A nanocellulose-stabilized plant oil-based self-repairing water-based photocurable coating and its preparation method

Abstract

A nanocellulose-stabilized vegetable oil-based self-repairing water-based photocurable coating and a preparation method thereof. The present invention first utilizes vegetable oil to react with maleic anhydride to generate maleic anhydride vegetable oil; then utilizes hydroxyethyl acrylate to perform anhydride ring-opening modification on the generated maleic anhydride vegetable oil to obtain a vegetable oil-based unsaturated polyester resin prepolymer; then uses an alkaline neutralizer to neutralize the carboxyl groups in the vegetable oil-based unsaturated polyester resin prepolymer to obtain an anionic water-based vegetable oil-based unsaturated polyester resin, adds a photoinitiator to obtain a photosensitive resin; finally, the resin is mixed with a nanocellulose suspension, and dispersed at high speed to obtain the final product. The prepared water-based photocurable resin has good thermal properties, mechanical properties, coating properties and self-repairing properties after photocuring, and can be used in the field of photocurable coatings. Most of the raw materials used in the present invention come from renewable resources, and the material preparation process is simple and environmentally friendly.

Description

Technical Field

[0001] The present invention belongs to the field of photocurable materials, and in particular relates to a nanocellulose-stabilized plant oil-based self-repairing water-based photocurable coating and a preparation method thereof. Background Art

[0002] As oil resources are increasingly depleted and environmental problems intensify, the development of biomass resources to replace them is essential. While vegetable oils are abundant, their processing methods are relatively backward, resulting in a low level of comprehensive utilization. Therefore, chemical modification can leverage the molecular structure of vegetable oils to develop high-value-added products for applications in inks, plasticizers, 3D printing, coatings, and other fields. Water-based coatings use water as a diluent instead of organic solvents. Compared to traditional coatings that typically use organic compounds as diluents, water-based coatings offer the advantages of low volatile organic compound (VOC) emissions, low toxicity, and safety. UV-curing technology is highly efficient, energy-efficient, widely adaptable, economical, and environmentally friendly. UV-curing coatings are also environmentally friendly, offering rapid crosslinking rates and low curing temperatures. Applying UV-curing technology to water-based coatings can combine the advantages of both. However, water-based coatings also face challenges such as poor mechanical properties, poor water resistance, and low stability. Further research is needed to improve the various properties of water-based coatings.

[0003] Pickering emulsion is an emulsion that uses solid particles instead of surfactants to stabilize water-oil systems. The solid particles have hydrophilic or lipophilic groups that can be wetted by water or oil and adsorbed at the interface between the two phases, effectively improving the stability of the emulsion and reducing the harm of surfactants to the human body and the environment. It can be widely used in food, medicine, chemicals, coatings and other fields. Pickering emulsions prepared with biomass solid particles such as nanocellulose, nanochitosan, protein, etc. are more green, environmentally friendly, non-toxic and safe. In addition, the application of nano-scale particles in water-based paints has increased the mechanical properties and film properties of the paint to a certain extent. Therefore, it is of great significance to use biomass particles to prepare Pickering emulsions for use in water-based paints.

[0004] Introducing self-healing properties into coatings is an effective solution to the problem of coating vulnerability to damage. Since researchers first proposed the concept of "Vitrimer" in 2011, materials based on dynamic covalent bonds, which achieve self-healing properties through reversible chemical bond exchange, have gradually developed. Dynamic covalent bonds offer greater stability and higher bond energies, endowing materials with excellent self-healing properties. Currently, dynamic covalent bonds, such as dynamic ester bonds, disulfide bonds, and hindered urea bonds, are being used in materials to achieve self-healing properties. Summary of the Invention

[0005] Technical problem to be solved: The present invention provides a nanocellulose-stabilized plant oil-based self-repairing water-based photocuring coating and a preparation method thereof, which solves the problems of high VOC emissions, serious environmental pollution, and health impacts of traditional coatings, and improves the problems of short storage period, low film-forming mechanical properties, and the need for a large amount of surfactants in water-based coatings.

