A preparation method of polyether modified silicone defoamer

Abstract

The present invention relates to the technical field of defoamers, and discloses a method for preparing a polyether-modified silicone defoamer. The present invention uses the hydroxyl contained in silicon dioxide and γ-glycidyloxypropyltrimethoxysilane to obtain epoxy-modified nano-silica through hydrolysis and condensation reaction. Cardanol, ethylene oxide, epoxy-modified nano-silica, etc. are used as raw materials, and modified polyether is obtained through ring-opening polymerization. Octamethylcyclotetrasiloxane, aminopropyltriethoxysilane, etc. are used as raw materials, and modified hydrogen-containing silicone oil is obtained under the catalytic reaction of concentrated sulfuric acid. Modified hydrogen-containing silicone oil and modified polyether are used as raw materials, and chloroplatinic acid is used as a catalyst to obtain polyether-modified silicone oil. Then, it is used as the main body, and a polyether-modified silicone defoamer is prepared by adding silicone paste, a thickener, etc. Thereto. The polyether-modified silicone defoamer prepared by the present invention has excellent defoaming effect and stability.

Description

Technical Field

[0001] The invention relates to the technical field of defoamers, and in particular to a method for preparing a polyether-modified organosilicon defoamer. Background Art

[0002] In the fields of coating processing, construction industry, textile printing and dyeing, etc., stirring operations are carried out during their processing and production, and the foam generated by stirring will lead to problems such as reduced production capacity and waste of raw materials. Therefore, it is necessary to eliminate the foam, and defoaming agents came into being.

[0003] Defoamers can be divided into polyether defoamers, silicone defoamers, and mineral oil defoamers. Mineral oil defoamers can be used under conditions where the liquid shear force is small and the foaming ability of the surfactant contained is relatively mild, but their ability to eliminate dense foam is relatively poor. Polyether defoamers can only play a defoaming role when the temperature of the foaming system exceeds the cloud point temperature. Silicone defoamers have attracted widespread attention due to their high defoaming efficiency, small dosage, and no physiological toxicity, but silicone defoamers have poor dispersibility and are difficult to emulsify. Based on this, the present invention provides a method for preparing a polyether-modified silicone defoamer.

[0004] Silicon dioxide is an inorganic compound with the characteristics of high temperature resistance and corrosion resistance, and is widely used in the fields of enamel, cement, glass, etc. For example, the patent application publication number CN103768834A discloses a defoamer composition, which uses branched polyether, modified nano-silica, and polyorganosiloxane as raw materials, and the prepared defoamer has excellent defoaming effect. Summary of the invention

[0005] 1. Technical issues to be resolved

[0006] In view of the deficiencies in the prior art, the present invention provides a method for preparing a polyether-modified organosilicon defoamer. The prepared polyether-modified organosilicon defoamer has excellent defoaming effect and stabilizing effect.

[0007] (II) Technical solution

[0008] A preparation method of a polyether-modified silicone defoamer, the preparation method comprising:

[0009] Step (1) adding silica to a flask containing 70-80% ethanol aqueous solution, ultrasonically dispersing for 10-20 minutes, adding 10-20% hydrochloric acid to adjust the pH to 3-4, then adding γ-glycidyloxypropyltrimethoxysilane, heating to 75-85° C., reacting for 8-12 hours, cooling to room temperature after the reaction is completed, filtering, washing with deionized water, and drying to obtain epoxy-modified nano-silica.

[0010] Step (2) under nitrogen conditions, add cardanol and sodium hydroxide to a high-pressure reactor, react at 20-35° C. for 20-50 min, after the reaction is completed, heat to 120-140° C., control the pressure to maintain at 0.2-0.4 MPa, add ethylene oxide and epoxy-modified nano-silica, react for 30-60 min, after the reaction is completed, cool to room temperature, neutralize with glacial acetic acid, and obtain a modified polyether.

[0011] Step (3) Under nitrogen conditions, octamethylcyclotetrasiloxane, aminopropyltriethoxysilane, tetramethyldihydrodisiloxane and concentrated sulfuric acid are added to a flask, stirred and dispersed, heated to 40-50° C., reacted for 4-8 hours, and after the reaction is completed, cooled to room temperature, sodium carbonate is added thereto to adjust the pH to 6-7, filtered, and dried to obtain modified hydrogenated silicone oil.

