A method for preparing a car seat leather

Abstract

This invention relates to the field of automotive interior materials technology, specifically to a method for preparing automotive seat leather. The method includes the following steps: pretreating raw hides; tanning the pretreated raw hides with an epoxy organic tanning agent, followed by retanning, dyeing, fatliquoring, fixation, and formaldehyde removal to obtain a finished leather blank; and then pretreating the finished leather blank, followed by applying a base coat, intermediate coat, and top coat to obtain leather. This invention uses an epoxy organic tanning agent to tan the pretreated raw hides, followed by retanning, dyeing, fatliquoring, fixation, and formaldehyde removal to obtain a finished leather blank; this method can balance the environmental friendliness, softness, and mechanical properties of the leather.

Description

Technical Field

[0001] This invention relates to the field of automotive interior materials technology, specifically to a method for preparing automotive seat leather. Background Technology

[0002] With the rapid development of the automotive industry, genuine leather seats have become a core component of car interiors due to their superior feel and texture. Consumers are also placing higher demands on the environmental safety, physical and mechanical properties, and skin-friendly comfort of automotive leather. Currently, the industrial production of automotive seat leather still mainly relies on the traditional chrome tanning process. This process uses chromium salts as the core tanning agent, which, while meeting basic physical property requirements, is prone to problems such as hexavalent chromium residue and heavy metal wastewater pollution. Furthermore, the accompanying metal complex dyes and aldehyde-containing auxiliaries can easily introduce allergens and VOCs, making it difficult to meet stringent international environmental standards such as OEKO-TEX baby contact grade.

[0003] Chinese invention patent application CN106755630A discloses a leather tanning method that uses a combination of vegetable tanning agents and aluminum tanning agents to replace chromium metal tanning agents. This method can eliminate the environmental and human health hazards of chromium salts to a certain extent, representing an important exploration in the field of chromium-free tanning. However, this solution still has significant shortcomings: First, the use of metal-based tanning agents such as aluminum salts in the process makes it impossible to achieve complete metal-free production, which is insufficient to meet the environmental protection requirements of zero heavy metals for high-end automotive interiors. Second, this solution is only developed for general-purpose leather and does not meet the special performance requirements of automotive seat leather, such as high abrasion resistance, light resistance, and aging resistance. Third, it does not control aldehyde and VOC residues in the leather and does not address the industry pain point of balancing the skin-friendly feel and physical properties of leather, thus failing to meet the market demand for high-end automotive interiors. Summary of the Invention

[0004] This invention provides a method for preparing automotive seat leather, comprising the following steps: pre-treating raw hides; tanning the pre-treated raw hides with an epoxy organic tanning agent, followed by retanning, dyeing, fatliquoring, fixing, and formaldehyde removal, and obtaining finished leather blanks through post-treatment; after pre-treating the finished leather blanks, applying a base coat, a middle coat, and a top coat to the pre-treated finished leather blanks in sequence to obtain leather.

