Thiourea-graphene grafted chitosan modified polyurethane resin and preparation method thereof

Abstract

The invention relates to the technical field of corrosion prevention, and discloses thiourea-graphene grafted chitosan modified polyurethane resin, a graphene material can form a corresponding physical barrier layer between a metal substrate and an active graft, the coating defect of a polyurethane coating is filled, a corresponding protective film is formed, and the corrosion resistance of the coating is improved. The graphene material has excellent wear resistance and mechanical properties, lone pair electrons provided by amino and hydroxyl on chitosan and sulfur atoms and nitrogen atoms contained in thiourea can also provide lone pair electrons to adsorb metal, water and dissolved oxygen are prevented from diffusing inwards after film forming, the metal is protected, thiourea is grafted to chitosan, and the metal is protected. According to the present invention, the active adsorption center of the chitosan is increased, the graphene is grafted to the chitosan so as to avoid agglomeration, and after the graphene is compounded with the matrix polyurethane, the graphene can uniformly cover the metal substrate to form the compact protective film coating, such that the obtained coating material has excellent metal corrosion resistance.

Description

Technical Field

[0001] The invention relates to the technical field of anti-corrosion, in particular to a thiourea-graphene grafted chitosan modified polyurethane resin and a preparation method thereof. Background Art

[0002] Metal corrosion refers to a phenomenon in which metals are destroyed by the electrochemical and chemical effects of environmental media. This phenomenon exists in various fields and has caused huge losses to the national economy. It not only causes serious metal waste, but the treatment of waste metals generated each year has also become a complex problem. Applying an anti-corrosion coating on the metal surface has become a mainstream method. This coating includes organic or inorganic protective materials, which protect the metal by blocking water molecules and chloride ions in the surrounding environment. This method has the characteristics of simple operation, good anti-corrosion effect and can be used on a large scale. It is a method worthy of optimization and research.

[0003] Graphene, as a new type of inorganic nanomaterial, has high hydrophobicity, high strength and chemical corrosion resistance. It is a good film-forming material and additive with good metal corrosion protection. Chitosan, as a natural polymer material, is widely present in nature. It is cheap and green and environmentally friendly. It has excellent biocompatibility and adsorption film-forming properties. At the same time, it contains a large number of active groups on the surface. It is a good corrosion inhibitor raw material. Adding it to anti-corrosion coatings can effectively improve the corrosion resistance of the substrate. Thiourea, as a traditional pickling corrosion inhibitor, has a good metal corrosion inhibition effect. Polyurethane coatings have good wear resistance and toughness, excellent adhesion and chemical corrosion resistance. They are widely used in ships, oceans, construction and other fields. It is a coating with excellent performance. By adding corrosion inhibition ingredients and inorganic anti-corrosion materials, the corrosion resistance of the polyurethane matrix to the metal substrate can be effectively improved.

[0004] 1. Technical issues to be resolved In view of the deficiencies in the prior art, the present invention provides a thiourea-graphene grafted chitosan modified polyurethane resin and a preparation method, thereby improving the anti-corrosion performance of the polyurethane coating.

[0005] (II) Technical solution To achieve the above object, the present invention provides the following technical solution: a thiourea-graphene grafted chitosan modified polyurethane resin, the thiourea-graphene grafted chitosan modified polyurethane resin and the preparation method are as follows: (1) adding deionized water solvent, amino-modified graphene and adipaldehyde into a reactor, performing ultrasonic dispersion, reacting, and after the reaction is completed, filtering, washing with ethyl acetate and ethanol, and drying to obtain aldehyde-modified graphene; (2) adding deionized water solvent, carboxymethyl chitosan and aldehyde-modified graphene into a reactor, stirring and mixing, heating the reaction system to react, and after the reaction is completed, filtering, washing with deionized water, and drying to obtain graphene-grafted chitosan; (3) adding isopropanol solvent, graphene grafted chitosan and glycidol into the reactor, stirring and mixing, adding dicyclohexylcarbodiimide and 4-dimethylaminopyridine, mixing and reacting, filtering after the reaction, washing with saturated sodium bicarbonate, and drying to obtain epoxy-modified graphene grafted chitosan; (4) adding N,N-dimethylformamide solvent, epoxy-modified graphene grafted chitosan and thiourea into a reactor, heating, stirring and mixing, reacting, filtering after the reaction, washing with ethanol and deionized water, and drying to obtain thiourea-graphene grafted chitosan; (5) Add cyclohexanone solvent, polyurethane resin, thiourea-graphene grafted chitosan and leveling agent silicone resin into the reactor, stir and mix evenly, and let stand to obtain thiourea-graphene grafted chitosan modified polyurethane resin.

