A weather-resistant luminescent coating and its preparation process

Abstract

This invention relates to the field of coating technology and discloses a weather-resistant luminescent coating and its preparation process. The invention involves reacting polyester polyol, isocyanate monomer, 2,2-dimethylolpropionic acid, and N-(acetoacetate-based)diethanolamine, followed by mixing with fillers, luminescent powder, emulsifying agents, and aminopropyl-terminated polydimethylsiloxane to obtain the weather-resistant luminescent coating. The aminopropyl-terminated polydimethylsiloxane and polyurethane undergo chemical cross-linking to form a tight three-dimensional chemical cross-linking network, which is not easily penetrated by corrosive media such as water. This significantly improves the water and weather resistance of the polyurethane coating film, preventing yellowing, chalking, and cracking even after long-term outdoor exposure. Furthermore, the high flexibility of the polysiloxane molecular chain achieves a dynamic balance between toughening and cross-linking rigidity of the polyurethane, improving the impact resistance and flexibility of the coating film, making it less prone to peeling and cracking.

Description

Technical Field

[0001] This invention relates to the field of coating technology, specifically to a weather-resistant luminescent coating and its preparation process. Background Technology

[0002] Waterborne polyurethane coatings are VOC-free, green, and pollution-free, and have important applications in road traffic signs, wooden furniture, building decoration, automobiles, and ships. Among them, polyester-based polyurethane has excellent mechanical strength, abrasion resistance, adhesion, and heat resistance, and is widely used. However, polyester-based polyurethane is prone to hydrolysis, has poor water resistance, and poor weather resistance. When exposed to the outdoors for a long time, it is prone to yellowing, chalking, and cracking.

[0003] To improve the water resistance and weather resistance of polyurethane coatings, chemical modification of polyurethane is necessary. This is typically achieved by adding functional monomers during the polymerization process to impart unique properties. Patent CN118652619B discloses an organosilicon-modified waterborne polyurethane coating, its preparation method, and its application. This patent uses a hydroxyl-terminated hyperbranched organosilicon polymer to modify the waterborne polyurethane emulsion, improving the water resistance, abrasion resistance, and weather resistance of the polyurethane coating. However, this patent does not improve the flexibility or impact resistance of the polyurethane coating. Summary of the Invention

[0004] (i) The technical problem solved by this invention is to solve the problem of poor weather resistance and waterproof performance of polyurethane coatings.

[0005] (II) The technical solution of the present invention is: a preparation process for a weather-resistant luminescent coating:

[0006] (1) Add solvent, acid-binding agent, diethanolamine, and 4-chloroacetoacetate to the reaction vessel, heat to 75-90℃, stir and reflux for 8-14 hours, filter after cooling, evaporate the filtrate by rotary evaporation, and separate the product by silica gel column chromatography to obtain N-(acetoacetate-based)diethanolamine. The reaction formula is:

[0007] .

[0008] (2) Add polyester polyol to the reaction vessel, heat to 100-110℃, dehydrate under vacuum, cool to 70-85℃, introduce nitrogen, add isocyanate monomer, stir and react for 2-3h, add 2,2-dimethylolpropionic acid and dibutyltin dilaurate, continue to react for 30-40min, cool to 40-45℃, then add acetone and N-(acetoacetyl)diethanolamine, continue to react for 20-30min, add triethylamine and water, stir and neutralize, remove acetone by vacuum distillation, add filler, luminescent powder, dispersant, defoamer and emulsifying agent, stir and disperse, finally add aminopropyl double-terminated polydimethylsiloxane, stir and mix to obtain weather-resistant luminescent coating.

[0009] Preferably, the solvent in (1) includes acetonitrile, tetrahydrofuran, and water.

[0010] Preferably, the ratio of acid-binding agent, diethanolamine and 4-chloroacetoacetate in (1) is (1.6-2.2) mol: (1-1.4) mol: 1 mol.

[0011] Preferably, in (1), the acid-binding agent solvent is sodium carbonate, potassium carbonate, or sodium hydroxide.

