Lightweight environment-friendly flame-retardant automobile sofa leather and preparation process thereof

Abstract

The invention discloses lightweight high-grade environment-friendly flame-retardant automobile sofa leather and a preparation method thereof, and belongs to the technical field of polymer composite materials and synthetic leather manufacturing. The invention aims to solve the technical problems in the prior art that the hand feeling of a product is hardened, the air permeability is reduced, the physical strength is reduced and the flame-retardant effect is not lasting due to poor compatibility of a flame retardant and a matrix. The automobile sofa leather is characterized in that the environment-friendly flame retardant contained in the automobile sofa leather is in a microcapsule form coated by a high polymer material, and is uniformly and firmly anchored in a three-dimensional microporous framework formed by polyurethane and superfine fibers. The preparation method comprises the following key steps: firstly, carrying out independent microencapsulation pretreatment on the environment-friendly flame retardant; through the collaborative design, the excellent physical properties such as light weight, softness and air permeability of the material are perfectly reserved while high-grade and permanent environment-friendly flame retardance is realized, and the comprehensive performance of the product is outstanding.

Description

Technical Field

[0001] This invention relates to the field of polymer composite materials and synthetic leather manufacturing technology, and in particular to a lightweight, environmentally friendly, flame-retardant automotive sofa leather and its preparation process. Background Technology

[0002] As a vital means of transportation in modern society, the quality of automotive interior materials directly impacts the comfort and safety of the driving experience. In recent years, with rising consumer demand and increasingly stringent safety regulations, the market has seen a surge in demand for high-performance automotive interior materials, such as leather upholstery, that combine excellent physical properties, high-level safety protection, lightweight construction, and environmental friendliness. Particularly in terms of flame retardant performance, meeting both stringent industry standards and the trend towards halogen-free environmental protection has become an essential requirement for industry development.

[0003] Polyurethane microfiber synthetic leather has been widely used in automotive interiors due to its appearance and feel closely resembling genuine leather, its lightweight nature, and its excellent breathability and moisture permeability. To impart flame-retardant properties, the common technique involves adding environmentally friendly halogen-free flame retardants, such as phosphorus-nitrogen system flame retardants, to the polyurethane slurry. However, existing technologies often face inherent performance contradictions in achieving this goal.

[0004] The fundamental flaw in existing technologies stems from the inherent compatibility issues between flame retardants and the polyurethane matrix. The significant difference in surface energy between these powdered flame retardant particles and the high-molecular-weight polyurethane resin makes uniform dispersion in the slurry extremely difficult, leading to agglomeration. This uneven distribution severely degrades the product's physical properties. Agglomerated, hard particles, like impurities, exist within the material, becoming stress concentration points. This results in a harder, more brittle final product, reduced tear and tensile strength, and severely impacting its reliability as a durable product. Simultaneously, the presence of these particles interferes with the formation of the polyurethane microporous structure during the wet-processing, clogging pores and significantly reducing the product's breathability and moisture permeability, thus sacrificing the comfort expected of synthetic leather. Even more seriously, due to the lack of a strong chemical or physical bond between the flame retardant and the matrix, they gradually migrate from the material's interior to the surface during subsequent cleaning, friction, or long-term use, even detaching. This not only causes surface defects such as "blooming" but also leads to a gradual loss of flame retardant properties, failing to provide permanent safety protection.

[0005] Therefore, how to fundamentally solve the problems of dispersion stability, compatibility and bonding strength of environmentally friendly flame retardants in polyurethane systems, and develop an automotive sofa leather that can meet the requirements of high-grade, long-lasting environmentally friendly flame retardancy while maintaining the material's lightweight, softness, breathability and excellent physical properties, and its preparation method, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] The technical problem this invention aims to solve is to provide a novel automotive sofa leather that simultaneously meets the automotive industry's requirements for lightweighting, high-level environmental protection and flame retardancy, excellent comfort, and durability, and to provide a stable and reliable manufacturing process for it. Existing technologies often sacrifice material softness, breathability, or increase material weight when achieving high-level flame retardancy; simultaneously, the dispersibility and stability of environmentally friendly flame retardants in polyurethane wet-process systems are also significant technical challenges, easily leading to uneven product performance and short-lasting flame retardant effects.

[0007] To address the aforementioned technical problems, the present invention provides the following technical solution.

[0008] The first aspect of this invention provides a lightweight, environmentally friendly, flame-retardant automotive sofa leather.

[0009] The automotive sofa leather, structurally, includes:

[0010] (a) A nonwoven base made of ultrafine polyamide-6 fibers;

[0011] (b) A microporous polyether-type polyurethane layer impregnated in and composited with the nonwoven substrate; and

[0012] (c) Microencapsulated halogen-free environmentally friendly flame retardant dispersed in the microporous polyether polyurethane layer.

[0013] In this scheme, the amount of the microencapsulated halogen-free environmentally friendly flame retardant is 15 to 30 parts by weight relative to 100 parts by weight of polyether polyurethane solids; the nonwoven fabric substrate has a unit area mass of 150 to 250 g / m² before lamination. 2 .

[0014] The innovative mechanism and beneficial effects of this invention are as follows:

[0015] Synergistic effects achieve a balance of high performance: This invention creatively combines microfiber technology, microporous polyurethane technology, and microcapsule flame-retardant technology. The microfiber-6 nonwoven fabric base provides the product with excellent lightweight properties and a soft, full feel. The microporous polyether polyurethane layer ensures the material's breathability and comfort.

