Development of plastic gravure water-based ink based on compound emulsion III

Viscosity is the most important control indicator in aqueous ink applications and is a property that prevents fluid flow. Since the viscosity directly affects the transferability of the ink without the quality of the print, the control of the viscosity of the ink is very important. In the printing process, the viscosity of water-based ink is too low to cause defects such as light color, dot enlargement, and uneven ink transfer. On the other hand, if the viscosity of the water-based ink is too high, the ink transfer performance is relatively poor, and dirty prints, etc. are prone to appear. Malady. In this paper, the influence of the amount of HEA on the viscosity of the PUA emulsion was examined, and the viscosity of the formulated aqueous ink was tested. The results are shown in Table 4.

From Table 4, it can be seen that as the molar ratio (r) of HEA to the remaining -NCO increases from 0.2 to 0.4, the viscosity of the PUA emulsion is almost constant, and the viscosity of the PUA emulsion is reached when the plant reaches 0.5. Significantly bigger. After the chain extension reaction with water, the molecular weight of the polyurethane containing a double bond at the end, as compared with the polyurethane containing no such functional group, decreases as the amount of HEA increases, and accordingly, the amount of the swelled MMA monomer increases. It also decreases. Both of these factors result in a decrease in the particle size of PUA latex particles and an increase in surface area. Therefore, this may increase the interaction between the particle surface charge and the isomeric ion in the electric double layer, resulting in an increase in the viscosity. It can also be seen in the table that the viscosity of the aqueous ink and the viscosity of the PUA emulsion have a similar trend with the change in the amount of HEA. When the factory increased from 0.2 to 0.3, the viscosity of the aqueous ink slightly increased; then it remained almost unchanged. When the plant is increased to 0.5, the viscosity of the aqueous ink is greatly increased resulting in the formation of a physical gel, which may be due to the increase in the compatibility of the PUA emulsion with the aqueous polyacrylate resulting in a PUA phase in the system. The interface with the PA phase disappears due to the increased interaction of the particles in the system.

2.4 Adhesion fastness of aqueous ink

If a single polyurethane is used as the ink connecting material, it has poor adhesion to non-polar substrates such as PP and PE widely used in the color printing industry. Zhou Wenxin, Zhang Weihong, etc. introduce hydroxyl-containing vinyl chloride-acrylic OH The ester copolymer significantly improves the adhesion of the ink to non-polar substrates such as PE and PP. In this experiment, PET film and OPP film were used as substrates, and a blue aqueous ink was formulated with a self-made PUA emulsion. The effects of different PUA film-forming emulsions on the adhesion of PET film and OPP film were investigated, and the single polymer was compared. Acrylic Emulsion and Polyurethane-Acrylate Emulsion Effect on Fastness of Aqueous Ink. The results showed that the water-based inks prepared with the self-made PUA emulsion had good fastness to the PET film and the fastness of the polyacrylate water-based ink to the PET film was poor. This is mainly due to the fact that the polar groups on the surface of the PET plastic film can form hydrogen bonds with the urethane bonds and ester bonds in the film forming emulsion to form a joint with a certain adhesive strength. However, there are few polar groups in the polyacrylate macromolecules, and it is difficult to form hydrogen bonds on the surface of the PET film, and only rely on the van der Waals force intermolecular adhesion on the film surface. It is known that polyacrylate aqueous inks have excellent fastness to OPP film. In the experiment, it was found that the waterborne polyurethane modified with an acrylate monomer also has a good fastness to the OPP film. It is generally believed that the PUA emulsion has a core-shell structure, and the shell layer has a substantial portion of the PU-containing hydrophilic phase. In this experiment, PUA emulsion was prepared by graft copolymerization. The shell phase was enriched in PU and PA phases. This was different from PUA emulsion prepared by seed method. During the drying process of the ink film prints, the ink shell phase is displaced toward the surface of the substrate and the properties of the polyurethane and the polyacrylate are integrated. Therefore, the PUA emulsion modified by the MMA also has a good attachment fastness to the OPP film.

2.5 water resistance of water-based ink

The water resistance of ink is important for the use of ink, because ink is often used in packaging and printing products, such as beer, beverages, etc., these products will be soaked in water for a long time, or long-term frozen in the refrigerator, if the water resistance of ink is poor , It will lead to water emulsion emulsification and loss of luster, in serious cases, will completely fade, affect product image; In printing ink water resistance is poor, in addition to emulsification, will also lead to paste version, not ink and other printing failures. In this experiment, the influence of the amount of HEA on the water absorption of the PUA emulsion was investigated, and the water resistance of the water-based ink was also tested. The results are shown in Table 5 and Table 6.

From Table 5, it can be seen that with the increase of the amount of HEA, the water absorption rate of the PUA film gradually decreases. This is mainly because the shell phase of the PUA is enriched in the PU phase and the PA phase, and with the increase of the amount of the HEA, the shell The content of PA phase in hydrophobic phase increases, which leads to the tendency of PUA membrane water absorption to decrease. Table 6 shows that aqueous inks using PUA emulsion as a film forming emulsion have good water resistance.

3 Conclusion

1) The PUA emulsion obtained by the emulsion copolymerization method in this experiment was proved to be the designed product by infrared characterization.

2) PUA emulsion and water-based acrylic resin blend system has good stability, but the stability of water-based ink is improved with the increase of the amount of HEA and then decreased.

3) The viscosity of PUA emulsion increases with the increase of the amount of HEA, and the water-based ink shows a similar pattern.

4) Aqueous ink with PUA emulsion as filming emulsion has excellent fastness to PET film and OPP film.

5) Water-based ink with PUA emulsion as filming emulsion has good water resistance

(Author/Cai Dongyu, Xiang Shanglin, Chen Xianyi, Nanjing University of Technology

Zhang Wen Nanjing Sote Packaging Products Co., Ltd.)

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