[0006] Technical solution: A method for preparing a nanocellulose-stabilized vegetable oil-based self-repairing water-based photocurable coating, comprising the following steps: (1) adding vegetable oil and maleic anhydride to a reactor, wherein the molar ratio of the vegetable oil to maleic anhydride is 1:(0.5-5), stirring evenly and heating to 110-180°C for reaction for 1-5 hours, then heating to 110-120°C in a glass drying furnace for reaction for 1-3 hours to obtain maleic anhydride vegetable oil; (2) adding acrylate, inhibitor and catalyst to the above reactor, wherein the molar ratio of acrylate to maleic anhydride is (0.5-2):1, the amount of inhibitor is 0.5-2% of the total mass of the maleic anhydride vegetable oil and acrylate, the amount of catalyst is 0.5-3% of the total mass of the maleic anhydride vegetable oil and acrylate, heating to 80-150°C for reaction for 1-5 hours, dissolving the product in dichloromethane, and washing with a 10wt.% NaCl aqueous solution at 30-50°C. The invention relates to a method for preparing an anionic waterborne vegetable oil-based unsaturated polyester resin. The method comprises the following steps: (1) washing the prepolymer, drying the prepolymer, and removing the solvent by rotary evaporation to obtain a vegetable oil-based unsaturated polyester resin prepolymer; (2) adding an alkaline neutralizer to the prepolymer to neutralize the carboxyl group, wherein the molar ratio of the alkaline neutralizer to the carboxyl group in the prepolymer is (1-1.5):1, heating the prepolymer to 30-80°C and reacting the prepolymer for 0.5-3 hours to obtain an anionic waterborne vegetable oil-based unsaturated polyester resin; (3) washing the prepolymer, drying the prepolymer, and removing the solvent by rotary evaporation to obtain a vegetable oil-based unsaturated polyester resin prepolymer; (4) adding a photoinitiator with a mass fraction of 1%-3% to the prepolymer, stirring the prepolymer to obtain a photosensitive resin; (5) mixing the photosensitive resin with a nanocellulose aqueous suspension, and then dispersing the nanocellulose in the nanocellulose aqueous suspension at a high speed, wherein the nanocellulose in the nanocellulose aqueous suspension is 1%-4% of the mass of the photosensitive resin, and the mass ratio of the photosensitive resin to the nanocellulose aqueous suspension is (0.5-3):10 to obtain a nanocellulose-stabilized vegetable oil-based self-repairing waterborne photocurable coating.

[0007] The vegetable oil in step (1) is at least one of tung oil, rubber seed oil, dehydrated castor oil, linseed oil, soybean oil and rapeseed oil, and the molar ratio of the vegetable oil to maleic anhydride is 1:3.

[0008] The acrylic ester described in step (2) is at least one of hydroxyethyl acrylate and hydroxyethyl methacrylate; the molar ratio of the acrylic ester to maleic anhydride is 1:1; the catalyst is at least one of 4-dimethylaminopyridine and triphenylphosphine, and the amount of the catalyst is 1% of the total mass of the maleic anhydride vegetable oil and the acrylic ester; the polymerization inhibitor is at least one of hydroquinone, p-benzoquinone, p-methoxyphenol and 2,6-di-tert-butyl-p-methylphenol, and the amount of the polymerization inhibitor is 0.5% of the total mass of the maleic anhydride vegetable oil and the acrylic ester.

[0009] The alkaline neutralizing agent described in step (3) is at least one of triethylamine, triethanolamine, diethylamine and diethanolamine; the molar ratio of the alkaline neutralizing agent to the carboxyl group in the vegetable oil-based unsaturated polyester resin prepolymer is 1:1.

[0010] The photoinitiator in step (4) is at least one of Darocur 1173, Irgacure 184, Irgacure 651 and Irgacure 369, and the amount of the photoinitiator is 2% of the total mass of the obtained anionic water-based vegetable oil-based unsaturated polyester resin.

[0011] The nanocellulose described in step (5) is at least one of nanofibrillar cellulose and cellulose nanocrystals.

