A silicone foam stabilizer and a method for preparing the same

Abstract

The present application relates to the technical field of foam material auxiliary agent, and particularly relates to a kind of organosilicon foam stabilizer and preparation method thereof.The stabilizer is based on siloxane copolymer main chain containing silicon-hydrogen bond and phenyl fragment, and is made by respectively grafting monoallyl polyether, diallyl polyether and MQ silicone resin containing vinyl group through segmented hydrosilication.The stabilizer has excellent thermal stability, interface film strength and system compatibility in high-temperature polyurethane foaming process, can effectively improve foam height retention rate, refine cell, reduce open cell rate, and significantly improve sagging, and is suitable for high index, high polarity and environmentally friendly foaming formula.By introducing phenyl fragment and covalently grafting MQ domain, the present application realizes the optimization control of foam stabilizer molecular thermal stability and interface structure, and has important significance for improving high-temperature forming quality of polyurethane foam.

Description

Technical Field

[0001] This invention relates to the field of foam material additives technology, and in particular to an organosilicon foam stabilizer and its preparation method. Background Technology

[0002] Polyurethane foam materials are widely used in building insulation, cold chain storage and transportation, and household appliance insulation due to their excellent thermal insulation, lightweight, and processing adaptability. With increasingly stringent environmental regulations and expanding application scenarios, polyurethane foam is evolving towards higher foaming temperatures, lower thermal conductivity, and more demanding service environments. Against this backdrop, the performance limitations of traditional foam stabilizers under high-temperature foaming conditions are becoming increasingly apparent, posing a key bottleneck to technological progress in the industry.

[0003] As a core component of polyurethane foam systems, silicone foam stabilizers primarily function to reduce liquid surface tension, stabilize cell structure, and regulate reaction rate matching. Traditional silicone stabilizers are mostly based on the polydimethylsiloxane backbone, with hydrophilic polyether segments introduced through side chain modification. During foaming, these segments migrate to the gas-liquid interface to form a monolayer, inhibiting cell coalescence and rupture. However, in high-temperature foaming environments, traditional stabilizers face numerous technical challenges:

[0004] First, insufficient thermal stability leads to a decline in interfacial performance. During high-temperature foaming, the reaction system temperature can reach 100-150℃. At this temperature, the traditional polydimethylsiloxane backbone is prone to pyrolysis and rearrangement, resulting in molecular weight degradation and decreased interfacial activity. Simultaneously, the thermal sensitivity of the silicon-oxygen bond makes the stabilizer susceptible to chain breakage in high-temperature shear environments, disrupting the integrity of the interfacial film. This manifests as increased cell coalescence and decreased height retention.

[0005] Secondly, balancing interfacial film strength and flowability is difficult. An ideal foam stabilizer needs to spread and wet rapidly at the nascent foam film while providing sufficient film strength to resist drainage in the later stages of cell expansion. Traditional stabilizers mostly rely on physical adsorption to form interfacial films, lacking an effective intermolecular cross-linking mechanism. Under high temperature and high shear conditions, they are prone to desorption and rearrangement, making it difficult to maintain the mechanical strength of the foam film. While excessively increasing the molecular weight can enhance film strength, it sacrifices the interfacial migration rate, leading to uneven wetting in the early stages of foaming and causing uneven cell distribution.

[0006] Secondly, compatibility with highly polar foaming systems is limited. Modern polyurethane formulations extensively utilize high-functionality polyols, highly active catalysts, and environmentally friendly blowing agents, significantly enhancing the system's polarity. The hydrophobic siloxane backbone of traditional organosilicon stabilizers exhibits decreased compatibility in such systems, easily leading to microphase separation and affecting the uniformity and continuity of interfacial film formation. Particularly in systems using HFO-based blowing agents, the stabilizer's solubility and interfacial activity are further challenged.

[0007] Furthermore, existing grafting modification methods suffer from structural design limitations. Traditional hydrosilylation reactions often employ a one-step process or a simple two-component grafting method, making it difficult to precisely control the grafting density and distribution of different functional segments. This results in a large number of unreacted silane-hydrogen bonds or incompletely grafted segments in the product. These structural defects not only affect the interfacial properties of the stabilizer but may also lead to further reactions during storage, impacting product stability.

[0008] While existing commercial products can alleviate the aforementioned problems to some extent by increasing the dosage or compounding with other additives, this often comes at the cost of cost-effectiveness and formulation simplicity, and it is difficult to achieve the optimal balance between high stability and cell refinement. Therefore, developing novel organosilicon foam stabilizers, through molecular structure optimization and innovative preparation processes, to simultaneously address key technical issues such as high-temperature stability, interfacial film strength, and compatibility, has significant theoretical and practical value. Summary of the Invention

[0009] In view of this, the purpose of this invention is to provide an organosilicon foam stabilizer and its preparation method, so as to simultaneously improve the high-temperature stability and cell refinement effect of the organosilicon foam stabilizer.

