Reactive short fluorocarbon chain gemini cationic surfactant and preparation method thereof

Abstract

The present application provides a kind of reactive short fluorocarbon chain gemini cationic surfactant and its preparation method.The reactive short fluorocarbon chain gemini cationic surfactant is used as wetting and leveling agent in water-based paint.Water-based paint is difficult to wet the surface of substrate due to high surface tension, and common coating defects in the process of coating construction include orange peel, fisheye, shrinkage, shrinkage, benard vortex, floating color, and so on. Fluorocarbon water-based wetting and leveling agent can significantly improve the above defects due to low surface tension of fluorocarbon chain, and obtain smooth surface.

Description

Technical Field

[0001] This invention belongs to the field of fluorocarbon surfactant technology, specifically relating to a reactive short-chain fluorocarbon twin cationic surfactant and its preparation method. Background Technology

[0002] Surfactant molecules are typically composed of both lipophilic and hydrophobic groups, possessing the ability to reduce surface and interfacial tension. At critical micelle concentrations (CMC) and above, they can form ordered assemblies. This unique amphiphilic property of surfactants gives them properties such as foaming, solubilizing, emulsifying, dispersing, wetting, antibacterial, and detergency. Fluorocarbon surfactants are formed when all or part of the hydrogen atoms in the hydrocarbon chain are replaced by fluorine atoms, creating surfactants with a fluorocarbon chain as the hydrophobic group. Fluorocarbon surfactants exhibit higher surface activity, greater chemical stability, and higher thermal stability than hydrocarbon surfactants.

[0003] Fluorocarbon surfactants, due to their excellent properties, are used in energy, materials, biomedicine, daily chemicals, textiles, and other fields. Among them, perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), as well as their derivatives, are the most widely used. However, long-chain fluorocarbon alkyl groups (C≥8) exhibit extremely high stability (currently considered among the most resilient organic pollutants to degrade), and PFOS / PFOA surfactants possess bioaccumulation, biotoxicity, and environmental mobility. In May 2009, the 4th Conference of the Parties to the Stockholm Convention on Persistent Organic Pollutants decided to include PFOS / PFOA in Annex B of the Convention, restricting their production and use. Internationally, agreements have been issued to phase out and replace the use of fluorocarbon surfactants with carbon chain lengths of C≥8. The U.S. Environmental Protection Agency (EPA) issued the 2010 / 2015 PFOAStewardship program, which has completely eliminated the use of products containing PFOA and its homologues, perfluorocarboxylic acids. Since 2008, my country has included PFOA in the "High Pollution, High Environmental Risk" product list (referred to as the "Double High" product list). Since 2013, the process of producing PTFE-coated non-stick materials using PFOA as an additive has been included in the list of heavily polluting processes, and domestic chemical companies have been encouraged to actively develop environmentally friendly processes using PFOA substitutes as additives. Recently, PFOA-related products were included in the POPs (Potential Organic Pollutants) regulations in 2020, and with the exception of a few exemptions or specific uses, the production, market placement, and use of these products are prohibited. Therefore, researching and developing high-performance fluorinated materials without potential bioaccumulation is of great significance to adapt to global sustainable development.

[0004] Current regulations consider PFCAs with fewer than 7 carbons and perfluoroalkane sulfonates (PFSAs) with fewer than 6 carbons to be non-bioaccumulative, and short-chain PFCAs and PFSAs are also much less toxic. Therefore, short-chain fluorocarbon surfactants have received considerable attention. Ito et al. reported that C4F9C6H4COCH(SO3Na)C6H13, with a CMC of 1.2 mmol / L and γcmc of 18.9 mN / m, can reduce the interfacial tension of n-octane / water and perfluorohexane / water to 2.7 and 1.2 mN / m, respectively. Tabor et al. reported the interfacial tension of short-chain sodium succinate sulfonate C4F9CH2OOCCH2CH(SO3Na)COOCH2C4F9. The former showed a better effect on reducing the interfacial tension of fluoroalkanes / water, while the latter, due to its CF2H end group, showed a significantly reduced ability to reduce the interfacial tension of fluoroalkanes / water. There are also reports of using polymerization reactions to oligomerize monomers with short fluorocarbon chains (such as C4F9), thereby enhancing surface activity while avoiding the use of small molecules containing long fluorocarbon chains. Compared to PFOA, these surfactants have shorter fluorocarbon chains, relatively lower toxicity, and no significant bioaccumulation.

