Manufacturing method for coating embossed leather by using dry method

Abstract

The invention discloses a manufacturing method for coating embossed leather by using a dry method, which adopts a solvent-free foaming PU (polyurethane) adhesive, so that the emission of volatile organic compounds is avoided, the modern environmental protection standard is met, and the pollution to the environment is reduced. Meanwhile, the manufacturing method of the dry coating embossed leather solves the problems that the performance of a material is reduced and the service life is shortened due to the fact that a traditional wet PU adhesive is prone to hydrolysis reaction in the environment with moisture, the solvent-free foaming PU adhesive is used, negative effects caused by hydrolysis of the wet PU adhesive are effectively avoided, and the manufacturing method of the dry coating embossed leather is suitable for large-scale popularization and application. The stability and durability of the embossed leather in a humid environment are ensured, and the air permeability and the hand feeling of the embossed leather are effectively improved through reasonable combination of multiple layers of PU glue and optimization of the base material layer in the manufacturing method of the dry coating embossed leather.

Description

Technical Field

[0001] The invention relates to a method for manufacturing embossed leather by dry coating, and belongs to the field of synthetic leather manufacturing. Background Art

[0002] In traditional PU synthetic leather products, the middle layer is solvent-based wet-process leather. Although leather is soft and feels good, it is not strong enough, especially after adding a certain amount of filler, the strength and hydrolysis resistance will be greatly reduced. Therefore, the service life of general PU synthetic leather is less than five years, and some products are less than one year resistant to hydrolysis. Water-based and two-component solvent-free foaming process products can achieve the softness and strength of the foaming layer by adding no or less filling materials, so its hydrolysis resistance can reach five years or even more than ten years. Adding the top layer of water-based resin can make products with very good wear resistance and scratch resistance. In addition, the present invention does not use any organic solvents in leather production, thus completely solving the problem that synthetic leather products are not ecological due to the use of organic solvents.

[0003] After searching, it is found that a Chinese patent document discloses a method for preparing a solvent-free PU synthetic leather [Application No.: 202410150360.3, Publication No.: CN118087283A], which discloses a method for preparing a solvent-free PU synthetic leather. This application applies solvent-free polyurethane resin to the preparation method of synthetic leather, which can more fully meet the market's urgent demand for green, low-odor, and low-emission products. However, this method is a wet preparation method and does not have the advantages of this solution. Summary of the invention

[0004] In view of the problems existing in the prior art, the object of the present invention is to provide a method for manufacturing embossed leather using dry coating.

[0005] A method for manufacturing embossed leather using dry coating, characterized in that: The production process includes the following: Step 1: Prepare the release layer, apply a layer of PU glue on the release layer, dry it, and obtain fabric 1; Step 2: Continue to apply a layer of PU glue on the side of fabric 1 coated with PU glue, and dry to obtain fabric 2; Step 3: Continue to apply a layer of solvent-free foaming PU glue on the side of fabric 2 coated with PU glue, pre-dry, and obtain fabric 3; Step 4: Lay the side of the fabric 3 coated with PU glue on the base material layer, dry it, and peel off the release layer after drying to obtain fabric 4; Step 5: Roll up the fabric to get the finished product.

[0006] Preferably, the formulation of the solvent-free foaming PU adhesive comprises the following components in parts by weight: solvent-free PU adhesive: 50-100 parts, filler: 10-50 parts.

[0007] Through the above technical solution, the formula of the solvent-free foaming PU adhesive can provide excellent foaming effect and material stability while ensuring being solvent-free.

[0008] Preferably, the filler in the formula is one or more of light calcium carbonate, heavy calcium carbonate, cellulose powder, wood pulp, paper pulp, and magnetite.

[0009] Through the above technical solution, the combination of fillers can be flexibly selected according to the needs of the finished product, thereby giving the solvent-free foaming PU adhesive different physical properties. The different combinations and proportions of these fillers not only bring rich touch options to the finished leather, but also ensure the foaming effect and uniformity of the material, effectively avoiding the problem of uneven bubble distribution. At the same time, the use of fillers improves the bonding force and molding stability of PU adhesive without adding solvents. The final embossed leather has good durability and retains the advantages of naturalness and environmental protection.

[0010] Preferably, the solvent-free foaming PU adhesive in the formula is a zero-solvent PU adhesive, and the molding process is accompanied by chain growth and cross-linking reactions between isocyanate groups and hydroxyl groups, and also includes a reaction between isocyanate and water.

