Preparation method of water-based solvent-free polyurethane synthetic leather

Abstract

The invention discloses a preparation method of water-based solvent-free polyurethane synthetic leather, and belongs to the technical field of polyurethane synthetic leather, and the preparation method comprises the following steps: S1, coating the surface of a release surface of release paper with surface layer slurry, after the surface layer slurry stands until the surface is flat, covering the surface of the surface layer slurry with a toughening net layer, heating and drying the surface layer slurry to obtain a synthetic leather surface layer, and embedding and fixing the toughening net layer on the surface of the synthetic leather surface layer; s2, the face, inlaid with the toughening net layer, of the synthetic leather surface layer is coated with foaming slurry, and the foaming slurry is heated to be foamed to form a foaming core layer; s3, base cloth is bonded to the surface of the foaming core layer and then dried, the release paper is stripped after drying, and the polyurethane synthetic leather composed of the synthetic leather surface layer, the toughening net layer, the foaming core layer and the base cloth is obtained; according to the polyurethane synthetic leather disclosed by the invention, the comfort in the use process is improved through thermal management and good internal softness and elasticity.

Description

Technical Field

[0001] The invention relates to the technical field of polyurethane synthetic leather, and in particular to a method for preparing water-based solvent-free polyurethane synthetic leather. Background Art

[0002] Polyurethane synthetic leather is a new type of polymer composite material with special properties. It is widely used in sofas, interior decoration, engineering decoration, automobile interior decoration and other fields. With people's pursuit of high quality of life, the surface of sofas and other products has gradually abandoned the use of knitted fabrics, and the high price of genuine leather will increase the cost of sofas. Polyurethane synthetic leather is an ideal substitute for genuine leather. Polyurethane synthetic leather is similar to genuine leather in appearance, touch, durability and other aspects. Leather sofas with polyurethane synthetic leather as the surface layer have high comfort during use; however, whether it is polyurethane synthetic leather or genuine leather, its breathability is not as good as knitted fabric. In seasons with higher temperatures, users sitting on leather sofas for a period of time are prone to heat accumulation in the surface layer due to lack of air permeability, causing users to feel stuffy or even sweat.

[0003] Based on the above situation, a Chinese patent with announcement number CN113863017A discloses a highly wear-resistant synthetic leather for sofas that is easy to remove dirt and is used for making a sofa, and a preparation method thereof. The highly wear-resistant synthetic leather for sofas that is easy to remove dirt and is used for making a sofa is made by coating the surface of a polyurethane synthetic leather base for sofas with an anti-fouling and wear-resistant slurry. The polyurethane synthetic leather base for sofas is compositely formed by a polyurethane membrane and a base cloth, and the polyurethane membrane is extruded by a polyurethane slurry through a T-shaped casting head. The polyurethane slurry includes the following raw materials: water-based polyurethane, N,N-dimethylformamide, ultrafine lignin, and nano-calcium carbonate; the anti-fouling and wear-resistant slurry includes the following raw materials: water-based polyurethane emulsion, an acrylate mixture, dodecafluoroheptyl methacrylate, an initiator, a nano-filler, a nano-modified gelatin, and a thickener; The preparation method comprises the following steps: (1) extruding a polyurethane slurry through a T-type casting head to obtain a polyurethane film, and compounding the polyurethane film with a base fabric through an embossing wheel to obtain a polyurethane synthetic leather base for a sofa; (2) mixing an aqueous polyurethane emulsion with an acrylic acid mixture, and then adding dodecafluoroheptyl methacrylate and an initiator and fully polymerizing, dispersing and emulsifying to obtain a modified aqueous polyurethane emulsion; (3) mixing and grinding a nanofiller with a nano-modified gelatin, stirring and mixing the nanofiller with the modified aqueous polyurethane emulsion, and then adding a thickener and stirring to obtain an anti-fouling and wear-resistant slurry; (4) coating the anti-fouling and wear-resistant slurry on the bottom surface of the polyurethane synthetic leather base for a sofa, and drying and cooling and drying to obtain an easy-to-remove and highly wear-resistant synthetic leather for a sofa.

[0004] The surface of the easy-to-clean and highly wear-resistant synthetic leather disclosed in the above patent is easy to clean and not easy to be stained, but the internal polyurethane membrane is made by a cast extrusion molding process. Although the raw materials of the polyurethane membrane contain ultrafine lignin and nano-calcium carbonate, which can form a breathable microporous structure during the molding process, its air permeability is still not as good as that of knitted fabrics or foamed polyurethane synthetic leathers, which makes the overall air permeability of the easy-to-clean and highly wear-resistant synthetic leather insufficient, resulting in a stuffy feeling during the use of the sofa product, so there is still room for improvement. Summary of the invention

