Modified siloxane defoaming agent and preparation method thereof

Abstract

The invention relates to the field of paint and ink auxiliaries, in particular to a modified siloxane defoaming agent and a preparation method thereof. The modified siloxane defoaming agent is prepared from the following raw materials: a composite modified siloxane matrix, basic siloxane, a synergist, a catalyst, a solvent and the like. The finally prepared defoaming agent product not only can effectively solve the compatibility problem and the durability problem of the conventional coating / printing ink defoaming agent, but also can further improve the multifunctionality of the defoaming agent, gives consideration to more synergistic improvement effects, enhances the application of the defoaming agent in a more complex and higher-requirement coating / printing ink system, and has a wide application prospect. The defoaming agent has excellent application potential, and a new idea is provided for improving the comprehensive performance of the defoaming agent.

Description

Technical Field

[0001] The present application relates to the field of coating and ink additives, and more particularly to a modified silicone defoamer and its preparation method. Background Art

[0002] During the production and construction of coatings and inks, due to the use of additives such as surfactants and dispersants, as well as process steps such as mechanical stirring and high-speed coating, bubbles in the micron to millimeter range are extremely likely to be generated. If these bubbles are not effectively eliminated, defects such as pinholes, orange peel, and shrinkage holes will appear on the coating surface, and at the same time, the printing uniformity and adhesion of the ink will be affected. Therefore, an efficient defoamer is an essential functional additive in the coating and ink formulations.

[0003] As a high-performance defoaming material, modified silicone defoamers have excellent defoaming and foam suppression capabilities due to their unique chemical structures. They are usually synthesized by introducing organic groups into the silicone chain, which enables them to have both the compatibility of organic compounds and retain the low surface tension characteristics of silicone. Such defoamers can effectively reduce or suppress the formation of foam and have good compatibility with both aqueous and solvent-based systems.

[0004] However, despite the many advantages of modified silicone defoamers, existing products and technologies still have some limitations. For example: compatibility issues. Although modified silicone defoamers have better compatibility than traditional silicone defoamers, in some specific coating and ink systems, incompatibility may still occur, resulting in surface defects such as shrinkage holes, orange peel, or blooming on the coating film; persistence issues. In some applications that require long-term stirring or continuous treatment of foam, the persistence of some defoamers is insufficient to maintain long-term effective defoaming effects; lack of multifunctionality. Existing products mainly focus on the single function of defoaming and are difficult to take into account the synergistic performance in aspects such as dispersion, leveling, or wetting, resulting in increased application difficulties. Summary of the Invention

[0005] Therefore, in order to effectively solve the above-mentioned existing problems, the present application provides a modified silicone defoamer and its preparation method. The finally prepared defoamer product of the present application can not only effectively solve the compatibility and persistence problems of conventional coating / ink defoamers, but also further improve the multifunctionality of the defoamer, take into account more synergistic improvement effects, enhance the application of the defoamer in more complex and higher requirement coating / ink systems, has excellent application potential, and provides new ideas for the improvement of the comprehensive performance of defoamers.

[0006] Modified silicone defoamer, calculated by mass parts, the raw materials are composed of the following components: 25-40 parts of composite modified silicone matrix, 15-25 parts of basic silicone, 3-8 parts of synergist, 1-3 parts of dispersant, 0.3-1 part of stabilizer, 0.1-0.4 part of catalyst, and 15-30 parts of solvent.

[0007] As a preferred embodiment, the mass ratio of the composite modified silicone matrix, basic silicone and synergist is (28-40):(20-24):(4-6).

[0008] As a more preferred embodiment, the mass ratio of the composite modified silicone matrix, basic silicone and synergist is (30-33):(21-22):(4.5-5.5).

[0009] As a preferred embodiment, the preparation method of the composite modified silicone matrix specifically includes the following steps: S1: Under nitrogen protection, add the main chain silicone and xylene into the reaction kettle, heat up and stir until completely dissolved; S2: Add the modified monomer and stir at a constant temperature, then add the initiator and heat up to react to obtain a graft copolymer; S3: Carry out vacuum distillation, and the final product is obtained after removing xylene.

