Synthesis and production process of a siloxane foam inhibitor

Abstract

This invention discloses a novel siloxane defoamer synthesis and production process. The defoamer comprises 2-10 parts of hydrophobically treated fumed silica or nano-silica filler, 40-70 parts of a concentrated silicone oil composition, 40-70 parts of high-viscosity polydimethylsiloxane, and 100-150 parts of a fatty alcohol-propylene oxide polymer. Two types of concentrated silicone oil compositions are used, exhibiting diverse structures and chain lengths, totaling 16 types, with clearly defined preparation methods. The filler undergoes special hydrophobication treatment, and the preparation process includes mixing with the concentrated silicone oil, reaction heating, and centrifugal separation. The production process involves mixing the components in a specific ratio, followed by high-speed stirring, addition of oleic acid, and heating to obtain the novel siloxane defoamer. The components of this invention work synergistically to enhance defoaming and foam suppression capabilities. The process is simple, easy to operate and control, and the product has strong versatility. It performs excellently in high-viscosity oily systems, effectively solving foaming problems in various oily systems. It is low-cost, high-efficiency, and its performance is adjustable, exhibiting good stability and compatibility.

Description

Technical Field

[0001] This invention relates to the chemical industry, specifically to the synthesis and production process of a siloxane defoamer, which is specifically used to prevent foaming in oily media, especially high-viscosity oily systems. Background Technology

[0002] Organosilicon composite defoamers possess extremely low interfacial tension, effectively inhibiting bubble formation. They remain stable at high temperatures, can be used in various chemical environments, and are non-toxic and stable. In recent years, researchers have been studying how to optimize the structure of organosilicon compounds to improve their performance. Polydimethylsiloxane (PDS) is a linear siloxane without hydrogen atoms, exhibiting low interfacial tension and excellent defoaming properties. In this case, hydrogen-containing PDS with hydrogen-substituted terminal or repeating units can enhance the defoaming effect. The methyl groups bound to hydrogen reduce interfacial tension through hydrogen bonds and van der Waals forces, which decreases foam stability and accelerates defoaming. Therefore, it can reduce bubble size, inhibit bubble formation, and help the defoamer function effectively. However, it affects the viscosity and flowability of the siloxane compound, reducing its stability; therefore, a proper balance must be maintained. Besides hydrogen content, siloxane chain length is also a significant factor influencing defoaming ability. Shorter chain lengths of siloxane have higher interfacial activity, resulting in better defoaming characteristics, but limited ability to stabilize and inhibit foam, thus leading to poorer sustainability. Longer chain lengths can provide higher viscosity, which can more stably suppress foam formation, but the defoaming performance is reduced, and the thermal and chemical stability is also increased.

[0003] It is well known that high-efficiency defoamers, also known as defoamer compounds, can be prepared from non-polar oils and fine solid particles as fillers. However, existing production methods are complex and uneconomical, and suffer from dispersibility and compatibility issues. According to patents US3235509A and US3560401A, the non-polar oil is typically polydimethylsiloxane, and the filler is prepared by heating to 100-300°C for several hours under alkaline catalysts such as alkali silicates or alkali hydroxides, resulting in hydrophobic silica. The use of partially rubberized crosslinked polydimethylsiloxane to enhance the defoamer's effect is already well-known in patent US2632736A. Furthermore, such products can also be prepared by free radical crosslinking of polydimethylsiloxane.

[0004] To produce composite siloxane defoamers with high defoaming capabilities, it is necessary to synthesize organosiloxanes and incorporate them into concentrated oil compositions. However, this is a multi-step process that is both complex and uneconomical. Furthermore, when using polydimethylsiloxane as a concentrated oil composition, individual polysiloxane oils may cause dispersibility and oil-in-water compatibility issues. Summary of the Invention

[0005] The purpose of this invention is to provide a synthesis and production process for a siloxane defoamer, specifically relating to a siloxane foam inhibitor containing hydrogen atoms, its preparation process, and a siloxane composite defoamer composition. More specifically, this invention relates to a defoamer based on silicone oil and fillers with hydrophobic properties, which is particularly suitable for limiting or inhibiting foam generation rather than reducing foam, and its application is in preventing foaming in oily media, especially high-viscosity oily systems.

[0006] The present invention relates to the synthesis and production process of siloxane defoamers, including the preparation process of siloxane foam inhibitors, the formulation design of siloxane composite defoamer compositions, and their application technology in oily systems. The chemical synthesis involves the processing and reaction of raw materials such as methylcyclosiloxanes, hydrogen-containing cyclosiloxanes, and linear siloxanes, as well as the application technology of catalysts, fillers, fumed silica, or nano-silica.

[0007] According to the production process of the siloxane defoamer provided by the present invention, a low-hydrogen silicone oil with a specific molecular weight and structure is prepared. This oil has a lower surface tension than general polydimethylsiloxanes and possesses the characteristics of low surface tension and easy dispersibility of polymers of nonionic surfactants fatty alcohols and propylene oxide. It can be blended with high-viscosity polysiloxanes to improve defoaming, degassing, and stability, as well as stability and compatibility, dispersibility, high-temperature resistance, and resistance to hydroxyl groups and inorganic salts in oils and oily fluids. It can be used for defoaming under difficult conditions. The hydrophobic treatment of the filler reduces interparticle attraction, achieving good dispersion and preventing agglomeration, thus more effectively suppressing foam. In oily systems, its surface properties are more compatible with the oily environment, enhancing compatibility, reducing adverse effects, and improving stability and applicability. It can also synergistically enhance defoaming and defoaming performance with other components and contribute to improving initial defoaming and defoaming properties.

[0008] This invention provides a formulation for a siloxane defoamer, comprising a specific ratio of filler, a concentrated silicone oil composition, high-viscosity polydimethylsiloxane, and a polymer of fatty alcohol and propylene oxide. The synergistic effect of these components achieves a better defoaming effect. The compounding method of the siloxane defoamer provided by this invention improves the stability of the defoamer, such as high-temperature stability, storage stability, absence of shrinkage cavities, phase transitions, and coloring phenomena. It can be used in all oily foaming liquid systems, especially high-viscosity oily systems.

[0009] This invention provides a siloxane defoamer, comprising: 2-10 parts filler, 40-70 parts silicone oil concentrate composition, 40-70 parts high-viscosity polydimethylsiloxane, and 100-150 parts fatty alcohol and propylene oxide polymer; wherein the filler is a hydrophobically treated filler.

[0010] The formulation of this invention employs a specific ratio and combination of components. A concentrated silicone oil composition, high-viscosity polydimethylsiloxane, and fatty alcohol are combined with an epoxy propylene polymer in a specific ratio. This combination effectively suppresses bubble formation and stabilizes foam in oily systems by altering the surface tension and interfacial properties of the system. The hydrophobic filler, at a ratio of 2-10 parts, disperses better in the defoamer system, preventing agglomeration and ensuring uniform distribution throughout the system, thus maximizing its foam-suppressing effect. In oily media, especially high-viscosity oily systems, hydrophobic treatment makes the filler more compatible with the system environment, reducing problems such as sedimentation and stratification caused by incompatibility, improving the stability and applicability of the defoamer in oily systems, and thus enhancing the overall defoaming effect. The filler can also synergistically work with other components to disrupt bubble stability, accelerate bubble breakage, and further improve the defoaming and foam-suppressing performance of the defoamer, especially in the early stages of foam formation, where it can quickly exert its effect, enhancing initial defoaming and foam-breaking properties.

[0011] Silicone oil concentrate is a key component of defoamers. As the core defoaming ingredient, silicone oil concentrate works synergistically with other components such as high-viscosity polydimethylsiloxane, fatty alcohols and propylene oxide polymers, and fillers to jointly suppress the generation of bubbles in oily systems. By adjusting its structure and component ratio, it can effectively change the surface tension and interfacial properties of the system, thereby achieving a good defoaming effect. Furthermore, by adjusting its structural parameters such as chain length and ratio, oily concentrated defoamer compositions with different structures and chain lengths can be prepared. This structural optimizability allows for precise improvement of defoaming ability and storage stability for different oily systems and application requirements. Moreover, its own stability and good compatibility with other components are crucial to ensuring the quality and stability of the defoamer product. During storage, a suitable silicone oil concentrate structure can prevent adverse phenomena such as phase separation, ensuring that the defoamer maintains good performance even after long-term storage.

