A core-shell type acrylate soap-free emulsion, its preparation method, and water-based ink.

Abstract

This invention discloses a core-shell type acrylate soap-free emulsion, its preparation method, and water-based ink, belonging to the technical field of the printing industry. The method includes: adding a solvent to a reaction flask, adding a first monomer and an initiator dropwise to the reaction flask, maintaining the temperature, adjusting the pH to 8, and adding deionized water to disperse and obtain a macromolecular acrylate emulsifier; mixing the macromolecular acrylate emulsifier, a portion of the second monomer, and deionized water, stirring to obtain a pre-emulsion; then heating the pre-emulsion, adding a portion of a pH buffer and a portion of ammonium persulfate to initiate the reaction; after blue light appears, simultaneously adding the remaining second monomer, the remaining ammonium persulfate, and the remaining pH buffer; maintaining the temperature; and adjusting the pH to 8. The core-shell type acrylate soap-free emulsion obtained by this invention, when used in water-based inks, can significantly improve coating adhesion, gloss, dry / wet rubbing resistance, anti-blocking properties, water resistance, and storage stability.

Description

Technical Field

[0001] This invention belongs to the technical field of the printing industry, specifically relating to a core-shell type acrylate soap-free emulsion, its preparation method, and water-based ink. Background Technology

[0002] Water-based inks use water as a solvent, without adding organic solvents, and their VOC emissions are close to zero. Due to their green and environmentally friendly characteristics, they are widely used in packaging printing for food, beverages, and pharmaceuticals. Under increasingly stringent environmental regulations, water-based inks account for over 80% of the market. However, due to insufficient technological maturity, the performance of water-based inks in my country still struggles to meet the actual needs of large-scale industrial production, resulting in solvent-based inks still holding the majority of the market share. Furthermore, China relies heavily on imports for high-end water-based inks, and their application on non-absorbent substrates such as PET is significantly limited, indicating that the overall development level still needs improvement.

[0003] In existing technologies, water-based inks that typically use polyacrylate emulsions as binders have advantages such as low raw material cost, simple synthesis process, excellent film-forming performance, and good weather resistance. However, they also suffer from prominent problems such as poor resolubility and inadequate water resistance, which restricts their widespread application. To address these shortcomings, several improvements have been attempted domestically. For example, Liu et al. synthesized a core-shell self-crosslinking polyacrylate emulsion using alkali-soluble resin ASR as a surfactant and diacetone acrylamide and dihydrazine adipic acid as a crosslinking system. While this method improved the water resistance of the coating to some extent, it led to a decrease in the emulsion's ethanol resistance and adhesion to the substrate, and its overall performance still needs further optimization. Summary of the Invention

[0004] To overcome the aforementioned technical problems in the prior art, this invention provides a core-shell type acrylate soap-free emulsion, its preparation method, and an aqueous ink. This invention utilizes a self-made macromolecular emulsifier, combined with soap-free emulsion polymerization technology, and through the synergistic effect of specific functional monomers, to obtain a core-shell type acrylate soap-free emulsion that, when used in aqueous inks, significantly improves coating adhesion, gloss, dry / wet rubbing resistance, anti-blocking properties, water resistance, and storage stability.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] In one aspect, this invention provides a method for preparing a core-shell type acrylate soap-free emulsion, comprising the following steps:

[0007] (1) Add solvent to the reaction flask, heat to 120~150℃, add the first monomer and initiator dropwise to the reaction flask, keep warm after the dropwise addition is complete, add pH adjuster to adjust pH to 8, add deionized water to disperse and obtain macromolecular acrylate emulsifier; the first monomer includes acrylic acid, butyl acrylate, methyl methacrylate, hydroxypropyl acrylate and hydroxyethyl methacrylate;

[0008] (2) Mix the macromolecular acrylate emulsifier, part of the second monomer and deionized water, stir to obtain a pre-emulsion, then heat the pre-emulsion, add part of the pH buffer and part of the ammonium persulfate to initiate the reaction, after blue light appears, simultaneously add the remaining second monomer, the remaining ammonium persulfate and the remaining pH buffer, after the addition is complete, keep warm, and then add pH adjuster to adjust the pH to 8 to obtain the core-shell type acrylate soap-free emulsion; the second monomer includes acrylic acid, butyl acrylate, methyl methacrylate and functional monomers, the functional monomers being hydroxypropyl acrylate, hydroxyethyl methacrylate and tributyl acetylacetate.

