High-content organic silicon defoaming agent composition and preparation method thereof

Abstract

The invention relates to the technical field of defoaming agent preparation, in particular to a high-content organic silicon defoaming agent composition and a preparation method thereof. The preparation method comprises the following steps: preparing a methyl hydrogen polysiloxane precursor through step-by-step ring opening polymerization; then sequentially introducing an allyl polyether end-capping compound, active allyl methoxyl end-capped polyether and active allyl epoxy end-capped polyether to obtain a core organic silicon active component; then, compounding with dimethyl silicone oil and hydrophobic fumed silica to prepare a high-content organic silicon defoaming agent composition; the obtained composition has relatively high initial defoaming performance and relatively good continuous foam inhibition performance in simulated high-alkali and high-salt white water, simulated alkali washing liquid and simulated high-salt liquid, and shows relatively low oil separation rate and relatively high redispersion speed.

Description

Technical Field

[0001] This invention relates to the field of defoamer preparation technology, specifically to a high-content organosilicon defoamer composition and its preparation method. Background Technology

[0002] Organosilicon defoamers are widely used in industries such as papermaking, textiles, water treatment, and chemical detergents due to their low surface tension, strong defoaming ability, and outstanding chemical inertness. In high-alkali and high-salt industrial water systems such as papermaking white water and alkaline washing solutions, foaming problems are particularly severe, affecting not only production efficiency and equipment operation but also potentially leading to a decline in product quality. Polyether-modified organosilicon defoamers, by introducing hydrophilic polyether segments, have improved the dispersibility and foam suppression persistence of traditional polysiloxane defoamers in aqueous phases to a certain extent, becoming one of the mainstream technologies for industrial defoamers.

[0003] However, existing high-content silicone defoamers still exhibit several performance shortcomings when dealing with harsh operating conditions such as high alkali, high salt, high shear, and cyclic bubbling. From a molecular structure perspective, commercially available polyether-modified silicone products typically employ a full-chain random grafting method, meaning that polyether segments are indiscriminately distributed on each silicon-oxygen unit of the polysiloxane backbone, and the molecular weight distribution of the polyether is relatively wide. While this structural design offers a relatively simple manufacturing process, it introduces three inherent drawbacks: First, the polysiloxane backbone is inherently highly hydrophobic. When polyether segments are randomly grafted, the hydrophobic and hydrophilic segments are randomly distributed, leading to chaotic molecular arrangement at the aqueous interface. In the initial stage after the defoamer is added to the foaming liquid, a large number of hydrophobic backbones are not effectively shielded, making it difficult for droplets to spread quickly and penetrate the foam film, resulting in slow dispersion and delayed defoaming. Second, during the rapid defoaming stage, the randomly grafted polyether segments tend to concentrate on the outer side of the backbone, making them prone to premature contact with the aqueous phase and consuming the driving force used to maintain foam film rupture. The hydrophobic region of the kinetic defoamer results in rapid initial defoaming, but as bubbles are repeatedly generated, the polyether segments are gradually swollen or hydrolyzed by the aqueous phase, leading to a rapid decrease in interfacial respreading ability and a significant reduction in defoaming effect after multiple cycles. Thirdly, the random distribution of polyether segments disrupts the regularity of polysiloxane molecular chains, resulting in poor compatibility between different molecules. During storage, low molecular weight components tend to migrate and aggregate, forming a free oil phase that precipitates from the system, a phenomenon known as oil separation and stratification. This problem is particularly prominent in high-content silicone defoamers (with an effective ingredient content typically higher than 95%), severely affecting the product's shelf stability and consistency in use.

[0004] Currently, block copolymer structures, crosslinking agents, or thickening stabilizers are often used to avoid the above problems. However, these methods either increase the complexity of the preparation process or sacrifice some defoaming activity in exchange for stability, and have never achieved an ideal balance between rapid defoaming, continuous foam suppression, and storage stability. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a high-content organosilicon defoamer composition and its preparation method, so as to solve the problem that the existing technology cannot achieve rapid defoaming, continuous alkali resistance and foam suppression and storage stability at the same time.

[0006] To achieve the above objectives, the present invention provides a method for preparing a high-content organosilicon defoamer composition, the specific steps of which are as follows:

[0007] (1) Anhydrous toluene, hexamethyldisiloxane and octamethylcyclotetrasiloxane were added to the reactor in sequence, and trifluoromethanesulfonic acid was added to carry out ring-opening polymerization. Then 2,4,6,8-tetramethylcyclotetrasiloxane was added to continue the reaction. Octamethylcyclotetrasiloxane was added again to continue the reaction. After the reaction was completed, light magnesium oxide was added to neutralize it. The neutralized product was removed by filtration, and toluene and low-boiling rings were removed to obtain methylhydropolysiloxane precursor.

