Synthetic leather as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of polyurethane, and relates to synthetic leather as well as a preparation method and application thereof. The preparation method of the synthetic leather comprises the following steps: coating the polyurethane surface layer with intermediate layer working slurry, and curing to obtain the intermediate layer; the middle layer working slurry comprises a combination of polyurethane resin A, a curing agent and a solvent A; the solvent A comprises any one or a combination of at least two of propylene glycol methyl ether acetate, methyl ethyl ketone, ethyl acetate, dimethyl carbonate, acetone and methylbenzene; a bonding layer is prepared on the middle layer, base cloth is attached to the bonding layer, and the synthetic leather is obtained. The synthetic leather obtained by the preparation method disclosed by the invention has special cracking lines, does not need knurling and rubbing treatment or additional addition of a cracking agent in the preparation process, and is simple in process, unique in lines and very suitable for industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of polyurethane, and in particular to synthetic leather and a preparation method and application thereof. Background Art

[0002] Polyurethane crackle pattern synthetic leather is a material with special visual effects and tactile feel. Its surface presents crackle-like fine lines, with high simulation and aesthetics. Polyurethane crackle pattern synthetic leather is widely used in footwear, clothing, furniture and other fields, with a unique appearance and feel.

[0003] CN101748613A discloses a method for preparing polyurethane synthetic leather with simulated leather effect. First, a wet synthetic leather semi-finished product is prepared; then a polyurethane finishing agent is applied to the surface of the wet synthetic leather semi-finished product for printing surface treatment; then a polyurethane film after the release paper pattern is transferred is bonded to the surface of the wet synthetic leather semi-finished product after printing, and the raw materials in the polyurethane slurry include cracking resin; finally, a rubbing treatment is performed. Although the surface of the obtained synthetic leather has a frosted and cracking effect, embossing and rubbing operations are performed during the preparation process, and the process is complicated.

[0004] CN118599301A discloses a polyurethane cracking resin for synthetic leather, comprising the following raw materials: polyurethane resin, ABS resin, polymethyl methacrylate, epoxy resin, modified attapulgite, oleic acid amide, solvent, polyethylene wax, leveling agent, catalyst, polydimethylsiloxane, and the obtained synthetic leather has good cracking effect and does not require complicated mechanical treatment. However, the above method adds a large amount of cracking agent, which may reduce the mechanical properties and chemical resistance of the synthetic leather and increase the cost.

[0005] CN102851981A discloses a fine crack color-changing resin for synthetic leather, which is composed of the following components: polyurethane resin, acrylic resin, acetone, DMF, high temperature resistant silica color-changing wax powder, wood powder, silicone leveling agent and 0.2 brown fluff. The obtained fine crack color-changing resin has good film-forming property, strong adhesion, and especially after rubbing treatment, fine cracking effect, strong leather feel, outstanding color change and fluffy feel, and the effect is very obvious. However, this method also needs to add a large amount of cracking agent, and needs to be matched with rubbing treatment.

[0006] In summary, most of the crack-patterned synthetic leathers currently on the market require embossing or rubbing treatment, or the addition of additional cracking agents. Not only are the processes complicated and costly, but the visual effects of the processed patterns are poor, which cannot meet people's high standards for both vision and performance, and needs further improvement. Summary of the invention

[0007] In order to solve the above technical problems, the present invention discloses a synthetic leather with a crack pattern and a preparation method and application thereof. The synthetic leather of the present invention has a special crack pattern, does not require embossing and kneading treatment or additional addition of a cracking agent during the preparation process, has a simple process, a unique pattern, and is very suitable for industrial production.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a method for preparing synthetic leather, the preparation method comprising:

[0010] The middle layer working slurry is coated on the polyurethane surface layer and cured to obtain the middle layer.

[0011] The intermediate layer working slurry includes a combination of polyurethane resin A, curing agent and solvent A.

[0012] The solvent A includes any one of propylene glycol methyl ether acetate, methyl ethyl ketone, ethyl acetate, dimethyl carbonate, acetone, and toluene, or a combination of at least two of them.

[0013] An adhesive layer is prepared on the intermediate layer, and a base fabric is laminated on the adhesive layer to obtain the synthetic leather.

[0014] The present invention adds a solvent of specific polarity to the working slurry of the middle layer and coats it on the polyurethane surface layer. When heated and cured, the solvent A volatilizes, and a small amount of solvent A in the middle layer volatilizes and penetrates into the surface layer, causing the polyurethane surface layer to swell and form a crack pattern. If the polarity of the solvent A is too large, the polyurethane surface layer dissolves; if the solvent A is a non-polar solvent, the polyurethane surface layer is completely insoluble and the crack pattern cannot be formed.

