Waterborne phenoxy resin emulsion and preparation method thereof

Abstract

The invention relates to the technical field of high polymer materials, and discloses a water-based phenoxy resin emulsion and a preparation method thereof.The emulsion contains an ionic hydrophilic structure and a nonionic hydrophilic structure and is obtained by introducing a composite hydrophilic reagent into a phenoxy resin molecular structure through a grafting reaction, the composite hydrophilic reagent is composed of polyethylene glycol methyl ether methacrylate and active sulfonate according to a mass ratio of 1: 1-1: 3. The invention has the advantages of simple preparation, mild reaction, small particle size, small viscosity and no need of pressure reaction equipment, and is suitable for industrial production. The water-based phenoxy resin emulsion can be widely applied to protective coatings of airplane, ship, building, traffic and automobile parts and marine fasteners.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and particularly relates to an aqueous phenoxy resin emulsion and a preparation method thereof. Background Art

[0002] Phenoxy resin is a thermoplastic resin, which is obtained by polycondensation of bisphenol A and phenoxy dichloropropane under alkaline conditions and contains phenoxy groups in its molecular structure. It is usually a colorless to light yellow transparent solid, with good solubility, thermal stability, mechanical properties, chemical corrosion resistance, insulation properties, etc., and has a wide range of applications in the fields of coatings, adhesives, electronic materials, etc. However, most traditional phenoxy resins are organic solvent-based, and a large amount of volatile organic compounds (VOCs) will be released during use, causing serious harm to the environment and human health. With the continuous improvement of environmental protection requirements, the development of aqueous phenoxy resin emulsion has become an inevitable trend.

[0003] Currently, the main methods for preparing aqueous phenoxy resin emulsion include external emulsification method, phase inversion method, chemical modification method, etc. However, the currently prepared aqueous phenoxy resin emulsion has technical problems such as larger emulsion particle size and poorer stability. Larger-sized emulsion particles are more affected by gravity, resulting in easier sedimentation and stratification of the aqueous phenoxy resin emulsion, especially more likely to occur sedimentation during storage. As time goes by, the emulsion may show obvious stratification, with clear liquid on the upper layer and concentrated emulsion layer on the lower layer. This not only affects the appearance of the product but also leads to uneven performance during use. For example, in the application of coatings, problems such as local color differences and uneven thickness may occur. The interaction force between large-sized particles is relatively weak, and it is easy to aggregate to form larger particle clusters. This aggregation may cause the demulsification of the emulsion and make the emulsion lose its stability. For example, in adhesives, demulsification may lead to a sharp decline in bonding performance and unable to achieve effective bonding. At the same time, it results in poor film-forming performance. When large-sized emulsion forms a film, defects are likely to occur. Larger particles are difficult to arrange closely during the film-forming process, resulting in a decrease in the denseness of the film. This may cause a decrease in the properties such as the strength, hardness, water resistance, and corrosion resistance of the film. In addition, it will also lead to a decrease in the gloss of the film-forming substance. Larger particles will cause light to scatter on the surface of the coating, rather than forming a relatively smooth reflection like small-sized emulsion, thus causing the coating to lose its gloss. This will affect the appearance quality of the product and reduce its decorative effect. Summary of the Invention

[0004] In order to solve the technical problems existing in the prior art, the purpose of the present invention is to provide an aqueous phenoxy resin emulsion with good stability and small particle size and a preparation method thereof. The aqueous phenoxy resin emulsion has a small particle size and good stability, and can be widely applied in the fields of coatings, adhesives, etc.

[0005] To achieve the above-mentioned invention object, the present invention adopts the following technical solutions: An aqueous phenoxy resin emulsion, the emulsion contains ionic and non-ionic hydrophilic structures, and is obtained by introducing a composite hydrophilic reagent into the molecular structure of the phenoxy resin through a grafting reaction. The composite hydrophilic reagent is composed of methoxypolyethylene glycol methacrylate and an active sulfonate in a mass ratio of 1:1 to 1:3. By using the active sites existing in the molecular structure of the phenoxy resin, an active sulfonate containing an unsaturated carbon-carbon double bond (C=C) and methoxypolyethylene glycol methacrylate are grafted onto the molecular chain of the phenoxy resin through a free radical graft polymerization reaction, so that the active sulfonate molecules and methoxypolyethylene glycol are continuously grafted onto the molecular chain of the phenoxy resin, thereby realizing the graft modification of the phenoxy resin by the active sulfonate and methoxypolyethylene glycol structures, and introducing excellent properties of the active sulfonate and methoxypolyethylene glycol, such as good hydrophilicity, weather resistance, film-forming property, etc. into the phenoxy resin to improve the properties of the phenoxy resin.