[0016] The core contradiction between flame retardancy and physical properties has been resolved: the key innovation lies in the use of microencapsulated halogen-free environmentally friendly flame retardants. By microencapsulating the flame retardant, it can be highly uniformly dispersed in the polyether-based polyurethane matrix as independent micro-units, avoiding the agglomeration of the flame retardant powder. This uniform dispersion not only ensures stable and consistent flame retardant performance throughout the final product, but also minimizes the damage to the microporous structure and polymer chain flexibility of the polyurethane caused by flame retardant agglomerates. Thus, while achieving high flame retardancy, the original soft feel and physical properties of the material are maintained.

[0017] The flame retardant effect is ensured to be permanent: the "shell" structure of the microcapsule physically anchors the active ingredients of the flame retardant in the polyurethane matrix, which greatly improves its resistance to washing and migration, and makes the flame retardant effect have excellent durability.

[0018] As a preferred embodiment, the microcapsule coating layer of the microencapsulated halogen-free environmentally friendly flame retardant is formed from an acrylate copolymer, which has good compatibility with polyurethane systems.

[0019] As a preferred embodiment, the ultrafine polyamide-6 fiber of the nonwoven fabric base is formed by splitting island fibers with polyamide-6 as the island component and low-density polyethylene as the sea component after removing the sea component. This is the fundamental way to obtain an ultrafine fiber structure and achieve a soft feel.

[0020] The second aspect of this invention provides a preparation process for the above-mentioned lightweight, environmentally friendly, flame-retardant automotive sofa leather.

[0021] The preparation process is characterized by including the following steps:

[0022] Step 1: Microencapsulation pretreatment step, the halogen-free environmentally friendly flame retardant powder is microencapsulated to obtain microencapsulated environmentally friendly flame retardant;

[0023] Step 2: Nonwoven fabric base preparation step, using island short fibers through opening, carding, needle punching and heat setting to obtain nonwoven fabric base;

[0024] Step 3: Wet impregnation and coagulation step. The microencapsulated environmentally friendly flame retardant obtained in Step 1 is dispersed in a dimethylformamide solution of polyether polyurethane to prepare an impregnation solution. The non-woven fabric substrate obtained in Step 2 is impregnated in the impregnation solution, then coagulated in a dimethylformamide aqueous solution, and then washed with water to obtain a wet substrate.

[0025] Step 4: Weight reduction and finishing steps. The wet substrate obtained in Step 3 is subjected to solvent reduction treatment to remove the marine components in the island fiber. Then, it is expanded, dried, oiled and stretched to obtain the finished product.

[0026] The innovation of this process lies in introducing the "microencapsulation pretreatment step" as an independent and prerequisite step into the traditional synthetic leather process, solving the application challenges of environmentally friendly flame retardants from the source. This step ensures the high stability and uniformity of the flame retardant in the subsequent wet impregnation solution, laying a solid foundation for the smooth progress of all subsequent processes and the high quality of the final product. Each step is interconnected and works synergistically to ultimately achieve the expected technical effect.

[0027] As a preferred implementation:

[0028] In step one, the step specifically includes: (a) suspending the halogen-free environmentally friendly flame retardant powder in an aqueous medium; (b) adding acrylate monomers and initiators, and carrying out an in-situ polymerization reaction at 60-85°C for 3-6 hours.

[0029] In step two, this step specifically includes: (a) using island-type short fibers with a weight ratio of polyamide-6 to low-density polyethylene of (60-80):(40-20); (b) weaving with a density of 1200-1800 needles / cm. 2 (c) Acupuncture; (d) Heat setting at 100-130℃.

[0030] In step three, the impregnation solution is prepared by dispersing 15-30 parts by weight of microencapsulated environmentally friendly flame retardant in a dimethylformamide solution containing 100 parts by weight of polyether polyurethane solids to form an impregnation solution with a solid content of 18-30%.

[0031] In step three, the coagulation specifically involves: coagulating the impregnated nonwoven fabric in a 15-25% dimethylformamide aqueous solution at a coagulation bath temperature of 20-50°C.

[0032] In step four, the solvent reduction treatment specifically involves treating the wet substrate in a toluene solution at 70-90°C for 15-30 minutes.

[0033] In step four, the expansion drying specifically involves: using an overfeed rate of 5-20% for relaxation drying at a temperature of 110-150℃, while simultaneously applying an oiling agent with a concentration of 2.5-3.0%. This specific finishing process allows the microfiber to fully relax and expand, resulting in a full and soft final product.

[0034] In summary, the present invention has at least one of the following beneficial technical effects:

[0035] 1. This invention creatively constructs a functionally synergistic composite structure by organically combining a microfiber nonwoven fabric base, microporous polyurethane, and microencapsulated flame retardant. This structure successfully solves the long-standing performance constraints and technical contradictions in the field of automotive interior materials between lightweight, high-grade environmentally friendly flame retardancy, and excellent comfort (softness and breathability), enabling the final product to simultaneously meet multiple stringent technical specifications.

[0036] 2. This invention endows the product with excellent and long-lasting environmentally friendly flame-retardant properties. The key lies in the use of microencapsulation technology to physically anchor the flame-retardant active components within the polymer matrix. This structural design significantly enhances the flame retardant's resistance to washing and migration, ensuring that its flame-retardant function does not diminish due to daily use, cleaning, or the passage of time, thus providing stable and reliable safety throughout the product's entire lifecycle.

