Lignin-modified waterborne polyurethane strippable coating and preparation method therefor
By preparing lignin-modified waterborne polyurethane coatings, and combining lignin quaternization modification with mesoporous silica framework-loaded corrosion inhibitors, the problems of peelable coatings being difficult to peel off and having insufficient weather resistance after long-term protection were solved, thus achieving a high-performance coating performance improvement.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- CNOOC CHANGZHOU PAINT & COATINGS IND RES INST
- Filing Date
- 2025-08-08
- Publication Date
- 2026-05-15
AI Technical Summary
Existing peelable coatings are difficult to peel off after long-term protection, and their applicability to substrates and weather resistance are insufficient, posing an environmental pollution risk and failing to meet market demands in harsh environments.
By preparing lignin-modified waterborne polyurethane coatings, the quaternization modification of lignin and the loading of corrosion inhibitors onto a mesoporous silica framework, combined with the molecular structure modification of fatty acid double bonds and carbon dioxide-based polyols, enhance the coating's aging resistance, self-healing properties, and interfacial compatibility.
It improves the coating's resistance to outdoor aging and peelability, provides self-healing capabilities, enhances the coating's physical barrier properties and chemical stability, and meets the application requirements in harsh environments.
Smart Images
Figure PCTCN2025113481-FTAPPB-I100001 
Figure PCTCN2025113481-FTAPPB-I100002 
Figure PCTCN2025113481-FTAPPB-I100003
Abstract
Description
A lignin-modified waterborne polyurethane peelable coating and its preparation method Technical Field
[0001] This invention belongs to the field of water-based coatings, specifically relating to a lignin-modified water-based polyurethane peelable coating and its preparation method. Background Technology
[0002] Peelable coatings are a special type of protective coating applied to the surface of a substrate to isolate it from external erosion, preventing damage from scratches, aging, contamination, dust, oil, fingerprints, etc., during production, transportation, or storage. Also known as temporary protective coatings, they provide temporary protection for various substrate surfaces, such as metals, plastics, wood, ceramics, glass, rubber, and pre-coated parts (e.g., pre-coated polyurethane topcoats). The protection period typically ranges from a few days to several years, and after protection ends, it can be easily peeled off the substrate surface without negatively impacting it. Peelable coatings have a wide range of applications, suitable for both metallic and non-metallic materials, both indoors and outdoors, for short-term and long-term use, pre-coated and non-pre-coated applications, and for protection at both room temperature and high temperatures.
[0003] Resins used in peelable coatings mainly include solvent-based resins, hot-melt resins, waterborne polyurethane, acrylic, and epoxy systems, but different systems have different performance characteristics. Currently, there are three main problems: First, solvent-based systems release large amounts of VOCs, causing significant negative environmental impacts, while waterborne systems significantly reduce or eliminate VOCs. Second, many peelable coatings are only suitable for certain substrates and lack peelability for many others, resulting in poor broad applicability. Third, almost all peelable coating systems are difficult or impossible to peel off after prolonged use, greatly reducing their application range. Currently, most peelable coatings rely on peelable additives to effectively reduce the adhesion between the paint film and the substrate. Common peelable additives include higher fatty acid esters, fatty acid salts, waxes, surfactants, and silicones. While these additives have some effect, they also have significant side effects, causing various adverse effects on the substrate surface.
[0004] Patent application number 201910851054.1 discloses a method for preparing a peelable waterborne polyurethane resin and its application in coatings. The method involves first preparing a peelable waterborne polyurethane resin, which is then mixed with pullulan and other ingredients to obtain a coating. This waterborne peelable coating is biodegradable, does not pollute the environment, and reduces the investment of human and financial resources. Compared with traditional films and other peelable resins, its environmental advantages are more significant.
[0005] Patent application number 201811435854.7 describes a method for manufacturing a room-temperature self-healing waterborne polyurethane car wrap with a self-matting effect. The prepared waterborne polyurethane car wrap emulsion has good room-temperature self-healing function, while providing different gloss levels and excellent weather resistance. After the resin is compounded with additives, it is sprayed onto the car surface to provide long-lasting protection for the car paint and can be peeled off at any time.
