Epoxy modified room temperature self-crosslinking water-based acrylate dispersion as well as preparation method and application thereof

Abstract

The invention discloses an epoxy modified room-temperature self-crosslinking water-based acrylate dispersion as well as a preparation method and application thereof, and belongs to the field of water-based acrylic resin. The dispersoid is obtained by extracting an organic solvent from an acrylate polymer, adjusting the pH value to 7.5-8.5, mixing with ionized water and binary hydrazide, dispersing and filtering. The acrylate polymer is obtained by carrying out solution polymerization on a mixed solution of a part of initiator, a hard monomer, a soft monomer, a first type of hydrophilic monomer, a second type of hydrophilic monomer, epoxy resin and a combined cross-linking monomer and a residual initiator dissolved in an organic solvent at 80-83 DEG C, wherein the mixed solution is prepared from the initiator, the hard monomer, the soft monomer, the first type of hydrophilic monomer, the second type of hydrophilic monomer, epoxy resin and the combined cross-linking monomer. The main solvent of the dispersion is water, the viscosity is low, and the content of the organic solvent is 1t; the water-based ink has the advantages of low content of VOCs (volatile organic compounds), multiple cross-linked network structure, high cross-linking degree (78-83%), excellent resolubility after being prepared into ink, good adhesive force on a plastic film, good water resistance, good storage stability and high glossiness.

Description

Technical Field

[0001] The invention relates to an epoxy-modified room temperature self-crosslinking waterborne acrylic ester dispersion, and in particular to a preparation method and application of an epoxy resin-modified waterborne acrylic resin with a high degree of crosslinking at room temperature, belonging to the field of waterborne resins. Background Art

[0002] Solvent-based inks are gradually being phased out because they contain a large amount of organic solvents, resulting in extremely high VOCs content, which seriously threatens the ecological environment, and water-based inks have become the focus of research. In terms of performance, compared with solvent-based inks, water-based inks generally have disadvantages such as low solubility, poor water resistance, insufficient gloss, and poor printing adaptability, and their application range is very limited. Among them, if the water-based ink has insufficient water resistance, the ink will easily fall off after absorbing water. If the water-based ink has poor solubility, the reproducibility of the shallow mesh part during continuous printing will be poor, and it is easy to cause blockage, affecting printing quality and production efficiency. At present, water-based acrylic resins are often used as binders for water-based inks for plastic film printing. There are three main types, namely water-soluble, water-dispersible and emulsion acrylic resins.

[0003] Emulsion acrylic resin is formed by emulsion polymerization, mainly using water as solvent, with high safety and environmental friendliness. Compared with water-soluble and water-dispersible acrylic resins, the molecular weight of the emulsion is large and contains a small amount of hydrophilic monomers, which makes the film-forming water-resistant, but sacrifices the solubility, which has certain difficulties in practical application. Chinese invention patent CN110128875B discloses a new type of self-crosslinking emulsion of water-based ink binder for flexographic printing and its preparation method, which improves the solubility and water resistance of the emulsion, but the solubility still cannot meet the requirements of actual continuous printing.

[0004] Water-soluble acrylic resins are mainly obtained by solution polymerization. The polymer molecular weight is not high, and the hydrophilic monomer content is high. Although the water-soluble resin has excellent solubility after being configured into water-based ink, it is easy to absorb water and swell, causing the ink to fall off. Compared with emulsions and water dispersions, water-soluble acrylic resins have strong hydrophilicity, high viscosity, and high organic solvent content, resulting in low flash point and flammability. Not only are they environmentally unfriendly, but they also have problems with low storage, transportation and use safety. Chinese invention patent CN113105571B discloses a low-temperature self-crosslinking water-based epoxy-modified acrylic resin and its preparation method and application, which greatly improves the water resistance of the ink, but uses organic solvents as the main solvent, and does not consider the solubility of the water-based ink. Chinese invention patent application CN116396423A discloses a metal ion-modified water-based acrylic resin and its preparation method and application. The water-based acrylic resin has good solubility and water resistance after being configured into ink, but uses organic solvents as the main solvent, and the problem of high VOCs content in the system has not been solved. If organic solvents are directly extracted from water-soluble acrylic resins to achieve the purpose of reducing VOCs content and increasing flash point, the viscosity of the resulting water-based acrylic resin will increase due to its excessive hydrophilicity, making it infeasible for practical application.

