Organic silicon emulsion defoaming agent and preparation method thereof

Abstract

The invention relates to the technical field of organic silicon defoaming agents, and discloses an organic silicon emulsion defoaming agent and a preparation method thereof.The organic silicon emulsion defoaming agent is prepared from, by weight, 1%-5% of white carbon black, 1%-5% of MQ silicon resin, 10%-20% of simethicone, 5%-20% of hydroxyl silicone oil, 5%-20% of hydrophobic polyether modified organic silicon polymer, 1%-10% of emulsifier and the balance water. 0.1%-1% of a thickening agent, 1%-3% of a stabilizing agent and the balance of deionized water. The organic silicon emulsion defoaming agent disclosed by the invention has good defoaming performance and short defoaming time, and the organic silicon emulsion defoaming agent still has relatively short defoaming time and good high temperature resistance after being subjected to heat treatment.

Description

Technical Field

[0001] The invention relates to the technical field of organosilicon defoamers, in particular to an organosilicon emulsion defoamer and a preparation method thereof. Background Art

[0002] Defoamers mainly include polyether defoamers, silicone defoamers, mineral oil defoamers, natural oil defoamers, etc. Among them, polyether modified silicone defoamers have the advantages of high surface activity and good water solubility, and are widely used in coatings, papermaking, textile printing and dyeing, petrochemical and other industries. Traditional polyether modified silicone defoamers are mainly prepared by hydrosilylation reaction with hydrogenated silicone oil, allyl polyoxyethylene ether and the like as raw materials, and have disadvantages such as poor defoaming performance and poor high temperature resistance.

[0003] In recent years, the development of new high-performance defoamers has been a research hotspot. The publication number CN114392587B discloses a method for preparing a fluorine-modified silicone polyether defoamer, which uses trifluoropropylmethylcyclotrisiloxane, heptamethyltrisiloxane, tert-butylpropylaminotrimethoxysilane, linear fatty alcohol polyoxyethylene polyoxypropylene ether, etc. as the ingredients to prepare a fluorine-modified silicone polyether defoamer, which has an excellent defoaming and defoaming effect. However, the silicone polyether defoamer of this patent does not have good high temperature resistance. The present invention aims to prepare a silicone emulsion defoamer with good defoaming performance and strong high temperature resistance. Summary of the invention

[0004] The technical problem solved by the invention is to provide an organosilicon emulsion defoamer with good defoaming performance and strong high temperature resistance and a preparation method thereof.

[0005] The technical solution of the present invention is: an organosilicon emulsion defoamer and a preparation method, characterized in that the organosilicon emulsion defoamer comprises the following components: in weight percentage, 1%-5% of white carbon black, 1%-5% of MQ silicone resin, 10%-20% of dimethyl silicone oil, 5%-20% of hydroxy silicone oil, 5%-20% of hydrophobic polyether-modified organosilicon polymer, 1%-10% of emulsifier, 0.1%-1% of thickener, 1%-3% of stabilizer, and the balance is deionized water.

[0006] The preparation method of the sparse polyether-modified silicone polymer is as follows: Step (1), adding 1,4-dioxane, 3-hydroxy-[1,1'-biphenyl]-4,4'-diformaldehyde, 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane and glacial acetic acid into a flask, controlling the mass ratio of 3-hydroxy-[1,1'-biphenyl]-4,4'-diformaldehyde, 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane and glacial acetic acid to be 1:(1.11-1.16):(0.26-0.35); heating to 50-65° C., stirring for reaction for 12-18 hours, adding sodium hydroxide aqueous solution to neutralize the reaction solution to pH 7, distilling under reduced pressure, washing with water and ethanol, and drying to obtain an organosilicon polymer.

