Preparation process of waterproof breathable synthetic leather
By reacting catechin compounds with isocyanates to form a covalent cross-linked network, the shortcomings of waterproof and breathable synthetic leather in terms of environmental pollution, antibacterial properties, and mechanical properties are solved, achieving high waterproofness, high breathability, strong antibacterial properties, and ultra-durability, thus improving the overall performance of synthetic leather.
Patent Information
- Application Number
- CN202511050518.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-29
- Publication Date
- 2025-11-14
AI Technical Summary
Existing waterproof and breathable synthetic leather has problems such as high solvent emissions, large solvent residues, environmental pollution, health hazards, poor antibacterial properties, unsatisfactory thermal stability, and insufficient mechanical properties during the production process. Moreover, existing modification methods are prone to leakage of functional substances or degradation of material properties.
The reaction of catechin compounds with isocyanates generates carbamate bonds, which are then combined with the oxidative coupling of unoxidized catechol to form a covalent cross-linked network. Hydrophobic groups and hydrophilic channels are introduced to construct a stable three-dimensional network structure, and the grafted antibacterial agent forms a dual antibacterial mechanism.
It achieves a synergistic effect of high waterproofness, high breathability, strong antibacterial properties and ultra-durability, reduces VOC emissions, improves the environmental friendliness and mechanical properties of the material, and maintains the continuity of antibacterial efficacy.
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Figure SMS_1
Abstract
Description
Technical Field
[0001] This invention belongs to the field of waterproof and breathable synthetic leather technology, and in particular, a preparation process for waterproof and breathable synthetic leather. Background Technology
[0002] Polyurethane synthetic leather, as an important alternative to natural leather, is widely used in clothing, footwear, and bags. Traditional solvent-based polyurethane synthetic leather relies on organic solvents such as DMF and toluene. Its production process suffers from high emissions of volatile organic compounds and large amounts of solvent residues, which not only endanger the health of operators but also cause serious environmental pollution. Waterborne polyurethane uses water as the dispersion medium and can be divided into three types according to particle size: water-emulsified, water-dispersible, and water-soluble. It contains little or no organic solvents, is non-flammable, non-toxic, does not pollute the environment, is easy to transport and store, and is convenient to use. It also has the inherent high strength and wear resistance of polyurethane. However, waterborne polyurethane is susceptible to bacterial invasion, especially mold, in the surrounding environment, and has poor antibacterial and anti-mold properties. Furthermore, the thermal stability of waterborne polyurethane with its single linear structure is not ideal.
[0003] Existing technologies for modifying polyurethane mainly focus on monomer functionalization. For example, while adding organosilicon can improve hydrophobicity, phase separation easily occurs when the addition exceeds 3%, resulting in a decrease in interlayer bonding strength. Although bio-based polyurethane aligns with sustainable development trends, the seasonal fluctuations in the supply of its raw materials lead to unstable costs, hindering industrial-scale promotion. Furthermore, existing functional modifications of waterproof and breathable synthetic leather often employ physical blending methods, such as adding silver-loaded activated carbon to achieve antibacterial properties. However, such non-covalent bonding methods easily lead to leakage of functional substances, and while adding breathability additives can improve moisture permeability, it significantly reduces the mechanical properties of the material.
[0004] In view of the above problems, this invention proposes a preparation process for waterproof and breathable synthetic leather. By modifying waterborne polyurethane with catechins, a stable carbamate bond is constructed by the directional reaction of the B-ring catechol structure of catechin compounds with isocyanate. The A-ring phenolic hydroxyl group is selectively chemically modified to introduce hydrophobic groups or hydrophilic channels while retaining antioxidant activity. A covalent cross-linking network is formed through the oxidative coupling of unoxidized catechol. Combined with functional group grafting technology, a balance between environmental protection, mechanical properties and functional durability is achieved simultaneously. Summary of the Invention
[0005] The purpose of this invention is to address the aforementioned problems in existing technologies by proposing a manufacturing process for waterproof and breathable synthetic leather.
