A branched modified silicon ether defoamer and its preparation method and application

Abstract

The present invention provides a branched modified silicone ether defoamer and a preparation method and application thereof. The branched modified silicone ether defoamer of the present invention comprises the following components in parts by weight: 100 parts of polyether modified silicone oil, 5 to 15 parts of low-viscosity hydroxy silicone oil, and 1 to 10 parts of filler; wherein the polyether modified silicone oil is a three-arm or four-arm branched polymer formed by connecting a polyether as shown in formula I and a polydimethylsilicone oil as shown in formula II through a carbon chain, wherein (a+b)>c: #imgabs0#

Description

Technical Field

[0001] The invention relates to the technical field of defoamers, in particular to a branched modified silane ether defoamer and a preparation method and application thereof. Background Art

[0002] In most coating industrial production and applications, a large amount of foam is often generated. The presence of foam will seriously affect the quality of the product, and in some cases even lead to the inability to carry out normal production. At present, the method widely used in industrial production is to add defoaming agent, which is a general term for substances that can control foam when added to the foaming system at a low concentration. This defoaming method is both simple and economical.

[0003] Due to different foaming systems and production processes, the defoamers used are also different. According to the composition of existing defoamers, they can be divided into polyether type, silicone type, non-silicon type and silicone ether mixed type: polyether defoamers are characterized by strong anti-foaming ability but poor foam breaking ability; silicone defoamers have poor anti-foaming ability; mineral oils, amides, low-grade alcohols, fatty acids and phosphates and other organic non-silicon defoamers have the advantages of easy raw materials, high environmental performance and low production cost, but their defoaming efficiency is low, they are highly specific and have harsh conditions for use.

[0004] In recent years, people have found that siloxane mixed defoamers have gradually increased in industrial production and applications because they have the advantages of both polyether defoamers and silicone defoamers. However, the siloxane mixed defoamers on the market now also have shortcomings. The siloxane mixed defoamers are introduced into the hydrophobic silicone segments by polyether segments of a certain molecular weight. The higher the proportion of silicone segments, the stronger the hydrophobicity and the better the defoaming performance, but the dispersion ability in the coating system is weakened and the compatibility is poor. The solution is to use the siloxane mixed defoamer as the main body, and compound the emulsifier, stabilizer and dispersant to prepare an emulsion type defoamer: for example, in patent CN 106474778 A, the prepared polyether modified silicone is compounded with ultrafine aluminum silicate, sorbitol, Tween 60, sodium carboxymethyl cellulose and water, and the dispersion and compatibility problems are adjusted by the emulsifier. However, its preparation process and time are too long, which greatly increases the cost and the instability of the system.

[0005] Therefore, the current research direction is committed to the self-emulsification of defoamers, which does not require the addition of emulsifiers. For example, patent CN102160939A uses the "arms" of star-shaped polymers to compound acetylenic alcohols, higher fatty alcohols, glycerol polyethers and silicone oils together, without the need for emulsifiers. Star-shaped polymers are used to achieve molecular-level design, so that the chemical properties of the defoamer are stable, not easy to aggregate, and have good dispersion stability. It can be placed for more than half a year without stratification. However, the introduction of star-shaped polymers will increase the viscosity of the system to a certain extent. Although the defoamer itself has good self-dispersion stability, it has a high viscosity and its dispersion stability in industrial systems (such as water-based coatings) will decrease, resulting in unstable defoaming performance. For example, patent CN11072974A prepares a hyperbranched polyether-modified silicone oil through the "azide-alkyne click chemistry method". Its highly cross-linked internal branched skeleton and internal cavity, as well as a large number of terminal functional groups, have excellent emulsifying ability. Although this solution solves the stability problem of the defoamer, due to its highly cross-linked structure and dense spatial network structure, the molecular weight of the system will be relatively large, and its compatibility with the industrial system is poor, and phase separation is prone to occur.

[0006] Therefore, it is necessary to provide a silicone ether defoamer that does not require an emulsifier and can be stably dispersed in an industrial system. Summary of the invention

[0007] The purpose of the present invention is to solve the problem that the existing silicone ether defoamer needs to add an emulsifier and the dispersibility and defoaming performance in the industrial system still need to be further improved, and to provide a branched modified silicone ether defoamer that does not require an emulsifier and can be stably dispersed in the industrial system. The present invention synthesizes a branched polydimethylsiloxane modified polyether through "azide-alkyne cycloaddition" and selects a polyether segment with a specific structure, so as to obtain a branched modified silicone ether defoamer with excellent self-emulsification performance and can be stably dispersed in the industrial system.