[0007] Step (2), add the organosilicon polymer and potassium hydroxide to the reaction kettle, evacuate and introduce nitrogen to replace the air, heat to 125-140°C, then introduce ethylene oxide, control the mass ratio of the organosilicon polymer, potassium hydroxide, and ethylene oxide to be 1: (0.0022-0.0028): (1.8-2.6); stir and react for 3-5 hours, cool and add dilute hydrochloric acid to neutralize to pH 7, decolorize with activated carbon, and dry to obtain a polyether-modified organosilicon polymer. The reaction route is: Preferably, the preparation method of 3-hydroxy-[1,1'-biphenyl]-4,4'-dicarbaldehyde is as follows: 4-formylphenylboronic acid, 4-bromo-2-hydroxybenzaldehyde, tetrakis(triphenylphosphine)palladium, and 1,4-dioxane are added to a flask, stirred, and then an aqueous solution of potassium phosphate is added, and the mass ratio of 4-formylphenylboronic acid, 4-bromo-2-hydroxybenzaldehyde, tetrakis(triphenylphosphine)palladium, and potassium phosphate is controlled to be 1:(1.3-1.5):(0.05-0.06):(2.4-2.8); nitrogen is introduced, heated to 80-90°C, stirred for reaction for 24-36h, distilled under reduced pressure, added water, filtered, and the product was recrystallized with ethanol to obtain 3-hydroxy-[1,1'-biphenyl]-4,4'-dicarbaldehyde. The reaction formula is as follows: Preferably, the emulsifier is any one or a combination of sorbitan oleate, polysorbate, fatty alcohol polyoxyethylene ether, and glycerol fatty acid ester.

[0008] Preferably, the thickener is any one or a combination of hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, xanthan gum, and polyacrylate.

[0009] Preferably, the stabilizer is polyoxyethylene stearate.

[0010] Preferably, the white carbon black has a particle size of 2-6 μm and a specific surface area of ​​140-160 m 2 / g.

[0011] Preferably, the ratio of M mer units to Q mer units in the MQ silicone resin is 0.6-1.5, and the molecular weight is 4000-12000.

[0012] The kinematic viscosity of the dimethyl silicone oil at 25°C is 50-50000mm 2 / s.

[0013] The kinematic viscosity of the hydroxy silicone oil at 25°C is 10-50 mm 2 / s.

[0014] Preferably, the preparation method of the organosilicon emulsion defoamer is: Step S1, adding white carbon black, MQ silicone resin and dimethyl silicone oil into a kneader, kneading at 175-185° C. for 4-6 hours, discharging after cooling, and obtaining a silicone paste.

[0015] Step S2, add the thickener and deionized water into the emulsifying kettle, heat to 80-85°C, add the stabilizer, hydroxy silicone oil, and emulsifier after stirring, stir evenly, then add the silicone paste, stir evenly, add the hydrophobic polyether-modified silicone polymer, stir evenly, cool to 30-35°C, turn on the homogenizer in the emulsifying kettle, homogenize to the emulsion defoamer particle size of 2-5um, filter, discharge, and obtain the silicone emulsion defoamer.

[0016] The technical effect of the present invention is as follows: the present invention utilizes 4-formylphenylboronic acid and 4-bromo-2-hydroxybenzaldehyde for coupling reaction, and then undergoes polymerization reaction with 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane to obtain an organosilicon polymer, and finally the phenolic hydroxyl group of the main chain initiates polymerization reaction of ethylene oxide to obtain a novel hydrophobic polyether-modified organosilicon polymer.

[0017] The hydrophobic polyether-modified silicone polymer of the present invention uses silicone polymer as the main chain, and introduces a large number of hydrophilic polyether segments into the side chain, so that the modified silicone polymer presents a unique hydrophobic structure, low surface tension, and good surface activity. In addition, the molecular main chain of the hydrophobic polyether-modified silicone polymer contains a high-temperature-resistant biphenyl structure. After high-temperature heat treatment, the hydrophobic polyether-modified silicone polymer is not easy to be thermally decomposed, maintains good structural stability, still has low surface tension, and has good surface activity.

[0018] The present invention uses a hydrophobic polyether-modified organic silicon polymer as an active organic silicon defoamer component, and white carbon black, MQ silicone resin dimethyl silicone oil, hydroxy silicone oil, an emulsifier, a thickener, a stabilizer polyoxyethylene stearate, etc. as auxiliary agents to compound the obtained organic silicon emulsion defoamer, which has good defoaming performance and a short defoaming time. Moreover, after the organic silicon emulsion defoamer is subjected to heat treatment, it still has a low defoaming time and has good high temperature resistance. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] Unless otherwise specified, the raw materials and reagents used in the present invention are commercially available or can be prepared by known methods.

[0021] Example 1 (1) Add 4 g of 4-formylphenylboronic acid, 5.2 g of 4-bromo-2-hydroxybenzaldehyde, 0.24 g of tetrakis(triphenylphosphine)palladium, and 70 mL of 1,4-dioxane into a flask, stir, then add 20 mL of an aqueous solution of 9.6 g of potassium phosphate, introduce nitrogen, heat to 90°C, stir and react for 24 h, evaporate under reduced pressure, add water, filter, and recrystallize the product with ethanol to obtain 3-hydroxy-[1,1'-biphenyl]-4,4'-dicarbaldehyde.

