Aqueous polyurethane-coated synthetic leather and a method for producing the same

Abstract

This invention relates to a waterborne polyurethane-coated synthetic leather and its preparation method. The waterborne polyurethane-coated synthetic leather has a composite layer structure, consisting of coating B, coating C, and microfiber base fabric from top to bottom, or further, coating A is placed above coating B. Coatings A, B, and C are all waterborne polyurethane coatings, with 100% moduli of the waterborne polyurethane in coatings A, B, and C being 1-3 MPa, 12-15 MPa, and 22-25 MPa, respectively. The preparation method is as follows: first, coating B slurry is coated onto release paper and dried to form coating B; then, coating C slurry is coated onto coating B, followed by the microfiber base fabric, dried, and peeled off from the release paper; finally, coating A slurry is applied to the surface of coating B by roller coating or printing, and dried to obtain the waterborne polyurethane-coated synthetic leather. The synthetic leather of this invention has excellent low-temperature folding resistance and resilience, and also possesses an excellent hand feel.

Description

Technical Field

[0001] This invention belongs to the field of polyurethane synthetic leather, and relates to a water-based polyurethane coated synthetic leather and its preparation method, particularly to a high-strength water-based polyurethane coated synthetic leather with excellent low-temperature folding resistance and its preparation method. Background Technology

[0002] Polyurethane materials, due to their excellent flexibility and abrasion resistance, are widely used as finishing materials for leather and are a key factor affecting the appearance-related properties of polyurethane synthetic leather. Polyurethane synthetic leather has good processing properties; through the development of coating technology, leather products with various textures and colors can be obtained, making it widely used in footwear, automotive interior coverings, and other fields. In the fields of footwear, automotive interiors, and everyday leather goods, processing requires directional bending of the leather, thus necessitating good unilateral flexural strength. Furthermore, the leather needs to be used in cold environments, therefore, high requirements are placed on its low-temperature flexural strength.

[0003] Existing technologies generally improve the low-temperature flexural strength of polyurethane by increasing the soft segments of polyurethane. However, increasing the soft segments of polyurethane reduces the modulus of polyurethane and the stress resilience of polyurethane materials, thereby affecting the feel of polyurethane coatings.

[0004] Compared to traditional flexible molecular chains, polybutadiene structures possess rubber-like properties, enabling elastic deformation rather than viscous flow deformation. For example, patent CN201911263927.3 discloses a low-temperature resistant, wear-resistant, non-yellowing polyurethane resin and the microfiber synthetic leather prepared from it. The polyurethane resin prepared in this patent is primarily composed of polycarbonate polyol, and the introduction of hydrogenated hydroxyl-terminated polybutadiene with a special structure can improve low-temperature folding resistance. However, the addition of hydrogenated hydroxyl-terminated polybutadiene to the polyurethane molecule increases its hydrophobicity. If hydrogenated hydroxyl-terminated polybutadiene is introduced into the waterborne polyurethane molecule, it can easily lead to instability in water, affecting the resilience of the microfiber synthetic leather.

[0005] As can be seen from the above, there are certain difficulties in obtaining both resilience and low-temperature folding resistance by modifying the molecular structure of traditional waterborne polyurethane, as proposed in the existing technology. Summary of the Invention

[0006] The purpose of this invention is to solve the problems existing in the prior art and to provide a water-based polyurethane coated synthetic leather and its preparation method.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A water-based polyurethane coated synthetic leather has a composite layer structure, consisting of coating B, coating C, and microfiber base fabric from top to bottom; or further, coating A is placed above coating B.

[0009] Coating A, coating B, and coating C are all water-based polyurethane coatings;

[0010] The 100% modulus of waterborne polyurethane in coating A is 1-3 MPa, the 100% modulus of waterborne polyurethane in coating B is 12-15 MPa, and the 100% modulus of waterborne polyurethane in coating C is 22-25 MPa.

[0011] The thickness of the microfiber base fabric is 1.0-1.3mm, the total thickness of the microfiber base fabric and coating C is ≤1.5mm, the total thickness of the microfiber base fabric, coating C and coating B is ≤1.8mm, and the total thickness of the microfiber base fabric, coating C, coating B and coating A is ≤2.0mm.

[0012] As a preferred technical solution:

[0013] The waterborne polyurethane coated synthetic leather described above uses one or more of the following: conventional polyester-type waterborne polyurethane, polyether-type waterborne polyurethane, polycarbonate-type waterborne polyurethane, polycarbonate-polyester-type waterborne polyurethane, polycarbonate-polyether-type waterborne polyurethane, and polyester-polyether-type polyurethane, but does not include polyolefin-type waterborne polyurethane.

[0014] The waterborne polyurethane coated synthetic leather described above also contains additives dispersed in the waterborne polyurethane coating.