[0010] To achieve the above objectives, this invention provides an organosilicon foam stabilizer, prepared by reacting a siloxane copolymer backbone containing silane-hydrogen bonds and phenyl segments with monoallyl polyether, diallyl polyether, and vinyl-containing MQ silicone resin via segmental hydrosilylation. The siloxane copolymer backbone comprises segments obtained by ring-opening copolymerization of octamethylcyclotetrasiloxane, methylphenylcyclotrisiloxane, and methylhydrocyclotrisiloxane, retaining silane-hydrogen bonds within the backbone. The vinyl-containing MQ silicone resin is covalently grafted onto the backbone via silane-hydroaddition. The monoallyl polyether and diallyl polyether are grafted onto the backbone via silane-hydroaddition. The hydrosilylation grafting sequence includes: first grafting monoallyl polyether, then grafting diallyl polyether, followed by grafting the vinyl-containing MQ silicone resin, and then supplementing with grafting monoallyl polyether.

[0011] Preferably, the siloxane copolymer backbone is prepared by ring-opening copolymerization of the following raw materials: 300 parts by mass of octamethylcyclotetrasiloxane, 40-100 parts by mass of methylphenylcyclotrisiloxane, 70-130 parts by mass of methylhydrocyclotrisiloxane, 5 parts by mass of hexamethyldisiloxane, and 1 part by mass of potassium hydroxide.

[0012] Preferably, the monoallyl polyether is prepared by addition reaction of allyl alcohol and propylene oxide; the mass ratio of allyl alcohol to propylene oxide is 6:116.

[0013] Preferably, the diallyl polyether is prepared by reacting 1,3-propanediol, propylene oxide and allyl glycidyl ether; the mass ratio of 1,3-propanediol, propylene oxide and allyl glycidyl ether is 8:120:40.

[0014] Preferably, the vinyl-containing MQ silicone resin is prepared by hydrolysis and polycondensation of silicon tetrachloride, trimethylchlorosilane and vinyltrichlorosilane in a solvent; the mass ratio of silicon tetrachloride, trimethylchlorosilane and vinyltrichlorosilane is 50:80:20.

[0015] Preferably, based on 100 parts by weight of the siloxane copolymer backbone, the mass parts of the feed of the copolymer and the grafting components during the hydrosilicification grafting stage are as follows: 17.5-40 parts of monoallyl polyether for the first addition, 7.5-15 parts of diallyl polyether, 4-10 parts of vinyl MQ silicone resin, and 4-7.5 parts of monoallyl polyether for supplementary addition.

[0016] Furthermore, the present invention also provides a method for preparing an organosilicon foam stabilizer, comprising the following steps:

[0017] (1) Preparation of siloxane copolymer backbone containing silane-hydrogen bonds and phenyl segments: anionic ring-opening polymerization was carried out under nitrogen protection, low-boiling substances were removed by distillation and neutralized, and the neutralizing agent was stripped under reduced pressure to constant weight;

[0018] (2) Preparation of diallyl polyether;

[0019] (3) Preparation of monoallyl polyether;

[0020] (4) Preparation of vinyl-containing MQ silicone resin;

[0021] (5) Preparation of platinum complex catalyst solution;

[0022] (6) Segmented hydrosilicification grafting: The siloxane copolymer backbone is hydrosilicified sequentially with monoallyl polyether, diallyl polyether and vinyl-containing MQ silicone resin in a solvent, and monoallyl polyether is added in addition. After adding an antioxidant, the solvent is removed under reduced pressure to constant weight to obtain an organosilicon foam stabilizer.

[0023] Preferably, the preparation conditions of the siloxane copolymer backbone in step (1) are as follows: anionic ring-opening polymerization is carried out by stirring at 60°C for 6 hours; the temperature is raised to 120°C and distilled under reduced pressure of 15 kPa until the distillation rate is less than 0.5 g / min; the temperature is lowered to 80°C and 2 parts by mass of tributyl phosphate are added for neutralization; the temperature is raised to 120°C and stripped under reduced pressure of 10 kPa until constant weight is achieved.

[0024] Preferably, the specific preparation steps of the platinum complex catalyst solution in step (5) are as follows: 5 parts by mass of chloroplatinic acid hexahydrate are dissolved in 95 parts by mass of isopropanol, and 10 parts by mass of divinyltetramethyldisiloxane are added and stirred for 1 hour to obtain the platinum complex catalyst solution.

[0025] Preferably, the specific steps of the segmented hydrosilicification grafting in step (6) are as follows: the siloxane copolymer backbone containing silane-hydrogen bonds and phenyl segments is added to cyclohexane, the temperature is raised to 55-70°C under nitrogen protection, a platinum complex catalyst solution is added and stirred for 30 min, then monoallyl polyether is slowly added dropwise, the reaction is maintained at 55-70°C for 2 h, a platinum complex catalyst solution is added and the temperature is raised to 70-85°C, diallyl polyether is added dropwise, the reaction is carried out for 3 h, the reaction temperature is lowered to 60-75°C, then vinyl MQ silicone resin is added and the reaction is continued for 2 h, monoallyl polyether is added to the reaction system, the reaction is carried out at 65-80°C for 1 h, then an antioxidant is added, the reaction is stirred at 50°C for 30 min, and then the cyclohexane is removed by vacuum distillation at 60°C and 0.5 kPa to constant weight, thus obtaining the organosilicon foam stabilizer.

