A TPU extrusion foamed synthetic leather and its preparation method

Abstract

The present application relates to the technical field of synthetic leather, and specifically discloses a TPU extrusion foamed synthetic leather and a preparation method thereof. The synthetic leather comprises a finishing layer, a glue layer, a foamed layer and a base fabric layer which are compounded with each other from top to bottom; the glue layer comprises the following raw materials in parts by weight: 90-110 parts of TPU clear material particles, 0.1-0.4 parts of light fastness aid, 0.1-0.3 parts of heat stabilizer, 5-10 parts of filler, and 3-5 parts of colorant; the foamed layer comprises the following raw materials in parts by weight: TPU composite particles, colorant, and foaming masterbatch. The preparation method of the synthetic leather comprises the following steps: laminating the foamed layer and the base fabric layer; laminating the glue layer and the foamed layer to obtain a semi-finished leather; and performing surface finishing on the semi-finished leather by using a finishing agent to obtain the synthetic leather. The synthetic leather obtained in the present application can have a folding resistance of more than 200,000 times at room temperature, and the synthetic leather has excellent heat aging resistance and light aging resistance.

Description

Technical Field

[0001] The present application relates to the field of synthetic leather, and more specifically, it relates to a TPU extrusion foamed synthetic leather and a preparation method thereof. Background Art

[0002] With the progress of synthetic leather technology and the improvement of processing techniques, various synthetic leather materials have emerged. Currently, the most widespread ones are PU synthetic leather and PVC synthetic leather. Due to the large amount of organic pollutants in the production process of PU synthetic leather and PVC synthetic leather, in recent years, the research has started to shift towards new TPU synthetic leather.

[0003] TPU is a thermoplastic polyurethane elastomer rubber, which is a polymer material formed by the copolymerization reaction of diisocyanate molecules such as diphenylmethane diisocyanate (MDI) or toluene diisocyanate (TDI) and macromolecular polyols and low molecular polyols (chain extenders). Its molecular structure is alternately composed of rigid segments obtained by the reaction of diphenylmethane diisocyanate (MDI) or toluene diisocyanate (TDI) and chain extenders, and flexible segments obtained by the reaction of diisocyanate molecules such as diphenylmethane diisocyanate (MDI) or toluene diisocyanate (TDI) and macromolecular polyols.

[0004] TPU synthetic leather is a kind of synthetic leather made by using thermoplastic polyurethane (TPU) as the base material and processed through processes such as coating, embossing, and printing. It is widely used in fields such as shoe materials, luggage, furniture, and automotive interiors.

[0005] Currently, as disclosed in the patent with the publication number CN111005236A, a TPU synthetic leather includes the following raw materials in parts by weight: 100 parts of TPU particles; 10 - 40 parts of filler; 1 - 8 parts of foaming agent; 1 - 10 parts of TPU color masterbatch; 1 - 4 parts of auxiliary agent. The preparation method of the TPU synthetic leather includes the following steps: 1) Weigh the raw materials according to the ratio, add them to a kneader, and mix them evenly; 2) Transfer the evenly mixed mixture to an open mill for open milling; 3) Transfer the plasticized material obtained in step 2) to a calender, and adjust the thickness of the film; 4) Bond the prepared base cloth; 5) Foam and emboss the bonded film to obtain the required product. Although the TPU synthetic leather prepared by the above process has better abrasion resistance, its bending resistance during use is poor, and it is extremely easy to age after being heated and irradiated by light. Summary of the Invention

[0006] In order to effectively improve the bending resistance of the synthetic leather during use and simultaneously improve the thermal aging and photoaging properties of the synthetic leather, the present application provides a TPU extrusion foamed synthetic leather and a preparation method thereof.