[0015] Preferably, the intermediate layer working slurry comprises the following components in parts by weight: 100 parts of polyurethane resin A, 5-10 parts of curing agent, and 5-10 parts of solvent A.

[0016] The amount of the curing agent can be 6 parts, 7 parts, 8 parts or 9 parts.

[0017] Wherein, the usage of the solvent A can be 6 parts, 7 parts, 8 parts or 9 parts, etc.

[0018] Preferably, the polyurethane resin A is prepared from polyester polyol A and isocyanate A.

[0019] In the present invention, isocyanate includes aliphatic isocyanate, aromatic isocyanate, alicyclic isocyanate, isocyanate prepolymer and the like.

[0020] Preferably, the curing agent includes any one of isophoronediamine, 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane, 4,4'-diaminodicyclohexylmethane, 4,4'-diaminodiphenylmethane, diethylenetriamine or triethylenetetramine, or a combination of at least two thereof.

[0021] Preferably, the curing temperature is 100-140°C, for example, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C or 135°C.

[0022] Preferably, the curing time is 4-6 min, for example, 4.3 min, 4.5 min, 5 min, 5.5 min or 5.8 min.

[0023] Preferably, the polyurethane resin A is a blocked polyurethane resin.

[0024] Preferably, the blocking agent used in the blocked polyurethane resin is a ketoxime blocking agent.

[0025] Preferably, the ketoxime blocking agent includes acetone oxime and / or butanone oxime.

[0026] Preferably, the mass content of NCO groups of the polyurethane resin A before blocking by the blocked polyurethane resin is 1%-4%, for example, 1.2%, 1.5%, 2%, 2.5% or 2.8%.

[0027] Preferably, the method for preparing the polyurethane surface layer comprises:

[0028] The polyurethane surface layer working slurry is coated on the release paper and dried to obtain the polyurethane surface layer.

[0029] Preferably, the polyurethane surface layer working slurry comprises a combination of polyurethane resin B, leveling agent, solvent B and color powder.

[0030] Preferably, the raw materials for preparing the polyurethane resin B include polyol B and isocyanate B.

[0031] Preferably, the polyol B includes polyether polyol and polyester polyol B.

[0032] Preferably, the mass content of the polyether polyol in the polyol B is 30%-70%, for example, 40%, 50%, 55%, 60% or 65%.

[0033] Preferably, the solvent B includes any one of N,N-dimethylformamide, methyl ethyl ketone, ethyl acetate, isopropanol, and toluene, or a combination of at least two thereof.

[0034] In the present invention, the polyurethane resin A is prepared only by polyester polyol A and isocyanate A, the raw materials for preparing the polyurethane resin B include polyol B and isocyanate B, and the polyol B includes polyether polyol and polyester polyol B. When the middle layer is heated and cured, the polyurethane resin B of the polyurethane surface layer and the polyurethane resin A of the middle layer are softened, and the polyurethane resin A penetrates into the polyurethane resin B. Due to the difference in the composition of the two, the compatibility of the two is poor, which further enhances the cracking effect of the pattern.

[0035] Preferably, the polyurethane surface working slurry comprises, in parts by weight: 100 parts of polyurethane resin B, 0.1-0.5 parts of leveling agent, 80-100 parts of solvent B, and 5-18 parts of color powder.

[0036] Wherein, the dosage of the leveling agent may be 0.15 parts, 0.2 parts, 0.3 parts, 0.4 parts or 0.45 parts.

[0037] Wherein, the amount of the solvent B can be 82 parts, 85 parts, 90 parts, 95 parts or 97 parts.

[0038] The amount of the toner can be 6 parts, 8 parts, 10 parts, 12 parts, 14 parts or 16 parts.

[0039] Preferably, the leveling agent comprises an organic silicon leveling agent.

[0040] In the present invention, a silicone leveling agent is added to the polyurethane surface layer working slurry to provide a slippery effect, which can not only improve the smoothness of the coating, but also promote the penetration of the solvent A and the polyurethane resin A in the middle layer working slurry, thereby enhancing the cracking effect of the pattern.

[0041] Preferably, the method for preparing the bonding layer comprises:

[0042] The bonding layer working slurry is coated on the intermediate layer and dried to obtain the bonding layer.