[0037] 3. The automotive sofa leather prepared by this invention has an excellent soft and full feel and the comfort of genuine leather. On the one hand, the "isolation" effect of the microcapsules avoids the damage of flame retardant particles to the microporous structure of polyurethane and the flexibility of polymer chains; on the other hand, the weight reduction step and relaxation finishing step in the preparation process work together to fully stimulate the fluffy and soft properties of the microfiber, ultimately achieving a high degree of unity between functionality and comfort.

[0038] 4. The preparation process of this invention has high stability, and the product quality is uniform and controllable, making it feasible for large-scale industrial production. By setting up an independent microencapsulation pretreatment step, the technical problems of uneven dispersion and easy sedimentation of environmentally friendly flame retardants in polyurethane wet process systems are solved from the source, ensuring the long-term stability of the impregnation solution and laying a solid foundation for the smooth progress of subsequent processes and the high consistency of the final product performance.

[0039] 5. This invention has significant environmental advantages. First, it uses a halogen-free, environmentally friendly flame retardant, avoiding the problem of toxic and corrosive gases produced during combustion of traditional halogenated flame retardants. Second, microencapsulation technology further encapsulates the flame retardant, reducing its potential release into the environment during use. Simultaneously, the overall lightweight design of the product also helps reduce vehicle energy consumption, aligning with the trend of energy conservation and emission reduction. Detailed Implementation

[0040] To further illustrate the present invention, the lightweight, environmentally friendly, and flame-retardant automotive sofa leather and its preparation process provided by the present invention are described in detail below with reference to embodiments. However, these embodiments are not intended to limit the present invention in any way.

[0041] Example 1

[0042] This embodiment uses intermediate value parameters within the scope of the claims for preparation.

[0043] Step 1: Pretreatment for microencapsulation of environmentally friendly flame retardants

[0044] In a reaction vessel, 300 parts by weight of deionized water and 3 parts by weight of emulsifier were added. While stirring, 100 parts by weight of environmentally friendly phosphorus-nitrogen flame retardant powder were added and ultrasonically dispersed for 45 minutes. Subsequently, 20 parts by weight of acrylate monomers were added, and the system was heated to 75°C. Then, 0.3 parts by weight of initiator were added, and the reaction was maintained at this temperature for 4.5 hours. After the reaction was completed, the product was filtered, washed with water, and vacuum dried at 70°C for 10 hours to obtain microencapsulated environmentally friendly flame retardant.

[0045] Step 2: Preparation of the ultrafine denier island-of-sea fiber nonwoven fabric substrate

[0046] The raw material is island-island staple fiber (fiber specification 3.5D, length 64mm) with a polyamide-6 to low-density polyethylene weight ratio of 70:30. After opening and carding into a web, it is processed with a needle density of 1500 / cm. 2 The needle-punch density was reinforced. Subsequently, heat setting was performed at 115℃ to obtain a unit area mass of 200 g / m². 2 The non-woven fabric base is ironed flat.

[0047] Step 3: Wet impregnation and solidification

[0048] 22 parts by weight of the microencapsulated environmentally friendly flame retardant prepared in step one were dispersed in a dimethylformamide solution containing 100 parts by weight of polyether-type polyurethane solids, adjusting the final impregnation solution solid content to 24%. The nonwoven fabric substrate prepared in step two was impregnated in the solution, and after being rolled at 0.2 MPa, it was introduced into a coagulation bath with a mass concentration of 20% and a temperature of 35°C, and left for 10 minutes. Finally, it was thoroughly washed with 60°C warm water to obtain the wet-process substrate.

[0049] Step 4: Reduction and post-processing / styling

[0050] The wet substrate obtained in step three was treated in toluene at 80°C for 22 minutes to reduce its weight. After washing with hot water at 90°C, it was sent to a stretching dryer and dried using a 12% overfeed rate, while simultaneously being oiled with a 2.7% concentration of oil. The drying temperature was set at 130°C, and finally, the substrate was stretched and set to obtain the finished product.

[0051] Example 2

[0052] This embodiment uses the lower limit parameter within the scope of the claims for preparation.

[0053] Step 1: Pretreatment for microencapsulation of environmentally friendly flame retardants

[0054] In a reaction vessel, 200 parts by weight of deionized water and 1 part by weight of emulsifier were added. While stirring, 100 parts by weight of environmentally friendly phosphorus-nitrogen flame retardant powder were added and ultrasonically dispersed for 30 minutes. Subsequently, 10 parts by weight of acrylate monomers were added, and the system was heated to 60°C. Then, 0.1 parts by weight of initiator was added, and the reaction was maintained at this temperature for 3 hours. After the reaction was completed, the product was filtered, washed with water, and vacuum dried at 60°C for 8 hours to obtain microencapsulated environmentally friendly flame retardant.

[0055] Step 2: Preparation of the ultrafine denier island-of-sea fiber nonwoven fabric substrate

[0056] The raw material is island-island staple fiber (fiber specification 2.5D, length 51mm) with a polyamide-6 to low-density polyethylene weight ratio of 60:40. After opening and carding into a web, it is processed with a needle density of 1200 needles / cm. 2 The needle-punch density was reinforced. Subsequently, heat setting was performed at 100℃ to obtain a mass per unit area of ​​150 g / m². 2 The non-woven fabric base is ironed flat.