[0015] As described above, the waterborne polyurethane coated synthetic leather uses one or more of the following additives: small molecule lubricants, leveling agents, thickeners, and color pastes. Small molecule lubricants, such as tributyl phosphate (in an example where water solubility is low and the amount added is small), propylene carbonate, triethyl phosphate, and polyethylene glycol (PEG-200) with a number average molecular weight of 200, can improve the material's ductility. Leveling agents, such as BYK-346 from BYK GmbH, are additives that improve wet film flow properties. Thickeners, such as those from Stahl GmbH, are widely available commercially. EVO RM-4417 EVO RM-4456 and other additives are used to increase the viscosity of waterborne polyurethane coatings.

[0016] As described above, the total thickness of coatings A, B, and C in a water-based polyurethane coated synthetic leather is 0.6-1 mm. This control is to meet the requirements of hand feel. The thickness of coating C is at least 30% of the total thickness of coatings A, B, and C, and the sum of the thicknesses of coatings C and B accounts for 80-100% of the total thickness of coatings A, B, and C.

[0017] The water-based polyurethane coated synthetic leather described above has the following properties: it can withstand at least 30,000 single-sided bends at -40℃; and after being subjected to a 150N tensile force for 30 minutes, the residual deformation of the water-based polyurethane coated synthetic leather is ≤5%. The smaller the residual deformation, the better the resilience.

[0018] This invention also provides a method for preparing a waterborne polyurethane coated synthetic leather as described in any of the preceding claims, comprising the following steps:

[0019] (1) Forming coating B;

[0020] Coating B slurry is applied to release paper and dried to form coating B;

[0021] The release paper method for coating preparation is a dry transfer film technology in the field of synthetic leather. Engineers skilled in the art can obtain the coating thickness required by the present invention by adjusting the coating amount based on relevant technical information and the target coating thickness.

[0022] (2) Forming coating C;

[0023] First, apply coating C slurry onto coating B, then attach the microfiber base fabric, dry it, and peel it off from the release paper;

[0024] (3) Forming coating A;

[0025] By using roller coating or printing, coating A slurry is applied to the surface of coating B and then dried to obtain water-based polyurethane coated synthetic leather.

[0026] The above-mentioned release paper method for preparing the coating is also a commonly used processing method in the synthetic leather industry for preparing the top coating by the above-mentioned roll coating or printing method. According to relevant technical information and in combination with the target coating thickness, engineers in this field can obtain the coating required by the present invention by adjusting the coating amount and drying process.

[0027] The preparation method of waterborne polyurethane coated synthetic leather is not limited to this. Coating C, coating B, and coating A can also be applied directly to the microfiber base fabric in sequence, or coating A, coating B, coating C, and microfiber base fabric can be applied directly to the release paper in sequence. This invention only provides one preparation method by way of example.

[0028] Invention Mechanism:

[0029] Polyurethane resin chains consist of hard segments and soft segments. Hard segments are formed on the polyurethane molecular backbone by the reaction of isocyanates, chain extenders, and crosslinking agents. These groups have high cohesive energy, large spatial volume, and high rigidity. Soft segments are carbon-carbon backbone polymer polyols, which have better flexibility and are flexible segments in the polyurethane backbone. The more hard segments there are, the higher the 100% modulus of the polyurethane; the more soft segments there are, the lower the 100% modulus of the polyurethane.

[0030] This invention is based on research into the relationship between 100% modulus and ultimate thickness. The smaller the 100% modulus, the more inversely proportional the deformation capacity of polyurethane is to its contribution to resilience. When a material is subjected to external force, it deforms. The greater the deformation under the same stress, the more easily the surface material dissipates external stress through molecular chain displacement rather than storing it as internal stress. When the stress is dissipated, the resilience after the external stress is removed deteriorates. To achieve a composite coating with both high resilience and high deformation capacity, it is necessary to rationally set the 100% modulus of the waterborne polyurethane in coating A (outermost layer), coating B (middle layer), and coating C (innermost layer).

[0031] If the 100% modulus of the waterborne polyurethane in coatings A, B, and C is relatively high, although the molecular chain structure of the product is more prone to energy storage deformation and has high resilience, it will also be difficult to dissipate the stress when the stress exceeds the limit due to the lack of appropriate viscous flow deformation, resulting in cracking. This manifests as poor performance during bending. If the 100% modulus of the waterborne polyurethane in coatings A, B, and C is relatively low, although the composite coating has high deformation capacity, its resilience is poor. Considering that the outer layer has the largest deformation and the inner layer has the smallest deformation during bending, this invention controls the 100% modulus of the waterborne polyurethane in coatings A, B, and C to gradually increase, that is, the polyurethane film gradually softens from the inside to the outside, forming a soft-hard gradient structure.

[0032] Experiments show that in order for composite coatings to achieve ideal low-temperature folding resistance under ideal resilience, it is necessary to strictly control the magnitude of the modulus gradient difference and the thickness ratio.

