Bio-based fluorine-containing polyol low-temperature curing fluorocarbon coating and preparation method thereof

Abstract

The invention relates to the technical field of coatings, in particular to a bio-based fluorine-containing polyol low-temperature curing fluorocarbon coating and a preparation method thereof. The bio-based fluorine-containing polyol low-temperature curing fluorocarbon coating is prepared from the following raw materials in parts by weight: 10 to 15 parts of epoxy resin, 52 to 60 parts of fluorocarbon resin, 4 to 6 parts of fluorine-containing polyol, 8 to 10 parts of filler, 50 to 60 parts of solvent and 7 to 10 parts of curing agent. The fluorocarbon coating prepared by the invention can be cured at low temperature, has higher hardness, and has excellent corrosion resistance and aging resistance.

Description

Technical Field

[0001] This invention relates to the field of coating technology, specifically to a bio-based fluorinated polyol low-temperature curing fluorocarbon coating and its preparation method. Background Technology

[0002] Fluorocarbon coatings are a class of high-performance coatings with fluoropolymers as the core film-forming material. Leveraging the unique electronegativity of fluorine atoms and the high bond energy of the CF bond, these coatings possess excellent weather resistance, corrosion resistance, chemical resistance, and self-cleaning properties, making them indispensable protective and decorative materials in high-end fields such as aerospace, marine engineering, building curtain walls, and new energy equipment. In recent years, the global industrial transformation and upgrading, along with accelerated infrastructure construction, has driven the continuous expansion of the fluorocarbon coatings market. Industry data shows that the global fluorocarbon coatings market size exceeded 35 billion yuan in 2024. China, as a major producer and consumer, accounted for over 45% of the market, with demand concentrated in areas such as high-end equipment protection and building energy-saving renovations.

[0003] Patent CN115058158B discloses a dihydroxyl hydrogenated rosin-modified fluorocarbon anticorrosive coating and its preparation method. By weight, it comprises the following components: hydroxyl fluorocarbon resin: 20-75 parts; dihydroxyl hydrogenated rosin derivative: 2-55 parts; pigment: 0-10 parts; filler: 0-40 parts; additives: 1-5 parts; solvent: 25-70 parts; curing agent: 5-50 parts. This invention applies renewable rosin derivatives to the modification of fluorocarbon coatings, reducing the raw material cost of fluorocarbon coatings. It results in higher hardness and adhesion, superior anticorrosive properties, heat resistance, and resistance to artificial weathering. This further promotes research on green bio-based fluorocarbon anticorrosive coating technology, expands the application of fluorocarbon coatings in marine engineering, and improves the level of marine anticorrosive coating technology in my country.

[0004] Patent CN119875442B discloses a fluorocarbon powder coating and its preparation method, belonging to the field of powder coating technology. The method includes the following steps: premixing methyl methacrylate, hydroxyethyl methacrylate, hexafluorobutyl methacrylate, and methyl p-coumarate to obtain a premixed liquid; transferring the premixed liquid to a reaction vessel, heating, adding an initiator, reacting, filtering, and drying to obtain a modified acrylic resin; melt-blending and extruding to obtain material A; placing PVDF fluorocarbon resin and filler into the reaction vessel, heating, and stirring to obtain material B; adding material A and modified PMMA, stirring, cooling, and pressing into sheets to obtain the powder coating. This fluorocarbon powder coating maintains high weather resistance while improving internal compatibility and UV resistance, and enhancing the internal adhesion of the double-layer powder.

[0005] Despite the superior performance of fluorocarbon coatings, existing technologies still have several shortcomings that urgently need to be addressed. Conventional fluorocarbon coatings require curing at temperatures above 150°C, which is not only energy-intensive but also unsuitable for heat-sensitive substrates such as wood, plastics, and foams, severely limiting their application in furniture manufacturing, automotive interiors, and lightweight components. Therefore, there is an urgent need for a high-performance fluorocarbon coating that can be cured at low temperatures. Summary of the Invention

[0006] In view of the problems existing in the prior art, the purpose of this invention is to obtain a fluorocarbon coating that not only has good mechanical strength, but also good anti-corrosion properties, can be cured at low temperature, and has a wide range of applications.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of this invention provides a bio-based fluorinated polyol low-temperature curing fluorocarbon coating, which, by weight, comprises the following raw materials: 10-15 parts epoxy resin, 52-60 parts fluorocarbon resin, 4-6 parts fluorinated polyol, 8-10 parts filler, 50-60 parts solvent, and 7-10 parts curing agent.