[0007] In a first aspect, a TPU extrusion foamed synthetic leather provided by the present application adopts the following technical solution:

[0008] A TPU extrusion foamed synthetic leather, comprising a finishing layer, a glue layer, a foaming layer and a base fabric layer which are compounded with each other from top to bottom;

[0009] The glue layer comprises the following raw materials in parts by weight: 90-110 parts of TPU clear material particles, 0.1-0.4 part of a light-fastness aid, 0.1-0.3 part of a heat stabilizer, 5-10 parts of a filler, and 3-5 parts of a colorant; the heat stabilizer is bismaleimide and / or phosphite; the light-fastness aid comprises dihydroxyphenylalanine and a hindered amine light stabilizer;

[0010] The foaming layer comprises the following raw materials in parts by weight: 95-110 parts of TPU composite particles, 3-5 parts of a colorant, and 6-10 parts of a foaming masterbatch.

[0011] Further, the thickness of the finishing layer is 0.001-0.0018 mm, the thickness of the glue layer is 0.1-0.15 mm, and the thickness of the foaming layer is 0.35-0.5 mm; the thicknesses of the finishing layer, the glue layer and the foaming layer can all be customized according to actual needs.

[0012] Further, the colorant is a masterbatch. The model and color of the masterbatch can be reasonably selected according to actual needs.

[0013] Further, the base fabric layer is one of non-woven fabric, polyester fabric, nylon fabric or ultra-fine fiber base fabric. The selection of the base fabric layer can also be made according to actual needs.

[0014] Further, the filler is one of calcium powder, zinc oxide, and titanium dioxide. More preferably, the filler is calcium powder. The particle size of the calcium powder is preferably 400-800 mesh. The calcium powder has a wide source and low cost. After being compounded with other raw materials, it can effectively improve the bending resistance of the product, and the cost of the enterprise is low.

[0015] TPU clear material particles are selected and combined with light stabilizers and heat stabilizers. Bismaleimide has excellent heat resistance, and phosphite synergistically assists in heat stabilization. After high-temperature heat aging, there is no obvious change on the surface of the product, and the product has a high gray level; Dihydroxyphenylalanine and hindered amine light stabilizers are selected as light stabilizers. The hindered amine light stabilizer can not only protect the product by absorbing ultraviolet and low-energy visible light in the light, but also absorb free radicals and incremental electrons through the amino group contained in it, thereby reducing the oxidation reaction of the material. At the same time, the hindered amine light stabilizer can also oxidize the active substances on the surface of the material to form a stable complex, assisting the material to resist the performance damage caused by ultraviolet photochemical reactions. Dihydroxyphenylalanine not only has a certain absorption effect on light, but also contains catechol hydroxyl groups, which can form more stable intermolecular forces with the hindered amine light stabilizer. It can not only effectively improve the stability of the light stabilizer under ultraviolet light, but also is more conducive to absorbing the adverse effects brought by light. At the same time, dihydroxyphenylalanine is also conducive to the uniform dispersion of the hindered amine light stabilizer. The two synergistically significantly improve the light aging resistance of the material. In addition, dihydroxyphenylalanine can further promote the composite with the coating layer to form a tight connection, synergistically improving the mechanical properties of the product, thereby improving the comprehensive performance of the synthetic leather.

[0016] Using TPU clear material particles as the main material, supplemented with light stabilizers and heat stabilizers, can endow the gelatinous layer with excellent light aging and heat aging resistance, thereby improving the heat aging and light aging performance of the product; After acting together with the filler, the product can have better bending times in a high-temperature environment, thereby further improving the bending resistance performance of the product.

[0017] The foaming layer is made by combining TPU composite particles and foaming masterbatch, which can not only increase the softness and elasticity of the product, endow the product with excellent hand feeling, but also effectively assist in improving the bending resistance performance of the product, so that the product has better bending times in a high-temperature environment.

[0018] Preferably, the heat stabilizer is bismaleimide and phosphite with a mass ratio of 1:(0.8 - 2). Further preferably, the phosphite is liquid phosphite.

[0019] Through further research experiments, it is found that whether the dosage of bismaleimide or phosphite is too much or too little, it cannot effectively delay the heat aging of the product at high temperature. Through research experiments, it is found that the dosage relationship between bismaleimide and phosphite is between 1:(0.8 - 2), which can further improve the heat stability of the gelatinous layer, thereby improving the heat aging performance of the product.

[0020] Preferably, the mass ratio of the dihydroxyphenylalanine and the hindered amine light stabilizer is 3:(7 - 13).