[0012] Step (4) Under nitrogen conditions, add the modified hydrogenated silicone oil and modified polyether into a flask filled with isopropanol solvent, stir and disperse, heat to 70-85° C., add chloroplatinic acid thereto, stir and react for 6-12 hours, and after the reaction is completed, perform reduced pressure distillation to obtain polyether modified silicone oil.

[0013] Step (5) adding silicone paste, polyether modified silicone oil, emulsifier and thickener into a reaction kettle filled with deionized water, heating to 70-80° C., stirring and mixing for 6-12 hours, and cooling to room temperature after stirring to obtain a polyether modified silicone defoamer.

[0014] Preferably, in step (1), the mass ratio of silicon dioxide to γ-glycidyloxypropyltrimethoxysilane is 100:15-30.

[0015] Preferably, in step (2), the mass ratio of cardanol, sodium hydroxide, ethylene oxide and epoxy-modified nano-silica is 100:0.04-0.2:50-100:50-100.

[0016] Preferably, in step (3), the mass ratio of octamethylcyclotetrasiloxane, aminopropyltriethoxysilane, tetramethyldihydrogendisiloxane, concentrated sulfuric acid and sodium carbonate is 100:30-50:5-10:1-3:3-10.

[0017] Preferably, in step (4), the mass ratio of modified hydrogen-containing silicone oil, modified polyether and chloroplatinic acid is 100:100-200:0.1-0.5.

[0018] Preferably, in step (5), the mass ratio of silicone paste, polyether-modified silicone oil, emulsifier, thickener and deionized water is 15-30:10-20:3-7:2-3:100.

[0019] Preferably, in step (5), the emulsifier is one or both of Span-60 and Span-80, and the thickener is sodium carboxymethyl cellulose.

[0020] (III) Beneficial technical effects

[0021] The present invention utilizes the hydroxyl contained in silicon dioxide and γ-glycidyloxypropyltrimethoxysilane to obtain epoxy-modified nano silicon dioxide through hydrolysis and condensation reaction. Using cardanol, ethylene oxide, epoxy-modified nano silicon dioxide and the like as raw materials, a modified polyether is obtained through ring-opening polymerization reaction. Using octamethylcyclotetrasiloxane, aminopropyltriethoxysilane and the like as raw materials, a modified hydrogen-containing silicone oil is obtained under the catalytic reaction of concentrated sulfuric acid. Using modified hydrogen-containing silicone oil and modified polyether as raw materials and chloroplatinic acid as a catalyst, a polyether-modified silicone oil is obtained. Then, using it as the main body, a silicone paste, a thickener and the like are added thereto to prepare a polyether-modified silicone defoamer.

[0022] The polyether-modified organosilicon defoamer prepared by the present invention contains nano-silicon dioxide. Due to the presence of nano-silicon dioxide, the defoamer attached to the surface of the particles is quickly spread in the foaming liquid, thereby improving the dispersion efficiency of the defoamer. In addition, since nano-silicon dioxide has a large specific surface area, high surface energy, and a three-dimensional network structure, it can form a huge force for adsorbing bubbles, which together with the defoamer constitutes a force for attacking the bubbles, causing the bubbles to burst, thereby improving the defoaming effect. However, since nano-silicon dioxide has a small particle size, a large specific surface area, and contains hydrophilic groups on the surface, it is very easy to agglomerate. The present invention organicizes it, improves the agglomeration degree of nano-silicon dioxide, improves its compatibility with organic matter, reduces its dissolution rate, and better exerts its defoaming effect.

[0023] The polyether-modified organosilicon defoamer prepared by the present invention uses aminopropyltriethoxysilane, which contains an amino group, which is a polar group. Due to the introduction of the amino group, the hydrophilic effect of the defoamer is increased, the dispersibility of the defoamer in water is improved, the stability of the defoamer in water is increased, and the defoaming effect of the defoamer is promoted. The polyether-modified organosilicon defoamer prepared by the present invention has excellent defoaming effect and stability. DETAILED DESCRIPTION

[0024] In order to make the technical problems, technical solutions and comparative effects to be solved by the present invention clearer, the present invention is further described in detail in conjunction with the embodiments. It should be understood that the specific implementation cases described herein are only used to explain the present invention and are not used to limit the present invention.

