A modified siloxane defoamer and its preparation method

Abstract

This application relates to the field of coatings and ink additives, and more specifically to a modified siloxane defoamer and its preparation method. The modified siloxane defoamer comprises raw materials including: a composite modified siloxane matrix, a base siloxane, a synergist, a catalyst, and a solvent. The defoamer product ultimately obtained by this application not only effectively solves the compatibility and durability problems of previous coating / ink defoamers, but also further improves the multifunctionality of the defoamer, taking into account more synergistic effects, enhancing the application of the defoamer in more complex and demanding coating / ink systems, and has excellent application potential. Furthermore, it provides a new approach to improving the overall performance of defoamers.

Description

Technical Field

[0001] This application relates to the field of coatings and ink additives, and more specifically to a modified siloxane defoamer and its preparation method. Background Technology

[0002] During the production and application of coatings and inks, micron- to millimeter-sized bubbles are easily generated due to the use of surfactants, dispersants, and other additives, as well as processes such as mechanical stirring and high-speed coating. If these bubbles are not effectively eliminated, they can lead to defects such as pinholes, orange peel, and craters on the coating surface, while also affecting the printing uniformity and adhesion of the ink. Therefore, high-efficiency defoamers are indispensable functional additives in coating and ink formulations.

[0003] Modified siloxane defoamers, as highly efficient defoaming materials, possess excellent defoaming and foam-suppressing capabilities due to their unique chemical structure. They are typically synthesized by introducing organic groups into the siloxane chain, which allows them to possess the compatibility of organic compounds while retaining the low surface tension properties of siloxanes. These defoamers can effectively reduce or inhibit foam formation and exhibit good compatibility with both aqueous and solvent-based systems.

[0004] However, despite the many advantages of modified siloxane defoamers, existing products and technologies still have some limitations, such as: compatibility issues—although modified siloxane defoamers have better compatibility than traditional silicone defoamers, incompatibility may still occur in certain coating and ink systems, leading to surface defects such as pinholes, orange peel, or blooming in the coating film; durability issues—in some applications requiring prolonged stirring or continuous foam treatment, some defoamers lack durability and cannot maintain long-term effective defoaming effects; and a lack of multifunctionality—existing products mostly focus on the single function of defoaming, making it difficult to take into account the synergistic performance of dispersion, leveling, or wetting, thus increasing the difficulty of application. Summary of the Invention

[0005] Therefore, in order to effectively solve the above-mentioned existing problems, this application provides a modified siloxane defoamer and its preparation method. The defoamer product finally obtained by this application can not only effectively solve the compatibility and durability problems of previous coating / ink defoamers, but also further improve the multifunctionality of the defoamer, take into account more synergistic improvement effects, enhance the application of the defoamer in more complex and higher-requirement coating / ink systems, have excellent application potential, and provide a new idea for improving the comprehensive performance of defoamers.

[0006] Modified siloxane defoamer, by weight, is composed of the following raw materials: 25-40 parts of composite modified siloxane body, 15-25 parts of base siloxane, 3-8 parts of synergist, 1-3 parts of dispersant, 0.3-1 parts of stabilizer, 0.1-0.4 parts of catalyst, and 15-30 parts of solvent.

[0007] In a preferred embodiment, the mass ratio of the base siloxane to the synergist in the composite modified siloxane body is (28-40):(20-24):(4-6).

[0008] In a more preferred embodiment, the mass ratio of the base siloxane to the synergist in the composite modified siloxane body is (30-33):(21-22):(4.5-5.5).

[0009] As a preferred embodiment, the preparation method of the composite modified siloxane specifically includes the following steps: S1: Under nitrogen protection, the main chain siloxane and xylene are added to a reaction vessel, heated and stirred until completely dissolved; S2: The modified monomer is added and stirred at a constant temperature, and then an initiator is added and heated to react to obtain a graft copolymer; S3: The xylene is removed by vacuum distillation to obtain the final product.