[0005] Current automotive seat leather manufacturing processes primarily rely on traditional chrome tanning, supplemented by metal-based composite tanning solutions. This not only presents environmental risks such as hexavalent chromium residue and heavy metal wastewater pollution, making complete metal-free production impossible, but also suffers from the industry pain point of balancing leather's softness and skin-friendliness with its tensile and tear resistance. Furthermore, it raises concerns about aldehydes and VOCs. The current system lacks comprehensive control over harmful substances, making it difficult to meet the stringent environmental and performance requirements of high-end automotive interiors. This invention uses epoxy organic tanning agents to tan pre-treated raw hides, followed by retanning, dyeing, fatliquoring, fixation, and formaldehyde removal to obtain the finished leather. The multifunctional synthetic tanning agents in the epoxy organic tanning agents undergo multi-point covalent cross-linking reactions with the amino, hydroxyl, and carboxyl groups on the collagen fiber molecular chains of the raw hide, constructing a stable three-dimensional network structure between the collagen fibers. This completely replaces the coordination and cross-linking effect of traditional metal tanning agents, eliminating the risk of heavy metal residues at the source. The combination of natural tanning agents and amine accelerators further enhances the efficiency of the cross-linking reaction, making the collagen fiber weave structure more uniform and dense, thus providing a solid foundation for excellent mechanical properties in the leather. Subsequent processing strictly follows the specific sequence of retanning, dyeing, fatliquoring, fixation, and formaldehyde removal. The retanning process introduces… Bio-based hyperbranched polymers rich in carboxyl and hydroxyl groups can form secondary crosslinks with epoxy-crosslinked modified collagen fibers. This further strengthens the fiber structure and provides ample binding sites for subsequent dyes and fatliquoring agents, ensuring dyeing uniformity and oil-oil binding fastness. Natural oils and synthetic fatliquoring agents introduced during the fatliquoring process can evenly penetrate the gaps between collagen fibers, lubricating and dispersing the fiber bundles, giving the leather excellent softness and fullness. The fixing process precisely controls the system pH using organic acids, making the binding of functional components such as tanning agents, dyes, and fatliquoring agents with collagen fibers more stable and preventing component loss in subsequent processes that could affect leather performance. The formaldehyde removal stage, placed after the fixing process, thoroughly captures free aldehydes in the system without damaging the previously constructed collagen crosslinking structure and the binding stability of functional components, thus achieving formaldehyde and VOC removal. It achieves efficient and deep removal of harmful substances while avoiding defects such as loose leather surface, uneven color, insufficient fullness, and hard feel caused by pre-formaldehyde removal process. Finally, through covalent cross-linking modification of epoxy organic tanning agents and precise synergistic control of the entire process sequence, it achieves simultaneous optimization of the structural strength of leather collagen fibers and the lubrication and dispersion effect between fibers, perfectly balancing the leather's softness and skin-friendliness with its tensile, tear, and abrasion resistance mechanical properties, while meeting the stringent environmental protection requirements of high-end automotive interiors for zero heavy metals, low VOCs, and low formaldehyde.

[0006] The tanning process is carried out at a temperature of 30-40℃ for 4-8 hours, with a pH of 3.5-4.0.

[0007] The retanning process is carried out at a temperature of 35-40℃ for 1-2 hours, with a pH of 4.5-5.5.

[0008] The staining temperature is 60-70℃, the time is 1-1.5h, and the pH is 3.5-4.0.

[0009] The fatliquoring temperature is 55-65℃, the time is 60-90 min, and the pH is 3.5-4.5.

[0010] The formaldehyde removal temperature is 40-50℃, and the treatment time is 60-90 minutes.

[0011] By weight, the components of the epoxy organic tanning agent include: 20-30 parts of synthetic tanning agent, 5-15 parts of natural tanning agent, and 1-5 parts of accelerator.

[0012] The accelerator includes at least one of triethanolamine, triisopropanolamine, N-methyldiethanolamine, N,N-dimethylethanolamine, diethanolamine, triethylamine, 2-methylimidazole, and tetramethylethylenediamine.

[0013] The synthetic tanning agent includes at least one of ethylene glycol diglycidyl ether, glycerol triglycidyl ether, 1,4-butanediol diglycidyl ether, trimethylolpropane triglycidyl ether, 1,6-hexanediol diglycidyl ether, pentaerythritol tetraglycidyl ether, polyethylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, sorbitol polyglycidyl ether, and polyglycerol polyglycidyl ether.

[0014] Optionally, the synthetic tanning agent includes ethylene glycol diglycidyl ether and glycerol triglycidyl ether.

[0015] Optionally, the mass ratio of ethylene glycol diglycidyl ether to glycerol triglycidyl ether is (1-4):1.

[0016] The retanning step uses retanning materials for retanning, and the components of the retanning materials, by weight, include: 100-150 parts water; 5-15 parts synthetic tanning agent; 2-8 parts natural tanning agent; 3-10 parts hyperbranched polymer; 1-5 parts auxiliary fatliquoring agent; and 0.5-3 parts pH adjuster.

[0017] The hyperbranched polymer is prepared by modification with starch, lignin, or tannic acid.

[0018] Optionally, the hyperbranched polymer contains carboxyl and hydroxyl groups.

[0019] The synthetic tanning agent includes aromatic sulfonate condensates and acrylic copolymers. The auxiliary fatliquoring agent includes natural plant oils or synthetic fatliquoring agents.