[0025] Preparation method of silicone paste: add 90g of dimethyl silicone oil, 60g of 107 silicone rubber, and 7g of white carbon black into a flask, heat to 130°C, stir and mix for 4h to obtain silicone paste.

[0026] Example 1

[0027] Step (1) adding 10 g of silica to a flask containing 70% ethanol aqueous solution, ultrasonically dispersing for 15 min, adding 20% ​​hydrochloric acid to adjust the pH to 3, then adding 2 g of γ-glycidyloxypropyltrimethoxysilane, heating to 80° C., reacting for 12 h, and after the reaction is completed, cooling to room temperature, filtering, washing with deionized water, and drying to obtain epoxy-modified nano-silica.

[0028] Step (2) Under nitrogen conditions, 25 g of cardanol and 0.05 g of sodium hydroxide are added to a high-pressure reactor, and the reaction is carried out at 35 ° C. for 40 min. After the reaction is completed, the temperature is raised to 130 ° C. and the pressure is controlled to be maintained at 0.4 MPa. 25 g of ethylene oxide and 12.5 g of epoxy-modified nano-silica are added thereto, and the reaction is carried out for 60 min. After the reaction is completed, it is cooled to room temperature and neutralized with glacial acetic acid to obtain a modified polyether.

[0029] Step (3) Under nitrogen conditions, 20 g of octamethylcyclotetrasiloxane, 6 g of aminopropyltriethoxysilane, 1.5 g of tetramethyldihydrogendisiloxane, and 0.5 g of concentrated sulfuric acid are added to a flask, stirred and dispersed, heated to 45° C., and reacted for 6 hours. After the reaction is completed, it is cooled to room temperature, 1 g of sodium carbonate is added thereto to adjust the pH to 7, filtered, and dried to obtain modified hydrogenated silicone oil.

[0030] Step (4) Under nitrogen conditions, 50 g of modified hydrogenated silicone oil and 60 g of modified polyether are added to a flask filled with isopropanol solvent, stirred and dispersed, heated to 75° C., 0.08 g of chloroplatinic acid is added thereto, stirred for reaction for 10 h, and after the reaction is completed, reduced pressure distillation is performed to obtain polyether modified silicone oil.

[0031] Step (5) Add 20 g of silicone paste, 8 g of polyether modified silicone oil, 2.4 g of emulsifier Span-80, and 1.6 g of sodium carboxymethyl cellulose thickener to a reactor containing 80 g of deionized water, heat to 75 ° C, stir and mix evenly for 12 hours, and after stirring, cool to room temperature to obtain a polyether modified silicone defoamer.

[0032] Example 2

[0033] Step (1) adding 10 g of silica to a flask containing 75% ethanol aqueous solution, ultrasonically dispersing for 14 min, adding 15% hydrochloric acid to adjust the pH to 4, then adding 2.5 g of γ-glycidyloxypropyltrimethoxysilane, heating to 80° C., reacting for 9 h, cooling to room temperature after the reaction, filtering, washing with deionized water, and drying to obtain epoxy-modified nano-silica.

[0034] Step (2) Under nitrogen conditions, 25 g of cardanol and 0.04 g of sodium hydroxide are added to a high-pressure reactor, and the reaction is carried out at 25 ° C. for 50 min. After the reaction is completed, the temperature is raised to 140 ° C. and the pressure is controlled to be maintained at 0.3 MPa. 22 g of ethylene oxide and 15 g of epoxy-modified nano-silica are added thereto, and the reaction is carried out for 40 min. After the reaction is completed, it is cooled to room temperature and neutralized with glacial acetic acid to obtain a modified polyether.

[0035] Step (3) Under nitrogen conditions, 20 g of octamethylcyclotetrasiloxane, 7 g of aminopropyltriethoxysilane, 1.5 g of tetramethyldihydrodisiloxane, and 0.5 g of concentrated sulfuric acid are added to a flask, stirred and dispersed, heated to 45° C., and reacted for 6 hours. After the reaction is completed, it is cooled to room temperature, 1.5 g of sodium carbonate is added thereto to adjust the pH to 7, filtered, and dried to obtain modified hydrogenated silicone oil.