[0010] As a more preferred embodiment, the preparation method of the composite modified siloxane specifically includes the following steps: S1: Methyl vinyl siloxane and xylene are added to a reaction vessel under nitrogen protection, heated to 75-80°C, and stirred at 200-300 rpm until completely dissolved; S2: Vinyl trifluoropropyl cyclotrisiloxane, dodecyl acrylate and allyl glycidyl ether are added, and the mixture is stirred at a constant temperature for 30-40 min, then dicumyl peroxide is added and the temperature is raised to 85-90°C for 5-6 h to obtain the graft copolymer; S3: Distillation is carried out at -0.09 MPa to -0.08 MPa and 90-95°C under reduced pressure to remove xylene and obtain the final product.

[0011] In a preferred embodiment, the average molecular weight of the methylvinylsiloxane is 5000-8000 Da.

[0012] In a preferred embodiment, the mass ratio of the methyl vinylsiloxane, vinyltrifluoropropylcyclotrisiloxane, dodecyl acrylate and allyl glycidyl ether is (9-10):(1.5-2):(1-1.2):(0.6-0.9).

[0013] In a more preferred embodiment, the mass ratio of the methyl vinylsiloxane, vinyltrifluoropropylcyclotrisiloxane, dodecyl acrylate and allyl glycidyl ether is (9.5-10):(1.5-1.8):(1-1.1):(0.7-0.8).

[0014] The addition of the aforementioned composite modified siloxane groups significantly improves the defoaming performance of the defoamer product, exhibiting excellent compatibility and defoaming durability, and further enhancing the stability, heat resistance, and multifunctionality of the defoamer. The introduced fluorinated groups possess extremely low surface tension, preferentially adsorbing onto the surface of the bubble film, disrupting the film's elasticity, accelerating bubble rupture, and anchoring at the bubble interface through the hydrophobic effect of the long-chain alkyl groups, forming a dense molecular layer that prevents gas diffusion and bubble regeneration. Ultimately, during the curing process of the coating / ink, it undergoes a ring-opening reaction with hydroxyl and carboxyl groups in the resin, forming a chemical bond network that fixes the defoamer molecules within the coating, achieving a powerful antifoaming effect over a long period.

[0015] On the other hand, the composite-modified siloxane has a higher CF bond energy, which, together with the thermal stability of the siloxane backbone, resists high-temperature degradation. Furthermore, the cyclic structure of trifluoropropylcyclotrisiloxane reduces chain breakage under high shear through steric hindrance. Moreover, the overall defoamer system is compatible with both polar (aqueous) and non-polar (solvent-based) systems. The long-chain alkyl groups and fluorinated segments form a hydrophobic core, while the epoxy groups are exposed on the molecular surface, dynamically balancing the polarity of different resin systems.

[0016] In a more preferred embodiment, the base siloxane is a combination of octamethylcyclotetrasiloxane and polydimethylsiloxane.

[0017] In a preferred embodiment, the mass ratio of the octamethylcyclotetrasiloxane to the polydimethylsiloxane is (2-3):(4.2-5).

[0018] In a more preferred embodiment, the mass ratio of the octamethylcyclotetrasiloxane to the polydimethylsiloxane is (2.2-2.5):(4.5-4.8).

[0019] In a preferred embodiment, the synergist is at least one selected from fumed silica, polytetrafluoroethylene, calcium stearate, dimethyl silicone oil, and hydrogenated castor oil.

[0020] In a more preferred embodiment, the synergist is a combination of calcium stearate and hydrogenated castor oil.

[0021] In a preferred embodiment, the mass ratio of calcium stearate to hydrogenated castor oil is (0.8-1.4):(4-5).

[0022] In a more preferred embodiment, the mass ratio of calcium stearate to hydrogenated castor oil is (1-1.2):(4.2-4.6).

