A bio-based coating and a preparation method thereof

Abstract

The present invention relates to a bio-based coating and a preparation method thereof. Specifically, the present invention provides a bio-based coating, which is composed of the following components: 40-50 parts of bio-based polyurethane, 20-30 parts of chitosan-modified graphene oxide, 1-3 parts of surfactant, 1-2 parts of leveling agent, and 50 parts of solvent. Wherein the bio-based polyurethane is synthesized by condensation of castor oil, diphenylmethane-4,4'-diisocyanate and 2,6-diaminopyridine. The present invention synthesizes bio-based polyurethane by condensation of castor oil, diphenylmethane-4,4'-diisocyanate and 2,6-diaminopyridine, and a large number of cross-linked hydrogen bonds can be formed between the urea groups contained in the obtained bio-based polyurethane, which has good mechanical strength and self-repairing function, and chitosan-modified graphene oxide is added to the coating. On the one hand, chitosan can prevent graphene oxide from self-aggregating in the coating, and on the other hand, the addition of graphene oxide significantly improves the mechanical properties and antifouling properties of the coating.

Description

Technical Field

[0001] The invention relates to a bio-based coating, and in particular to an anti-fouling self-repairing coating and a preparation method and application thereof. Background Art

[0002] When a ship is sailing on the ocean, various microorganisms or crustaceans in the ocean will attach to the bottom of the hull and the corrosion of seawater will cause serious damage to the hull in the long run. The above problems can be effectively solved by using paint to form a special anti-corrosion coating on the surface of the ship. However, with the development of my country's shipbuilding industry and increasingly stringent environmental protection regulations, the requirements for ship coatings are no longer just focused on the protective performance of the hull as in the past. At present, the requirements for ship coatings are already multifaceted, including anti-corrosion and rust prevention, durability, environmental protection, safety, and compliance with international standards.

[0003] At present, the commonly used traditional coatings are copper-based or organic tin-containing antifouling coatings. However, the antifouling agents in the above coatings, such as cuprous oxide and Dyson zinc, will be released into the ocean during use, which is very toxic to marine life and damages the ecological environment. In recent years, environmentally friendly silicone and organic fluorine antifouling coatings have been gradually developed. Although they basically do not contain antifouling agents or contain a small amount of antifouling agents, they are relatively expensive, have low mechanical strength and are easily damaged, which limits the promotion and use of corresponding products.

[0004] Therefore, based on the shortcomings and limited applications of conventional antifouling coatings, it is particularly important to develop a new type of environmentally friendly coating. Summary of the invention

[0005] One of the purposes of the present invention is to provide a bio-based coating, which has the characteristics of being green, environmentally friendly, corrosion-resistant, long-lasting, and self-repairing. It can be used as a ship coating, has a synergistic effect between the components, has a stable use effect, and has excellent anti-fouling performance.

[0006] To achieve the above purpose, the present invention provides the following technical solution, wherein the bio-based coating is composed of the following components: 40-50 parts of bio-based polyurethane, 20-30 parts of chitosan-modified graphene oxide, 1-3 parts of surfactant, 1-2 parts of leveling agent, and 50 parts of solvent.

[0007] In the above scheme, the bio-based polyurethane is synthesized by condensation of castor oil, diphenylmethane-4,4'-diisocyanate and 2,6-diaminopyridine.

[0008] In the above scheme, the solvent is specifically selected from a mixture of water and ethanol.

[0009] In the above scheme, the leveling agent is specifically selected from at least one of polydimethylsiloxane, polymethylphenylsiloxane, acrylic resin or urea-formaldehyde resin.

[0010] In the above scheme, the surfactant is specifically selected from at least one of sodium dodecyl sulfate, sodium dodecyl sulfonate, and fatty alcohol polyoxyethylene ether.

[0011] In the above scheme, the bio-based coating is composed of the following ingredients: 45 parts of bio-based polyurethane, 25 parts of chitosan-modified graphene oxide, 2 parts of surfactant, 1 part of leveling agent, and 50 parts of solvent.

[0012] Another object of the present invention is to provide a method for preparing a bio-based coating, the specific steps of which are:

[0013] S1: Preparation of bio-based polyurethane: castor oil and solvent anhydrous tetrahydrofuran are added to a reactor equipped with a stirrer and stirred to mix. When the temperature rises to 45-50°C, diphenylmethane-4,4'-diisocyanate is slowly added to the reactor, the temperature is maintained at 60-65°C, and the reaction is carried out for 4 hours; then the temperature is cooled to room temperature, 2,6-diaminopyridine is slowly added dropwise, and the reaction is stirred at room temperature for 12 hours in a N2 atmosphere; finally, the reaction mixture is poured into an evaporating dish and allowed to stand at room temperature for 8 hours to evaporate the solvent, and then dried in a vacuum oven at 40°C for 6 hours to obtain bio-based polyurethane;

[0014] S2: Preparation of chitosan-modified graphene oxide: graphene oxide powder was dispersed in deionized water and ultrasonicated for 30 minutes to obtain a suspension, chitosan was dissolved in acetic acid and added to the suspension and stirred for 2 hours; the solution after the reaction was filtered and centrifuged to obtain a solid, which was washed several times with an acetic acid solution and dried to obtain chitosan-modified graphene oxide powder;

[0015] S3: Preparation of bio-based coating: chitosan-modified graphene oxide powder is uniformly dispersed in a water / ethanol mixed solvent, bio-based polyurethane, surfactant and leveling agent are added to the above solution, and the bio-based coating is prepared by stirring at room temperature for 3 hours.