[0036] Step (4) Under nitrogen conditions, 50 g of modified hydrogenated silicone oil and 60 g of modified polyether are added to a flask filled with isopropanol solvent, stirred and dispersed, heated to 80° C., 0.1 g of chloroplatinic acid is added thereto, stirred for reaction for 10 h, and after the reaction is completed, reduced pressure distillation is performed to obtain polyether modified silicone oil.

[0037] Step (5) Add 12 g of silicone paste, 10 g of polyether modified silicone oil, 5.6 g of emulsifier Span-60, and 2 g of sodium carboxymethyl cellulose thickener to a reactor containing 80 g of deionized water, heat to 80° C., stir and mix evenly for 10 hours, and after stirring, cool to room temperature to obtain a polyether modified silicone defoamer.

[0038] Example 3

[0039] Step (1) adding 10 g of silica to a flask containing 80% ethanol aqueous solution, ultrasonically dispersing for 20 min, adding 10% hydrochloric acid to adjust the pH to 4, then adding 3 g of γ-glycidyloxypropyltrimethoxysilane, heating to 85° C., reacting for 8 h, cooling to room temperature after the reaction is completed, filtering, washing with deionized water, and drying to obtain epoxy-modified nano-silica.

[0040] Step (2) Under nitrogen conditions, 25 g of cardanol and 0.01 g of sodium hydroxide are added to a high-pressure reactor, and the reaction is carried out at 20 ° C. for 20 min. After the reaction is completed, the temperature is raised to 120 ° C. and the pressure is controlled to be maintained at 0.2 MPa. 18 g of ethylene oxide and 18 g of epoxy-modified nano-silica are added thereto, and the reaction is carried out for 40 min. After the reaction is completed, it is cooled to room temperature and neutralized with glacial acetic acid to obtain a modified polyether.

[0041] Step (3) Under nitrogen conditions, add 20 g of octamethylcyclotetrasiloxane, 8 g of aminopropyltriethoxysilane, 2 g of tetramethyldihydrodisiloxane, and 0.2 g of concentrated sulfuric acid into a flask, stir and disperse, heat to 45 ° C, react for 6 hours, and after the reaction is completed, cool to room temperature, add 2 g of sodium carbonate to adjust the pH to 6, filter, and dry to obtain modified hydrogenated silicone oil.

[0042] Step (4) Under nitrogen conditions, 50 g of modified hydrogenated silicone oil and 90 g of modified polyether are added to a flask filled with isopropanol solvent, stirred and dispersed, heated to 75° C., 0.08 g of chloroplatinic acid is added thereto, stirred for reaction for 6 h, and after the reaction is completed, reduced pressure distillation is performed to obtain polyether modified silicone oil.

[0043] Step (5) Add 34 g of silicone paste, 12 g of polyether modified silicone oil, 4 g of emulsifier Span-80, and 2.4 g of sodium carboxymethyl cellulose thickener into a reactor containing 80 g of deionized water, heat to 70° C., stir and mix evenly for 6 hours, and after stirring, cool to room temperature to obtain a polyether modified silicone defoamer.

[0044] Example 4

[0045] Step (1) adding 10 g of silicon dioxide into a flask containing 75% ethanol aqueous solution, ultrasonically dispersing for 20 min, adding 15% hydrochloric acid to adjust the pH to 4, then adding 2 g of γ-glycidyloxypropyltrimethoxysilane, heating to 80° C., reacting for 12 h, cooling to room temperature after the reaction is completed, filtering, washing with deionized water, and drying to obtain epoxy-modified nano-silica.

[0046] Step (2) Under nitrogen conditions, 25 g of cardanol and 0.04 g of sodium hydroxide are added to a high-pressure reactor, and the reaction is carried out at 25 ° C. for 30 min. After the reaction is completed, the temperature is raised to 130 ° C. and the pressure is controlled to be maintained at 0.3 MPa. 25 g of ethylene oxide and 20 g of epoxy-modified nano-silica are added thereto, and the reaction is carried out for 40 min. After the reaction is completed, it is cooled to room temperature and neutralized with glacial acetic acid to obtain a modified polyether.