[0026] This invention, by introducing phenyl segments into the siloxane backbone and employing segmented hydrosilylation grafting modification technology, achieves a synergistic improvement in the performance retention and cell refinement of organosilicon foam stabilizers under high-temperature polyurethane foaming conditions, resulting in the following significant beneficial effects:

[0027] Enhanced High-Temperature Stability: By introducing methylphenylcyclotrisiloxane units into the siloxane copolymer backbone, the thermal stability of the molecular backbone is effectively enhanced. The phenyl group possesses a strong intramolecular conjugation effect and significant steric hindrance, which can significantly increase the thermal decomposition temperature of the silicon-oxygen bond and inhibit chain breakage and rearrangement reactions under high-temperature conditions. Furthermore, the rigid structure of the phenyl group enhances intermolecular π-π interactions, improving the stabilizer's resistance to degradation in high-temperature shear environments and ensuring the persistence of interfacial activity.

[0028] Enhanced interfacial film strength: Vinyl-containing MQ silicone resin is covalently grafted onto the molecular backbone via hydrosilylation, constructing limitedly branched rigid structural domains between molecules. These rigid structural domains form a three-dimensional network structure at the bubble-film interface, significantly enhancing the mechanical strength and liquid drainage resistance of the interfacial film. Compared to traditional physically adsorbed interfacial films, the covalently anchored MQ resin is less prone to desorption under high temperature and high shear conditions, ensuring the structural integrity of the bubble film in the later stages of foaming.

[0029] Optimizing interfacial flow balance: By introducing monoallyl polyether and diallyl polyether in segments, a composite interfacial structure with differentiated functions was constructed. Monoallyl polyether, as a single-point anchored migratory segment, provides rapid spreading and wetting capabilities at the nascent cell membrane, endowing the interfacial film with the necessary self-healing fluidity. Diallyl polyether forms an intramolecular bridging structure through multi-point grafting, providing the interfacial film with tensile strength and drainage resistance. The synergistic effect of the two polyether segments achieves a strength-flow balance in interfacial film formation, effectively inhibiting cell coalescence and coarsening.

[0030] Improved compatibility: The introduction of the phenyl group increases the polarity of the siloxane backbone and intermolecular forces, significantly improving the compatibility of the stabilizer with the highly polar polyurethane system. The phenyl group can form hydrogen bonds or dipole interactions with polyol molecules, promoting uniform dispersion and interfacial migration of the stabilizer in the reaction system and avoiding uneven film formation caused by microphase separation. Simultaneously, the improved compatibility facilitates rapid wetting and spreading of the stabilizer in the initial foaming stage.

[0031] Achieving precise structural control: A segmented hydrosilylation process was employed, allowing for precise control of the grafting density and distribution of different functional segments by adjusting the reaction temperature, catalyst dosage, and feed sequence. Partial hydrosilylation of monoallyl polyether was first performed, followed by sequential grafting of diallyl polyether and MQ resin, avoiding competing side reactions and uneven grafting issues common in one-step reactions. This controllable molecular design ensures the uniformity of the product structure and maximizes its functionality.

[0032] Reduced open-cell ratio: Through the synergistic effect of the above-mentioned multiple technical features, the stabilizer of this invention can maintain a more complete and uniform cell structure under high-temperature foaming conditions, significantly reducing the open-cell ratio of the foam. The refined and closed-cell structure not only improves the thermal insulation performance of the foam material, but also enhances its mechanical strength and dimensional stability. Detailed Implementation

[0033] 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. Example 1

[0034] (1) 300g of octamethylcyclotetrasiloxane, 40g of methylphenylcyclotrisiloxane, 70g of methylhydrocyclotrisiloxane, 5g of hexamethyldisiloxane, and 1g of potassium hydroxide were added to a 1000mL three-necked flask. Anionic ring-opening polymerization was carried out by stirring at 60℃ for 6h under nitrogen protection. The temperature was raised to 120℃ and the low-boiling substances were removed by distillation under 15 kPa reduced pressure until the distillation rate was less than 0.5g / min. The temperature was lowered to 80℃ and 2g of tributyl phosphate was added to neutralize the catalyst. The temperature was raised to 120℃ and the excess neutralizing agent was stripped under 10 kPa reduced pressure until constant weight was obtained to obtain a siloxane copolymer backbone containing silane-hydrogen bonds and phenyl fragments (Si-H content 3.27mmol / g, bromination titration method).

[0035] (2) After dehydrating 8g of 1,3-propanediol and 1g of potassium hydroxide at 80℃ for 2h, 120g of propylene oxide was introduced under controlled pressure not exceeding 0.15MPa and reacted at 90℃ for 6h. After cooling to 60℃, 40g of allyl glycidyl ether was added and stirred for 3h. After neutralizing the residual alkali, the mixture was filtered to remove salt and diallyl polyether was obtained.

[0036] (3) After dehydrating 6g allyl alcohol and 1g potassium hydroxide at 70℃ for 1h, 116g propylene oxide was introduced and reacted at 80℃ for 12h. The residual alkali was neutralized and filtered to obtain monoallyl polyether.

[0037] (4) Add 50g silicon tetrachloride, 80g trimethylchlorosilane and 20g vinyltrichlorosilane to 500mL of anhydrous toluene. Add 300g deionized water slowly in an ice bath to carry out hydrolysis and condensation. After standing and separating into layers, wash the organic phase with saturated sodium bicarbonate solution until neutral. After drying with anhydrous magnesium sulfate, evaporate the solvent to obtain vinyl-containing MQ silicone resin.

