Leather with light, thin, breathable and wear-resistant coating and preparation process thereof

Abstract

The invention relates to leather with a light, thin, breathable and wear-resistant coating and a preparation process of the leather. Firstly, leather to be coated is subjected to buffing and patching treatment, and the surface consistency of the leather is ensured; then, two different coating agents are used for conducting bottom sealing and prime pulp coating treatment on the leather, so that the performance of the coating is improved; and finally, finishing leather by using a surface slurry finishing agent and top layer gloss oil to obtain a leather product with a light, thin, breathable and wear-resistant coating. High-wear-resistance polyurethane and acrylic resin coating agents are selected to construct the light, thin, breathable and wear-resistant coating, meanwhile, multiple hand feeling agents and hand feeling oil wax are matched, the hand feeling and the appearance effect of leather are improved, and the problem that wear resistance and breathability of an existing leather coating are difficult to consider at the same time is successfully solved. The leather product provided by the invention not only has excellent durability, scratch resistance and hand feeling comfort, but also can keep the characteristics of lightness, thinness, breathability and the like.

Description

Technical Field

[0001] The invention relates to the technical field of leather processing, and in particular to leather with a light, thin, breathable, and wear-resistant coating and a preparation process thereof. Background Art

[0002] In the prior art, multi-layer coating and increasing the thickness of each coating are usually used to improve the wear resistance and surface protection performance of leather. However, this will also lead to a series of problems such as insufficient flexibility of the leather, poor air permeability, coating adhesion needs to be improved, coating easily falls off or cracks in high wear areas, poor environmental protection, and high VOC (volatile organic compound) content, which greatly reduces the softness and air permeability of leather products and limits their application in the field of high-end leather products.

[0003] In recent years, as consumers have increased their demands for environmental protection, health, comfort and functionality, it is of great significance to prepare leather coatings that are wear-resistant, light, thin and breathable. Summary of the invention

[0004] The main purpose of the present invention is to solve the above problems existing in the prior art and provide a leather preparation process with a thin, breathable and wear-resistant coating, comprising: sequentially performing backing treatment, base slurry finishing treatment, surface slurry finishing treatment and top varnish finishing treatment on the leather.

[0005] Furthermore, the leather needs to be polished and repaired before the backing treatment to ensure its surface consistency. This is because the leather raw material is usually genuine leather with damage, so necessary pretreatment is required before finishing.

[0006] Furthermore, the specific method of the leather grinding treatment is: using sandpaper with different mesh sizes to repeatedly grind the leather and clean it.

[0007] Furthermore, when sanding the leather, first use high-grit sandpaper for rough sanding, and then use low-grit sandpaper for fine sanding. The grit of the sandpaper is 400-1000.

[0008] Furthermore, the specific method of the repair treatment is: use leather repair paste (such as elastic polyurethane repair paste with good filling properties) to repeatedly scrape and fill the scarred and concave parts of the leather until they are flat, then dry them naturally or dry them at a low temperature of 30-50°C and polish them.

[0009] Furthermore, the leather is any one of the conventionally tannable animal skins such as cattle skin, sheep skin, pig skin, etc. that has completed the basic leather making process before finishing.

[0010] Furthermore, the composition of the bottom sealing coating agent used for the bottom sealing treatment includes, by mass percentage: 60%-80% of high-performance wear-resistant water-based polyurethane resin, 10%-30% of auxiliary agent, and 10%-20% of water, which is 100% in total.

[0011] Furthermore, the base coating agent used in the base coating treatment comprises, by mass percentage, 30%-60% of high-performance wear-resistant water-based polyurethane resin, 30%-50% of acrylic resin, 5%-30% of additives, and 10%-30% of water, which totals 100%.

[0012] Furthermore, the composition of the paste finishing agent used in the paste finishing treatment includes, by mass percentage: 60%-80% of high-performance wear-resistant water-based polyurethane resin, 15%-50% of acrylic resin, 3%-12% of hand-feel oil wax, 5%-30% of additives, and 5%-20% of water, totaling 100%.

[0013] Furthermore, the top varnish used in the top varnish finishing treatment is selected from matting agents such as silica and modified polyurethane or polyurethane varnish.

[0014] Furthermore, the high-performance wear-resistant waterborne polyurethane resin is specifically a mixture of nano-aluminum oxide or nano-silicon oxide and waterborne polyurethane resin, wherein the content of nano-aluminum oxide or nano-silicon oxide is 1wt%-2wt%.

