Preparation method of polyester nylon composite fiber and preparation method of synthetic leather of polyester nylon composite fiber

Abstract

The invention discloses a preparation method of polyester nylon composite fiber and synthetic leather, polyamide is modified by cationized graphene oxide, and a coaxial spinning structure is adopted, so that positive charges are given to graphene oxide to preliminarily reduce agglomeration and improve dispersity; by means of cationization, graphene oxide and negatively charged dye molecules form strong electrostatic interaction in a shell layer, so that dye adsorption uniformity and binding force are enhanced, the dyeing effect and color fastness are improved, meanwhile, graphene oxide is well dispersed in a polyamide matrix, and the mechanical strength is improved through the nanometer enhancement effect; the coaxial design of the cross-shaped core layer and the circular shell layer synergistically optimizes the stress distribution and surface characteristics of the fiber, and finally realizes multiple improvements of mechanical properties, dyeing depth and durability; the cross-shaped core layer structure provides a huge anchoring surface and a capillary channel for subsequent infiltration of polyvinyl alcohol and polyurethane, and the mechanical occlusion and chemical bonding strength between the polyurethane and the fiber is enhanced.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and more particularly to a method for preparing polyester nylon composite fibers and synthetic leather thereof. Background Technology

[0002] Synthetic leather, as an ideal substitute for natural leather, has been widely used in footwear, bags, clothing, automotive interiors, and many other fields due to its ability to effectively avoid environmental pollution and animal welfare issues during production, as well as its customizable properties. Among these, synthetic leather based on polyester and nylon composite fibers has become an important direction in the development of high-performance synthetic leather because it can achieve a soft feel comparable to natural leather, excellent mechanical strength and breathability through special spinning and post-processing techniques, and can be given rich color expression through refined dyeing. The preparation of this type of synthetic leather typically involves complex processes such as co-extrusion spinning of multi-component fibers, web formation, pre-impregnation of nonwoven fabrics and polyurethane impregnation, formation of microfibers, dyeing, and surface coating, aiming to endow the final product with superior comprehensive performance.

[0003] In existing technologies, researchers have attempted to introduce nanoscale functional fillers to further improve the mechanical properties, durability, and functionality of polyester-nylon composite fiber synthetic leather. Graphene oxide (GO), with its unique two-dimensional sheet structure, extremely high specific surface area, excellent mechanical properties, and multifunctional surface functional groups, is considered a highly promising reinforcing material. However, the dispersion stability of unmodified GO in polymer spinning solutions is an inherent contradiction that urgently needs to be addressed. The surface of GO sheets is rich in oxygen-containing functional groups such as carboxyl, hydroxyl, and epoxy groups, giving it a certain degree of hydrophilicity in polar solvents. However, the strong π-π stacking and hydrogen bonding between these functional groups and between GO sheets cause GO to readily aggregate in polymer solutions. This aggregation is particularly pronounced in high-concentration or long-term stored spinning solutions. Aggregated GO not only struggles to achieve uniform dispersion, forming macroscopic aggregates of varying sizes, but these aggregates also cannot be effectively incorporated into the fiber interior or uniformly distributed throughout the fiber cross-section during subsequent spinning.

[0004] Furthermore, in the polyurethane impregnation process of synthetic leather, especially when cationic waterborne polyurethane is used as the impregnating agent, there is limited electrostatic attraction or even local repulsion between the anionic surface of GO and the cationic polyurethane, which limits the formation of strong chemical or physical bonds between GO and the polyurethane matrix.

[0005] The aforementioned technical contradictions—namely, the inherent dispersion stability of unmodified graphene oxide in polymer spinning solutions and its fundamental limitations in interfacial bonding with polymers—constitute the key challenges that urgently need to be addressed in the existing technology.

[0006] Therefore, overcoming the tendency of graphene oxide to agglomerate in spinning solution and endowing it with the ability to form strong interactions with dye systems and polymer matrices more effectively, thereby achieving multiple and synergistic enhancements in mechanical properties, dyeing effects and color fastness of polyester nylon composite fiber synthetic leather, has become a key challenge and a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0007] This invention overcomes the shortcomings of the prior art and provides a method for preparing polyester nylon composite fibers and synthetic leather thereof.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a method for preparing polyester nylon composite fibers, comprising the following steps:

[0009] S1: Graphene oxide is cationized using a quaternary ammonium salting agent to obtain cationized graphene oxide;

[0010] S2: The cationic graphene oxide, caprolactam monomer and catalyst are placed in a reaction vessel to react and generate modified polyamide;

[0011] S2: The modified polyamide and polyester chips are respectively made into modified polyamide spinning solution and polyester spinning solution. Coaxial spinning fibers are prepared with the polyester spinning solution as the core layer and the modified polyamide spinning solution as the shell layer. The core layer has a cross-shaped cross-section and the outer periphery of the shell layer has a circular cross-section, thus obtaining polyester nylon composite fiber.

[0012] In a preferred embodiment of the present invention, the mass fractions of the materials are: 50-60 parts of the caprolactam monomer, 20-30 parts of polyester chips, 10-15 parts of graphene oxide, 1.0-2.0 parts of catalyst, and 5-10 parts of quaternization reagent.

[0013] In a preferred embodiment of the present invention, the specific process of cationization is as follows: the graphene oxide is prepared into a 0.2-0.25 wt% graphene oxide aqueous dispersion with a pH of 9.0-10.0, a quaternization reagent is added, and the mixture is stirred at 60-80°C for 8-10 hours. After centrifugation, washing, and freeze-drying, the cationized graphene oxide is obtained. The quaternization reagent is 3-chloro-2-hydroxypropyltrimethylammonium chloride.