[0043] Preferably, the bonding layer working slurry comprises, by weight: 100 parts of polyurethane resin C and 30-60 parts of solvent C.

[0044] Wherein, the amount of the solvent C can be 35 parts, 40 parts, 45 parts, 50 parts or 55 parts.

[0045] Preferably, the solvent C includes any one of N,N-dimethylformamide, methyl ethyl ketone, ethyl acetate, isopropanol, and toluene, or a combination of at least two thereof.

[0046] Preferably, the preparation method comprises:

[0047] The polyurethane surface working slurry is coated on the release paper with a coating thickness of 0.1-0.25 mm (for example, 0.12 mm, 0.15 mm, 0.18 mm, 0.2 mm or 0.23 mm, etc.), and baked at 80-120° C. (for example, 85° C., 90° C., 100° C., 110° C. or 115° C., etc.) for 3-5 min (for example, 3.2 min, 3.5 min, 4 min, 4.5 min or 4.8 min, etc.) to obtain a polyurethane surface layer.

[0048] The polyurethane surface working slurry comprises, by weight: 100 parts of polyurethane resin B, 0.1-0.5 parts of leveling agent, 80-100 parts of solvent B, and 5-18 parts of color powder.

[0049] An intermediate layer of working slurry is coated on the polyurethane surface layer with a coating thickness of 0.2-0.4 mm (for example, 0.22 mm, 0.25 mm, 0.3 mm, 0.35 mm or 0.37 mm, etc.), and baked and cured at 100-140°C (for example, 105°C, 110°C, 120°C, 130°C or 135°C, etc.) for 4-6 min (for example, 4.2 min, 4.5 min, 5 min, 5.5 min or 5.8 min, etc.) to obtain an intermediate layer.

[0050] The intermediate layer working slurry comprises the following components in parts by weight: 100 parts of polyurethane resin A, 5-10 parts of curing agent, and 5-10 parts of solvent A.

[0051] Coat the bonding layer working slurry on the middle layer with a coating thickness of 0.15-0.25 mm (for example, 0.17 mm, 0.19 mm, 0.2 mm, 0.21 mm or 0.23 mm, etc.), and bake at 100-120°C (for example, 103°C, 105°C, 110°C, 115°C or 117°C, etc.) for 10-20s (for example, 12s, 14s, 15s, 16s or 18s, etc.) to obtain a bonding layer.

[0052] The bonding layer working slurry comprises, by weight: 100 parts of polyurethane resin C and 30-60 parts of solvent C.

[0053] The base fabric is laminated and baked at 120-140° C. (eg, 122° C., 125° C., 130° C., 135° C., or 137° C., etc.) for 3-6 min (eg, 3.5 min, 4 min, 4.5 min, 5 min, or 5.5 min, etc.) to obtain the synthetic leather.

[0054] In a second aspect, the present invention provides a synthetic leather, which is prepared by the preparation method described in the first aspect.

[0055] In a third aspect, the present invention provides a use of the synthetic leather as described in the second aspect in footwear, clothing or furniture.

[0056] Compared with the prior art, the present invention has at least the following beneficial effects:

[0057] The synthetic leather prepared by the preparation method of the present invention has a special crack pattern, and no embossing and kneading treatment or additional addition of a cracking agent is required during the preparation process. The process is simple, the pattern is unique, and the leather is very suitable for industrial production. At the same time, the synthetic leather prepared by the preparation method of the present invention is not damaged after being folded 100,000 times at room temperature, and is not damaged after being folded 40,000 times at -15°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 This is a physical picture of the synthetic leather provided in Example 1.

[0059] Figure 2 This is a physical picture of the synthetic leather provided for Comparative Example 1.

[0060] Figure 3 This is a physical picture of the synthetic leather provided in Example 4. DETAILED DESCRIPTION

[0061] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and through specific implementation methods. However, the following examples are only simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0062] The sources of the raw materials used in the examples and comparative examples of the present invention are as follows:

[0063] Table 1

[0064]

[0065] Example 1

[0066] A synthetic leather and a preparation method thereof, the preparation method comprising:

[0067] (1) Preparation of polyurethane surface layer:

[0068] A polyurethane surface layer working slurry is provided, which comprises, by weight: 100 parts of polyurethane resin B, 0.3 parts of organosilicon leveling agent, 80 parts of solvent B, and 5 parts of color powder.

[0069] The raw materials for preparing the polyurethane surface layer resin B include polyol B and isocyanate B.

