Water-based acrylic varnish, preparation method thereof and application of water-based acrylic varnish in paperboard

Abstract

The invention relates to the technical field of varnish, and discloses water-based acrylic varnish, a preparation method thereof and application of the water-based acrylic varnish in paperboard, the water-based acrylic varnish comprises 60-85 parts by weight of shell-core type cationic water-based acrylic resin, 15-40 parts by weight of sulfonate modified epoxy resin, 4-12 parts by weight of a curing agent and 0.1-0.4 part by weight of a defoaming agent; the acrylic resin contains quaternary ammonium salt cationic groups, the epoxy resin contains sulfonate cationic groups, electrostatic interaction is formed in the curing process, the compatibility between the acrylic resin and the epoxy resin is improved, meanwhile, the interface bonding force and the molecular chain interaction force are enhanced, and the molecular chain crosslinking degree of the acrylic resin and the epoxy resin is improved; the pencil hardness and impact resistance of the paint film can be improved, the adhesive force grade reaches the first grade, and the paint film is not prone to falling off from the surface of a base material. Meanwhile, the salt fog resistance is excellent, and the corrosion resistance is good.

Description

Technical Field

[0001] The invention relates to the technical field of varnishes, and in particular to a water-based acrylic varnish, a preparation method thereof, and application of the varnish in cardboard. Background Art

[0002] Acrylic resin varnish has the advantages of low cost, good weather resistance, excellent color and gloss retention, etc. It is widely used in gold and silver cardboard, anti-corrosion coatings, etc. When preparing acrylic resin, adding acrylic acid, quaternary ammonium salt and other water-based monomers can give the resin good hydrophilicity. The obtained water-based acrylic resin does not contain organic volatile solvents and is green and environmentally friendly.

[0003] The mechanical and anti-corrosion properties of acrylic resin can be improved by grafting or blending epoxy resin with acrylic resin. The invention patent with the announcement number CN113603841B discloses hybrid compounding of epoxy resin and acrylic resin, which combines the advantages of the two resins to obtain a resin dispersion with the characteristics of hardness, high gloss, excellent aging resistance and salt spray resistance. However, the acrylic resin dispersion uses trimethylbenzene, naphtha, diethylene glycol butyl ether, isopropyl alcohol and the like as solvents, which is highly polluting. Summary of the invention

[0004] The invention solves the problems of poor adhesion, impact resistance, hardness and the like of acrylic resin varnish.

[0005] The technical scheme provided by the invention is: a water-based acrylic varnish, comprising 60-85 parts by weight of core-shell cationic water-based acrylic resin, 4-9 parts by weight of water-based polyurethane, 15-40 parts by weight of sulfonate-modified epoxy resin, 4-12 parts by weight of curing agent, 0.1-0.4 parts by weight of defoaming agent, and 0.2-0.6 parts by weight of wetting agent.

[0006] The preparation method of the core-shell cationic water-based acrylic resin comprises: adding acrylic resin to water in a nitrogen atmosphere, adding sodium hydroxide to adjust the pH to 7.5-8, adding olefin monomer, 4-vinylbenzyltriethanolamine quaternary ammonium salt and emulsifier after stirring, adding an aqueous solution of ammonium persulfate dropwise after stirring and emulsifying, stirring to carry out polymerization reaction, cooling, and obtaining the core-shell cationic water-based acrylic resin.

[0007] The olefin monomer is any one or a combination of methyl methacrylate, isooctyl methacrylate, butyl acrylate and styrene.

[0008] Preferably, the mass ratio of acrylic resin, vinyl monomer, 4-vinylbenzyltriethanolamine quaternary ammonium salt, and ammonium persulfate is (16-25):(54-59):(2-8):(0.56-0.74).

[0009] Preferably, the emulsifier is composed of OP-10 and sodium lauryl sulfate in a mass ratio of (30-36):(64-70). The emulsifier accounts for 1-3% of the total mass of the vinyl monomer.

[0010] Preferably, the polymerization reaction is carried out at 80-85°C for 1-2.5 hours.

[0011] Preferably, the preparation method of 4-vinylbenzyltriethanolamine quaternary ammonium salt comprises: adding 4-chloromethylstyrene and triethanolamine in a molar ratio of 1:1 to ethanol, adding a polymerization inhibitor 4-methoxyphenol after stirring, heating to 50-55° C., reacting for 18-24 hours, distilling under reduced pressure, washing with petroleum ether, and drying to obtain 4-vinylbenzyltriethanolamine quaternary ammonium salt. The reaction formula is as follows:

[0012]

[0013] Preferably, the curing agent is a polyetheramine curing agent, and the defoaming agent is a polyether-modified silicone.