[0012] Preferably, the silicone oil concentrate composition comprises two silicone oil concentrate components with the structure of Formula 1:

[0013]

[0014] Japanese Style 2:

[0015] ,

[0016] In the construct:

[0017] R1 is a methyl group, R2 is a hydrogen atom, m is 0 to 50, n is 1 to 150, and the structure includes a variety of different chain lengths;

[0018] Specifically, when n is 2 to 5 times m, it is preferably 2.8 to 4 times m, including:

[0019] 0≤m≤25 (Equation 1-1), (Equation 2-1);

[0020] 26≤m≤55 (Equation 1-2), (Equation 2-2);

[0021] 56≤m≤85 (Equation 1-3), (Equation 2-3);

[0022] 86≤m≤125 (Equation 1-4), (Equation 2-4);

[0023] When n is 20 to 50 times m, preferably 28 to 40 times, including:

[0024] 0≤m≤25 (Equation 1-5), (Equation 2-5);

[0025] 26≤m≤55 (Equation 1-6), (Equation 2-6);

[0026] 56≤m≤85 (Equation 1-7), (Equation 2-7);

[0027] 86≤m≤125 (Equation 1-8), (Equation 2-8).

[0028] The preparation steps of the silicone oil concentrated composition of this invention describe the specific preparation process of two silicone oil concentrated compositions with hydrogen atoms at the ends, including steps such as raw material addition amount, catalyst, reaction conditions, and post-treatment. A specific technical solution is adopted, including mixing and stirring methyl cyclic siloxane, hydrogen-containing cyclic siloxane, and linear siloxane or methyl linear siloxane with hydrogen atoms at the ends; adding a catalyst, refluxing and heating; adding a specific substance to complete the reaction; and removing the solvent and low-boiling-point water, etc., to prepare an oily concentrated defoamer composition. The method is simple and low-cost. Compared with commercially available defoamers based on polyether-modified organosilicon oil, this invention only requires one step to obtain the oil concentrated composition, and the defoaming ability of some examples is the same as or better than that of commercially available defoamers, reducing costs while ensuring performance. The relatively simple preparation method of the silicone oil concentrated composition, compared with some complex multi-step production processes, helps to reduce the overall production cost of the defoamer. At the same time, while ensuring defoaming performance, it improves the cost-effectiveness of the product, giving it a certain advantage in market competition.

[0029] This invention optimizes the structure of concentrated silicone oil compositions: by adjusting the chain length m and the ratio of m to n, oily concentrated defoamer compositions with different structures and chain lengths are prepared. This optimizability of the structure can be adjusted according to actual needs to improve defoaming ability and storage stability.

[0030] Furthermore, the silicone oil concentrate composition of Formula 1 is prepared by the following method:

[0031] S11 solution preparation: In a container, considering the ratio of m to n, add octamethylcyclotetrasiloxane and tetramethylcyclotetrasiloxane, and add tetramethyldisiloxane according to the chain length.

[0032] S12 catalyst addition: Add 1-5% concentrated sulfuric acid by total mass as catalyst, condense and reflux under nitrogen atmosphere and heat and stir, control the reaction temperature at 50-70℃, and the polymerization reaction lasts for 4-7 hours.

[0033] S13 Cooling and Neutralization: Add solid sodium carbonate for neutralization, stop the reaction, stir until the pH value reaches neutral, and cool naturally to room temperature;

[0034] S14 Filtration and Distillation: The filtered and neutralized solid material is distilled under reduced pressure at 70-90℃ for 3-5 hours to distill off low-boiling-point substances, yielding a transparent liquid product, silicone oil concentrate composition formula 1.

[0035] Furthermore, the silicone oil concentrate composition of formula 2 is prepared by the following method:

[0036] S21 solution preparation: In a container, considering the ratio of m to n, add octamethylcyclotetrasiloxane and tetramethylcyclotetrasiloxane, and add hexamethyldisiloxane according to the chain length.

[0037] S22 catalyst addition: Add 1-5% concentrated sulfuric acid by total mass as catalyst, condense and reflux under nitrogen atmosphere and heat and stir, control the reaction temperature at 50-70℃, and the polymerization reaction lasts for 4-7 hours.

[0038] S23 Cooling and Neutralization: Add solid sodium carbonate for neutralization, stop the reaction, stir until the pH value reaches neutral, and cool naturally to room temperature;

[0039] S24 Filtration and Distillation: The filtered and neutralized solid material is distilled under reduced pressure at 70-90℃ for 3-5 hours to distill off low-boiling-point substances, yielding a transparent liquid product, silicone oil concentrate composition formula 2.

[0040] Octamethylcyclotetrasiloxane and tetramethylcyclotetrasiloxane are key raw materials for constructing the basic structure of silicone oil concentrate compositions. Their combination and addition with tetramethyldisiloxane in a specific ratio provide a suitable chemical structural basis for subsequent reactions, determining the chain length distribution and chemical properties of the final product, thus affecting its performance as an antifoaming agent. Different chain lengths and ratios result in differences in antifoaming ability and stability of silicone oil concentrate compositions to meet the needs of different oily systems. The addition of hexamethyldisiloxane instead of tetramethyldisiloxane based on chain length makes Formula 2 structurally different from Formula 1. This structural difference leads to different chemical and physical properties, thus affecting its mode of action and effect in antifoaming agents. It exhibits unique characteristics in its interaction with oily systems, its bubble suppression mechanism, and its compatibility with other components, providing more options to meet the antifoaming needs of different oily systems.

[0041] Concentrated sulfuric acid, acting as a catalyst, lowers the activation energy of the reaction, accelerating the polymerization process. Cooling and stirring are performed under nitrogen atmosphere, where nitrogen acts as a protective layer, preventing oxidation of raw materials and products, ensuring the stability of the reaction environment, and avoiding the introduction of impurities that could affect product quality. Precise control of the reaction temperature at 50-70℃ and the polymerization duration at 4-7 hours ensures the reaction proceeds under suitable kinetic conditions, guaranteeing complete reaction of the raw materials and the formation of a concentrated silicone oil composition with the desired structure and properties. Excessive temperature or time will increase side reactions, affecting product quality; conversely, insufficient temperature or time will result in incomplete reaction and poor product performance. Precise control of reaction conditions is crucial for ensuring consistent product quality and performance, enabling Formulas 1 and 2 to function stably in the antifoaming agent system and achieve repeatable performance in mass production.

[0042] Add solid sodium carbonate to neutralize the concentrated sulfuric acid, stopping the reaction and adjusting the pH of the system to neutral. This step is crucial because residual acidic substances can negatively impact the product's stability, corrosiveness, and compatibility with other components. Natural cooling to room temperature provides suitable temperature conditions for subsequent filtration operations, facilitating the process and contributing to product stability. This prevents structural changes or performance fluctuations caused by sudden temperature variations, ensuring the product is in optimal condition before proceeding to the next stage. This facilitates smooth filtration and distillation operations, improving the overall quality of the product.

[0043] Filtration and neutralization of the solids remove insoluble impurities generated during the reaction, such as unreacted catalysts and neutralized salts, improving product purity and providing a pure raw material basis for subsequent applications. Vacuum distillation at 70-90℃ for 3-5 hours effectively removes low-boiling-point substances, further purifying the product and removing residual solvents, unreacted small-molecule raw materials, and other impurities. The resulting transparent liquid silicone oil concentrate compositions (Formulas 1 and 2) have higher purity and more stable performance, allowing them to better function in defoamer formulations. For example, they more effectively reduce surface tension and improve synergistic effects with other components, thereby enhancing the overall performance of the defoamer, ensuring stability during storage and use, and extending the product's lifespan and effectiveness.

[0044] The silicone oil concentrate compositions prepared in the process of this invention have 16 different types, which are precisely adapted to the needs of different oily systems, optimize the defoaming performance, improve the product flexibility and adaptability, and achieve performance balance and optimization.

