Thermal insulation synthetic leather based on phase change material microcapsules and its continuous production process

Abstract

This invention discloses a heat-insulating synthetic leather based on phase change material microcapsules and its continuous production process, belonging to the field of synthetic leather material technology. The synthetic leather, from the inside out, includes a base fabric layer, an adhesive layer, a functional layer, and a protective surface layer. The production process includes: 1) substrate preparation and feeding; 2) coating and curing the adhesive layer; 3) coating and curing the foamed functional layer; 4) coating and curing the protective surface layer; 5) finishing and winding. This invention first prepares adhesive layer slurry, functional layer slurry, and protective surface layer slurry, then coats them respectively onto the surface of an asymmetrically grafted nonwoven fabric and cures them to obtain the heat-insulating synthetic leather. This invention introduces phase change microcapsules and improves the mechanical properties of the material through interfacial chemical bonding and nanocellulose reinforcement. Intelligent temperature control is achieved through a synergistic mechanism of phase change latent heat buffering and microporous insulation. A multi-level pore structure and asymmetric moisture-wicking structure are designed to produce an advanced synthetic leather that is heat-insulating, highly tough, durable, and breathable and moisture-wicking.

Description

Technical Field

[0001] This invention relates to the field of synthetic leather materials technology, and in particular to heat-insulating synthetic leather based on phase change material microcapsules and its continuous production process. Background Technology

[0002] With the increasing demand for multifunctional materials, traditional synthetic leather faces severe challenges in terms of thermal comfort, mechanical strength, and functional durability.

[0003] In the existing technology, inorganic fillers or ordinary microcapsules are often introduced to give synthetic leather thermal insulation properties.

[0004] However, the interaction between these functional components and the polymer matrix is ​​mostly a simple physical mixture, resulting in weak interfacial bonding. This makes them prone to stress concentration points, leading to decreased material toughness, coating embrittlement, and even cracking. Meanwhile, traditional passive insulation mechanisms (such as those relying on the low thermal conductivity of foams or fillers) fail after heat saturation and cannot cope with dynamic thermal environments.

[0005] Even more fatally, the densification process adopted in pursuit of heat insulation severely hinders the expulsion of moisture, resulting in poor breathability and moisture permeability of the product, causing stuffiness and discomfort when wearing it.

[0006] Furthermore, if phase change materials are used directly without proper encapsulation, they are prone to leakage and oxidation, leading to rapid functional degradation.

[0007] Therefore, how to synergistically resolve the contradictions between "heat insulation and breathability", "functionality and high strength", and "high efficiency and long life" in a single material system has become a technical bottleneck that urgently needs to be overcome in this field. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings of existing technologies by proposing a heat-insulating synthetic leather based on phase change material microcapsules and its continuous production process.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] This invention first proposes a heat-insulating synthetic leather based on phase change material microcapsules, which includes, from the inside out: a base fabric layer, an adhesive layer, a functional layer, and a surface protective layer;

[0011] The base fabric layer is made of microfiber nonwoven fabric.

[0012] The adhesive layer is formed by coating with an adhesive layer paste comprising the following parts by weight:

[0013] Waterborne polyurethane adhesive: 100 parts; Alkali-swellable anionic thickener: 1-2 parts; Wetting and leveling agent: 0.5 parts; Deionized water: 10-15 parts;

[0014] The functional layer is formed by coating with a functional layer slurry comprising the following components in parts by weight:

[0015] Aqueous anionic polyurethane dispersion: 100 parts; modified phase change microcapsules: 40-50 parts; nanocellulose crystals: 3-5 parts; physical foaming agent: 2-3 parts; foam stabilizer: 1-2 parts; wetting and dispersing agent: 1 part; nonionic polyurethane associative thickener: 1-2 parts;

[0016] The top protective layer is formed by coating with a top protective layer slurry comprising the following components in parts by weight:

[0017] Waterborne aliphatic polyurethane: 100 parts; nano silica dispersion: 5-10 parts; leveling agent: 0.5 parts; nonionic polyurethane associative thickener: 0.5-1 parts; defoamer: 0.3 parts.

[0018] Preferably, the method for preparing the microfiber nonwoven fabric includes:

[0019] Nylon 6 / polyethylene composite nonwoven fabric was impregnated in a phenol / tetrachloroethane mixed solvent, and polyethylene was selectively dissolved and washed away at 40°C to obtain fiber isomerized base fabric.

[0020] Plasma activation was performed on the fiber isomerized base fabric, and one side was selected as the skin-contact side and the other side as the outer side. Then, acrylic vapor was introduced into the skin-contact side and the outer side was treated with perfluorooctyl ethyl acrylate vapor to obtain an ultrafine fiber nonwoven fabric with asymmetric grafting on the surface.

[0021] In the phenol / tetrachloroethane mixed solvent, the volume ratio of phenol to tetrachloroethane is 6:4.

[0022] The mixed solvent has a stronger swelling capacity for polyethylene than for nylon 6. By penetrating the polyethylene molecules, it disrupts the crystalline structure of polyethylene, achieving two-phase separation, increasing the porosity and specific surface area of ​​the base fabric, and facilitating subsequent grafting reactions. Plasma bombardment of the base fabric surface breaks the CC and CN bonds of the nylon 6 fibers, generating surface free radicals (-・) and polar groups (hydroxyl -OH, carboxyl -COOH), providing reaction sites for grafting monomers.

[0023] Acrylic vapor is introduced into the skin-contact side, and the carbon-carbon double bonds (C=C) of the acrylic molecules react with free radicals on the surface of the base fabric. The free radicals initiate the opening of the double bonds, forming a chain polymerization, and finally grafting polyacrylic acid (PAA) segments onto the fiber surface.

