Polyether siloxane defoaming agent for water-based paint and preparation method of polyether siloxane defoaming agent

Abstract

The invention discloses a polyether siloxane defoaming agent for water-based paint and a preparation method of the polyether siloxane defoaming agent, and relates to the technical field of defoaming agents. The polyether siloxane defoaming agent for the water-based paint comprises the following raw materials in parts by weight: 60-75 parts of polyether modified silicone oil, 5-8 parts of silicon paste, 3-5 parts of a dispersing agent, 2-4 parts of silicon dioxide, 5-10 parts of an emulsifying agent and 2-5 parts of a surfactant. The polyether siloxane defoaming agent for the water-based paint, prepared by the invention, has good defoaming and foam-inhibiting properties and stability.

Description

Technical Field

[0001] The present invention relates to the technical field of defoamers, and particularly to a polyether silicone defoamer for waterborne coatings and a preparation method thereof. Background Art

[0002] With the acceleration of the industrialization process and the increasingly strict environmental protection standards, waterborne coatings have gradually replaced traditional oil-based coatings in the market and become the mainstream choice due to their low volatile organic compound (VOC) emissions, good safety, and convenient usability. However, waterborne coatings are prone to generating bubbles during production and construction, and these bubbles can cause defects in the paint film, affecting its appearance and performance.

[0003] To solve this problem, defoamers are widely used in waterborne coatings. They destroy the bubble stability through the incompatibility principle, causing the bubbles to burst rapidly. However, there is a problem that the carrier material of traditional defoamers is not fully compatible with the coating system, making it difficult for the two to blend evenly. The coating system regards the defoamer as an "alien substance", thus forming defects such as shrinkage holes on the surface of the paint film. In addition, the defoamer has poor dispersibility in the coating and aggregates in local areas, unable to function evenly, thereby affecting the stability and persistence of the defoaming effect. It is difficult to meet the requirements of waterborne coatings for high compatibility, good stability, and excellent dispersibility of defoamers, resulting in surface defects such as shrinkage holes and pinholes in the paint film, which not only affect the aesthetics of the coating but also may weaken its protective performance and shorten its service life.

[0004] Chinese Patent No. CN119097962A discloses a polyether silicone defoamer for waterborne coatings and a preparation method thereof. The components of the defoamer include polyether-modified silicone oil, silicone paste, emulsifier, and auxiliary agent, and the auxiliary agent includes perfluoroalkyl ethanol polyoxyethylene ether. The defoamer of this patent can effectively reduce defects such as shrinkage holes and pinholes in the paint film after being used in waterborne coatings, but its antibacterial property is poor. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a polyether silicone defoamer for waterborne coatings and a preparation method thereof.

[0006] To achieve the above purpose, the present invention is realized through the following technical solutions: A polyether silicone defoamer for waterborne coatings, comprising the following raw materials in parts by weight: Polyether-modified silicone oil: 60 - 75 parts, silicone paste: 5 - 8 parts, dispersant: 3 - 5 parts, silica: 2 - 4 parts, emulsifier: 5 - 10 parts, surfactant: 2 - 5 parts; The emulsifier is prepared by the following method: S1: N-(4-(2,5-dioxo-4-oxazolidinyl)butyl)-2,2,2-trifluoroacetamide undergoes a ring-opening reaction under the action of n-hexylamine to obtain a fluorinated amide polymer; S2: The fluorinated amide polymer reacts with sodium azide to generate an azide compound; S3: The azide compound reacts with N,N,N-trimethylpent-4-yn-1-amine quaternary ammonium salt under the action of copper(I) bromide to generate an emulsifier.

[0007] In the step S1, the mass ratio of N-(4-(2,5-dioxo-4-oxazolidinyl)butyl)-2,2,2-trifluoroacetamide to n-hexylamine is (18 - 20):1.

[0008] In the step S2, the mass ratio of the fluorinated amide polymer to sodium azide is (2 - 3):1.

