Specializing in the research, development, and production of eco-friendly water-based inks
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Improved ink solvent formulation to reduce VOC emissions.
Ink improvement is one of the optional methods for controlling VOCs in the printing process. Compared to other VOCs treatment methods, for enterprises, choosing an ink that can significantly reduce VOC emissions is clearly a feasible and economical solution.
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Ink improvement is one of the optional methods for controlling VOCs in the printing process. Compared to other VOCs treatment methods, for enterprises, choosing an ink that can significantly reduce VOC emissions is clearly a feasible and economical approach at present.
Yesterday, we introduced the formulation design of polyurethane ink using a model similar to high solid low viscosity adhesives, which allows for an appropriate increase in the working concentration of the ink while maintaining a low working viscosity, thus reducing the amount of solvent required for the same dry ink.
Today, we continue to introduce methods to simplify the solvent formulation of inks to reduce VOC emissions.
Due to the special nature of its application system, the solvent composition of gravure polyurethane ink is relatively complex, which is not conducive to the recycling and reuse of solvents. We simplified the solvent formulation according to customer requirements, eliminating special solvents in the ink and retaining only basic ester and alcohol solvents. This not only improves the ester solubility of the solvent system and reduces the difficulty of solvent recovery but also allows the solvent to dry more easily while reducing energy consumption.
From the formulation perspective, the ink binder itself is mainly ester-soluble, and alcohol solvents cannot be completely eliminated. What we need to do is enhance the compatibility of additives and pigments in the ester solvent system, increase the proportion of ester solvents while maintaining the printability of the ink. For example, low molecular weight and good ester solubility chlorinated vinyl can be selected, and dispersants that match the functional groups of pigments and binders can be chosen. We tested the compatibility of these two types of raw materials in the system, and the test results for the original red are as follows:
Note: Ester mixed solvents are used in combination with pigments for sand milling.
After determining the formulation, the production process must confirm the order of adding materials, cooling water, and other control parameters, as the fluidity of ink raw materials during the sand milling stage is crucial. At this time, pigment particles are continuously crushed and refined, while various additives, resins, and solvents continuously wet their surfaces, forming a stable suspension. If not controlled properly, the storage time of the finished product will be short, leading to risks such as thickening or even flocculation, greatly reducing the stability of the system. Therefore, this process cannot be calculated conventionally.
Based on experimental evaluations, we selected a more adaptable D3 dispersant combined with E2 chlorinated vinyl, resulting in a finished ink with a thickening rate of less than 2% after long-term storage. In actual applications, users dilute and print with over 90% ester solvents, maintaining the printability, color, and light mesh effects unchanged. Feedback from customers after normal use indicates that during the drying and recycling of solvents, energy savings of over 10% can be achieved, while printing costs have not increased. Additionally, the printed film of this ink has no risk of slow-drying solvent residue, which can reduce interference in the composite process, resulting in lower solvent residues in the final composite product.
Similarly, alcohol-soluble polyurethane ink can also be developed with a focus on alcohol solvents as the main component and ester solvents as a supplement. Additionally, we have been experimenting with increasing the water solubility of the ink binder, researching towards water-based inks.
Currently, the approach is that ink formulations generally do not contain water, and customers can add it during use. When using this alcohol-soluble ink for printing, the ratio of water to solvent in the mixed solvent reaches 1:1, and the ink can still be printed normally, with the remaining ink usable the next day.
Many experts have already experimented with this idea. The key is to ensure that the printing equipment is reasonably matched and that the residual moisture poses certain risks in post-processing, requiring strict real-time monitoring during production and effective preventive measures.
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Shaanxi Xinaohua Material Technology Co., Ltd
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South Hualong Road, Fufeng Science and Technology Industrial Park, Jiangzhang Town, Fufeng County, Baoji City, Shaanxi Province