[0021] Further optimizing the dosage ratio of dihydroxyphenylalanine and hindered amine light stabilizer is beneficial to the product having no obvious change on the surface, a high product gray level, and good light aging resistance performance after the product is subjected to light aging.

[0022] Preferably, the TPU cleaning particles comprise the following raw materials in parts by weight: 100 - 120 parts of polyurethane rubber, 30 - 60 parts of calcium powder, 1 - 3 parts of chain extender, 6 - 12 parts of lubricant, and 6 - 10 parts of grafting agent.

[0023] Furthermore, the chain extender is epoxy chain extender 4370, the grafting agent is grafting agent 328, and the lubricant is polyethylene wax.

[0024] By adopting the above technical solution, the polyurethane rubber is modified by using the chain extender and the grafting agent to improve the viscosity of the TPU cleaning particles, which can effectively combine with other raw material components and be tightly connected, so that the internal structure of the product is dense and has excellent processability.

[0025] Preferably, the TPU composite particles comprise the following raw materials in parts by weight: 80 - 100 parts of polyurethane rubber, 30 - 50 parts of filler, 1 - 5 parts of epoxy chain extender, and 6 - 10 parts of grafting agent.

[0026] More preferably, the filler is calcium carbonate fine powder with a particle size of 2000 - 2500 mesh.

[0027] Using the TPU composite particles as the main material of the foaming layer can endow the foaming layer with good strength, assist in improving the bending resistance performance of the product, so that the product has a better number of bending times in a high - temperature environment.

[0028] Preferably, the foaming masterbatch comprises the following raw materials in parts by weight: 3 - 10 parts of foam stabilizer, 3 - 5 parts of AC blowing agent, 0.2 - 0.4 parts of white blowing agent, and 1 - 5 parts of stabilizer.

[0029] Furthermore, the foam stabilizer is acrylic resin, the AC blowing agent is azodicarbonamide AC5000; the white blowing agent is sodium bicarbonate.

[0030] Furthermore, the stabilizer is sodium succinate and hydrotalcite, and preferably the mass ratio of sodium succinate to hydrotalcite is 1:(1 - 2.5).

[0031] By adopting the above technical solutions, under certain conditions, the foaming masterbatch forms tiny bubbles in the system, with uniform foaming and a certain foam stabilizing effect, forming an independent bubble structure inside the product, which helps the product have a delicate hand feeling and excellent bend resistance. Sodium succinate and hydrotalcite are selected as stabilizers, and the organic and inorganic substances are compounded, greatly improving the particle fluidity, promoting the crystallization of the polymer and improving its crystal grain structure, reducing the shrinkage and expansion of the system, playing a good role in stabilizing the system, and assisting in obtaining a foaming masterbatch with excellent performance.

[0032] Combining the foaming masterbatch with the TPU composite particles can effectively endow the foaming layer with excellent mechanical properties, and reduce the shrinkage and expansion of the product under high-temperature environments or when exposed to light, thereby improving the heat aging resistance and light resistance of the product.

[0033] In a second aspect, the present application provides a method for preparing a TPU extrusion foamed synthetic leather, adopting the following technical solutions:

[0034] A method for preparing a TPU extrusion foamed synthetic leather includes the following steps:

[0035] After mixing the TPU composite particles, the foaming masterbatch and the colorant, dry them at a temperature of 75 - 90 °C, and then extrude to form a foaming layer, which is laminated with the base cloth layer;

[0036] Mix the TPU clear particles with the colorant, light fastness aid, heat stabilizer, and filler, extrude after drying to obtain a gelatinous layer, and laminate the gelatinous layer on the surface of the foaming layer away from the base cloth layer to obtain a semi-finished leather;

[0037] Use a finishing agent to perform surface finishing on the semi-finished leather to obtain the synthetic leather.

[0038] By adopting the above technical solutions, the entire production process does not use wet or dry production lines, nor any organic solvents, without VOC emissions. The entire process production line is green and environmentally friendly, recyclable, has extremely low carbon emissions, low energy consumption for enterprises, and a significant reduction in costs.

[0039] Preferably, the finishing agent includes dopamine micropowder and polyurethane glue with a mass ratio of 1:(8 - 15).