[0015] Furthermore, the auxiliary agent includes at least one of a cross-linking agent, a leveling agent, a film-forming agent, a hand-feeling agent, a softener, a colorant, and an auxiliary solvent.

[0016] Furthermore, the cross-linking agent is selected from any one of polyisocyanate compounds and nitrogen pyridine compounds.

[0017] Furthermore, the leveling agent is selected from any one of polyether compounds and modified polyurethane.

[0018] Furthermore, the film-forming agent is selected from natural or synthetic compounds, specifically any one of casein, nitrocellulose, cellulose acetate, polyurethane, and vinyl polymers.

[0019] Furthermore, the hand feeling agent is specifically paraffin wax, vegetable wax, etc.

[0020] Furthermore, the softener is specifically silicone oil emulsion, castor oil modified emulsion, etc.

[0021] Furthermore, the colorant is specifically a dye or pigment for leather chemical industry.

[0022] Furthermore, the auxiliary solvent is usually an organic solvent, including polyester compounds and polyether compounds.

[0023] Furthermore, the leather is subjected to backing treatment and base coating treatment in a step-by-step coating manner. After the backing coating, the leather is dried naturally or dried at a low temperature of 50-60°C before base coating. After the base coating is completed, the leather is dried naturally or dried at a low temperature of 50-60°C.

[0024] Furthermore, the coating amount of the coating agent during the back cover treatment is 5-10g / m 2 The coating amount of the primer during the base coating treatment is 8-15g / m 2 The total coating amount of the backing treatment and the base coating treatment shall not exceed 20g / m 2 .

[0025] Furthermore, the leather is subjected to a step-by-step finishing process of surface slurry coating and a top varnish coating. After surface slurry coating, the leather is naturally dried or low-temperature dried at 60-70°C before the top varnish coating is applied. After the top varnish coating is completed, the leather is naturally dried or low-temperature dried at 60-70°C.

[0026] Furthermore, the coating amount of the surface paste is controlled at 3-8g / m 2 The top varnish coating amount is controlled at 2-5g / m 2 The total coating amount of the surface coating and the top varnish coating shall not exceed 10g / m 2 .

[0027] The second purpose of the present invention is to provide a leather with a thin, breathable and wear-resistant coating prepared according to the above method, wherein the coating on the surface of the leather has a multi-layer structure, including a sealing layer, a base layer, a surface layer and a varnish layer.

[0028] Furthermore, the leather has no wear under the conditions of grinding wheel CS-10, 500g, 800r, folding fastness ≥ 50,000 times, color fastness ≥ 4 levels, total volatile organic matter (VOCs) ≤ 80mg / kg, air permeability and water vapor permeability reach 1000mL·cm -2 ·h -1 and 4500mg·cm -2 ·h -1 above.

[0029] Compared with existing similar products or processes, the improved effects of the present invention are embodied in the following aspects:

[0030] (1) When forming a composite coating on the leather surface, highly wear-resistant polyurethane and acrylic resin finishing agents are selected as raw materials, combined with a variety of hand feel agents and hand feel oil waxes, which not only improves the wear resistance of the leather coating, but also gives the leather products a good feel.

[0031] (2) The entire coating process adopts a thin coating process, strictly controlling the coating amount of each coating and the total coating amount, greatly reducing the coating amount and coating thickness, ensuring the lightness and breathability of the leather. The glossiness (matte or high gloss) can also be flexibly adjusted according to needs, and finally obtaining a wear-resistant leather coating and leather products with high wear resistance, lightness and breathability, and excellent hand feel.

[0032] (3) This process has a wide range of applications and can be used for a variety of common animal skins such as cattle skin, sheep skin, pig skin, etc. The resulting coating is not only relatively uniform but also has a moderate thickness, making it highly competitive in high-end leather products.

[0033] (4) Existing coating materials can be quickly modified by compounding. Multiple coating materials can be used together to form a composite coating, which has the advantages of simple formula, easy operation, and significant effect, and is suitable for large-scale production in factories. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The present invention is a schematic diagram of the wear-resistant coating structure of the thin and breathable leather. DETAILED DESCRIPTION

[0035] In order to enable ordinary technicians in the field to fully understand the technical solutions and beneficial effects of the present invention, the following is further described in detail with reference to specific embodiments and drawings. It should be emphasized that the following embodiments are only preferred embodiments of the present invention and not all, and any simple improvements or replacements made on this basis should fall within the scope of protection of the present invention.