[0005] Compared with emulsion resins, water-dispersible acrylic resins have moderate molecular weight, high hydrophilic monomer content, and good solubility; compared with water-soluble resins, water-dispersible acrylic resins have low organic solvent content. For water-dispersible acrylic resins, if the hydrophilicity of the resin chain segment is strong, the resin is often a mixture of water-soluble resin and dispersion resin, so that the viscosity of the dispersion increases abnormally with the increase of hydroxyl and carboxyl content, which seriously hinders the practical application of acrylic acid ester aqueous dispersions. Chinese invention patent CN103396508B discloses a low-temperature self-crosslinking water-based acrylic resin and its preparation method and application. Most of the organic solvent is removed by direct vacuum distillation of the polymer after solution polymerization, and the viscosity of the resin rises, making it difficult to use directly. Chinese invention patent CN109867743A discloses a room temperature self-crosslinking water-based acrylic resin dispersion and its preparation method, which improves the water resistance of the resin, but does not take into account the solubility, and the organic solvent content is still high. Chinese invention patent CN115304957B discloses a water-based ink dispersion and a preparation method thereof, which improves solubility and reduces VOCs content, but has insufficient water resistance.

[0006] In view of the problems existing in the use of water-based acrylic resin as a binder for current plastic film printing, it is of great significance to develop a water-based acrylic resin with excellent solubility, water resistance and low VOCs. Summary of the invention

[0007] The purpose of the present invention is to provide a room temperature self-crosslinking epoxy resin modified acrylate aqueous dispersion which has low VOCs content, excellent solubility, water resistance and adhesion on plastic films, and low viscosity, and a preparation method thereof, in order to address the problems that the VOCs content of water-based acrylic resins is high, water resistance and solubility are difficult to balance, and the viscosity of the aqueous dispersion is abnormally increased due to the high hydroxyl and carboxyl content.

[0008] Another object of the present invention is to provide the use of the room temperature cross-linked epoxy resin modified acrylate aqueous dispersion as a water-based ink binder.

[0009] In order to achieve the purpose of the present invention, the present invention provides the following technical solutions:

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

[0011] The combined cross-linking monomer is a monomer combination of one or more of diacetone acrylamide, N-methylol acrylamide, N-hydroxyethyl acrylamide and acetoacetoxyethyl methacrylate and one or more of trimethylolpropane triacrylate, tetramethyldivinyldisiloxane, allyl methacrylate and triallyl isocyanurate.

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

[0013] Hard monomer: 35-55 parts

[0014] Soft monomer: 25-40 parts

[0015] The first type of hydrophilic monomer: 6-15 parts

[0016] The second type of hydrophilic monomer: 2 to 7 parts

[0017] Initiator: 3-5 parts

[0018] Organic solvent: 70-90 parts

[0019] Epoxy resin: 4-7 parts

[0020] Combined cross-linking monomer: 2 to 10 parts

[0021] Dihydrazide: 2-4 parts

[0022] Deionized water: 160-200 parts.

[0023] Preferably, the epoxy-modified room temperature self-crosslinking aqueous acrylate dispersion has an average particle size of 16 to 50 nm and an acid value of 20 to 60 mgKOH / 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; the dihydrazide is carbonate dihydrazide, oxalic acid dihydrazide, adipic acid dihydrazide or succinic acid dihydrazide.

[0025] Preferably, the pH value is adjusted by adding a pH adjuster, and the pH adjuster is one or more of ammonia water, 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 comprises the following steps:

[0028] 1) mixing part of the initiator, the hard monomer, the soft monomer, the first hydrophilic monomer, the second hydrophilic monomer, the epoxy resin, and the crosslinking monomer to obtain a mixed solution, reacting the mixed solution with the remaining initiator dissolved in the organic solvent, and controlling the temperature of the reaction system to be 80-83° C.;

[0029] 2) The temperature of the product obtained in step 1) is lowered to 35-45° C., the organic solvent is extracted under reduced pressure, the pH is adjusted to 7.5-8.5, a mixed solution of deionized water and dihydrazide is added for dispersion, and the mixture is filtered and discharged to obtain an epoxy-modified room temperature self-crosslinking waterborne acrylate dispersion.

[0030] Preferably, the reaction of the mixed solution with the remaining initiator dissolved in the organic solvent is performed by dripping the mixed solution into a reaction kettle containing the remaining initiator dissolved in the organic solvent, the dripping time is controlled to be 2.5 to 3 hours, and the temperature is kept warm for 2 to 4 hours after the dripping is completed; the dispersion is carried out in a high-speed dispersion equipment, and the dispersion speed is controlled to be 3000r / min-3500r / min.

[0031] Application of epoxy-modified room temperature self-crosslinking water-based acrylic ester dispersion in water-based ink: The epoxy-modified room temperature self-crosslinking water-based acrylic ester dispersion is compounded with water-based 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.