[0006] Further, the active sulfonate is one or a mixture of several of sodium allyloxyhydroxypropane sulfonate, 2-acrylamido-2-methylpropane sulfonic acid, sodium p-styrene sulfonate, and sodium allyl sulfonate.

[0007] The present invention also discloses a preparation method of an aqueous phenoxy resin emulsion, comprising the following steps: Step (1): Add phenoxy resin, solvent, composite hydrophilic reagent, and initiator into a reactor, and carry out a grafting reaction at a temperature of 60 - 120°C; wherein the composite hydrophilic reagent is composed of methoxypolyethylene glycol methacrylate and an active sulfonate compound in a mass ratio of 1:1 to 1:3; Step (2): After the reaction product obtained in Step 1 is cooled, add a hyperdispersant, triethanolamine, and deionized water, and carry out emulsification at a temperature of 30 - 70°C; after emulsification, the solvent is removed to obtain an aqueous phenoxy resin emulsion.

[0008] This preparation method has a mild reaction, does not require pressure reaction equipment, has a simple preparation process, is easy to operate, and is suitable for industrial production.

[0009] Further, in the step (1), the mass ratio of the phenoxy resin to the composite hydrophilic reagent is 1:0.12 - 0.24.

[0010] Further, the initiator is 0.5 - 2% of the total mass of the active sulfonate.

[0011] Further, the hyperdispersant is one of a polyester type hyperdispersant, a polyether type hyperdispersant, a polyacrylate type hyperdispersant, and a polyolefin type hyperdispersant.

[0012] Further, the initiator is benzoyl peroxide or azobisisobutyronitrile.

[0013] Furthermore, the reaction temperature in step (1) is 80 - 100 °C.

[0014] Furthermore, the emulsification temperature in step (2) is 40 - 60 °C.

[0015] By further adjusting and optimizing the parameters of the preparation method, the stability of the obtained emulsion is improved.

[0016] Furthermore, a preparation method of an aqueous phenoxy resin emulsion includes the following steps: Step (1): In a 2L small reactor equipped with a stirring device, a reflux condenser, a thermometer, and a feeding port, 500 grams of phenoxy resin, 500 ml of ethylene glycol monobutyl ether solvent, 30 grams of poly(ethylene glycol) methyl ether methacrylate, 90 grams of an active sulfonate compound, and 0.06 grams of benzoyl peroxide initiator are subjected to a grafting reaction at a temperature of 90 °C for 6 hours. Step (2): After the reaction product obtained in step (1) is cooled, 2 grams of a polyether type hyperdispersant, 20 grams of triethanolamine, and 500 ml of deionized water are added and emulsified at a temperature of 50 °C. After emulsification, the solvent is removed to obtain an aqueous phenoxy resin emulsion.

[0017] The present invention utilizes some active sites existing in the molecular structure of phenoxy resin. Through free radical graft polymerization reaction, an active sulfonate containing unsaturated carbon-carbon double bonds (C=C) and poly(ethylene glycol) methyl ether methacrylate are used to graft the active sulfonate molecules and poly(ethylene glycol) methyl ether onto the molecular chain of phenoxy resin continuously, thereby realizing the graft modification of phenoxy resin by the structures of active sulfonate and poly(ethylene glycol) methyl ether. The excellent properties of active sulfonate and poly(ethylene glycol) methyl ether, such as good hydrophilicity, weather resistance, film-forming property, etc., are introduced into phenoxy resin to improve the properties of phenoxy resin. The grafted resin not only retains some characteristics of phenoxy resin, such as high mechanical strength, good heat resistance, etc., but also has the advantages of active sulfonate and poly(ethylene glycol) methyl ether, making the finally prepared emulsion more excellent in performance. Then, according to the precise stoichiometric ratio, triethanolamine is added as a salt-forming agent to prepare an aqueous phenoxy resin emulsion with small particle size. This aqueous phenoxy resin emulsion can be widely applied in the technical field of the preparation of coating emulsions for aircraft, ships, buildings, transportation, and various mechanical equipment, and can meet the usage requirements of aqueous phenoxy products.