[0036] Example 1

[0037] The leather raw material in this embodiment is specifically conventional cowhide shoe upper leather to be coated.

[0038] The preparation process of the high-performance wear-resistant waterborne polyurethane resin used for preparing the bottom coating agent, the base coating agent and the surface coating agent is as follows: 1.5 wt% of nano-alumina is added to the waterborne polyurethane resin and stirred evenly.

[0039] The formula (by mass percentage) of the bottom seal finishing agent is: 70% of high-performance wear-resistant water-based polyurethane resin, 20% of water, and 10% of auxiliary agent (crosslinking agent + leveling agent). The preparation method of the finishing agent is as follows: high-performance wear-resistant water-based polyurethane resin, crosslinking agent (nitropyridine compound), leveling agent (polyether compound) and water are mixed in proportion, and stirred evenly to obtain the bottom seal finishing agent.

[0040] The base coating agent formula (by mass percentage) is: 45% of high-performance wear-resistant water-based polyurethane resin, 30% of acrylic resin, 13% of auxiliary agent (softener + leveling agent), and 12% of water. The preparation method of the coating agent is as follows: high-performance wear-resistant water-based polyurethane resin, acrylic resin, softener (castor oil modified emulsion), leveling agent (polyether compound) and water are mixed in proportion, and stirred evenly to obtain the base coating agent.

[0041] The formula of the surface paste finishing agent (by mass percentage) is: 70% of high-performance wear-resistant water-based polyurethane resin, 15% of acrylic resin, 3% of hand-feeling oil wax (paraffin), 5% of auxiliary agent (polyether compound leveling agent + castor oil modified emulsion softener), and 7% of water. The preparation method of the finishing agent is as follows: directly mix these raw materials in proportion to obtain the surface paste finishing agent.

[0042] The top varnish is specifically a silica-based, modified polyurethane-based matting agent or polyurethane varnish.

[0043] The method for preparing cowhide shoe upper leather with a light, thin, breathable, and wear-resistant coating using the above raw materials is as follows:

[0044] (1) First, the damaged and injured parts of the leather surface of the conventional cowhide shoe upper to be coated are polished and repaired. First, the defective and damaged parts are smoothed with sandpaper with a grit of 800 mesh, then the sandpaper with a grit of 400 mesh is used for finishing and polishing, and finally the fine powder on the leather surface is wiped off.

[0045] (2) Use an elastic polyurethane paste with good adhesion and filling properties to repair the leather. Repeatedly scrape and apply it to fill the scars and depressions until they are flat. Then place the leather in a 40°C oven and dry it at low temperature for 15 minutes. Finally, use 400-grit sandpaper to finely polish and slightly trim the leather.

[0046] (3) The treated leather is coated with the above-mentioned bottom coating agent and base coating agent in steps. First, the bottom coating is applied with a coating amount of 7g / m 2 After the back cover is painted, place the leather in a 50℃ oven and dry it at low temperature for about 15 minutes. After the back cover is completely dry, take out the leather and then apply the base paste. The coating amount is 10g / m 2 After the base coating is completed, the leather is placed in a 50°C oven and dried at low temperature for about 15 minutes.

[0047] (4) The leather is coated with the above-mentioned top coating agent and top varnish in steps. First, the top coating is performed with a coating amount of 5g / m 2 After the surface paste is applied, the leather is placed in a 65℃ oven for low temperature drying for about 15 minutes. After the surface paste is completely dry, take out the leather and then apply the top layer of varnish with a coating amount of 3g / m 2After the top layer of varnish is applied, the leather is placed in a 65°C oven and dried at low temperature for about 15 minutes, thereby obtaining a cowhide upper leather sample with a thin, breathable, and wear-resistant coating.

[0048] The coating structure of the cowhide upper leather sample prepared in Example 1 is as follows: Figure 1 In order to fully understand the various properties of the cowhide upper leather samples, the following tests were carried out:

[0049] (1) Wear resistance test

[0050] The leather wear resistance test was carried out with reference to the standard QB / T 2726-2005 "Determination of wear resistance of leather by physical and mechanical tests". The test conditions are: grinding wheel: CS-10, 500g, 800r.

[0051] The test results show that the leather sample has no wear, which indicates that the leather coating prepared according to the method of the present invention has excellent wear resistance.