[0011] Through the above technical solution, this zero-solvent PU adhesive forms a dense and stable molecular structure through the chain growth and cross-linking reaction of isocyanate groups and hydroxyl groups during the molding process, thereby improving the strength, wear resistance and durability of the leather. In addition, the reaction of isocyanate and water will release carbon dioxide to form uniform tiny bubbles to achieve a foaming effect. This microporous structure gives the material light weight, good elasticity and breathability, making the leather softer and more comfortable.

[0012] Preferably, the release layer is made of polyacrylic resin, silicone resin or thermoplastic resin with release adhesive.

[0013] Through the above technical solution, the material selection of the release layer makes it easier to separate the embossed leather from the mold during the molding process, ensuring the integrity and clarity of the surface texture. These materials have good heat resistance and chemical stability and can withstand multiple coating and drying processes, ensuring that the release layer maintains stable performance throughout the manufacturing process.

[0014] Preferably, the material of the substrate layer is fiber woven cloth, non-woven fabric, a composite material of fiber and resin, paper, foam, thermoplastic resin sheet and its composite sheet and thermosetting resin sheet and its composite sheet.

[0015] Through the above technical solution, the material selection of the substrate layer makes the embossed leather more flexible and diverse in performance and application range, which not only improves the comprehensive performance of the embossed leather, but also expands its application potential in various fields, so that the product can better meet the diverse needs of the market and consumers.

[0016] Preferably, the PU adhesive can be one layer or more layers.

[0017] Through the above technical solution, the PU glue application can be flexibly designed as one or more layers. This design gives the embossed leather stronger functionality and adaptability. The chemical cross-linking reaction between layers can increase the bonding strength between layers and further improve the overall stability of the material.

[0018] Preferably, the drying process is performed at 60° C. for 30 minutes.

[0019] The above technical solutions are designed to ensure that the applied PU adhesive can fully cure and achieve optimal performance. This combination of temperature and time can effectively remove excess solvent and moisture in the coating, thereby improving the bonding strength and durability of the material.

[0020] Preferably, the pre-drying step is drying at 40° C. for 10 minutes.

[0021] The purpose of the above technical solution is to make adequate preparations for the subsequent coating and drying steps. The pre-drying process is carried out at a lower temperature, which can effectively remove residual moisture and solvents in the coating process while avoiding excessive thermal damage to the material.

[0022] Compared with the prior art, the present invention has the following advantages: 1. The manufacturing method of the dry-coated embossed leather adopts solvent-free foaming PU adhesive, avoids the emission of volatile organic compounds, meets modern environmental protection standards, and reduces pollution to the environment.

[0023] 2. The manufacturing method of dry-coated embossed leather solves the problem that traditional wet PU glue is prone to hydrolysis in the presence of moisture, resulting in decreased material performance and shortened service life. This patent effectively avoids the negative impact of wet PU glue hydrolysis by using solvent-free foaming PU glue, ensuring the stability and durability of embossed leather in a humid environment.

[0024] 3. The dry-coated embossed leather manufacturing method effectively improves the air permeability and feel of the embossed leather through the reasonable combination of multiple layers of PU glue and the optimal substrate layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the process of the present invention; Figure 2is a schematic diagram of Embodiments 1-5 of the present invention; Figure 3 is a schematic diagram of Embodiment 6-8 of the present invention; Figure 4 is a schematic diagram of Embodiment 9 of the present invention; Figure 5 This is a schematic diagram after processing of Example 9 of the present invention. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] See also Figure 1-5 The present invention provides a technical solution: a method for manufacturing embossed leather using dry coating.

[0028] Specific: A method for manufacturing embossed leather using dry coating, characterized in that: The production process includes the following: Method 1 Step 1: Prepare the release layer, apply a layer of PU glue on the release layer, dry it, and obtain fabric 1; Step 2: Continue to apply a layer of PU glue on the side of fabric 1 coated with PU glue, and dry to obtain fabric 2; Step 3: Continue to apply a layer of solvent-free foaming PU glue on the side of fabric 2 coated with PU glue, pre-dry, and obtain fabric 3; Step 4: Lay the side of the fabric 3 coated with PU glue on the base material layer, dry it, and peel off the release layer after drying to obtain fabric 4; Step 5: Roll up the fabric to get the finished product.