[0006] The objective of this invention can be achieved through the following technical solutions:
[0007] A process for preparing waterproof and breathable synthetic leather includes the following steps:
[0008] S1: The prepolymer solution containing catechin compounds is reacted with isocyanate through the B-ring catechol structure to generate urethane bonds;
[0009] The preparation of the prepolymer solution includes the following steps:
[0010] S11: Raw material mixing: Diisocyanate, catechin compounds and tannic acid are added to an acetone solution containing a crosslinking agent in a mass ratio of (10-20):(5-15):(1-5);
[0011] S12: Prepolymerization reaction: Under nitrogen protection, the mixture is heated to 70-85℃ and stirred at 300-500 rpm for 2-4 hours to form a prepolymer solution;
[0012] S13: Chain extension and neutralization: Add dimethylolpropionic acid (DMPA) and a chain extender, continue the reaction for 1-2 hours, then add a catalyst and react for 30-60 minutes.
[0013] The chain extender is a mixture of 1,4-butanediol (BDO) and diethylene glycol (DEG) in a mass ratio of BDO:DEG = (1-2):1, and the catalyst is dibutyltin dilaurate (DBTDL), which is added at 0.15%-0.25% of the mass of the prepolymer solution.
[0014] S14: Dilution and discharge: Cool the reaction solution to 40-50℃, add deionized water to dilute, adjust the solid content to 25%-35%, and filter to obtain the modified polyurethane prepolymer solution.
[0015] S2: The phenolic hydroxyl group of catechin A ring remaining after step S1 modification is chemically modified by at least one of acylation, methylation or grafting hydrophilic polymer.
[0016] S3: Covalent cross-linking bonds are formed by oxidative coupling reaction using the incompletely oxidized catechol structure;
[0017] S4: Functional groups selected from antibacterial agents or hydrophilic polymers are grafted onto urethane groups;
[0018] S5: Apply the modified prepolymer solution to the surface of the pretreated base fabric and dry and cure it to form a synthetic leather layer.
[0019] Preferably, the raw materials, by weight, include: 80-100 parts of waterborne polyurethane resin, 5-15 parts of catechin compounds, 10-20 parts of isocyanate, 0.5-1.5 parts of crosslinking agent, 0.5-1 part of breathability aid, 2-5 parts of hydrophilic modifier, and 1-3 parts of antibacterial agent;
[0020] Among them, the crosslinking agent is aziridine crosslinking agent or glutaraldehyde solution, the air permeability aid is modified ether siloxane nonionic surfactant or decamethylcyclopentasiloxane, the hydrophilic modifier is lauroyl chloride or polyethylene glycol, and the antibacterial agent is silver-loaded biomass activated carbon or hepatophospholipid.
[0021] Preferably, the specific method for chemical modification in step S2 includes:
[0022] S21: Acylation: Under alkaline conditions, the hydroxyl group of ring A is reacted with lauroyl chloride or palmitoyl chloride to introduce a hydrophobic group;
[0023] S22: Methylation: The phenolic hydroxyl group is converted to a methoxy group using methyl iodide or dimethyl sulfate;
[0024] S23: Grafted hydrophilic polymer: Polyethylene glycol or monosaccharides are grafted onto residual phenolic hydroxyl groups to form water vapor transport channels.
[0025] Preferably, the diisocyanate is one of hexamethylene diisocyanate (HDI) or isophorone diisocyanate (IPDI).
[0026] Preferably, the mass of the acetone solution is 1.5-3 times the mass of the diisocyanate, and the mass concentration of the crosslinking agent in the acetone solution is 3%-4%.
[0027] Preferably, in the dilution step, the deionized water is added at a rate of 5-10 mL / min, and the pH of the diluted solution is adjusted to 6.5-7.5.
[0028] Preferably, the conditions for the oxidative coupling reaction in step S3 are: under the catalysis of an oxidant or an enzyme, catechol is oxidized to catechol quinone, forming a covalent cross-link;
[0029] The oxidant is sodium periodate or hydrogen peroxide, and the enzyme is horseradish peroxidase.