[0012] Preferably, in (1), the solvents for 4-chloroacetoacetate are methyl 4-chloroacetoacetate and ethyl 4-chloroacetoacetate.

[0013] Preferably, the molar ratio of polyester polyol and isocyanate monomer in (2) is (2.3-2.6):1.

[0014] Preferably, in (2), the ratio of isocyanate monomer, 2,2-dimethylolpropionic acid, dibutyltin dilaurate, N-(acetoacetyl)diethanolamine, and aminopropyl-terminated polydimethylsiloxane is (2.3-2.6) mol: (1-1.3) mol: (3.5-4.3) g: (0.2-0.4) mol: (40-150) g.

[0015] Preferably, the isocyanate monomer in (2) includes hexamethylene diisocyanate and isophorone diisocyanate.

[0016] Preferably, in (2), the filler solvent is barium sulfate, titanium dioxide, or fumed silica.

[0017] (III) Beneficial technical effects: This invention uses N-(acetoacetate)diethanolamine as a chain extender, which is polymerized with polyester polyols, isocyanate monomers, etc. The active β-carbonyl ester structure is introduced into the side chain of the polyurethane molecular chain. Finally, it is compounded with luminescent powder, filler, aminopropyl double-terminated polydimethylsiloxane, etc. to obtain a weather-resistant luminescent coating. In the β-carbonyl ester structure, the methylene group is located between the carbonyl and ester groups. The strong electron-withdrawing effect of the two carbonyl groups significantly reduces the electron cloud density of the methylene group. This electron-deficient state further lowers the electron cloud density of the ketone carbonyl group, making the positive charge on the carbonyl carbon more concentrated and increasing its activity. During curing, the multiple active ketone carbonyl groups on the polyurethane side chains readily undergo condensation reactions with the double-terminated amino groups of aminopropyl-terminated polydimethylsiloxane, causing chemical cross-linking between the polysiloxane and polyurethane. This forms a tight three-dimensional chemical cross-linked network, which is not easily penetrated by corrosive media such as water. Simultaneously, the polysiloxane molecular chain exhibits excellent water resistance and weather resistance, significantly improving the water and weather resistance of the polyurethane coating film. Even after long-term outdoor exposure, the film is less prone to yellowing, chalking, and cracking. Furthermore, the high flexibility of the polysiloxane molecular chain achieves a dynamic balance between the toughening and cross-linking rigidity of the polyurethane, improving the impact resistance and flexibility of the film, making it less prone to peeling and cracking. Detailed Implementation

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Polyester polyol, model ALL, manufactured by UGREEN (Jining) Chemical Technology Co., Ltd. Luminescent powder, model YD-4F2, manufactured by Shenzhen Yaodesheng Technology Co., Ltd. Emulsifying agent, model DR-300D, manufactured by Shanghai Gerunning Chemical Technology Co., Ltd. Aminopropyl double-terminated polydimethylsiloxane, 98% active ingredient content, manufactured by Guangzhou Shanghe Chemical Technology Co., Ltd. Polydimethylsiloxane, CAS number 9016-00-6, 99% active ingredient content, manufactured by Guangzhou Shanghe Chemical Technology Co., Ltd.

[0020] Example 1:

[0021] (1) Add 600 mL tetrahydrofuran, 450 mL water, 0.66 mol sodium carbonate, 0.42 mol diethanolamine, and 0.3 mol ethyl 4-chloroacetoacetate to the reaction vessel, heat to 90 °C, stir and reflux for 10 h, filter after cooling, evaporate the filtrate by rotary evaporation, separate the product by silica gel column chromatography, and elute with ethyl acetate-petroleum ether solution to obtain N-(acetoacetate)diethanolamine.