[0008] Another object of the present invention is to provide a method for preparing the branched modified silyl ether defoamer.

[0009] Another object of the present invention is to provide application of the branched modified silicone ether defoamer in the field of aqueous industrial defoaming.

[0010] To achieve the above object, the present invention adopts the following technical solution:

[0011] A branched modified silicone ether defoamer comprises the following components in parts by weight:

[0012] 100 parts of polyether modified silicone oil;

[0013] 5-15 parts of low viscosity hydroxy silicone oil;

[0014] 1 to 10 parts of filler;

[0015] Wherein, the polyether-modified silicone oil is a three-arm or four-arm branched polymer formed by connecting the polyether shown in Formula I and the polydimethylsilicone oil shown in Formula II through a carbon chain, wherein (a+b)>c:

[0016]

[0017] The branched molecular structure of the polyether-modified silicone oil of the present invention can improve the self-emulsification performance of the defoamer without the need for adding an emulsifier. When the defoamer is applied to an aqueous working system, since the polyether segment of the present invention introduces two relatively large methyl groups connected to the same carbon atom at one end close to the branched structure, multiple polyether segments can be dispersed and expanded; at the same time, a polyether structural unit containing a methyl group is also connected to the distal end of the branched structure. Under the interaction of the methyl groups in the polydimethylsilicone oil and the hydroxyl groups in the low-viscosity hydroxyl silicone oil, the methyl groups at the distal end of the branched structure drive the longer polyether segment to be coated on the surface of the relatively shorter silicone oil segment, forming a physical coating structure. This coating structure can expose more flexible hydrophilic segments on the surface of the polyether-modified silicone oil, further improving the compatibility of the polyether-modified silicone oil with the aqueous working system, and the physical adsorption effect can also be in a dynamic balance of coating-expansion in the working system, rather than permanently coating the siloxane segment with excellent defoaming performance inside. This dynamic balance can give full play to the low surface tension foam breaking performance of siloxane and the anti-foaming ability of polyether, significantly improving the defoaming effect and the compatibility and stability in the aqueous working system.

[0018] It should be noted that the "three-arm or four-arm branched polymer formed by connecting the polyether shown in Formula I and the polydimethylsilicone oil shown in Formula II through carbon chains" described in the present invention is specifically a polymer with the following structure:

[0019]

[0020]

[0021] Preferably, in the polyether-modified silicone oil, 1.5<(a+b) / c<10. a+b represents the length of the polyether segment, and c represents the length of the polydimethylsilicone segment. It is necessary to ensure that the length of the polyether segment is greater than the length of the polydimethylsilicone segment so that a physically coated microsphere structure can be formed in the defoamer; however, if the length of the polyether segment is too long, the flexible polyether segment is easily entangled. After entanglement, the outer coating layer is uneven and easily dispersed under the action of external force, and a stable coating structure cannot be formed.

[0022] Preferably, the degree of polymerization c of the polydimethylsilicone oil is maintained between 1 and 30. If the polydimethylsilicone oil chain segment is too long, the particle size of the obtained coated microspheres is too large, and sedimentation is likely to occur, which leads to a decrease in both emulsification and defoaming properties. It should be noted that in the polydimethylsilicone oil of the present invention, the side chain also contains hydrogen atoms, and the hydrogen atoms in the side chain are connected to the branched structure through a substitution reaction, and further connected with the polyether segment to form the three-arm or four-arm branched polymer.

[0023] Preferably, in the formula I, a / b=0.25-0.75. In the polyether segment, the methyl group in the propylene oxide polyether segment b (-C3H6O-) has hydrophobic lipophilicity, and is mutually adsorbed with the methyl group in the silicone oil segment, and has good compatibility, but poor compatibility with the hydroxy silicone oil in the defoamer. Under the joint action of the hydroxy silicone oil and the filler dispersant, a stable coated microsphere structure can be formed in the defoamer. Therefore, as the proportion of the propylene oxide polyether segment (-C3H6O-) increases, the coating structure of the polyether-modified silicone oil is more stable, but when the proportion of -C3H6O- is too large, due to the large proportion of the hydrophobic group in the system, it is easy to cause the compatibility with the aqueous working system to be defoamed to deteriorate, and the defoaming effect shows a downward trend. Within the above-mentioned ratio range, a defoamer with self-emulsification stability and excellent defoaming performance can be obtained.