[0030] Preferably, the pretreatment of the base fabric includes: immersing the base fabric in a formic acid solution, then washing it in an aqueous acetic acid solution, and drying it before use.
[0031] Preferably, in step S5, the coating thickness is 0.1-0.5 mm, the drying temperature is 80-120℃, and the drying time is 10-30 min.
[0032] Compared with existing technologies, the medium-frequency heat treatment process for this support roller has the following advantages:
[0033] 1. The present invention provides a preparation process for waterproof and breathable synthetic leather. Through the specific reaction between the B-ring catechol structure of catechin compounds and isocyanates, natural antibacterial components are introduced into the molecular chain. At the same time, the oxidative coupling crosslinking of incompletely oxidized catechol forms a three-dimensional network structure. Combined with the water vapor transport channels constructed by grafted hydrophilic polymers, the waterproof and breathable effect of traditional synthetic leather is improved, thereby achieving a synergistic effect of improving the high waterproof, high breathable, strong antibacterial and ultra-durable properties of synthetic leather.
[0034] 2. The present invention provides a process for preparing waterproof and breathable synthetic leather. By using an aqueous polyurethane system and acetone dilution process, the VOC emissions are reduced compared to solvent-based processes. Combined with bio-based raw material tannic acid and enzyme-catalyzed oxidation technology, the entire production process is made low-carbon.
[0035] 3. The present invention provides a preparation process for waterproof and breathable synthetic leather, which constructs a dual antibacterial mechanism by chemically modifying the phenolic hydroxyl group of catechin A ring and grafting it with silver-loaded biomass activated carbon: contact sterilization and photocatalytic sterilization, and maintains high antibacterial efficacy against Staphylococcus aureus and Escherichia coli. Detailed Implementation
[0036] The following are specific embodiments of the present invention, which further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.
[0037] Example 1:
[0038] A process for preparing waterproof and breathable synthetic leather, wherein the raw materials include, by weight, the following:
[0039] The mixture contains 90 parts of waterborne polyurethane resin of type IPDI, 10 parts of catechin compound EGCG, 15 parts of hexamethylene diisocyanate (HDI), 1 part of aziridine crosslinking agent, 0.8 parts of breathability aid (modified ether siloxane), 3 parts of hydrophilic modifier (lauroyl chloride), and 2 parts of antibacterial agent.
[0040] The preparation process includes the following steps:
[0041] S1: Preparation of prepolymer solution:
[0042] S11: Add HDI, catechin, and tannic acid to an acetone solution containing a aziridine crosslinking agent. The concentration of the crosslinking agent in the acetone is 3%. Mix 90 parts of waterborne polyurethane resin with HDI under nitrogen protection. Catechin and tannic acid are pre-ground to 200 mesh to ensure uniform dispersion. The aziridine crosslinking agent is dissolved in 30 parts of acetone. Filter through a 0.45μm membrane to remove impurities.
[0043] S12: Under nitrogen protection, the 5L glass-jacketed reactor is heated to 75℃, the stirring paddle speed is 400rpm, and nitrogen gas is continuously introduced at a flow rate of 0.5L / min. After reacting for 3 hours, the viscosity of the prepolymer is measured by an NDJ-1 type rotational viscometer, with a target value of 2000-3000mPa·s, thus forming a prepolymer solution.
[0044] S13: Add DMPA (2.5 parts) and a chain extender (total mass 4 parts) with BDO:DEG = 1.5:1. DMPA and BDO:DEG are added in three parts, with an interval of 30 minutes between each addition. 0.2% of the prepolymer mass of DBTDL catalyst is added dropwise at 40°C. After reacting for 40 minutes, the amount of urethane bond formation is monitored by FTIR.
[0045] S14: After cooling to 45℃, add deionized water at a rate of 8mL / min, while using an electric stirrer at 200rpm to assist dispersion. Adjust the solid content to 30%, and determine the solid content by gravimetric method. Adjust the pH value to 7.0±0.2 using a precision pH meter. Filter and set aside.
