Organic silicon emulsion defoaming agent and preparation method thereof

Abstract

The invention relates to the technical field of organic silicon defoaming agents, in particular to an organic silicon emulsion defoaming agent and a preparation method thereof.The organic silicon emulsion defoaming agent is prepared from, by weight, 10-50 parts of silicone grease, 1-10 parts of emulsifier, 1-5 parts of thickener and 40-80 parts of dispersion medium, and the silicone grease is synthesized through reaction of silicone oil and acrylate monomers. The organic silicon emulsion defoaming agent has the characteristics of strong defoaming capability, lasting foam inhibition, high compatibility, stable chemical property, no toxicity, no odor and the like, has a very wide market application value, is particularly suitable for foam elimination of water-based ink and water-based paint, and effectively avoids the problems of needle eyes, shrinkage cavities and the like of a water-based ink paint system caused by the compatibility problem.

Description

Technical Field

[0001] The present invention relates to the technical field of silicone defoamers, and particularly relates to a silicone emulsion defoamer and a preparation method thereof. Background Art

[0002] With the enhancement of human environmental protection awareness, oil-based inks and oil-based coatings can cause environmental pollution. Therefore, oil-based inks and coatings have lost market demand, while the consumption of water-based inks and water-based coatings has shown an increasing trend year by year. Many chemical additives are used in the production process of water-based coatings, such as dispersants, wetting agents, thickeners, pigments, fillers, etc. The main functions of the dispersant and the wetting agent are to redisperse the fine particles of the pigment and the filler into individual particles. When dispersing at high speed, a large amount of foam will be generated due to air entering the aqueous solution of these additives. If these foams are not eliminated, it will affect the construction of the coating and the quality of the coating itself. Therefore, it is necessary to add a defoamer to completely remove the air adsorbed on the surface of the fine pigment during the high-speed dispersion process.

[0003] Currently, the commonly used defoamers mainly include higher fatty alcohol defoamers, polyether defoamers, silicone defoamers, mineral oil defoamers, and higher carbon alcohol defoamers. Among them, the defoaming effects of higher fatty alcohol defoamers, polyether defoamers, and higher carbon alcohol defoamers on the foams generated by chemical additives such as dispersants and wetting agents are relatively poor. The main raw material of the mineral oil defoamer is mineral oil, and its density is relatively small. When used in an aqueous system, it is very easy to float on the surface. Moreover, the mineral oil defoamer will also affect the gloss of the water-based ink coating.

[0004] Compared with general defoamers, silicone defoamers have the characteristics of strong defoaming ability, not easily reacting with the foaming medium chemically, non-toxic, and physiologically inert for the foams generated by chemical additives such as dispersants and wetting agents, and are the defoamers with the widest application range. From the perspective of defoaming, the silicone defoamer formed by silicone oxygen and white carbon black has the strongest defoaming ability. However, due to compatibility problems, it is very difficult to disperse in the water-based ink coating system, and thus problems such as "shrinking holes" and "pinholes" will occur. Summary of the Invention

[0005] In order to overcome the disadvantages and deficiencies existing in the prior art, one of the purposes of the present invention is to provide a silicone emulsion defoamer, which has the characteristics of strong defoaming ability, long-lasting foam suppression, high compatibility, stable chemical properties, non-toxic and odorless, has broad market application value, and is particularly suitable for eliminating the foams of water-based inks and water-based coatings, effectively avoiding problems such as pinholes and shrinking holes in the water-based ink coating system caused by compatibility problems.

[0006] Another purpose of the present invention is to provide a preparation method of the silicone emulsion defoamer. The preparation method is simple to operate, convenient to control, has high production efficiency and low production cost, and can be used for large-scale production.

[0007] One of the objectives of the present invention is achieved through the following technical solutions: an organosilicon emulsion defoamer, comprising raw materials in the following parts by weight: 10 - 50 parts of silicone grease, 1 - 10 parts of emulsifier, 1 - 5 parts of thickener, and 40 - 80 parts of dispersion medium, wherein the silicone grease is synthesized by reacting silicone oil and acrylate monomers.

