Highly stable solvent-free defoamer and preparation method thereof

Abstract

This invention discloses a highly stable solvent-free defoamer and its preparation method, belonging to the field of defoamer technology. The highly stable solvent-free defoamer comprises the following raw materials in parts by weight: 50-60 parts of polydimethylsiloxane, 8-12 parts of polyether-modified polysiloxane, 3-5 parts of polyurea-modified polysiloxane, 2-5 parts of nonionic emulsifier, and 8-10 parts of modified silica. The polyurea-modified polysiloxane is prepared by the following method: isophorone diisocyanate and hexamethylene diisocyanate are prepolymerized with diaminopropyl-terminated polysiloxane, followed by reaction with nonylphenol polyoxyethylene ether under the action of a catalyst to obtain polyurea-modified polysiloxane. The highly stable solvent-free defoamer prepared by this invention has a short defoaming time, good foam suppression performance, and excellent centrifugal stability and high-temperature stability.

Description

Technical Field

[0001] This invention relates to the field of defoamer technology, specifically to a highly stable solvent-free defoamer and its preparation method. Background Technology

[0002] In numerous industrial production and application processes, such as coatings, inks, papermaking, textile printing and dyeing, fermentation engineering, and water treatment, materials generate significant amounts of foam during mechanical stirring, fluid pumping, and the presence of surfactants. Foam accumulation not only reduces equipment production capacity and extends production cycles but can also lead to overflows and inaccurate product level gauge readings. Therefore, defoamers are typically added for defoaming and foam suppression. Traditional defoamers usually contain large amounts of volatile organic solvents, posing not only flammable and explosive safety hazards but also health risks to operators. Existing solvent-free defoamers still have shortcomings in practical application and storage. Due to differences in polarity and density between components, the hydrophobic active ingredients in solvent-free defoamers (such as hydrophobic silica, silicone oil, and polyethers) are prone to particle aggregation, flocculation, and sedimentation after long-term storage or exposure to high and low temperatures, leading to defoamer ineffectiveness.

[0003] Chinese invention patent CN119075391A discloses a method for preparing a solvent-free defoamer with good stability, comprising the following steps: (1) under a nitrogen atmosphere, 60-70 parts by weight of terminal allyl polyether, 8-10 parts by weight of antioxidant, and 0.2-0.6 parts by weight of platinum catalyst are mixed and heated to 55-58℃ and stirred evenly to obtain mixture A; (2) 30-40 parts by weight of hydrogen-containing silicone oil and 4-9 parts by weight of 4A molecular sieve are added to mixture A, the temperature is maintained at 80-100℃, and the mixture is stirred at a constant temperature for 2-3 hours to obtain mixture B; (3) 10-14 parts by weight of modified filler are added to mixture B, and the mixture is stirred for 30-50 minutes to obtain a solvent-free defoamer. This invention improves the defoaming performance of the defoamer by using specific raw material composition and ratio; the addition of modified filler can help the defoamer to be better dispersed in aqueous or oily systems, thereby improving its efficiency; however, its stability still needs to be improved. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this invention is to provide a highly stable solvent-free defoamer and its preparation method.

[0005] A highly stable solvent-free defoamer comprises the following raw materials in parts by weight: 50-60 parts of polydimethylsiloxane, 8-12 parts of polyether-modified polysiloxane, 3-5 parts of polyurea-modified polysiloxane, 2-5 parts of nonionic emulsifier, and 8-10 parts of modified silica. The polyurea-modified polysiloxane is prepared by the following method: Isophorone diisocyanate and hexamethylene diisocyanate were prepolymerized with diaminopropyl-terminated polysiloxane, and then reacted with nonylphenol polyoxyethylene ether under the action of a catalyst to obtain polyurea-modified polysiloxane. The mass ratio of isophorone diisocyanate, hexamethylene diisocyanate, diaminopropyl-terminated polysiloxane, and nonylphenol polyoxyethylene ether is 0.18:0.06:1:0.22. The modified silica is prepared by the following method: A silane coupling agent was dispersed in an aqueous ethanol solution, the pH was adjusted, and then silica was added to react and obtain modified silica.