[0009] In the step S3, the mass ratio of the azide compound to N,N,N-trimethylpent-4-yn-1-amine quaternary ammonium salt is (2 - 4):1.

[0010] The dispersant is prepared by the following method: A1: Lignin reacts under the action of concentrated sulfuric acid to generate sulfonated lignin; A2: Sulfonated lignin reacts with dodecyl bromide under the action of sodium hydroxide to generate alkyl-modified lignin; A3: Alkyl-modified lignin reacts with propylene oxide under the action of phosphoric acid to generate a dispersant.

[0011] In the step A1, the mass ratio of lignin to concentrated sulfuric acid is 6:1.

[0012] In the step A2, the mass ratio of sulfonated lignin to dodecyl bromide is 3:1.

[0013] In the step A3, the mass ratio of alkyl-modified lignin to propylene oxide is 7:1.

[0014] The surfactant is prepared by mixing perfluoroalkyl ethanol polyoxyethylene ether and polyethylene glycol phosphate ester in a weight ratio of 4:1.

[0015] A preparation method of a polyether silicone defoamer for waterborne coatings comprises the following steps: (1) Weigh by weight: polyether-modified silicone oil: 60 - 75 parts, silicone paste: 5 - 8 parts, dispersant: 3 - 5 parts, silica: 2 - 4 parts, emulsifier: 5 - 10 parts, surfactant: 2 - 5 parts; (2) Mix polyether-modified silicone oil, silicone paste, dispersant, silica, emulsifier, and surfactant in proportion, and emulsify them with an emulsifying and dispersing machine for 20 - 40 minutes to obtain a polyether siloxane defoamer for waterborne coatings.

[0016] Due to the above technical solutions, the beneficial effects of the present invention include: (1) The emulsifier prepared in the present invention realizes the dual optimization of dispersibility and compatibility: its amphiphilic structure and cationic characteristics significantly improve the dispersion efficiency, while the polar / non-polar groups ensure high compatibility with the polyether siloxane system.

[0017] (2) The dispersant prepared in the present invention constitutes amphiphilic characteristics through the hydrophilicity of the sulfonic acid group and the hydrophobicity of the dodecyl group, significantly reducing the interfacial tension and promoting the uniform dispersion of polyether siloxane; in terms of defoaming performance, the strong affinity between the dodecyl group and the hydrophobic group of the siloxane accelerates the spreading of the defoamer on the surface of the foam liquid film, and the rigid lignin skeleton embeds in the liquid film to destroy the continuity, synergistically with the electrostatic repulsion of the sulfonic acid group to achieve efficient defoaming. Specific Embodiments

[0018] The following is further described in conjunction with embodiments, but the present invention is not limited to these embodiments.

[0019] Example 1 Preparation of emulsifier: S1: Under ice bath, add 1000 g of DMF and 180 g of N-(4-(2,5-dioxo-4-oxazolidinyl)butyl)-2,2,2-trifluoroacetamide to the reactor, then add 10 g of n-hexylamine, stir and mix evenly. After reacting at 4°C for 20 h, add a mixed solution of 5000 ml of cold n-hexane and ether (n-hexane:ether (V / V)=1:1), stir and mix evenly, let it stand, precipitate, filter, and vacuum dry at 70°C for 3 h to obtain a fluorinated amide polymer; the reaction equation is shown as follows:

[0020] S2: Add 100 ml of DMF, 20 g of fluorinated amide polymer, and 10 g of sodium azide to the reactor, stir and mix evenly, heat up to 50°C, react for 50 h, then cool to room temperature, filter, carry out vacuum distillation at 60°C for 2 h, then add 100 ml of dichloromethane and stir to dissolve, filter again, add 100 ml of methanol, stir for 10 min, precipitate, centrifuge, and vacuum dry at 70°C for 4 h to obtain an azide compound; the reaction equation is shown as follows:

[0021] S3: Under airtight conditions, add 300 ml of DMF, 20 g of azide compound and 10 g of N,N,N-trimethylpent-4-yn-1-amine quaternary ammonium salt to the reactor, stir and mix evenly, then add 7 g of cuprous bromide and 8 g of N,N,N′,N′′,N′′-pentamethyldiethylenetriamine, react at room temperature for 24 h, then expose to air for 1 h to quench the reaction, dialyze in a 2 wt% EDTA DMF solution (MwCO = 5 KDa) for 24 h, then dialyze in deionized water (MwCO = 5 KDa) for 24 h, and freeze-dry at -20 °C for 12 h to obtain the emulsifier; the reaction equation is shown as follows:

[0022] Example 2 Preparation of emulsifier: S1: Under an ice bath, add 1000 g of DMF and 190 g of N-(4-(2,5-dioxo-4-oxazolidinyl)butyl)-2,2,2-trifluoroacetamide to the reactor, then add 10 g of n-hexylamine, stir and mix evenly, react at 4 °C for 22 h, then add a mixed solution of 5000 ml of cold n-hexane and ether (n-hexane:ether (V / V) = 1:1), stir and mix evenly, let stand, precipitate, filter, and vacuum dry at 70 °C for 3 h to obtain the fluorinated amide polymer; S2: Add 100 ml of DMF, 25 g of fluorinated amide polymer, and 10 g of sodium azide to the reactor, stir and mix evenly, heat to 60 °C, react for 48 h, then cool to room temperature, filter, distill under reduced pressure at 60 °C for 2 h, then add 100 ml of dichloromethane and stir to dissolve, filter again, add 100 ml of methanol, stir for 10 min, precipitate, centrifuge, and vacuum dry at 70 °C for 4 h to obtain the azide compound; S3: Under airtight conditions, add 300 ml of DMF, 30 g of azide compound and 10 g of N,N,N-trimethylpent-4-yn-1-amine quaternary ammonium salt to the reactor, stir and mix evenly, then add 7 g of cuprous bromide and 8 g of N,N,N′,N′′,N′′-pentamethyldiethylenetriamine, react at room temperature for 22 h, then expose to air for 1 h to quench the reaction, dialyze in a 2 wt% EDTA DMF solution (MwCO = 5 KDa) for 24 h, then dialyze in deionized water (MwCO = 5 KDa) for 24 h, and freeze-dry at -20 °C for 12 h to obtain the emulsifier.

[0023] Example 3 Preparation of emulsifier: S1: Under an ice bath, add 1000 g of DMF and 200 g of N-(4-(2,5-dioxo-4-oxazolidinyl)butyl)-2,2,2-trifluoroacetamide to the reactor, then add 10 g of n-hexylamine, stir and mix evenly. After reacting at 4 °C for 24 h, add a mixed solution of 5000 ml of cold n-hexane and ether (n-hexane:ether (V / V) = 1:1), stir and mix evenly, let it stand, precipitate, filter, and dry in vacuum at 70 °C for 3 h to obtain a fluorinated amide polymer; S2: Add 100 ml of DMF, 30 g of fluorinated amide polymer, and 10 g of sodium azide to the reactor, stir and mix evenly, heat up to 70 °C, after reacting for 45 h, cool to room temperature, filter, distill under reduced pressure at 60 °C for 2 h, then add 100 ml of dichloromethane and stir to dissolve, filter again, add 100 ml of methanol, stir for 10 min, precipitate, centrifuge, and dry in vacuum at 70 °C for 4 h to obtain an azide compound; S3: Under airtight conditions, add 300 ml of DMF, 40 g of azide compound and 10 g of N,N,N-trimethylpent-4-yn-1-amine quaternary ammonium salt to the reactor, stir and mix evenly, then add 7 g of cuprous bromide and 8 g of N,N,N′,N′′,N′′-pentamethyldiethylenetriamine, react at room temperature for 20 h, then expose to air for 1 h to quench the reaction, dialyze in a 2 wt% EDTA DMF solution (MwCO = 5 KDa) for 24 h, then dialyze in deionized water (MwCO = 5 KDa) for 24 h, and freeze-dry at -20 °C for 12 h to obtain an emulsifier.