[0008] (2) Methylhydropolysiloxane precursor is mixed with anhydrous toluene. Under the catalysis of platinum-divinyltetramethyldisiloxane complex xylene solution, allyl polyether end-capping material is added for the first grafting reaction, followed by active allyl methoxy end-capping polyether for the second grafting reaction, and then active allyl epoxy end-capping polyether for the third grafting reaction. After the reaction is completed, activated carbon is added, filtered and toluene is removed to obtain the core organosilicon active component.

[0009] (3) Mix the core organosilicon active component with dimethyl silicone oil to form an oil phase. Take another part of the core organosilicon active component and pre-wet it with hydrophobic fumed silica to form a pre-dispersed slurry, and then add it back to the oil phase. Then add hydrophobic fumed silica to the system for dispersion and defoaming to obtain a high-content organosilicon defoamer composition.

[0010] Preferably, the weight ratio of hexamethyldisiloxane, octamethylcyclotetrasiloxane, 2,4,6,8-tetramethylcyclotetrasiloxane and the added octamethylcyclotetrasiloxane in step (1) is 11-13:118-122:4-6:28-32.

[0011] Preferably, the ring-opening polymerization temperature in step (1) is 30-33℃ and the reaction time is 18-22min.

[0012] Preferably, the addition of 2,4,6,8-tetramethylcyclotetrasiloxane in step (1) is completed within 12-18 minutes, and the system temperature is maintained at 30-35°C. After the addition is completed, the reaction continues for 18-22 minutes.

[0013] Preferably, the addition of octamethylcyclotetrasiloxane in step (1) is completed within 12-18 minutes, and the system temperature is maintained at 32-35°C. After the addition is completed, the reaction continues for 22-28 minutes.

[0014] Preferably, the neutralization time in step (1) is 18-22 min.

[0015] Preferably, the removal of toluene and low-boiling rings in step (1) is carried out at 95-100℃ and 5kPa.

[0016] Preferably, the weight ratio of the methylhydropolysiloxane precursor, allyl polyether end-capping compound, active allyl methoxy end-capping polyether and active allyl epoxy end-capping polyether in step (2) is 155-165:30-34:14-16:4-6.

[0017] Preferably, in step (2), the first grafting reaction is carried out at 72-75°C, the allyl polyether end-capping agent is added at a time of 28-32 min, and the temperature is maintained for another 45-55 min after addition.

[0018] Preferably, the allyl polyether end-capped material in step (2) has an average molecular weight of 750, a moisture content of no more than 0.15%, an unsaturation of no less than 1.2 mmol / g, and an end-capping rate of no less than 95%.

[0019] Preferably, the second grafting reaction in step (2) is carried out at 78-80°C, the active allyl methoxy-terminated polyether is added at a time of 18-22 min, and the temperature is maintained for 35-45 min after addition.

[0020] Preferably, the average molecular weight of the active allyl methoxy-terminated polyether in step (2) is 500, the moisture content is not higher than 0.5%, and the end-capping rate is not lower than 90%.

[0021] Preferably, the third grafting reaction in step (2) is carried out at 74-78°C, the active allyl epoxy-terminated polyether is added at a time of 12-18 min, and the temperature is maintained for 60-90 min after addition.

[0022] Preferably, the average molecular weight of the active allyl epoxy-terminated polyether in step (2) is 450, the epoxy value is not less than 1.90 eq / 1000g, and the double bond content is 2.00-2.35 mmol / g.

[0023] Preferably, the toluene removal in step (2) is carried out at 90°C and 5 kPa.

[0024] Preferably, the weight ratio of the core organosilicon active component, dimethyl silicone oil, part of the core organosilicon active component, and hydrophobic fumed silica in step (3) is 68-74:18-24:7-9:7.2-8.8.

[0025] Preferably, the addition of hydrophobic fumed silica to the system in step (3) is carried out in three separate steps, and each addition is followed by high-speed dispersion at 50-55°C for 12-18 minutes.

[0026] Preferably, the degassing in step (3) is carried out at 55°C and 10 kPa.

[0027] Furthermore, the present invention provides a high-content silicone defoamer composition, wherein the high-content silicone defoamer composition comprises, by weight, 75-83 parts of core silicone active component, 18-24 parts of dimethyl silicone oil and 7.2-8.8 parts of hydrophobic fumed silica.

