Solvent-free polyurethane coating for steel structures and containers and preparation method of solvent-free polyurethane coating

Abstract

The invention relates to a solvent-free polyurethane coating for a steel structure and a container and a preparation method of the solvent-free polyurethane coating, and belongs to the technical field of high polymer materials. The solvent-free polyurethane coating for the steel structure and the container is prepared from the following components in parts by weight: 30 to 40 parts of polyol, 0.01 to 0.2 part of a de-foaming agent, 0.1 to 0.5 part of a dispersing agent, 0.1 to 0.5 part of a flatting agent, 1 to 10 parts of pigment, 20 to 25 parts of diphenylmethane diisocyanate, 0.1 to 5 parts of a modified anti-aging agent and 0.1 to 3 parts of a modified flame retardant, hydroxybenzophenone in the modified anti-aging agent is irradiated by ultraviolet rays to generate thermal vibration and cooperates with silane, and maleimide improves the melting point and reduces aging caused by high temperature. Phosphonitrilic chloride trimer in the modified flame retardant absorbs heat and cooperates with phosphorus-oxygen double bonds for flame retardance; the prepared solvent-free polyurethane coating for the steel structure and the container not only has a good anti-aging effect, but also has excellent heat resistance and flame retardance.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and in particular relates to a solvent-free polyurethane coating for steel structures and containers and a preparation method thereof. Background Art

[0002] Polyurethane coating is a functional coating. With its high strength, high elasticity, oil resistance, low temperature resistance, ozone aging resistance and sealing properties, it occupies an important position in anti-corrosion and functional coatings and is widely used in industries such as shipping, aviation, machinery, medical care, transportation and construction.

[0003] In particular, solvent-free polyurethane coatings, as environmentally friendly high-performance coatings, are receiving increasing attention. With the acceleration of global industrialization, the market demand for solvent-free polyurethane coatings with high bonding strength and excellent high temperature resistance is growing. However, traditional solvent-free polyurethane coatings are easily affected by ultraviolet rays, which leads to material aging and affects the use effect. In addition, although solvent-free polyurethane coatings for steel structures and containers have certain flame retardancy, with the increase in actual application needs, their own flame retardancy can no longer meet the needs. Therefore, the research and development of solvent-free polyurethane coatings with excellent performance suitable for steel structures and containers has important practical significance and application value. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a solvent-free polyurethane coating for steel structures and containers and a preparation method thereof.

[0005] The purpose of the present invention can be achieved through the following technical solutions: A solvent-free polyurethane coating for steel structures and containers and a preparation method thereof, comprising the following raw materials in parts by weight: 30-40 parts of polyol, 0.01-0.2 parts of defoaming agent, 0.1-0.5 parts of dispersant, 0.1-0.5 parts of leveling agent, 1-10 parts of pigment, 20-25 parts of diphenylmethane diisocyanate, 0.1-5 parts of modified anti-aging agent, and 0.1-3 parts of modified flame retardant; The polyol is BASF Sovermol 805; The defoamer is BYK-057; The dispersant is dispersant BYK-163; The leveling agent is leveling agent EFKA-3777; The pigment is barium sulfate.

