A core-shell type acrylate polyurethane emulsion primer, a preparation method and application thereof
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHEJIANG SCI-TECH UNIV
- Filing Date
- 2023-12-28
- Publication Date
- 2026-05-29
Abstract
Description
Technical Field
[0001] This invention belongs to the field of polymer film technology, specifically relating to a core-shell type acrylate polyurethane emulsion primer, its preparation method, and its application. Background Technology
[0002] Polymer films such as polyethylene (PE), polypropylene (PP), polyester (PET), polycarbonate (PC), polyvinyl chloride (PVC), and nylon (PA) are widely used in packaging products. Due to the non-polar, high crystallinity, and low surface energy characteristics of these films, PE, PP, and PET films typically require pretreatment before printing. Corona treatment is currently the most economical and effective way to improve ink adhesion on film surfaces, but it cannot guarantee timeliness and stability. To improve the printing effect of plastic films, a common method is to pre-coat functional primers onto the plastic film to improve printing quality, increase scratch resistance, enhance oil resistance, and maintain the adhesion of surface coatings for a longer period. Due to environmental pressures, more water-based primers are being used to modify polymer films. These water-based primers include water-based chlorinated polypropylene modified with acrylate, water-based polyacrylate, water-based polyurethane, and water-based acrylate modified with polyurethane. Chlorinated polypropylene, due to its chlorine content, is easily affected by light and heat, causing the chlorine to dissipate and resulting in yellowing of the film. Furthermore, countries and regions such as the EU have halogen-restricted requirements. Waterborne acrylic emulsions generally suffer from drawbacks such as hot stickiness and cold brittleness, leading to easy adhesion of the film coating after winding. Polyurethane contains a large number of polar groups such as urethane, exhibiting excellent adhesion to films like PET and inks, but it is more expensive and has poor adhesion to low surface energy substrates such as PP and PE. Currently, most applications use waterborne acrylic-modified polyurethane emulsions as primers, reducing costs while improving adhesion to film substrates and inks. The preparation of waterborne acrylic-modified polyurethane emulsions typically involves first preparing a waterborne polyurethane emulsion from polyester or polyether polyols, isocyanates, and waterborne chain extenders, followed by the addition of acrylates for polymerization to obtain hybrid modified or core-shell structured waterborne polyurethane. In plastic film primers, the polyurethane content is usually high, generally exceeding 20%. Further reducing the polyurethane content will lead to emulsion instability. Therefore, further reducing the cost of pre-coating plastic films while maintaining excellent printability is a pressing industry need.
[0003] To address the aforementioned issues, this invention proposes a core-shell type acrylate polyurethane emulsion primer with low polyurethane content and low preparation cost. It is suitable for primer coating of plastic films such as polyethylene, polypropylene, and polyethylene terephthalate, exhibiting excellent adhesion to films and inks, superior abrasion resistance, and excellent printability. Summary of the Invention
[0004] To address the problems in existing technologies, this invention provides a core-shell type acrylic polyurethane emulsion primer. This solves both the hot-stickiness and cold-brittleness issues of conventional acrylic emulsions and the instability caused by low polyurethane content in acrylic-modified waterborne polyurethane emulsion primers. The invention utilizes a starved feed polymerization method to prepare a soft-core, hard-shell type acrylic polyurethane emulsion. The acrylic monomers within the shell layer increase its adhesion to the surfaces of polyethylene, polypropylene, and other ground plastic films. Simultaneously, the acrylic monomers in the shell layer can form a cross-linked network, ensuring the structural strength of the coating.
[0005] To achieve the above technical objectives, the technical solution of the present invention is as follows:
[0006] A core-shell type acrylic polyurethane emulsion primer is a soft-core hard-shell type acrylic polyurethane emulsion, wherein the core layer has a Tg of -30 to -5℃, the shell layer containing a small amount of polyurethane has a Tg of 10-45℃, the monomer mass ratio of the core layer to the shell layer is 1:1-6, and the polymerizable polyurethane acrylate accounts for 1-10% of the shell layer monomers.
