A transparent, self-lubricating, organosilicon hybrid antifouling coating with a negatively charged surface and its preparation method.

Abstract

This invention belongs to the field of marine antifouling, and specifically relates to a transparent, self-lubricating organosilicon hybrid antifouling coating with a negatively charged surface and its preparation method. The antifouling coating is obtained by a sol-gel reaction of modified nanocellulose, hydroxy acid, and functional fluorine / siloxane monomers; the mass ratio of the hydroxy acid to the modified nanocellulose is 10–100:1; the mass ratio of the functional fluorine / siloxane monomer to the modified nanocellulose is 10–300:1. This invention, based on a multi-element green antifouling strategy, constructs a material surface with negative charge, self-lubrication, and low surface energy. The prepared antifouling coating exhibits excellent transparency, mechanical properties, and static antifouling performance. This antifouling coating is environmentally friendly and has broad application prospects in the field of marine antifouling.

Description

Technical Field

[0001] This invention belongs to the field of marine antifouling, and specifically relates to a transparent, self-lubricating organosilicon hybrid antifouling coating with a negatively charged surface and its preparation method. Background Technology

[0002] Biofouling refers to the undesirable deposition of microfouling organisms (such as bacteria and microalgae) and macrofouling organisms (such as hydra, barnacles, and large algae) on the surfaces of marine industrial facilities. Biofouling can affect the normal operation of coastal (nuclear) power plants, ship navigation, and various marine operating platforms, causing serious losses to my country's national economic development.

[0003] For a long time, antifouling coatings have been the most widely used and simplest antifouling technology applied to the surfaces of marine underwater facilities. Since the International Maritime Organization (IMO) completely banned the use of organotin antifouling paints in 2008, Wuxi self-polishing antifouling coating (TF-SPC) has dominated the domestic and international antifouling coating market. However, TF-SPC resin hydrolysis in seawater forms microplastic components, and the released Cu2O can cause copper accumulation and environmental problems. Therefore, TF-SPC will gradually be restricted.

[0004] Fouling-releasing silicone-based antifouling coatings without biocides have received widespread attention in recent years due to their chemical stability, high elasticity, and low surface energy (<25 mJ / m²). 2 With its smooth surface and other characteristics, silicone-based antifouling coatings are difficult for fouling organisms to adhere to, or their adhesion is weak, making them a good, green approach to solving fouling problems. However, in low-velocity seawater environments, silicone-based antifouling coatings cannot remove the slime layer secreted by diatoms and bacteria, resulting in poor antifouling performance on static underwater facilities. Furthermore, silicone-based antifouling coatings are generally elastomers with low mechanical strength, making them easily damaged by debris in the water, thus reducing their service life and limiting their application.

[0005] Researchers have discovered that uronic acid, pyruvate, and various acyl-containing components in the extracellular polymeric matrix (EPS) secreted by bacteria and other microorganisms result in an overall negative charge on the EPS, promoting the attachment or adsorption of bacteria and other microorganisms to the substrate surface. Therefore, theoretically, it is possible to construct negatively charged surfaces based on repulsive interactions to inhibit microbial attachment or biofilm formation.

[0006] In addition, inspired by the antifouling properties of mucus secreted by organisms such as dolphins and earthworms, researchers have developed a biomimetic silicone antifouling coating by infusing silicone oil lubricant into polymer resin and releasing the lubricant continuously through the osmotic pressure of flowing seawater. This achieves a highly smooth and antifouling surface. However, silicone oil lubricant releases too quickly in a fluid environment and is prone to rapid loss, and its release may also have potential adverse effects on the marine environment. Therefore, the antifouling lifespan and environmental friendliness of this type of coating in marine environments still need further investigation. Summary of the Invention

[0007] To address the issue that current single green antifouling strategies cannot meet the requirements for the broad spectrum and long-lasting effect of silicone-based antifouling coatings, this invention provides a transparent, self-lubricating silicone hybrid antifouling coating with a negatively charged surface and its preparation method.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A transparent, self-lubricating, organosilicon hybrid antifouling coating with a negatively charged surface is obtained by a sol-gel reaction of modified nanocellulose, hydroxy acid, and functional fluorine / siloxane monomer; the mass ratio of the hydroxy acid to the modified nanocellulose is 10-100:1; the mass ratio of the functional fluorine / siloxane monomer to the modified nanocellulose is 10-300:1.