[0008] In some embodiments, the method for preparing the fluorinated polyol includes the following steps: (1) Add hyaluronic acid to DMSO and stir at 25-35℃ for 2-3h. Adjust the pH to 6.5-7, then add 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 4-dimethylaminopyridine and stir at room temperature for 30-40min. Then add 4,4,4-trifluorobutanol and react at 30-40℃ for 48-50h. After that, under nitrogen protection, add acrylic acid and polymerization inhibitor and continue to react at 35-40℃ for 36-40h. After post-treatment, the product is obtained. (2) Add castor oil and glycerol to the reaction vessel, then add the catalyst, replace the air in the reaction vessel with nitrogen, heat to 220-240℃, control the stirring rate at 300-500rpm, react for 4-6 hours, cool to 70-80℃, add deionized water to dilute, adjust the pH, wash, and distill under reduced pressure to obtain castor oil polyol. (3) Add the product obtained in step (1), castor oil polyol, and initiator to the solvent and react at 55-65℃ for 1-2 hours to obtain fluorinated polyol.

[0009] Although fluorocarbon resins have excellent weather resistance and hydrophobicity, their compatibility with components such as epoxy resins and curing agents is limited. Especially under low-temperature curing conditions, the mobility of molecular chain segments decreases, which can easily lead to phase separation and reduced coating density. While the introduction of epoxy resin can improve adhesion and hardness, it weakens the inherent low surface energy characteristics of fluorocarbon resins, reducing the coating's stain resistance and water resistance. At the same time, insufficient reactivity during low-temperature curing may result in an incomplete cross-linking network, affecting the mechanical strength of the coating.

[0010] This invention catalyzes the esterification of hyaluronic acid with trifluorobutanol, then grafts it with acrylic acid, and finally copolymerizes it with castor oil polyol via free radicals to form a block structure, resulting in a bio-based fluorinated polyol. The sugar ring structure of hyaluronic acid has weak ultraviolet absorption characteristics, which can partially scatter and absorb ultraviolet light. The strongly polar CF bond in the grafted trifluorobutyl group can effectively bind electrons, reduce the photoexcitation probability of the polymer backbone, and serve as an energy dissipation site, thus improving the aging resistance of the coating. In addition, the fluorinated polyol has hydroxyl groups, which can fully react with the curing agent at low temperatures to form a denser and more uniform three-dimensional cross-linked network. This network not only directly hinders the penetration of water, oxygen, and ions, but also acts as a compatibilizer to strengthen the interfacial bonding between fluorocarbon resin and epoxy resin. Furthermore, during the coating curing process, the fluorocarbon segments in the fluorinated polyol migrate and accumulate directionally to the coating-air interface, forming a dense, low-surface-energy fluorine atom shielding layer on the coating surface. This effectively resists the direct erosion and adhesion of corrosive media such as acids, alkalis, and salts, further enhancing the anti-fouling and anti-corrosion properties.

[0011] In some embodiments, the mass ratio of hyaluronic acid to 4,4,4-trifluorobutanol is 1:(3-5).

[0012] In some embodiments, the mass ratio of hyaluronic acid to acrylic acid is 1:(0.5-1).

[0013] In some embodiments, the mass ratio of castor oil to glycerin is 1:(0.3-0.5).

[0014] In some embodiments, the mass ratio of castor oil polyol to product in step (3) is (3-4):1.

[0015] In some embodiments, the filler is a mixture of titanium dioxide and fumed silica.

[0016] In some embodiments, the mass ratio of titanium dioxide to fumed silica is 1:(3-5).

[0017] In some embodiments, the solvent is acetone.

[0018] In some embodiments, the curing agent is a polyisocyanate.

[0019] A second aspect of this invention provides a method for preparing a bio-based fluorinated polyol low-temperature curing fluorocarbon coating, comprising the following steps: Epoxy resin and filler are added to a solvent and stirred for 20-30 minutes. Then, fluorocarbon resin, fluorinated polyol and curing agent are added and stirred for another 20-30 minutes to obtain a fluorocarbon coating.

[0020] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention prepares a fluorocarbon coating that can be cured at low temperature by using epoxy resin, fluorocarbon resin, fluorinated polyol and other additives. The coating obtained after curing has high hardness, high corrosion resistance and aging resistance.

