A silicone emulsion defoamer and a method for preparing the same

Abstract

The present application relates to the technical field of silicone defoaming agent, in particular to a kind of silicone emulsion defoaming agent and preparation method thereof, the silicone emulsion defoaming agent includes the following weight parts of raw materials: 10-50 parts of silicon grease, 1-10 parts of emulsifier, 1-5 parts of thickening agent, and 40-80 parts of dispersion medium, the silicon grease is synthesized by silicon oil and acrylate monomer reaction.The silicone emulsion defoaming agent has the characteristics of strong defoaming capacity, long-lasting bubble inhibition, high compatibility, stable chemical properties, non-toxic and odorless, etc., has very wide market application value, especially suitable for water-based ink and water-based paint foam elimination, effectively avoid the pinhole, shrinkage and other problems caused by compatibility problem in water-based ink coating system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of silicone defoaming agent, in particular to a kind of silicone emulsion defoaming agent and preparation method thereof. BACKGROUND

[0002] With the enhancement of human environmental protection consciousness, oily ink and oily paint can cause environmental pollution, so oily ink and paint have lost market demand, and the consumption of water-based ink and water-based paint has shown an increasing trend year by year. Many chemical additives, such as dispersants, wetting agents, thickeners, pigments and fillers, etc., are used in the production process of water-based paint. The main function of dispersants and wetting agents is to disperse the fine particles of pigments and fillers into single particles. When high-speed dispersion is carried out, a large amount of foam will be generated due to the entry of air into the water solution of these additives. If these foams are not eliminated, they will affect the construction of the paint and the quality of the paint itself, so it is necessary to add a defoaming agent to completely remove the air adsorbed on the fine pigments during high-speed dispersion.

[0003] The commonly used defoaming agents at present mainly include high-grade fatty alcohol defoaming agents, polyether defoaming agents, silicone defoaming agents, mineral oil defoaming agents and high-carbon alcohol defoaming agents. Among them, high-grade fatty alcohol defoaming agents, polyether defoaming agents and high-carbon alcohol defoaming agents have poor defoaming effect on the foam generated by chemical additives such as dispersants and wetting agents. The main raw material of mineral oil defoaming agent is mineral oil, which has a relatively small density and is easy to float on the surface when used in water-based systems. In addition, mineral oil defoaming agent will also affect the gloss of water-based ink and paint.

[0004] Compared with general defoaming agents, silicone defoaming agents have strong defoaming ability, are not easy to react with foaming media, are non-toxic and physiologically inert, and have other characteristics, so they are the most widely used defoaming agents. From the perspective of defoaming, the silicone defoaming agent formed by siloxane and white carbon black has the strongest defoaming ability, but it is difficult to disperse in the water-based ink and paint system due to compatibility problems, which may cause problems such as shrinkage and pinholes. SUMMARY

[0005] In order to overcome the shortcomings and deficiencies in the prior art, one of the purposes of the present application is to provide a kind of silicone emulsion defoaming agent, which has the characteristics of strong defoaming ability, long-lasting inhibition, high compatibility, stable chemical properties, non-toxic and odorless, has a very wide market application value, and is especially suitable for foam elimination of water-based ink and water-based paint, effectively avoiding the problems of pinholes and shrinkage in water-based ink and paint system caused by compatibility problems.

[0006] The second purpose of the present application is to provide a preparation method of the silicone emulsion defoaming agent, which is simple to operate, easy to control, high in production efficiency and low in production cost, and can be used for large-scale production.

[0007] The organic silicone emulsion defoamer of the present application comprises the following raw materials in the following weight parts: 10-50 parts of silicone grease, 1-10 parts of emulsifier, 1-5 parts of thickening agent, and 40-80 parts of dispersion medium, wherein the silicone grease is synthesized by reacting silicone oil and acrylate monomer.

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

[0009] (R1), octamethylcyclotetrasiloxane, methyltrimethoxysilane and silicone coupling agent are mixed uniformly, a catalyst is added, and reaction is carried out at a temperature of 100-120℃ for 2-3h, then the temperature is lowered to 80-90℃, water is added and stirred uniformly, then the temperature is raised to 170-200℃, and low-boiling-point substances in the product are removed by vacuumization to obtain silicone oil;

[0010] (R2), the silicone oil of step (R1) is mixed with acrylate monomer, then concentrated sulfuric acid is added and stirred uniformly, reaction is carried out at a temperature of 50-60℃ for 2-3h, and the sulfuric acid is removed by standing and separation, then sodium bicarbonate is added for neutralization and filtration to obtain silicone grease.

