Epoxy-modified room temperature self-crosslinking waterborne acrylate dispersion, and preparation method and application thereof

Abstract

The application discloses an epoxy-modified room-temperature self-crosslinking water-based acrylate dispersion and a preparation method and application thereof, and belongs to the field of water-based acrylate resins. The dispersion is obtained by adjusting the pH value of an acrylate polymer after extracting an organic solvent to 7.5-8.5, mixing with deionized water and a dihydrazide, dispersing, filtering and the like; the acrylate polymer is obtained by solution polymerization of a mixed solution of part of an initiator, a hard monomer, a soft monomer, a first type of hydrophilic monomer, a second type of hydrophilic monomer, an epoxy resin and a combined crosslinking monomer and the rest of the initiator dissolved in an organic solvent at 80-83 DEG C. The main solvent of the dispersion is water, the viscosity is low, the content of the organic solvent is less than 5%, VOCs is low, the dispersion has a multiple crosslinking network structure, the crosslinking degree is high (78%-83%), the resolubility of ink prepared from the dispersion is excellent, the adhesion, water resistance, storage stability on a plastic film are good, and the glossiness is high.

Description

Technical Field

[0001] This invention relates to epoxy-modified room-temperature self-crosslinking waterborne acrylate dispersions, specifically to a method for preparing and applying an epoxy resin-modified waterborne acrylate resin with high crosslinking degree at room temperature, belonging to the field of waterborne resins. Background Technology

[0002] Solvent-based inks, due to their high content of organic solvents leading to extremely high VOCs levels, seriously threaten the ecological environment and are gradually being phased out, while water-based inks have become a research focus. In terms of performance, compared to solvent-based inks, water-based inks generally suffer from drawbacks such as low resolubility, poor water resistance, insufficient gloss, and poor printability, severely limiting their application range. Specifically, insufficient water resistance in water-based inks makes them prone to peeling off after absorbing water; poor resolubility results in poor reproducibility of shallow areas during continuous printing, easily causing plate clogging and affecting print quality and production efficiency. Currently, water-based acrylic resins are commonly used as binders for water-based inks in plastic film printing, mainly of three types: water-soluble, water-dispersion, and emulsion acrylic resins.

[0003] Emulsion-type acrylic resins are produced through emulsion polymerization, primarily using water as a solvent. They are highly safe and environmentally friendly. Compared to water-soluble and water-dispersible acrylic resins, emulsions have a larger molecular weight and contain a small amount of hydrophilic monomers, resulting in better water resistance after film formation. However, this sacrifices resolubility, posing certain difficulties in practical applications. Chinese invention patent CN110128875B discloses a novel self-crosslinking emulsion for water-based ink binders in flexographic printing and its preparation method, improving the resolubility and water resistance of the emulsion. However, the resolubility still cannot meet the requirements of practical continuous printing.

[0004] Water-soluble acrylic resins are mainly obtained through solution polymerization. The polymers have low molecular weights and high hydrophilic monomer content. While they exhibit excellent resolubility when formulated into water-based inks, they are prone to water absorption and swelling, leading to ink detachment. Compared to emulsions and aqueous dispersions, water-soluble acrylic resins are highly hydrophilic, have high viscosity, and their high organic solvent content results in a low flash point and flammability. This not only poses environmental problems but also issues with storage, transportation, and safety during use. Chinese invention patent CN113105571B discloses a low-temperature self-crosslinking water-based epoxy-modified acrylic resin, its preparation method, and its application, significantly improving the water resistance of inks. However, it uses organic solvents as the main solvent and does not consider the resolubility of water-based inks. Chinese invention patent application CN116396423A discloses a metal ion-modified water-based acrylic resin, its preparation method, and its application. This water-based acrylic resin exhibits good resolubility and water resistance when formulated into inks, but the high VOC content within the system remains unresolved due to the use of organic solvents as the main solvent. If organic solvents are directly extracted from water-soluble acrylic resins to reduce VOC content and increase flash point, the viscosity of the resulting water-based acrylic resin will increase due to excessive hydrophilicity, making it unsuitable for practical applications.

[0005] Compared to emulsion resins, water-dispersible acrylic resins have a moderate molecular weight, a higher content of hydrophilic monomers, and good resolubility. Compared to water-soluble resins, water-dispersible acrylic resins have a lower organic solvent content. For water-dispersible acrylic resins, if the resin segments are highly hydrophilic, the resin is often a mixture of water-soluble and dispersed resins, causing the viscosity of the dispersion to increase abnormally with increasing hydroxyl and carboxyl group content, severely hindering the practical application of aqueous acrylate dispersions. Chinese invention patent CN103396508B discloses a low-temperature self-crosslinking waterborne acrylic resin and its preparation method and application. This method removes most of the organic solvent by direct vacuum distillation of the polymer after solution polymerization, but the resin viscosity increases significantly, making direct application difficult. Chinese invention patent CN109867743A discloses a room-temperature self-crosslinking waterborne acrylic resin dispersion and its preparation method, improving the resin's water resistance, but it does not consider resolubility, and the organic solvent content remains high. Chinese invention patent CN115304957B discloses a water-based ink dispersion and its preparation method, which improves resolubility and reduces VOC content, but has insufficient water resistance.

[0006] To address the problems existing in using water-based acrylic resins as binders in plastic film printing, it is of great significance to develop a water-based acrylic resin with excellent resolubility, water resistance, and low VOCs. Summary of the Invention

[0007] The purpose of this invention is to address the problems of high VOC content, difficulty in balancing water resistance and resolubility of waterborne acrylic resins, and abnormally increased viscosity of aqueous dispersions due to high hydroxyl and carboxyl group content. This invention provides a room-temperature self-crosslinking epoxy resin modified acrylic ester aqueous dispersion with low VOC content, excellent resolubility, water resistance and adhesion on plastic films, and low viscosity, as well as its preparation method.

