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

The spectrum b is basically similar to the spectrum a, and 3304-3400 cm-1 1535-1555 cm-1 is an NH-specific peak. The C=0 stretching vibration peak appears at 1730 cm-1, and the ratio of the absorption intensity of the peak to the absorption intensity of a characteristic peak of an NH-1 is significantly larger than that of the spectrum a. This is mainly due to the inclusion of MMA in the waterborne polyurethane. C=0. The characteristic peak of ester bond of MMA appeared at 1150 cm-1, further illustrating that a polyurethane-polyacrylate composite emulsion was formed in the system.

2.2 Water-based ink stability

The production process of water-based ink is generally divided into three steps, the amination of the water-based resin, the grinding of the color paste, and the ink formulation. The color paste used herein consists mainly of indocyanine blue pigments and aminated aqueous polyacrylates, and a self-made PUA emulsion is used instead of the commonly used polyacrylic emulsion as the film-forming resin formulation ink to achieve the purpose of improving the performance of the water-based ink. Therefore, the mechanical stability of the aqueous ink is mainly determined by the dispersion of the pigment in the aqueous millbase system, the stability of the PUA emulsion, and the compatibility of the aqueous polyacrylate abrasive with the PUA emulsion. PUA emulsion stability is mainly affected by the ionic group content and acrylate content. In this paper, the effects of the pigment content and the amount of acrylic acid-p-hydroxyethyl ester (HEA) used as the capping agent on the stability of the ink were examined. The results are shown in Table 2 and Table 3.

  As can be seen from the data in Table 2, when the pigment content is 15%, the stability of the aqueous ink becomes poor. According to the DELVO theory and the theory of steric hindrance, as the concentration of the pigment in the aqueous medium increases, the anionic polymer adsorbed on the surface of each pigment particle decreases, resulting in a reduction in the thickness of the double electric layer on the surface of the ion and a reduction in steric hindrance. The mechanical stability of aqueous inks decreases. It is generally believed that the pigment concentration of the water-based ink is a solvent type; when it is 1.5 times that of the ink, it is more suitable for practical use. The experiment found that 13% of the pigment content is more appropriate, while ensuring the stability of the ink, the color of the coating is more vivid.

As can be seen from Table 3, as the amount of HEA increases, the stability of the ink first becomes better, and then decreases again. In the experiment, it was found that when the dispersion resin used for polishing the colorant is an aqueous acrylic resin, the stability of the aqueous ink prepared by using the unmodified polyurethane emulsion as the film-forming emulsion and the color paste blending is poor due to the polyurethane emulsion and Poor compatibility of aqueous polyacrylates. In this blending system, the mutual entanglement of PU macromolecular chains and PA macromolecular chains only occurs in the surface layer of latex particles, so the blending effect is quite limited. PUA emulsion as a film-forming emulsion has greatly improved the blending effect. This may be due to the copolymerization of the PU macromolecule chain with the acrylate monomer via the capped double bond. The shell phase of the PUA emulsion is enriched in the PU and PA phases. According to the principle of compatibility, the PUA and the waterborne acrylic resin have good Compatibility, but with the increase in the amount of HEA, PU macromolecule chain copolymerized with methyl methacrylate terminal increases, the compatibility of PUA and aqueous polyacrylic acid resin increases, and may eventually lead to PUA phase and PA phase. The interface disappears and the ink forms a physical gel.