[0006] The modified antioxidant is prepared by the following method: Step A1: uniformly mix oxybenzone, triethylamine and tetrahydrofuran, then dropwise add acryloyl chloride in an ice bath for 1-2 hours, react in an ice bath for 5 hours, precipitate in ice water after the reaction, wash, and vacuum dry to obtain a compound; Further, the usage ratio of oxybenzone, triethylamine, tetrahydrofuran, and acryloyl chloride is 1.62-8.11 g: 1.7-4.5 mL: 20-30 mL: 1.12-5.62 g; Firstly, the hydroxyl group of oxybenzone reacts with the acyl chloride of acryloyl chloride to synthesize the compound; Step A2: the compound and vinyl triethoxysilane are mixed evenly, and then toluene, anhydrous ethanol and azobisisobutyronitrile are added and mixed, the temperature is raised to 55° C., the reaction is carried out for 10 minutes, the temperature is kept for 2 hours, and the pre-product is obtained by rotary evaporation; Further, the usage ratio of the compound, vinyltriethoxysilane, toluene, anhydrous ethanol, and azobisisobutyronitrile is 0.01-0.03 mol: 1.72-5.17 g: 20-30 mL: 20-30 mL: 0.005 g; Secondly, the carbon-carbon double bond of the compound is combined with the carbon-carbon double bond of vinyltriethoxysilane to synthesize the pre-product; Step A3: N-phenylmaleimide and benzoyl peroxide are dispersed uniformly in xylene, and then the pre-product is added and stirred uniformly. Under nitrogen protection, the mixture is heated to 90° C. for reaction for 4.5 hours, and the mixture is distilled under reduced pressure, cooled, washed, filtered, and dried in vacuum to obtain a modified antioxidant. Further, the usage ratio of N-phenylmaleimide, benzoyl peroxide, xylene, and pre-product is 3-5 g: 0.16 g: 70 mL: 5-10 g; Finally, the modified antioxidant was synthesized by copolymerizing the pre-product with the carbon-carbon double bond of N-phenylmaleimide.

[0007] The modified flame retardant is prepared by the following method: Step B1: p-Hydroxybenzaldehyde and chloroform are stirred under nitrogen protection, cooled to -6°C, and then hexachlorocyclotriphosphazene and triethylamine are added, and the temperature is raised to 60°C for reaction for 5 hours. When the temperature drops to room temperature, the mixture is washed, rotary evaporated, and dried at 60°C to obtain a compound; Further, the dosage ratio of p-hydroxybenzaldehyde, chloroform, hexachlorocyclotriphosphazene, and triethylamine is 3.66-7.32 g: 40-60 mL: 1.74-3.49 g: 0.08-0.12 mol; First, the chlorine atom of hexachlorocyclotriphosphazene reacts with the hydroxyl group of p-hydroxybenzaldehyde to synthesize the compound; Step B2: mixing the compound and dichloromethane under ultrasonic conditions, adding 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, mixing, reacting at 85° C. for 4 hours, and drying to obtain a modified flame retardant; Further, the usage ratio of the compound, dichloromethane, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is 0.01 mol: 5-20 mL: 30-31 g; The aldehyde group of the compound is then used to react with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to synthesize a modified flame retardant; A method for preparing a solvent-free polyurethane coating for a steel structure and a container, comprising the following steps: S1. Mix the polyol, defoamer, dispersant and leveling agent evenly, heat to 60°C, add pigment, heat to 120-180°C, dehydrate for 3-10h to obtain a mixture; S2. Add diphenylmethane diisocyanate to the mixture, react at 80°C for 2h, cool to 70°C, add modified anti-aging agent, modified flame retardant and defoaming agent, react for 0.5h, stir evenly, and obtain solvent-free polyurethane coating for steel structure and container.

[0008] Beneficial effects of the present invention: The solvent-free polyurethane coating for steel structures and containers of the present invention has good anti-aging effect, and also has excellent heat resistance and flame retardancy, thereby extending the service life of the material.

[0009] The modified anti-aging agent prepared by the present invention has the advantage of a macromolecular polymer and exhibits performance that exceeds that of a traditional small-molecule anti-aging agent. Hydroxybenzone in the modified anti-aging agent can form a hydrogen bond between its hydroxyl hydrogen and carbonyl oxygen to form a chelate ring. When irradiated by ultraviolet rays, the molecule undergoes thermal vibration, causing the electron excitation to transition to a high energy level, and then releases energy in the form of weak long-wave emission to resist the harm of high-energy ultraviolet rays. At the same time, the benzene ring and methoxy structure of oxybenzone can effectively absorb ultraviolet rays and convert them into harmless heat energy, synergizing with vinyl triethoxysilane to protect the material from ultraviolet damage; in addition, the maleimide group increases the glass transition temperature and melting point of the material by enhancing the intermolecular force, increases the rigidity and heat resistance of the molecular chain, and reduces the aging of the material caused by high-temperature thermal aging.