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

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

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

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

[0015] Preferably, the acrylate monomer is butyl acrylate and / or methyl methacrylate.

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

[0017] Preferably, the thickening agent is sodium polyacrylate; and the dispersion medium is deionized water.

[0018] The second object of the present application is achieved by the following technical solution: the preparation method of the organic silicone emulsion defoaming agent comprises the following steps:

[0019] (S1), take silicone grease, emulsifier, thickening agent and dispersion medium by weight parts, standby;

[0020] (S2), the silicone grease and the emulsifier are added into the reaction kettle in sequence, stirred uniformly at a speed of 600-800 rpm, heated to 30-50 DEG C, then the dispersion medium is added dropwise while stirring, and then incubated for 1-3 h to obtain a first mixture;

[0021] (S3), the thickening agent is added to the first mixture, and stirred and dispersed at a speed of 300-500 rpm for 1-2 h to obtain a second mixture;

[0022] (S4), the second mixture is treated by colloid mill and filtered to obtain the organic silicone emulsion defoaming agent.

[0023] The present application has the following advantages:

[0024] Firstly, the organic silicone emulsion defoaming agent has the characteristics of strong defoaming ability, long-lasting foam suppression, high compatibility, stable chemical properties, non-toxic and odorless, and has a wide market application value, especially suitable for foam elimination of water-based ink and water-based paint, effectively avoiding the problem of compatibility causing pinholes, shrinkage and other problems of water-based ink and paint system.

[0025] Secondly, the organic silicone emulsion defoaming agent uses silicone grease, the inner layer of which is composed of silicone oil and the outer layer is composed of acrylic ester monomer, which not only retains the high-efficiency foam elimination effect of the inner layer siloxane, but also utilizes the characteristics of the outer layer acrylic ester to obtain better compatibility with the paint, which complements each other, is conducive to maintaining excellent defoaming and foam suppression performance, and is conducive to avoiding the problem of compatibility causing pinholes, shrinkage and other problems of water-based ink and paint system.

[0026] Thirdly, the outer layer of the silicone grease used in the organic silicone emulsion defoaming agent is composed of acrylic ester monomer, and the acrylic ester in the outer layer is more matched with the components in the paint.

[0027] Fourthly, the inner layer of the silicone grease used in the organic silicone emulsion defoaming agent is composed of methyltrimethoxysilane, octamethylcyclotetrasiloxane and siloxane coupling agent to form a spherical network structure, which is stable and not easy to decompose, so it has the characteristics of fast defoaming and long-lasting foam suppression. Moreover, the siloxane coupling agent uses gamma-methacryloyloxypropyltrimethoxysilane, which has low surface tension and excellent wetting performance, and improves the wettability and adhesion of the material surface.

[0028] The fifth, the silicone emulsion defoamer, the emulsifier and thickener are added to make the silicone defoamer more stable, keep its long-lasting defoaming and bubble suppressing performance, and overcome the difficulty in transportation and storage, and be more convenient in transportation, storage and use.

[0029] The sixth, the preparation method of the silicone emulsion defoamer is simple, the production cost is low, the processing technology is mature, and the silicone emulsion defoamer can be prepared, has good defoaming effect, long-lasting bubble suppressing performance, is environment-friendly and pollution-free, and has good performance indexes. DETAILED DESCRIPTION

[0030] In order to facilitate the understanding of those skilled in the art, the present application is further described below in combination with examples, and the content mentioned in the embodiments is not a limitation on the present application.

[0031] The silicone emulsion defoamer of the present application is suitable for foam elimination of water-based ink and water-based paint, and effectively avoids the pinhole, shrinkage and other problems of the water-based ink and paint system caused by the compatibility problem.