[0020] The natural tanning agent includes at least one of the following: tara tannin, vitex bark tannin, chestnut tannin, hardwood tannin, larch tannin, bayberry tannin, rubber tannin, amla tannin, cardamom tannin, and red root tannin.

[0021] The dyeing step uses a dye for dyeing, and the dye components, by weight, include: 100-150 parts water, 1-5 parts non-azo acid dye, 0.5-3 parts non-metallic complex dye, 1-3 parts surfactant, 0.5-1 part bio-based penetrant, 0.5-3 parts fixative, and 0.5-3 parts pH adjuster. The non-azo acid dye is selected from at least one of anthraquinones, triphenylmethanes, and indigo groups.

[0022] The surfactant includes at least one of nonionic or anionic surfactants.

[0023] The fatliquoring step uses fatliquoring materials for fatliquoring. By weight, the fatliquoring materials consist of: 100-150 parts water, 2-8 parts natural oils, 5-10 parts fatliquoring agent, and 1-3 parts fixative.

[0024] The fatliquoring agent includes at least one of phosphorylated, sulfonated, and sulfite-treated synthetic fatliquoring agents.

[0025] The natural oils include at least one of castor oil, refined rapeseed oil, sunflower oil, soybean oil, palm oil, flaxseed oil, olive oil, tea seed oil, coconut oil, refined tallow, and lanolin.

[0026] The fixation step uses a fixation material for fixation. By weight, the fixation material comprises: 100-150 parts water, 1-3 parts fixative, and 0.5-5 parts pH adjuster; the fixative includes organic acids.

[0027] The organic acid includes at least one of formic acid, acetic acid, lactic acid, citric acid, and oxalic acid.

[0028] The pH adjuster includes at least one of sodium formate, sodium acetate, sodium citrate, sodium bicarbonate, sodium carbonate, sodium lactate, and disodium hydrogen phosphate.

[0029] The formaldehyde removal step uses a formaldehyde removal agent to remove formaldehyde, and the formaldehyde removal agent includes a polyamine compound with not less than 3 amino groups.

[0030] Optionally, the formaldehyde removal agent includes at least one of diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, and tri(2-aminoethyl)amine.

[0031] The pretreatment steps for the finished leather blanks include: washing the formaldehyde-removed leather blanks with water, removing them from the drum, letting them stand overnight, drying them to a humidity of 10-16%, letting them stand to regain moisture, softening them by shaking or tumbling, and trimming and finishing them to obtain the finished leather blanks.

[0032] The number of vibrations is 2-4 times.

[0033] The primer is applied by roller coating and has a wet weight of 8-15 g / sf.

[0034] The primer coating formulation, by weight, is as follows: 80-120 parts water, 400-800 parts water-based resin, 100-130 parts pigment paste, and 20-40 parts crosslinking agent.

[0035] The aqueous resin is selected from at least one of the following grades: Stahl UP-B, Stahl UP-C, Stahl UP-D, Stahl UP-E, Stahl UP-F, Stahl UP-G.

[0036] The crosslinking agent includes polycarbodiimide, selected from at least one of the following brands: Stahl XR-5530, Stahl XR-5535, Stahl XR-5540, Stahl XR-5545, Stahl XR-5550.

[0037] The intermediate coating is applied by roller coating, with a wet weight of 2-6 g / sf.

[0038] The coating formulation for the intermediate coat, by weight, is as follows: 80-120 parts water, 250-300 parts aliphatic polyurethane resin, 10-30 parts silicone-based hand feel agent, 400-600 parts matting agent, 100-130 parts pigment paste, and 60-80 parts aliphatic polyisocyanate crosslinking agent.

[0039] The top coating is applied by spraying and has a wet weight of 1-5 g / sf.

[0040] The coating formula for the topcoat, by weight, is as follows: 100-150 parts water, 200-600 parts matting agent, 170 parts aliphatic polyester brightening agent, 60-100 parts silicone hand feel agent, 10-20 parts pigment paste, and 70-100 parts aliphatic polyisocyanate crosslinking agent.