[0023] In a preferred embodiment, the dispersant is at least one selected from polyacrylate, polyvinylpyrrolidone, castor oil derivative, and phosphate salt.

[0024] In a preferred embodiment, the dispersant is polyvinylpyrrolidone or a phosphate salt.

[0025] In a preferred embodiment, the stabilizer is at least one of 2,6-di-tert-butyl-p-cresol, triphenyl phosphite, and epoxidized soybean oil.

[0026] In a preferred embodiment, the stabilizer is 2,6-di-tert-butyl-p-cresol.

[0027] In a preferred embodiment, the catalyst is at least one of tetramethylammonium hydroxide, dibutyltin dilaurate, and tetraisopropyl titanate.

[0028] In a preferred embodiment, the catalyst is dibutyltin dilaurate.

[0029] In a preferred embodiment, the solvent is at least one selected from butyl acetate, cyclohexanone, isopropanol, and propylene glycol methyl ether acetate.

[0030] In a preferred embodiment, the solvent is butyl acetate or isopropanol.

[0031] The preparation method of modified siloxane defoamer specifically includes the following steps: S1: Add the composite modified siloxane matrix, the base siloxane, and the synergist to the solvent, heat in a water bath at 50-55℃, and disperse at high speed at 1500-2000 rpm for 30-40 min; S2: Add the dispersant and stabilizer, and process the mixture three times using a high-pressure homogenizer at a pressure of 45-50 MPa to obtain a uniform dispersion with a particle size <200 nm; S3: Add the catalyst, and react at a constant temperature of 60-65℃ for 2-3 h, controlling the final viscosity at 800-1000 cP. After completion, filter through a 4.5-5 μm filter to remove impurities, thus obtaining the final product.

[0032] This application has the following beneficial effects:

[0033] 1. The modified siloxane defoamer provided in this application can not only effectively solve the compatibility and durability problems of previous coating / ink defoamers, but also further improve the multifunctionality of the defoamer, take into account more synergistic improvement effects, enhance the application of the defoamer in more complex and demanding coating / ink systems, have excellent application potential, and provide a new idea for improving the comprehensive performance of defoamers.

[0034] 2. The modified siloxane defoamer provided in this application has a fluorinated group with extremely low surface tension introduced by the added composite modified siloxane body. It preferentially adsorbs on the surface of the bubble liquid film, destroys the elasticity of the film layer, accelerates the bubble rupture, and anchors at the bubble interface through the hydrophobic effect of the long-chain alkyl group to form a dense molecular layer, which prevents gas diffusion and bubble regeneration. Finally, during the curing process of the coating / ink, it undergoes a ring-opening reaction with hydroxyl and carboxyl groups in the resin to form a chemical bond network, fixing the defoamer molecules inside the coating and achieving a strong foam suppression effect over a long period of time.

[0035] 3. The modified siloxane defoamer provided in this application, with its composite modified siloxane matrix, can resist high-temperature degradation through higher CF bond energies and the combined thermal stability of the siloxane backbone. Furthermore, the cyclic structure of trifluoropropylcyclotrisiloxane reduces chain breakage under high shear through steric hindrance. The overall defoamer system is compatible with both polar (aqueous) and non-polar (solvent-based) systems. The long-chain alkyl groups and fluorinated segments form a hydrophobic core, while the epoxy groups are exposed on the molecular surface, dynamically balancing the polarity of different resin systems. Detailed Implementation

[0036] The specific implementation examples will be used to more intuitively demonstrate and explain the content of the invention in this application.

[0037] Example 1

[0038] The modified siloxane defoamer, by weight, is composed of the following raw materials: 30 parts of composite modified siloxane body, 21.5 parts of base siloxane, 4.5 parts of synergist, 1.6 parts of dispersant, 0.5 parts of stabilizer, 0.16 parts of catalyst, and 22.5 parts of solvent.