[0038] (5) Dissolve 5g of chloroplatinic acid hexahydrate in 95g of isopropanol, add 10g of divinyltetramethyldisiloxane and stir for 1h to obtain a platinum complex catalyst solution;

[0039] (6) 200g of siloxane copolymer backbone containing silane-hydrogen bonds and phenyl fragments was added to 200g of cyclohexane. The mixture was heated to 55°C under nitrogen protection. 0.8g of platinum complex catalyst solution was added and stirred for 30min. 35g of monoallyl polyether was slowly added dropwise. The reaction was maintained at 55°C for 2h. 0.8g of platinum complex catalyst solution was added and the temperature was raised to 70°C. 15g of diallyl polyether was added dropwise and the reaction was carried out for 3h. The reaction temperature was lowered to 60°C. 8g of vinyl MQ silicone resin was added and the reaction was continued for 2h. 8g of monoallyl polyether was added to the reaction system and the reaction was carried out at 65°C for 1h. 2g of 2,6-di-tert-butyl-p-methylphenol antioxidant was added and the mixture was stirred at 50°C for 30min. The cyclohexane was removed by vacuum distillation at 60°C and 0.5kPa to constant weight, and the organosilicon foam stabilizer was obtained. Example 2

[0040] (1) 300g of octamethylcyclotetrasiloxane, 60g of methylphenylcyclotrisiloxane, 90g of methylhydrocyclotrisiloxane, 5g of hexamethyldisiloxane, and 1g of potassium hydroxide were added to a 1000mL three-necked flask. Anionic ring-opening polymerization was carried out by stirring at 60℃ for 6h under nitrogen protection. The temperature was raised to 120℃ and the low-boiling substances were removed by distillation under 15 kPa reduced pressure until the distillation rate was less than 0.5g / min. The temperature was lowered to 80℃ and 2g of tributyl phosphate was added to neutralize the catalyst. The temperature was raised to 120℃ and the excess neutralizing agent was stripped under 10 kPa reduced pressure until constant weight was obtained to obtain a siloxane copolymer backbone containing silane-hydrogen bonds and phenyl segments (Si-H content 2.81mmol / g, bromination titration method).

[0041] (2) After dehydrating 8g of 1,3-propanediol and 1g of potassium hydroxide at 80℃ for 2h, 120g of propylene oxide was introduced under controlled pressure not exceeding 0.15MPa and reacted at 90℃ for 6h. After cooling to 60℃, 40g of allyl glycidyl ether was added and stirred for 3h. After neutralizing the residual alkali, the mixture was filtered to remove salt and diallyl polyether was obtained.

[0042] (3) After dehydrating 6g allyl alcohol and 1g potassium hydroxide at 70℃ for 1h, 116g propylene oxide was introduced and reacted at 80℃ for 12h. The residual alkali was neutralized and filtered to obtain monoallyl polyether.

[0043] (4) Add 50g silicon tetrachloride, 80g trimethylchlorosilane and 20g vinyltrichlorosilane to 500mL of anhydrous toluene. Add 300g deionized water slowly in an ice bath to carry out hydrolysis and condensation. After standing and separating into layers, wash the organic phase with saturated sodium bicarbonate solution until neutral. After drying with anhydrous magnesium sulfate, evaporate the solvent to obtain vinyl-containing MQ silicone resin.

[0044] (5) Dissolve 5g of chloroplatinic acid hexahydrate in 95g of isopropanol, add 10g of divinyltetramethyldisiloxane and stir for 1h to obtain a platinum complex catalyst solution;

[0045] (6) Add 200g of siloxane copolymer backbone containing silane-hydrogen bonds and phenyl fragments to 200g of cyclohexane, heat to 60°C under nitrogen protection, add 1g of platinum complex catalyst solution and stir for 30min, then slowly add 50g of monoallyl polyether, maintain reaction at 60°C for 2h, add 1g of platinum complex catalyst solution and heat to 75°C, add 20g of diallyl polyether and react for 3h, then lower the reaction temperature to 65°C, add 12g of vinyl MQ silicone resin and continue reaction for 2h, add 10g of monoallyl polyether to the reaction system and react at 70°C for 1h, then add 2g of 2,6-di-tert-butyl-p-methylphenol antioxidant and stir at 50°C for 30min, then remove cyclohexane by vacuum distillation at 60°C and 0.5kPa to constant weight to obtain organosilicon foam stabilizer. Example 3

[0046] (1) 300g of octamethylcyclotetrasiloxane, 80g of methylphenylcyclotrisiloxane, 110g of methylhydrocyclotrisiloxane, 5g of hexamethyldisiloxane, and 1g of potassium hydroxide were added to a 1000mL three-necked flask. Anionic ring-opening polymerization was carried out by stirring at 60℃ for 6h under nitrogen protection. The temperature was raised to 120℃ and the low-boiling substances were removed by distillation under 15 kPa reduced pressure until the distillation rate was less than 0.5g / min. The temperature was lowered to 80℃ and 2g of tributyl phosphate was added to neutralize the catalyst. The temperature was raised to 120℃ and the excess neutralizing agent was stripped under 10 kPa reduced pressure until constant weight was obtained to obtain a siloxane copolymer backbone containing silane-hydrogen bonds and phenyl segments (Si-H content 3.67mmol / g, bromination titration method).