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

[0033] During compounding, the epoxy-modified room temperature self-crosslinking water-based acrylic ester dispersion is added with deionized water and ethanol and stirred at a low speed for 10 to 25 minutes, and then the water-based color paste is added and stirred at a high speed for more than 10 to 25 minutes to obtain the epoxy-modified room temperature self-crosslinking water-based acrylic ester dispersion ink; the rotation speed of the low-speed stirring is 30 to 100 r / min; the rotation speed of the high-speed stirring is 500 to 800 r / min.

[0034] The water-based ink prepared by the invention can be applied on 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 molecular weight and hydrophilicity are suitable, and it has a multiple network structure with a high degree of crosslinking, and it also has excellent solubility, water resistance and adhesion. The molecular weight and hydrophilicity of the resin coating of the present invention are suitable. The hydrophilicity of the ink is still strong within 30 minutes after scraping the ink, and it is easily dissolved by an aqueous solution of ethanol. The ink re-dissolution rate is more than 85%, and it will not cause blockage. The epoxy resin, the crosslinking monomer combination and the acrylic acid and its ester monomer are introduced to undergo preliminary crosslinking in the polymerization reaction stage to obtain a multiple crosslinking network structure with a certain degree of crosslinking. After the self-crosslinking reaction at room temperature is completed, the crosslinking structure will further form a more compact three-dimensional network structure, which enhances the crosslinking density of the acrylic resin, not only improves the water resistance of the resin, but also enhances the combination between the acrylic resin and plastic films of various materials, and improves the adhesion of the resin on the plastic film. The epoxy-modified room temperature self-crosslinking aqueous acrylate dispersion obtained by the present invention is configured into ink and applied to plastic films PE, BOPP and PET. After being pulled apart with 3M600 tape, the adhesion strength reaches 100%, 97% and 95% respectively, and the adhesion is excellent; after being completely dried and immersed in water for 24 hours, the wet adhesion is still excellent, the ink layer basically does not fall off, and the adhesion strength is 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 water-based acrylic ester dispersion prepared by the present invention first adopts a solution polymerization method to obtain an acrylic polymer with a hydrophilic and hydrophobic monomer ratio, and then decompresses and removes the solvent, adjusts the neutralization degree, and utilizes the self-emulsification ability of the polymer to achieve the reversal of the oil phase to the water phase. The organic solvent content is less than 5%, the VOCs content is low, and the viscosity is controlled at 24s-87s when the solid content is 30%-35%. The flash point is increased to 50°C. Compared with water-soluble acrylic resins, it will not burn when exposed to open flames, which greatly improves the storage, transportation and use safety of the resin. This preparation method not only solves the problem of high viscosity of the aqueous dispersion, but also does not require complicated and cumbersome operations. At the same time, the solvent can be recycled, which greatly avoids waste of resources and is convenient for large-scale production.

[0039] 3) Excellent stability

[0040] The one-component self-crosslinking system introduced by the epoxy-modified room temperature self-crosslinking aqueous acrylate dispersion of the present invention will not undergo premature crosslinking under alkaline conditions and can be stably stored for more than 300 days; it will not stratify when centrifuged at 5000 r / min for 30 minutes, 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 water-based acrylic ester dispersion of the present invention can remove unreacted monomers while removing the solvent under reduced pressure, thereby reducing the smell of the resin, weakening the smell of the resin, and reducing the impact on the health of construction workers.

[0043] 5) Drying speed can be controlled, suitable for fast printing in factories

[0044] The epoxy-modified room temperature self-crosslinking aqueous acrylate dispersion of the present invention has good alcohol dilution, and the drying speed can be adjusted by adding a volatile solvent (such as ethanol) to meet the requirements of ink making. The resin prepared by the present invention is added with color paste, deionized water, and anhydrous ethanol to prepare ink, which is applied to plastic film. The 11.4 μm thick ink coating can be dried within 10 seconds at 25° C., and industrial plastic film printing of 60-100 m / min can be achieved. DETAILED DESCRIPTION

[0045] In order to better understand the present invention, the present invention is further described below in conjunction with embodiments, but the scope of protection claimed by the present invention is not limited to the scope expressed in the embodiments.

[0046] The synthesis method of epoxy-modified room temperature self-crosslinking water-based acrylic ester dispersion is based on solution polymerization, wherein the organic solvent is extracted from acrylic ester polymer, the pH value is adjusted to 7.5-8.5, the mixture is mixed with ionized water and dihydrazide, dispersed, and filtered to obtain the obtained product; the acrylic ester polymer is obtained by solution polymerization of a mixed solution of a part of initiator, hard monomer, soft monomer, first-class hydrophilic monomer, second-class hydrophilic monomer, epoxy resin, combined crosslinking monomer and the remaining initiator dissolved in organic solvent at 80-83°C; the first-class hydrophilic monomer is an acrylic monomer containing carboxyl or a methacrylic monomer containing carboxyl; the second-class hydrophilic monomer is an acrylic monomer containing hydroxyl or a methacrylic monomer containing hydroxyl; the combined crosslinking monomer is one or more of diacetone acrylamide, N-hydroxymethyl acrylamide, N-hydroxyethyl acrylamide and acetoacetoxyethyl methacrylate and one of trimethylolpropane triacrylate, tetramethyl divinyl disiloxane, allyl methacrylate and triallyl isocyanurate.

