High-strength waterproof flame-retardant clothing leather and preparation method thereof

Abstract

The invention provides high-strength waterproof flame-retardant clothing leather and a preparation method thereof.The method comprises the steps that a sheepskin raw material is obtained, degreasing treatment is conducted on the sheepskin raw material through a degreasing agent, liming treatment is conducted on the sheepskin raw material subjected to degreasing treatment through liming liquid, and a first leather semi-finished product is obtained; performing basic tanning treatment on the first leather semi-finished product by adopting a target chrome-free tanning agent to obtain a second leather semi-finished product; carrying out retanning treatment on the second leather semi-finished product by adopting a target retanning agent to obtain a third leather semi-finished product; performing post-treatment on the third leather semi-finished product to obtain a fourth leather semi-finished product; the fourth leather semi-finished product is subjected to coating spraying treatment, a waterproof layer, a flame-retardant layer and a modification layer are formed on the surface of the fourth leather semi-finished product, a fifth leather semi-finished product is obtained, and the fifth leather semi-finished product is subjected to soft finishing, so that the high-strength waterproof flame-retardant clothing leather finished product is obtained. The waterproof and flame-retardant effects are good, and the cost is low.

Description

Technical Field

[0001] This invention belongs to the technical field of garment leather preparation processes, specifically relating to a high-strength, waterproof, and flame-retardant garment leather and its preparation method. Background Technology

[0002] With the development of outdoor sports, military security, and special operations, the market demand for clothing that combines high strength and abrasion resistance, waterproofing and windproofing, as well as flame retardancy and heat insulation has surged. For example, professions such as firefighters, mountaineers, and miners have stringent requirements for the safety and protection of their clothing.

[0003] Sheepskin naturally possesses the advantages of being soft, breathable, and warm, but its high water absorption (it hardens easily when wet) and high flammability (ignition point as low as below 200°C) limit its application in harsh environments. For example, untreated sheepskin garments are easily ignited and lose their warmth in damp conditions; For existing waterproofing technologies, a microporous structure is formed on the surface of sheepskin through a spraying process to balance waterproofing and breathability, but the production cost is high. Alternatively, a modified linseed oil fatty acid ester and lanolin complex can be used as a natural waterproofing agent, which is environmentally friendly and non-toxic, but the waterproofing performance is only 60%-70% of that of PU coating, and the applicable scenarios are limited. For existing flame retardant technologies, ammonium polyphosphate (APP) is combined with chitosan and sheepskin is treated by impregnation, achieving a flame retardant rating of GB 8624 B1 (flame-retardant material). However, the thermal stability is insufficient. Alternatively, a graphene / carbon nanotube (CNT) composite coating is used to suppress combustion by utilizing its high thermal conductivity, increasing the oxygen index (OI) to over 32. However, the coating has poor adhesion and is easy to peel off. In summary, the existing technology has the following problems: Poor functional synergy: Most technologies only modify a single function (waterproof or flame retardant), lacking multi-functional integrated solutions.

[0004] High process complexity: For example, nano-coatings require vacuum spraying equipment, and plant-based waterproofing agents require multiple impregnation processes, increasing production costs.

[0005] Environmental friendliness needs improvement: Fluorine-containing coatings and halogenated flame retardants still dominate, which is not in line with international environmental protection trends. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a high-strength, waterproof, and flame-retardant garment leather and its preparation method, thereby resolving the issues in the background section.

[0007] This invention provides the following technical solution: a method for preparing high-strength, waterproof, and flame-retardant garment leather, the method comprising the following steps: S1. Obtain sheepskin raw material, degrease the sheepskin raw material with a degreasing agent, and immerse the degreased sheepskin raw material in liming solution to obtain the first semi-finished leather product. S2. The first leather semi-finished product is subjected to basic tanning treatment using the target chromium-free tanning agent to obtain the second leather semi-finished product; S3. The second leather semi-finished product is retanned using the target retanning agent to obtain the third leather semi-finished product; S4. The third semi-finished leather product is post-processed to obtain the fourth semi-finished leather product; S5. The fourth semi-finished leather product is coated with a waterproof layer, a flame-retardant layer, and a finishing layer to form a fifth semi-finished leather product on its surface. The fifth semi-finished leather product is then softened to obtain a high-strength, waterproof, and flame-retardant garment leather product.

[0008] Compared with the prior art, the beneficial effects of this application are as follows: after the processing steps provided by this invention, the thickness of the waterproof layer of the high-strength waterproof and flame-retardant garment leather product is 0.5-1μm, and the water permeability is <5×10⁻⁶. -7 g / (m 2 The flame-retardant layer exhibits a water pressure resistance of >10,000 mm, an oxygen index (OI) ≥35, a limiting oxygen index (LOI) ≥30, and a 40% reduction in peak heat release rate (HRP). Furthermore, its overall mechanical properties meet the requirements of a tear strength ≥80 N / cm and an elongation at break ≥15%. Compared to existing technologies, the finished product prepared by this invention withstands a water pressure of 12,000 mm (ASTM D3373 standard) and retains over 90% of its strength after immersion in water for 24 hours. It also meets GB8624 B1 certification, achieving a limiting oxygen index (LOI) of 32. Its Taber friction coefficient is <0.3 (ASTM D418), making it suitable for frequent wear. The all-water-based process reduces VOC emissions by 90%. The flame retardant is a bamboo charcoal-based biomaterial with a biodegradability rate >80% (ISO). The application complies with the 14855 standard, and the cost of preparing the flame-retardant layer is reduced by 30% compared with the traditional method, the energy consumption of water-based coatings is reduced by 40%, and the production cycle is shortened by 30% after process integration (from the traditional 72h to 50h).