[0010] As a more preferred embodiment, the preparation method of the composite modified silicone matrix specifically includes the following steps: S1: Under nitrogen protection, add methyl vinyl silicone and xylene into the reaction kettle, heat up to 75-80 °C, and stir at 200-300 rpm until completely dissolved; S2: Add vinyltrifluoropropylcyclotrisiloxane, dodecyl acrylate and allyl glycidyl ether, then stir at a constant temperature for 30-40 min, and then add diisopropylbenzene peroxide and heat up to 85-90 °C to react for 5-6 h to obtain a graft copolymer; S3: Carry out vacuum distillation at -0.09 MPa to -0.08 MPa and 90-95 °C, and the final product is obtained after removing xylene.

[0011] As a preferred embodiment, the average molecular weight of the methyl vinyl silicone is 5000-8000 Da.

[0012] As a preferred embodiment, the mass ratio of the methyl vinyl silicone, vinyltrifluoropropylcyclotrisiloxane, dodecyl acrylate and allyl glycidyl ether is (9-10):(1.5-2):(1-1.2):(0.6-0.9).

[0013] As a more preferred embodiment, the mass ratio of the methyl vinyl silicone, vinyltrifluoropropylcyclotrisiloxane, dodecyl acrylate and allyl glycidyl ether is (9.5-10):(1.5-1.8):(1-1.1):(0.7-0.8).

[0014] The addition of the above-mentioned composite modified silicone matrix can significantly improve the defoaming performance of the defoamer product of the present application, and has excellent compatibility and defoaming persistence, and further improves the stability, heat resistance and versatility of the defoamer. The introduced fluorine-containing group has an extremely low surface tension, preferentially adsorbs on the surface of the bubble liquid film, destroys the elasticity of the film layer, accelerates the bubble rupture, and is anchored at the bubble interface through the hydrophobic effect of the long-chain alkyl group to form a dense molecular layer, preventing gas diffusion and bubble regeneration, and finally undergoes a ring-opening reaction with hydroxyl groups, carboxyl groups, etc. in the resin during the curing process of the coating / ink to form a chemical bonding network, fixing the defoamer molecules inside the coating to achieve a strong defoaming effect under long-term conditions.

[0015] On the other hand, the composite modified silicone has a higher C-F bond energy, and together with the thermal stability of the silicone main chain, it resists high-temperature degradation. Moreover, the cyclic structure of trifluoropropylcyclotrisiloxane reduces the breakage of molecular chains under high shear through steric hindrance effects. And the overall defoamer system is compatible with both polar (water-based) and non-polar (solvent-based) systems. The long-chain alkyl group and the fluorine chain segment form a hydrophobic core, and the epoxy group is exposed on the molecular surface, matching the polarity of different resin systems through dynamic equilibrium.

[0016] As a more preferred embodiment, the base silicone is a composition of octamethylcyclotetrasiloxane and polydimethylsiloxane.

[0017] As a preferred embodiment, the mass ratio of octamethylcyclotetrasiloxane to polydimethylsiloxane is (2 - 3):(4.2 - 5).

[0018] As a more preferred embodiment, the mass ratio of octamethylcyclotetrasiloxane to polydimethylsiloxane is (2.2 - 2.5):(4.5 - 4.8).

[0019] As a preferred embodiment, the synergist is at least one of fumed silica, polytetrafluoroethylene, calcium stearate, dimethyl silicone oil, and hydrogenated castor oil.

[0020] As a more preferred embodiment, the synergist is a composition of calcium stearate and hydrogenated castor oil.

[0021] As a preferred embodiment, the mass ratio of calcium stearate to hydrogenated castor oil is (0.8 - 1.4):(4 - 5).

[0022] As a more preferred embodiment, the mass ratio of calcium stearate to hydrogenated castor oil is (1 - 1.2):(4.2 - 4.6).

[0023] As a preferred embodiment, the dispersant is at least one of polyacrylate, polyvinylpyrrolidone, castor oil derivatives, and phosphate salts.