[0009] As a further aspect of the present invention: in step (1), the solvent is diethylene glycol dimethyl ether, and the amount used is 13.5~14.5% of the total weight of the first monomer;

[0010] And / or, in step (1), the amount of acrylic acid in the first monomer is 14-17% of the total weight of the first monomer, the amount of butyl acrylate is 33-36% of the total weight of the first monomer, the amount of methyl methacrylate is 44-46% of the total weight of the first monomer, the amount of hydroxypropyl acrylate is 3.5-4.0% of the total weight of the first monomer, and the amount of hydroxyethyl methacrylate is 1.6-1.8% of the total weight of the first monomer;

[0011] And / or, in step (1), the initiator is selected from one or two of benzoyl peroxide, tert-butyl peroxide, tert-butyl hydroperoxide, dicarbonate peroxide, dicumyl peroxide, and azobisisobutyronitrile;

[0012] And / or, in step (1), the amount of the initiator is 3% to 6.5% of the total weight of the first monomer;

[0013] And / or, in step (1), the pH adjuster is selected from one or two of ammonia, sodium hydroxide, potassium hydroxide, and 2-amino-2-methyl-1-propanol;

[0014] And / or, in step (1), the amount of deionized water is 8% to 10% of the total weight of the macromolecular acrylate emulsifier.

[0015] As a further embodiment of the present invention: in step (1), the initiator is benzoyl peroxide and tert-butyl peroxide in a mass ratio of 9.5~10.5:1;

[0016] And / or, in step (1), the pH adjuster is ammonia.

[0017] As a further aspect of the present invention: in step (1), the dripping time is 2-4 hours;

[0018] And / or, in step (1), the heat preservation time is 1 hour.

[0019] As a further aspect of the present invention: in step (2), the amount of the macromolecular acrylate emulsifier accounts for 1.30% to 2.0% of the total weight of the core-shell type acrylate soap-free emulsion;

[0020] And / or, in step (2), in the second monomer, the mass ratio of butyl acrylate to methyl methacrylate is 1:4 to 7:3, the amount of acrylic acid is 0.82 to 0.99% of the total weight of the second monomer, the amount of butyl acrylate is 34 to 52% of the total weight of the second monomer, and the amount of methyl methacrylate is 34 to 52% of the total weight of the second monomer;

[0021] And / or, in step (2), the amount of the functional monomer is 13% to 15% of the total weight of the second monomer; the amount of hydroxypropyl acrylate is 33% to 34% of the total weight of the functional monomer; the amount of hydroxyethyl methacrylate is 17% to 18% of the total weight of the functional monomer; and the amount of tributyl acetyl citrate is 49% to 50% of the total weight of the functional monomer.

[0022] And / or, in step (2), the amount of the second monomer used accounts for 9-11% of the total weight of the second monomer;

[0023] And / or, in step (2), the amount of deionized water used accounts for 57% to 60% of the total weight of the core-shell type acrylate soap-free emulsion;

[0024] And / or, in step (2), the pH buffer is one of sodium bicarbonate, sodium dihydrogen phosphate or ammonium bicarbonate;

[0025] And / or, in step (2), the amount of the pH buffer is 0.19% to 0.33% of the total weight of the core-shell acrylate soap-free emulsion;

[0026] And / or, in step (2), the amount of the partial pH buffer used is 30-35% of the total weight of the pH buffer;

[0027] And / or, in step (2), the amount of ammonium persulfate used is 0.66% to 0.83% of the total weight of the second monomer;

[0028] And / or, in step (2), the amount of ammonium persulfate used is 30-35% of the total weight of the ammonium persulfate;

[0029] And / or, in step (2), the pH adjuster is selected from one or two of ammonia, sodium hydroxide, potassium hydroxide, and 2-amino-2-methyl-1-propanol.

[0030] As a further aspect of the present invention: in step (2), the pH buffer is sodium bicarbonate;

[0031] And / or, in step (2), the pH adjuster is ammonia water with a mass fraction of 25%.

[0032] As a further embodiment of the present invention: in step (2), the stirring speed is 1200 r / min;

[0033] And / or, in step (2), the stirring time is 30 min;

[0034] And / or, in step (2), the temperature at which the pre-emulsion is heated is 85~95℃;

[0035] And / or, in step (2), the dripping time is 3 hours;

[0036] And / or, in step (2), the heat preservation time is 1 hour.

[0037] In another aspect, the present invention provides a core-shell type acrylate soap-free emulsion, which is prepared by the above-described method for preparing core-shell type acrylate soap-free emulsion.

[0038] In a third aspect, the present invention also provides an aqueous ink comprising the above-described core-shell acrylate soap-free emulsion.

[0039] As a further embodiment of the present invention, the composition by mass fraction is as follows: 41.7% core-shell type acrylate soap-free emulsion, 15.64% deionized water, 31.28% ethanol, 0.26% OT-75 wetting agent, 0.12% slip agent DHX-51, 3% polyethylene wax emulsion, and 8% pigment yellow 83.

[0040] The beneficial effects of this invention are as follows:

[0041] (1) This invention uses a self-made macromolecular polymerizable acrylate emulsifier to prepare a core-shell type water-resistant acrylate emulsion by soap-free emulsion polymerization. By adjusting the ratio of butyl acrylate to methyl methacrylate, the amount of initiator and functional monomer, the film-forming properties of the emulsion are effectively improved and the hardness of the coating film is increased. After being made into an ink coating, the problems of anti-blocking are solved.