[0014] In a preferred embodiment of the present invention, the graphene oxide is graphene oxide powder with a sheet diameter of 0.5-20 μm and a specific surface area of ​​500-1000 m2 / g.

[0015] In a preferred embodiment of the present invention, the catalyst in S2 is sodium hydroxide, and the reaction process is carried out at 0.15-0.90 MPa and inert atmosphere at 230-260°C for 1-3 hours.

[0016] In a preferred embodiment of the present invention, the modified polyamide spinning solution in S2 is prepared by dissolving modified polyamide chips in a formic acid / acetic acid mixed solvent with a volume ratio of 1:1-2 to prepare a 20-25 wt% solution, and stirring at 40-45°C for 6-8 hours until completely dissolved; the polyester spinning solution is prepared by dissolving polyester chips in a trifluoroacetic acid / dichloromethane mixed solvent with a volume ratio of 1:1-3 to prepare a 15-20 wt% solution, and stirring at room temperature for 4-6 hours until completely dissolved.

[0017] In a preferred embodiment of the present invention, the propulsion rates of the modified polyamide spinning solution and the polyester spinning solution are 0.5-0.6 mL / h and 0.6-0.8 mL / h, respectively; the length of the cross-shaped arm is 0.15-0.25 mm; the arm width is 0.04-0.06 mm; and the outer diameter of the shell cross-section is 0.25-0.35 mm.

[0018] To achieve the above objectives, the second technical solution adopted by the present invention is as follows: a method for preparing polyester nylon composite fiber synthetic leather, the preparation process being as follows: the polyester nylon composite fiber is made into a non-woven fabric, the non-woven fabric is immersed in a polyvinyl alcohol solution for 2-5 minutes, taken out and dried, and then immersed in a polyurethane impregnation solution containing a crosslinking agent and a foaming agent for 3-10 minutes, taken out and dried to obtain a synthetic leather base fabric; the synthetic leather base fabric is dyed with dye, dried and shaped to obtain a polyester nylon composite fiber synthetic leather;

[0019] The synthetic leather comprises the following components by weight: 86-117 parts polyester nylon composite fiber, 5-10 parts polyurethane, 1-1.5 parts polyvinyl alcohol, 1.5-2.0 parts crosslinking agent, 1.0-1.5 parts foaming agent, and 1.0-2.0 parts dye.

[0020] In a preferred embodiment of the present invention, the polyvinyl alcohol solution is an aqueous solution with a concentration of 8-10 wt%, the polyurethane impregnation liquid includes 20-30 wt% polyurethane, 1-1.5 wt% foaming agent, 0.5-1.0 wt% crosslinking agent, and the remainder is water, and the number average molecular weight of the polyurethane is 80,000-120,000 g / mol.

[0021] In a preferred embodiment of the present invention, the dye is an anionic acid dye with a dye concentration of 2-3%, and the drying and setting process is to set the dye in a heat setting machine at 180-200°C for 1-2 minutes.

[0022] This invention addresses the shortcomings of the prior art and has the following beneficial effects:

[0023] (1) This invention provides a method for preparing polyester nylon composite fiber. By modifying polyamide with cationic graphene oxide and adopting a coaxial spinning structure, graphene oxide is given a positive charge to initially reduce agglomeration and improve dispersibility. Compared with the existing method for preparing fibers with graphene oxide, cationicization enables graphene oxide to form a strong electrostatic interaction with negatively charged dye molecules in the shell, thereby enhancing the uniformity and binding force of dye adsorption, improving dyeing effect and color fastness. At the same time, the good dispersion of graphene oxide in the polyamide matrix improves mechanical strength through nano-reinforcement effect. The coaxial design of the cross-shaped core layer and the circular shell layer synergistically optimizes the stress distribution and surface characteristics of the fiber, ultimately achieving multiple improvements in mechanical properties, dyeing depth and durability.

[0024] (2) In this invention, the cross-shaped core structure provides a huge anchoring surface and capillary channels for the subsequent impregnation of polyvinyl alcohol and polyurethane. Compared with the prior art, this allows the interface treatment agent to penetrate deeper into the fiber and interact more fully with the shell, thereby enhancing the mechanical interlocking and chemical bonding strength between polyurethane and fiber.

[0025] (3) In this invention, cationic graphene oxide introduces strong positive charge and reactive sites into the fiber, while the cross-shaped fiber structure provides a huge specific surface area and a unique geometric anchoring effect. The cationic graphene oxide is uniformly embedded in the nylon shell, making the fiber surface positively charged and rich in functional groups. Compared with the prior art, it promotes the electrostatic adsorption and chemical bonding of the fiber with acid dyes. The cross-shaped structure not only significantly increases the specific surface area of ​​the fiber, allowing these active sites to be exposed to the maximum extent, but its sharp edges and concave areas also create excellent mechanical locking points. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, 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 recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a flowchart illustrating the method steps of a preferred embodiment of the present invention. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein. Therefore, the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0030] Traditional composite fibers typically incorporate graphene oxide using simple physical blending methods. This method easily leads to agglomeration of the nanofiller in the spinning solution due to interfacial incompatibility, significantly reducing its reinforcing effect and creating stress defects that impair the fiber's mechanical properties. Furthermore, the bonding of conventional circular cross-section fibers and their nonwoven fabrics with polyurethane relies primarily on limited physical anchoring, resulting in weak interfacial adhesion. This makes the base fabric prone to interlayer delamination under stress, and also limits the fiber's dyeing performance and colorfastness.

