Wear-resistant UV (ultraviolet) photocuring protective coating film and preparation process thereof

Abstract

The invention relates to the technical field of photocuring materials, and discloses a wear-resistant UV photocuring protective film and a preparation process thereof.The wear-resistant UV photocuring protective film is prepared through the steps that polyol, isocyanate monomers, a chain extender, an alkenyl end-capping reagent and the like are subjected to a reaction, and a polyurethane solution is obtained; then adding a reactive diluent, a photoinitiator and the like, stirring and dispersing, spraying on the surface of a base material, and irradiating and photocuring in a UV curing machine to obtain the wear-resistant UV photocuring protective coating film. The phenyl imide ring is introduced into a polyurethane molecular chain, so that the rigidity of the polyurethane molecular chain is improved, the structural strength and the structural stability are improved, and the wear resistance, the mechanical strength and the heat resistance of a coating film are improved.

Description

Technical Field

[0001] This invention relates to the field of photocurable materials technology, specifically to a wear-resistant UV-curable protective coating and its preparation process. Background Technology

[0002] UV curing technology utilizes ultraviolet light irradiation to rapidly crosslink and cure liquid resins into solid materials via a photoinitiator, resulting in fast curing speed, simple operation, and wide application range. Common UV-curable resins include polyurethane acrylates and epoxy acrylates. Polyurethanes possess excellent elasticity, high toughness, and superior adhesion properties, along with good structural designability, making them widely used. Introducing alkenyl groups at the end positions of polyurethanes typically imparts excellent UV curing characteristics.

[0003] Traditional UV-cured polyurethane suffers from low hardness and strength, and poor wear resistance, which limits the practical application of polyurethane. Patent CN112795300B discloses a UV coating and its preparation method, which uses N-alkylmaleimide modified polyurethane acrylate, acrylate monomers and other raw materials to prepare a UV coating with advantages such as low initiator dosage and low odor. However, this patent does not solve the problems of poor hardness, strength and wear resistance of UV-cured polyurethane. Summary of the Invention

[0004] This invention solves the problem of poor hardness and wear resistance of polyurethane membrane materials.

[0005] The technical solution of this invention is: a preparation process for a wear-resistant UV-curable protective coating. (1) Toluene, phthaloylglycine, glycidyl methacrylate and tetrabutylammonium bromide were added to the reaction flask. After the reaction, the mixture was filtered, the filtrate was distilled under reduced pressure, washed with petroleum ether, and the product was recrystallized in ethyl acetate to obtain an alkenyl end-capping agent.

[0006] (2) Add dehydrated polyol and isocyanate monomer to the reactor, introduce nitrogen gas, stir the prepolymerization reaction, then add acetone, chain extender and catalyst to carry out chain extension reaction, add alkenyl end-capping agent to carry out end-capping reaction, and obtain polyurethane solution.

[0007] (3) Add reactive diluent and defoamer to polyurethane solution, stir and disperse, add photoinitiator, stir and disperse, then spray the solution onto the substrate surface, and irradiate and cure in a UV curing machine to obtain wear-resistant UV curable protective coating.

[0008] Furthermore, in (1), the ratio of phthaloylglycine, glycidyl methacrylate, and tetrabutylammonium bromide is (1.2-1.8) mol: 1 mol: (0.06-0.07) mol.

[0009] Furthermore, in (1), the reaction temperature is 90-110℃ and the reaction time is 5-8h.

[0010] Furthermore, in (2), the ratio of polyol, isocyanate monomer, chain extender and alkenyl end-capping agent is 1 mol: (2.6-3) mol: (1.3-1.5) mol: (0.5-0.6) mol.

[0011] Furthermore, in (2), the polyol is a polyester polyol or a polyether polyol; the polyester polyol includes poly(1,4-butanediol adipate); the polyether polyol includes polytetrahydrofuran ether diol, polyethylene glycol, and polypropylene glycol.

[0012] Furthermore, the isocyanate monomers in (2) include diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and toluene diisocyanate.

[0013] Furthermore, the chain extender in (2) includes diethylene glycol, 1,4-butanediol, and 2,2-dimethylolpropionic acid.

[0014] Furthermore, the catalyst in (2) includes dibutyltin dilaurate.

[0015] Furthermore, in (2), the temperature during the prepolymerization reaction is 70-80℃ and the reaction time is 2-3h.

[0016] Furthermore, in (2), the chain extension reaction is carried out at a temperature of 45-50℃ and a reaction time of 40-60min.

[0017] Furthermore, in (2), the temperature during the end-capping reaction is 45-50℃ and the reaction time is 30-40min.

[0018] Furthermore, the active diluents in (3) include dipropylene glycol diacrylate, dipropylene glycol diacrylate, and trimethylolpropane triacrylate.