[0045] Preferably, the silicone oil concentrate composition contains 8 siloxanes in each structural formula of Formula 1 and Formula 2 based on the m:n ratio, depending on the chain length, resulting in a total of 16 siloxanes and 16 silicone oil concentrate compositions.

[0046] Formulas 1 and 2 show the concentrated oily defoamer composition used in this invention, distinguished by whether the terminal group of the polymer is hydroxyl or methyl; and further divided into 16 groups according to the chain length of the concentrated oily defoamer composition m and the ratio of m to n:

[0047] The dynamic viscosity of formulas 1-1, 1-5, 2-1, and 2-5 is 10 to 40 cSt, preferably 15 to 29 cSt;

[0048] The dynamic viscosity of formulas 1-2, 1-6, 2-2, and 2-6 is 40 to 120 cSt, preferably 42 to 117 cSt;

[0049] The dynamic viscosity of formulas 1-3, 1-7, 2-3, and 2-7 is 90 to 200 cSt, preferably 99 to 183 cSt;

[0050] The dynamic viscosity of formulas 1-4, 1-8, 2-4, and 2-8 is 120 to 500 cSt, preferably 130 to 437 cSt.

[0051] Different oil-based systems vary in viscosity, composition, and foaming properties. The 16 silicone oil concentrate compositions, based on a diversity of chain lengths and proportions, can be more precisely adapted to various oil-based systems. Some high-viscosity oil-based systems require silicone oil concentrate compositions with specific chain lengths and proportions to achieve optimal defoaming effects. These 16 different combinations provide a wide range of choices, ensuring that the most suitable formulation for a specific oil-based system can be found, thereby improving the effectiveness of the defoamer in different application scenarios.

[0052] Variations in chain length and proportion affect the chemical structure and physical properties of silicone oil concentrate compositions, thus influencing their defoaming performance. By offering 16 different siloxane combinations, the defoaming ability of the defoamer can be tailored to specific needs. Some combinations excel in suppressing bubble formation, while others are superior in stabilizing existing foam or accelerating bubble collapse. This diversity allows for the selection of the most suitable silicone oil concentrate composition to achieve optimized defoaming performance, improving defoaming efficiency and effectiveness, tailored to the characteristics of foams in different oily systems.

[0053] The market offers a wide variety of oil-based systems that are constantly evolving. Having 16 concentrated silicone oil compositions allows for greater flexibility and adaptability in defoamer products. Whether it's an existing oil-based system or one that may emerge in the future, it's more likely to find a suitable concentrated silicone oil composition to create a defoamer that meets specific needs. This facilitates wider application across different industries and fields, enhances the product's market competitiveness, and provides users with more customized solutions.

[0054] When considering defoaming performance, other properties such as storage stability and compatibility with oily systems also need to be taken into account. The existence of 16 silicone oil concentrate compositions allows for trade-offs and optimization among different properties. Some combinations achieve a better balance between defoaming performance and storage stability, while others excel in both defoaming performance and compatibility with specific oily systems. By selecting the appropriate silicone oil concentrate composition, the overall performance can be optimized according to the key requirements of specific applications, thereby improving the overall quality and usability of the product.

[0055] The filler is hydrophobically treated, which helps improve the performance of the defoamer in complex environments and distinguishes it from other conventional defoamer components.

[0056] Preferably, the hydrophobically treated filler is hydrophobically treated fumed silica or nano-silica with a specific surface area of ​​70-150 m². 2 / g, the proportion of the siloxane defoamer component is maintained at 5-20wt%.

[0057] By selecting hydrophobically treated fumed silica or nano silica and controlling its parameters, dispersion requirements can be enhanced, adapting to the characteristics of oily systems, optimizing defoaming performance, balancing initial defoaming and defoaming capabilities, and maintaining the stability of the system structure.

[0058] A specific surface area of ​​70-150 m² / g provides abundant surface active sites for the filler. These sites can strongly interact with other components such as silicone oil concentrates, high-viscosity polydimethylsiloxane, and fatty alcohol-propylene oxide polymers, promoting more uniform dispersion of the filler throughout the defoamer system. Uniformly dispersed fillers prevent agglomeration, ensuring they exert their foam-suppressing effect at all locations in the oily system, thereby improving the overall effectiveness of the defoamer. If the specific surface area is too small, insufficient active sites may lead to uneven dispersion; conversely, an excessively large specific surface area may exacerbate filler agglomeration, also hindering dispersion.

[0059] For oily media, especially high-viscosity oily systems, hydrophobic treatment is crucial. This treatment enables the filler surface properties to be compatible with the oily environment, enhancing its compatibility with the oily system. In such a system, the filler can better integrate, reducing adverse phenomena such as precipitation and stratification caused by incompatibility. This improves the stability and applicability of the defoamer in the oily system, allowing it to effectively suppress the generation of bubbles in the oily system.

[0060] Fillers work synergistically with other components to disrupt bubble stability and accelerate bubble collapse. Fumed silica or nano-silica particles can adsorb onto the bubble film surface, altering the local surface tension and causing the bubble film to thin until it ruptures. Maintaining their proportion in the siloxane defoamer component at 5-20 wt% is an optimized range derived from extensive experiments and research. Within this range, sufficient filler is ensured to effectively suppress foam without excessive content interfering with the synergistic effects between other components or causing the system to become too viscous, thus affecting its dispersion and effectiveness in oily systems.

[0061] The hydrophobic treatment of the filler helps it take effect quickly in the early stages of foam formation, enhancing its initial defoaming ability. During foam formation, it can efficiently disrupt the bubble structure and improve defoaming properties. This is because the appropriate specific surface area and hydrophobic treatment allow the filler to quickly contact newly formed bubbles and interfere with their stable existence, while the controlled proportion ensures the balance and continuity of this ability throughout the defoaming process, enabling the defoamer to effectively control foam at different stages.

[0062] A specific proportion of filler in the defoamer system helps maintain the stability of the overall structure. It works with other components to construct a relatively stable microstructure, preventing component separation and sedimentation, and ensuring the consistent performance of the defoamer during storage and use. This stable system structure ensures the defoamer functions effectively for a long time, extending the product's lifespan and enabling it to reliably suppress foam generation in oily systems under various application scenarios.

[0063] Hydrophobic treatment imparts hydrophobicity to the filler, improves the synergistic effect between the filler and other components, enhances the antifoaming performance of the filler, and optimizes the physicochemical properties of the filler.

[0064] Furthermore, the hydrophobic treatment method is as follows: under the action of the prepared silicone oil composition, fumed silica or nano silica is heated to 100 to 300°C for 2 to 5 hours to make it hydrophobic, wherein the ratio of the silicone oil composition to fumed silica or nano silica is 1:5-20.

[0065] Under the action of the prepared silicone oil composition, heating fumed silica or nano-silica to 100 to 300°C for 2-5 hours can change the chemical properties of the filler surface, thereby achieving hydrophobicity. This hydrophobicity gives the filler better compatibility in oily systems, allowing it to better integrate into oily media, reducing problems such as precipitation and agglomeration caused by incompatibility with oily systems, improving the stability and dispersibility of the defoamer in oily systems, and thus enhancing the overall performance of the defoamer.

[0066] After hydrophobication treatment, the properties of the filler surface are more compatible with other components such as silicone oil concentrate, high-viscosity polydimethylsiloxane, and fatty alcohol and propylene oxide polymers. This helps the filler to work synergistically with other components in the defoamer system, jointly exerting its function of suppressing foam. In the process of suppressing bubble formation and stabilizing foam, the hydrophobic filler can cooperate with other components to more effectively change the surface tension and interfacial properties of the system, thereby improving the defoaming effect.

[0067] When hydrophobically treated fillers come into contact with air bubbles, their surface properties reduce the stability of the bubble film and accelerate its collapse. Filler particles can adhere to the surface of the bubble film; due to their hydrophobicity, they alter the local surface tension distribution of the bubble film, making it easier for the bubble film to thin and break. This improves the defoaming performance of the filler in defoamers, especially in high-viscosity oily systems, where this improvement is more pronounced, helping to better meet the defoaming requirements in practical applications.