[0024] When perfluorooctyl ethyl acrylate vapor is introduced into the outer layer, similarly, the C=C in its molecule undergoes free radical polymerization with surface free radicals, grafting fluoropolymer segments (-CH2-CH(COO-CH2CH2-C8F)). 17 )n -). The low surface energy of the fluorinated segments imparts hydrophobicity to the outer side, enhancing water resistance and achieving the asymmetric properties of the base fabric: "skin-friendly and hydrophobic on the outer side".

[0025] Preferably, the method for preparing the adhesive layer slurry includes:

[0026] While stirring at 200-300 rpm, add the wetting and leveling agent and deionized water to the waterborne polyurethane adhesive in sequence. While stirring at 100-200 rpm, add the alkali-swellable anionic thickener. After the addition is complete, increase the speed to 600-800 rpm and stir for 10-15 minutes until the slurry is smooth and delicate. Stir at 200-300 rpm and vacuum degas for 20 minutes to obtain the adhesive layer slurry.

[0027] The viscosity of the adhesive layer slurry is 3000-5000 cP.

[0028] Preferably, the method for preparing the functional layer slurry includes:

[0029] Nanocellulose crystals were pre-dispersed in deionized water for 15 min to form a gel-like cellulose dispersion; wetting and dispersing agent and cellulose dispersion were added to water-based foaming polyurethane under stirring at 300 rpm, and stirred at 400-500 rpm for 10 min.

[0030] Reduce the rotation speed to 200-300 rpm, pass the microcapsule phase material through a 100-mesh sieve, and sieve it into the slurry; disperse at 1500-2000 rpm for 5-8 minutes, reduce to 800-1000 rpm, add physical foaming agent and foam stabilizer, and continue stirring for 8-10 minutes; use nonionic polyurethane associative thickener to adjust the viscosity, and obtain the functional layer slurry;

[0031] The surface of the microcapsule shell is rough and porous. Before the coating slurry cures, polymer molecules penetrate and fill these micropores and grooves. After curing, the capsule and the matrix are physically locked together. Simultaneously, the microcapsule shell contains polyurethane, and the coating is also a polyurethane system; the -NCO in the coating slurry can react with the -OH or -NH2 in the microcapsule shell to form strong chemical bonds.

[0032] The viscosity of the functional layer slurry is 8000-12000 cP; the preparation process of the modified phase change microcapsules includes the following steps:

[0033] Octadecylene and polyurethane prepolymer were mixed evenly to obtain an aqueous phase; melamine-formaldehyde resin prepolymer, deionized water, sodium dodecyl sulfate and polyvinylpyrrolidone were completely dissolved to obtain an oil phase; the oil phase was added to the aqueous phase at a speed of 8000 rpm in a high-speed shear emulsifier and emulsified at 10000 rpm for 10 min to form a microcapsule emulsion.

[0034] Under high-speed shear (8000-10000 rpm), the oil phase (n-octadecane, solvent-based polyurethane prepolymer) is dispersed in the aqueous phase (melamine-formaldehyde prepolymer, emulsifier sodium dodecyl sulfate) to form an O / W emulsion;

[0035] Add ammonium carbonate to the emulsion at 400 rpm, adjust the pH of the emulsion to 4.0-4.5 with citric acid solution, heat to 60℃, and keep warm for 120 min;

[0036] Under acidic conditions, the hydroxymethyl groups (-CH2OH) in hydroxymethyl melamine undergo a condensation reaction, removing water molecules and forming ether bonds (-O-) or methylene bonds (-CH2-), thus constructing a three-dimensional network of melamine-formaldehyde resin, which gradually coats the oil phase (n-octadecane) to form a preliminary shell.

[0037]

[0038] The isocyanate group (-NCO) of the solvent-based polyurethane prepolymer (generated by the reaction of TDI and HTPB, containing -NCO groups) reacts with the hydroxymethyl (-CH2OH), amino (-NH-), or water of melamine-formaldehyde resin to form urea bonds (-NH-CO-NH-) or urethane bonds (-NH-CO-O-), thus forming an "interpenetrating network" between melamine-formaldehyde resin and polyurethane.

[0039]

[0040] At 80-85℃, the condensation reaction of melamine-formaldehyde-polyurethane is complete, the cross-linking density of the shell is increased, and the mechanical strength is enhanced; ammonium carbonate ((NH4)2CO3) decomposes under acidic high temperature to generate NH3, CO2, and H2O gases, forming micropores inside the shell. Polyvinylpyrrolidone (PVP) is washed out with hot deionized water, leaving tiny channels in the shell, and finally forming a through structure to achieve air permeability.

[0041] By using ammonium carbonate and PVP to create pores, a rough structure and pores at the micro-nano scale are formed on the shell surface, which greatly increases the contact area between the capsule and the coating, providing a perfect structural basis for mechanical interlocking.

[0042] The temperature was raised to 80-85℃ and the reaction continued for 90 minutes. The mixture was then naturally cooled to room temperature. The pH was adjusted to 7-8 with sodium hydroxide solution. The mixture was then vacuum filtered. The filter cake was washed with hot deionized water and dried by forced air to obtain modified phase change microcapsules.

[0043] The mass ratio of n-octadecane, polyurethane prepolymer, melamine-formaldehyde resin prepolymer, deionized water, sodium dodecyl sulfate, and polyvinylpyrrolidone is 50:5:150:200:2:3.

[0044] Among them, the polyurethane prepolymer is a solvent-based polyurethane prepolymer with a solid content of 60-75%, which is prepared by reacting toluene diisocyanate with hydroxyl-terminated polybutadiene and has an isocyanate content of 5-7%; the melamine-formaldehyde resin prepolymer has a solid content of 30-50%.