[0040] Furthermore, the dopamine micropowder is preferably a powder with a particle size of 100 - 150 μm.

[0041] By adopting the above technical solutions, dopamine micropowder and polyurethane glue are selected as the finishing agent. Among them, the dopamine micropowder can combine with the catechol group in dihydroxyphenylalanine to form a substance with excellent adhesion and form a protective film after drying and shaping. This not only helps to form a tight connection between the finishing layer and the gelatinous layer, but also can further improve the comprehensive performance of the product.

[0042] Preferably, a TPU composite particle is prepared by mixing polyurethane rubber, a filler, a chain extender, and a grafting agent and then pelletizing them with an extruder.

[0043] Preferably, a foaming masterbatch is prepared by mixing a solid foaming agent, an AC foaming agent, a self-foaming agent, and a stabilizer and then extruding and pelletizing them.

[0044] By adopting the above technical solution, using the extrusion pelletizing method can not only effectively control the size and shape of the particles, with uniform particle size, which is further beneficial to improving the product quality, but also the production method is green, environmentally friendly, recyclable, with extremely low carbon emissions and low energy consumption for the enterprise.

[0045] In summary, the present application has the following beneficial effects:

[0046] 1. Using the TPU clear material particles as the main material, supplemented with a light-resistant auxiliary agent and a heat stabilizer, can endow the gum layer with excellent light aging resistance and heat aging resistance, thereby improving the thermal aging and light aging properties of the product; after acting together with the filler, the product can have better bending times in a high-temperature environment, thus further improving the bending resistance performance of the product.

[0047] 2. Combining the foaming masterbatch with the TPU composite particles can effectively endow the foaming layer with excellent mechanical properties and reduce the shrinkage and expansion of the product in a high-temperature environment or under light action, thereby improving the heat aging resistance and light resistance of the product.

[0048] 3. Selecting dopamine micropowder and polyurethane glue as the finishing agent, where the dopamine micropowder can combine with the catechol group in dihydroxyphenylalanine to form a substance with excellent adhesion and form a protective film after drying and forming. This not only facilitates the formation of a tight connection between the finishing layer and the gum layer but also can further improve the comprehensive performance of the product. Specific Embodiments

[0049] The following further elaborates on the present application with reference to embodiments. It should be specifically noted that: for those conditions not specified in the following embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer; except as otherwise specified, the raw materials used in the following embodiments are all from ordinary commercial sources.

[0050] Embodiments

[0051] Example 1

[0052] A TPU extrusion foamed synthetic leather includes a finishing layer, a gum layer, a foaming layer, and a base fabric layer that are compounded with each other from top to bottom. The base fabric layer is made of non-woven fabric;

[0053] The gelatinous layer comprises the following raw materials: 90 parts of TPU clear material particles, 0.1 part of light fastness aid, 0.1 part of bismaleimide, 5 parts of zinc oxide, and 3 parts of color masterbatch; the light fastness aid comprises dihydroxyphenylalanine and hindered amine light stabilizer in a mass ratio of 3:7; the TPU clear material particles comprise the following raw materials: 100 parts of polyurethane rubber, 30 parts of calcium powder, 1 part of chain extender, 6 parts of polyethylene wax, and 6 parts of grafting agent;

[0054] The foaming layer comprises the following raw materials: 95 parts of TPU composite particles, 3 parts of color masterbatch, and 6 parts of foaming masterbatch;

[0055] The TPU composite particles comprise the following raw materials: 80 parts of polyurethane rubber, 30 parts of calcium carbonate fine powder, 1 part of epoxy chain extender, and 6 parts of grafting agent;

[0056] The foaming masterbatch comprises the following raw materials: 10 parts of acrylic resin, 5 parts of azodicarbonamide, 0.4 part of sodium bicarbonate, 5 parts of stabilizer, and the stabilizer is sodium succinate and hydrotalcite in a mass ratio of 1:2.5.