[0014] Preferably, the preparation method of the sulfonate-modified epoxy resin comprises: adding epoxy resin E44 to tetrahydrofuran, adding taurine after stirring, heating to 40-60° C., reacting for 1-1.5 hours, distilling under reduced pressure, adding 80 mL of water, stirring and mixing, adding sodium hydroxide to adjust the pH to 8, and obtaining the sulfonate-modified epoxy resin.

[0015] Preferably, the mass ratio of epoxy resin E44 and taurine is (75-82):(18-25).

[0016] Preferably, the preparation method of the water-based acrylic varnish is: add core-shell cationic water-based acrylic resin, sulfonate-modified epoxy resin, defoamer, wetting agent into a container, stir and then add curing agent to obtain the water-based acrylic varnish.

[0017] Preferably, the water-based acrylic varnish is used in cardboard.

[0018] The technical effect is as follows: the present invention utilizes 4-vinylbenzyl triethanolamine quaternary ammonium salt to carry out polymerization reaction with methyl methacrylate and n-butyl acrylate to obtain a core-shell type cationic waterborne acrylic resin. The amino group of taurine is used to carry out a ring-opening reaction with the epoxy group of the epoxy resin, thereby introducing a sodium sulfonate group into the molecular chain of the epoxy resin to obtain a waterborne sulfonate-modified epoxy resin.

[0019] The invention uses core-shell cationic water-based acrylic resin and sulfonate-modified epoxy resin as film-forming substances of the varnish, wherein the acrylic resin contains quaternary ammonium salt and multiple hydroxyl hydrophilic groups, and the epoxy resin E44 is modified with taurine and sodium sulfonate hydrophilic groups are introduced into the molecular chain, so that the acrylic resin and the epoxy resin have good hydrophilicity and good dispersibility in water, thereby making the water-based varnish emulsion show good dispersibility and storage stability.

[0020] The acrylic resin of the invention contains a quaternary ammonium salt cationic group, and the epoxy resin contains a sulfonate cationic group, so that an electrostatic interaction is formed during the curing process, thereby improving the compatibility between the two, enhancing the interface bonding force and the molecular chain interaction force, and improving the molecular chain crosslinking degree of the two, which is beneficial to improving the pencil hardness and impact resistance of the paint film, and the adhesion grade reaches Grade 1, and the paint film is not easy to fall off from the surface of the substrate. At the same time, the paint film has excellent salt spray resistance and good anticorrosion performance. The paint film has good practical applications in gold and silver cardboard, wood paint, metal substrate anticorrosion, etc. DETAILED DESCRIPTION

[0021] In order to make the technical solution of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below. It should be noted that the following embodiments are only used to better understand the technical solution of the present invention and should not be understood as limiting the present invention.

[0022] Example 1

[0023] (1) Add 82 g of epoxy resin E44 to 400 mL of tetrahydrofuran, stir, add 18 g of taurine, heat to 50° C., react for 1.5 h, distill under reduced pressure, add 80 mL of water, stir and mix, add sodium hydroxide to adjust the pH to 8, and obtain a sulfonate-modified epoxy resin.

[0024] (2) Add 12 mmol 4-chloromethylstyrene and 12 mmol triethanolamine to 10 mL ethanol, stir, add 0.023 mmol 4-methoxyphenol as a polymerization inhibitor, heat to 55°C, react for 18 hours, distill under reduced pressure, wash with petroleum ether, and dry to obtain 4-vinylbenzyltriethanolamine quaternary ammonium salt. The structural formula is:

[0025]

[0026] (3) In a nitrogen atmosphere, 750 mL of water and 160 g of acrylic resin (model BASF JONCRYL 678, the same below) were added to a reaction kettle, and sodium hydroxide was added to adjust the pH to 7.5. After stirring, 230 g of methyl methacrylate, 130 g of isooctyl methacrylate, 180 g of butyl acrylate, 20 g of 4-vinylbenzyltriethanolamine quaternary ammonium salt, 1.95 g of OP-10, and 3.45 g of sodium dodecyl sulfate were added. After stirring and emulsification, 20 mL of an aqueous solution containing 7.4 g of ammonium persulfate was added dropwise, and the mixture was stirred at 85° C. for 1 h for polymerization reaction. The mixture was cooled to obtain a core-shell type cationic waterborne acrylic resin.