[0008] Another object of the present invention is to provide the application of the room temperature crosslinked epoxy resin modified acrylate aqueous dispersion as a binder for water-based inks.

[0009] To achieve the objectives of this invention, the following technical solutions are provided:

[0010] An epoxy-modified room-temperature self-crosslinking waterborne acrylate dispersion is obtained by extracting organic solvent from an acrylate polymer, adjusting the pH to 7.5–8.5, mixing with deionized water and dihydrazide, dispersing, and filtering. The acrylate polymer is obtained by solution polymerization at 80–83°C of a mixed solution of a partial initiator, hard monomers, soft monomers, a first type of hydrophilic monomer, a second type of hydrophilic monomer, epoxy resin, and combined crosslinking monomers, along with the remaining initiator dissolved in the organic solvent. The first type of hydrophilic monomer is an acrylic monomer containing a carboxyl group or a methacrylic monomer containing a carboxyl group; the second type of hydrophilic monomer is an acrylic monomer containing a hydroxyl group or a methacrylic monomer containing a hydroxyl group; the partial initiator and the remaining initiator constitute all initiators, with the remaining initiator accounting for 25–45% of the total initiator mass, and the initiator is a free radical type initiator.

[0011] The combined crosslinking monomers are one or more of diacetone acrylamide, N-hydroxymethylacrylamide, N-hydroxyethylacrylamide, and acetoacetoxyethyl methacrylate, combined with one or more of trimethylolpropane triacrylate, tetramethyldivinyldisiloxane, allyl methacrylate, and triallyl isocyanurate.

[0012] To further achieve the objectives of this invention, preferably, the raw material composition, by weight, is as follows:

[0013] Hard monomer: 35-55 parts

[0014] Soft monomer: 25-40 parts

[0015] Type I hydrophilic monomers: 6-15 parts

[0016] Type II hydrophilic monomers: 2-7 parts

[0017] Initiator: 3-5 parts

[0018] Organic solvent: 70-90 parts

[0019] Epoxy resin: 4-7 parts

[0020] Combined crosslinking monomers: 2-10 parts

[0021] Dihydrazide: 2-4 parts

[0022] Deionized water: 160-200 parts.

[0023] Preferably, the epoxy-modified room-temperature self-crosslinking waterborne acrylate dispersion has an average particle size of 16-50 nm and an acid value of 20-60 mg KOH / g; the hard monomer is one or more of methyl methacrylate, methyl acrylate, ethyl methacrylate, isobutyl methacrylate, and isobornyl methacrylate; the soft monomer is one or more of ethyl acrylate, butyl acrylate, 2-ethylethyl acrylate, n-octyl acrylate, lauryl methacrylate, and octadecyl methacrylate.

[0024] Preferably, the first type of hydrophilic monomer is one or both of acrylic acid and methacrylic acid; the second type of hydrophilic monomer is one or more of hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, and hydroxypropyl acrylate; the epoxy resin is one or more of epoxy resin E-44, epoxy resin E-51, epoxy resin E-54, epoxy resin NPEL-128, and epoxy resin P430; and the dihydrazide is dihydrazide carbonate, dihydrazide oxalate, dihydrazide adipic acid, or dihydrazide succinate.

[0025] Preferably, the pH adjustment is achieved by adding a pH adjuster, which is one or more of ammonia, triethylamine, dimethylethanolamine, and triethanolamine.

[0026] Preferably, the initiator is one or more of azobisisobutyronitrile, azobisisoheptanenitrile, and benzoyl peroxide; and the organic solvent is one or more of ethanol, isopropanol, and propylene glycol methyl ether.

[0027] The preparation method of the epoxy-modified room temperature self-crosslinking aqueous acrylate dispersion includes the following steps:

[0028] 1) Mix a portion of the initiator, hard monomer, soft monomer, first-type hydrophilic monomer, second-type hydrophilic monomer, epoxy resin, and crosslinking monomer to obtain a mixed solution. The mixed solution reacts with the remaining initiator dissolved in the organic solvent, and the temperature of the reaction system is controlled at 80-83℃.

[0029] 2) Reduce the temperature of the product obtained in step 1) to 35-45℃, extract the organic solvent under reduced pressure, adjust the pH to 7.5-8.5, add a mixture of deionized water and dihydrazide for dispersion, filter and discharge to obtain epoxy-modified room temperature self-crosslinking waterborne acrylate dispersion.

[0030] Preferably, the reaction between the mixed solution and the remaining initiator dissolved in the organic solvent is carried out by adding the mixed solution dropwise to a reaction vessel containing the remaining initiator dissolved in the organic solvent, with the dropwise addition time controlled at 2.5 to 3 hours, and then maintaining the temperature for another 2 to 4 hours after the dropwise addition is completed; the dispersion is carried out in a high-speed dispersion device, with the dispersion speed controlled at 3000 r / min to 3500 r / min.

[0031] Application of epoxy-modified room temperature self-crosslinking waterborne acrylate dispersion in waterborne inks: The epoxy-modified room temperature self-crosslinking waterborne acrylate dispersion is compounded with waterborne color paste, ethanol and water to obtain plastic film ink. The solid content of the plastic film ink is controlled to be 5% to 35% by mass percentage.

[0032] Preferably, by mass parts, the amount of epoxy-modified room temperature self-crosslinking waterborne acrylate dispersion is 40-60 parts, the amount of waterborne pigment is 20-40 parts, the amount of ethanol is 10-20 parts, and the amount of deionized water is 5-10 parts.

[0033] During compounding, the epoxy-modified room temperature self-crosslinking waterborne acrylate dispersion is added to deionized water and ethanol and stirred at low speed for 10-25 minutes. Then, waterborne pigment is added and stirred at high speed for more than 10-25 minutes to obtain epoxy-modified room temperature self-crosslinking waterborne acrylate dispersion ink. The stirring speed at low speed is 30-100 r / min, and the stirring speed at high speed is 500-800 r / min.