[0028] The beneficial effects of this invention are:

[0029] This invention achieves a balance between rapid defoaming and excellent dispersibility in liquid: a methylhydropolysiloxane precursor is prepared by a stepwise feeding method. First, an allyl polyether end-capping material is introduced with an inner low-polarity grafting zone, and then a medium-polarity transition zone and sparse high-polarity points are constructed sequentially. This structure, with its increasing polarity gradient from the inside to the outside, allows the outer high-polarity points to preferentially interact with the aqueous phase after the defoamer is added to the foaming liquid, guiding the molecules to spread and disperse rapidly, while the inner low-polarity region maintains sufficient driving force for bubble film rupture, thereby completing defoaming in a very short time.

[0030] This invention enhances sustained defoaming ability under alkaline and high-salt conditions by concentrating reactive allyl methoxy-terminated polyether and reactive allyl epoxy-terminated polyether at the center of the molecule. The former provides moderate hydrophilicity and alkali resistance, while the latter introduces epoxy groups, which can form stable anchoring points with the hydrophobic fumed silica surface. During cyclic bubbling, because the polyether segments are confined to the central region, the hydrophobic segments at both ends maintain complete defoaming activity. Even after multiple bubble regenerations, the molecules can still quickly rearrange at the gas-liquid interface, inhibiting foam accumulation. Simultaneously, the binding of epoxy groups to silica enhances the uniform positioning of particles in the oil phase, avoiding the decrease in defoaming activity caused by particle agglomeration, enabling the product to maintain stable defoaming performance under high alkalinity, high salt, and long-term cyclic conditions.

[0031] This invention significantly improves the resistance to oil separation during storage and the redispersibility during use: by first constructing an inner low-polarity grafted band, then an outer medium-polarity transition band, and finally an outermost sparse high-polarity point, polyether segments of different polarities form a regular hierarchical distribution on the molecular backbone, greatly improving intermolecular compatibility. Low molecular weight components are less likely to migrate and precipitate. Even after long-term storage, the defoamer can still be quickly dispersed in the foaming liquid without any floating oil residue, ensuring the stability and reliability of the effect between batches. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0033] Source or nature of raw materials:

[0034] Octamethylcyclotetrasiloxane: Merck, type 814750, purity not less than 98.0%; 2,4,6,8-Tetramethylcyclotetrasiloxane: Merck, type 512990, purity not less than 98.5%; Hexamethyldisiloxane: Merck, type 205389; Light magnesium oxide: Merck, type 105862; Platinum-divinyltetramethyldisiloxane complex xylene solution: Gelest, type SIP6831.2, platinum mass fraction 2%; Dimethyl silicone oil: kinematic viscosity 1000 mmHg at 25°C. 2 / s; Hydrophobic fumed silica: AEROSIL R 972 type, with a specific surface area of ​​90-130m² / g. Allyl polyether end-capped material: Liaoning Kelong Fine Chemical Co., Ltd., KLF-A750 type allyl polyether end-capped material, average molecular weight 750, moisture content not higher than 0.15%, unsaturation degree not lower than 1.2 mmol / g, end-capping rate not lower than 95%; Reactive allyl methoxy end-capped polyether: Liaoning Kelong Fine Chemical Co., Ltd., MX-500 type reactive allyl methoxy end-capped polyether, average molecular weight 500, moisture content not higher than 0.5%, end-capping rate not lower than 90%; Reactive allyl epoxy end-capped polyether: Liaoning Kelong Fine Chemical Co., Ltd., KL-11 type reactive allyl epoxy end-capped polyether, average molecular weight 450, epoxy value not lower than 1.90 eq / 1000g, double bond content 2.00-2.35 mmol / g; All three allyl polyethers were dehydrated at 70℃ and below 5kPa for 1 hour before use.

[0035] Example 1: A method for preparing a high-content organosilicon defoamer composition, the specific steps of which are as follows:

[0036] Preparation of methylhydropolysiloxane precursor S1: 40g anhydrous toluene, 12g hexamethyldisiloxane, and 120g octamethylcyclotetrasiloxane were added sequentially to a dried and nitrogen-protected four-necked flask. 50mg trifluoromethanesulfonic acid was added at 32℃ with stirring at 350r / min, and the reaction continued for 20min. Then, 5g 2,4,6,8-tetramethylcyclotetrasiloxane was added dropwise over 15min at 33℃, and the reaction continued for 20min. Next, 30g octamethylcyclotetrasiloxane was added dropwise over 15min, and the reaction continued at 34℃ for 25min. Immediately after the reaction, 800mg of light magnesium oxide was added to neutralize the mixture for 20min. The neutralized product was removed by filtration, and toluene and low-boiling rings were removed at 98℃ and below 5kPa for 60min to obtain the methylhydropolysiloxane precursor.