[0068] The heating and interaction process with the silicone oil composition not only imparts hydrophobicity to the filler but also has other beneficial effects on its physicochemical properties. Utilizing heat for dehydration and hydrophobic treatment, the Si-OH or Si-O-Si in the concentrated silicone oil composition reacts with the Si-OH in fumed silica or nano-silica to form chemical bonds. This chemical bonding makes the silicone oil concentrated composition more firmly cross-linked on the filler surface, stabilizing surface hydrophobicity. This means that the filler's compatibility in oily systems is enhanced, allowing it to better integrate into oily media and reducing problems such as sedimentation and agglomeration. In addition to hydrophobic stability, this process alters the filler's surface morphology and pore structure, further increasing its specific surface area or active sites. This allows the filler to function better in antifoaming agent systems, improving the overall performance of the antifoaming agent. Simultaneously, it improves the filler's temperature resistance and chemical resistance, broadening its application range under different conditions. In practical applications, this treated filler can adapt to more complex oily system environments, effectively suppressing foam generation. The heating and silicone oil composition work together to better match the surface properties of the filler with the oily system, thereby improving the dispersibility of the filler in the oily system. The uniformly dispersed filler can avoid agglomeration and ensure that it can play its role in suppressing foam at various locations in the oily system, thus improving the overall effectiveness of the defoamer. The change in the surface properties of the filler enhances its synergistic effect with other components such as the silicone oil concentrate composition, high-viscosity polydimethylsiloxane, and fatty alcohol and propylene oxide polymer. In the process of suppressing bubble generation and stabilizing foam, it can more effectively change the surface tension and interfacial properties of the system, thereby improving the defoaming effect. The enhanced synergistic effect helps to maintain the stability of the overall structure of the defoamer system, prevent the separation and precipitation of components, and ensure the performance consistency of the defoamer during storage and use. This allows the defoamer to play an effective role for a long time and extend the service life of the product.

[0069] In the process of this invention, when preparing the hydrophobic filler, the filler is uniformly dispersed in the silicone oil concentrate composition, which enhances the filler's hydrophobicity, dispersibility, stability, and compatibility with other components; strict control of reaction conditions ensures stable and consistent filler performance, improving product quality reliability; centrifugal separation removes impurities and recovers unreacted filler, improving raw material utilization, reducing costs, and decreasing waste emissions, bringing economic and environmental benefits; it provides a basis for optimizing antifoaming agent formulations, facilitating flexible adjustments to the formulation to achieve the best antifoaming effect and meet different needs.

[0070] Furthermore, the method for preparing the hydrophobic filler is as follows:

[0071] a. Mixing the filler with the silicone oil concentrate: Add hydrophobically treated fumed silica or nano silica to the prepared silicone oil concentrate at a ratio of 1:8-70 and mix and stir.

[0072] b. Reaction and heating: The mixture is heated to 150-180℃ and reacted with stirring for 6-8 hours to obtain a hydrophobically treated filler with a silicone oil concentrate composition on its surface;

[0073] c. Post-reaction processing: The hydrophobically treated packing material containing the concentrated silicone oil composition is stored and preserved directly without centrifugation. Unused packing material is used after centrifugation and drying. Unreacted concentrated silicone oil composition is collected for recycling.

[0074] In the preparation method of hydrophobic fillers, hydrophobically treated fumed silica or nano-silica is mixed with a concentrated silicone oil composition at a specific ratio of 1:8-70. This step aims to ensure that the filler surface is in full contact with the concentrated silicone oil composition. On the one hand, the concentrated silicone oil composition can further modify and enhance the filler to a certain extent, improving its compatibility with subsequent additives. On the other hand, the initial mixing of the two provides a uniform reaction system for subsequent reactions, ensuring that the filler is uniformly dispersed throughout the system, allowing each filler particle to participate in the reaction. This lays the foundation for obtaining a hydrophobically treated filler with stable and uniform performance.

[0075] The mixture is heated to 150-180°C and stirred for 6-8 hours. This process induces a chemical reaction or physical interaction between the concentrated silicone oil composition and the hydrophobically treated filler. The high temperature and stirring conditions accelerate the reaction, promoting better coating of the concentrated silicone oil composition onto the filler surface and forming a stable structure. This surface treatment further enhances the hydrophobicity of the filler, improving its dispersibility and stability in oily systems. Simultaneously, it strengthens the bond between the filler and the concentrated silicone oil composition, thereby improving the overall performance of the filler in the defoamer and enabling it to play a more effective role in suppressing foam generation and stabilizing foam.

[0076] The centrifugation step is primarily for collecting the hydrophobically treated filler with the concentrated silicone oil composition on its surface after the reaction, while simultaneously recovering unreacted concentrated silicone oil composition. The collected filler can be directly used in the subsequent formulation of defoamers, ensuring consistent product quality and performance. Recovering unused filler and silicone oil composition improves raw material utilization, reduces production costs, and is also beneficial to environmental protection by reducing waste emissions. Furthermore, centrifugation removes impurities or agglomerates that may be generated during the reaction, further purifying the hydrophobically treated filler and improving its purity and quality, allowing it to function better in the defoamer system.

[0077] The siloxane defoamer production process provided by this invention involves mixing hydrophobically treated fillers, concentrated silicone oil compositions, high-viscosity polydimethylsiloxane, and nonionic surfactants in specific proportions. The synergistic effect of these components enhances both defoaming and foam suppression capabilities. The defined component ratio range allows for precise formulation according to the needs of oily systems, improving product versatility and practicality, and effectively addressing foaming issues in various scenarios. Reasonable raw material selection and ratio design reduce production costs and improve production efficiency, making the product more competitive in the market. The prepared defoamer can be widely used in various oily foaming liquid systems, especially performing exceptionally well in high-viscosity oily systems, effectively solving foaming problems in different oily systems.

[0078] This invention provides a production process for a siloxane defoaming agent, the specific steps of which are as follows:

[0079] Mix 1-5 parts of hydrophobic filler with 40-70 parts of concentrated silicone oil composition and stir. Then add 40-70 parts of high-viscosity polydimethylsiloxane and 100-150 parts of nonionic surfactant and stir at high speed. Add oleic acid to the foam suppressant base formulation while stirring and heat to react to obtain a siloxane foam suppressant.

[0080] The production process of the siloxane defoamer of the present invention involves mixing hydrophobically treated filler, silicone oil concentrate, high-viscosity polydimethylsiloxane, and nonionic surfactant in a specific ratio. The components work synergistically to effectively suppress foam generation in oily systems. The hydrophobically treated filler helps to disrupt the stability of bubbles, the silicone oil concentrate can change the surface tension of the system, the high-viscosity polydimethylsiloxane enhances the stability of the system, and the nonionic surfactant improves the dispersibility of each component, thus jointly enhancing the defoaming and foam suppression capabilities, thereby obtaining a high-performance defoamer that meets the defoaming needs of various oily systems.

[0081] The mixing and stirring steps ensure that all components are mixed evenly, providing a good foundation for subsequent reactions. High-speed stirring further promotes full contact and interaction of the components, forming a stable system, effectively preventing component separation, and ensuring the stability of the defoamer's performance. The heating reaction causes chemical reactions or physical interactions between the components, enhancing their binding force, further improving the product's stability, extending its shelf life, and reducing the possibility of performance fluctuations during storage.

[0082] Oleic acid, a natural biodegradable component, is introduced and combined with siloxanes. As an unsaturated fatty acid, oleic acid has good emulsifying and dispersing properties, which can improve the dispersion effect of the defoamer in the foaming system, allowing the defoamer to play a more uniform role. At the same time, oleic acid itself is easily decomposed by microorganisms in nature, and after being combined with siloxanes, it can improve the biodegradability of the entire defoamer system to a certain extent.

[0083] The well-defined component ratio range and specific process steps allow this process to be adjusted according to the characteristics of different oily systems, thereby preparing defoamers suitable for various oily foaming liquid systems and improving product applicability. Whether in low-viscosity or high-viscosity oily systems, this defoamer can exert a good defoaming effect and has wide applicability. In particular, its performance advantages are more prominent in high-viscosity oily systems, which can effectively solve the foaming problems that are prone to occur in high-viscosity oily systems, providing an effective foam control solution for industries such as coatings, inks, and lubricants.