[0052] (2) Air permeability test

[0053] The air permeability of the leather samples was tested using a leather air permeability tester (GT-7007-0, Gaotie Testing Instrument Co., Ltd.). The test method was as follows: three samples were cut using a cutter, and the samples were placed in a constant temperature and humidity chamber at 20°C and 65% humidity for 24-48 hours, and then taken out for testing.

[0054] The test results show that the air permeability of the leather sample is not less than 1500mL·cm -2 ·h -1 .

[0055] (3) Water and air permeability test

[0056] The water permeability of leather samples was tested using a low-temperature permeation tester (GT-7045-EV, Dongguan High-speed Railway Testing Instrument Co., Ltd.). The test method is: use a cutter to cut three samples each, place the samples in a constant temperature and humidity chamber at 20°C and 65% humidity for 24-48 hours, and then take them out for testing.

[0057] The test results show that the water vapor permeability of the leather sample is not less than 7500mg·cm -2 ·h -1 .

[0058] Example 2

[0059] The leather raw material in this embodiment is specifically conventional cowhide shoe upper leather to be coated.

[0060] The content of nano aluminum oxide in the high-performance wear-resistant water-based polyurethane resin is 1wt%.

[0061] The formula of the bottom coating agent (by mass percentage) is: 65% of high-performance wear-resistant water-based polyurethane resin, 20% of water, and 15% of auxiliary agent (nitrogen pyridine cross-linking agent + polyether leveling agent).

[0062] The base coating agent formula (by mass percentage) is: 40% of high-performance wear-resistant water-based polyurethane resin, 40% of acrylic resin, 8% of additives (castor oil modified emulsion softener, polyether leveling agent), and 12% of water.

[0063] The formula of the surface coating agent (by mass percentage) is: 60% of high-performance wear-resistant water-based polyurethane resin, 25% of acrylic resin, 3% of hand-feel oil wax (paraffin), 7% of additives (polyether leveling agent + castor oil modified emulsion softener), and 5% of water.

[0064] The top varnish is specifically a silica-based, modified polyurethane-based matting agent or polyurethane varnish.

[0065] The method for preparing cowhide shoe upper leather with a light, thin, breathable, and wear-resistant coating using the above raw materials is as follows:

[0066] (1) First, the damaged and injured parts of the leather surface of the conventional cowhide shoe upper to be coated are polished. First, the defective and damaged parts are smoothed with sandpaper with a grit of 800 mesh, then the sandpaper with a grit of 400 mesh is used for finishing and polishing, and finally the fine powder on the leather surface is wiped off.

[0067] (2) Use an elastic polyurethane paste with good adhesion and filling properties to repair the leather. Repeatedly scrape and apply it to fill the scars and depressions until they are flat. Then place the leather in a 40°C oven and dry it at low temperature for 15 minutes. Finally, use 400-grit sandpaper to finely polish and slightly trim the leather.

[0068] (3) The treated leather is coated with the above-mentioned bottom coating agent and base coating agent in steps. First, the bottom coating is applied with a coating amount of 7g / m 2 After the back cover is painted, place the leather in a 50℃ oven and dry it at low temperature for about 15 minutes. After the back cover is completely dry, take out the leather and then apply the base paste. The coating amount is 10g / m 2 After the base coating is completed, the leather is placed in a 50°C oven and dried at low temperature for about 15 minutes.

[0069] (4) The leather is coated with the above-mentioned top coating agent and top varnish in steps. First, the top coating is performed with a coating amount of 5g / m 2 After the surface paste is applied, the leather is placed in a 65℃ oven for low temperature drying for about 15 minutes. After the surface paste is completely dry, take out the leather and then apply the top layer of varnish with a coating amount of 3g / m 2After the top layer of varnish is applied, the leather is placed in a 65°C oven and dried at low temperature for about 15 minutes, thereby obtaining a cowhide upper leather sample with a thin, breathable, and wear-resistant coating.

[0070] The leather upper leather sample prepared in Example 2 was tested for wear resistance, air permeability, and water vapor permeability by referring to the method in Example 1. The results showed that the leather sample had no wear, and the air permeability and water vapor permeability reached 1200 mL·cm -2 ·h -1 and 4500mg·cm -2 ·h -1 above.

[0071] Example 3

[0072] The leather raw material in this embodiment is specifically conventional sheepskin upper leather to be coated.

[0073] The content of nano-aluminum oxide in the high-performance wear-resistant water-based polyurethane resin is 1.5wt%.