[0042] (2) Traditional small-molecule emulsifiers, due to their small molecular weight, easily move freely within the system and migrate to the molecular surface, resulting in problems such as high pollution and difficulty in recycling. When applied to water-based inks, the migration of hydrophilic small-molecule emulsifiers leads to a decrease in the gloss and water resistance of the water-based ink coating. Direct removal of the emulsifier can easily cause emulsion aggregation. This invention uses a self-made macromolecular emulsifier to replace the traditional emulsifier for soap-free emulsion polymerization, minimizing particle surface pollution caused by emulsifier adsorption. While avoiding aggregation, it significantly improves the dispersion stability of the emulsion and the water resistance of the coating. Detailed Implementation

[0043] The present invention is further illustrated below by way of examples, but these examples do not limit the invention to the scope of the embodiments described. Experimental methods in the following examples, unless otherwise specified, were performed according to conventional methods and conditions, or as selected in the product instructions. Furthermore, all reagents and raw materials used in this invention are commercially available.

[0044] Example 1

[0045] A method for preparing a core-shell type acrylate soap-free emulsion includes the following steps:

[0046] (1) Preparation of macromolecular acrylate emulsifier: Add 5 parts of diethylene glycol dimethyl ether to a reaction flask and heat to 140℃. Weigh 5 parts of acrylic acid, 12 parts of butyl acrylate, 16 parts of methyl methacrylate, 1.3 parts of hydroxypropyl acrylate, and 0.6 parts of hydroxyethyl methacrylate and stir to mix. Add 1.5 parts of benzoyl peroxide and 0.15 parts of tert-butyl peroxide dropwise to the reaction flask. Add dropwise for 3 hours, keep warm for 1 hour, cool to room temperature, add 12 parts of ammonia water to neutralize to pH=8, and add 5 parts of deionized water to disperse and obtain macromolecular acrylate emulsifier AT1.

[0047] (2) Add 2 parts of macromolecular acrylate emulsifier AT1 and 64.4 parts of deionized water to the reaction flask and stir well. Add 1 / 10 of the mixed monomers (0.6 parts acrylic acid, 26 parts butyl acrylate, 26 parts methyl methacrylate, 2.7 parts hydroxypropyl acrylate, 1.4 parts hydroxyethyl methacrylate, and 4 parts tributyl acetyl citrate) to the reaction flask and stir at 1200 rpm for 30 minutes. Heat to 90°C and add 1 / 3 of the weight of ammonium persulfate aqueous solution (0.5 parts sodium bicarbonate, 0.5 parts ammonium persulfate, and 22 parts deionized water) to the reaction flask to initiate the reaction. After the appearance of blue light, start to add the remaining mixed monomers and ammonium persulfate aqueous solution dropwise. The dropwise addition time is 3 hours, the temperature is kept warm for 1 hour, and then cooled to room temperature. Add 1.5 parts of ammonia water to adjust the pH to 8 to obtain a core-shell type acrylate soap-free emulsion.

[0048] Preparation of water-based ink: The water-based ink was prepared according to the following mass fractions: 41.7% of the emulsion prepared in this example, 15.64% deionized water, 31.28% ethanol, 0.26% OT-75 wetting agent, 0.12% DHX-51 slip agent, 3% polyethylene wax emulsion, and 8% pigment yellow 83. The ink was dispersed using a high-speed disperser at 1000 rpm for 10 minutes, and allowed to stand until defoaming to occur, thus obtaining the water-based ink.

[0049] Preparation of water-based ink coating: Drip 2-3 drops of ink onto aluminum foil, use a 10µm wire bar coater to evenly coat the ink onto the aluminum foil, bake in an oven at 120℃ for 35 seconds, remove and let cool to obtain water-based ink coating.

[0050] Example 2

[0051] A method for preparing a core-shell type acrylate soap-free emulsion includes the following steps:

[0052] (1) Preparation of macromolecular acrylate emulsifier: Add 5 parts of diethylene glycol dimethyl ether to a reaction flask and heat to 130℃. Weigh 6 parts of acrylic acid, 12 parts of butyl acrylate, 16 parts of methyl methacrylate, 1.3 parts of hydroxypropyl acrylate, and 0.6 parts of hydroxyethyl methacrylate and stir to mix. Add 1.0 parts of benzoyl peroxide and 0.10 parts of tert-butyl peroxide dropwise to the reaction flask. Add for 3 hours, keep warm for 1 hour, cool to room temperature, add 13 parts of ammonia water to neutralize to pH=8, and add 5 parts of deionized water to disperse and obtain macromolecular acrylate emulsifier AT2.

