Environmental Tips: Preparation of "Green" Printing Inks
With the rapid development of the global economy and the continuous improvement of the quality of life of the people, people's environmental health awareness is constantly increasing. Water-based inks have attracted more and more attention because of their environmental protection advantages and huge market potential. And trends. Water-based ink is abbreviated as water ink, which is mainly made of water as a solvent through scientific processing. Compared with other printing inks, water-based ink does not contain volatile and toxic organic solvents, so it is a health problem for printing press operators during the printing process No adverse effects, no pollution to the atmosphere, and no pollution to the printed matter itself. It is called "green" printing ink. Since ink is non-flammable, it can also eliminate the flammable and explosive hazards in the printing workshop, which is conducive to safe production. Of course, the application scope of ink and ink is not the same. Ink is mainly offset printing, and ink is mainly flexo printing and gravure printing. In developed countries such as Europe, America and Japan, ink has gradually replaced ink and has become a special ink for printing methods other than offset printing. Taking the United States as an example, 95% of flexographic prints use ink, and 80% of gravure prints use ink. Ink is also particularly suitable for packaging and printing products with strict hygienic conditions such as cigarettes, wine, food, beverages, medicines, children's toys and so on.
In recent years, with the continuous modification of resins, the structure of new products such as paints and inks has also undergone great changes. Developed countries have developed many water-based inks in consideration of environmental protection requirements. They have begun to be used in paper and plastics. Film, packaging bags and special printing. The annual output of water-based inks in China is about 100,000 tons, mainly for the production of low-grade paper packaging printing inks. At present, the film-forming materials used in water-based inks are mainly acrylic resins, because water-based polyacrylates have the advantages of high stability, good gloss, rheological properties and surface adsorption properties. In this experiment, the solution polymerization method was used, using methyl methacrylate, a-methacrylic acid, acrylic acid, butyl acrylate, vinyl acetate, ammonia, triethylamine as the main reaction reagents, and adding ammonium persulfate (initiator); Sodium bisulfite (reducing agent); sodium dodecyl sulfate (emulsifier) ​​to prepare acrylic resin. .The above resin is added into pigment, defoamer, dispersant, etc. to make water-based ink, and the film-forming property, drying time, water resistance and abrasion resistance of the water-based ink are measured, and the water-based ink meets the standards required for printing.
1. Preparation scheme of water-based resin
2. Preparation method of water-based resin
Add 1/3 of the basic monomers (methyl methacrylate, a-methacrylic acid, acrylic acid, butyl acrylate, and vinyl acetate reagents) to the 2000mL three-necked flask, and then add water and isopropyl Alcohol, heating, stirring to reflux (about 80 ℃), adding reducing agent, initiator, at the same time began to drop the remaining 2/3 of the amount of monomer and vinyl acetate (acrylamide was added in scheme one, more in scheme two) Polyvinyl alcohol), titration time is about 1h. When all monomers are dripped, keep at about 85 ℃ for 2 hours and add polymerization inhibitor. After 2 hours, reduce the temperature to 60 ℃, add ammonia to neutralize. Dilute with water at the same time, and adjust the pH to about 8-9. After stirring for 0.5h, cool it to room temperature and then pour it out.
3. Development of water-based ink
Add 240mL of water / alcohol mixture (4 parts of water and 1 part of alcohol) to the resins of formulas 1, 2, and 3 respectively, stir them evenly, and add them to the SFJ container with shearing, stirring, and emulsifying functions, and then add Disperse pigment (W-45 pigmented carbon or Kabo-400R carbon black, ie CB-400) 100g, defoamer 10mL, dispersant 10mL and other additives, after high-speed shearing, emulsification, dispersion, sand grinding, and then Then add 500mL of water / alcohol mixture and continue to stir for 30min. The product is poured into a filter vessel and suction filtered to obtain the finished ink. Continue to add water or alcohol to adjust the desired viscosity.
4. Performance of water-based resin (viscosity based on GB1723-9)
5. Ink performance
The performance tests are all printing tests performed on plastic films. The solubility of the film means that it is immersed in water for 60 hours and 4% acetic acid for 45 hours, and the color of the film does not fall off.
6 Conclusion
â‘ The test shows that the acrylic resin modified by adding polyvinyl alcohol and vinyl acetate is more suitable for the printing of PE film, and its performance in all aspects is better;
â‘¡Adding enoic acid in batches during the polymerization process can improve the hydrophilicity of the product (called semi-continuous starvation supplement method), which can make the polymerization reaction more full;
③The polymerization temperature should not exceed 90 ℃, the polymerization time should be 4 hours, the ammonia solution + triethylamine is more stable for the neutralization solution, and the pH value should be controlled at 8-9;
â‘£Compared with similar products, the products obtained by the experiment have better solid content and viscosity. Experimental tests show that the performance of water-based ink formulated with acrylic resin meets or exceeds national standards and practical application requirements.
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