[0084] The process steps of this invention are relatively simple, easy to operate and control, and do not require complex equipment or harsh reaction conditions. The optimized production process is conducive to large-scale production. The reasonable selection and proportion design of raw materials not only ensures the performance of the product, but also reduces the production cost. During the production process, each component can be fully utilized, reducing the waste of raw materials, improving production efficiency, making the product more competitive in the market, and also conforming to the principle of sustainable development, bringing economic and environmental benefits to enterprises.

[0085] Meanwhile, this process can adjust the performance of the defoamer by changing the type and proportion of raw materials; by changing the structure and chain length of the silicone oil concentrate composition and selecting different types of nonionic surfactants, the defoamer can be adapted to different usage environments and special needs, such as improving high temperature resistance and chemical resistance; this performance adjustment capability enables the defoamer to meet diverse market demands, expand the application range of the product, and play an important role in different fields and industries.

[0086] Nonionic surfactants have good compatibility and dispersibility, can reduce surface tension and stabilize; oleic acid can enhance antifoaming performance, while balancing performance and cost.

[0087] Preferably, the nonionic surfactant is a polymer of fatty alcohol and propylene oxide, with a neutral pH and a hydroxyl value less than or equal to 35 mg KOH / g; the amount of oleic acid is 0.5-3.0% of the total mass of the defoamer.

[0088] The polymer of fatty alcohols and propylene oxide, as a nonionic surfactant, possesses a molecular structure that ensures good compatibility in oily systems. This allows for better and more uniform mixing with other components, preventing agglomeration or stratification, thus improving the stability of the defoamer in oily systems and ensuring its sustained and effective defoaming action. Simultaneously, its good dispersibility allows the surfactant to be evenly distributed throughout the system, fully utilizing its surface activity and further enhancing the defoaming effect. The polymer's low surface tension effectively reduces the surface energy of oily systems, making it difficult for bubbles to remain stable in their early stages, thereby improving the defoamer's ability to suppress bubble formation. Furthermore, its neutral pH value does not significantly affect the acidity or alkalinity of oily systems during use, ensuring the system's chemical stability. The hydroxyl value of less than or equal to 35 mg KOH / g helps control the balance between the surfactant's hydrophilicity and lipophilicity, allowing it to function effectively in oily systems without being overly hydrophilic and affecting overall performance, further enhancing its applicability and stability as a defoamer.

[0089] Oleic acid should be used at a concentration of 0.5-3.0% of the total mass of the defoamer. Within this range, oleic acid can synergistically work with other components to further optimize the performance of the defoamer. Oleic acid molecules have a unique structure that allows them to form an adsorption layer on the surface of bubbles, altering the surface properties of the bubbles and making the bubble film easier to break, thereby improving the defoaming and foam-suppressing capabilities of the defoamer. Appropriate addition of oleic acid can compensate for the shortcomings of other components in suppressing bubbles, forming a more complete defoaming system. By precisely controlling the dosage of oleic acid between 0.5-3.0%, not only can a good defoaming effect be achieved, but production costs can also be reasonably controlled while ensuring product performance. Insufficient oleic acid will not fully exert its synergistic effect, affecting the overall performance of the defoamer; while excessive dosage will increase costs and negatively impact other product properties, affecting the stability or compatibility of the system. Therefore, optimizing the dosage of oleic acid can find the best balance between performance and cost, improving the product's cost-effectiveness and making it more competitive in the market.

[0090] This invention provides an effective method for developing a concentrated defoamer composition based on factors such as hydrogen content and structural length. It uses siloxane as the defoamer composition and provides a method for formulating a siloxane-based defoamer. This defoamer is easy to manufacture, low in cost, and exhibits excellent defoaming effect, especially in high-viscosity oil-based systems. It can be used in all oily foaming liquid systems, particularly high-viscosity oily systems, solving the problems of poor compatibility and insufficient defoaming ability of traditional defoamers in certain situations. The siloxane defoamer production process of this invention prepares the defoamer by mixing hydrophobically treated fillers, a concentrated silicone oil composition, high-viscosity polydimethylsiloxane, and fatty alcohol with a propylene oxide polymer through specific mixing, stirring, and heating reaction steps. This multi-component synergistic reaction production process design fully considers the interactions between the components, enabling the production of a high-performance defoamer, which differs from traditional defoamer production processes that simply mix components. The filler treated with hydrophobic coating has a lower surface tension than ordinary polydimethylsiloxane, while possessing the easy dispersibility of nonionic surfactants. It can be blended with high-viscosity polysiloxanes to enhance defoaming, degassing ability and stability, as well as stability, compatibility, dispersibility, high temperature resistance, resistance to hydroxyl groups and inorganic salts in oil and oily fluids. It can be used for foam suppression under difficult conditions.

[0091] In summary, the present invention has the following beneficial effects:

[0092] 1. In the synthesis process of the siloxane defoamer of the present invention, the defoaming performance is optimized by using a concentrated silicone oil composition. The concentrated silicone oil composition forms 16 different types based on variations in chain length and proportion, precisely adapting to various oily systems. The combination of different chain lengths and proportions results in diverse chemical structures and physical properties of the composition, each with its own advantages in inhibiting bubble formation, stabilizing foam, or accelerating bubble breakage. It can be specifically selected according to the foaming characteristics of different oily systems, improving defoaming efficiency and effect, enhancing the applicability of the product in different fields and industries, and improving market competitiveness.

[0093] 2. The synthesis of the siloxane defoamer of the present invention enhances defoaming by improving the performance of fillers. The hydrophobic filler is hydrophobic fumed silica or nano silica, which has a suitable specific surface area, enhances dispersibility at a specific ratio, has good compatibility with oily systems, reduces precipitation and stratification, and works synergistically with other components to destroy bubble stability, enhance initial defoaming and defoaming ability, and maintain the stability of the system structure.

[0094] 3. The production process of the siloxane defoamer of the present invention improves the overall performance by adding nonionic surfactants and oleic acid. Nonionic surfactants ensure good dispersion of each component, reduce surface tension, ensure the chemical stability of the system, and improve the applicability and stability of the defoamer. Oleic acid improves the dispersion effect, increases biodegradability, and synergistically optimizes the defoaming performance. The overall production process is simple and easy to control, can be adjusted as needed, and is suitable for a variety of oily systems. It has outstanding advantages in high-viscosity oily systems and effectively solves the foaming problem.

[0095] 4. In the synthesis and production process of the siloxane defoamer of the present invention, reasonable raw material selection and process design reduce costs and improve production efficiency; centrifugal separation during filler preparation can recover unreacted fillers, improve raw material utilization, reduce waste emissions, and bring economic and environmental benefits.

[0096] 5. The present invention provides a synthesis and production process for a siloxane defoamer, wherein the preparation method of the concentrated silicone oil composition is simple, the product has high purity and stable performance, and good compatibility with other components, ensuring the quality and stability of the defoamer, preventing adverse phenomena such as phase separation, and extending the product's service life and effectiveness; the components of the defoamer synergistically construct a stable microstructure, preventing component separation and precipitation, ensuring consistent performance during storage and use, and effectively inhibiting the generation of foam in oily systems for a long time, providing users with a reliable and durable foam control solution. Attached Figure Description

[0097] Figure 1 This is a schematic diagram showing the evaluation results of the foam suppression ability of each group of defoamers. Detailed Implementation

[0098] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

[0099] 1. Experimental Methods

[0100] 1.1 Preparation of concentrated silicone oil composition

[0101] 1.1.1 Preparation of concentrated silicone oil composition (Formula 1)

[0102] The first type of silicone oil concentrate composition 1, which contains hydrogen atoms at both ends, is prepared by the following method:

[0103] In a nitrogen atmosphere, S11 is prepared by first adding octamethylcyclotetrasiloxane and tetramethylcyclotetrasiloxane to a 500 mL four-necked flask, and then adding tetramethyldisiloxane according to the chain length.

[0104] S12 is added with 2% concentrated sulfuric acid as a catalyst, and the mixture is refluxed and heated under nitrogen atmosphere. The reaction temperature is controlled at 50-70℃ and the polymerization reaction lasts for 4-7 hours.