[0074] The formula of the bottom coating agent (by mass percentage) is: 70% of high-performance wear-resistant water-based polyurethane resin, 20% of water, and 10% of auxiliary agent (nitrogen pyridine cross-linking agent + polyether leveling agent).

[0075] The base coating agent formula (by mass percentage) is: 45% of high-performance wear-resistant water-based polyurethane resin, 30% of acrylic resin, 13% of auxiliary agent (castor oil modified emulsion softener + polyether leveling agent), and 12% of water.

[0076] The formula of the surface coating agent (by mass percentage) is: 70% high-performance wear-resistant water-based polyurethane resin, 15% acrylic resin, 3% hand-feel oil wax (paraffin), 5% additives (polyether leveling agent + castor oil modified emulsion softener), and 7% water.

[0077] The top varnish is specifically a silica-based, modified polyurethane-based matting agent or polyurethane varnish.

[0078] The method for preparing sheepskin shoe upper leather with a light, thin, breathable, and wear-resistant coating using the above raw materials is as follows:

[0079] (1) First, the damaged and injured parts of the conventional sheepskin upper leather to be coated are polished and repaired. First, the defective and damaged parts are smoothed with sandpaper with a grit of 600 mesh, then the sandpaper with a grit of 400 mesh is used for finishing and polishing, and finally the fine powder on the leather surface is wiped off.

[0080] (2) Use an elastic polyurethane paste with good adhesion and filling properties to repair the leather. Repeatedly scrape and apply it to fill the scratches and depressions until they are flat. Then place the leather in a 50°C oven and dry it at low temperature for 10 minutes. Finally, use 400-grit sandpaper to finely polish and slightly trim the leather.

[0081] (3) The treated leather is coated with the above-mentioned bottom coating agent and base coating agent in steps. First, the bottom coating is applied with a coating amount of 10 g / m 2 After the back cover is painted, place the leather in a 60℃ oven and dry it for about 10 minutes. After the back cover is completely dry, take out the leather and then apply the base paste. The coating amount is 10g / m 2 After the base coating is completed, the leather is placed in a 60°C oven and dried at low temperature for about 10 minutes.

[0082] (4) The leather is coated with the above-mentioned top paste and top varnish in steps. First, the top paste is coated with a coating amount of 7g / m 2 After the surface paste is applied, the leather is placed in a 70℃ oven for low temperature drying for about 10 minutes. After the surface paste is completely dry, take out the leather and then apply the top layer of varnish with a coating amount of 3g / m 2 After the top layer of varnish is applied, the leather is placed in a 70°C oven and dried at low temperature for about 10 minutes, thereby obtaining a sheepskin upper leather sample with a thin, breathable, and wear-resistant coating.

[0083] The sheepskin upper leather sample prepared in Example 3 was tested for wear resistance, air permeability, and water vapor permeability by referring to the method in Example 1. The wear resistance test results show that the leather sample has no wear, which indicates that nano-aluminum oxide or nano-silicon oxide can improve the wear resistance of the finished leather. In addition, the air permeability and water vapor permeability of the leather sample reached 1000 mL·cm -2 ·h -1 and 4000mg·cm -2 ·h -1 above.

[0084] Comparative Example 1

[0085] The leather raw material in this embodiment is specifically conventional cowhide shoe upper leather to be coated.

[0086] Ordinary water-based polyurethane resin (i.e. water-based polyurethane resin without adding nano-aluminum oxide and nano-silicon oxide) is used to replace the original high-performance wear-resistant water-based polyurethane resin, and it is used to prepare the bottom coating agent, base coating agent and surface coating agent (other additives remain unchanged).

[0087] The formula of the bottom sealing coating agent (by mass percentage) is: 70% of waterborne polyurethane resin, 20% of water, and 10% of auxiliary agent (nitrogen pyridine cross-linking agent + polyether leveling agent).

[0088] The base coating agent formula (by mass percentage) is: 45% waterborne polyurethane resin, 30% acrylic resin, 13% auxiliary agent (castor oil modified emulsion softener + polyether leveling agent), and 12% water.

[0089] The formula of the surface coating agent (by mass percentage) is: 70% water-based polyurethane resin, 15% acrylic resin, 3% hand-feel oil wax (paraffin), 5% additives (castor oil modified emulsion softener + polyether leveling agent), and 7% water.