[0008] Preferably, the synthesis method of the silicone grease comprises the following steps:

[0009] (R1), Mix octamethylcyclotetrasiloxane, methyltrimethoxysilane, and siloxane coupling agent evenly, then add a catalyst and react at a temperature of 100 - 120 °C for 2 - 3 h, then cool down to 80 - 90 °C, add water and stir evenly, then heat up to 170 - 200 °C, and evacuate to remove low-boiling substances in the product to obtain silicone oil;

[0010] (R2), Add acrylate monomers to the silicone oil obtained in step (R1) and mix, then add concentrated sulfuric acid and stir evenly, react at a temperature of 50 - 60 °C for 2 - 3 h, let stand and separate to remove sulfuric acid, add sodium bicarbonate for neutralization and filtration to obtain silicone grease.

[0011] Preferably, the weight ratio of the usage amounts of octamethylcyclotetrasiloxane and methyltrimethoxysilane is 8:1 - 10:1.

[0012] Preferably, the weight part usage amount of the siloxane coupling agent is 1% - 5% of the total usage amounts of octamethylcyclotetrasiloxane and methyltrimethoxysilane; the siloxane coupling agent is γ-methacryloyloxypropyltrimethoxysilane.

[0013] Preferably, the weight part usage amount of the catalyst is 0.01 - 0.02% of the total usage amounts of octamethylcyclotetrasiloxane, methyltrimethoxysilane, and siloxane coupling agent; the catalyst is potassium hydroxide.

[0014] Preferably, the weight ratio of the usage amounts of the silicone oil and acrylate monomers is 1:1 - 2:1; the weight part usage amount of the concentrated sulfuric acid is 2 - 4% of the total usage amounts of the silicone oil and acrylate monomers.

[0015] Preferably, the acrylate monomers are butyl acrylate and / or methyl methacrylate.

[0016] Preferably, the emulsifier is at least one of polyoxyethylene sorbitan monostearate, polyoxyethylene dehydrated sorbitan monooleate, sorbitan monostearate, and sorbitan monooleate.

[0017] Preferably, the thickener is sodium polyacrylate; the dispersion medium is deionized water.

[0018] The second object of the present invention is achieved by the following technical solutions: The preparation method of the above-mentioned silicone emulsion defoamer includes the following steps:

[0019] (S1) Weigh silicone grease, emulsifier, thickener and dispersion medium by parts by weight and set aside.

[0020] (S2) Add silicone grease and emulsifier into the reaction kettle in sequence. After stirring evenly at a speed of 600 - 800 rpm, heat up to 30 - 50 °C, then dropwise add the dispersion medium while stirring, and then keep warm for 1 - 3 h to obtain the first mixture.

[0021] (S3) Add thickener to the first mixture and stir and disperse at a speed of 300 - 500 rpm for 1 - 2 h to obtain the second mixture.

[0022] (S4) Subject the second mixture to colloid mill treatment and then filter to obtain the silicone emulsion defoamer.

[0023] The beneficial effects of the present invention are as follows:

[0024] First, the silicone emulsion defoamer of the present invention has the characteristics of strong defoaming ability, long-lasting foam inhibition, high compatibility, stable chemical properties, non-toxic and odorless, etc. It has a wide market application value, especially suitable for eliminating foam in water-based inks and water-based coatings, effectively avoiding problems such as pinholes and shrinkage holes in the water-based ink and coating systems caused by compatibility problems.

[0025] Second, for the silicone emulsion defoamer, the silicone grease used has an inner layer composed of silicone oil and an outer layer synthesized from acrylate monomers. In this way, it not only retains the high-efficiency foam elimination effect of the inner layer siloxane on foam, but also utilizes the characteristics of the outer layer acrylate to obtain better compatibility with the coating. The two complement each other, which is beneficial to maintaining excellent defoaming and foam inhibition performance and avoiding problems such as pinholes and shrinkage holes in the water-based ink and coating systems caused by compatibility problems.

[0026] Third, for the silicone emulsion defoamer, the outer layer of the silicone grease used is synthesized from acrylate monomers. And the acrylate in the outer layer is more compatible with the components in the coating.

[0027] Fourth, for the silicone emulsion defoamer, the inner layer silicone oil of the silicone grease used is synthesized into a spherical network structure by methyltrimethoxysilane, octamethylcyclotetrasiloxane and siloxane coupling agent. Its structure is stable and not easy to decompose, so it has the characteristics of fast defoaming and long-lasting foam inhibition. Moreover, the siloxane coupling agent uses γ-methacryloxypropyltrimethoxysilane, which has low surface tension and excellent wetting performance, improving the wettability and adhesion of the material surface.

