Waterproof and foldable acrylic emulsion and preparation method thereof

Abstract

The application discloses a waterproof and fold-resistant acrylic emulsion and a preparation method thereof, and belongs to the technical field of coating. The preparation method comprises the following steps: preparing material A by taking zirconium tetrachloride, 2,5-dimercaptoterephthalic acid, glacial acetic acid and N,N-dimethylformamide; preparing material B by taking the material A, castor oil and photoinitiator 1173; preparing a double bond end-capped waterborne polyurethane prepolymer emulsion by taking the material B, diisocyanate, hydroxyl silicone oil, polytetrahydrofuran 2000, a catalyst, hydroxyethyl acrylate and deionized water; and preparing the waterproof and fold-resistant acrylic emulsion by taking the double bond end-capped waterborne polyurethane prepolymer emulsion, acrylic acid, methyl methacrylate, butyl acrylate, an emulsifier, deionized water and an initiator, so that the acrylic emulsion has good fold resistance while maintaining good waterproof performance.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, specifically relating to a waterproof and fold-resistant water-based acrylic emulsion and its preparation method. Background Technology

[0002] Acrylic emulsions are generally high-molecular-weight polymer emulsions made from acrylic acid, methacrylic acid, and acrylate monomers (such as methyl acrylate, ethyl acrylate, and butyl acrylate) through emulsion polymerization. They are characterized by good film-forming properties, high transparency, excellent weather resistance, and environmental friendliness and non-toxicity. During polymerization, hydrophobic monomers (such as styrene and long-chain acrylates) are introduced to provide water repellency and prevent liquid water penetration. While existing acrylic emulsions possess some waterproof properties, their application in packaging paper suffers from poor folding endurance, leading to unsatisfactory results. Therefore, there is an urgent need to optimize and improve the composition and processing of existing waterproof acrylic emulsions to enhance their folding endurance. Summary of the Invention

[0003] The purpose of this invention is to provide a waterproof and fold-resistant water-based acrylic emulsion and its preparation method, so as to achieve good waterproof performance while maintaining good fold resistance.

[0004] The objective of this invention can be achieved through the following technical solutions:

[0005] A method for preparing a waterproof and fold-resistant water-based acrylic emulsion includes the following steps:

[0006] S1. Mix zirconium tetrachloride, 2,5-dimercaptoterephthalic acid, glacial acetic acid and N,N-dimethylformamide, ultrasonically stir for 20-30 min, place in a hydrothermal reactor and hydrothermally react in an oven at 120℃ for 20 h, centrifuge to separate, take the solid phase, wash and vacuum dry to obtain material A.

[0007] S2. Take the material A, castor oil and photoinitiator 1173, mix and stir evenly, and carry out mercapto-alkene click reaction under ultraviolet light for 2-3 hours. Then dilute the product with ethyl acetate, wash it three times with saturated brine, dry it with anhydrous magnesium sulfate to remove water, filter it, and rotary evaporate it to obtain material B.

[0008] S3. Under a nitrogen atmosphere, take the material B, diisocyanate, hydroxy silicone oil, polytetrahydrofuran 2000 and catalyst, mix them, heat and stir at 60°C for 2-4 hours, add hydroxyethyl acrylate dropwise, raise the temperature to 70°C and continue stirring for 2-3 hours, cool down to 40°C, add deionized water, stir and emulsify for 15-25 minutes, filter and discharge to obtain double bond-terminated waterborne polyurethane prepolymer emulsion.

[0009] S4. Take the double-bond-terminated waterborne polyurethane prepolymer emulsion and heat it in a water bath at 85°C for 5 minutes. Add acrylic acid, methyl methacrylate, butyl acrylate, emulsifier, and deionized water. Stir until uniform. Slowly add the initiator. Keep warm and stir for 3-4 hours. Cool and discharge to obtain the waterproof and fold-resistant waterborne acrylic emulsion.

[0010] As a preferred embodiment of the present invention, in step S1, the ratio of zirconium tetrachloride, 2,5-dimercaptoterephthalic acid, glacial acetic acid, and N,N-dimethylformamide is 0.4-0.5g: 0.32-0.35g: 50-60mL: 50mL.

[0011] As a preferred embodiment of the present invention, in step S2, the mass ratio of material A, castor oil, and photoinitiator 1173 is 0.08-0.12:5-6:0.05-0.06.

[0012] As a preferred embodiment of the present invention, in step S3, the mass ratio of material B, diisocyanate, hydroxyl silicone oil, polytetrahydrofuran 2000, catalyst, hydroxyethyl acrylate, and deionized water is 2.8-3.2:13-15:2-4:25-35:0.03-0.04:5-8:100-120.