[0018] The aqueous phenoxy resin emulsion of the present invention combines a free radical grafting reaction to introduce a large number of carboxyl groups and non-ionic structures such as polyethylene glycol methyl ether into the phenoxy resin molecule. After the active sulfonate and polyethylene glycol methyl ether are grafted onto the phenoxy resin, acidic groups such as unreacted carboxyl groups (-COOH) may exist in the molecular structure. Triethanolamine is an organic base with a lone pair of electrons on the nitrogen atom in its molecular structure, showing weak basicity. In the reaction system, the basic group (-NH2) of triethanolamine can undergo an acid-base neutralization reaction with the carboxyl group on the active sulfonate-grafted phenoxy resin to form the corresponding carboxylate. The formation of this carboxylate increases the hydrophilicity of the resin molecule, making the originally water-insoluble phenoxy resin capable of being dispersed in water, endowing it with better dispersion and emulsification properties, and making its emulsion have high stability, and being less likely to show phenomena such as stratification and precipitation.

[0019] Furthermore, the salt generated by the reaction of triethanolamine and carboxyl group used in the present invention will ionize in water to produce positively charged ammonium ions (NH4 + ) and negatively charged carboxylate ions (RCOO - ). These ions will form a double-layer structure on the surface of the emulsion particles, generating electrostatic repulsion to prevent the mutual aggregation and sedimentation of the emulsion particles, thereby playing a role in stabilizing the emulsion. At the same time, the addition of triethanolamine can also adjust the pH value of the emulsion to be within a suitable range, further enhancing the stability of the emulsion.

[0020] Furthermore, the present invention does not contain organic solvents, is green and environmentally friendly. The aqueous phenoxy resin prepared by the present invention has excellent adhesion: it has good adhesion to various substrates such as metals, woods, and concretes.

[0021] The preparation method of the present invention has mild reactions, does not require pressure reaction equipment, has a simple preparation process, is convenient to operate, is suitable for industrial production, and can be widely used in the preparation of protective coatings for airplanes, ships, buildings, transportation, and various mechanical equipment. Specific Embodiments

[0022] The present invention and its beneficial technical effects will be described in detail below in combination with specific embodiments.

[0023] The sources of the reagents and instruments used in the following examples are as follows: Table 1 Reagents and Instruments Used in Examples Example 1 Step 1: In a 2L small reactor equipped with a stirring device, a reflux condenser, a thermometer, and a feeding port, 500 grams of phenoxy resin, 400 ml of ethylene glycol butyl ether solvent, 30 grams of polyethylene glycol methyl ether methacrylate, 30 grams of active sulfonate compound, and 0.06 grams of benzoyl peroxide initiator are subjected to a grafting reaction at 80°C for 5 hours; Step 2: After the reaction product obtained in Step 1 is cooled, 2 grams of polyacrylate hyperdispersant, 20 grams of triethanolamine, and 500 ml of deionized water are added and emulsified at 40°C; after emulsification, the solvent is removed to obtain an aqueous phenoxy resin emulsion.

[0024] Example 2 Step 1: In a 2L small reactor equipped with a stirring device, a reflux condenser, a thermometer, and a feeding port, 500 grams of phenoxy resin, 300 ml of ethylene glycol butyl ether solvent, 30 grams of polyethylene glycol methyl ether methacrylate, 60 grams of active sulfonate compound, and 0.06 grams of benzoyl peroxide initiator are subjected to a grafting reaction at 100°C for 4 hours; Step 2: After the reaction product obtained in Step 1 is cooled, 2 grams of polyester hyperdispersant, 20 grams of triethanolamine, and 500 ml of deionized water are added and emulsified at 60°C; after emulsification, the solvent is removed to obtain an aqueous phenoxy resin emulsion.

[0025] Example 3 Step 1: In a 2L small reactor equipped with a stirring device, a reflux condenser, a thermometer, and a feeding port, 500 grams of phenoxy resin, 500 ml of ethylene glycol butyl ether solvent, 30 grams of polyethylene glycol methyl ether methacrylate, 90 grams of active sulfonate compound, and 0.06 grams of benzoyl peroxide initiator are subjected to a grafting reaction at 90°C for 6 hours; Step 2: After the reaction product obtained in Step 1 is cooled, 2 grams of polyether hyperdispersant, 20 grams of triethanolamine, and 500 ml of deionized water are added and emulsified at 50°C; after emulsification, the solvent is removed to obtain an aqueous phenoxy resin emulsion.

[0026] Comparative Example 1 A certain amount of phenoxy resin is added to an appropriate amount of organic solvent and stirred to completely dissolve it to form a uniform resin solution. Under high-speed stirring, sodium dodecyl sulfonate and deionized water are slowly dropped into the resin solution, and stirring is continued for a period of time to form an emulsion in the system. After the stirring ends, the organic solvent is removed by vacuum distillation to obtain an aqueous phenoxy resin emulsion.