[0028] Fifth, the addition of emulsifier and thickener to the organosilicon emulsion defoamer can make the organosilicon defoamer more stable, maintain its lasting defoaming and anti-foaming properties, and overcome the disadvantages of difficult transportation and storage, making it more convenient in transportation, storage and use.

[0029] Sixth, the preparation method of the organosilicon emulsion defoamer of the present invention is relatively simple, and the production cost is low, the processing technology is mature, and an organosilicon emulsion defoamer can be made, and the defoaming effect is good, the foam suppression is long-lasting, the environment is environmentally friendly and pollution-free, and various performance indicators are good. DETAILED DESCRIPTION

[0030] In order to facilitate the understanding of those skilled in the art, the present invention is further described below in conjunction with embodiments, and the contents mentioned in the implementation modes are not intended to limit the present invention.

[0031] The organosilicon emulsion defoamer of the present invention is suitable for eliminating foam of water-based inks and water-based coatings, and can effectively avoid the problems of pinholes, shrinkage holes, etc. in the water-based ink coating system caused by compatibility problems.

[0032] The organosilicon emulsion defoamer of the present invention comprises the following raw materials in parts by weight: 10-50 parts of silicone grease, 1-10 parts of emulsifier, 1-5 parts of thickener, and 40-80 parts of dispersion medium, wherein the silicone grease is synthesized by reacting silicone oil and acrylate monomers;

[0033] The organosilicon emulsion defoamer of the present invention adopts special synthetic silicone grease, which is synthesized by the reaction of silicone oil and acrylate monomers to form a special structure consisting of silicone oil in the inner layer and acrylate monomers in the outer layer. The organosilicon emulsion defoamer of the present invention not only retains the efficient foam elimination effect of the inner layer siloxane on foam, but also utilizes the characteristics of the outer layer acrylate to obtain better compatibility with the coating. The two complement each other, which is conducive to maintaining excellent defoaming and foam suppression performance, and is conducive to avoiding the problems of pinholes and shrinkage holes in the water-based ink coating system caused by compatibility problems. It is more stable and maintains its lasting defoaming and foam suppression performance in conjunction with an emulsifier, a thickener and a dispersion medium. At the same time, it overcomes the disadvantages of transportation and storage difficulties, and is more convenient in transportation, storage and use. The organosilicon emulsion defoamer has the characteristics of strong defoaming ability, lasting foam suppression, high compatibility, stable chemical properties, non-toxic and tasteless, etc., has a wide market application value, is particularly suitable for the foam elimination of water-based inks and water-based coatings, and effectively avoids the problems of pinholes and shrinkage holes in the water-based ink coating system caused by compatibility problems.

[0034] The weight proportion of silicone grease may be, but is not limited to, 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, and 50 parts;

[0035] The weight proportion of the emulsifier may be, but is not limited to, 2 parts, 3 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, and 10 parts;

[0036] The weight parts of the thickener can be but are not limited to 1 part, 2 parts, 3 parts, 4 parts, and 5 parts.

[0037] As a technical solution of the present invention, the synthesis method of the silicone grease includes the following steps:

[0038] (R1) After uniformly mixing octamethylcyclotetrasiloxane, methyltrimethoxysilane, and a siloxane coupling agent, a catalyst is added and reacted at a temperature of 100 - 120 °C for 2 - 3 h, then cooled to 80 - 90 °C, water is added and stirred evenly, and then heated to 170 - 200 °C, and the low-boiling substances in the product are removed by vacuum pumping to obtain silicone oil;

[0039] (R2) An acrylate monomer is added to the silicone oil in step (R1) and mixed, then concentrated sulfuric acid is added and stirred evenly, and the reaction is carried out at a temperature of 50 - 60 °C for 2 - 3 h, allowed to stand for separation to remove sulfuric acid, sodium bicarbonate is added for neutralization and filtration to obtain silicone grease.

[0040] In the above synthesis method of silicone grease, in step (R1), a spherical network structure is synthesized using methyltrimethoxysilane, octamethylcyclotetrasiloxane, and a siloxane coupling agent. Its structure is stable and not easily decomposed, so it has the characteristics of fast defoaming and long-lasting foam suppression. In step (R2), an acrylate monomer is introduced, and an inner and outer layer structure is formed after the reaction. The acrylate in the outer layer is more compatible with the components in the coating and has better compatibility.