[0045] Preferably, the method for preparing the surface protective layer slurry includes:

[0046] At 400-500 rpm, add waterborne aliphatic polyurethane to the nano silica dispersion and stir for 15 min. Then add leveling agent and defoamer in sequence and stir for 10 min. At 200-300 rpm, add nonionic polyurethane associative thickener. Vacuum degas at 100 rpm for 25-30 min until the slurry is smooth and free of bubbles, and pass it through a 200-mesh filter. The viscosity of the surface protective layer slurry is 2000-3000 cP.

[0047] This invention also proposes a continuous production process for the aforementioned heat-insulating synthetic leather, comprising the following steps:

[0048] S1. Substrate preparation and loading:

[0049] Install the microfiber nonwoven fabric on the unwinding machine, guide the base fabric through each guide roller, ensuring that the skin-contact side is facing up and the outer side is facing down, start the production line, set the initial tension, and perform base fabric correction;

[0050] S2. Coating and curing of the adhesive layer:

[0051] The adhesive layer slurry is pumped to the first coating station, the coating roller speed ratio and blade gap are adjusted, and it is evenly coated on the skin-contact side of the base fabric. It is then placed in the first oven for pre-curing.

[0052] S3, Coating and Foaming Curing Functional Layer:

[0053] Using a doctor blade coater, the functional layer slurry is evenly coated onto the semi-cured adhesive layer, and then placed in the second oven for complete curing.

[0054] S4. Coating and curing of the protective surface layer:

[0055] Using a precision scraper, the surface protective layer slurry is applied to the cooled surface of the functional layer and then placed in the third oven to cure at a higher temperature, so that the surface polyurethane is fully cross-linked and forms a protective film.

[0056] S5. Post-processing and winding:

[0057] The synthetic leather coming out of the third oven passes through cooling rollers to lower the temperature below room temperature and set the material. If necessary, it is embossed by embossing rollers and then wound into large rolls by a winding machine with constant tension to obtain heat-insulating synthetic leather.

[0058] Preferably, in step S1, the unwinding machine is set to automatic constant tension, with a setting range of 10-15 N / cm.

[0059] Preferably, in step S2, the blade gap is 0.1-0.15 mm and the coating speed is 10-15 m / min;

[0060] The first oven is a multi-stage hot air circulation oven with three temperature stages of 80℃, 100℃, and 110℃, and each stage lasts for 1.5-2 minutes.

[0061] As the moisture content decreases, the concentration of latex particles in the waterborne polyurethane adhesive continuously increases, causing them to come closer together. Under the influence of capillary forces and surface tension, the latex particles deform and coalesce, transforming from a dispersed granular state into a continuous, dense polymer film.

[0062] Driven by high temperature, the pre-placed crosslinking agent in the adhesive system is activated and reacts with the carboxyl groups on the polyurethane molecular chain to form acylurea or amide structures, which improves the cohesive strength, heat resistance and solvent resistance of the adhesive layer.

[0063] Preferably, in step S3, the blade gap is 0.3-0.5 mm and the coating speed is 10-15 m / min;

[0064] The second oven is a multi-stage hot air circulation oven with four temperature stages of 70℃, 85℃, 100℃ and 110℃, and each stage lasts for 2.5-3.5 minutes.

[0065] Under the influence of stirring and heat, the physical foaming agent encapsulates air to form a large number of uniform and fine initial bubbles. At the curing temperature, the residual -NCO groups of the polyurethane prepolymer on the surface of the microcapsule shell become active. They diffuse to the interface and react with the -OH or -NH2 groups on the molecular chains of the functional layer polyurethane matrix to form strong covalent bonds.

[0066] Preferably, in step S4, the blade gap is 0.05-0.08 mm and the coating speed is 15-20 m / min;

[0067] The third oven is a multi-stage hot air circulation oven with three stages at temperatures of 90℃, 110℃, and 120℃, and each stage lasts for 1.5-2 minutes.

[0068] Compared with the prior art, the beneficial effects of the present invention are:

[0069] 1. In existing technologies, inorganic fillers or simple microcapsules are only physically mixed with polymer matrices, resulting in weak interfacial bonding and easy formation of stress concentration points, leading to increased material brittleness and cracking. Simultaneously, adding functional fillers easily generates stress concentration, causing coating brittleness; direct mixing of phase change materials can lead to leakage and compromise the integrity of the matrix.

[0070] This invention achieves efficient stress transfer by designing the compatibility and active functional groups of the microcapsule shell and the coating polymer to form covalent chemical bonds at the interface. This effectively disperses external forces from the flexible matrix to the rigid filler, thereby strengthening and toughening the material while adding functional fillers, and solving the core contradiction of functionalization leading to the deterioration of mechanical properties.

[0071] The matrix is ​​reinforced with nanocellulose and toughened with an interpenetrating polymer network shell. The nanocellulose enhances the coating strength through hydrogen bonding. The interpenetrating polymer network shell of the microcapsules has excellent toughness. Furthermore, the shell and coating polymer achieve efficient stress transfer through interfacial chemical bonding, fundamentally preventing the interface from becoming a source of defects.

[0072] 2. Existing technologies rely on the low thermal conductivity of foam or fillers for passive insulation, and the temperature continues to rise after the heat flow is saturated.

[0073] This invention establishes a synergistic mechanism between phase change latent heat storage and microporous air layer insulation. The phase change material absorbs / releases a large amount of latent heat through solid-liquid reversible change, forming a plateau effect during the temperature peak period; the stagnant air within the foamed coating and microporous shell provides continuous thermal resistance. The synergy of these two mechanisms achieves intelligent temperature delay and buffering.

[0074] 3. In the prior art, the dense coating or outer film of synthetic leather completely blocks water vapor in order to achieve heat insulation, resulting in stuffiness.

[0075] The nanopores in the microcapsule shell of this invention allow water vapor to diffuse while blocking liquid water; the foam coating and the microfiber base fabric provide micron-level breathable channels; the asymmetric grafting of the base fabric (hydrophilic inside / hydrophobic outside) forms a chemical potential gradient, actively adsorbing, transporting and evaporating sweat from the skin to the outside.