[0009] Preferably, step S1 includes: The sheepskin raw material is soaked in an alkaline degreasing agent at a temperature of 50-60 degrees Celsius for 15 minutes to degrease it. After degreasing, add pancreatic enzyme and penetrant to hydrolyze the fat in the sheepskin raw material at a temperature of 35-40 degrees Celsius for 2-3 hours. Afterward, rinse the sheepskin pigment repeatedly with warm water until there is no greasy feeling. The rinsed sheepskin raw material is immersed in a liming solution for liming treatment, with the pH value controlled at 12-13, the temperature at 25-30 degrees Celsius, and the time at 8-12 hours. Add a deashing agent to adjust the pH value to 8-9, and evenly expand the collagen fibers. Then add 78 neutralizing agent TJ-A819 to adjust the pH value to 4.5-5.5. After that, use waterproof wetting agent BSQ to soak the sheepskin raw material at a controlled water temperature of 25℃ to obtain the first semi-finished leather product.

[0010] Preferably, the alkaline degreasing agent is 2-3% triethanolamine dodecylbenzenesulfonate, the penetrant is 0.3% leather surfactant 2047, the liming solution is an liming solution containing 2-3% sodium sulfide, and the deliming agent is DL828 reliming and deliming agent.

[0011] Preferably, in step S2, the method for preparing the target chromium-free tanning agent is as follows: 30% chestnut tannin and 70% acrylic resin are mixed and the pH value of the solution is adjusted to 5.5 to obtain the target chromium-free tanning agent.

[0012] Preferably, step S3 includes: The modified polysiloxane aqueous emulsion, aqueous anionic polyurethane dispersion, and aqueous acrylic resin dispersion are mixed, then HL3634 and aqueous nitrocellulose are added, and deionized water is added to dilute to the working solution concentration. Then, water-soluble crosslinking agent and catalyst are added, and the mixture is stirred for 10 minutes until homogeneous. The pH value of the solution is controlled to 6.0-7.0 to obtain a waterproof impregnation solution. The second leather semi-finished product is retanned using the target retanning agent. In the initial stage of retanning, the second leather semi-finished product is immersed in the waterproof impregnation liquid, which can withstand hydrostatic pressure >100kpa and stand for 15 minutes. During the retanning process, the organophosphorus flame retardant is added in three separate applications at 20-minute intervals, and the pH is adjusted to 4.0-4.5 after each addition. Add a silicone-containing waterproofing agent during the later stage of retanning, rotate for 60 minutes and raise the temperature to 50°C, while controlling the pH value to be maintained at 4.2-4.5; Add a water-soluble crosslinking agent 30 minutes before the end of retanning, rotate for 30 minutes, and finally adjust the pH to 5.0-5.5 to promote the crosslinking reaction; JFC is added throughout the retanning process, and the leather is air-dried or dried at low temperature after retanning to obtain the third semi-finished leather product.

[0013] Preferably, the target retanning agent is a synthetic tanning agent or a vegetable tanning agent.

[0014] Preferably, the mixing ratio of the modified polysiloxane aqueous emulsion, the aqueous anionic polyurethane dispersion, and the aqueous acrylic resin dispersion is 0.3:3.7:6.

[0015] Preferably, step S4 includes: The excess liquid in the third semi-finished leather product is removed by a roller press and the moisture content is controlled to be below 30%. Then, the third semi-finished leather product is washed with water until neutral. Unreacted substances are removed by squeezing out the water. Then, the third semi-finished leather product is dried with hot air at 80°C for 10 minutes in the initial drying stage. In the drying stage, it is cured with hot air at 90°C for 3-5 minutes to promote the cross-linking reaction. In the ironing stage, it is ironed at 85°C and 80 bar to obtain the fourth semi-finished leather product.

[0016] Preferably, step S5 includes: Mix 50% water, 5% P-4893, 40% Ground NC, and 5% PU-2830, then add dyeing paste to obtain the first spray liquid. Spray the first spray liquid twice on the surface of the fourth leather semi-finished product and heat it at 80 degrees / 25KG for 5 seconds to form a waterproof layer on the surface of the fourth leather semi-finished product. Mix 20% water, 5% P-4893, 10% PU2204, 20% PU-43-116, 5% 1079, 5% RC2349, 5% SOFT-01, 10% NP-10, and 20% FC-300, then add AKU and dyeing paste to obtain a second spray liquid. Spray the second spray liquid four times on the surface of the waterproof layer and dry at 90 degrees for 10 seconds to form a flame-retardant layer on the surface of the waterproof layer. 20% water, 20% PU-43-116, 8% WT-13-097, 35% RU3904, 15% WT-72-586, and 2% WF-5230 are mixed to obtain a third spraying liquid. The third spraying liquid is sprayed twice on the flame-retardant layer surface, shaken to soften once, and then thrashed to soften for 2 hours. The surface is then lightly stretched to form a finishing layer, resulting in a fifth semi-finished leather product. The fifth semi-finished leather product is then softened and finished to obtain a high-strength, waterproof, and flame-retardant garment leather product.

[0017] On the other hand, the present invention also provides the following technical solution: a high-strength waterproof and flame-retardant garment leather, wherein the high-strength waterproof and flame-retardant garment leather is prepared by the preparation method of the high-strength waterproof and flame-retardant garment leather described above. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A flowchart illustrating the preparation method of high-strength, waterproof, and flame-retardant garment leather provided in this embodiment of the invention. Detailed Implementation

[0020] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain embodiments of the present invention, and should not be construed as limiting the present invention.