[0033] The 100% modulus of waterborne polyurethane in coating A is 1-3 MPa. Since coating A is located on the outermost layer, it experiences the greatest deformation force. Therefore, the total thickness of the microfiber base fabric, coating C, coating B, and coating A needs to be controlled to be ≤2.0 mm to ensure that the deformation capacity of coating A can match the actual deformation it experiences. The total thickness of the microfiber base fabric, coating C, coating B, and coating A determines the amount of high-elastic deformation that coating A will undergo during bending. When the total thickness is too large, the coating film will crack due to excessive deformation of coating A.

[0034] The 100% modulus of the waterborne polyurethane in coating B is 12-15 MPa. Since coating B is located in the intermediate layer, it experiences moderate deformation force. The total thickness of the microfiber base fabric, coating C, and coating B determines the amount of high-elastic deformation that coating B will undergo during bending. If the total thickness is too large, excessive deformation of coating B will also induce cracking of the coating film. It is necessary to control the total thickness of the microfiber base fabric, coating C, and coating B to ≤1.8 mm to ensure that the deformation capacity of coating B matches the actual deformation it experiences.

[0035] The 100% modulus of the waterborne polyurethane in coating C is 22-25 MPa. Since coating C is located in the innermost layer, it experiences the least deformation force. Therefore, the total thickness of the microfiber base fabric and coating C needs to be controlled to be ≤1.5 mm. The total thickness determines the amount of high-elastic deformation that coating C will undergo during bending. When the total thickness is too large, white streaks will appear due to excessive deformation of coating C.

[0036] The thickness of the microfiber base fabric is generally at least 1 mm to ensure a stiff skeleton structure, and 1-2 mm is commonly chosen. This invention controls it to be 1-1.3 mm to minimize the overall thickness of the synthetic leather, thereby relatively increasing the thickness ratio of the coating C. When the thickness of the microfiber base fabric exceeds 1.3 mm, it means that the thickness of the high-modulus coating C will be less than 0.2 mm, and it will be difficult to obtain suitable elastic energy storage under external force. When the thickness exceeds 1.5 mm, it is even impossible to establish a high-modulus coating C.

[0037] The total thickness of coatings A, B, and C is 0.6-1 mm. This control is to meet the requirements of hand feel. The thickness of coating C is at least 30% of the total thickness of coatings A, B, and C. The sum of the thicknesses of coatings C and B accounts for 80-100% of the total thickness of coatings A, B, and C to ensure that the film has appropriate elastic recovery.

[0038] Beneficial effects:

[0039] (1) The composite coating of the waterborne polyurethane coated synthetic leather prepared by the present invention has a certain soft-hard gradient change from the outside to the inside. Under the premise of satisfying the low temperature folding resistance of the coating film, the resilience of the material is improved; or in other words, under the same resilience, it has better low temperature folding resistance.

[0040] (2) The water-based polyurethane coated synthetic leather prepared by the present invention has an excellent hand feel by controlling the total thickness of its coating within the range of 0.6-1mm. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the composite layer structure of the present invention;

[0042] Among them, 1-coating A, 2-coating B, 3-coating C, and 4-microfiber base fabric. Detailed Implementation

[0043] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0044] The following are the performance testing methods in each embodiment:

[0045] Single-sided bending resistance: Tested according to ISO 5402-1-2017, the test temperature is -40℃, and the number of bending cycles is 30,000. If cracking occurs, it is unqualified; otherwise, it is qualified.

[0046] 100% Modulus: According to GB / T13022-1991, the tensile strength of the material when the elongation reaches 100% is determined, that is, the tensile strength corresponding to the polyurethane film with an elongation of 100% divided by the cross-sectional area of ​​the polyurethane film sample before stretching.

[0047] Residual deformation: The waterborne polyurethane coated synthetic leather prepared in the following examples was cut into pieces of 200mm × 50mm and tested according to the testing instrument in GB / T13022-1991 standard. Before the test, the length L0 of the synthetic leather between the two clamps was measured and the test position was marked. Then, the synthetic leather was stretched with a constant tensile force of 150N for 30 minutes. After the tensile force was removed, it was left for 10 minutes. Then, the length L1 of the synthetic leather at the marked position was measured. The residual deformation rate of the synthetic leather = (L1-L0) / L0 × 100%.

[0048] Example 1

[0049] A water-based polyurethane coated synthetic leather having a composite layer structure, such as Figure 1 As shown, from top to bottom, the layers are: coating A1, coating B2, coating C3, and microfiber base fabric 4.