[0006] The water-based peelable coating synthesized by the above method failed to comprehensively modify the molecular structure of the base resin, and the resin's resistance to chemical media did not change significantly. At the same time, the aging performance and peelability of the coating film after more than one year of outdoor exposure were not considered, and it could not meet the market demand for peelable coatings under harsh actual conditions. Summary of the Invention
[0007] This invention is proposed to solve the problems existing in the prior art, and its purpose is to provide a lignin-modified waterborne polyurethane peelable coating and its preparation method.
[0008] This invention is achieved through the following technical solution:
[0009] A lignin-modified waterborne polyurethane peelable coating, wherein the peelable coating comprises the following components and the mass fractions of each component are as follows:
[0010] In the above technical solution, the components and their mass fractions in the waterborne epoxy ester modified carbon dioxide-based polyurethane are as follows:
[0011] In the above technical solution, the isocyanate monomer is any one of isoflurane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, or pentamethylene diisocyanate; the carbon dioxide-based polyol is any one or more of PPCD-222, PCD-621, or PCD-632; the small molecule diol is any one or more of neopentyl glycol, 1,4-butanediol, or 1,6-hexanediol; the hydrophilic monomer is any one or two of dimethylolpropionic acid or dimethylolbutyric acid; and the dihydrazide small molecule chain extender is oxalic acid dihydrazide.
[0012] In the above technical solution, the color paste is any one of EC701, EW6102 or EI6200; the defoamer is any one of Airex 902W or BYK-025; the anti-sticking agent is any one of DC-51 or HY-51Z; and the thickener is any one of ASE-60 or RM-8W.
[0013] A method for preparing a lignin-modified waterborne polyurethane peelable coating includes the following steps:
[0014] (I) Preparation of waterborne epoxy ester modified carbon dioxide-based polyurethane
[0015] 1,6-hexanediol diglycidyl ether, linoleic acid, and tetrabutylammonium bromide were added to a reactor in proportion and reacted at 110℃~130℃ for 2h~3h. Then, carbon dioxide-based polyol, isocyanate monomer, and dibutyltin dilaurate were added and reacted at 90℃~110℃ for 3h~5h. After that, a small molecule diol and a hydrophilic monomer were added and mixed and reacted at 75℃~85℃ under a protective atmosphere for 2h~6h. Triethylamine was added to neutralize the carboxyl groups on the aqueous chain extender. Acetone was then added and the mixture was fully dispersed. The resulting dispersion system was fully dispersed in an aqueous solution containing a dihydrazide small molecule chain extender. After high-speed dispersion reaction, acetone was removed by rotary evaporation to obtain an aqueous epoxy ester modified carbon dioxide-based polyurethane.
[0016] (II) Preparation of Functionalized Lignin / Silica Fillers
[0017] Sodium lignin sulfonate and water were added to the reactor, and stirring was started. When the temperature reached 70℃~90℃, 3-chloro-2-hydroxypropyl ammonium chloride was added dropwise, and the reactants were kept at this temperature for 3h~5h. Then, hexadecyltrimethylammonium bromide and a corrosion inhibitor were added, and the mixture was heated and stirred at 70℃~90℃ for 0.5h~1h. Then, tetraethyl orthosilicate was added dropwise over 1h~2h. After the addition was completed, the reaction continued for 2h~5h. During the above reaction, sodium hydroxide solution was added to maintain the pH of the reaction system above 11. After the reaction was completed, the mixture was cooled to room temperature, filtered, washed with appropriate deionized water, and dried in a 60℃ drying oven for 24h to obtain functionalized lignin / silica filler.
[0018] (III) Preparation of lignin-modified waterborne polyurethane peelable coatings
[0019] Add the waterborne epoxy ester modified carbon dioxide-based polyurethane prepared in step (I), the functionalized lignin / silica filler prepared in step (II), and the color paste to the mixing tank in sequence, and stir at high speed until uniform. During the stirring process, add the defoamer, anti-sticking agent, and thickener to the mixing tank and disperse them evenly. Finally, add deionized water and stir evenly to obtain the lignin-modified waterborne polyurethane peelable coating.