[0012] The speed range of the above high-speed dispersion is 25000-30000 rpm.

[0013] The nanocellulose-stabilized plant oil-based self-repairing water-based photocurable coating prepared by the above method.

[0014] Beneficial effects: (1) The vegetable oil-based water-based photocurable resin synthesized by the present invention has high stability, and the tensile properties, thermal properties, coating properties and self-repairing properties of the cured material are excellent, and can be used as a water-based photocurable coating.

[0015] (2) The synthesis method used in the present invention is to first modify the vegetable oil with maleic anhydride, then use acrylate to perform anhydride ring opening on the synthesized maleic anhydride vegetable oil, then use an alkaline neutralizer to neutralize the carboxyl group and add a photoinitiator, and finally use nanocellulose as a stabilizer to prepare a water-based light-curing coating; the raw materials used in this method are mostly derived from biomass, which is green and environmentally friendly, and the preparation process is simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is the FT-IR spectrum of tung oil-based hydroxyethyl acrylate prepolymer;

[0017] Figure 2 Tung oil-based hydroxyethyl acrylate prepolymer 1H NMR spectrum;

[0018] Figure 3 This is a synthetic route for tung oil-based acrylate prepolymers. DETAILED DESCRIPTION

[0019] The following examples of the present invention are only intended to further illustrate the present invention and are not intended to limit the present invention or its scope.

[0020] Example 1

[0021] (1) Tung oil and maleic anhydride in a molar ratio of 1:3 were added to a reactor, reacted at 150°C for 3.5 hours, and then heated to 110°C in a glass drying oven for 3 hours to obtain maleic anhydride tung oil.

[0022] (2) Add hydroxyethyl acrylate (the molar ratio of hydroxyethyl acrylate to maleic anhydride is 1:1), inhibitor 4-methoxyphenol (the amount of inhibitor is 0.5% of the total mass of maleated vegetable oil and acrylate) and catalyst 4-dimethylaminopyridine (the amount of catalyst is 1% of the total mass of maleated vegetable oil and acrylate) to the above reactor, heat to 110° C. and react for 5 hours. Dissolve the product in dichloromethane, wash with a 10 wt% NaCl aqueous solution at 40° C., dry and remove the solvent by rotary evaporation to obtain a vegetable oil-based unsaturated polyester resin prepolymer.

[0023] (3) Add triethylamine to the above vegetable oil-based unsaturated polyester resin prepolymer, heat to 60° C. and react for 30 minutes to obtain an anionic water-based vegetable oil-based unsaturated polyester resin.

[0024] (4) Add 2% by mass of photoinitiator Darocur 1173 to the generated anionic water-based vegetable oil-based unsaturated polyester resin and stir evenly to obtain a photosensitive resin.

[0025] (5) Adding photosensitive resin to the nanocellulose suspension, the mass ratio of nanocellulose suspension to resin is 10:1, nanocellulose is 1% of the mass of the photosensitive resin, and the suspension is evenly dispersed at 30,000 rpm to obtain a vegetable oil-based self-healing water-based photocurable coating.

[0026] Example 2

[0027] (1) Tung oil and maleic anhydride in a molar ratio of 1:3 were added to a reactor, reacted at 150°C for 3.5 hours, and then heated to 110°C in a glass drying oven for 3 hours to obtain maleic anhydride tung oil.

[0028] (2) Add hydroxyethyl acrylate (the molar ratio of hydroxyethyl acrylate to maleic anhydride is 1:1), inhibitor 4-methoxyphenol (the amount of inhibitor is 0.5% of the total mass of maleated vegetable oil and acrylate) and catalyst 4-dimethylaminopyridine (the amount of catalyst is 1% of the total mass of maleated vegetable oil and acrylate) to the above reactor, heat to 110° C. and react for 5 hours. Dissolve the product in dichloromethane, wash with a 10 wt% NaCl aqueous solution at 40° C., dry and remove the solvent by rotary evaporation to obtain a vegetable oil-based unsaturated polyester resin prepolymer.