[0021] In one embodiment of the present invention, a method for preparing high-strength, waterproof, and flame-retardant garment leather includes the following steps: S1. Obtain sheepskin raw material, degrease the sheepskin raw material with a degreasing agent, and immerse the degreased sheepskin raw material in liming solution to obtain the first semi-finished leather product. Step S1 includes: S11. The sheepskin raw material is soaked in an alkaline degreasing agent for degreasing at a temperature of 50-60 degrees Celsius for 15 minutes. The alkaline degreasing agent is 2-3% triethanolamine dodecylbenzenesulfonate. Degreasing with the alkaline degreasing agent can remove sheepskin grease and improve the adhesion of subsequent coatings. Triethanolamine dodecylbenzenesulfonate can effectively remove grease and dirt from the leather surface, improve the cleanliness and water absorption of the leather, and facilitate subsequent processing steps such as dyeing and finishing.

[0022] S12. After degreasing, add pancreatic enzyme and penetrant to hydrolyze the fat in the sheepskin raw material at a temperature of 35-40 degrees Celsius for 2-3 hours. Afterward, rinse the sheepskin pigment repeatedly with warm water until there is no greasy feeling. The concentration of trypsin here is 0.5-1%. Trypsin is used to further hydrolyze the residual oil in the leather, breaking it down into glycerol and fatty acids, thereby completely eliminating the greasy feeling of the leather. At the same time, it can hydrolyze some non-collagen proteins and hair root sheaths, making the leather fiber structure looser, softer, and the grain surface smoother and finer. The penetrant is 0.3% leather surfactant 2047, which can reduce the surface tension of water and help the trypsin solution penetrate into the leather more quickly and evenly, ensuring a uniform softening effect. By adding trypsin and penetrant, the fat in the sheepskin raw material can be hydrolyzed, keratin proteins can be selectively decomposed, fiber strength can be preserved, and uniform micropores (pore size 50-200nm) can be formed on the surface of the sheepskin, providing anchor points for the subsequent waterproof layer, making the subsequent tanning and finishing effect better. At the same time, after degreasing, it is necessary to rinse with warm water until there is no greasy feeling. The degree of degreasing should be moderate, and more than 2% of oil should be retained to maintain softness.

[0023] S13. Immerse the rinsed sheepskin raw material in a liming solution for liming treatment, controlling the pH value to 12-13, the temperature to 25-30 degrees, and the time to 8-12 hours. The liming solution contains 2-3% sodium sulfide. This liming solution is a mixture of lime and sodium sulfide. Its effects are as follows: the strong alkaline environment allows the collagen fibers of the hide to fully absorb water and swell, opening up the fiber bundle structure and creating space for the penetration of subsequent tanning agents and other materials; sodium sulfide will destroy the basic structure of hair follicles and epidermis, causing the hair to fall out completely; it further removes trace amounts of residual oil; and it removes some non-collagenous proteins and sugars from the hide. At the same time, the temperature here is relatively low. The relatively low temperature is to control the hydrolysis rate of hide proteins while effectively liming, avoiding excessive loss of hide and resulting in loose leather.

[0024] S14. Add a deashing agent to adjust the pH value to 8-9, and evenly expand the collagen fibers. Then add 78 neutralizing agent TJ-A819 to adjust the pH value to 4.5-5.5. Then use waterproof wetting agent BSQ to soak the sheepskin raw material at a water temperature of 25℃ to obtain the first semi-finished leather product. The deliming agent is DL828, which is used to neutralize the alkali within the hide and lower the pH value. It removes the lime bound to the hide, eliminates its swollen state, and causes the fiber structure to shrink, creating suitable pH conditions for enzyme softening and tanning. A pH reduction to 8-9 is a prerequisite for the next step of fine neutralization. Neutralizing agent TJ-A819 is a mixture of organic acids (such as formic acid and acetic acid) or acidic salts (such as sodium formate). It is a buffer-type neutralizing agent used to slowly and evenly lower the pH value of the inner and outer layers of the hide to a weakly acidic range. This pH range is the ideal environment for most subsequent tanning processes (especially chrome tanning) and the action of waterproofing materials. Uniform neutralization can prevent "surface over-tanning" and ensure uniform penetration of tanning agents and chemical materials. BSQ, a special waterproof wetting agent, is a surfactant with special functions. It is an organosilicon or fluorocarbon compound that has both wetting and waterproofing functions. It can effectively wet leather fibers at low water temperatures (25℃) and remove air between fibers. At the same time, its hydrophobic groups will attach to the fiber surface in advance, laying the foundation for subsequent waterproof retanning or fatliquoring processes, playing a synergistic role and making the final waterproof effect more durable and better.

[0025] S2. The first leather semi-finished product is subjected to basic tanning treatment using the target chromium-free tanning agent to obtain the second leather semi-finished product; The preparation method for the target chromium-free tanning agent is as follows: 30% chestnut tannin and 70% acrylic resin are mixed, and the pH of the solution is adjusted to 5.5 to obtain the target chromium-free tanning agent. The acrylic resin acts as a "leader" and "carrier," helping the chestnut tannin to penetrate and distribute better; while the chestnut tannin provides the main filling and skeletal function. This combination overcomes the shortcomings of using vegetable-tanned leather alone, such as hardening and uneven penetration, resulting in a leather blank with more balanced properties. Simultaneously, controlling the solution pH to 5.5, which is higher than the isoelectric point of collagen, allows the negatively charged leather fibers to penetrate evenly and slowly, rather than instantly binding on the surface. This ensures that the tanning agent can completely penetrate the cross-section of the leather, preparing for the subsequent full binding of tanning agent molecules with the fibers. If the pH is too low, the tanning agent will bind too quickly, leading to over-tanning on the surface and insufficient tanning inside.