[0039] The preparation method of the composite modified siloxane, by weight, specifically includes the following steps: S1: Under nitrogen protection, 9.8 parts of methyl vinyl siloxane and 50 parts of xylene are added to a reaction vessel, heated to 80℃, and stirred at 200 rpm until completely dissolved; S2: 1.6 parts of vinyltrifluoropropylcyclotrisiloxane, 1.1 parts of dodecyl acrylate and 0.7 parts of allyl glycidyl ether are added, and the mixture is stirred at a constant temperature for 35 min. Then, dicumyl peroxide is added and the mixture is heated to 85℃ for 5 h to obtain the graft copolymer; S3: The xylene is removed by vacuum distillation at -0.09 MPa and 90℃ to obtain the final product.

[0040] The average molecular weight of the methyl vinyl siloxane is 6000 Da, and it was purchased from Dow Chemical Company, USA, as the DC1107 Fluid model product.

[0041] The base siloxane is a composition of octamethylcyclotetrasiloxane and polydimethylsiloxane in a mass ratio of 2.3:4.7.

[0042] Octamethylcyclotetrasiloxane was purchased as a premium-grade product from Shandong Shouhua Chemical Co., Ltd., China.

[0043] The polydimethylsiloxane was purchased from Dow Corning Incorporated, USA, as the PMX-200 model product.

[0044] The synergist is a combination of calcium stearate and hydrogenated castor oil in a mass ratio of 1:4.5; the hydrogenated castor oil was purchased from Wuhan Huaxiang Kejie Biotechnology Co., Ltd., China, as a PEG-7 hydrogenated castor oil product.

[0045] The dispersant is polyvinylpyrrolidone K30; the stabilizer is 2,6-di-tert-butyl-p-cresol; the catalyst is dibutyltin dilaurate; and the solvent is isopropanol.

[0046] The preparation method of modified siloxane defoamer includes the following steps: S1: Add the composite modified siloxane body, the base siloxane and the synergist to the solvent, heat in a water bath at 50℃, and disperse at high speed at 2000rpm for 30min; S2: Add the dispersant and stabilizer, and process the mixture three times through a high-pressure homogenizer at a pressure of 50MPa to obtain a uniform dispersion with a particle size <200nm; S3: Add the catalyst, stir and react at a constant temperature of 60℃ for 3h, control the final viscosity at 900cP, and filter through a 5μm filter to remove impurities to obtain the final product.

[0047] Example 2

[0048] The only difference between this embodiment and Example 1 is as follows: The modified siloxane defoamer, by mass, is composed of the following components: 38.5 parts of composite modified siloxane body, 20 parts of base siloxane, 5.8 parts of synergist, 1.8 parts of dispersant, 0.4 parts of stabilizer, 0.18 parts of catalyst, and 24.5 parts of solvent.

[0049] The base siloxane is a composition of octamethylcyclotetrasiloxane and polydimethylsiloxane in a mass ratio of 3:4.2.

[0050] Example 3

[0051] The only difference between this embodiment and Example 1 is as follows: The modified siloxane defoamer, by mass, is composed of the following components: 28.5 parts of composite modified siloxane body, 23.8 parts of base siloxane, 4.2 parts of synergist, 1.4 parts of dispersant, 0.6 parts of stabilizer, 0.16 parts of catalyst, and 27.5 parts of solvent.

[0052] The base siloxane is a combination of octamethylcyclotetrasiloxane and polydimethylsiloxane in a mass ratio of 2:5.

[0053] Comparative Example 1

[0054] The only difference between this comparative example and Example 1 is as follows: the modified siloxane defoamer, by mass, consists of the following components: 15.5 parts of composite modified siloxane body, 40 parts of base siloxane, 6.6 parts of synergist, 2.2 parts of dispersant, 0.8 parts of stabilizer, 0.22 parts of catalyst, and 30 parts of solvent.