[0047] Take E-51 as an example of epoxy resin, and the combined crosslinking monomer is a monomer combination of diacetone acrylamide and tetramethyl divinyl disiloxane as an example. The reaction mechanism of other combined crosslinking agents is basically the same:

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

[0049] Epoxy resin E-51 has relatively active α-H groups on the carbon of the epoxy group and H atoms on the tertiary carbon in its molecular structure. Under the action of the initiator, it can generate multiple active free radicals, which serve as active centers to initiate graft copolymerization reactions with acrylic acid and its ester monomers, thereby connecting different acrylic acid polymer chain segments. In the combined cross-linking monomer, 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 introduced epoxy resin, cross-linking monomer combination, and acrylic acid and its ester monomers will undergo preliminary cross-linking during the polymerization reaction stage, forming a multi-cross-linked network structure with a certain degree of cross-linking.

[0050]

[0051] 2) Introduce ammonia water into the resin for neutralization

[0052]

[0053] At this time, the pH in the system is > 7, the room temperature self-crosslinking reaction is inhibited, and the epoxy-modified room temperature self-crosslinking water-based acrylate dispersion can be stably stored.

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

[0055]

[0056] 4) Resin drying and film formation

[0057] In the process of drying and forming a film of the epoxy-modified room temperature self-crosslinking waterborne acrylate dispersion prepared by the present invention, since ammonia and amine salts are easily volatilized from the film in a storage environment at normal temperature and pressure, the specific drying process is as follows:

[0058] (1) Large amount of volatilization of water and solvents;

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

[0060]

[0061] It can be seen from the above reaction process that when the resin is forming a film and drying, the cross-linking monomer DAAM and dihydrazide undergo a cross-linking reaction, which will further link different polymer segments to form a denser multi-cross-linked network structure, thereby increasing the cross-linking density of the resin and making it difficult for water molecules to penetrate into the coating film, thereby improving the water resistance of the resin.

[0062] It can also be seen from the above reaction process that the core of the present invention is the preparation of acrylate polymers, in which the initiator, epoxy resin, hard monomer and soft monomer are relatively common raw materials in the field; the first type of hydrophilic monomer, the second type of hydrophilic monomer, and the combined cross-linking monomer must be defined as above, and the dihydrazide is preferably carbonate dihydrazide, oxalic acid dihydrazide, adipic acid dihydrazide or succinic acid dihydrazide; 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 the relevant raw materials involved, it can be obtained through experiments based on the above mechanism and combined with the purpose of the present invention.

[0063] The present invention controls the content of hydrophilic monomers and removes the solubilizing organic solvent under reduced pressure, and then adjusts the polymer to have appropriate hydrophilicity and self-emulsification ability, and finally achieves water-based conversion to obtain such a dispersion-type resin with appropriate molecular weight and low viscosity, and can also reduce the VOCs content of the resin. When the solid content is 30%-35%, the viscosity is controlled at 24s-87s. After the dispersion is configured into a water-based ink sample, the appropriate molecular weight and hydrophilicity make the ink re-dissolve at a rate of 85% or more within 30 minutes, and the re-dissolution performance is excellent, which can meet the needs of continuous and efficient printing production; the introduced multiple cross-linked network structure, after complete curing at room temperature (cross-linking degree is 78%-83%), the ink has an adhesion fastness of 95% to 100% on a variety of low-polarity plastics such as PE, PET, BOPP, etc., and the adhesion fastness after immersion in water for 24 hours can still reach more than 95%, and the water resistance is excellent.

[0064] The test method for the water-based ink product prepared by the epoxy-modified room temperature self-crosslinking water-based acrylate dispersion prepared in each embodiment of the present invention is tested according to the following test standards:

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

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

[0067] Stability test: refer to GB6753.3-1986, seal the water dispersion resin, place it in a cool place at room temperature, and observe whether the fluidity of the resin solution is abnormal or gel appears.

[0068] Water resistance test: Apply ink film on plastic film, wait for the film to be completely cured, and then soak it in 25℃ deionized water for 24 hours. After taking it out, observe the shedding of the ink film on the plastic film and in the deionized water, and calculate the shedding ratio and its corresponding adhesion strength.