[0041] The aliphatic polyurethane resin is selected from at least one of the following grades: Stahl WT06B, Stahl WT06C, Stahl WT06D, Stahl WT06E, Stahl WT06F, and Stahl WT06G.

[0042] The matting agent is selected from at least one of the following brands: Stahl WT492, Stahl WT985, Stahl WT493, Stahl WT494, Stahl WT986, Stahl WT987, Stahl WT988.

[0043] The brightening agent is selected from at least one of the following brands: Stahl WT433, Stahl WT434, Stahl WT435, Stahl WT436, Stahl WT437, Stahl WT438.

[0044] The silicon-based tactile agent is selected from the Stahl HM series.

[0045] Optionally, the silicone-based feel agent in the coating formulation used for the topcoat is selected from Stahl HM720 and Stahl HM377, and the weight ratio of Stahl HM720 to Stahl HM377 is 1:(1-2).

[0046] Beneficial effects 1. This invention uses epoxy organic tanning agents to tan pretreated raw hides, followed by retanning, dyeing, fatliquoring, fixation, and formaldehyde removal to obtain finished leather blanks; it can balance the environmental friendliness, softness, and mechanical properties of leather.

[0047] 2. This invention, through standardized pretreatment procedures and precise moisture content control, can ensure the stability of the collagen fiber structure of the raw material, providing a high-quality base for subsequent coating processes.

[0048] 3. By controlling the number of times the leather is softened by vibration / thumping, this invention can maintain the integrity of the collagen fiber structure while ensuring the softness of the leather, thus balancing the feel and mechanical properties.

[0049] 4. This invention, through roller coating process and precise wet weight control, can form a uniform, continuous, and highly adhesive base coating, balancing the abrasion resistance and soft feel of leather.

[0050] 5. By precisely controlling the tanning process parameters, this invention can ensure that epoxy organic tanning agents and collagen fiber active groups undergo efficient and uniform multi-point covalent cross-linking, constructing a stable three-dimensional network structure, and ensuring the mechanical properties and subsequent processing performance of the leather.

[0051] 6. By precisely controlling the compounding ratio of the two silicone-based feel agents in the topcoat step, this invention can simultaneously optimize the skin-friendly feel of leather, the abrasion resistance of the coating, and the color fastness. Detailed Implementation

[0052] A method for preparing automotive seat leather includes the following steps: Step 1: Soak the raw hides in water, remove hair, ash, peel, deash, soften, and acid soak.

[0053] Step 2: The pretreated raw hide is tanned using an epoxy organic tanning agent. After tanning, the hide is removed from the drum, allowed to stand, shaved evenly, and weighed to obtain wet white hide. The epoxy organic tanning agent comprises, by weight, 25 parts of synthetic tanning agent (a mixture of ethylene glycol diglycidyl ether and glycerol triglycidyl ether in a mass ratio of 2.5:1), 10 parts of natural tanning agent (tara tannin), and 3 parts of accelerator (triethanolamine). The tanning temperature is 30-40℃, the time is 4-8 hours, and the pH is 3.5-4.0.

[0054] Step 3: The wet white leather is placed in a drum and retanned using a retanning material to obtain a retanned leather blank. The retanning material comprises, by weight, 135 parts water; 8 parts synthetic tanning agent (selected from aromatic sulfonate condensates and acrylic copolymers, models: Tanicor MLB, Relugan Soft AP); 4.5 parts natural tanning agent (tara tannin); 6.5 parts hyperbranched polymer (a hyperbranched polymer prepared by modifying natural materials (such as starch, lignin, and tannic acid), rich in carboxyl and hydroxyl groups, model: MABRATAN PF LIQ); 2.5 parts auxiliary fatliquoring agent (natural vegetable oil or synthetic fatliquoring agent, model: Prinol EMS); and 1.5 parts pH adjuster (sodium formate). The retanning temperature is 35-40℃, the time is 1-2 hours, and the pH is 4.5-5.5.