[0006] Preferably, in step (1), the mass ratio of deionized water, amination-modified graphene and adipaldehyde is 5000-8000:100:150-350.

[0007] Preferably, the reaction temperature in step (1) is 40-60° C., and the reaction time is 1-3 h.

[0008] Preferably, in step (2), the mass ratio of deionized water, carboxymethyl chitosan and aldehyde-modified graphene is 2000-4500:100:40-65.

[0009] Preferably, in step (3), the mass ratio of isopropanol, graphene-grafted chitosan, glycidol, dicyclohexylcarbodiimide and 4-dimethylaminopyridine is 1400-2500:100:20-40:15-35:4-8.

[0010] Preferably, the reaction temperature in step (3) is 15-30° C., and the reaction time is 5-10 h.

[0011] Preferably, in step (4), the mass ratio of N,N-dimethylformamide, epoxy-modified graphene grafted chitosan and thiourea is 1200-3000:100:260-400.

[0012] Preferably, the reaction temperature in step (4) is 50-70° C., and the reaction time is 12-24 h.

[0013] Preferably, in step (5), the mass ratio of cyclohexanone, polyurethane resin, thiourea-graphene grafted chitosan and silicone alkyd resin is 80-130:100:1-5.5:0.5-1.2.

[0014] 3. Beneficial technical effects Compared with the prior art, the present invention has the following beneficial technical effects: The invention discloses a thiourea-graphene grafted chitosan modified polyurethane resin. The amino groups on the aminated graphene and the aldehyde groups on the adipaldehyde undergo Schiff base reaction to obtain aldehyde-modified graphene. The amino groups on the carboxymethyl chitosan and the amino groups on the aldehyde-modified graphene undergo Schiff base reaction to obtain graphene-grafted chitosan. In a dichloromethane solvent, the carboxyl groups on the graphene-grafted chitosan and the hydroxyl groups on the glycidol undergo esterification reaction under the action of a condensation agent, dicyclohexylcarbodiimide, and a catalyst, 4-dimethylaminopyridine, to obtain epoxy-modified graphene-grafted chitosan. The epoxy groups on the epoxy-modified graphene-grafted chitosan and the amino groups on the thiourea undergo ring-opening reaction to obtain thiourea-graphene grafted chitosan. After being mixed with polyurethane, the thiourea-graphene grafted chitosan modified polyurethane resin is obtained.

[0015] The thiourea-graphene grafted chitosan modified polyurethane resin has good shielding properties and can effectively form a corresponding physical barrier layer between the metal substrate and the active graft. Due to the nano-size effect, it can effectively fill the coating defects of the polyurethane coating and form a corresponding protective film. It has good corrosion resistance, thereby preventing corrosion factors such as water and oxygen from contacting the metal surface and effectively protecting the metal substrate. At the same time, the excellent wear resistance and mechanical properties of the graphene material effectively improve the strength of the coating, thereby extending the service life of the coating. The lone pair electrons provided by the amino and hydroxyl groups on the chitosan have high electronegativity. It can form coordination bonds with empty orbitals of metal atoms or ions to achieve adsorption and has excellent corrosion inhibition performance. The sulfur atoms and nitrogen atoms contained in thiourea can also provide lone pairs of electrons and adsorb to metals. After film formation, it hinders the diffusion of water and dissolved oxygen into the interior and protects the metal. Thiourea is grafted onto chitosan to increase the active adsorption center of chitosan, which can better adsorb on the metal surface. Graphene is grafted onto chitosan to effectively avoid the agglomeration of graphene. After compounding with the matrix polyurethane, it can evenly cover the metal substrate to form a dense protective film coating. The resulting coating has excellent metal corrosion resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the structure of graphene grafted chitosan.

