Breathable solvent-free polyurethane synthetic leather and preparation method thereof

Abstract

The invention discloses breathable solvent-free polyurethane synthetic leather and a preparation method thereof, and relates to the technical field of automotive interiors. The fabric comprises a compact breathable layer, a foaming layer and a base cloth layer which are sequentially arranged from outside to inside, the compact breathable layer is of a gradient cell structure and used for improving breathability and wear resistance, the compact breathable layer comprises a wear-resistant functional layer on the surface layer and a breathable buffer layer arranged in the wear-resistant functional layer, the cell diameter of the wear-resistant functional layer is smaller than that of the breathable buffer layer, and the thickness of the breathable buffer layer is smaller than that of the wear-resistant functional layer. The foaming layer is used for providing elastic support; the compact breathable layer comprises the following components in parts by weight: polyurethane resin, a plant-based composite foaming agent and a hand feeling aid; the foaming layer is made of solvent-free polyurethane; the base cloth layer is a polyester non-woven fabric or a polyester needle-punched fabric; according to the invention, the gradient cell structure design, the plant-based composite foaming agent system and the precise hot-pressing composite process are synergistically innovated, so that the unification of high air permeability, high wear resistance, environmental protection property and antibacterial property of the synthetic leather is realized.

Description

Technical Field

[0001] This invention relates to the field of automotive interior technology, specifically to a breathable solvent-free polyurethane synthetic leather and its preparation method. Background Technology

[0002] With the rapid development of the automotive industry, consumers are increasingly demanding higher levels of environmental friendliness, comfort, and durability in automotive interiors. Polyurethane (PU) synthetic leather, due to its advantages such as simulated leather feel, high processing flexibility, and controllable cost, has become the mainstream material for automotive interior components such as seats, dashboards, and door panels.

[0003] However, existing polyurethane (PU) synthetic leather has poor breathability when used in car seats, resulting in a poor user experience. To improve the poor breathability of traditional PU synthetic leather, the industry generally uses CNC drilling to create holes in the leather surface. While drilling can improve the breathability and heat dissipation of the seat surface, especially in hot weather or during long periods of sitting, effectively reducing sweat and improving comfort, the perforated leather surface is prone to dust and dirt accumulation, requiring special tools for daily cleaning and resulting in high maintenance costs. In addition, drilling also damages the mechanical structure of PU synthetic leather, leading to decreased abrasion resistance and a shorter lifespan compared to genuine leather seats. In other words, breathability and abrasion resistance are mutually restrictive, affecting the application of PU synthetic leather.

[0004] Therefore, developing a method for preparing polyurethane synthetic leather that combines high breathability, high wear resistance, and environmental friendliness has become a technical challenge that the industry urgently needs to solve. Summary of the Invention

[0005] This invention, through the synergistic innovation of gradient cell structure design, plant-based composite foaming agent system and precise hot-pressing composite process, eliminates the traditional CNC punching process, achieving a unified combination of high breathability, high wear resistance, environmental friendliness and antibacterial properties in synthetic leather, meeting the usage needs of high-end fields such as new energy vehicles and medical care.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a breathable solvent-free polyurethane synthetic leather, comprising a dense breathable layer, a foam layer, and a base fabric layer arranged sequentially from the outside to the inside, wherein the dense breathable layer has a gradient cell structure to improve breathability and abrasion resistance, and includes an abrasion-resistant functional layer on the surface and a breathable buffer layer disposed within the abrasion-resistant functional layer, wherein the cell diameter of the abrasion-resistant functional layer is smaller than the cell diameter of the breathable buffer layer, and the foam layer is used to provide elastic support;

[0007] The components of the dense and breathable layer, by weight, include 95-105 parts of polyurethane resin, 3-5 parts of plant-based composite foaming agent, and 1-2 parts of hand feel additive; The foam layer is made of solvent-free polyurethane; The base fabric layer is made of polyester nonwoven fabric or polyester needle-punched fabric.

[0008] Furthermore, in the aforementioned breathable solvent-free polyurethane synthetic leather, the pore diameter of the abrasion-resistant functional layer is 5-10 μm, and the pore diameter of the breathable buffer layer is 20-30 μm.

[0009] Furthermore, in the aforementioned breathable solvent-free polyurethane synthetic leather, the thickness of the abrasion-resistant functional layer is ≥10μm, and the thickness of the breathable buffer layer is ≥30μm.