[0006] The catalyst is dibutyltin dilaurate.

[0007] The prepolymerization reaction was carried out at a temperature of 30°C for 4 hours; the reaction with nonylphenol polyoxyethylene ether was carried out at a temperature of 70°C for 3 hours.

[0008] The silane coupling agent is a mixture of single-terminated trimethoxysilyl-terminated polydimethylsiloxane and (methoxy-terminated polyethylene glycol propyl)trimethoxysilane in a mass ratio of 3:1.

[0009] The mass ratio of the silane coupling agent to the silica is 1:10.

[0010] The reaction was carried out at a temperature of 65°C for 5 hours.

[0011] The nonionic emulsifier is fatty alcohol polyoxyethylene ether.

[0012] A method for preparing a highly stable solvent-free defoamer includes the following steps: (1) Weigh the raw materials according to the following parts by weight: 50-60 parts of polydimethylsiloxane, 8-12 parts of polyether-modified polysiloxane, 3-5 parts of polyurea-modified polysiloxane, 2-5 parts of nonionic emulsifier, and 8-10 parts of modified silica. (2) Mix polydimethylsiloxane, polyether-modified polysiloxane and nonionic emulsifier, add modified silica for high-speed dispersion, add polyurea-modified polysiloxane and mix well, defoam and let stand to mature, and obtain a highly stable solvent-free defoamer.

[0013] Due to the adoption of the above technical solutions, the beneficial effects of the present invention include: This invention uses polydimethylsiloxane as a low surface tension continuous phase, polyether-modified polysiloxane and nonionic emulsifiers to adjust the interfacial compatibility and dispersion in aqueous foaming media, modified silica as a solid defoaming active component, and the reversible association structure formed by polyurea-modified polysiloxane to improve the system's anti-settling ability. Polydimethylsiloxane and polyether-modified polysiloxane can rapidly migrate and spread at the gas-liquid interface, while modified silica synergistically enters the bubble film and promotes bubble film instability and rupture. Polyurea-modified polysiloxane provides suspension stability and structural support for the modified silica. Through the synergistic effects of interfacial spreading, particle defoaming, compatibility adjustment, and weak network stabilization, the resulting solvent-free defoamer simultaneously possesses excellent defoaming and foam-suppressing properties, as well as excellent centrifugal stability and high-temperature storage stability. Attached Figure Description

[0014] Figure 1 The Fourier transform infrared spectrum of the polyurea-modified polysiloxane prepared in Example 1 is shown.

[0015] Figure 2 The image shows the X-ray photoelectron spectrum of the polyurea-modified polysiloxane prepared in Example 1.

[0016] Figure 3 The Fourier transform infrared spectra of the silica and modified silica prepared in Example 2 are shown.

[0017] Figure 4 Thermogravimetric curves of the silica and modified silica prepared in Example 2 are shown. Detailed Implementation

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

[0019] Example 1: Preparation of polyurea-modified polysiloxane Under nitrogen protection, 400 ml of anhydrous toluene, 18 g of isophorone diisocyanate, and 6 g of hexamethylene diisocyanate were added to a reaction flask and stirred until homogeneous. Then, 100 ml of anhydrous toluene and 100 g of diaminopropyl-terminated polysiloxane (number average molecular weight 1000) were mixed evenly and added dropwise to the reaction flask over 2 hours, during which the temperature inside the reaction flask was controlled not to exceed 30°C. The temperature was then raised to 30°C and the reaction was allowed to proceed for 4 hours. 22 g of nonylphenol polyoxyethylene ether (NP-10) and 0.04 g of dibutyltin dilaurate were added, and the temperature was raised to 70°C and the reaction was allowed to proceed for 3 hours. The mixture was then rotary evaporated to constant weight at 70°C and a gauge pressure of -0.09 MPa to obtain polyurea-modified polysiloxane. The apparent number average molecular weight of the polyurea-modified polysiloxane was determined to be 8732 by gel permeation chromatography.