[0022] (2) Add polyester polyol to the reactor, heat to 110℃, dehydrate under vacuum, cool to 80℃, purge with nitrogen, add 2.3 mol of isophorone diisocyanate, the molar ratio of polyester polyol to isophorone diisocyanate (nNCO / nOH) is 2.3:1; stir the reaction for 2 h, add 1.1 mol of 2,2-dimethylolpropionic acid and 4.3 g of dibutyltin dilaurate, continue the reaction for 30 min, cool to 40℃, then add acetone and 0.2 mol of... N-(acetoacetyl)diethanolamine was reacted for another 30 minutes. Then, 1.1 mol of triethylamine and 2.6 L of water were added, and the mixture was stirred and neutralized. Acetone was removed by vacuum distillation. 600 g of fumed silica, 140 g of luminescent powder, 13 g of dispersant EFKA-4530, 10 g of defoamer DAPROAP7010 (a water-based defoamer from Hemingside) and 0.6 g of emulsifying agent were added and stirred to disperse the mixture. Finally, 40 g of aminopropyl double-terminated polydimethylsiloxane was added and stirred to mix the mixture, thus obtaining the weather-resistant luminescent coating.

[0023] Example 2:

[0024] (1) Add 700 mL tetrahydrofuran, 500 mL water, 0.88 mol sodium carbonate, 0.56 mol diethanolamine, and 0.4 mol methyl 4-chloroacetoacetate to the reaction vessel, heat to 75 °C, stir and reflux for 14 h, filter after cooling, evaporate the filtrate by rotary evaporation, separate the product by silica gel column chromatography, and elute with ethyl acetate-petroleum ether solution to obtain N-(acetoacetate)diethanolamine.

[0025] (2) Add polyester polyol to the reactor, heat to 110°C, dehydrate under vacuum, cool to 85°C, introduce nitrogen gas, add 2.6 mol isophorone diisocyanate, the molar ratio of polyester polyol to isophorone diisocyanate nNCO / nOH is 2.6:1; stir the reaction for 2 h, add 1.3 mol 2,2-dimethylolpropionic acid and 3.5 g dibutyltin dilaurate, continue the reaction for 40 min, cool to 45°C, then add acetone and 0.3 mol N-(acetoacetyl)diethanolamine, continue the reaction for 30 min, add 1.3 mol triethylamine and 2.4 L water, stir to neutralize, remove acetone by vacuum distillation, add 700 g barium sulfate, 140 g luminescent powder, 14 g dispersant EFKA-4530, and 7 g defoamer Hemings Deqian water-based defoamer DAPRO. AP7010 and 1.4g of emulsifying agent were stirred and dispersed. Finally, 100g of aminopropyl double-terminated polydimethylsiloxane was added and stirred to obtain a weather-resistant luminescent coating.

[0026] Example 3:

[0027] (1) Add 1.2 L of acetonitrile, 0.96 mol of potassium carbonate, 0.6 mol of diethanolamine and 0.6 mol of ethyl 4-chloroacetoacetate to the reaction vessel, heat to 80 °C, stir and reflux for 8 h, filter after cooling, evaporate the filtrate by rotary evaporation, separate the product by silica gel column chromatography, and elute with ethyl acetate-petroleum ether solution to obtain N-(acetoacetate)diethanolamine.

[0028] (2) Add polyester polyol to the reactor, heat to 100°C, dehydrate under vacuum, cool to 70°C, introduce nitrogen gas, add 2.4 mol hexamethylene diisocyanate, the molar ratio of polyester polyol to hexamethylene diisocyanate nNCO / nOH is 2.4:1; stir the reaction for 3 h, add 1 mol 2,2-dimethylolpropionic acid and 4 g dibutyltin dilaurate, continue the reaction for 40 min, cool to 45°C, then add acetone and 0.4 mol N-(acetoacetyl)diethanolamine, continue the reaction for 20 min, add 1 mol triethylamine and 2.7 L water, stir to neutralize, remove acetone by vacuum distillation, add 400 g titanium dioxide, 170 g luminescent powder, 20 g dispersant EFKA-4530, and 9 g defoamer Hemings Deqian water-based defoamer DAPRO. AP7010 and 2g of emulsifying agent were stirred and dispersed. Finally, 150g of aminopropyl double-terminated polydimethylsiloxane was added and stirred to obtain a weather-resistant luminescent coating.