[0024] As a preferred embodiment, the dispersant is polyvinylpyrrolidone or phosphate salt.

[0025] As a preferred embodiment, the stabilizer is at least one of 2,6 - di - tert - butyl - p - cresol, triphenyl phosphite and epoxidized soybean oil.

[0026] As a preferred embodiment, the stabilizer is 2,6 - di - tert - butyl - p - cresol.

[0027] As a preferred embodiment, the catalyst is at least one of tetramethylammonium hydroxide, dibutyltin dilaurate and tetra - isopropyl titanate.

[0028] As a preferred embodiment, the catalyst is dibutyltin dilaurate.

[0029] As a preferred embodiment, the solvent is at least one of butyl acetate, cyclohexanone, isopropyl alcohol and propylene glycol monomethyl ether acetate.

[0030] As a preferred embodiment, the solvent is butyl acetate or isopropyl alcohol.

[0031] A preparation method of a modified silicone defoamer specifically comprises the following steps: S1: adding a composite - modified silicone matrix, a basic silicone and a synergist into a solvent, heating in a water bath at 50 - 55°C, and dispersing at a high speed of 1500 - 2000 rpm for 30 - 40 min; S2: adding a dispersant and a stabilizer, and circulating and treating through a high - pressure homogenizer 3 times, with a pressure of 45 - 50 MPa, to obtain a uniform dispersion with a particle size < 200 nm; S3: adding a catalyst, stirring and reacting at a constant temperature of 60 - 65°C for 2 - 3 h, controlling the final viscosity at 800 - 1000 cP, and filtering through a 4.5 - 5 μm filter element to remove impurities after completion, thus obtaining the product.

[0032] The beneficial effects of this application are as follows:

[0033] 1. A modified silicone defoamer provided in this application can not only effectively solve the compatibility problem and durability problem of conventional paint / ink defoamers, but also further improve the multifunctionality of the defoamer, take into account more synergistic improvement effects, enhance the application of the defoamer in more complex and higher - requirement paint / ink systems, has excellent application potential, and provides a new idea for improving the comprehensive performance of the defoamer.

[0034] 2. A modified silicone defoamer provided in the present application. The fluorine-containing groups introduced by the composite modified silicone matrix have extremely low surface tension, are preferentially adsorbed on the surface of the bubble liquid film, destroy the elasticity of the film layer, accelerate the rupture of the bubbles, and are anchored at the bubble interface through the hydrophobic action of the long-chain alkyl group to form a dense molecular layer, preventing gas diffusion and bubble regeneration. And finally, during the curing process of the coating / ink, ring-opening reactions occur with hydroxyl groups, carboxyl groups, etc. in the resin to form a chemical bonding network, fixing the defoamer molecules inside the coating to achieve a strong defoaming effect over a long time.

[0035] 3. A modified silicone defoamer provided in the present application. The composite modified silicone matrix can also resist high-temperature degradation by the higher bond energy of the C-F bond and the thermal stability of the silicone main chain. And the cyclic structure of the trifluoropropylcyclotrisiloxane reduces the breakage of the molecular chain under high shear through the steric hindrance effect. And the overall defoamer system is compatible with both polar (aqueous) and non-polar (solvent-based) systems. The long-chain alkyl group and the fluorine chain segment form a hydrophobic core, and the epoxy group is exposed on the molecular surface to match the polarity of different resin systems through dynamic equilibrium. Detailed implementation manners

[0036] In the detailed implementation manners, specific implementation cases will be used to more intuitively display and illustrate the content in the inventive content of the present application.

[0037] Example 1

[0038] The modified silicone defoamer, by mass, is composed of the following components: 30 parts of the composite modified silicone matrix, 21.5 parts of the basic silicone, 4.5 parts of the synergist, 1.6 parts of the dispersant, 0.5 part of the stabilizer, 0.16 part of the catalyst, and 22.5 parts of the solvent.