[0076] In summary, this invention addresses the core contradiction between functionalization and toughness by enhancing the mechanical properties of materials through interfacial chemical bonding and nanocellulose reinforcement, while simultaneously introducing phase change microcapsules. The unique synergistic mechanism of phase change latent heat buffering and microporous insulation enables intelligent temperature control. Furthermore, through multi-level channels and asymmetric moisture-wicking structures, it breaks through the traditional limitations of stuffy insulation materials, ultimately producing an advanced synthetic leather that combines intelligent thermal management, high strength and toughness, long-lasting durability, and breathability and moisture wicking. Attached Figure Description

[0077] Figure 1 This is a process flow diagram for producing heat-insulating synthetic leather according to the present invention;

[0078] Figure 2 This is a process flow diagram for producing modified phase change microcapsules according to the present invention. Detailed Implementation

[0079] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0080] Preparation Example 1:

[0081] The base fabric layer is made of microfiber nonwoven fabric;

[0082] The adhesive layer is formed by coating with an adhesive layer paste comprising the following parts by weight:

[0083] Waterborne polyurethane adhesive: 100kg; Alkali-swellable anionic thickener: 2kg; Wetting and leveling agent: 0.5kg; Deionized water: 15kg;

[0084] The functional layer is formed by coating with a functional layer slurry comprising the following components in parts by weight:

[0085] Aqueous anionic polyurethane dispersion: 100kg; Modified phase change microcapsules: 40kg; Nanocellulose crystals: 5kg; Physical foaming agent: 2kg; Foam stabilizer: 2kg; Wetting and dispersing agent: 1kg; Nonionic polyurethane associative thickener: 1kg;

[0086] The top protective layer is formed by coating with a top protective layer slurry comprising the following components in parts by weight:

[0087] Waterborne aliphatic polyurethane: 100kg; Nano silica dispersion: 10kg; Leveling agent: 0.5kg; Nonionic polyurethane associative thickener: 0.5kg; Defoamer: 0.3kg.

[0088] The method for preparing the microfiber nonwoven fabric includes:

[0089] Nylon 6 / polyethylene composite nonwoven fabric was impregnated in a phenol / tetrachloroethane mixed solvent, and polyethylene was selectively dissolved and washed away at 40°C to obtain fiber isomerized base fabric.

[0090] Plasma activation was performed on the fiber isomerized base fabric, and one side was selected as the skin-contact side and the other side as the outer side. Then, acrylic vapor was introduced into the skin-contact side and the outer side was treated with perfluorooctyl ethyl acrylate vapor to obtain an ultrafine fiber nonwoven fabric with asymmetric grafting on the surface.

[0091] In the phenol / tetrachloroethane mixed solvent, the volume ratio of phenol to tetrachloroethane is 6:4.

[0092] The method for preparing the adhesive layer slurry includes:

[0093] While stirring at 300 rpm, add wetting and leveling agent and deionized water to waterborne polyurethane adhesive in sequence. While stirring at 100 rpm, add alkali-swellable anionic thickener. After the addition is complete, increase the speed to 800 rpm and stir for 10 minutes until the slurry is smooth and delicate. Stir at 300 rpm and vacuum degas for 20 minutes to obtain the adhesive layer slurry.

[0094] The viscosity of the adhesive layer slurry is 3000-5000 cP.

[0095] The preparation method of the functional layer slurry includes:

[0096] Nanocellulose crystals were pre-dispersed in deionized water for 15 min to form a gel-like cellulose dispersion; a wetting and dispersing agent and the cellulose dispersion were added to an aqueous foaming polyurethane under stirring at 300 rpm, and stirred at 40 rpm for 10 min.

[0097] Reduce the rotation speed to 300 rpm, pass the modified phase change microcapsules through a 100-mesh sieve and sieve them into the slurry; disperse at 1500 rpm for 8 min, reduce to 800 rpm, add physical foaming agent and foam stabilizer, and continue stirring for 10 min; use nonionic polyurethane associative thickener to adjust the viscosity and obtain the functional layer slurry.

[0098] The viscosity of the functional layer slurry is 8000-12000 cP;

[0099] according to Figure 2 The process for preparing modified phase change microcapsules includes the following steps:

[0100] Octadecylene and polyurethane prepolymer were mixed evenly to obtain an aqueous phase. Melamine-formaldehyde resin prepolymer, deionized water, sodium dodecyl sulfate, and polyvinylpyrrolidone were completely dissolved to obtain an oil phase. The oil phase was added to the aqueous phase at 8000 rpm in a high-speed shear emulsifier, and emulsified at 10000 rpm for 10 min to form a microcapsule emulsion. Ammonium carbonate was added to the emulsion at 400 rpm, and the pH of the emulsion was adjusted to 4.0-4.5 with citric acid solution. The temperature was raised to 60℃ and held for 120 min. The temperature was raised to 80℃ and the reaction was continued for 90 min. The mixture was then naturally cooled to room temperature, and the pH was adjusted to 7-8 with sodium hydroxide solution. The mixture was then vacuum filtered, and the filter cake was washed with hot deionized water and dried by forced air to obtain modified phase change microcapsules.

[0101] The mass ratio of n-octadecane, polyurethane prepolymer, melamine-formaldehyde resin prepolymer, deionized water, sodium dodecyl sulfate, and polyvinylpyrrolidone is 50:5:150:200:2:3.

[0102] Among them, the polyurethane prepolymer is a solvent-based polyurethane prepolymer with a solid content of 60%, which is prepared by reacting toluene diisocyanate with hydroxyl-terminated polybutadiene and has an isocyanate content of 7%; the melamine-formaldehyde resin prepolymer has a solid content of 30%.