[0031] The applicant discovered that by using quaternizing agents to cationize graphene oxide, the negatively charged functional groups on its surface are transformed into positively charged quaternary ammonium groups. This transformation allows it to chemically bond with caprolactam monomers during polymerization, thereby achieving uniform molecular dispersion within the polyamide shell and completely preventing aggregation. Secondly, a composite fiber structure with a cross-shaped core and a circular shell was designed, which significantly increased the specific surface area of ​​the fibers and provided a strong mechanical interlocking effect for the impregnation and fixation of the polyurethane resin.

[0032] This process allows for the stable and uniform fixation of graphene oxide within the fiber shell, maximizing its reinforcing effect and providing numerous cationic dye sites. The cross-shaped fiber structure and subsequent polyurethane impregnation form a robust, three-dimensional, interpenetrating bond. The synergistic effect of these two elements significantly enhances the peel strength of the resulting synthetic leather, while also achieving a dyeing effect with uniform depth and excellent colorfastness.

[0033] like Figure 1 As shown, a method for preparing polyester-nylon composite fibers includes the following steps:

[0034] S1: Graphene oxide is cationized using a quaternary ammonium salting agent to obtain cationized graphene oxide;

[0035] S2: Cationic graphene oxide, caprolactam monomer and catalyst are placed in a reaction vessel to react and generate modified polyamide;

[0036] S2: Modified polyamide and polyester chips are respectively made into modified polyamide spinning solution and polyester spinning solution. Coaxial spinning fibers are prepared with polyester spinning solution as core layer and modified polyamide spinning solution as shell layer. The cross-section of the core layer is cross-shaped and the outer periphery of the shell layer cross-section is circular, thus obtaining polyester nylon composite fiber.

[0037] The mass fractions of the materials are: 50-60 parts caprolactam monomer, 20-30 parts polyester chips, 10-15 parts graphene oxide, 1.0-2.0 parts catalyst, and 5-10 parts quaternization reagent.

[0038] The following details each step:

[0039] In step S1,

[0040] The specific process of cationization is as follows: 0.2-0.25 wt% of graphene oxide is prepared as an aqueous dispersion of graphene oxide with a pH of 9.0-10.0. Quaternary ammonium salting reagent is added and stirred at 60-80℃ for 8-10 h. After centrifugation and washing, the mixture is freeze-dried to obtain cationized graphene oxide. The quaternary ammonium salting reagent is 3-chloro-2-hydroxypropyltrimethylammonium chloride.

[0041] Graphene oxide is graphene oxide powder with a sheet size of 0.5-20 μm and a specific surface area of ​​500-1000 m2 / g.

[0042] Cationic modification of graphene oxide under weakly alkaline conditions successfully acquired positively charged quaternary ammonium groups on the surface of graphene oxide. This not only significantly enhanced its dispersion stability in the aqueous phase to prevent aggregation during the pretreatment stage, but also introduced strong reaction sites for its subsequent copolymerization reaction with caprolactam monomer, thus initially ensuring that the modifier and the polymer matrix are connected by strong covalent bonds.

[0043] The cationization treatment gives the graphene oxide surface a strong positive charge, which promotes its compatibility and combination with the negative caprolactam ring-opening polymerization system. This chemically ensures that the graphene oxide is stably embedded in the polyamide molecular chain in a single layer, completely avoiding agglomeration caused by interfacial incompatibility in the spinning solution.

[0044] The dispersed state provides the fiber with a uniform and positively charged active shell, which allows the negatively charged polyurethane impregnation components to come into close contact with the fiber surface through strong electrostatic attraction during impregnation, thereby enhancing the efficiency of the crosslinking agent in building bridges and the interfacial bonding strength.

[0045] Graphene oxide, uniformly embedded in the shell and carrying a positive charge, undergoes efficient ionic bonding with anionic acid dyes during the dyeing stage, thereby improving the dye uptake rate and binding strength.

[0046] Sodium hydroxide was used as a catalyst, and the reaction was carried out under specific high temperature, high pressure, and inert conditions. This ensured the efficient and complete progress of the caprolactam ring-opening polymerization reaction and promoted the formation of strong covalent bonds between the active groups on the graphene oxide surface and the ends of the polyamide molecular chains. This laid a solid foundation for the generation of modified polyamides with regular structures and stable interfaces. These optimized reaction conditions effectively avoided excessively wide molecular weight distributions or interfacial defects caused by incomplete reactions or side reactions, and initially guaranteed the chemical stability and spinnability of the subsequent spinning solution.

[0047] In step S2,

[0048] The catalyst is sodium hydroxide, and the reaction process is carried out at 0.15-0.90 MPa and inert atmosphere at 230-260℃ for 1-3 hours.

[0049] The preparation process of the modified polyamide spinning solution is as follows: the modified polyamide chips are dissolved in a formic acid / acetic acid mixed solvent with a volume ratio of 1:1-2 to prepare a 20-25 wt% solution, and stirred at 40-45℃ for 6-8 hours until completely dissolved; the preparation process of the polyester spinning solution is as follows: the polyester chips are dissolved in a trifluoroacetic acid / dichloromethane mixed solvent with a volume ratio of 1:1-3 to prepare a 15-20 wt% solution, and stirred at room temperature for 4-6 hours until completely dissolved.

[0050] By selecting specific mixed solvent systems and dissolution conditions for modified polyamide and polyester, this feature ensures that the two polymers can form a uniform and stable spinning solution without degradation or aggregation. The acidic mixed solvent for modified polyamide can effectively maintain the stability of its molecular chain and chemically bonded graphene oxide, while the solvent system for polyester ensures the ideal rheological properties of the core layer solution, laying a preliminary technological foundation for the successful preparation of structurally regular core-shell fibers.