[0007] A method for preparing a core-shell type acrylic polyurethane emulsion primer includes the following steps:
[0008] Step 1, preparation of core-shell acrylate polyurethane emulsion, wherein the polymerization of the emulsion is carried out by a semi-continuous starvation feeding method;
[0009] The method for preparing the nuclear emulsion includes: a1, adding water and emulsifier to a beaker at room temperature and stirring evenly, then adding core layer monomer and stirring at high speed to obtain a nuclear monomer pre-emulsion; a2, adding initiator to water to prepare an initiator aqueous solution; a3, adding water and buffer to a reaction flask, heating to 80±2℃, and after stabilization, adding 5-10% of the nuclear monomer pre-emulsion and one-quarter of the initiator aqueous solution, reacting for 10-30 minutes, then adding the remaining nuclear monomer pre-emulsion and the remaining initiator aqueous solution dropwise into the reaction flask, continuing to add dropwise for 1-1.5 hours, and continuing to keep warm for 1-2.5 hours after the addition is completed to obtain the nuclear emulsion;
[0010] Preparation of the acrylate polyurethane core-shell emulsion: b1, at room temperature, water and emulsifier are added to a beaker and mixed evenly, then shell monomers are added and stirred at high speed to form a shell monomer pre-emulsion; b2, the above shell monomer pre-emulsion is divided into shell monomer pre-emulsion A and shell monomer pre-emulsion B, and the volume ratio of shell monomer pre-emulsion A to shell monomer pre-emulsion B is 1:2, wherein polymerizable polyurethane acrylate is added to shell monomer pre-emulsion B, and emulsification is continued to obtain mixed shell monomer pre-emulsion B; b3, an initiator is added to water. Prepare an initiator aqueous solution; b4, add shell monomer pre-emulsion A and one-third of the initiator aqueous solution dropwise to the core emulsion; after the shell monomer pre-emulsion A is added, continue to add mixed shell monomer pre-emulsion B and the remaining initiator solution dropwise, the entire addition time is 2-5h, and keep the temperature constant at 80±2℃; b5, after the addition is completed, continue to keep warm for 1.5-2h, after the warming is completed, cool down to 40℃, add ammonia water to adjust the pH value to 8-9, then add crosslinking agent, stir evenly and filter to obtain core-shell type acrylate polyurethane emulsion;
[0011] Step 2, Preparation of core-shell acrylate polyurethane emulsion primer: Under room temperature conditions, the core-shell acrylate polyurethane emulsion, film-forming aid, other additives, and ink absorber are mixed evenly to obtain a core-shell acrylate polyurethane emulsion primer for film modification. The amount of film-forming agent added is 1-20% of the mass of the core-shell acrylate polyurethane emulsion, the amount of other additives added is 0.1-2% of the mass of the core-shell acrylate polyurethane emulsion, and the amount of ink absorber added is 0.1-1% of the mass of the core-shell acrylate polyurethane emulsion.
[0012] The core layer monomer includes a hard monomer, a soft monomer, and a crosslinking monomer. The hard monomer is one or more of methyl methacrylate, styrene, and vinyl acetate. The soft monomer is one or more of ethyl acrylate, butyl acrylate, and isooctyl acrylate. The crosslinking monomer is ethylene glycol di(meth)acrylate.
[0013] The shell monomers include hard monomers, soft monomers, functional monomers, and crosslinking monomers. The hard monomers are one or more of methyl methacrylate, lauryl acrylate, styrene, and vinyl acetate. The soft monomers are one or more of ethyl acrylate, butyl acrylate, and isooctyl acrylate. The functional monomers are one or more of isobornyl methacrylate, dicyclopentenyl methacrylate, methacrylic acid, hydroxyethyl methacrylate, N-vinylimidazolium, and N-vinylpyrrolidone. The crosslinking monomers are one or more of polymerizable polyurethane acrylate, diacetone acrylamide, ethylene glycol di(meth)acrylate, and trimethylolpropane triacrylate.