[0005] However, due to the shortened carbon-fluorine chain, short-chain fluorocarbon products exhibit significantly reduced efficiency in reducing surface tension, film-forming ability, and film stability, while their water solubility increases. Long-chain amphiphilic fluorocarbons with 8 or 10 carbon atoms (such as carboxylic acid and sulfonic acid fluorosurfactants) readily form robust, insoluble monolayers with high collapse pressures on water surfaces, while their corresponding 4 or 6-carbon homologues typically fail to form stable molecular films. Furthermore, self-assembly ability, ordered arrangement, formation of ordered liquid condensed phases, and the viscoelasticity of surfactant interfacial films are also extremely sensitive to the length of the carbon-fluorine chain.

[0006] Gemini surfactants are amphiphilic compounds with two hydrophilic groups and two hydrophobic groups covalently linked together. The linking groups are classified as flexible groups with good rotational flexibility (such as straight-chain alkanes and polyoxyethylene chains) and rigid groups with poor rotational flexibility (such as groups with triple bonds or benzene ring structures). A single molecule of a Gemini surfactant possesses two hydrophobic groups and two hydrophilic groups, resulting in a more compact arrangement at the interface between two phases, forming a unique micelle structure. Differences in molecular structure, such as the linking groups, have a significant impact on their properties: the length of the linking groups determines the magnitude of the repulsive force between the ionic head groups, thus affecting surface activity; differences in the functional groups of the linking groups affect the surfactant's aggregation and degradation capabilities; and the confinement effect of the linking groups and the affinity effect of the groups in Gemini surfactants determine their adsorption mode, significantly enhancing their activity compared to traditional surfactants. Because the two hydrophilic head groups in Gemini surfactant molecules are linked by chemical bonds, stronger hydrophobic interactions easily occur between the alkyl chains. The repulsive forces between the hydrophilic head groups are greatly weakened by the chemical bonds, allowing for a more compact arrangement. This results in interfacial properties in aqueous media that are one to several orders of magnitude superior to those of traditional surfactants. In recent years, the use of short fluorocarbon chains + Gemini strategy for PFOS / PFOA has become increasingly significant.

[0007] Reactive surfactants have reactive groups that can chemically react with the adsorbed matrix, stably adsorbing onto the matrix surface in the form of chemical bonds and exerting surface activity on the matrix. They have become a research hotspot both domestically and internationally.

[0008] In 1956, Bistline et al. first applied reactive surfactants to polymerization reactions. Subsequently, various novel reactive surfactants were synthesized and applied to the manufacture of various high-performance materials. Literature indicates that these surfactants not only possess good surface activity but also reactivity, and can significantly improve the stability, anti-aging properties, and electrolyte resistance of the products. For example, they can be used for surface modification of fabrics and polymer materials; as a primer in coatings, they provide excellent adhesion and water resistance; pressure-sensitive adhesives made from them exhibit excellent water resistance; they have good bioactivity and can stably bond with bioactive substances; furthermore, when applied to emulsion polymerization, they can form water- and heat-resistant films.

[0009] Although gemini surfactants have received considerable attention, with numerous reports and performance tests published in the Journal of Fluorine Chemistry 239(2020) 109632, reactive short-chain fluorocarbon surfactants have yet to be documented. Therefore, developing a high-performance, environmentally friendly reactive fluorocarbon surfactant is of great significance. Summary of the Invention

[0010] To address the shortcomings of existing technologies, the present invention aims to provide a reactive short-chain fluorocarbon twin cationic surfactant and its preparation method. This surfactant is environmentally friendly and has excellent surface properties, and can be used in energy, materials, biomedicine, daily chemicals, textiles and other fields. It can persistently change the surface properties of the interface. When used as a wetting and leveling agent in water-based coatings, it has efficient wetting, long-lasting and antibacterial effects.

[0011] To achieve the above objectives, the present invention provides the following technical solution: A reactive short-chain fluorocarbon twin cationic surfactant has the following structure: Where n = 0, 1, 2; R is CF3 (CF2). m Where m = 3, 5.