[0021] (2) The present invention improves the aging resistance of coatings by preparing a bio-based fluorinated polyol; in addition, the fluorinated polyol has hydroxyl groups, which can react fully with the curing agent at low temperature to form a denser and more uniform three-dimensional cross-linked network that can effectively resist the direct erosion and adhesion of corrosive media such as acids, alkalis and salts, thereby further improving the stain resistance and corrosion resistance. Detailed Implementation

[0022] The present invention will be described below with reference to specific embodiments. It should be noted that the following embodiments are examples of the present invention and are used only to illustrate the invention, not to limit it. Other combinations and various modifications within the scope of the present invention can be made without departing from its spirit or scope.

[0023] In the following examples and comparative examples, the compounds and related reagents used were all commercially available. The titanium dioxide was model R909, manufactured by Shanghai Yuejiang Titanium Dioxide; the fumed silica was model AEROSIL R106, manufactured by Evonik Degussa; the fluorocarbon resin was model FEVE TFB-G1, manufactured by Shanghai Puweili; and the HDI trimer was HT-600, manufactured by Wanhua Chemical.

[0024] Unless otherwise specified, the post-processing steps such as "washing", "drying", "filtering", and "vacuum distillation" used below are routine operations for those skilled in the art, and can be selected according to actual operation.

[0025] Preparation Example 1 The preparation method of fluorinated polyol-1 includes the following steps: (1) Add 100g of hyaluronic acid to 8000ml of DMSO and stir at 30℃ for 2.5h. Adjust the pH to 7 with triethylamine, then add 20g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 1.5g of 4-dimethylaminopyridine and stir at room temperature for 35min. Then add 400g of 4,4,4-trifluorobutanol and react at 35℃ for 49h. After that, under nitrogen protection, add 80g of acrylic acid and 1g of hydroquinone and continue to react at 37℃ for 38h. Add 5 times the volume of anhydrous ethanol to precipitate, filter, wash with acetone and dry to obtain the product. (2) Add 100g castor oil and 40g glycerol to the reaction vessel, then add 1g sodium hydroxide, replace the air in the reaction vessel with nitrogen, heat to 230℃, control the stirring speed at 400rpm, react for 5 hours, cool to 75℃, add 30ml deionized water to dilute, adjust pH=7 with 10wt% dilute hydrochloric acid, wash, and distill under reduced pressure to obtain castor oil polyol; (3) Add 10g of the product obtained in step (1), 35g of castor oil polyol, and 0.3g of azobisisobutyronitrile to 200ml of anhydrous ethanol and react at 60℃ for 1.5h to obtain fluorinated polyol-1.

[0026] Preparation Example 2 The preparation method of fluorinated polyol-2 is the same as that of preparation example 1, except that the amount of 4,4,4-trifluorobutanol added in step (1) is 510g.

[0027] Preparation Example 3 The preparation method of fluorinated polyol-3 is the same as that of preparation example 1, except that the amount of acrylic acid added in step (1) is 110g.

[0028] Preparation Example 4 The preparation method of fluorinated polyol-4 is the same as that of preparation example 1, except that the amount of castor oil polyol added in step (3) is 45g.

[0029] Preparation Example 5 The preparation method of bio-based polyols includes the following steps: (1) Under nitrogen protection, 100g of hyaluronic acid was added to 8000ml of DMSO and stirred at 30℃ for 2.5h. The pH was adjusted to 7 with triethylamine, and then 20g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 1.5g of 4-dimethylaminopyridine were added and stirred at room temperature for 35min. Then 80g of acrylic acid and 1g of hydroquinone were added and the reaction was continued at 37℃ for 38h. The product was precipitated in 5 times the volume of anhydrous ethanol, filtered, washed with acetone and dried to obtain the product. (2) Add 100g castor oil and 40g glycerol to the reaction vessel, then add 1g sodium hydroxide, replace the air in the reaction vessel with nitrogen, heat to 230℃, control the stirring speed at 400rpm, react for 5 hours, cool to 75℃, add 30ml deionized water to dilute, adjust pH=7 with 10wt% dilute hydrochloric acid, wash, and distill under reduced pressure to obtain castor oil polyol; (3) Add 10g of the product obtained in step (1), 35g of castor oil polyol, and 0.3g of azobisisobutyronitrile to 200ml of anhydrous ethanol and react at 60℃ for 1.5h to obtain bio-based polyol.