[0039] The preparation method of the composite modified silicone matrix, by mass, specifically includes the following steps: S1: Under nitrogen protection, 9.8 parts of methyl vinyl siloxane and 50 parts of xylene are added to the reaction kettle, heated to 80 °C, and stirred at 200 rpm until completely dissolved; S2: 1.6 parts of vinyltrifluoropropylcyclotrisiloxane, 1.1 parts of dodecyl acrylate, and 0.7 part of allyl glycidyl ether are added and stirred at a constant temperature for 35 min, and then dicumyl peroxide is added and the temperature is raised to 85 °C for reaction for 5 h to obtain a graft copolymer; S3: Under -0.09 MPa and 90 °C, vacuum distillation is carried out to remove xylene to obtain the final product.

[0040] The average molecular weight of methyl vinyl siloxane is 6000 Da, and it is purchased from the product of the DC1107Fluid model sold by Dow Chemical Company in the United States.

[0041] The basic silicone is a composition of octamethylcyclotetrasiloxane and polydimethylsiloxane, and the mass ratio is 2.3:4.7.

[0042] Octamethylcyclotetrasiloxane was purchased as a high-quality product sold by Shouhua Chemical Co., Ltd. in Shandong, China.

[0043] Polydimethylsiloxane was purchased as the PMX-200 model product sold by Dow Corning Corporation in the United States.

[0044] The synergist is a composition of calcium stearate and hydrogenated castor oil, with a mass ratio of 1:4.5; the hydrogenated castor oil was purchased as the PEG-7 hydrogenated castor oil product sold by Wuhan Huaxiang Kejie Biotechnology Co., Ltd. in China.

[0045] The dispersant is polyvinylpyrrolidone K30; the stabilizer is 2,6-di-tert-butyl-p-cresol; the catalyst is dibutyltin dilaurate; the solvent is isopropanol.

[0046] A method for preparing a modified silicone defoamer specifically includes the following steps: S1: Add the composite modified silicone matrix, basic silicone and synergist to the solvent, heat in a water bath at 50°C, and disperse at high speed at 2000 rpm for 30 min; S2: Add the dispersant and stabilizer, and circulate through a high-pressure homogenizer 3 times at a pressure of 50 MPa to obtain a uniform dispersion with a particle size <200 nm; S3: Add the catalyst, stir and react at a constant temperature of 60°C for 3 h, control the final viscosity at 900 cP, and after completion, filter through a 5-μm filter element to remove impurities to obtain the product.

[0047] Example 2

[0048] This example only differs from Example 1 in the following aspects: For the modified silicone defoamer, by mass, the raw materials consist of the following components: 38.5 parts of the composite modified silicone matrix, 20 parts of the basic silicone, 5.8 parts of the synergist, 1.8 parts of the dispersant, 0.4 part of the stabilizer, 0.18 part of the catalyst, and 24.5 parts of the solvent.

[0049] The basic silicone is a composition of octamethylcyclotetrasiloxane and polydimethylsiloxane, with a mass ratio of 3:4.2.

[0050] Example 3

[0051] This example only differs from Example 1 in the following aspects: For the modified silicone defoamer, by mass, the raw materials consist of the following components: 28.5 parts of the composite modified silicone matrix, 23.8 parts of the basic silicone, 4.2 parts of the synergist, 1.4 parts of the dispersant, 0.6 part of the stabilizer, 0.16 part of the catalyst, and 27.5 parts of the solvent.

[0052] The basic silicone is a composition of octamethylcyclotetrasiloxane and polydimethylsiloxane, with a mass ratio of 2:5.

[0053] Comparative Example 1

[0054] This comparative example is only different from Example 1 in the following aspects: For the modified silicone defoamer, calculated by mass, the raw materials are composed of the following components: 15.5 parts of composite modified silicone matrix, 40 parts of basic silicone, 6.6 parts of synergist, 2.2 parts of dispersant, 0.8 part of stabilizer, 0.22 part of catalyst, and 30 parts of solvent.

[0055] Comparative Example 2

[0056] This comparative example is only different from Example 1 in the following aspects: For the modified silicone defoamer, calculated by mass, the raw materials are composed of the following components: 55 parts of composite modified silicone matrix, 5.5 parts of basic silicone, 4.8 parts of synergist, 1.1 parts of dispersant, 0.5 part of stabilizer, 0.12 part of catalyst, and 24 parts of solvent.