[0020] In the above technical solution, the mass fractions of each component in the preparation of functionalized lignin / silica filler in step (II) are as follows:
[0021] In the above technical solution, the corrosion inhibitor is any one or more of benzotriazole or 3-amino-5-mercapto-1,2,4-triazole.
[0022] The beneficial effects of this invention are:
[0023] This invention provides a lignin-modified waterborne polyurethane peelable coating and its preparation method. The prepared peelable coating has good outdoor aging resistance and peelability.
[0024] The lignin-modified waterborne polyurethane peelable coating provided by this invention modifies lignin under alkaline conditions through quaternization, followed by hydrolysis of lignin and corrosion inhibitors on the surface of lignin and corrosion inhibitors using tetraethyl orthosilicate to form a mesoporous silica framework. This allows lignin and corrosion inhibitors to be directly loaded into the mesoporous structure of the silica, successfully preventing the reaction between the corrosion inhibitor and lignin and the coating resin components, while ensuring the effective storage and controlled release of the corrosion inhibitor and lignin. On the one hand, lignin contains a large number of chromophores and co-chromophores (phenolic hydroxyl groups, ketones, sulfonates) and conjugated benzene ring structures, continuously absorbing ultraviolet light and preventing coating degradation and aging. On the other hand, when metal corrosion occurs, the corrosion inhibitor can interact with the surface of the steel material to form a complex film, inhibiting the intensification of the corrosion reaction, thereby endowing the coating with a certain degree of self-healing properties.
[0025] The lignin-modified waterborne polyurethane peelable coating provided by this invention contains double bonds of fatty acids and long-chain epoxy esters and carbon dioxide-based polyols in its resin molecular structure system. Both are secondary hydroxyl groups and have low reactivity. By reacting them together at a higher temperature, the reactivity is improved, and both are successfully introduced into the molecular backbone. On the one hand, the double bonds of fatty acids can undergo oxidative cross-linking during film curing, thus improving the water and solvent resistance of the film. On the other hand, the carbon dioxide-based polyol is an aliphatic polycarbonate diol with excellent high mechanical properties and high hydrolysis resistance. When added with epoxy esters in the early stage, it balances the hardness and flexibility of the system.
[0026] The lignin-modified waterborne polyurethane peelable coating provided by this invention, due to the amphiphilic molecular structure of lignin, gives the functionalized lignin / silica filler good dispersibility and interfacial compatibility, providing good physical barrier properties for its coating. Detailed Implementation
[0027] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be further described below through specific embodiments.
[0028] Example 1
[0029] A method for preparing a lignin-modified waterborne polyurethane peelable coating includes the following steps:
[0030] (I) In a four-necked flask equipped with a spherical condenser, a nitrogen inlet tube, a stirrer, and a thermometer, 12g of 1,6-hexanediol diglycidyl ether, 14g of linolenic acid, and 0.3g of tetrabutylammonium bromide were added and reacted at 110℃ for 3h. Then, 120g of carbon dioxide-based polyol PPCD-222, 60g of isoflurane diisocyanate, and 0.2g of dibutyltin dilaurate were added and reacted at 90℃ for 3h. After that, 4g of neopentyl glycol and 12g of dimethylolpropionic acid were added and the mixture was heated to 75℃ under a protective atmosphere and reacted for 3h. Then, 9g of triethylamine was added for neutralization, and then 50g of acetone was added for thorough dispersion. The resulting dispersion system was then fully dispersed in 480g of an aqueous solution containing oxalic acid dihydrazide, of which 5g of oxalic acid dihydrazide was added. After high-speed dispersion reaction, acetone was removed by rotary evaporation to obtain waterborne epoxy ester modified carbon dioxide-based polyurethane.
[0031] (II) In a four-necked flask equipped with a spherical condenser, stirrer, and thermometer, 5g of sodium lignosulfonate and 4000g of water were added. Stirring was started, and when the temperature reached 70℃, 2g of 3-chloro-2-hydroxypropyl ammonium chloride was added dropwise. The reaction mixture was kept at this temperature for 3 hours. Then, 4g of hexadecyltrimethylammonium bromide and 3g of benzotriazole were added, and the mixture was heated and stirred at 70℃ for 0.5h. 40g of tetraethyl orthosilicate was added dropwise over 1h. After the addition was complete, the reaction continued for 2h. During the above reaction, sodium hydroxide solution was added to maintain the pH of the reaction system above 11. After cooling to room temperature and filtration, the mixture was washed with appropriate deionized water and dried in a 60℃ drying oven for 24h to obtain the functionalized lignin / silica filler.