[0024] Preferably, the viscosity of the low-viscosity hydroxy silicone oil at 25°C is 25 to 100 mPa·s. As a plasticizer, the low-viscosity hydroxy silicone oil can reduce the viscosity of the defoamer system. At the same time, the selection of hydroxy silicone oil can also utilize the hydrophilicity of its hydroxyl group, which can not only improve the compatibility of the defoamer in the aqueous working system to be defoamed, but also interact with the filler and the methyl group in the polyether segment, driving the longer polyether segment to be coated on the surface of the relatively short silicone oil segment, forming a polyether-modified silicone oil microsphere with a physical coating structure.

[0025] Preferably, the filler is at least one of hydrophobic fumed silica, precipitated hydrophobic white carbon black or aluminum silicate. The filler can play the role of dispersing the plasticizer and polyether-modified silicone oil microspheres in the defoamer.

[0026] More preferably, the filler has a specific surface area of ​​110 to 150 m 2 / g of hydrophobic fumed silica, the research results of the present invention show that the dispersion stability and defoaming performance of the defoaming agent added with hydrophobic fumed silica are better.

[0027] The present invention also protects a method for preparing the branched modified silicon ether defoamer, comprising the following steps:

[0028] The polyether modified silicone oil, low viscosity hydroxy silicone oil and filler are uniformly mixed, reacted at 160-180° C. for 2-3 hours, and cooled to 20-30° C. to obtain the branched modified silicone ether defoaming agent.

[0029] Wherein, the preparation method of the polyether-modified silicone oil comprises the following steps:

[0030] S1. Preparation of polyethers containing branched structures

[0031] S11. Introducing an azide group into a branched structural segment: dissolving a halogen-substituted branched alkyl alcohol and an azide salt in an organic solvent, stirring at 75 to 85° C. to complete the reaction, and obtaining a branched product 1 after separation and drying;

[0032] S12. The branched product 1 obtained in step S11, the tertiary acetylene alcohol polyether, the catalyst 1 and the organic amine ligand are dissolved in an organic solvent, and a polyether containing a branched structure is obtained by an azide-alkyne cycloaddition reaction under an inert atmosphere at 20 to 30° C.;

[0033] S2. After uniformly mixing the branched polyether obtained in step S12 and the catalyst 2, polydimethylsilicone oil containing hydrogen in the side chain is added dropwise at 90-110° C. with stirring. After the reaction is complete, the catalyst 2 is removed to obtain the polyether-modified silicone oil.

[0034] The present invention obtains a polyether containing a branched structure through an azide-alkyne cycloaddition reaction, and by controlling the number of halogen substituents and hydroxyl groups on the halogen-substituted branched alkyl alcohol, the number of polyether segments and polydimethylsilicone segments of the obtained polyether-modified silicone oil can be regulated, thereby preparing different polyether-modified silicone oils for better matching with different operating systems.

[0035] Preferably, the halogen-substituted branched alkyl alcohol includes but is not limited to at least one of 2-(bromomethyl)-2-(hydroxymethyl)-1,3-propanediol, 1-bromo-2-bromomethyl-3-hydroxypropane, and 2,2-bis(bromomethyl)-1,3-propanediol.

[0036] Preferably, the azide salt is at least one of sodium azide, potassium azide, cesium azide, ammonium azide, calcium azide or copper azide.

[0037] Preferably, the organic amine ligand is at least one of pentamethyldiethylenetriamine, tris[(1-benzyl-1H-1,2,3-triazol-4-yl)methyl]amine, and 2-(4-((bis((1-tert-butyl-1H-1,2,3-triazol-4-yl)methyl)amino)methyl)-1H-1,2,3-triazol-1-yl)acetic acid.

[0038] Preferably, the catalyst 1 is cuprous bromide.