[0022] (2) Add 200 mL of 1,4-dioxane, 10 g of 3-hydroxy-[1,1'-biphenyl]-4,4'-dicarbaldehyde, 11.6 g of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, and 3.5 g of glacial acetic acid into a flask, heat to 65°C, stir and react for 12 h, add sodium hydroxide aqueous solution to neutralize the reaction solution to pH 7, distill under reduced pressure, wash with water and ethanol, and dry to obtain an organosilicon polymer.

[0023] (3) Add 50 g of silicone polymer and 0.13 g of potassium hydroxide into a reaction kettle, evacuate and introduce nitrogen to replace the air, heat to 125°C, then introduce 110 g of ethylene oxide, stir and react for 5 h, cool, add dilute hydrochloric acid to neutralize to pH 7, decolorize with activated carbon, and dry to obtain a hydrophobic polyether-modified silicone polymer.

[0024] (4) Add 15 g of white carbon black, 28 g of MQ silicone resin, and 140 g of dimethyl silicone oil into a kneader, knead at 175° C. for 6 h, and discharge after cooling to obtain a silicone paste.

[0025] (5) Step S2, add 6g thickener hydroxyethyl cellulose and 480g deionized water into an emulsifier, heat to 80°C, stir, add 12g stabilizer polyoxyethylene stearate, 200g hydroxy silicone oil, 69g emulsifier sorbitan oleate, stir evenly, then add silicone paste, stir evenly, add 50g hydrophobic polyether modified silicone polymer, stir evenly, cool to 35°C, turn on the homogenizer in the emulsifier, homogenize until the emulsion defoamer particle size is 2um, filter, discharge, and obtain a silicone emulsion defoamer.

[0026] Example 2 (1) Add 4 g of 4-formylphenylboronic acid, 6 g of 4-bromo-2-hydroxybenzaldehyde, 0.2 g of tetrakis(triphenylphosphine)palladium, and 80 mL of 1,4-dioxane into a flask, stir, then add 25 mL of an aqueous solution of 11.2 g of potassium phosphate, introduce nitrogen, heat to 80°C, stir and react for 36 h, evaporate under reduced pressure, add water, filter and recrystallize the product with ethanol to obtain 3-hydroxy-[1,1'-biphenyl]-4,4'-dicarboxaldehyde.

[0027] (2) Add 150 mL of 1,4-dioxane, 10 g of 3-hydroxy-[1,1'-biphenyl]-4,4'-dicarbaldehyde, 11.1 g of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, and 2.6 g of glacial acetic acid into a flask, heat to 50°C, stir and react for 18 h, add sodium hydroxide aqueous solution to neutralize the reaction solution to pH 7, distill under reduced pressure, wash with water and ethanol, and dry to obtain an organosilicon polymer.

[0028] (3) Add 50 g of silicone polymer and 0.14 g of potassium hydroxide into a reaction kettle, evacuate and introduce nitrogen to replace the air, heat to 125°C, then introduce 90 g of ethylene oxide, stir and react for 4 h, cool and add dilute hydrochloric acid to neutralize to pH 7, decolorize with activated carbon, and dry to obtain a hydrophobic polyether-modified silicone polymer.

[0029] (4) Add 50 g of white carbon black, 10 g of MQ silicone resin, and 160 g of dimethyl silicone oil into a kneader, knead at 180° C. for 4 h, and discharge after cooling to obtain a silicone paste.

[0030] (5) Step S2, add 10g thickener polyacrylate and 490g deionized water into an emulsifier, heat to 80°C, stir, add 30g stabilizer polyoxyethylene stearate, 130g hydroxy silicone oil, 40g emulsifier polysorbate, stir evenly, then add silicone paste, stir evenly, add 80g hydrophobic polyether modified silicone polymer, stir evenly, cool to 30°C, turn on the homogenizer in the emulsifier, homogenize until the emulsion defoamer particle size is 5um, filter, discharge, and obtain a silicone emulsion defoamer.

