New Generation Aqueous Ink Base Material for Packaging Film and Paper (4)

Fig. 6 Relationship between the proportion of MFT and size particles in a two-particle mixture system containing 0, 10%, and 30% oligomers, respectively

Fig. 7 At a particle size ratio of 80/20, the particle packing of the two particle size mixtures forms a double continuous phase.

Fig. 8 AFM image of the surface of the coating formed after the drying of the NeoCryl A-110 at room temperature

MFFT/Anti-stickback performance

As mentioned above, an important relationship to be considered in commercial applications is the balance between MFFT/resistance and stickiness. To avoid the use of environmentally unfriendly co-solvents, low MFFT is required, but important properties such as anti-tack resistance and film hardness are required. Therefore, base materials for paints and inks need to have both a low MFFT and a good anti-tack resistance. In order to study the MFFT/tack-resistance relationship of the oligomer/polymer system described above, the anti-tack properties of oligomeric systems containing different proportions of particles and 0, 10%, and 30% oligomers were determined. As shown in Fig. 5, it is clear that in the absence of oligomers and low Tg-containing oligomers, detackification is not very good. This may be due to the lower Tg (both 20 °C) of the oligomers and polymers. Temperature at the time of anti-sticking test ( 52 °C). However, when high Tg oligomers are added, the resistance to back tack is very good even if a small amount (10%) is added. This is due to the fact that oligomers may actually coat the polymer particles to form a hard shell, resulting in the polymer film being less likely to be compressed, and in fact the oligomer portion will migrate to the surface of the film during film formation. The resistance to back-tacking is affected both by the bulk and surface (primary) properties, and the presence of hard oligomers has a beneficial effect on both. The MFFT/tack-resistance balance of a mixed system of hard oligomers and polymers is very good. With a low MFFT, good resistance to back tack is obtained (adding hard oligomers hardly improves MFFT, see the film section).

in conclusion

The above results show that a system of a mixture of an alkali-soluble oligomer and a polymer particle having two particle size distributions exhibits interesting properties, and is particularly suitable for use in printing ink base materials. The presence of oligomers leads to an extension of the flocculation phase of the film formation process, thereby rendering the polymer film reversible. The reversibility is directly related to the oligomer's coverage on the surface of the polymer particles and is therefore affected by the amount of oligomer added and the total surface area. The lower the total surface area, the better the reversibility can be obtained with fewer oligomers if two particle size distributions are used. Low amount of oligomers can improve the durability of dry film. From the rheological test, it was found that when both oligomers are added, it is very important that the oligomer/polymer latex system with two size distributions has a higher maximum filling ratio than a system with a single particle size distribution. Practical significance. For example, high solids latexes can be developed, which have a very short drying time and are very useful in many applications. Studies on dryness show that even a small amount of oligomers can increase the drying time, possibly due to residual water.

The MFFT measurement showed a high oligomer content. From the MFFT vs. size ratio curve, it was found that the lowest MFFT value appeared at the L/S ratio of 80/20, which is the same as the previous pure polymer system. This can be explained by the best particle accumulation. When a small amount of oligomer is added, this minimum value does not exist, indicating that the particle filling changes, and the presence of oligomers contributes to the positive effect of the film formation. This may be due to the low molecular weight of the oligomers and their dissolution, which facilitates the coalescence and self-adhesion stages during film formation. The anti-back tack test showed that adding a low amount (10%) of hard oligomer to the soft polymer particle mixture gave good anti-tack properties, resulting in good MFFT/anti-tack resistance balancing properties. In this way, it can be concluded that the use of oligomers in a mixture of polymer particles of two size distributions yields a reversibly good emulsion with a third-generation ink aqueous polymer and a high solids content (50% ~60%), it has a very short drying time, and has a satisfactory MFFT/anti-tack resistance balance, making it ideal for printing inks.

Source: Coatings Technology Information Network