Environmental tips: Preparation of "green" printing inks

With the rapid development of the global economy, the continuous improvement of the national quality of life, people's awareness of environmental protection and health is constantly increasing, water-based ink because of its environmental advantages, huge market potential, more and more attention, has become the direction and trend of the development of the ink industry. Water-based ink is referred to as ink, which is mainly based on water as a solvent by scientific processing, water-based ink compared with other printing inks, because it does not contain volatile toxic organic solvents, so in the printing process on the printing press operator's health no adverse effects, no pollution to the atmospheric environment, no pollution to the print itself, known as "green" printing ink. Because the ink has the characteristics of non-flammable, it can also eliminate the hidden danger of flammable and explosive in the printing workshop, which is conducive to safe production.

Of course, the scope of application of ink and ink is not the same, water-based paint, ink to offset printing, ink to flexo printing, gravure printing. In developed countries such as Europe, the United States and Japan, ink has gradually replaced ink and become a special ink for other printing methods in addition to offset printing. In the United States, for example, 95% of flexo prints use ink, and 80% of intaglio prints use ink. Ink painting is also especially suitable for tobacco, wine, food, beverage, medicine, children's toys and other packaging and printing products with strict sanitary conditions.

In recent years, with the continuous modification of resins, the structure of new products of coatings and inks has also changed greatly, developed countries to consider the requirements of environmental protection, has developed a lot of water-based inks, they have begun to be used in paper, plastic film, packaging bags and special printing. China's annual output of water-based ink is about 100,000 tons, mainly to produce low-grade paper packaging printing ink. At present, the film forming of water-based inks is mainly acrylic resins, which is because water-based polyacrylates have the advantages of high stability, good gloss, rheological properties and good surface adsorption properties. In this experiment, methyl methacrylate, A-methacrylic acid, acrylic acid, butyl acrylate, vinyl acetate, ammonia, triethylamine were used as the main reaction reagents, and ammonium persulfate (initiator) was added. Sodium bisulfite (reducing agent); Acrylic resin was prepared from sodium dodecyl sulfate (emulsifier). The resin is added to the pigment, defoamer, dispersant and so on to make water-based ink. After measuring its film formation, drying time, water resistance and wear resistance, the water-based ink has reached the required standard in printing.

1. Preparation scheme of water-based resin

2. Preparation method of water-based resin

Add 1/3 of the evenly mixed basic monomer (methyl methacrylate, A-methacrylic acid, acrylic acid, butyl acrylate, vinyl acetate reagent) into a 2000mL three-neck flask, then add water and isopropyl alcohol, heat, stir to reflux (about 80℃), add reducing agent, initiator, and so on. At the same time, the remaining 2/3 amount of monomer and vinyl acetate (more than acrylamide was added in scheme 1, and more than polyvinyl alcohol was added in scheme 2) were added, and the titration time was about 1h. When all monomer drops are completed, hold the heat for 2 hours at about 85℃ and add polymerization inhibitor. After 2 hours, reduce the temperature to 60℃ and add ammonia water for neutralization. At the same time, dilute with water, and adjust the pH value to about 8 ~ 9, continue to stir for 0.5h, cool it to room temperature before pouring out.

3. The development of water-based ink

The resin of formula 1, 2, and 3 was added into 240mL water/alcohol mixture (4 parts water and 1 part alcohol), stirred evenly, and added into the SFJ container with cutting, stirring and emulsifying functions, and then added disperse pigments (W-45 pigment carbon or carbo-400R carbon black). Namely, CB-400)100g, 10mL of defoamer, 10mL of dispersant and other additives, after high-speed shear, emulsification, dispersion, and then sanding, and then add 500mL of water/alcohol mixture, continue to stir for 30min, the product is poured into the filter, pumped filter, to obtain the finished ink, continue to add water or alcohol to adjust the required viscosity. Fingerprint resistant paint

4. Properties of water-based resin(viscosity based on GB1723-9)

5. Ink performance

The performance test is carried out on the plastic film printing test, the solubility of the film refers to the immersion in water for 60h, 4% acetic acid for 45h, the color of the film does not fall off.

6. Conclusion

① The test shows that the acrylic resin modified by adding polyvinyl alcohol and vinyl acetate is suitable for the printing of PE film, and its performance is better in all aspects;

(2) Adding oleic acid in batches during the polymerization process can improve the hydrophilicity of the product (called semi-continuous starvation addition), which can make the polymerization reaction more adequate;

(3) The polymerization temperature should not exceed 90℃, the polymerization time is appropriate for 4 hours, the neutralization solution is more stable, and the pH value is controlled at 8 ~ 9.

④ Compared with similar products, the product obtained by the experiment has better solid holdup and viscosity. The experimental results show that the performance technical index of the water-based ink made of acrylic resin meets or exceeds the national standard and practical application requirements.