[0031] Example 3 (1) 50 g of an organosilicon polymer (prepared in the same manner as in Example 1) and 0.11 g of potassium hydroxide were added to a reaction kettle, the reaction mixture was evacuated and nitrogen was introduced to replace the air. The reaction mixture was heated to 140° C., and then 90 g of ethylene oxide was introduced. The reaction mixture was stirred for 3 h. After cooling, dilute hydrochloric acid was added to neutralize the mixture to a pH of 7. The reaction mixture was decolorized with activated carbon and dried to obtain a hydrophobic polyether-modified organosilicon polymer.

[0032] (2) Add 10 g of white carbon black, 50 g of MQ silicone resin, and 100 g of dimethyl silicone oil into a kneader, knead at 175° C. for 4 h, and discharge after cooling to obtain a silicone paste.

[0033] (3) Step S2, add 1g of thickener xanthan gum and 570g of deionized water into an emulsifier, heat to 80°C, stir, add 10g of stabilizer polyoxyethylene stearate, 129g of hydroxy silicone oil, and 10g of emulsifier fatty alcohol polyoxyethylene ether AEO-9, stir evenly, then add silicone paste, stir evenly, add 120g of hydrophobic polyether modified silicone polymer, stir evenly, cool to 35°C, turn on the homogenizer in the emulsifier, homogenize until the emulsion defoamer particle size is 5um, filter, and discharge to obtain a silicone emulsion defoamer.

[0034] Example 4 (1) 50 g of an organosilicon polymer (prepared in the same manner as in Example 1) and 0.12 g of potassium hydroxide were added to a reaction kettle, evacuated and nitrogen was introduced to replace the air, heated to 130° C., and then 100 g of ethylene oxide was introduced and stirred to react for 5 h. After cooling, dilute hydrochloric acid was added to neutralize to a pH of 7, activated carbon was used for decolorization, and the reaction was dried to obtain a hydrophobic polyether-modified organosilicon polymer.

[0035] (2) Add 40 g of white carbon black, 25 g of MQ silicone resin, and 200 g of dimethyl silicone oil into a kneader, knead at 185° C. for 4 h, and discharge after cooling to obtain a silicone paste.

[0036] (3) Step S2, add 5g thickener hydroxymethyl cellulose and 450g deionized water into an emulsifier, heat to 80°C, stir, add 18g stabilizer polyoxyethylene stearate, 80g hydroxy silicone oil, and 22g emulsifier glycerol fatty acid ester, stir evenly, then add silicone paste, stir evenly, add 160g hydrophobic polyether modified silicone polymer, stir evenly, cool to 30°C, turn on the homogenizer in the emulsifier, homogenize until the emulsion defoamer particle size is 2um, filter, and discharge to obtain a silicone emulsion defoamer.

[0037] Example 5 (1) Add 50 g of white carbon black, 50 g of MQ silicone resin, and 150 g of dimethyl silicone oil into a kneader, knead at 180° C. for 4 h, and discharge after cooling to obtain a silicone paste.

[0038] (2) Add 3 g of thickener hydroxypropyl cellulose and 390 g of deionized water into an emulsifier, heat to 85°C, stir, add 10 g of stabilizer polyoxyethylene stearate, 100 g of hydroxy silicone oil, and 47 g of emulsifier fatty alcohol polyoxyethylene ether AEO-9, stir evenly, then add silicone paste, stir evenly, add 200 g of hydrophobic polyether modified silicone polymer (same as the preparation method in Example 1), stir evenly, cool to 30°C, turn on the homogenizer in the emulsifier, homogenize until the emulsion defoamer particle size is 2 um, filter, and discharge to obtain a silicone emulsion defoamer.

[0039] Comparative Example 1 (1) Add 6 g of thickener hydroxyethyl cellulose and 480 g of deionized water into an emulsifier, heat to 80°C, stir, add 12 g of stabilizer polyoxyethylene stearate, 200 g of hydroxy silicone oil, and 69 g of emulsifier sorbitan oleate, stir evenly, then add silicone paste (prepared according to the method of Example 1), stir evenly, cool to 35°C, turn on the homogenizer in the emulsifier, homogenize until the emulsion defoamer particle size is 2 μm, filter, and discharge to obtain a silicone emulsion defoamer.