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

[0070] Example 1

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

[0072] Take 1.2g of azobisisobutyronitrile and 75g of anhydrous ethanol, fully dissolve them, add them into a reactor with a reflux condenser, and keep reflux at 80°C for 10 minutes; 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 azobisisobutyronitrile, and 6g of anhydrous ethanol, and then use a peristaltic pump to uniformly add the mixed solution to the reactor within 3 hours, and control the reaction temperature. The temperature is 83°C. After the addition is completed, it is kept warm for 3 hours and then cooled to 35°C. The solvent in the reactor is extracted by a water pump under reduced pressure for 40 minutes, and the vacuum degree is 0.090Mpa. The temperature of the reactor is raised to 45°C, and 3g of ammonia water and 1g of dimethylethanolamine are added for neutralization for 20 minutes. Then it is transferred to a dispersion equipment, and 180g of deionized water and 2.4g of adipic acid dihydrazide are added at a dispersion speed of 3500r / min. High-speed dispersion is performed for 30 minutes, and the material is 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 water-based acrylic ester dispersion ink

[0074] Add 40g of room temperature self-crosslinking modified epoxy acrylate aqueous dispersion, 5g of water and 15g of ethanol into the mixing tank, and stir at 100r / min for 10min; then add 25g of Nami Fresh Specialty Pulp, 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 and 70g of anhydrous ethanol, dissolve them fully, add them into a reactor with a reflux condenser, and keep reflux at 80°C for 10 minutes; add 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-hydroxyethyl acrylamide, 3g tetramethyldivinyldisiloxane, 2.2g azobisisobutyronitrile and 6g anhydrous ethanol were mixed, and then the mixed solution was uniformly added to the reactor within 3 hours by a peristaltic pump, and the reaction temperature was controlled to be 83°C. After the addition was completed, the mixture was kept warm for 3 hours and then cooled to 35°C; the solvent in the reactor was extracted by a water pump under reduced pressure for 40 minutes, and the vacuum degree was 0.090Mpa; the temperature of the reactor was raised to 45°C, 4g ammonia water and 1g dimethylethanolamine were added and neutralized for 20 minutes; the mixture was transferred to a dispersion device, 180g deionized water was added at a dispersion speed of 3500r / min, the mixture was dispersed at a high speed for 30 minutes, filtered and discharged, and a room temperature self-crosslinking modified epoxy acrylate aqueous dispersion was obtained.

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

[0079] Add 40g of room temperature self-crosslinking modified epoxy acrylate aqueous dispersion, 5g of water and 15g of ethanol into the mixing tank, and stir at 100r / min for 10min; then add 25g of Nami Fresh Specialty Pulp, 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 azobisisoheptanenitrile, 65g of anhydrous ethanol, and 10g of isopropanol, and after fully dissolving, add them into a reactor with a reflux condenser and keep reflux at 80°C for 10 minutes; add 45g of methyl methacrylate, 30g of butyl acrylate, 9g of methacrylic acid, 3g of hydroxypropyl acrylate, 4.5g of E-54 epoxy resin, and 3.5g of N-hydroxymethyl acrylamide, 3g tetramethyl divinyl disiloxane, 2.4g azobisisoheptanitrile and 6g anhydrous ethanol were mixed, and then the mixed solution was uniformly added to the reactor within 3 hours by a peristaltic pump, and the reaction temperature was controlled to be 83°C. After the addition was completed, the mixture was kept warm for 3 hours and then cooled to 35°C; the solvent in the reactor was extracted by a water pump under reduced pressure for 40 minutes, and the vacuum degree was 0.090Mpa; the temperature of the reactor was raised to 45°C, 5g ammonia water and 1g triethylamine were added for neutralization for 20 minutes; the mixture was transferred to a dispersion device, 180g deionized water was added at a dispersion speed of 3500r / min, the mixture was dispersed at a high speed for 30 minutes, filtered and discharged, and a room temperature self-crosslinking modified epoxy acrylate aqueous dispersion was obtained.

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

[0084] Add 40g of room temperature self-crosslinking modified epoxy acrylate aqueous dispersion, 5g of water and 15g of ethanol into the mixing tank, and stir at 100r / min for 10min; then add 25g of Nami Fresh Specialty Pulp, 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] Take 1g of benzoyl peroxide and 75g of anhydrous ethanol, fully dissolve them, add them into a reactor with a reflux condenser, and keep reflux at 80°C 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 acetoacetoxyethyl methacrylate, 1g of allyl methacrylate, 2g of benzoyl peroxide, and 6g of anhydrous ethanol, and then use a peristaltic pump to uniformly add the mixed solution to the reactor within 3 hours. The reaction temperature was controlled at 83°C. After the addition was completed, the temperature was kept at 35°C for 3 hours and then cooled to 35°C. The solvent in the reactor was extracted by a water pump under reduced pressure for 40 minutes, and the vacuum degree was 0.090 MPa. The temperature of the reactor was raised to 45°C, 5 g of ammonia water and 3 g of triethanolamine were added for neutralization for 20 minutes. The reactor was then transferred to a dispersion device, 180 g of deionized water and 3 g of succinic acid dihydrazide were added at a dispersion speed of 3500 r / min, and high-speed dispersion was performed for 30 minutes. The product was 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 water-based acrylic ester dispersion ink

