Water-based low-glossiness stain-resistant leather surface finishing agent, and preparation method and application thereof

Abstract

The application discloses a water-based low-glossiness stain-resistant leather surface finishing agent and a preparation method and application thereof, and comprises a base coating and a top coating, wherein the base coating is a carboxyl functional group-containing polyurethane; the top coating comprises, in mass parts, 100 parts of water-based fluorosilicon modified acrylic resin, 10-40 parts of organic matting resin, 30-40 parts of water, 3-10 parts of crosslinking resin, 3-6 parts of defoaming agent, 2-4 parts of wetting agent and 1-20 parts of hand feel agent. The water-based fluorosilicon modified acrylic resin and the organic matting resin in the leather surface finishing agent synergistically act, so that the leather surface finishing agent has a better gloss-reducing effect and can be applied to light-colored leather.

Description

Technical Field

[0001] This invention belongs to the field of stain-resistant resin coating technology, specifically relating to a water-based, low-gloss, stain-resistant leather surface coating agent, its preparation method, and its application. Background Technology

[0002] Following Tesla's initial launch of a car with a white interior, the visual appeal and perceived quality of light-colored interiors have become highly sought after. Various new energy vehicle manufacturers are increasingly focusing on interior color schemes, successively launching cars with light-colored interiors and gradually increasing their market share. Surface treatment agents used in this field require low gloss; low-gloss leather surfaces are superior to glossy leather in both appearance and safety. Light-colored interiors, especially light-colored leather seats, also require very high levels of stain and colorfastness during use. Currently, there is a need to develop a water-based anti-fouling surface coating agent that offers low gloss, excellent stain resistance, and also provides wear and aging resistance.

[0003] Chinese invention patent application CN107987699A discloses a water-based surface coating agent suitable for polyvinyl chloride (PVC) artificial leather used in automotive seats and its preparation method. The coating formed by this invention has advantages such as good flexibility, low gloss, wear resistance, flexural resistance, stain resistance, and good resistance to xenon lamp aging.

[0004] Chinese invention patent application CN114958194A discloses a durable stain-resistant leather surface coating agent and its preparation method. This invention incorporates a polyorganosiloxane containing at least two or more vinyl groups at the chain ends or side chains, and at least one POSS functional group in the main chain or side chains, into the formulation to improve the abrasion resistance of the formulation by introducing POSS. Simultaneously, it introduces nitrogen-boron modified silicone resin, that is, by introducing boron, polycyanate, and titanium into the silicone resin through specific modification methods to improve the adhesion between the silicone and polyurethane. This invention exhibits excellent abrasion resistance and ensures durable stain resistance.

[0005] However, the aforementioned inventions still have some shortcomings. For example, CN114958194A only focuses on improving the abrasion resistance and stain resistance of leather, without studying the gloss on light-colored leather. On the other hand, the resin prepared in this patent is a solvent system, which does not conform to the national green and environmental protection concept. For example, the water-based surface coating agent disclosed in CN107987699A does not evaluate the stain resistance and anti-graffiti performance, nor does it study the gloss on light-colored leather. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, this invention discloses a water-based, low-gloss, stain-resistant leather surface coating agent, employing the following technical solution:

[0007] A water-based, low-gloss, stain-resistant leather surface coating agent includes a base coat and a top coat. The base coat is a polyurethane containing carboxyl functional groups. The top coat, by weight, includes: 100 parts of water-based fluorosilicone-modified acrylic resin, 10-40 parts of organic matting resin, 30-40 parts of water, 3-10 parts of crosslinking resin, 3-6 parts of defoamer, 2-4 parts of wetting agent, and 1-20 parts of hand feel agent.

[0008] This invention reduces gloss by adding an organic matte resin to the top coat of a leather surface finishing agent. The organic matte resin forms a dense, matte surface structure during the drying stage, thus reducing gloss. Furthermore, this invention adds a water-based fluorosilicone-modified acrylic resin to the top coat of the leather surface finishing agent. The organosilicon and organofluorine segments in the water-based fluorosilicone-modified acrylic resin have lower surface tension and are incompatible with hydrocarbon components. After curing, they tend to migrate to the surface, forming different levels of phase separation structures, thereby achieving a stain-resistant effect. Simultaneously, the water-based fluorosilicone-modified acrylic resin itself has low gloss. The synergistic effect of the water-based fluorosilicone-modified acrylic resin and the organic matte resin enhances the gloss-reducing effect of the leather surface finishing agent, making it suitable for light-colored leather.