[0005] In view of the technical defects existing in the background technology, the present invention proposes a method for preparing a water-based solvent-free polyurethane synthetic leather, which solves the above technical problems and meets the actual needs. The specific technical scheme is as follows: A method for preparing a water-based solvent-free polyurethane synthetic leather comprises the following steps: S1, coating the surface slurry on the release surface of the release paper, and after the surface slurry is left to stand until the surface is flat, covering the surface of the surface slurry with a toughening mesh layer, heating and drying the surface slurry to obtain a synthetic leather surface layer, and embedding and fixing the toughening mesh layer on the surface of the synthetic leather surface layer; S2, applying the foaming slurry on the side of the synthetic leather surface layer inlaid with the toughening mesh layer, and heating the foaming slurry to foam to form a foaming core layer; S3, bonding the base fabric to the surface of the foamed core layer and drying it, and after drying, peeling off the release paper to obtain a polyurethane synthetic leather consisting of a synthetic leather surface layer, a toughening mesh layer, a foamed core layer, and a base fabric; The surface layer slurry includes the following components by mass percentage: 77% to 93% aqueous solvent-free polyurethane emulsion, 5% to 15% thermal conductive filler, and 2% to 8% surface layer additive; The foaming slurry comprises the following components by mass percentage: 81% to 92% of aqueous solvent-free polyurethane emulsion, 5% to 10% of phase change particles, 1% to 3% of foaming agent, and 2% to 6% of core layer auxiliary agent.

[0006] As a further technical solution of the present invention, in step S1, the toughening mesh layer is manufactured by the following method: S1-1, forming a cotton thread net by combing, spinning, twisting, and weaving the cotton fibers; S1-2, immersing the cotton thread net in the liquid phase change slurry, taking out the cotton thread net after the phase change slurry completely penetrates into the inside of the cotton thread net and spraying the hydrophilic material evenly on the surface, forming a phase change layer on the surface of the cotton thread net after the phase change slurry is cured, and the hydrophilic material is embedded on the surface of the phase change layer to form a hydrophilic layer; S1-3, immersing the cotton mesh obtained in step S1-2 in an aqueous solvent-free polyurethane emulsion, then taking it out and drying it, and heating and drying it after the aqueous solvent-free polyurethane emulsion on the surface dries to a gel state to form an isolation film. The cotton mesh, phase change layer, hydrophilic layer, and isolation film together constitute a toughened mesh layer.

[0007] As a further technical solution of the present invention, the phase change temperature of the phase change slurry is 25~32°C.

[0008] As a further technical solution of the present invention, the hydrophilic material is selected from one or more of polyvinyl alcohol powder, silicon dioxide powder, aluminum oxide powder, cellulose fiber, and cotton fiber.

[0009] As a further technical solution of the present invention, the thermally conductive filler is selected from one or more of aluminum oxide powder, zinc oxide powder, magnesium oxide powder, silicon carbide powder, boron carbide powder, graphene powder, and graphite powder.

[0010] As a further technical solution of the present invention, the surface layer additive includes the following components by mass percentage: 20% to 30% dispersant, 10% to 40% thickener, 5% to 15% leveling agent, 10% to 20% softener, and 10% to 40% colorant.

[0011] As a further technical solution of the present invention, the phase change particles are composed of an internal phase change core layer and a polyurethane resin wrapped outside the phase change core layer, and the phase change temperature of the phase change core layer is 20-30°C.

[0012] As a further technical solution of the present invention, the foaming temperature of the foaming agent is 100-150°C.

[0013] As a further technical solution of the present invention, the core layer additive includes the following components by mass percentage: 30% to 50% chain extender, 10% to 30% dispersant, 10% to 30% thickener, and 10% to 30% antibacterial agent.

[0014] As a further technical solution of the present invention, the base fabric is selected from one of knitted fabric, woven fabric and non-woven fabric.

[0015] The beneficial effects of the present invention are: The polyurethane synthetic leather of the present invention is composed of a synthetic leather surface layer, a toughening mesh layer, a foaming layer and a base fabric in sequence along the thickness direction. The heat conductive filler in the synthetic leather surface layer can improve the wear resistance and strength of the synthetic leather surface layer. The heat conductive filler can also realize efficient heat transfer between the synthetic leather surface layer and the toughening mesh layer and the foaming core layer. The phase change particles and the phase change layer inside the polyurethane synthetic leather perform heat management by absorbing heat or releasing latent heat, which can improve the cool feeling in hot weather and keep warm in cold weather. The elasticity and softness of the foaming core layer are combined to improve the comfort of the polyurethane synthetic leather during use. DETAILED DESCRIPTION

[0016] The implementation mode of the present invention is described below in conjunction with relevant embodiments. The implementation mode of the present invention is not limited to the following embodiments, and the present invention relates to relevant necessary components in the technical field, which should be regarded as the known technology in the technical field and can be known and mastered by the technical personnel in the technical field.

[0017] A method for preparing a water-based solvent-free polyurethane synthetic leather comprises the following steps: S1, coating the surface slurry on the release surface of the release paper, and after the surface slurry is left to stand until the surface is flat, covering the surface of the surface slurry with a toughening mesh layer, heating and drying the surface slurry to obtain a synthetic leather surface layer, and embedding and fixing the toughening mesh layer on the surface of the synthetic leather surface layer; S2, applying the foaming slurry on the side of the synthetic leather surface layer inlaid with the toughening mesh layer, and heating the foaming slurry to foam to form a foaming core layer; S3, bonding the base fabric to the surface of the foamed core layer and drying it, and after drying, peeling off the release paper to obtain a polyurethane synthetic leather consisting of a synthetic leather surface layer, a toughening mesh layer, a foamed core layer and a base fabric.