[0013] As a preferred technical solution of the present invention, in step S3, the hydroxyl silicone oil is a linear polydimethylsiloxane with hydroxyl end groups and a molecular weight of 600-4000 g / mol.

[0014] As a preferred technical solution of the present invention, in step S3, the hydroxyl silicone oil is a linear polydimethylsiloxane with hydroxyl end groups and a molecular weight of 1000-2000 g / mol.

[0015] As a preferred embodiment of the present invention, in step S4, the mass ratio of the double-bond-terminated waterborne polyurethane prepolymer emulsion, acrylic acid, methyl methacrylate, butyl acrylate, emulsifier, deionized water, and initiator is 8-10:5-7:12-18:10-12:0.4-0.8:35-45:1-2.

[0016] A waterproof and fold-resistant water-based acrylic emulsion was prepared using the above-described method.

[0017] The beneficial effects of this invention are:

[0018] This invention utilizes a double-bond-terminated waterborne polyurethane prepolymer to copolymerize with monomers such as acrylic acid and methyl methacrylate, forming a dense polyurethane-acrylate interpenetrating network structure, thereby improving the water resistance of the cured film. Simultaneously, a zirconium-based organic framework grafted with castor oil participates as a functional filler in the synthesis of the double-bond-terminated waterborne polyurethane prepolymer and is dispersed in the emulsion-cured film matrix during subsequent acrylate copolymerization, forming micro- and nano-scale rough surfaces and cross-linking sites, further enhancing the network's density. This dense cross-linked network extends the penetration path of water molecules, hindering their diffusion into the matrix, thus improving the water resistance of the cured film. The long carbon chains of castor oil, the flexible chains of hydroxyl silicone oil, and the long-chain ether bonds of polytetrahydrofuran incorporated into the polyurethane possess good rotational freedom and can serve as flexible connecting arms between molecular chains, effectively dispersing localized stress generated during bending and preventing stress concentration leading to molecular chain breakage or matrix cracking. Furthermore, the entanglement of the long chains forms an elastic network, allowing the structure to recover its shape after bending through chain segment rebound, improving resistance to repeated bending. Detailed Implementation

[0019] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

[0020] Example 1

[0021] A method for preparing a waterproof and fold-resistant water-based acrylic emulsion includes the following steps:

[0022] S1. Zirconium tetrachloride, 2,5-dimercaptoterephthalic acid, glacial acetic acid, and N,N-dimethylformamide are mixed and ultrasonically stirred for 20 min. The mixture is then placed in a hydrothermal reactor and hydrothermally reacted in an oven at 120℃ for 20 h. After centrifugation, the solid phase is washed and vacuum dried to obtain material A. The ratio of zirconium tetrachloride, 2,5-dimercaptoterephthalic acid, glacial acetic acid, and N,N-dimethylformamide is 0.4 g: 0.32 g: 50 mL: 50 mL.

[0023] S2. After mixing and stirring the material A, the product is subjected to a mercapto-olefin click reaction under ultraviolet light for 2-3 hours. The product is then diluted with ethyl acetate, washed three times with saturated brine, dried with anhydrous magnesium sulfate, filtered, and rotary evaporated to obtain material B. The mass ratio of the material A, castor oil, and photoinitiator 1173 is 0.08:5:0.05.

[0024] S3. Under a nitrogen atmosphere, mix the aforementioned material B, 4,4′-dicyclohexylmethane diisocyanate, hydroxyl silicone oil 2000, polytetrahydrofuran 2000, and dibutyltin dilaurate. Heat and stir at 60°C for 2 hours. Add hydroxyethyl acrylate dropwise, raise the temperature to 70°C and continue stirring for 2 hours. Cool down to 40°C, add deionized water, stir and emulsify for 15 minutes, filter and discharge to obtain a double-bond-terminated waterborne polyurethane prepolymer emulsion. The mass ratio of the aforementioned material B, 4,4′-dicyclohexylmethane diisocyanate, hydroxyl silicone oil 2000, polytetrahydrofuran 2000, dibutyltin dilaurate, hydroxyethyl acrylate, and deionized water is 2.8:13:2:25:0.03:5:100.