[0019] Furthermore, (3) includes photoinitiator 1173 or photoinitiator 184.

[0020] Furthermore, in (3), the power of the UV curing machine is 1-2kW, the center wavelength is 365nm, the irradiation distance is 10-20cm, and the irradiation curing time is 40-90s.

[0021] Beneficial technical effects: The alkenyl end-capping agent of the present invention contains hydroxyl groups, which can react with the terminal isocyanates of polyurethane prepolymers to introduce alkenyl groups at the polyurethane end positions. It then undergoes a crosslinking reaction with an active diluent and is photocured to form a coating film. The introduction of phenylimide rings into the polyurethane molecular chain improves the rigidity of the polyurethane molecular chain, increases the structural strength and structural stability, and enhances the wear resistance, mechanical strength, and heat resistance of the coating film. Detailed Implementation

[0022] The present invention will be further described below with reference to specific embodiments, so that those skilled in the art can better understand and implement the present invention, but the embodiments are not intended to limit the present invention.

[0023] The UV curing machine described below has a power of 1kW and a center wavelength of 365nm.

[0024] Example 1: (1) Add 150 mL of toluene, 50 mmol of phthaloylglycine, 90 mmol of glycidyl methacrylate, and 3 mmol of tetrabutylammonium bromide to a reaction flask, heat to 110 °C, stir for 5 h, filter, distill under reduced pressure, wash with petroleum ether, and recrystallize the product in ethyl acetate to obtain an alkenyl end-capping agent. The reaction formula is: .

[0025] (2) Add 0.1 mol of dehydrated polytetrahydrofuran ether diol 1000 (molecular weight about 1000) and 0.28 mol of toluene-2,4-diisocyanate to the reaction vessel, purge with nitrogen, stir and react at 70°C for 3 h, then add 50 mL of acetone, 0.14 mol of 1,4-butanediol and 0.6 g of dibutyltin dilaurate, react at 45°C for 60 min, add 0.054 mol of alkenyl end-capping agent, stir and react at 45°C for 30 min to obtain polyurethane solution.

[0026] (3) Add 13g of tripropylene glycol diacrylate, 3.8g of trimethylolpropane triacrylate, and 2.6g of defoamer EFKA PB 2001 to the above polyurethane solution, stir and disperse, add 7.4g of photoinitiator 1173, stir and disperse, then spray the solution onto the substrate surface, and irradiate it in a 1kW UV curing machine for 50s with an irradiation distance of 15cm to obtain a wear-resistant UV curing protective coating.

[0027] Example 2: (1) Add 130 mL toluene, 50 mmol phthaloyl glycine, 60 mmol glycidyl methacrylate and 3.5 mmol tetrabutylammonium bromide to the reaction flask, heat to 90 °C, stir for 8 h, filter, distill under reduced pressure, wash with petroleum ether, recrystallize the product in ethyl acetate to obtain alkenyl end-capping agent.

[0028] (2) Add 0.1 mol of dehydrated poly(1,4-butanediol adipate) diol 2000 and 0.26 mol of isophorone diisocyanate to the reaction vessel, purge with nitrogen, and stir at 70°C for 3 h. Then add 50 mL of acetone, 0.13 mol of 1,4-butanediol and 0.6 g of dibutyltin dilaurate, and react at 50°C for 40 min. Add 0.05 mol of alkenyl end-capping agent and stir at 50°C for 30 min to obtain a polyurethane solution.

[0029] (3) Add 14g of dipropylene glycol diacrylate, 3g of trimethylolpropane triacrylate and 3g of defoamer EFKA PB 2001 to the above polyurethane solution, stir and disperse, add 7.8g of photoinitiator 1173, stir and disperse, then spray the solution onto the substrate surface, and irradiate it in a 1kW UV curing machine for 45s with an irradiation distance of 15cm to obtain a wear-resistant UV curing protective coating.

[0030] Example 3: (1) Add 0.1 mol of dehydrated polyethylene glycol 2000 and 0.3 mol of isophorone diisocyanate to the reaction vessel, purge with nitrogen, stir and react at 80°C for 2 h, then add 70 mL of acetone, 0.15 mol of 1,4-butanediol and 0.5 g of dibutyltin dilaurate, react at 45°C for 60 min, add 0.06 mol of alkenyl end-capping agent (same as the preparation process in Example 1), stir and react at 45°C for 40 min to obtain a polyurethane solution.

[0031] (2) Add 16g of tripropylene glycol diacrylate, 3.4g of trimethylolpropane triacrylate, and 2.6g of defoamer EFKA PB 2001 to the above polyurethane solution, stir and disperse, add 8.5g of photoinitiator 184, stir and disperse, then spray the solution onto the substrate surface, and irradiate it with a 1kW UV curing machine for 70s with an irradiation distance of 15cm to obtain a wear-resistant UV curing protective coating.