[0050] Coating A, coating B, and coating C are all water-based polyurethane coatings;

[0051] The waterborne polyurethane in coating A is manufactured by Covestro Polymers (China) Co., Ltd., and its brand name is [Brand Name Missing]. DAH, 100% modulus is 1MPa;

[0052] The manufacturer of the waterborne polyurethane in coating B is Stahl Fine Coatings (Suzhou) Co., Ltd., and the brand name is: DRU-94-226, 100% modulus is 12MPa;

[0053] The manufacturer of the waterborne polyurethane in coating C is Stahl Fine Coatings (Suzhou) Co., Ltd., and the brand name is: D EX-RU-94-424, 100% modulus is 23MPa;

[0054] The thickness of coating A is 0.1 mm, the thickness of coating B is 0.3 mm, and the thickness of coating C is 0.2 mm. The total thickness of coatings A, B, and C is 0.6 mm. The thickness of coating C accounts for 33% of the total thickness of coatings A, B, and C. The sum of the thicknesses of coatings C and B accounts for 83% of the total thickness of coatings A, B, and C.

[0055] The microfiber base fabric is manufactured by Toray Industries, Inc. The 500Z series product (1.7mm thick) is obtained through a sanding process, resulting in a thickness of 1.3mm.

[0056] The method for preparing the waterborne polyurethane coated synthetic leather as described above includes the following steps:

[0057] (1) Preparation of raw materials:

[0058] Waterborne polyurethane in coating A;

[0059] Waterborne polyurethane in coating B;

[0060] Waterborne polyurethane in coating C;

[0061] Microfiber base fabric;

[0062] Release paper;

[0063] (2) Forming coating B;

[0064] Coating B slurry is applied to release paper and dried to form coating B;

[0065] (3) Forming coating C;

[0066] First, apply coating C slurry onto coating B, then attach the microfiber base fabric, dry it, and peel it off from the release paper;

[0067] (4) Forming coating A;

[0068] By using a roller coating method, coating slurry A is applied to the surface of coating B and then dried to obtain water-based polyurethane coated synthetic leather.

[0069] The final waterborne polyurethane coated synthetic leather passed the test for single-sided bending resistance at -40℃, and the residual deformation after the tension was removed after being subjected to a tensile force of 150N for 30 minutes was 4.82%.

[0070] Comparative Example 1

[0071] A waterborne polyurethane coated synthetic leather, basically the same as in Example 1, except that the waterborne polyurethane in coating B is manufactured by Covestro Polymers (China) Co., Ltd., and its brand name is [Brand Name Missing]. DL 519, 100% modulus is 7MPa.

[0072] The method for preparing the waterborne polyurethane coated synthetic leather as described above is basically the same as in Example 1.

[0073] The final waterborne polyurethane coated synthetic leather passed the test for single-sided bending resistance at -40℃, and the residual deformation after the tension was removed after being subjected to a tensile force of 150N for 30 minutes was 17.99%.

[0074] Comparing Comparative Example 1 and Example 1, it can be seen that because the 100% modulus of waterborne polyurethane in coating B of Comparative Example 1 is too small, it is difficult to store stress, which will lead to poor elasticity of the final waterborne polyurethane coated synthetic leather. In addition, after bending, coating B and coating C will bulge due to the large difference in elongation and recovery.

[0075] Comparative Example 2

[0076] A waterborne polyurethane coated synthetic leather, basically the same as in Example 1, except that the waterborne polyurethane in coating B is manufactured by Covestro Polymers (China) Co., Ltd., and its brand name is [Brand Name Missing]. DL 1007, 100% modulus is 18MPa.

[0077] The method for preparing the waterborne polyurethane coated synthetic leather as described above is basically the same as in Example 1.

[0078] The final waterborne polyurethane coated synthetic leather failed to meet the single-sided bending resistance test at -40℃, and the residual deformation after removing the tension was 4.31% after being subjected to a tensile force of 150N for 30 minutes.

[0079] Comparing Comparative Example 2 and Example 1, it can be seen that the excessively high 100% modulus of the waterborne polyurethane in coating B of Comparative Example 2 leads to a rapid decrease in the number of folding cycles at low temperatures.

[0080] Example 2

[0081] A water-based polyurethane coated synthetic leather has a composite layer structure, consisting of coating A, coating B, coating C, and microfiber base fabric from top to bottom;

[0082] Coating A, coating B, and coating C are all water-based polyurethane coatings;

[0083] The manufacturer of the waterborne polyurethane in coating A is Zhejiang Huafeng Synthetic Resin Co., Ltd., with the grade JF-PDY-836HY and a 100% modulus of 3 MPa.

[0084] The manufacturer of the waterborne polyurethane in coating B is Stahl Fine Coatings (Suzhou) Co., Ltd., and the brand name is: DRU-94-226, 100% modulus is 12MPa;

[0085] The manufacturer of the waterborne polyurethane in coating C is Stahl Fine Coatings (Suzhou) Co., Ltd., and the brand name is: D EX-RU-94-424, 100% modulus is 23MPa;

[0086] The thickness of coating A is 0 mm, the thickness of coating B is 0.35 mm, and the thickness of coating C is 0.25 mm. The total thickness of coatings A, B, and C is 0.6 mm. The thickness of coating C accounts for 42% of the total thickness of coatings A, B, and C. The sum of the thicknesses of coatings C and B accounts for 100% of the total thickness of coatings A, B, and C.