[0046] S15: The prepolymer solution containing catechin compounds is reacted with isocyanate through the B-ring catechol structure to generate a carbamate bond;
[0047] S2: A-ring phenolic hydroxyl modification: lauroyl chloride (3.0 parts) reacts with the residual phenolic hydroxyl groups in the prepolymer under alkaline conditions of pH=9.0 to introduce hydrophobic groups.
[0048] S3: Oxidative coupling crosslinking: Add sodium periodate (0.5 parts), react at 40°C for 1 hour, and catechol is oxidized to catechol quinone, forming covalent crosslinking bonds.
[0049] S4: Functional grafting: Add silver-loaded biomass activated carbon (2.0 parts) and graft it with urethane groups to form an antibacterial network.
[0050] S5: Coating and Curing: Coat to a thickness of 0.3 mm, dry at 100℃ for 20 minutes to form a synthetic leather layer.
[0051] Example 2:
[0052] A process for preparing waterproof and breathable synthetic leather, wherein the raw materials include, by weight, the following:
[0053] The mixture contains 90 parts of waterborne polyurethane resin IPDI type, 10 parts of catechin compound EGCG, 15 parts of isophorone diisocyanate (IPDI), 1 part of aziridine crosslinking agent, 0.8 parts of breathability aid (modified ether siloxane), 3 parts of hydrophilic modifier (lauroyl chloride), and 2 parts of antibacterial agent.
[0054] The preparation process includes the following steps:
[0055] S1: Preparation of prepolymer solution:
[0056] S11: Add isophorone diisocyanate (IPDI) (15 parts), catechin (10 parts), and tannic acid (3 parts) to an acetone solution (30 parts) containing a aziridine crosslinking agent (1.0 part), with the crosslinking agent concentration in the acetone being 3%.
[0057] S12: Under nitrogen protection, the mixture is stirred at 75°C (400 rpm) for 3 hours to form a prepolymer solution.
[0058] S13: Add DMPA (2.5 parts) and chain extender (4 parts by total mass) with BDO:DEG = 1.5:1, and continue the reaction for 1.5 hours; add 0.2% of the prepolymer mass of DBTDL catalyst and react for 40 minutes.
[0059] S14: Cool to 45℃, add deionized water at a rate of 8mL / min, adjust the solid content to 30%, pH=7.0, filter and set aside.
[0060] S15: A prepolymer solution containing catechin compounds is reacted with isocyanate via a B-ring catechol structure to generate a carbamate bond.
[0061] S2: A-ring phenolic hydroxyl modification: Under alkaline conditions of pH=9.0, lauroyl chloride (3.0 parts) was added, and the reaction was carried out at 60℃ for 2 hours to introduce hydrophobic groups.
[0062] S3: Oxidative coupling crosslinking: Add sodium periodate (0.5 parts), react at 40°C for 1 hour, and catechol is oxidized to catechol quinone, forming covalent crosslinking bonds.
[0063] S4: Functional grafting: Add silver-loaded biomass activated carbon (2.0 parts) and graft it with urethane groups to form an antibacterial network.
[0064] S5: Coating and Curing: Coat to a thickness of 0.3 mm, dry at 100℃ for 20 minutes to form a synthetic leather layer.
[0065] Example 3:
[0066] A process for preparing waterproof and breathable synthetic leather, wherein the raw materials include, by weight, the following:
[0067] The mixture contains 90 parts of waterborne polyurethane resin of type IPDI, 10 parts of catechin compound EGCG, 15 parts of hexamethylene diisocyanate (HDI), 1 part of aziridine crosslinking agent, 0.8 parts of breathability aid (modified ether siloxane), 3 parts of hydrophilic modifier (lauroyl chloride), and 2 parts of antibacterial agent.