[0027] (4) 850 g of core-shell cationic water-based acrylic resin, 40 g of water-based polyurethane (model Tangyi 6516, the same below), 150 g of sulfonate-modified epoxy resin, 4 g of polyether-modified silicone defoamer Anjeka5062, and 3 g of wetting agent TEGO Wet270 were added to a container, and after stirring, 40 g of curing agent polyetheramine D230 was added to obtain a water-based acrylic varnish.

[0028] Example 2

[0029] (1) Add 78 g of epoxy resin E44 to 350 mL of tetrahydrofuran, stir, add 22 g of taurine, heat to 40° C., react for 1.5 h, distill under reduced pressure, add 80 mL of water, stir and mix, add sodium hydroxide to adjust the pH to 8, and obtain a sulfonate-modified epoxy resin.

[0030] (2) Add 12 mmol 4-chloromethylstyrene and 12 mmol triethanolamine to 10 mL ethanol, stir, add 0.02 mmol 4-methoxyphenol as a polymerization inhibitor, heat to 50°C, react for 24 hours, distill under reduced pressure, wash with petroleum ether, and dry to obtain 4-vinylbenzyltriethanolamine quaternary ammonium salt.

[0031] (3) In a nitrogen atmosphere, 750 mL of water and 160 g of acrylic resin were added to a reaction kettle, and sodium hydroxide was added to adjust the pH to 7.5. After stirring, 230 g of methyl methacrylate, 130 g of isooctyl methacrylate, 180 g of butyl acrylate, 80 g of 4-vinylbenzyltriethanolamine quaternary ammonium salt, 2.4 g of OP-10, and 5.6 g of sodium dodecyl sulfate were added. After stirring and emulsification, 20 mL of an aqueous solution containing 7.4 g of ammonium persulfate was added dropwise, and the polymerization reaction was carried out at 85° C. with stirring for 1 h. The mixture was cooled to obtain a core-shell cationic water-based acrylic resin.

[0032] (4) 850 g of core-shell cationic water-based acrylic resin, 90 g of water-based polyurethane, 150 g of sulfonate-modified epoxy resin, 1 g of polyether-modified silicone defoamer Anjeka5062, and 6 g of wetting agent TEGO Wet270 were added to a container, and after stirring, 40 g of curing agent polyetheramine D230 was added to obtain a water-based acrylic varnish.

[0033] Example 3

[0034] (1) Add 75 g of epoxy resin E44 to 300 mL of tetrahydrofuran, stir, add 25 g of taurine, heat to 60° C., react for 1 h, distill under reduced pressure, add 80 mL of water, stir and mix, add sodium hydroxide to adjust the pH to 8, and obtain a sulfonate-modified epoxy resin.

[0035] (2) In a nitrogen atmosphere, 800 mL of water and 250 g of acrylic resin were added to a reaction kettle, and sodium hydroxide was added to adjust the pH to 8. After stirring, 190 g of methyl methacrylate, 370 g of styrene, 30 g of butyl acrylate, 50 g of 4-vinylbenzyltriethanolamine quaternary ammonium salt (prepared in the same manner as in Example 1), 5.3 g of OP-10, and 12.3 g of sodium dodecyl sulfate were added. After stirring and emulsification, 20 mL of an aqueous solution containing 5.6 g of ammonium persulfate was added dropwise, and the mixture was stirred at 80° C. for 2.5 h for polymerization reaction. The mixture was cooled to obtain a core-shell cationic water-based acrylic resin.

[0036] (3) 850 g of core-shell cationic water-based acrylic resin, 60 g of water-based polyurethane, 150 g of sulfonate-modified epoxy resin, 4 g of polyether-modified silicone defoamer Anjeka5062, and 2 g of wetting agent TEGO Wet270 were added to a container, and after stirring, 40 g of curing agent polyetheramine D230 was added to obtain a water-based acrylic varnish.

[0037] Example 4

[0038] (1) 760 g of a core-shell cationic water-based acrylic resin (prepared in the same manner as in Example 1), 240 g of a sulfonate-modified epoxy resin, 40 g of an aqueous polyurethane, 4 g of a polyether-modified silicone defoamer Anjeka5062, and 3 g of a wetting agent TEGO Wet270 were added to a container, and after stirring, 75 g of a curing agent polyetheramine D230 was added to obtain a water-based acrylic varnish.

[0039] Example 5

[0040] (1) 680 g of a core-shell cationic water-based acrylic resin (prepared in the same manner as in Example 1), 40 g of an aqueous polyurethane, 320 g of a sulfonate-modified epoxy resin, 4 g of a polyether-modified silicone defoamer Anjeka5062, and 3 g of a wetting agent TEGO Wet270 were added to a container, and after stirring, 92 g of a curing agent polyetheramine D230 was added to obtain a water-based acrylic varnish.