[0010] The modified nanocellulose is prepared by surface chemical grafting modification of carboxylated nanocellulose dispersed in an organic solvent using a lubricant under catalytic conditions, wherein the mass ratio of lubricant, carboxylated nanocellulose and catalyst is 1-20:1:0.01-0.4.

[0011] The carboxylated nanocellulose is prepared by oxidizing one or more of cellulose nanocrystals, cellulose nanofibers, and bacterial cellulose dispersed in water using 2,2,6,6-tetramethylpiperidine oxide (TEMPO), NaBr, and NaClO solution with an effective chlorine content of 14.5% at a pH of around 10. The mass ratio of TEMPO, NaBr to nanocellulose is 3-5:1:9-15.

[0012] The lubricant is one or more of the following: hydroxyl-terminated polysiloxanes of different molecular weights, hydroxyl-terminated polytrifluoropropylmethylsiloxanes, and castor oil.

[0013] The general formula for hydroxyl-terminated polysiloxane structural units is as follows:

[0014]

[0015] Where n is a natural number greater than 1;

[0016] The general formula of the hydroxyl-terminated polytrifluoropropylmethylsiloxane structural unit is as follows:

[0017] Where m is a natural number greater than 1.

[0018] The hydroxyl-terminated polysiloxane has a molecular weight of 1,000 to 20,000; the hydroxyl-terminated polytrifluoropropylmethylsiloxane has a molecular weight of 1,000 to 30,000.

[0019] Preferably, the hydroxyl-terminated polysiloxane is α,ω-dihydroxypolydimethylsiloxane with a molecular weight of 1000 to 20000.

[0020] Preferably, the hydroxyl-terminated polysiloxane is α,ω-dihydroxypolytrifluoropropylmethylsiloxane with a molecular weight of 1000 to 30000.

[0021] The catalyst is one or more of tin isooctanoate, stannous octanoate, tetrabutyl titanate, and dibutyltin dilaurate;

[0022] The hydroxy acid has a chemical structure that contains both hydroxyl and carboxyl groups.

[0023] The hydroxy acid is one or more of the following: cholic acid, glycyrrhetinic acid, citric acid, lactic acid, tartaric acid, salicylic acid, malic acid, gallic acid, and uronic acid (including D-glucuronic acid, D-mannuronic acid, D-galacturonic acid, L-iduronic acid, L-guluronic acid, etc.).

[0024] The functional fluoro / siloxane monomer is one or more of the following fluoro / silane monomers with trimethoxy or triethoxy end groups: tetraethyl orthosilicate, trimethoxysilane, methyltrimethoxysilane, octyltrimethoxysilane, dodecyltrimethoxysilane, octadecyltrimethoxysilane, n-octyltriethoxysilane, n-dodecyltriethoxysilane, n-octadecyltriethoxysilane, (3,3,3-trifluoropropyl)trimethoxysilane, tridecafluorooctyltrimethoxysilane, heptadecylfluorodecyltriethoxysilane, etc.

[0025] A method for preparing the aforementioned negatively charged transparent self-lubricating organosilicon hybrid antifouling coating:

[0026] Modified nanocellulose, hydroxy acid, and functional fluorine / siloxane monomers were dissolved in an organic solvent according to the above proportions. After thorough mixing, acid (HCl) was added to catalyze and adjust the pH to about 3. After a sol-gel reaction at room temperature for 24 hours, the mixture was drop-coated onto a substrate and cured at room temperature to obtain a hybrid antifouling coating.

