A method for preparing an ink-resistable waterborne polyurethane primer coating

Abstract

A water-based, environmentally friendly polyurethane primer coating capable of ink retention and its preparation method are disclosed. The method is characterized by using water-based polyurethane emulsion and sulfonate modifier as main raw materials to prepare the water-based, ink-retention-resistant polyurethane primer coating. The mixture comprises 30-45 parts polyurethane emulsion and 7-10 parts sulfonate modifier, reacted at room temperature, followed by the addition of anionic emulsifier, nonionic emulsifier, leveling agent, and defoamer. The mixture is then dispersed by high-speed stirring to obtain the water-based, environmentally friendly, ink-retention-resistant polyurethane primer coating, achieving an ink retention rate of up to 98%. Compared with existing technologies, this invention has the following characteristics: the introduction of sulfonate modifier synthesizes a sulfonic acid-based water-based polyurethane coating, which exhibits good particle regularity and dispersibility, and extremely low volatile organic compound (VOC) content; the coating has good film-forming properties, high gloss on metallized paper, and excellent ink retention and leveling effects.

Description

Technical Field

[0001] This invention relates to the field of waterborne coatings technology, specifically to a method for preparing an ink-retention waterborne polyurethane primer coating using sulfonate modifiers as chain extenders and emulsifiers for waterborne polyurethane emulsions. Background Technology

[0002] As environmental protection gains increasing international attention, the labeling and packaging industry is raising its requirements for the performance of environmentally friendly labels in the domestic market. Ink retention refers to the ability of the ink layer on the beer label surface to adhere to the base paper during the label removal process in an alkaline bath, after immersion in a sodium hydroxide solution, without peeling off or dissolving in the alkaline bath. This prevents contamination of the alkaline solution, ensures the cleanliness of the alkaline bath, significantly saves water and alkaline solution, and improves the utilization rate of the alkaline solution. The primer coating, located between the paper substrate and the vacuum-metallized film, seals the substrate, improves the smoothness of the base layer to enhance the mirror effect of the metallized film, and improves the adhesion between the substrate and the metallized film, thus giving the substrate and the metallized film good adhesion, leveling, and heat resistance. Currently, in domestic vacuum-metallized packaging materials, most ink-retention-enabled aluminum beer label primer coatings are solvent-based products, with base materials such as rosin, dibutyl phthalate, polyvinyl butyral, and xylene. These have high production and post-processing costs and pose significant environmental hazards. However, water-based bulk products lack ink retention properties due to their poor alkali resistance. Chinese patent CN102041720B proposes a primer coating scheme for beer label paper and evaluates its alkali resistance based on the fact that the aluminum layer is not washed with alkali, but it does not address the crucial issue of ink retention. Chinese patent CN105331233A discloses a water-based environmentally friendly coating for direct plating of beer labels with ink retention, achieving an ink retention rate of 95%, but this coating requires high preparation temperatures, consumes a lot of energy, and uses ammonia as a pH adjuster, making it environmentally unfriendly. Summary of the Invention

[0003] The purpose of this invention is to prepare an environmentally friendly waterborne polyurethane primer coating that can leave ink residue, replacing the traditional solvent-based vacuum metallized film primer coating, and solving the problems of complex formulations, inability to operate at room temperature, and large use of acid-base adjusters in existing waterborne primer coatings.

[0004] Based on the above, the present invention relates to a method for preparing an ink-retaining waterborne polyurethane primer coating, characterized by adding 35-45 parts of polyurethane emulsion and 7-11 parts of sulfonate modifier to a reaction vessel and stirring at 300-500 r / min at room temperature; adding 40-50 parts of deionized water and 0.5-2.0 parts of anionic emulsifier and stirring at 600-800 r / min at room temperature for 30 min; adding 5-8 parts of nonionic emulsifier to the reaction vessel and stirring at 600-800 r / min at room temperature for 5 min; adding 0.01-0.3 parts of leveling agent to the mixture and stirring and dispersing at 800-1000 r / min at room temperature for 5 min; adding 0.03-0.05 parts of defoamer to the mixture and stirring and dispersing at 800-1000 r / min at room temperature for 10 min, thereby obtaining an ink-retaining waterborne polyurethane primer coating, the coating having a solid content of 20-25% and a pH value between 7.5 and 8.5.

[0005] This invention solves this technical problem through the following technical solution:

[0006] The specific technical solution is illustrated using an example of a waterborne polyurethane coating prepared by a mass ratio of polyurethane emulsion and sodium N-(2-aminoethyl)-2-aminoethane sulfonate modifier of 5:1.