[0037] S2 Preparation of Core Organosilicon Active Components: 160g of methylhydropolysiloxane precursor and 30g of anhydrous toluene were added to a dried four-necked flask. Under nitrogen protection, the mixture was dehydrated at 90℃ and below 10kPa for 20min. The temperature was then lowered to 72℃, and 250mg of a platinum-divinyltetramethyldisiloxane complex xylene solution was added. After stirring for 10min, 32g of allyl polyether end-capping compound KLF-A750 was added dropwise over 30min at 74℃, maintaining stirring at 350r / min during the addition. After the addition was complete, the temperature was maintained for another 50min. The system temperature was then raised to 7... At 9℃ and 350 r / min, 15 g of active allyl methoxy-terminated polyether MX-500 was added dropwise over 20 min, and the mixture was kept at this temperature for another 40 min. The temperature of the resulting reaction solution was then adjusted to 76℃, and 5 g of active allyl epoxy-terminated polyether KL-11 was added dropwise over 15 min, while stirring at 350 r / min. The mixture was kept at this temperature for another 75 min. Subsequently, the temperature of the reaction solution was lowered to 60℃, 1000 mg of activated carbon was added, and the mixture was stirred for 20 min. The mixture was then filtered, and toluene was removed at 90℃ and below 5 kPa for 30 min to obtain the core organosilicon active component.

[0038] S3 Preparation of a high-content silicone defoamer composition: Take 70g of the core silicone active component and place it in a dry container. Add 22g of dimethyl silicone oil at 53℃ and stir for 20min to form a homogeneous oil phase. Take another 8g of the above core silicone active component and 2g of hydrophobic fumed silica and pre-wet it at room temperature for 15min to form a pre-dispersed slurry. Then add it back to the oil phase. Add the remaining 6g of hydrophobic fumed silica in three portions. After each addition, disperse it at high speed at 53℃ for 15min. Finally, defoam at 55℃ and below 10kPa for 30min to obtain the high-content silicone defoamer composition.

[0039] Example 2: A method for preparing a high-content organosilicon defoamer composition, the specific steps of which are as follows:

[0040] Preparation of methylhydropolysiloxane precursor S1: 38 g of anhydrous toluene, 11 g of hexamethyldisiloxane, and 118 g of octamethylcyclotetrasiloxane were added sequentially to a dried and nitrogen-protected four-necked flask. 45 mg of trifluoromethanesulfonic acid was added at 30 °C with stirring at 300 r / min, and the reaction was continued for 18 min. Then, 4 g of 2,4,6,8-tetramethylcyclotetrasiloxane was added dropwise over 12 min at 30 °C, and the reaction was continued for 18 min. Next, 28 g of octamethylcyclotetrasiloxane was added dropwise over 12 min, and the reaction was continued at 32 °C for 22 min. Immediately after the reaction was complete, 750 mg of light magnesium oxide was added to neutralize the mixture for 18 min. The neutralized product was filtered off, and then toluene and low-boiling rings were removed at 95 °C and below 5 kPa for 55 min to obtain the methylhydropolysiloxane precursor.

[0041] S2 Preparation of Core Organosilicon Active Components: 155g of methylhydropolysiloxane precursor and 28g of anhydrous toluene were added to a dried four-necked flask. Under nitrogen protection, the mixture was dehydrated at 90℃ and below 10kPa for 18min. The temperature was then lowered to 70℃, and 230mg of a platinum-divinyltetramethyldisiloxane complex xylene solution was added. After stirring for 8min, 30g of allyl polyether end-capping compound KLF-A750 was added dropwise over 28min at 72℃, maintaining a stirring speed of 300r / min during the addition. After the addition was complete, the temperature was maintained for another 45min. Subsequently, the system temperature was raised to... At 78℃ and with stirring at 300 rpm, 14 g of active allyl methoxy-terminated polyether MX-500 was added dropwise over 18 min. After the addition was complete, the temperature was maintained for another 35 min. The temperature of the resulting reaction solution was then adjusted to 74℃, and with stirring at 300 rpm, 4 g of active allyl epoxy-terminated polyether KL-11 was added dropwise over 12 min. The temperature was maintained for another 60 min. Subsequently, the reaction solution was cooled to 60℃, 900 mg of activated carbon was added, and the mixture was stirred for 18 min. After filtration, toluene was removed at 90℃ and below 5 kPa for 25 min to obtain the core organosilicon active component.