[0030] Example 1 A bio-based fluorinated polyol low-temperature curing fluorocarbon coating comprises, by weight, the following raw materials: 13 parts epoxy resin E51, 56 parts fluorocarbon resin, 5 parts fluorinated polyol-1, 9 parts filler, 55 parts acetone, and 8 parts HDI trimer. The filler is a mixture of titanium dioxide and fumed silica in a mass ratio of 1:4.

[0031] The preparation method of the bio-based fluorinated polyol low-temperature curing fluorocarbon coating in this embodiment includes the following steps: Epoxy resin E51 and filler were added to acetone and stirred for 25 minutes. Then, fluorocarbon resin, fluorinated polyol-1 and HDI trimer were added and stirred for another 25 minutes to obtain fluorocarbon coating.

[0032] Example 2 A bio-based fluorinated polyol low-temperature curing fluorocarbon coating, by weight, comprises the following raw materials: 10 parts epoxy resin E51, 52 parts fluorocarbon resin, 4 parts fluorinated polyol-1, 8 parts filler, 50 parts acetone, and 7 parts HDI trimer. The filler is a mixture of titanium dioxide and fumed silica in a mass ratio of 1:3.

[0033] The preparation method of the bio-based fluorinated polyol low-temperature curing fluorocarbon coating in this embodiment includes the following steps: Epoxy resin E51 and filler were added to acetone and stirred for 20 minutes. Then, fluorocarbon resin, fluorinated polyol-1 and HDI trimer were added and stirred for another 20 minutes to obtain fluorocarbon coating.

[0034] Example 3 A bio-based fluorinated polyol low-temperature curing fluorocarbon coating comprises, by weight, the following raw materials: 15 parts epoxy resin E51, 60 parts fluorocarbon resin, 6 parts fluorinated polyol-1, 10 parts filler, 60 parts acetone, and 10 parts HDI trimer. The filler is a mixture of titanium dioxide and fumed silica in a mass ratio of 1:5.

[0035] The preparation method of the bio-based fluorinated polyol low-temperature curing fluorocarbon coating in this embodiment includes the following steps: Epoxy resin E51 and filler were added to acetone and stirred for 30 minutes. Then, fluorocarbon resin, fluorinated polyol-1 and HDI trimer were added and stirred for another 30 minutes to obtain fluorocarbon coating.

[0036] Example 4 A bio-based fluorinated polyol low-temperature curing fluorocarbon coating and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that fluorinated polyol-1 is replaced with fluorinated polyol-2 in equal amounts.

[0037] Example 5 A bio-based fluorinated polyol low-temperature curing fluorocarbon coating and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that fluorinated polyol-1 is replaced with fluorinated polyol-3 in equal amounts.

[0038] Example 6 A bio-based fluorinated polyol low-temperature curing fluorocarbon coating and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that fluorinated polyol-1 is replaced with fluorinated polyol-4 in equal amounts.

[0039] Comparative Example 1 A bio-based fluorinated polyol low-temperature curing fluorocarbon coating and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that the fluorinated polyol-1 is replaced with an equal amount of bio-based polyol.

[0040] Comparative Example 2 A bio-based fluorinated polyol low-temperature curing fluorocarbon coating and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that fluorinated polyol-1 is replaced with 4,4,4-trifluorobutanol in equal amounts.

[0041] Performance testing Using treated aluminum alloy as the substrate, the coatings obtained in each embodiment and comparative example were applied to the aluminum alloy surface with a coating thickness of 100 μm and cured at 35°C for 72 h. The following tests were then conducted: 1. Hardness: Tested according to GB / T 6739-2022 "Determination of Hardness of Paints and Varnishes by Pencil Method"; 2. Corrosion resistance: According to GB / T 10125-2021, the salt spray resistance test is carried out for 900 hours. The results are required as follows: In the marked area: unidirectional corrosion ≤2.0mm, and in the unmarked area: no abnormality.

[0042] 3. Aging resistance: According to standard GB / T1865-2009, artificial weathering for 1000 hours, irradiance: 0.51 (W / m²). 2 @340nm), BST: 65℃, chamber temperature: 38℃, chamber humidity: 50%RH, observe for any abnormal phenomena such as powdering, bubbles, cracking, peeling, etc.