[0017] Figure 2 Schematic diagram of the structure of epoxy-modified graphene grafted chitosan.

[0018] Figure 3 It is a schematic diagram of the structure of thiourea-graphene grafted chitosan. DETAILED DESCRIPTION

[0019] To achieve the above object, the present invention provides the following specific implementation methods and examples: A method for preparing a thiourea-graphene grafted chitosan modified polyurethane resin is as follows: (1) adding deionized water solvent, amino-modified graphene and adipaldehyde in a mass ratio of 5000-8000:100:150-350 into a reactor, performing ultrasonic dispersion, reacting at 40-60° C. for 1-3 h. After the reaction is completed, filtering, washing with ethyl acetate and ethanol, and drying to obtain aldehyde-modified graphene; (2) adding deionized water solvent, carboxymethyl chitosan and aldehyde-modified graphene in a mass ratio of 2000-4500:100:40-65 into a reactor, stirring and mixing, heating the reaction system to react, and after the reaction is completed, filtering, washing with deionized water, and drying to obtain graphene-grafted chitosan; (3) adding isopropanol solvent, graphene grafted chitosan and glycidol to the reactor, stirring and mixing, adding dicyclohexylcarbodiimide and 4-dimethylaminopyridine, mixing, the mass ratio of the added isopropanol, graphene grafted chitosan, glycidol, dicyclohexylcarbodiimide and 4-dimethylaminopyridine is 1400-2500:100:20-40:15-35:4-8, reacting at 15-30°C for 5-10 hours, filtering after the reaction, washing with saturated sodium bicarbonate, and drying to obtain epoxy-modified graphene grafted chitosan; (4) Adding N,N-dimethylformamide solvent, epoxy-modified graphene grafted chitosan and thiourea in a mass ratio of 1200-3000:100:260-400 into a reactor, heating, stirring and mixing, reacting at 50-70° C. for 12-24 hours. After the reaction is completed, filtering, washing with ethanol and deionized water, and drying to obtain thiourea-graphene grafted chitosan; (5) Add cyclohexanone solvent, polyurethane resin, thiourea-graphene grafted chitosan and leveling agent silicone resin in a mass ratio of 80-130:100:1-5.5:0.5-1.2 into the reactor, stir and mix evenly, and let it stand to obtain thiourea-graphene grafted chitosan modified polyurethane resin.

[0020] Example 1

[0021] (1) adding deionized water solvent, amino-modified graphene and adipaldehyde in a mass ratio of 5000:100:150 into a reactor, performing ultrasonic dispersion, reacting at 40°C for 1 hour, and after the reaction, filtering, washing with ethyl acetate and ethanol, and drying to obtain aldehyde-modified graphene; (2) adding deionized water solvent, carboxymethyl chitosan and aldehyde-modified graphene in a mass ratio of 2000:100:40 into a reactor, stirring and mixing, heating the reaction system to react, and after the reaction is completed, filtering, washing with deionized water, and drying to obtain graphene-grafted chitosan; (3) adding isopropanol solvent, graphene grafted chitosan and glycidol to the reactor, stirring and mixing, adding dicyclohexylcarbodiimide and 4-dimethylaminopyridine, mixing, the mass ratio of the added isopropanol, graphene grafted chitosan, glycidol, dicyclohexylcarbodiimide and 4-dimethylaminopyridine is 1400:100:20:15:4, reacting at 15°C for 5 hours. After the reaction is completed, filtering, washing with saturated sodium bicarbonate, and drying to obtain epoxy-modified graphene grafted chitosan; (4) Adding N,N-dimethylformamide solvent, epoxy-modified graphene grafted chitosan and thiourea in a mass ratio of 1200:100:260 into the reactor, heating, stirring and mixing, reacting at 50°C for 12 hours. After the reaction, filtering, washing with ethanol and deionized water, and drying to obtain thiourea-graphene grafted chitosan; (5) Add cyclohexanone solvent, polyurethane resin, thiourea-graphene grafted chitosan and leveling agent silicone resin in a mass ratio of 80:100:1:0.5 into a reactor, stir and mix evenly, and let stand to obtain thiourea-graphene grafted chitosan modified polyurethane resin.