[0034] The water-based ink produced by this invention can be applied to plastic film substrates such as PE, BOPP and PET.

[0035] Compared with the prior art, the present invention has the following advantages:

[0036] 1) The resin coating of this invention has suitable molecular weight and hydrophilicity, and possesses a multi-layered network structure with a high degree of cross-linking, while also exhibiting excellent resolubility, water resistance, and adhesion. The resin coating film of this invention has suitable molecular weight and hydrophilicity; the ink retains strong hydrophilicity within 30 minutes after ink scraping, is easily dissolved in an aqueous ethanol solution, and has a resolubility of over 85%, without causing plate clogging. The introduction of epoxy resin, cross-linking monomers, and acrylic acid and its ester monomers during the polymerization reaction stage results in a multi-layered cross-linked network structure with a certain degree of cross-linking. After the self-cross-linking reaction at room temperature is completed, this cross-linked structure further forms a denser three-dimensional network structure, enhancing the cross-linking density of the acrylic resin. This not only improves the water resistance of the resin but also enhances the bonding between the acrylic resin and various plastic films, improving the adhesion of the resin to plastic films. The epoxy-modified room-temperature self-crosslinking waterborne acrylate dispersion obtained in this invention was formulated into an ink and applied to plastic films PE, BOPP and PET. After being pulled apart with 3M 600 tape, the adhesion strength reached 100%, 97% and 95% respectively, showing excellent adhesion. After being completely dried and immersed in water for 24 hours, the wet adhesion was still excellent, with the ink layer basically not falling off and the adhesion strength still above 95%.

[0037] 2) Low viscosity, low VOCs content (organic solvent content <5%), high flash point.

[0038] The epoxy-modified room-temperature self-crosslinking waterborne acrylate dispersion prepared by this invention is first obtained by solution polymerization to obtain an acrylic polymer with a certain ratio of hydrophilic and hydrophobic monomers. Then, the solvent is removed under reduced pressure, the degree of neutralization is adjusted, and the oil phase is reversed to the aqueous phase by utilizing the polymer's self-emulsification ability. It has an organic solvent content of <5%, low VOCs content, and a viscosity controlled at 24s-87s when the solid content is 30%-35%. The flash point is increased to 50℃. Compared to water-soluble acrylic resins, it will not ignite upon exposure to an open flame, greatly improving the safety of resin storage, transportation, and use. This preparation method not only solves the problem of high viscosity in aqueous dispersions but also eliminates the need for complex and cumbersome operations. Furthermore, it allows for solvent recycling, greatly avoiding resource waste and facilitating large-scale production.

[0039] 3) Excellent stability

[0040] The epoxy-modified room-temperature self-crosslinking waterborne acrylate dispersion of the present invention introduces a single-component self-crosslinking system that does not undergo premature crosslinking under alkaline conditions and can be stably stored for more than 300 days; it does not separate into layers after centrifugation at 5000 r / min for 30 min, and the resin of the present invention also has excellent centrifugal stability.

[0041] 4) Low resin odor

[0042] The epoxy-modified room-temperature self-crosslinking aqueous acrylate dispersion of the present invention can remove unreacted monomers while removing solvent under reduced pressure, thereby reducing and weakening the resin odor and minimizing its impact on the health of construction workers.

[0043] 5) The drying speed is controllable, suitable for rapid printing in factories.

[0044] The epoxy-modified room-temperature self-crosslinking aqueous acrylate dispersion of this invention exhibits good alcohol dilution properties, and the drying speed can be adjusted by adding volatile solvents (such as ethanol) to meet ink production requirements. The resin prepared by this invention is mixed with color paste, deionized water, and anhydrous ethanol to formulate ink, which, when applied to plastic films, achieves surface drying of 11.4 μm thick ink film within 10 seconds at 25°C, enabling industrial-scale plastic film printing at speeds of 60-100 m / min. Detailed Implementation

[0045] To better understand the present invention, the following embodiments are provided to further illustrate the invention, but the scope of protection claimed by the present invention is not limited to the scope expressed in the embodiments.

[0046] The present invention discloses a method for synthesizing epoxy-modified room-temperature self-crosslinking waterborne acrylate dispersions based on solution polymerization. The method involves extracting an organic solvent from the acrylate polymer, adjusting the pH to 7.5–8.5, mixing it with deionized water and dihydrazide, dispersing, and filtering. The acrylate polymer is obtained by solution polymerization at 80–83°C of a mixed solution of a partial initiator, hard monomers, soft monomers, a first type of hydrophilic monomer, a second type of hydrophilic monomer, epoxy resin, and combined crosslinking monomers, along with the remaining initiator dissolved in the organic solvent. The first type of hydrophilic monomer is an acrylic monomer containing a carboxyl group or a methacrylic monomer containing a carboxyl group; the second type of hydrophilic monomer is an acrylic monomer containing a hydroxyl group or a methacrylic monomer containing a hydroxyl group; the combined crosslinking monomer is one or more of diacetone acrylamide, N-hydroxymethylacrylamide, N-hydroxyethylacrylamide, and acetoacetoxyethyl methacrylate, and one of trimethylolpropane triacrylate, tetramethyldivinyldisiloxane, allyl methacrylate, and triallyl isocyanurate.