[0032] (III) Add 85g of waterborne epoxy ester modified carbon dioxide-based polyurethane prepared in step (I), 2g of functionalized lignin / silica filler prepared in step (II), and 4g of color paste EC701 to the mixing tank in sequence, and stir at high speed until uniform. During the stirring process, add 0.2g of defoamer Airex902W, 0.2g of anti-sticking agent DC-51, and 0.2g of thickener ASE-60 to the mixing tank and disperse them evenly. Finally, add 3g of deionized water and stir evenly to obtain lignin-modified waterborne polyurethane peelable coating.
[0033] Example 2
[0034] A method for preparing a lignin-modified waterborne polyurethane peelable coating includes the following steps:
[0035] (I) In a four-necked flask equipped with a spherical condenser, a nitrogen inlet tube, a stirrer, and a thermometer, 12g of 1,6-hexanediol diglycidyl ether, 20g of linolenic acid, and 0.3g of tetrabutylammonium bromide were added and reacted at 120℃ for 3h. Then, 140g of carbon dioxide-based polyol PCD-621, 70g of dicyclohexylmethane diisocyanate, and 0.2g of dibutyltin dilaurate were added and reacted at 100℃ for 4h. After that, 6g of 1,4-butanediol and 13g of dimethylolbutyric acid were added and the mixture was heated to 80℃ under a protective atmosphere and reacted for 4h. Then, 9.5g of triethylamine was added for neutralization, and then 70g of acetone was added for thorough dispersion. The resulting dispersion system was then fully dispersed in 500g of an aqueous solution containing oxalic acid dihydrazide, of which 5g of oxalic acid dihydrazide was added. After high-speed dispersion reaction, acetone was removed by rotary evaporation to obtain waterborne epoxy ester modified carbon dioxide-based polyurethane.
[0036] (II) In a four-necked flask equipped with a spherical condenser, stirrer, and thermometer, 7g of sodium lignin sulfonate and 5000g of water were added. Stirring was started, and when the temperature reached 80℃, 3g of 3-chloro-2-hydroxypropyl ammonium chloride was added dropwise. The reaction mixture was kept at this temperature for 4 hours. Then, 4g of hexadecyltrimethylammonium bromide and 3g of 3-amino-5-mercapto-1,2,4-triazole were added, and the mixture was heated and stirred at 80℃ for 0.5h. 40g of tetraethyl orthosilicate was added dropwise over 1h, and the reaction continued for another 3h. Throughout the reaction, sodium hydroxide solution was added to maintain the pH of the reaction system above 11. After cooling to room temperature and filtration, the mixture was washed with appropriate deionized water and dried in a 60℃ oven for 24h to obtain the functionalized lignin / silica filler.
[0037] (III) Add 90g of waterborne epoxy ester modified carbon dioxide-based polyurethane prepared in step (I), 4g of functionalized lignin / silica filler prepared in step (II), and 4g of color paste EW6102 to the mixing tank in sequence, and stir at high speed until uniform. During the stirring process, add 0.3g of defoamer BYK-025, 0.4g of anti-sticking agent DC-51, and 0.2g of thickener RM-8W to the mixing tank and disperse them evenly. Finally, add 3g of deionized water and stir evenly to obtain lignin-modified waterborne polyurethane peelable coating.