[0025] S4. Take the double-bond-terminated waterborne polyurethane prepolymer emulsion and heat it in a water bath at 85°C for 5 minutes. Add acrylic acid, methyl methacrylate, butyl acrylate, emulsifier OP-10, and deionized water. Stir until uniform. Slowly add potassium persulfate initiator. Keep warm and stir for 3 hours. Cool and discharge to obtain the waterproof and fold-resistant waterborne acrylic emulsion. The mass ratio of the double-bond-terminated waterborne polyurethane prepolymer emulsion, acrylic acid, methyl methacrylate, butyl acrylate, emulsifier, deionized water, and initiator is 8:5:12:10:0.4:35:1.

[0026] Example 2

[0027] A method for preparing a waterproof and fold-resistant water-based acrylic emulsion includes the following steps:

[0028] S1. Zirconium tetrachloride, 2,5-dimercaptoterephthalic acid, glacial acetic acid, and N,N-dimethylformamide are mixed and ultrasonically stirred for 25 min. The mixture is then placed in a hydrothermal reactor and hydrothermally reacted in an oven at 120℃ for 20 h. After centrifugation, the solid phase is washed and vacuum dried to obtain material A. The ratio of zirconium tetrachloride, 2,5-dimercaptoterephthalic acid, glacial acetic acid, and N,N-dimethylformamide is 0.45 g: 0.34 g: 55 mL: 50 mL.

[0029] S2. After mixing and stirring the material A, castor oil and photoinitiator 1173 evenly, carry out a mercapto-olefin click reaction under ultraviolet light for 2.5 h. Then, dilute the product with ethyl acetate, wash it three times with saturated brine, dry it with anhydrous magnesium sulfate to remove water, filter it, and rotary evaporate it to obtain material B. The mass ratio of the material A, castor oil and photoinitiator 1173 is 0.10:5.5:0.055.

[0030] S3. Under a nitrogen atmosphere, mix the aforementioned material B, 4,4′-dicyclohexylmethane diisocyanate, hydroxyl silicone oil 2000, polytetrahydrofuran 2000, and dibutyltin dilaurate. Heat and stir at 60°C for 3 hours. Add hydroxyethyl acrylate dropwise, raise the temperature to 70°C and continue stirring for 2.5 hours. Cool down to 40°C, add deionized water, stir and emulsify for 20 minutes, filter and discharge to obtain a double-bond-terminated waterborne polyurethane prepolymer emulsion. The mass ratio of the aforementioned material B, 4,4′-dicyclohexylmethane diisocyanate, hydroxyl silicone oil 2000, polytetrahydrofuran 2000, dibutyltin dilaurate, hydroxyethyl acrylate, and deionized water is 3.0:14:3:30:0.035:6.5:110.

[0031] S4. Take the double-bond-terminated waterborne polyurethane prepolymer emulsion and heat it in a water bath at 85°C for 5 minutes. Add acrylic acid, methyl methacrylate, butyl acrylate, emulsifier OP-10, and deionized water. Stir until uniform. Slowly add potassium persulfate initiator. Keep warm and stir for 3.5 hours. Cool and discharge to obtain the waterproof and fold-resistant waterborne acrylic emulsion. The mass ratio of the double-bond-terminated waterborne polyurethane prepolymer emulsion, acrylic acid, methyl methacrylate, butyl acrylate, emulsifier, deionized water, and initiator is 9:6:15:11:0.6:40:1.5.

[0032] Example 3

[0033] A method for preparing a waterproof and fold-resistant water-based acrylic emulsion includes the following steps:

[0034] S1. Zirconium tetrachloride, 2,5-dimercaptoterephthalic acid, glacial acetic acid, and N,N-dimethylformamide are mixed and ultrasonically stirred for 30 min. The mixture is then placed in a hydrothermal reactor and hydrothermally reacted in an oven at 120℃ for 20 h. After centrifugation, the solid phase is washed and vacuum dried to obtain material A. The ratio of zirconium tetrachloride, 2,5-dimercaptoterephthalic acid, glacial acetic acid, and N,N-dimethylformamide is 0.5 g: 0.35 g: 60 mL: 50 mL.

[0035] S2. Take the material A, castor oil, and photoinitiator 1173, mix and stir evenly, and carry out a mercapto-olefin click reaction under ultraviolet light for 3 hours. Dilute the product with ethyl acetate, wash it three times with saturated brine, dry it with anhydrous magnesium sulfate to remove water, filter, and rotary evaporate to obtain material B. The mass ratio of the material A, castor oil, and photoinitiator 1173 is 0.12:6:0.06.