[0055] Step 4: The retanned hide is placed in a drum for dyeing to obtain the dyed hide. The dye composition, by weight, is as follows: 135 parts water, 2.5 parts non-azo acid dye (selected from anthraquinone, triphenylmethane, and indigo groups, model: Meliodern HF Black R p), 1 part non-metallic complex dye (Coriacide Black AF 135P), 1.2 parts leveling agent (nonionic or anionic surfactant, model: Sincal MS), 0.8 parts bio-based penetrant (model: MARALEN POL), 1 part fixative (85wt% formic acid aqueous solution), and 1.5 parts pH adjuster (sodium formate). The dyeing temperature is 60-70℃, the time is 1-1.5 hours, and the pH is 3.5-4.0.

[0056] Step 5: The dyed hide blank is placed in a rotating drum and fatliquoring material is added for fatliquoring to obtain the fatliquored hide blank. The fatliquoring material comprises, by weight, 135 parts water, 4.5 parts natural oil (castor oil), 8 parts synthetic fatliquoring agent (selected from phosphorylated, sulfonated, and sulfite-treated synthetic fatliquoring agents, model: Polyol CT 688), and 1 part fixative (85wt% formic acid aqueous solution). The fatliquoring temperature is 55-65℃, the time is 60-90 min, and the pH is 3.5-4.5.

[0057] Step 6: The fatliquored leather blanks are sequentially fixed and deformaldehyde-removed to obtain semi-finished leather blanks. By weight, the materials used for fixing include 135 parts water, 1 part fixative (85wt% formic acid aqueous solution), and pH adjuster (sodium formate). The fixing and deformaldehyde-removal steps are as follows: the fatliquored leather blanks are immersed in the fixing materials, and the pH is adjusted to 4.0 using the pH adjuster for material fixing; subsequently, a deformaldehyde remover (diethylenetriamine) is added for deformaldehyde removal; the amount of deformaldehyde remover added is 1wt% of the dry weight of the leather blanks, the deformaldehyde removal temperature is 40-50℃, and the treatment time is 60-90 minutes.

[0058] Step 7: Wash the semi-finished leather blanks with water, remove them from the drum, let them rest overnight, then dry them to a humidity of 12-14%, let them rest to regain moisture, then shake them to soften them 3 times, and trim and finish them to obtain the finished leather blanks.

[0059] Step 8: After pre-treating the finished leather blank (softening by drum tumbling and mechanical vibration), the finished leather blank is coated. The coating process includes base coat, intermediate coat and top coat in sequence to obtain leather.

[0060] After the primer is applied, the mixture is left to stand (8 hours) and then softened by repeated shaking before applying the intermediate coat.

[0061] After top coating, let it stand and hang to dry for 24 hours. After shaking to soften and flatten, you will get leather.

[0062] The primer is applied by roller coating, with a wet weight of 10 g / sf. The primer formulation is as follows: 100 parts water, 420 parts water-based primer resin (Stahl UP-B), 230 parts aliphatic polyurethane resin (Stahl RU537), 120 parts pigment paste (Stahl PP series water-based pigment paste), and 30 parts crosslinking agent (polycarbodiimide: Stahl XR-5525).

[0063] The intermediate coat is applied by roller coating, with a wet weight of 3.5 g / sf. By weight, the coating formulation of the intermediate coat is as follows: 120 parts water, 220 parts aliphatic polyurethane resin (Stahl WT06B), 15 parts silicone-based hand feel agent (Stahl HM series), 480 parts matting agent (220 parts Stahl WT492, 260 parts Stahl WT985), 120 parts pigment paste (Stahl PP series water-based pigment paste), and 65 parts aliphatic polyisocyanate crosslinking agent (Stahl XR85).

[0064] The topcoat is applied by spraying, with a wet weight of 2.8 g / sf. The coating formula for the topcoat is as follows (by weight): 125 parts water, 480 parts matting agent (220 parts Stahl WT492 and 260 parts Stahl WT985), 170 parts aliphatic polyester brightening agent (Stahl WT433), 80 parts silicone hand feel agent (35 parts Stahl HM720 and 45 parts HM377), 15 parts pigment paste (Stahl PP series water-based pigment paste), and 85 parts aliphatic polyisocyanate crosslinking agent (Stahl XR85).

[0065] Comparative Example 1 The specific implementation method is the same as in Example 1, except that the formaldehyde removal step is performed after retanning.

[0066] Comparative Example 2 The specific implementation method is the same as in Example 1, except that the formaldehyde removal step is performed after dyeing.