[0010] Furthermore, in the aforementioned breathable solvent-free polyurethane synthetic leather, the plant-based composite foaming agent is a compound of soybean protein foaming agent and tea saponin foaming agent in a weight ratio of 3:1.

[0011] Furthermore, in the aforementioned breathable solvent-free polyurethane synthetic leather, the hand-feel additive is a compound of an organosilicon slip agent and a polyester softener in a weight ratio of 1:2.

[0012] Furthermore, in the above-mentioned breathable solvent-free polyurethane synthetic leather, the dense breathable layer also includes a silver ion antibacterial agent, and the amount of the silver ion antibacterial agent added is 0.5%-1% of the weight of the polyurethane resin.

[0013] Another technical solution provided by this invention: a method for preparing breathable solvent-free polyurethane synthetic leather, comprising the following steps: Step 1: Calculate the raw materials according to the following ratio: 95-105 parts polyurethane resin, 3-5 parts plant-based composite foaming agent, 1-2 parts hand feel additive, and 0.5-1 parts silver ion antibacterial additive. Step 2: After mixing the above raw materials evenly, coat them onto release paper and use a step-by-step heating process to obtain a dense and breathable layer; Step 3: Coat the base fabric layer with solvent-free polyurethane prepolymer evenly, with the coating thickness controlled at 0.1-0.3 mm. Place the coated base fabric in an oven for pre-curing to obtain the foamed layer. Step 4: Remove the release paper from the dense, breathable layer and place it on the side of the foam layer away from the base fabric layer. Hot-press and cure to obtain breathable, solvent-free polyurethane synthetic leather.

[0014] Furthermore, in the above-mentioned method for preparing breathable solvent-free polyurethane synthetic leather, the step-by-step heating process in step 2 includes: Step 21: Raise the temperature to 75~85℃ and keep it warm for 2-3 minutes; Step 22: Raise the temperature to 100-105℃ and hold for 2-4 minutes; Step 23: Curing at 110°C for 5 minutes.

[0015] Furthermore, in the above-mentioned method for preparing breathable solvent-free polyurethane synthetic leather, in step 3, the temperature of the oven is set to 120-140℃, and the pre-curing time is 3-5 minutes.

[0016] Furthermore, in the above-mentioned method for preparing breathable solvent-free polyurethane synthetic leather, in step 4, the hot-pressing composite conditions are a pressure of 0.5-0.8 MPa and a temperature of 100-110°C, and the curing time is 10-15 min.

[0017] Compared with the prior art, the beneficial effects of the present invention are: 1. This breathable solvent-free polyurethane synthetic leather features an innovative design with a dense, breathable layer. The gradient cell structure of this layer achieves a breathability of ≥450L without the need for perforation, comparable to traditional perforated PU leather. Furthermore, the dense, small-diameter cells on the surface ensure that the leather can withstand 20,000 abrasion cycles without damage, surpassing the 15,000-cycle abrasion limit of traditional perforated PU synthetic leather. In addition, eliminating the CNC perforation process increases production efficiency by over 30%, reduces material waste by 15%, and lowers subsequent maintenance costs.

[0018] 2. This breathable solvent-free polyurethane synthetic leather uses a solvent-free process throughout, with VOC emissions ≤50mg / m³, far lower than the 300mg / m³ of traditional solvent-based PU synthetic leather.

[0019] 3. This breathable solvent-free polyurethane synthetic leather has dense, small-pore foam in its breathable layer, which allows it to maintain a color difference ΔE≤2 and a strength retention rate ≥90% after 500 hours of UV aging. This is far superior to traditional perforated PU synthetic leather. Moreover, the depth of stain penetration is ≤0.1mm, and no special tools are required for daily cleaning.

[0020] 4. With the addition of silver ion antibacterial additives, this breathable solvent-free polyurethane synthetic leather has an antibacterial rate of ≥99% against Escherichia coli, making it suitable for special applications such as medical chairs and children's furniture.

[0021] 5. The preparation method of this breathable solvent-free polyurethane synthetic leather requires minimal adjustments to the equipment and process compared to existing processes. The method is simple and easy to operate, with low implementation costs. It is easy to directly improve upon existing methods and has a wide range of applications. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the positional relationship of the layered structure of the present invention.