[0016] In the above solution, the bio-based coating is applied to the protective coating of the ship.

[0017] In the above scheme, chitosan-modified graphene oxide refers to the grafting reaction of graphene oxide carboxyl groups with chitosan amino groups, and the reaction process is as follows:

[0018]

[0019] The reaction process of bio-based polyurethane in the above scheme is as follows

[0020]

[0021] The beneficial effects brought about by the technical solution provided by the present invention include at least:

[0022] 1. Castor oil is used as a bio-based polyol to replace conventional commercial petroleum-based polyols as a chain extender and condensed with diphenylmethane-4,4'-diisocyanate and 2,6-diaminopyridine to synthesize bio-based polyurethane. The mechanical properties of the obtained polyurethane are significantly improved. At the same time, castor oil contains double bonds, which can cross-link in the presence of oxygen, accelerate the curing reaction, and thus increase the hardness of the coating.

[0023] 2. A large number of cross-linking hydrogen bonds can be formed between the urea groups contained in bio-based polyurethane. After scratches occur, hydrogen bonds can be quickly formed between polyurethane molecules, enabling the coating to self-repair at room temperature.

[0024] 3. In the present invention, the carboxyl groups of graphene oxide and the amino groups of chitosan are grafted and modified. Chitosan can effectively reduce the aggregation of graphene oxide. Both graphene and chitosan contain abundant oxygen-containing groups, which can form hydrogen bonds with polyurethane molecular chains, which is conducive to the uniform dispersion of graphene oxide in bio-based polyurethane. The introduction of chitosan-modified graphene oxide improves the tensile strength and antifouling performance of the coating. DETAILED DESCRIPTION

[0025] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be described in further detail below.

[0026] Embodiment 1:

[0027] S1: Preparation of bio-based polyurethane: 10 parts of castor oil and 100 ml of anhydrous tetrahydrofuran solvent are added to a reactor equipped with a stirrer and stirred and mixed. When the temperature rises to 45-50°C, 30 parts of diphenylmethane-4,4'-diisocyanate are slowly added to the reactor, the temperature is maintained at 60-65°C, and the reaction is carried out for 4 hours; then the temperature is cooled to room temperature, 20 parts of 2,6-diaminopyridine are slowly added dropwise, and the reaction is stirred at room temperature for 12 hours in a N2 atmosphere; finally, the reaction mixture is poured into an evaporating dish and allowed to stand at room temperature for 8 hours to evaporate the solvent, and then dried in a vacuum oven at 40°C for 6 hours to obtain bio-based polyurethane;

[0028] S2: Preparation of chitosan-modified graphene oxide: 10 parts of graphene oxide powder were dispersed in deionized water and ultrasonicated for 30 minutes to obtain a suspension, 30 parts of chitosan were dissolved in acetic acid and added to the suspension and stirred for 2 hours; the solution after the reaction was centrifuged to obtain a solid, which was washed several times with an acetic acid solution and dried to obtain chitosan-modified graphene oxide powder;

[0029] S3: Preparation of bio-based coating: Chitosan-modified graphene oxide powder was uniformly dispersed in a water / ethanol (volume ratio 1:1) mixed solvent, bio-based polyurethane, surfactant, and leveling agent were added to the above solution, and stirred at room temperature for 3 hours to obtain the bio-based coating. The amount of each component is shown in Table 1

[0030] Examples 2 to 5 provide a series of bio-based coatings, the component amounts of which are shown in Table 1, and the preparation steps are the same as in Example 1.

[0031] Table 1 Dosage of different sample components

[0032]

[0033]

[0034] Examples 6 to 10 provide a series of bio-based coatings, the component amounts of which are shown in Table 2, and the preparation steps are the same as those of Example 1.

[0035] Table 2 Dosages of different sample components

[0036]

[0037] Comparative Example

[0038] The amounts of the components and the preparation steps in Comparative Example 1 are substantially the same as those in Example 8, except that the graphene oxide in Comparative Example 1 is not modified.

[0039] The amounts of the components and the preparation steps in Comparative Example 2 are substantially the same as those in Example 8, except that the bio-based polyurethane synthesis process in Comparative Example 2 does not include 2,6-diaminopyridine.