[0040] Comparative Example 2 (1) Step S2: Add 6 g of thickener hydroxyethyl cellulose and 480 g of deionized water into an emulsifier, heat to 80° C., stir, add 12 g of stabilizer polyoxyethylene stearate, 200 g of hydroxy silicone oil, and 69 g of emulsifier sorbitan oleate, stir evenly, then add silicone paste (prepared according to the method of Example 1), stir evenly, add 50 g of organosilicon polymer (prepared according to the method of Example 1), stir evenly, cool to 35° C., turn on the homogenizer in the emulsifier, homogenize until the particle size of the emulsion defoamer is 2 μm, filter, and discharge to obtain an organosilicon emulsion defoamer.

[0041] Comparative Example 3 (1) Add hydrogenated silicone resin (active hydrogen molar content of 0.8%, M mer unit / Q mer unit ratio of 0.6, molecular weight of 4000) and allyl polyoxyethylene ether (average molar mass of 1600 / mol, unsaturation of 1.5 mmol / g) into a reactor, dropwise add isopropanol solution of chloroplatinic acid as catalyst, n(Si-H):n(C=C) is 1:1.20, the amount of catalyst is 0.003% of the total mass of hydrogenated silicone resin and allyl polyoxyethylene ether, heat to 80°C, react for 5 hours, cool and discharge to obtain polyether modified silicone.

[0042] (2) Step S2, add 6g of thickener hydroxyethyl cellulose and 480g of deionized water into an emulsifier, heat to 80°C, stir, add 12g of stabilizer polyoxyethylene stearate, 200g of hydroxy silicone oil, and 69g of emulsifier sorbitan oleate, stir evenly, then add silicone paste, stir evenly, add 50g of polyether modified silicone, stir evenly, cool to 35°C, turn on the homogenizer in the emulsifier, homogenize until the emulsion defoamer particle size is 2um, filter, and discharge to obtain a silicone emulsion defoamer.

[0043] The hydrophobic polyether-modified organosilicon polymer of each example, the organosilicon polymer of comparative example 2, and the polyether-modified organosilicon of comparative example 3 were added to water to prepare solutions with different mass fractions, and the surface tension of the solutions was tested using an automatic interfacial tension meter at a test temperature of 25°C.

[0044] Table 1 The hydrophobic polyether-modified silicone polymer of each embodiment, the silicone polymer of comparative example 2, and the polyether-modified silicone of comparative example 3 were added to water to prepare a solution with a mass fraction of 1%, added to a flask equipped with a condenser reflux tube, and kept at 25-100° C. for 6 h, cooled, and the surface tension of the solution was tested using an automatic interfacial tension meter.

[0045] Table 2 After testing, it was found that the organosilicon polymer of Comparative Example 2 did not contain hydrophilic polyether molecular chains, and the surface tension of solutions with different mass fractions was very large, and the surface activity was very poor.

[0046] The hydrophobic polyether-modified silicone polymers prepared in Examples 1-5 use silicone polymers as the main chain and introduce a large number of hydrophilic polyether segments into the side chains, so that the modified silicone polymers present a unique hydrophobic structure with good surface activity. Solutions of different mass fractions have uniformly low surface tension, and the molecular main chain of the hydrophobic polyether-modified silicone polymer contains a high-temperature-resistant biphenyl structure. After high-temperature heat treatment, the hydrophobic polyether-modified silicone polymer is not easily thermally decomposed, maintains good structural stability, still has low surface tension, and has good surface activity.

[0047] In Comparative Example 3, conventional hydrogenated silicone resin and allyl polyoxyethylene ether are used for a hydrosilylation reaction. Since there are fewer Si-H molecules in the main chain of the hydrogenated silicone resin molecule, there are fewer grafted hydrophilic polyoxyethylene ether molecular chains. The surface tension of the obtained polyether-modified silicone is higher than that of the hydrophobic polyether-modified silicone polymer, and the surface activity is poor. Moreover, after high-temperature heat treatment, the surface tension increases significantly, the surface activity deteriorates, and the high-temperature resistance is poor.

[0048] Add the silicone emulsion defoamer to a flask equipped with a condenser reflux tube, keep it at 25-100℃ for 6h, and cool it. Use the gas blowing method to test the defoaming and defoaming performance of the silicone emulsion defoamer. Take 200mL of the foaming liquid and add it to a 1000mL measuring cylinder. Stop bubbling when the foam rises to 1000mL, add 2mL of the silicone emulsion defoamer, and record the time when all the foam disappears, that is, the defoaming time.