[0012] The R group is a short-chain hydrophobic group, which can be perfluorobutyl or perfluorohexyl. Fluorocarbon chains have the lowest known surface tension, thus exhibiting good surface activity and meeting environmental protection requirements while providing excellent hydrophobicity. The hydroxyl group is a reactive group with high activity, capable of reacting with isocyanate, carboxyl, and amino groups, avoiding surfactant migration and precipitation issues. Simultaneously, the hydroxyl group also possesses some hydrophilicity, improving the surfactant's solubility tolerance. Among the four amino groups, two are sterically hindered tertiary amines, which can be further quaternized.

[0013] Preferably, in the reactive short-chain fluorocarbon gemini surfactant, n is preferably 0 or 1. When n=0, it is obtained by reacting ethylene glycol diglycidyl ether; when n=1, it is obtained by reacting 1,4-butanediol diglycidyl ether. To improve the arrangement of gemini surfactants, the linking groups should not be too long.

[0014] The reactive short-chain fluorocarbon twin cationic surfactant described above can be provided in the form of a quaternary ammonium salt. The quaternized substance can be obtained by refluxing the surfactant described above with two moles of iodomethane or bromomethane in solvents such as acetonitrile, methanol, or ethanol for 12-14 hours.

[0015] The method for preparing the reactive short-chain fluorocarbon gemini surfactant includes the following steps: S1. Fluoroaldehyde and dimethylpropanediamine were added to a solvent in a 1:1 molar ratio. Formic acid was added, and the mixture was heated for 12-48 hours. The reaction was confirmed by GC-MS to be complete. The solvent was removed by distillation to obtain aminopropylfluoromethylamine, which was product A. This is a typical Leuckart-Wallach reaction. Fluoroaldehyde and dimethylpropanediamine react to form a Schiff base, which is then reduced in situ with formic acid to give a secondary amine. The reaction mechanism can be found in the following references: Reactions 2023, 4, 117-147; BULLETIN OF THE CHEMICALSOCIETY OF JAPAN, VOL.49 (9), 2485-2490 (1976).

[0016] The fluorinated aldehydes used in this reaction include perfluorobutyl formaldehyde and perfluorohexyl formaldehyde, which can be obtained by oxidation of perfluorohexylethylene or perfluorobutylethylene. The reaction scheme can be found in the invention patent CN202210270015.4 or the literature Journal of Fluorine Chemistry, 35 (1987) 359-371.

[0017] S2. Add product A and diglycidyl ether to the solvent and heat the reaction for 6-24 h to obtain a reactive short-chain fluorocarbon gemini cationic surfactant. This reaction is a ring-opening reaction between a secondary amine and propylene oxide, and the reaction proceeds easily.

[0018] Preferably, in the synthesis of short-chain fluorocarbon gemini surfactants, the solvent in step S1 is toluene, xylene, or trimethylbenzene; formic acid decomposes at higher temperatures to provide reducing hydrogen atoms, thus requiring a higher temperature for the reaction. For complete reaction, formic acid needs to be in excess, with the amount of formic acid being 3-15 times the molar amount of the fluoroaldehyde.

[0019] Preferably, in the synthesis of reactive short-chain fluorocarbon gemini surfactants, the solvent in step S2 is a polar solvent, such as acetonitrile, methanol, ethanol, tert-butanol, or butanol. Polar solvents provide excellent solubility for the raw materials and also promote the reaction between propylene oxide and secondary amines.

[0020] Preferably, the reaction temperature in step S1 is 140-180℃.

[0021] Preferably, the reaction temperature in step S2 is 40-80℃.

[0022] The aforementioned reactive short-chain fluorocarbon twin surfactant is used as a wetting and leveling agent in water-based coatings. Water-based coatings, due to their high surface tension, are difficult to wet on substrate surfaces, often resulting in coating defects such as orange peel, fisheyes, pinholes, edge shrinkage, Bénard vortices, floating color, and blooming. Fluorocarbon water-based wetting and leveling agents, due to the low surface tension of the fluorocarbon chains, can significantly improve these defects, resulting in a smooth and even surface.

[0023] Compared with the prior art, the present invention has the following beneficial effects: (1) The limiting effect of the linker group and the affinity effect of the group of the novel Gemini-type surfactant synthesized in this invention determine its adsorption mode, which greatly improves its activity compared with traditional surfactants.