[0047] Taking epoxy resin E-51 as an example, and the combination of crosslinking monomers, specifically diacetone acrylamide and tetramethyldivinyldisiloxane, as an example, the reaction mechanisms of other crosslinking agents are basically the same:

[0048] 1) Polymerization stage of acrylic acid and its ester monomers, epoxy resin, and combined crosslinking monomers:

[0049] Epoxy resin E-51 has a relatively active α-H atom on the carbon group and H atom on the tertiary carbon group in its molecular structure. Under the action of an initiator, it can generate multiple active free radicals, which can be used as active centers to initiate graft copolymerization with acrylic acid and its ester monomers, linking different acrylate polymer segments. In the combined crosslinking monomers, DAAM contains one unsaturated carbon-carbon double bond and tetramethyldivinyldisiloxane contains two unsaturated carbon-carbon double bonds, both of which can directly undergo polymerization reactions with acrylic acid and its ester monomers. Therefore, the combination of epoxy resin and crosslinking monomers will undergo preliminary crosslinking with acrylic acid and its ester monomers during the polymerization reaction stage, forming a multi-layer crosslinked network structure with a certain degree of crosslinking.

[0050]

[0051] 2) Neutralize the resin by introducing ammonia water.

[0052]

[0053] At this point, the pH in the system is greater than 7, the room temperature self-crosslinking reaction is inhibited, and the epoxy-modified room temperature self-crosslinking waterborne acrylate dispersion can be stored stably.

[0054] 3) The neutralized polymer segments are dispersed to achieve self-emulsification.

[0055]

[0056] 4) Resin drying to form a film

[0057] In the preparation of epoxy-modified room-temperature self-crosslinking aqueous acrylate dispersions according to this invention, during the drying and film-forming process, ammonia and amine salts are easily volatilized from the film in a storage environment at room temperature and pressure. The specific drying process is as follows:

[0058] (1) Large-scale evaporation of water and solvents;

[0059] (2) Deamination film formation: As ammonia volatilizes, when the pH is less than 7, diacetone acrylamide and dihydrazide undergo a cross-linking reaction;

[0060]

[0061] As can be seen from the above reaction process, when the resin is drying as a film, the crosslinking monomer DAAM and dihydrazide undergo a crosslinking reaction, which further links different polymer segments together to form a denser multi-linked network structure, increasing the crosslinking density of the resin. This makes it difficult for water molecules to penetrate into the interior of the coating, thereby improving the water resistance of the resin.

[0062] As can be seen from the above reaction process, the core of this invention is the preparation of acrylate polymers. Initiators, epoxy resins, hard monomers, and soft monomers are common raw materials in the field. The first type of hydrophilic monomers, the second type of hydrophilic monomers, and the combined crosslinking monomers must be as defined above. The dihydrazides are preferably dihydrazides of carbonate, dihydrazides of oxalate, dihydrazides of adipic acid, or dihydrazides of succinate. Adjusting the pH value is a common adjustment method, mainly to control the pH value to 7.5-8.5. As for the amount of raw materials involved, it can be obtained through experiments based on the above mechanism and in combination with the purpose of this invention.

[0063] This invention achieves a suitable hydrophilicity and self-emulsifying ability in the polymer by controlling the content of hydrophilic monomers and removing co-solubilizing organic solvents under reduced pressure, followed by neutralization adjustments. This is achieved through a phase inversion to obtain a water-based dispersion resin with suitable molecular weight and low viscosity, while also reducing VOC content. When the solid content is 30%-35%, the viscosity is controlled at 24s-87s. When the dispersion is formulated into a water-based ink sample, the suitable molecular weight and hydrophilic properties allow the ink to achieve a resolubility of 85% or higher within 30 minutes, demonstrating excellent resolubility and meeting the needs of continuous and efficient printing production. The introduced multi-crosslinked network structure, after complete curing at room temperature (78%-83% crosslinking), results in an adhesion strength of 95%-100% on various low-polarity plastics such as PE, PET, and BOPP. Even after immersion in water for 24 hours, the adhesion strength still reaches over 95%, demonstrating excellent water resistance.

[0064] The waterborne ink products prepared from the epoxy-modified room-temperature self-crosslinking aqueous acrylate dispersions in various embodiments of the present invention were tested according to the following test standards:

[0065] Viscosity test: GB / T 13217.4-2020, using the Forecast 4 cup method.

[0066] Adhesion test: GB / T 13217.7-2023

[0067] Stability test: Refer to GB6753.3-1986, seal the aqueous dispersion resin, place it in a cool place at room temperature, and observe whether the flow of the resin solution is abnormal or gelation occurs.

[0068] Water resistance test: The ink film is coated on the plastic film. After the coating is completely cured, it is immersed in deionized water at 25°C for 24 hours. After removal, the ink film peeling off the plastic film and the deionized water is observed, and the peeling ratio and the corresponding adhesion strength are calculated.

[0069] Resolubility test: Apply a layer of ink to tinplate and leave it for 30 minutes. Then tilt the tinplate at an angle of about 30° and pour 50 mL of diluent (water: anhydrous ethanol = 3:7) onto the ink layer. After 3 minutes, observe the dissolution of the ink on the tinplate and classify it into four grades: excellent, good, medium and poor according to the amount of ink dissolved.

[0070] Example 1

[0071] 1) Preparation of room temperature self-crosslinking modified epoxy acrylate aqueous dispersion

[0072] Dissolve 1.2g of azobisisobutyronitrile (AIBN) and 75g of anhydrous ethanol thoroughly, then add the solution to a reaction vessel equipped with a reflux condenser and maintain reflux at 80℃ for 10 min. Mix 40g of methyl methacrylate, 30g of butyl acrylate, 6g of acrylic acid, 6g of hydroxyethyl acrylate, 4g of E-51 epoxy resin, 3g of diacetone acrylamide, 1g of trimethylolpropane triacrylate, 2g of AIBN, and 6g of anhydrous ethanol. Then, use a peristaltic pump to add the mixed solution dropwise to the reaction vessel at a uniform rate over 3 hours, while controlling the reaction temperature. The temperature was 83℃. After the addition was completed, the temperature was kept at 83℃ for 3 hours and then cooled to 35℃. The solvent in the reactor was removed by vacuum pump for 40 minutes, with a vacuum degree of 0.090 MPa. The temperature of the reactor was raised to 45℃, and 3g of ammonia and 1g of dimethylethanolamine were added for neutralization for 20 minutes. The mixture was then transferred to a dispersion device, and 180g of deionized water and 2.4g of adipate dihydrazide were added at a dispersion speed of 3500r / min. The mixture was dispersed at high speed for 30 minutes, filtered, and discharged to obtain a room temperature self-crosslinking modified epoxy acrylate aqueous dispersion.