[0057] A preparation method of the TPU extrusion foaming synthetic leather comprises the following steps:

[0058] Mix polyurethane rubber, calcium carbonate fine powder, chain extender, and grafting agent, and then use a twin-screw extruder to carry out underwater extrusion granulation to obtain TPU composite particles for standby; mix acrylic resin, azodicarbonamide, sodium bicarbonate, and stabilizer, and put them into a twin-screw extruder for extrusion granulation to obtain foaming masterbatch for standby; mix polyurethane rubber, calcium powder, chain extender, polyethylene wax, and grafting agent evenly, and then use a twin-screw extruder to carry out underwater extrusion granulation to obtain TPU clear material particles for standby;

[0059] Mix the TPU composite particles, foaming masterbatch, and color masterbatch, dry them at a temperature of 80°C, then extrude to form a foaming layer with a thickness of 0.4 mm, and carry out online lamination with the base fabric layer;

[0060] Mix the TPU clear material particles, color masterbatch, light fastness aid, bismaleimide, and zinc oxide, dry them at a temperature of 80°C for 4 hours, then carry out single-screw extrusion to obtain a gelatinous layer with a thickness of 0.1 mm, and laminate the gelatinous layer on the surface of the foaming layer away from the base fabric layer to obtain semi-finished leather;

[0061] Use a finishing agent to carry out surface finishing on the semi-finished leather to form a finishing layer with a thickness of 0.0018 mm to obtain synthetic leather; the finishing agent is a mixture of dopamine powder and polyurethane glue in a mass ratio of 1:8.

[0062] Example 2

[0063] The TPU extrusion foaming synthetic leather comprises a finishing layer, a gelatinous layer, a foaming layer, and a base fabric layer which are compounded with each other from top to bottom, and the base fabric layer is made of polyester fabric;

[0064] The glue layer comprises the following raw materials: 110 parts of TPU clear material particles, 0.4 part of light-fastness aid, 0.3 part of liquid phosphite, 10 parts of titanium dioxide, and 5 parts of masterbatch; the light-fastness aid comprises dihydroxyphenylalanine and hindered amine light stabilizer with a mass ratio of 3:13; the TPU clear material particles comprise the following raw materials: 120 parts of polyurethane rubber, 60 parts of calcium powder, 3 parts of chain extender, 12 parts of polyethylene wax, and 10 parts of grafting agent;

[0065] The foaming layer comprises the following raw materials: 110 parts of TPU composite particles, 4 parts of masterbatch, and 8 parts of foaming masterbatch;

[0066] The TPU composite particles comprise the following raw materials: 90 parts of polyurethane rubber, 50 parts of calcium carbonate fine powder, 5 parts of epoxy chain extender, and 10 parts of grafting agent;

[0067] The foaming masterbatch comprises the following raw materials: 3 parts of acrylic resin, 3 parts of azodicarbonamide, 0.2 part of sodium bicarbonate, 1 part of stabilizer, and the stabilizer is succinic acid sodium and hydrotalcite with a mass ratio of 1:1.

[0068] A preparation method of the TPU extrusion foaming synthetic leather comprises the following steps:

[0069] Mix the polyurethane rubber, calcium carbonate fine powder, chain extender, and grafting agent, and use a twin-screw extruder to carry out underwater extrusion granulation to obtain TPU composite particles for standby; mix the acrylic resin, azodicarbonamide, sodium bicarbonate, and stabilizer, and input them into a twin-screw extruder for extrusion granulation to obtain foaming masterbatch for standby; mix the polyurethane rubber, calcium powder, chain extender, polyethylene wax, and grafting agent evenly, and use a twin-screw extruder to carry out underwater extrusion granulation to obtain TPU clear material particles for standby;

[0070] Mix the TPU composite particles, foaming masterbatch, and masterbatch, dry them at a temperature of 90 °C, then extrude to form a foaming layer with a thickness of 0.45 mm, and carry out online lamination with a base cloth layer;

[0071] Mix the TPU clear material particles, masterbatch, light-fastness aid, bismaleimide, and titanium dioxide, dry them at a temperature of 80 °C for 4 hours, then carry out single-screw extrusion to obtain a glue layer with a thickness of 0.1 mm, and laminate the glue layer on the surface of the foaming layer away from the base cloth layer to obtain a semi-finished leather;

[0072] Use a finishing agent to carry out surface finishing on the semi-finished leather to obtain a synthetic leather; the finishing agent is a mixture of dopamine powder and polyurethane glue with a mass ratio of 1:15.