[0018] The polyurethane synthetic leather of the present invention is composited by a synthetic leather surface layer, a toughening mesh layer, a foaming core layer, and a base fabric, wherein in step S1, the surface layer slurry comprises the following components by mass percentage: 77% to 93% of an aqueous solvent-free polyurethane emulsion, 5% to 15% of a thermal conductive filler, and 2% to 8% of a surface layer additive; the surface layer slurry is mainly composed of an aqueous solvent-free polyurethane emulsion, and the aqueous solvent-free polyurethane emulsion contains a crosslinking agent and a catalyst. During the process of coating the surface layer slurry on the surface of a release paper and drying, the crosslinking agent and the catalyst work together to form chemical bonds between polyurethane molecules, thereby connecting the polyurethane molecules into a three-dimensional network structure, and drying. After drying, it will solidify on the surface of the release paper to form a uniform and continuous polyurethane film. In the drying process, due to the volatilization of water in the aqueous solvent-free polyurethane emulsion and the rearrangement of polyurethane molecules, many tiny, breathable and liquid-impermeable pores or channels will be formed, so that the synthetic leather surface layer has good air permeability. As the side of the polyurethane synthetic leather that is in direct contact with the human body, the good air permeability of the synthetic leather surface layer is conducive to reducing the stuffiness generated during use. In addition, coating the surface layer slurry on the surface of the release paper can make the formed synthetic leather surface layer easier to peel off, and the surface of the synthetic leather surface layer is smoother after peeling, thereby improving the touch of the polyurethane synthetic leather surface.

[0019] Furthermore, in the process of covering the toughening mesh layer on the surface of the surface layer slurry, since the surface layer slurry is still in liquid state, the toughening mesh layer will be partially embedded in the surface layer slurry. After the surface layer slurry is dried and solidified into a synthetic leather surface layer, the toughening mesh layer will be fixed on the surface. The toughening mesh layer adopts a mesh structure, which can improve the toughness and tensile strength of the synthetic leather surface layer.

[0020] In step S2, the foaming slurry includes the following components in percentage by mass: 81% to 92% of aqueous solvent-free polyurethane emulsion, 5% to 10% of phase change particles, 1% to 3% of foaming agent, and 2% to 6% of core layer additive; during the process of coating the foaming slurry on the surface of the toughening mesh layer and heating, the aqueous solvent-free polyurethane emulsion can form chemical bonds between polyurethane molecules under the joint action of the crosslinking agent and the catalyst, thereby gradually connecting the polyurethane molecules into a three-dimensional network structure, and at the same time, the foaming agent will decompose under heat to produce gas to form many bubbles inside the foaming slurry, so that the foaming slurry forms a rich pore structure inside while curing, and finally obtains a foaming core layer; the foaming core layer has good elasticity and softness due to the rich pore structure inside, which can improve the comfort of the polyurethane synthetic leather during use.

[0021] After adopting the above structure, it should be noted that the phase change particles are composed of an internal phase change core layer and a polyurethane resin wrapped outside the phase change core layer. The phase change temperature of the phase change core layer is 20~30℃, preferably 28~30℃. The phase change core layer can use paraffin or other phase change materials that match the phase change temperature. The phase change particles are distributed inside the foaming core layer. The phase change core layer maintains a constant temperature during the phase change process. When polyurethane synthetic leather is used as the surface material of the sofa, the polyurethane synthetic leather will be in direct contact with the human body. The heat of the human body will be transferred to the foaming core layer through the synthetic leather surface layer. The thermal conductive filler in the synthetic leather surface layer can improve the heat transfer efficiency and avoid heat accumulation in the synthetic leather. The polyurethane synthetic leather surface layer is filled with air and the temperature of the foaming core layer is maintained at below 33°C for a long time. The phase change particles can make the temperature of the foaming and synthetic leather surface layer maintained below 33°C for a long time, which can make the human body feel cool when touching the sofa surface layer, thereby improving the comfort of the polyurethane synthetic leather. In addition, the air temperature in the pore structure of the foaming core layer will be close to the phase change temperature of the phase change core layer. When the human body sits on the sofa, the polyurethane synthetic leather will be squeezed by external force, and part of the air in the foaming core layer will be discharged from the micropores on the surface of the synthetic leather surface layer and contact the human body. Since the temperature of the air is lower than the human skin temperature, the cool feeling and comfort of the human body can be further improved.

[0022] In addition, in cold weather, after a person sits on a sofa for a period of time, the phase change particles will absorb a large amount of heat and store it. When the person leaves the sofa, the phase change particles can release heat to keep the temperature of the sofa surface constant. When the person sits on the sofa again, he will not feel cold due to the low surface temperature of the sofa. Therefore, polyurethane synthetic leather can perform thermal management on the surface of products such as sofas through the internal phase change particles, increase the coolness in hot weather, and maintain warmth in cold weather, thereby improving the comfort of the product.

[0023] Furthermore, the phase change particles can be prepared by the following method: adding the phase change material to the aqueous polyurethane emulsion, adding an emulsifier and fully emulsifying the mixture into a mixed emulsion of a water-in-oil system, wherein the aqueous polyurethane emulsion serves as the water phase and the phase change material serves as the oil phase, stirring and heating the mixed emulsion to allow the polyurethane in the aqueous polyurethane emulsion to crosslink and solidify while volatilizing the water, cooling after the reaction is completed and filtering to obtain solid particles, washing and drying the solid particles to obtain phase change particles.