[0022] Example 2

[0023] (1) adding deionized water solvent, amino-modified graphene and adipaldehyde in a mass ratio of 5500:100:180 into a reactor, performing ultrasonic dispersion, reacting at 45°C for 1.5 hours. After the reaction, filtering, washing with ethyl acetate and ethanol, and drying to obtain aldehyde-modified graphene; (2) adding deionized water solvent, carboxymethyl chitosan and aldehyde-modified graphene in a mass ratio of 2500:100:45 into a reactor, stirring and mixing, heating the reaction system to react, and after the reaction is completed, filtering, washing with deionized water, and drying to obtain graphene-grafted chitosan; (3) adding isopropanol solvent, graphene grafted chitosan and glycidol to the reactor, stirring and mixing, adding dicyclohexylcarbodiimide and 4-dimethylaminopyridine, mixing, the mass ratio of the added isopropanol, graphene grafted chitosan, glycidol, dicyclohexylcarbodiimide and 4-dimethylaminopyridine is 1600:100:25:18:5, reacting at 20°C for 6 hours. After the reaction is completed, filtering, washing with saturated sodium bicarbonate, and drying to obtain epoxy-modified graphene grafted chitosan; (4) Adding N,N-dimethylformamide solvent, epoxy-modified graphene grafted chitosan and thiourea in a mass ratio of 1500:100:280 into the reactor, heating, stirring and mixing, reacting at 55°C for 14 hours. After the reaction, filtering, washing with ethanol and deionized water, and drying to obtain thiourea-graphene grafted chitosan; (5) Add cyclohexanone solvent, polyurethane resin, thiourea-graphene grafted chitosan and leveling agent silicone resin in a mass ratio of 95:100:2.5:0.6 into a reactor, stir and mix evenly, and let stand to obtain thiourea-graphene grafted chitosan modified polyurethane resin.

[0024] Example 3

[0025] (1) adding deionized water solvent, amino-modified graphene and adipaldehyde in a mass ratio of 6500:100:200 into a reactor, performing ultrasonic dispersion, reacting at 50°C for 2 hours, and after the reaction, filtering, washing with ethyl acetate and ethanol, and drying to obtain aldehyde-modified graphene; (2) adding deionized water solvent, carboxymethyl chitosan and aldehyde-modified graphene in a mass ratio of 3000:100:50 into a reactor, stirring and mixing, heating the reaction system to react, and after the reaction is completed, filtering, washing with deionized water, and drying to obtain graphene-grafted chitosan; (3) adding isopropanol solvent, graphene grafted chitosan and glycidol to the reactor, stirring and mixing, adding dicyclohexylcarbodiimide and 4-dimethylaminopyridine, mixing, the mass ratio of the added isopropanol, graphene grafted chitosan, glycidol, dicyclohexylcarbodiimide and 4-dimethylaminopyridine is 2000:100:30:24:6, reacting at 20°C for 8 hours. After the reaction is completed, filtering, washing with saturated sodium bicarbonate, and drying to obtain epoxy-modified graphene grafted chitosan; (4) Adding N,N-dimethylformamide solvent, epoxy-modified graphene-grafted chitosan and thiourea in a mass ratio of 2200:100:320 into the reactor, heating, stirring and mixing, reacting at 60°C for 18 hours. After the reaction is completed, filtering, washing with ethanol and deionized water, and drying to obtain thiourea-graphene-grafted chitosan; (5) Add cyclohexanone solvent, polyurethane resin, thiourea-graphene grafted chitosan and leveling agent silicone resin in a mass ratio of 105:100:3.5:0.8 into a reactor, stir and mix evenly, and let stand to obtain thiourea-graphene grafted chitosan modified polyurethane resin.