[0029] (3) Add triethylamine to the above vegetable oil-based unsaturated polyester resin prepolymer, heat to 60° C. and react for 30 minutes to obtain an anionic water-based vegetable oil-based unsaturated polyester resin.

[0030] (4) Add 2% by mass of photoinitiator Darocur 1173 to the generated anionic water-based vegetable oil-based unsaturated polyester resin and stir evenly to obtain a photosensitive resin.

[0031] (5) Adding photosensitive resin to the nanocellulose suspension, the mass ratio of the nanocellulose suspension to the resin is 10:1, the nanocellulose is 2% of the mass of the photosensitive resin, and the suspension is evenly dispersed at 30,000 rpm to obtain a vegetable oil-based self-healing water-based photocurable coating.

[0032] Example 3

[0033] (1) Tung oil and maleic anhydride in a molar ratio of 1:3 were added to a reactor, reacted at 150°C for 3.5 hours, and then heated to 110°C in a glass drying oven for 3 hours to obtain maleic anhydride tung oil.

[0034] (2) Add hydroxyethyl acrylate (the molar ratio of hydroxyethyl acrylate to maleic anhydride is 1:1), inhibitor 4-methoxyphenol (the amount of inhibitor is 0.5% of the total mass of maleated vegetable oil and acrylate) and catalyst 4-dimethylaminopyridine (the amount of catalyst is 1% of the total mass of maleated vegetable oil and acrylate) to the above reactor, heat to 110° C. and react for 5 hours. Dissolve the product in dichloromethane, wash with a 10 wt% NaCl aqueous solution at 40° C., dry and remove the solvent by rotary evaporation to obtain a vegetable oil-based unsaturated polyester resin prepolymer.

[0035] (3) Add triethylamine to the above vegetable oil-based unsaturated polyester resin prepolymer, heat to 60° C. and react for 30 minutes to obtain an anionic water-based vegetable oil-based unsaturated polyester resin.

[0036] (4) Add 2% by mass of photoinitiator Darocur 1173 to the generated anionic water-based vegetable oil-based unsaturated polyester resin and stir evenly to obtain a photosensitive resin.

[0037] (5) Adding photosensitive resin to the nanocellulose suspension, the mass ratio of the nanocellulose suspension to the resin is 10:1, the nanocellulose is 3% of the mass of the photosensitive resin, and the suspension is evenly dispersed at 30,000 rpm to obtain a vegetable oil-based self-repairing water-based photocurable coating.

[0038] Example 4

[0039] (1) Tung oil and maleic anhydride in a molar ratio of 1:3 were added to a reactor, reacted at 150°C for 3.5 hours, and then heated to 110°C in a glass drying oven for 3 hours to obtain maleic anhydride tung oil.

[0040] (2) Add hydroxyethyl acrylate (the molar ratio of hydroxyethyl acrylate to maleic anhydride is 1:1), inhibitor 4-methoxyphenol (the amount of inhibitor is 0.5% of the total mass of maleated vegetable oil and acrylate) and catalyst 4-dimethylaminopyridine (the amount of catalyst is 1% of the total mass of maleated vegetable oil and acrylate) to the above reactor, heat to 110° C. and react for 5 hours. Dissolve the product in dichloromethane, wash with a 10 wt% NaCl aqueous solution at 40° C., dry and remove the solvent by rotary evaporation to obtain a vegetable oil-based unsaturated polyester resin prepolymer.

[0041] (3) Add triethylamine to the above vegetable oil-based unsaturated polyester resin prepolymer, heat to 60° C. and react for 30 minutes to obtain an anionic water-based vegetable oil-based unsaturated polyester resin.

[0042] (4) Add 2% by mass of photoinitiator Darocur 1173 to the generated anionic water-based vegetable oil-based unsaturated polyester resin and stir evenly to obtain a photosensitive resin.

[0043] (5) Adding photosensitive resin to the nanocellulose suspension, the mass ratio of nanocellulose suspension to resin is 10:1, nanocellulose is 4% of the mass of the photosensitive resin, and the suspension is evenly dispersed at 30,000 rpm to obtain a vegetable oil-based self-healing water-based photocurable coating.