[0103] The method for preparing the surface protective layer slurry includes:

[0104] At 400-500 rpm, add waterborne aliphatic polyurethane to nano silica dispersion and stir for 15 min. Then add leveling agent and defoamer in sequence and stir for 10 min. At 300 rpm, add thickener. Vacuum degas at 100 rpm for 25 min until the slurry is smooth and free of bubbles. Pass through a 200-mesh filter. The viscosity of the surface protective layer slurry is 2000-3000 cP.

[0105] Preparation Example 2:

[0106] The preparation method is the same as in Preparation Example 1, but the adhesive layer is formed by coating an adhesive layer slurry with the following components in parts by weight:

[0107] Waterborne polyurethane adhesive: 100kg; Alkali-swellable anionic thickener: 1.5kg; Wetting and leveling agent: 0.5kg; Deionized water: 12.5kg;

[0108] The functional layer is formed by coating with a functional layer slurry comprising the following components in parts by weight:

[0109] Aqueous anionic polyurethane dispersion: 100kg; Modified phase change microcapsules: 45kg; Nanocellulose crystals: 4kg; Physical foaming agent: 2.5kg; Foam stabilizer: 1.5kg; Wetting and dispersing agent: 1kg; Nonionic polyurethane associative thickener: 1.5kg;

[0110] The top protective layer is formed by coating with a top protective layer slurry comprising the following components in parts by weight:

[0111] Waterborne aliphatic polyurethane: 100kg; Nano silica dispersion: 7.5kg; Leveling agent: 0.5kg; Nonionic polyurethane associative thickener: 0.75kg; Defoamer: 0.3kg.

[0112] The polyurethane prepolymer is a solvent-based polyurethane prepolymer with a solid content of 65%, which is prepared by reacting toluene diisocyanate with hydroxyl-terminated polybutadiene and has an isocyanate content of 6%; the melamine-formaldehyde resin prepolymer has a solid content of 4%.

[0113] Preparation Example 3:

[0114] The preparation method is the same as in Preparation Example 1, but the adhesive layer is formed by coating an adhesive layer slurry with the following components in parts by weight:

[0115] Waterborne polyurethane adhesive: 100kg; Alkali-swellable anionic thickener: 2kg; Wetting and leveling agent: 0.5kg; Deionized water: 10kg;

[0116] The functional layer is formed by coating with a functional layer slurry comprising the following components in parts by weight:

[0117] Aqueous anionic polyurethane dispersion: 100kg; Modified phase change microcapsules: 50kg; Nanocellulose crystals: 3kg; Physical foaming agent: 3kg; Foam stabilizer: 1kg; Wetting and dispersing agent: 1kg; Nonionic polyurethane associative thickener: 2kg;

[0118] The top protective layer is formed by coating with a top protective layer slurry comprising the following components in parts by weight:

[0119] Waterborne aliphatic polyurethane: 100kg; Nano silica dispersion: 5kg; Leveling agent: 0.5kg; Nonionic polyurethane associative thickener: 1kg; Defoamer: 0.3kg.

[0120] The polyurethane prepolymer is a solvent-based polyurethane prepolymer with a solid content of 75%, prepared by reacting toluene diisocyanate with hydroxyl-terminated polybutadiene, and has an isocyanate content of 5%; the melamine-formaldehyde resin prepolymer has a solid content of 50%.

[0121] Example 1:

[0122] according to Figure 1 The continuous production process for heat-insulating synthetic leather based on phase change material microcapsules, using the slurry prepared in Preparation Example 3, includes the following steps:

[0123] S1. Substrate preparation and loading:

[0124] Install the microfiber nonwoven fabric on the unwinding machine, guide the base fabric through each guide roller, ensuring that the skin-contact side is facing up and the outer side is facing down, start the production line, set the initial tension, and perform base fabric correction;

[0125] S2. Coating and curing of the adhesive layer:

[0126] The adhesive layer slurry is pumped to the first coating station, the coating roller speed ratio and blade gap are adjusted, and it is evenly coated on the skin-contact side of the base fabric. It is then placed in the first oven for pre-curing.

[0127] S3, Coating and Foaming Curing Functional Layer:

[0128] Using a doctor blade coater, the functional layer slurry is evenly coated onto the semi-cured adhesive layer, and then placed in the second oven for complete curing.

[0129] S4. Coating and curing of the protective surface layer:

[0130] Using a precision scraper, the surface protective layer slurry is applied to the cooled surface of the functional layer and then placed in the third oven to cure at a higher temperature, so that the surface polyurethane is fully cross-linked and forms a protective film.

[0131] S5. Post-processing and winding:

[0132] The synthetic leather coming out of the third oven passes through cooling rollers to lower the temperature below room temperature and set the material. If necessary, it is embossed by embossing rollers and then wound into large rolls by a winding machine with constant tension to obtain heat-insulating synthetic leather.

[0133] In step S1, the unwinding machine is set to automatically maintain a constant tension of 10 N / cm.

[0134] In S2, the blade gap is 0.15 mm and the coating speed is 10 m / min;

[0135] The first oven is a multi-stage hot air circulation oven with three temperature stages of 80℃, 100℃, and 110℃, and each stage lasts for 2 minutes.

[0136] In S3, the blade gap is 0.3 mm and the coating speed is 15 m / min;

[0137] The second oven is a multi-stage hot air circulation oven with four temperature stages of 70℃, 85℃, 100℃ and 110℃, and each stage lasts for 2.5 minutes.

[0138] In step S4, the blade gap is 0.08 mm and the coating speed is 15 m / min;

[0139] The third oven is a multi-stage hot air circulation oven with three stages at temperatures of 90℃, 110℃, and 120℃, and each stage lasts for 2 minutes.

[0140] Example 2: The preparation method is the same as in Example 1, but the slurry prepared in Preparation Example 2 is used;

[0141] In S1, the unwinding machine is set to automatic constant tension, with a setting range of 10-15 N / cm.