[0027] To elaborate further:

[0028] Step 1: First, take a certain amount of unmodified nanocellulose (cellulose nanocrystals, cellulose nanofibers, or bacterial cellulose) and disperse it in deionized water. Sonicate at room temperature for a period of time until completely homogeneous. Then, add an aqueous solution containing NaBr and TEMPO to the dispersion and stir for a period of time. Subsequently, add a NaClO solution with an effective chlorine content of 14.5% dropwise, and adjust the pH of the entire solution system to approximately 10 with 0.5M NaOH. When the pH no longer changes, add 0.5M HCl until the solution becomes turbid. Centrifuge at high speed several times and freeze-dry to obtain carboxylated nanocellulose.

[0029] Step 2: Prepare a 1 wt% DMF dispersion of carboxylated nanocellulose and sonicate it until homogeneous. Then add an excess of lubricant and a small amount of catalyst to the dispersion and stir at 90°C for 6 hours. After the reaction is complete, centrifuge and dialyze to remove residual catalyst and unreacted lubricant to obtain modified nanocellulose.

[0030] Step 3: Dissolve a certain mass ratio of modified nanocellulose, hydroxy acid and functional fluorine / siloxane monomer in THF, stir thoroughly for 1 hour, then add a certain amount of HCl for catalysis, and after the sol-gel reaction at room temperature for 24 hours, drop-coat onto different substrates, and cure at room temperature for a period of time to obtain a hybrid antifouling coating.

[0031] Application of the aforementioned negatively charged transparent self-lubricating silicone hybrid antifouling coating in the field of marine antifouling.

[0032] Beneficial effects of the present invention

[0033] This invention relates to a transparent, self-lubricating organosilicon hybrid antifouling coating with a negatively charged surface, based on a multi-element green antifouling strategy. This coating constructs a material surface with negative charge, self-lubrication, and low surface energy. The prepared antifouling coating exhibits excellent transparency, mechanical properties, and static antifouling performance. The antifouling coating of this invention is environmentally friendly, pollution-free, uses readily available raw materials, is simple to prepare, highly practical, and easy to promote. Specifically:

[0034] (1) The transparent, self-lubricating, organosilicon hybrid antifouling coating with a negatively charged surface of the present invention introduces modified nanocellulose components into the hybrid network by forming chemical bonds, and fully covalently bonds with other functional components at the nanoscale and molecular scale. The prepared coating has good light transmittance, with a visible light transmittance of more than 95%. At the same time, the coating also has excellent mechanical properties (including hardness and flexibility). The pencil hardness of the coating can reach 7H while the flexibility is 2mm.

[0035] (2) This invention prepares a transparent, self-lubricating organosilicon hybrid antifouling coating with a negatively charged surface based on a multi-component, green antifouling strategy. A multi-component, multi-scale hybrid approach is used to construct a material surface with negative charge, self-lubrication, and low surface energy properties by reacting hydroxy acids, modified nanocellulose, and functional fluorinated / siloxane monomers through a sol-gel reaction. The modified nanocellulose component imparts self-lubricating properties to the coating surface, the hydroxy acid component imparts negative charge, and the functional fluorinated / siloxane monomer imparts low surface energy. Therefore, by simultaneously controlling the physical properties of surface charge, lubricity, and surface energy, this invention significantly enhances the static antifouling capability of organosilicon-based coatings, providing a new design concept and technical foundation for developing long-lasting, durable, and green broad-spectrum antifouling coatings.

[0036] (3) The transparent self-lubricating organosilicon hybrid antifouling coating with negative surface charge based on the multi-element green antifouling strategy of the present invention is green and environmentally friendly, the raw materials are readily available, it is highly practical, the preparation process is simple and efficient, it has universality and is easy to promote. Attached Figure Description

[0037] Figure 1 Infrared spectrum of modified nanocellulose provided by the present invention (Example 1).

[0038] Figure 2 SEM image of modified nanocellulose provided for this invention (Example 1).