[0014] The polymerizable polyurethane acrylate accounts for 1-10% of the mass of the shell monomer.
[0015] The emulsifier is one or more of sodium dodecyl sulfate, fatty alcohol polyoxyethylene ether (AEO-9), allyloxy fatty alcohol oxyethylene ether ammonium sulfate, and 1-allyloxy-3-(4-nonylphenol)-2-propanol polyoxyethylene (10) ether ammonium sulfate.
[0016] The initiator is ammonium persulfate and / or potassium persulfate.
[0017] The buffer is sodium bicarbonate and / or disodium hydrogen phosphate.
[0018] The crosslinking agent used is adipamide (ADH).
[0019] In the core-shell type acrylate polyurethane emulsion, the mass ratio of each component of the core layer emulsion is as follows (taking 100 parts as an example): hard monomer 7.5-16; soft monomer 10-24; crosslinking monomer 0-1.5; emulsifier 0.6-2; initiator 0.3-0.6; buffer 0.6-1.2; water balance.
[0020] The mass ratio of each component in the shell emulsion is as follows (taking 100 parts as an example): hard monomer 4.5-13.5; soft monomer 6.0-16.5; functional monomer 5-10; crosslinking monomer 0.5-3.5; polyurethane acrylate 0.5-4; emulsifier 0.6-2; initiator 0.3-0.6; water balance.
[0021] In the mass ratio of the core-shell acrylate polyurethane emulsion, the total amount of core layer monomers and shell layer monomers is 20-40% of the mass of the core-shell acrylate polyurethane emulsion, and the mass ratio of core layer monomers to shell layer monomers is 1:1-6. The core layer Tg of the core-shell acrylate polyurethane emulsion is -30 to -5℃, and the shell layer Tg is 10-45℃.
[0022] The film-forming aid in step 2 is one or more of methanol, ethanol, ethylene glycol dimethyl ether, diethylene glycol ethyl ether, (di)ethylene glycol butyl ether, and dipropylene glycol methyl ether.
[0023] The other additives are silicone-based surface wetting agents or leveling agents.
[0024] The ink absorber is made of silicon dioxide and / or kaolin.
[0025] The application of the core-shell type acrylate polyurethane emulsion primer prepared according to the above method in polymer film printing or printing is specifically as a primer before printing or printing polyethylene, polypropylene, poly(diethyl terephthalate), etc., and then drying.
[0026] As can be seen from the above description, the present invention has the following advantages:
[0027] 1. This invention utilizes a core-shell emulsion structure to overcome the drawbacks of traditional acrylic emulsions, such as hot adhesion and cold brittleness; it also addresses the instability of the emulsion caused by low polyurethane content in acrylic-modified polyurethane waterborne primers; and it employs a starved feed polymerization method to prepare a soft-core, hard-shell acrylic polyurethane emulsion. The soft core imparts flexibility to the coating, while the hard shell prevents coating adhesion. The acrylic monomers within the shell increase adhesion to surfaces of polyethylene, polypropylene, and other ground plastic films, while the acrylate monomers in the shell form a cross-linked network, ensuring the structural strength of the coating.
[0028] 2. The present invention uses a small amount of polymerizable polyurethane acrylate in the shell layer to significantly improve the wear resistance of the coating and the adhesion to ink, while avoiding the cumbersome process of conventional preparation of polyurethane acrylate emulsion.
[0029] 3. This invention utilizes the combination of film-forming aids and ink absorbers to form a porous ink-absorbing layer during the coating drying process, thereby achieving rapid adsorption and good adhesion of ink.
