Development and Discussion of Screen Printing Water-based Ink(2)

Third, product characteristics

Screen printing ink adhesion fastness, must reach the ink layer on the print can withstand the friction in the daily use of the package without falling off, with dry and wet friction to test, usually 10 times, we made 30 times. After the printed product was dried, we used adhesive tape to make a peel test, and the ink layer did not fall off. Because the polymer resin is used as a binder, its thixotropy is large. We generally control the fluidity at 30 to 50 mm. For paper products and polyethylene plastic products, the screen printing thickness was 20 μm, and the printing time was about 14 min at 20 °C. The ink could not dry on the printing plate within 4 h. The developed ink product has been satisfactorily tested by the relevant units. Paper prints show full color, clear graphics, strong hiding power, no traces of ink film, blisters, spots, pinholes, etc., have a strong reproducibility and three-dimensional sense, and non-toxic, tasteless, water-resistant, Light and abrasion resistance. Plastics prints also show clear prints, bright colors, high hiding power, good hardness, good firmness, scratch resistance, and wear resistance. It has good screen printing property, moderate viscosity, non-sticky plate, no blocking mesh, good flowability, fast drying speed, no blocking and deterioration, easy cleaning and rapid color change. In view of this, paper products, screen printing inks can be used in advertising, magazines, calendars, kites, fine art, stickers, labels and carton boxes, paper boxes, various package decorations and wallpapers, etc. Plastic screen printing ink can be used in soft Layers of toys, school bags, various panels, dials, bottles, barrels, boxes, and a variety of instruments used in plastic parts.

IV. Discussion

Screen printing waterborne inks are generally composed of linking materials, pigments, additives and the like.

1. The choice of binder The nature of the ink depends primarily on the aqueous resin. The binder in the aqueous ink is a water-soluble resin and an aqueous polymer emulsion. The types and properties of waterborne resins are shown in Table 2.

Table 2 Types and Properties of Waterborne Resins

Type Properties Water-soluble Resin Polymer Emulsion Appearance and Condition Translucent, Dispersion Opaque, Dispersed Particle Size (m) 0.001~0.1 0.1~1.0
Relative molecular weight 10 000~1000 or above Viscosity Medium and low solids Medium and high pigment Dispersion Excellent~Good poor Dispersion stability Good viscosity Adjustment Add water Solvent, Solvent Additive Tackifier, Solvent Gloss Good Good ~ Poor ink film Excellent strength ~ Good use Easy to use Good Good ~ Poor

The water-soluble resins include rosin maleic acid resin, styrene maleic acid resin, acrylic acid copolymer, ethyl acrylate, etc., and polymer emulsions that are water-dispersible resins include vinyl acetate copolymers, acrylic copolymers, polyurethane resins, and epoxy resins. Wait. Through comparative tests, we adopted water-based acrylic copolymer resin and emulsion-type resin compound as the linking material, so that the water-based ink can exhibit excellent performance in terms of adhesion, gloss, viscosity, drying and adaptability.

2. The choice of pigment

Water-based ink pigments, in addition to common powders, also include pigment filter cakes, aqueous pigment dispersions and readily dispersible pigments in water. Since aqueous inks are mostly alkaline and often combined with alcohols, pigments with poor alkali resistance should be avoided as much as possible, and alcohol resistance should also be taken into consideration. The oil absorption values ​​of domestic pigments are generally high and are not suitable for aqueous systems. Water-based inks are mainly colored by pigments. We have selected high-solid-content pigment filter cakes and brightly colored organic pigments, such as golden red, phthalocyanine blue, and permanent yellow, and then added surfactants to help dispersion of pigment particles. And stability.

3. Selection of additives

Water-based ink is very important in the use of additives, through the additives can improve the shortcomings of water-based ink and improve its stability, can reduce the surface tension of water-based ink, increase the wetting of the plastic, but also help to dissolve the resin, improve the drying speed. In addition, we also made some auxiliaries, such as brighteners, adaptive agents, dispersants, electrostatic agents, etc., the use of effects are better.

V. Conclusion

"Water-based ink" can significantly reduce the emission of organic solvent volatiles (VOC) into the atmosphere, prevent atmospheric pollution, improve the printing environment, and contribute to the health of employees. At the same time, it can completely eliminate some toxic and harmful substances in solvent-based inks. Human hazards and contamination of packaged goods. Screen printing has the advantages of low cost and fast effect, which can adapt to the printing of irregular substrates, and has the characteristics of thick ink layer, strong three-dimensional impression, wide range of substrates, and large printing format. The relevant data shows that in the next five years, water-based inks will account for more than 50% of screen printing. We need to develop serialized products as soon as possible, and have different drying times to facilitate the transport of various substrates to promote water-based screen printing in China. The rapid development of the ink market.