[0020] Figure 1 The image shows the Fourier transform infrared spectrum of polyurea-modified polysiloxane. As can be seen from the image, at 3342 cm⁻¹...-1 The absorption peaks appearing nearby are attributed to the stretching vibrations of the NH groups in the urea and carbamate groups; 1642 cm⁻¹ -1 and 1682cm -1 The nearby absorption peaks correspond to the stretching vibrations of the hydrogen-bonded associated state and the free state C=O in the urea group, respectively; 1723 cm⁻¹ -1 An absorption peak for the stretching vibration of the C=O group in the urethane group appeared nearby, at 1227 cm⁻¹. -1 The absorption peaks appearing nearby are related to the stretching vibrations of CN and CO in the carbamate structure and the absorption of the aryl ether structure; 1542 cm⁻¹ -1 The nearby absorption peaks are attributed to the NH bending vibration and CN stretching vibration in the urea group; at 1107 cm⁻¹ -1 and 1023cm -1 The nearby absorption peak is attributed to the overlapping absorption of the stretching vibrations of Si-O-Si and COC; 1261 cm⁻¹ -1 The strong absorption peak nearby is attributed to the symmetric deformation vibration of the methyl group in Si-CH3, 800 cm⁻¹ -1 The strong absorption peaks nearby are attributed to Si-C stretching vibrations and Si-CH3 rocking vibrations; 3062 cm⁻¹ -1 The nearby absorption peak and 1607 cm⁻¹ -1 1512cm -1 The nearby absorption peaks are attributed to the aromatic CH stretching vibrations and the skeletal vibrations of the benzene ring, respectively; 2962 cm⁻¹ -1 2927cm -1 and 2857cm -1 The nearby absorption peak is attributed to the stretching vibration of aliphatic CH4; 1463 cm⁻¹ -1 1412cm -1 and 1377cm -1 The nearby absorption peaks are related to the bending vibrations of the corresponding methylene and methyl groups.

[0021] Figure 2 The image shows the full X-ray photoelectron spectroscopy (XPS) spectrum of polyurea-modified polysiloxane. As can be seen, C, O, Si, and N elements were detected in the polyurea-modified polysiloxane, consistent with the elemental composition of the target product. Specifically, the characteristic peak near 284.8 eV is attributed to C 1s, and the characteristic peak near 532.5 eV is attributed to O 1s; characteristic peaks of Si 2p and Si 2s appear near 102.2 eV and 153.5 eV, respectively; and a characteristic peak of N 1s appears near 399.8 eV. Figure 1 and Figure 2The characteristic peaks indicate that the diaminopropyl-terminated polysiloxane reacts with isophorone diisocyanate to form a polyurea structure, and the remaining isocyanate groups further react with the terminal hydroxyl groups of NP-10 to form a urethane structure, thus obtaining polyurea-modified polysiloxane.

[0022] This polyurea-modified polysiloxane contains polysiloxane soft segments, polyurea segments, urethane linking structures, and nonylphenol polyoxyethylene ether end-capped segments. The polysiloxane soft segments possess low surface tension and good interfacial spreading ability, facilitating the rapid migration of active components to the foam surface. The polyurea segments can construct a reversible weak network through hydrogen bonding and molecular chain entanglement, increasing the system's structural viscosity and thixotropy, and enhancing the suspension stabilization of defoaming particles. The nonylphenol polyoxyethylene ether end-capped segments can regulate the hydrophilic-hydrophobic balance of molecules, improving its compatibility with polydimethylsiloxane, polyether-modified polysiloxane, and nonionic emulsifiers. Therefore, the polyurea-modified polysiloxane combines interfacial spreading, structural stabilization, and compatibility regulation, which is beneficial for improving the rapid defoaming performance, sustained foam suppression ability, and storage stability of the defoamer.