[0024] In step S3, the base fabric is selected from one of knitted fabric, woven fabric and non-woven fabric, and the base fabric is bonded to the surface of the foamed core layer by an environmentally friendly water-based adhesive. In the process of drying the adhesive by heating, the foamed core layer can be aged at the same time. The aging treatment is beneficial to improving the strength and other properties of the foamed core layer and improving the structural strength of the polyurethane synthetic leather. After the heating and drying treatment is completed, the temperature is lowered, and the release paper is peeled off to obtain the polyurethane synthetic leather. The polyurethane synthetic leather is composed of a synthetic leather surface layer, a toughening mesh layer, a foaming layer and a base fabric in the thickness direction.

[0025] As one of the preferred embodiments of the present invention, in step S1, the toughening mesh layer is made by the following method: S1-1, the cotton fibers are combed, spun, twisted, and warp and weft woven to form a cotton mesh; S1-2, immersing the cotton thread net in the liquid phase change slurry, taking out the cotton thread net after the phase change slurry completely penetrates into the inside of the cotton thread net and spraying the hydrophilic material evenly on the surface, forming a phase change layer on the surface of the cotton thread net after the phase change slurry is cured, and the hydrophilic material is embedded on the surface of the phase change layer to form a hydrophilic layer; S1-3, immersing the cotton mesh obtained in step S1-2 in an aqueous solvent-free polyurethane emulsion, then taking it out and drying it, and heating and drying it after the aqueous solvent-free polyurethane emulsion on the surface dries to a gel state to form an isolation film. The cotton mesh, phase change layer, hydrophilic layer, and isolation film together constitute a toughened mesh layer.

[0026] In the toughening mesh layer of the present invention, the cotton thread mesh serves as the skeleton structure inside the toughening mesh layer, and the cotton thread mesh is composed of cotton fibers, so that the cotton thread mesh has good flexibility and absorbency; the phase change temperature of the phase change slurry is 25-32°C, preferably 28-30°C, and the phase change slurry can use paraffin or other phase change materials with phase change temperature matching, and the cotton thread mesh is immersed in the phase change slurry heated to a liquid state, and the viscosity of the phase change slurry can be reduced by increasing the heating temperature. The cotton thread mesh absorbs the phase change slurry inside through good absorbency, and after the cotton thread mesh is taken out, its inside It contains a certain amount of phase change slurry and has a layer of phase change slurry attached to the surface. After cooling and solidification, the phase change slurries are fixed to the cotton thread net to form a phase change layer. After the phase change slurry is solidified into the phase change layer, since paraffin is hydrophobic, the surface of the phase change layer will also be hydrophobic. Therefore, before the phase change slurry is cooled and solidified, a layer of hydrophilic material is sprayed on the surface to embed the hydrophilic material on the surface of the phase change slurry, so that the surface of the solidified phase change layer is embedded with a hydrophilic layer composed of hydrophilic materials. The hydrophilic layer can make the water-based solvent-free polyurethane emulsion better adhere to the surface of the phase change layer.

[0027] Furthermore, the hydrophilic material is selected from one or more of polyvinyl alcohol powder, silica powder, alumina powder, cellulose fiber, and cotton fiber. These powdered or fibrous materials have good hydrophilicity. Before the phase change layer is cured, it can be sprayed and attached to the surface of the phase change layer by embedding, so that the surface of the cured phase change layer is embedded with a hydrophilic layer composed of hydrophilic materials. The hydrophilic layer allows the aqueous solvent-free polyurethane emulsion to evenly adhere to the surface of the phase change layer to form a liquid film through the hydrophilicity. This liquid film needs to be naturally dried in the shade or air-dried to remove part of the moisture and transform into a gel state, and then cured by heating and drying to prevent the phase change layer from melting into liquid and penetrating the liquid film and dripping during the heating process. During the heating and drying process of the liquid film, the polyurethane molecules are cured into a polyurethane film under the joint action of the cross-linking agent and the catalyst. The polyurethane film is the isolation film. The isolation film can isolate the phase change layer from the outside world to prevent the phase change layer from melting due to heat and flowing out of the toughening mesh layer.

[0028] The toughening mesh layer of the present invention contains a certain amount of phase change material inside, and the phase change temperature of the phase change material is 25-32°C, preferably 28-30°C. Since one side of the toughening mesh layer is embedded in the synthetic leather surface layer, the toughening mesh layer can efficiently absorb the heat in the synthetic leather surface layer through the internal phase change material, and the phase change material can keep the temperature unchanged during the phase change process, so that the temperature of the synthetic leather surface layer is maintained close to the phase change temperature of the phase change material. When the polyurethane synthetic leather is used as the sofa surface material, the polyurethane synthetic leather will be in direct contact with the human body, and the heat of the human body will be transferred to the toughening mesh layer through the synthetic leather surface layer. Thermal management is performed through the phase change layer inside the toughening mesh layer, thereby further improving the comfort of the polyurethane synthetic leather during use.