[0057] Step 3: Wet impregnation and solidification

[0058] 15 parts by weight of the microencapsulated environmentally friendly flame retardant prepared in step one were dispersed in a dimethylformamide solution containing 100 parts by weight of polyether-type polyurethane solids, adjusting the final impregnation solution solid content to 18%. The nonwoven fabric substrate prepared in step two was impregnated in the solution, and after being rolled at 0.1 MPa, it was introduced into a coagulation bath with a DMF aqueous solution of 15% by mass concentration and a temperature of 20°C, and left for 5 minutes. Finally, it was thoroughly washed with warm water at 50°C to obtain the wet-process substrate.

[0059] Step 4: Reduction and post-processing / styling

[0060] The wet substrate obtained in step three was treated in toluene at 70°C for 15 minutes to reduce its weight. After washing with hot water at 80°C, it was sent to a stretching dryer and dried using a 5% overfeed rate, while simultaneously being oiled with a 2.5% concentration of oil. The drying temperature was set at 110°C, and finally, the substrate was stretched and set to obtain the finished product.

[0061] Example 3

[0062] This embodiment uses the upper limit parameter within the scope of the claims for preparation.

[0063] Step 1: Pretreatment for microencapsulation of environmentally friendly flame retardants

[0064] In a reaction vessel, 400 parts by weight of deionized water and 5 parts by weight of emulsifier were added. While stirring, 100 parts by weight of environmentally friendly phosphorus-nitrogen flame retardant powder were added and ultrasonically dispersed for 60 minutes. Subsequently, 30 parts by weight of acrylate monomers were added, and the system was heated to 85°C. Then, 0.5 parts by weight of initiator were added, and the reaction was maintained at this temperature for 6 hours. After the reaction was completed, the product was filtered, washed with water, and vacuum dried at 80°C for 12 hours to obtain microencapsulated environmentally friendly flame retardant.

[0065] Step 2: Preparation of the ultrafine denier island-of-sea fiber nonwoven fabric substrate

[0066] The raw material is island-island staple fiber (4.5D fiber length 76mm) with a polyamide-6 to low-density polyethylene weight ratio of 80:20. After opening and carding into a web, it is processed with 1800 needles / cm. 2 The needle-punch density was reinforced. Subsequently, heat setting was performed at 130℃ to obtain a unit area mass of 250 g / m². 2 The non-woven fabric base is ironed flat.

[0067] Step 3: Wet impregnation and solidification

[0068] 30 parts by weight of the microencapsulated environmentally friendly flame retardant prepared in step one were dispersed in a dimethylformamide solution containing 100 parts by weight of polyether-type polyurethane solids, adjusting the final impregnation solution solid content to 30%. The nonwoven fabric substrate prepared in step two was impregnated in the solution, and after being rolled at 0.3 MPa, it was introduced into a coagulation bath with a DMF aqueous solution of 25% by mass concentration and a temperature of 50°C, and left for 15 minutes. Finally, it was thoroughly washed with warm water at 70°C to obtain the wet-process substrate.

[0069] Step 4: Reduction and post-processing / styling

[0070] The wet substrate obtained in step three was treated in toluene at 90°C for 30 minutes to reduce its weight. After washing with hot water at 95°C, it was sent to a stretching dryer and dried using a 20% overfeed rate, while simultaneously being oiled with a 3.0% concentration of oil. The drying temperature was set at 150°C, and finally, the substrate was stretched and set to obtain the finished product.

[0071] Comparative Example 1:

[0072] Compared with Example 1, the difference is that step one is omitted; in the preparation of the impregnation solution in step three, 22 parts by weight of environmentally friendly phosphorus-nitrogen system flame retardant powder that has not undergone microencapsulation treatment is directly added, and the rest are the same.

[0073] Comparative Example 2:

[0074] Compared with Example 1, the difference is that in the preparation of the impregnation solution in step three, the amount of the microencapsulated environmentally friendly flame retardant obtained in step one is increased from 22 parts by weight to 40 parts by weight, while the rest are the same.

[0075] Comparative Example 3:

[0076] Compared with Example 1, the difference is that in the preparation of the impregnation solution in step three, the amount of the microencapsulated environmentally friendly flame retardant obtained in step one is reduced from 22 parts by weight to 10 parts by weight, while the rest are the same.

[0077] Comparative Example 4:

[0078] Compared with Example 1, the difference is that no microencapsulated environmentally friendly flame retardant is added in the preparation of the impregnation solution in step three, while the rest are the same.

[0079] Comparative Example 5:

[0080] Compared with Example 1, the difference is that the reduction process in step four is omitted, and the wet substrate after washing in step three is directly subjected to post-finishing and shaping. All other aspects are the same.

[0081] Comparative Example 6:

[0082] Compared with Example 1, the difference is that in the finishing and shaping of step four, the large overfeed relaxation drying process is not used, but the conventional stretching drying process (i.e., the overfeed rate is 0) is used. All other aspects are the same.

[0083] Test Example 1: Validation of the effectiveness of microencapsulation technology

[0084] I. Experimental Instructions

[0085] This test aims to verify the effect of the microencapsulation pretreatment step on the stability of the impregnation solution, the softness of the product, and the durability of its flame retardant properties. The experimental subjects were the samples and intermediate products of Example 1 (using microencapsulated flame retardant) and Comparative Example 1 (using an equal amount of unencapsulated flame retardant powder).

[0086] 1. Stability test of the impregnation solution

[0087] Experimental steps:

[0088] 1000 mL of polyurethane impregnation solution was prepared under the same conditions according to the formulations of Example 1 and Comparative Example 1, respectively.

