Introduced the application and technical development of water-based ink in China. Specifically introduced the application of ink flexo printing in food packaging. Finally pointed out the development trend of water-based inks.
First, the application of water-based ink in China
China's water-based ink was introduced in 1975. It was first developed and put into production by the Tianjin Ink Factory. It was mainly gravure printing service. In the 1990s, China's economy developed rapidly, and people’s awareness of packaging aesthetics and environmental protection continued to increase. From 1995 to the end of 1998, China has introduced more than 130 modular flexo lines in just a few years. It is distributed in more than 20 provinces and cities across the country, 90 percent of which are narrow flexo presses. The number of stations around is increasing, and there are also many imported high-end tri-color and four-color water-based ink printing slot machines for color printing of corrugated paper.
The introduction and development of flexographic printing in China began in the 1970s. Now we have been able to manufacture our own flexographic printing presses and their substrates, as well as various flexographic printing inks. In particular, the regular production of water-based inks and water-based polishes can be applied to other types of inks to cover the waterborne coating of the same color, obstructing the volatilization of the remaining toxic solvents, and direct contact with foods to ensure food safety and hygiene.
In China, flexible packaging printing has made great progress in the past 10 years, but its development momentum is not fast and progress is not remarkable. At present, flexo printing only accounts for about 3% of the printing industry. However, with the increasing popularity of green packaging and environmentally-friendly packaging, many tobacco companies, wineries, pharmaceutical companies, cosmetics, and children's toy companies are preparing to use flexographic printing products. The proportion of flexo printing in the printing field will gradually increase, especially in the field of packaging and printing. It is estimated that by 2010, flexographic printing will reach about 15% in the printing field, and annual demand will be over 100,000 tons of water-based ink. Therefore, it is imperative to vigorously develop, develop, and produce high-grade water-based inks with great market potential.
Second, the development of water-based ink technology
The types of inks currently used for gravure printing can be roughly classified into oil inks and water-based inks. The difference lies in the carrier used. Oily ink carriers are organic solvents, while water-based inks are water and alcohols. The so-called organic solvent is a generic term for solvents using many chemical substances such as toluene and ethyl acetate.
Water-based inks are also referred to as liquid inks. In appearance, due to the water-based use of water-based inks, apart from the overall clarity, it seems that there is no other difference. In addition, in terms of flexible packaging, the printing surface is a three-layer sandwich structure made of a plastic film, and the printed portion does not directly contact the contents. Therefore, printing with oil-based ink does not seem to be a problem, but the organic solvent is volatile. With very fast chemicals, the tiny solvent in the ink penetrates the film and penetrates into the bag or into the bag. When we open the snack bag, we often smell the unique odor, which is the odor of the organic solvent (chemical substance) that has penetrated. The chemical substances used in oil-based inks almost all have special irritating odors. Today, the solvent that fills the bag is called residual solvent. And the presence of this residual solvent is a very big headache for oily inks. Basically, water-based ink solvents use only water and alcohol, which can effectively solve the above problems and have now attracted attention.
When oily ink is used, the depth of the recessed hole of the roller is about 30 μm. However, for the shallow version of the water-based ink, the depth of the recessed hole can be 12 to 15 μm. Therefore, as long as the water-based ink is successful, it is equivalent to reducing the coating amount of the ink. After testing, the coating amount was reduced by about 10% compared to the oil ink. In addition, the printing plate for water-based inks is lighter and uses darker ink, and the reproducibility of the ink color is better than that of the oil ink. Of course, water-based inks also have drawbacks. Compared to oil-based inks, carriers have a slow drying speed and require extended drying time. Extended drying time is equivalent to slowing the printing speed. In addition, when using water-based ink, it is necessary to improve the original equipment or introduce new corresponding models.
Water-based inks are no worse than oil-based inks in printed products and finished products. At present, there are still funds that need to be invested in retrofitting technology. Therefore, it is not always possible to require the use of water-based ink in an environment. However, from the perspective of environmental protection, it is necessary to gradually increase the water-based ratio.
Third, the development of water-based ink technology
At present, whether it is imported water-based inks or domestic water-based inks, there are disadvantages such as non-alkaline resistance, non-ethanol resistance, non-water resistance, slow drying, poor gloss, and easy to cause paper shrinkage. To overcome these disadvantages, some use UV inks. , This not only increases the printing process, but also increases the printing cost, and some use high-priced imported high-grade water-based ink, also increased the printing cost. Therefore, we must further increase the development of high-performance aqueous ink.
1, high temperature
A high-temperature resistant water-based ink for pre-printing corrugated cartons has been successfully developed in Shanghai, filling the gaps in the domestic ink industry's technology in a timely manner, and laying the foundation for improving the quality of printed products. This type of water-based ink is the first in China and has the best performance compared with the current high-temperature water-based ink. Last year, Sichuan Deyang Color Printing Co., Ltd. imported a 1.2 m web press from Italy, which belongs to the satellite-based gravure ink preprinting equipment. The machine can not pass the water-based ink in the trial production stage, including the import of water-based ink, because the cardboard paste of the upper corrugated board production line is subjected to a high temperature of 180-200 °C. Fukuda Co., Ltd. and Deyang cooperated to accept this scientific research project. After six months of trial and error, it has finally succeeded.
The ink has the following characteristics: (1) high temperature resistance. At a high temperature of 200 °C, the ink does not change color, does not wrinkle, does not blistering, maintains the inherent printing effect, and effectively guarantees the quality of the printed product. (2) Wear resistance. During the transportation of the container, it is ensured that the printed product can maintain the invariability of printing color after being subjected to collision and friction. (3) Fast drying. In high-speed printing operations, due to the speed, the ink cannot be completely dried, causing problems such as drag ink and paste ink quality. The drying speed of the new ink has been further improved and the occurrence of such undesirable phenomena has been alleviated. . (4) Low viscosity, high color density, bright color and beautiful appearance, this special water-based ink is suitable for printing on coated white card and polishing white card box surface. When used on multi-color water printing machine, remove the high-temperature resistant formula. It can also be used after reducing the cost of ink production.
2. Environmental protection
The water-based ink series developed by Wuhan Modern Industrial Technology Research Institute has non-toxic, non-irritating odor, non-corrosive, non-flammable, non-explosive, and good safety of use. As a new type of green printing material, it has obtained national patents. , And passed the national ink quality testing center testing and appraisal. The new ink series production technology can be widely used in gold, silver cardboard, coated paper, white paper, corrugated paper, adhesive paper, cartons, paper bags and books and magazines.
Aqueous ammonia is commonly used with water-soluble acrylic resins and other water-soluble resins. Two methods have been developed to reduce the ammonia odor. First of all, we replaced a small part of the ammonia with less volatile odorless amines. The optimum amount is about pH 8.1. At this point, the resin still has good solubility, and there is almost no ammonia odor, and ammonia is all combined with the resin to form an ammonium salt. If you try to avoid the use of other amines, you can reduce the ammonia residue, but this will result in a higher viscosity of the resin solution or dispersion. Low-scent products of this type include Hydro-Rez 3110 and 4120. It is also possible not to use ammonia or amines at all. These ammonia-free/amine inks use a unique system consisting of a sulfonated polyester resin and a water-soluble acrylic resin. (to be continued)