[0053] (2) Add 2 parts of macromolecular acrylate emulsifier AT2 and 64.4 parts of deionized water to the reaction flask and stir well. Add 1 / 10 of the mixed monomers (0.6 parts acrylic acid, 20.8 parts butyl acrylate, 31.2 parts methyl methacrylate, 2.7 parts hydroxypropyl acrylate, 1.4 parts hydroxyethyl methacrylate, and 4 parts tributyl acetyl citrate) to the reaction flask and stir at 1200 rpm for 30 minutes. Heat to 90°C and add 1 / 3 of the weight of ammonium persulfate aqueous solution (0.5 parts sodium bicarbonate, 0.5 parts ammonium persulfate, and 22 parts deionized water) to the reaction flask to initiate the reaction. After the appearance of blue light, start to add the remaining mixed monomers and ammonium persulfate aqueous solution dropwise. The dropwise addition time is 3 hours, the temperature is kept warm for 1 hour, and then cooled to room temperature. Add 1.5 parts of ammonia water to adjust the pH to 8 to obtain a core-shell type acrylate soap-free emulsion.

[0054] The preparation of water-based inks and the fabrication of water-based ink coatings are the same as in Example 1.

[0055] Example 3

[0056] A method for preparing a core-shell type acrylate soap-free emulsion includes the following steps:

[0057] (1) Preparation of macromolecular acrylate emulsifier: Add 5 parts of diethylene glycol dimethyl ether to a reaction flask and heat to 130℃. Weigh 5 parts of acrylic acid, 12 parts of butyl acrylate, 16 parts of methyl methacrylate, 1.3 parts of hydroxypropyl acrylate, and 0.6 parts of hydroxyethyl methacrylate and stir to mix. Add 2.0 parts of benzoyl peroxide and 0.20 parts of tert-butyl peroxide to the reaction flask dropwise. Add for 3 hours, keep warm for 1 hour, cool to room temperature, add 12 parts of ammonia water to neutralize to pH=8, and add 5 parts of deionized water to disperse to obtain macromolecular acrylate emulsifier AT3.

[0058] (2) Add 2 parts of macromolecular acrylate emulsifier AT3 and 64.4 parts of deionized water to the reaction flask and stir well. Add 1 / 10 of the mixed monomers (0.5 parts acrylic acid, 31.2 parts butyl acrylate, 20.8 parts methyl methacrylate, 2.7 parts hydroxypropyl acrylate, 1.4 parts hydroxyethyl methacrylate, and 4 parts tributyl acetyl citrate) to the reaction flask and stir at 1200 rpm for 30 minutes. Heat to 90°C and add 1 / 3 of the weight of ammonium persulfate aqueous solution (0.5 parts sodium bicarbonate, 0.5 parts ammonium persulfate, and 22 parts deionized water) to the reaction flask to initiate the reaction. After the appearance of blue light, start to add the remaining mixed monomers and ammonium persulfate aqueous solution dropwise. The dropwise addition time is 3 hours, the temperature is kept warm for 1 hour, and then cooled to room temperature. Add 1.5 parts of ammonia water to adjust the pH to 8 to obtain a core-shell type acrylate soap-free emulsion.

[0059] The preparation of water-based inks and the fabrication of water-based ink coatings are the same as in Example 1.

[0060] Example 4

[0061] A method for preparing a core-shell type acrylate soap-free emulsion includes the following steps:

[0062] (1) Preparation of macromolecular acrylate emulsifier: Add 5 parts of diethylene glycol dimethyl ether to a reaction flask and heat to 140℃. Weigh 5 parts of acrylic acid, 12 parts of butyl acrylate, 16 parts of methyl methacrylate, 1.3 parts of hydroxypropyl acrylate, and 0.6 parts of hydroxyethyl methacrylate and stir to mix. Add 1.5 parts of benzoyl peroxide and 0.15 parts of tert-butyl peroxide dropwise to the reaction flask. Add dropwise for 3 hours, keep warm for 1 hour, cool to room temperature, add 12 parts of ammonia water to neutralize to pH=8, and add 5 parts of deionized water to disperse and obtain macromolecular acrylate emulsifier AT4.

[0063] (2) Add 2 parts of macromolecular acrylate emulsifier AT4 and 64.4 parts of deionized water to the reaction flask and stir well. Add 1 / 10 of the mixed monomers (0.5 parts acrylic acid, 26 parts butyl acrylate, 26 parts methyl methacrylate, 2.7 parts hydroxypropyl acrylate, 1.4 parts hydroxyethyl methacrylate, and 4 parts tributyl acetyl citrate) to the reaction flask and stir at 1200 rpm for 30 minutes. Heat to 90°C and add 1 / 3 of the weight of the ammonium persulfate aqueous solution (0.5 parts sodium bicarbonate, 0.5 parts ammonium persulfate, and 22 parts deionized water) to the reaction flask to initiate the reaction. After the appearance of blue light, start adding the remaining mixed monomers and ammonium persulfate aqueous solution dropwise. The dropwise addition time is 3 hours, the temperature is kept warm for 1 hour, and then cooled to room temperature. Add 1.5 parts of ammonia water to adjust the pH to 8 to obtain a core-shell type acrylate soap-free emulsion.

[0064] The preparation of water-based inks and the fabrication of water-based ink coatings are the same as in Example 1.

[0065] The present invention also provides the following comparative examples.