[0032] The silicone emulsion defoamer of the present application comprises the following raw materials 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 reaction of silicone oil and acrylate monomer;

[0033] The silicone emulsion defoamer of the present application adopts special synthetic silicone grease, the silicone grease is synthesized by reaction of silicone oil and acrylate monomer, forms a special structure composed of silicone oil in the inner layer and acrylate monomer in the outer layer, retains the high-efficiency elimination effect of the inner layer siloxane on the foam, utilizes the characteristics of the outer layer acrylate to obtain better compatibility with the paint, and the two complement each other, which is beneficial to maintaining excellent defoaming and bubble suppressing performance and avoiding the pinhole, shrinkage and other problems of the water-based ink and paint system caused by the compatibility problem, and the emulsifier, thickener and dispersion medium jointly act to make the silicone emulsion defoamer more stable, keep its long-lasting defoaming and bubble suppressing performance, overcome the difficulty in transportation and storage, and be more convenient in transportation, storage and use, so that the silicone emulsion defoamer has the characteristics of strong defoaming ability, long-lasting bubble suppressing performance, high compatibility, stable chemical properties, non-toxicity and odorlessness, and has wide market application value, especially is suitable for foam elimination of water-based ink and water-based paint, and effectively avoids the pinhole, shrinkage and other problems of the water-based ink and paint system caused by the compatibility problem.

[0034] The weight fraction of the silicone grease can be but is not limited to 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts or 50 parts;

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

[0036] The weight fraction of the thickening agent can be, but is not limited to, 1 part, 2 parts, 3 parts, 4 parts, or 5 parts.

[0037] As a technical solution of the present application, the synthesis method of the silicone oil comprises the following steps:

[0038] (R1), octamethylcyclotetrasiloxane, methyltrimethoxysilane, and a siloxane coupling agent are uniformly mixed, a catalyst is added, and reaction is carried out at a temperature of 100-120°C for 2-3h, then the temperature is lowered to 80-90°C, water is added and stirred uniformly, then the temperature is raised to 170-200°C, low-boiling-point substances in the product are removed by vacuum extraction, and a silicone oil is obtained;

[0039] (R2), the silicone oil obtained in step (R1) is mixed with an acrylic ester monomer, then concentrated sulfuric acid is added and stirred uniformly, reaction is carried out at a temperature of 50-60°C for 2-3h, the sulfuric acid is removed by standing and separation, sodium bicarbonate is added for neutralization and filtration, and a silicone oil is obtained.

[0040] In the above synthesis method of the silicone oil, the spherical network structure is synthesized by using methyltrimethoxysilane, octamethylcyclotetrasiloxane, and a siloxane coupling agent in step (R1), which has stable structure and is not easy to decompose, thus having the characteristics of fast defoaming and long-lasting defoaming inhibition. In step (R2), the acrylic ester monomer is introduced, and an inner-outer layer structure is formed after reaction, and the outer layer of the acrylic ester is more compatible with the components in the paint.

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

[0042] As a technical solution of the present application, the weight amount of the siloxane coupling agent is 1%-5% of the total amount of the octamethylcyclotetrasiloxane and the methyltrimethoxysilane; and the siloxane coupling agent is γ-methacryloyloxypropyltrimethoxysilane.

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

[0044] As a technical solution of the present application, the weight ratio of the silicone oil and the acrylic ester monomer is 1:1-2:1; and the weight amount of the concentrated sulfuric acid is 2-4% of the total amount of the silicone oil and the acrylic ester monomer.

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

[0046] As a technical scheme of the present application, 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 to 2:1.

[0047] As a technical scheme of the present application, the thickening agent is sodium polyacrylate; and the dispersion medium is deionized water.

[0048] The preparation method of the silicone emulsion defoaming agent of the present application comprises the following steps:

[0049] (S1), take silicone oil, emulsifier, thickening agent and dispersion medium by weight parts, for standby;

[0050] (S2), add silicone oil and emulsifier into a reaction kettle in sequence, stir uniformly at a rotation speed of 600-800 rpm, then heat to 30-50℃, then add the dispersion medium while stirring, and then keep the temperature for 1-3 h to obtain a first mixture;

[0051] (S3), add the thickening agent into the first mixture, stir and disperse at a rotation speed of 300-500 rpm for 1-2 h to obtain a second mixture;

[0052] (S4), filter the second mixture after colloid mill treatment to obtain the silicone emulsion defoaming agent.

[0053] To better illustrate the purpose, technical scheme and beneficial effects of the present application, the present application will be further described below in combination with specific examples. It should be noted that the following implementation of the method is a further explanation and description of the present application, and should not be regarded as a limitation of the present application.