[0010] The modified flame retardant prepared by the invention has a good flame retardant effect. During the combustion process, hexachlorocyclotriphosphazene absorbs a large amount of heat, slows down the temperature rise of the material, and improves the flame retardant performance. At the same time, a glassy or stable foam covering layer is formed at a high temperature to insulate heat and oxygen and prevent the escape of flammable gases. In addition, the phosphorus and nitrogen main chains in the hexachlorocyclotriphosphazene show a conjugated effect, giving it excellent thermal stability and chemical stability, making it difficult to be oxidized and ring-opened. The phosphorus element forms a phosphoric acid or polyphosphoric acid protective film to isolate oxygen, and the nitrogen element releases non-flammable gas to dilute the combustion. The oxygen concentration at that time is further suppressed, and combustion is further suppressed; in addition, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, as a phosphaphenanthrene compound with high thermal stability, promotes the formation of a dense and continuous carbon layer during combustion, effectively isolates oxygen, blocks heat and combustible gas exchange, suppresses combustion, and also cooperates with the phosphorus oxygen double bond to achieve flame retardancy and prolong its service life; in addition, the modified flame retardant prepared by the present invention is halogen-free, helps to reduce pollution to the environment and damage to the ecosystem, is harmless to human health, and achieves sustainable development. DETAILED DESCRIPTION

[0011] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0012] Embodiment 1: A method for preparing a solvent-free polyurethane coating for steel structures and containers, comprising the following steps: S1. Weigh the raw materials by weight: 30 parts of polyol, 0.01 parts of defoamer, 0.1 parts of dispersant, 0.1 parts of leveling agent, 1 part of pigment, 20 parts of diphenylmethane diisocyanate, 0.1 parts of modified anti-aging agent (prepared in this example), and 0.1 parts of modified flame retardant (prepared in this example); mix BASF Sovermol 805, defoamer BYK-057, dispersant BYK-163 and leveling agent EFKA-3777 evenly, heat to 60° C., add barium sulfate, heat to 120° C., and dehydrate for 3 hours to obtain a mixture; S2, adding diphenylmethane diisocyanate to the mixture, reacting at 80°C for 2h, cooling to 70°C, adding modified anti-aging agent, modified flame retardant and defoaming agent, reacting for 0.5h, stirring evenly, and preparing solvent-free polyurethane coating for steel structure and container; The modified antioxidant is prepared by the following method: Step A1: 1.62 g of oxybenzone, 1.7 mL of triethylamine and 20 mL of tetrahydrofuran were mixed evenly, and then 1.12 g of acryloyl chloride was added dropwise under an ice bath for 1 h. The mixture was reacted under an ice bath for 5 h. After the reaction, the mixture was precipitated in ice water, washed, and dried under vacuum to obtain a compound; Step A2: 0.01 mol of the compound and 1.72 g of vinyltriethoxysilane were mixed evenly, and then 20 mL of toluene, 20 mL of anhydrous ethanol and 0.005 g of azobisisobutyronitrile were added and mixed, the temperature was raised to 55° C., the reaction was carried out for 10 min, the temperature was kept for 2 h, and the pre-product was obtained by rotary evaporation; Step A3: Disperse 3 g of N-phenylmaleimide and 0.16 g of benzoyl peroxide in 70 mL of xylene, add 5 g of the pre-product and stir evenly, heat to 90° C. under nitrogen protection for 4.5 h, distill under reduced pressure, cool, wash, filter, and vacuum dry to obtain a modified antioxidant; The modified flame retardant is prepared by the following method: Step B1: 3.66 g of p-hydroxybenzaldehyde and 40 mL of chloroform were stirred under nitrogen protection, cooled to -6°C, and then 1.74 g of hexachlorocyclotriphosphazene and 0.08 mol of triethylamine were added, and the temperature was raised to 60°C for reaction for 5 h. When the temperature dropped to room temperature, the mixture was washed, rotary evaporated, and dried at 60°C to obtain a compound; Step B2: 0.01 mol of the compound and 5 mL of dichloromethane were mixed under ultrasonic conditions, and 30 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide was added and mixed. The mixture was reacted at 85° C. for 4 h and dried to obtain a modified flame retardant.