[0042] S3 Preparation of a high-content silicone defoamer composition: Take 68g of the core silicone active component and place it in a dry container. Add 18g of dimethyl silicone oil at 50℃ and stir for 18min to form a homogeneous oil phase. Take another 7g of the above core silicone active component and 1.8g of hydrophobic fumed silica and pre-wet for 12min at room temperature to form a pre-dispersed slurry. Add the slurry back to the oil phase. Then add the remaining 5.4g of hydrophobic fumed silica in three portions. After each addition, disperse at high speed at 50℃ for 12min. Finally, defoam at 55℃ and below 10kPa for 25min to obtain the high-content silicone defoamer composition.

[0043] Example 3: A method for preparing a high-content organosilicon defoamer composition, the specific steps of which are as follows:

[0044] Preparation of methylhydropolysiloxane precursor S1: 42g anhydrous toluene, 13g hexamethyldisiloxane, and 122g octamethylcyclotetrasiloxane were added sequentially to a dried and nitrogen-protected four-necked flask. 55mg trifluoromethanesulfonic acid was added at 33°C with stirring at 400r / min, and the reaction continued for 22min. Then, 6g 2,4,6,8-tetramethylcyclotetrasiloxane was added dropwise over 18min at 35°C, and the reaction continued for 22min. Next, 32g octamethylcyclotetrasiloxane was added dropwise over 18min, and the reaction continued at 35°C for 28min. Immediately after the reaction was complete, 850mg of light magnesium oxide was added to neutralize the mixture for 22min. The neutralized product was removed by filtration, and toluene and low-boiling rings were removed at 100°C and below 5kPa for 65min to obtain the methylhydropolysiloxane precursor.

[0045] S2 Preparation of the core organosilicon active component: 165g of methylhydropolysiloxane precursor and 32g of anhydrous toluene were added to a dried four-necked flask. The mixture was dehydrated for 22 min at 90℃ and below 10kPa under nitrogen protection, then cooled to 74℃. 270mg of a platinum-divinyltetramethyldisiloxane complex xylene solution was added, and the mixture was stirred for 12 min. Then, 34g of allyl polyether end-capping compound KLF-A750 was added dropwise over 32 min at 75℃, maintaining a stirring speed of 400 r / min during the addition. After the addition was complete, the temperature was maintained for another 55 min. Subsequently, the system temperature was raised to... At 80℃ and with stirring at 400 rpm, 16 g of active allyl methoxy-terminated polyether MX-500 was added dropwise over 22 min. After the addition was complete, the temperature was maintained for another 45 min. The temperature of the resulting reaction solution was then adjusted to 78℃, and with stirring at 400 rpm, 6 g of active allyl epoxy-terminated polyether KL-11 was added dropwise over 18 min. The temperature was maintained for another 90 min. Subsequently, the reaction solution was cooled to 60℃, 1100 mg of activated carbon was added, and the mixture was stirred for 22 min. After filtration, toluene was removed at 90℃ and below 5 kPa for 35 min to obtain the core organosilicon active component.

[0046] S3 Preparation of a high-content silicone defoamer composition: Take 74g of the core silicone active component and place it in a dry container. Add 24g of dimethyl silicone oil at 55℃ and stir for 22min to form a homogeneous oil phase. Take another 9g of the above core silicone active component and 2.2g of hydrophobic fumed silica and pre-wet it at room temperature for 18min to form a pre-dispersed slurry. Then add it back to the oil phase. Add the remaining 6.6g of hydrophobic fumed silica in three portions. After each addition, disperse it at high speed at 55℃ for 18min. Finally, defoam at 55℃ and below 10kPa for 35min to obtain the high-content silicone defoamer composition.

[0047] Comparative Example 1: The difference from Example 1 is that in step S1, 40g of anhydrous toluene, 12g of hexamethyldisiloxane, 120g of octamethylcyclotetrasiloxane, 5g of 2,4,6,8-tetramethylcyclotetrasiloxane and 30g of octamethylcyclotetrasiloxane were added to a four-necked flask at once, and then 50mg of trifluoromethanesulfonic acid was added at 32°C to carry out the reaction; the remaining conditions were the same as in Example 1.