[0030] 4. The low-polyurethane-content core-shell acrylate polyurethane emulsion primer prepared by this invention is suitable for various plastic film substrates such as polyethylene, polypropylene, and polyethylene terephthalate. It can achieve grade 0 adhesion to both films and inks, and has the characteristics of good ink absorption and excellent abrasion resistance. Detailed Implementation
[0031] The present invention will be described in detail with reference to the embodiments, but the claims of the present invention are not intended to limit the scope of the invention.
[0032] Example 1
[0033] A method for preparing a core-shell type acrylic polyurethane primer includes the following steps:
[0034] Step 1, the preparation of the acrylate polyurethane emulsion, includes the following steps:
[0035] The preparation method of the core emulsion includes: a1, adding 25g of water, 0.3g of sodium dodecyl sulfate and 1.2g of fatty alcohol polyoxyethylene ether (AEO-9) to a beaker at room temperature and mixing them evenly, then adding a core layer monomer composed of 3g of ethyl acrylate, 8g of butyl acrylate, 4g of isooctyl acrylate and 5g of methyl methacrylate, and stirring at high speed to obtain a core monomer pre-emulsion; a2, dissolving 0.3g of ammonium persulfate in 5.7g of water to obtain an initiator aqueous solution; a3, adding 0.6g of sodium bicarbonate buffer and 100g of water to a reaction flask and heating to 80±2℃; after stabilization, adding 10wt% of the core monomer pre-emulsion and 1.5g of the initiator aqueous solution, reacting for 20 minutes, then adding the remaining core monomer pre-emulsion and 4.5g of the initiator aqueous solution dropwise to the reaction flask, continuing to add dropwise for 1.2h, maintaining the temperature at 80±2℃, and continuing to maintain the temperature for 1.5h after the addition is completed to obtain an acrylate core emulsion;
[0036] The preparation of the acrylate polyurethane core-shell emulsion includes the following steps: b1, at room temperature, 25g of water, 0.36g of sodium dodecyl sulfate and 1.44g of fatty alcohol polyoxyethylene ether AEO-9 are added to a beaker and mixed evenly. Then, a shell monomer composed of 6g of methyl acrylate, 6g of butyl acrylate, 8.5g of methyl methacrylate, 6.0g of isobornyl acrylate, 2.0g of hydroxyethyl acrylate, 1.0g of acrylic acid and 0.5g of diacetone acrylamide shell acrylate is added, and the mixture is stirred at high speed to form a shell monomer preemulsion. b2, the above shell monomer preemulsion is divided into shell monomer preemulsion A and shell monomer preemulsion B. The volume ratio of B is 1:2. In this process, 5g of monofunctional polymerizable polyurethane acrylate is added to the shell monomer preemulsion B, and emulsification continues to obtain a mixed shell monomer preemulsion B. b3, 0.45g of ammonium persulfate is added to 8.55g of water to prepare an initiator aqueous solution. b4, shell monomer preemulsion A and 3g of initiator aqueous solution are added dropwise to the core emulsion. After the addition of shell monomer preemulsion A is completed, the mixed shell monomer preemulsion B and the remaining initiator solution are added dropwise over a total of 4.5 hours, maintaining a constant temperature of 80±2℃. b5, after the addition is completed, the temperature is maintained for 1.5-2 hours. After the temperature maintenance, the temperature is lowered to 40℃, ammonia is added to adjust the pH to 8-9, and then 1.0g of ADH crosslinking agent is added. After stirring evenly, the mixture is filtered to obtain a core-shell type acrylate polyurethane emulsion.
[0037] Step 2, Preparation of core-shell acrylate polyurethane emulsion primer: Weigh 50g of core-shell acrylate polyurethane emulsion, 5g of ethylene glycol dimethyl ether, 5g of methanol, 1g of leveling agent (EFKA3033 leveling agent), and 0.5g of silica particles. Mix thoroughly at room temperature to obtain the primer solution for film modification.