[0023] In the diagram: 1. Dense and breathable layer; 2. Foamed layer; 3. Base fabric layer. Detailed Implementation

[0024] To prepare car floor mats that can better meet the growing needs of users in more aspects, this invention designs a breathable, solvent-free polyurethane synthetic leather. (See attached document.) Figure 1 The structure comprises, from the outside in, a dense breathable layer 1, a foam layer 2, and a base fabric layer 3, arranged sequentially from the outside in. The dense breathable layer 1 has a gradient pore structure to improve breathability and abrasion resistance. It includes a surface abrasion-resistant functional layer and a breathable buffer layer within the abrasion-resistant functional layer. The abrasion-resistant functional layer has pores with a diameter of 5-10 μm, characterized by small size and dense distribution, forming an abrasion-resistant protective layer that prevents deep penetration of stains and improves the product's scratch and chemical resistance. The breathable buffer layer has pores with a diameter of 20-30 μm, characterized by large size and good connectivity, forming gas flow channels to ensure high breathability of the synthetic leather. The thickness of both the abrasion-resistant functional layer and the breathable buffer layer is greater than or equal to the diameter of their respective pores. The thickness of the dense breathable layer 1 is 0.05-0.1 mm. The abrasion-resistant functional layer and the breathable buffer layer have different pore sizes to form a gradient pore structure, which can achieve an air permeability of ≥450L without drilling, comparable to traditional perforated PU synthetic leather. The dense small-pore pores on the surface ensure that the material can withstand 20,000 abrasion cycles without damage, which is better than the 15,000 abrasion resistance limit of traditional perforated PU synthetic leather. After 500 hours of UV aging, the color difference ΔE≤2 and the strength retention rate≥90%, which is far superior to traditional perforated PU synthetic leather. Moreover, the stain penetration depth is ≤0.1mm, and daily cleaning does not require special tools. In addition, the elimination of the CNC drilling process increases production efficiency by more than 30%, reduces material waste by 15%, and reduces subsequent maintenance costs. The foam layer 2 is used to provide elastic support. The components of the dense and breathable layer 1, by weight, include 95-105 parts of polyurethane resin, 3-5 parts of plant-based composite foaming agent, and 1-2 parts of hand feel additive. The second foam layer is made of solvent-free polyurethane, with VOC emissions ≤50mg / m³, which is far lower than the 300mg / m³ of traditional solvent-based PU synthetic leather; The base fabric layer 3 is a polyester nonwoven fabric or a polyester needle-punched fabric.

[0025] In a preferred embodiment, the plant-based composite foaming agent is composed of soybean protein foaming agent and tea saponin foaming agent in a weight ratio of 3:1. Soybean protein foaming agent and tea saponin foaming agent are natural plant extracts, biodegradable, and have no VOC (volatile organic compounds) emissions, which conforms to the trend of low-carbon environmental protection and sustainable development, avoids toxic residues and environmental hazards, and meets the requirements of environmental regulations such as EU REACH. Soybean protein foaming agent provides a high foaming ratio and can quickly generate a large number of bubbles; tea saponin foaming agent has excellent foam stability and can delay the merging and collapse of cells. After the two are combined, the uniformity and stability of the cells are significantly better than those of a single foaming agent. After foaming, the cell walls have good toughness and are not easy to break, ensuring the structural integrity of the finished product.

[0026] In a preferred embodiment, the feel-enhancing agent is a compound of an organosilicon slip agent and a polyester softener in a weight ratio of 1:2 to improve the feel of the leather surface.

[0027] In a preferred embodiment, the dense breathable layer 1 further includes a silver ion antibacterial agent, wherein the amount of the silver ion antibacterial agent added is 0.5%-1% of the weight of the polyurethane resin. After adding the silver ion antibacterial agent, the antibacterial rate against Escherichia coli is ≥99%, which can be adapted to special scenarios such as medical chairs and children's furniture.