[0090] The top varnish is specifically a silica-based, modified polyurethane-based matting agent or polyurethane varnish.

[0091] The method for preparing cowhide shoe upper leather with a light, thin, breathable, and wear-resistant coating using the above raw materials is as follows:

[0092] (1) First, the damaged and injured parts of the leather surface of the conventional cowhide shoe upper to be coated are polished. First, the defective and damaged parts are smoothed with sandpaper with a grit of 800 mesh, then the sandpaper with a grit of 400 mesh is used for finishing and polishing, and finally the fine powder on the leather surface is wiped off.

[0093] (2) Use an elastic polyurethane paste with good adhesion and filling properties to repair the leather. Repeatedly scrape and apply it to fill the scratches and depressions until they are flat. Then place the leather in a 40°C oven and dry it at low temperature for 15 minutes. Finally, use 400-grit sandpaper to finely polish and slightly trim the leather.

[0094] (3) The treated leather is coated with the above-mentioned bottom coating agent and base coating agent in steps. First, the bottom coating is applied with a coating amount of 7g / m 2 After the back cover is painted, place the leather in a 50℃ oven and dry it at low temperature for about 15 minutes. After the back cover is completely dry, take out the leather and then apply the base paste. The coating amount is 10g / m 2 After the base coating is completed, the leather is placed in a 50°C oven and dried at low temperature for about 15 minutes.

[0095] (4) The leather is coated with the above-mentioned top paste and top varnish in steps. First, the top paste is coated with a coating amount of 5g / m 2 After the surface paste is applied, the leather is placed in a 65℃ oven for low temperature drying for about 15 minutes. After the surface paste is completely dry, take out the leather and then apply the top layer of varnish with a coating amount of 3g / m 2 After the top layer of varnish is applied, the leather is placed in a 65°C oven and dried at low temperature for about 15 minutes, thereby obtaining a cowhide upper leather sample with a thin, breathable, and wear-resistant coating.

[0096] The leather upper leather sample prepared in Comparative Example 1 was tested for wear resistance, air permeability, and water vapor permeability by referring to the method in Example 1. The results showed that the leather sample was worn at 300r under the same conditions, but because the coating amount of each layer was maintained at a reasonable level, the air permeability and water vapor permeability were basically not affected, and could exceed 1500mL·cm -2 ·h -1 and 7500mg·cm -2 ·h -1 .

[0097] Comparative Example 2

[0098] The leather raw material in this embodiment is specifically conventional cowhide shoe upper leather to be coated.

[0099] Ordinary water-based polyurethane resin (i.e. water-based polyurethane resin without adding nano-aluminum oxide and nano-silicon oxide) is used to replace the original high-performance wear-resistant water-based polyurethane resin, and it is used to prepare the bottom coating agent, base coating agent and surface coating agent (other additives remain unchanged).

[0100] The formula of the bottom coating agent (by mass percentage) is: 70% of waterborne polyurethane resin, 20% of water, and 10% of auxiliary agent (nitrogen pyridine cross-linking agent + polyether leveling agent).

[0101] The base coating agent formula (by mass percentage) is: 45% waterborne polyurethane resin, 30% acrylic resin, 13% auxiliary agent (castor oil modified emulsion softener + polyether leveling agent), and 12% water.

[0102] The formula of the surface coating agent (by mass percentage) is: 70% water-based polyurethane resin, 15% acrylic resin, 3% hand-feel oil wax (paraffin), 5% additives (castor oil modified emulsion softener + polyether leveling agent), and 7% water.

[0103] The top varnish is specifically a silica-based, modified polyurethane-based matting agent or polyurethane varnish.

[0104] The method for preparing cowhide shoe upper leather with a light, thin, breathable, and wear-resistant coating using the above raw materials is as follows:

[0105] (1) First, the damaged and injured parts of the leather surface of the conventional cowhide shoe upper to be coated are polished. First, the defective and damaged parts are smoothed with sandpaper with a grit of 800 mesh, then the sandpaper with a grit of 400 mesh is used for finishing and polishing, and finally the fine powder on the leather surface is wiped off.

[0106] (2) Use an elastic polyurethane paste with good adhesion and filling properties to repair the leather. Repeatedly scrape and apply it to fill the scratches and depressions until they are flat. Then place the leather in a 40°C oven and dry it at low temperature for 15 minutes. Finally, use 400-grit sandpaper to finely polish and slightly trim the leather.