[0024] Example 4 Preparation of dispersant: A1: Add 300 ml of deionized water and 60 g of lignin to the reactor, stir to form a suspension; slowly add 10 g of 95 wt% concentrated sulfuric acid (control the temperature <50 °C), add dropwise for 20 min; after heating up to 60 °C, add another 150 ml of deionized water, stir and mix evenly. After reacting for 2 h, slowly add 500 ml of cold water, adjust the pH to neutral with 10 wt% NaOH solution, precipitate, centrifuge, wash with deionized water 3 times (200 ml each time), and dry in vacuum at 60 °C for 12 h to obtain sulfonated lignin; in this reaction, some hydroxyl groups in lignin are sulfonated into sulfonic acid groups; A2: Add 200 ml of absolute ethanol, 30 g of sulfonated lignin, 10 g of bromododecane, and 4 g of sodium hydroxide to the reactor, stir and mix evenly, heat up to reflux and react for 4 h, then cool to room temperature, distill under reduced pressure at 70 °C for 2 h to obtain a crude product. Dissolve the crude product in 200 ml of hot ethanol at 50 °C, filter while it is hot, and solid will precipitate after the filtrate cools. Dry in vacuum at 40 °C for 6 h to obtain alkyl-modified lignin; in this reaction, the unreacted hydroxyl groups in lignin react with the bromine atoms in bromododecane to undergo substitution reactions; A3: Under nitrogen protection, add 300 ml of anhydrous ethanol, 70 g of alkyl-modified lignin, 50 g of propylene oxide, and 8 g of 85 wt% phosphoric acid to the reactor. Stir and mix evenly, heat up to 60 °C and react for 4 h, then slowly add 200 ml of ice water to terminate the reaction. Then add 5 wt% sodium bicarbonate solution to adjust the pH to neutral, centrifuge to separate the solid, wash it 3 times with deionized water (200 ml each time), and dry it under vacuum at 50 °C for 24 h to obtain the dispersant; in this reaction, the unreacted hydroxyl groups in lignin undergo a ring-opening reaction with the epoxy groups in propylene oxide.

[0025] Example 5 Preparation of polyether silicone defoamer for waterborne coatings: (1) Weigh: polyether-modified silicone oil: 600 g, silicone paste: 50 g, dispersant (prepared in Example 4): 30 g, silica: 20 g, emulsifier (prepared in Example 1): 50 g, surfactant (16 g of perfluoroalkyl ethanol polyoxyethylene ether + 4 g of polyethylene glycol phosphate): 20 g; (2) Mix the polyether-modified silicone oil, silicone paste, dispersant, silica, emulsifier, and surfactant in proportion, and emulsify them with an emulsifying and dispersing machine at 2700 r / min for 20 min to obtain a polyether silicone defoamer for waterborne coatings.

[0026] Example 6 Preparation of polyether silicone defoamer for waterborne coatings: (1) Weigh: polyether-modified silicone oil: 700 g, silicone paste: 60 g, dispersant (prepared in Example 4): 40 g, silica: 30 g, emulsifier (prepared in Example 2): 80 g, surfactant (24 g of perfluoroalkyl ethanol polyoxyethylene ether + 6 g of polyethylene glycol phosphate): 30 g; (2) Mix the polyether-modified silicone oil, silicone paste, dispersant, silica, emulsifier, and surfactant in proportion, and emulsify them with an emulsifying and dispersing machine at 2700 r / min for 30 min to obtain a polyether silicone defoamer for waterborne coatings.