[0041] As a technical solution of the present invention, the weight part ratio of the octamethylcyclotetrasiloxane to the methyltrimethoxysilane is 8:1 - 10:1.

[0042] As a technical solution of the present invention, the weight part dosage of the siloxane coupling agent is 1% - 5% of the total dosage of the octamethylcyclotetrasiloxane and the methyltrimethoxysilane; the siloxane coupling agent is γ-methacryloxypropyltrimethoxysilane.

[0043] As a technical solution of the present invention, the weight part dosage of the catalyst is 0.01 - 0.02% of the total dosage of the octamethylcyclotetrasiloxane, the methyltrimethoxysilane, and the siloxane coupling agent; the catalyst is potassium hydroxide.

[0044] As a technical solution of the present invention, the weight part ratio of the silicone oil to the acrylate monomer is 1:1 - 2:1; the weight part dosage of the concentrated sulfuric acid is 2 - 4% of the total dosage of the silicone oil and the acrylate monomer.

[0045] As a technical solution of the present invention, the acrylate monomer is butyl acrylate and / or methyl methacrylate. Preferably, the acrylate monomer is composed of butyl acrylate and methyl methacrylate mixed in a weight ratio of 1:3 - 1:5.

[0046] As a technical solution of the present invention, the emulsifier is at least one of polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, sorbitan monostearate, and sorbitan monooleate. Preferably, the emulsifier is a mixture of polyoxyethylene sorbitan monostearate (Tween 60) and sorbitan monostearate (Span 60) in a weight ratio of 1:1 - 2:1.

[0047] As a technical solution of the present invention, the thickener is sodium polyacrylate; the dispersion medium is deionized water.

[0048] The preparation method of the silicone emulsion defoamer of the present invention includes the following steps:

[0049] (S1) Weigh silicone grease, emulsifier, thickener, and dispersion medium by parts by weight and set aside.

[0050] (S2) Add silicone grease and emulsifier to the reaction kettle in sequence. After stirring evenly at a speed of 600 - 800 rpm, heat up to 30 - 50 °C, then dropwise add the dispersion medium while stirring, and then keep warm for 1 - 3 h to obtain the first mixture.

[0051] (S3) Add the thickener to the first mixture and stir and disperse for 1 - 2 h at a speed of 300 - 500 rpm to obtain the second mixture.

[0052] (S4) Perform colloid mill treatment on the second mixture and then filter to obtain the silicone emulsion defoamer.

[0053] To better illustrate the purpose, technical solution, and beneficial effects of the present invention, the present invention will be further described below in conjunction with specific embodiments. It should be noted that the methods described in the following embodiments are further explanatory descriptions of the present invention and should not be regarded as limitations on the present invention.

[0054] The preparation method of silicone oil A includes the following steps: Mix octamethylcyclotetrasiloxane and methyltrimethoxysilane in a weight ratio of 10:1, add 1% of siloxane coupling agent (γ - methacryloxypropyltrimethoxysilane) based on the total weight of octamethylcyclotetrasiloxane and methyltrimethoxysilane. After mixing evenly, add 0.01% of potassium hydroxide based on the total amount of octamethylcyclotetrasiloxane, methyltrimethoxysilane, and siloxane coupling agent. Heat up to 100 °C and react for 2 h. Cool down to 90 °C, add deionized water, stir evenly, heat up to 170 °C, and evacuate to remove low - boiling substances in the silicone oil to obtain it.

[0055] The preparation method of silicone oil B comprises the following steps: Octamethylcyclotetrasiloxane and methyltrimethoxysilane are mixed in a weight ratio of 8:1, 5% of siloxane coupling agent (γ-methacryloxypropyltrimethoxysilane) based on the total weight of octamethylcyclotetrasiloxane and methyltrimethoxysilane is added, after mixing evenly, 0.01% of potassium hydroxide based on the total amount of octamethylcyclotetrasiloxane, methyltrimethoxysilane and siloxane coupling agent is added, the temperature is raised to 120 °C, the reaction is carried out for 3 h, the temperature is lowered to 80 °C, deionized water is added, stirred evenly, the temperature is raised to 200 °C, and the low-boiling substances in the silicone oil are removed by vacuum pumping to obtain the product.