[0142] In step S2, the blade gap is 0.1-0.15 mm, and the coating speed is 10-15 m / min;

[0143] The first oven is a multi-stage hot air circulation oven with three temperature stages of 80℃, 100℃, and 110℃, and each stage lasts for 1.5-2 minutes.

[0144] In step S3, the blade gap is 0.3-0.5 mm, and the coating speed is 10-15 m / min;

[0145] The second oven is a multi-stage hot air circulation oven with four temperature stages of 70℃, 85℃, 100℃ and 110℃, and each stage lasts for 2.5-3.5 minutes.

[0146] In step S4, the blade gap is 0.05-0.08 mm, and the coating speed is 15-20 m / min;

[0147] The third oven is a multi-stage hot air circulation oven with three stages at temperatures of 90℃, 110℃, and 120℃, and each stage lasts for 1.5-2 minutes.

[0148] Example 3: The preparation method is the same as in Example 1, but the slurry prepared in Preparation Example 3 is used;

[0149] In S1, the unwinding machine is set to automatically maintain a constant tension of 15 N / cm.

[0150] In S2, the blade gap is 0.1 mm and the coating speed is 15 m / min;

[0151] The first oven is a multi-stage hot air circulation oven with three temperature stages of 80℃, 100℃, and 110℃, and each stage lasts for 1.5 minutes.

[0152] In S3, the blade gap is 0.5 mm and the coating speed is 10 m / min;

[0153] The second oven is a multi-stage hot air circulation oven with four temperature stages of 70℃, 85℃, 100℃ and 110℃, and each stage lasts for 3.5 minutes.

[0154] In step S4, the blade gap is 0.05 mm and the coating speed is 20 m / min;

[0155] The third oven is a multi-stage hot air circulation oven with three stages at temperatures of 90℃, 110℃, and 120℃, and each stage lasts for 1.5 minutes.

[0156] Based on this, the following design was also created:

[0157] Comparative Example 1: The formulation and experimental method were the same as in Example 2, but the phase change microcapsules added during the preparation of the functional layer slurry were n-octadecane cores and melamine-formaldehyde resin shells.

[0158] Comparative Example 2: The formulation and experimental methods were the same as in Example 2, but modified phase change microcapsules were not added when preparing the functional layer slurry;

[0159] Comparative Example 3: The formulation and experimental methods were the same as in Example 2, but the polyethylene was not selectively dissolved when preparing the microfiber nonwoven fabric.

[0160] Comparative Example 4: The formulation and experimental methods are the same as in Example 2, but no foaming agent is used in the functional layer slurry;

[0161] According to the standards and test methods of GB / T-2951.41-2008, GB / T-19466.3-2004, GB / T-3923.1-2013, GB / T-3917.2-2009, GB / T-2790-1995, GB / T-12704.1-2009, and GB / T-29862-2013, the thermal properties, mechanical properties, moisture permeability, and abrasion resistance of this invention were tested.

[0162] The corresponding results are summarized in Table 1:

[0163] Table 1. Test data of various properties of synthetic leather

[0164]

[0165] Data analysis shows that:

[0166] From the phase change enthalpy data, Examples 1-3 reached 92.5, 105.3, and 118.7 J / g respectively, showing an increasing trend, which is directly related to the increased amount of modified phase change microcapsules added to the functional layer. The highest enthalpy value of Example 3 is due to its highest microcapsule content and optimized shell structure, in which the polyurethane prepolymer solid content reaches 75% and the isocyanate content is 5%. This molecular design gives the shell a better encapsulation effect. In contrast, Comparative Example 1 only uses ordinary melamine-formaldehyde resin shell, and the phase change enthalpy value drops to 78.2 J / g, with a core material leakage rate as high as 2.15%. This indicates that the unmodified shell has insufficient density and is prone to microcracks under stress. Comparative Example 2 does not add microcapsules, and the enthalpy value is only 3.1 J / g, completely losing the phase change temperature regulation function.

[0167] From the perspective of thermal management mechanisms, the sample in the example simultaneously achieves the synergistic effect of passive thermal insulation and active temperature regulation. The abundant microporous structure in the foamed coating forms a highly efficient thermal resistance layer, while the phase change microcapsules absorb a large amount of heat through solid-liquid transition when the temperature reaches the phase change point. This dual mechanism enables the material to establish a temperature buffer plateau in high-temperature environments, extending the thermal comfort period.

[0168] The example series significantly outperformed the comparative examples in both tensile strength (18.3-22.5 MPa) and tear strength (22.8-27.6 N / cm). This enhancing effect primarily stems from a synergistic effect across three levels:

[0169] The reinforcing mechanism of nanocellulose: Nanocellulose crystals form a strong hydrogen bond network with polyurethane molecular chains through numerous hydroxyl groups on their surface, constructing a three-dimensional reinforcing framework in the matrix. In Example 3, the nanocellulose content was 3 kg, lower than in other examples, but due to its more uniform dispersion, it still exhibited the best reinforcing effect.

[0170] Interfacial bonding effect: The polyurethane segments in the modified microcapsule shell and the coated polyurethane matrix form molecular-level entanglement through the principle of similar compatibility, and the residual isocyanate groups can form covalent bonds with the active hydrogens in the matrix. This strong interfacial bonding ensures the effective transfer of stress from the flexible matrix to the rigid filler, avoiding interfacial debonding.

[0171] IPN Shell Toughening: The rigid network of melamine-formaldehyde resin and the flexible segments of polyurethane form an interpenetrating network structure, giving the shell itself excellent toughness and the ability to resist stress impacts during processing and use.