[0039] Preferably, the catalyst 2 is at least one of tetramethylammonium hydroxide, tetrabutylammonium fluoride, tetramethylammonium hydroxide or diammonium hydrogen phosphate. The amount of the catalyst 2 added is 800-1000 ppm of the reaction raw materials.

[0040] Conventional organic solvents can be used in the present invention, including but not limited to dimethylformamide, dimethylacetamide or anhydrous toluene.

[0041] Preferably, in step S11., the molar ratio of the halogen-substituted branched alkyl alcohol to the azide salt is 1:(8-20), and the azide salt is slightly excessive, which can ensure that the azide group is fully introduced into the branched structure segment.

[0042] Preferably, in step S12., the molar ratio of the branched product 1, tertiary acetylene alcohol polyether, catalyst 1 and organic amine ligand is 1:(1-3):0.15:1.5.

[0043] Preferably, the inert atmosphere in step S12 is an atmosphere composed of at least one of nitrogen, helium or argon.

[0044] The application of the branched modified silicone ether defoamer in the field of water-based industrial defoaming is also within the protection scope of the present invention.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] The present invention synthesizes branched polydimethylsiloxane modified polyether through "azide-alkyne cycloaddition" and selects polyether segments with specific structures, thereby obtaining a branched modified silicone ether defoamer with excellent self-emulsification performance and capable of being stably dispersed in an industrial system. The defoamer of the present invention can completely remove foam within 20 seconds when the addition amount is 0.1%, and has excellent defoaming performance. DETAILED DESCRIPTION

[0047] To better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific examples, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art. Unless otherwise specified, the reagents and materials used in the present invention are commercially available.

[0048] Example 1

[0049] This embodiment provides a polyether-modified silicone oil, which is prepared according to a method comprising the following steps:

[0050] S1. Preparation of polyethers containing branched structures

[0051] S11. Introduction of azide groups into branched structural segments:

[0052] 2-(Bromomethyl)-2-(hydroxymethyl)-1,3-propanediol and sodium azide were dissolved in an organic solvent dimethylformamide (DMF) at a molar ratio of 1:8, and stirred at 80°C for 48 hours. The obtained product was then cooled to room temperature (20-30°C), diluted with dichloromethane, and the mixture was washed with deionized water and brine respectively, and then adsorbed and dried with anhydrous sodium sulfate. After separation and concentration, it was precipitated with glacial ether to obtain compound 1 (as described in the following reaction equation);

[0053] S12. Compound 1 obtained in step S11, tertiary acetylene alcohol polyether (a=8, b=12), catalyst 1 (cuprous bromide) and organic amine ligand (pentamethyldiethylenetriamine) are dissolved in an organic solvent (anhydrous toluene), and stirred at room temperature (20-30° C.) in an inert atmosphere composed of nitrogen to carry out an azide-alkyne cycloaddition reaction. After the reaction is completed (after about 24 hours), a polyether containing a branched structure (compound 2 in the following reaction equation) is obtained;

[0054] The molar ratio of the compound 1, tertiary acetylene alcohol polyether, catalyst cuprous bromide and pentamethyldiethylenetriamine is 1:1:0.15:1.5;

[0055] S2. The polyether (compound 2) containing a branched structure obtained in step S12 and catalyst 2 (tetramethylammonium hydroxide) are mixed uniformly and heated to dissolve, and polydimethylsilicone oil (c=4) containing hydrogen in the side chain is added dropwise at 100° C. under stirring conditions. After the reaction is complete (about 2 hours), the catalyst 2 is removed to obtain the polyether-modified silicone oil (compound 3 in the following reaction equation), and in the obtained polyether-modified silicone oil, (a+b) / c=5;

[0056] The molar ratio of compound 2 to the polydimethylsilicone oil containing hydrogen on the side chain is 1:3, and the added amount of catalyst 2 is 800 ppm of the total weight of the reaction monomers of compound 2 and the polydimethylsilicone oil containing hydrogen on the side chain.