[0013] Embodiment 2: A method for preparing a solvent-free polyurethane coating for steel structures and containers, comprising the following steps: S1. Weigh the raw materials by weight: 35 parts of polyol, 0.1 parts of defoamer, 0.3 parts of dispersant, 0.3 parts of leveling agent, 5.5 parts of pigment, 22.5 parts of diphenylmethane diisocyanate, 3 parts of modified anti-aging agent (prepared in this example), and 2 parts of modified flame retardant (prepared in this example); mix BASF Sovermol 805, defoamer BYK-057, dispersant BYK-163 and leveling agent EFKA-3777 evenly, heat to 60° C., add barium sulfate, heat to 150° C., and dehydrate for 6.5 hours to obtain a mixture; S2, adding diphenylmethane diisocyanate to the mixture, reacting at 80°C for 2h, cooling to 70°C, adding modified anti-aging agent, modified flame retardant and defoaming agent, reacting for 0.5h, stirring evenly, and preparing solvent-free polyurethane coating for steel structure and container; The modified antioxidant is prepared by the following method: Step A1: 4.86 g of oxybenzone, 3.1 mL of triethylamine and 25 mL of tetrahydrofuran were mixed evenly, and 3.37 g of acryloyl chloride was added dropwise under an ice bath for 1.5 h. The mixture was reacted under an ice bath for 5 h. After the reaction, the mixture was precipitated in ice water, washed and dried under vacuum to obtain a compound; Step A2: 0.02 mol of the compound and 3.45 g of vinyltriethoxysilane were mixed evenly, and then 25 mL of toluene, 25 mL of anhydrous ethanol and 0.005 g of azobisisobutyronitrile were added and mixed, the temperature was raised to 55° C., the reaction was carried out for 10 min, the temperature was kept for 2 h, and the pre-product was obtained by rotary evaporation; Step A3: Disperse 4 g of N-phenylmaleimide and 0.16 g of benzoyl peroxide in 70 mL of xylene, add 7.5 g of the pre-product and stir evenly, heat to 90° C. under nitrogen protection for 4.5 h, distill under reduced pressure, cool, wash, filter, and vacuum dry to obtain a modified antioxidant; The modified flame retardant is prepared by the following method: Step B1: 5.49 g of p-hydroxybenzaldehyde and 50 mL of chloroform were stirred under nitrogen protection, cooled to -6°C, and then 2.62 g of hexachlorocyclotriphosphazene and 0.1 mol of triethylamine were added, and the temperature was raised to 60°C for reaction for 5 h. When the temperature dropped to room temperature, the mixture was washed, rotary evaporated, and dried at 60°C to obtain a compound; Step B2: 0.01 mol of the compound and 12 mL of dichloromethane were mixed under ultrasonic conditions, and 30.5 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide was added and mixed. The mixture was reacted at 85° C. for 4 h and dried to obtain a modified flame retardant.