[0089] Place the two impregnation solutions into two identical 1000mL glass graduated cylinders, seal the cylinder openings, and let them stand at room temperature (25℃).

[0090] After standing for 24 hours, visually observe and record the state of the slurry in the graduated cylinder, focusing on whether there is stratification, precipitation of transparent liquid, and the shape and quantity of sediment at the bottom.

[0091] 2. Flame retardant performance and durability test

[0092] Experimental steps:

[0093] Sufficient test samples were cut from the automotive sofa leather finally obtained in Example 1 and Comparative Example 1.

[0094] The two sets of samples were subjected to 10 cycles of household washing and drying according to the ISO 6330 standard.

[0095] Remove the washed sample and conditioned it for 24 hours under standard atmospheric conditions (temperature 20±2℃, humidity 65±5%).

[0096] According to GB / T 5455-2014 "Determination of vertical damage length, smoldering and afterflame time of textile flammability test", vertical burning tests were conducted on the conditioned samples, and the afterflame time and smoldering time of each group of samples were recorded.

[0097] 3. Softness test

[0098] Experimental steps:

[0099] Standard-sized samples were cut from the automotive sofa leather (unwashed) finally obtained in Example 1 and Comparative Example 1.

[0100] Humidify for 24 hours under standard atmospheric conditions.

[0101] Using a digital flexibility tester, and in accordance with the method of GB / T 8942, the bending stiffness of the sample in the warp and weft directions was tested, and the average value was calculated as the final result.

[0102] II. Experimental Data

[0103] Table 1 Performance comparison test data between Example 1 and Comparative Example 1

[0104]

[0105] III. Experiment Summary

[0106] The test data above clearly demonstrates the fundamental technological advancements brought about by the microencapsulation pretreatment step. In Example 1, thanks to microencapsulation, the flame retardant exhibited excellent dispersion stability in the polyurethane slurry, remaining homogeneous even after standing for 24 hours. This is attributed to the formation of the microcapsule shell, which alters the surface properties of the flame retardant particles, significantly improving their compatibility with the organic polyurethane system. Simultaneously, the steric hindrance effect prevents the aggregation and rapid sedimentation of high-density inorganic particles due to gravity, providing a process guarantee for preparing high-quality products with uniform performance.

[0107] Regarding the physical properties of the final product, the bending stiffness of the sample in Example 1 was significantly lower than that in Comparative Example 1, indicating a softer feel. The mechanism is that the unencapsulated flame retardant powder in Comparative Example 1 exists as independent rigid particles and is prone to agglomeration into larger aggregates. These aggregates disrupt the continuity and flexibility of the polyurethane matrix polymer chains and may interfere with the normal formation of microporous structures, resulting in overall material hardening and a poorer feel. Conversely, the microencapsulated flame retardant in Example 1 is uniformly distributed as independent, flexible micro-units, minimizing its impact on the mechanical properties of the polyurethane matrix. Thus, while introducing functionality, it successfully retains the original softness and comfort of the material.

[0108] Most importantly, the results of the flame retardant durability test strongly demonstrate the innovation of this invention in functional durability. After multiple washes, the sample of Example 1 still maintained excellent flame retardant effect, with extremely short afterflame and smoldering times. In contrast, the sample of Comparative Example 1 almost lost its flame retardant ability. This profoundly reveals the physical anchoring mechanism of the microcapsule: the polymer shell firmly locks the flame retardant active ingredients inside the polyurethane matrix, effectively resisting loss caused by mechanical force and solvent action during water washing. This structural innovation makes the flame retardant function no longer a temporary surface treatment, but an inherent and durable property of the material itself, ensuring the safety of the product throughout its entire service life.

[0109] Test Example 2: Verification of Flame Retardant Dosage Range

[0110] I. Experimental Instructions

[0111] This test aims to verify the decisive influence of the addition range of microencapsulated flame retardant on the final flame retardant performance and physical strength of the product. The experimental subjects were samples from Example 1 (addition amount within a moderate range), Comparative Example 2 (addition amount exceeding the upper limit), and Comparative Example 3 (addition amount below the lower limit).

[0112] 1. Ultimate Flame Retardant Performance Test

[0113] Experimental steps:

[0114] Standard-sized samples were cut from the automotive sofa leather finally obtained in Example 1, Comparative Example 2, and Comparative Example 3, respectively.

[0115] All samples were conditioned for 24 hours under standard atmospheric conditions (temperature 20±2℃, humidity 65±5%).

[0116] According to GB / T 5455-2014 standard, vertical burning tests were conducted on the conditioned samples, and the afterburning time and damage length of each group of samples were recorded.

[0117] 2. Physical strength test

[0118] Experimental steps:

[0119] Samples for tensile and tear tests were cut from the automotive sofa leather finally obtained in Example 1, Comparative Example 2, and Comparative Example 3, respectively, according to standard requirements.

[0120] Humidify for 24 hours under standard atmospheric conditions.

[0121] Using a tensile testing machine, test the tensile strength of the specimen according to GB / T 3923.1 and the tear strength of the specimen according to GB / T 3917.3, and record the data.