[0057]

[0058] Example 2

[0059] This embodiment provides a polyether-modified silicone oil, which is prepared according to a method comprising the following steps:

[0060] S1. Preparation of polyethers containing branched structures

[0061] S11. Introduction of azide groups into branched structural segments:

[0062] 1-Bromo-2-bromomethyl-3-hydroxypropane and sodium azide were dissolved in an organic solvent dimethylformamide (DMF) at a molar ratio of 1:15, and stirred at 80°C for 48 hours. The obtained product was then cooled to room temperature (20-30°C), diluted with dichloromethane, and the mixture was washed with deionized water and brine respectively, and then adsorbed and dried with anhydrous sodium sulfate. After separation and concentration, the compound 1′ was precipitated with glacial ether to obtain the compound 1′ (as described in the following reaction equation);

[0063] S12. Compound 1′ obtained in step S11, tertiary acetylene alcohol polyether (a=6, b=9), catalyst 1 (cuprous bromide) and organic amine ligand (pentamethyldiethylenetriamine) are dissolved in an organic solvent (anhydrous toluene), and stirred at room temperature (20-30° C.) in an inert atmosphere composed of nitrogen to carry out an azide-alkyne cycloaddition reaction. After the reaction is completed (after about 24 hours), a polyether containing a branched structure (compound 2′ in the following reaction equation) is obtained;

[0064] The molar ratio of the compound 1′, tertiary acetylene alcohol polyether, catalyst cuprous bromide and organic amine pentamethyldiethylenetriamine is 1:2:0.15:1.5;

[0065] S2. The polyether (compound 2′) having a branched structure obtained in step S12 and catalyst 2 (tetramethylammonium hydroxide) are mixed uniformly and heated to dissolve, and polydimethylsilicone oil (c=5) having a hydrogenated side chain is added dropwise at 100° C. with stirring. After the reaction is complete (about 2 h), catalyst 2 is removed to obtain the polyether-modified silicone oil (compound 3′ in the following reaction equation), wherein (a+b) / c=3 in the obtained polyether-modified silicone oil;

[0066] The molar ratio of compound 2′ to the polydimethylsilicone oil containing hydrogen on the side chain is 1:1, and the added amount of catalyst 2 is 800 ppm of the total weight of the reaction monomers of compound 2′ and the polydimethylsilicone oil containing hydrogen on the side chain.

[0067]

[0068] Example 3

[0069] This embodiment provides a polyether-modified silicone oil, which is prepared according to a method comprising the following steps:

[0070] S1. Preparation of polyethers containing branched structures

[0071] S11. Introduction of azide groups into branched structural segments:

[0072] 2,2-bis(bromomethyl)-1,3-propanediol and sodium azide were dissolved in an organic solvent dimethylformamide (DMF) at a molar ratio of 1:20, and stirred at 80°C for 48 hours, and then the obtained product was cooled to room temperature (20-30°C), diluted with dichloromethane, and then the mixture was washed with deionized water and brine respectively, and then adsorbed and dried with anhydrous sodium sulfate, separated and concentrated, and precipitated with glacial ether to obtain compound 1" (as described in the following reaction equation);

[0073] S12. Compound 1″ obtained in step S11, tertiary acetylene alcohol polyether (a=6, b=9), catalyst 1 (cuprous bromide) and organic amine ligand (pentamethyldiethylenetriamine) are dissolved in an organic solvent (anhydrous toluene), stirred under an inert atmosphere consisting of nitrogen at room temperature (20-30° C.), and an azide-alkyne cycloaddition reaction is carried out. After the reaction is completed (after about 24 hours), a polyether containing a branched structure (compound 2″ in the following reaction equation) is obtained;

[0074] The molar ratio of the compound 1″, tertiary acetylene alcohol polyether, catalyst cuprous bromide and organic amine pentamethyldiethylenetriamine is 1:2:0.15:1.5;

[0075] S2. The polyether (compound 2″) containing a branched structure obtained in step S12 and catalyst 2 (tetramethylammonium hydroxide) are mixed uniformly and heated to dissolve, and polydimethylsilicone oil (c=3) containing hydrogen in the side chain is added dropwise at 100° C. with stirring. After the reaction is complete (about 2 hours), the catalyst 2 is removed to obtain the polyether-modified silicone oil (compound 3″ in the following reaction equation), wherein (a+b) / c=5 in the obtained polyether-modified silicone oil;

[0076] The molar ratio of compound 2″ to the polydimethylsilicone oil containing hydrogen on the side chain is 1:2, and the added amount of catalyst 2 is 800 ppm of the total weight of the reaction monomers of compound 2″ and the polydimethylsilicone oil containing hydrogen on the side chain.