[0054] The preparation method of the silicone oil A comprises the following steps: mix octamethylcyclotetrasiloxane and methyltrimethoxysilane in a weight ratio of 10:1, add 1% of siloxane coupling agent (γ-methacryloyloxypropyltrimethoxysilane) based on the total weight of octamethylcyclotetrasiloxane and methyltrimethoxysilane, uniformly mix, then add 0.01% of potassium hydroxide based on the total amount of octamethylcyclotetrasiloxane, methyltrimethoxysilane and siloxane coupling agent, heat to 100℃, react for 2 h, cool to 90℃, add deionized water, stir uniformly, heat to 170℃, and remove low-boiling-point substances in the silicone oil by vacuum to obtain the silicone oil.

[0055] The preparation method of the silicone oil B comprises the following steps: mixing octamethylcyclotetrasiloxane and methyltrimethoxysilane according to the weight ratio of 8:1, adding 5% of siloxane coupling agent (γ-methacryloyloxypropyltrimethoxysilane) of the total weight of the octamethylcyclotetrasiloxane and the methyltrimethoxysilane, uniformly mixing, adding 0.01% of potassium hydroxide of the total amount of the octamethylcyclotetrasiloxane, the methyltrimethoxysilane and the siloxane coupling agent, increasing the temperature to 120 DEG C, reacting for 3h, decreasing the temperature to 80 DEG C, adding deionized water, uniformly stirring, increasing the temperature to 200 DEG C, and removing low-boiling substances in the silicone oil by vacuumizing to obtain the silicone oil.

[0056] The synthesis method of the silicone grease A comprises the following steps: mixing silicone oil A, butyl acrylate and methyl methacrylate according to the weight ratio of 4:1:3, adding 3% of concentrated sulfuric acid of the total amount of the silicone oil A, the butyl acrylate and the methyl methacrylate, stirring, reacting for 2h under the temperature condition of 50 DEG C, separating and removing the sulfuric acid, adding sodium bicarbonate for neutralization and filtering to obtain the silicone grease A.

[0057] The synthesis method of the silicone grease B comprises the following steps: mixing silicone oil A, butyl acrylate and methyl methacrylate according to the weight ratio of 6:1:5, adding 3% of concentrated sulfuric acid of the total amount of the silicone oil A, the butyl acrylate and the methyl methacrylate, stirring, reacting for 2h under the temperature condition of 60 DEG C, separating and removing the sulfuric acid, adding sodium bicarbonate for neutralization and filtering to obtain the silicone grease B.

[0058] The synthesis method of the silicone grease C comprises the following steps: mixing silicone oil B, butyl acrylate and methyl methacrylate according to the weight ratio of 4:1:3, adding 3% of concentrated sulfuric acid of the total amount of the silicone oil B, the butyl acrylate and the methyl methacrylate, stirring, reacting for 3h under the temperature condition of 50 DEG C, separating and removing the sulfuric acid, adding sodium bicarbonate for neutralization and filtering to obtain the silicone grease C.

[0059] The synthesis method of the silicone grease D comprises the following steps: mixing silicone oil B, butyl acrylate and methyl methacrylate according to the weight ratio of 6:1:5, adding 3% of concentrated sulfuric acid of the total amount of the silicone oil B, the butyl acrylate and the methyl methacrylate, stirring, reacting for 3h under the temperature condition of 60 DEG C, separating and removing the sulfuric acid, adding sodium bicarbonate for neutralization and filtering to obtain the silicone grease D.

[0060] The synthesis method of the silicone grease E comprises the following steps: mixing silicone oil B, butyl acrylate and methyl methacrylate according to the weight ratio of 8:1:3, adding 3% of concentrated sulfuric acid of the total amount of the silicone oil B, the butyl acrylate and the methyl methacrylate, stirring, reacting for 3h under the temperature condition of 60 DEG C, separating and removing the sulfuric acid, adding sodium bicarbonate for neutralization and filtering to obtain the silicone grease E.

[0061] The synthesis method of the silicone grease F comprises the following steps: mixing silicone oil A, butyl acrylate and methyl methacrylate in a weight ratio of 3:1:5, adding 3% concentrated sulfuric acid of the total amount of silicone oil B, butyl acrylate and methyl methacrylate, stirring, reacting at 60°C for 3h, separating and removing sulfuric acid, adding sodium bicarbonate for neutralization and filtering to obtain the silicone grease F.