[0024] (2) The Gemini short fluorocarbon chain surfactant provided by the present invention solves the contradiction between the poor surface activity of short fluorocarbon chains and the poor environmental safety of long fluorocarbon chains. It is a highly active and environmentally friendly fluorocarbon surfactant.

[0025] (3) The fluorocarbon surfactant provided by the present invention has better leveling properties than ordinary perfluorobutyl sulfonic acid water-based leveling agents due to the linking of difluorocarbon chains; at the same time, the introduction of reactive groups avoids the problems of fluorocarbon chains not lasting and easy to be lost. Attached Figure Description

[0026] Figure 1 The NMR spectrum of compound 1; Figure 2 The NMR spectrum of compound 2; Figure 3 This is the NMR spectrum of compound 3. Detailed Implementation

[0027] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0028] Nonafluorobutylethylene and tridecafluorohexylethylene were provided by Fujian Sannong New Materials Co., Ltd.; dimethylpropylene diamine was purchased from BASF; butanediol diglycidyl ether and hexanediol diglycidyl ether were purchased from Jiangsu Sanmu Group Co., Ltd.; formic acid, xylene, and trimethylbenzene were purchased from Aladdin Reagent Co., Ltd. Perfluorobutyl formaldehyde and perfluorohexyl formaldehyde were synthesized according to invention patent CN202210270015.4, and their purity was 99.6% as determined by liquid chromatography.

[0029] Example 1 A method for preparing a reactive short-fluorocarbon chain geminal cationic surfactant with the structure described above includes the following steps: Add a magnetic stir bar to a 500 ml three-necked flask, then add 24.8 g of perfluorobutyl formaldehyde, 250 ml of xylene, 10.2 g of dimethylpropylenediamine, and 46 g of anhydrous formic acid. Reflux at 140 °C for 16 h. Take a sample for GC-MS testing. The perfluorobutyl formaldehyde has been completely converted. Remove the solvent and unreacted small molecules by vacuum distillation to obtain a pale yellow transparent solution A.

[0030] Add 300 ml of butanol and 10.2 g of 1,4-butanediol diglycidyl ether to A, and react at 80°C for 12 h. Then cool to 40°C, add 14.1 g of iodomethane, and react for 24 h.

[0031] The solvent was removed by vacuum distillation of the resulting solution, and then recrystallized in methanol to give 58.1 g of white solid (i.e., compound 1), with a yield of 90.6%.

[0032] Example 2 A method for preparing a reactive short-fluorocarbon chain geminal cationic surfactant with the structure described above includes the following steps: Add a magnetic stir bar to a 500 ml three-necked flask, then add 34.8 g of perfluorohexyl formaldehyde, 280 ml of thiol, 10.2 g of dimethylpropanediamine, and 42 g of anhydrous formic acid. Incubate at 160 °C for 12 h. Take a sample for GC-MS testing. The perfluorohexyl formaldehyde has been completely converted. Remove the solvent and unreacted small molecules by vacuum distillation to obtain a pale yellow transparent solution A.

[0033] Add 300 ml butanol and 10.2 g 1,4-butanediol diglycidyl ether to A, and react at 40 °C for 18 h. Add 14.1 g iodomethane, and react for 24 h.

[0034] The solvent was removed by vacuum distillation of the obtained solution, and then recrystallized in methanol to give 63.1 g of white solid (i.e. compound 2), with a yield of 91.7%.

[0035] Example 3 A method for preparing a reactive short-fluorocarbon chain geminal cationic surfactant with the structure described above includes the following steps: Add a magnetic stir bar to a 500 ml three-necked flask, then add 34.8 g of perfluorohexyl formaldehyde, 260 ml of thiol, 10.2 g of dimethylpropylenediamine, and 42 g of anhydrous formic acid. Incubate at 180 °C for 6 h. Perform GC-MS analysis on the sample. The perfluorohexyl formaldehyde has been completely converted. Remove the solvent and unreacted small molecules by vacuum distillation to obtain a pale yellow transparent solution A.

[0036] Add 300 ml butanol and 8.7 g ethylene glycol diglycidyl ether to A, and react at 40 °C for 18 h. Add 14.1 g iodomethane, and react for 24 h.

[0037] The solvent was removed by vacuum distillation of the resulting solution, and then recrystallized in methanol to give 56.1 g of white solid (i.e., compound 3), with a yield of 93.7%.