[0077]

[0078] Example 4

[0079] This embodiment provides a polyether-modified silicone oil, which is prepared according to the preparation method of Example 1. The difference from Example 1 is that in the tertiary acetylene alcohol polyether, a=2, b=18; that is, a / b=0.11.

[0080] Example 5

[0081] This embodiment provides a polyether-modified silicone oil, which is prepared according to the preparation method of Example 1. The difference from Example 1 is that in the tertiary acetylene alcohol polyether, a=12, b=8; that is, a / b=1.5.

[0082] Example 6

[0083] This embodiment provides a polyether-modified silicone oil, which is prepared according to the preparation method of Example 1. The difference from Example 1 is that in the tertiary acetylene alcohol polyether, a=300, b=100; that is, (a+b) / c=10.

[0084] Comparative Example 1

[0085] This comparative example provides a polyether-modified silicone oil, which is prepared according to the preparation method of Example 1. The difference from Example 1 is that the tertiary acetylene alcohol at the end group of the polyether segment in step S12 is replaced by a primary acetylene alcohol.

[0086] Comparative Example 2

[0087] This comparative example provides a polyether-modified silicone oil, which is prepared according to the preparation method of Example 1. The difference from Example 1 is that: a=8, b=12 in the tertiary acetylene alcohol polyether; c=40 in the polydimethylsilicone oil containing hydrogen in the side chain; i.e., a+b <c。

[0088] Examples 7 to 16, Comparative Examples 3 to 6

[0089] A series of silicone ether defoamers are provided, which are prepared according to a method comprising the following steps:

[0090] According to the raw material formula in Table 1, the polyether modified silicone oil, low viscosity hydroxy silicone oil and filler are uniformly mixed, reacted at 160-180° C. for 2-3 hours, and cooled to 20-30° C. to obtain the branched modified silicone ether defoamer.

[0091] Listed below are the raw materials and sources used in this application:

[0092] Low viscosity hydroxy silicone oil:

[0093] 1: The viscosity at 25°C is 25 mPa·s, brand RL-30, manufacturer Tongxiang Rongli Chemical Co., Ltd.;

[0094] 2: The viscosity at 25°C is 70 mPa·s, brand PMX0156, manufacturer Dow Corning;

[0095] filler:

[0096] Hydrophobic fumed silica: Specific surface area of ​​120m 2 / g, brand R972, manufacturer Evonik Specialty Chemicals (Shanghai) Co., Ltd.;

[0097] Precipitation hydrophobic silica: brand YH266, manufacturer Evonik Specialty Chemicals (Shanghai) Co., Ltd.

[0098] Aluminum silicate: brand 820A, manufacturer Evonik Specialty Chemicals (Shanghai) Co., Ltd.

[0099] Table 1 Formula of silicone ether defoamer (parts by weight)

[0100]

[0101]

[0102] Performance Testing

[0103] The defoaming performance of the defoamers obtained in Examples 6 to 14 and Comparative Examples 3 to 6 was characterized. The specific test steps were as follows: the defoamers prepared in the above examples and comparative examples were added to the water-based container chassis paint (brand: JT-321), the addition amount of the defoamer was 0.1%, and the defoaming time (s) was observed and recorded in Table 2.

[0104] Table 2 Test results of the defoamers obtained from the embodiments and comparative examples

[0105]

[0106] From the above results we can see that:

[0107] The defoamer prepared by the invention has good defoaming performance and can completely remove foam within 20 seconds when the added amount is only 0.1%.

[0108] The results of Examples 7 to 9 and Example 12 show that the higher the proportion of the polyether segment (a+b), the better the coating effect and the better the defoaming performance obtained; however, when the length of the polyether segment (a+b) is too long (such as Example 12), the flexible polyether segment is easily entangled. After entanglement, the outer coating layer is uneven and is easily dispersed under the action of external force, and a stable coating structure cannot be formed.

[0109] The results of Examples 6 and 10 to 11 show that as the proportion of propylene oxide polyether chain segments (—C3H6O—) increases, the coating structure of the polyether-modified silicone oil becomes more stable. However, when the proportion of —C3H6O— is too large, due to the large proportion of hydrophobic groups in the system, it is easy to cause the compatibility with the aqueous working system to be defoamed to deteriorate, and the defoaming effect shows a downward trend. Within the above-mentioned ratio range, a defoaming agent with self-emulsification stability and excellent defoaming performance can be obtained.