[0172] Comparative Example 1, lacking polyurethane modification in the shell, exhibited weak interfacial bonding and significantly reduced mechanical properties. Comparative Example 3, due to the absence of ultrafine fiber opening treatment in the base fabric, suffered from insufficient inter-fiber entanglement points, resulting in a tear strength reduced to 19.8 N / cm. Comparative Example 4, although not foamed, achieved a tensile strength of 21.3 MPa due to its dense coating; however, this increased material brittleness and reduced wear resistance.

[0173] The moisture permeability data clearly reflects the structure-property relationship between the material's structure and its moisture permeability. Example 2 shows a moisture permeability of 5650 g / (m³). 2 Its superior performance (24h) stems from the construction of a multi-stage moisture permeability channel:

[0174] Microporous diffusion channels: The nanoscale micropores in the microcapsule shell allow water vapor molecules to pass through while blocking liquid water. This molecular sieve effect provides the basis for achieving "air-permeable but water-impermeable".

[0175] Foamed coating through-holes: The open structure formed by physical foaming constitutes micron-level gas channels, which not only ensures air circulation, but also provides a path for water vapor diffusion.

[0176] Gradient-driven mechanism: The asymmetric grafting treatment of the base fabric creates a chemical potential gradient of internal hydrophilicity and external hydrophobicity. The polyacrylic acid chains on the skin-contact side strongly capture water molecules through hydrogen bonds, which are then directionally transported to the hydrophobic side driven by the concentration gradient, and finally evaporate rapidly on the surface of the perfluoroalkane segments.

[0177] Comparative Example 3, lacking ultrafine fiber opening, suffered from insufficient capillary channels between fibers, resulting in a moisture permeability reduced to 2860 g / (m²). 2 • 24h). Comparative Example 4 did not use a foaming agent; the coating formed a dense film that completely blocked water vapor transmission, with a moisture permeability of only 1250 g / (m²). 2 •24h).

[0178] Core leakage rate and abrasion resistance data reflect the long-term stability of the material. Example 3 exhibited the lowest core leakage rate (0.38%), thanks to its optimized shell crosslinking density and interfacial bonding strength. Melamine-formaldehyde resin in the shell provides rigid support, polyurethane segments impart toughness, and the microporous structure formed by ammonium carbonate and polyvinylpyrrolidone pore-forming agents ensures moisture permeability without compromising encapsulation integrity.

[0179] In the abrasion resistance test, Example 3 showed the best performance with a mass loss of only 6.8 mg. This is attributed to: ① the nano-silica-reinforced surface layer providing abrasion protection; ② the uniformly dispersed nanocellulose enhancing the coating cohesion; and ③ the good interfacial bonding preventing the wear initiation point formed by microcapsule debonding.

[0180] Comparative Example 1, due to insufficient shell toughness, is prone to cracking during wear, leading to increased leakage rate and decreased wear resistance. Comparative Example 4, lacking a foamed buffer layer, experiences increased material hardness but decreased toughness, making it more susceptible to fatigue cracks under repeated stress.

[0181] The continuous production process employed in this embodiment ensures optimized molding of each functional layer through precise control of temperature gradient and residence time. The four-zone temperature setting of the second oven enables gradient foaming and curing of the functional layers: initial foaming at 70℃ forms bubble nuclei, foaming is completed at 85℃, and full cross-linking is achieved at 100-110℃. This progressive curing process avoids bubble merging and structural collapse caused by rapid foaming.

[0182] The plasma treatment of the base fabric enhances the surface activity of the fibers. The grafted polyacrylic acid chains and perfluoroalkane segments not only create asymmetric wettability, but their good compatibility with the coating polymer also improves the interlayer bonding force, as evidenced by the interlayer peel strength of 4.2 N / cm in Example 2.

[0183] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A heat-insulating synthetic leather based on phase change material microcapsules, characterized in that, From the inside out, it includes a base fabric layer, an adhesive layer, a functional layer, and a top protective layer; The base fabric layer is made of microfiber nonwoven fabric. The adhesive layer is formed by coating with an adhesive layer paste comprising the following parts by weight: Waterborne polyurethane adhesive: 100 parts; Alkali-swellable anionic thickener: 1-2 parts; Wetting and leveling agent: 0.5 parts; Deionized water: 10-15 parts; The functional layer is formed by coating with a functional layer slurry comprising the following components in parts by weight: Aqueous anionic polyurethane dispersion: 100 parts; modified phase change microcapsules: 40-50 parts; nanocellulose crystals: 3-5 parts; physical foaming agent: 2-3 parts; foam stabilizer: 1-2 parts; wetting and dispersing agent: 1 part; nonionic polyurethane associative thickener: 1-2 parts; The top protective layer is formed by coating with a top protective layer slurry comprising the following components in parts by weight: Waterborne aliphatic polyurethane: 100 parts; Nano silica dispersion: 5-10 parts; Leveling agent: 0.5 parts; Nonionic polyurethane associative thickener: 0.5-1 parts; Defoamer: 0.3 parts; The method for preparing the microfiber nonwoven fabric includes: Nylon 6 / polyethylene composite nonwoven fabric was impregnated in a phenol / tetrachloroethane mixed solvent, and polyethylene was selectively dissolved and washed away at 40°C to obtain fiber isomerized base fabric. Plasma activation was performed on the fiber isomerized base fabric, and one side was selected as the skin-contact side and the other side as the outer side. Then, acrylic vapor was introduced into the skin-contact side and the outer side was treated with perfluorooctyl ethyl acrylate vapor to obtain an ultrafine fiber nonwoven fabric with asymmetric surface grafting. In the phenol / tetrachloroethane mixed solvent, the volume ratio of phenol to tetrachloroethane is 6:

4.