[0087] The microfiber base fabric is manufactured by Toray Industries, Inc. The 500Z series product (1.7mm thick) is obtained through a sanding process, resulting in a thickness of 1.2mm.

[0088] The method for preparing the waterborne polyurethane coated synthetic leather as described above includes the following steps:

[0089] (1) Preparation of raw materials:

[0090] Waterborne polyurethane in coating A;

[0091] Waterborne polyurethane in coating B;

[0092] Waterborne polyurethane in coating C;

[0093] Microfiber base fabric;

[0094] Release paper;

[0095] (2) Forming coating B;

[0096] Coating B slurry is applied to release paper and dried to form coating B;

[0097] (3) Forming coating C;

[0098] First, apply coating C slurry onto coating B, then attach the microfiber base fabric, dry it, and peel it off from the release paper;

[0099] (4) Forming coating A;

[0100] By using a roller coating method, coating slurry A is applied to the surface of coating B and then dried to obtain water-based polyurethane coated synthetic leather.

[0101] The final waterborne polyurethane coated synthetic leather passed the test for single-sided bending resistance at -40℃, and the residual deformation after the tension was removed after being subjected to a tensile force of 150N for 30 minutes was 3.55%.

[0102] Comparative Example 3

[0103] A waterborne polyurethane coated synthetic leather, basically the same as in Example 2, except that the waterborne polyurethane in coating C is manufactured by Covestro Polymers (China) Co., Ltd., and its brand name is [Brand Name Missing]. DL 1007, 100% modulus is 18MPa.

[0104] The method for preparing the waterborne polyurethane coated synthetic leather as described above is basically the same as in Example 2.

[0105] The final waterborne polyurethane coated synthetic leather passed the test for single-sided bending resistance at -40℃, and the residual deformation after the tension was removed after being subjected to a tensile force of 150N for 30 minutes was 13.21%.

[0106] Comparing Comparative Example 3 and Example 2, it can be seen that because the 100% modulus of waterborne polyurethane in coating C of Comparative Example 3 is too small, the material has too little energy storage when subjected to stress, resulting in poor resilience.

[0107] Comparative Example 4

[0108] A waterborne polyurethane coated synthetic leather is basically the same as in Example 2, except that the waterborne polyurethane in coating C is manufactured by Shanghai Qizhan New Material Technology Co., Ltd., with the grade ML3003 and a 100% modulus of 44 MPa.

[0109] The method for preparing the waterborne polyurethane coated synthetic leather as described above is basically the same as in Example 2.

[0110] The final waterborne polyurethane coated synthetic leather failed to meet the single-sided bending resistance test at -40℃, and the residual deformation after removing the tension was 2.91% after being subjected to a tensile force of 150N for 30 minutes.

[0111] Comparing Comparative Example 4 and Example 2, it can be seen that the low-temperature folding resistance decreases rapidly because the 100% modulus of the waterborne polyurethane in coating C of Comparative Example 4 is too large.

[0112] Comparative Example 5

[0113] A water-based polyurethane coated synthetic leather is basically the same as in Example 2, except that the thickness of coating C is 0.5 mm and the thickness of coating B is 0.1 mm.

[0114] The method for preparing the waterborne polyurethane coated synthetic leather as described above is basically the same as in Example 2.

[0115] The final waterborne polyurethane coated synthetic leather failed to meet the single-sided bending resistance test at -40℃, and the residual deformation after removing the tension was 3.24% after being subjected to a tensile force of 150N for 30 minutes.

[0116] Comparing Comparative Example 5 and Example 2, it can be seen that since the total thickness of the microfiber base fabric and coating C in Comparative Example 5 is greater than 1.5 mm, the coating C will crack after 30,000 single-sided bends at -40°C due to excessive deformation during bending.

[0117] Comparative Example 6

[0118] A water-based polyurethane coated synthetic leather is basically the same as in Example 2, except that the thickness of coating C is 0.15 mm and the thickness of coating B is 0.45 mm.

[0119] The method for preparing the waterborne polyurethane coated synthetic leather as described above is basically the same as in Example 2.

[0120] The final waterborne polyurethane coated synthetic leather passed the test for single-sided bending resistance at -40℃, and the residual deformation after the tension was removed after being subjected to a tensile force of 150N for 30 minutes was 10.96%.

[0121] Comparing Comparative Example 6 and Example 2, it can be seen that the thickness of coating C in Comparative Example 6 is too small, which leads to poor resilience. This is because the thickness of coating C, which contributes to energy storage, is relatively too thin, which makes the overall resilience of the coating not meet the requirements.