[0048] Comparative Example 2: The difference from Example 1 is that in step S2, 32g of allyl polyether end-capping compound KLF-A750 is replaced by an equal amount of active allyl methoxy end-capping polyether MX-500; the other conditions are the same as in Example 1.

[0049] Comparative Example 3: The difference from Example 1 is that in step S2, 32g of allyl polyether end-capping compound KLF-A750 and 15g of active allyl methoxy end-capping polyether MX-500 are mixed and added dropwise at 74°C. In step S3, active allyl methoxy end-capping polyether MX-500 is not added. The other conditions are the same as in Example 1.

[0050] Comparative Example 4: The difference from Example 1 is that in step S2, 15g of active allyl methoxy-terminated polyether MX-500 and 5g of active allyl epoxy-terminated polyether KL-11 were mixed and added dropwise together; the other conditions were the same as in Example 1.

[0051] Comparative Example 5: The difference from Example 1 is that in step S2, 5g of active allyl methoxy-terminated polyether MX-500 is used to replace 5g of active allyl epoxy-terminated polyether KL-11; the other conditions are the same as in Example 1.

[0052] Comparative Example 6: The difference from Example 1 is that steps S2 and S3 are both performed at 78°C; the other conditions are the same as in Example 1.

[0053] Performance testing

[0054] High-content silicone defoamer compositions were prepared according to the methods of the examples and comparative examples. After each sample was prepared, it was sealed and allowed to stand at 25°C for 24 hours. Then, it was stirred at 1000 r / min for 3 minutes at 25°C to make the sample homogeneous. Samples were taken and each sample was tested in parallel 3 times. The arithmetic mean was taken as the final result.

[0055] Appearance, solid content, and centrifugal stability: The testing methods for the appearance, stability, and related physicochemical indicators of organosilicon defoamers were conducted according to GB / T 26527-2024 and HG / T 4385-2012. Appearance was observed under natural light at 25℃, and the presence of obvious stratification, sedimentation, and agglomeration was recorded. For the solid content test, 2.0000g of sample was accurately weighed into a pre-weighed aluminum box, dried in an oven at 105℃ for 2 hours, cooled in a desiccator for 30 minutes, and then weighed. This process was repeated until the difference between two consecutive weighings did not exceed 0.005g, and the solid content was calculated. For the centrifugal stability test, 50.0mL of sample was placed in a stoppered centrifuge tube and centrifuged at 3000r / min at 25℃ for 30 minutes, and the volume of each layer was recorded.

[0056] Initial defoaming performance of simulated high-alkalinity and high-salinity white water: The defoaming performance test was conducted according to the testing method in HG / T 4385-2012. The simulated high-alkalinity and high-salinity white water was prepared with the following composition: Na2SO4 2.0 g / L, Na2CO3 1.0 g / L, NaCl 1.0 g / L, CaCl2·2H2O 0.3 g / L of oxidized starch, 0.5 g / L of sodium dodecyl sulfate, and 0.20 g / L of sodium dodecyl sulfate were added. The pH was adjusted to 10.0 ± 0.1 with NaOH. 500.0 mL of the foaming solution was placed in a 1000 mL jacketed glass graduated cylinder with an inner diameter of 70 mm. The liquid temperature was controlled at 40 °C. Clean air was introduced through the lower sand core aerator at a flow rate of 2.0 L / min. After pre-bubbling for 60 s, 0.0500 g of the sample to be tested was quickly added to the center of the liquid surface, and timing was started at the same time. Timing was stopped when the continuous bubble layer was completely broken and the residual foam height was less than 5 mm. This time was recorded as the initial defoaming time.

[0057] Simulated high-alkali and high-salt white water continuous defoaming performance: After the initial defoaming performance test of simulated high-alkali and high-salt white water is completed (the sample completes the first defoaming), 100 cycles are continuously performed with 10 seconds of bubbling followed by 20 seconds of gas stopping as one cycle. The time required for the bubble layer to drop below 5 mm after the 10th and 100th cycles is recorded respectively.

[0058] Alkali resistance and defoaming performance of simulated alkaline washing solution: The defoaming evaluation method was carried out in accordance with GB / T 26527-2024 and HG / T 4385-2012. The simulated alkaline washing solution was prepared with the following composition: NaOH 5.0g / L, Na2CO3 3.0g / L, Na2SO4 1.0g / L, sodium dodecyl sulfate 0.20g / L. 500.0mL of the simulated alkaline washing solution was placed in a 1000mL jacketed glass graduated cylinder with an inner diameter of 70mm. The liquid temperature was controlled at 60℃. After pre-bubbling with air at 2.0L / min for 60s, 0.0500g of the sample to be tested was added, and the initial defoaming time was recorded.