[0009] Furthermore, the organic matting resin is a polyurethane matting resin. Compared with other organic matting resins, such as acrylic matting resins, polyurethane matting resin exhibits better flexural resistance. Because the waterborne fluorosilicone-modified acrylic resin system has poor toughness, adding polyurethane matting resin can improve the overall toughness of the surface coating. Compared with PTFE matting resin, which exists in the surface coating in a physically blended form, PTFE matting resin also has poorer scratch resistance, resulting in significant changes in gloss on light-colored leather before and after wiping. Compared with inorganic matting resins, such as silica, which also exists in the surface coating in a physically blended form, polyurethane matting resin exhibits poorer stain resistance.

[0010] Furthermore, the waterborne fluorosilicone modified acrylic resin contains 8-12 wt% fluorinated monomers, 1.4-4 wt% silicon monomers, has a weight-average molecular weight of 50,000-70,000, and a particle size Dv(50) = 6 μm. When the fluorine content, silicon content, weight-average molecular weight, and particle size of the waterborne fluorosilicone modified acrylic resin are within this range, the stain resistance and gloss reduction effects are better. When these ranges are exceeded, the stain resistance and gloss reduction effects are somewhat limited.

[0011] Furthermore, the crosslinking resin is one or a combination of aziridine and carbodiimide. When aziridine or carbodiimide is selected, the polyurethane containing carboxyl functional groups in the primer can undergo a crosslinking polymerization reaction with aziridine or carbodiimide, thereby enhancing adhesion.

[0012] Furthermore, the defoamer is a mixture of organosilicon and polyurea; and / or, the wetting agent is nonionic polyether silicone oil; and / or, the hand feel agent is a silicone oil emulsion.

[0013] This invention also discloses a method for preparing a water-based, low-gloss, stain-resistant leather surface coating agent, characterized in that: the leather surface coating agent comprises a base coat and a top coat;

[0014] The preparation method of the topcoat is as follows: 100 parts of waterborne fluorosilicone modified acrylic resin, 10-40 parts of organic matting resin, 30-40 parts of water, 3-10 parts of crosslinking resin, 3-6 parts of defoamer, 2-4 parts of wetting agent and 1-20 parts of hand feel agent are mixed evenly.

[0015] Furthermore, the preparation method of the waterborne fluorosilicone modified acrylic resin is as follows:

[0016] By weight, 80-120 parts isopropanol, 15-25 parts laurate methacrylate and 5-15 parts acrylic acid-modified siloxane are mixed evenly to prepare mixture A; 1-2 parts azobisisobutyronitrile, 18-27 parts perfluorooctyl ethyl methacrylate, 25-30 parts acrylic acid, 5-10 parts laurate methacrylate and 50-80 parts isobornyl methacrylate are mixed evenly to prepare mixture B;

[0017] Mixture A is heated to 70-90℃ under stirring. Mixture B is added dropwise to mixture A, and the dropping rate is controlled so that the dropping is completed in 2-4 hours. After reacting for 2-4 hours, the mixture is cooled down. A neutralizing agent is added during the cooling process. After cooling, deionized water is added and emulsified for 2-4 hours. Then, rotary evaporation is performed to obtain an aqueous dispersion of fluorosilicone modified acrylic resin with a solid content of 25-35%.

[0018] Furthermore, the preparation method of the primer is as follows:

[0019] By weight, 10-15 parts of polyurethane containing carboxyl functional groups are mixed with 4-6 parts of deionized water until homogeneous, and then 0.1-0.4 parts of wetting agent are added and the mixture is stirred until homogeneous.

[0020] The present invention also discloses an application of any of the above-described leather surface coating agents for coating automotive interiors.

[0021] Furthermore, the coating method is as follows: a primer is applied to the automotive interior trim using a 30# wire rod. After surface drying, it is cured at 110-130°C for 2-4 minutes to obtain the base coating layer; a top coat is applied over the base coating layer, and after surface drying, it is cured at 110-130°C for 2-4 minutes.