[0028] The specific preparation method of the breathable solvent-free polyurethane synthetic leather of the present invention can be referred to the following steps: Step 1: Calculate the raw materials according to the following ratio: 95-105 parts polyurethane resin, 3-5 parts plant-based composite foaming agent, 1-2 parts hand feel additive, and 0.5-1 parts silver ion antibacterial additive. Step 2: After the above raw materials are mixed evenly, they are coated onto release paper. A dense and breathable layer 1 is obtained using a step-by-step heating process. The step-by-step heating process includes: Step 21: Raise the temperature to 75~85℃ and keep it warm for 2-3 minutes; Step 22: Raise the temperature to 100-105℃ and hold for 2-4 minutes; Step 23: Curing at 110℃ for 5 minutes; By leveraging the time difference in heat conduction and the dynamic changes in material viscosity, the pores in the surface layer (wear-resistant functional layer) and the inner layer (breathable buffer layer) grow and solidify at different stages, ultimately forming a gradient distribution of "small pores on the surface + large pores in the inner layer." Upon heating, the heat first acts on the surface layer, causing the plant-based composite foaming agent to decompose first. At this point, the overall viscosity of the system is high, constraining the lateral expansion of the bubbles, which can only grow within the limited space on the surface, forming tiny pores with a diameter of 5–10 μm. The surface pores also quickly solidify, forming a dense "constraint layer" that provides the physical boundary for subsequent inner layer foaming. With continued heating, the heat gradually conducts to the inner layer, causing the plant-based composite foaming agent to decompose rapidly. Since the surface layer is already solidified, the inner layer bubbles cannot expand towards the surface and can only expand inwards, ultimately forming pores with a diameter of 20–30 μm. The large pores of the tea saponin can delay the merging and collapse of the inner pores, ensuring the uniformity of the large pores; after heating to 110℃, the polyurethane resin undergoes a cross-linking reaction and is quickly cured and molded.

[0029] Step 3: Coat the base fabric layer 3 with solvent-free polyurethane prepolymer evenly, with the coating thickness controlled at 0.1-0.3 mm. Place the coated base fabric in an oven at 120-140℃ for pre-curing for 3-5 minutes to obtain the foamed layer 2. Step 4: Remove the release paper from the dense breathable layer 1 and place it on the side of the foam layer 2 away from the base fabric layer 3. Hot press the composite at a pressure of 0.5-0.8MPa and a temperature of 100-110℃ to avoid crushing of the foam cells and improve the interlayer bonding strength, forming a process barrier. After lamination, continue to cure for 10-15 minutes to obtain breathable solvent-free polyurethane synthetic leather. The dense and breathable layer 1 and the foamed layer 2 are tightly bonded together by hot pressing, with no gaps at the interface, a peel strength ≥3N / cm, and no delamination.

[0030] In the following embodiments, the raw materials for the dense breathable layer 1 are selected as follows: the polyurethane resin is BASF Luwax AF31, the soybean protein foaming agent is Shansong Bio SD-100, the tea saponin foaming agent is Jiyesheng 3865 (60% content), the silicone slip agent is Heyan Yuese Plastic Pigment Additives Co., Ltd. silicone slip feel agent 45A, the polyester softener is Gaobao Chemical: GB-HQ663 (polyester block silicone softener), the silver ion antibacterial additive is silver ion antibacterial powder with an average particle size of 50-100nm, and the solvent-free polyurethane is Wanhua Chemical: WANNATE HT-100 (solvent-free HDI curing agent); since the base fabric layer 3 does not provide performance effects, the raw materials do not need to be specially selected.

[0031] Example 1 Step 1: Calculate the raw materials according to the following ratio: 100 parts polyurethane resin, 3 parts plant-based composite foaming agent, 1 part hand feel additive, and 0.5 parts silver ion antibacterial additive. Step 2: After the above raw materials are mixed evenly, they are coated onto release paper. A dense and breathable layer 1 is obtained using a step-by-step heating process. The step-by-step heating process includes: Step 21: Heat to 80℃ and hold for 2 minutes; Step 22: Heat to 100℃ and hold for 3 minutes; Step 23: Curing at 110℃ for 5 minutes; Step 3: Coat the base fabric layer 3 with solvent-free polyurethane prepolymer evenly, with the coating thickness controlled at 0.1 mm. Place the coated base fabric in an oven at 120°C for 3 min to pre-cur it, and obtain the foam layer 2. Step 4: Remove the release paper from the dense breathable layer 1 and place it on the side of the foam layer 2 away from the base fabric layer 3. Hot press the composite at a pressure of 0.5 MPa and a temperature of 100°C. After lamination, continue to cure for 10 minutes to obtain breathable solvent-free polyurethane synthetic leather.

[0032] Using conventional scanning electron microscopes or optical microscopes, the pore diameter of the wear-resistant functional layer was measured to be between 5 and 6 μm.