[0038] Example 3
[0039] A method for preparing a lignin-modified waterborne polyurethane peelable coating includes the following steps:
[0040] (I) In a four-necked flask equipped with a spherical condenser, a nitrogen inlet tube, a stirrer, and a thermometer, add 12g of 1,6-hexanediol diglycidyl ether, 23g of linolenic acid, and 0.3g of tetrabutylammonium bromide. React at 130℃ for 3h. Then add 160g of carbon dioxide-based polyol PCD-632, 70g of dicyclohexylmethane diisocyanate, 20g of hexamethylene diisocyanate, and 0.2g of dibutyltin dilaurate. React at 100℃ for 4h. Finally, add 6g of... 1,6-Hexanediol and 13g of dimethylolpropionic acid were mixed and reacted at 80°C for 4 hours under a protective atmosphere. Then, 9.5g of triethylamine was added for neutralization, followed by the addition of 100g of acetone for thorough dispersion. The resulting dispersion system was then fully dispersed in 600g of an aqueous solution containing 10g of oxalic acid dihydrazide. After high-speed dispersion, the acetone was removed by rotary evaporation to obtain waterborne epoxy ester modified carbon dioxide-based polyurethane.
[0041] (II) In a four-necked flask equipped with a spherical condenser, stirrer, and thermometer, 9g of sodium lignin sulfonate and 5000g of water were added. Stirring was started, and when the temperature reached 90℃, 4g of 3-chloro-2-hydroxypropyl ammonium chloride was added dropwise. The reaction mixture was kept at this temperature for 5 hours. Then, 5g of hexadecyltrimethylammonium bromide and 6g of 3-amino-5-mercapto-1,2,4-triazole were added, and the mixture was heated and stirred at 80℃ for 0.5h. 60g of tetraethyl orthosilicate was added dropwise over 2h. After the addition was complete, the reaction continued for 5h. During the above reaction, sodium hydroxide solution was added to maintain the pH of the reaction system above 11. After cooling to room temperature and filtration, the mixture was washed with appropriate deionized water and dried in a 60℃ drying oven for 24h to obtain the functionalized lignin / silica filler.
[0042] (III) Add 95g of waterborne epoxy ester modified carbon dioxide-based polyurethane prepared in step (I), 9g of functionalized lignin / silica filler prepared in step (II), and 4g of color paste EI6200 to the mixing tank in sequence, and stir at high speed until uniform. During the stirring process, add 0.3g of defoamer Airex902W, 0.2g of anti-sticking agent HY-51Z, 0.2g of anti-sticking agent DC-51, and 0.2g of thickener RM-8W to the mixing tank and disperse them evenly. Finally, add 5g of deionized water and stir evenly to obtain the lignin-modified waterborne polyurethane peelable coating.
[0043] Example 4
[0044] A method for preparing a lignin-modified waterborne polyurethane peelable coating includes the following steps:
[0045] (I) Add 23g to a four-necked flask equipped with a spherical condenser, a nitrogen inlet tube, a stirrer, and a thermometer. 1,6-Hexanediol diglycidyl ether, 28g linoleic acid, and 0.3g tetrabutylammonium bromide were reacted at 130℃ for 3h. Then, 180g of carbon dioxide-based polyol PCD-621, 100g of dicyclohexylmethane diisocyanate, 20g of isoflurane diisocyanate, and 0.4g of dibutyltin dilaurate were added, and the mixture was reacted at 110℃ for 5h. After that, 6g of neopentyl glycol and 15g of dimethylolpropionic acid were added, and the mixture was heated to 80℃ under a protective atmosphere and reacted for 6h. Then, 11g of triethylamine was added for neutralization, and then 150g of acetone was added for thorough dispersion. The resulting dispersion system was then fully dispersed in 660g of an aqueous solution containing oxalic acid dihydrazide, of which 15g of oxalic acid dihydrazide was added. After high-speed dispersion, the acetone was removed by rotary evaporation to obtain waterborne epoxy ester modified carbon dioxide-based polyurethane.
[0046] (II) In a four-necked flask equipped with a spherical condenser, stirrer, and thermometer, 9 g of sodium lignosulfonate and 6000 g of water were added. Stirring was started, and when the temperature reached 85°C, 4 g of 3-chloro-2-hydroxypropyl ammonium chloride was added dropwise. The reaction mixture was kept at this temperature for 5 hours. Then, 12 g of hexadecyltrimethylammonium bromide and 7 g of 3-amino-5-mercapto-1,2,4-triazole were added, and the mixture was heated and stirred at 90°C for 1 hour. 70 g of tetraethyl orthosilicate was added dropwise over 2 hours, and the reaction continued for another 5 hours. During the above reaction, sodium hydroxide solution was added to maintain the pH of the reaction system above 11. After cooling to room temperature and filtration, the mixture was washed with appropriate deionized water and dried in a 60°C oven for 24 hours to obtain the functionalized lignin / silica filler.