[0073] Example 3

[0074] TPU extrusion foamed synthetic leather, which includes a finishing layer, a gum layer, a foaming layer and a base fabric layer that are compounded with each other from top to bottom. The base fabric layer is made of non-woven fabric;

[0075] The gum layer includes the following raw materials: 100 parts of TPU clear material particles, 0.2 part of light fastness aid, 0.2 part of heat stabilizer, 10 parts of calcium powder, and 4.5 parts of color masterbatch; The heat stabilizer is a bismaleimide and a liquid phosphite with a mass ratio of 1:0.8, and the light fastness aid includes dihydroxyphenylalanine and a hindered amine light stabilizer with a mass ratio of 3:7;

[0076] The TPU clear material particles include the following raw materials: 100 parts of polyurethane rubber, 48 parts of calcium powder, 1.7 parts of chain extender, 10 parts of polyethylene wax, and 9 parts of grafting agent;

[0077] The foaming layer includes the following raw materials: 100 parts of TPU composite particles, 5 parts of color masterbatch, and 10 parts of foaming masterbatch;

[0078] The TPU composite particles include the following raw materials: 100 parts of polyurethane rubber, 42 parts of calcium carbonate fine powder, 2.5 parts of epoxy chain extender, and 8 parts of grafting agent;

[0079] The foaming masterbatch includes the following raw materials: 10 parts of acrylic resin, 4.5 parts of azodicarbonamide, 0.3 part of sodium bicarbonate, 3.5 parts of stabilizer, and the stabilizer is sodium succinate and hydrotalcite with a mass ratio of 1:2.5.

[0080] The preparation method of the TPU extrusion foamed synthetic leather is the same as that of Example 1.

[0081] Example 4

[0082] The difference from Example 3 is that the heat stabilizer is a bismaleimide and a liquid phosphite with a mass ratio of 1:2, and the rest are the same as those in Example 3.

[0083] Example 5

[0084] The difference from Example 3 is that the heat stabilizer is a bismaleimide and a liquid phosphite with a mass ratio of 1:5, and the rest are the same as those in Example 3.

[0085] Example 6

[0086] The difference from Example 4 is that the light fastness aid includes dihydroxyphenylalanine and a hindered amine light stabilizer with a mass ratio of 3:10; The rest are the same as those in Example 4.

[0087] Example 7

[0088] The difference from Example 4 is that the light fastness aid includes dihydroxyphenylalanine and a hindered amine light stabilizer with a mass ratio of 10:3; The rest are the same as those in Example 4.

[0089] Example 8

[0090] The difference from Example 6 is that the stabilizer is sodium succinate and hydrotalcite with a mass ratio of 1:2, and the rest are the same as in Example 6.

[0091] Example 9

[0092] The difference from Example 6 is that the stabilizer is hydrotalcite, and the rest are the same as in Example 6.

[0093] Example 10

[0094] The difference from Example 8 is that in the preparation method of the TPU extrusion foamed synthetic leather, a finishing agent composed of dopamine micropowder and polyurethane glue with a mass ratio of 1:10 is used to perform surface finishing on the semi-finished leather to obtain the synthetic leather; the rest are the same as in Example 8.

[0095] Comparative Example

[0096] Comparative Example 1

[0097] The difference from Example 10 is that the light fastness aid is a benzotriazole ultraviolet absorber, and the rest are the same as in Example 10.

[0098] Comparative Example 2

[0099] The difference from Example 10 is that the light fastness aid is dihydroxyphenylalanine; the rest are the same as in Example 10.

[0100] Comparative Example 3

[0101] The difference from Example 10 is that the heat stabilizer is zinc stearate, and the rest are the same as in Example 10.

[0102] Comparative Example 4

[0103] The difference from Example 10 is that an equal amount of polyurethane rubber is used to replace the TPU clear material particles and TPU comprehensive particles respectively, and the rest are the same as in Example 10.