[0029] Comparative Example 1:

[0030] (1) Add polyester polyol to the reactor, heat to 110℃, dehydrate under vacuum, cool to 80℃, purge with nitrogen, add 2.3 mol of isophorone diisocyanate, the molar ratio of polyester polyol to isophorone diisocyanate (nNCO / nOH) is 2.3:1; stir the reaction for 2 h, add 1.1 mol of 2,2-dimethylolpropionic acid and 4.3 g of dibutyltin dilaurate, continue the reaction for 30 min, cool to 40℃, then add acetone and 0.2 mol of... N-(acetoacetyl)diethanolamine was reacted for another 30 minutes. Then, 1.1 mol of triethylamine and 2.6 L of water were added, and the mixture was stirred and neutralized. Acetone was removed by vacuum distillation. 600 g of fumed silica, 140 g of luminescent powder, 13 g of dispersant EFKA-4530, 10 g of defoamer DAPROAP7010 (a water-based defoamer from Hemingside) and 0.6 g of emulsifying agent were added and stirred to disperse the mixture. Finally, 40 g of polydimethylsiloxane was added and stirred to mix the mixture to obtain the luminescent coating.

[0031] Comparative Example 2:

[0032] (1) Add polyester polyol to the reactor, heat to 110°C, dehydrate under vacuum, cool to 80°C, introduce nitrogen gas, add 2.3 mol isophorone diisocyanate, the molar ratio of polyester polyol to isophorone diisocyanate nNCO / nOH is 2.3:1; stir the reaction for 2 h, add 1.1 mol 2,2-dimethylolpropionic acid and 4.3 g dibutyltin dilaurate, continue the reaction for 30 min, cool to 40°C, then add acetone and 0.2 mol N-methyldiethanolamine, continue the reaction for 30 min, add 1.1 mol triethylamine and 2.6 L water, stir to neutralize, remove acetone by vacuum distillation, add 600 g fumed silica, 140 g luminescent powder, 13 g dispersant EFKA-4530, and 10 g defoamer DAPRO water-based defoamer. AP7010 and 0.6g of emulsifying agent were stirred and dispersed. Finally, 40g of aminopropyl double-terminated polydimethylsiloxane was added and stirred to obtain the luminescent coating.

[0033] Comparative Example 3:

[0034] (1) Add 600 mL tetrahydrofuran, 450 mL water, 0.66 mol sodium carbonate, 0.42 mol diethanolamine, and 0.3 mol 4-chloro-2-butanone to a reaction vessel. Heat to 90 °C, stir, reflux, and cool for 10 h. Filter after cooling, evaporate the filtrate by rotary evaporation, and separate the product by silica gel column chromatography. Elute with ethyl acetate-petroleum ether solution to obtain N-butanone diethanolamine, with the structural formula: .

[0035] (2) Add polyester polyol to the reactor, heat to 110°C, dehydrate under vacuum, cool to 80°C, introduce nitrogen gas, add 2.3 mol isophorone diisocyanate, the molar ratio of polyester polyol to isophorone diisocyanate nNCO / nOH is 2.3:1; stir the reaction for 2 h, add 1.1 mol 2,2-dimethylolpropionic acid and 4.3 g dibutyltin dilaurate, continue the reaction for 30 min, cool to 40°C, then add acetone and 0.2 mol N-butanone diethanolamine, continue the reaction for 30 min, add 1.1 mol triethylamine and 2.6 L water, stir to neutralize, remove acetone by vacuum distillation, add 600 g fumed silica, 140 g luminescent powder, 13 g dispersant EFKA-4530, and 10 g defoamer DAPRO water-based defoamer. AP7010 and 0.6g of emulsifying agent were stirred and dispersed. Finally, 40g of aminopropyl double-terminated polydimethylsiloxane was added and stirred to obtain the luminescent coating.