[0073] 2) Preparation of epoxy-modified room temperature self-crosslinking waterborne acrylic dispersion ink

[0074] Add 40g of room temperature self-crosslinking modified epoxy acrylate aqueous dispersion, 5g of water and 15g of ethanol to the mixing tank, and stir at 100r / min for 10min; then add 25g of Nami Fresh Color Specialty Paste, and stir at 500r / min for 15min; the desired water-based ink is obtained.

[0075] Example 2

[0076] 1) Preparation of room temperature self-crosslinking modified epoxy acrylate aqueous dispersion

[0077] Take 1g of azobisisobutyronitrile (AIBN) and 70g of anhydrous ethanol, dissolve them thoroughly, and add them to a reactor equipped with a reflux condenser. Maintain reflux at 80℃ for 10 minutes. Mix 40g of methyl methacrylate, 35g of butyl acrylate, 8g of acrylic acid, 4g of hydroxypropyl acrylate, 5g of E-51 epoxy resin, 3g of N-hydroxyethylacrylamide, 3g of tetramethyldivinyldisiloxane, 2.2g of AIBN, and 6g of anhydrous ethanol. Then, use a peristaltic pump to add the mixed solution dropwise to the reactor at a uniform rate over 3 hours. The reaction temperature was controlled at 83℃. After the addition was completed, the temperature was kept at 3℃ for 3 hours and then cooled to 35℃. The solvent in the reactor was removed by a water pump for 40 minutes with a vacuum degree of 0.090 MPa. The temperature of the reactor was raised to 45℃, and 4g of ammonia and 1g of dimethylethanolamine were added for neutralization for 20 minutes. The mixture was then transferred to a dispersion device, and 180g of deionized water was added at a dispersion speed of 3500r / min. The mixture was dispersed at high speed for 30 minutes, filtered, and discharged to obtain a room temperature self-crosslinking modified epoxy acrylate aqueous dispersion.

[0078] 2) Preparation of epoxy-modified room temperature self-crosslinking waterborne acrylic dispersion ink

[0079] Add 40g of room temperature self-crosslinking modified epoxy acrylate aqueous dispersion, 5g of water and 15g of ethanol to the mixing tank, and stir at 100r / min for 10min; then add 25g of Nami Fresh Color Specialty Paste, and stir at 500r / min for 15min; the desired water-based ink is obtained.

[0080] Example 3

[0081] 1) Preparation of room temperature self-crosslinking modified epoxy acrylate aqueous dispersion

[0082] Take 1g of azobisisobutyronitrile, 65g of anhydrous ethanol, and 10g of isopropanol, dissolve them thoroughly, and add them to a reaction vessel equipped with a reflux condenser. Maintain reflux at 80℃ for 10 minutes. Mix 45g of methyl methacrylate, 30g of butyl acrylate, 9g of methacrylic acid, 3g of hydroxypropyl acrylate, 4.5g of E-54 epoxy resin, 3.5g of N-hydroxymethylacrylamide, 3g of tetramethyldivinyldisiloxane, 2.4g of azobisisobutyronitrile, and 6g of anhydrous ethanol. Then, use a peristaltic pump to reflux the mixture at a constant rate over 3 hours. The solution was added dropwise to the reactor, and the reaction temperature was controlled at 83℃. After the addition was completed, the temperature was kept at 3h and then cooled to 35℃. The solvent in the reactor was removed by vacuum pump for 40min, with a vacuum degree of 0.090Mpa. The temperature of the reactor was raised to 45℃, and 5g of ammonia and 1g of triethylamine were added for neutralization for 20min. The solution was then transferred to a dispersion device, and 180g of deionized water was added at a dispersion speed of 3500r / min. The solution was dispersed at high speed for 30min, filtered, and discharged to obtain a room temperature self-crosslinking modified epoxy acrylate aqueous dispersion.

[0083] 2) Preparation of epoxy-modified room temperature self-crosslinking waterborne acrylic dispersion ink

[0084] Add 40g of room temperature self-crosslinking modified epoxy acrylate aqueous dispersion, 5g of water and 15g of ethanol to the mixing tank, and stir at 100r / min for 10min; then add 25g of Nami Fresh Color Specialty Paste, and stir at 500r / min for 15min; the desired water-based ink is obtained.

[0085] Example 4

[0086] 1) Preparation of room temperature self-crosslinking modified epoxy acrylate aqueous dispersion

[0087] Dissolve 1g of benzoyl peroxide and 75g of anhydrous ethanol thoroughly, then add the solution to a reactor equipped with a reflux condenser and maintain reflux at 80℃ for 10 minutes. Mix 50g of methyl methacrylate, 35g of butyl acrylate, 10g of acrylic acid, 3g of hydroxyethyl methacrylate, 4g of epoxy resin NPEL-128, 4g of acetyl acetoxyethyl methacrylate, 1g of allyl methacrylate, 2g of benzoyl peroxide, and 6g of anhydrous ethanol. Then, use a peristaltic pump to uniformly add the mixed solution dropwise to the reactor over 3 hours. The reaction temperature was controlled at 83℃. After the addition was completed, the temperature was kept at 3℃ for 3 hours and then cooled to 35℃. The solvent in the reactor was removed by a water pump for 40 minutes under reduced pressure, with a vacuum degree of 0.090 MPa. The temperature of the reactor was raised to 45℃, and 5g of ammonia and 3g of triethanolamine were added for neutralization for 20 minutes. The mixture was then transferred to a dispersion device, and 180g of deionized water and 3g of succinic acid dihydrazide were added at a dispersion speed of 3500 r / min. The mixture was dispersed at high speed for 30 minutes, filtered, and discharged to obtain a room temperature self-crosslinking modified epoxy acrylate aqueous dispersion.