[0104] Comparative Example 5

[0105] The difference from Example 10 is that the stabilizer is calcium carbonate micropowder, and the rest are the same as in Example 10.

[0106] Comparative Example 6

[0107] The difference from Example 10 is that the finishing agent is polyurethane glue, and the rest are the same as in Example 10.

[0108] Performance Detection Test

[0109] The samples prepared in Examples 1-10 and Comparative Examples 1-6 were subjected to a flame retardancy test according to GB 8410-2006, and the burning speed of the samples was not higher than 100 mm / min.

[0110] The samples prepared in Examples 1-10 and Comparative Examples 1-6 were subjected to a folding endurance test at room temperature according to QB / T 2714-2005 "Determination of Folding Endurance of Leather - Physical and Mechanical Tests", and the results were recorded in Table 1.

[0111] The samples prepared in Examples 1-10 and Comparative Examples 1-6 were placed in an incubator for heat aging. The heat aging temperature was 120 °C. It was required that the gray level of the samples after heat aging was not lower than 4.5 levels and there was no obvious change on the surface. The number of days of heat aging of the samples was recorded, and the results were recorded in Table 1.

[0112] The samples prepared in Examples 1-10 and Comparative Examples 1-6 were subjected to a light aging test according to SAE J2412 with a light energy of 600 KJ. It was required that the gray level of the samples after light aging was not lower than 4 levels and there was no obvious change on the surface. The number of days of light aging of the samples was recorded, and the results were recorded in Table 1.

[0113] Table 1

[0114]

[0115]

[0116] Combined with Examples 1-10 and Table 1, it can be seen that the synthetic leather obtained by this application can have a folding endurance of more than 200,000 times at room temperature, has excellent folding endurance performance, and in a high-temperature environment or a light irradiation environment, there is no obvious change on the surface of the product, the gray level of the product is high, and the synthetic leather has excellent heat aging resistance and light aging resistance.

[0117] Combined with Example 10 and Comparative Examples 1-2 and Table 1, it can be seen that using a commercially available common benzotriazole ultraviolet absorber to replace the light-resistant additive of the present application, or lacking the corresponding components, both have a significant impact on the light aging resistance of the product, and at the same time affect the bending resistance and thermal aging performance of the product. This is because the hindered amine light stabilizer can not only protect the product by absorbing ultraviolet and low-energy visible light in the light, but also absorb free radicals and incremental electrons through the amino groups contained therein, thereby reducing the oxidation reaction of the material. At the same time, the hindered amine light stabilizer can also oxidize the active substances on the surface of the material to form a stable complex, assisting the material to resist the performance damage caused by ultraviolet photochemical reactions. Dihydroxyphenylalanine not only has a certain absorption effect on light, but also contains catechol hydroxyl groups, which can form a more stable intermolecular force with the hindered amine light stabilizer. It can not only effectively improve the stability of the light-resistant additive under ultraviolet light, but also is more conducive to absorbing the adverse effects brought by light. At the same time, dihydroxyphenylalanine is also conducive to the uniform dispersion of the hindered amine light stabilizer. The two cooperate to significantly improve the light aging resistance of the material. In addition, dihydroxyphenylalanine can further promote the composite with the coating layer to form a tight connection, synergistically improving the mechanical properties of the product, thereby improving the comprehensive performance of the synthetic leather.

[0118] Combined with Example 10 and Comparative Examples 3-4 and Table 1, it can be seen that in Comparative Example 3, zinc stearate commonly used in the art was used to replace the heat stabilizer of the present application. In a high-temperature environment, the number of days of aging resistance of the product was significantly reduced, and the thermal aging performance was significantly reduced. In Comparative Example 4, polyurethane rubber was used to replace the corresponding TPU clear material particles and TPU composite particles, resulting in a decrease in the quality of both the gelatinous layer and the foaming layer, thus leading to poor comprehensive quality of the product.

[0119] Combined with Example 10 and Comparative Example 5 and Table 1, it can be seen that although using calcium carbonate micropowder as a stabilizer can play a role in strengthening and stabilizing to a certain extent, it cannot effectively improve the crystal grain structure of the system. The synergistic effect of sodium succinate and hydrotalcite can play an excellent role in the stability of the system. When the system is subjected to high temperature and light aging, it can reduce its expansion and contraction, thereby assisting in effectively improving the comprehensive performance of the product.