[0047] (III) Add 95g of the waterborne epoxy ester modified carbon dioxide-based polyurethane prepared in step (I), 5g of the functionalized lignin / silica filler prepared in step (II), and 5g of color paste EC701 to the mixing tank in sequence, and stir at high speed until uniform. During the stirring process, add 0.3g of defoamer Airex 902W, 0.6g of anti-sticking agent DC-51, and 0.2g of thickener ASE-60 to the mixing tank and disperse them evenly. Finally, add 3g of deionized water and stir evenly to obtain the lignin-modified waterborne polyurethane peelable coating.
[0048] Comparative Example 1
[0049] The addition of functionalized lignin / silica fillers was not involved; all other operations were the same as in Example 4.
[0050] (I) Add 23g to a four-necked flask equipped with a spherical condenser, a nitrogen inlet tube, a stirrer, and a thermometer. 1,6-Hexanediol diglycidyl ether, 28g linoleic acid, and 0.3g tetrabutylammonium bromide were reacted at 130℃ for 3h. Then, 180g of carbon dioxide-based polyol PPCD-222, 100g dicyclohexylmethane diisocyanate, 20g isoflurane diisocyanate, and 0.4g dibutyltin dilaurate were added, and the mixture was reacted at 110℃ for 5h. After that, 6g neopentyl glycol and 15g dimethylolpropionic acid were added, and the mixture was heated to 80℃ under a protective atmosphere and reacted for 4h. Then, 11g triethylamine was added for neutralization, and then 150g acetone was added for thorough dispersion. The resulting dispersion system was then fully dispersed in 660g of an aqueous solution containing oxalic acid dihydrazide, of which 15g of oxalic acid dihydrazide was added. After high-speed dispersion, the acetone was removed by rotary evaporation to obtain waterborne epoxy ester modified carbon dioxide-based polyurethane.
[0051] (II) Add 95g of the waterborne epoxy ester modified carbon dioxide-based polyurethane and 5g of color paste EC701 to the mixing tank in sequence, and stir at high speed until uniform. During the stirring process, add 0.3g of defoamer Airex 902W, 0.6g of anti-sticking agent DC-51 and 0.2g of thickener ASE-60 to the mixing tank and disperse them evenly. Finally, add 3g of deionized water and stir evenly to obtain the waterborne polyurethane peelable coating.
[0052] Comparative Example 2
[0053] The addition of 1,6-hexanediol diglycidyl ether and 28g of linoleic acid was not involved; all other operations were the same as in Example 4.
[0054] (I) In a four-necked flask equipped with a spherical condenser, a nitrogen inlet tube, a stirrer, and a thermometer, 180g of carbon dioxide-based polyol PPCD-222, 100g of dicyclohexylmethane diisocyanate, 20g of isoflurane diisocyanate, and 0.4g of dibutyltin dilaurate were added and reacted at 110℃ for 5h. Then, 6g of neopentyl glycol and 15g of dimethylolbutyric acid were added and the mixture was heated to 80℃ under a protective atmosphere and reacted for 4h. Then, 11g of triethylamine was added for neutralization, and then 150g of acetone was added for thorough dispersion. The resulting dispersion system was then fully dispersed in 660g of an aqueous solution containing oxalic acid dihydrazide, of which 15g of oxalic acid dihydrazide was added. After high-speed dispersion reaction, acetone was removed by rotary evaporation to obtain aqueous carbon dioxide-based polyurethane.