[0023] Example 2 Preparation of Modified Silica Add 50 ml of 90 wt% ethanol aqueous solution, 3 g of single-terminated trimethoxysilyl-terminated polydimethylsiloxane, and 1 g of (methoxy-terminated polyethylene glycol propyl)trimethoxysilane to a reaction flask, stir and mix well, adjust the pH to 4 with 5 wt% acetic acid aqueous solution, stir for 30 min to obtain silane coupling agent solution; add 40 g of silica to 500 ml of 90 wt% ethanol aqueous solution, sonicate at 30 kHz and 200 W for 30 min, then add all the prepared silane coupling agent solution dropwise to the reaction system, complete the addition in 30 min, maintain the pH at 4 with 5 wt% acetic acid aqueous solution during the addition, stir and heat to 65 ℃, react for 5 h, cool to room temperature, filter, wash with anhydrous ethanol (3 × 100 ml), and vacuum dry at 90 ℃ and gauge pressure -0.09 MPa for 5 h to obtain modified silica.

[0024] Figure 3 The figures show the Fourier transform infrared spectra of silica and modified silica. As can be seen from the figures, compared to silica, modified silica exhibits better performance at 3425 cm⁻¹. -1 The nearby broad peak and 958cm -1 The near-terminal Si-OH absorption peaks all decreased, indicating that some of the silanol groups on the surface of the silica participated in the condensation reaction with the hydrolysis products of silanes; Meanwhile, at 2962 cm⁻¹... -1 and 2905cm -1 The CH stretching vibration of Si-CH3 in polydimethylsiloxane was observed nearby, at 2868 cm⁻¹. -1 and 1463cm -1Nearby, symmetric stretching vibration peaks and scissor vibration peaks of the methylene CH group in the polyethylene glycol segment were observed; 1261 cm⁻¹ -1 The nearby absorption peak is attributed to the deformation vibration of the methyl group in Si-CH3, 840 cm⁻¹ -1 and 760cm -1 The nearby absorption peaks are attributed to the rocking vibration of Si-CH3. The appearance of these characteristic peaks indicates that both polysiloxane and polyether segments have been introduced into the modified silica.

[0025] Thermogravimetric analysis was used to test the silica and modified silica respectively: 10 mg of sample was weighed and placed in an alumina crucible, and nitrogen gas with a flow rate of 20 mL / min was introduced and the temperature was increased from 25°C to 800°C at a heating rate of 10°C / min. Figure 4 The thermogravimetric curves (TGA) of silica and modified silica are shown in the figure. As can be seen, both exhibit slight weight loss within the temperature range of 30-150℃, mainly due to the volatilization of adsorbed water and residual solvents. With further temperature increases, silica only experiences slow weight loss, primarily related to the removal of bound water and surface Si-OH condensation dehydration. In contrast, modified silica shows significant weight loss in the temperature range of 250-550℃, which is related to the thermal decomposition of surface-grafted organic segments and the cracking of organopolysiloxanes. With further temperature increases, the sample mass change gradually plateaus.

[0026] The modified silica incorporates both polydimethylsiloxane (PDMS) and polyethylene glycol (PEG) segments on its surface. The PDMS segments reduce the surface polarity of the silica, improve particle hydrophobicity and compatibility with the continuous organosilicon phase, promote particle entry into the bubble film, and induce localized dewetting, thinning, and rupture of the bubble film. The PEG segments enhance the interfacial interaction between the modified silica, polyether-modified polysiloxane, and nonionic emulsifiers, improving particle wetting and dispersion. These two segments work together to regulate the hydrophilic-hydrophobic balance of the silica surface, reducing secondary particle agglomeration and sedimentation, resulting in modified silica exhibiting excellent defoaming activity, uniform dispersion, and suspension stability.

[0027] Example 3 Preparation of a highly stable solvent-free defoamer (1) Weigh out: 50g of polydimethylsiloxane, 8g of polyether-modified polysiloxane, 3g of polyurea-modified polysiloxane (prepared in Example 1), 2g of nonionic emulsifier (fatty alcohol polyoxyethylene ether), and 8g of modified silica (prepared in Example 2); (2) Mix polydimethylsiloxane, polyether-modified polysiloxane and nonionic emulsifier, stir at 23°C and 500 rpm for 30 min, add modified silica in batches (divided into 3 batches, with an interval of 5 min between each batch), heat to 50°C, stir at 2000 rpm for 30 min, add polyurea-modified polysiloxane and stir at 500 rpm for 30 min, defoam at a gauge pressure of -0.09 MPa for 20 min, cool to room temperature, and let stand for 4 h to mature, to obtain a highly stable solvent-free defoamer.