[0120] Combined with Example 10 and Comparative Example 6 and Table 1, it can be seen that using polyurethane glue to coat the surface of the gelatinous layer can only play a good bonding role and has a certain impact on the comprehensive performance of the product. This is because dopamine micropowder can combine with the catechol groups in dihydroxyphenylalanine to form a substance with excellent adhesion and form a protective film after drying and molding, which can improve the bending resistance and mechanical properties of the product, and assist in improving the heat aging and light aging resistance of the product.

[0121] This specific embodiment is only an interpretation of the present application and does not limit the present application. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions as needed, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A TPU extrusion foamed synthetic leather, characterized in that, it comprises a finishing layer, a gum layer, a foaming layer and a base fabric layer which are compounded with each other from top to bottom; the gum layer is adhered to the surface of the foaming layer away from the base fabric layer to obtain a semi-finished leather; the synthetic leather is obtained by surface-finishing the semi-finished leather with a finishing agent; the finishing agent comprises dopamine powder and polyurethane glue with a mass ratio of 1:(8 - 15); the gum layer comprises the following raw materials in parts by weight: 90 - 110 parts of TPU clear material particles, 0.1 - 0.4 part of light-fastness aid, 0.1 - 0.3 part of heat stabilizer, 5 - 10 parts of filler, 3 - 5 parts of colorant; the heat stabilizer is bismaleimide and phosphite; the light-fastness aid comprises dihydroxyphenylalanine and hindered amine light stabilizer; the TPU clear material particles comprise the following raw materials in parts by weight: 100 - 120 parts of polyurethane rubber, 30 - 60 parts of calcium powder, 1 - 3 parts of chain extender, 6 - 12 parts of lubricant, 6 - 10 parts of grafting agent; the foaming layer comprises the following raw materials in parts by weight: 95 - 110 parts of TPU composite particles, 3 - 5 parts of colorant, 6 - 10 parts of foaming masterbatch; the TPU composite particles comprise the following raw materials in parts by weight: 80 - 100 parts of polyurethane rubber, 30 - 50 parts of filler, 1 - 5 parts of epoxy chain extender, 6 - 10 parts of grafting agent; the foaming masterbatch comprises the following raw materials in parts by weight: 3 - 10 parts of acrylic resin, 3 - 5 parts of AC blowing agent, 0.2 - 0.4 part of white blowing agent, 1 - 5 parts of stabilizer; the stabilizer is sodium succinate and hydrotalcite.

2. The TPU extrusion foamed synthetic leather according to claim 1, characterized in that: the heat stabilizer is bismaleimide and phosphite with a mass ratio of 1:(0.8 - 2).

3. The TPU extrusion foamed synthetic leather according to claim 2, characterized in that: the mass ratio of dihydroxyphenylalanine and hindered amine light stabilizer is 3:(7 - 13).

4. The preparation method of the TPU extrusion foamed synthetic leather according to any one of claims 1 - 3, characterized in that: it comprises the following steps: After mixing the TPU composite particles, the foaming masterbatch and the colorant, drying them at a temperature of 75 - 90 °C, and then extruding to form a foaming layer, which is adhered to the base fabric layer; Mix the TPU clear material particles with the colorant, light-fastness aid, heat stabilizer and filler, and extrude after drying to obtain a gum layer; adhere the gum layer to the surface of the foaming layer away from the base fabric layer to obtain a semi-finished leather; Surface-finish the semi-finished leather with a finishing agent to obtain the synthetic leather.

5. The preparation method of the TPU extrusion foamed synthetic leather according to claim 4, characterized in that: Mix the polyurethane rubber, filler, chain extender and grafting agent, and then extrude and pelletize them with an extruder to obtain TPU composite particles.

6. The preparation method of the TPU extrusion foamed synthetic leather according to claim 4, characterized in that: Mix the acrylic resin, AC blowing agent, white blowing agent and stabilizer, and extrude and pelletize them to obtain a foaming masterbatch.

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