[0047] (2) After dehydrating 8g of 1,3-propanediol and 1g of potassium hydroxide at 80℃ for 2h, 120g of propylene oxide was introduced under controlled pressure not exceeding 0.15MPa and reacted at 90℃ for 6h. After cooling to 60℃, 40g of allyl glycidyl ether was added and stirred for 3h. After neutralizing the residual alkali, the mixture was filtered to remove salt and diallyl polyether was obtained.

[0048] (3) After dehydrating 6g allyl alcohol and 1g potassium hydroxide at 70℃ for 1h, 116g propylene oxide was introduced and reacted at 80℃ for 12h. The residual alkali was neutralized and filtered to obtain monoallyl polyether.

[0049] (4) Add 50g silicon tetrachloride, 80g trimethylchlorosilane and 20g vinyltrichlorosilane to 500mL of anhydrous toluene. Add 300g deionized water slowly in an ice bath to carry out hydrolysis and condensation. After standing and separating into layers, wash the organic phase with saturated sodium bicarbonate solution until neutral. After drying with anhydrous magnesium sulfate, evaporate the solvent to obtain vinyl-containing MQ silicone resin.

[0050] (5) Dissolve 5g of chloroplatinic acid hexahydrate in 95g of isopropanol, add 10g of divinyltetramethyldisiloxane and stir for 1h to obtain a platinum complex catalyst solution;

[0051] (6) Add 200g of siloxane copolymer backbone containing silane-hydrogen bonds and phenyl fragments to 200g of cyclohexane, heat to 65°C under nitrogen protection, add 1.2g of platinum complex catalyst solution and stir for 30min, then slowly add 65g of monoallyl polyether, maintain reaction at 65°C for 2h, add 1.2g of platinum complex catalyst solution and heat to 80°C, add 25g of diallyl polyether and react for 3h, then lower the reaction temperature to 70°C, add 16g of vinyl MQ silicone resin and continue reaction for 2h, add 12g of monoallyl polyether to the reaction system and react at 75°C for 1h, then add 2g of 2,6-di-tert-butyl-p-methylphenol antioxidant and stir at 50°C for 30min, then remove cyclohexane by vacuum distillation at 60°C and 0.5kPa to constant weight to obtain organosilicon foam stabilizer. Example 4

[0052] (1) 300g of octamethylcyclotetrasiloxane, 100g of methylphenylcyclotrisiloxane, 130g of methylhydrocyclotrisiloxane, 5g of hexamethyldisiloxane, and 1g of potassium hydroxide were added to a 1000mL three-necked flask. Anionic ring-opening polymerization was carried out by stirring at 60℃ for 6h under nitrogen protection. The temperature was raised to 120℃ and the low-boiling substances were removed by distillation under 15 kPa reduced pressure until the distillation rate was less than 0.5g / min. The temperature was lowered to 80℃ and 2g of tributyl phosphate was added to neutralize the catalyst. The temperature was raised to 120℃ and the excess neutralizing agent was stripped under 10 kPa reduced pressure until constant weight was obtained to obtain a siloxane copolymer backbone containing silane-hydrogen bonds and phenyl segments (Si-H content 4.05mmol / g, bromination titration method).

[0053] (2) After dehydrating 8g of 1,3-propanediol and 1g of potassium hydroxide at 80℃ for 2h, 120g of propylene oxide was introduced under controlled pressure not exceeding 0.15MPa and reacted at 90℃ for 6h. After cooling to 60℃, 40g of allyl glycidyl ether was added and stirred for 3h. After neutralizing the residual alkali, the mixture was filtered to remove salt and diallyl polyether was obtained.

[0054] (3) After dehydrating 6g allyl alcohol and 1g potassium hydroxide at 70℃ for 1h, 116g propylene oxide was introduced and reacted at 80℃ for 12h. The residual alkali was neutralized and filtered to obtain monoallyl polyether.

[0055] (4) Add 50g silicon tetrachloride, 80g trimethylchlorosilane and 20g vinyltrichlorosilane to 500mL of anhydrous toluene. Add 300g deionized water slowly in an ice bath to carry out hydrolysis and condensation. After standing and separating into layers, wash the organic phase with saturated sodium bicarbonate solution until neutral. After drying with anhydrous magnesium sulfate, evaporate the solvent to obtain vinyl-containing MQ silicone resin.

[0056] (5) Dissolve 5g of chloroplatinic acid hexahydrate in 95g of isopropanol, add 10g of divinyltetramethyldisiloxane and stir for 1h to obtain a platinum complex catalyst solution;

[0057] (6) 200g of siloxane copolymer backbone containing silane-hydrogen bonds and phenyl fragments was added to 200g of cyclohexane. The mixture was heated to 70°C under nitrogen protection. 1.5g of platinum complex catalyst solution was added and stirred for 30min. 80g of monoallyl polyether was slowly added dropwise. The reaction was maintained at 70°C for 2h. 1.5g of platinum complex catalyst solution was added and the temperature was raised to 85°C. 30g of diallyl polyether was added dropwise and the reaction was carried out for 3h. The reaction temperature was lowered to 75°C. 20g of vinyl MQ silicone resin was added and the reaction was continued for 2h. 15g of monoallyl polyether was added to the reaction system and the reaction was carried out at 80°C for 1h. 2g of 2,6-di-tert-butyl-p-methylphenol antioxidant was added and the mixture was stirred at 50°C for 30min. The cyclohexane was removed by vacuum distillation at 60°C and 0.5kPa to constant weight, and the organosilicon foam stabilizer was obtained.