[0027] Example 7 Preparation of polyether silicone defoamer for waterborne coatings: (1) Weigh: polyether-modified silicone oil: 750 g, silicone paste: 80 g, dispersant (prepared in Example 4): 50 g, silica: 40 g, emulsifier (prepared in Example 3): 100 g, surfactant (40 g of perfluoroalkyl ethanol polyoxyethylene ether + 10 g of polyethylene glycol phosphate): 50 g; (2) Mix the polyether-modified silicone oil, silicone paste, dispersant, silica, emulsifier, and surfactant in proportion, and emulsify them with an emulsifying and dispersing machine at 2700 r / min for 40 min to obtain a polyether silicone defoamer for waterborne coatings.

[0028] Comparative Example 1 The preparation method of the polyether silicone defoamer for waterborne coatings is basically the same as that of Example 6, except that the emulsifier is replaced with an equal weight of an emulsifier prepared by the following method: S1: Under an ice bath, add 30 mL of anhydrous THF to the reactor, and add 10 mL of phosgene solution (15% by weight dissolved in toluene) through a syringe, then add 2.37 g of L-glutamic acid γ-benzyl ester, stir and mix evenly, place it in an oil bath at 50 °C and react for 2 h, perform vacuum distillation at 50 °C for 30 min, dissolve the crude product in 10 mL of dry THF, and recrystallize it in 100 mL of n-hexane, and vacuum dry it at 60 °C for 2 h to obtain Intermediate 1; S2: Under an ice bath, add 1000 g of DMF and 190 g of Intermediate 1 to the reactor, then add 10 g of n-hexylamine, stir and mix evenly, after reacting at 4 °C for 22 h, add 5000 mL of a mixed solution of cold n-hexane and ether (n-hexane: ether (V / V) = 1:1), stir and mix evenly, let it stand, precipitate, filter, and vacuum dry it at 70 °C for 3 h to obtain Intermediate 2; S3: Add 2000 mL of dichloromethane, 160 g of Intermediate 2, 10 g of catalyst 18-crown-6, 120 mL of phosphate buffer solution with pH = 7, and 250 g of N-(4-(2,5-dioxo-4-oxazolidinyl)butyl)-2,2,2-trifluoroacetamide to the reactor, stir and mix evenly, react at room temperature for 24 h, extract to remove water, then dry it with 300 g of anhydrous sodium sulfate for 1 h, filter, perform vacuum distillation at 30 °C for 40 min, then slowly add 2000 mL of cold n-hexane / ether (v / v = 1 / 1) to precipitate, centrifuge and filter, and vacuum dry it at 60 °C for 6 h to obtain Intermediate 3; S4: Add 100 mL of DMF, 25 g of Intermediate 3, and 10 g of sodium azide to the reactor, stir and mix evenly, heat up to 60 °C, after reacting for 48 h, cool to room temperature, filter, perform vacuum distillation at 60 °C for 2 h, then add 100 mL of dichloromethane to stir and dissolve, filter again, add 100 mL of methanol, stir for 10 min, precipitate, centrifuge, and vacuum dry it at 70 °C for 4 h to obtain Intermediate 4; S5: Under airtight conditions, add 300 mL of DMF, 30 g of Intermediate 4, and 10 g of N,N,N-trimethylpent-4-yn-1-amine quaternary ammonium salt to the reactor, stir and mix evenly, then add 7 g of copper(I) bromide and 8 g of N,N,N′,N′′,N′′-pentamethyldiethylenetriamine, react at room temperature for 22 h, then expose it to air for 1 h to quench the reaction, dialyze it in a 2 wt% EDTA DMF solution (MwCO = 5 KDa) for 24 h, then dialyze it in deionized water (MwCO = 5 KDa) for 24 h, and freeze-dry it at -20 °C for 12 h to obtain the emulsifier.