[0059] Salt resistance and defoaming performance of simulated high-salt solution: The defoaming evaluation method was carried out in accordance with GB / T 26527-2024 and HG / T 4385-2012. The simulated high-salt solution was prepared with the following composition: NaCl 30.0 g / L, Na2SO4 2.0 g / L, sodium dodecyl sulfate 0.20 g / L. The pH was adjusted to 10.0±0.1 with NaOH. 500.0 mL of the simulated high-salt solution was placed in a 1000 mL jacketed glass graduated cylinder with an inner diameter of 70 mm. The liquid temperature was controlled at 25℃. After pre-bubbling with air at 2.0 L / min for 60 s, 0.0500 g of the sample to be tested was added, and the initial defoaming time was recorded.

[0060] Accelerated storage anti-oil separation stability and liquid dispersion performance: The stability evaluation methods in GB / T 26527-2024 and HG / T 4385-2012 were followed. 80.0g of each sample was weighed into a 100mL stoppered graduated cylinder and stored in a 54℃ constant temperature oven for 14 days. After removal, the sample was allowed to stand at 25℃ for 24 hours. The mass of the upper layer of precipitated oil phase was recorded, and the oil separation rate was calculated. The sample was then gently mixed again, and 0.0500g was added to 500.0mL of simulated high-alkalinity, high-salt white water at 25℃. The time was recorded when the liquid surface no longer had a continuous oil film and no floating oil droplets larger than 1mm were visually observed. This time was recorded as the liquid dispersion time. The test results are shown in Table 1.

[0061] Table 1 Performance Test Results

[0062]

[0063] Data analysis: As can be seen from the data of the embodiments in Table 1, the high-content organosilicon defoamer composition prepared by the present invention exhibits fast initial defoaming, good continuous foam suppression and stable storage state in simulated high-alkali and high-salt white water, simulated alkaline washing liquid and simulated high-salt liquid, and still maintains fast liquid dispersion ability after accelerated storage. The results indicate that by first preparing a methylhydropolysiloxane precursor using a stepwise feeding method with octamethylcyclotetrasiloxane, 2,4,6,8-tetramethylcyclotetrasiloxane, and octamethylcyclotetrasiloxane, and then sequentially introducing allyl polyether end-capped compound KLF-A750, reactive allyl methoxy end-capped polyether MX-500, and reactive allyl epoxy end-capped polyether KL-11, the core organosilicon active component can simultaneously possess sufficient hydrophobic defoaming ability, moderate liquid dispersion ability, and good interfacial respreading ability. Simultaneously, the hydrophobic fumed silica is more stably wetted and positioned in the system formed by the core organosilicon active component and dimethyl silicone oil, thus enabling the resulting composition to maintain good bubble film rupture ability and oil separation stability under high alkalinity, high salt, and cyclic bubbling conditions.

[0064] As can be seen from the data in Table 1 for Example 1 and Comparative Example 1, after only changing the way octamethylcyclotetrasiloxane and 2,4,6,8-tetramethylcyclotetrasiloxane were added in step S1, although the initial defoaming of the samples remained at a certain level, the sustained foam suppression, accelerated storage anti-oil separation stability, and liquid dispersion all significantly deteriorated. The main reason is that the one-time addition weakens the orderly distribution of silane-hydrogen bonds in the methylhydrogen polysiloxane precursor, making it difficult to form a hierarchical structure from the inside out. Therefore, only a locally effective defoaming state can be obtained, which is difficult to maintain for a long time.

[0065] As can be seen from the data in Example 1 and Comparative Example 2 in Table 1, after replacing the allyl polyether end-capped compound KLF-A750 with an equal amount of active allyl methoxy end-capped polyether MX-500, the sustained foam suppression, alkali-resistant defoaming, and oil separation stability decreased more significantly. The main reason is that if the active allyl methoxy end-capped polyether MX-500 is used directly, the inner layer of the main chain is more likely to be biased towards the hydrophilic side, and it is easier to introduce competitive reactions, causing the core organosilicon active component to enter the high-alkali, high-salt water phase too early, making it difficult to maintain long-term foam suppression.