[0066] Comparative Example 1

[0067] The difference from Example 1 is only that in step (1) preparation of macromolecular acrylate emulsifier, the weight parts of benzoyl peroxide are 0.5 parts, the weight parts of tert-butyl peroxide are 0.5 parts, and the reaction temperature is 100℃, so as to obtain macromolecular acrylate emulsifier AT1A.

[0068] Comparative Example 2

[0069] The difference from Example 2 is that in step (1) the preparation of the macromolecular acrylate emulsifier, the weight of acrylic acid is 4 parts, resulting in macromolecular acrylate emulsifier AT2A. In step (2) the preparation of the core-shell acrylate emulsion, the mass of ammonium persulfate is 0.3 parts.

[0070] Comparative Example 3

[0071] The difference from Example 3 is only that in step (2) of preparing the core-shell acrylate emulsion, the mass fraction of butyl acrylate is 36.4 parts, the mass fraction of methyl methacrylate is 15.6 parts, and the mass fraction of ammonium persulfate is 0.7 parts.

[0072] Comparative Example 4

[0073] The only difference from Example 4 is that sodium bicarbonate is not added in step (2) of the preparation of the core-shell acrylate emulsion.

[0074] Comparative Example 5

[0075] The difference from Example 1 is only that in step (2), the macromolecular acrylate emulsifier is replaced with a commercially available small molecule emulsifier - disodium ethoxylated alkyl alcohol ether sulfosuccinate (HANERCHEM®DNS-330), which is 2 parts by weight.

[0076] Comparative Example 6

[0077] The only difference from Example 1 is that in step (2), the functional monomer is not added with acetylthiocitrate.

[0078] Comparative Example 7

[0079] The difference from Example 1 is that in step (2), hydroxyethyl methacrylate is replaced with hydroxyethyl acrylate in the functional monomer, and the mass fraction is 1.4 parts.

[0080] Comparative Example 8

[0081] The only difference from Example 1 is that the mass fraction of the functional monomer hydroxypropyl acrylate in step (2) is 1.0 parts.

[0082] Comparative Example 9

[0083] The commercially available product is Wantipro® 0831 manufactured by Wanhua Chemical Company.

[0084] Example 1

[0085] The performance of the macromolecular acrylate emulsifiers in the examples and comparative examples was tested using the following methods or standards:

[0086] I. Viscosity: The viscosity was tested using an NDJ-79 rotational viscometer according to GB / T 22235-2008 standard, with a 100x rotor and a temperature of 25℃.

[0087] II. Weight-average relative molecular mass: In accordance with GB / T 21863-2008 standard, a dilute solution of emulsifier sample with a mass concentration of 3 mg / ml was prepared. The molecular weight was determined using a gel permeation chromatography instrument manufactured by Waters Corporation, USA, model: Waters 2695GPC, and the mobile phase was DMF (N,N-dimethylformamide).

[0088] III. Particle size: In accordance with GB / T 29023.1-2012 standard, a small amount of emulsifier sample was placed in a 20ml sample bottle, diluted 100 times with deionized water, and then subjected to ultrasonic treatment for 2 hours. The particle size of the emulsifier was tested using a Zano ZS 3500 manufactured by Malvern at a test temperature of 25℃.

[0089] IV. Conversion Rate: The conversion rate was determined by gravimetric method according to GB / T 11175-2021 standard. The calculation formula is as follows:

[0090] Conversion rate = (Actual solid content) / (Theoretical solid content) × 100%

[0091] Actual solid content: Cut a 5cm diameter circular aluminum foil into a box and weigh the sample inside. After drying in an oven at 120℃ until constant temperature, remove and weigh M. 2。 The following formula is used for calculation:

[0092] Actual solid content = (M2 - M0) / M1 × 100%

[0093] Where: M0 - mass of aluminum foil, g;

[0094] M1 - Sample mass, g;

[0095] M2 - Overall mass after drying, in grams.

[0096] Theoretical solids content: The proportion of the total mass of all substances except water to the total mass of all raw materials.

[0097] The samples from the examples and comparative examples were tested, and the results are shown in Table 1.

[0098] Table 1

[0099]

[0100] Table 1 shows that at lower temperatures, the initiator is less likely to decompose fully, resulting in a lower concentration of free radicals and a lower probability of chain termination reactions in the polymer, leading to an increase in molecular weight and system viscosity. Larger particle sizes, with increasing reaction temperature, accelerate initiator decomposition, increase free radical concentration, and increase the probability of effective collisions. This makes the polymer more prone to chain termination reactions during polymerization, resulting in shorter polymer chains, lower molecular weight, smaller particle size, lower viscosity, and higher conversion rate, leading to a more complete reaction. Furthermore, under the same reaction conditions, with increasing acrylic acid (AA) content, the latex particle size increases, possibly due to the formation of hydrogen bonds between carboxyl groups and water molecules.