[0122] II. Experimental Data

[0123] Table 2 Performance comparison test data of Example 1, Comparative Example 2 and Comparative Example 3

[0124] Test Project Example 1 Comparative Example 2 Comparative Example 3 Afterburn time (s) 1.8 1.1 32.5 Damaged length (mm) 45 38 Burn through Tensile strength (N) 415 278 435 Tear strength (N) 88 51 92

[0125] III. Experiment Summary

[0126] The test data above reveals that the amount of flame retardant added is a key parameter that plays a decisive role in the final performance of the product and must be controlled within a precise balance range. The results of Comparative Example 3 show that when the amount of microencapsulated flame retardant added is insufficient, although the material exhibits excellent physical strength, its afterflame time is extremely long in combustion tests, and even burns through. This indicates that at this addition amount, the number of flame-retardant functional units available per unit volume is too small, making it impossible to form an effective and dense carbon layer to insulate against heat and oxygen during combustion, thus failing to achieve the high level of safety protection target pursued by this invention.

[0127] Conversely, Comparative Example 2 demonstrates the negative effects of excessive flame retardant addition. While its combustion test data were excellent, its tensile strength and tear strength both showed a significant decrease. The underlying mechanism is that, as a functional filler, excessively high volume fraction of microcapsules severely disrupts the continuity and integrity of the polyether-based polyurethane matrix. These excessive, non-reinforcing microparticles become "defects" or stress concentration points in the polymer network, easily inducing the generation and propagation of microcracks when the material is under stress. This leads to a sharp deterioration in the macroscopic mechanical properties of the material, failing to meet the basic requirements for durable products.

[0128] The comprehensive performance of Example 1 perfectly illustrates the innovation of this invention in terms of component ratio. The amount of flame retardant added ensures that sufficient functional units migrate to the surface during combustion, rapidly forming an effective protective barrier through synergistic effects such as melt dripping, char formation, and the release of non-flammable gases, exhibiting excellent flame retardant performance. Simultaneously, this addition amount is precisely controlled within a threshold that will not cause catastrophic damage to the mechanical properties of the polyurethane matrix. This proves that the component range determined by this invention is not a simple addition, but rather achieves a delicate balance between "functionality" and "structure," enabling the final product to possess both excellent safety performance and outstanding physical durability.

[0129] Test Example 3: Verification of the Necessity of Flame Retardant Components

[0130] I. Experimental Instructions

[0131] This test aims to verify, through direct comparison, the decisive role and necessity of microencapsulated halogen-free environmentally friendly flame retardant in imparting flame-retardant properties to the product. The experimental subjects were samples from Example 1 (containing the flame-retardant component) and Comparative Example 4 (not containing the flame-retardant component).

[0132] 1. Basic flame retardant performance test

[0133] Experimental steps:

[0134] Standard-sized samples were cut from the automotive sofa leather finally obtained in Example 1 and Comparative Example 4, respectively.

[0135] Both sets of samples were conditioned for 24 hours under standard atmospheric conditions (temperature 20±2℃, humidity 65±5%).

[0136] According to GB / T 5455-2014 standard, a vertical burning test was conducted on the conditioned samples. After ignition for 12 seconds, the flame was removed, and the afterflame time, smoldering time, and length of damage caused by flame spread were immediately recorded and observed.

[0137] II. Experimental Data

[0138] Table 3 shows the performance comparison test data between Example 1 and Comparative Example 4.

[0139] Test Project Example 1 Comparative Example 4 Afterburn time (s) 1.7 Continue burning to the clamp Smoldering time (s) 1.3 Not applicable (sample completely burned) Damaged length (mm) 42 Total length of the sample

[0140] III. Experiment Summary

[0141] The test results showed a significant difference, directly demonstrating the core role of the flame-retardant functional component in this invention. The sample in Example 1 self-extinguished rapidly after the flame was removed, with the damaged length effectively controlled within a very small range, exhibiting excellent flame-retardant performance. In contrast, the sample in Comparative Example 4, which contained no flame-retardant component, burned violently upon ignition, with the flame spreading rapidly until the entire sample was completely burned. This phenomenon clearly indicates that the flame-retardant properties of the material do not originate from the substrate itself, but are entirely imparted by the added microencapsulated halogen-free environmentally friendly flame retardant.

[0142] The underlying mechanism lies in the fact that, when the composite material of Example 1 is heated, the microencapsulated flame retardant in the polyurethane matrix responds rapidly and exerts its effect through a phosphorus-nitrogen synergistic effect. It forms a dense, expanded carbon layer on the material surface, which acts as a solid physical barrier, effectively isolating external heat sources and oxygen from being transferred to the internal substrate. Simultaneously, the non-combustible gases (such as ammonia and water vapor) produced by its decomposition dilute the concentration of combustible gases in the combustion zone, inhibiting the chain reaction of combustion from the gas phase. This dual effect of solid-phase charring and gas-phase flame suppression together constructs a highly efficient flame retardant system.

[0143] In contrast, the sample in Comparative Example 4 is essentially a composite of pure polyurethane and polyamide fibers, both of which are flammable polymers. Without the intervention of flame retardants, its combustion process follows a typical polymer combustion path: thermal decomposition produces a large amount of flammable small-molecule gases. These gases mix with air, sustaining and intensifying combustion, ultimately leading to catastrophic and complete destruction. Therefore, this test irrefutably confirms that the composition design containing specific functional components proposed in this invention is the fundamental premise and cornerstone of achieving high-level product safety performance.

[0144] Test Example 4: Verification of the synergistic effect of the reduction steps

[0145] I. Experimental Instructions

[0146] This test aims to verify the crucial role of the solvent reduction process in the softness, breathability, and moisture permeability of the final product, and to reveal its synergistic effect with island-sea fiber technology. The experimental subjects were samples from Example 1 (after reduction treatment) and Comparative Example 5 (without reduction treatment).