[0105] S13 was neutralized by adding solid sodium carbonate to end the reaction. The mixture was stirred until the pH value reached neutral and then allowed to cool naturally to room temperature.

[0106] The solid material after S14 filtration and neutralization is distilled under reduced pressure at 70-90℃ for 3-5 hours to remove low-boiling-point substances, yielding a transparent liquid product, silicone oil concentrate 1, with the following chemical formula. The addition amounts of different embodiments of the methyl silicone oil concentrate are detailed in Table 1 below:

[0107]

[0108] Table 1 Examples of silicone oil concentrate compositions based on different m:n ratios and chain lengths with hydrogen atoms at the ends.

[0109] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Octamethylcyclotetrasiloxane / wt% 68.93 82.77 76.16 93.25 77.21 94.99 77.77 95.67 Tetramethylcyclotetrasiloxane / wt% 29.02 2.24 20.38 2.52 20.69 2.58 20.81 2.60 Tetramethyldisiloxane / wt% 12.50 14.99 3.46 4.23 2.10 2.43 1.42 1.73 Chemical formula Formula 1-1 Formula 1-5 Formula 1-2 Formula 1-6 Formula 1-3 Formula 1-7 Formula 1-4 Formula 1-8

[0110] 1.1.2 Preparation of concentrated silicone oil composition (Formula 2)

[0111] The second type, silicone oil concentrate composition 2, with hydrogen atoms at both ends, is prepared as follows:

[0112] In a nitrogen atmosphere, S21 is prepared by first adding octamethylcyclotetrasiloxane and tetramethylcyclotetrasiloxane to a 500 mL four-necked flask, and then adding hexamethyldisiloxane according to the chain length.

[0113] S22 was added with 2% concentrated sulfuric acid as a catalyst, and the mixture was refluxed and heated under nitrogen atmosphere. The reaction temperature was controlled at 50-70℃ and the polymerization reaction lasted for 4-7 hours.

[0114] S23 is added to solid sodium carbonate for neutralization, the reaction is stopped, and the mixture is stirred until the pH value reaches neutral. It is then allowed to cool naturally to room temperature.

[0115] The solid material after S24 filtration and neutralization is distilled under reduced pressure at 70-90℃ for 3-5 hours to remove low-boiling-point substances, yielding a transparent liquid product, silicone oil concentrate composition 2, with the following chemical formula. The addition amounts of different embodiments of methyl silicone oil concentrate composition are detailed in Table 2 below:

[0116]

[0117] Table 2 Examples of silicone oil concentrate compositions with different embodiments based on m:n ratio and chain length, with methyl groups at the end.

[0118] Example 9 Example 10 Example 11 Example 12 Example 13 Example 14 Example 15 Example 16 Octamethylcyclotetrasiloxane / wt% 67.87 68.26 75.63 94.83 76.88 94.51 77.55 96.33 Tetramethylcyclotetrasiloxane / wt% 17.39 1.85 20.23 2.57 20.6 2.56 79.25 2.66 Hexamethyldisiloxane / wt% 14.74 29.89 4.14 2.60 2.52 2.93 1.70 1.01 Chemical formula Equation 2-1 Formula 2-5 Equation 2-2 Formula 2-6 Equation 2-3 Formula 2-7 Equation 2-4 Formula 2-8

[0119] 1.2 Preparation of packing material

[0120] The hydrophobication treatment method is as follows: Under the action of the prepared silicone oil composition, fumed silica or nano-silica is heated to 100 to 300°C for 2-5 hours to make it hydrophobic. The ratio of silicone oil composition to fumed silica or nano-silica is 1:10. The hydrophobic filler is prepared by:

[0121] S31 filler mixed with silicone oil concentrate composition: add hydrophobically treated fumed silica or nano silica to the prepared silicone oil concentrate composition at a ratio of 1:8-70 and mix and stir.

[0122] S32 Reaction and Heating: The mixture is heated to 150-180℃ and reacted for 6-8 hours under stirring to obtain a hydrophobically treated filler with a silicone oil concentrate composition on its surface;

[0123] After the S33 reaction is completed, the hydrophobically treated filler containing the concentrated silicone oil composition is stored and preserved directly without centrifugation. Unused filler is used after centrifugation and drying. Unreacted concentrated silicone oil composition is collected for recycling.

[0124] 1.3 Preparation of siloxane defoaming agents

[0125] The specific steps in the production process of compounding siloxane defoamers are as follows:

[0126] Mix 1-5 parts of hydrophobic filler with 40-70 parts of concentrated silicone oil composition and stir. Then add 40-70 parts of high-viscosity polydimethylsiloxane and 100-150 parts of nonionic surfactant and stir at high speed. Add oleic acid to the foam suppressant base formulation while stirring and heat to react to obtain a siloxane foam suppressant sample.

[0127] 1.4 Example: Siloxane Defoamer Sample

[0128] a. Sample 1: An example of a siloxane defoamer sample prepared by compounding with a silicone oil concentrate for hydrophobic treatment of silica, using the silicone oil concentrate composition of Example 1.

[0129] b. Sample 2: An example of a siloxane defoamer sample prepared by compounding with a silicone oil concentrate for hydrophobic treatment of silica, using the silicone oil concentrate composition of Example 2;

[0130] c. Sample 3: An example of a siloxane defoamer sample prepared by compounding with a silicone oil concentrate for hydrophobic treatment of silica, using the silicone oil concentrate of Example 3.

[0131] d. Sample 4: An example of a siloxane defoamer sample prepared by compounding with a silicone oil concentrate for hydrophobic treatment of silica, as described in Example 4 using the silicone oil concentrate composition.

[0132] e. Sample 5: An example of a siloxane defoamer sample prepared by compounding with a silicone oil concentrate for hydrophobic treatment of silica, using the silicone oil concentrate of Example 5.

[0133] f. Sample 6: An example of a siloxane defoamer sample prepared by compounding with a silicone oil concentrate for hydrophobic treatment of silica, using the silicone oil concentrate of Example 6.

[0134] g. Sample 7: An example of a siloxane defoamer sample prepared by compounding with a silicone oil concentrate for hydrophobic treatment of silica, using the silicone oil concentrate composition of Example 7.

[0135] h. Sample 8: An example of a siloxane defoamer sample prepared by compounding with a silicone oil concentrate for hydrophobic treatment of silica, using the silicone oil concentrate composition of Example 8.

[0136] i. Sample 9: An example of a siloxane defoamer sample prepared by compounding with a silicone oil concentrate for hydrophobic treatment of silica using Example 9 of silicone oil concentrate composition;

[0137] j. Sample 10: An example of a siloxane defoamer sample prepared by compounding with a silicone oil concentrate for hydrophobic treatment of silica, using the silicone oil concentrate composition of Example 10.

[0138] k. Sample 11: An example of a siloxane defoamer sample prepared by compounding with a silicone oil concentrate for hydrophobic treatment of silica using the silicone oil concentrate composition Example 11.

[0139] 1. Sample 12: An example of a siloxane defoamer sample prepared by compounding with a silicone oil concentrate for hydrophobic treatment of silica using silicone oil concentrate composition Example 12.

[0140] m. Sample 13: An example of a siloxane defoamer sample prepared by compounding with a silicone oil concentrate for hydrophobic treatment of silica using silicone oil concentrate composition Example 13.

[0141] n. Sample 14: An example of a siloxane defoamer sample prepared by compounding with a silicone oil concentrate for hydrophobic treatment of silica using silicone oil concentrate composition Example 14.

[0142] o. Sample 15: An example of a siloxane defoamer sample prepared by compounding with a silicone oil concentrate for hydrophobic treatment of silica using silicone oil concentrate composition Example 15.

[0143] p. Sample 16: An example of a siloxane defoamer sample prepared by a compounding method using the silicone oil concentrate composition of Example 16, which is mixed with the silicone oil concentrate composition for hydrophobic treatment of silica.