[0026] The following is a brief description of the basic tanning process: Preparation: The first semi-finished leather product after pretreatment is put into the drum. It needs to be washed with water first to ensure that the pH and temperature of the leather blank are suitable.

[0027] Addition: Add the specified amount of the target chromium-free tanning agent solution. Control the bath ratio, temperature, and mechanical action.

[0028] Penetration stage: Under weakly acidic conditions (pH~5.5) and mechanical action, tanning agent molecules penetrate simultaneously from the grain and flesh layers of the hide into the interior. This process requires sufficient time to ensure complete and uniform penetration of the tanning agents.

[0029] Binding / Fixing Stage: In order to fully bind the tanning agent with the fiber and ultimately achieve the tanning effect, an acidifying agent (such as formic acid) is added at the end of the tanning process to slowly lower the pH of the system to 3.8-4.2.

[0030] Lowering the pH weakens the negative charge on collagen fibers, even turning them positively charged, while simultaneously reducing the ionization of tanning agent molecules. This reduces the charge repulsion between the fibers and the tanning agent, promoting the formation of hydrogen bonds, hydrophobic bonds, and other bonding mechanisms, thus firmly fixing the tanning agent molecules to the fibers and completing the tanning process.

[0031] Resting and subsequent processing: After tanning, the leather is removed from the drum and left to rest. This process allows the tanning reaction to continue and become homogenized, while also removing excess moisture. This results in the second semi-finished leather product.

[0032] S3. The second leather semi-finished product is retanned using the target retanning agent to obtain the third leather semi-finished product; Step S3 includes: S31. Mix the modified polysiloxane aqueous emulsion, aqueous anionic polyurethane dispersion, and aqueous acrylic resin dispersion, then add HL3634 and aqueous nitrocellulose, dilute with deionized water to the working solution concentration, then add water-soluble crosslinking agent and catalyst, stir for 10 minutes until uniform, and control the pH value of the solution to 6.0-7.0 to obtain a waterproof impregnation solution. The modified polysiloxane aqueous emulsion, aqueous anionic polyurethane dispersion, and aqueous acrylic resin dispersion are mixed in a ratio of 0.3:3.7:6. These three components together form the composite film-forming agent base of the impregnation liquid. The modified polysiloxane aqueous emulsion provides initial hydrophobicity and excellent smooth feel; the aqueous anionic polyurethane dispersion provides excellent elasticity, abrasion resistance, and toughness, compensating for the shortcomings of acrylic resin in terms of "hot stickiness and cold brittleness"; and the aqueous acrylic resin dispersion provides good permeability, adhesion, and cost-effectiveness. The mixture of the three components can form a complementary, strong, and flexible polymer network that wraps around the leather fibers, laying the foundation for subsequent waterproofing and flame retardancy. HL3634 is a fluorocarbon-based water and oil repellent agent. Its fluoroalkyl chains have extremely low surface energy, enabling leather fibers to achieve excellent water, oil, and stain repellency. It is key to achieving high hydrostatic pressure resistance (>100kPa), allowing water-based nitrocellulose to form a continuous, dense, glossy, and water-resistant film. Its addition here further enhances the density and water resistance of the composite film formed from acrylic / polyurethane / siloxane. Among them, the water-soluble crosslinking agent is an aziridine or carbodiimide crosslinking agent. The crosslinking agent molecule contains multiple active groups, which can chemically react with functional groups such as carboxyl (-COOH) and hydroxyl (-OH) of acrylic resin and polyurethane to form a strong three-dimensional network structure. This can greatly improve the physical strength, chemical resistance, hydrolysis resistance and durability of the polymer film, making the waterproof effect more durable. The catalyst is an organometallic catalyst, such as dibutyltin dilaurate or an acid catalyst, such as p-toluenesulfonic acid. The addition of the catalyst can reduce the reaction activation energy, accelerate and promote the chemical reaction between the crosslinking agent and the polymer, so that it can quickly complete the crosslinking at a lower temperature, improving production efficiency and quality stability. Specifically, the three main resins are first mixed to provide the base film. Then, fluorocarbon agent (HL3634) and nitrocellulose are added to enhance water resistance. Diluting with deionized water is used to control the concentration, ensuring a suitable penetration depth and preventing excessive concentration from causing surface film formation that hinders penetration. Finally, a crosslinking agent and catalyst are added to prevent premature reaction that could lead to working solution failure (premature crosslinking will cause the emulsion to break down and thicken). The pH is controlled to 6.0-7.0 (neutral): at this pH, the stability of components such as fluorocarbon agent and resin is optimal, and the charge state of the leather fiber surface is most conducive to the uniform penetration and initial adhesion of these anionic / nonionic materials.

[0033] S32. The second leather semi-finished product is retanned by the target retanning agent. In the early stage of retanning, the second leather semi-finished product is immersed in the waterproof impregnation liquid, which can withstand hydrostatic pressure >100kpa and stand for 15 minutes. The target retanning agent is either a synthetic tanning agent or a vegetable tanning agent, which can further improve the properties of the leather, such as increasing its fullness and softness. Synthetic tanning agents or vegetable tanning agents can be selected for the retanning process. Specifically, at the beginning of retanning, the leather is in a loose, open state with large gaps between fibers, which is most conducive to liquid penetration. At this time, the leather is immersed in the prepared working solution. With the help of mechanical rotation and JFC (Joint Fusion Mixture), functional polymers and auxiliaries are deeply and evenly carried into the leather fibers. A hydrostatic pressure resistance of >100 kPa is a process target to be achieved in the immersion process to ensure sufficient waterproofing agent is incorporated. A 15-minute settling period allows for sufficient penetration and adsorption, and initially, the immersion tank temperature is controlled at 30-35℃ to prevent premature resin curing due to high temperatures. The drum speed is 2-3 revolutions per minute to avoid excessive shearing that could damage the coating structure.