[0058] Comparative Example 1:

[0059] The difference between Comparative Example 1 and Example 2 is that: no phenyl fragment is introduced, and methylphenylcyclotrisiloxane is replaced with equimolar octamethylcyclotetrasiloxane in step (1). Other raw materials, proportions and operations are the same; the remaining conditions are the same as in Example 2.

[0060] Comparative Example 2:

[0061] The difference between Comparative Example 2 and Example 2 is that vinyl MQ silicone resin is not introduced, step (4) is omitted, and vinyl MQ resin is not added in step (6); the other conditions are the same as in Example 2.

[0062] Comparative Example 3:

[0063] The difference between Comparative Example 3 and Example 2 is that diallyl polyether is not used, and in step (6), monoallyl polyether with an equivalent amount of double bonds is used to replace the total amount of double bonds in diallyl polyether; the other conditions are the same as in Example 2.

[0064] Comparative Example 4:

[0065] The difference between Comparative Example 4 and Example 2 is that monoallyl polyether is not used, and in step (6), dielyl polyether with an equivalent amount of double bonds is used to replace the total amount of double bonds in all monoallyl polyether; the other conditions are the same as in Example 2.

[0066] Comparative Example 5:

[0067] The difference between Comparative Example 5 and Example 2 is that the vinyl MQ silicone resin was replaced by an equal mass of methyl MQ silicone resin (which does not contain vinyl and does not participate in the hydrosilylation reaction); the other conditions were the same as in Example 2.

[0068] Comparative Example 6:

[0069] The difference between Comparative Example 6 and Example 2 is that the order of hydrosilicification feeding was changed, and monoallyl polyether, diallyl polyether and vinyl MQ were added at one time, and the reaction was carried out at 60–75°C for 6 h; the other conditions were the same as those in Example 2.

[0070] Unified foaming system and test prerequisites:

[0071] Basic system (high-index rigid PU foam, hot plate simulates high-temperature foaming window):

[0072] 1000g of polyol (glycerol polyether, hydroxyl value approximately 380 mgKOH / g);

[0073] 15g of water;

[0074] Physical foaming agent: HFO-1233zd(E) 80g;

[0075] Catalyst: 8g tertiary amine, 2.5g stannous octoate;

[0076] Foam stabilizer: The foam stabilizer prepared in the examples and comparative examples, with a standard dosage of 12g.

[0077] Isocyanate: pMDI (approximately 31% NCO), index fixed at 120.

[0078] Process conditions: Mix the raw materials, stir at 2000 rpm for 8 seconds, and immediately pour into a preheated metal mold. Coat the inner surface of the mold with a release agent. The mold cavity is 100×100×300 mm and the mold temperature is 100°C.

[0079] Performance testing:

[0080] High-temperature foaming stability: The mold was kept at the target temperature, and the mixture was mixed and poured according to a uniform process. The gelation time, the maximum free foaming height, and the height 10 minutes after the highest point were recorded. The height retention rate was calculated as (height at 10 minutes / maximum height) × 100%. The sag and local collapse were recorded by lateral camera, and the sag length (mm) was measured. The results are shown in Table 1.

[0081] Cell structure and porosity: A 30×30×30 mm cubic sample was cut from the center of the cell, and the pore diameter distribution was measured by optical microscopy (random measurement points ≥100). The average pore diameter and coefficient of variation were statistically analyzed, and the porosity was determined by gas gravity method.

[0082] Table 1 Performance Test Results

[0083]

[0084] Data Analysis:

[0085] As shown in Tables 1 (Examples 1–4), under the same foaming system and process, the gel time was maintained at 32–36 seconds, the maximum free foaming height was approximately 270–285 mm, the height retention rate was 86.3%–93.5%, the sag length was controlled at 4–9 mm, the average pore size was approximately 210–255 µm with a coefficient of variation of 14.0%–21.7%, and the open-cell ratio was 7.8%–12.8%. This data shows a consistent trend of overall stability and cell refinement during the high-temperature foaming stage, which is presumably related to the introduction of phenyl segments into the polysiloxane backbone while retaining an appropriate amount of silane-hydrogen bonds, followed by the sequential hydrosilylation of monoallyl polyether, diallyl polyether, and vinyl-containing silicone resin. The above structure forms a thin film at the interface that combines a certain degree of rigidity and fluidity. It can maintain the support of the foam wall and resist liquid drainage in the high temperature range, without excessive cross-linking and loss of wetting and migration. At the same time, the polysiloxane backbone containing phenyl enhances thermal stability and polar compatibility, which is conducive to compatibility and spreading in the exothermic stage of polyurethane reaction. Thus, it achieves a synergistic performance of high height retention and low open porosity within a wide temperature window.