[0038] Application Example: The polymer products obtained in Examples 1-3 were used as leveling agents in coatings, with sodium perfluorobutyl sulfonate as Comparative Example 1 and sodium perfluorooctyl sulfonate as Comparative Example 2. The specific steps are as follows: 60g of hydroxyl acrylic resin (brand name Antkote® 2701, Wanhua), 6g of propylene glycol methyl ether acetate (PMA), and 0.15g of leveling agent (prepared in Examples 1-3, as well as sodium perfluorobutyl sulfonate and sodium perfluorooctyl sulfonate) were placed in a clamping vibrating mixer and shaken for 15 minutes. Then, 30g of water-dispersible curing agent (brand name Aquolin 166, Wanhua) was added to prepare a curable varnish. The prepared varnish was applied to the tinplate surface for 2-3mm and baked at 80℃ for 30 minutes. During each brushing process, the leveling effect of the leveling agent was evaluated from the perspectives of the leveling speed of the coating and the smoothness of the coating surface, and rated from 1 to 5, with grade 1 being the worst leveling performance and grade 5 being the best leveling performance. Meanwhile, during the second coat, the adhesion and bonding strength of the paint to the surface of the first coating layer were observed. The recoating effect was evaluated based on factors such as the presence of a clear interface between the two coating layers and the strength of the adhesion between the layers, using a rating of 1-5, where 1 represents the worst recoating effect and 5 represents the best. The results are shown in Table 1. A blank group without leveling agent was also included. Slip properties were expressed as the coefficient of friction and tested using an MXS05A tin can paint surface slip property tester. Gloss was tested using an XD1050 gloss meter. The test results are shown in Table 1 below. Table 1 Table 1 rates the severity of pinholes from 1 to 10, with smaller numbers indicating better anti-pinhole performance and larger numbers indicating poorer performance. As shown in Table 1, the gemini-type short fluorocarbon chain surfactant prepared in this invention, when used as a leveling agent in oil-based coatings, provides excellent leveling, recoatability, and anti-pinhole performance. Due to the synergistic effect of the bifluorocarbon chains, it exhibits superior surface activity compared to single chains, thus demonstrating a superior ability to reduce surface tension and consequently superior anti-pinhole performance. The resulting coatings exhibit good compatibility, leveling, and anti-pinhole properties, showing promising application prospects.

[0039] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A reactive short-chain fluorocarbon twin-type cationic surfactant, characterized in that, Its structure is as follows: ； Where n = 0, 1, 2; R is CF3 (CF2). m -; where m=3, 5.

2. The reactive short-chain fluorocarbon twin cationic surfactant according to claim 1, characterized in that, n is 0 or 1.

3. The reactive short-chain fluorocarbon twin cationic surfactant according to claim 1, characterized in that, It is provided in the form of quaternary ammonium salt, and the quaternizing agent is iodomethane or bromomethane.

4. A method for preparing a reactive short-fluorocarbon chain geminal cationic surfactant as described in claim 1, characterized in that, Includes the following steps: S1. Fluoroaldehyde and dimethylpropanediamine are added to a solvent in a 1:1 molar ratio. Formic acid is added, and the mixture is heated to react for 12-48 hours. The reaction of fluoroaldehyde is confirmed by GC-MS. The solvent is removed by distillation to obtain aminopropylfluoromethylamine, which is product A. S2. Add product A, ethylene glycol diglycidyl ether or 1,4-butanediol diglycidyl ether to the solvent, and heat the reaction for 6-24 h to obtain a reactive short fluorocarbon chain gemini cationic surfactant. The structural formula of the fluorinated aldehyde is as follows: x = 3 or 5.

5. The preparation method according to claim 4, characterized in that, The solvent mentioned in step S1 is toluene, xylene, or trimethylbenzene; the amount of formic acid used is 3-15 times the amount of the fluorinated aldehyde.

6. The preparation method according to claim 4, characterized in that, The solvent mentioned in step S2 is a polar solvent, including acetonitrile, methanol, ethanol, and butanol.

7. The preparation method according to claim 4, characterized in that, The reaction temperature in step S1 is 140-180℃.

8. The preparation method according to claim 4, characterized in that, The reaction temperature in step S2 is 40-80℃.

9. The application of the reactive short-fluorocarbon chain twin cationic surfactant of claim 1 as a wetting and leveling agent in coatings.

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