[0057] Comparative Example 3

[0058] This comparative example is only different from Example 1 in the following aspects: The basic silicone is a composition of octamethylcyclotetrasiloxane and polydimethylsiloxane, and the mass ratio is 5:1.

[0059] Comparative Example 4

[0060] This comparative example is only different from Example 1 in the following aspects: The basic silicone is a composition of octamethylcyclotetrasiloxane and polydimethylsiloxane, and the mass ratio is 1:8.

[0061] Comparative Example 5

[0062] This comparative example is only different from Example 1 in the following aspects: For the preparation method of the composite modified silicone matrix, calculated by mass, it specifically includes the following steps: S1: Under nitrogen protection, add 9.8 parts of methyl vinyl silicone and 50 parts of xylene to the reaction kettle, heat up to 80 °C, and stir at 200 rpm until completely dissolved; S2: Add 2.8 parts of vinyltrifluoropropylcyclotrisiloxane, 0.4 part of dodecyl acrylate, and 0.2 part of allyl glycidyl ether, then stir at a constant temperature for 35 min, and then add diisopropylbenzene peroxide and heat up to 85 °C for reaction for 5 h to obtain a graft copolymer; S3: Under -0.09 MPa and 90 °C, carry out vacuum distillation to remove xylene to obtain the final product.

[0063] Comparative Example 6

[0064] This comparative example is only different from Example 1 in the following aspects: The preparation method of the composite modified silicone matrix, in parts by mass, specifically includes the following steps: S1: Under nitrogen protection, add 9.8 parts of methyl vinyl silicone and 50 parts of xylene to the reaction kettle, heat up to 80 °C, and stir at 200 rpm until completely dissolved; S2: Add 0.8 part of vinyltrifluoropropylcyclotrisiloxane, 2.6 parts of dodecyl acrylate and 0.5 part of allyl glycidyl ether, then stir at a constant temperature for 35 min, and then add diisopropylbenzene peroxide and heat up to 85 °C for reaction for 5 h to obtain a graft copolymer; S3: Carry out vacuum distillation at -0.09 MPa and 90 °C, and remove xylene to obtain the final product.

[0065] Performance Evaluation

[0066] 1. Use the defoamers prepared in the comparative example and the example, adopt the same existing commercially available acrylic resin emulsion system (solid content 50%, purchased from the A378X model product sold by BASF Corporation, Germany), the addition amount of the defoamer is 1 wt%, introduce bubbles with a high-speed disperser by stirring at 2000 rpm for 5 min; immediately take 100 mL of the coating and inject it into a graduated transparent measuring cylinder, record the initial foam volume, and record the test foam volume at the 5 min time point after standing. The defoaming efficiency % = (1 - test foam volume / initial foam volume) × 100%, and the results of 10 tests are averaged and recorded in Table 1.

[0067] 2. Place the defoamer samples prepared in the example and the comparative example in an oven at 150 °C and heat for 168 h. After cooling to room temperature, test the defoaming efficiency according to the scheme in Performance Test 1, calculate the retention rate of the defoaming efficiency, and use a rotational rheometer (25 °C, shear rate 10^4 s-1) to test the viscosity change rate. The results of 10 tests are averaged and recorded in Table 1.

[0068] 3. Add the defoamer samples prepared in the example and the comparative example to the carbon black slurry, with an addition amount of 0.3 wt%, and measure the Hegman fineness grade. The results are recorded in Table 1.

[0069] Table 1 Performance Evaluation Table

[0070]

[0071]

[0072] ​From the final performance test results of the examples and comparative examples, Comparative Examples 1-6 achieved worse performance results compared to the examples. The examples, by adopting better technical solutions, prepared a composite modified silicone matrix with fluorine-containing groups having an extremely low surface tension, which preferentially adsorbed on the surface of the bubble liquid film, destroyed the elasticity of the film layer, accelerated the bubble rupture, and was anchored at the bubble interface through the hydrophobic effect of the long-chain alkyl group to form a dense molecular layer, preventing gas diffusion and bubble regeneration. And finally, during the curing process of the coating / ink, ring-opening reactions occurred with hydroxyl groups, carboxyl groups, etc. in the resin to form a chemical bonding network, fixing the defoamer molecules inside the coating and achieving a strong defoaming effect and comprehensive performance over a long period of time.

