Printing ink application in dairy packaging industry

China's dairy industry is the fastest growing subsector in the food industry. Dairy production has increased by more than 20% year-on-year since 1999. In 2003, China's dairy output has reached about 13 million tons, an increase of more than 30% year-on-year. It is predicted that in the next six years, the momentum of rapid development will continue to be maintained. In order to comply with the rapidly developing dairy market, dairy packaging is also rapidly developing. Therefore, many new requirements have been put forward for dairy packaging printing inks.

Dairy packaging printing inks vary according to the starting point of the classification. There are the following types.

According to the type of printing plate, it can be divided into flexographic printing ink and gravure printing ink;
According to environmental performance, can be divided into non-benzene ink and benzene ink;
According to the post-processing form, it can be divided into compound ink and table printing ink;
According to the printing substrate, it can be divided into paper gravure ink, plastic film printing ink and other printing ink;
According to the type of binder in the ink, it can be divided into polyamide type surface printing ink, polyurethane type surface printing or compound printing ink and chlorinated polypropylene type compound ink.

Milk powder packaging printing ink

At present, the packaging and printing of milk powder is mainly based on plastic composite flexible packaging, and there are also metal cans, plastic composite flexible packaging printing is basically printed on BOPP film or PET film, and then composited with aluminized film or aluminum foil and heat sealing material .

For general milk powder packaging, chlorinated polypropylene resin inks are mainly used for printing. Although ink manufacturers have adopted various methods to adjust the ink structure and reduce the residual of benzene-based toxic solvents in packaging, there is still a small amount of residue in the packaging. In order to completely eliminate toxic solvent residues, some companies have used benzene-free inks for printing. However, due to the quality problems of benzene-free inks in printing, the composite strength and heat-sealing properties cannot meet the requirements, so there are few applications.

Non-benzene ink generally refers to the use of polyurethane resin as the main resin ink, basically does not contain benzene solvent, even to achieve a certain printing effect, use a small amount of benzene solvent, the ink after drying the benzene solvent residue is also very small. Therefore, benzene-free ink will gradually be welcomed by dairy producers.

For milk powder packaging and printing inks, the future direction of technology development will be mainly benzene-free ink. With the improvement of people's environmental protection and health awareness, such inks are likely to become the mainstream of printing ink in the next few years. In addition, some ink manufacturers are currently studying more environmentally friendly water-based plastic printing inks and have entered the trial printing stage.

Liquid dairy packaging printing ink

Liquid dairy packaging printing inks differ in the characteristics of liquid dairy packaging materials and fall into the following two categories.

1. Paper plastic aluminum or paper plastic packaging printing ink

Paper-plastic aluminum or paper-plastic materials are the main packaging materials for aseptic packaging of dairy beverages. Tetra Pak is a typical product in this market, accounting for more than 90% of the market share, approximately RMB 4 billion, and 20% to 30% annually. The speed of growth is estimated to reach 6 billion Tetra Pak in China in 2004. Most of these types of packaging use flexographic ink for printing, and a few use gravure ink for printing. Since the surface of the substrate is paper, offset printing can also be used. In order to prevent the benzene-based solvent from corroding the flexographic printing plate, the flexo-printing ink does not contain any benzene-based solvent, thereby making the environmental protection of such packaging better.

In order for the flexographic printing to exert its printing characteristics, the printing quality is more refined, and the flexographic printing equipment is continuously improving the printing fineness, so the flexographic printing ink will also be more refined. In terms of ink environmental protection, the research of water-based flexographic printing inks has been increased. At present, flexo printing inks that use paper as a printing substrate have entered a small amount of use. In the near future, the printing of paper-plastic aluminum or paper-plastic packaging materials will be the first to achieve full-water ink printing.

2. PE film and co-extruded PE film printing ink

Some liquid dairy products, especially fresh dairy products, are packed in PE films or multilayer coextruded PE films. Milk packaging printing inks for printing PE films and coextruded PE films, in addition to the general performance of surface printing inks, also have the characteristics of good water resistance, high temperature resistance, and ability to withstand sterilization treatment. This type of film printing is mainly based on gravure printing. In the past, polyamide-type surface printing inks were mostly used. However, such inks are resistant to high temperatures and poor water resistance. In recent years, they have basically been replaced by polyurethane type surface printing inks. In order to achieve good water resistance and high temperature resistance and meet the sterilization requirements of the hot-filling process, a certain amount of curing agent must be added at the time of printing. For this purpose, the ink factory provides supporting curing agents.

The rapid development of the dairy industry and the improvement of the quality of dairy packaging will certainly promote the development of printing inks in the direction of high quality and non-toxic. In the development of inks from benzene-solvent inks to benzene-free inks, based on the availability of water-based printing ink products, the era of dairy packaging printing inks entering benzene-free inks and water-based inks is not far off.