[0014] Embodiment 3: A method for preparing a solvent-free polyurethane coating for steel structures and containers, comprising the following steps: S1. Weigh the raw materials by weight: 40 parts of polyol, 0.2 parts of defoamer, 0.5 parts of dispersant, 0.5 parts of leveling agent, 10 parts of pigment, 25 parts of diphenylmethane diisocyanate, 5 parts of modified anti-aging agent (prepared in this example), and 3 parts of modified flame retardant (prepared in this example); mix BASF Sovermol 805, defoamer BYK-057, dispersant BYK-163 and leveling agent EFKA-3777 evenly, heat to 60° C., add barium sulfate, heat to 180° C., and dehydrate for 10 hours to obtain a mixture; S2, adding diphenylmethane diisocyanate to the mixture, reacting at 80°C for 2h, cooling to 70°C, adding modified anti-aging agent, modified flame retardant and defoaming agent, reacting for 0.5h, stirring evenly, and preparing solvent-free polyurethane coating for steel structure and container; The modified antioxidant is prepared by the following method: Step A1: 8.11 g of oxybenzone, 4.5 mL of triethylamine and 30 mL of tetrahydrofuran were mixed evenly, and then 5.62 g of acryloyl chloride was added dropwise under an ice bath for 2 h. The mixture was reacted under an ice bath for 5 h. After the reaction, the mixture was precipitated in ice water, washed, and dried under vacuum to obtain a compound; Step A2: 0.03 mol of the compound and 5.17 g of vinyltriethoxysilane were mixed evenly, and then 30 mL of toluene, 30 mL of anhydrous ethanol and 0.005 g of azobisisobutyronitrile were added and mixed, the temperature was raised to 55° C., the reaction was carried out for 10 min, the temperature was kept for 2 h, and the pre-product was obtained by rotary evaporation; Step A3: Disperse 5 g of N-phenylmaleimide and 0.16 g of benzoyl peroxide in 70 mL of xylene, add 10 g of the pre-product and stir evenly, heat to 90° C. under nitrogen protection for 4.5 h, distill under reduced pressure, cool, wash, filter, and vacuum dry to obtain a modified antioxidant; The modified flame retardant is prepared by the following method: Step B1: Stir 7.32 g of p-hydroxybenzaldehyde and 60 mL of chloroform under nitrogen protection, cool to -6°C, add 3.49 g of hexachlorocyclotriphosphazene and 0.12 mol of triethylamine, heat to 60°C for reaction for 5 h, wait until the temperature drops to room temperature, wash, rotary evaporate, and dry at 60°C to obtain a compound; Step B2: 0.01 mol of the compound and 20 mL of dichloromethane were mixed under ultrasonic conditions, and 31 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide was added and mixed. The mixture was reacted at 85° C. for 4 h and dried to obtain a modified flame retardant.

[0015] Comparative Example 1: This comparative example is a solvent-free polyurethane coating for steel structures and containers. The difference from Example 3 is that an equal amount of ultraviolet absorber UV531 is used to replace the modified anti-aging agent prepared in Example 3, and the rest is the same.

[0016] Comparative Example 2: This comparative example is a solvent-free polyurethane coating for steel structures and containers. The difference from Example 3 is that an equal amount of magnesium hydroxide is used to replace the modified flame retardant prepared in Example 3, and the rest is the same.

[0017] Performance test: The solvent-free polyurethane coating for steel structure and container prepared in Examples 1-3 and Comparative Examples 1-2 was applied to the template. After baking in an oven at 125°C for 48 hours, the coating was still well applied to the template surface without obvious deformation or falling off. A UVC-LED disinfection lamp (30W, 254nm wavelength) was used to irradiate at a vertical distance of 10cm for 40 hours, and the color difference before and after UVC-LED irradiation was detected according to the CIE1976L*a*b* standard. The samples were cut into standard test sizes and placed in a UV aging box at 60°C, 0.86w / cm2 , UV light for 1000h, test the difference in yellow index change, the larger the difference, the worse the anti-aging performance; GB / T2048-1996 plastic combustion performance test method was used to test vertical combustion performance; the test results are shown in the following table: Table 1

[0018] It can be seen from the test data in Table 1 that the solvent-free polyurethane coating for steel structures and containers prepared by the present invention has excellent aging resistance. It can also be seen from the above table that the solvent-free polyurethane coating for steel structures and containers prepared by the present invention has good heat resistance and flame retardant properties.