[0036] Comparative Example 4:

[0037] (1) Add polyester polyol to the reactor, heat to 110°C, dehydrate under vacuum, cool to 80°C, introduce nitrogen gas, add 2.3 mol isophorone diisocyanate, the molar ratio of polyester polyol to isophorone diisocyanate nNCO / nOH is 2.3:1; stir the reaction for 2 h, add 1.1 mol 2,2-dimethylolpropionic acid and 4.3 g dibutyltin dilaurate, continue the reaction for 30 min, cool to 40°C, then add acetone, 0.2 mol N-methyldiethanolamine and 40 g aminopropyl double-terminated polydimethylsiloxane, continue the reaction for 30 min, add 1.1 mol triethylamine and 2.6 L water, stir to neutralize, remove acetone by vacuum distillation, add 600 g fumed silica, 140 g luminescent powder, 13 g dispersant EFKA-4530, and 10 g defoamer DAPRO water-based defoamer. AP7010 and 0.6g of emulsifying agent were mixed and dispersed to obtain a luminescent coating.

[0038] The luminescent coating was baked at 50℃ for 2 hours and then left at room temperature for 24 hours to form a coating film. The impact resistance of the coating film was tested according to GB / T 1732-2020 standard. The flexibility was tested according to GB / T 1731-2020 standard. The water resistance was tested according to GB / T 1733-1993 standard.

[0039] The weather resistance of the paint film was tested according to GB / T 1865-2009 and GB / T 1766-2008 standards, and the color difference value ∆E before and after artificial radiation was calculated.

[0040] Table 1 Performance of Coatings

[0041] Impact resistance (kg·cm) Flexibility (mm) Water resistance (480h) Color difference value ∆E Example 1 45 1 No bubbling, no peeling 5.28 Example 2 60 1 No bubbling, no peeling 3.41 Example 3 55 2 No bubbling, no peeling 3.26 Comparative Example 1 30 3 Bubbling, peeling 6.62 Comparative Example 2 30 3 Bubbling, peeling 6.54 Comparative Example 3 40 2 It bubbles but doesn't peel off. 5.70 Comparative Example 4 35 1 It bubbles but doesn't peel off. 6.19

[0042] Table 1 shows that the polyurethane coating films of each embodiment have excellent impact resistance, flexibility, and water resistance, and low color difference value ∆E, as well as excellent UV resistance and weather resistance. This is mainly because N-(acetoacetate)diethanolamine is used as a chain extender to extend the active β-carbonyl ester structure ( Introduced into the side chains of polyurethane molecular chains, multiple active ketone carbonyl groups of the side chains undergo condensation reactions with the double-terminated amino groups of aminopropyl-terminated polydimethylsiloxane, causing chemical cross-linking between polysiloxane and polyurethane to form a tight three-dimensional chemical cross-linking network that is not easily penetrated by corrosive media such as water. At the same time, the polysiloxane molecular chains have excellent water resistance and weather resistance, significantly improving the water and weather resistance of polyurethane coatings. Furthermore, the polysiloxane molecular chains have high flexibility, which can achieve a dynamic balance between toughening and cross-linking rigidity of polyurethane, giving the coating film better impact resistance and flexibility.

[0043] The polydimethylsiloxane in Comparative Example 1 does not contain double-terminated amino groups and cannot undergo cross-linking reaction with the ketone carbonyl group of polyurethane. Furthermore, the compatibility between polydimethylsiloxane and polyurethane is very poor, resulting in lower impact resistance, flexibility, and water resistance of the coating film compared to Example 1. Additionally, the color difference value ∆E is relatively large, indicating poor weather resistance.

[0044] Comparative Example 2 used N-methyldiethanolamine as a chain extender. The polyurethane prepared did not contain an active β-carbonyl ester structure and a ketone carbonyl group, and could not undergo a crosslinking reaction with aminopropyl double-terminated polydimethylsiloxane. As a result, the impact resistance, flexibility, and water resistance of the coating film were lower than those of Example 1, and the color difference value ∆E was larger, indicating poor weather resistance.