[0022] By adopting the above technical solution, the beneficial effects of the present invention are as follows:

[0023] This invention reduces gloss by adding an organic matte resin to the top coat of a leather surface finishing agent. The organic matte resin forms a dense, matte surface structure during the drying stage, thus reducing gloss. Furthermore, this invention adds a water-based fluorosilicone-modified acrylic resin to the top coat of the leather surface finishing agent. The organosilicon and organofluorine segments in the water-based fluorosilicone-modified acrylic resin have lower surface tension and are incompatible with hydrocarbon components. After curing, they tend to migrate to the surface, forming different levels of phase separation structures, thereby achieving a stain-resistant effect. Simultaneously, the water-based fluorosilicone-modified acrylic resin itself has low gloss. The synergistic effect of the water-based fluorosilicone-modified acrylic resin and the organic matte resin enhances the gloss-reducing effect of the leather surface finishing agent, making it suitable for light-colored leather.

[0024] After treating leather with the leather surface coating agent of the present invention, the gloss of light-colored leather can be as low as 1.0, and the gloss of black leather can be as low as 0.5; oil-based pens and ballpoint pens can be easily wiped clean with alcohol; coffee and chili oil stains reach level 4-5 after 24 hours; and the wear resistance, flexural resistance and aging resistance are also superior. Detailed Implementation

[0025] The test methods for various properties of the leather coated with the leather surface finishing agent prepared in the examples and comparative examples are as follows:

[0026] 1) Gloss test:

[0027] The gloss was tested at 60° using a gloss tester.

[0028] 2) Gloss variation value

[0029] Wipe the leather 100 times with a dry cotton cloth dampened with dish soap, and test the change in gloss before and after wiping.

[0030] 3) Anti-graffiti test:

[0031] Using a Mitsubishi Pencil Corporation ballpoint pen (blue) and a Deli oil-based pen, write "#" on the treated leather, wipe it with alcohol, and observe whether there is any residue.

[0032] 4) Stain resistance test:

[0033] Apply 2.5% coffee and chili oil (at 80℃) to the treated leather for 24 hours, then wipe it 10 times with water and detergent. Assess the staining effect according to JIS L 0805 grayscale rating. Rate the staining effect on a scale of 1-5, with "1" representing the most severe staining.

[0034] 5) Denim abrasion resistance test:

[0035] Using a Martindale abrasion tester, with a friction head of (795±10)g, 1000 abrasions were performed, and the gray level of the leather sample surface after abrasion was evaluated according to GB / T250.

[0036] 6) Flexural resistance test:

[0037] 180° folding: Fold the treated black leather repeatedly 1000 times and observe the condition of the coating at the folds. Evaluate according to the following criteria:

[0038] ○ indicates that the coating has no obvious cracks or whitening.

[0039] ▲ indicates that the coating is slightly whitish due to folding.

[0040] × indicates that the coating is cracking or peeling off in the early stages of coating folding.

[0041] 7) Resistance to xenon lamp aging:

[0042] According to ISO 105-B06 601kJ / m 2 test.

[0043] 8) Adhesion test:

[0044] Referring to the GB / T6739-2006 standard "Cross-cut test for paint and varnish film", the adhesion of the coating was tested using the cross-cut test method.

[0045] The raw materials used in the examples and comparative examples, except for the water-based fluorosilicone-modified acrylic resin, were all common commercially available products. Specifically:

[0046] The crosslinking resin used in the examples and comparative examples is a aziridine crosslinking agent, the defoamer is a mixture of organosilicon and polyurea, the wetting agent is nonionic polyether silicone oil, and the hand feel agent is silicone oil emulsion.

[0047] The preparation method of the waterborne fluorosilicone modified acrylic resin in Examples 1 and 2 is as follows:

[0048] By weight, 100 parts isopropanol, 18 parts laurate methacrylate, and 5.25 parts acrylic acid-modified siloxane were added to a round-bottom four-necked flask and mixed thoroughly to prepare a transparent solution, namely mixture A; 2 parts azobisisobutyronitrile, 18 parts perfluorooctyl ethyl methacrylate, 25.5 parts acrylic acid, 13.25 parts laurate methacrylate, and 70 parts isobornyl methacrylate were mixed thoroughly in a flask to prepare a transparent solution, namely mixture B;

[0049] Mixture A was heated to 80°C under stirring. Mixture B was added dropwise to mixture A, and the dropping rate was controlled so that the addition was completed in 3 hours. After reacting for 3 hours, the mixture was cooled down. A neutralizing agent was added during the cooling process. After cooling down, deionized water was added and emulsified for 3 hours. The mixture was then rotary evaporated to obtain an aqueous dispersion of fluorosilicone modified acrylic resin with a solid content of 30%.