[0038] The core-shell type acrylic polyurethane emulsion primer is a milky white liquid. This emulsion, either directly or diluted with water, is applied using a coating machine. It exhibits good leveling properties and a smooth coating surface. After baking at 80-110℃ for 30-50 seconds, the coating becomes colorless and transparent. Ink can then be printed onto the coated film. Using 3M 610 tape, the adhesion between the sample coating and PP, PET, and PE base films, as well as the adhesion of the printed ink on the samples, were tested. Both the primer coating and ink adhesion achieved a grade of 0.
[0039] Example 2
[0040] A method for preparing a core-shell type acrylic polyurethane primer includes the following steps:
[0041] Step 1, the preparation of the acrylate polyurethane emulsion, includes the following steps:
[0042] The preparation method of the core emulsion includes: a1, adding 20g of water and 1.0g of allyl oxy fatty alcohol oxyethylene ether ammonium sulfate to a beaker at room temperature and mixing them evenly, then adding a core layer monomer composed of core layer acrylates such as 4g of ethyl acrylate, 4g of butyl acrylate, 3g of isooctyl acrylate, and 4g of methyl methacrylate, and stirring at high speed to obtain a core monomer pre-emulsion; a2, dissolving 0.225g of ammonium persulfate in 4.275g of water to obtain an initiator aqueous solution; a3, adding 0.6g of sodium bicarbonate buffer and 100g of water to a reaction flask and heating to 80±2℃; after stabilization, adding 8wt% of acrylate core monomer pre-emulsion and 0.9g of initiator aqueous solution, reacting for 20 minutes, then adding the remaining core monomer pre-emulsion and 3.6g of initiator aqueous solution dropwise to the reaction flask, continuing to add dropwise for 1.2h, maintaining the temperature at 80±2℃, and continuing to maintain the temperature for 1.5h after the addition is completed to obtain the core emulsion;
[0043] The preparation of the acrylate polyurethane core-shell emulsion includes the following steps: b1, at room temperature, 30g of water and 1.6g of allyl oxy fatty alcohol oxyethylene ether ammonium sulfate are added to a beaker and mixed evenly. Then, a shell monomer composed of 5.0g ethyl acrylate, 7.0g butyl acrylate, 4.0g methyl acrylate, 10.0g methyl methacrylate, 4.0g isoborneol acrylate, 2.0g dicyclopentenyl acrylate, 1.0g acrylic acid, 1.0g N-vinylimidazole, and 1.0g diacetone acrylamide is added, and the mixture is stirred at high speed to form a shell monomer preemulsion. b2, the above shell monomer preemulsion is divided into shell monomer preemulsion A and shell monomer preemulsion B, and the shell monomer preemulsion A and shell monomer preemulsion B are... The volume ratio of shell monomer preemulsion B is 1:2. 3g of bifunctional polymerizable polyurethane acrylate is added to shell monomer preemulsion B, and emulsification continues to obtain mixed shell monomer preemulsion B. b3, 0.525g of ammonium persulfate is added to 10g of water to prepare an initiator aqueous solution. b4, shell monomer preemulsion A and 3.5g of initiator aqueous solution are added dropwise to the core emulsion. After the addition of shell monomer preemulsion A is completed, mixed shell monomer preemulsion B and the remaining initiator solution are added dropwise. The entire addition time is 4.5h, and the temperature is kept constant at 80±2℃. b5, after the addition is completed, the temperature is maintained for 1.5-2h. After the temperature maintenance, the temperature is lowered to 40℃, ammonia is added to adjust the pH to 8-9, and then 1.5g of ADH crosslinking agent is added. After stirring evenly, the mixture is filtered to obtain a core-shell type acrylate polyurethane emulsion.