[0036] S3. Under a nitrogen atmosphere, mix the aforementioned material B, 4,4′-dicyclohexylmethane diisocyanate, hydroxyl silicone oil 2000, polytetrahydrofuran 2000, and dibutyltin dilaurate. Heat and stir at 60°C for 4 hours. Add hydroxyethyl acrylate dropwise, raise the temperature to 70°C and continue stirring for 3 hours. Cool down to 40°C, add deionized water, stir and emulsify for 25 minutes, filter and discharge to obtain a double-bond-terminated waterborne polyurethane prepolymer emulsion. The mass ratio of the aforementioned material B, 4,4′-dicyclohexylmethane diisocyanate, hydroxyl silicone oil 2000, polytetrahydrofuran 2000, dibutyltin dilaurate, hydroxyethyl acrylate, and deionized water is 3.2:15:4:35:0.04:8:120.

[0037] S4. Heat the double-bond-terminated waterborne polyurethane prepolymer emulsion in a water bath at 85°C for 5 minutes. Add acrylic acid, methyl methacrylate, butyl acrylate, emulsifier OP-10, and deionized water. Stir until homogeneous. Slowly add potassium persulfate initiator. Keep warm and stir for 4 hours. Cool and discharge to obtain the waterproof and fold-resistant waterborne acrylic emulsion. The mass ratio of the double-bond-terminated waterborne polyurethane prepolymer emulsion, acrylic acid, methyl methacrylate, butyl acrylate, emulsifier, deionized water, and initiator is 10:7:18:12:0.8:45:2.

[0038] Comparative Example 1

[0039] A method for preparing a waterproof and fold-resistant water-based acrylic emulsion includes the following steps:

[0040] S1. Under a nitrogen atmosphere, castor oil, 4,4′-dicyclohexylmethane diisocyanate, hydroxyl silicone oil 2000, polytetrahydrofuran 2000, and dibutyltin dilaurate were mixed and heated and stirred at 60°C for 3 hours. Hydroxyethyl acrylate was added dropwise, the temperature was raised to 70°C and stirring was continued for 2.5 hours. The temperature was lowered to 40°C, deionized water was added, and the mixture was stirred and emulsified for 20 minutes. The mixture was then filtered to obtain a double-bond-terminated waterborne polyurethane prepolymer emulsion. The mass ratio of castor oil, 4,4′-dicyclohexylmethane diisocyanate, hydroxyl silicone oil 2000, polytetrahydrofuran 2000, dibutyltin dilaurate, hydroxyethyl acrylate, and deionized water was 3.0:14:3:30:0.035:6.5:110.

[0041] S2. Take the double-bond-terminated waterborne polyurethane prepolymer emulsion and heat it in a water bath at 85°C for 5 minutes. Add acrylic acid, methyl methacrylate, butyl acrylate, emulsifier OP-10, and deionized water. Stir until uniform. Slowly add potassium persulfate initiator. Keep warm and stir for 3.5 hours. Cool and discharge to obtain the waterproof and fold-resistant waterborne acrylic emulsion. The mass ratio of the double-bond-terminated waterborne polyurethane prepolymer emulsion, acrylic acid, methyl methacrylate, butyl acrylate, emulsifier, deionized water, and initiator is 9:6:15:11:0.6:40:1.5.

[0042] Comparative Example 2

[0043] A method for preparing a waterproof and fold-resistant water-based acrylic emulsion includes the following steps:

[0044] S1. Zirconium tetrachloride, 2,5-dimercaptoterephthalic acid, glacial acetic acid, and N,N-dimethylformamide are mixed and ultrasonically stirred for 25 min. The mixture is then placed in a hydrothermal reactor and hydrothermally reacted in an oven at 120℃ for 20 h. After centrifugation, the solid phase is washed and vacuum dried to obtain material A. The ratio of zirconium tetrachloride, 2,5-dimercaptoterephthalic acid, glacial acetic acid, and N,N-dimethylformamide is 0.45 g: 0.34 g: 55 mL: 50 mL.

[0045] S2. After mixing and stirring the material A, castor oil and photoinitiator 1173 evenly, carry out a mercapto-olefin click reaction under ultraviolet light for 2.5 h. Then, dilute the product with ethyl acetate, wash it three times with saturated brine, dry it with anhydrous magnesium sulfate to remove water, filter it, and rotary evaporate it to obtain material B. The mass ratio of the material A, castor oil and photoinitiator 1173 is 0.10:5.5:0.055.

[0046] S3. Take the aforementioned material B, acrylic acid, methyl methacrylate, butyl acrylate, emulsifier OP-10, and deionized water, stir evenly, slowly add the initiator potassium persulfate, keep warm and stir for 3.5 hours, cool and discharge to obtain the waterproof and water-resistant acrylic emulsion; the mass ratio of the aforementioned material B, acrylic acid, methyl methacrylate, butyl acrylate, emulsifier, deionized water, and initiator is 9:6:15:11:0.6:40:1.5.