[0032] Example 4: (1) Add 0.1 mol of dehydrated polytetrahydrofuran ether diol 1000 and 0.26 mol of diphenylmethane-4,4-diisocyanate to the reaction vessel, purge with nitrogen, stir and react at 75°C for 3 h, then add 70 mL of acetone, 0.13 mol of 1,4-butanediol and 0.4 g of dibutyltin dilaurate, react at 50°C for 40 min, add 0.05 mol of alkenyl end-capping agent (same preparation process as in Example 1), stir and react at 50°C for 30 min to obtain polyurethane solution.

[0033] (2) Add 12g of tripropylene glycol diacrylate, 5g of trimethylolpropane triacrylate, and 3.6g of defoamer EFKA PB 2001 to the above polyurethane solution, stir and disperse, add 7.5g of photoinitiator 1173, stir and disperse, then spray the solution onto the substrate surface, and irradiate it with a 1kW UV curing machine for 60s with an irradiation distance of 15cm to obtain a wear-resistant UV curing protective coating.

[0034] Comparative Example 1: (1) Add 0.1 mol of dehydrated polytetrahydrofuran ether diol 1000 and 0.28 mol of toluene-2,4-diisocyanate to the reaction vessel, introduce nitrogen gas, stir and react at 70°C for 3 h, then add 50 mL of acetone and 0.14 mol of 1,4-hydroxyethyl acrylate, stir and react at 45°C for 30 min to obtain a polyurethane solution.

[0035] (2) Add 13g of tripropylene glycol diacrylate, 3.8g of trimethylolpropane triacrylate, and 2.6g of defoamer EFKA PB 2001 to the above polyurethane solution, stir and disperse, add 7.4g of photoinitiator 1173, stir and disperse, then spray the solution onto the substrate surface, and irradiate it in a 1kW UV curing machine for 50s with an irradiation distance of 15cm to obtain a wear-resistant UV curing protective coating.

[0036] Comparative Example 2: (1) Add 0.1 mol of dehydrated polytetrahydrofuran ether diol 1000 and 0.28 mol of toluene-2,4-diisocyanate to the reaction vessel, purge with nitrogen, stir and react at 70°C for 3 h, then add 50 mL of acetone, 0.14 mol of 1,4-butanediol and 0.6 g of dibutyltin dilaurate, react at 45°C for 60 min, add 0.054 mol of N-(2-hydroxyethyl) phthalimide (CAS No. 3891-07-4), stir and react at 45°C for 30 min to obtain a polyurethane solution.

[0037] (2) Add 13g of tripropylene glycol diacrylate, 3.8g of trimethylolpropane triacrylate, and 2.6g of defoamer EFKA PB 2001 to the above polyurethane solution, stir and disperse, add 7.4g of photoinitiator 1173, stir and disperse, then spray the solution onto the substrate surface, and irradiate it for 50s in a 1kW UV curing machine at a distance of 15cm. It is semi-gel-like and does not form a film.

[0038] Comparative Example 3: (1) Add 0.1 mol of dehydrated polytetrahydrofuran ether diol 1000 and 0.28 mol of toluene-2,4-diisocyanate to the reaction vessel, purge with nitrogen, stir at 70°C for 3 h, then add 50 mL of acetone, 0.14 mol of 1,4-butanediol and 0.6 g of dibutyltin dilaurate, react at 45°C for 60 min, add 0.054 mol of N-allyl phthalimide (CAS No. 5428-09-1), stir at 45°C for 30 min to obtain a polyurethane solution.

[0039] (2) Add 13g of tripropylene glycol diacrylate, 3.8g of trimethylolpropane triacrylate, and 2.6g of defoamer EFKA PB 2001 to the above polyurethane solution, stir and disperse, add 7.4g of photoinitiator 1173, stir and disperse, then spray the solution onto the substrate surface, and irradiate it for 50s in a 1kW UV curing machine at a distance of 15cm. It is semi-gel-like and does not form a film.

[0040] The abrasion resistance of the coating was tested according to GB / T 1768-2006. The hardness was tested according to GB / T 6739-2022.

[0041] Weigh 6 mg of the coating film and place it in a thermogravimetric analyzer. Perform thermal performance testing in a nitrogen atmosphere at a heating rate of 5 °C / min.