[0028] Example 4: Preparation of a highly stable solvent-free defoamer (1) Weigh out: 55g of polydimethylsiloxane, 10g of polyether-modified polysiloxane, 4g of polyurea-modified polysiloxane (prepared in Example 1), 4g of nonionic emulsifier (fatty alcohol polyoxyethylene ether), and 9g of modified silica (prepared in Example 2). (2) Mix polydimethylsiloxane, polyether-modified polysiloxane and nonionic emulsifier, stir at 23°C and 500 rpm for 30 min, add modified silica in batches (divided into 3 batches, with an interval of 5 min between each batch), heat to 50°C, stir at 2000 rpm for 30 min, add polyurea-modified polysiloxane, stir at 500 rpm for 30 min, defoam at a gauge pressure of -0.09 MPa for 20 min, cool to room temperature, and let stand for 4 h to mature, to obtain a highly stable solvent-free defoamer.

[0029] Example 5: Preparation of a highly stable solvent-free defoamer (1) Weigh out: 60g of polydimethylsiloxane, 12g of polyether-modified polysiloxane, 5g of polyurea-modified polysiloxane (prepared in Example 1), 5g of nonionic emulsifier (fatty alcohol polyoxyethylene ether), and 10g of modified silica (prepared in Example 2); (2) Mix polydimethylsiloxane, polyether-modified polysiloxane and nonionic emulsifier, stir at 23°C and 500 rpm for 30 min, add modified silica in batches (divided into 3 batches, with an interval of 5 min between each batch), heat to 50°C, stir at 2000 rpm for 30 min, add polyurea-modified polysiloxane and stir at 500 rpm for 30 min, defoam at a gauge pressure of -0.09 MPa for 20 min, cool to room temperature, and let stand for 4 h to mature, to obtain a highly stable solvent-free defoamer.

[0030] Comparative Example 1 The raw material composition and preparation method of the highly stable solvent-free defoamer are basically the same as those in Example 4, except that the polyurea-modified polysiloxane added to the component is replaced with an equal weight of polyurea-modified polysiloxane prepared by the following method: The preparation method of polyurea-modified polysiloxane is basically the same as that in Example 1, except that isophorone diisocyanate is replaced with 14.1g of 2,4-toluene diisocyanate.

[0031] Comparative Example 2 The raw material composition and preparation method of the highly stable solvent-free defoamer are basically the same as those in Example 4, except that the polyurea-modified polysiloxane added to the component is replaced with an equal weight of polyurea-modified polysiloxane prepared by the following method: The preparation method of polyurea-modified polysiloxane is basically the same as that in Example 1, except that the amount of isophorone diisocyanate added is replaced with 20g and the amount of nonylphenol polyoxyethylene ether added is replaced with 34g.

[0032] Comparative Example 3 The raw material composition and preparation method of the highly stable solvent-free defoamer are basically the same as those in Example 4, except that the polyurea-modified polysiloxane added to the component is replaced with an equal weight of polyurea-modified polysiloxane prepared by the following method: The preparation method of polyurea-modified polysiloxane is basically the same as that in Example 1, except that the amount of isophorone diisocyanate added is replaced with 15g and the amount of nonylphenol polyoxyethylene ether added is replaced with 4.2g.

[0033] Comparative Example 4 The raw material composition and preparation method of the highly stable solvent-free defoamer are basically the same as those in Example 4, except that the polyurea-modified polysiloxane added to the component is replaced with an equal weight of polyurea-modified polysiloxane prepared by the following method: The preparation method of polyurea-modified polysiloxane is basically the same as that in Example 1, except that nonylphenol polyoxyethylene ether (NP-10) is replaced with 13.5g of nonylphenol polyoxyethylene ether (NP-4).