[0049] Table 3 After testing, compared with comparative examples 1-3, the organosilicon emulsion defoamer prepared in Examples 1-5 has good defoaming performance and short defoaming time, and the organosilicon emulsion defoamer still has a low defoaming time after heat treatment and has good high temperature resistance.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A silicone emulsion defoamer, characterized in that: The organosilicon emulsion defoamer comprises the following components: by weight percentage, 1%-5% of white carbon black, 1%-5% of MQ silicone resin, 10%-20% of dimethyl silicone oil, 5%-20% of hydroxy silicone oil, 5%-20% of hydrophobic polyether-modified organosilicon polymer, 1%-10% of emulsifier, 0.1%-1% of thickener, 1%-3% of stabilizer, and the balance is deionized water; The preparation method of the sparse polyether-modified silicone polymer is as follows: Step (1), adding 1,4-dioxane, 3-hydroxy-[1,1'-biphenyl]-4,4'-dicarbaldehyde, 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane and glacial acetic acid into a flask, heating to 50-65° C., stirring for reaction for 12-18 hours, adding sodium hydroxide aqueous solution for neutralization, distilling under reduced pressure, washing and drying to obtain an organosilicon polymer; Step (2), adding the organosilicon polymer and potassium hydroxide into a reaction kettle, evacuating the reactor and introducing nitrogen to replace the air, heating the reactor to 125-140° C., then introducing ethylene oxide, stirring and reacting for 3-5 hours, cooling the reactor, adding dilute hydrochloric acid for neutralization, decolorizing with activated carbon, and drying the reactor to obtain a hydrophobic polyether-modified organosilicon polymer.

2. The organosilicon emulsion defoamer according to claim 1, characterized in that: In the step (1), the mass ratio of 3-hydroxy-[1,1'-biphenyl]-4,4'-dicarbaldehyde, 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, and glacial acetic acid is 1:(1.11-1.16):(0.26-0.35).

3. The organosilicon emulsion defoamer according to claim 1, characterized in that: In the step (2), the mass ratio of the organosilicon polymer, potassium hydroxide and ethylene oxide is 1:(0.0022-0.0028):(1.8-2.6).

4. The organosilicon emulsion defoamer according to claim 1, characterized in that: The preparation method of 3-hydroxy-[1,1'-biphenyl]-4,4'-dicarbaldehyde is as follows: 4-formylphenylboronic acid, 4-bromo-2-hydroxybenzaldehyde, tetrakis(triphenylphosphine)palladium, and 1,4-dioxane are added into a flask, and an aqueous solution of potassium phosphate is added after stirring, nitrogen is introduced, the mixture is heated to 80-90° C., the mixture is stirred for reaction for 24-36 hours, the mixture is distilled under reduced pressure, water is added, and the product is filtered and recrystallized to obtain 3-hydroxy-[1,1'-biphenyl]-4,4'-dicarbaldehyde.

5. The organosilicon emulsion defoamer according to claim 4, characterized in that: The mass ratio of the 4-formylphenylboronic acid, 4-bromo-2-hydroxybenzaldehyde, tetrakis(triphenylphosphine)palladium and potassium phosphate is 1:(1.3-1.5):(0.05-0.06):(2.4-2.8).

6. The organosilicon emulsion defoamer according to claim 1, characterized in that: The emulsifier is any one or a combination of sorbitan oleate, polysorbate, fatty alcohol polyoxyethylene ether, and glycerol fatty acid ester.

7. The organosilicon emulsion defoamer according to claim 1, characterized in that: The thickener is any one or a combination of hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, xanthan gum, and polyacrylate.

8. The organosilicon emulsion defoamer according to claim 1, characterized in that: The stabilizer is polyoxyethylene stearate.

9. A method for preparing the organosilicon emulsion defoamer according to any one of claims 1 to 8, characterized in that: The preparation method is: Step S1, adding white carbon black, MQ silicone resin and dimethyl silicone oil into a kneader, kneading at 175-185° C. for 4-6 hours, discharging after cooling, and obtaining a silicone paste; Step S2, add the thickener and deionized water into the emulsifying kettle, heat to 80-85°C, add the stabilizer, hydroxy silicone oil, and emulsifier after stirring, stir evenly, then add the silicone paste, stir evenly, add the hydrophobic polyether-modified silicone polymer, stir evenly, cool to 30-35°C, turn on the homogenizer in the emulsifying kettle, homogenize to the emulsion defoamer particle size of 2-5um, filter, discharge, and obtain the silicone emulsion defoamer.

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