[0019] The above contents are merely examples and explanations of the concept of the present invention. The technicians in this technical field may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a solvent-free polyurethane coating for steel structures and containers, characterized in that: The specific steps include: S1. Weigh the raw materials by weight: 30-40 parts of polyol, 0.01-0.2 parts of defoamer, 0.1-0.5 parts of dispersant, 0.1-0.5 parts of leveling agent, 1-10 parts of pigment, 20-25 parts of diphenylmethane diisocyanate, 0.1-5 parts of modified anti-aging agent, and 0.1-3 parts of modified flame retardant; mix the polyol, defoamer, dispersant and leveling agent evenly, heat to 60°C, add pigment, heat to 120-180°C, dehydrate for 3-10 hours, and obtain a mixture; S2, adding diphenylmethane diisocyanate to the mixture, reacting at 80°C for 2h, cooling to 70°C, adding modified anti-aging agent, modified flame retardant and defoaming agent, reacting for 0.5h, stirring evenly, and preparing solvent-free polyurethane coating for steel structure and container; The modified antioxidant is prepared by the following method: Step A1: uniformly mix oxybenzone, triethylamine and tetrahydrofuran, then dropwise add acryloyl chloride in an ice bath for 1-2 hours, react in an ice bath for 5 hours, precipitate in ice water after the reaction, wash, and vacuum dry to obtain a compound; Step A2: the compound and vinyl triethoxysilane are mixed evenly, and then toluene, anhydrous ethanol and azobisisobutyronitrile are added and mixed, the temperature is raised to 55° C., the reaction is carried out for 10 minutes, the temperature is kept for 2 hours, and the pre-product is obtained by rotary evaporation; Step A3: Disperse N-phenylmaleimide and benzoyl peroxide evenly in xylene, add the pre-product and stir evenly, heat to 90°C under nitrogen protection for reaction for 4.5h, distill under reduced pressure, cool, wash, filter, and vacuum dry to obtain a modified antioxidant.

2. The method for preparing a solvent-free polyurethane coating for steel structures and containers according to claim 1, characterized in that: In step A1, the usage ratio of oxybenzone, triethylamine, tetrahydrofuran and acryloyl chloride is 1.62-8.11 g: 1.7-4.5 mL: 20-30 mL: 1.12-5.62 g.

3. The method for preparing a solvent-free polyurethane coating for steel structures and containers according to claim 1, characterized in that: In step A2, the usage ratio of the compound, vinyl triethoxysilane, toluene, anhydrous ethanol and azobisisobutyronitrile is 0.01-0.03 mol: 1.72-5.17 g: 20-30 mL: 20-30 mL: 0.005 g.

4. The method for preparing a solvent-free polyurethane coating for steel structures and containers according to claim 1, characterized in that: In step A3, the usage ratio of N-phenylmaleimide, benzoyl peroxide, xylene and pre-product is 3-5 g: 0.16 g: 70 mL: 5-10 g.

5. The method for preparing a solvent-free polyurethane coating for steel structures and containers according to claim 1, characterized in that: The modified flame retardant is prepared by the following method: Step B1: p-Hydroxybenzaldehyde and chloroform are stirred under nitrogen protection, cooled to -6°C, and then hexachlorocyclotriphosphazene and triethylamine are added, and the temperature is raised to 60°C for reaction for 5 hours. When the temperature drops to room temperature, the mixture is washed, rotary evaporated, and dried at 60°C to obtain a compound; Step B2: Mix the compound and dichloromethane under ultrasonic conditions, then add 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and mix, react at 85° C. for 4 hours, and dry to obtain a modified flame retardant.

6. The method for preparing a solvent-free polyurethane coating for steel structures and containers according to claim 5, characterized in that: In step B1, the usage ratio of p-hydroxybenzaldehyde, chloroform, hexachlorocyclotriphosphazene and triethylamine is 3.66-7.32 g: 40-60 mL: 1.74-3.49 g: 0.08-0.12 mol.

7. The method for preparing a solvent-free polyurethane coating for steel structures and containers according to claim 5, characterized in that: In step B2, the usage ratio of the compound, dichloromethane and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is 0.01 mol: 5-20 mL: 30-31 g.

8. The method for preparing a solvent-free polyurethane coating for steel structures and containers according to claim 1, characterized in that: The polyol is BASF Sovermol 805, the defoamer is defoamer BYK-057, the dispersant is dispersant BYK-163, and the leveling agent is leveling agent EFKA-3777.

9. A solvent-free polyurethane coating for steel structures and containers, characterized in that: Prepared according to the preparation method according to any one of claims 1 to 8.

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