[0089] Add 40g of room temperature self-crosslinking modified epoxy acrylate aqueous dispersion, 5g of water and 15g of ethanol into the mixing tank, and stir at 100r / min for 10min; then add 25g of Nami Fresh Specialty Pulp, 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 azobisisoheptanonitrile and 75g of anhydrous ethanol, dissolve them fully, add them into a reactor with a reflux condenser, and keep reflux at 80°C for 10 minutes; 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 azobisisoheptanonitrile, and 6g of anhydrous ethanol, and then use a peristaltic pump to uniformly add the mixed solution to the reactor within 3 hours. and control the reaction temperature to 83°C. After the addition is completed, keep warm for 3 hours and then cool to 35°C. Use a water pump to reduce pressure and extract the solvent in the reactor for 40 minutes, and the vacuum degree is 0.090Mpa. Raise the temperature of the reactor to 45°C, add 7g of ammonia water to neutralize for 20 minutes; then transfer to a dispersion equipment, add 180g of deionized water and 2g of dihydrazide carbonate at a dispersion speed of 3500r / min, disperse at high speed for 30 minutes, filter and discharge to obtain a room temperature self-crosslinking modified epoxy acrylate aqueous dispersion.

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

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

[0095] Comparative Example 1 (cited 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 reaction kettle with a reflux condenser, stirred and heated to 70°C, and a mixed solvent was obtained after the reflux was stable; 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 acetoacetoxyethyl methacrylate, 0.4g of azobisisoheptonitrile and 0.2g of benzoyl peroxide were mixed and stirred to obtain a raw material ; Heat the reactor to 75°C, and after the reflux stabilizes, drip the raw materials into the reactor, control the temperature at 75°C, and the dripping time is 2 hours; after the dripping is completed, continue to keep warm for 1 hour; after the insulation is completed, vacuum distill the obtained crude acrylate resin to extract unreacted monomers and most of the solvent; after the vacuum distillation is completed, cool to 40°C; drip 3g triethylamine and 5g ammonia water to adjust the pH value of the resin to 8.0-8.5, add 60g water, stir for 30 minutes and then discharge.

[0098] 2) Preparation of water-based ink

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

[0100] Comparative Example 2 (cited CN109867743A)

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

[0102] 0.5 g of azobisisobutyronitrile was dissolved in part of n-butanol and fully dissolved for standby use; 10 g of methyl methacrylate, 6 g of styrene, 31 g of butyl acrylate, 11 g of acrylic acid, 4 g of hydroxypropyl acrylate, 2 g of diacetone acrylamide, 0.02 g of n-dodecyl mercaptan, and 1 g of sodium bicarbonate were weighed and mixed to form a monomer mixture; the remaining solvent and the monomer mixture with a mass fraction of 15% were added to a reactor equipped with a condenser, a stirring rod and a thermometer, and the mixture was kept at a constant temperature of 85° C., and 1 / 3 of the initiator was added to react for 30 minutes; 1 / 3 of the initiator was added, and then the remaining mixed monomers were added at a uniform speed, the temperature was kept constant for 1 hour, the remaining initiator was added, and the temperature was raised to 93° C. and kept constant for 2 hours to obtain a water-based acrylic resin; the temperature was adjusted to 50° C., an appropriate amount of triethylamine was added, the pH was adjusted to 8.0, deionized water was added for high-speed dispersion to form a water-based acrylic dispersion, and finally a crosslinking agent was added and the material was filtered to obtain a room temperature self-crosslinking water-based acrylic resin dispersion.

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

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

[0105] Comparative Example 3 (citing CN115304957B)

[0106] 1) Preparation of aqueous ink dispersion

[0107] Dissolve 0.1g of azobisisobutyronitrile in 2.5g of ethanol to prepare an initiator solution; mix 6.4g of methyl methacrylate, 10g of butyl acrylate, 10g of hydroxyethyl acrylate, 5.5g of methacrylic acid, 0.5g of allyl polyoxyethylene ether and 2g of mercaptoethanol to prepare a monomer mixture; add 22.5g of ethanol into a reactor, heat it to 70°C while stirring, and start dripping the monomer mixture and the initiator solution at the same time. The dripping time is 3 hours, and the temperature is kept for 2 hours after the dripping is completed; after the insulation is completed, add 5.5g of triethylamine, stir for 0.5 hour, add 5g of deionized water, disperse evenly, and evaporate the ethanol under reduced pressure; add 20g of deionized water and 10g of aqueous phenolic formaldehyde, stir evenly, cool to room temperature and discharge to obtain an aqueous ink dispersion.