[0086] As can be seen from the data in Table 1 for Example 2 and Comparative Example 1, the height retention rate of Example 2 is 93.5%, higher than that of Comparative Example 1 (74.8%). Simultaneously, the sag length decreased from 18 mm to 4 mm, the average pore size decreased from 290 µm to 210 µm, the coefficient of variation of pore size distribution decreased from 28.3% to 14.0%, and the open porosity decreased from 19.5% to 7.8%. The main difference between the two is that the siloxane backbone copolymerization in Example 2 introduced phenyl segments, while Comparative Example 1 did not. Based on the data, it can be inferred that the introduction of phenyl segments improves the thermal stability and interfacial polarity matching of the backbone during the high-temperature foaming stage, making it easier for the stabilizer to spread on the newly formed bubble film and form a stronger interfacial film in the early stage of the reaction, reducing the probability of liquid drainage and bubble merging. At the same time, phenyl segments increase intermolecular forces and shear tolerance, providing more effective support to the bubble wall during the rapid rise phase, thus resulting in a higher height retention rate and smaller pore size and open porosity.

[0087] As can be seen from the data in Table 1 for Example 2 and Comparative Example 2, the height retention rate of Example 2 was 93.5%, while that of Comparative Example 2 was 79.3%. The sagging length of Example 2 was 4 mm, lower than that of Comparative Example 2 (14 mm). The average pore size decreased from 275 µm to 210 µm, the coefficient of variation of pore size distribution decreased from 24.1% to 14.0%, and the open porosity decreased from 16.8% to 7.8%. The difference corresponds to the introduction of a vinyl-containing silicone resin in Example 2, which was grafted onto the molecular backbone through a hydrosilylation reaction, while Comparative Example 2 did not introduce this resin. Based on the data, it is speculated that reactive silicone resin constructs a limited branched rigid structural domain between molecules, enhancing the bubble film's resistance to drainage and stretching, and inhibiting pore coalescence and coarsening. Its covalent anchoring reduces the risk of desorption under high-temperature shear, allowing the interfacial film to maintain its integrity after the highest point, thereby improving the height retention rate and reducing sagging and open porosity.

[0088] As can be seen from the data in Table 1 for Example 2 and Comparative Examples 3 and 4, Example 2 has significant advantages in terms of height retention, anti-sagging, and cell refinement in the later stages. It can be inferred that Example 2 simultaneously introduces monoallyl polyether and diallyl polyether to construct a composite interface structure with migratory segments and multi-point anchoring: monoallyl polyether is beneficial for rapid spreading and wetting at the nascent cell membrane, giving the film the necessary self-healing flow; diallyl polyether provides film strength and anti-drainage support through multi-point grafting and intramolecular bridging, thereby synergistically inhibiting cell merging and coarsening. In Comparative Example 3, which only uses monoallyl polyether, the anchoring point density and bridging probability are reduced, and the interface film is more easily weakened by drainage after the highest point, resulting in a decrease in height retention, increased sagging, and a widened pore size distribution; in Comparative Example 4, which only uses diallyl polyether, the proportion of local rigid structural domains increases, dissolution dispersion and interface migration are restricted, the drainage time before gelation is relatively prolonged, and cell merging is easily induced, resulting in a larger average pore size, a higher coefficient of variation, and an open porosity. The above-mentioned data-based mechanistic speculation and numerical changes corroborate each other, suggesting that the ratio window of monoallyl polyether to diallyl polyether plays a decisive role in the strength-flow balance of interfacial film formation, thereby bringing about the overall stability improvement shown in Example 2.

[0089] As can be seen from the data in Table 1 for Example 2 and Comparative Example 5, Example 2 exhibits advantages in height retention, sag length, average pore size, pore size distribution variation coefficient, and open area ratio. The difference lies in the fact that Example 2 uses a vinyl-containing silicone resin to participate in hydrosilylation to form covalent anchoring, while Comparative Example 5 uses a vinyl-free methyl silicone resin, which only serves as a physical thickener and diluent. It can be inferred that resins lacking chemical anchoring are prone to phase separation at the interface due to the influence of flow field and temperature gradient, making it difficult to construct stable rigid structural domains. This results in insufficient bubble strength and resistance to liquid drainage, manifested as greater sag, coarsening, and open areas.

[0090] As can be seen from the data in Table 1 for Example 2 and Comparative Example 6, the gelation time of Example 2 was 32 seconds, while that of Comparative Example 6 was extended to 38 seconds. Although the highest free foaming height of Comparative Example 6 reached 290 mm, the height retention rate was only 76.4%, the sag length increased to 19 mm, the average pore size and the coefficient of variation of pore size distribution were 295 µm and 29.1%, respectively, and the open porosity was 20.5%, all of which were inferior to those of Example 2. Comparative Example 6 added all alkenyl-containing and silane-containing reactants at once, lacking segmented control. This was mainly due to the disordered grafting distribution caused by reaction competition, resulting in local microgels or uneven chain segment lengths, which reduced the dispersibility of the product in the matrix and the uniformity of interfacial film formation, exhibiting the characteristic of high initial expansion but insufficient retention in the later stage. It is speculated that this is related to the fact that the interfacial film is prone to weak areas and is eroded by the draining liquid during the height retention stage.