[0122] Comparative Example 7

[0123] A water-based polyurethane coated synthetic leather is basically the same as in Example 2, except that the thickness of coating B is 0.5 mm.

[0124] The method for preparing the waterborne polyurethane coated synthetic leather as described above is basically the same as in Example 2.

[0125] The final waterborne polyurethane coated synthetic leather failed to meet the single-sided bending resistance test at -40℃, and the residual deformation after removing the tension was 5.05% after being subjected to a tensile force of 150N for 30 minutes.

[0126] Comparing Comparative Example 7 and Example 2, it can be seen that because the total thickness of the microfiber base fabric, coating C, and coating B in Comparative Example 7 is too large, the deformation of coating B during bending is too large, resulting in the final waterborne polyurethane coated synthetic leather cracking after 30,000 single-sided bends at -40°C.

[0127] Comparative Example 8

[0128] A water-based polyurethane coated synthetic leather is basically the same as in Example 2, except that the thickness of coating B is 0.15 mm and the thickness of coating A is 0.2 mm.

[0129] The method for preparing the waterborne polyurethane coated synthetic leather as described above is basically the same as in Example 2.

[0130] The final waterborne polyurethane coated synthetic leather passed the test for single-sided bending resistance at -40℃, and the residual deformation after the tension was removed after being subjected to a tensile force of 150N for 30 minutes was 18.51%.

[0131] Comparing Comparative Example 8 and Example 2, it can be seen that since the coating of Comparative Example 8 partially replaces the thickness of coating B, the resulting waterborne polyurethane coated synthetic leather will have insufficient energy storage and poor resilience when subjected to stress.

[0132] Comparative Example 9

[0133] A water-based polyurethane coated synthetic leather is basically the same as in Example 2, except that the thickness of coating A is 0.3 mm.

[0134] The method for preparing the waterborne polyurethane coated synthetic leather as described above is basically the same as in Example 2.

[0135] The final waterborne polyurethane coated synthetic leather failed to meet the single-sided bending resistance test at -40℃, and the residual deformation after removing the tension was 21.74% after being subjected to a tensile force of 150N for 30 minutes.

[0136] Comparing Comparative Example 9 and Example 2, it can be seen that since the total thickness of the microfiber base fabric, coating C, coating B and coating A in Comparative Example 9 is greater than 2.0 mm, coating A will crack after 30,000 cycles at -40°C due to excessive deformation during bending. Furthermore, the excessive thickness of coating A will also lead to poor resilience.

[0137] Example 3

[0138] A water-based polyurethane coated synthetic leather has a composite layer structure, consisting of coating A, coating B, coating C, and microfiber base fabric from top to bottom;

[0139] Coating A, coating B, and coating C are all water-based polyurethane coatings;

[0140] The manufacturer of the waterborne polyurethane in coating A is Zhejiang Huafeng Synthetic Resin Co., Ltd., with the grade JF-PDY-S820W and a 100% modulus of 2MPa.

[0141] The waterborne polyurethane in coating B is manufactured by Dai Nippon Ink & Chemical Co., Ltd. (DIC), with the brand name HYDRAN APX-101H and a 100% modulus of 14 MPa.

[0142] The waterborne polyurethane in coating C is manufactured by Covestro Polymers (China) Co., Ltd., and its brand name is [Brand Name Missing]. 2077, 100% modulus is 25MPa;

[0143] The thickness of coating A is 0.1 mm, the thickness of coating B is 0.2 mm, and the thickness of coating C is 0.4 mm. The total thickness of coatings A, B, and C is 0.7 mm. The thickness of coating C accounts for 57% of the total thickness of coatings A, B, and C, and the sum of the thicknesses of coatings C and B accounts for 86% of the total thickness of coatings A, B, and C.

[0144] The microfiber base fabric is manufactured by Toray Industries, Inc. The 500Z series product (1.7mm thick) is obtained through a sanding process, resulting in a thickness of 1.1mm.

[0145] The method for preparing the waterborne polyurethane coated synthetic leather as described above includes the following steps:

[0146] (1) Preparation of raw materials:

[0147] Waterborne polyurethane in coating A;

[0148] Waterborne polyurethane in coating B;

[0149] Waterborne polyurethane in coating C;

[0150] Microfiber base fabric;

[0151] Release paper;

[0152] (2) Forming coating B;

[0153] Coating B slurry is applied to release paper and dried to form coating B;

[0154] (3) Forming coating C;

[0155] First, apply coating C slurry onto coating B, then attach the microfiber base fabric, dry it, and peel it off from the release paper;

[0156] (4) Forming coating A;

[0157] By printing, coating A paste is applied to the surface of coating B and then dried to obtain water-based polyurethane coated synthetic leather.