[0070] The polyol B is a mixed polyol of polyethylene adipate glycol-1,4-butylene glycol ester glycol and polypropylene glycol in a mass ratio of 7:3.

[0071] The solvent B is N,N-dimethylformamide.

[0072] The polyurethane surface layer working slurry was coated on the release paper with a coating thickness of 0.15 mm and dried at 100° C. for 4 min to obtain the polyurethane surface layer.

[0073] (2) Preparation of the intermediate layer:

[0074] An intermediate layer working slurry is provided, which comprises: 100 parts of polyurethane resin A, 8 parts of curing agent, and 10 parts of solvent A in parts by weight.

[0075] The polyurethane resin A is prepared from polyester polyol A and isocyanate A.

[0076] The polyol A is polyethylene adipate glycol-1,4-butylene adipate glycol.

[0077] The curing agent is isophorone diamine.

[0078] The solvent A is propylene glycol methyl ether acetate.

[0079] The intermediate layer working slurry is coated on the polyurethane surface layer obtained in step (1) with a coating thickness of 0.3 mm and cured at 120° C. for 5 minutes to obtain an intermediate layer.

[0080] (3) Preparation of bonding layer:

[0081] A bonding layer working slurry is provided, which comprises, by weight: 100 parts of polyurethane resin C and 30 parts of solvent C.

[0082] The solvent C is N,N-dimethylformamide.

[0083] The bonding layer working slurry is coated on the intermediate layer obtained in step (2) to a coating thickness of 0.2 mm and baked at 110° C. for 15 seconds to obtain a bonding layer.

[0084] (4) Bonding the base fabric to obtain synthetic leather:

[0085] The base fabric is laminated onto the adhesive layer obtained in step (3), and baked at 130° C. for 5 minutes to obtain the synthetic leather.

[0086] Example 2

[0087] A synthetic leather and a preparation method thereof, the preparation method comprising:

[0088] (1) Preparation of polyurethane surface layer:

[0089] A polyurethane surface layer working slurry is provided, which comprises, by weight: 100 parts of polyurethane resin B, 0.1 parts of organosilicon leveling agent, 90 parts of solvent B, and 10 parts of color powder.

[0090] The raw materials for preparing the polyurethane surface layer resin B include polyol B and isocyanate B.

[0091] The polyol B is a mixed polyol of polyethylene adipate glycol-1,4-butylene glycol ester glycol and polypropylene glycol in a mass ratio of 3:7.

[0092] The solvent B is isopropanol.

[0093] The polyurethane surface layer working slurry was coated on the release paper with a coating thickness of 0.1 mm and dried at 80° C. for 3 min to obtain the polyurethane surface layer.

[0094] (2) Preparation of the intermediate layer:

[0095] An intermediate layer working slurry is provided, which comprises: 100 parts of polyurethane resin A, 5 parts of curing agent, and 5 parts of solvent A in parts by weight.

[0096] The polyurethane resin A is prepared from polyester polyol A and isocyanate A.

[0097] The polyol A is polyethylene adipate glycol-1,4-butylene adipate glycol.

[0098] The curing agent is 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane.

[0099] The solvent A is propylene glycol methyl ether acetate.

[0100] The intermediate layer working slurry is coated on the polyurethane surface layer obtained in step (1) with a coating thickness of 0.2 mm and cured at 100° C. for 4 minutes to obtain an intermediate layer.

[0101] (3) Preparation of bonding layer:

[0102] A bonding layer working slurry is provided, which comprises, by weight: 100 parts of polyurethane resin C and 30 parts of solvent C.

[0103] The solvent C is N,N-dimethylformamide.

[0104] The bonding layer working slurry is coated on the intermediate layer obtained in step (2) with a coating thickness of 0.15 mm and baked at 100° C. for 10 seconds.

[0105] (4) Bonding the base fabric to obtain synthetic leather:

[0106] The base fabric is laminated onto the adhesive layer obtained in step (3), and baked at 120° C. for 3 minutes to obtain the synthetic leather.

[0107] Example 3

[0108] A synthetic leather and a preparation method thereof, the preparation method comprising:

[0109] (1) Preparation of polyurethane surface layer:

[0110] A polyurethane surface layer working slurry is provided, which comprises, by weight: 100 parts of polyurethane resin B, 0.5 parts of organic silicon leveling agent, 100 parts of solvent B, and 18 parts of color powder.

[0111] The raw materials for preparing the polyurethane surface layer resin B include polyol B and isocyanate B.