[0110] The results of Examples 6 and 13 to 15 show that low-viscosity hydroxy silicone oil has little effect on the defoaming performance; when fumed silica is used as the filler, the defoaming performance of the obtained defoamer is better.

[0111] In the defoamer of Comparative Example 1, in the polyether-modified silicone oil, the polyether segment does not contain a methyl group on the carbon atom at one end of the branched structure, resulting in uneven dispersion of the polyether segment and failure to form a uniform coating structure, which in turn leads to poor defoaming performance.

[0112] The polyether segment in Comparative Example 2 is shorter than the silicone oil segment, resulting in the inability to form a coating structure and poor defoaming performance.

[0113] The results of Example 6 and Comparative Examples 3 and 4 show that the polyether-modified silicone oil, low-viscosity hydroxy silicone oil and filler in the defoamer work synergistically to improve the defoaming performance of the defoamer.

[0114] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A branched modified silicone ether defoamer, characterized in that: The composition comprises the following components in parts by weight: 100 parts of polyether modified silicone oil; 5-15 parts of low viscosity hydroxy silicone oil; 1~10 parts of filler; Wherein, the filler is at least one of hydrophobic fumed silica, precipitated hydrophobic white carbon black or aluminum silicate; The polyether-modified silicone oil has the structure shown below: 、 、 ； In the formula, 1.5<(a+b) / c<10.

2. The branched modified silicone ether defoamer according to claim 1, characterized in that: a / b=0.25~0.

75.

3. The branched modified silicone ether defoamer according to claim 1, characterized in that: c is an integer ranging from 1 to 30.

4. The branched modified silicon ether defoamer according to claim 1, characterized in that: The low-viscosity hydroxy silicone oil has a viscosity of 25-100 mPa·s at 25° C.

5. The method for preparing the branched modified silicon ether defoamer according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: uniformly mixing polyether modified silicone oil, low-viscosity hydroxy silicone oil and filler, reacting at 160-180° C. for 2-3 hours, and cooling to 20-30° C. to obtain the branched modified silicone ether defoamer.

6. The method for preparing the branched modified silicon ether defoamer according to claim 5, characterized in that: The preparation method of the polyether-modified silicone oil comprises the following steps: S1. Preparation of polyethers containing branched structures S11. Introducing an azide group into a branched structural segment: dissolving a halogen-substituted branched alkyl alcohol and an azide salt in an organic solvent, stirring at 75-85°C for complete reaction, and obtaining a branched product 1 after separation and drying; The halogen-substituted branched alkyl alcohol is at least one of 2-(bromomethyl)-2-(hydroxymethyl)-1,3-propanediol, 1-bromo-2-bromomethyl-3-hydroxypropane or 2,2-bis(bromomethyl)-1,3-propanediol; S12. The branched product 1 obtained in step S11, the tertiary acetylene alcohol polyether, the catalyst 1 and the organic amine ligand are dissolved in an organic solvent, and a polyether containing a branched structure is obtained by an azide-alkyne cycloaddition reaction under an inert atmosphere at 20 to 30°C; The catalyst 1 is cuprous bromide; The organic amine ligand is at least one of pentamethyldiethylenetriamine, tris[(1-benzyl-1H-1,2,3-triazol-4-yl)methyl]amine, and 2-(4-((bis((1-tert-butyl-1H-1,2,3-triazol-4-yl)methyl)amino)methyl)-1H-1,2,3-triazol-1-yl)acetic acid; S2. After the polyether containing a branched structure obtained in step S12 and the catalyst 2 are uniformly mixed, a side chain hydrogen-containing polydimethylsilicone oil is added dropwise at 90 to 110° C. under stirring conditions. After the reaction is complete, the catalyst 2 is removed to obtain the polyether-modified silicone oil; The catalyst 2 is at least one of tetramethylammonium hydroxide, tetrabutylammonium fluoride, tetramethylammonium hydroxide or diammonium hydrogen phosphate.

7. Use of the branched modified silicon ether defoamer according to any one of claims 1 to 4 in the field of aqueous industrial defoaming.

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