[0055] (II) In a four-necked flask equipped with a spherical condenser, stirrer, and thermometer, 9 g of sodium lignosulfonate and 6000 g of water were added. Stirring was started, and when the temperature reached 85°C, 4 g of 3-chloro-2-hydroxypropyl ammonium chloride was added dropwise. The reaction mixture was kept at this temperature for 5 hours. Then, 12 g of hexadecyltrimethylammonium bromide and 7 g of 3-amino-5-mercapto-1,2,4-triazole were added, and the mixture was heated and stirred at 90°C for 1 hour. 70 g of tetraethyl orthosilicate was added dropwise over 2 hours, and the reaction continued for another 5 hours. During the above reaction, sodium hydroxide solution was added to maintain the pH of the reaction system above 11. After cooling to room temperature and filtration, the mixture was washed with appropriate deionized water and dried in a 60°C oven for 24 hours to obtain the functionalized lignin / silica filler.
[0056] (III) Add 95g of the waterborne carbon dioxide-based polyurethane prepared in step (I), 5g of the functionalized lignin / silica filler prepared in step (II), and 5g of color paste EC701 to the mixing tank in sequence, and stir at high speed until uniform. During the stirring process, add 0.3g of defoamer Airex 902W, 0.6g of anti-sticking agent DC-51, and 0.2g of thickener RM-8W to the above mixing tank and disperse them evenly. Finally, add 3g of deionized water and stir evenly to obtain the waterborne polyurethane peelable coating.
[0057] Coating performance testing:
[0058] The coatings of Examples 1-4 and Comparative Examples 1-2 were applied to their respective substrates with a thickness controlled at 70-100 μm, and then cured at room temperature for 7 days to prepare the coating films of Examples 1-4 and Comparative Examples 1-2. The obtained coating films were subjected to peelability tests, water resistance tests, outdoor weathering resistance tests, tensile strength tests, elongation tests, and peel strength tests, and the results are shown in Table 1.
[0059] The coating film properties of the coatings prepared in Examples 1-4 and the coatings in Comparative Examples 1-2 were compared, and the results are shown in Table 1.
[0060] Table 1: Coating performance test results of Examples 1-4 and Comparative Examples 1-2
[0061] As shown in Table 1, compared with the coatings of Comparative Examples 1-2, the lignin-modified waterborne polyurethane peelable coatings prepared in Examples 1-4 of this invention have significantly better peelability, water resistance, fastest peeling time, and anti-corrosion performance than Comparative Examples 1-2. In contrast, Comparative Example 1, lacking corrosion inhibitors loaded in the filler, failed to inhibit the intensification of corrosion reaction when metal corrosion occurred, resulting in poor salt water resistance. Furthermore, lacking chemical groups that continuously absorb ultraviolet light, especially when adhered to tinplate, the coating structure changed after two years of outdoor exposure, leading to poor peelability.
[0062] Compared with Example 4, Comparative Example 2, although both contain functionalized lignin / silica fillers, relies solely on the reaction between carbon dioxide-based polyols and isocyanates. Its molecular structure does not contain fatty acid double bonds, making it unable to undergo oxidative crosslinking. Consequently, its crosslinking density is relatively low, and in particular, the fastest peeling time is relatively long, making it difficult to meet the requirements of certain fast-drying applications. Furthermore, its water and salt water resistance are slightly inferior.
[0063] Therefore, the water-based peelable coating prepared by this invention has undergone comprehensive molecular structure modification of the matrix resin and filler, resulting in a significant improvement in anti-corrosion performance. At the same time, the peelability of the coating film remains excellent after two years of outdoor exposure, fully meeting the market demand for peelable coatings under harsh actual conditions.
[0064] The applicant declares that the above description is only a specific embodiment 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 conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.
Claims
1. A lignin-modified waterborne polyurethane peelable coating, characterized in that: The components and their mass fractions in the peelable coating are as follows:
2. The lignin-modified waterborne polyurethane peelable coating according to claim 1, characterized in that: The components and their mass fractions in the waterborne epoxy ester modified carbon dioxide-based polyurethane are as follows:
3. The lignin-modified waterborne polyurethane peelable coating according to claim 2, characterized in that: The isocyanate monomer is any one of isoflurane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, or pentamethylene diisocyanate; the carbon dioxide-based polyol is any one or more of PPCD-222, PCD-621, or PCD-632; the small molecule diol is any one or more of neopentyl glycol, 1,4-butanediol, or 1,6-hexanediol; the hydrophilic monomer is any one or two of dimethylolpropionic acid or dimethylolbutyric acid; and the dihydrazide small molecule chain extender is oxalic acid dihydrazide.