[0144] 1.5 Comparative Examples: Antifoaming Agent Samples Not Present in This Invention

[0145] r. Comparative Example 1 Sample: Hydrophilic fumed silica or nano silica was added to the sample prepared in Example 8 above and reacted at a temperature of 150-180°C for 6-8 hours. After heating and stirring, the product was obtained and collected by centrifugation as needed. Unused hydrophobically treated fumed silica or nano silica did not need to be centrifuged and could be used as needed. The concentrated composition of Example 8 and the hydrophobically treated filler were mixed in a flask, stirred, and a polymer of fatty alcohol and propylene oxide was further added. The mixture was then stirred and heated at high speed to obtain an antifoaming agent.

[0146] s. Comparative Example 2 Sample: Hydrophilic fumed silica or nano-silica was added to 100,000 cSt of polydimethylsiloxane for reaction at 150-180℃ for 6-8 hours. After heating and stirring, the product was obtained and collected by centrifugation as needed. Unused hydrophobically treated fumed silica or nano-silica did not need to be centrifuged and could be used as needed. 100,000 cSt of polydimethylsiloxane and hydrophobically treated filler were mixed in a flask, stirred, and a polymer of fatty alcohol and propylene oxide was further added. The mixture was then stirred and heated at high speed to obtain an antifoaming agent.

[0147] t. Comparative Example 3: Airex 901W (Evonik), a commercially available defoamer based on polyether modified silicone oil, was used. The active ingredients of this product-grade oily defoamer are 100% polyether siloxane copolymer and hydrophilic fumed silica or nano silica filler.

[0148] 2. Experimental Testing

[0149] 2.1 Evaluation of foam suppression ability

[0150] 2.1.1 Criteria for Determining Foam Suppression Ability

[0151] Antifoaming ability refers to the ability of an antifoaming agent to suppress the generation of bubbles in a high-viscosity oil-based coating system synthesized from an oil-based acrylic resin.

[0152] 2.1.2 Evaluation Indicators

[0153] The foam suppression performance f (%) is quantified by the following formula: t0 represents the number of bubbles in the control group, and t1 represents the number of bubbles after the addition of the inhibitor. The number of bubbles indicates the quantity of bubbles, regardless of their size. The inhibitory ability of the defoamer is evaluated by calculating the defoaming performance f; the larger the f value, the stronger the defoaming performance of the defoamer.

[0154] 2.2.3 Specific evaluation procedures

[0155] The specific steps for evaluating and testing foam suppression performance are as follows:

[0156] S41 Take 100g of high-viscosity oil-based coating synthesized with acrylic resin and slowly pour it into a clean and dry beaker, taking care to avoid splashing the coating or mixing in air bubbles;

[0157] S42 accurately weighed 1% of the total mass of the coating defoamer and carefully added it to the coating in the beaker. The control group did not add siloxane defoamer.

[0158] S43 Place the agitator paddle of the high-speed mixer into the coating in the beaker, adjust the mixer to 1000-1500 rpm and stir for 5-10 minutes to generate microbubbles in the coating. During the stirring process, ensure that the agitator paddle is completely submerged in the coating and that the mixture is stirred evenly to avoid over- or under-stirring in certain areas.

[0159] After stirring S44, immediately use a dropper or glass rod to dip a small amount of paint and slowly pour a thin layer of oil-based paint about 1-2 mm thick evenly onto the prepared glass plate. During the operation, try to avoid generating new air bubbles.

[0160] S45 Place the glass plate on a horizontal, stable table. After the coating has flowed and stabilized naturally on the glass plate for 1-2 minutes, observe it with a magnifying glass or low-power microscope. Accurately measure the number of bubbles on the glass plate using manual counting or image analysis software, and record the number of bubbles at this time as t1. The number of bubbles in the control group is recorded as t0. Calculate the foam suppression performance f value according to the following formula. This value is the quantitative result of the foam suppression performance of the siloxane defoamer under the experimental conditions. Evaluate the storage stability of Example Samples 1-16 and Comparative Examples 1-3, and record their corresponding foam suppression performance indicators. The evaluation results of the foam suppression ability of each group of defoamers are shown in [the table below]. Figure 1 .

[0161]

[0162] 2.2 Storage stability evaluation

[0163] 2.2.1 Stability Judgment Criteria

[0164] Stability means that the component will not separate from the surrounding environment within 3 months.

[0165] 2.2.2 Evaluation Indicator Representation

[0166] The symbol [◎] indicates excellent storage stability, meaning that not only will phase separation not occur within 3 months, but good stability can also be maintained for a longer period of time;

[0167] The symbol [○] indicates that phase separation will not occur within 3 months, but obvious phase separation will gradually occur after storage for more than 3 months;

[0168] The symbol [Χ] indicates that phase separation occurred within 3 months.

[0169] 2.2.3 Specific evaluation procedures

[0170] Storage stability evaluation and testing, the specific operation is as follows:

[0171] Observe whether phase separation occurs in the samples during storage without artificially altering the external environment. Then, evaluate and record the storage stability of the samples according to the above standards and symbols. The storage stability of samples 1-16 and comparative examples 1-3 is evaluated, and their corresponding storage stability indices are recorded. The results are shown in Table 3 below.

[0172] Table 3 Storage stability evaluation

[0173]

[0174] 2.3 Evaluation of spreadability

[0175] 2.3.1 Criteria for determining spreadability

[0176] Spreadability refers to the ease with which an antifoaming agent can be applied to a surface as a coating, as well as the quality characteristics of the resulting coating.

[0177] 2.3.2 Evaluation Indicators

[0178] By observing the surface of the applied coating, we can check for defects such as brush marks, orange peel, runs, pinholes, and bubbles as coating performance indicators. We can also record the severity of each defect, including none, slight, moderate, and severe.

[0179] 2.3.3 Specific evaluation procedures

[0180] The specific steps for evaluating the smearability are as follows:

[0181] S51 prepares multiple test boards of the same material, size and flatness, and applies the coating sample containing antifoaming agent evenly to these test boards to ensure that the coating thickness is basically the same.

[0182] Under normal lighting conditions, S52 observes the coated surface from different angles such as vertical and 45-degree angles to check for defects such as brush marks, orange peel, runs, pinholes, and bubbles; record the severity of each defect as none, slight, moderate, or severe.

[0183] S53 makes a comprehensive evaluation based on the observed defects; if the coating surface is smooth and flat with no obvious visible defects, the spreadability is good; if there are a few minor defects, the spreadability is considered good; if there are many and serious defects, the spreadability is poor. The spreadability of samples 1-16 and comparative examples 1-3 was evaluated, and their corresponding spreadability indices were recorded. The results are shown in Table 4 below.

[0184] Table 4. Evaluation of spreadability

[0185]

[0186] 3. Results Analysis

[0187] 3.1 Data Analysis of Foam Suppression Ability Evaluation

[0188] The antifoaming performance f-values ​​of Examples 1-16 are mainly concentrated in the relatively high range of 90%-97%. Among them, some samples, such as Sample 9 (96.96%), Sample 10 (95.26%), and Sample 11 (92.05%), all exhibit extremely high antifoaming performance. Only Sample 16 has a relatively low antifoaming performance of 87.03%. The average antifoaming performance of Examples 1-16 is calculated to be 93.65%, indicating that the siloxane antifoaming agent of the present invention has a strong overall ability to suppress the generation of bubbles in high-viscosity oil-based coating systems synthesized with acrylic resin. Most formulations can achieve a high level of antifoaming, and there is a certain consistency among the examples. This shows that the effect of adjusting the formulation composition on the antifoaming performance within a certain range is relatively stable, and the product has good reliability.

[0189] The antifoaming performance of Comparative Examples 1 and 2 was significantly lower than that of the Examples. Comparative Example 1 had an antifoaming performance of 68.41% and Comparative Example 2 had an antifoaming performance of 71.36%, which was significantly lower than that of the Examples. Comparative Example 3 had an antifoaming performance of 95.15%, which was relatively high but still lower than that of most Examples. This clearly shows that the antifoaming agent of the present invention has a significant advantage in antifoaming ability compared with the comparative sample.