[0050] The prepared waterborne fluorosilicone modified acrylic resin has a fluorine content of 8wt%, a silicon content of 1.4wt%, a Mw of 60000, and a particle size Dv(50) = 6um.

[0051] The preparation methods of the waterborne fluorosilicone-modified acrylic resins in Examples 3-10 and Comparative Examples 5-6 differ from those in Examples 1-2 only in the mass fraction of acrylic acid-modified siloxane in mixture A and the mass fraction of perfluorooctyl ethyl methyl methacrylate in mixture B. The mass fractions of other raw materials and the preparation methods are the same as in Examples 1-2. The fluorine and silicon contents of the waterborne fluorosilicone-modified acrylic resins prepared in Examples 2-10 and Comparative Examples 5-6 are shown in Table 1.

[0052] Table 1

[0053]

[0054] Example 1

[0055] A polyurethane primer containing carboxyl functional groups was applied to light-colored and black leather, and cured at 120°C for 2 minutes after surface drying. Waterborne fluorosilicone-modified acrylic resin, matte resin, deionized water, crosslinking resin, wetting agent, defoamer, and hand-feeling agent were mixed according to the mass proportions in Table 2 and stirred evenly to prepare a topcoat. The topcoat prepared in this example was then applied to the leather with the primer and cured in an oven at 120°C for 3 minutes.

[0056] Black leather was tested for gloss and flexural strength, while white leather was tested for gloss, abrasion resistance, stain resistance, graffiti resistance, and xenon aging resistance. The test results are shown in Table 2.

[0057] Examples 2-10

[0058] The difference between Examples 2-10 and Example 1 lies in the different mass percentages of each component in the topcoat, as detailed in Table 2. Additionally, the parameters of the waterborne fluorosilicone acrylic resin are also different, as detailed in Table 1. The remaining raw materials, preparation methods, and testing methods are exactly the same as in Example 1, and the test results are shown in Table 2.

[0059] Comparative Examples 1-3

[0060] The only difference between Comparative Examples 1-3 and Example 7 is the choice of matting resin. Examples 7 and Comparative Example 2 also tested the change in gloss of light-colored leather before and after wiping, as detailed in Table 3.

[0061] Comparative Example 4

[0062] The only difference between Comparative Example 4 and Example 7 is that the primer in Comparative Example 4 is a polyurethane without carboxyl functional groups; otherwise, they are identical. Furthermore, in both Example 7 and Comparative Example 4, the primer and topcoat were applied to the sanded tinplate using the same method, and adhesion tests were performed. See Table 3 for details.

[0063] Comparative Examples 5-6

[0064] The only difference between Comparative Examples 5-6 and Example 7 is the fluorine and silicon content in the waterborne fluorosilicone modified acrylic resin, as detailed in Table 1. The test results are shown in Table 3.

[0065] Table 2

[0066]

[0067] Table 3

[0068]

[0069] As shown in Tables 2 and 3, compared with the comparative example, the surface coating agent of the present invention has lower gloss, better adhesion, aging resistance, and excellent anti-graffiti and stain resistance, which meets the requirements of light-colored automotive interiors.

[0070] Meanwhile, as shown in Table 2, when the fluorine content of the waterborne fluorosilicone modified acrylic resin is 8-12 wt%, the silicon content is 1.4-4 wt%, the weight-average molecular weight is 50,000-70,000, and the particle size Dv(50) = 6 μm, the stain resistance is better and the gloss is lower. The gloss obtained after treatment on light-colored leather can be as low as 1.0, and the gloss of black leather can be as low as 0.5. In Comparative Example 6 in Table 3, due to the high fluorine and silicon content, the process control conditions during synthesis were very strict, and the stability of the prepared emulsion was extremely poor, so performance testing was not conducted. In Comparative Example 5, due to the low fluorine and silicon content, the stain resistance and anti-graffiti performance were poor and could not meet the usage requirements.