[0044] Step 2, Preparation of core-shell acrylic polyurethane emulsion primer: Weigh 50g of core-shell acrylic polyurethane emulsion, 3g of ethylene glycol dimethyl ether, 5g of methanol, 2g of ethanol, 1g of leveling agent (EFKA3033 leveling agent), 0.6g of silica particles, and 0.2g of kaolin, and mix them evenly at room temperature to obtain the primer liquid for film modification.
[0045] The core-shell type acrylic polyurethane emulsion primer is a milky white liquid. This emulsion, either directly or diluted with water, is applied using a coating machine. It exhibits good leveling properties and a smooth coating surface. After baking at 80-110℃ for 30-50 seconds, the coating becomes colorless and transparent. Ink can then be printed onto the coated film. Using 3M 610 tape, the adhesion between the sample coating and PP, PET, and PE base films, as well as the adhesion of the printed ink on the samples, were tested. Both the primer coating and ink adhesion achieved a grade of 0.
[0046] Example 3
[0047] A method for preparing a core-shell type acrylic polyurethane primer includes the following steps:
[0048] Step 1, the preparation of the acrylate polyurethane emulsion, includes the following steps:
[0049] The preparation method of nuclear emulsion includes: a1, at room temperature, 15g of water and 0.50g of... 1-Allyloxy-3-(4-nonylphenol)-2-propanol polyoxyethylene (10) ether ammonium sulfate and 0.25g sodium dodecyl sulfate were mixed evenly, and a core layer monomer composed of 3g ethyl acrylate, 3g butyl acrylate, 3g isooctyl acrylate and 3g methyl methacrylate was added. The mixture was stirred at high speed to obtain a core monomer preemulsion; a2, 0.188g ammonium persulfate was dissolved in 3.562g water to obtain an initiator aqueous solution; a3, 0.6g sodium bicarbonate buffer and 100g water were added to the reaction flask and the temperature was raised to 80±2℃; after stabilization, 10wt% acrylate core monomer preemulsion and 0.93g initiator aqueous solution were added. After reacting for 20 minutes, the remaining acrylate core monomer preemulsion and 2.82g initiator aqueous solution were added dropwise to the reaction flask. The addition was continued for 1.2h, and the temperature was kept at 80±2℃. After the addition was completed, the temperature was kept at 80±2℃ for another 1.5h to obtain the core emulsion.
[0050] The preparation of the acrylate polyurethane core-shell emulsion includes the following steps: b1, at room temperature, 35g of water, 1.2g of 1-allyloxy-3-(4-nonylphenol)-2-propanol polyoxyethylene (10) ether ammonium sulfate and 0.3g of sodium dodecyl sulfate are added to a beaker and mixed evenly. Then, a shell acrylate monomer composed of 5.0g ethyl acrylate, 6.0g butyl acrylate, 4.0g methyl acrylate, 10.0g methyl methacrylate, 5.0g isoborneol acrylate, 2.5g dicyclopentenyl acrylate, 0.5g acrylic acid, 1.5g N-vinylpyrrolidone, and 1.5g diacetone acrylamide is added and stirred at high speed to form a shell monomer preemulsion. b2, the above shell monomer preemulsion is divided into shell monomer preemulsion A and shell monomer preemulsion B, and the shell monomer preemulsion A and shell monomer preemulsion B are further divided into shell monomer preemulsion A and shell monomer preemulsion B. Emulsion B has a volume ratio of 1:2. 4g of monofunctional polymerizable polyurethane acrylate is added to the shell monomer pre-emulsion B, and emulsification continues to obtain a mixed shell monomer pre-emulsion B. b3, 0.56g of ammonium persulfate is added to 10.69g of water to prepare an initiator aqueous solution. b4, Shell monomer pre-emulsion A and 3.75g of initiator aqueous solution are added dropwise to the core emulsion. After the addition of shell monomer pre-emulsion A is completed, the mixed shell monomer pre-emulsion B and the remaining initiator solution are added dropwise. The entire addition time is 4.5h, and the temperature is kept constant at 80±2℃. b5, After the addition is completed, the temperature is maintained for 1.5-2h. After the temperature maintenance, the temperature is lowered to 40℃, ammonia is added to adjust the pH to 8-9, and then 1.8g of ADH crosslinking agent is added. After stirring evenly, the mixture is filtered to obtain a core-shell type acrylate polyurethane emulsion.