[0029] As one of the preferred embodiments of the present invention, the thermally conductive filler is selected from one or more of aluminum oxide powder, zinc oxide powder, magnesium oxide powder, silicon carbide powder, boron carbide powder, graphene powder, and graphite powder. The above thermally conductive fillers have good thermal conductivity. When the human body comes into contact with the synthetic leather surface layer, the heat of the human body will be transferred to the inside of the synthetic leather surface layer and quickly diffused through the thermally conductive filler, thereby avoiding heat accumulation inside the synthetic leather surface layer; the thermally conductive filler can be processed by ball milling or the like to improve the smoothness of the surface. When the synthetic leather surface layer is worn, the thermally conductive filler may be exposed. The thermally conductive filler with a smooth surface can reduce the roughness of the worn part of the synthetic leather surface layer; in addition, the synthetic leather surface layer after adding the thermally conductive filler has higher wear resistance, which can improve the durability of the polyurethane synthetic leather.

[0030] As one of the preferred embodiments of the present invention, the surface layer additive includes the following components by mass percentage: 20% to 30% dispersant, 10% to 40% thickener, 5% to 15% leveling agent, 10% to 20% softener, and 10% to 40% colorant.

[0031] The dispersant in the surface layer additive can be selected from common inorganic dispersants, organic small molecule dispersants, and polymer dispersants. The dispersant can reduce the surface tension of the surface layer slurry, increase the dispersibility of the thermal conductive filler in the surface layer slurry, make the thermal conductive filler evenly dispersed in the synthetic leather surface layer and improve the thermal conductivity of the synthetic leather surface layer.

[0032] The thickener in the surface layer additive can be selected from common associative thickeners, non-ionic thickeners, and cellulose thickeners. The thickener can improve the film-forming properties of the surface layer slurry. When the surface layer slurry is cured to form a synthetic leather surface layer, the surface of the synthetic leather surface layer can be made smoother and more lustrous.

[0033] The leveling agent in the surface additive can be selected from common silicone leveling agents, fluorocarbon leveling agents, and polymer leveling agents. The leveling agent can make the surface slurry level quickly after coating, thereby improving coating efficiency. The leveling agent can also improve the adhesion and anti-stick properties of the surface slurry and improve the durability of polyurethane synthetic leather.

[0034] The softener in the surface additive can be selected from common silicone softeners and fatty acid softeners. The softener can improve the softness of the surface layer of synthetic leather. As the side of the polyurethane synthetic leather that is in direct contact with the human body, the synthetic leather surface layer can improve comfort. The softener can also improve the wear resistance and wrinkle resistance of the synthetic leather surface layer, thereby improving the durability of the polyurethane synthetic leather.

[0035] The colorant in the surface additive can be selected from common organic dyes and acid dyes. The synthetic leather surface layer is the outermost side of the polyurethane synthetic leather, and its color determines the appearance of the polyurethane synthetic leather. The colorant can be selected according to the appearance of the product made of polyurethane synthetic leather to adaptively adjust the color of the synthetic leather surface layer.

[0036] As one of the preferred embodiments of the present invention, the foaming temperature of the foaming agent is 100-150°C, and the foaming slurry usually needs to be heated to 100-150°C for drying and promoting internal cross-linking reaction. The foaming agent is preferably modified sodium bicarbonate. By selecting a foaming agent whose foaming temperature matches the heating temperature, the foaming slurry is foamed simultaneously during the heating and curing process, thereby forming a foamed core layer with a rich pore structure.

[0037] As one of the preferred embodiments of the present invention, the core layer additive includes the following components by mass percentage: 30% to 50% chain extender, 10% to 30% dispersant, 10% to 30% thickener, and 10% to 30% antibacterial agent.

[0038] The chain extender in the core layer additive can be selected from small molecule diol chain extenders and dimethylol propionic acid. The chain extender can extend the molecular chain of the polyurethane molecule during the cross-linking reaction of the polyurethane molecule and improve the strength of the foaming core layer.

[0039] The dispersant in the core layer additive can be selected from common inorganic dispersants, organic small molecule dispersants, and polymer dispersants. The dispersant can reduce the surface tension of the foaming slurry, increase the dispersibility of the phase change particles in the foaming slurry, and make the phase change particles evenly dispersed in the foaming core layer, so that the foaming core layer can evenly absorb heat through the internal phase change particles.

[0040] The thickener in the core layer additive can be selected from common associative thickeners, non-ionic thickeners, and cellulose thickeners. The thickener can increase the viscosity and adhesion of the core layer slurry, thereby making it easier to coat the core layer slurry on the side of the synthetic leather surface layer close to the toughening mesh layer.

[0041] The antibacterial agent in the core layer additive can be selected from inorganic silver ion antibacterial agents, inorganic zinc ion antibacterial agents, pyridine antibacterial agents, and quaternary ammonium salt antibacterial agents. The foaming core layer has a rich pore structure. When the polyurethane synthetic leather circulates with the outside air, water vapor is easily retained inside the foaming core layer, causing bacteria to breed and produce odors, and even causing the polyurethane synthetic leather to become moldy and cracked. The antibacterial agent improves the antibacterial properties of the polyurethane synthetic leather by killing bacteria and preventing them from multiplying inside the foaming core layer.