[0068] The preparation process includes the following steps:
[0069] S1: Preparation of prepolymer solution:
[0070] S11: Add HDI (15 parts), catechin (10 parts), and tannic acid (3 parts) to an acetone solution (30 parts) containing a aziridine crosslinking agent (1.0 part), with the crosslinking agent concentration in the acetone being 3%.
[0071] S12: Under nitrogen protection, the mixture is stirred at 75°C (400 rpm) for 3 hours to form a prepolymer solution.
[0072] S13: Add DMPA (2.5 parts) and chain extender (4 parts by total mass) with BDO:DEG = 1.5:1, and continue the reaction for 1.5 hours; add 0.2% of the prepolymer mass of DBTDL catalyst and react for 40 minutes.
[0073] S14: Cool to 45℃, add deionized water at a rate of 8mL / min, adjust the solid content to 30%, pH=7.0, filter and set aside.
[0074] S15: A prepolymer solution containing catechin compounds is reacted with isocyanate via a B-ring catechol structure to generate a carbamate bond.
[0075] S2: Grafted hydrophilic polymer: Polyethylene glycol is grafted onto the residual A-ring phenolic hydroxyl group, with an amount of 4.0 parts, and the reaction is carried out at 60°C for 3 hours.
[0076] S3: Oxidative coupling crosslinking: Add sodium periodate (0.5 parts), react at 40°C for 1 hour, and catechol is oxidized to catechol quinone, forming covalent crosslinking bonds.
[0077] S4: Functional grafting: Add silver-loaded biomass activated carbon (2.0 parts) and graft it with urethane groups to form an antibacterial network.
[0078] S5: Coating and Curing: Coat to a thickness of 0.3 mm, dry at 100℃ for 20 minutes to form a synthetic leather layer.
[0079] Example 4:
[0080] A process for preparing waterproof and breathable synthetic leather, wherein the raw materials include, by weight, the following:
[0081] The mixture contains 90 parts of waterborne polyurethane resin of type IPDI, 10 parts of catechin compound EGCG, 15 parts of hexamethylene diisocyanate (HDI), 1 part of aziridine crosslinking agent, 0.8 parts of breathability aid (modified ether siloxane), 3 parts of hydrophilic modifier (lauroyl chloride), and 2 parts of antibacterial agent.
[0082] The preparation process includes the following steps:
[0083] S1: Preparation of prepolymer solution:
[0084] S11: Add HDI (15 parts), catechin (10 parts), and tannic acid (3 parts) to an acetone solution (30 parts) containing a aziridine crosslinking agent (1.0 part), with the crosslinking agent concentration in the acetone being 3%.
[0085] S12: Under nitrogen protection, the mixture is stirred at 75°C (400 rpm) for 3 hours to form a prepolymer solution.
[0086] S13: Add DMPA (2.5 parts) and chain extender (4 parts by total mass) with BDO:DEG = 1.5:1, and continue the reaction for 1.5 hours; add 0.2% of the prepolymer mass of DBTDL catalyst and react for 40 minutes.
[0087] S14: Cool to 45℃, add deionized water at a rate of 8mL / min, adjust the solid content to 30%, pH=7.0, filter and set aside.
[0088] S15: A prepolymer solution containing catechin compounds is reacted with isocyanate via a B-ring catechol structure to generate a carbamate bond.
[0089] S2: A-ring phenolic hydroxyl modification: Under alkaline conditions of pH=9.0, lauroyl chloride (3.0 parts) was added, and the reaction was carried out at 60℃ for 2 hours to introduce hydrophobic groups.
[0090] S3: Horseradish peroxidase catalysis: enzyme dosage 0.2 parts, H2O2 (0.5 parts), pH=6.0, reaction at 30℃ for 2 hours.
[0091] S4: Functional grafting: Add silver-loaded biomass activated carbon (2.0 parts) and graft it with urethane groups to form an antibacterial network.
[0092] S5: Coating and Curing: Coat to a thickness of 0.3 mm, dry at 100℃ for 20 minutes to form a synthetic leather layer.