4. The lignin-modified waterborne polyurethane peelable coating according to claim 1, characterized in that: The colorant is any one of EC701, EW6102, or EI6200; the defoamer is any one of Airex 902W or BYK-025; the anti-sticking agent is any one of DC-51 or HY-51Z; and the thickener is any one of ASE-60 or RM-8W.
5. A method for preparing a lignin-modified waterborne polyurethane peelable coating according to any one of claims 1 to 4, characterized in that: Includes the following steps: (I) Preparation of waterborne epoxy ester modified carbon dioxide-based polyurethane In a reactor, 1,6-hexanediol diglycidyl ether, linoleic acid, and tetrabutylammonium bromide were added in proportion and reacted. Then, carbon dioxide-based polyol, isocyanate monomer, and dibutyltin dilaurate were added and reacted. After that, small molecule diol and hydrophilic monomer were added and reacted. After the reaction, triethylamine and acetone were added in sequence and the mixture was fully dispersed. The resulting dispersion system was fully dispersed in an aqueous solution containing a dihydrazide small molecule chain extender. After high-speed dispersion reaction, acetone was removed by rotary evaporation to obtain waterborne epoxy ester modified carbon dioxide-based polyurethane. (II) Preparation of Functionalized Lignin / Silica Fillers Sodium lignin sulfonate and water were added to the reactor, and 3-chloro-2-hydroxypropyl ammonium chloride was added dropwise under stirring. Then hexadecyltrimethylammonium bromide and corrosion inhibitor were added, followed by the addition of tetraethyl orthosilicate. The reaction continued. After the reaction was completed, the mixture was cooled to room temperature, filtered, washed, and dried to obtain functionalized lignin / silica filler. (III) Preparation of lignin-modified waterborne polyurethane peelable coatings Add the waterborne epoxy ester modified carbon dioxide-based polyurethane prepared in step (I), the functionalized lignin / silica filler prepared in step (II), and the color paste to the mixing tank in sequence, and stir at high speed until uniform. During the stirring process, add defoamer, anti-sticking agent and thickener to the mixing tank and disperse them evenly. Finally, add deionized water and stir evenly to obtain the lignin-modified waterborne polyurethane peelable coating.
6. The method for preparing the lignin-modified waterborne polyurethane peelable coating according to claim 5, characterized in that: In step (I), the reaction temperature and time for 1,6-hexanediol diglycidyl ether, linoleic acid, and tetrabutylammonium bromide are 110℃~130℃ for 2h~3h; the reaction temperature and time after adding carbon dioxide-based polyol, isocyanate monomer, and dibutyltin dilaurate are 90℃~110℃ for 3h~5h; the reaction temperature and time after adding small molecule diol and hydrophilic monomer are: mixed and reacted at 75℃~85℃ under a protective atmosphere for 2h~6h.
7. The method for preparing the lignin-modified waterborne polyurethane peelable coating according to claim 5, characterized in that: The mass fractions of each component in the preparation of the functionalized lignin / silica filler in step (II) are as follows:
8. The lignin-modified waterborne polyurethane peelable coating according to claim 7, characterized in that: The corrosion inhibitor is any one or more of benzotriazole or 3-amino-5-mercapto-1,2,4-triazole.
9. The method for preparing the lignin-modified waterborne polyurethane peelable coating according to claim 5, characterized in that: In step (II), after adding 3-chloro-2-hydroxypropylammonium chloride, the reactants are kept at a constant temperature for 3-5 hours; after adding hexadecyltrimethylammonium bromide and corrosion inhibitor, the reaction temperature and duration are 70-90°C with stirring for 0.5-1 hours; the addition of tetraethyl orthosilicate takes 1-2 hours; after the addition of tetraethyl orthosilicate is completed, the reaction continues for 2-5 hours; during the preparation of the functionalized lignin / silica filler in step (II), sodium hydroxide solution is added to maintain the pH of the reaction system above 11; the drying conditions are drying in a 60°C drying oven for 24 hours.