Claims

1. A modified silicone defoamer, characterized in that: By mass, the raw materials consist of the following components: 25-40 parts of a composite modified silicone matrix, 15-25 parts of a base silicone, 3-8 parts of a synergist, 1-3 parts of a dispersant, 0.3-1 part of a stabilizer, 0.1-0.4 part of a catalyst, and 15-30 parts of a solvent; The preparation method of the composite modified silicone matrix specifically includes the following steps: S1: Under nitrogen protection, add the main-chain silicone and xylene to a reaction kettle, heat up and stir until completely dissolved; S2: Add the modified monomer and stir at a constant temperature, then add the initiator and heat up to react to obtain a graft copolymer; S3: Perform vacuum distillation to remove xylene to obtain the final product; The base silicone is a composition of octamethylcyclotetrasiloxane and polydimethylsiloxane, and the mass ratio is (2-3):(4.2-5).

2. The modified silicone defoamer according to claim 1, wherein: The synergist is at least one of fumed silica, polytetrafluoroethylene, calcium stearate, dimethyl silicone oil, and hydrogenated castor oil.

3. The modified silicone defoamer according to claim 2, wherein: The mass ratio of the composite modified silicone matrix, the base silicone, and the synergist is (28-40):(20-24):(4-6).

4. The modified silicone defoamer according to claim 3, wherein: The preparation method of the composite modified silicone matrix specifically includes the following steps: S1: Under nitrogen protection, add methyl vinyl silicone and xylene to a reaction kettle, heat up to 75-80 °C, and stir at 200-300 rpm until completely dissolved; S2: Add vinyltrifluoropropylcyclotrisiloxane, dodecyl acrylate, and allyl glycidyl ether, then stir at a constant temperature for 30-40 min, and then add diisopropylbenzene peroxide and heat up to 85-90 °C to react for 5-6 h to obtain a graft copolymer; S3: Perform vacuum distillation at -0.09 MPa to -0.08 MPa and 90-95 °C to remove xylene to obtain the final product.

5. The modified silicone defoamer according to claim 4, wherein: The average molecular weight of the methyl vinyl silicone is 5000-8000 Da.

6. The modified silicone defoamer according to claim 5, wherein: The mass ratio of the methyl vinyl silicone, vinyltrifluoropropylcyclotrisiloxane, dodecyl acrylate, and allyl glycidyl ether is (9-10):(1.5-2):(1-1.2):(0.6-0.9).

7. The modified silicone defoamer according to claim 6, characterized in that: The dispersant is at least one of polyacrylate, polyvinylpyrrolidone, castor oil derivative, and phosphate salt.

8. The modified silicone defoamer according to claim 7, wherein: The stabilizer is at least one of 2,6-di-tert-butyl-p-cresol, triphenyl phosphite, and epoxidized soybean oil.

9. The modified silicone defoamer according to claim 8, wherein: The solvent is at least one of butyl acetate, cyclohexanone, isopropyl alcohol, and propylene glycol monomethyl ether acetate.

10. A preparation method of the modified silicone defoamer according to any one of claims 1 to 9, characterized in that: Specifically includes the following steps: S1: Add the composite modified silicone matrix, the base silicone, and the synergist to the solvent, heat in a water bath at 50-55 °C, and disperse at high speed at 1500-2000 rpm for 30-40 min; S2: Add the dispersant and the stabilizer, and circulate through a high-pressure homogenizer 3 times at a pressure of 45-50 MPa to obtain a uniform dispersion with a particle size <200 nm; S3: Add the catalyst, stir and react at a constant temperature of 60-65 °C for 2-3 h, control the final viscosity at 800-1000 cP, and after completion, filter through a 4.5-5 μm filter element to remove impurities to obtain the product.

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