[0047] Step (3) Under nitrogen conditions, 20 g of octamethylcyclotetrasiloxane, 9 g of aminopropyltriethoxysilane, 1 g of tetramethyldihydrodisiloxane, and 0.6 g of concentrated sulfuric acid are added to a flask, stirred and dispersed, heated to 50° C., and reacted for 8 h. After the reaction is completed, cooled to room temperature, 1 g of sodium carbonate is added thereto to adjust the pH to 6, filtered, and dried to obtain modified hydrogenated silicone oil.

[0048] Step (4) Under nitrogen conditions, 50 g of modified hydrogenated silicone oil and 100 g of modified polyether are added to a flask filled with isopropanol solvent, stirred and dispersed, heated to 70° C., 0.05 g of chloroplatinic acid is added thereto, stirred for reaction for 12 h, and after the reaction is completed, reduced pressure distillation is performed to obtain polyether modified silicone oil.

[0049] Step (5) Add 34 g of silicone paste, 14 g of polyether modified silicone oil, 2.4 g of emulsifier Span-60, 2.4 g of emulsifier Span-80, and 2 g of sodium carboxymethyl cellulose thickener to a reactor containing 80 g of deionized water, heat to 75 ° C, stir and mix evenly for 12 hours, and after stirring, cool to room temperature to obtain a polyether modified silicone defoamer.

[0050] Example 5

[0051] Step (1) adding 10 g of silica to a flask containing 80% ethanol aqueous solution, ultrasonically dispersing for 10 min, adding 10% hydrochloric acid to adjust the pH to 3, then adding 1.5 g of γ-glycidyloxypropyltrimethoxysilane, heating to 75° C., reacting for 10 h, cooling to room temperature after the reaction is completed, filtering, washing with deionized water, and drying to obtain epoxy-modified nano-silica.

[0052] Step (2) under nitrogen conditions, 25g of cardanol and 0.05g of sodium hydroxide are added to a high-pressure reactor, and the reaction is carried out at 20°C for 30min. After the reaction is completed, the temperature is raised to 140°C, and the pressure is controlled to be maintained at 0.2MPa. 12.5g of ethylene oxide and 25g of epoxy-modified nano-silica are added thereto, and the reaction is carried out for 50min. After the reaction is completed, the mixture is cooled to room temperature and neutralized with glacial acetic acid to obtain a modified polyether.

[0053] Step (3) Under nitrogen conditions, 20 g of octamethylcyclotetrasiloxane, 10 g of aminopropyltriethoxysilane, 1.5 g of tetramethyldihydrodisiloxane, and 0.4 g of concentrated sulfuric acid are added to a flask, stirred and dispersed, heated to 40° C., and reacted for 4 hours. After the reaction is completed, cooled to room temperature, 0.6 g of sodium carbonate is added thereto to adjust the pH to 7, filtered, and dried to obtain modified hydrogenated silicone oil.

[0054] Step (4) Under nitrogen conditions, 50 g of modified hydrogenated silicone oil and 80 g of modified polyether are added to a flask filled with isopropanol solvent, stirred and dispersed, heated to 85° C., 0.1 g of chloroplatinic acid is added thereto, stirred for reaction for 10 h, and after the reaction is completed, reduced pressure distillation is performed to obtain polyether modified silicone oil.

[0055] Step (5) Add 20 g of silicone paste, 16 g of polyether modified silicone oil, 3.6 g of emulsifier Span-60, and 2 g of sodium carboxymethyl cellulose thickener to a reactor containing 80 g of deionized water, heat to 75° C., stir and mix evenly for 10 hours, and after stirring, cool to room temperature to obtain a polyether modified silicone defoamer.

[0056] Comparative Example 1

[0057] The difference between this comparative example and Example 1 is that 3.6 g of modified hydrogenated silicone oil is used in step (5) instead of 8 g of polyether modified silicone oil.

[0058] Comparative Example 2

[0059] The difference between this comparative example and Example 1 is that in step (5), 4.4 g of modified polyether is used instead of 8 g of polyether-modified silicone oil.

[0060] Refer to ASTM-D892-46T to test the defoaming and antifoaming performance of the defoaming agent. Add 200mL of 2.5% sodium dodecyl sulfate foaming solution into a 1000mL measuring cylinder, insert the bubbling tube to the bottom of the measuring cylinder at 25°C, introduce nitrogen at a rate of 3L / min until the foam height reaches 800mL, then add 1mL of 30-fold diluted defoaming agent, start the stopwatch at the same time, record the time when all the foam is eliminated, and then record the time required for the foam to reach 500mL.