[0101] Example 2

[0102] The performance of the samples from the examples and comparative examples was tested using the following methods or standards:

[0103] I. Conversion Rate: The conversion rate was determined by gravimetric method according to GB / T 11175-2021 standard. The calculation formula is as follows:

[0104] Conversion rate = (Actual solid content) / (Theoretical solid content) × 100%

[0105] Actual solid content: Cut a 5cm diameter circular aluminum foil into a box and weigh the sample inside. After drying in an oven at 120℃ until constant temperature, remove and weigh M. 2。 The following formula is used for calculation:

[0106] Actual solid content = (M2 - M0) / M1 × 100%

[0107] Where: M0 - mass of aluminum foil, g;

[0108] M1 - Sample mass, g;

[0109] M2 - Overall mass after drying, in grams.

[0110] Theoretical solids content: The proportion of the total mass of all substances except water to the total mass of all raw materials.

[0111] II. Gel Ratio: According to GB / T 11175-2021 standard, after the reaction is complete, collect the gel, wash it with deionized water, place it in an oven to constant weight, remove it, cool it to room temperature, and weigh the gel. Calculate the gel ratio using the following formula.

[0112] Gelation rate = (Gel mass / Sample mass) × 100%

[0113] III. Water Absorption Rate: According to GB / T 11175-2021 standard, under room temperature conditions, weigh 20-23g of sample onto a polytetrafluoroethylene plate, allow it to stand to defoam, and then dry it at room temperature to form a film. Cut off a portion of the dried coating film, soak it in deionized water at room temperature for 24 hours to remove surface moisture, and calculate its water absorption rate using the following formula.

[0114] Water absorption rate = (W2 - W1) / W1 × 100%

[0115] Where: W1 - mass of the cut coating, g;

[0116] Weight of W2-24h coating after water absorption, in g.

[0117] IV. Rotational viscosity: The viscosity was tested using an NDJ-79 rotational viscometer according to GB / T 22235-2008 standard, with a 100x rotor and a temperature of 25℃.

[0118] V. Hardness Test: Following GB / T 7124-2008 standard, the sample was cut into dumbbell shapes using a mold. The tensile strength was tested using a Shanghai Qunhong XWW-20B universal testing machine at a uniform tensile speed of 100 mm / min. The tensile strength value reflects the hardness; generally, the higher the tensile strength, the higher the hardness.

[0119] The samples from the examples and comparative examples were tested, and the results are shown in Table 2.

[0120] Table 2

[0121]

[0122] Table 2 shows that within a certain range, as the initiator concentration increases, the number of free radicals increases, the reaction rate accelerates, and the conversion rate increases. However, further increasing the initiator dosage increases the probability of latex particle collisions within the system, resulting in a decrease in conversion rate. Furthermore, an excessively fast reaction rate leads to insufficient heat dissipation, causing excessive emulsion viscosity. Changing the ratio of the hard monomer methyl methacrylate to the soft monomer butyl acrylate has little effect on conversion rate and gelation rate. Compared to Example 3, in Comparative Example 3, the emulsion viscosity gradually increases with the increase of the proportion of the soft monomer butyl acrylate in the emulsion. This is because butyl acrylate contains polar ester groups with flexible chains, which on the one hand increases the attraction between latex particles in the emulsion, and on the other hand makes the chain segments more tightly entangled and forms hydrogen bonds, thus leading to an increase in apparent viscosity. As polar ester groups are hydrophilic groups, the greater the amount used, the greater the water absorption rate of the latex film. In addition, the commercially available small-molecule emulsifier used in Comparative Example 5 migrates, greatly increasing the water absorption rate of the coating film. The addition of the soft monomer butyl acrylate reduces the rigidity of the polymer emulsion, increases its flexibility, reduces its tensile strength, and decreases its hardness.

[0123] Example 3

[0124] The water-based ink coatings of the samples in the examples and comparative examples were prepared according to the following method:

[0125] Preparation of water-based ink: Prepare water-based ink according to the following mass fraction formula: emulsion prepared in this example and comparative example 41.7%, deionized water 15.64%, ethanol 31.28%, OT-75 wetting agent 0.26%, slip agent DHX-51 0.12%, polyethylene wax emulsion 3%, pigment yellow 83 8%. Use a high-speed disperser to disperse at a rotation speed of 1000 r / min for 10 min, and let it stand until defoamed to obtain water-based ink.

[0126] Production of water-based ink coating: Drop 2 - 3 drops of ink on aluminum foil paper, and use a 10-μm wire bar coater to evenly scrape the ink on the aluminum foil paper. Take it out after drying in an oven at 120 °C for 35 s, and let it stand and cool to obtain a water-based ink coating.

[0127] I. Viscosity: According to the national standard GB / T 13217.4-2020, use a No. 4 cup to test the viscosity of the water-based ink at a temperature of 21 - 25 °C.

[0128] II. Adhesion fastness test: Conduct the test according to the national standard GB / T 13217.7-2009. Stick a standard 3M tape on the ink surface, uniformly press it with a certain load on the surface, and pull it evenly at an angle of 180°. Cover a 2-mm × 2-mm semi-transparent grid paper on it, and record the number of peeled-off grids. Calculate the adhesion fastness according to the following formula.