[0034] Comparative Example 5 The raw material composition and preparation method of the highly stable solvent-free defoamer are basically the same as those in Example 4, except that the modified silica added to the components is replaced with an equal weight of modified silica prepared by the following method: The preparation method of modified silica is basically the same as that in Example 2, except that the amount of single-terminated trimethoxysilyl-terminated polydimethylsiloxane is replaced with 2.5g and the amount of (methoxy-terminated polyethylene glycol propyl)trimethoxysilane is replaced with 1.5g.

[0035] Comparative Example 6 The raw material composition and preparation method of the highly stable solvent-free defoamer are basically the same as those in Example 4, except that the modified silica added to the components is replaced with an equal weight of modified silica prepared by the following method: The preparation method of modified silica is basically the same as that in Example 2, except that the amount of single-terminated trimethoxysilyl-terminated polydimethylsiloxane is replaced with 3.2g and the amount of (methoxy-terminated polyethylene glycol propyl)trimethoxysilane is replaced with 0.8g.

[0036] Comparative Example 7 The raw material composition and preparation method of the highly stable solvent-free defoamer are basically the same as those in Example 4, except that the modified silica added to the components is replaced with an equal weight of modified silica prepared by the following method: The preparation method of modified silica is basically the same as that in Example 2, except that the amount of (methoxy-terminated polyethylene glycol propyl)trimethoxysilane added is replaced with an equal weight of (methoxy-terminated polyethylene glycol propyl)trimethoxysilane (number average molecular weight 2000).

[0037] Comparative Example 8 The raw material composition and preparation method of the highly stable solvent-free defoamer are basically the same as those in Example 4. The difference is that the modified silica added to the component is replaced with an equal weight of silica.

[0038] Comparative Example 9 The raw material composition and preparation method of the highly stable solvent-free defoamer are basically the same as those in Example 4, except that the modified silica added to the components is replaced with an equal weight of modified silica prepared by the following method: Add 50 ml of 90 wt% ethanol aqueous solution and 3 g of single-terminated trimethoxysilyl-terminated polydimethylsiloxane to a reaction flask, stir and mix well, adjust the pH to 4 with 5 wt% acetic acid aqueous solution, stir for 30 min to obtain silane coupling agent solution; add 40 g of silica to 500 ml of 90 wt% ethanol aqueous solution, sonicate at 30 kHz and 200 W for 30 min, then add all the prepared silane coupling agent solution dropwise to the reaction system, complete the addition in 30 min, during which the pH is maintained at 4 with 5 wt% acetic acid aqueous solution, stir and heat to 65 ℃, react for 5 h, cool to room temperature, filter, wash with anhydrous ethanol (3 × 100 ml), and vacuum dry at 90 ℃ and gauge pressure -0.09 MPa for 5 h to obtain modified silica.

[0039] Unless otherwise specified, the polydimethylsiloxane used in the embodiments and comparative examples of this application is model QL-201-350, produced by Jiangsu Quanli Chemical Co., Ltd.; the silica is model GH-1A type silica; the polyether-modified polysiloxane is model DY-ET133, produced by Shandong Dayi Chemical Co., Ltd.; the number average molecular weight of the single-terminated trimethoxysilyl-terminated polydimethylsiloxane is 1000; the CAS number of (methoxy-terminated polyethylene glycol propyl)trimethoxysilane is 65994-07-2, and the number average molecular weight is 1000; the fatty alcohol polyoxyethylene ether is model AEO-9. It should be noted that the diaminopropyl-terminated polysiloxane and nonylphenol polyoxyethylene ether are pre-dehydrated under vacuum conditions before use to reduce the moisture content to below 0.05 wt%.

[0040] The defoamers prepared in the examples and comparative examples were tested for defoaming, foam suppression, centrifugal stability and high temperature stability. The test results are shown in Table 1.