[0043] The test results are shown in Table 1: Table 1 As shown in Table 1, the coatings obtained after curing of the coatings in Examples 1-3 exhibit strong hardness and good corrosion resistance and aging resistance. A comparison of the data from Example 4 and Example 1 shows that changing the ratio of hyaluronic acid to 4,4,4-trifluorobutanol may increase the grafting density of 4,4,4-trifluorobutanol, increasing steric hindrance and decreasing the hydrogen bonding between molecular chains, resulting in a slight decrease in coating hardness. A comparison of the data from Example 5 and Example 1 shows that changing the ratio of hyaluronic acid to acrylic acid may lead to excessive crosslinking, resulting in increased internal stress in the coating. An overly rigid network restricts the movement of molecular chain segments, hindering the migration and enrichment of fluorinated segments to the surface, leading to increased surface fluorine content. The reduced content of 4,4,4-trifluorobutanol impairs the hydrophobic barrier, leading to decreased aging and corrosion resistance. A comparison of data from Example 6 and Example 1 shows that the altered ratio of castor oil polyol to the product, with an excess of flexible segments, results in decreased coating hardness and a relatively loose coating structure, further reducing corrosion resistance. A comparison of data from Comparative Example 1 and Example 1 shows that without fluorinated segments, the hyaluronic acid skeleton is rigid, and the flexible castor oil chains cannot effectively buffer its curing shrinkage stress, leading to decreased hardness. Additionally, the increased hydrophilic segments reduce aging and corrosion resistance. A comparison of Comparative Example 2 and Example 1 shows that using only 4,4,4-trifluorobutanol reduces the coating's hardness, corrosion resistance, and aging resistance.

[0044] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A bio-based fluorinated polyol low-temperature curing fluorocarbon coating, characterized in that, By weight, it includes the following raw materials: 10-15 parts epoxy resin, 52-60 parts fluorocarbon resin, 4-6 parts fluorinated polyol, 8-10 parts filler, 50-60 parts solvent, and 7-10 parts curing agent.

2. The bio-based fluorinated polyol low-temperature curing fluorocarbon coating according to claim 1, characterized in that, The method for preparing the fluorinated polyol includes the following steps: (1) Add hyaluronic acid to DMSO and stir at 25-35℃ for 2-3h. Adjust the pH to 6.5-7, then add 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 4-dimethylaminopyridine and stir at room temperature for 30-40min. Then add 4,4,4-trifluorobutanol and react at 30-40℃ for 48-50h. After that, under nitrogen protection, add acrylic acid and polymerization inhibitor and continue to react at 35-40℃ for 36-40h. After post-treatment, the product is obtained. (2) Add castor oil and glycerol to the reaction vessel, then add the catalyst, replace the air in the reaction vessel with nitrogen, heat to 220-240℃, control the stirring rate at 300-500rpm, react for 4-6 hours, cool to 70-80℃, add deionized water to dilute, adjust the pH, wash, and distill under reduced pressure to obtain castor oil polyol. (3) Add the product obtained in step (1), castor oil polyol, and initiator to the solvent and react at 55-65℃ for 1-2 hours to obtain fluorinated polyol.

3. The bio-based fluorinated polyol low-temperature curing fluorocarbon coating according to claim 2, characterized in that, The mass ratio of hyaluronic acid to 4,4,4-trifluorobutanol is 1:(3-5).

4. The bio-based fluorinated polyol low-temperature curing fluorocarbon coating according to claim 2, characterized in that, The mass ratio of hyaluronic acid to acrylic acid is 1:(0.5-1).

5. The bio-based fluorinated polyol low-temperature curing fluorocarbon coating according to claim 2, characterized in that, The mass ratio of castor oil polyol to product in step (3) is (3-4):

1.

6. The bio-based fluorinated polyol low-temperature curing fluorocarbon coating according to claim 1, characterized in that, The filler is a mixture of titanium dioxide and fumed silica.

7. The bio-based fluorinated polyol low-temperature curing fluorocarbon coating according to claim 6, characterized in that, The mass ratio of titanium dioxide to fumed silica is 1:(3-5).

8. The bio-based fluorinated polyol low-temperature curing fluorocarbon coating according to claim 1, characterized in that, The solvent is acetone.

9. The bio-based fluorinated polyol low-temperature curing fluorocarbon coating according to claim 1, characterized in that, The curing agent is a polyisocyanate.

10. A method for preparing a bio-based fluorinated polyol low-temperature curing fluorocarbon coating according to any one of claims 1-9, characterized in that, Includes the following steps: Add epoxy resin and filler to solvent and stir for 20-30 minutes. Then add fluorocarbon resin, polyol and curing agent and continue stirring for 20-30 minutes to obtain fluorocarbon coating.

Images