[0029] Comparative Example 2 The preparation method of the polyether silicone defoamer for waterborne coatings is basically the same as that of Example 6, except that the emulsifier is replaced with an emulsifier of equal weight prepared by the following method: S1: Add 100 ml of DMF, 25 g of N-(4-(2,5-dioxo-4-oxazolidinyl)butyl)-2,2,2-trifluoroacetamide, and 10 g of sodium azide to the reactor, stir and mix evenly, heat up to 50 °C, react for 50 h, then cool to room temperature, filter, distill under reduced pressure at 60 °C for 2 h, then add 100 ml of dichloromethane and stir to dissolve, filter again, add 100 ml of methanol, stir for 10 min, precipitate, centrifuge, and vacuum dry at 70 °C for 4 h to obtain the azide compound; S2: Under closed conditions, add 300 ml of DMF, 30 g of the azide compound and 10 g of N,N,N-trimethylpent-4-yn-1-amine quaternary ammonium salt to the reactor, stir and mix evenly, then add 7 g of copper(I) bromide and 8 g of N,N,N′,N′′,N′′-pentamethyldiethylenetriamine, react at room temperature for 24 h, then expose to air for 1 h to quench the reaction, dialyze (MwCO = 5 KDa) in a 2 wt% EDTA DMF solution for 24 h, then dialyze (MwCO = 5 KDa) in deionized water for 24 h, and freeze-dry at -20 °C for 12 h to obtain the emulsifier.

[0030] Comparative Example 3 The preparation method of the polyether silicone defoamer for waterborne coatings is basically the same as that of Example 6, except that the emulsifier is replaced with an emulsifier of equal weight prepared by the following method: The preparation method of the emulsifier is basically the same as that of Example 2, except that the addition amount of N-(4-(2,5-dioxo-4-oxazolidinyl)butyl)-2,2,2-trifluoroacetamide in step S1 is 300 g, and the reaction time at 4 °C is increased from 22 h to 30 h.

[0031] Comparative Example 4 The preparation method of the polyether silicone defoamer for waterborne coatings is basically the same as that of Example 6, except that the dispersant is replaced with a dispersant of equal weight prepared by the following method: The preparation method of the dispersant is basically the same as that of Example 4, except that bromododecane in step A2 is replaced with an equal weight of bromobutane.

[0032] Comparative Example 5 The preparation method of the polyether silicone defoamer for waterborne coatings is basically the same as that of Example 6, except that the dispersant is replaced with an alkyl-modified lignin prepared by step A2 of equal weight.

[0033] Comparative Example 6 A polyether silicone defoamer for waterborne coatings prepared with the raw materials and their ratios in Example 4 of the Chinese invention patent with the publication number CN119097962A.

[0034] The preparation steps of N,N,N-trimethylpent-4-yn-1-amine quaternary ammonium salt are as follows: Dissolve 10 g of N,N-dimethylpent-4-yn-1-amine in 100 mL of acetonitrile, stir to dissolve, slowly add 31 g of methyl iodide dropwise, add dropwise for 20 min, heat up to reflux and react for 24 hours, then cool to room temperature, rotary evaporate at 70 °C for 3 h, then add 50 mL of cold ether, stir to precipitate white solid, filter by suction and wash with ether 3 times (20 mL each time), and dry in vacuum at 40 °C for 12 h to obtain N,N,N-trimethylpent-4-yn-1-amine quaternary ammonium salt.

[0035] The polyether-modified silicone oil used in the examples and comparative examples of this application is Dow Corning OFX-0400; the silicone paste model is Dow Corning DC4; the perfluoroalkyl ethanol polyoxyethylene ether model is FEO-300; the polyethylene glycol phosphate is PEG400MO phosphate, produced by Hai'an Petrochemical Factory, Jiangsu Province; the lignin used is guaiacyl lignin with a molecular weight of 2000.

[0036] Dispersion test: Stir and dilute the polyether silicone defoamer prepared in the examples and comparative examples with water to form a 10 wt% solution, store it at (70 ± 5) °C for 48 h, and observe whether there is precipitation and oil floating in the emulsion.