[0129] Adhesion fastness (%) = S1 / (S1 + S2) × 100%

[0130] In the formula: S1—the number of ink layer grids;

[0131] S2—the number of peeled-off ink layer pieces

[0132] III. Dry rubbing resistance: Conduct the test according to the national standard GB / T 7706-2008. Use test paper to wipe back and forth. If there is no ink layer peeling off on the paper after 50 times, it is qualified.

[0133] IV. Wet rubbing resistance: According to the standard of GB / T 7706-2008, use a wet cotton cloth to wipe the ink paper back and forth with a constant and uniform pressure, record the number of times of showing white, and if it does not show white after 50 times, it is qualified.

[0134] V. Anti-blocking property: The anti-blocking property of the ink coating was tested according to the national standard GB / T 13217.8-2009. The coated aluminum foil paper was dried in a 60℃ oven for 5 minutes. After natural cooling, the ink-coated paper was folded and a piece of white paper was inserted in the middle. It was then pressed between two glass plates, and a 2Kg weight was placed on top. The paper was placed in a 50℃ oven for 2 hours and then removed to observe the coloring on the white paper.

[0135] VI. Storage stability: After the prepared water-based ink sample is sealed in a container, it is placed in a cool, ventilated place and left to stand for 60 days. Then it is taken out and scraped to observe the appearance of the water-based ink and the scraping effect. If there is no water separation, clumping and particles, it is considered that the storage stability has passed.

[0136] VII. Gloss Test: The gloss of the ink surface was tested using an XGP portable specular gloss meter at an incident angle of 60°, in accordance with the national standard GB / T 13217.2-2009.

[0137] 8. Water resistance test: According to the national standard GB / T 1733-2021, under room temperature conditions, cut the ink paper into rectangles of 2cm×5cm, paste them on a glass slide, immerse them in water for 2 hours, and observe whether the deionized water changes color and the state of ink coating peeling off.

[0138] The samples from the examples and comparative examples were tested, and the results are shown in Table 3.

[0139] Table 3

[0140]

[0141] Table 3 shows that with the increase of AA dosage, the number of hydrogen bonds in the system increases, and the emulsion viscosity gradually increases. Since AA contains polar groups, introducing it into the polymer can enhance the adhesion between the ink coating and the substrate; however, when the dosage is too high, the cross-linked structure within the polymer becomes too dense, and the adhesion decreases. Sodium bicarbonate plays a certain role in stabilizing the emulsion. The results of Comparative Example 3 indicate that when the ratio of the soft monomer butyl acrylate to the hard monomer methyl methacrylate is too high, it adversely affects the anti-blocking properties of the coating and results in unsatisfactory storage stability, failing to meet the requirements of practical applications.

[0142] Using a self-made macromolecular polymerizable acrylic emulsifier significantly improves the performance of the coating compared to commercially available small-molecule emulsifiers.

[0143] The experimental data from Comparative Examples 6 and 8 show that hydroxypropyl acrylate and tributyl acetylacetonate have a combined effect on the adhesion of the coating. Their absence will significantly reduce the adhesion of the coating. Functional monomers and emulsifiers have a positive effect on the various test results of the coating.

[0144] In this embodiment of the invention, Embodiment 1 is the optimal embodiment and has significant technical effects.

[0145] Finally, it should be noted that in this invention, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0146] Although this disclosure has been described above through specific embodiments, it should be understood that those skilled in the art can devise various modifications, improvements, or equivalents to this disclosure within the spirit and scope of the appended solutions. Such modifications, improvements, or equivalents should also be considered to be included within the scope of protection claimed in this disclosure.

Claims

1. A method for preparing a core-shell type acrylate soap-free emulsion, characterized in that, Includes the following steps: (1) Add solvent to the reaction flask, heat to 120~150℃, add the first monomer and initiator dropwise to the reaction flask, keep warm after the dropwise addition is complete, add pH adjuster to adjust pH to 8, add deionized water to disperse and obtain macromolecular acrylate emulsifier; the first monomer includes acrylic acid, butyl acrylate, methyl methacrylate, hydroxypropyl acrylate and hydroxyethyl methacrylate; (2) Mix the macromolecular acrylate emulsifier, part of the second monomer and deionized water, stir to obtain a pre-emulsion, then heat the pre-emulsion, add part of the pH buffer and part of the ammonium persulfate to initiate the reaction, after blue light appears, simultaneously add the remaining second monomer, the remaining ammonium persulfate and the remaining pH buffer, after the addition is complete, keep warm, and then add pH adjuster to adjust the pH to 8 to obtain the core-shell type acrylate soap-free emulsion; the second monomer includes acrylic acid, butyl acrylate, methyl methacrylate and functional monomers, the functional monomers being hydroxypropyl acrylate, hydroxyethyl methacrylate and tributyl acetylacetate.