[0051] The modified polyamide dissolves completely under mild acidic conditions, protecting the chemical bond between graphene oxide and the polyamide molecular chain. This prevents the nanoparticles from re-aggregating due to harsh solvents or uneven dissolution, fundamentally ensuring the ultimate dispersion stability of graphene oxide in the shell spinning solution.

[0052] In step S3,

[0053] The propulsion rates of the modified polyamide spinning solution and the polyester spinning solution are 0.5-0.6 mL / h and 0.6-0.8 mL / h, respectively. The length of the cross-shaped arm is 0.15-0.25 mm, the arm width is 0.04-0.06 mm, and the outer diameter of the shell cross-section is 0.25-0.35 mm.

[0054] The obtained perfect core-shell fiber structure provides a substrate for the subsequent uniform pretreatment of polyvinyl alcohol solution, so that the formed interface transition layer can completely cover each fiber, thereby creating a maximum contact area for the impregnation and crosslinking of high molecular weight polyurethane and greatly enhancing the bonding strength.

[0055] Thanks to the protection of the solvent system, the graphene oxide, which is uniformly exposed in the fiber shell, has its active surface and charge interaction fully demonstrated in the dyeing process, which significantly improves the binding strength of dye molecules.

[0056] By precisely controlling the propulsion rate of the spinning solution in the core and shell layers and adopting a specific irregular cross-section design, it is ensured that the core polyester can be completely and uniformly wrapped by the shell modified polyamide, forming a stable core-shell fiber with a strong interfacial bond. The cross-shaped core layer significantly increases the contact area between the two polymers, thereby strengthening the mechanical interlocking, while the circular shell ensures the overall continuity and smoothness of the fiber. This lays the initial structural foundation for obtaining composite fibers with excellent mechanical properties and functionality.

[0057] The shell solution advances at a slightly slower rate than the core layer, ensuring that the shell material can fully extend and completely encapsulate the core layer. This allows the graphene oxide, which is uniformly dispersed in the polyamide through in-situ polymerization, to be stably fixed to the outer periphery of the fiber, further preventing the formation of agglomerates from a physical perspective.

[0058] The cross-shaped core structure provides a large anchoring surface and capillary channels for subsequent impregnation of polyvinyl alcohol and polyurethane. This feature allows the interface treatment agent to penetrate deeper into the fiber and interact more fully with the shell, thereby greatly enhancing the mechanical interlocking and chemical bonding strength between polyurethane and fiber.

[0059] The shell, perfectly encapsulated and positioned on the periphery of the fiber, maximizes the exposure of the huge specific surface area of ​​graphene oxide, providing an abundance of readily accessible active sites for dye adsorption.

[0060] The special fiber geometry created by the spinning process not only solidifies and amplifies the effect of preventing agglomeration in the early stage, but also provides an enhanced environment for subsequent strong bonding and efficient dyeing by greatly increasing the effective interface area.

[0061] Cationic graphene oxide introduces strong positive charge and reactive sites into the fiber, while the cross-shaped fiber structure provides a huge specific surface area and a unique geometric anchoring effect. The uniform embedding of cationic graphene oxide into the nylon shell makes the fiber surface positively charged and rich in functional groups, which greatly promotes its electrostatic adsorption and chemical bonding with acid dyes. The cross-shaped structure not only significantly increases the specific surface area of ​​the fiber, maximizing the exposure of these active sites, but its sharp edges and recessed areas also create excellent mechanical locking points.

[0062] The large physical surface provided by the cross-shaped structure becomes the chemically active matrix for cationic graphene oxide, which greatly increases the bonding strength. The strong interfacial bonding achieved through chemical bonding also ensures that the cross-shaped structure will not become a weak point when subjected to stress, thus giving full play to its physical anchoring advantages and endowing synthetic leather products with excellent peel strength, durability and deep and firm dyeing effects.

[0063] A method for preparing polyester nylon composite fiber synthetic leather includes the following steps: polyester nylon composite fibers are made into nonwoven fabric; the nonwoven fabric is immersed in a polyvinyl alcohol solution for 2-5 minutes, dried, and then immersed in a polyurethane impregnation solution containing a crosslinking agent and a foaming agent for 3-10 minutes; the fabric is then dried to obtain a synthetic leather base fabric; the synthetic leather base fabric is dyed with dye and dried to obtain a polyester nylon composite fiber synthetic leather.

[0064] The synthetic leather comprises the following components by weight: 86-117 parts polyester nylon composite fiber, 5-10 parts polyurethane, 1-1.5 parts polyvinyl alcohol, 1.5-2.0 parts crosslinking agent, 1.0-1.5 parts foaming agent, and 1.0-2.0 parts dye.

[0065] The polyvinyl alcohol solution is an aqueous solution with a concentration of 8-10 wt%. The polyurethane impregnation solution includes 20-30 wt% polyurethane, 1-1.5 wt% foaming agent, 0.5-1.0 wt% crosslinking agent, and the remainder is water. The number average molecular weight of the polyurethane is 80,000-120,000 g / mol.

[0066] The dye is an anionic acid dye with a concentration of 2-3%. The drying and setting process involves setting the dye in a heat setter at 180-200℃ for 1-2 minutes.

[0067] By setting specific concentrations of polyvinyl alcohol aqueous solution and polyurethane impregnation solution containing precise components, polyvinyl alcohol can form an activated coating with excellent thickness and integrity on the fiber surface, which effectively improves the hydrophilicity of hydrophobic fibers while retaining sufficient porosity.