[0007] 5 kg of polyurethane monomer and 1.2 kg of N-(2-aminoethyl)-2-aminoethane sulfonate sodium salt were added to a 20 L reactor. While stirring at 400 rpm at room temperature, 5.6 L of deionized water and 0.2 kg of fatty alcohol polyoxyethylene ether zinc carboxylate were added to the reactor. After the addition was complete, the mixture was stirred at 700 rpm at room temperature for 30 min. 0.9 g of isomeric tridecyl alcohol ether was added to the reactor, and the mixture was stirred at 800 rpm at room temperature for 5 min. 30 g of polyether-modified organosiloxane was added to the mixture, and the mixture was stirred and dispersed at 800 rpm at room temperature for 5 min. 6 g of polydimethylsiloxane was added to the mixture, and the mixture was stirred and dispersed at 1000 rpm at room temperature for 10 min. This yielded an ink-retention waterborne polyurethane primer with an ink retention rate of 98%, a solid content of 20.3%, and a pH of 7.9.

[0008] Compared with the prior art, the present invention has the following beneficial effects:

[0009] 1. The reaction conditions are mild, the operation is simple, and it is safe and environmentally friendly;

[0010] 2. A sulfonic acid-based waterborne polyurethane was prepared, which does not require the addition of acid-base regulators or co-solvents, thus reducing process costs;

[0011] 3. The product has extremely low volatile organic compound (VOC) content and no irritating odor;

[0012] 4. The coating has good film-forming properties and high aluminum plating brightness, which improves the ink retention rate. Specific implementation methods

[0013] The method of the present invention will be further described below with reference to embodiments, but this is not intended to limit the present invention.

[0014] Example 1: 35 parts of polyurethane emulsion and 7 parts of sodium N-(2-aminoethyl)-2-aminoethane sulfonate were added to a reaction vessel and stirred at 300 rpm at room temperature. 40 parts of deionized water and 0.5 parts of anionic emulsifier C12 fatty alcohol polyoxyethylene ether zinc carboxylate were added and stirred at 600 rpm for 30 min at room temperature. 5 parts of nonionic emulsifier isotridecyl ether were added to the reaction vessel and stirred at 600 rpm for 5 min at room temperature. 0.01 parts of leveling agent polyether-modified organosiloxane were added to the mixture and stirred at 800 rpm for 5 min at room temperature. 0.03 parts of defoamer polydimethylsiloxane were added to the mixture and stirred at 800 rpm for 10 min at room temperature to obtain an ink-retention waterborne polyurethane primer coating with a solid content of 21.0% and a pH of 7.6.

[0015] Comparative Example 1: Soybean oil fatty acids, castor oil fatty acids, pentaerythritol, and neopentyl glycol were added to a reaction vessel, CO2 gas was introduced, and the temperature was raised to 120°C. Dibutyltin dilaurate was added and stirred, and the temperature was raised to 220°C for 3 hours. The temperature was then lowered to 180°C, and isophthalic acid, benzotricarboxylic anhydride, and 2,2-dimethylolpropionic acid (DMPA) were added. After reacting at 180°C for 2 hours, the acid value was measured every 30 minutes until it reached 75 mg KOH / g and the hydroxyl value was 80. The temperature was then lowered to 120°C, toluene was added, and the temperature was raised to 132°C. After dehydration, the solution is cooled to 65°C and 10% phenol-toluene solution is added and stirred until homogeneous. Toluene diisocyanate (TDI) is added to the monomer dropping vessel, and the temperature is raised to 70°C and reacted for 4 hours. 50% phenol solution is added and stirred until homogeneous. The temperature is raised to 90°C and reacted for 15 minutes. Two-thirds of the toluene is removed under vacuum. Isobutanol is added and the temperature is lowered to 50°C. Triethylamine, xyleneethanolamine, and one-third of the deionized water are added, and the pH is adjusted to 8.6. The temperature is raised to 60°C and reacted until transparent. All toluene is removed under vacuum, and the remaining deionized water is added to obtain the waterborne polyurethane coating.

[0016] Comparative Example 2: 40 parts of deionized water were added to the reactor, and the stirrer was turned on at a medium speed of 700 rpm. 50 parts of water-based acrylic emulsion were added to the reactor and stirred at 800 rpm for 60 minutes until the mixture was uniform. 20 parts of ethanol were added at a speed of 1200 rpm and stirred until the mixture was uniform. 0.1 parts of leveling agent TEGO Flow 425 were added to the reactor and stirred at a medium speed of 800 rpm for 20 minutes. TEGO Foamex 825 defoamer was added to the reactor and stirred at a high speed of 1000-1200 rpm for 20 minutes to obtain the primer coating.