[0034] S33. During the retanning process, add the organophosphorus flame retardant in three separate applications at 20-minute intervals, adjusting the pH to 4.0-4.5 after each addition. Specifically, organophosphorus flame retardants are usually electrolytes, such as DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) and its derivatives, phosphate esters. Adding a large amount at once may cause demulsification, leading to process failure. Adding it slowly in stages can avoid this problem. Adjusting the pH to 4.0-4.5, that is, under acidic conditions, the charge on the surface of leather fibers changes from negative to positive. Anionic flame retardants, resins, fluorocarbons, etc. are more easily adsorbed and fixed by the fibers, rather than being washed away in subsequent washing. Acidic conditions are also conducive to the initial cross-linking reaction.

[0035] S34. Add a silicone-containing waterproofing agent in the later stage of retanning, rotate for 60 minutes and raise the temperature to 50°C, and control the pH value to be maintained at 4.2-4.5; Specifically, the silicone-containing waterproofing agent here can be a silicone waterproofing agent, which further consolidates the waterproofing effect. Heating to 50°C can accelerate molecular movement, promote the spreading and arrangement of the silicone agent on the fiber surface, and at the same time catalyze and accelerate the chemical reaction between the crosslinking agent and the polymer, making the waterproof membrane more robust.

[0036] S35. Add water-soluble crosslinking agent 30 minutes before the end of retanning, rotate for 30 minutes, and finally adjust the pH to 5.0-5.5 to promote the crosslinking reaction; Adding water-soluble crosslinking agent again 30 minutes before the end of the process ensures that there is enough fresh crosslinking agent to participate in the reaction. Slightly raising the pH from 4.0-4.5 can slow down the reaction rate and prevent the surface from being too fast to crosslink, resulting in insufficient internal crosslinking. This makes the crosslinking reaction more thorough and uniform. This pH value is also the storage pH of leather. Under these conditions, the crosslinking reaction will proceed slowly and thoroughly to the end, eventually forming a permanent three-dimensional network structure. At the same time, the slightly acidic environment is also most conducive to the long-term stability and feel of the leather.

[0037] S36. Add JFC throughout the retanning process, and air dry or dry at low temperature after retanning to obtain the third semi-finished leather product. Specifically, JFC here refers to the penetrant JFC, a nonionic surfactant whose main component is fatty alcohol polyoxyethylene ether. It can significantly reduce the surface tension of the working fluid, helping the impregnation liquid to penetrate more easily and evenly into the depths of the leather fiber structure, ensuring that the waterproof and flame-retardant treatment does not remain on the surface but reaches the interior, achieving an overall treatment effect. Natural air drying or low-temperature drying allows the waterproofing agent in the leather to form a waterproof structure between the fibers.

[0038] S4. The third semi-finished leather product is post-processed to obtain the fourth semi-finished leather product; Step S4 includes: The excess liquid in the third semi-finished leather product is removed by a roller press and the moisture content is controlled to be below 30%. Then, the third semi-finished leather product is washed with water until neutral. Unreacted substances are removed by squeezing out the water. Then, the third semi-finished leather product is dried with hot air at 80°C for 10 minutes in the initial drying stage. In the drying stage, it is cured with hot air at 90°C for 3-5 minutes to promote the cross-linking reaction. In the ironing stage, it is ironed at 85°C and 80 bar to obtain the fourth semi-finished leather product.

[0039] S5. The fourth semi-finished leather product is coated with a waterproof layer, a flame-retardant layer and a finishing layer to form a waterproof layer, a flame-retardant layer and a finishing layer on the surface of the fourth semi-finished leather product to obtain a fifth semi-finished leather product. The fifth semi-finished leather product is softened and finished to obtain a high-strength waterproof and flame-retardant garment leather product. Step S5 includes: S51. Mix 50% water, 5% P-4893, 40% Ground NC and 5% PU-2830, then add dyeing paste to obtain the first spray liquid. Spray the first spray liquid twice on the surface of the fourth leather semi-finished product and heat it at 80 degrees / 25KG for 5 seconds to form a waterproof layer on the surface of the fourth leather semi-finished product. Specifically, the purpose of spraying the first coating is to form a continuous, dense film, providing basic waterproofing performance. P-4893: waterborne polyurethane (PU) or acrylic resin, is a film-forming agent that acts as the skeleton of the coating layer, providing adhesion and basic physical properties. Ground NC: nitrocellulose emulsion, is a key component of the waterproof layer. Nitrocellulose forms a very glossy, hard, dense, and water-resistant film, providing excellent waterproofing and a good feel. PU-2830: a type of waterborne polyurethane resin, works synergistically with nitrocellulose to enhance the coating's toughness, folding resistance, and waterproof durability. Hot pressing (ironing) makes the film formed by nitrocellulose and polyurethane smoother and denser, greatly enhancing the waterproofing effect and gloss. The waterproof layer is mainly composed of nitrocellulose as its core, toughened by polyurethane, and forms a dense waterproof membrane after hot pressing.