[0062] The synthesis method of the silicone grease G comprises the following steps: mixing silicone oil B, butyl acrylate and methyl methacrylate in a weight ratio of 9:1:3, adding 3% concentrated sulfuric acid of the total amount of silicone oil B, butyl acrylate and methyl methacrylate, stirring, reacting at 60°C for 3h, separating and removing sulfuric acid, adding sodium bicarbonate for neutralization and filtering to obtain the silicone grease G.

[0063] Example 1

[0064] The silicone emulsion defoamer of the example comprises the following raw materials in parts by weight: 25g of silicone grease A, 1.5g of polyoxyethylene sorbitan monostearate, 1.5g of sorbitan monostearate, 5g of sodium polyacrylate, 60g of deionized water.

[0065] The preparation method of the silicone emulsion defoamer of the example comprises the following steps: in the first step, the formula amount of silicone grease A, polyoxyethylene sorbitan monostearate and sorbitan monostearate are sequentially added to a reaction kettle, stirred uniformly at a speed of 600rpm, heated to 50°C, and deionized water is added dropwise while stirring, and the first mixture is obtained after 3h of incubation; in the second step, the thickening agent sodium polyacrylate is added to the first mixture, and the second mixture is obtained after 2h of stirring and dispersion at a speed of 500rpm; in the third step, the second mixture is treated by a colloid mill and filtered to obtain the silicone emulsion defoamer.

[0066] Example 2

[0067] The silicone emulsion defoamer of the example comprises the following raw materials in parts by weight: 25g of silicone grease A, 1.5g of polyoxyethylene sorbitan monostearate, 1.5g of sorbitan monostearate, 5g of sodium polyacrylate, 60g of deionized water.

[0068] The preparation method of the silicone emulsion defoamer of the example comprises the following steps: in the first step, the formula amount of silicone grease B, polyoxyethylene sorbitan monostearate and sorbitan monostearate are sequentially added to a reaction kettle, stirred uniformly at a speed of 800rpm, heated to 45°C, and deionized water is added dropwise while stirring, and the first mixture is obtained after 3h of incubation; in the second step, the thickening agent sodium polyacrylate is added to the first mixture, and the second mixture is obtained after 2h of stirring and dispersion at a speed of 500rpm; in the third step, the second mixture is treated by a colloid mill and filtered to obtain the silicone emulsion defoamer.

[0069] Example 3

[0070] The silicone emulsion defoamer of the present example comprises the following raw materials 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 of the present example comprises the following steps: first, the formula amount of silicone grease C, polyoxyethylene sorbitan monostearate, and sorbitan monostearate are sequentially added to a reaction kettle, stirred uniformly at a speed of 800 rpm, heated to 40°C, and deionized water is added dropwise while stirring, and kept for 3 h to obtain a first mixture; second, a thickening agent, sodium polyacrylate, is added to the first mixture, stirred and dispersed at a speed of 500 rpm for 2 h to obtain a second mixture; third, the second mixture is subjected to colloid mill treatment and then filtered to obtain the silicone emulsion defoamer.

[0072] Example 4

[0073] The silicone emulsion defoamer of the present example comprises the following raw materials 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 of the present example comprises the following steps: first, the formula amount of silicone grease D, polyoxyethylene sorbitan monostearate, and sorbitan monostearate are sequentially added to a reaction kettle, stirred uniformly at a speed of 800 rpm, heated to 35°C, and deionized water is added dropwise while stirring, and kept for 3 h to obtain a first mixture; second, a thickening agent, sodium polyacrylate, is added to the first mixture, stirred and dispersed at a speed of 500 rpm for 2 h to obtain a second mixture; third, the second mixture is subjected to colloid mill treatment and then filtered to obtain the silicone emulsion defoamer.

[0075] Example 5

[0076] The silicone emulsion defoamer of the present example comprises the following raw materials 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 organic silicone emulsion defoamer of the embodiment comprises the following steps: in the first step, formula amount of silicone grease E, polyoxyethylene sorbitan monostearate and sorbitan monostearate are sequentially added into a reaction kettle, after being uniformly stirred at a rotation speed of 800 rpm, the temperature is raised to 30 DEG C, deionized water is added dropwise while stirring, and the first mixture is obtained after 3h of heat preservation; in the second step, thickener sodium polyacrylate is added into the first mixture, and the second mixture is obtained after 2h of dispersion stirring at a rotation speed of 500 rpm; in the third step, the second mixture is treated by a colloid mill and filtered to obtain the organic silicone emulsion defoamer.