[0056] The synthesis method of silicone grease A comprises the following steps: Silicone oil A, butyl acrylate and methyl methacrylate are mixed in a weight ratio of 4:1:3, 3% of concentrated sulfuric acid based on the total amount of silicone oil A, butyl acrylate and methyl methacrylate is added and stirred, the reaction is carried out at 50 °C for 2 h, left to stand for separation to remove sulfuric acid, sodium bicarbonate is added for neutralization and filtration to obtain silicone grease A.

[0057] The synthesis method of silicone grease B comprises the following steps: Silicone oil A, butyl acrylate and methyl methacrylate are mixed in a weight ratio of 6:1:5, 3% of concentrated sulfuric acid based on the total amount of silicone oil A, butyl acrylate and methyl methacrylate is added and stirred, the reaction is carried out at 60 °C for 2 h, left to stand for separation to remove sulfuric acid, sodium bicarbonate is added for neutralization and filtration to obtain silicone grease B.

[0058] The synthesis method of silicone grease C comprises the following steps: Silicone oil B, butyl acrylate and methyl methacrylate are mixed in a weight ratio of 4:1:3, 3% of concentrated sulfuric acid based on the total amount of silicone oil B, butyl acrylate and methyl methacrylate is added and stirred, the reaction is carried out at 50 °C for 3 h, left to stand for separation to remove sulfuric acid, sodium bicarbonate is added for neutralization and filtration to obtain silicone grease C.

[0059] The synthesis method of silicone grease D comprises the following steps: Silicone oil B, butyl acrylate and methyl methacrylate are mixed in a weight ratio of 6:1:5, 3% of concentrated sulfuric acid based on the total amount of silicone oil B, butyl acrylate and methyl methacrylate is added and stirred, the reaction is carried out at 60 °C for 3 h, left to stand for separation to remove sulfuric acid, sodium bicarbonate is added for neutralization and filtration to obtain silicone grease D.

[0060] The synthesis method of silicone grease E comprises the following steps: Silicone oil B, butyl acrylate and methyl methacrylate are mixed in a weight ratio of 8:1:3, 3% of concentrated sulfuric acid based on the total amount of silicone oil B, butyl acrylate and methyl methacrylate is added and stirred, the reaction is carried out at 60 °C for 3 h, left to stand for separation to remove sulfuric acid, sodium bicarbonate is added for neutralization and filtration to obtain silicone grease E.

[0061] The synthesis method of silicone grease F includes the following steps: Mix silicone oil A, butyl acrylate, and methyl methacrylate in a weight ratio of 3:1:5, add 3% concentrated sulfuric acid based on the total amount of silicone oil B, butyl acrylate, and methyl methacrylate, stir, react at 60 °C for 3 h, let it stand and separate to remove sulfuric acid, add sodium bicarbonate for neutralization and filtration to obtain silicone grease F.

[0062] The synthesis method of silicone grease G includes the following steps: Mix silicone oil B, butyl acrylate, and methyl methacrylate in a weight ratio of 9:1:3, add 3% concentrated sulfuric acid based on the total amount of silicone oil B, butyl acrylate, and methyl methacrylate, stir, react at 60 °C for 3 h, let it stand and separate to remove sulfuric acid, add sodium bicarbonate for neutralization and filtration to obtain silicone grease G.

[0063] Example 1

[0064] This example is an organosilicon emulsion defoamer, which includes the following raw materials in parts by weight: 25 g of silicone grease A, 1.5 g of polyoxyethylene sorbitan monostearate, 1.5 g of sorbitan monostearate, 5 g of sodium polyacrylate, and 60 g of deionized water.

[0065] The preparation method of the organosilicon emulsion defoamer in this example includes the steps: First step, add the formulated amounts of silicone grease A, polyoxyethylene sorbitan monostearate, and sorbitan monostearate into the reaction kettle in sequence. After stirring evenly at 600 rpm, raise the temperature to 50 °C, dropwise add deionized water while stirring, and keep warm for 3 h to obtain the first mixture; Second step, add the thickener sodium polyacrylate to the first mixture, and stir and disperse at 500 rpm for 2 h to obtain the second mixture; Third step, perform colloid mill treatment on the second mixture and then filter to obtain the organosilicon emulsion defoamer.

[0066] Example 2

[0067] This example is an organosilicon emulsion defoamer, which includes the following raw materials in parts by weight: 35 g of silicone grease B, 1.1 g of polyoxyethylene sorbitan monostearate, 1.1 g of sorbitan monostearate, 4 g of sodium polyacrylate, and 70 g of deionized water.