[0017] Example 2: 35 parts of polyurethane emulsion and 9 parts of sodium N-(2-aminoethyl)-2-aminoethane sulfonate were added to a reaction vessel and stirred at 300 rpm at room temperature. 40 parts of deionized water and 2 parts of anionic emulsifier C12 fatty alcohol polyoxyethylene ether zinc carboxylate were added and stirred at 600 rpm for 30 min at room temperature. 6.5 parts of nonionic emulsifier isotridecyl alcohol ether were added to the reaction vessel and stirred at 600 rpm for 5 min at room temperature. 0.15 parts of leveling agent polyether-modified organosiloxane were added to the mixture and stirred at 900 rpm for 5 min at room temperature. 0.04 parts of defoamer polydimethylsiloxane were added to the mixture and stirred at 800 rpm for 10 min at room temperature to obtain an ink-retention waterborne polyurethane primer coating with a solid content of 19.8% and a pH of 8.1.

[0018] Example 3: 35 parts of polyurethane emulsion and 11 parts of sodium N-(2-aminoethyl)-2-aminoethane sulfonate were added to a reaction vessel and stirred at 300 rpm at room temperature. 40 parts of deionized water and 1.25 parts of anionic emulsifier C16 fatty alcohol polyoxyethylene ether zinc carboxylate were added and stirred at 800 rpm for 30 min at room temperature. 8 parts of nonionic emulsifier isotridecyl ether were added to the reaction vessel and stirred at 600 rpm for 5 min at room temperature. 0.3 parts of leveling agent polyether-modified organosiloxane were added to the mixture and stirred at 1000 rpm for 5 min at room temperature. 0.05 parts of defoamer polydimethylsiloxane were added to the mixture and stirred at 800 rpm for 10 min at room temperature to obtain an ink-retention waterborne polyurethane primer coating with a solid content of 19.2% and a pH of 8.3.

[0019] Example 4: 35 parts of polyurethane emulsion and 7 parts of sodium N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonate were added to a reaction vessel and stirred at 300 rpm at room temperature. 40 parts of deionized water and 2 parts of anionic emulsifier C16 fatty alcohol polyoxyethylene ether zinc carboxylate were added and stirred at 600 rpm for 30 min at room temperature. 5 parts of nonionic emulsifier nonylphenol polyoxyethylene ether were added to the reaction vessel and stirred at 600 rpm for 5 min at room temperature. 0.01 parts of leveling agent polyether-modified organosiloxane were added to the mixture and stirred at 800 rpm for 5 min at room temperature. 0.03 parts of defoamer polydimethylsiloxane were added to the mixture and stirred at 800 rpm for 10 min at room temperature to obtain an ink-retention waterborne polyurethane primer coating with a solid content of 20.6% and a pH of 7.8.

[0020] Example 5: 40 parts of polyurethane emulsion and 10 parts of sodium N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonate were added to a reaction vessel and stirred at 400 rpm at room temperature. 45 parts of deionized water and 0.5 parts of anionic emulsifier C12 fatty alcohol polyoxyethylene ether carboxylic acid ferric salt were added and stirred at 700 rpm for 30 min at room temperature. 6.5 parts of nonionic emulsifier nonylphenol polyoxyethylene ether were added to the reaction vessel and stirred at 700 rpm for 5 min at room temperature. 0.15 parts of leveling agent polyether-modified organosiloxane were added to the mixture and stirred at 800 rpm for 5 min at room temperature. 0.04 parts of defoamer polydimethylsiloxane were added to the mixture and stirred at 900 rpm for 10 min at room temperature to obtain an ink-retention waterborne polyurethane primer coating with a solid content of 20.8% and a pH of 7.7.

[0021] Example 6: 40 parts of polyurethane emulsion and 11 parts of sodium N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonate were added to a reaction vessel and stirred at 400 rpm at room temperature. 45 parts of deionized water and 2 parts of anionic emulsifier C12 fatty alcohol polyoxyethylene ether carboxylate were added and stirred at 800 rpm for 30 min at room temperature. 8 parts of nonionic emulsifier nonylphenol polyoxyethylene ether were added to the reaction vessel and stirred at 700 rpm for 5 min at room temperature. 0.3 parts of leveling agent polyether-modified organosiloxane were added to the mixture and stirred at 1000 rpm for 5 min at room temperature. 0.05 parts of defoamer polydimethylsiloxane were added to the mixture and stirred at 900 rpm for 10 min at room temperature to obtain an ink-retention waterborne polyurethane primer coating with a solid content of 19.7% and a pH of 8.1.