[0147] 1. Softness test

[0148] Experimental steps:

[0149] Standard-sized samples were cut from the automotive sofa leather finally obtained in Example 1 and Comparative Example 5, respectively.

[0150] After conditioning for 24 hours under standard atmospheric conditions, the average bending stiffness of the sample was tested using a digital flexibility tester according to the method of GB / T 8942.

[0151] 2. Breathability test

[0152] Experimental steps:

[0153] Circular samples were cut from the samples of Example 1 and Comparative Example 5, respectively.

[0154] After conditioning for 24 hours under standard atmospheric conditions, the air permeability of the sample was tested using a fully automatic air permeability meter according to GB / T 5453 standard under a pressure difference of 100Pa.

[0155] 3. Moisture permeability test

[0156] Experimental steps:

[0157] Circular samples were cut from the samples of Example 1 and Comparative Example 5, respectively.

[0158] According to the positive cup method of GB / T 12704.2-2009, the sample is sealed in a permeable cup containing desiccant.

[0159] Place the permeation cup in a constant temperature and humidity chamber at 38℃ and 90% relative humidity.

[0160] After 24 hours, weigh the increase in weight of the permeation cup and calculate the permeation rate of the sample.

[0161] II. Experimental Data

[0162] Table 4 shows the performance comparison test data between Example 1 and Comparative Example 5.

[0163] Test Project Example 1 Comparative Example 5 Bending stiffness (mN) 142 458 <![CDATA[Air permeability (L / m 2 ·s)]]> 1.52 0.09 <![CDATA[Water vapor transmission rate (g / m 2 ·24h)]]> 6850 1120

[0164] III. Experiment Summary

[0165] The significant differences in the above test results strongly demonstrate that the solvent reduction step is an indispensable and crucial step in the preparation process of this invention. The sample in Example 1 exhibits superior performance compared to the cloud-like material in Comparative Example 5 in all three core comfort indicators: softness, air permeability, and moisture permeability. This leap in performance is entirely attributed to the fundamental reshaping of the material's microstructure caused by the solvent reduction process.

[0166] The core mechanism lies in the fact that the island fiber used in this invention is a composite fiber precursor, consisting of a soluble "sea" component (low-density polyethylene) encapsulating an insoluble "island" component (ultrafine polyamide-6 fiber). The solvent reduction step utilizes a specific solvent (such as toluene) to completely dissolve and remove the "sea" component. This process causes the originally bound single composite fiber to instantly split into bundles of extremely fine ultrafine polyamide-6 fibers. It is this structural fission from "one" to "many" that endows the material with drastically different physical properties. The fibers become finer and freer, and the sliding resistance between them decreases dramatically, macroscopically manifesting as a significant reduction in the material's bending stiffness, thus achieving the soft, full-bodied feel characteristic of the sample in Example 1.

[0167] Meanwhile, this fiber splitting process also creates a three-dimensional network structure composed of countless tiny channels and pores within the nonwoven fabric substrate. These newly formed pores provide unobstructed pathways for the migration of air and water vapor, resulting in a qualitative improvement in the material's air permeability and moisture permeability. In contrast, Comparative Example 5, due to the omission of the weight reduction step, still retains the "sea" component, which acts like a dense film filling the spaces between the fibers, blocking all potential pores. This leads to a final product with a dense, non-porous structure that is both rigid and almost impermeable to air and moisture. Therefore, the weight reduction step is the key to activating the "ultrafineness" and "porousness" potential of sea-island fibers, and is the core process supporting this invention's innovative goal of combining lightweight, high comfort, and functionality.

[0168] Test Example 5: Verification of the Synergistic Effect of Post-Finishing Processes

[0169] I. Experimental Instructions

[0170] This test aims to verify the key role of a relaxation drying process with a specific overfeed rate in improving product thickness, fullness, and elasticity. The experimental subjects were samples from Example 1 (using relaxation drying) and Comparative Example 6 (using conventional stretch drying).

[0171] 1. Product thickness test

[0172] Experimental steps:

[0173] Five samples were cut from different positions on the car sofa leather finally obtained in Example 1 and Comparative Example 6, respectively.

[0174] After conditioning for 24 hours under standard atmospheric conditions, the thickness of each sample was measured using a digital fabric thickness gauge under specified pressure.

[0175] Calculate the average thickness of the five samples in each group as the final result.

[0176] 2. Elastic recovery rate test

[0177] Experimental steps:

[0178] Standard-sized stretch strips were cut from the samples of Example 1 and Comparative Example 6 along the warp direction.

[0179] Humidify for 24 hours under standard atmospheric conditions.

[0180] On a tensile testing machine, the specimen is stretched at a constant rate to the specified elongation (e.g., 20%) and held for 1 minute.

[0181] Quickly remove the load and allow the spline to recover freely under no-tension conditions for 1 minute.

[0182] Measure the length of the spline at this point and calculate its elastic recovery rate.

[0183] II. Experimental Data

[0184] Table 5 Performance comparison test data between Example 1 and Comparative Example 6

[0185] Test Project Example 1 Comparative Example 6 Product thickness (mm) 1.38 0.95 Elastic recovery rate (%) 97.2 84.6

[0186] III. Experiment Summary

[0187] The test data above clearly demonstrates the decisive impact of the choice of finishing and shaping process on the final product's form and performance. The sample in Example 1, which used a relaxation drying process, had a significantly greater thickness than the sample in Comparative Example 6, which used a conventional stretch drying process, and its elastic recovery rate was also far superior. This indicates that a specific finishing process is a key synergistic step in activating the material's potential superior properties.