[0067] Comparative Example 3 The specific implementation method is the same as in Example 1, except that the formaldehyde removal step is performed after fat addition.

[0068] Comparative Example 4 The specific implementation method is the same as in Example 1, except that the formaldehyde removal step is performed before coating the finished leather blank.

[0069] Comparative Example 5 The specific implementation method is the same as in Example 1, except that the formaldehyde removal step is not performed.

[0070] Comparative Example 6 The specific implementation method is the same as in Example 1, except that no fixed steps are performed.

[0071] Comparative Example 7 The specific implementation method is the same as in Example 1, except that the silicone-based hand feel agent in the coating formulation used for the topcoat consists of 20 parts Stahl HM720 and 60 parts HM377.

[0072] Comparative Example 8 The specific implementation method is the same as in Example 1, except that the silicone-based hand feel agent in the coating formula used for the topcoat is adjusted to 100 parts, which consists of 60 parts Stahl HM720 and 40 parts HM377.

[0073] Comparative Example 9 The specific implementation method is the same as in Example 1, except that the silicone-based hand feel agent in the coating formula used for the topcoat is adjusted to 80 parts, which consists of 50 parts Stahl HM720 and 30 parts HM377.

[0074] Comparative Example 10 The specific implementation method is the same as in Example 1, except that the silicone-based hand feel agent in the coating formulation used for the topcoat is adjusted to 100 parts, which consists of 30 parts Stahl HM720 and 70 parts HM377.

[0075] Comparative Example 11 The specific implementation method is the same as in Example 1, except that the pH of the tanning process is 3.0.

[0076] Comparative Example 12 The specific implementation method is the same as in Example 1, except that the pH of the tanning process is 5.0.

[0077] Comparative Example 13 The specific implementation method is the same as in Example 1, except that the drying is carried out to a humidity of 8%.

[0078] Comparative Example 14 The specific implementation method is the same as in Example 1, except that the drying is carried out to a humidity of 18%.

[0079] Comparative Example 15 The specific implementation method is the same as in Example 1, except that the wet weight of the primer is 6 g / sf.

[0080] Comparative Example 16 The specific implementation method is the same as in Example 1, except that the wet weight of the primer is 16 g / sf.

[0081] Comparative Example 17 The specific implementation method is the same as in Example 1, except that step 7 does not involve vibration softening.

[0082] Comparative Example 18 The specific implementation method is the same as in Example 1, except that the number of vibrations in step 7 is adjusted to 5.

[0083] Performance testing methods 1. The leather prepared in Example 1 was subjected to performance testing. The test data are listed in Table 1, where ND indicates not detected.

[0084] 2. The leathers prepared in Comparative Examples 1-4 were subjected to performance tests, and the test data are listed in Table 2. 3. The leathers prepared in Comparative Examples 5-6 were subjected to performance tests, and the test data are listed in Table 3. 4. The leathers prepared in Comparative Examples 7-10 were subjected to performance tests, and the test data are listed in Table 4. 5. The leathers prepared in Comparative Examples 11-18 were subjected to performance tests, and the test data are listed in Table 5. Table 1