[0027] Comparative Example 2 A certain amount of phenoxy resin was added to an appropriate amount of organic solvent and stirred to completely dissolve it to form a homogeneous resin solution. Under high-speed stirring, sodium dodecyl sulfate and deionized water were slowly dropped into the resin solution, and stirring was continued for a period of time to form an emulsion in the system. After the stirring ended, the organic solvent was removed by vacuum distillation to obtain an aqueous phenoxy resin emulsion.

[0028] Experiment: Stability test The aqueous phenoxy emulsions obtained in Example 1, Example 2, Example 3, Comparative Example 1, and Comparative Example 2 were subjected to a stability test, and the results are shown in the following table: Table 2 Performance test table Stratification retention time / min Average particle size Example 1 351 603nm Example 2 526 459nm Example 3 669 320nm Comparative Example 1 23 1500nm Comparative Example 2 19 2001nm Analysis of test results: The aqueous phenoxy resin emulsions of Example 1, Example 2, and Example 3 have small average particle sizes, long delamination retention times, and good stability; among them, Example 3 has the smallest average particle size and the best stability.

[0029] The particle size distributions of Comparative Example 1 and Comparative Example 2 are relatively wide, and the average particle sizes are relatively large; after standing for a period of time, the emulsion shows a delamination phenomenon and has poor stability.

[0030] The above-mentioned content is only the basic description under the concept of the present invention, and any equivalent transformation made according to the technical solution of the present invention shall fall within the protection scope of the present invention.

Claims

1. An aqueous phenoxy resin emulsion, characterized in that The described emulsion contains ionic and non-ionic hydrophilic structures, which are obtained by introducing them into the molecular structure of phenoxy resin through grafting reaction with a composite hydrophilic reagent. The composite hydrophilic reagent is composed of polyethylene glycol methyl ether methacrylate and active sulfonate in a mass ratio of 1:1 to 1:

3.

2. The aqueous phenoxy resin emulsion according to claim 1, wherein The active sulfonate is one or a mixture of several of sodium allyloxyhydroxypropane sulfonate, 2-acrylamido-2-methylpropanesulfonic acid, sodium styrene sulfonate, and sodium allyl sulfonate.

3. The preparation method of the aqueous phenoxy resin emulsion according to any one of claims 1-2, characterized in that It includes the following steps: Step (1): Add phenoxy resin, solvent, composite hydrophilic reagent, and initiator into a reactor, and conduct grafting reaction at a temperature of 60 - 120 °C; wherein the composite hydrophilic reagent is composed of polyethylene glycol methyl ether methacrylate and active sulfonate compound in a mass ratio of 1:1 to 1:

3. Step (2): After cooling the reaction product obtained in step (1), add a hyperdispersant, triethanolamine, and deionized water, and conduct emulsification at a temperature of 30 - 70 °C; after emulsification, remove the solvent to obtain an aqueous phenoxy resin emulsion.

4. The preparation method of an aqueous phenoxy resin emulsion according to claim 3, wherein In step (1), the mass ratio of phenoxy resin to composite hydrophilic reagent is 1:0.12 to 0.

24.

5. The preparation method of an aqueous phenoxy resin emulsion according to claim 3, characterized in that The initiator is 0.5 - 2% of the total mass of the active sulfonate.

6. The preparation method of an aqueous phenoxy resin emulsion according to claim 3, characterized in that The hyperdispersant is one of polyester type hyperdispersant, polyether type hyperdispersant, polyacrylate type hyperdispersant, and polyolefin type hyperdispersant.

7. The preparation method of an aqueous phenoxy resin emulsion according to claim 3, characterized in that The initiator is benzoyl peroxide or azobisisobutyronitrile.

8. The preparation method of an aqueous phenoxy resin emulsion according to claim 3, characterized in that, The reaction temperature in step (1) is 80 - 100 °C.

9. The preparation method of an aqueous phenoxy resin emulsion according to claim 3, characterized in that The emulsification temperature in step (2) is 40 - 60 °C.

10. The preparation method of an aqueous phenoxy resin emulsion according to claim 3, characterized in that It includes the following steps: Step (1): In a 2L small reactor equipped with a stirring device, reflux condenser, thermometer, and feeding port, 500 grams of phenoxy resin, 500 ml of ethylene glycol monobutyl ether solvent, 30 grams of polyethylene glycol methyl ether methacrylate, 90 grams of active sulfonate compound, and 0.06 grams of benzoyl peroxide initiator conduct grafting reaction at a temperature of 90 °C for 6 hours. Step (2): After cooling the reaction product obtained in step (1), add 2 grams of polyether type hyperdispersant, 20 grams of triethanolamine, and 500 ml of deionized water, and conduct emulsification at a temperature of 50 °C; after emulsification, remove the solvent to obtain an aqueous phenoxy resin emulsion.

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