In order to better respond to the standard 'Technical Requirements for Environmental Labeling Products: Gravure Inks and Flexographic Inks' and achieve green production, the printing industry has recently launched a project to promote the use of non-benzene inks in PE packaging gravure printing.
Work to be done for promoting non-benzene inks
1. Fully consider the transfer of ink: Since the solvent power of non-benzene inks is not as strong as that of benzene-containing inks, comprehensive consideration must be given to the transfer of non-benzene inks. This can be emphasized in the plate-making process, especially in the shallow mesh areas, where the depth of the mesh holes should be appropriately increased to avoid incomplete transfer of non-benzene inks in shallow mesh areas.
2. Reasonably adjust ink viscosity: During the printing process, there is a certain correlation between printing speed and ink viscosity. Additionally, the viscosity of the ink should be adjusted appropriately based on the condition of the printed product during actual printing.
3. Appropriate solvent ratio: Generally, a medium-drying solvent ratio, such as ethyl acetate:isopropanol = 1:1, can meet the requirements for thin film gravure printing under normal circumstances. However, the ratio of alcohol-based solvents to ester-based solvents should be adjusted appropriately based on actual conditions.
Precautions for using non-benzene inks
(1) Non-benzene inks should be stored in a cooler environment. Before formal printing, it is essential to shake the non-benzene ink in the ink barrel evenly to ensure good flow properties. It is worth noting that when diluting the ink, a mixed solvent should be used as a diluent, rather than a single type of solvent.
(2) If high temperatures are encountered during the printing process or if there is a blocking phenomenon in the shallow mesh areas, an appropriate amount of slow-drying diluent can be added for adjustment. When selecting a slow-drying diluent, it should be noted that butyl acetate and butanol have strong residual odors that can affect the usability of the printed product, so they should be used cautiously.
(3) When the ambient temperature is below 0°C, the surface of the ink may sometimes exhibit gelation. For gravure printing companies, in addition to avoiding storing ink in environments below 0°C, timely handling of the gelation phenomenon should also be carried out. Heating the ink with hot water or steam to raise its temperature to 15-25°C can effectively alleviate the gelation phenomenon. Remember, open flame heating is strictly prohibited during this process to prevent fire hazards.
(4) In the actual printing process, to prevent unnecessary losses due to the complexity of printing substrates, printing conditions, and printing requirements, it is recommended that standard procedure performance tests be conducted in advance before using non-benzene inks for new product printing to ensure the smooth progress of subsequent printing work.
(5) The viscosity, consistency, and drying speed of non-benzene inks should all meet the requirements for machine use. If the ink is too thick, an appropriate amount of ethanol (which can speed up drying) or butanol (which can slow down drying) can be added for dilution, or a special diluent can be used for dilution. If the ink dries too slowly due to high printing equipment speed or low winter temperatures, a fast-drying agent can be added to accelerate drying.
(6) Non-benzene inks of the same model can be mixed for adjusting various colors, but they should not be mixed with non-benzene inks of other models to avoid issues such as resin precipitation that could render them unusable.
Reasons hindering the benzene-free process of gravure inks: Looking at the entire gravure printing industry, I believe that the main reasons hindering the benzene-free process of gravure inks are as follows.
(1) Poor printing quality: Currently, the printability of non-benzene inks on plastic films is poor, and the final printing effect is not as good as that of solvent-based inks. Our company has also encountered many tricky quality issues during the actual application of non-benzene inks, mainly due to the poor transferability of non-benzene inks, resulting in quality defects such as lines on the printed products.
(2) Compared to solvent-based inks, the cost of solvents and materials used in non-benzene inks is relatively higher.
Therefore, efforts are being made to actively develop non-benzene inks, hoping to solve the existing problems with non-benzene inks. As a production technician in a gravure printing company, I strongly urge relevant ink suppliers to increase their investment in funds and technology to transition from solvent-based inks to environmentally friendly inks, effectively promoting the benzene-free process of gravure inks.
Current technical rectification direction for ink suppliers
The promotion and application of non-benzene inks is not achieved overnight. To meet the current production needs of gravure printing companies, ink suppliers should gradually carry out technical rectification of the gravure inks used in the market according to policy requirements and actual production conditions, mainly including the following measures.
(1) Reduce the solvent residue in existing benzene-containing ink products. These inks are benzene-soluble composite inks based on chlorinated polypropylene. By screening them, it is possible to select binders with good solvent release properties or add additives to facilitate the volatilization of aromatic hydrocarbons. However, due to the complex system of the ink itself, it is impossible for aromatic hydrocarbons to completely volatilize. Currently, the best result is that the residue of benzene solvents in printed products is around 1mg/m2. It can be seen that using benzene-containing inks cannot reduce the solvent residue in printed products. Therefore, from an environmental protection perspective, such inks are expected to be completely eliminated in the coming years.
(2) Remove aromatic hydrocarbons from the ink, which is known as the benzene-free process of ink. In Europe and the United States, many large food companies explicitly state in their internal quality standards that no aromatic hydrocarbons should be added to any packaging materials. To meet this requirement, non-benzene inks have emerged. Theoretically, these inks do not contain aromatic hydrocarbon solvents, but due to the raw materials being mixed with small amounts of aromatic hydrocarbon solvents during storage, transportation, manufacturing, and use, the understanding of 'benzene-free' should be that the aromatic hydrocarbon content in the ink system is ≤1%, which can be defined as 'non-benzene ink'. The printability and printing effect of such inks can meet basic requirements, but further improvement is still needed in printing effects.
(3) Promote alcohol-soluble system inks. In recent years, stricter solvent residue requirements from end-user companies have led major ink suppliers to launch alcohol-soluble inks. These inks do not contain aromatic hydrocarbons or ketone solvents, only ester and alcohol solvents, making them the optimal choice from an environmental perspective. However, due to the difficulty in reasonably adjusting the ink during use, there is still a significant gap in printability, printing effects, and costs compared to ordinary benzene-containing inks, so the promotion and application of such inks still seem to be a long way off.