[0042] In summary, the polyurethane synthetic leather of the present invention is composed of a synthetic leather surface layer, a toughening mesh layer, a foaming layer, and a base fabric in sequence along the thickness direction. The thermal conductive filler in the synthetic leather surface layer can improve the wear resistance and strength of the synthetic leather surface layer. The thermal conductive filler can also enable efficient heat transfer between the synthetic leather surface layer and the toughening mesh layer and the foaming core layer. The phase change particles and the phase change layer inside the polyurethane synthetic leather perform thermal management by absorbing heat or releasing latent heat, which can improve the cool feeling in hot weather and keep warm in cold weather. Combined with the elasticity and softness of the foaming core layer, the comfort of the polyurethane synthetic leather during use is improved.

[0043] The present invention is further described below by way of examples and comparative examples.

[0044] Example 1

[0045] S1. Combing, spinning, twisting, and weaving cotton fibers into a cotton thread net, immersing the cotton thread net in a liquid phase change slurry with a phase change temperature of 28-30°C, taking out the cotton thread net after the phase change slurry completely penetrates into the inside of the cotton thread net, and spraying aluminum oxide powder evenly on the surface, forming a phase change layer on the surface of the cotton thread net after the phase change slurry is cured, and the aluminum oxide powder is embedded on the surface of the phase change layer to form a hydrophilic layer; S2, immersing the cotton thread net obtained in step S1 in an aqueous solvent-free polyurethane emulsion, then taking it out to dry, and heating and drying after the aqueous solvent-free polyurethane emulsion on the surface is dried to a gel state to form an isolation film, and the cotton thread net, phase change layer, hydrophilic layer, and isolation film together constitute a toughening mesh layer; S3, coating the surface slurry on the release surface of the release paper, and after the surface slurry is left to stand until the surface is flat, covering the surface of the surface slurry with a toughening mesh layer, heating and drying the surface slurry to obtain a synthetic leather surface layer, and embedding and fixing the toughening mesh layer on the surface of the synthetic leather surface layer; the surface slurry includes the following components by mass percentage: 89% aqueous solvent-free polyurethane emulsion, 5% thermal conductive filler, 0.5% dispersant, 2% thickener, 0.5% leveling agent, 1% softener, and 2% toner; S4, coating the foaming slurry on the side of the synthetic leather surface layer inlaid with the toughening mesh layer, and heating the foaming slurry to foam to form a foaming core layer; the foaming slurry includes the following components by mass percentage: 85% of aqueous solvent-free polyurethane emulsion, 8% of phase change particles, 2% of foaming agent, 1.5% of chain extender, 1% of dispersant, 1.5% of thickener, and 1% of antibacterial agent; S5, bonding the base fabric to the surface of the foamed core layer and drying it, and after drying, peeling off the release paper to obtain a polyurethane synthetic leather consisting of a synthetic leather surface layer, a toughening mesh layer, a foamed core layer and a base fabric.

[0046] Example 2

[0047] The difference between this embodiment and the above-mentioned embodiment 1 is that in step S3, the surface layer slurry includes the following components in percentage by mass: 84% aqueous solvent-free polyurethane emulsion, 10% thermal conductive filler, 1% dispersant, 1.5% thickener, 0.5% leveling agent, 1% softener, and 2% colorant; the operations and component ratios of the remaining steps are the same.

[0048] Example 3

[0049] The difference between this embodiment and the above-mentioned embodiment 1 is that in step S3, the surface layer slurry includes the following components in percentage by mass: 79% aqueous solvent-free polyurethane emulsion, 15% thermal conductive filler, 1.5% dispersant, 1% thickener, 0.5% leveling agent, 1% softener, and 2% colorant; the operations and component ratios of the remaining steps are the same.

[0050] Comparative Example 1 S1. Combing, spinning, twisting, and weaving cotton fibers into a cotton thread net, immersing the cotton thread net in a liquid phase change slurry with a phase change temperature of 28-30°C, taking out the cotton thread net after the phase change slurry completely penetrates into the inside of the cotton thread net, and spraying aluminum oxide powder evenly on the surface, forming a phase change layer on the surface of the cotton thread net after the phase change slurry is cured, and the aluminum oxide powder is embedded on the surface of the phase change layer to form a hydrophilic layer; S2, immersing the cotton thread net obtained in step S1 in an aqueous solvent-free polyurethane emulsion, then taking it out to dry, and heating and drying after the aqueous solvent-free polyurethane emulsion on the surface is dried to a gel state to form an isolation film, and the cotton thread net, phase change layer, hydrophilic layer, and isolation film together constitute a toughening mesh layer; S3, coating the surface slurry on the release surface of the release paper, and after the surface slurry is left to stand until the surface is flat, covering the surface of the surface slurry with a toughening mesh layer, heating and drying the surface slurry to obtain a synthetic leather surface layer, wherein the toughening mesh layer is embedded and fixed on the surface of the synthetic leather surface layer; the surface slurry includes the following components by mass percentage: 94% aqueous solvent-free polyurethane emulsion, 2% thickener, 0.5% leveling agent, 1% softener, and 2.5% toner; S4, coating the foaming slurry on the side of the synthetic leather surface layer inlaid with the toughening mesh layer, and heating the foaming slurry to foam to form a foaming core layer; the foaming slurry includes the following components by mass percentage: 85% of aqueous solvent-free polyurethane emulsion, 8% of phase change particles, 2% of foaming agent, 1.5% of chain extender, 1% of dispersant, 1.5% of thickener, and 1% of antibacterial agent; S5, bonding the base fabric to the surface of the foamed core layer and drying it, and after drying, peeling off the release paper to obtain a polyurethane synthetic leather consisting of a synthetic leather surface layer, a toughening mesh layer, a foamed core layer and a base fabric.