[0039] Figure 3 Infrared spectrum of the transparent self-lubricating organosilicon hybrid antifouling coating with negatively charged surface provided by the present invention (Example 1).

[0040] Figure 4 An appearance diagram of the transparent, self-lubricating, silicone hybrid antifouling coating with a negatively charged surface provided by the present invention.

[0041] Figure 5 Visible light transmittance of the transparent, self-lubricating, silicone hybrid antifouling coating with a negatively charged surface provided by the present invention. Detailed Implementation

[0042] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0043] The present invention provides a transparent, self-lubricating organosilicon hybrid antifouling coating with a negatively charged surface, constructed using a multi-component and multi-scale hybrid approach. Furthermore, the nanocellulose surface exposes a large number of active hydroxyl groups, allowing for the chemical modification of the nanocellulose surface using a lubricating agent. Subsequently, the modified nanocellulose with lubricating properties is chemically bonded to the organosilicon hybrid network to construct a self-lubricating antifouling surface without external lubricant release. This results in a material surface with negative charge, self-lubrication, and low surface energy properties. By simultaneously controlling the physical properties of the material surface charge, lubricity, and surface energy, the antifouling capability of the organosilicon-based coating is comprehensively enhanced.

[0044] The specific preparation method is as follows: First, carboxylated nanocellulose is prepared by TEMPO oxidation. Then, different lubricants are used to chemically modify the surface of the carboxylated nanocellulose to obtain modified nanocellulose. Finally, the modified nanocellulose, hydroxy acid, and functional fluorine / siloxane monomers are reacted via sol-gel and cured at room temperature. This invention presents a negatively charged, transparent, self-lubricating organosilicon hybrid antifouling coating based on a multi-element green antifouling strategy. This coating constructs a material surface with negative charge, self-lubrication, and low surface energy. The prepared antifouling coating exhibits excellent transparency, mechanical properties, and static antifouling performance. This antifouling coating is environmentally friendly and has broad application prospects in the field of marine antifouling.

[0045] This invention improves the static antifouling ability of low surface energy silicone antifouling coatings while exhibiting excellent transparency and mechanical properties. Specifically, a multi-component and multi-scale hybrid approach is used to construct a material surface with negative charge, self-lubrication, and low surface energy properties by reacting hydroxy acids, modified nanocellulose, and functional fluorinated / siloxane monomers through a sol-gel reaction. The resulting coating has good light transmittance, with a visible light transmittance greater than 95%, and also possesses excellent mechanical properties, achieving a pencil hardness of 8H. Furthermore, by simultaneously controlling the physical properties of the material's surface charge, lubricity, and surface energy, the static antifouling ability of the silicone-based coating is significantly enhanced.

[0046] Example 1:

[0047] (1) First, 0.5 g of unmodified cellulose nanocrystals were dispersed in 50 mL of deionized water and sonicated at room temperature for 30 minutes until completely homogeneous. Then, 162 mg of NaBr and 57.3 mg of TEMPO were dissolved in 50 mL of distilled water by sonication, and the solution was slowly added to the cellulose nanocrystal dispersion prepared above and stirred at room temperature for 30 min. Subsequently, 3 mL of NaClO solution with an effective chlorine content of 14.5% was added dropwise, and the pH of the entire solution system was adjusted to about 10 with 0.5 M NaOH. When the pH no longer changed, 0.5 M HCl was added until the solution became turbid. The solution was centrifuged three times at 8000 r / min, the lower precipitate was collected, and the solution was freeze-dried for 24 h to obtain carboxylated cellulose nanocrystals.

