.05-0.2 parts of catalyst; the antibacterial agent is any one of silver-loaded mesoporous silica, zinc-loaded silica, and zinc-loaded zeolite; the chain extender is any one of 1,4-butanediol, ethylene glycol, and neopentyl glycol; the catalyst is any one of organic bismuth catalyst, dibutyltin dilaurate, and organic zinc catalyst; and the polyether polyol is any one of polyether polyols with a functionality of 2-4 and a molecular weight of 2000-6000.

2. The high-efficiency flame-retardant antibacterial polyurethane synthetic leather according to claim 1, characterized in that, The polyether polyol is a polyoxypropylene triol with a functionality of 3 and a molecular weight of 3000-5000.

3. The high-efficiency flame-retardant antibacterial polyurethane synthetic leather according to claim 1, characterized in that, The diisocyanate is 4,4'-diphenylmethane diisocyanate.

4. The high-efficiency flame-retardant antibacterial polyurethane synthetic leather according to claim 1, characterized in that, The synergistic flame retardant is a blend of melamine polyphosphate and amino POSS at a mass ratio of 2-5:

1.

5. The high-efficiency flame-retardant antibacterial polyurethane synthetic leather according to claim 4, characterized in that, The preparation method of the synergistic flame retardant is as follows: the amino POSS is first dispersed in a proper amount of anhydrous ethanol, and ultrasonic treatment is performed for 10-20 min to obtain a suspension; then the suspension is mixed with melamine polyphosphate powder at a mass ratio, and high-speed stirring is performed at a speed of 500-700 rpm for 20-40 min to form a slurry; the solvent is removed by vacuum drying to obtain the blend.

6. The preparation method of the high-efficiency flame-retardant antibacterial polyurethane synthetic leather according to claim 1, characterized in that, The composite flame retardant is an organic-inorganic composite aluminum hypophosphite powder.

7. The preparation method of the high-efficiency flame-retardant antibacterial polyurethane synthetic leather according to claim 6, characterized in that, The preparation method of the organic-inorganic composite aluminum hypophosphite powder is as follows: aluminum sulfate is dissolved in deionized water, stirred until clear at 75-85℃, then slowly add sodium hypophosphite solution, the Al 3+ :H2PO 2− Molar ratio is 1:0.8-1.2, under the power of 250-350W microwave assisted reaction 1-2h, get inorganic aluminum hypophosphite crystal nucleus suspension; keep constant temperature, while adding dropwise diethyl hypophosphite ethanol solution and KH-550 silane coupling agent ethanol solution, the diethyl hypophosphite and Al 3+ Molar ratio is 0.6-0.9:1, KH-550 silane coupling agent dosage is 3-5% of the mass of aluminum sulfate, adjust pH to 4.5-5.5 with acetic acid, constant temperature reaction 2-3h, after the reaction is finished, centrifugal, washing, drying to constant weight, get organic-inorganic composite aluminum hypophosphite powder.

8. A method for preparing the high-efficiency flame-retardant antibacterial polyurethane synthetic leather according to any one of claims 1-7, characterized in that, The preparation method comprises the following steps: (1) polyether polyol, composite flame retardant, synergistic flame retardant, and antibacterial agent are added to a reaction kettle, high-speed stirring and dispersion are performed at 600-700 r / min for 25-35 min, then chain extender and catalyst are added, dehydration is performed at a temperature of 55-75 ℃ under vacuum for 1-2 h; (2) cooling is performed to 35-45 ℃, diisocyanate is added under nitrogen protection, and then temperature is increased to 60-80 ℃ for reaction, NCO characteristic peak intensity is monitored by online FTIR until the content reaches more than 99% of the theoretical calculation value, to obtain flame-retardant and antibacterial polyurethane slurry; (3) the flame-retardant and antibacterial polyurethane slurry is coated on the surface of the base cloth by roll coating, is sent into an oven, is cured at 105-110 ℃ for 8-12 min, and is aged at 130-140 ℃ for 2-4 h, and after embossing and surface treatment, the high-efficiency flame-retardant and antibacterial polyurethane synthetic leather is obtained.

9. The use of the high-efficiency flame-retardant antibacterial polyurethane synthetic leather in the medical industry, food packaging industry, baby product industry, characterized in that, The high-efficiency flame-retardant and antibacterial polyurethane synthetic leather is prepared by using the high-efficiency flame-retardant and antibacterial polyurethane synthetic leather or the preparation method of the high-efficiency flame-retardant and antibacterial polyurethane synthetic leather according to any one of claims 1-7.

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