2. The heat-insulating synthetic leather based on phase change material microcapsules according to claim 1, characterized in that, The method for preparing the adhesive layer slurry includes: While stirring at 200-300 rpm, add the wetting and leveling agent and deionized water to the waterborne polyurethane adhesive in sequence. While stirring at 100-200 rpm, add the alkali-swellable anionic thickener. After the addition is complete, increase the speed to 600-800 rpm and stir for 10-15 minutes until the slurry is smooth and delicate. Stir at 200-300 rpm and vacuum degas for 20 minutes to obtain the adhesive layer slurry. The viscosity of the adhesive layer slurry is 3000-5000 cP; The preparation method of the functional layer slurry includes: Nanocellulose crystals were pre-dispersed in deionized water for 15 min to form a gel-like cellulose dispersion; wetting and dispersing agent and cellulose dispersion were added to the aqueous anionic polyurethane dispersion under stirring at 300 rpm, and stirred at 400-500 rpm for 10 min. Reduce the rotation speed to 200-300 rpm, pass the modified phase change microcapsules through a 100-mesh sieve, and sieve them into the slurry; disperse at 1500-2000 rpm for 5-8 minutes, reduce to 800-1000 rpm, add physical foaming agent and foam stabilizer, and continue stirring for 8-10 minutes; add nonionic polyurethane associative thickener to adjust the viscosity and obtain the functional layer slurry; The viscosity of the functional layer slurry is 8000-12000 cP; The preparation process of the modified phase change microcapsules includes the following steps: Octadecylene and polyurethane prepolymer were mixed evenly to obtain an aqueous phase. Melamine-formaldehyde resin prepolymer, deionized water, sodium dodecyl sulfate, and polyvinylpyrrolidone were completely dissolved to obtain an oil phase. The oil phase was added to the aqueous phase at 8000 rpm in a high-speed shear emulsifier, and emulsified at 10000 rpm for 10 min to form a microcapsule emulsion. Ammonium carbonate was added to the emulsion at 400 rpm, and the pH of the emulsion was adjusted to 4.0-4.5 with citric acid solution. The temperature was raised to 60℃ and held for 120 min. The temperature was raised to 80-85℃ and the reaction was continued for 90 min. The mixture was then naturally cooled to room temperature, and the pH was adjusted to 7-8 with sodium hydroxide solution. The mixture was vacuum filtered, and the filter cake was washed with hot deionized water and dried by forced air to obtain modified phase change microcapsules. The mass ratio of n-octadecane, polyurethane prepolymer, melamine-formaldehyde resin prepolymer, deionized water, sodium dodecyl sulfate, and polyvinylpyrrolidone is 50:5:150:200:2:

3. Among them, the polyurethane prepolymer is a solvent-based polyurethane prepolymer with a solid content of 60-75%, prepared by reacting toluene diisocyanate with hydroxyl-terminated polybutadiene, and has an isocyanate content of 5-7%; the melamine-formaldehyde resin prepolymer has a solid content of 30-50%. The method for preparing the surface protective layer slurry includes: Add waterborne aliphatic polyurethane to nano-silica dispersion at 400-500 rpm and stir for 15 min. Then add leveling agent and defoamer in sequence and stir for 10 min. Add nonionic polyurethane associative thickener at 200-300 rpm. Vacuum degas at 100 rpm for 25-30 min until the slurry is smooth and free of bubbles. Pass through a 200-mesh filter. The viscosity of the top protective layer slurry is 2000-3000 cP.

3. The continuous production process for heat-insulating synthetic leather based on phase change material microcapsules as described in any one of claims 1-2, characterized in that, Includes the following steps: S1. Substrate preparation and loading: Install the microfiber nonwoven fabric on the unwinding machine, guide the base fabric through each guide roller, ensuring that the skin-contact side is facing up and the outer side is facing down, start the production line, set the initial tension, and perform base fabric correction; S2. Coating and curing of the adhesive layer: The adhesive layer slurry is pumped to the first coating station, the coating roller speed ratio and blade gap are adjusted, and it is evenly coated on the skin-contact side of the base fabric. It is then placed in the first oven for pre-curing. S3, Coating and Foaming Curing Functional Layer: Using a doctor blade coater, the functional layer slurry is evenly coated onto the semi-cured adhesive layer, and then placed in the second oven for complete curing. S4. Coating and curing of the protective surface layer: Using a precision scraper, the surface protective layer slurry is applied to the cooled surface of the functional layer and then placed in the third oven for curing, so that the surface polyurethane is fully cross-linked to form a protective film. The third oven is a multi-stage hot air circulation oven with three stages at temperatures of 90℃, 110℃, and 120℃, and each stage lasts for 1.5-2 minutes. S5. Post-processing and winding: The synthetic leather coming out of the third oven passes through cooling rollers to lower the temperature below room temperature and set the material. If necessary, it is embossed by embossing rollers and then wound into large rolls by a winding machine with constant tension to obtain heat-insulating synthetic leather.

4. The continuous production process for heat-insulating synthetic leather based on phase change material microcapsules according to claim 3, characterized in that, In S1, the unwinding machine is set to automatic constant tension, with a setting range of 10-15 N / cm.

5. The continuous production process for heat-insulating synthetic leather based on phase change material microcapsules according to claim 3, characterized in that, In step S2, the blade gap is 0.1-0.15 mm, and the coating speed is 10-15 m / min; The first oven is a multi-stage hot air circulation oven with three temperature stages of 80℃, 100℃, and 110℃, and each stage lasts for 1.5-2 minutes.

6. The continuous production process for heat-insulating synthetic leather based on phase change material microcapsules according to claim 3, characterized in that, In step S3, the blade gap is 0.3-0.5 mm, and the coating speed is 10-15 m / min; The second oven is a multi-stage hot air circulation oven with four temperature stages of 70℃, 85℃, 100℃ and 110℃, and each stage lasts for 2.5-3.5 minutes.

7. The continuous production process for heat-insulating synthetic leather based on phase change material microcapsules according to claim 3, characterized in that, In S4, the blade gap is 0.05-0.08mm and the coating speed is 15-20m / min.

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