[0068] This impregnation formulation ensures that polyurethane, foaming agent, and crosslinking agent coexist in the optimal ratio, initially guaranteeing that the polyurethane can be fully crosslinked and cured and that foaming is uniform and moderate during the subsequent drying process. This lays the foundation for forming a three-dimensional network structure that combines porosity, flexibility, and high strength.

[0069] Pretreatment with a moderate concentration of polyvinyl alcohol solution creates a uniform transition layer on the surface of the nonwoven fabric composed of irregularly shaped composite fibers. This transition layer, which can strongly adhere to the fibers and is rich in active hydroxyl groups, acts as a medium and greatly promotes the spreading and penetration of the subsequent waterborne polyurethane impregnation liquid into the fiber assembly, thus providing a key bridge for the formation of a strong fiber-resin interface.

[0070] Polyurethane impregnation containing a quantitative crosslinking agent can achieve efficient crosslinking with the polyvinyl alcohol layer on the fiber surface and its own molecules through this bridge. This not only strengthens the bulk strength of the polyurethane resin, but also tightly binds it to the fiber through chemical bonds, greatly enhancing the interfacial bonding strength.

[0071] This robust and well-bonded base fabric structure allows dye molecules to act more stably on the structurally intact and graphene-rich fiber shell surface during the dyeing stage, thereby improving color durability.

[0072] Solution concentration design fully transforms the excellent fiber structure potential formed in the previous process into the final practical performance. By constructing an interface transition layer and a three-dimensional resin network, the structural uniformity obtained by avoiding agglomeration, the interfacial activity required to enhance bonding, and the surface stability dependent on color fastness are synergistically amplified and ultimately cured.

[0073] By selecting anionic acid dyes and combining them with a specific high-temperature rapid drying and setting process, this feature enables the dye molecules to form efficient ionic bonds with the positively charged regions on the surface of graphene oxide in the fiber shell and the amino groups on the polyamide molecular chains, thus initially ensuring a high initial dyeing rate.

[0074] High-temperature treatment intensifies the movement of polyurethane molecular chain segments and further cross-links them in a short period of time, and also makes the fiber crystal structure more perfect, achieving rapid color fixation and stable base fabric morphology.

[0075] The uniform dispersion of graphene oxide in the polyamide shell provides a large number of uniformly distributed and strong ionic bonding sites for anionic dyes. This feature enhances the binding force between dyes and fibers from the essence of dyeing.

[0076] The robust three-dimensional network interface constructed through polyvinyl alcohol pretreatment and polyurethane impregnation ensures that the base fabric maintains its structural integrity during subsequent high-temperature treatment, avoiding dye migration or shedding due to interface damage, and creating conditions for high-temperature setting.

[0077] The high-temperature rapid setting process not only allows dye molecules to completely penetrate and fix inside the fiber, but also promotes further cross-linking of the polyurethane resin and strengthens its interface with the fiber, thereby improving color fastness and, in turn, enhancing the overall structural durability.

[0078] The use of graphene oxide powder with small flake size and huge specific surface area is specified. Its surface is rich in a large number of active functional groups and has a large contact area with the polymer matrix, which helps to achieve more complete chemical bonding with caprolactam monomers during the polymerization reaction. This initially ensures its nanoscale dispersion and interfacial bonding in the polyamide matrix, laying a solid foundation for ultimately endowing the fiber with excellent mechanical and functional properties.

[0079] The use of thermoplastic polyurethane with a high number-average molecular weight results in longer polyurethane molecular chains and stronger intermolecular forces, which initially ensures that the polyurethane resin body has excellent cohesive strength and mechanical properties after impregnation molding. This makes the final three-dimensional network structure more tough and durable, and significantly improves the macroscopic physical properties of the synthetic leather base fabric.

[0080] By using graphene oxide with a high specific surface area to polymerize in situ with caprolactam monomers, this feature enables it to be chemically bonded to the polyamide molecular chain, fundamentally avoiding the agglomeration problem caused by physical blending during spinning, and initially ensuring the uniform and stable dispersion of functional nanomaterials in the fiber shell.

[0081] Impregnation with high molecular weight thermoplastic polyurethane, combined with the active surface provided by polyvinyl alcohol pretreatment, allows the long polyurethane chains to form strong mechanical interlocking and physical entanglement with the fibers, significantly enhancing the interfacial bonding strength between the polyurethane and the fiber surface during impregnation.

[0082] The large specific surface area and electrostatic adsorption of graphene oxide uniformly dispersed in the fiber shell provide a large number of anchoring sites for dye molecules, thereby improving the dye uptake rate and binding force.

[0083] Using polyester chips with appropriate intrinsic viscosity and suitable molecular chain length initially ensures that the core spinning solution has good spinnability and that the final fiber can form a high-strength core structure with sufficient intermolecular forces and crystallinity, providing a stable skeletal support for the composite fiber.

[0084] The use of polyvinyl alcohol with a specific molecular weight and partial alcoholysis gives it both good water solubility and film-forming properties, as well as the flexibility brought by suitable hydroxyl activity and acetyl residue. This ensures that the pretreatment solution can effectively wet and adhere to the surface of the composite fiber, forming a transitional interface layer that can improve hydrophilicity and has a certain degree of toughness, laying the foundation for the successful bonding with polyurethane in the future.

[0085] The provided mass fraction ratios optimize material performance and cost-effectiveness through precise control of the content of each component. The high amount of caprolactam ensures the full generation of modified polyamide, providing a stable carrier for graphene oxide, while polyester chips, as the core layer, maintain the skeletal strength of the fiber.