[0112] The polyol B is a mixed polyol of polyethylene adipate glycol-1,4-butylene glycol ester glycol and polypropylene glycol in a mass ratio of 5:5.

[0113] The solvent B is isopropanol.

[0114] The polyurethane surface layer working slurry was coated on the release paper with a coating thickness of 0.25 mm and dried at 120° C. for 5 min to obtain the polyurethane surface layer.

[0115] (2) Preparation of the intermediate layer:

[0116] An intermediate layer working slurry is provided, which comprises: 100 parts of polyurethane resin A, 10 parts of curing agent, and 10 parts of solvent A in parts by weight.

[0117] The polyurethane resin A is prepared from polyester polyol A and isocyanate A.

[0118] The polyol A is polyethylene adipate glycol-1,4-butylene adipate glycol.

[0119] The curing agent is 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane.

[0120] The solvent A is propylene glycol methyl ether acetate.

[0121] The intermediate layer working slurry is coated on the polyurethane surface layer obtained in step (1) with a coating thickness of 0.4 mm and cured at 140° C. for 6 minutes to obtain an intermediate layer.

[0122] (3) Preparation of bonding layer:

[0123] A bonding layer working slurry is provided, which comprises, by weight: 100 parts of polyurethane resin C and 60 parts of solvent C.

[0124] The solvent C is N,N-dimethylformamide.

[0125] The bonding layer working slurry is coated on the intermediate layer obtained in step (2) with a coating thickness of 0.25 mm and baked at 120° C. for 20 seconds.

[0126] (4) Bonding the base fabric to obtain synthetic leather:

[0127] The base fabric is laminated onto the adhesive layer obtained in step (3), and baked at 140° C. for 6 minutes to obtain the synthetic leather.

[0128] Example 4

[0129] The difference between this embodiment and embodiment 1 is that the polyol used in the surface layer is poly(1,4-butylene adipate diol).

[0130] Example 5

[0131] The difference between this embodiment and embodiment 1 is that the polyol used in the surface layer is poly(1,4-butylene adipate diol); and the resin in the middle layer is polytetramethylene glycol ether diol.

[0132] Example 6

[0133] The difference between this embodiment and embodiment 1 is that the polyol used in the middle layer is a mixed polyol of polyethylene adipate-1,4-butylene glycol ester diol and polypropylene glycol in a mass ratio of 1:9.

[0134] Example 7

[0135] The difference between this embodiment and embodiment 1 is that the polyol used in the middle layer is polypropylene glycol polyol.

[0136] Example 8

[0137] The difference between this embodiment and embodiment 1 is that 0.3 parts of the organosilicon leveling agent is replaced by 0.3 parts of an acrylate copolymer leveling agent (Shanghai Tiger Polymer Tech-15360).

[0138] Comparative Example 1

[0139] The difference between this comparative example and Example 1 is that the solvent A is N,N-dimethylformamide.

[0140] Comparative Example 2

[0141] The difference between this comparative example and Example 1 is that the solvent A is n-hexane.

[0142] The above synthetic leather was subjected to the following performance tests:

[0143] (1) Surface performance: Visually inspect whether the synthetic leather surface has cracks.

[0144] (2) Performance test of smooth effect: Observe visually whether the synthetic leather has a smooth effect.

[0145] (3) Folding resistance at room temperature: Test according to the method provided in GB / T20991-2007.

[0146] (4) -15℃ folding resistance: Tested according to the method provided in GB / T20991-2007.

[0147] The test results are shown in Table 2:

[0148] Table 2

[0149]

[0150] The test results show that:

[0151] (1) It can be seen from Examples 1 to 8 that the present invention can form cracks by selecting a specific solvent for the intermediate layer working slurry, and the resulting synthetic leather has good folding resistance at both room temperature and low temperature.

[0152] (2) It can be seen from Examples 1 to 3 that the present invention can obtain obvious cracks and the synthetic leather has a smooth effect by further selecting the types of polyurethane resins for the middle layer and the surface layer and selecting a specific type of leveling agent.

[0153] (3) It can be seen from Example 1 and Comparative Examples 1 and 2 that when a solvent having a specific intermediate layer working slurry is not used, no cracks can be obtained.

[0154] In summary, the synthetic leather prepared by the preparation method of the present invention has a special crack pattern, and no embossing or additional cracking agent is required during the preparation process. The process is simple, the pattern is unique, and it is very suitable for industrial production. At the same time, the synthetic leather obtained by the preparation method of the present invention can be folded 100,000 times at room temperature without damage, and folded 40,000 times at -15°C without damage.