[0091] 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. An organosilicon foam stabilizer, characterized in that, The product is prepared by reacting a siloxane copolymer backbone containing silane-hydrogen bonds and phenyl segments with monoallyl polyether, diallyl polyether, and vinyl-containing MQ silicone resin via segmental hydrosilylation. The siloxane copolymer backbone comprises segments obtained by ring-opening copolymerization of octamethylcyclotetrasiloxane, methylphenylcyclotrisiloxane, and methylhydrocyclotrisiloxane, retaining silane-hydrogen bonds within the backbone. The vinyl-containing MQ silicone resin is covalently grafted onto the backbone via silane-hydroaddition. The monoallyl polyether and diallyl polyether are grafted onto the backbone via silane-hydroaddition. The hydrosilylation grafting sequence includes: first grafting monoallyl polyether, then grafting diallyl polyether, followed by grafting the vinyl-containing MQ silicone resin, and then supplementing with grafting monoallyl polyether.

2. The organosilicon foam stabilizer according to claim 1, characterized in that, The siloxane copolymer backbone is prepared by ring-opening copolymerization of the following raw materials: 300 parts by mass of octamethylcyclotetrasiloxane, 40-100 parts by mass of methylphenylcyclotrisiloxane, 70-130 parts by mass of methylhydrocyclotrisiloxane, 5 parts by mass of hexamethyldisiloxane, and 1 part by mass of potassium hydroxide.

3. The organosilicon foam stabilizer according to claim 1, characterized in that, The monoallyl polyether is prepared by addition reaction of allyl alcohol and propylene oxide; the mass ratio of allyl alcohol to propylene oxide is 6:

116.

4. The organosilicon foam stabilizer according to claim 1, characterized in that, The diallyl polyether is prepared by reacting 1,3-propanediol, propylene oxide and allyl glycidyl ether; the mass ratio of 1,3-propanediol, propylene oxide and allyl glycidyl ether is 8:120:

40.

5. The organosilicon foam stabilizer according to claim 1, characterized in that, The vinyl-containing MQ silicone resin is prepared by hydrolysis and condensation polymerization of silicon tetrachloride, trimethylchlorosilane and vinyltrichlorosilane in a solvent; the mass ratio of silicon tetrachloride, trimethylchlorosilane and vinyltrichlorosilane is 50:80:

20.

6. The organosilicon foam stabilizer according to claim 1, characterized in that, Based on 100 parts by mass of the siloxane copolymer backbone, the mass parts of the feed of the copolymer and the grafting components during the hydrosilicification grafting stage are as follows: 17.5-40 parts of monoallyl polyether for the first addition, 7.5-15 parts of diallyl polyether, 4-10 parts of vinyl MQ silicone resin, and 4-7.5 parts of monoallyl polyether for supplementary addition.

7. A method for preparing an organosilicon foam stabilizer according to any one of claims 1-6, comprising the steps of: (1) Preparation of siloxane copolymer backbone containing silane-hydrogen bonds and phenyl segments: anionic ring-opening polymerization was carried out under nitrogen protection, low-boiling substances were removed by distillation and neutralized, and the neutralizing agent was stripped under reduced pressure to constant weight; (2) Preparation of diallyl polyether; (3) Preparation of monoallyl polyether; (4) Preparation of vinyl-containing MQ silicone resin; (5) Preparation of platinum complex catalyst solution; (6) Segmented hydrosilicification grafting: The siloxane copolymer backbone is hydrosilicified sequentially with monoallyl polyether, diallyl polyether and vinyl-containing MQ silicone resin in a solvent, and monoallyl polyether is added in addition. After adding an antioxidant, the solvent is removed under reduced pressure to constant weight to obtain an organosilicon foam stabilizer.

8. The method for preparing the organosilicon foam stabilizer according to claim 7, characterized in that, The preparation conditions for the siloxane copolymer backbone in step (1) are as follows: anionic ring-opening polymerization is carried out by stirring at 60°C for 6 hours; the temperature is raised to 120°C and distilled under reduced pressure of 15 kPa until the distillation rate is less than 0.5 g / min; the temperature is lowered to 80°C and 2 parts by mass of tributyl phosphate are added for neutralization; the temperature is raised to 120°C and stripped under reduced pressure of 10 kPa until constant weight is achieved.

9. The method for preparing the organosilicon foam stabilizer according to claim 7, characterized in that, The specific preparation steps of the platinum complex catalyst solution in step (5) are as follows: 5 parts by mass of chloroplatinic acid hexahydrate are dissolved in 95 parts by mass of isopropanol, and 10 parts by mass of divinyltetramethyldisiloxane are added and stirred for 1 hour to obtain the platinum complex catalyst solution.

10. The method for preparing the organosilicon foam stabilizer according to claim 7, characterized in that, The specific steps of the segmented hydrosilicification grafting described in step (6) are as follows: the siloxane copolymer backbone containing silane-hydrogen bonds and phenyl segments is added to cyclohexane, the temperature is raised to 55-70°C under nitrogen protection, a platinum complex catalyst solution is added and stirred for 30 min, then monoallyl polyether is slowly added dropwise, the reaction is maintained at 55-70°C for 2 h, a platinum complex catalyst solution is added and the temperature is raised to 70-85°C, diallyl polyether is added dropwise, the reaction is carried out for 3 h, the reaction temperature is lowered to 60-75°C, then vinyl MQ silicone resin is added and the reaction is continued for 2 h, monoallyl polyether is added to the reaction system, the reaction is carried out at 65-80°C for 1 h, an antioxidant is added, the reaction is stirred at 50°C for 30 min, and then the cyclohexane is removed by vacuum distillation at 60°C and 0.5 kPa to constant weight, thus obtaining the organosilicon foam stabilizer.

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