[0071] Table 3 shows that polyurethane matte resin exhibits better flexural resistance compared to acrylic matte resin. This is because the waterborne fluorosilicone-modified acrylic resin system has poor toughness; adding polyurethane matte resin improves the overall toughness of the surface coating. When silica or PTFE is added to the system, it exists in the surface coating in a physically blended form. However, the addition of silica leads to a decrease in stain resistance. PTFE has poor scratch resistance, and the gloss of light-colored leather changes significantly before and after wiping.

[0072] In Comparative Example 6, the high fluorine-silicone content resulted in stringent process control conditions during synthesis, leading to extremely poor emulsion stability, and therefore no performance testing was conducted. In Comparative Example 5, the low fluorine-silicone content resulted in poor stain resistance and anti-graffiti properties, failing to meet the application requirements.

[0073] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A water-based, low-gloss, stain-resistant leather surface coating agent, characterized in that: Including primer and topcoat, The primer, by weight, consists of 10-15 parts of polyurethane containing carboxyl functional groups, 4-6 parts of deionized water, and 0.1-0.4 parts of wetting agent; The topcoat, by weight, comprises: 100 parts of waterborne fluorosilicone modified acrylic resin, 10-40 parts of organic matting resin, 30-40 parts of water, 3-10 parts of crosslinking resin, 3-6 parts of defoamer, 2-4 parts of wetting agent, and 1-20 parts of hand feel agent. The organic matting resin is a polyurethane matting resin; The waterborne fluorosilicone modified acrylic resin has a fluorine content of 8-12 wt%, a silicon content of 1.4-4 wt%, a weight-average molecular weight of 50,000-70,000, and a particle size D50 of 6. The crosslinking resin is one or a combination of aziridine and carbodiimide.

2. The leather surface coating agent according to claim 1, characterized in that: The defoamer is a mixture of silicone and polyurea.

3. The leather surface coating agent according to claim 1, characterized in that: The wetting agent is nonionic polyether silicone oil.

4. The leather surface coating agent according to claim 1, characterized in that: The feel agent is a silicone oil emulsion.

5. A method for preparing a water-based, low-gloss, stain-resistant leather surface coating agent according to any one of claims 1 to 4, characterized in that: The leather surface coating agent includes a base coat and a top coat; The preparation method of the topcoat is as follows: 100 parts of waterborne fluorosilicone modified acrylic resin, 10-40 parts of organic matting resin, 30-40 parts of water, 3-10 parts of crosslinking resin, 3-6 parts of defoamer, 2-4 parts of wetting agent and 1-20 parts of hand feel agent are mixed evenly.

6. The preparation method according to claim 5, characterized in that: The preparation method of the waterborne fluorosilicone modified acrylic resin is as follows: By weight, 80-120 parts isopropanol, 15-25 parts laurate methacrylate and 5-15 parts acrylic acid-modified siloxane are mixed evenly to prepare mixture A; 1-2 parts azobisisobutyronitrile, 18-27 parts perfluorooctyl ethyl methacrylate, 25-30 parts acrylic acid, 5-10 parts laurate methacrylate and 50-80 parts isobornyl methacrylate are mixed evenly to prepare mixture B; Mixture A is heated to 70-90℃ under stirring. Mixture B is added dropwise to mixture A, and the dropping rate is controlled so that the dropping is completed in 2-4 hours. After reacting for 2-4 hours, the mixture is cooled down. A neutralizing agent is added during the cooling process. After cooling down, deionized water is added and emulsified for 2-4 hours. Then, the mixture is rotary evaporated to obtain a waterborne fluorosilicone modified acrylic resin with a solid content of 25-35%.

7. The preparation method according to claim 5, characterized in that: The preparation method of the primer is as follows: By weight, 10-15 parts of polyurethane containing carboxyl functional groups are mixed with 4-6 parts of deionized water until homogeneous, and then 0.1-0.4 parts of wetting agent are added and the mixture is stirred until homogeneous.

8. The application of a leather surface coating agent according to any one of claims 1 to 4, characterized in that: Used for coating automotive interiors.

9. The application according to claim 8, characterized in that, The coating method is as follows: apply a primer to the automotive interior, and after it is surface dry, cure it at 110-130°C for 2-4 minutes to obtain a base coat; apply a top coat on the base coat, and after it is surface dry, cure it at 110-130°C for 2-4 minutes.

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