[0088] 2) Preparation of epoxy-modified room temperature self-crosslinking waterborne acrylic dispersion ink

[0089] Add 40g of room temperature self-crosslinking modified epoxy acrylate aqueous dispersion, 5g of water and 15g of ethanol to the mixing tank, and stir at 100r / min for 10min; then add 25g of Nami Fresh Color Specialty Paste, and stir at 500r / min for 15min; the desired water-based ink is obtained.

[0090] Example 5

[0091] 1) Preparation of room temperature self-crosslinking modified epoxy acrylate aqueous dispersion

[0092] Take 1.4g of azobisisoheptanenitrile and 75g of anhydrous ethanol, dissolve them completely, and add them to a reactor equipped with a reflux condenser. Maintain reflux at 80℃ for 10min. Mix 45g of isobutyl methacrylate, 35g of butyl acrylate, 11g of methacrylic acid, 2g of hydroxypropyl methacrylate, 5g of epoxy resin P430, 4g of diacetone acrylamide, 1g of triallyl isocyanurate, 2.2g of azobisisoheptanenitrile, and 6g of anhydrous ethanol. Then, use a peristaltic pump to add the mixed solution dropwise to the reactor at a uniform rate over 3h. The reaction temperature was controlled at 83℃. After the addition was completed, the temperature was kept at 3℃ for 3 hours and then cooled to 35℃. The solvent in the reactor was removed by vacuum pump for 40 minutes, with a vacuum degree of 0.090 MPa. The temperature of the reactor was raised to 45℃, and 7g of ammonia water was added for neutralization for 20 minutes. The mixture was then transferred to a dispersion device, and 180g of deionized water and 2g of dihydrazide carbonate were added at a dispersion speed of 3500r / min. The mixture was dispersed at high speed for 30 minutes, filtered, and discharged to obtain a room temperature self-crosslinking modified epoxy acrylate aqueous dispersion.

[0093] 2) Preparation of epoxy-modified room temperature self-crosslinking waterborne acrylic dispersion ink

[0094] Add 40g of room temperature self-crosslinking modified epoxy acrylate aqueous dispersion, 5g of water and 15g of ethanol to the mixing tank, and stir at 100r / min for 10min; then add 25g of Nami Fresh Color Specialty Paste, and stir at 500r / min for 15min; the desired water-based ink is obtained.

[0095] Comparative Example 1 (cited in CN103396508B)

[0096] 1) Preparation of low-temperature self-crosslinking waterborne acrylic resin

[0097] First, 30g of ethylene glycol monobutyl ether and 20g of N,N-dimethylformamide were added to a reactor equipped with a reflux condenser, stirred, and heated to 70°C. After reflux stabilization, a mixed solvent was obtained. Then, 15g of methyl methacrylate, 5g of butyl acrylate, 10g of isooctyl acrylate, 4g of acrylic acid, 2g of itaconic acid, 1g of hydroxyethyl methacrylate, 1g of acetyl acetoxyethyl methacrylate, 0.4g of azobisisobutyronitrile, and 0.2g of benzoyl peroxide were mixed and stirred to obtain the raw material. The reactor was heated to 75°C. After the reflux stabilized, the raw material was dripped into the reactor, and the temperature was controlled at 75°C for 2 hours. After the dripping was completed, the reaction was continued at the temperature for 1 hour. After the temperature was maintained, the crude acrylate resin was subjected to vacuum distillation to remove unreacted monomers and most of the solvent. After the vacuum distillation was completed, the temperature was lowered to 40°C. 3g of triethylamine and 5g of ammonia were added dropwise to adjust the pH of the resin to 8.0-8.5. 60g of water was added, and the mixture was stirred for 30 minutes before being discharged.

[0098] 2) Preparation of water-based inks

[0099] Add 40g of low-temperature self-crosslinking waterborne acrylic resin, 5g of water and 15g of ethanol to the mixing tank, and stir at 100r / min for 10min; then add 25g of Nami Fresh Color Special Paste, and stir at 500r / min for 15min; the desired waterborne ink is obtained.

[0100] Comparative Example 2 (cited in CN109867743A)

[0101] 1) Preparation of room temperature self-crosslinking aqueous acrylic resin dispersion

[0102] Dissolve 0.5g of azobisisobutyronitrile in a portion of n-butanol until fully dissolved and set aside. Weigh 10g of methyl methacrylate, 6g of styrene, 31g of butyl acrylate, 11g of acrylic acid, 4g of hydroxypropyl acrylate, 2g of diacetone acrylamide, 0.02g of n-dodecyl mercaptan, and 1g of sodium bicarbonate and mix them to form a monomer mixture. Add the remaining solvent and 15% by mass of the monomer mixture to a reactor equipped with a condenser, stir bar, and thermometer. Maintain the temperature at 85℃, add 1 / 3 of the initiator, and react for 30 minutes. Add another 1 / 3 of the initiator, then add the remaining mixed monomers at a uniform rate, maintain the temperature for 1 hour, add the remaining initiator, and raise the temperature to 93℃ and maintain the temperature for 2 hours to obtain an aqueous acrylic resin. Adjust the temperature to 50℃, add an appropriate amount of triethylamine, adjust the pH to 8.0, add deionized water, and disperse at high speed to form an aqueous acrylic dispersion. Finally, add a crosslinking agent and filter to obtain a room temperature self-crosslinking aqueous acrylic resin dispersion.