[0037] Defoaming test: In a 1 L graduated cylinder, add 100 mL of an aqueous solution of sodium dodecylbenzenesulfonate with a mass fraction of 0.2% as the foaming liquid, heat it in a water bath to 70 °C, and bubble with N2 at a gas flow rate of 2 L / min; when the foam volume reaches 500 mL, add 1 ml of the polyether silicone defoamer prepared in the examples and comparative examples with a mass fraction of 10%, and start timing at the same time, record the time when all the foam disappears. The shorter the time, the better the defoaming effect. Keep bubbling, and record the time when the foam height reaches 500 mL again. The longer the time, the better the foam inhibition property of the defoamer.

[0038] Film performance test: 1. Weigh the waterborne coating components by weight: resin wantipro®0626: 88.3 g, polyether silicone defoamer (prepared in the examples or comparative examples): 0.1 g, film-forming aid Texanol: 6.6 g, film-forming aid DPM: 4.6 g, anti-flash rust aid FA-179: 0.4 g; 2. Add the above components to a mixer in turn under stirring conditions and stir evenly to prepare a waterborne coating; 3. After the water-based coating is placed at a constant temperature of 25°C for 24 hours, it is film-coated on a transparent glass plate. After the paint film dries, observe for shrinkage holes and qualitatively represent them using an index of 1-5, where: Level 1: Obvious shrinkage holes (diameter > 1 mm) are densely distributed on the surface of the paint film, and obvious depressions or pinholes are visible to the naked eye, with the distribution area exceeding 50%; Level 2: The number of shrinkage holes is relatively large (diameter 0.5-1 mm), appearing in patches in local areas, affecting the surface flatness, and the distribution area is 20%-50%; Level 3: A small number of isolated shrinkage holes (diameter < 0.5 mm), scattered, and need to be observed closely to be found, with the distribution area < 10%; Level 4: Almost no visible shrinkage holes, and only a very small number of tiny defects (diameter < 0.2 mm) are found under specific-angle light; Level 5: The paint film is completely smooth and flat, without any shrinkage holes, depressions or orange peel phenomena, and the surface reflects light evenly.

[0039] Antibacterial property test: Refer to GB / T21866-2008 for implementation.

[0040] Table 1

[0041] The emulsifier prepared by the present invention has a strongly polar quaternary ammonium group, which can effectively reduce the interfacial tension between polyether silicone and water-based / oil-based media, and promote the uniform dispersion of silicone oil droplets. The cationic property of the quaternary ammonium salt endows the emulsifier with a positive charge, which prevents aggregation through electrostatic repulsion, and significantly improves the kinetic stability of the dispersion system. The polar head group of the quaternary ammonium salt binds to the polyether chain segment in the polyether silicone through hydrogen bonding or dipole interaction, enhancing the compatibility between the emulsifier and the main structure of the defoamer, and reducing the risk of phase separation. In addition, the triazole structure contained in the emulsifier can form specific interactions with bacterial target proteins through hydrogen bonding, inhibit the activity of key enzymes, and has a certain antibacterial effect.

[0042] The dispersant prepared by the present invention endows lignin with strong hydrophilicity through the sulfonic acid groups introduced by the sulfonation reaction. The grafting of bromododecane introduces long-chain alkyl hydrophobic groups, forming an amphiphilic structure, enabling the dispersant to be oriented in the polyether silicone system, reducing the interfacial tension, preventing the aggregation of the defoamer, and improving the system stability. The epoxy group of propylene oxide opens the ring under acidic conditions and undergoes a nucleophilic addition reaction with the phenolic hydroxyl group of lignin to form a polyether side chain; the steric hindrance effect of the polyether side chain prevents particle aggregation, improves the dispersion efficiency; at the same time, it can reduce the surface tension, improve the wettability and interfacial compatibility; the introduction of the ether bond (C-O-C) increases the flexibility of the molecular chain and reduces the risk of molecular chain breakage at high temperatures.