[0107] (3) The treated leather is coated with the above-mentioned bottom coating agent and base coating agent in steps. First, the bottom coating is applied with a coating amount of 18g / m 2 After the back cover is painted, place the leather in a 50℃ oven and dry it for about 15 minutes. After the back cover is completely dry, take out the leather and then apply the base paste. The coating amount is 25g / m 2 After the base coating is completed, the leather is placed in a 50°C oven and dried at low temperature for about 15 minutes.

[0108] (4) The leather is coated with the above-mentioned top paste and top varnish in steps. First, the top paste is coated with a coating amount of 15g / m 2 After the surface paste is applied, the leather is placed in a 65℃ oven for low temperature drying for about 15 minutes. After the surface paste is completely dry, take out the leather and then apply the top layer of varnish with a coating amount of 5g / m 2 After the top layer of varnish is applied, the leather is placed in a 65°C oven and dried at low temperature for about 15 minutes, thereby obtaining a cowhide upper leather sample with a thin, breathable, and wear-resistant coating.

[0109] The leather upper leather sample prepared in Comparative Example 2 was tested for wear resistance, air permeability, and water vapor permeability by referring to the method in Example 1. The results showed that the leather sample was worn out at 300r under the same conditions. At the same time, the air permeability and water vapor permeability were greatly affected due to the large amount of coating on each layer, and were reduced to about 600mL·cm -2 ·h -1 and 2000mg·cm -2 ·h -1 .

[0110] Comparative Example 3

[0111] The leather raw material in this comparative example is specifically conventional cowhide shoe upper leather to be coated.

[0112] The content of nano aluminum oxide in the high-performance wear-resistant water-based polyurethane resin is 1wt%.

[0113] The backing and base coating are combined into a one-step process, and the coating agent formula used (by mass percentage) is: 50% high-performance wear-resistant water-based polyurethane resin, 22% acrylic resin, 12% additives (nitrogen pyridine cross-linking agent + polyether leveling agent + castor oil modified emulsion softener), and 16% water.

[0114] The formula of the surface coating agent (by mass percentage) is: 60% of high-performance wear-resistant water-based polyurethane resin, 25% of acrylic resin, 3% of hand-feel oil wax (paraffin), 7% of additives (polyether leveling agent + castor oil modified emulsion softener), and 5% of water.

[0115] The top varnish is specifically a silica-based, modified polyurethane-based matting agent or polyurethane varnish.

[0116] The method for preparing cowhide shoe upper leather with a light, thin, breathable, and wear-resistant coating using the above raw materials is as follows:

[0117] (1) First, the damaged and injured parts of the leather surface of the conventional cowhide shoe upper to be coated are polished. First, the defective and damaged parts are smoothed with sandpaper with a grit of 800 mesh, then the sandpaper with a grit of 400 mesh is used for finishing and polishing, and finally the fine powder on the leather surface is wiped off.

[0118] (2) Use an elastic polyurethane paste with good adhesion and filling properties to repair the leather. Repeatedly scrape and apply it to fill the scratches and depressions until they are flat. Then place the leather in a 50°C oven and dry it at low temperature for 15 minutes. Finally, use 400-grit sandpaper to finely polish and slightly trim the leather.

[0119] (3) The treated leather is coated with the above-mentioned backing and base composite coating agent, and the coating amount is 20g / m 2 After finishing, place the leather in a 50℃ oven to dry for about 20 minutes. Take out the leather after the coating is completely dry.

[0120] (4) The leather is coated with the above-mentioned top coating agent and top varnish in steps. First, the top coating is performed with a coating amount of 5g / m 2 After the surface paste is applied, the leather is placed in a 65℃ oven for low temperature drying for about 15 minutes. After the surface paste is completely dry, take out the leather and then apply the top layer of varnish with a coating amount of 3g / m 2 After the top layer of varnish is applied, the leather is placed in a 65°C oven and dried at low temperature for about 15 minutes, thereby obtaining a cowhide upper leather sample with a thin, breathable, and wear-resistant coating.

[0121] The leather upper leather sample prepared in Comparative Example 3 was tested for wear resistance, air permeability, and water vapor permeability by referring to the method in Example 1. The results showed that the leather sample had no wear, and the air permeability and water vapor permeability were basically unaffected, reaching 1000 mL·cm -2 ·h -1 and 4000mg·cm -2 ·h -1However, surface observation revealed that the coating obtained by this method had defects, the coating layer was not smooth enough, and due to the single primer step and excessive coating amount, the coating was prone to cracks after being bent multiple times.