[0103] 2) Preparation of room temperature self-crosslinking waterborne acrylic resin dispersion ink

[0104] Add 40g of room temperature self-crosslinking modified waterborne acrylic resin dispersion, 5g of water and 15g of ethanol to the mixing tank, and stir at 100r / min for 10min; then add 25g of Nami Fresh Color Special Paste, and stir at 500r / min for 15min; the desired waterborne ink is obtained.

[0105] Comparative Example 3 (cited in CN115304957B)

[0106] 1) Preparation of water-based ink dispersions

[0107] 0.1 g of azobisisobutyronitrile (AIBN) was dissolved in 2.5 g of ethanol to prepare an initiator solution. 6.4 g of methyl methacrylate, 10 g of butyl acrylate, 10 g of hydroxyethyl acrylate, 5.5 g of methacrylic acid, 0.5 g of allyl polyoxyethylene ether, and 2 g of mercaptoethanol were mixed to form a monomer mixture. 22.5 g of ethanol was added to a reaction vessel, and the temperature was raised to 70°C with stirring. Simultaneously, the monomer mixture and initiator solution were added dropwise over 3 hours. After the addition was complete, the reaction was maintained at this temperature for 2 hours. After the temperature maintenance, 5.5 g of triethylamine was added, and after stirring for 0.5 hours, 5 g of deionized water was added. After dispersion, the ethanol was removed by vacuum evaporation. 20 g of deionized water and 10 g of aqueous phenolic resin were added, stirred evenly, and discharged at room temperature to obtain an aqueous ink dispersion.

[0108] 2) Preparation of water-based inks

[0109] Add 40g of water-based ink dispersion, 5g of water and 15g of ethanol to the mixing tank, and stir at 100r / min for 10min; then add 25g of Nami Fresh Special Paste, and stir at 500r / min for 15min; the desired water-based ink is obtained.

[0110] Performance testing

[0111] The water-based inks obtained in Examples 1-5 and Comparative Examples 1-3 of this application were subjected to adhesion tests on BOPP, PE, and PET films; water resistance tests were conducted on PET films; and resolubility tests were conducted on tinplate films. The test results are shown in Table 1.

[0112] Table 1

[0113]

[0114]

[0115] Comparative Example 1 improved the water resistance of the resin by introducing a low-temperature self-crosslinking system to enhance the three-dimensional network structure inside the resin. Compared with Examples 1-5, the acrylic resin of Comparative Example 1, after being made into ink, exhibited a slower crosslinking reaction rate at room temperature and could not achieve a high degree of crosslinking at room temperature. It also showed poor adhesion and water resistance on various plastic films and mediocre resolubility.

[0116] Comparative Example 2 improved the resin's water resistance by introducing a room-temperature crosslinking system to enhance the resin's internal three-dimensional network structure and increase the resin's crosslinking density. Compared with Examples 1-5, the ink made from the aqueous dispersion of Comparative Example 2 showed poor adhesion and water resistance on plastic films, mediocre resolubility, and still had a high organic solvent content. Furthermore, the resin had a high VOC content, making it less environmentally friendly.

[0117] Comparative Example 3 improves the resolubility, water resistance, and pigment dispersibility and wetting properties of the dispersion by introducing special molecular groups into the resin backbone. Compared with Examples 1-5, the crosslinking structure of the aqueous dispersion in Comparative Example 3 is simple and the crosslinking density is low, so the adhesion and water resistance of the ink made from it are still difficult to meet the application requirements.

[0118] The results in the table above confirm that the epoxy-modified room-temperature self-crosslinking waterborne acrylate dispersion prepared by this invention not only has low VOC content and low viscosity, but also has a suitable internal crosslinking network structure and moderate density. It exhibits excellent resolubility before complete curing at room temperature and excellent water resistance after complete curing. Furthermore, it demonstrates excellent adhesion to various plastic films, providing a new approach for waterborne acrylic resins to balance water resistance and resolubility while reducing VOCs.

[0119] The epoxy-modified room-temperature self-crosslinking waterborne acrylate dispersion prepared by this invention has an average particle size of 16–50 nm, an acid value of 20–60 mg KOH / g, a viscosity range of 24–87 s, a solid content of 30–35%, and excellent stability after storage at room temperature for >300 days. The main solvent of the dispersion prepared by this invention is water, which has low viscosity, an organic solvent content of <5%, low VOCs, a high flash point (>50℃), adjustable drying speed, and the extracted organic solvent can be reused. It also exhibits suitable hydrophilicity, a multi-layer crosslinked network structure, and a high degree of crosslinking (78%–83%).

[0120] The epoxy-modified room-temperature self-crosslinking waterborne acrylate dispersion of this invention achieves an ink resolubility of over 85% after formulation, demonstrating excellent resolubility. When applied to BOPP, PE, and PET films, it exhibits an adhesion strength of 95%–100%. After immersion in water for 24 hours, its wet adhesion strength remains above 95%, demonstrating excellent resolubility, adhesion, and water resistance. Furthermore, the organic solvent remaining after the polymerization reaction can be recycled by vacuum removal, resulting in water as the primary solvent in the final water dispersion. This not only increases the flash point of the waterborne acrylic resin and significantly reduces the VOC content of the product but also avoids resource waste.

[0121] This invention, an epoxy-modified room-temperature self-crosslinking waterborne acrylate dispersion, solves the problems of waterborne acrylic resins having difficulty in achieving both water resistance and resolubility, high VOC content, and high viscosity of water-dispersion resins. The ink formulated with the water dispersion has excellent resolubility, water resistance, adhesion, and stability, which can meet the needs of factory production, storage, transportation, and printing, and has broad application prospects in fields such as outer packaging.