[0045] The N-butanone diethanolamine in Comparative Example 3 does not contain a β-carbonyl ester structure, and its carbonyl activity is low. Its crosslinking reaction with aminopropyl double-terminated polydimethylsiloxane is weak, resulting in poor crosslinking effect. Consequently, the impact resistance, flexibility, and water resistance of the paint film are lower than those in Example 1, and the color difference value ∆E is large, indicating poor weather resistance.

[0046] In the preparation of polyurethane in Comparative Example 4, aminopropyl double-terminated polydimethylsiloxane was added. Its double-terminated amino groups underwent a linear polymerization reaction with the isocyanate monomer. As a result, the polyurethane did not form a three-dimensional chemical cross-linking network, which led to the impact resistance, flexibility, and water resistance of the coating film being lower than those in Example 1.

[0047] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. 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 of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A preparation process for a weather-resistant luminescent coating, characterized in that, The preparation process includes the following steps: adding polyester polyol to a reaction vessel, heating to 100-110℃, vacuum dehydration, cooling to 70-85℃, introducing nitrogen gas, adding isocyanate monomer, stirring and reacting for 2-3 hours, adding 2,2-dimethylolpropionic acid and dibutyltin dilaurate, continuing the reaction for 30-40 minutes, cooling the temperature to 40-45℃, then adding acetone and N-(acetoacetyl)diethanolamine, continuing the reaction for 20-30 minutes, adding triethylamine and water, stirring and neutralizing, removing acetone by vacuum distillation, adding filler, luminescent powder, dispersant, defoamer, and emulsifying agent, stirring and dispersing, and finally adding aminopropyl double-terminated polydimethylsiloxane, stirring and mixing to obtain a weather-resistant luminescent coating; The structural formula of the N-(acetoacetyl)diethanolamine is as follows: The R group is either methyl or ethyl.

2. The preparation process of the weather-resistant luminescent coating according to claim 1, characterized in that, The molar ratio of the polyester polyol and isocyanate monomer, nNCO / nOH, is (2.3-2.6):

1.

3. The preparation process of the weather-resistant luminescent coating according to claim 1, characterized in that, The ratio of the isocyanate monomer, 2,2-dimethylolpropionic acid, dibutyltin dilaurate, N-(acetoacetyl)diethanolamine, and aminopropyl dimethylsiloxane is (2.3-2.6) mol: (1-1.3) mol: (3.5-4.3) g: (0.2-0.4) mol: (40-150) g.

4. The preparation process of the weather-resistant luminescent coating according to claim 3, characterized in that, The isocyanate monomer is hexamethylene diisocyanate or isophorone diisocyanate.

5. The preparation process of the weather-resistant luminescent coating according to claim 3, characterized in that, The preparation process of N-(acetoacetate-based)diethanolamine includes the following steps: adding solvent, an acid-binding agent in a ratio of (1.6-2.2) mol:(1-1.4) mol:1 mol, diethanolamine, and 4-chloroacetoacetate to a reaction vessel, heating to 75-90℃, stirring and refluxing for 8-14 hours, filtering after cooling, rotary evaporating the filtrate, and separating the product by silica gel column chromatography to obtain N-(acetoacetate-based)diethanolamine.

6. The preparation process of the weather-resistant luminescent coating according to claim 3, characterized in that, The solvent is any one or a combination of acetonitrile, tetrahydrofuran, and water.

7. The preparation process of the weather-resistant luminescent coating according to claim 3, characterized in that, The acid-binding agent is sodium carbonate or potassium carbonate.

8. The preparation process of the weather-resistant luminescent coating according to claim 3, characterized in that, The 4-chloroacetoacetate is methyl 4-chloroacetoacetate or ethyl 4-chloroacetoacetate.

9. The preparation process of the weather-resistant luminescent coating according to claim 1, characterized in that, The filler is barium sulfate, titanium dioxide, or fumed silica.

10. A weather-resistant luminescent coating obtained by the preparation process according to any one of claims 1-9.

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