Claims

1. A process for preparing leather with a light, breathable, and wear-resistant coating, characterized in that The process includes: sequentially performing backing treatment, base slurry finishing treatment, surface slurry finishing treatment and top varnish finishing treatment on the leather.

2. The process according to claim 1, characterized in that: The leather needs to be polished and repaired before the backing treatment. The specific method of the polishing treatment is: use sandpaper of different mesh sizes to repeatedly polish the leather and clean it; the specific method of the repairing treatment is: use leather repair cream to repeatedly scrape and fill the scars and concave parts of the leather until it is flat, then dry it naturally or dry it at a low temperature of 30-50℃ and polish it thoroughly.

3. The process according to claim 2, characterized in that: When grinding leather, first use high-grit sandpaper for rough grinding, and then use low-grit sandpaper for fine grinding. The mesh number of sandpaper is 400-1000.

4. The process according to claim 1, characterized in that: The leather is specifically any one of yellow cattle hide, sheep hide and pig hide which has completed the basic leather making process before coating.

5. The process according to claim 1, characterized in that: The composition of the bottom coating agent used in the bottom coating treatment includes, by mass percentage, 60%-80% of high-performance wear-resistant water-based polyurethane resin, 10%-30% of additives, and 10%-20% of water, which is 100% in total; the composition of the bottom coating agent used in the bottom slurry coating treatment includes, by mass percentage, 30%-60% of high-performance wear-resistant water-based polyurethane resin, 30%-50% of acrylic resin, 5%-30% of additives, and 10%-30% of water, which is 100% in total; the composition of the top slurry coating agent used in the top slurry coating treatment includes, by mass percentage, 60%-80% of high-performance wear-resistant water-based polyurethane resin, 15%-50% of acrylic resin, 3%-12% of hand-feel oil wax, 5%-30% of additives, and 5%-20% of water, which is 100% in total; the top varnish used in the top varnish coating treatment is selected from silica, modified polyurethane matting agents or polyurethane varnish.

6. The process according to claim 5, characterized in that: The high-performance wear-resistant waterborne polyurethane resin is a mixture of nano-aluminum oxide or nano-silicon oxide and waterborne polyurethane resin, wherein the content of nano-aluminum oxide or nano-silicon oxide is 1wt%-2wt%.

7. The process according to claim 5, characterized in that: The auxiliary agent includes at least one of a cross-linking agent, a leveling agent, a film-forming agent, a hand-feeling agent, a softener, a colorant, and an auxiliary solvent; wherein The cross-linking agent is selected from any one of polyisocyanate compounds and nitrogen pyridine compounds; the leveling agent is selected from any one of polyether compounds and modified polyurethane; the film-forming agent is selected from any one of casein, nitrocellulose, acetate fiber, polyurethane, and vinyl polymers; the hand feeling agent is selected from any one of paraffin and vegetable wax; the softener is selected from any one of silicone oil emulsion and castor oil modified emulsion; the colorant is specifically a dye or pigment for leather chemical industry; the auxiliary solvent includes polyester compounds and polyether compounds.

8. The process of claim 1, wherein: The leather is treated with backing treatment and base coating by step-by-step coating. The coating amount of the coating agent during backing treatment is 5-10g / m 2 After the bottom coating, the leather is dried naturally or at a low temperature of 50-60℃ before the base coating is applied. The coating amount of the base coating is 8-15g / m 2 After the base coating is completed, the leather should be dried naturally or at a low temperature of 50-60℃. The total coating amount of the bottom treatment and base coating treatment should not exceed 20g / m 2 .

9. The process of claim 1, wherein: The leather is treated with a step-by-step coating method for the top paste coating and the top varnish coating. The amount of top paste coating is controlled at 3-8g / m 2 ; After the top paste is applied, the leather is dried naturally or at a low temperature of 60-70℃ before the top varnish is applied. The amount of top varnish applied is controlled at 2-5g / m 2 After the top varnish is applied, the leather shall be dried naturally or at a low temperature of 60-70°C. The total amount of the top varnish and top varnish shall not exceed 10g / m 2 .

10. A leather having a light, breathable, wear-resistant coating, characterized in that: The coating on the leather surface has a multi-layer structure, comprising a sealing layer, a base slurry layer, a surface slurry layer and a varnish layer.

Images