Claims

1. An epoxy-modified room-temperature self-crosslinking aqueous acrylate dispersion, characterized in that: The acrylate polymer is obtained by removing organic solvent from the acrylate polymer, adjusting the pH to 7.5–8.5, mixing it with deionized water and dihydrazide, dispersing, and filtering. The acrylate polymer is obtained by solution polymerization at 80–83°C of a mixed solution of a partial initiator, hard monomers, soft monomers, first-type hydrophilic monomers, second-type hydrophilic monomers, epoxy resin, and combined crosslinking monomers, along with the remaining initiator dissolved in the organic solvent. The first-type hydrophilic monomers are carboxyl-containing acrylic monomers or carboxyl-containing methacrylic monomers; the second-type hydrophilic monomers are hydroxyl-containing acrylic monomers or hydroxyl-containing methacrylic monomers. The partial initiator and the remaining initiator constitute all initiators, with the remaining initiator accounting for 25–45% of the total initiator mass. The initiator is a free radical type initiator. The combined crosslinking monomers are one or more of diacetone acrylamide, N-hydroxymethylacrylamide, N-hydroxyethylacrylamide and acetylacetoxyethyl methacrylate, combined with one or more of trimethylolpropane triacrylate, tetramethyldivinyldisiloxane, allyl methacrylate and triallyl isocyanurate. By weight, the raw material composition is as follows: Hard monomer: 35-55 parts Soft monomer: 25-40 parts Type I hydrophilic monomers: 6-15 parts Type II hydrophilic monomers: 2-7 parts Initiator: 3-5 parts Organic solvent: 70-90 parts Epoxy resin: 4-7 parts Combined crosslinking monomers: 2-10 parts Dihydrazide: 2-4 parts Deionized water: 160-200 parts.

2. The epoxy-modified room-temperature self-crosslinking aqueous acrylate dispersion as described in claim 1, characterized in that: The epoxy-modified room-temperature self-crosslinking waterborne acrylate dispersion has an average particle size of 16–50 nm and an acid value of 20–60 mg KOH / g. The hard monomer is one or more of methyl methacrylate, methyl acrylate, ethyl methacrylate, isobutyl methacrylate, and isobornyl methacrylate; the soft monomer is one or more of ethyl acrylate, butyl acrylate, 2-ethylethyl acrylate, n-octyl acrylate, lauryl methacrylate, and octadecyl methacrylate.

3. The epoxy-modified room-temperature self-crosslinking aqueous acrylate dispersion as described in claim 1, characterized in that: The first type of hydrophilic monomer is one or both of acrylic acid and methacrylic acid; the second type of hydrophilic monomer is one or more of hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, and hydroxypropyl acrylate. The epoxy resin is one or more of epoxy resin E-44, epoxy resin E-51, epoxy resin E-54, epoxy resin NPEL-128, and epoxy resin P430. The dihydrazide is a dihydrazide carbonate, a dihydrazide oxalate, adipic acid dihydrazide, or a dihydrazide succinate.

4. The epoxy-modified room-temperature self-crosslinking aqueous acrylate dispersion as described in claim 1, characterized in that: The pH value is adjusted by adding a pH adjuster, which is one or more of ammonia, triethylamine, dimethylethanolamine, and triethanolamine.

5. The epoxy-modified room-temperature self-crosslinking aqueous acrylate dispersion as described in claim 1, characterized in that: The initiator is one or more of azobisisobutyronitrile, azobisisoheptanenitrile, and benzoyl peroxide; the organic solvent is one or more of ethanol, isopropanol, and propylene glycol methyl ether.

6. The method for preparing the epoxy-modified room-temperature self-crosslinking aqueous acrylate dispersion according to claim 1, characterized in that... Includes the following steps: 1) Mix a portion of the initiator, hard monomer, soft monomer, first-type hydrophilic monomer, second-type hydrophilic monomer, epoxy resin, and crosslinking monomer to obtain a mixed solution. The mixed solution reacts with the remaining initiator dissolved in the organic solvent, and the temperature of the reaction system is controlled at 80-83℃. 2) Reduce the temperature of the product obtained in step 1) to 35-45℃, extract the organic solvent under reduced pressure, adjust the pH to 7.5-8.5, add a mixture of deionized water and dihydrazide for dispersion, filter and discharge to obtain epoxy-modified room temperature self-crosslinking waterborne acrylate dispersion.

7. The method for preparing the epoxy-modified room-temperature self-crosslinking aqueous acrylate dispersion according to claim 6, characterized in that, The reaction between the mixed solution and the remaining initiator dissolved in the organic solvent is carried out by adding the mixed solution dropwise to a reaction vessel containing the remaining initiator dissolved in the organic solvent. The dropwise addition time is controlled at 2.5 to 3 hours, and the temperature is maintained for another 2 to 4 hours after the dropwise addition is completed. The dispersion is carried out in a high-speed dispersion device, with the dispersion speed controlled at 3000 r / min-3500 r / min.

8. The application of the epoxy-modified room-temperature self-crosslinking waterborne acrylate dispersion according to claim 1 in waterborne inks, characterized in that: An epoxy-modified room-temperature self-crosslinking waterborne acrylate dispersion is compounded with waterborne pigment, ethanol, and water to obtain a plastic film ink. The solid content of the plastic film ink is controlled to be 5%–35% by mass percentage.

9. The application of the epoxy-modified room-temperature self-crosslinking waterborne acrylate dispersion according to claim 8 in waterborne inks, characterized in that: By mass, the amount of epoxy-modified room temperature self-crosslinking waterborne acrylate dispersion is 40-60 parts, the amount of waterborne pigment is 20-40 parts, the amount of ethanol is 10-20 parts, and the amount of deionized water is 5-10 parts. During compounding, the epoxy-modified room temperature self-crosslinking waterborne acrylate dispersion is added to deionized water and ethanol and stirred at low speed for 10-25 minutes. Then, waterborne pigment is added and stirred at high speed for more than 10-25 minutes to obtain epoxy-modified room temperature self-crosslinking waterborne acrylate dispersion ink. The stirring speed at low speed is 30-100 r / min, and the stirring speed at high speed is 500-800 r / min.

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