[0066] As can be seen from the data in Table 1 for Example 1 and Comparative Example 3, although allyl polyether end-capping compound KLF-A750 and active allyl methoxy end-capping polyether MX-500 were added simultaneously in step S2, the sustained foam suppression and storage stability were both poor. The main reason for this is that the present invention does not simply rely on the coexistence of the two polyethers, but rather on the moderate polarity gradient formed by the sequential grafting, in order to achieve a better balance between rapid foam breaking and subsequent respreading.

[0067] As can be seen from the data in Table 1 for Example 1 and Comparative Examples 4 and 5, the post-introduction method of the third grafting stage and the type of epoxy end groups have a significant impact on the accelerated storage stability against oil separation, cyclic foam suppression, and salt-resistant defoaming of the samples. This indicates that the introduction position of the active allyl epoxy-terminated polyether KL-11 has a synergistic contribution to the system stability and long-term foam suppression.

[0068] As can be seen from the data of Example 1 and Comparative Example 6 in Table 1, when the first, second and third grafting reactions in step S2 are carried out at the same temperature, the initial defoaming, continuous foam suppression and storage stability of the sample all decrease, indicating that segmented temperature control helps to improve the overall performance of the obtained active components.

[0069] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A method for preparing a high-content organosilicon defoamer composition, characterized in that, Includes the following steps: (1) Anhydrous toluene, hexamethyldisiloxane and octamethylcyclotetrasiloxane were added to the reactor in sequence, trifluoromethanesulfonic acid was added to carry out ring-opening polymerization, and then 2,4,6,8-tetramethylcyclotetrasiloxane was added to continue the reaction. Octamethylcyclotetrasiloxane was added again to continue the reaction to obtain methylhydropolysiloxane precursor. (2) Methylhydropolysiloxane precursor is mixed with anhydrous toluene. Under the catalysis of platinum-divinyltetramethyldisiloxane complex xylene solution, allyl polyether end-capping material is added for the first grafting reaction, followed by active allyl methoxy end-capping polyether for the second grafting reaction, and then active allyl epoxy end-capping polyether for the third grafting reaction. After the reaction is completed, activated carbon is added, filtered and toluene is removed to obtain the core organosilicon active component. (3) Mix the core organosilicon active component with dimethyl silicone oil to form an oil phase. Take another part of the core organosilicon active component and pre-wet it with hydrophobic fumed silica to form a pre-dispersed slurry, and then add it back to the oil phase. Then add hydrophobic fumed silica to the system for dispersion and defoaming to obtain a high-content organosilicon defoamer composition.

2. The preparation method according to claim 1, characterized in that, The weight ratio of hexamethyldisiloxane, octamethylcyclotetrasiloxane, 2,4,6,8-tetramethylcyclotetrasiloxane and the added octamethylcyclotetrasiloxane in step (1) is 11-13:118-122:4-6:28-32.

3. The preparation method according to claim 1, characterized in that, The ring-opening polymerization temperature in step (1) is 30-33℃, and the reaction time is 18-22 min.

4. The preparation method according to claim 1, characterized in that, The weight ratio of the methylhydropolysiloxane precursor, allyl polyether end-capped material, active allyl methoxy end-capped polyether and active allyl epoxy end-capped polyether in step (2) is 155-165:30-34:14-16:4-6.

5. The preparation method according to claim 1, characterized in that, The allyl polyether end-capped material in step (2) has an average molecular weight of 750, a moisture content of no more than 0.15%, an unsaturation degree of no less than 1.2 mmol / g, and an end-capping rate of no less than 95%.

6. The preparation method according to claim 1, characterized in that, The average molecular weight of the active allyl methoxy-terminated polyether in step (2) is 500, the moisture content is not higher than 0.5%, and the end-capping rate is not lower than 90%.

7. The preparation method according to claim 1, characterized in that, The average molecular weight of the active allyl epoxy-terminated polyether in step (2) is 450, the epoxy value is not less than 1.90 eq / 1000g, and the double bond content is 2.00-2.35 mmol / g.

8. The preparation method according to claim 1, characterized in that, The weight ratio of the core organosilicon active component, dimethyl silicone oil, part of the core organosilicon active component, and hydrophobic fumed silica in step (3) is 68-74:18-24:7-9:7.2-8.

8.

9. The preparation method according to claim 1, characterized in that, The degassing in step (3) is carried out at 55°C and 10 kPa.

10. A high-content organosilicon defoamer composition, characterized in that, The high-content organosilicon defoamer composition prepared according to any one of claims 1-9 comprises, by weight, 75-83 parts of core organosilicon active component, 18-24 parts of dimethyl silicone oil and 7.2-8.8 parts of hydrophobic fumed silica.

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