[0078] Comparative Example 1

[0079] The organic silicone emulsion defoamer of the comparative example comprises the following raw materials in weight parts: 45g of silicone grease F, 1.5g of polyoxyethylene sorbitan monostearate, 1.5g of sorbitan monostearate, 4g of sodium polyacrylate and 70g of deionized water.

[0080] The preparation method of the organic silicone emulsion defoamer of the comparative example comprises the following steps: in the first step, formula amount of silicone grease F, polyoxyethylene sorbitan monostearate and sorbitan monostearate are sequentially added into a reaction kettle, after being uniformly stirred at a rotation speed of 800 rpm, the temperature is raised to 40 DEG C, deionized water is added dropwise while stirring, and the first mixture is obtained after 3h of heat preservation; in the second step, thickener sodium polyacrylate is added into the first mixture, and the second mixture is obtained after 2h of dispersion stirring at a rotation speed of 500 rpm; in the third step, the second mixture is treated by a colloid mill and filtered to obtain the organic silicone emulsion defoamer.

[0081] Comparative Example 2

[0082] The organic silicone emulsion defoamer of the comparative example comprises the following raw materials in weight parts: 45g of silicone grease G, 1.5g of polyoxyethylene sorbitan monostearate, 1.5g of sorbitan monostearate, 4g of sodium polyacrylate and 70g of deionized water.

[0083] The preparation method of the organic silicone emulsion defoamer of the comparative example comprises the following steps: in the first step, formula amount of silicone grease G, polyoxyethylene sorbitan monostearate and sorbitan monostearate are sequentially added into a reaction kettle, after being uniformly stirred at a rotation speed of 800 rpm, the temperature is raised to 40 DEG C, deionized water is added dropwise while stirring, and the first mixture is obtained after 3h of heat preservation; in the second step, thickener sodium polyacrylate is added into the first mixture, and the second mixture is obtained after 2h of dispersion stirring at a rotation speed of 500 rpm; in the third step, the second mixture is treated by a colloid mill and filtered to obtain the organic silicone emulsion defoamer.

[0084] Performance test

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

[0086] (1) Compatibility test:

[0087] In a 300 mL beaker, 200 mL of acrylic emulsion or styrene-acrylic emulsion was weighed, 1 mL of each defoamer was added, and magnetic stirring was performed for 30 min. After standing for 5 min, a 75 um paint film was prepared on a black and white grid paper using a film applicator, and the film forming effect of each sample was compared. The data is shown in Table 1.

[0088] Table 1 Compatibility performance test

[0089] Acrylic emulsion compatibility Styrene-acrylic emulsion compatibility Example 1 Smooth and free of shrinkage Smooth and free of shrinkage Example 2 Smooth and free of shrinkage Smooth and free of shrinkage Example 3 Smooth and free of shrinkage Smooth and free of shrinkage Example 4 Smooth and free of shrinkage Smooth and free of shrinkage Example 5 Smooth and free of shrinkage Smooth and free of shrinkage Comparative Example 1 Smooth and free of shrinkage Slight shrinkage Comparative Example 2 Slight shrinkage Slight shrinkage Silicone defoamer AT-990 Severe shrinkage Severe shrinkage Polyether defoamer DT-057 Smooth and free of shrinkage Smooth and free of shrinkage Mineral oil defoamer ST2410 Slight shrinkage Slight shrinkage

[0090] (2) Defoaming performance:

[0091] In a 300 mL beaker, 200 mL of acrylic emulsion or styrene-acrylic emulsion was weighed, 2.0 mL of each defoamer was added, and high-speed dispersion was performed at a speed of 2000 rpm for 20 min. After completion, the emulsion was immediately poured into a 100 mL density cup that had been peeled off on an electronic scale until the cup cover was just overflowing, and the corresponding weight m was read. At this time, the greater the density of the emulsion, the better the defoaming performance of the defoamer, and the data is shown in Table 2.