[0085] Table 2

[0086] Table 3

[0087] Table 4

[0088] Table 5

[0089] As shown in Tables 1-5, the automotive seat leather prepared in Example 1 of this invention, after performance testing, fully meets the requirements of relevant standards such as TL 52064, OEKO-TEX, and VDA270 in terms of its physical and mechanical properties (softness, abrasion resistance, folding resistance, tensile and tear strength), environmental indicators (formaldehyde, VOC, heavy metals, azo dyes, etc.), and comprehensive performance (color fastness, stain resistance, odor level, etc.). Many indicators far exceed the standard limits, with formaldehyde content as low as 0.03 mg / m³. 3 VOCs are only 0.2 mg / m³ 3 Heavy metals and azo dyes were not detected. The coating showed no damage after 2000 Taber abrasion tests and 100,000 normal folding tests, demonstrating excellent overall performance. However, all comparative examples exhibited varying degrees of performance defects after adjusting core process parameters and the order of procedures. Comparative examples 1-4, which placed the formaldehyde removal process before retanning, dyeing, fatliquoring, or finishing, all showed defects in appearance and feel, such as loose leather surface, uneven coloring, insufficient fullness, and a stiff leather body. Furthermore, formaldehyde and VOC content significantly exceeded standards, and tear strength and softness also decreased to varying degrees. Comparative example 5, which did not include a formaldehyde removal step, had a formaldehyde content as high as 5.2 mg / m³. 3The following issues were found: In Comparative Example 6, omitting the fixed steps resulted in excessive sour odor in the leather, substandard tensile and tear strength, flat and stiff leather, and poor smoothness. In Comparative Examples 7-10, adjusting the compound ratio of the top-coated silicone hand feel agents HM720 and HM377 resulted in excessive stickiness coefficient, decreased coating abrasion resistance, and substandard wet and dry color fastness, failing to balance hand feel and coating performance. In Comparative Examples 11-12, deviating from the tanning pH range of 3.5-4.0 resulted in defects such as sticky leather surface, insufficient fiber swelling, and stiff, shrinking, and cracked leather blanks. In Comparative Examples 13-14, deviating from the drying humidity range of 12-14% resulted in fiber embrittlement, substandard dryness and softness, and increased fiber looseness and loose surface rate. In Comparative Examples 15-16, the wet weight of the base coating exceeded the range of 8-15 g / sf, resulting in an excessively thin coating exposing the base and reduced abrasion resistance, and a thickened, stiff coating with increased loose surface rate. In Comparative Example 17… Without vibration softening treatment, the leather's softness cannot meet the standard. In Comparative Example 18, excessive vibration softening caused excessive fiber loosening and breakage, loose surface defects, and increased production energy consumption. This fully demonstrates the crucial role of precise control of process parameters and process sequence in the comprehensive performance of leather.

Claims

1. A method for preparing automotive seat leather, characterized in that, Includes the following steps: Raw hides are pretreated; epoxy organic tanning agents are used to tan the pretreated raw hides, followed by retanning, dyeing, fatliquoring, fixation, and aldehyde removal to obtain finished hide blanks; after pretreatment, the finished hide blanks are coated with base coat, intermediate coat, and top coat to obtain leather.

2. The preparation method according to claim 1, characterized in that, The pretreatment steps for the finished leather blanks include: washing the finished leather blanks with water, removing them from the drum, letting them stand, drying them to a humidity of 10-16%, letting them stand to regain moisture, and then softening them by shaking or tumbling.

3. The preparation method according to claim 2, characterized in that, The number of times the material is vibrated or dropped to soften it is 2-4 times.

4. The preparation method according to claim 1, characterized in that, The tanning process is carried out at a temperature of 30-40℃ for 4-8 hours, with a pH of 3.5-4.

0.

5. The preparation method according to claim 1, characterized in that, The primer is applied by roller coating and has a wet weight of 8-15 g / sf.

6. The preparation method according to claim 1, characterized in that, By weight, the components of the epoxy organic tanning agent include: 20-30 parts of synthetic tanning agent, 5-15 parts of natural tanning agent, and 1-5 parts of accelerator.

7. The preparation method according to claim 1, characterized in that, The retanning step uses a retanning material for retanning, which, by weight, comprises: 100-150 parts water, 5-15 parts synthetic tanning agent, 2-8 parts natural tanning agent, 3-10 parts hyperbranched polymer, 1-5 parts auxiliary fatliquoring agent, and 0.5-3 parts pH adjuster.

8. The preparation method according to claim 1, characterized in that, The fixation step uses a fixation material for fixation. By weight, the fixation material comprises: 100-150 parts water, 1-3 parts fixative, and 0.5-5 parts pH adjuster; the fixative includes organic acids.

9. The preparation method according to claim 1, characterized in that, The formaldehyde removal step uses a formaldehyde removal agent to remove formaldehyde, and the formaldehyde removal agent includes a polyamine compound with not less than 3 amino groups.

10. The preparation method according to claim 1, characterized in that, The coating used in the topcoat includes a silicone-based hand-feel agent, the brand of which is selected from Stahl HM720 and Stahl HM377, and the weight ratio of Stahl HM720 to Stahl HM377 is 1:(1-2).

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