[0026] Example 4

[0027] (1) adding deionized water solvent, amino-modified graphene and adipaldehyde in a mass ratio of 7000:100:300 into a reactor, performing ultrasonic dispersion, reacting at 55°C for 2.5 hours. After the reaction, filtering, washing with ethyl acetate and ethanol, and drying to obtain aldehyde-modified graphene; (2) adding deionized water solvent, carboxymethyl chitosan and aldehyde-modified graphene in a mass ratio of 3800:100:55 into a reactor, stirring and mixing, heating the reaction system to react, and after the reaction is completed, filtering, washing with deionized water, and drying to obtain graphene-grafted chitosan; (3) adding isopropanol solvent, graphene grafted chitosan and glycidol to the reactor, stirring and mixing, adding dicyclohexylcarbodiimide and 4-dimethylaminopyridine, mixing, the mass ratio of the added isopropanol, graphene grafted chitosan, glycidol, dicyclohexylcarbodiimide and 4-dimethylaminopyridine is 2200:100:35:32:7, reacting at 25°C for 9 hours, filtering after the reaction, washing with saturated sodium bicarbonate, and drying to obtain epoxy-modified graphene grafted chitosan; (4) Adding N,N-dimethylformamide solvent, epoxy-modified graphene grafted chitosan and thiourea in a mass ratio of 2800:100:340 into the reactor, heating, stirring and mixing, reacting at 65°C for 20 hours. After the reaction is completed, filtering, washing with ethanol and deionized water, and drying to obtain thiourea-graphene grafted chitosan; (5) Add cyclohexanone solvent, polyurethane resin, thiourea-graphene grafted chitosan and leveling agent silicone resin in a mass ratio of 120:100:4:0.9 into a reactor, stir and mix evenly, and let stand to obtain thiourea-graphene grafted chitosan modified polyurethane resin.

[0028] Example 5

[0029] (1) adding deionized water solvent, amino-modified graphene and adipaldehyde in a mass ratio of 8000:100:350 into a reactor, performing ultrasonic dispersion, reacting at 60°C for 3 hours, and after the reaction, filtering, washing with ethyl acetate and ethanol, and drying to obtain aldehyde-modified graphene; (2) adding deionized water solvent, carboxymethyl chitosan and aldehyde-modified graphene in a mass ratio of 4500:100:65 into a reactor, stirring and mixing, heating the reaction system to react, and after the reaction is completed, filtering, washing with deionized water, and drying to obtain graphene-grafted chitosan; (3) adding isopropanol solvent, graphene grafted chitosan and glycidol to the reactor, stirring and mixing, adding dicyclohexylcarbodiimide and 4-dimethylaminopyridine, mixing, the mass ratio of the added isopropanol, graphene grafted chitosan, glycidol, dicyclohexylcarbodiimide and 4-dimethylaminopyridine is 2500:100:40:35:8, reacting at 30°C for 10 hours. After the reaction is completed, filtering, washing with saturated sodium bicarbonate, and drying to obtain epoxy-modified graphene grafted chitosan; (4) Adding N,N-dimethylformamide solvent, epoxy-modified graphene grafted chitosan and thiourea in a mass ratio of 3000:100:400 into the reactor, heating, stirring and mixing, reacting at 70°C for 24 hours. After the reaction is completed, filtering, washing with ethanol and deionized water, and drying to obtain thiourea-graphene grafted chitosan; (5) Add cyclohexanone solvent, polyurethane resin, thiourea-graphene grafted chitosan and leveling agent silicone resin in a mass ratio of 130:100:5.5:1.2 into a reactor, stir and mix evenly, and let stand to obtain thiourea-graphene grafted chitosan modified polyurethane resin.

[0030] Comparative Example 1 (1) adding deionized water solvent, amino-modified graphene and adipaldehyde in a mass ratio of 6500:100:250 into a reactor, performing ultrasonic dispersion, reacting at 50°C for 2 hours, and after the reaction, filtering, washing with ethyl acetate and ethanol, and drying to obtain aldehyde-modified graphene; (2) adding deionized water solvent, carboxymethyl chitosan and aldehyde-modified graphene in a mass ratio of 3200:100:50 into a reactor, stirring and mixing, heating the reaction system to react, and after the reaction is completed, filtering, washing with deionized water, and drying to obtain graphene-grafted chitosan; (3) Add cyclohexanone solvent, polyurethane resin, graphene grafted chitosan and leveling agent silicone alkyd resin in a mass ratio of 110:100:3:0.8 into a reactor, stir and mix evenly, and let stand to obtain graphene grafted chitosan modified polyurethane resin.