[0061] Add a drop of defoamer into the flask containing deionized water, shake it, and observe whether stratification occurs.

[0062] Defoaming time / s Anti-foam time / s Dilution stability Example 1 39 64 excellent Example 2 32 69 excellent Example 3 24 76 excellent Example 4 16 83 excellent Example 5 15 85 excellent Comparative Example 1 42 50 good Comparative Example 2 45 48 good

[0063] The shorter the defoaming time, the better the defoaming performance, and the longer the antifoaming time, the better the antifoaming performance. As can be seen from the table, the polyether-modified silicone defoamer prepared by the present invention has excellent defoaming, antifoaming performance and stability.

[0064] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing a polyether-modified silicone defoamer, characterized in that: The preparation method is: Step (1) adding silica to a flask containing 70-80% ethanol aqueous solution, ultrasonically dispersing for 10-20 minutes, adding 10-20% hydrochloric acid to adjust the pH to 3-4, then adding γ-glycidyloxypropyltrimethoxysilane, heating to 75-85° C., reacting for 8-12 hours, cooling to room temperature after the reaction is completed, filtering, washing with deionized water, and drying to obtain epoxy-modified nano-silica; Step (2) under nitrogen conditions, adding cardanol and sodium hydroxide to a high-pressure reactor, reacting at 20-35° C. for 20-50 min, heating to 120-140° C. after the reaction, controlling the pressure to maintain at 0.2-0.4 MPa, adding ethylene oxide and epoxy-modified nano-silica, reacting for 30-60 min, cooling to room temperature after the reaction, neutralizing with glacial acetic acid to obtain a modified polyether; Step (3) under nitrogen conditions, octamethylcyclotetrasiloxane, aminopropyltriethoxysilane, tetramethyldihydrodisiloxane and concentrated sulfuric acid are added to a flask, stirred and dispersed, heated to 40-50° C., reacted for 4-8 hours, cooled to room temperature after the reaction, added sodium carbonate to adjust the pH to 6-7, filtered and dried to obtain modified hydrogen-containing silicone oil; Step (4) under nitrogen conditions, adding the modified hydrogenated silicone oil and the modified polyether into a flask containing an isopropanol solvent, stirring and dispersing, heating to 70-85° C., adding chloroplatinic acid thereto, stirring and reacting for 6-12 hours, and after the reaction is completed, performing reduced pressure distillation to obtain a polyether-modified silicone oil; Step (5) Add silicone paste, polyether modified silicone oil, emulsifier and thickener into a reaction kettle filled with deionized water, heat to 70-80° C., stir and mix evenly for 6-12 hours, and after stirring, cool to room temperature to obtain a polyether modified silicone defoamer.

2. The method for preparing the polyether-modified silicone defoamer according to claim 1, characterized in that: In the step (1), the mass ratio of silicon dioxide to γ-glycidyloxypropyltrimethoxysilane is 100:15-30.

3. The method for preparing the polyether-modified silicone defoamer according to claim 1, characterized in that: In the step (2), the mass ratio of cardanol, sodium hydroxide, ethylene oxide, and epoxy-modified nano-silica is 100:0.04-0.2:50-100:50-100.

4. The method for preparing the polyether-modified silicone defoamer according to claim 1, characterized in that: In the step (3), the mass ratio of octamethylcyclotetrasiloxane, aminopropyltriethoxysilane, tetramethyldihydrogendisiloxane, concentrated sulfuric acid and sodium carbonate is 100:30-50:5-10:1-3:3-10.

5. The method for preparing the polyether-modified silicone defoamer according to claim 1, characterized in that: In the step (4), the mass ratio of the modified hydrogen-containing silicone oil, the modified polyether, and the chloroplatinic acid is 100:100-200:0.1-0.

5.

6. The method for preparing the polyether-modified silicone defoamer according to claim 1, characterized in that: In the step (5), the mass ratio of silicone paste, polyether modified silicone oil, emulsifier, thickener and deionized water is 15-30:10-20:3-7:2-3:

100.

7. The method for preparing the polyether-modified silicone defoamer according to claim 1, characterized in that: In the step (5), the emulsifier is one or both of Span-60 and Span-80, and the thickener is sodium carboxymethyl cellulose.