[0092] Table 2 Defoaming performance test

[0093]

[0094]

[0095] From the results of Table 1 and Table 2, the compatibility and defoaming performance of the silicone defoamers of Examples 1-5 are better than those of Comparative Examples 1-2 and the silicone defoamer AT-990, the polyether defoamer DT-057 and the mineral oil defoamer ST 2410. This is mainly due to the special synthetic silicone grease contained in Examples 1-5, which improves the defoaming performance and compatibility of the defoamers. Specifically, the silicone grease has an inner layer composed of methyltrimethoxysilane, octamethylcyclotetrasiloxane and γ-methacryloyloxypropyltrimethoxysilane, which is stable and not easy to decompose, and has a spherical network structure. The outer layer of the silicone grease is composed of butyl acrylate and methyl methacrylate, which wraps the inner layer, thus preserving the rapid elimination and long-term antifoaming effect of the inner layer siloxane on the foam, while the acrylate monomers in the outer layer are more compatible with the components in the coating, and do not cause pinholes and shrinkage holes during the coating process to affect the appearance quality of the coating.

[0096] The above embodiments are the preferred implementation of the present application, in addition to this, the present application can be implemented in other ways, without departing from the concept of the present application, any obvious replacement within the protection scope of the present application.

Claims

1. A silicone emulsion antifoam agent characterized in that, The raw materials include 10-50 parts of silicone oil, 1-10 parts of emulsifier, 1-5 parts of thickening agent, and 40-80 parts of dispersion medium, wherein the silicone oil is synthesized by reacting silicone oil and acrylate monomer; The synthesis method of the silicone oil comprises the following steps: (R1), uniformly mix octamethylcyclotetrasiloxane, methyltrimethoxysilane and siloxane coupling agent, then add catalyst, react at 100-120℃ for 2-3h, then cool to 80-90℃, add water and stir uniformly, then heat to 170-200℃, remove low boiling point substances in the product by vacuum, to obtain silicone oil; (R2), add acrylate monomer to the silicone oil of step (R1) and mix, then add concentrated sulfuric acid and stir uniformly, react at 50-60℃ for 2-3h, separate and remove sulfuric acid, add sodium bicarbonate to neutralize and filter, to obtain silicone oil; The weight ratio of the silicone oil and acrylate monomer is 1:1-2:1; the weight amount of the concentrated sulfuric acid is 2-4% of the total amount of the silicone oil and acrylate monomer; The acrylate monomer is a mixture of butyl acrylate and methyl methacrylate in a weight ratio of 1:3-1:

5.

2. The silicone emulsion defoamer according to claim 1, characterized in that: The weight ratio of the octamethylcyclotetrasiloxane and methyltrimethoxysilane is 8:1-10:

1.

3. The silicone emulsion defoamer according to claim 1, characterized in that: The weight amount of the siloxane coupling agent is 1%-5% of the total amount of the octamethylcyclotetrasiloxane and methyltrimethoxysilane; the siloxane coupling agent is γ-methacryloyloxypropyltrimethoxysilane.

4. The silicone emulsion defoamer of claim 1, wherein: The weight amount of the catalyst is 0.01-0.02% of the total amount of the octamethylcyclotetrasiloxane, methyltrimethoxysilane and siloxane coupling agent; the catalyst is potassium hydroxide.

5. The silicone emulsion defoamer of claim 1, wherein: The emulsifier is at least one of polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, sorbitan monostearate and sorbitan monooleate.

6. The silicone emulsion defoamer of claim 1, wherein: The thickening agent is sodium polyacrylate; the dispersion medium is deionized water.

7. A process for the preparation of a silicone emulsion antifoam agent as claimed in any one of claims 1 to 6, characterized in that The method comprises the following steps: (S1), take silicone oil, emulsifier, thickening agent and dispersion medium by weight parts, for standby use; (S2), add silicone oil and emulsifier into a reaction kettle in sequence, stir uniformly at a speed of 600-800rpm, then heat to 30-50℃, then add dispersion medium dropwise while stirring, and keep for 1-3h to obtain a first mixture; (S3), add thickening agent to the first mixture and stir and disperse at a speed of 300-500rpm for 1-2h to obtain a second mixture; (S4), filter after colloid mill treatment of the second mixture to obtain silicone emulsion defoamer.

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