[0093] Comparative Example 1:
[0094] A process for preparing waterproof and breathable synthetic leather, wherein the raw materials include, by weight parts:
[0095] The mixture contains 90 parts of waterborne polyurethane resin of type IPDI, 10 parts of catechin compound EGCG, 15 parts of hexamethylene diisocyanate (HDI), 1 part of aziridine crosslinking agent, 0.8 parts of breathability aid (modified ether siloxane), 3 parts of hydrophilic modifier (lauroyl chloride), and 2 parts of antibacterial agent.
[0096] The preparation process includes the following steps:
[0097] S1: Preparation of prepolymer solution:
[0098] S11: Add HDI (15 parts), catechin (10 parts), and tannic acid (3 parts) to an acetone solution (30 parts) containing a aziridine crosslinking agent (1.0 part), with the crosslinking agent concentration in the acetone being 3%.
[0099] S12: Under nitrogen protection, the mixture is stirred at 75°C (400 rpm) for 3 hours to form a prepolymer solution.
[0100] S13: Add DMPA (2.5 parts) and chain extender (4 parts by total mass) with BDO:DEG = 1.5:1, and continue the reaction for 1.5 hours; add 0.2% of the prepolymer mass of DBTDL catalyst and react for 40 minutes.
[0101] S14: Cool to 45℃, add deionized water at a rate of 8mL / min, adjust the solid content to 30%, pH=7.0, filter and set aside.
[0102] S15: A prepolymer solution containing catechin compounds is reacted with isocyanate via a B-ring catechol structure to generate a carbamate bond.
[0103] S2: A-ring phenolic hydroxyl modification: Under alkaline conditions of pH=9.0, lauroyl chloride (3.0 parts) was added, and the reaction was carried out at 60℃ for 2 hours to introduce hydrophobic groups.
[0104] S4: Functional grafting: Add silver-loaded biomass activated carbon (2.0 parts) and graft it with urethane groups to form an antibacterial network.
[0105] S5: Coating and Curing: Coat to a thickness of 0.3 mm, dry at 100℃ for 20 minutes to form a synthetic leather layer.
[0106] Comparative Example 2:
[0107] A process for preparing waterproof and breathable synthetic leather, wherein the raw materials include, by weight parts:
[0108] The mixture contains 90 parts of waterborne polyurethane resin of type IPDI, 10 parts of catechin compound EGCG, 15 parts of hexamethylene diisocyanate (HDI), 1 part of aziridine crosslinking agent, 0.8 parts of breathability aid (modified ether siloxane), 3 parts of hydrophilic modifier (lauroyl chloride), and 2 parts of antibacterial agent.
[0109] The preparation process includes the following steps:
[0110] S1: Preparation of prepolymer solution:
[0111] S11: Add HDI (15 parts), catechin (20 parts), and tannic acid (3 parts) to an acetone solution (30 parts) containing a aziridine crosslinking agent (1.0 part), with the crosslinking agent concentration in the acetone being 3%.
[0112] S12: Under nitrogen protection, the mixture is stirred at 75°C (400 rpm) for 3 hours to form a prepolymer solution.
[0113] S13: Add DMPA (2.5 parts) and chain extender (4 parts by total mass) with BDO:DEG = 1.5:1, and continue the reaction for 1.5 hours; add 0.2% of the prepolymer mass of DBTDL catalyst and react for 40 minutes.
[0114] S14: Cool to 45℃, add deionized water at a rate of 8mL / min, adjust the solid content to 30%, pH=7.0, filter and set aside.
[0115] S15: A prepolymer solution containing catechin compounds is reacted with isocyanate via a B-ring catechol structure to generate a carbamate bond.
[0116] S2: A-ring phenolic hydroxyl modification: Under alkaline conditions of pH=9.0, lauroyl chloride (3.0 parts) was added, and the reaction was carried out at 60℃ for 2 hours to introduce hydrophobic groups.
[0117] S3: Oxidative coupling crosslinking: Add sodium periodate (0.5 parts), react at 40°C for 1 hour, and catechol is oxidized to catechol quinone, forming covalent crosslinking bonds.