[0048] (2) Prepare 50 mL of DMF dispersion containing 1 wt% carboxylated cellulose nanocrystals and sonicate until homogeneous. Then add 10 g of lubricant α,ω-dihydroxypolydimethylsiloxane (1000 Mw) and 0.3 mL of catalyst tin isooctanoate to the dispersion, and stir at 800 r / min at 90 °C for 6 hours. After the reaction is complete, centrifuge three times at 8000 r / min and collect the lower precipitate. Subsequently, dialyze the centrifuged product with ethanol for 2 days to remove residual catalyst and unreacted lubricant, obtaining modified cellulose nanocrystals (see [link to product description]). Figure 1 and Figure 2 );

[0049] (3) 0.01 g of modified cellulose nanocrystals, 1.05 g of tetraethyl orthosilicate, 0.3 g of n-octadecyltriethoxysilane, 0.1 g of cholic acid, and 0.84 g of (3,3,3-trifluoropropyl)trimethoxysilane were dissolved in THF and stirred thoroughly for 1 hour. Then, 1 mL of 0.1 M HCl was added for catalysis, and the mixture was stirred at room temperature for 24 hours. After the reaction was stopped, the solution was drop-coated onto a glass substrate and cured at room temperature for 2 days to finally prepare a negatively charged transparent self-lubricating organosilicon hybrid antifouling coating 1 (see Figure 4 ).

[0050] Depend on Figure 1 The infrared spectrum reveals characteristic peaks of various groups in the polymer, such as Si-O-Si and Si-OH, confirming the successful grafting of α,ω-dihydroxypolydimethylsiloxane onto the surface of cellulose nanocrystals. Figure 2 The SEM images clearly show the surface morphology of the modified nanocellulose. (From...) Figure 3 Infrared spectroscopy reveals -COOH and Si-CH3 groups distributed on the coating surface. Figure 4 and Figure 5 The coating demonstrates good transparency, with a visible light transmittance greater than 95%.

[0051] Examples 2-11 and Comparative Example 1

[0052] Except for changing the type of unmodified nanocellulose, the type and molecular weight of the lubricant, and the type and amount of hydroxy acid, the remaining steps and conditions were the same as in Example 1, resulting in different antifouling coatings, as detailed in Table 1.

[0053] Table 1

[0054]

[0055]

[0056] To evaluate the static antifouling performance of the antifouling coating of this invention, a real-sea immersion test was conducted. Referring to GB / T5370-2007 (Antifouling Paint Sample Shallow Sea Immersion Test Method), the antifouling coating system prepared in the examples was immersed in the coastal waters of Qingdao to examine its antifouling performance. Scoring was performed based on the area of ​​fouling organisms attached to the sample surface (see Table 1). The scoring rules are as follows: 100 points for no biological attachment; 95 points for only primary attached organisms such as biofilms; and 95 points for large fouling organisms such as barnacles, calculated using the following formula: 95 - number of individual attachments - coverage area of ​​the colony.

[0057] Table 2 shows the static antifouling effects achievable by different coatings.

[0058]

[0059] Table 2 shows that increasing the amount of modified nanocellulose and hydroxy acid significantly improves the static antifouling ability of the coating, demonstrating that the dispersion of modified nanocellulose and hydroxy acid on the coating surface gives the coating good antimicrobial adhesion ability, which may be due to the enhanced lubricity and negative charge of the coating surface. Meanwhile, the table also shows that the hybrid coating prepared using 1000 Mw α,ω-dihydroxypolydimethylsiloxane-modified cellulose nanocrystals and cholic acid exhibits good antifouling performance.

[0060] To evaluate the mechanical properties of the antifouling coating of the present invention, the pencil hardness of different coatings was measured (referring to GB / T6739-2006 "Determination of Hardness of Paint Film by Pencil Method for Paints and Varnishes"), and the results are shown in Table 3.

[0061] Table 3 shows the pencil hardness of different coatings.

[0062] Coating number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Pencil hardness 4H 5H 7H 4H 4H 3H 4H 3H 6H 4H 6H 7H 6H 1H 8B

[0063] As shown in Table 3, the pencil hardness of the coating gradually increases with the increase of the amount of modified nanocellulose, proving that the distribution of modified nanocellulose in the hybrid network increases the crosslinking density of the coating and effectively improves the hardness of the coating.