[0041] Defoaming performance test: The high-stability solvent-free defoamer was tested according to the vertical oscillation method specified in 6.6 of GB / T 26527-2024. 100 mL of standard foaming liquid was added to a 250 mL polyester bottle, along with 0.015 g of defoamer. The bottle was kept at a constant temperature of 25°C in a water bath. The polyester bottle was placed on a vertical shaker, with an oscillation speed of 400 r / min, an amplitude of 30 mm, and an oscillation time of 10 s. Timing was started immediately after oscillation stopped, and the time required for the foam to completely dissipate was recorded. This operation was repeated for 6 consecutive rounds, and the average foam dissipation time of the last 3 rounds was taken as the defoaming time.

[0042] Foam suppression performance test: The high-stability solvent-free defoamer was tested according to the air blasting method specified in 6.8 of GB / T 26527-2024. 100 mL of standard foaming liquid was measured, and 0.100 g of defoamer was weighed and added to the foaming liquid. The mixture was stirred evenly and then poured into a clean measuring cylinder of a bubble apparatus. The temperature was kept constant at 25°C, and the flow pump was turned on with an air flow rate of 95 mL / min. The total volume of foam and foaming liquid after 30 minutes of air blasting was recorded as the foam suppression volume.

[0043] Centrifugation stability test: Measure 10 mL of defoamer into two 10 mL graduated centrifuge tubes, place them symmetrically into a centrifuge, and centrifuge at 3000 r / min for 15 min. After centrifugation, remove the tubes and observe whether the defoamer exhibits stratification or precipitation.

[0044] High-temperature stability test: Weigh 50g of the highly stable solvent-free defoamer prepared in the examples and comparative examples and place them in a 100mL transparent sealed glass bottle. Place the bottle in a 70℃ constant temperature oven and let it stand for 7 days. Take out the sample, cool it to 23℃ and let it stand for 24 hours. Observe whether the sample has layering or precipitation.

[0045] Table 1 Performance Test Data

[0046] As can be seen from the data in Table 1, the highly stable solvent-free defoamer prepared by the present invention has a short defoaming time, good foam suppression performance, and good centrifugal stability and high temperature stability.

[0047] Comparative Example 1, which replaced isophorone diisocyanate with 2,4-toluene diisocyanate, resulted in aromatic polyurea with higher rigidity of the hard segments. This increased tendency for urea group hydrogen bonding and hard segment aggregation reduced its compatibility with the continuous phase of polydimethylsiloxane, leading to decreased centrifugal stability and affecting defoaming and foam suppression performance. Comparative Example 2, by increasing the amounts of isophorone diisocyanate and nonylphenol polyoxyethylene ether, decreased the average chain length, molecular weight, and viscosity of the polyurea-modified polysiloxane. The suspending effect of molecular chain entanglement and hydrogen bond network on silica was weakened. Simultaneously, the increased proportion of polyether end groups and enhanced hydrophilicity led to decreased centrifugal stability and foam suppression performance. Comparative Example 3, by decreasing the amount of isophorone diisocyanate, increased the average chain length and molecular weight of the polyurea-modified polysiloxane, enhanced molecular chain entanglement and hydrogen bond network, increased system viscosity, and reduced the diffusion and spreading rate of the active component to the gas-liquid interface, resulting in decreased defoaming performance. Comparative Example 4 uses NP-4 with short polyether chains for end-capping, which enhances the hydrophobicity of polyurea-modified polysiloxane. However, the compatibility regulation and steric stabilization between it and polyether-modified polysiloxane and nonionic emulsifier are weakened, making it more prone to aggregation, precipitation or stratification during high-temperature storage, resulting in decreased high-temperature stability.