[0043] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. However, for those of ordinary skill in the art, within the scope of the technical solution of the present invention, any minor changes, modifications, and equivalent variations made by using the technical content disclosed above are all equivalent embodiments of the present invention. At the same time, any changes, modifications, and equivalent variations made to the above embodiments based on the substantial technology of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A polyether silicone defoamer for waterborne coatings, characterized in that, It includes raw materials in the following parts by weight: Polyether-modified silicone oil: 60 - 75 parts, silicone paste: 5 - 8 parts, dispersant: 3 - 5 parts, silicon dioxide: 2 - 4 parts, emulsifier: 5 - 10 parts, surfactant: 2 - 5 parts; The emulsifier is prepared by the following method: S1: N-(4-(2,5-dioxo-4-oxazolidinyl)butyl)-2,2,2-trifluoroacetamide undergoes a ring-opening reaction under the action of n-hexylamine to obtain a fluorinated amide polymer; S2: The fluorinated amide polymer reacts with sodium azide to generate an azide compound; S3: The azide compound reacts with N,N,N-trimethylpent-4-yn-1-amine quaternary ammonium salt under the action of copper(I) bromide to generate the emulsifier.

2. The polyether silicone defoamer for waterborne coatings according to claim 1, wherein In step S1, the mass ratio of N-(4-(2,5-dioxo-4-oxazolidinyl)butyl)-2,2,2-trifluoroacetamide to n-hexylamine in the feed is (18 - 20):

1.

3. The polyether silicone defoamer for waterborne coatings according to claim 1, wherein, In step S2, the mass ratio of the fluorinated amide polymer to sodium azide in the feed is (2 - 3):

1.

4. The polyether silicone defoamer for waterborne coatings according to claim 1, characterized in that, In step S3, the mass ratio of the azide compound to N,N,N-trimethylpent-4-yn-1-amine quaternary ammonium salt in the feed is (2 - 4):

1.

5. A polyether silicone defoamer for waterborne coatings according to claim 1, characterized in that, The dispersant is prepared by the following method: A1: Lignin reacts under the action of concentrated sulfuric acid to generate sulfonated lignin; A2: Sulfonated lignin reacts with dodecyl bromide under the action of sodium hydroxide to generate alkyl-modified lignin; A3: Alkyl-modified lignin reacts with propylene oxide under the action of phosphoric acid to generate the dispersant.

6. The polyether silicone defoamer for waterborne coatings according to claim 5, wherein, In step A1, the mass ratio of lignin to concentrated sulfuric acid in the feed is 6:

1.

7. The polyether silicone defoamer for waterborne coatings according to claim 5, characterized in that, In step A2, the mass ratio of sulfonated lignin to dodecyl bromide in the feed is 3:

1.

8. The polyether silicone defoamer for waterborne coatings according to claim 5, characterized in that, In step A3, the mass ratio of alkyl-modified lignin to propylene oxide in the feed is 7:

10.

9. The polyether silicone defoamer for waterborne coatings according to claim 1, characterized in that, The surfactant is prepared by compounding perfluoroalkyl ethanol polyoxyethylene ether and polyethylene glycol phosphate ester in a weight ratio of 4:

1.

10. A method for preparing a polyether silicone defoamer for waterborne coatings according to any one of claims 1-9, characterized in that, It includes the following steps: (1) Weigh by parts by weight: polyether-modified silicone oil: 60 - 75 parts, silicone paste: 5 - 8 parts, dispersant: 3 - 5 parts, silicon dioxide: 2 - 4 parts, emulsifier: 5 - 10 parts, surfactant: 2 - 5 parts; (2) Mix the polyether-modified silicone oil, silicone paste, dispersant, silicon dioxide, emulsifier, and surfactant in proportion, and emulsify with an emulsifying and dispersing machine for 20 - 40 min to obtain a polyether silicone defoamer for waterborne coatings.

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