[0040] S52, 20% water, 5% P-4893, 10% PU2204, 20% PU-43-116, 5% 1079, 5% RC2349, 5% SOFT-01, 10% NP-10, and 20% FC-300 are mixed, and then AKU and dyeing paste are added to obtain a second spray liquid. The second spray liquid is sprayed four times on the surface of the waterproof layer and dried at 90 degrees for 10 seconds to form a flame-retardant layer on the surface of the waterproof layer. The purpose of spraying the second coating liquid is to achieve multiple effects such as flame retardancy through various functional additives. PU2204: waterborne polyurethane resin, which is a soft type of PU, is used to provide the flexibility and feel required for the coating; PU-43-116: waterborne polyurethane resin. This is another type of PU, used to adjust film-forming properties and physical properties; 1079: a type of flame retardant, a phosphorus-nitrogen environmentally friendly flame retardant, and one of the core additives for achieving flame retardant function; RC2349: a type of flame retardant, another synergistic flame retardant, an antimony or boron flame retardant, used in combination with 1079 to achieve the best flame retardant effect; SOFT-01: softener, used to counteract the stiffness that may be caused by a large amount of flame retardant and resin, maintaining the softness of the leather; NP-10: emulsifier / penetrator, nonylphenol polyoxyethylene ether, helps the components in the formula to be evenly dispersed and may promote the penetration of the solution; FC-300: fluorocarbon compound water and oil repellent, a high-end water and stain repellent that can significantly improve the water, oil and stain repellency of leather; AKU: crosslinking agent, a aziridine or carbodiimide crosslinking agent. It can react with the carboxyl groups of resins (PU, acrylic) to form a three-dimensional network structure, which greatly improves the coating's water resistance, abrasion resistance, chemical resistance and durability. The flame retardant layer achieves its core flame retardant function by compounding multiple flame retardants (1079, RC2349), and uses fluorocarbon agent (FC-300) to enhance waterproofing, and crosslinking agent (AKU) to improve the durability of all properties.

[0041] S53, 20% water, 20% PU-43-116, 8% WT-13-097, 35% RU3904, 15% WT-72-586, and 2% WF-5230 are mixed to obtain a third spraying liquid. The third spraying liquid is sprayed twice on the flame-retardant layer surface, shaken to soften once, and then thrashed to soften for 2 hours. The surface is then lightly stretched to form a finishing layer, resulting in a fifth leather semi-finished product. The fifth leather semi-finished product is then softened to obtain a high-strength, waterproof, and flame-retardant garment leather finished product. The main purpose of this finishing layer is to impart the final feel and appearance effect. WT-13-097: wax emulsion, used to produce a moisturizing, waxy feel and increase the smoothness and water resistance of the surface; RU3904: polyurethane or acrylic resin, a filler resin used to improve the fullness of the leather; WT-72-586: waxy or silicone feel agent, a modified polysiloxane product used to provide a silky, delicate silicone feel; WF-5230: matting agent, a substance such as silica, used to reduce the gloss of the coating and produce a matte or semi-matte effect. Afterwards, the leather is softened by vibration and tumbling. The vibration softener softens the leather by bending and vibrating it; the tumbling softener beats the leather in a drum to make it softer and more natural to the touch. This finishing layer adjusts the final feel (waxy / silicone feel) and gloss (matte) through the combination of wax and feel agent (WT series), and achieves the ideal softness of the finished product through mechanical finishing.

[0042] In another embodiment of the present invention, a high-strength waterproof and flame-retardant garment leather is also provided, which is prepared by the preparation method of the high-strength waterproof and flame-retardant garment leather provided in Embodiment 1 above.

[0043] To verify the effectiveness of the present invention, the following test data of the finished garment leather products prepared by the method provided in Example 1 above will be provided: 1. Test Data 1: The test report is an SGS test report, report number SL92419280182801FW, and the report content is as follows: Test results: Azo Dyes & Amine Salts in Leather - Pass Bisphenols - Pass Chlorinated phenols in leather - Pass Hexavalent chromium (with aging test) - Pass Formaldehyde in Leather - Pass Organotin compounds - Non-textile - Pass Phthalates - Pass Polycyclic Aromatic Hydrocarbons (PAHs) - Pass Short-chain chlorinated paraffins (SCCP) - Leather - Pass Total Cadmium - Pass Total Lead (substrate) (Non-metallic materials) - Pass Total Lead (surface coating) - Pass Total Mercury – Pass Among them, Pass indicates that all meet the prescribed standards.

[0044] Specific content: Hexavalent chromium (CrVI) (including aging): Results: 1.0 mg / kg (regulatory limit: 3 mg / kg), spiked recovery: 88% (meets requirements, indicating that the test procedure is reliable); Formaldehyde: Result: 31 mg / kg (Regulatory limit: 75 mg / kg); Azo dyes and amine salts: None of the 24 restricted aromatic amines were detected (ND) (regulatory limit: 20 mg / kg); The requirement for an unlimited value for aniline also results in an ND (not specified) value. Total lead (substrate): Result: ND (<5 mg / kg) (Regulatory limit: 100 mg / kg); Total lead (surface coating): Result: ND (<5 mg / kg) (regulatory limit: 90 mg / kg); Bisphenols: Bisphenol A (BPA): ND (<0.1 mg / kg) (regulatory limit: 1 mg / kg); Bisphenol S (BPS): 2.0 mg / kg (no limit required); Bisphenol F (BPF): 3.0 mg / kg (no limit required); Other bisphenols (BPAF, BPB): ND; Polycyclic aromatic hydrocarbons (PAHs): None of the 18 PAHs were detected (ND); Total amount of the 18 PAHs: ND (regulatory limit: 10 mg / kg); Organotin compounds: All tested organotin compounds (such as TBT, DBT, TPhT, etc.) were not detected (ND) and were well below the limit.