[0040] Performance Testing

[0041] Self-healing performance:

[0042] The coating was applied to the surface of the substrate and allowed to dry to form a coating. A 2 cm long crack was scratched on the surface of the coating using a surgical blade and placed at room temperature for 24 hours to observe the self-healing process. If more than 80% of the scratches on the sample were repaired, the self-healing performance of the sample was evaluated as excellent, if 50%-80% of the scratches on the sample were repaired, the self-healing performance of the sample was evaluated as medium, and if less than 50% of the scratches on the sample were repaired, the self-healing performance of the sample was evaluated as poor.

[0043] As shown in Table 3

[0044] Table 3 Self-healing performance of different samples after 24 hours

[0045]

[0046]

[0047] Mechanical strength test

[0048] The coating was applied to the surface of the substrate and allowed to dry to form a coating. The mechanical properties of the coating were tested, including tensile strength and elongation at break. The test method was based on GB / T10654 Determination of tensile strength and elongation at break of polymer porous elastic materials. As shown in Table 4

[0049] Table 4 Mechanical strength of different samples

[0050] Tensile Strength Elongation at break Example 3 44.2Mpa 722％ Example 6 16.1Mpa 577％ Example 7 42.7Mpa 718％ Example 8 45.3Mpa 741％ Example 9 45.1Mpa 735％ Example 10 44.9Mpa 711％ Comparative Example 1 40.0Mpa 704％

[0051] Anti-fouling grade test

[0052] The test method is in accordance with GB / T 9780-2013, and the grade classification is in accordance with HG / T4756-2014

[0053] Table 5 Anti-fouling grade of different samples

[0054] Stain resistance level Example 3 Level 1 Example 8 Level 1 Comparative Example 2 Coating damage

[0055] It can be seen from the above experimental data that the present invention introduces urea groups into bio-based polyurethane by selecting 2,6-diaminopyridine, and a large number of cross-linked hydrogen bonds can be formed between the urea groups so that the coating has a self-repairing function, which greatly improves the service life of the coating. By comparing Examples 1-5 and Comparative Example 2, it can be seen that when the number of components in the coating is further limited within the scope of the present invention, its self-repairing performance is best. By comparing Examples 3, 6-10 and Comparative Example 1, it can be seen that the lack of chitosan-modified graphene oxide or the change in the number of components in the present invention will affect the mechanical properties of the coating. The introduction of chitosan-modified graphene oxide improves the tensile strength and elongation at break of the coating, achieving the purpose of strengthening and toughening at the same time, and has good antifouling performance.

[0056] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A bio-based coating, characterized in that: The bio-based coating is composed of the following ingredients: 40-50 parts of bio-based polyurethane, 20-30 parts of chitosan-modified graphene oxide, 1-3 parts of surfactant, 1-2 parts of leveling agent, and 50 parts of solvent; Preparation of the bio-based polyurethane: castor oil and anhydrous tetrahydrofuran solvent are added to a reaction kettle equipped with a stirrer and stirred and mixed, diphenylmethane-4,4'-diisocyanate is slowly added to the reaction kettle when the temperature rises to 45-50°C, the temperature is maintained at 60-65°C, and the reaction is carried out for 4 hours; then the temperature is lowered to room temperature, 2,6-diaminopyridine is slowly added dropwise, and the reaction is stirred at room temperature for 12 hours in a N2 atmosphere; finally, the reaction mixture is poured into an evaporating dish, left to stand at room temperature for 8 hours to evaporate the solvent, and dried in a vacuum oven at 40°C for 6 hours to obtain the bio-based polyurethane; The preparation of the chitosan-modified graphene oxide is as follows: graphene oxide powder is dispersed in deionized water and ultrasonicated for 30 minutes to obtain a suspension, chitosan is dissolved in acetic acid and added to the suspension and stirred for 2 hours; the solution after the reaction is centrifuged to obtain a solid, which is washed several times with an acetic acid solution and then dried to obtain chitosan-modified graphene oxide powder; the solvent is selected from a mixture of water and ethanol.

2. The bio-based coating according to claim 1, characterized in that The leveling agent is selected from at least one of polydimethylsiloxane, polymethylphenylsiloxane, acrylic resin or urea-formaldehyde resin.

3. The bio-based coating according to claim 1, characterized in that The surfactant is selected from at least one of sodium lauryl sulfate, sodium lauryl sulfonate, and fatty alcohol polyoxyethylene ether.

4. The bio-based coating according to claim 1, characterized in that The bio-based coating consists of the following ingredients: 45 parts of bio-based polyurethane, 25 parts of chitosan-modified graphene oxide, 2 parts of surfactant, 1 part of leveling agent, and 50 parts of solvent.

5. The method for preparing the bio-based coating according to any one of claims 1 to 4, characterized in that: Preparation of the bio-based coating: chitosan-modified graphene oxide powder is uniformly dispersed in the solvent, bio-based polyurethane, surfactant and leveling agent are added to the solution, and the bio-based coating is prepared by stirring at room temperature for 3 hours.

6. The use of the bio-based coating according to any one of claims 1 to 4, characterized in that: The bio-based coating is applied as a protective coating on ships.

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