[0051] Step 2, Preparation of core-shell acrylate polyurethane emulsion primer: Weigh 50g core-shell acrylate polyurethane emulsion, 1g ethylene glycol dimethyl ether, 6g methanol, 3g ethanol, 1g leveling agent (EFKA3033 leveling agent), 0.4g silica particles and 0.6g kaolin, and mix them evenly at room temperature to obtain the primer liquid for film modification.
[0052] The core-shell type acrylic polyurethane emulsion primer is a milky white liquid. This emulsion, either directly or diluted with water, is applied using a coating machine. It exhibits good leveling properties and a smooth coating surface. After baking at 80-110℃ for 30-50 seconds, the coating becomes colorless and transparent. Ink can then be printed onto the coated film. Using 3M 610 tape, the adhesion between the sample coating and PP, PET, and PE base films, as well as the adhesion of the printed ink on the samples, were tested. Both the primer coating and ink adhesion achieved a grade of 0.
[0053] It is understood that the above detailed description of the present invention is for illustrative purposes only and is not intended to limit the technical solutions described in the embodiments of the present invention. Those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention to achieve the same technical effects; as long as the usage requirements are met, they are all within the protection scope of the present invention.
Claims
1. A core-shell type acrylic polyurethane emulsion primer, characterized in that, The core-shell acrylic polyurethane emulsion in the primer is a soft-core, hard-shell acrylic polyurethane emulsion, wherein the core layer Tg is -30 to -5℃ and the shell layer Tg is 10-45℃. The preparation method of the core-shell type acrylic polyurethane emulsion primer includes the following steps: Step 1, preparation of core-shell acrylate polyurethane emulsion, wherein the polymerization of the emulsion is carried out by a semi-continuous starvation feeding method; The method for preparing the nuclear emulsion includes: a1, adding water and emulsifier to a beaker at room temperature and stirring evenly, then adding the core layer monomer and stirring at high speed to obtain a nuclear monomer pre-emulsion; a2, adding the initiator to water to prepare an initiator aqueous solution; a3, adding water and buffer to a reaction flask, heating to 80±2℃, and after stabilization, adding 5-10% of the nuclear monomer pre-emulsion and one-quarter of the initiator aqueous solution, reacting for 10-30 minutes, then adding the remaining nuclear monomer pre-emulsion and three-quarters of the initiator aqueous solution dropwise into the reaction flask, continuing to add dropwise for 1-1.5 hours, and continuing to keep warm for 1-2.5 hours after the addition is completed to obtain the nuclear emulsion; The preparation method of the core-shell type acrylate polyurethane emulsion is as follows: b1, at room temperature, water and emulsifier are added to a beaker and mixed evenly, then shell monomer is added and stirred at high speed to form a shell monomer pre-emulsion; b2, the above shell monomer pre-emulsion is divided into shell monomer pre-emulsion A and shell monomer pre-emulsion B, and the volume ratio of shell monomer pre-emulsion A to shell monomer pre-emulsion B is 1:
2. Polymerizable polyurethane acrylate is added to shell monomer pre-emulsion B, and emulsification is continued to obtain mixed shell monomer pre-emulsion B; b3, an initiator is added to water to prepare an initiator aqueous solution. b4. Add shell monomer pre-emulsion A and one-third of the initiator aqueous solution dropwise to the core emulsion; after the addition of shell monomer pre-emulsion A is completed, continue to add mixed shell monomer pre-emulsion B and the remaining initiator solution dropwise, with the entire addition time being 2-5 hours, maintaining a constant temperature of 80±2℃; b5. After the addition is completed, continue to maintain the temperature for 1.5-2 hours, then cool to 40℃, add ammonia to adjust the pH to 8-9, then add the crosslinking agent, stir evenly, and filter to obtain a core-shell type acrylate polyurethane emulsion; the polymerizable polyurethane acrylate accounts for 1-10% of the shell monomer mass. Step 2, Preparation of core-shell acrylate polyurethane emulsion primer: Under room temperature conditions, the core-shell acrylate polyurethane emulsion, film-forming aid, other additives and ink absorber are mixed evenly to obtain the core-shell acrylate polyurethane emulsion primer. The amount of film-forming aid added is 1-20% of the mass of the core-shell acrylate polyurethane emulsion, the amount of other additives added is 0.1-2% of the mass of the core-shell acrylate polyurethane emulsion, and the amount of ink absorber added is 0.1-1% of the mass of the core-shell acrylate polyurethane emulsion. The core layer monomer includes a hard monomer, a soft monomer, and a crosslinking monomer. The hard monomer is one or more of methyl methacrylate, styrene, and vinyl acetate. The soft monomer is one or more of ethyl acrylate, butyl acrylate, and isooctyl acrylate. The crosslinking monomer is ethylene glycol di(meth)acrylate. The shell monomers include hard monomers, soft monomers, functional monomers, and crosslinking monomers. The hard monomers are one or more of methyl methacrylate, styrene, and vinyl acetate. The soft monomers are one or more of ethyl acrylate, butyl acrylate, and isooctyl acrylate. The functional monomers are one or more of isobornyl methacrylate, dicyclopentenyl methacrylate, methacrylic acid, hydroxyethyl methacrylate, N-vinylimidazolium, and N-vinylpyrrolidone. The crosslinking monomers are one or more of polymerizable polyurethane acrylate, diacetone acrylamide, ethylene glycol di(meth)acrylate, and trimethylolpropane triacrylate.
2. The core-shell type acrylic polyurethane emulsion primer according to claim 1, characterized in that: The emulsifier is one or more of sodium dodecyl sulfate, fatty alcohol polyoxyethylene ether, allyloxy fatty alcohol oxyethylene ether ammonium sulfate, and 1-allyloxy-3-(4-nonylphenol)-2-propanol polyoxyethylene (10) ether ammonium sulfate.
3. The core-shell type acrylic polyurethane emulsion primer according to claim 1, characterized in that: The initiator is ammonium persulfate and / or potassium persulfate; the buffer is sodium bicarbonate and / or disodium hydrogen phosphate; and the crosslinking agent is adipic hydrazide.
4. The core-shell type acrylic polyurethane emulsion primer according to claim 1, characterized in that: In the preparation of the core-shell type acrylic polyurethane emulsion, based on a total of 100 parts, the mass ratio of each component in the core layer emulsion is: 7.5-16 parts of hard monomer; 10-24 parts of soft monomer. Crosslinking monomer 0-1.5 parts; emulsifier 0.6-2 parts; initiator 0.3-0.6 parts; buffer 0.6-1.2 parts; water balance; Based on a total of 100 parts, the mass ratio of each component in the shell emulsion is as follows: 4.5–13.5 parts hard monomer; 6.0–16.5 parts soft monomer; 5–10 parts functional monomer; 0.5–3.5 parts crosslinking monomer; 0.5–4 parts polymerizable polyurethane acrylate; 0.6–2 parts emulsifier; 0.3–0.6 parts initiator; and water as the balance.
5. The core-shell type acrylic polyurethane emulsion primer according to claim 1, characterized in that: The film-forming aid in step 2 is one or more of methanol, ethanol, ethylene glycol dimethyl ether, diethylene glycol ethyl ether, diethylene glycol butyl ether, and dipropylene glycol methyl ether; the other aids are organosilicon surface wetting agents or leveling agents; and the ink absorber is silica and / or kaolin.