[0108] 2) Configuration of water-based ink

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

[0110] Performance Testing

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

[0112] Table 1

[0113]

[0114]

[0115] Comparative Example 1 introduces a low-temperature self-crosslinking system to enhance the three-dimensional network structure inside the resin to improve the water resistance of the resin. By comparison with Examples 1 to 5, after the acrylic resin of Comparative Example 1 is made into ink, the crosslinking reaction speed at room temperature is slow, and a high degree of crosslinking cannot be obtained at room temperature. The adhesion and water resistance on various plastic films are poor, and the solubility is average.

[0116] Comparative Example 2 introduces a room temperature crosslinking system to enhance the three-dimensional network structure inside the resin, increase the crosslinking density of the resin, and improve the water resistance of the resin. By comparison with Examples 1 to 5, after the aqueous dispersion of Comparative Example 2 is made into ink, the adhesion and water resistance on the plastic film are poor, the solubility is average, and the organic solvent content is still high. The VOCs content of the resin is high, which is not green and environmentally friendly.

[0117] Comparative Example 3 introduces a special molecular group into the main chain of the dispersion resin to improve the solubility, water resistance, dispersibility and wettability of the dispersion to the pigment. By comparing with Examples 1 to 5, the cross-linking structure in the water dispersion of Comparative Example 3 is simple, the cross-linking density is low, and the adhesion and water resistance of the ink after being made still cannot meet the application requirements.

[0118] By comparing the results in the above table, it can be determined that the epoxy-modified room temperature self-crosslinking waterborne acrylic ester dispersion prepared by the present invention not only has low VOCs content and low viscosity, but also has a relatively suitable internal crosslinking network structure and moderate density. It has excellent solubility before being completely cured into a film at room temperature, and also has excellent water resistance after being completely cured into a film. It also has excellent adhesion to a variety of plastic films, which provides a new idea for waterborne acrylic resins in balancing water resistance and solubility and reducing VOCs.

[0119] The epoxy-modified room temperature self-crosslinking water-based acrylate aqueous dispersion prepared by the present invention has an average particle size of 16 to 50 nm, an acid value of 20 to 60 mgKOH / g, a viscosity range of 24 to 87 s, a solid content of 30 to 35%, and is stored at room temperature for more than 300 days, and the product has excellent stability. The main solvent of the dispersion prepared by the present invention is water, with low viscosity, an organic solvent content of less than 5%, low VOCs, a high flash point (>50°C), an adjustable drying speed, and the extracted organic solvent can be reused, has suitable hydrophilic properties, has a multi-crosslinked network structure, and a high degree of crosslinking (78%-83%).

[0120] After the epoxy-modified room temperature self-crosslinking water-based acrylic ester dispersion of the present invention is configured into ink, the ink re-dissolution rate reaches more than 85%, and the re-dissolution property is excellent; when applied to BOPP, PE and PET films, the adhesion fastness reaches 95% to 100%; after being immersed in water for 24 hours, the wet adhesion fastness reaches more than 95%, and it has excellent re-dissolution, adhesion and water resistance. In addition, the organic solvent after the polymerization reaction is completed in the present invention can be recycled by decompression removal, and the main solvent in the final water dispersion is water, which can not only improve the flash point of the water-based acrylic resin, significantly reduce the VOCs content of the product, but also avoid waste of resources.

[0121] The epoxy-modified room temperature self-crosslinking water-based acrylic ester dispersion of the present invention solves the problems of difficulty in balancing water resistance and redissolubility of water-based acrylic resins, high VOCs content, and high viscosity of water-dispersible resins. The ink prepared by configuring the water dispersion has excellent redissolubility, water resistance, adhesion, stability and other properties, can meet the production, storage, transportation and printing needs of factories, and has broad application prospects in the fields of outer packaging and the like.

Claims

1. Epoxy-modified room temperature self-crosslinking waterborne acrylate dispersion, characterized in that: The organic solvent is extracted from the acrylic polymer, and the pH value is adjusted to 7.5-8.5, and the mixture is mixed with ionized water and dihydrazide, dispersed, and filtered to obtain the obtained product; the acrylic polymer is obtained by solution polymerization of a mixed solution of a part of initiator, hard monomer, soft monomer, first-class hydrophilic monomer, second-class hydrophilic monomer, epoxy resin, combined cross-linking monomer, and the remaining initiator dissolved in the organic solvent at 80-83°C; the first-class hydrophilic monomer is an acrylic monomer containing a carboxyl group or a methacrylic monomer containing a carboxyl group; the second-class hydrophilic monomer is an acrylic monomer containing a hydroxyl group or a methacrylic monomer containing a hydroxyl group; the part of the initiator and the remaining initiator constitute all the initiators, the remaining initiator accounts for 25-45% of the total mass of the initiator, and the initiator is a free radical initiator; The combined cross-linking monomer is a monomer combination of one or more of diacetone acrylamide, N-methylol acrylamide, N-hydroxyethyl acrylamide and acetoacetoxyethyl methacrylate and one or more of trimethylolpropane triacrylate, tetramethyldivinyldisiloxane, allyl methacrylate and triallyl isocyanurate.