[0031] The coatings in the embodiments and comparative examples were coated on the surface of the metal aluminum substrate by dip coating, and dried and cured in air to obtain a sample coated with the composite coating. A standard three-electrode system was used, in which the working electrode was the sample coated with the composite coating, the reference electrode was a saturated calomel electrode, the counter electrode was a platinum electrode, and the test solution was a 3.5% NaCl solution. During the test, the scanning rate was 0.6 mV / s, the amplitude was 15 mV, and the frequency variation range was 10 -2 -10 5 Hz, at room temperature, the electrochemical test was carried out using a CHI660E electrochemical tester for 15 days.

[0032]

Claims

1. A thiourea-graphene grafted chitosan modified polyurethane resin, characterized in that: The thiourea-graphene grafted chitosan modified polyurethane resin and the preparation method are as follows: (1) adding deionized water solvent, amino-modified graphene and adipaldehyde into a reactor, performing ultrasonic dispersion, reacting, and after the reaction is completed, filtering, washing with ethyl acetate and ethanol, and drying to obtain aldehyde-modified graphene; (2) adding deionized water solvent, carboxymethyl chitosan and aldehyde-modified graphene into a reactor, stirring and mixing, heating the reaction system to react, and after the reaction is completed, filtering, washing with deionized water, and drying to obtain graphene-grafted chitosan; (3) adding isopropanol solvent, graphene grafted chitosan and glycidol into the reactor, stirring and mixing, adding dicyclohexylcarbodiimide and 4-dimethylaminopyridine, mixing and reacting, filtering after the reaction, washing with saturated sodium bicarbonate, and drying to obtain epoxy-modified graphene grafted chitosan; (4) adding N,N-dimethylformamide solvent, epoxy-modified graphene grafted chitosan and thiourea into a reactor, heating, stirring and mixing, reacting, filtering after the reaction, washing with ethanol and deionized water, and drying to obtain thiourea-graphene grafted chitosan; (5) Add cyclohexanone solvent, polyurethane resin, thiourea-graphene grafted chitosan and leveling agent silicone resin into the reactor, stir and mix evenly, and let stand to obtain thiourea-graphene grafted chitosan modified polyurethane resin.

2. A thiourea-graphene grafted chitosan modified polyurethane resin according to claim 1, characterized in that: In the step (1), the mass ratio of deionized water, amination-modified graphene and adipaldehyde is 5000-8000:100:150-350.

3. The thiourea-graphene grafted chitosan modified polyurethane resin according to claim 1, characterized in that: The reaction temperature in step (1) is 40-60° C. and the reaction time is 1-3 h.

4. The thiourea-graphene grafted chitosan modified polyurethane resin according to claim 1, characterized in that: In the step (2), the mass ratio of deionized water, carboxymethyl chitosan and aldehyde-modified graphene is 2000-4500:100:40-65.

5. The thiourea-graphene grafted chitosan modified polyurethane resin according to claim 1, characterized in that: In the step (3), the mass ratio of isopropanol, graphene-grafted chitosan, glycidol, dicyclohexylcarbodiimide and 4-dimethylaminopyridine is 1400-2500:100:20-40:15-35:4-8.

6. The thiourea-graphene grafted chitosan modified polyurethane resin according to claim 1, characterized in that: The reaction temperature in step (3) is 15-30°C and the reaction time is 5-10h.

7. The thiourea-graphene grafted chitosan modified polyurethane resin according to claim 1, characterized in that: In the step (4), the mass ratio of N,N-dimethylformamide, epoxy-modified graphene grafted chitosan and thiourea is 1200-3000:100:260-400.

8. The thiourea-graphene grafted chitosan modified polyurethane resin according to claim 1, characterized in that: The reaction temperature in step (4) is 50-70° C. and the reaction time is 12-24 h.

9. The thiourea-graphene grafted chitosan modified polyurethane resin according to claim 1, characterized in that: In the step (5), the mass ratio of cyclohexanone, polyurethane resin, thiourea-graphene grafted chitosan and silicone alkyd resin is 80-130:100:1-5.5:0.5-1.2.

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