[0118] S4: Functional grafting: Add silver-loaded biomass activated carbon (2.0 parts) and graft it with urethane groups to form an antibacterial network.
[0119] S5: Coating and Curing: Coat to a thickness of 0.3 mm, dry at 100℃ for 20 minutes to form a synthetic leather layer.
[0120] Table 1. Statistics of performance test results for different leather layers in the examples and comparative examples.
[0121]
[0122] Measurement method:
[0123] (1) Water vapor transmission rate (WVTR): Refer to GB / T 12704-2009: Textiles - Test methods for moisture permeability of fabrics - Part 1: Repeated linear compression method (permeability meter method)
[0124] (2) Hydrostatic pressure: Refer to GB / T 22890.1-2024 "Determination of water resistance of soft leather - Part 1";
[0125] (3) Tensile strength and elongation at break: Refer to GB / T 38612-2020 "Test Methods for Artificial Leather and Synthetic Leather: Determination of Tensile Load and Elongation at Break";
[0126] (4) Antibacterial rate: Refer to GB / T 43722.1—2024 "Determination of antibacterial properties of leather - Part 1: Membrane contact method";
[0127] (5) Contact angle: The static water absorption method was used for testing, referring to the domestic standard GB / T 4621-2008.
[0128] (6) Efficiency of breathable additives: Refer to QB / T 2799-2006 "Test Method for Breathability of Leather".
[0129] Conclusions: Table 1 shows that Example 1, through oxidative crosslinking in step S3, forms a uniform network with balanced overall performance, achieving above-average levels in breathability and waterproofing within the industry. Example 2, by replacing HDI with IPDI, increases the hydrostatic pressure to 14.0 MPa and tensile strength to 31.0 MPa due to the ring structure of IPDI, but slightly reduces breathability, indicating its suitability for high waterproofing requirements, although the loss of breathability needs to be balanced. Example 3, by constructing hydrophilic channels and grafting polyethylene glycol, shows an increase in WVTR and a decrease in contact angle, forming efficient water vapor transport channels, but the hydrostatic pressure decreases, requiring adjustment of crosslinking density to improve waterproofing. Example 4, through enzyme-catalyzed crosslinking, horseradish peroxidase catalysis increases crosslinking density and hydrostatic pressure, and low-temperature processing reduces energy consumption, making it suitable for processing sensitive materials. Comparative Example 1 shows that without the formation of a covalent crosslinked network, both WVTR and hydrostatic pressure decrease significantly, indicating that step S3, oxidative coupling, is a core step for performance assurance and cannot be omitted. Comparative Example 2 results show that the dosage of catechins needs to be strictly controlled, as excessive dosage can lead to the opposite effect.
[0130] In summary, this invention provides a preparation process for waterproof and breathable synthetic leather. By specifically reacting the B-ring catechol structure of catechin compounds with isocyanates, natural antibacterial components are introduced into the molecular chain. At the same time, a three-dimensional network structure is formed by the oxidative coupling crosslinking of incompletely oxidized catechol. Combined with water vapor transport channels constructed by grafted hydrophilic polymers, the waterproof and breathable effects are synergistically improved, enhancing the waterproof and breathable performance of traditional synthetic leather and improving the overall performance of synthetic leather.
[0131] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.