2. The method for preparing the core-shell type acrylate soap-free emulsion according to claim 1, characterized in that, In step (1), the solvent is diethylene glycol dimethyl ether, and the amount used is 13.5~14.5% of the total weight of the first monomer; And / or, in step (1), the amount of acrylic acid in the first monomer is 14-17% of the total weight of the first monomer, the amount of butyl acrylate is 33-36% of the total weight of the first monomer, the amount of methyl methacrylate is 44-46% of the total weight of the first monomer, the amount of hydroxypropyl acrylate is 3.5-4.0% of the total weight of the first monomer, and the amount of hydroxyethyl methacrylate is 1.6-1.8% of the total weight of the first monomer; And / or, in step (1), the initiator is selected from one or two of benzoyl peroxide, tert-butyl peroxide, tert-butyl hydroperoxide, dicarbonate peroxide, dicumyl peroxide, and azobisisobutyronitrile; And / or, in step (1), the amount of the initiator is 3% to 6.5% of the total weight of the first monomer; And / or, in step (1), the pH adjuster is selected from one or two of ammonia, sodium hydroxide, potassium hydroxide, and 2-amino-2-methyl-1-propanol; And / or, in step (1), the amount of deionized water is 8% to 10% of the total weight of the macromolecular acrylate emulsifier.

3. The method for preparing the core-shell type acrylate soap-free emulsion according to claim 2, characterized in that, In step (1), the initiator is benzoyl peroxide and tert-butyl peroxide in a mass ratio of 9.5~10.5:1; And / or, in step (1), the pH adjuster is ammonia.

4. The method for preparing the core-shell type acrylate soap-free emulsion according to claim 1, characterized in that, In step (1), the dripping time is 2-4 hours; And / or, in step (1), the heat preservation time is 1 hour.

5. The method for preparing the core-shell type acrylate soap-free emulsion according to claim 1, characterized in that, In step (2), the amount of the macromolecular acrylate emulsifier is 1.30% to 2.0% of the total weight of the core-shell type acrylate soap-free emulsion; And / or, in step (2), in the second monomer, the mass ratio of butyl acrylate to methyl methacrylate is 1:4 to 7:3, the amount of acrylic acid is 0.82 to 0.99% of the total weight of the second monomer, the amount of butyl acrylate is 34 to 52% of the total weight of the second monomer, and the amount of methyl methacrylate is 34 to 52% of the total weight of the second monomer; And / or, in step (2), the amount of the functional monomer is 13% to 15% of the total weight of the second monomer; the amount of hydroxypropyl acrylate is 33% to 34% of the total weight of the functional monomer; the amount of hydroxyethyl methacrylate is 17% to 18% of the total weight of the functional monomer; and the amount of tributyl acetyl citrate is 49% to 50% of the total weight of the functional monomer. And / or, in step (2), the amount of the second monomer used accounts for 9-11% of the total weight of the second monomer; And / or, in step (2), the amount of deionized water used accounts for 57% to 60% of the total weight of the core-shell type acrylate soap-free emulsion; And / or, in step (2), the pH buffer is one of sodium bicarbonate, sodium dihydrogen phosphate or ammonium bicarbonate; And / or, in step (2), the amount of the pH buffer is 0.19% to 0.33% of the total weight of the core-shell acrylate soap-free emulsion; And / or, in step (2), the amount of the partial pH buffer used is 30-35% of the total weight of the pH buffer; And / or, in step (2), the amount of ammonium persulfate used is 0.66% to 0.83% of the total weight of the second monomer; And / or, in step (2), the amount of ammonium persulfate used is 30-35% of the total weight of the ammonium persulfate; And / or, in step (2), the pH adjuster is selected from one or two of ammonia, sodium hydroxide, potassium hydroxide, and 2-amino-2-methyl-1-propanol.

6. The method for preparing the core-shell type acrylate soap-free emulsion according to claim 5, characterized in that, In step (2), the pH buffer is sodium bicarbonate; And / or, in step (2), the pH adjuster is ammonia water with a mass fraction of 25%.

7. The method for preparing the core-shell type acrylate soap-free emulsion according to claim 1, characterized in that, In step (2), the stirring speed is 1200 r / min; And / or, in step (2), the stirring time is 30 min; And / or, in step (2), the temperature at which the pre-emulsion is heated is 85~95℃; And / or, in step (2), the dripping time is 3 hours; And / or, in step (2), the heat preservation time is 1 hour.

8. A core-shell type acrylate soap-free emulsion, characterized in that, It is prepared by the method for preparing core-shell type acrylate soap-free emulsion according to any one of claims 1 to 7.

9. A water-based ink, characterized in that, It includes the core-shell type acrylate soap-free emulsion as described in claim 8.

10. The water-based ink according to claim 9, characterized in that, By mass fraction, its composition is as follows: 41.7% core-shell acrylate soap-free emulsion, 15.64% deionized water, 31.28% ethanol, 0.26% OT-75 wetting agent, 0.12% slip agent DHX-51, 3% polyethylene wax emulsion, and 8% pigment yellow 83.

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