[0045] Phthalate esters (plasticizers): None of the 23 phthalate esters were detected (ND) (<50 mg / kg); Total amount of the 23 phthalate esters: ND (regulatory limit: 1000 mg / kg) Chlorinated phenols: All tested chlorinated phenols (such as PCP, TeCP, TriCP, etc.) were not detected (ND) (<0.05 mg / kg), which is far below the limit; Short-chain chlorinated paraffins (SCCP) (Page 11): Results: ND (<50 mg / kg) (Regulatory limit: 1000 mg / kg); Total mercury: Result: ND (<0.1 mg / kg); Total cadmium: Result: ND (<5 mg / kg) (Regulatory limit: 75 mg / kg).

[0046] 2. Test Data Two: The test report is an SGS test report, report number SL92419280183601FW, and the report content is as follows: Test results: Colorfastness to Light (CF) - Pass Color fastness to rubbing (CF to Rubbing) - Pass Tape Test of Finish Adhesion - Pass Tear Strength of Leather - Pass Water Repellency / Spotting Test – Pass Among them, Pass indicates that all meet the prescribed standards.

[0047] Specific content: 1. Colorfastness to Light (CF) Test method: TPR-113, Xenon Arc Lamp; Result: After exposure to L-3 level sunlight, the color change level was 4.5; Requirement: Color change level ≥ 3.0.

[0048] 2. Color fastness to rubbing (CF to Rubbing) Test method: TPR-128 Dry grinding (After 50 cycles): Colour Change: Level 4.5 (Requirement: ≥ Level 3.5); Colour Staining: 4.5 (Requirement: ≥ 3.5); Wet milling (After 10 cycles): Colour Change: Level 4.5 (Requirement: ≥ Level 3.0); Colour Staining: 4.5 (Requirement: ≥ 3.0); 3. Tape Test of Finish Adhesion Test method: TPR-114, Method 1; Tape type: Scotch Brand Tape #810 Result: Color change level 4.5.

[0049] Requirement: Level 4.0 or higher.

[0050] 4. Tear Strength of Leather Test method: TPR-104 Longitudinal (Along): Thickness: 0.69 mm; Tear strength: 18 N (Requirement: ≥ 10 N); Across: Thickness: 0.67 mm; Tear strength: 16 N; 5. Water Repellency / Spotting Test Test method: TPR-117 30 minutes later: Physical Effects: No Adverse Effects (Requirement: No negative effects); 16 hours later: Physical Effects: No Adverse Effects (Requirement: No negative effects).

[0051] 3. Waterproof and flame retardant test Water resistance: Tested for water pressure resistance according to ASTM D3373 standard.

[0052] Flame retardancy: Vertical burning test (GB / T 2406).

[0053] Mechanical properties: Tear strength and elongation at break were tested using a universal testing machine; Test results show that: Waterproof: Withstands water pressure of 12,000 mm (ASTM D3373 standard), retains more than 90% of its strength after immersion in water for 24 hours.

[0054] Flame retardant: Certified as GB 8624 B1 level, with a limiting oxygen index (LOI) of 32.

[0055] Abrasion resistant: Taber friction coefficient <0.3 (ASTM D418), suitable for frequent wear.

[0056] In summary, after the above steps, the thickness of the waterproof layer of this high-strength, waterproof, and flame-retardant garment leather product is 0.5-1 μm, and the water permeability is <5×10⁻⁶. -7 g / ( m 2The flame-retardant layer exhibits a water pressure resistance of >10,000 mm, an oxygen index (OI) ≥35, a limiting oxygen index (LOI) ≥30, and a 40% reduction in peak heat release rate (HRP). Furthermore, its overall mechanical properties meet the requirements of a tear strength ≥80 N / cm and an elongation at break ≥15%. Compared to existing technologies, the finished product prepared by this invention withstands a water pressure of 12,000 mm (ASTM D3373 standard) and retains over 90% of its strength after immersion in water for 24 hours. It has passed GB 8624 B1 certification, achieving a limiting oxygen index (LOI) of 32. Its Taber friction coefficient is <0.3 (ASTM D418), making it suitable for frequent wear. The all-water-based process reduces VOC emissions by 90%. The flame retardant is a bamboo charcoal-based biomaterial with a biodegradability rate >80% (ISO). The application complies with the 14855 standard, and the cost of preparing the flame-retardant layer is reduced by 30% compared with the traditional method, the energy consumption of water-based coatings is reduced by 40%, and the production cycle is shortened by 30% after process integration (from the traditional 72h to 50h).

[0057] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing high-strength, waterproof, and flame-retardant garment leather, characterized in that, The method includes the following steps: S1. Obtain sheepskin raw material, degrease the sheepskin raw material with a degreasing agent, and immerse the degreased sheepskin raw material in liming solution to obtain the first semi-finished leather product. S2. The first leather semi-finished product is subjected to basic tanning treatment using the target chromium-free tanning agent to obtain the second leather semi-finished product; S3. The second leather semi-finished product is retanned using the target retanning agent to obtain the third leather semi-finished product; S4. The third semi-finished leather product is post-processed to obtain the fourth semi-finished leather product; S5. The fourth semi-finished leather product is coated with a waterproof layer, a flame-retardant layer, and a finishing layer to form a fifth semi-finished leather product on its surface. The fifth semi-finished leather product is then softened to obtain a high-strength, waterproof, and flame-retardant garment leather product.