[0041] Example 6

[0042] (1) 600 g of a core-shell cationic water-based acrylic resin (prepared in the same manner as in Example 1), 40 g of an aqueous polyurethane, 400 g of a sulfonate-modified epoxy resin, 4 g of a polyether-modified silicone defoamer Anjeka5062, and 3 g of a wetting agent TEGO Wet270 were added to a container, and after stirring, 120 g of a curing agent polyetheramine D230 was added to obtain a water-based acrylic varnish.

[0043] Comparative Example 1

[0044] (1) 850 g of a core-shell cationic water-based acrylic resin (prepared in the same manner as in Example 1), 40 g of an aqueous polyurethane, 150 g of an epoxy resin E44, 4 g of a polyether-modified silicone defoamer Anjeka5062, and 3 g of a wetting agent TEGO Wet270 were added to a container, and after stirring, 40 g of a curing agent polyetheramine D230 was added to obtain a water-based acrylic varnish.

[0045] Comparative Example 2

[0046] (1) In a nitrogen atmosphere, 750 mL of water and 160 g of acrylic resin were added to a reaction kettle, and sodium hydroxide was added to adjust the pH to 7.5. After stirring, 230 g of methyl methacrylate, 130 g of isooctyl methacrylate, 180 g of butyl acrylate, 1.95 g of OP-10, and 3.45 g of sodium dodecyl sulfate were added. After stirring and emulsification, 20 mL of an aqueous solution containing 7.4 g of ammonium persulfate was added dropwise, and the mixture was stirred at 85° C. for 1 h for polymerization reaction. The mixture was cooled to obtain a core-shell acrylic resin.

[0047] (2) 850 g of core-shell acrylic resin, 40 g of waterborne polyurethane, 150 g of sulfonate-modified epoxy resin (prepared in the same manner as in Example 1), 4 g of polyether-modified silicone defoamer Anjeka5062, and 3 g of wetting agent TEGOWet270 were added to a container, and after stirring, 40 g of curing agent polyetheramine D230 was added to obtain an acrylic resin varnish.

[0048] The water-based acrylic varnish was placed at room temperature for 2 months and the dispersibility of the varnish was observed. The results are shown in Table 1.

[0049] Table 1 Varnish dispersibility test

[0050] Resin dispersion Example 1 The emulsion is transparent, non-stratified, uniform and stable Example 2 The emulsion is transparent, non-stratified, uniform and stable Example 3 The emulsion is transparent, non-stratified, uniform and stable Example 4 The emulsion is transparent, non-stratified, uniform and stable Example 5 The emulsion is transparent, non-stratified, uniform and stable Example 6 The emulsion is transparent, non-stratified, uniform and stable Comparative Example 1 The emulsion is turbid and does not separate Comparative Example 2 The lotion is obviously separated

[0051] As can be seen from Table 1, the emulsions of the water-based acrylic varnishes of Examples 1-6 are transparent, non-stratified, uniform and stable, with good dispersibility and storage stability. This is because the acrylic resin in the varnish contains a quaternary ammonium salt and multiple hydroxyl hydrophilic groups, and the epoxy resin E44 is modified with taurine to introduce a sodium sulfonate hydrophilic group into the molecular chain, so that the acrylic resin and the epoxy resin have good hydrophilicity and good dispersibility in water, so that the water-based varnish emulsion exhibits good dispersibility and storage stability.

[0052] The epoxy resin E44 of Comparative Example 1 has not been modified with aminosulfonic acid and does not contain a sodium sulfonate hydrophilic group. It has very poor dispersibility in an aqueous system and the varnish emulsion is turbid.

[0053] In Comparative Example 2, when preparing acrylic resin, 4-vinylbenzyltriethanolamine quaternary ammonium salt was not added. The acrylic resin did not contain quaternary ammonium salt and multiple hydroxyl hydrophilic groups, had poor dispersibility in the aqueous system, and the emulsion was obviously stratified.

[0054] The water-based acrylic varnish was first cured at 90°C for 2h and then at 130°C for 2h. The appearance of the paint film was observed. The hardness of the paint film was tested according to GB / T 6739-2022. The impact resistance was tested according to GB / T1732-2020. The adhesion grade was tested according to GB / T 1720-2020. The salt spray resistance was tested according to GB / T 1771-2007. The substrate was tinplate. The results are shown in Table 2.