[0022] Example 7: 40 parts of polyurethane emulsion and 7 parts of sodium N-(2-aminoethyl)-2-aminoethane sulfonate were added to a reaction vessel and stirred at 400 rpm at room temperature. 45 parts of deionized water and 0.5 parts of anionic emulsifier C16 fatty alcohol polyoxyethylene ether carboxylic acid ferric salt were added and stirred at 600 rpm for 30 min at room temperature. 5 parts of nonionic emulsifier Span 20 were added to the reaction vessel and stirred at 700 rpm for 5 min at room temperature. 0.01 parts of leveling agent fluorinated acrylic polymer were added to the mixture and stirred at 800 rpm for 5 min at room temperature. 0.03 parts of defoamer polydimethylsiloxane were added to the mixture and stirred at 900 rpm for 10 min at room temperature to obtain an ink-retention waterborne polyurethane primer coating with a solid content of 21.5% and a pH of 7.4.

[0023] Example 8: 40 parts of polyurethane emulsion and 9 parts of sodium N-(2-aminoethyl)-2-aminoethane sulfonate were added to a reaction vessel and stirred at 400 rpm at room temperature. 45 parts of deionized water and 2 parts of anionic emulsifier C16 fatty alcohol polyoxyethylene ether carboxylic acid ferric salt were added and stirred at 700 rpm for 30 min at room temperature. 6.5 parts of nonionic emulsifier Span 20 were added to the reaction vessel and stirred at 700 rpm for 5 min at room temperature. 0.15 parts of leveling agent fluorinated acrylic polymer were added to the mixture and stirred at 900 rpm for 5 min at room temperature. 0.04 parts of defoamer polydimethylsiloxane were added to the mixture and stirred at 900 rpm for 10 min at room temperature to obtain an ink-retention waterborne polyurethane primer coating with a solid content of 20.4% and a pH of 7.8.

[0024] Example 9: 45 parts of polyurethane emulsion and 11 parts of sodium N-(2-aminoethyl)-2-aminoethane sulfonate were added to a reaction vessel and stirred at 500 rpm at room temperature. 50 parts of deionized water and 1.25 parts of anionic emulsifier C12 fatty alcohol polyoxyethylene ether carboxylate ferrous salt were added and stirred at 800 rpm for 30 min at room temperature. 8 parts of nonionic emulsifier Span 20 were added to the reaction vessel and stirred at 800 rpm for 5 min at room temperature. 0.3 parts of leveling agent fluorinated acrylic polymer were added to the mixture and stirred at 1000 rpm for 5 min at room temperature. 0.05 parts of defoamer polydimethylsiloxane were added to the mixture and stirred at 1000 rpm for 10 min at room temperature to obtain an ink-retention waterborne polyurethane primer coating with a solid content of 20.5% and a pH of 7.8.

[0025] Example 10: 45 parts of polyurethane emulsion and 7 parts of sodium N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonate were added to a reaction vessel and stirred at 500 rpm at room temperature. 50 parts of deionized water and 2 parts of anionic emulsifier C12 fatty alcohol polyoxyethylene ether carboxylic acid ferrous salt were added and stirred at 600 rpm for 30 min at room temperature. 5 parts of nonionic emulsifier Tween 20 were added to the reaction vessel and stirred at 800 rpm for 5 min at room temperature. 0.01 parts of leveling agent fluorinated acrylic polymer were added to the mixture and stirred at 800 rpm for 5 min at room temperature. 0.03 parts of defoamer polydimethylsiloxane were added to the mixture and stirred at 1000 rpm for 10 min at room temperature to obtain an ink-retention waterborne polyurethane primer coating with a solid content of 21.7% and a pH of 7.4.

[0026] Example 11: 45 parts of polyurethane emulsion and 9 parts of sodium N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonate were added to a reaction vessel and stirred at 500 rpm at room temperature. 50 parts of deionized water and 0.5 parts of anionic emulsifier C16 fatty alcohol polyoxyethylene ether carboxylic acid ferrous salt were added and stirred at 700 rpm for 30 min at room temperature. 6.5 parts of nonionic emulsifier Tween 20 were added to the reaction vessel and stirred at 800 rpm for 5 min at room temperature. 0.15 parts of leveling agent fluorinated acrylic polymer were added to the mixture and stirred at 900 rpm for 5 min at room temperature. 0.04 parts of defoamer polydimethylsiloxane were added to the mixture and stirred at 1000 rpm for 10 min at room temperature to obtain an ink-retention waterborne polyurethane primer coating with a solid content of 21.2% and a pH of 7.5.