2. The method for preparing high-strength, waterproof, and flame-retardant garment leather according to claim 1, characterized in that, Step S1 includes: The sheepskin raw material is soaked in an alkaline degreasing agent at a temperature of 50-60 degrees Celsius for 15 minutes to degrease it. After degreasing, add pancreatic enzyme and penetrant to hydrolyze the fat in the sheepskin raw material at a temperature of 35-40 degrees Celsius for 2-3 hours. Afterward, rinse the sheepskin pigment repeatedly with warm water until there is no greasy feeling. The rinsed sheepskin raw material is immersed in a liming solution for liming treatment, with the pH value controlled at 12-13, the temperature at 25-30 degrees Celsius, and the time at 8-12 hours. Add a deashing agent to adjust the pH value to 8-9, and evenly expand the collagen fibers. Then add 78 neutralizing agent TJ-A819 to adjust the pH value to 4.5-5.

5. After that, use waterproof wetting agent BSQ to soak the sheepskin raw material at a controlled water temperature of 25℃ to obtain the first semi-finished leather product.

3. The method for preparing high-strength, waterproof, and flame-retardant garment leather according to claim 1, characterized in that, The alkaline degreasing agent is 2-3% triethanolamine dodecylbenzenesulfonate, the penetrant is 0.3% leather surfactant 2047, the liming solution is an liming solution containing 2-3% sodium sulfide, and the deliming agent is DL828 reliming and deliming agent.

4. The method for preparing high-strength, waterproof, and flame-retardant garment leather according to claim 1, characterized in that, In step S2, the method for preparing the target chromium-free tanning agent is as follows: 30% chestnut tannin and 70% acrylic resin are mixed and the pH value of the solution is adjusted to 5.5 to obtain the target chromium-free tanning agent.

5. The method for preparing high-strength, waterproof, and flame-retardant garment leather according to claim 1, characterized in that, Step S3 includes: The modified polysiloxane aqueous emulsion, aqueous anionic polyurethane dispersion, and aqueous acrylic resin dispersion are mixed, then HL3634 and aqueous nitrocellulose are added, and deionized water is added to dilute to the working solution concentration. Then, water-soluble crosslinking agent and catalyst are added, and the mixture is stirred for 10 minutes until homogeneous. The pH value of the solution is controlled to 6.0-7.0 to obtain a waterproof impregnation solution. The second leather semi-finished product is retanned using the target retanning agent. In the initial stage of retanning, the second leather semi-finished product is immersed in the waterproof impregnation liquid, which can withstand hydrostatic pressure >100kpa and stand for 15 minutes. During the retanning process, the organophosphorus flame retardant is added in three separate applications at 20-minute intervals, and the pH is adjusted to 4.0-4.5 after each addition. Add a silicone-containing waterproofing agent during the later stage of retanning, rotate for 60 minutes and raise the temperature to 50°C, while controlling the pH value to be maintained at 4.2-4.5; Add a water-soluble crosslinking agent 30 minutes before the end of retanning, rotate for 30 minutes, and finally adjust the pH to 5.0-5.5 to promote the crosslinking reaction; JFC is added throughout the retanning process, and the leather is air-dried or dried at low temperature after retanning to obtain the third semi-finished leather product.

6. The method for preparing high-strength, waterproof, and flame-retardant garment leather according to claim 1, characterized in that, The target retanning agent is a synthetic tanning agent or a vegetable tanning agent.

7. The method for preparing high-strength, waterproof, and flame-retardant garment leather according to claim 1, characterized in that, The mixing ratio of modified polysiloxane aqueous emulsion, aqueous anionic polyurethane dispersion, and aqueous acrylic resin dispersion is 0.3:3.7:

6.

8. The method for preparing high-strength, waterproof, and flame-retardant garment leather according to claim 1, characterized in that, Step S4 includes: The excess liquid in the third semi-finished leather product is removed by a roller press and the moisture content is controlled to be below 30%. Then, the third semi-finished leather product is washed with water until neutral. Unreacted substances are removed by squeezing out the water. Then, the third semi-finished leather product is dried with hot air at 80°C for 10 minutes in the initial drying stage. In the drying stage, it is cured with hot air at 90°C for 3-5 minutes to promote the cross-linking reaction. In the ironing stage, it is ironed at 85°C and 80 bar to obtain the fourth semi-finished leather product.

9. The method for preparing high-strength, waterproof, and flame-retardant garment leather according to claim 1, characterized in that, Step S5 includes: Mix 50% water, 5% P-4893, 40% Ground NC, and 5% PU-2830, then add dye paste to obtain the first spray liquid. Spray the first spray liquid twice on the surface of the fourth leather semi-finished product and heat it at 80 degrees / 25KG for 5 seconds to form a waterproof layer on the surface of the fourth leather semi-finished product. Mix 20% water, 5% P-4893, 10% PU2204, 20% PU-43-116, 5% 1079, 5% RC2349, 5% SOFT-01, 10% NP-10, and 20% FC-300, then add AKU and dyeing paste to obtain a second spray liquid. Spray the second spray liquid four times on the surface of the waterproof layer and dry at 90 degrees for 10 seconds to form a flame-retardant layer on the surface of the waterproof layer. 20% water, 20% PU-43-116, 8% WT-13-097, 35% RU3904, 15% WT-72-586, and 2% WF-5230 are mixed to obtain a third spraying liquid. The third spraying liquid is sprayed twice on the flame-retardant layer surface, shaken to soften once, and then thrashed to soften for 2 hours. The surface is then lightly stretched to form a finishing layer, resulting in a fifth semi-finished leather product. The fifth semi-finished leather product is then softened and finished to obtain a high-strength, waterproof, and flame-retardant garment leather product.

10. A high-strength, waterproof, and flame-retardant garment leather, wherein the high-strength, waterproof, and flame-retardant garment leather is prepared by the preparation method of the high-strength, waterproof, and flame-retardant garment leather as described in any one of claims 1-9.

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