[0055] Comparative Example 2

[0056] The only difference between this comparative example and Example 1 is as follows: the modified siloxane defoamer, by mass, consists of the following components: 55 parts of composite modified siloxane body, 5.5 parts of base siloxane, 4.8 parts of synergist, 1.1 parts of dispersant, 0.5 parts of stabilizer, 0.12 parts of catalyst, and 24 parts of solvent.

[0057] Comparative Example 3

[0058] The only difference between this comparative example and Example 1 is that the base siloxane is a combination of octamethylcyclotetrasiloxane and polydimethylsiloxane in a mass ratio of 5:1.

[0059] Comparative Example 4

[0060] The only difference between this comparative example and Example 1 is that the base siloxane is a combination of octamethylcyclotetrasiloxane and polydimethylsiloxane in a mass ratio of 1:8.

[0061] Comparative Example 5

[0062] The only difference between this comparative example and Example 1 is as follows: The preparation method of the composite modified siloxane, by mass, specifically includes the following steps: S1: Under nitrogen protection, 9.8 parts of methyl vinyl siloxane and 50 parts of xylene are added to a reaction vessel, heated to 80°C, and stirred at 200 rpm until completely dissolved; S2: 2.8 parts of vinyltrifluoropropylcyclotrisiloxane, 0.4 parts of dodecyl acrylate and 0.2 parts of allyl glycidyl ether are added, and the mixture is stirred at a constant temperature for 35 min. Then, dicumyl peroxide is added and the temperature is raised to 85°C for 5 h to obtain the graft copolymer; S3: Distillation is carried out at -0.09 MPa and 90°C under reduced pressure to remove xylene and obtain the final product.

[0063] Comparative Example 6

[0064] The only difference between this comparative example and Example 1 is the following: The preparation method of the composite modified siloxane, by mass, specifically includes the following steps: S1: Under nitrogen protection, 9.8 parts of methyl vinyl siloxane and 50 parts of xylene are added to a reaction vessel, heated to 80°C, and stirred at 200 rpm until completely dissolved; S2: 0.8 parts of vinyltrifluoropropylcyclotrisiloxane, 2.6 parts of dodecyl acrylate and 0.5 parts of allyl glycidyl ether are added, and the mixture is stirred at a constant temperature for 35 min. Then, dicumyl peroxide is added and the temperature is raised to 85°C for 5 h to obtain the graft copolymer; S3: Distillation is carried out at -0.09 MPa and 90°C under reduced pressure to remove xylene and obtain the final product.

[0065] Performance Evaluation

[0066] 1. Using the defoamer prepared in the comparative examples and embodiments, the same commercially available acrylic resin emulsion system (50% solids content, purchased from BASF, Germany) was used. For product A378X, the defoamer addition amount is 1wt%. Use a high-speed disperser to stir at 2000rpm for 5min to introduce air bubbles. Immediately take 100mL of the coating and pour it into a graduated transparent cylinder. Record the initial foam volume. After standing, record the test foam volume at the 5min time point. Defoaming efficiency % = (1 - test foam volume / initial foam volume) × 100%. The result is the average of 10 tests and recorded in Table 1.

[0067] 2. The defoamer samples prepared in the examples and comparative examples were placed in an oven at 150°C and heated for 168 hours. After cooling to room temperature, the defoaming efficiency was tested according to the scheme in performance test 1. The retention rate of defoaming efficiency was calculated. The viscosity change rate was tested using a rotational rheometer (25°C, shear rate 10^4 s-1). The average value of 10 tests was recorded in Table 1.

[0068] 3. The defoamer samples prepared in the examples and comparative examples were added to the carbon black slurry at an amount of 0.3 wt%, and the Hergmann fineness grade was determined. The results were recorded in Table 1.