[0068] The preparation method of the organosilicon emulsion defoamer in this example includes the steps: First step, add the formulated amounts of silicone grease B, polyoxyethylene sorbitan monostearate, and sorbitan monostearate into the reaction kettle in sequence. After stirring evenly at 800 rpm, raise the temperature to 45 °C, dropwise add deionized water while stirring, and keep warm for 3 h to obtain the first mixture; Second step, add the thickener sodium polyacrylate to the first mixture, and stir and disperse at 500 rpm for 2 h to obtain the second mixture; Third step, perform colloid mill treatment on the second mixture and then filter to obtain the organosilicon emulsion defoamer.

[0069] Example 3

[0070] This example is a silicone emulsion defoamer, which comprises raw materials in the following parts by weight: 40 g of silicone grease C, 1.5 g of polyoxyethylene sorbitan monostearate, 1.5 g of sorbitan monostearate, 3 g of sodium polyacrylate, and 60 g of deionized water.

[0071] The preparation method of the silicone emulsion defoamer in this example includes the steps: First step, sequentially add the formulated amounts of silicone grease C, polyoxyethylene sorbitan monostearate, and sorbitan monostearate into a reaction kettle, stir evenly at a speed of 800 rpm, then heat up to 40 °C, dropwise add deionized water while stirring, and keep warm for 3 h to obtain a first mixture; Second step, add the thickener sodium polyacrylate to the first mixture, and stir and disperse for 2 h at a speed of 500 rpm to obtain a second mixture; Third step, perform colloid mill treatment on the second mixture and then filter to obtain the silicone emulsion defoamer.

[0072] Example 4

[0073] This example is a silicone emulsion defoamer, which comprises raw materials in the following parts by weight: 45 g of silicone grease D, 1.5 g of polyoxyethylene sorbitan monostearate, 1.5 g of sorbitan monostearate, 4 g of sodium polyacrylate, and 70 g of deionized water.

[0074] The preparation method of the silicone emulsion defoamer in this example includes the steps: First step, sequentially add the formulated amounts of silicone grease D, polyoxyethylene sorbitan monostearate, and sorbitan monostearate into a reaction kettle, stir evenly at a speed of 800 rpm, then heat up to 35 °C, dropwise add deionized water while stirring, and keep warm for 3 h to obtain a first mixture; Second step, add the thickener sodium polyacrylate to the first mixture, and stir and disperse for 2 h at a speed of 500 rpm to obtain a second mixture; Third step, perform colloid mill treatment on the second mixture and then filter to obtain the silicone emulsion defoamer.

[0075] Example 5

[0076] This example is a silicone emulsion defoamer, which comprises raw materials in the following parts by weight: 45 g of silicone grease E, 1.5 g of polyoxyethylene sorbitan monostearate, 1.5 g of sorbitan monostearate, 4 g of sodium polyacrylate, and 70 g of deionized water.

[0077] The preparation method of the silicone emulsion defoamer in this embodiment includes the following steps: First step, add the formulated amounts of silicone grease E, polyoxyethylene sorbitan monostearate, and sorbitan monostearate into the reaction kettle in sequence. After stirring evenly at a speed of 800 rpm, raise the temperature to 30 °C, and while stirring, dropwise add deionized water and keep warm for 3 h to obtain the first mixture; Second step, add the thickener sodium polyacrylate to the first mixture, and stir and disperse for 2 h at a speed of 500 rpm to obtain the second mixture; Third step, perform colloid mill treatment on the second mixture and then filter to obtain the silicone emulsion defoamer.

[0078] Comparative Example 1

[0079] This comparative example is a silicone emulsion defoamer, which includes the following raw materials in parts by weight: 45 g of silicone grease F, 1.5 g of polyoxyethylene sorbitan monostearate, 1.5 g of sorbitan monostearate, 4 g of sodium polyacrylate, and 70 g of deionized water.

[0080] The preparation method of the silicone emulsion defoamer in this comparative example includes the following steps: First step, add the formulated amounts of silicone grease F, polyoxyethylene sorbitan monostearate, and sorbitan monostearate into the reaction kettle in sequence. After stirring evenly at a speed of 800 rpm, raise the temperature to 40 °C, and while stirring, dropwise add deionized water and keep warm for 3 h to obtain the first mixture; Second step, add the thickener sodium polyacrylate to the first mixture, and stir and disperse for 2 h at a speed of 500 rpm to obtain the second mixture; Third step, perform colloid mill treatment on the second mixture and then filter to obtain the silicone emulsion defoamer.