[0158] The final waterborne polyurethane coated synthetic leather passed the test for single-sided bending resistance at -40℃, and the residual deformation after the tension was removed after being subjected to a tensile force of 150N for 30 minutes was 1.73%.

[0159] Example 4

[0160] A water-based polyurethane coated synthetic leather has a composite layer structure, consisting of coating A, coating B, coating C, and microfiber base fabric from top to bottom;

[0161] Coating A, coating B, and coating C are all water-based polyurethane coatings;

[0162] The manufacturer of the waterborne polyurethane in coating A is Zhejiang Huafeng Synthetic Resin Co., Ltd., with the grade JF-PDY-515Y and a 100% modulus of 1.5 MPa.

[0163] The waterborne polyurethane in coating B is manufactured by Dai Nippon Ink & Chemical Co., Ltd. (DIC), with the brand name HYDRAN APX-101H and a 100% modulus of 14 MPa.

[0164] The manufacturer of the waterborne polyurethane in coating C is Shanghai Qizhan New Material Technology Co., Ltd., with the grade ML3010 and a 100% modulus of 24 MPa.

[0165] The thickness of coating A is 0.2 mm, the thickness of coating B is 0.3 mm, and the thickness of coating C is 0.5 mm. The total thickness of coatings A, B, and C is 1 mm. The thickness of coating C accounts for 50% of the total thickness of coatings A, B, and C, and the sum of the thicknesses of coatings C and B accounts for 80% of the total thickness of coatings A, B, and C.

[0166] The microfiber base fabric is manufactured by Toray Industries, Inc. The 500Z series product (1.7mm thick) is obtained through a sanding process, resulting in a thickness of 1mm.

[0167] The method for preparing the waterborne polyurethane coated synthetic leather as described above includes the following steps:

[0168] (1) Preparation of raw materials:

[0169] Waterborne polyurethane in coating A;

[0170] Waterborne polyurethane in coating B;

[0171] Waterborne polyurethane in coating C;

[0172] Microfiber base fabric;

[0173] Release paper;

[0174] (2) Forming coating B;

[0175] Coating B slurry is applied to release paper and dried to form coating B;

[0176] (3) Forming coating C;

[0177] First, apply coating C slurry onto coating B, then attach the microfiber base fabric, dry it, and peel it off from the release paper;

[0178] (4) Forming coating A;

[0179] By printing, coating A paste is applied to the surface of coating B and then dried to obtain water-based polyurethane coated synthetic leather.

[0180] The final waterborne polyurethane coated synthetic leather passed the test for single-sided bending resistance at -40℃, and the residual deformation after the tension was removed after being subjected to a tensile force of 150N for 30 minutes was 2.28%.

[0181] Comparative Example 10

[0182] A waterborne polyurethane coated synthetic leather, basically the same as in Example 4, except that: the waterborne polyurethane in coating A is manufactured by Covestro Polymers (China) Co., Ltd., and its brand name is [Brand Name Missing]. 1030, 100% modulus is 0.5MPa.

[0183] The method for preparing the waterborne polyurethane coated synthetic leather as described above is basically the same as in Example 4.

[0184] The final waterborne polyurethane coated synthetic leather passed the test for single-sided bending resistance at -40℃, and the residual deformation after the tension was removed after being subjected to a tensile force of 150N for 30 minutes was 19.47%.

[0185] Comparing Comparative Example 10 and Example 4, it can be seen that the 100% modulus of waterborne polyurethane in coating A of Comparative Example 10 is too small, which will cause the stress to be consumed by coating A. When the stress is removed, the resulting waterborne polyurethane coated synthetic leather has poor resilience.

[0186] Comparative Example 11

[0187] A waterborne polyurethane coated synthetic leather, basically the same as in Example 4, except that: the waterborne polyurethane in coating A is manufactured by Covestro Polymers (China) Co., Ltd., and its brand name is [Brand Name Missing]. 3040, 100% modulus is 5MPa.

[0188] The method for preparing the waterborne polyurethane coated synthetic leather as described above is basically the same as in Example 4.

[0189] The final waterborne polyurethane coated synthetic leather failed to meet the single-sided bending resistance test at -40℃, and the residual deformation after removing the tension was 3.98% after being subjected to a tensile force of 150N for 30 minutes.

[0190] Comparing Comparative Example 11 with Example 1, it can be seen that the excessively high 100% modulus of waterborne polyurethane in coating A of Comparative Example 11 leads to a rapid decrease in the low-temperature folding resistance of the resulting waterborne polyurethane coated synthetic leather.