[0055] Table 1 Water-based acrylic varnish test

[0056]

[0057] As can be seen from Table 2, the pencil hardness and impact resistance of the water-based acrylic varnish of Examples 1-6 are much better than those of Comparative Examples 1 and 2. This is because each embodiment uses a core-shell cationic water-based acrylic resin and a sulfonate-modified epoxy resin as film-forming substances for the varnish, the acrylic resin contains a quaternary ammonium salt cationic group, and the epoxy resin contains a sulfonate cationic group, which forms an electrostatic interaction during the curing process, thereby improving the compatibility between the two, while enhancing the interface bonding force and the molecular chain interaction force, and improving the molecular chain crosslinking degree of the two, which is beneficial to improving the pencil hardness and impact resistance of the paint film, and the adhesion grade reaches Grade 1, the paint film is not easy to fall off from the surface of the substrate, and at the same time, it has excellent salt spray resistance and good anti-corrosion performance.

[0058] Obviously, the above embodiments of the present disclosure are merely examples for clearly illustrating the present disclosure, and are not limitations on the implementation methods of the present disclosure. Technicians in the relevant technical field may make various modifications or supplements to the described specific embodiments or replace them in a similar manner. As long as they do not deviate from the structure of the invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

Claims

1. A water-based acrylic varnish, characterized in that The water-based acrylic varnish comprises 60-85 parts by weight of core-shell cationic water-based acrylic resin, 4-9 parts by weight of water-based polyurethane, 15-40 parts by weight of sulfonate-modified epoxy resin, 4-12 parts by weight of curing agent, 0.1-0.4 parts by weight of defoaming agent, and 0.2-0.6 parts by weight of wetting agent; The preparation method of the core-shell cationic water-based acrylic resin comprises: adding acrylic resin to water in a nitrogen atmosphere, adding sodium hydroxide to adjust the pH to 7.5-8, adding olefin monomer, 4-vinylbenzyltriethanolamine quaternary ammonium salt, and emulsifier after stirring, adding an aqueous solution of ammonium persulfate dropwise after stirring and emulsifying, stirring to carry out polymerization reaction, cooling, and obtaining the core-shell cationic water-based acrylic resin; The olefin monomer is any one or a combination of methyl methacrylate, isooctyl methacrylate, butyl acrylate and styrene.

2. The water-based acrylic varnish according to claim 1, characterized in that The mass ratio of the acrylic resin, the vinyl monomer, the quaternary ammonium salt of 4-vinylbenzyltriethanolamine and the ammonium persulfate is (16-25):(54-59):(2-8):(0.56-0.74).

3. The water-based acrylic varnish according to claim 1, characterized in that The emulsifier is composed of OP-10 and sodium dodecyl sulfate in a mass ratio of (30-36):(64-70); the emulsifier accounts for 1-3% of the total mass of the ethylenic monomer.

4. The water-based acrylic varnish according to claim 1, characterized in that The polymerization reaction is carried out at 80-85°C for 1-2.5 hours.

5. The water-based acrylic varnish according to claim 1, characterized in that The preparation method of 4-vinylbenzyltriethanolamine quaternary ammonium salt comprises: adding 4-chloromethylstyrene and triethanolamine in a molar ratio of 1:1 into ethanol, adding a polymerization inhibitor 4-methoxyphenol after stirring, heating to 50-55° C., reacting for 18-24 hours, distilling under reduced pressure, washing with petroleum ether, and drying to obtain 4-vinylbenzyltriethanolamine quaternary ammonium salt.

6. The water-based acrylic varnish according to claim 1, characterized in that The curing agent is a polyetheramine curing agent, and the defoaming agent is a polyether modified silicone.

7. The water-based acrylic varnish according to claim 1, characterized in that The preparation method of the sulfonate modified epoxy resin comprises: adding epoxy resin E44 to tetrahydrofuran, adding taurine after stirring, heating to 40-60° C., reacting for 1-1.5 hours, performing reduced pressure distillation, adding water, stirring and mixing, and adding sodium hydroxide to obtain the sulfonate modified epoxy resin.

8. The water-based acrylic varnish according to claim 6, characterized in that The mass ratio of the epoxy resin E44 to taurine is (75-82):(18-25).

9. A method for preparing a water-based acrylic varnish as claimed in any one of claims 1 to 8, characterized in that: The preparation method comprises: adding core-shell cationic water-based acrylic resin, sulfonate-modified epoxy resin, defoamer and wetting agent into a container, stirring and then adding curing agent to obtain water-based acrylic varnish.

10. Use of the water-based acrylic varnish obtained by the preparation method according to claim 9 in cardboard.

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