[0033] Example 2 Step 1: Calculate the raw materials according to the ratio of 100 parts polyurethane resin, 5 parts plant-based composite foaming agent, 2 parts hand feel additive and 1 part silver ion antibacterial additive; Step 2: After the above raw materials are mixed evenly, they are coated onto release paper. A dense and breathable layer 1 is obtained using a step-by-step heating process. The step-by-step heating process includes: Step 21: Heat to 80℃ and hold for 2 minutes; Step 22: Heat to 100℃ and hold for 3 minutes; Step 23: Curing at 110℃ for 5 minutes; Step 3: Coat the base fabric layer 3 with solvent-free polyurethane prepolymer evenly, with the coating thickness controlled at 0.3 mm. Place the coated base fabric in an oven at 140℃ for 5 min to pre-cur it, and obtain the foam layer 2. Step 4: Remove the release paper from the dense breathable layer 1 and place it on the side of the foam layer 2 away from the base fabric layer 3. Hot press the composite at a pressure of 0.8 MPa and a temperature of 110°C. After lamination, continue curing for 15 minutes to obtain breathable solvent-free polyurethane synthetic leather.

[0034] Using conventional scanning electron microscopes or optical microscopes, the pore diameter of the wear-resistant functional layer was measured to be between 8 and 10 μm.

[0035] Comparative Example 1 Step 1: Calculate the raw materials according to the following ratio: 100 parts polyurethane resin, 2 parts plant-based composite foaming agent, 1 part hand feel additive, and 0.5 parts silver ion antibacterial additive; Step 2: After the above raw materials are mixed evenly, they are coated onto release paper. A dense and breathable layer 1 is obtained using a step-by-step heating process. The step-by-step heating process includes: Step 21: Heat to 80℃ and hold for 2 minutes; Step 22: Heat to 100℃ and hold for 3 minutes; Step 23: Curing at 110℃ for 5 minutes; Step 3: Coat the base fabric layer 3 with solvent-free polyurethane prepolymer evenly, with the coating thickness controlled at 0.1 mm. Place the coated base fabric in an oven at 120°C for 3 min to pre-cur it, and obtain the foam layer 2. Step 4: Remove the release paper from the dense breathable layer 1 and place it on the side of the foam layer 2 away from the base fabric layer 3. Hot press the composite at a pressure of 0.5 MPa and a temperature of 100°C. After lamination, continue to cure for 10 minutes to obtain breathable solvent-free polyurethane synthetic leather.

[0036] Using conventional scanning electron microscopes or optical microscopes, the pore diameter of the wear-resistant functional layer was measured to be between 3 and 4 μm. This is because the amount of plant-based composite foaming agent was insufficient, resulting in insufficient gas production, reduced number of pores but denser distribution, and smaller average pore size.

[0037] Comparative Example 2 Step 1: Calculate the raw materials according to the following ratio: 100 parts polyurethane resin, 3 parts plant-based composite foaming agent, 1 part hand feel additive, and 0.5 parts silver ion antibacterial additive. Step 2: After the above raw materials are mixed evenly, they are coated onto release paper. A dense and breathable layer 1 is obtained using a step-by-step heating process. The step-by-step heating process includes: Step 21: Heat to 80℃ and hold for 5 minutes; Step 22: Heat to 100℃ and hold for 3 minutes; Step 23: Curing at 110℃ for 5 minutes; Step 3: Coat the base fabric layer 3 with solvent-free polyurethane prepolymer evenly, with the coating thickness controlled at 0.1 mm. Place the coated base fabric in an oven at 120°C for 3 min to pre-cur it, and obtain the foam layer 2. Step 4: Remove the release paper from the dense breathable layer 1 and place it on the side of the foam layer 2 away from the base fabric layer 3. Hot press the composite at a pressure of 0.5 MPa and a temperature of 100°C. After lamination, continue to cure for 10 minutes to obtain breathable solvent-free polyurethane synthetic leather.

[0038] Using conventional scanning electron microscopes or optical microscopes, the pore diameter of the wear-resistant functional layer was measured to be between 11 and 13 μm, which is due to the extended heat preservation time in step 21.

[0039] Comparative Example 3 The seat leather is made using traditional solvent-based polyurethane resin and CNC perforation process, with perforation parameters of 10 holes per square centimeter and a hole diameter of 1mm.

[0040] Comparative Example 4 The existing solvent-free polyurethane synthetic leather preparation process was used, but a gradient cell structure was not designed.