[0042] Table 1 Performance of the coating Comparative Example 1 used conventional hydroxyethyl acrylate to end-encapsulate the polyurethane prepolymer with alkenyl groups. The resulting UV polyurethane coating exhibited significant tribological loss, a pencil hardness of only 3H, and low abrasion resistance and mechanical strength. Furthermore, a 5% thermogravimetric mass loss occurred at a temperature (T). 5% Its properties are low and its heat resistance is poor.

[0043] The alkenyl end-capping agents prepared in Examples 1-3 contain hydroxyl groups, which can react with the terminal isocyanates of the polyurethane prepolymer to introduce alkenyl groups at the polyurethane end positions. These alkenyl groups then undergo a crosslinking reaction with the reactive diluent. The resulting photocured coating exhibits lower frictional mass loss, a higher thermogravimetric temperature, and a pencil hardness of 3-4H. Improved wear resistance, heat resistance, and mechanical strength are primarily due to the addition of the phenylimide ring (…). Introducing this into the polyurethane molecular chain increases the rigidity of the polyurethane molecular chain, resulting in greater structural strength and stability, as well as improved mechanical properties and heat resistance.

[0044] The N-(2-hydroxyethyl)phthalimide in Comparative Example 2 does not contain an alkenyl group, so the polyurethane cannot undergo a crosslinking reaction with the reactive diluent and cannot be photocured into a film.

[0045] The N-allyl phthalimide in Comparative Example 3 does not contain hydroxyl groups and cannot react with the terminal isocyanate of the polyurethane prepolymer. The prepared polyurethane does not contain alkenyl groups and cannot undergo crosslinking reaction with the reactive diluent, thus it cannot be photocured into a film.

[0046] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A process for preparing a wear-resistant UV-curable protective coating, characterized in that, The preparation process includes the following steps: S1. Add dehydrated polyol and isocyanate monomer to the reactor, introduce nitrogen gas, stir and prepolymerize, then add acetone, chain extender and catalyst to carry out chain extension reaction, add alkenyl end-capping agent to carry out end-capping reaction, and obtain polyurethane solution. S1. Add reactive diluent and defoamer to polyurethane solution, stir and disperse, add photoinitiator, stir and disperse, then spray the solution onto the substrate surface, and irradiate and cure in a UV curing machine to obtain a wear-resistant UV-cured protective coating.

2. The preparation process of the wear-resistant UV-curable protective coating according to claim 1, characterized in that, The ratio of the polyol, isocyanate monomer, chain extender, and alkenyl end-capping agent is 1 mol: (2.6-3) mol: (1.3-1.5) mol: (0.5-0.6) mol.

3. The preparation process of the wear-resistant UV-curable protective coating according to claim 2, characterized in that, The polyol is a polyester polyol or a polyether polyol; the polyester polyol includes poly(1,4-butanediol adipate); the polyether polyol includes polytetrahydrofuran ether diol, polyethylene glycol, and polypropylene glycol.

4. The preparation process of the wear-resistant UV-curable protective coating according to claim 2, characterized in that, The isocyanate monomers include diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and toluene diisocyanate.

5. The preparation process of the wear-resistant UV-curable protective coating according to claim 2, characterized in that, The chain extender includes diethylene glycol, 1,4-butanediol, and 2,2-dimethylolpropionic acid; the catalyst includes dibutyltin dilaurate.

6. The preparation process of the wear-resistant UV-curable protective coating according to claim 1, characterized in that, The temperature for the prepolymerization reaction is 70-80℃, and the reaction time is 2-3 hours; the temperature for the chain extension reaction is 45-50℃, and the reaction time is 40-60 minutes; the temperature for the end-capping reaction is 45-50℃, and the reaction time is 30-40 minutes.

7. The preparation process of the wear-resistant UV-curable protective coating according to claim 1, characterized in that, The reactive diluents include tripropylene glycol diacrylate, dipropylene glycol diacrylate, and trimethylolpropane triacrylate; the photoinitiators include photoinitiator 1173 or photoinitiator 184.

8. The preparation process of the wear-resistant UV-curable protective coating according to claim 1, characterized in that, The UV curing machine has a power of 1-2kW, a center wavelength of 365nm, an irradiation distance of 10-20cm, and an irradiation curing time of 40-90s.

9. The preparation process of the wear-resistant UV-curable protective coating according to claim 2, characterized in that, The preparation process of the alkenyl end-capping agent is as follows: toluene, phthaloyl glycine, glycidyl methacrylate, and tetrabutylammonium bromide in a ratio of (1.2-1.8) mol: 1 mol: (0.06-0.07) mol are added to a reaction flask, heated to 90-110℃, stirred for 5-8 hours, filtered, and the filtrate is distilled under reduced pressure to wash the product and recrystallize to obtain the alkenyl end-capping agent.

10. A wear-resistant UV-curable protective coating obtained by the preparation process according to any one of claims 1-9.

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