[0155] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention are within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing synthetic leather, characterized in that: The preparation method comprises: Applying an intermediate layer of working slurry on the polyurethane surface layer and curing the slurry to obtain an intermediate layer; The intermediate layer working slurry comprises a combination of polyurethane resin A, curing agent and solvent A; The solvent A includes any one or a combination of at least two of propylene glycol methyl ether acetate, methyl ethyl ketone, ethyl acetate, dimethyl carbonate, acetone, and toluene; An adhesive layer is prepared on the intermediate layer, and a base fabric is laminated on the adhesive layer to obtain the synthetic leather.

2. The preparation method according to claim 1, characterized in that: The intermediate layer working slurry comprises the following components in parts by weight: 100 parts of polyurethane resin A, 5-10 parts of curing agent, and 5-10 parts of solvent A; The polyurethane resin A is prepared by polyester polyol A and isocyanate A; The curing agent includes any one of isophorone diamine, 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane, 4,4'-diaminodicyclohexylmethane, 4,4'-diaminodiphenylmethane, diethylenetriamine or triethylenetetramine, or a combination of at least two thereof; The curing temperature is 100-140°C; The curing time is 4-6 min.

3. The preparation method according to claim 1 or 2, characterized in that: The polyurethane resin A is a blocked polyurethane resin; The blocking agent used in the blocked polyurethane resin is a ketoxime blocking agent; The ketoxime blocking agent includes acetone oxime and / or butanone oxime; The blocked polyurethane resin has an NCO group mass content of 1%-4% before blocking.

4. The preparation method according to claim 1, characterized in that: The preparation method of the polyurethane surface layer comprises: Applying the polyurethane surface layer working slurry onto the release paper and drying it to obtain the polyurethane surface layer; The polyurethane surface working slurry comprises a combination of polyurethane resin B, leveling agent, solvent B and color powder; The raw materials for preparing the polyurethane resin B include polyol B and isocyanate B; The polyol B includes polyether polyol and polyester polyol B; The mass content of the polyether polyol in the polyol B is 30%-70%; The solvent B includes any one of N,N-dimethylformamide, methyl ethyl ketone, ethyl acetate, isopropanol, and toluene, or a combination of at least two thereof.

5. The preparation method according to claim 4, characterized in that: The polyurethane surface working slurry comprises, by weight: 100 parts of polyurethane resin B, 0.1-0.5 parts of leveling agent, 80-100 parts of solvent B, and 5-18 parts of color powder.

6. The preparation method according to claim 4, characterized in that: The leveling agent includes an organic silicon leveling agent.

7. The preparation method according to claim 1, characterized in that: The preparation method of the bonding layer comprises: Coating a bonding layer working slurry on the intermediate layer and drying the slurry to obtain the bonding layer; The bonding layer working slurry comprises, by weight: 100 parts of polyurethane resin C and 30-60 parts of solvent C; The solvent C includes any one of N,N-dimethylformamide, methyl ethyl ketone, ethyl acetate, isopropanol, and toluene, or a combination of at least two of them.

8. The preparation method according to claim 1, characterized in that: The preparation method comprises: Applying the polyurethane surface layer working slurry onto the release paper with a coating thickness of 0.1-0.25 mm, and baking at 80-120° C. for 3-5 minutes to obtain the polyurethane surface layer; The polyurethane surface working slurry comprises, by weight: 100 parts of polyurethane resin B, 0.1-0.5 parts of leveling agent, 80-100 parts of solvent B, and 5-18 parts of color powder; Coating an intermediate layer of working slurry on the polyurethane surface layer with a coating thickness of 0.2-0.4 mm, and baking and curing at 100-140° C. for 4-6 minutes to obtain an intermediate layer; The intermediate layer working slurry comprises the following components in parts by weight: 100 parts of polyurethane resin A, 5-10 parts of curing agent, and 5-10 parts of solvent A; Coating the bonding layer working slurry on the middle layer with a coating thickness of 0.15-0.25 mm, and baking at 100-120° C. for 10-20 seconds to obtain a bonding layer; The bonding layer working slurry comprises, by weight: 100 parts of polyurethane resin C and 30-60 parts of solvent C; The base fabric is laminated and baked at 120-140° C. for 3-6 minutes to obtain the synthetic leather.

9. A synthetic leather, characterized in that: The synthetic leather is prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the synthetic leather according to claim 9 in footwear, clothing or furniture.

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