[0086] The ratio of graphene oxide to polyurethane ensures that the former provides reinforcement without affecting processing fluidity due to excessive dosage, while the latter achieves effective impregnation without excessive hardening. The use of small amounts of various additives ensures that their key functions such as catalysis, crosslinking, and foaming are performed, while minimizing the potential negative impact of residues on the performance of the final product.

[0087] The caprolactam monomer was selected from BASF ULTRAMID B27L polyamide 6 chips, the polyester chips were selected from Toray TritanTX1500 polyester chips, the graphene oxide was selected from Changzhou Sixth Element SE2410 graphene oxide, the quaternizing agent was selected from Aladdin 3-chloro-2-hydroxypropyltrimethylammonium chloride, grade CAS 3026-10-8, the polyurethane was selected from Covestro Desmopan 9865A polyurethane, the polyvinyl alcohol was selected from Kuraray PVA-205, the catalyst was selected from BASF CAT-100 sodium hydroxide, the crosslinking agent was selected from Lanxess Perocal 200 crosslinking agent, the foaming agent was selected from Shandong Xurui AC foaming agent (azodicarbonamide), with a decomposition temperature of 190-210℃ and a gas evolution of 200-220mL / g, and the dye was selected from Huntsman Nylosan Blue EL-NF anionic acid dye.

[0088] Example 1: This example provides a method for preparing polyester-nylon composite fiber synthetic leather, including the following steps:

[0089] A 0.2 wt% aqueous dispersion of graphene oxide with a pH of 9.0 was prepared, a quaternization reagent was added, and the mixture was stirred at 70 °C for 8 h. After centrifugation, washing, and freeze-drying, cationic graphene oxide was obtained. The quaternization reagent was 3-chloro-2-hydroxypropyltrimethylammonium chloride. The cationic graphene oxide, caprolactam monomer, and catalyst were placed in a reaction vessel to react and generate modified polyamide. The catalyst was sodium hydroxide. The reaction was carried out at 0.50 MPa and an inert atmosphere at 250 °C for 2 h.

[0090] Modified polyamide and polyester chips were respectively made into modified polyamide spinning solution and polyester spinning solution. Coaxial spinning fibers were prepared with polyester spinning solution as core layer and modified polyamide spinning solution as shell layer to obtain polyester nylon composite fiber.

[0091] The modified polyamide spinning solution was prepared by dissolving modified polyamide chips in a 1:1 mixture of formic acid and acetic acid to prepare a 20 wt% solution, and stirring at 45°C for 6 hours until completely dissolved. The polyester spinning solution was prepared by dissolving polyester chips in a 1:2 mixture of trifluoroacetic acid and dichloromethane to prepare a 15 wt% solution, and stirring at room temperature for 4 hours until completely dissolved.

[0092] The feed rates of the modified polyamide spinning solution and the polyester spinning solution are 0.6 mL / h and 0.8 mL / h, respectively. The core layer cross-section is cross-shaped, the outer periphery of the shell layer cross-section is circular, the length of the cross arm is 0.1 mm, the width of the arm is 0.05 mm, and the outer periphery diameter of the shell layer cross-section is 0.30 mm.

[0093] Polyester nylon composite fibers are made into nonwoven fabric. The nonwoven fabric is immersed in polyvinyl alcohol solution for 2 minutes, taken out and dried, and then immersed in polyurethane impregnation solution containing crosslinking agent and foaming agent for 3 minutes. It is then taken out and dried to obtain synthetic leather base fabric.

[0094] The polyvinyl alcohol solution is an 8 wt% aqueous solution, and the polyurethane impregnation solution includes 20 wt% polyurethane, 1.5 wt% foaming agent, 1.0 wt% crosslinking agent, and the remainder is water.

[0095] A synthetic leather base fabric was dyed with dye and dried to obtain a polyester-nylon composite fiber synthetic leather. The dye was an anionic acid dye with a dye concentration of 2%. The drying and setting process was to set the fabric in a heat setter at 180°C for 1 minute.

[0096] 55 parts caprolactam monomer, 30 parts polyester chips, 10 parts graphene oxide, 5 parts quaternization reagent, 5 parts polyurethane, 1.5 parts polyvinyl alcohol, 1.0 part catalyst, 1.5 parts crosslinking agent, 1.0 part foaming agent and 1.5 parts dye.

[0097] Graphene oxide is graphene oxide powder with a sheet diameter of 5 μm and a specific surface area of ​​500 m². 2 / g, the number average molecular weight of polyurethane is 80000 g / mol.

[0098] The intrinsic viscosity of the polyester chips is 0.65 dL / g, the number-average molecular weight of polyvinyl alcohol is 0000, and the degree of hydrolysis is 88%.

[0099] Example 2: The difference between this example and Example 1 is that the length of the cross-shaped arm is 0.15 mm, but the rest are the same.

[0100] Example 3: The difference between this example and Example 1 is that the length of the cross-shaped arm is 0.20 mm, and the rest are the same.

[0101] Example 4: The difference between this example and Example 1 is that the length of the cross-shaped arm is 0.25 mm, and the rest are the same.

[0102] Example 5: The difference between this example and Example 1 is that the length of the cross-shaped arm is 0.30 mm, and the rest are the same.

[0103] Example 6: The difference between this example and Example 3 is that the mass fraction of the quaternization reagent is 2.5 parts, and the rest are the same.

[0104] Example 7: The difference between this example and Example 3 is that the mass fraction of the quaternization reagent is 7.5 parts, while the rest are the same.

[0105] Example 8: The difference between this example and Example 3 is that the mass fraction of the quaternization reagent is 10 parts, and the rest are the same.