[0064] To evaluate the charge properties of the antifouling coating surface of the present invention, the Zeta potential of different coating surfaces was tested in a water environment with pH=8 (the pH value of natural seawater is generally between 7.9 and 8.4) using a solid surface Zeta potential tester. The results are shown in Table 4.

[0065] Table 4 shows the Zeta potentials of different coated surfaces.

[0066]

[0067] As shown in Table 4, the Zeta potential on the coating surface gradually decreases with the increase of hydroxy acid dosage, proving that the negative charge on the coating surface gradually increases, which is not conducive to the adhesion of fouling organisms. This further confirms the static antifouling effect of different coatings in Table 2.

[0068] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A transparent, self-lubricating, organosilicon hybrid antifouling coating with a negatively charged surface, characterized in that: The antifouling coating is obtained by sol-gel reaction of modified nanocellulose, hydroxy acid and functional fluorine / siloxane monomer; the mass ratio of hydroxy acid to modified nanocellulose is 10~100:1; the mass ratio of functional fluorine / siloxane monomer to modified nanocellulose is 10~300:

1. The modified nanocellulose is prepared by surface chemical grafting modification of carboxylated nanocellulose dispersed in an organic solvent using a lubricant under catalytic conditions, wherein the mass ratio of lubricant, carboxylated nanocellulose and catalyst is 1~20:1:0.01~0.

4. The functional fluoro / siloxane monomer is one or more of the following: tetraethyl orthosilicate, trimethoxysilane, methyltrimethoxysilane, octyltrimethoxysilane, dodecyltrimethoxysilane, octadecyltrimethoxysilane, n-octyltriethoxysilane, n-dodecyltriethoxysilane, n-octadecyltriethoxysilane, (3,3,3-trifluoropropyl)trimethoxysilane, tridecafluorooctyltrimethoxysilane, and heptadecylfluorodecyltriethoxysilane, with a trimethoxy or triethoxy end group. The lubricant is one or more of the following: hydroxyl-terminated polysiloxanes of different molecular weights, hydroxyl-terminated polytrifluoropropylmethylsiloxanes, and castor oil. The general formula for hydroxyl-terminated polysiloxane structural units is as follows: Where n is a natural number greater than 1; The general formula of the hydroxyl-terminated polytrifluoropropylmethylsiloxane structural unit is as follows: Where m is a natural number greater than 1; The catalyst is one or more of tin isooctanoate, tin octanoate, tetrabutyl titanate, and dibutyltin dilaurate.

2. The transparent, self-lubricating, organosilicon hybrid antifouling coating with a negatively charged surface as described in claim 1, characterized in that: The hydroxyl-terminated polysiloxane has a molecular weight of 1000~20000; the hydroxyl-terminated polytrifluoropropylmethylsiloxane has a molecular weight of 1000~30000.

3. The transparent, self-lubricating, organosilicon hybrid antifouling coating with a negatively charged surface as described in claim 1, characterized in that: The hydroxy acid has a chemical structure that contains both hydroxyl and carboxyl groups.

4. The transparent, self-lubricating, organosilicon hybrid antifouling coating with a negatively charged surface as described in claim 1, characterized in that: The hydroxy acid is one or more of the following: cholic acid, glycyrrhetinic acid, citric acid, lactic acid, tartaric acid, salicylic acid, malic acid, gallic acid, and uronic acid.

5. A method for preparing a transparent, self-lubricating, organosilicon hybrid antifouling coating with a negatively charged surface as described in claim 1, characterized in that: Modified nanocellulose, hydroxy acid, and functional fluorine / siloxane monomers were dissolved in an organic solvent according to the above proportions. After thorough mixing, acid was added to adjust the pH to about 3. After a sol-gel reaction at room temperature for 24 hours, the mixture was drop-coated onto the substrate and cured at room temperature to obtain a hybrid antifouling coating.

6. The application of the transparent self-lubricating silicone hybrid antifouling coating with negatively charged surface as described in claim 1, wherein the transparent self-lubricating silicone hybrid antifouling coating with negatively charged surface is used in the field of marine antifouling.

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