[0029] Example 1-Example 5 are made according to the method 1, the production conditions are the same, and different solvent-free foaming PU glue fillers are selected. The solvent-free foaming PU glue fillers are selected from Example 1 to Example 5 in the order of: heavy calcium carbonate, pulp, wood pulp, cellulose, light calcium carbonate, and the product schematic diagram is shown in Figure 2 .

[0030] It can be seen from the figure that although the embossing effects of heavy calcium and wood pulp are clear, there is over-embossing and edge overflow at the arc position. The embossing of cellulose and light calcium is not clear, and the pulp embossing LOGO is clearly visible without missing or overflowing.

[0031] Example 6-Example 8 are made in the same way as in Method 1, with the same production conditions. The solvent-free foamed PU adhesive filler is selected from pulp, and the proportion of pulp from Example 6 to Example 8 is 30%, 50%, and 60% respectively. See the product schematic diagram Figure 3 .

[0032] It can be seen from the figure that the texture of 30% pulp is shallow and unclear after embossing; the texture of 50% pulp is clear and intact after embossing; the texture of 60% pulp has overflow at the arc corners such as R and E.

[0033] Example 9 was made according to method 1, and the solvent-free foamed PU adhesive filler was selected from pulp, and the proportion was selected to be 50%, and compared with the conventional wet product. The product schematic diagram is shown in Figure 4 .

[0034] As can be seen from the figure, judging from the embossing effect alone, both the dry and wet leather embossing effects meet the requirements, and there is no shallow embossing, missing or overflowing.

[0035] The two experimental products were subjected to high temperature hydrolysis test and heated at 60℃ for 10h. The schematic diagram of the products after heating is shown in Figure 5 .

[0036] As can be seen from the figure, wet leather becomes peelable after high-temperature hydrolysis, while dry leather shows no peeling on the surface after high-temperature hydrolysis test. The illustration shows the side of dry leather, which still appears as a whole after high-temperature hydrolysis without stratification.

[0037] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0038] What is described above is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for producing embossed leather using dry coating, characterized in that: The production process includes the following: Step 1: Prepare the release layer, apply a layer of PU glue on the release layer, dry it, and obtain fabric 1; Step 2: Continue to apply a layer of PU glue on the side of fabric 1 coated with PU glue, and dry to obtain fabric 2; Step 3: Continue to apply a layer of solvent-free foaming PU glue on the side of fabric 2 coated with PU glue, pre-dry, and obtain fabric 3; Step 4: Lay the side of the fabric 3 coated with PU glue on the base material layer, dry it, and peel off the release layer after drying to obtain fabric 4; Step 5: Roll up the fabric to get the finished product.

2. The method for manufacturing embossed leather using dry coating according to claim 1, characterized in that: The formula of the solvent-free foaming PU adhesive comprises the following components in parts by weight: 50-100 parts of solvent-free PU adhesive and 10-50 parts of filler.

3. The formula of the solvent-free foaming PU adhesive according to claim 2, characterized in that: The filler in the formula is one or more of light calcium carbonate, heavy calcium carbonate, cellulose powder, wood pulp, paper pulp and magnetite.

4. The formula of the solvent-free foaming PU adhesive according to claim 2, characterized in that: The solvent-free foaming PU adhesive in the formula is a zero-solvent PU adhesive, and the molding process is accompanied by chain growth and cross-linking reactions between isocyanate groups and hydroxyl groups, and also includes the reaction between isocyanate and water.

5. The method for manufacturing embossed leather using dry coating according to claim 1, characterized in that: The release layer is made of polyacrylic resin, silicone resin or thermoplastic resin with release adhesive.

6. The method for manufacturing embossed leather using dry coating according to claim 1, characterized in that: The substrate layer is made of fiber woven cloth, non-woven cloth, composite material of fiber and resin, paper, foam, thermoplastic resin sheet and composite sheet thereof, and thermosetting resin sheet and composite sheet thereof.

7. The method for manufacturing embossed leather using dry coating according to claim 1, characterized in that: The PU adhesive may be one layer or multiple layers.

8. The method for manufacturing embossed leather using dry coating according to claim 1, characterized in that: The drying process is to dry at 60°C for 30 minutes.

9. The method for manufacturing embossed leather using dry coating according to claim 1, characterized in that: The pre-drying process is drying at 40°C for 10 minutes.

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