[0081] Comparative Example 2

[0082] This comparative example is a silicone emulsion defoamer, which includes the following raw materials in parts by weight: 45 g of silicone grease G, 1.5 g of polyoxyethylene sorbitan monostearate, 1.5 g of sorbitan monostearate, 4 g of sodium polyacrylate, and 70 g of deionized water.

[0083] The preparation method of the silicone emulsion defoamer in this comparative example includes the following steps: First step, add the formulated amounts of silicone grease G, polyoxyethylene sorbitan monostearate, and sorbitan monostearate into the reaction kettle in sequence. After stirring evenly at a speed of 800 rpm, raise the temperature to 40 °C, and while stirring, dropwise add deionized water and keep warm for 3 h to obtain the first mixture; Second step, add the thickener sodium polyacrylate to the first mixture, and stir and disperse for 2 h at a speed of 500 rpm to obtain the second mixture; Third step, perform colloid mill treatment on the second mixture and then filter to obtain the silicone emulsion defoamer.

[0084] Performance Test

[0085] The silicone emulsion defoamers in Examples 1 - 5 and Comparative Examples 1 - 2, the commercially available silicone defoamer AT - 990, the commercially available polyether defoamer DT - 057, and the commercially available mineral oil defoamer ST 2410 were respectively tested for compatibility and defoaming and foam - suppressing performance. The test sample was acrylic emulsion and styrene - acrylic emulsion, and the test conditions were as follows. The test results are shown in Tables 1 - 2.

[0086] (1) Compatibility test:

[0087] In a 300 mL beaker, weigh 200 mL of acrylic emulsion or styrene - acrylic emulsion, add 1 mL of each defoamer respectively, stir magnetically for 30 min, and after standing for 5 min, scrape - coat on the black - and - white grid paper with a 75 - um film applicator. Compare the film - forming effects of the films respectively. The data are shown in Table 1:

[0088] Table 1 Compatibility performance test

[0089] Acrylic emulsion compatibility Styrene-acrylic emulsion compatibility Example 1 Smooth, flat and no shrinkage holes Smooth, flat and no shrinkage holes Example 2 Smooth, flat and no shrinkage holes Smooth, flat and no shrinkage holes Example 3 Smooth, flat and no shrinkage holes Smooth, flat and no shrinkage holes Example 4 Smooth, flat and no shrinkage holes Smooth, flat and no shrinkage holes Example 5 Smooth, flat and no shrinkage holes Smooth, flat and no shrinkage holes Comparative example 1 Smooth, flat and no shrinkage holes Slight shrinkage holes Comparative example 2 Slight shrinkage holes Slight shrinkage holes Silicone defoamer AT-990 Serious shrinkage holes Serious shrinkage holes Polyether defoamer DT-057 Smooth, flat and no shrinkage holes Smooth, flat and no shrinkage holes Mineral oil defoamer ST2410 Slight shrinkage holes Slight shrinkage holes

[0090] (2) Defoaming and foam - suppressing performance:

[0091] In a 300 mL beaker, weigh 200 mL of acrylic emulsion or styrene - acrylic emulsion, add 2.0 mL of each defoamer respectively, disperse at a high speed of 2000 rpm for 20 min. After completion, immediately pour the emulsion into a 100 - mL density cup that has been tared on an electronic scale until the cup lid just overflows, and read the corresponding weight m. At this time, the density of the emulsion is m / 100 (g / mL). And the greater the density of the emulsion, the better the defoaming and foam - suppressing performance of the defoamer. The data are shown in Table 2.

[0092] Table 2 Defoaming and foam - suppressing performance test

[0093]

[0094]

[0095] As can be seen from the results of Table 1 and Table 2, compared with Comparative Examples 1-2, silicone defoamer AT-990, polyether defoamer DT-057 and mineral oil defoamer ST 2410, the comprehensive effects of the compatibility and defoaming and foam-inhibiting properties of the silicone defoamers in Examples 1-5 are better. This is mainly because the special synthetic silicone grease contained in Examples 1-5 improves the defoaming and foam-inhibiting properties and compatibility of the defoamer. Specifically, the silicone grease has a spherical network structure with a stable and non-decomposable inner layer synthesized from methyltrimethoxysilane, octamethylcyclotetrasiloxane and γ-methacryloxypropyltrimethoxysilane, and the outer layer of the silicone grease is composed of butyl acrylate and methyl methacrylate. The outer layer wraps the inner layer, which not only preserves the rapid foam elimination and long-term foam inhibition effect of the inner layer silicone oxygen alkane, but also the acrylate monomers in the outer layer are more compatible with the components in the coating, and will not cause problems such as pinholes and shrinkage during the coating construction process, affecting the appearance quality of the coating.