[0051] Comparative Example 2 S1, forming a cotton thread net after combing, spinning, twisting, and weft and warp weaving the cotton fibers; S2, coating the surface slurry on the release surface of the release paper, and after the surface slurry is left to stand until the surface is flat, covering the surface of the surface slurry with a cotton thread net, heating and drying the surface slurry to obtain a synthetic leather surface layer, and embedding and fixing the cotton thread net on the surface of the synthetic leather surface layer; the surface slurry includes the following components by mass percentage: 84% aqueous solvent-free polyurethane emulsion, 10% thermal conductive filler, 1% dispersant, 1.5% thickener, 0.5% leveling agent, 1% softener, and 2% toner; S3, coating the foaming slurry on the side of the synthetic leather surface layer inlaid with the cotton mesh, and heating the foaming slurry to foam to form a foaming core layer; the foaming slurry includes the following components by mass percentage: 85% of aqueous solvent-free polyurethane emulsion, 8% of phase change particles, 2% of foaming agent, 1.5% of chain extender, 1% of dispersant, 1.5% of thickener, and 1% of antibacterial agent; S4, bonding the base fabric to the surface of the foamed core layer and drying it, and peeling off the release paper after drying to obtain a polyurethane synthetic leather consisting of a synthetic leather surface layer, a cotton thread net, a foamed core layer and a base fabric.

[0052] Comparative Example 3 S1, forming a cotton thread net after combing, spinning, twisting, and weft and warp weaving the cotton fibers; S2, coating the surface slurry on the release surface of the release paper, and after the surface slurry is left to stand until the surface is flat, covering the surface of the surface slurry with a cotton thread net, heating and drying the surface slurry to obtain a synthetic leather surface layer, and embedding and fixing the cotton thread net on the surface of the synthetic leather surface layer; the surface slurry includes the following components by mass percentage: 94% aqueous solvent-free polyurethane emulsion, 2% thickener, 0.5% leveling agent, 1% softener, and 2.5% toner; S3, applying the foaming slurry on the side of the synthetic leather surface layer inlaid with the cotton mesh, and heating the foaming slurry to foam to form a foaming core layer; the foaming slurry includes the following components by mass percentage: 93% of aqueous solvent-free polyurethane emulsion, 2.5% of foaming agent, 2% of chain extender, 1.5% of thickener, and 1% of antibacterial agent; S4, bonding the base fabric to the surface of the foamed core layer and drying it, and peeling off the release paper after drying to obtain a polyurethane synthetic leather consisting of a synthetic leather surface layer, a cotton thread net, a foamed core layer and a base fabric.

[0053] Comparative Example 4 The polyurethane synthetic leather is obtained based on Example 1 in the specification of a Chinese patent for an easily decontaminated and highly wear-resistant synthetic leather for sofas and a preparation method thereof (Announcement No.: CN113863017A).

[0054] The air permeability of the polyurethane synthetic leathers obtained in Examples 1, 2, 3 and Comparative Examples 1, 2, 4 was tested, and the test results are shown in Table 1 below.

[0055]

[0056] Table 1 It can be seen from the data in Table 1 that the raw materials of the synthetic leather surface layers of Examples 1, 2, 3 and Comparative Examples 1 and 2 are mainly aqueous solvent-free polyurethane emulsions, and the moisture in the synthetic leather surface layers evaporates during the molding process to form many breathable micropores, so they all have high air permeability. Since the thermal conductive filler can also form breathable micropores in the synthetic leather surface layer, the difference in air permeability of these polyurethane synthetic leathers also depends on the content of the thermal conductive filler in the synthetic leather surface layer; and the polyurethane synthetic leather of Comparative Example 4 is made of a polyurethane diaphragm inside by a cast extrusion molding process. Although the raw materials of the polyurethane diaphragm contain ultrafine lignin and nano-calcium carbonate, which can form a breathable microporous structure during the molding process, some of the breathable micropores formed by the filler cannot penetrate both sides of the polyurethane diaphragm, so the air permeability of the polyurethane synthetic leather is low.

[0057] The following test was performed on the polyurethane synthetic leather obtained in Examples 1, 2, 3 and Comparative Examples 1, 2, 3: a sponge was set on one side of the base fabric of the polyurethane synthetic leather to simulate the structure of a sofa, the temperature measuring end of the thermocouple was implanted into the surface layer of the synthetic leather, and in an environment of 25°C, an object with a constant temperature of 36.5°C was pressed on the surface of the polyurethane synthetic leather relative to the temperature measuring end of the thermocouple, and the time required for the temperature measured by the thermocouple to rise to 33°C was recorded; the test results are shown in Table 2 below.