2. The epoxy-modified room temperature self-crosslinking aqueous acrylate dispersion according to claim 1, characterized in that: The raw material composition is as follows by weight: Hard monomer: 35-55 parts Soft monomer: 25-40 parts The first type of hydrophilic monomer: 6-15 parts The second type of hydrophilic monomer: 2 to 7 parts Initiator: 3-5 parts Organic solvent: 70-90 parts Epoxy resin: 4-7 parts Combined cross-linking monomer: 2 to 10 parts Dihydrazide: 2-4 parts Deionized water: 160-200 parts.

3. The epoxy-modified room temperature self-crosslinking aqueous acrylate dispersion according to claim 1 or 2, characterized in that: The epoxy-modified room temperature self-crosslinking aqueous acrylate dispersion has an average particle size of 16 to 50 nm and an acid value of 20 to 60 mgKOH / 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.

4. The epoxy-modified room temperature self-crosslinking aqueous acrylate dispersion according to claim 1 or 2, 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 carbonate dihydrazide, oxalic acid dihydrazide, adipic acid dihydrazide or succinic acid dihydrazide.

5. The epoxy-modified room temperature self-crosslinking aqueous acrylate dispersion according to claim 1 or 2, characterized in that: The pH value is adjusted by adding a pH adjuster, and the pH adjuster is one or more of ammonia water, triethylamine, dimethylethanolamine and triethanolamine.

6. The epoxy-modified room temperature self-crosslinking aqueous acrylate dispersion according to claim 1 or 2, 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.

7. The method for preparing the epoxy-modified room temperature self-crosslinking aqueous acrylate dispersion according to claim 1 or 2, characterized in that The steps include: 1) mixing part of the initiator, the hard monomer, the soft monomer, the first hydrophilic monomer, the second hydrophilic monomer, the epoxy resin, and the crosslinking monomer to obtain a mixed solution, reacting the mixed solution with the remaining initiator dissolved in the organic solvent, and controlling the temperature of the reaction system to be 80-83° C.; 2) The temperature of the product obtained in step 1) is lowered to 35-45° C., the organic solvent is extracted under reduced pressure, the pH is adjusted to 7.5-8.5, a mixed solution of deionized water and dihydrazide is added for dispersion, and the mixture is filtered and discharged to obtain an epoxy-modified room temperature self-crosslinking waterborne acrylate dispersion.

8. The method for preparing the epoxy-modified room temperature self-crosslinking aqueous acrylate dispersion according to claim 7, characterized in that: The mixed solution reacts with the remaining initiator dissolved in the organic solvent by dropping the mixed solution into a reaction kettle filled with the remaining initiator dissolved in the organic solvent, the dropping time is controlled to be 2.5 to 3 hours, and the temperature is kept for 2 to 4 hours after the dropping is completed; The dispersion is carried out in a high-speed dispersion device, and the dispersion speed is controlled to be 3000r / min-3500r / min.

9. Use of the epoxy-modified room temperature self-crosslinking aqueous acrylate dispersion according to claim 1 or 2 in aqueous ink, characterized in that: The epoxy-modified room temperature self-crosslinking water-based acrylic ester dispersion is compounded with water-based 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.

10. The use of the epoxy-modified room temperature self-crosslinking aqueous acrylate dispersion in water-based ink according to claim 9, characterized in that: In parts by mass, the amount of epoxy-modified room temperature self-crosslinking water-based acrylic dispersion is 40 to 60 parts, the amount of water-based color paste is 20 to 40 parts, the amount of ethanol is 10 to 20 parts, and the amount of deionized water is 5 to 10 parts. During compounding, the epoxy-modified room temperature self-crosslinking water-based acrylic ester dispersion is added with deionized water and ethanol and stirred at a low speed for 10 to 25 minutes, and then the water-based color paste is added and stirred at a high speed for more than 10 to 25 minutes to obtain the epoxy-modified room temperature self-crosslinking water-based acrylic ester dispersion ink; the rotation speed of the low-speed stirring is 30 to 100 r / min; the rotation speed of the high-speed stirring is 500 to 800 r / min.

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