[0106] Example 9: The difference between this example and Example 3 is that the mass fraction of the quaternization reagent is 12.5 parts, and the rest are the same.

[0107] Comparative Example 1: Comparative Example 1 provides a method for preparing synthetic leather, the steps of which are as follows:

[0108] This embodiment provides a method for preparing polyester-nylon composite fiber synthetic leather, including the following steps:

[0109] Graphene oxide, caprolactam monomer and catalyst were placed in a reaction vessel to react and generate modified polyamide. The catalyst was sodium hydroxide. The reaction process was carried out at 0.50 MPa and inert atmosphere and 250 °C for 2 h.

[0110] Modified polyamide and polyester chips were respectively made into modified polyamide spinning solution and polyester spinning solution. Coaxial spinning fibers were prepared with polyester spinning solution as core layer and modified polyamide spinning solution as shell layer to obtain polyester nylon composite fiber.

[0111] The modified polyamide spinning solution was prepared by dissolving modified polyamide chips in a 1:1 mixture of formic acid and acetic acid to prepare a 20 wt% solution, and stirring at 45°C for 6 hours until completely dissolved. The polyester spinning solution was prepared by dissolving polyester chips in a 1:2 mixture of trifluoroacetic acid and dichloromethane to prepare a 15 wt% solution, and stirring at room temperature for 4 hours until completely dissolved.

[0112] The feed rates of the modified polyamide spinning solution and the polyester spinning solution were 0.6 mL / h and 0.8 mL / h, respectively. The outer diameter of the core layer cross-section was 0.15 mm, and the outer diameter of the shell layer cross-section was 0.30 mm.

[0113] Polyester nylon composite fibers are made into nonwoven fabric. The nonwoven fabric is immersed in polyvinyl alcohol solution for 2 minutes, taken out and dried, and then immersed in polyurethane impregnation solution containing crosslinking agent and foaming agent for 3 minutes. It is then taken out and dried to obtain synthetic leather base fabric.

[0114] The polyvinyl alcohol solution is an 8 wt% aqueous solution, and the polyurethane impregnation solution includes 20 wt% polyurethane, 1.5 wt% foaming agent, 1.0 wt% crosslinking agent, and the remainder is water.

[0115] A synthetic leather base fabric was dyed with dye and dried to obtain a polyester-nylon composite fiber synthetic leather. The dye was an anionic acid dye with a dye concentration of 2%. The drying and setting process was to set the fabric in a heat setter at 180°C for 1 minute.

[0116] 55 parts caprolactam monomer, 30 parts polyester chips, 10 parts graphene oxide, 5 parts quaternization reagent, 5 parts polyurethane, 1.5 parts polyvinyl alcohol, 1.0 part catalyst, 1.5 parts crosslinking agent, 1.0 part foaming agent and 1.5 parts dye.

[0117] Graphene oxide is graphene oxide powder with a sheet diameter of 5 μm and a specific surface area of ​​500 m². 2 / g, the number average molecular weight of polyurethane is 80000 g / mol.

[0118] The intrinsic viscosity of the polyester chips is 0.65 dL / g, the number-average molecular weight of polyvinyl alcohol is 0000, and the degree of hydrolysis is 88%.

[0119] Samples of the same area were taken from the polyester-nylon composite fiber synthetic leather prepared in Examples 1-9 and the synthetic leather prepared in Comparative Example 1, and a number of performance tests were conducted, including peel strength and light fastness tests. The test data are shown in Table 1.

[0120] Peel strength test: The peel strength test was conducted using a peel strength tester in accordance with GB / T 2790-1995 standard.

[0121] Lightfastness test: The color of the samples was tested using a spectrophotometer. After being irradiated with a 40W ultraviolet lamp for 100 hours, the samples were placed in the dark for 2 hours and then tested again using a spectrophotometer. The color before and after irradiation was compared to obtain the color difference. The larger the color difference, the greater the degree of fading after irradiation, that is, the worse the lightfastness.

[0122] Table 1. Peel strength and staining depth test data of Examples 1-9 and Comparative Example 1

[0123] Data source Peel strength (N / cm) Color difference Example 1 3.6 4.54 Example 2 3.9 4.27 Example 3 4.0 3.87 Example 4 3.8 4.02 Example 5 3.5 4.19 Example 6 3.8 4.05 Example 7 4.2 3.57 Example 8 4.0 3.73 Example 9 3.7 4.17 Comparative Example 1 2.9 4.89

[0124] As shown in Table 1, the peel strength and light fastness of Examples 1-9 are all greater than those of Comparative Example 1, indicating that this application has superiority.

[0125] In Examples 1-5, as the length of the cross-shaped arms gradually increases, both peel strength and light fastness first increase and then decrease. This is because the increase in arm length increases the interfacial contact area between the core layer and the shell layer, enhancing the mechanical interlocking effect and stress dispersion ability of the fibers, thereby strengthening the bonding force. Simultaneously, a larger specific surface area facilitates the adsorption and fixation of anionic dyes in the modified polyamide shell layer, improving dyeing uniformity and lightfastness. However, when the arm length increases excessively, the core layer structure becomes fragile and easily deformed, leading to a reduction in the actual effective interfacial area and stress concentration, weakening the peel strength. Furthermore, an excessively long arm length causes uneven shell layer coverage, increasing dye exposure and reducing light fastness. Example 3 is the preferred embodiment.