Claims
1. A preparation process for waterproof and breathable synthetic leather, characterized in that, Includes the following steps: S1: The prepolymer solution containing catechin compounds is reacted with isocyanate through the B-ring catechol structure to generate urethane bonds; The preparation of the prepolymer solution includes the following steps: S11: Raw material mixing: Diisocyanate, catechin compounds and tannic acid are added to an acetone solution containing a crosslinking agent in a mass ratio of (10-20):(5-15):(1-5); S12: Prepolymerization reaction: Under nitrogen protection, the mixture is heated to 70-85℃ and stirred at 300-500 rpm for 2-4 hours to form a prepolymer solution; S13: Chain extension and neutralization: Add dimethylolpropionic acid (DMPA) and a chain extender, continue the reaction for 1-2 hours, then add a catalyst and react for 30-60 minutes. The chain extender is a mixture of 1,4-butanediol (BDO) and diethylene glycol (DEG) in a mass ratio of BDO:DEG = (1-2):1, and the catalyst is dibutyltin dilaurate (DBTDL), which is added at 0.15%-0.25% of the mass of the prepolymer solution. S14: Dilution and discharge: Cool the reaction solution to 40-50℃, add deionized water to dilute, adjust the solid content to 25%-35%, and filter to obtain the modified polyurethane prepolymer solution. S2: The phenolic hydroxyl group of catechin A ring remaining after step S1 modification is chemically modified by at least one of acylation, methylation or grafting hydrophilic polymer. S3: Covalent cross-linking bonds are formed by oxidative coupling reaction using the incompletely oxidized catechol structure; S4: Functional groups selected from antibacterial agents or hydrophilic polymers are grafted onto urethane groups; S5: Apply the modified prepolymer solution to the surface of the pretreated base fabric and dry and cure it to form a synthetic leather layer.
2. The preparation process of a waterproof and breathable synthetic leather as described in claim 1, characterized in that, The raw materials, by weight, include: 80-100 parts of waterborne polyurethane resin, 5-15 parts of catechin compounds, 10-20 parts of isocyanate, 0.5-1.5 parts of crosslinking agent, 0.5-1 part of breathability aid, 2-5 parts of hydrophilic modifier, and 1-3 parts of antibacterial agent; Among them, the crosslinking agent is aziridine crosslinking agent or glutaraldehyde solution, the air permeability aid is modified ether siloxane nonionic surfactant or decamethylcyclopentasiloxane, the hydrophilic modifier is lauroyl chloride or polyethylene glycol, and the antibacterial agent is silver-loaded biomass activated carbon or hepatophospholipid.
3. The preparation process of a waterproof and breathable synthetic leather as described in claim 1 or 2, characterized in that, The specific methods for chemical modification in step S2 include: S21: Acylation: Under alkaline conditions, the hydroxyl group of ring A is reacted with lauroyl chloride or palmitoyl chloride to introduce a hydrophobic group; S22: Methylation: The phenolic hydroxyl group is converted to a methoxy group using methyl iodide or dimethyl sulfate; S23: Grafted hydrophilic polymer: Polyethylene glycol or monosaccharides are grafted onto residual phenolic hydroxyl groups to form water vapor transport channels.
4. The preparation process of a waterproof and breathable synthetic leather as described in claim 3, characterized in that, The diisocyanate is one of hexamethylene diisocyanate (HDI) or isophorone diisocyanate (IPDI).
5. The preparation process of a waterproof and breathable synthetic leather as described in claim 1, characterized in that, The mass of the acetone solution is 1.5-3 times the mass of the diisocyanate, and the mass concentration of the crosslinking agent in the acetone solution is 3%-4%.
6. The preparation process of a waterproof and breathable synthetic leather as described in claim 1, characterized in that, In the dilution step, deionized water is added at a rate of 5-10 mL / min, and the pH of the diluted solution is adjusted to 6.5-7.
5.
7. The preparation process of a waterproof and breathable synthetic leather as described in claim 1 or 6, characterized in that, The conditions for the oxidative coupling reaction in step S3 are: under the catalysis of an oxidant or an enzyme, catechol is oxidized to catechol quinone, forming a covalent cross-link; The oxidant is sodium periodate or hydrogen peroxide, and the enzyme is horseradish peroxidase.
8. The preparation process of a waterproof and breathable synthetic leather as described in claim 1, characterized in that, The pretreatment of the base fabric includes: immersing the base fabric in a formic acid solution, then washing it in an aqueous acetic acid solution, and drying it before use.
9. The preparation process of a waterproof and breathable synthetic leather as described in claim 1, characterized in that, In step S5, the coating thickness is 0.1-0.5 mm, the drying temperature is 80-120℃, and the drying time is 10-30 min.