[0047] Performance testing

[0048] The emulsions obtained from Examples 1-3 and Comparative Examples 1-2 were formulated into primers and coated on test panels. The dry film thickness was controlled at 30 μm, and then the tests were conducted.

[0049] The primer formulation by weight is as follows: 80 parts waterproof and fold-resistant water-based acrylic emulsion, 0.1 parts defoamer (BYK-021), 2 parts dipropylene glycol methyl ether, 0.1 parts wetting agent (BYK346), 0.4 parts thickener (ACRYSOL ASE-60), and 17.4 parts deionized water. Apply evenly to the polished aluminum sheet surface and cure at 150°C for 10 minutes to obtain the corresponding cured film.

[0050] 1) Water contact angle test: The water contact angle of the cured film surface was measured using the seat drop method. The test results are shown in Table 1.

[0051] 2) First, fold the aluminum sheet sample coated with the corresponding emulsion primer inward and outward by 180 degrees, repeating 10 times to simulate the bending force in actual use. Then, stick standard 3M tape on the crease area, flatten it, and peel off the tape at a uniform speed to pick up the loose aluminum layer. Observe and measure the area of ​​aluminum layer falling off at the crease, compare it with the total area of ​​the test area, and calculate the percentage of falling off. The test results are shown in Table 1 below.

[0052] Table 1

[0053]

[0054] As shown in Table 1, the acrylate emulsions prepared in Examples 1-3 of this application exhibit better waterproof and folding resistance after curing and forming films compared to the comparative examples. In Comparative Example 1, the matrix relies solely on the copolymer network of polyurethane and acrylate, resulting in low crosslinking density, reduced water resistance, and easy slippage and breakage of molecular chains during bending, making it impossible to form a stable elastic support system. In Comparative Example 2, the lack of interpenetrating network construction of double-bond-terminated waterborne polyurethane prepolymer leads to a loose matrix structure, insufficient toughness, and failure of the synergistic effect of waterproofing and folding resistance.

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing a waterproof and fold-resistant water-based acrylic emulsion, characterized in that, Includes the following steps: S1. Prepare material A by hydrothermal reaction of zirconium tetrachloride, 2,5-dimercaptoterephthalic acid, glacial acetic acid, and N,N-dimethylformamide. S2. Take the aforementioned material A, castor oil, and photoinitiator and perform a mercapto-olefin click reaction to prepare material B; S3. In a nitrogen atmosphere, take the material B, diisocyanate, hydroxyl silicone oil, polytetrahydrofuran 2000, catalyst, hydroxyethyl acrylate and deionized water to prepare a double bond-terminated waterborne polyurethane prepolymer emulsion. S4. Prepare a waterproof and fold-resistant waterborne acrylic emulsion by taking the double-bond-terminated waterborne polyurethane prepolymer emulsion, acrylic acid, methyl methacrylate, butyl acrylate, emulsifier, deionized water, and initiator. In step S1, the ratio of zirconium tetrachloride, 2,5-dimercaptoterephthalic acid, glacial acetic acid, and N,N-dimethylformamide is 0.4-0.5g: 0.32-0.35g: 50-60mL: 50mL; In step S2, the mass ratio of material A, castor oil, and photoinitiator is 0.08-0.12:5-6:0.05-0.

06.

2. The method for preparing a waterproof and fold-resistant water-based acrylic emulsion according to claim 1, characterized in that, In step S3, the mass ratio of material B, diisocyanate, hydroxyl silicone oil, polytetrahydrofuran 2000, catalyst, hydroxyethyl acrylate, and deionized water is 2.8-3.2:13-15:2-4:25-35:0.03-0.04:5-8:100-120.

3. The method for preparing a waterproof and fold-resistant water-based acrylic emulsion according to claim 1, characterized in that, In step S3, the hydroxyl silicone oil is a linear polydimethylsiloxane with hydroxyl end groups and a molecular weight of 600-4000 g / mol.

4. The method for preparing a waterproof and fold-resistant water-based acrylic emulsion according to claim 1, characterized in that, In step S4, the mass ratio of the double-bond-terminated waterborne polyurethane prepolymer emulsion, acrylic acid, methyl methacrylate, butyl acrylate, emulsifier, deionized water, and initiator is 8-10:5-7:12-18:10-12:0.4-0.8:35-45:1-2.

5. A waterproof and fold-resistant water-based acrylic emulsion prepared by the preparation method according to any one of claims 1-4.

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