[0188] The underlying mechanism lies in the fact that, after the solvent reduction step, countless microfibers have formed within the material. During the relaxation drying process, by applying a positive overfeed rate, the fabric enters the drying oven in a tension-free, relaxed state. The high-temperature environment not only evaporates moisture but, more importantly, provides energy for the movement of the polymer chains and microfibers. Without external constraints, these "liberated" microfibers spontaneously curl and shrink, evolving from a two-dimensional planar arrangement to a three-dimensional spatial network structure, thereby creating numerous tiny gaps between the fibers. This makes the entire material fluffy and full, macroscopically manifested as an increase in thickness and excellent elasticity.

[0189] In contrast, the conventional stretching and drying process used in Comparative Example 6 applies tension to the material throughout the drying process. This tension forces the still-active microfibers to be straightened, aligned parallel to each other, and tightly bound along the stretching direction, completely suppressing their natural tendency to stretch in three-dimensional space. The result is a dense, plate-like structure with high internal stress, thin thickness, and lack of elasticity. When this pre-stretched structure is subjected to external stretching again, its fibers have almost no extra deformation space, easily leading to irreversible slippage and thus a low elastic recovery rate. This comparison powerfully demonstrates that the relaxation finishing process used in this invention is not an isolated step, but rather interconnected and synergistic with the preceding island fiber reduction technology. It is a necessary guarantee for maximizing the advantages of microfiber and achieving a soft, full, and highly elastic feel in the product.

[0190] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A lightweight, environmentally friendly, flame-retardant automotive sofa leather, characterized in that, include: (a) A nonwoven base made of ultrafine polyamide-6 fibers; (b) A microporous polyether polyurethane layer impregnated in and composited with a nonwoven substrate; as well as (c) Microencapsulated halogen-free environmentally friendly flame retardant dispersed in a microporous polyether polyurethane layer; The amount of microencapsulated halogen-free environmentally friendly flame retardant used is 15 to 30 parts by weight relative to 100 parts by weight of polyether polyurethane solids; the nonwoven substrate has a unit area mass of 150 to 250 g / m² before lamination. 2 .

2. The automotive sofa leather according to claim 1, characterized in that, The microcapsule coating of the microencapsulated halogen-free environmentally friendly flame retardant is formed from an acrylate copolymer.

3. The automotive sofa leather according to claim 1 or 2, characterized in that, The ultrafine polyamide-6 fiber of the nonwoven fabric base is formed by splitting island fibers with polyamide-6 as the island component and low-density polyethylene as the sea component after removing the sea component.

4. A manufacturing process for lightweight, environmentally friendly, flame-retardant automotive sofa leather as described in any one of claims 1 to 3, characterized in that, Includes the following steps: Step 1: Microencapsulation pretreatment step, the halogen-free environmentally friendly flame retardant powder is microencapsulated to obtain microencapsulated environmentally friendly flame retardant; Step 2: Nonwoven fabric base preparation step, using island short fibers through opening, carding, needle punching and heat setting to obtain nonwoven fabric base; Step 3: Wet impregnation and coagulation step. The microencapsulated environmentally friendly flame retardant obtained in Step 1 is dispersed in a dimethylformamide solution of polyether polyurethane to prepare an impregnation solution. The non-woven fabric substrate obtained in Step 2 is impregnated in the impregnation solution, then coagulated in a dimethylformamide aqueous solution, and then washed with water to obtain a wet substrate. Step 4: Weight reduction and finishing steps. The wet substrate obtained in Step 3 is subjected to solvent reduction treatment to remove the marine components in the island fiber. Then, it is expanded, dried, oiled and stretched to obtain the finished product.

5. The preparation process according to claim 4, characterized in that, Step one specifically includes: (a) Suspending halogen-free environmentally friendly flame retardant powder in an aqueous medium; (b) Add acrylate monomers and initiators, and carry out in-situ polymerization at 60-85°C for 3-6 hours.

6. The preparation process according to claim 4, characterized in that, Step two specifically includes: (a) Using island-type short fibers with a weight ratio of polyamide-6 to low-density polyethylene of (60-80):(40-20); (b) With a needle density of 1200-1800 needles / cm 2 Acupuncture; (c) Heat set at 100-130℃.

7. The preparation process according to claim 4, characterized in that, The impregnation solution preparation in step three is specifically as follows: 15-30 parts by weight of microencapsulated environmentally friendly flame retardant are dispersed in a dimethylformamide solution containing 100 parts by weight of polyether-type polyurethane solids to form an impregnation solution with a solid content of 18-30%.

8. The preparation process according to claim 4, characterized in that, The coagulation in step three specifically involves coagulating the impregnated nonwoven fabric in a 15-25% dimethylformamide aqueous solution at a coagulation bath temperature of 20-50°C.

9. The preparation process according to claim 4, characterized in that, The solvent reduction treatment in step four specifically involves treating the wet substrate in a toluene solution at 70-90°C for 15-30 minutes.

10. The preparation process according to claim 4, characterized in that, The expansion drying in step four specifically involves: using an overfeed rate of 5-20% for relaxation drying, a drying temperature of 110-150℃, and simultaneously using an oiling agent with a concentration of 2.5-3.0% for oiling treatment.

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