[0191] Example 5

[0192] A water-based polyurethane coated synthetic leather has a composite layer structure, consisting of coating A, coating B, coating C, and microfiber base fabric from top to bottom;

[0193] Coating A, coating B, and coating C are all water-based polyurethane coatings;

[0194] The waterborne polyurethane in coating A is manufactured by Covestro Polymers (China) Co., Ltd., and its brand name is [Brand Name Missing]. DL1537, 100% modulus is 2MPa;

[0195] The waterborne polyurethane in coating B is manufactured by Dai Nippon Ink & Chemical Co., Ltd. (DIC), with the brand name HYDRAN APX-101H and a 100% modulus of 14 MPa.

[0196] The waterborne polyurethane in coating C is manufactured by Covestro Polymers (China) Co., Ltd., and its brand name is [Brand Name Missing]. 2077, 100% modulus is 25MPa;

[0197] The thickness of coating A is 0.2 mm, the thickness of coating B is 0.5 mm, and the thickness of coating C is 0.3 mm. The total thickness of coatings A, B, and C is 1 mm. The thickness of coating C accounts for 30% of the total thickness of coatings A, B, and C, and the sum of the thicknesses of coatings C and B accounts for 80% of the total thickness of coatings A, B, and C.

[0198] The microfiber base fabric is manufactured by Toray Industries, Inc. The 500Z series product (1.7mm thick) is obtained through a sanding process, resulting in a thickness of 1mm.

[0199] The method for preparing the waterborne polyurethane coated synthetic leather as described above includes the following steps:

[0200] (1) Preparation of raw materials:

[0201] Waterborne polyurethane in coating A;

[0202] Waterborne polyurethane in coating B;

[0203] Waterborne polyurethane in coating C;

[0204] Microfiber base fabric;

[0205] Release paper;

[0206] (2) Forming coating B;

[0207] Coating B slurry is applied to release paper and dried to form coating B;

[0208] (3) Forming coating C;

[0209] First, apply coating C slurry onto coating B, then attach the microfiber base fabric, dry it, and peel it off from the release paper;

[0210] (4) Forming coating A;

[0211] By printing, coating A paste is applied to the surface of coating B and then dried to obtain water-based polyurethane coated synthetic leather.

[0212] The final waterborne polyurethane coated synthetic leather passed the test for single-sided bending resistance at -40℃, and the residual deformation after the tension was removed after being subjected to a tensile force of 150N for 30 minutes was 5.17%.

Claims

1. An aqueous polyurethane-coated synthetic leather, characterized by, It has a composite layer structure, consisting of coating A, coating B, coating C, and microfiber base fabric from top to bottom; Coating A, coating B, and coating C are all water-based polyurethane coatings; The 100% modulus of waterborne polyurethane in coating A is 1-3 MPa, the 100% modulus of waterborne polyurethane in coating B is 12-15 MPa, and the 100% modulus of waterborne polyurethane in coating C is 22-25 MPa. The waterborne polyurethane in coating A is of the brand Impranil® DAH, JF-PDY-836HY, JF-PDY-S820W, JF-PDY-515Y or Impranil® DL1537; The waterborne polyurethane in coating B is either NuVera® D RU-94-226 or HYDRAN APX-101H. The waterborne polyurethane in coating C is of the grades NuVera® D EX-RU-94-424, Impranil® 2077, or ML3010; The thickness of the microfiber base fabric is 1.0-1.3mm, the total thickness of the microfiber base fabric and coating C is ≤1.5mm, the total thickness of the microfiber base fabric, coating C, and coating B is ≤1.8mm, and the total thickness of the microfiber base fabric, coating C, coating B, and coating A is ≤2.0mm; the total thickness of coating A, coating B, and coating C is 0.6-1mm, the thickness of coating C is at least 30% of the total thickness of coating A, coating B, and coating C, and the sum of the thicknesses of coating C and coating B accounts for 80-100% of the total thickness of coating A, coating B, and coating C.

2. The aqueous polyurethane-coated synthetic leather according to claim 1, characterized in that, Additives are also dispersed in the waterborne polyurethane coating.

3. The aqueous polyurethane-coated synthetic leather according to claim 2, characterized in that, The additives are one or more of the following: small molecule lubricants, leveling agents, thickeners, and color pastes.

4. The waterborne polyurethane coated synthetic leather according to any one of claims 1-3, characterized in that, Waterborne polyurethane coated synthetic leather can withstand no less than 30,000 single-sided bends at -40℃; the residual deformation of waterborne polyurethane coated synthetic leather after being subjected to a tensile force of 150N for 30 minutes and then the tensile force is removed is ≤5%.

5. A method for preparing a waterborne polyurethane coated synthetic leather as described in any one of claims 1 to 4, characterized in that, Includes the following steps: (1) Forming coating B; Coating B slurry is applied to release paper and dried to form coating B; (2) Forming coating C; First, apply coating C slurry onto coating B, then attach the microfiber base fabric, dry it, and peel it off from the release paper; (3) Forming coating A; By using roller coating or printing, coating A slurry is applied to the surface of coating B and then dried to obtain water-based polyurethane coated synthetic leather.

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