[0044] Example 5

[0045] The water-based coatings of Examples 1 to 4 were poured into a homemade polytetrafluoroethylene mold or coated on a tinplate sheet. After the water was completely evaporated at room temperature, the film was then cured by UV. Tensile properties: The mechanical properties of the photocured films were measured according to ASTM D638-2008 using a SANS7CMT-4304 universal testing machine (Shenzhen Xinsansi Instrument Co., Ltd.), with a gauge length of 30 mm and a tensile rate of 5.0 mm / min. Glass transition temperature: The glass transition temperature was measured using a DSC8000 differential scanning calorimeter (PE Company, USA). Thermogravimetric analysis: The thermodynamic stability of the photocured films was measured using a STA 409PC thermogravimetric analyzer (Netzsch Company, Germany). The heating range was 40-800°C, and the heating rate was 15°C / min. Coating Performance: Adhesion was tested according to GB / T 9286-1998, with grade 1 being the best and grade 7 being the worst. Flexibility was tested according to GB / T 1731-93, with a minimum mandrel diameter of 2 mm. A smaller mandrel diameter indicates better toughness. Hardness was measured according to GB / T 6739-2006, with grades 6H, 5H, 4H, 3H, 2H, H, HB, B, 2B, 3B, 4B, 5B, and 6B, with 6H being the hardest and 6B the softest. Self-Healing Rate: The self-healing rate was calculated by observing the reduction in scratch width before and after repair using an ICC50W Leica optical microscope. The test results for each example are shown in Table 1.

[0046] Table 1 Main coating performance indicators of resin samples of Examples 1-4

[0047]

[0048] It can be seen from the data in the table that the coating prepared by the vegetable oil-based water-based light-curing coating of the present invention has good tensile properties and film properties, and can be used as a protective coating for surfaces such as metal and wood.

Claims

1. A method for preparing a nanocellulose-stabilized plant oil-based self-repairing water-based light-curing coating, characterized in that: (1) Tung oil and maleic anhydride in a molar ratio of 1:3 were added to a reactor, and the mixture was reacted at 150°C for 3.5 hours, and then heated to 110°C in a glass drying furnace for 3 hours to obtain maleic anhydride tung oil; (2) Hydroxyethyl acrylate, a polymerization inhibitor 4-methoxyphenol, and a catalyst 4-dimethylaminopyridine were added to the above reactor, wherein the molar ratio of hydroxyethyl acrylate to maleic anhydride was 1:1, the amount of the polymerization inhibitor was 0.5% of the total mass of the maleic anhydride tung oil and hydroxyethyl acrylate, and the amount of the catalyst was 1% of the total mass of the maleic anhydride tung oil and hydroxyethyl acrylate, and the mixture was heated to 110°C for 5 hours. The product was dissolved in dichloromethane and 10 wt% 40°C water was added. The mixture was washed with a NaCl aqueous solution, dried, and then the solvent was removed by rotary evaporation to obtain a vegetable oil-based unsaturated polyester resin prepolymer; (3) triethylamine was added to the above vegetable oil-based unsaturated polyester resin prepolymer, heated to 60°C for reaction for 30 minutes, and an anionic water-based vegetable oil-based unsaturated polyester resin was obtained; (4) 2% by mass of photoinitiator Darocur 1173 was added to the generated anionic water-based vegetable oil-based unsaturated polyester resin, and the mixture was stirred evenly to obtain a photosensitive resin; (5) the photosensitive resin was added to the nanocellulose suspension, the mass ratio of the nanocellulose suspension to the photosensitive resin was 10:1, and the nanocellulose was 2% of the mass of the photosensitive resin. The mixture was evenly dispersed at 30,000 rpm to obtain a vegetable oil-based self-repairing water-based photocurable coating.

2. The nanocellulose-stabilized plant oil-based self-repairing water-based photocurable coating prepared by the method of claim 1.

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