[0027] Example 12: 45 parts of polyurethane emulsion and 11 parts of sodium N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonate were added to a reaction vessel and stirred at 500 rpm at room temperature. 50 parts of deionized water and 2 parts of anionic emulsifier C16 fatty alcohol polyoxyethylene ether carboxylic acid ferrous salt were added and stirred at 800 rpm for 30 min at room temperature. 8 parts of nonionic emulsifier Tween 20 were added to the reaction vessel and stirred at 800 rpm for 5 min at room temperature. 0.3 parts of leveling agent fluorinated acrylic polymer were added to the mixture and stirred at 1000 rpm for 5 min at room temperature. 0.05 parts of defoamer polydimethylsiloxane were added to the mixture and stirred at 1000 rpm for 10 min at room temperature to obtain an ink-retention waterborne polyurethane primer coating with a solid content of 20.3% and a pH of 7.9.

[0028] Ink Retention Test Method:

[0029] 1. Sample preparation: The coatings of Comparative Examples 1-2 and Examples 1-12 were diluted with water to 20wt%. The primer was applied to wet strength paper using a 10# wire rod, followed by aluminizing using a molecular pump to a thickness of 0.04µm. The topcoat and ink were then applied using a 5# wire rod. The drying temperature was 110℃ and the drying time was 15 seconds.

[0030] 2. Cut the coated sample into 3cm x 3cm paper pieces according to the specifications;

[0031] 3. Prepare a 2.0 wt% NaOH solution and heat it to 80℃;

[0032] 4. Place the sample paper in NaOH solution, set the stirring speed to 350 r / min, and the stirring time to 10 min; 5. Take out the sample paper, measure the ink residue area per unit area, and calculate the ink retention rate.

[0033] Table 1 Ink Retention Test Results

[0034] Example 1 91％ Comparative Example 1 88％ Comparative Example 2 90％ Example 2 95％ Example 3 97％ Example 4 89％ Example 5 94％ Example 6 98％ Example 7 88％ Example 8 94％ Example 9 97％ Example 10 91％ Example 11 93％ Example 12 98％

Claims

1. A method for preparing an ink-retention waterborne polyurethane primer coating, characterized in that, The coating consists of polyurethane emulsion, sulfonate modifier, deionized water, anionic emulsifier, nonionic emulsifier, leveling agent, and defoamer; the polyurethane emulsion has a solid content of 50-55 wt%, a particle size of 50-80 nm, and a softening point of 20-55 °C. The sulfonate modifier is one of N-(2-aminoethyl)-2-aminoethanesulfonate sodium salt or N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonate sodium salt; By weight, 35-45 parts of polyurethane emulsion and 7-11 parts of sulfonate modifier are added to a reaction vessel and stirred at 300-500 rpm at room temperature; 40-50 parts of deionized water and 0.5-2.0 parts of anionic emulsifier are added and stirred at 600-800 rpm at room temperature for 30 min; 5-8 parts of nonionic emulsifier are added to the reaction vessel and stirred at 600-800 rpm at room temperature for 5 min; 0.01-0.3 parts of leveling agent are added to the mixture and stirred and dispersed at 800-1000 rpm at room temperature for 5 min; 0.03-0.05 parts of defoamer are added to the mixture and stirred and dispersed at 800-1000 rpm at room temperature for 10 min to obtain an ink-retention waterborne polyurethane primer coating with a solid content of 20-25% and a pH value between 7.5 and 8.

5.

2. The method for preparing an ink-retention waterborne polyurethane primer coating according to claim 1, characterized in that, The anionic emulsifier is one of fatty alcohol polyoxyethylene ether zinc carboxylate, fatty alcohol polyoxyethylene ether iron carboxylate, and fatty alcohol polyoxyethylene ether iron carboxylate; the number of carbon atoms in the carbon chain of the fatty alcohol is one of C12 and C16.

3. The method for preparing an ink-retention waterborne polyurethane primer coating according to claim 1, characterized in that, The nonionic emulsifier is one of isotridecyl ether, nonylphenol polyoxyethylene ether, Span 20, and Tween 20.

4. The method for preparing an ink-retention waterborne polyurethane primer coating according to claim 1, characterized in that, The leveling agent is one of polyether-modified organosiloxane or fluorine-modified acrylic polymer.

5. The method for preparing an ink-retention waterborne polyurethane primer coating according to claim 1, characterized in that, The defoamer is polydimethylsiloxane.