[0041] The various embodiments and comparative examples were tested, and the test methods and structures are shown in Table 1 below: Table 1 Test methods and results

[0042] The above data analysis shows that when the pore diameter of the abrasion-resistant functional layer is 3-4μm, the surface layer is too dense, causing excessive compression of gas and a significant decrease in air permeability. Simultaneously, its abrasion resistance decreases instead of increasing. This is because the pore walls are too thin and the pore density is too high, resulting in concentrated stress and making it prone to wear through. Furthermore, it is prone to shrinkage and coalescence during the heat curing stage. Additionally, the high rigidity and poor elastic recovery of the abrasion-resistant functional layer surface result in a stiff leather feel. When the pore diameter of the abrasion-resistant functional layer is 11-13μm, the excessively large pores reduce the effective surface bearing area, causing a significant decrease in abrasion resistance. This also creates localized structural weaknesses, making it prone to tearing under stress. Although the air permeability increases significantly, its abrasion resistance and mechanical strength are insufficient, failing to meet the requirements for synthetic leather / In addition to the requirements for the use of automotive leather, the increased pore size of the foam cells leads to a decrease in the smoothness of the leather surface. Therefore, the pore diameter of the abrasion-resistant functional layer is controlled at 5-10μm to resolve the technical contradiction of "breathability and abrasion resistance being mutually exclusive" in traditional PU synthetic leather.

[0043] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

[0044] Any aspects of this invention not described in detail are well-known to those skilled in the art.

Claims

1. A breathable, solvent-free polyurethane synthetic leather, characterized in that: It includes a dense breathable layer, a foam layer and a base fabric layer arranged sequentially from the outside to the inside. The dense breathable layer has a gradient cell structure to improve breathability and abrasion resistance. It includes an abrasion-resistant functional layer on the surface and a breathable buffer layer set in the abrasion-resistant functional layer. The cell diameter of the abrasion-resistant functional layer is smaller than that of the breathable buffer layer. The foam layer is used to provide elastic support. The components of the dense and breathable layer, by weight, include 95-105 parts of polyurethane resin, 3-5 parts of plant-based composite foaming agent, and 1-2 parts of hand feel additive; The foam layer is made of solvent-free polyurethane; The base fabric layer is made of polyester nonwoven fabric or polyester needle-punched fabric.

2. The breathable solvent-free polyurethane synthetic leather according to claim 1, characterized in that: The wear-resistant functional layer has a pore diameter of 5-10 μm, and the breathable buffer layer has a pore diameter of 20-30 μm.

3. The breathable solvent-free polyurethane synthetic leather according to claim 1, characterized in that: The thickness of the wear-resistant functional layer is ≥10μm, and the thickness of the breathable buffer layer is ≥30μm.

4. The breathable solvent-free polyurethane synthetic leather according to claim 1, characterized in that: The plant-based composite foaming agent is a compound of soybean protein foaming agent and tea saponin foaming agent in a weight ratio of 3:

1.

5. The breathable solvent-free polyurethane synthetic leather according to claim 1, characterized in that: The hand feel additive is a compound of silicone slip agent and polyester softener in a weight ratio of 1:

2.

6. The breathable solvent-free polyurethane synthetic leather according to claim 1, characterized in that: The dense, breathable layer also includes a silver ion antibacterial agent, the amount of which is 0.5%-1% of the weight of the polyurethane resin.

7. A method for preparing breathable solvent-free polyurethane synthetic leather as described in any one of claims 1 to 6, characterized in that, Includes the following steps: Step 1: Calculate the raw materials according to the following ratio: 95-105 parts polyurethane resin, 3-5 parts plant-based composite foaming agent, 1-2 parts hand feel additive, and 0.5-1 parts silver ion antibacterial additive. Step 2: After mixing the above raw materials evenly, coat them onto release paper and use a step-by-step heating process to obtain a dense and breathable layer; Step 3: Coat the base fabric layer with solvent-free polyurethane prepolymer evenly, with the coating thickness controlled at 0.1-0.3 mm. Place the coated base fabric in an oven for pre-curing to obtain the foamed layer. Step 4: Remove the release paper from the dense, breathable layer and place it on the side of the foam layer away from the base fabric layer. Hot-press and cure to obtain breathable, solvent-free polyurethane synthetic leather.

8. The preparation method according to claim 7, characterized in that: The step-by-step heating process in step 2 includes: Step 21: Raise the temperature to 75~85℃ and keep it warm for 2-3 minutes; Step 22: Raise the temperature to 100-105℃ and hold for 2-4 minutes; Step 23: Curing at 110°C for 5 minutes.

9. The preparation method according to claim 7, characterized in that: In step 3, the oven temperature is set to 120-140℃, and the pre-curing time is 3-5 minutes.

10. The preparation method according to claim 7, characterized in that: In step 4, the hot-pressing composite conditions are a pressure of 0.5-0.8 MPa and a temperature of 100-110°C, and the curing time is 10-15 min.

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