[0126] In Examples 3 and 6-9, as the mass fraction of the quaternizing agent gradually increased, the peel strength and light fastness both first increased and then decreased. This is because when the amount of quaternizing agent is appropriately increased, it can more fully convert the carboxyl groups and other functional groups on the surface of graphene oxide into positively charged quaternary ammonium groups. This feature significantly enhances the dispersion stability of graphene oxide in the aqueous phase and polymerization system, as well as its chemical bonding with the nylon matrix. At the same time, it provides abundant electrostatic binding sites for subsequent bonding with anionic polyurethane and dyes, thereby simultaneously improving the interfacial bonding strength and dye binding force. However, when the amount of quaternizing agent is excessive, the over-modified graphene oxide surface will agglomerate due to the increased steric hindrance of the quaternary ammonium groups and charge imbalance. These agglomerates, as stress defect points, will weaken the fiber mechanical properties and fiber-resin interfacial stability. They will also block effective dyeing sites and hinder uniform dye adsorption, ultimately leading to a decrease in both peel strength and light fastness. The preferred embodiment is Example 7.

[0127] Based on the preferred embodiments of the present invention described above, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for preparing polyester-nylon composite fibers, characterized in that, Includes the following steps: S1: Graphene oxide is cationized using a quaternary ammonium salting agent to obtain cationized graphene oxide; S2: The cationic graphene oxide, caprolactam monomer and catalyst are placed in a reaction vessel to react and generate modified polyamide; S2: The modified polyamide and polyester chips are respectively made into modified polyamide spinning solution and polyester spinning solution. Coaxial spinning fibers are prepared with the polyester spinning solution as the core layer and the modified polyamide spinning solution as the shell layer. The core layer has a cross-shaped cross-section and the outer periphery of the shell layer has a circular cross-section, thus obtaining polyester nylon composite fiber.

2. The method for preparing a polyester-nylon composite fiber according to claim 1, characterized in that: The mass fractions of the materials are as follows: 50-60 parts of caprolactam monomer, 20-30 parts of polyester chips, 10-15 parts of graphene oxide, 1.0-2.0 parts of catalyst, and 5-10 parts of quaternization reagent.

3. The method for preparing a polyester-nylon composite fiber according to claim 1, characterized in that: The specific process of cationization is as follows: the graphene oxide is prepared into a 0.2-0.25 wt% graphene oxide aqueous dispersion with a pH of 9.0-10.0, a quaternization reagent is added, and the mixture is stirred at 60-80℃ for 8-10 h. After centrifugation and washing, the mixture is freeze-dried to obtain the cationized graphene oxide. The quaternization reagent is 3-chloro-2-hydroxypropyltrimethylammonium chloride.

4. The method for preparing a polyester-nylon composite fiber according to claim 1, characterized in that: The graphene oxide is graphene oxide powder with a sheet size of 0.5-20 μm and a specific surface area of ​​500-1000 m². 2 / g.

5. The method for preparing a polyester-nylon composite fiber according to claim 1, characterized in that: The catalyst in S2 is sodium hydroxide, and the reaction process is carried out at 0.15-0.90 MPa and inert atmosphere at 230-260℃ for 1-3 hours.

6. The method for preparing a polyester-nylon composite fiber according to claim 1, characterized in that: The preparation process of the modified polyamide spinning solution in S2 is as follows: the modified polyamide chips are dissolved in a formic acid / acetic acid mixed solvent with a volume ratio of 1:1-2 to prepare a 20-25 wt% solution, and stirred at 40-45℃ for 6-8 hours until completely dissolved; the preparation process of the polyester spinning solution is as follows: the polyester chips are dissolved in a trifluoroacetic acid / dichloromethane mixed solvent with a volume ratio of 1:1-3 to prepare a 15-20 wt% solution, and stirred at room temperature for 4-6 hours until completely dissolved.

7. The method for preparing a polyester-nylon composite fiber according to claim 1, characterized in that: The propulsion rates of the modified polyamide spinning solution and the polyester spinning solution are 0.5-0.6 mL / h and 0.6-0.8 mL / h, respectively. The length of the cross-shaped arm is 0.15-0.25 mm, the arm width is 0.04-0.06 mm, and the outer diameter of the shell cross-section is 0.25-0.35 mm.

8. A method for preparing polyester-nylon composite fiber synthetic leather, prepared according to any one of the methods for preparing polyester-nylon composite fibers according to claims 1-7, characterized in that, The preparation process is as follows: the polyester nylon composite fiber is made into a non-woven fabric, the non-woven fabric is immersed in a polyvinyl alcohol solution for 2-5 minutes, taken out and dried, and then immersed in a polyurethane impregnation solution containing a crosslinking agent and a foaming agent for 3-10 minutes, taken out and dried to obtain a synthetic leather base fabric; the synthetic leather base fabric is dyed with dye, dried and shaped to obtain a polyester nylon composite fiber synthetic leather. The synthetic leather comprises the following components by weight: 86-117 parts polyester nylon composite fiber, 5-10 parts polyurethane, 1-1.5 parts polyvinyl alcohol, 1.5-2.0 parts crosslinking agent, 1.0-1.5 parts foaming agent, and 1.0-2.0 parts dye.

9. The method for preparing a polyester-nylon composite fiber synthetic leather according to claim 8, characterized in that: The polyvinyl alcohol solution is an aqueous solution with a concentration of 8-10 wt%. The polyurethane impregnation solution includes 20-30 wt% polyurethane, 1-1.5 wt% foaming agent, 0.5-1.0 wt% crosslinking agent, and the remainder is water. The number average molecular weight of the polyurethane is 80,000-120,000 g / mol.

10. The method for preparing a polyester-nylon composite fiber synthetic leather according to claim 8, characterized in that: The dye is an anionic acid dye with a concentration of 2-3%, and the drying and setting process is to set the dye in a heat setting machine at 180-200℃ for 1-2 minutes.

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