[0069] Table 1 Performance Evaluation Table

[0070]

[0071]

[0072] Based on the final performance test results of the examples and comparative examples, comparative examples 1-6 achieved worse performance results compared to the examples. The examples, however, achieved better results by adopting a better technical solution. The fluorinated groups introduced into the composite modified siloxane body have extremely low surface tension, preferentially adsorb onto the surface of the bubble liquid film, destroy the elasticity of the film layer, accelerate bubble rupture, and anchor to the bubble interface through the hydrophobic effect of the long-chain alkyl groups, forming a dense molecular layer that prevents gas diffusion and bubble regeneration. Finally, during the curing process of the coating / ink, it undergoes a ring-opening reaction with hydroxyl and carboxyl groups in the resin to form a chemical bond network, fixing the defoamer molecules inside the coating, achieving a strong antifoaming effect and comprehensive performance over a long period of time.

Claims

1. A modified siloxane defoamer, characterized in that: By weight, the raw material consists of the following components: 25-40 parts of composite modified siloxane, 15-25 parts of base siloxane, 3-8 parts of synergist, 1-3 parts of dispersant, 0.3-1 part of stabilizer, 0.1-0.4 parts of catalyst, and 15-30 parts of solvent. The preparation method of the composite modified siloxane specifically includes the following steps: S1: Under nitrogen protection, methyl vinylsiloxane and xylene are added to a reaction vessel, heated to 75~80℃, and stirred at 200~300rpm until completely dissolved; S2: Vinyltrifluoropropylcyclotrisiloxane, dodecyl acrylate and allyl glycidyl ether are added, and the mixture is stirred at a constant temperature for 30~40min, then dicumyl peroxide is added and the temperature is raised to 85~90℃ for 5~6h to obtain the graft copolymer; S3: Distillation is carried out at -0.09MPa~-0.08MPa at 90~95℃ under reduced pressure to remove xylene and obtain the final product; The average molecular weight of the methylvinylsiloxane is 5000~8000 Da; The mass ratio of the methyl vinylsiloxane, vinyltrifluoropropylcyclotrisiloxane, dodecyl acrylate and allyl glycidyl ether is (9~10):(1.5~2):(1~1.2):(0.6~0.9). The base siloxane is a composition of octamethylcyclotetrasiloxane and polydimethylsiloxane in a mass ratio of (2~3):(4.2~5). The preparation method of the modified siloxane defoamer is characterized by the following steps: S1: The composite modified siloxane matrix, the base siloxane, and the synergist are added to a solvent, heated in a water bath at 50-55°C, and dispersed at high speed at 1500-2000 rpm for 30-40 min; S2: A dispersant and a stabilizer are added, and the mixture is circulated three times using a high-pressure homogenizer at a pressure of 45-50 MPa to obtain a uniform dispersion with a particle size <200 nm; S3: A catalyst is added, and the mixture is stirred at a constant temperature of 60-65°C for 2-3 h. The final viscosity is controlled at 800-1000 cP. After completion, the mixture is filtered through a 4.5-5 μm filter to remove impurities, thus obtaining the final product. The catalyst is dibutyltin dilaurate.

2. The modified siloxane defoamer according to claim 1, characterized in that: The synergist is at least one of fumed silica, polytetrafluoroethylene, calcium stearate, dimethyl silicone oil, and hydrogenated castor oil.

3. The modified siloxane defoamer according to claim 2, characterized in that: The mass ratio of the base siloxane to the synergist in the composite modified siloxane is (28~40):(20~24):(4~6).

4. The modified siloxane defoamer according to claim 3, characterized in that: The dispersant is at least one of polyacrylate, polyvinylpyrrolidone, castor oil derivative and phosphate salt.

5. The modified siloxane defoamer according to claim 4, characterized in that: The stabilizer is at least one of 2,6-di-tert-butyl-p-cresol, triphenyl phosphite, and epoxidized soybean oil.

6. The modified siloxane defoamer according to claim 5, characterized in that: The solvent is at least one of butyl acetate, cyclohexanone, isopropanol, and propylene glycol methyl ether acetate.

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