[0190] By observing the types of silicone oil concentrate compositions (Formulas 1-1 to 1-8, Formulas 2-1 to 2-8) and their defoaming performance data in different embodiments, it was found that the defoaming performance showed a certain trend when the chain length and structure of the silicone oil concentrate composition changed. For example, in Formula 1, Examples 1 and 2 showed higher defoaming performance when the m value was small and the n value was within a certain range; while in Formula 2, Examples 9 and 10 with similar structures also showed high defoaming performance. This indicates that within a certain chain length ratio range, the silicone oil concentrate composition is more conducive to exerting a defoaming effect. Different chain lengths and structures all affect the surface tension, interfacial properties, and synergistic effects with other components of the system.

[0191] Comparing Comparative Example 1, which uses hydrophilic fumed silica or nano-silica, with the embodiments of the present invention, the hydrophilic filler caused a significant decrease in antifoaming performance, indicating that hydrophobic treatment is crucial for improving antifoaming performance. In the embodiments, when the filler ratio is in the range of 5-20 wt%, although the overall data shows that a good antifoaming effect can be achieved within this range, it can still be observed that the antifoaming performance fluctuates with the change of the filler ratio, indicating that the degree and ratio of hydrophobic treatment of the filler also have an influence on the antifoaming performance.

[0192] 3.2 Analysis of Storage Stability Evaluation Results

[0193] Storage stability evaluation results are represented by symbols. In the examples, [◎] indicates excellent storage stability in most cases, such as examples 1, 2, 5, 9, 13, 14, 15, and 16. [○] indicates no phase separation within 3 months, but a certain proportion of cases will gradually separate after 3 months, such as examples 3, 4, 6, 7, 10, and 12. Overall, the results show a polarized state, with good stability being the majority. In the comparative examples, [Χ] indicates that phase separation occurs more frequently within 3 months, such as in comparative examples 1 and 2, while only comparative example 3 shows [◎].

[0194] Most embodiments of the siloxane defoamer of the present invention exhibit good storage stability, with some showing excellent stability within 3 months and a long-term stable trend, while a few may show phase separation after 3 months. In the comparative examples, except for Comparative Example 3, the other comparative examples showed stability problems in a short period of time, indicating that the defoamer formulation of the present invention has a significant advantage in storage stability, and reasonable raw material selection and process design help maintain product stability.

[0195] 3.3 Analysis of the results of the spreadability evaluation

[0196] In the spreadability evaluation, Examples 1-16 showed "none" for most of the defect indicators related to brush marks, orange peel, runs, pinholes, and bubbles, indicating good or relatively good overall spreadability. In the comparative examples, Examples 1 and 2 showed severe defects in brush marks, orange peel, runs, and pinholes, while Comparative Example 3 only had slight defects in brush marks, orange peel, and bubbles. The data distribution shows a significant difference in spreadability between the examples and the comparative examples.

[0197] The siloxane defoamer of this invention, as a coating additive, exhibits excellent spreadability and produces virtually no defects affecting coating quality. This is attributed to the synergistic effect of its components and a rational process, ensuring good coating performance during application. In contrast, the comparative example, due to differences in composition or process, encountered numerous problems during application, further highlighting the advantages of the defoamer of this invention in practical applications. It not only possesses strong defoaming ability but also ensures the quality of coating application.

[0198] The comprehensive experimental results show that the siloxane defoamer of this invention exhibits significant advantages in many aspects. In the defoaming ability evaluation, the defoaming performance f-values ​​of Examples 1-16 are mostly between 90% and 97%, with an average of 93.65%. Furthermore, the hydrophobic treatment of the silicone oil concentrate composition with a specific chain length ratio and the filler significantly affects the defoaming performance, while the comparative examples are far inferior to the examples. Regarding storage stability, most examples show good performance, with some exhibiting excellent stability and a long-term stable trend, while the comparative examples mostly show phase separation problems in the short term. In the spreadability evaluation, the examples are basically without defects, with good or relatively good spreadability, while the comparative examples have many serious defects. Overall, this defoamer demonstrates outstanding advantages in defoaming, storage stability, and spreadability. The components work synergistically, the product performance is reliable, and it possesses strong practicality and market competitiveness. It can effectively solve the foaming problem in oily systems, and is especially suitable for high-viscosity oily systems.

Claims

1. A siloxane defoaming agent, characterized in that, include: 2-10 parts filler, 40-70 parts silicone oil concentrate composition, 40-70 parts high viscosity polydimethylsiloxane and 100-150 parts fatty alcohol and propylene oxide polymer; The filler is a hydrophobically treated filler; The silicone oil concentrate composition comprises two silicone oil concentrate components with the structure of Formula 1: ； Japanese Style 2: ； In the construct: R1 is a methyl group, R2 is a hydrogen atom, m is 0 to 50, n is 1 to 150, the structure includes a variety of different chain lengths, each structural formula contains 8 siloxanes based on the m:n ratio, a total of 16 siloxanes, resulting in 16 concentrated silicone oil compositions. The hydrophobic treatment method is as follows: under the action of the prepared silicone oil composition, fumed silica or nano silica is heated to 100 to 300°C for 2 to 5 hours to make it hydrophobic. The ratio of silicone oil composition to fumed silica or nano silica is 1:5-20. The method for preparing the hydrophobic filler is as follows: a. Mixing the filler with the silicone oil concentrate: Add hydrophobically treated fumed silica or nano silica to the prepared silicone oil concentrate at a ratio of 1:8-70 and mix and stir. b. Reaction and heating: The mixture is heated to 150-180℃ and reacted with stirring for 6-8 hours to obtain a hydrophobic filler with a silicone oil concentrate composition on its surface; c. Post-reaction processing: The hydrophobically treated filler containing the concentrated silicone oil composition is stored and preserved directly without centrifugation. Unused filler is used after centrifugation and drying. Unreacted concentrated silicone oil composition is collected for recycling. The silicone oil concentrate composition of formula 1 is prepared by the following method: S11 solution preparation: In a container, considering the ratio of m to n, add octamethylcyclotetrasiloxane and tetramethylcyclotetrasiloxane, and add tetramethyldisiloxane according to the chain length. S12 catalyst addition: Add 1-5% concentrated sulfuric acid by total mass as catalyst, condense and reflux under nitrogen atmosphere and heat and stir, control the reaction temperature at 50-70℃, and the polymerization reaction lasts for 4-7 hours. S13 Cooling and Neutralization: Add solid sodium carbonate for neutralization, stop the reaction, stir until the pH value reaches neutral, and cool naturally to room temperature; S14 Filtration and Distillation: After filtration and neutralization, the solid material is distilled under reduced pressure at 70-90℃ for 3-5 hours to remove low-boiling-point substances, resulting in a transparent liquid product, silicone oil concentrate composition formula 1. The silicone oil concentrate composition of formula 2 is prepared by the following method: S21 solution preparation: In a container, considering the ratio of m to n, add octamethylcyclotetrasiloxane and tetramethylcyclotetrasiloxane, and add hexamethyldisiloxane according to the chain length. S22 catalyst addition: Add 1-5% concentrated sulfuric acid by total mass as catalyst, condense and reflux under nitrogen atmosphere and heat and stir, control the reaction temperature at 50-70℃, and the polymerization reaction lasts for 4-7 hours. S23 Cooling and Neutralization: Add solid sodium carbonate for neutralization, stop the reaction, stir until the pH value reaches neutral, and cool naturally to room temperature; S24 Filtration and Distillation: The filtered and neutralized solid material is distilled under reduced pressure at 70-90℃ for 3-5 hours to distill off low-boiling-point substances, yielding a transparent liquid product, silicone oil concentrate composition formula 2.

2. A production process for preparing the siloxane defoamer according to claim 1, characterized in that, The specific steps are as follows: Mix 1-5 parts of hydrophobic filler with 40-70 parts of concentrated silicone oil composition and stir. Further add 40-70 parts of high-viscosity polydimethylsiloxane and 100-150 parts of nonionic surfactant and stir at high speed. Add oleic acid to the foam suppressant base formulation while stirring and heat to react to obtain a siloxane foam suppressant.

3. The production process of a siloxane defoamer according to claim 2, characterized in that, The nonionic surfactant is a polymer of fatty alcohol and propylene oxide, with a neutral pH and a hydroxyl value less than or equal to 35 mg KOH / g. The amount of oleic acid used accounts for 0.5-3.0% of the total mass of the defoamer.

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