[0096] The above embodiments are the preferred implementation schemes of the present invention. In addition, the present invention can also be implemented in other ways. Any obvious replacement without departing from the concept of the present invention is within the protection scope of the present invention.

Claims

1. An organosilicon emulsion defoamer, characterized in that, It comprises raw materials in the following parts by weight: 10 - 50 parts of silicone grease, 1 - 10 parts of emulsifier, 1 - 5 parts of thickener, and 40 - 80 parts of dispersion medium, and the silicone grease is synthesized by reacting silicone oil and acrylate monomers.

2. An organosilicon emulsion defoamer according to claim 1, characterized in that, The synthesis method of the silicone grease comprises the following steps: (R1) Take octamethylcyclotetrasiloxane, methyltrimethoxysilane, and a siloxane coupling agent, mix them evenly, add a catalyst, and react at a temperature of 100 - 120 °C for 2 - 3 h. Then cool down to 80 - 90 °C, add water and stir evenly, then heat up to 170 - 200 °C, and evacuate to remove low-boiling substances in the product to obtain silicone oil; (R2) Add acrylate monomers to the silicone oil obtained in step (R1), mix them, then add concentrated sulfuric acid and stir evenly. React at a temperature of 50 - 60 °C for 2 - 3 h, let it stand for separation to remove sulfuric acid, add sodium bicarbonate for neutralization and filtration to obtain silicone grease.

3. The silicone emulsion defoamer according to claim 2, wherein: The weight ratio of the usage amounts of octamethylcyclotetrasiloxane and methyltrimethoxysilane is 8:1 - 10:

1.

4. The silicone emulsion defoamer according to claim 2, wherein: The weight part usage amount of the siloxane coupling agent is 1% - 5% of the total usage amounts of octamethylcyclotetrasiloxane and methyltrimethoxysilane; the siloxane coupling agent is γ-methacryloxypropyltrimethoxysilane.

5. The silicone emulsion defoamer according to claim 2, wherein: The weight part usage amount of the catalyst is 0.01 - 0.02% of the total usage amounts of octamethylcyclotetrasiloxane, methyltrimethoxysilane, and the siloxane coupling agent; the catalyst is potassium hydroxide.

6. The silicone emulsion defoamer according to claim 2, wherein: The weight ratio of the usage amounts of the silicone oil and acrylate monomers is 1:1 - 2:1; the weight part usage amount of the concentrated sulfuric acid is 2 - 4% of the total usage amounts of the silicone oil and acrylate monomers.

7. An organosilicon emulsion defoamer according to claim 1, characterized in that: The acrylate monomer is butyl acrylate and / or methyl methacrylate.

8. An organosilicon emulsion defoamer according to claim 1, characterized in that: The emulsifier is at least one of polyoxyethylene sorbitan monostearate, polyoxyethylene dehydrated sorbitan monooleate, sorbitan monostearate, and sorbitan monooleate.

9. An organosilicon emulsion defoamer according to claim 1, characterized in that: The thickener is sodium polyacrylate; the dispersion medium is deionized water.

10. A preparation method of the silicone emulsion defoamer according to any one of claims 1-9, characterized in that, It comprises the following steps: (S1) Take silicone grease, emulsifier, thickener, and dispersion medium according to parts by weight, and set aside; (S2) Add the silicone grease and emulsifier into a reaction kettle in sequence, stir evenly at a rotation speed of 600 - 800 rpm, heat up to 30 - 50 °C, then add the dispersion medium dropwise while stirring, and then keep warm for 1 - 3 h to obtain a first mixture; (S3) Add the thickener to the first mixture, stir and disperse at a rotation speed of 300 - 500 rpm for 1 - 2 h to obtain a second mixture; (S4) Perform colloid mill treatment on the second mixture and then filter to obtain an organosilicon emulsion defoamer.

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