[0058]

[0059] Table 2 The data in Table 2 are analyzed, and Comparative Example 3 is used as a blank control group. In Comparative Example 1, no thermal conductive filler is added to the synthetic leather surface layer, and the heat in the synthetic leather surface layer is difficult to be efficiently transferred to the toughening mesh layer and the foaming core layer. Even if the toughening mesh layer and the foaming core layer can absorb a large amount of latent heat, the heat accumulation in the synthetic leather surface layer still causes its temperature to rise to 33°C in a short time; in Comparative Example 2, the synthetic leather surface layer contains a thermal conductive filler. Since the inside of the foaming core layer is relatively fluffy, the efficiency of absorbing the heat in the synthetic leather surface layer through the phase change particles is still low, and the heat in the synthetic leather surface layer can be transferred to the toughening mesh layer and the foaming core layer. The thermally conductive filler is conducted along the extension direction of the synthetic leather surface layer, so the time it takes for the polyurethane synthetic leather to rise to 33°C during the test is longer than that in Comparative Example 1; in Examples 1, 2, and 3, the difference between the polyurethane synthetic leathers lies in the amount of thermally conductive filler added in the synthetic leather surface layer, and the thermally conductive filler in the synthetic leather surface layer can be coordinated with the toughening mesh layer of the mesh structure, so that the heat in the synthetic leather surface layer can be diffused over a large range to avoid heat accumulation in the synthetic leather surface layer, and the phase change layer and the phase change particles can absorb a large amount of latent heat, so that the polyurethane synthetic leather can rise to 33°C after a longer period of time.

[0060] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a water-based solvent-free polyurethane synthetic leather, characterized in that: The following steps are involved: S1, coating the surface slurry on the release surface of the release paper, and after the surface slurry is left to stand until the surface is flat, covering the surface of the surface slurry with a toughening mesh layer, heating and drying the surface slurry to obtain a synthetic leather surface layer, and embedding and fixing the toughening mesh layer on the surface of the synthetic leather surface layer; S2, applying the foaming slurry on the side of the synthetic leather surface layer inlaid with the toughening mesh layer, and heating the foaming slurry to foam to form a foaming core layer; S3, bonding the base fabric to the surface of the foamed core layer and drying it, and after drying, peeling off the release paper to obtain a polyurethane synthetic leather consisting of a synthetic leather surface layer, a toughening mesh layer, a foamed core layer, and a base fabric; The surface layer slurry includes the following components by mass percentage: 77% to 93% aqueous solvent-free polyurethane emulsion, 5% to 15% thermal conductive filler, and 2% to 8% surface layer additive; The foaming slurry comprises the following components by mass percentage: 81% to 92% of aqueous solvent-free polyurethane emulsion, 5% to 10% of phase change particles, 1% to 3% of foaming agent, and 2% to 6% of core layer auxiliary agent.

2. The method for preparing the water-based solvent-free polyurethane synthetic leather according to claim 1, characterized in that: In step S1, the toughening mesh layer is made by the following method: S1-1, forming a cotton thread net by combing, spinning, twisting, and weaving the cotton fibers; S1-2, immersing the cotton thread net in the liquid phase change slurry, taking out the cotton thread net after the phase change slurry completely penetrates into the inside of the cotton thread net and spraying the hydrophilic material evenly on the surface, forming a phase change layer on the surface of the cotton thread net after the phase change slurry is cured, and the hydrophilic material is embedded on the surface of the phase change layer to form a hydrophilic layer; S1-3, immersing the cotton mesh obtained in step S1-2 in an aqueous solvent-free polyurethane emulsion, then taking it out and drying it, and heating and drying it after the aqueous solvent-free polyurethane emulsion on the surface dries to a gel state to form an isolation film. The cotton mesh, phase change layer, hydrophilic layer, and isolation film together constitute a toughened mesh layer.

3. The method for preparing the water-based solvent-free polyurethane synthetic leather according to claim 2, characterized in that: The phase change temperature of the phase change slurry is 25-32°C.

4. The method for preparing the water-based solvent-free polyurethane synthetic leather according to claim 2, characterized in that: The hydrophilic material is selected from one or more of polyvinyl alcohol powder, silicon dioxide powder, aluminum oxide powder, cellulose fiber, and cotton fiber.

5. The method for preparing water-based solvent-free polyurethane synthetic leather according to claim 1, characterized in that: The thermally conductive filler is selected from one or more of aluminum oxide powder, zinc oxide powder, magnesium oxide powder, silicon carbide powder, boron carbide powder, graphene powder, and graphite powder.

6. The method for preparing water-based solvent-free polyurethane synthetic leather according to claim 1, characterized in that: The surface layer additive includes the following components by mass percentage: 20% to 30% of a dispersant, 10% to 40% of a thickener, 5% to 15% of a leveling agent, 10% to 20% of a softener, and 10% to 40% of a toner.

7. The method for preparing water-based solvent-free polyurethane synthetic leather according to claim 1, characterized in that: The phase change particles are composed of an internal phase change core layer and a polyurethane resin wrapped outside the phase change core layer, and the phase change temperature of the phase change core layer is 20-30°C.

8. The method for preparing water-based solvent-free polyurethane synthetic leather according to claim 1, characterized in that: The foaming temperature of the foaming agent is 100-150°C.

9. The method for preparing water-based solvent-free polyurethane synthetic leather according to claim 1, characterized in that: The core layer additive includes the following components by mass percentage: 30% to 50% of a chain extender, 10% to 30% of a dispersant, 10% to 30% of a thickener, and 10% to 30% of an antibacterial agent.

10. The method for preparing water-based solvent-free polyurethane synthetic leather according to claim 1, characterized in that: The base fabric is selected from knitted fabric, woven fabric and non-woven fabric.

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