[0048] Comparative Example 5 increased the proportion of polyether chains and decreased the proportion of polysiloxane chains on the surface of silica, reducing the hydrophobicity of the particle surface. In the aqueous foaming system, the hydration layer formed by the polyether chains shields some hydrophobic active sites, weakening the ability of silica to enter the foam film and induce dewetting and film rupture, resulting in decreased defoaming and foam suppression performance. Comparative Example 6 increased the proportion of polysiloxane chains and decreased the proportion of polyether chains on the surface of silica, shifting the hydrophilic-hydrophobic balance of the particle surface towards hydrophobicity. The interfacial interaction between the particles and the polyether-modified polysiloxane and nonionic emulsifier weakened, increasing the tendency to agglomerate and leading to decreased centrifugal stability. Comparative Example 7 used excessively long polyether chains, reducing the number of anchoring groups, decreasing the grafting density on the silica surface and increasing the coverage of long-chain polyethers on the surface. Furthermore, the long polyether chains shielded the hydrophobic surface, resulting in decreased foam suppression performance and high-temperature stability. Comparative Example 8 used unmodified silica, which has high particle polarity and surface energy, resulting in poor wettability and compatibility with the polydimethylsiloxane continuous phase, leading to decreased centrifugal and high-temperature stability. Simultaneously, the strong hydrophilicity of silica reduces the synergistic defoaming effect with the polysiloxane oil phase, thus decreasing both defoaming and foam-suppressing performance. Comparative Example 9 modified silica using only the polydimethylsiloxane structure, lacking the steric hindrance and interfacial compatibility regulation provided by the polyether segments. This resulted in decreased compatibility between the particles and the polyether-modified polysiloxane and nonionic emulsifier, leading to decreased sustained foam suppression performance, centrifugal stability, and high-temperature storage stability.

[0049] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. However, any modifications, alterations, and variations made by those skilled in the art without departing from the scope of the present invention based on the disclosed technical content are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, and variations made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the present invention.

Claims

1. A highly stable solvent-free defoamer, characterized in that, The ingredients include the following parts by weight: 50-60 parts of polydimethylsiloxane, 8-12 parts of polyether-modified polysiloxane, 3-5 parts of polyurea-modified polysiloxane, 2-5 parts of nonionic emulsifier, and 8-10 parts of modified silica. The polyurea-modified polysiloxane is prepared by the following method: Isophorone diisocyanate and hexamethylene diisocyanate were prepolymerized with diaminopropyl-terminated polysiloxane, and then reacted with nonylphenol polyoxyethylene ether under the action of a catalyst to obtain polyurea-modified polysiloxane. The mass ratio of isophorone diisocyanate, hexamethylene diisocyanate, diaminopropyl-terminated polysiloxane, and nonylphenol polyoxyethylene ether is 0.18:0.06:1:0.

22. The modified silica is prepared by the following method: A silane coupling agent was dispersed in an aqueous ethanol solution, the pH was adjusted, and then silica was added to react and obtain modified silica.

2. The highly stable solvent-free defoamer according to claim 1, characterized in that, The catalyst is dibutyltin dilaurate.

3. The highly stable solvent-free defoamer according to claim 1, characterized in that, The prepolymerization reaction was carried out at a temperature of 30°C for 4 hours; the reaction with nonylphenol polyoxyethylene ether was carried out at a temperature of 70°C for 3 hours.

4. The highly stable solvent-free defoamer according to claim 1, characterized in that, The silane coupling agent is a mixture of single-terminated trimethoxysilyl-terminated polydimethylsiloxane and (methoxy-terminated polyethylene glycol propyl)trimethoxysilane in a mass ratio of 3:

1.

5. The highly stable solvent-free defoamer according to claim 1, characterized in that, The mass ratio of the silane coupling agent to the silica is 1:

10.

6. The highly stable solvent-free defoamer according to claim 1, characterized in that, The reaction was carried out at a temperature of 65°C for 5 hours.

7. The highly stable solvent-free defoamer according to claim 1, characterized in that, The nonionic emulsifier is fatty alcohol polyoxyethylene ether.

8. A method for preparing a highly stable solvent-free defoamer as described in any one of claims 1-7, characterized in that, Includes the following steps: (1) Weigh the raw materials according to the following parts by weight: 50-60 parts of polydimethylsiloxane, 8-12 parts of polyether-modified polysiloxane, 3-5 parts of polyurea-modified polysiloxane, 2-5 parts of nonionic emulsifier, and 8-10 parts of modified silica. (2) Mix polydimethylsiloxane, polyether-modified polysiloxane and nonionic emulsifier, add modified silica for high-speed dispersion, add polyurea-modified polysiloxane and mix well, defoam and let stand to mature, and obtain a highly stable solvent-free defoamer.

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