Analysis of Food-grade Inks for Flexographic Printing
Date: Apr 08 2025 From: Star Color Views:
In the field of food packaging, flexographic printing occupies an important position due to its advantages such as high efficiency, flexibility, and good printing quality. Food-grade inks used in flexographic printing, as key materials that come into direct contact with food or may indirectly affect food safety, have attracted much attention in terms of their characteristics, safety, and applications.
Working Principle and Characteristics of Flexographic Printing
Flexographic printing, often referred to as aniline printing, uses a flexible raised graphic printing plate, which is usually made of materials such as photosensitive resin. During the printing process, the ink is transferred to the raised part of the printing plate, and then, through the pressure of the impression cylinder, the ink is transferred onto the substrate, forming clear graphics and text. The characteristics of flexographic printing are as follows:
• Wide Adaptability to Substrates: It can print on a variety of materials, including paper, plastic films, aluminum foils, and composite materials. This enables it to meet the requirements of different types of food packaging in the food packaging field.
• Lower Printing Costs: Compared with some other printing methods, the investment in flexographic printing equipment is relatively small, and the cost of making printing plates is also more economical. With a relatively fast printing speed, it can complete a large number of printing tasks within a unit of time, further reducing the production cost.
• Good Printing Quality: With the continuous advancement of technology, the resolution and color reproduction of flexographic printing have been significantly improved. It can print fine patterns and text, meeting the requirements of food packaging for aesthetics and the accuracy of information transmission.
Requirements for Food-grade Inks
(1) Safety as the Primary Consideration
Food-grade inks must ensure that no harmful substances will migrate into the food during the contact process with food, so as not to affect food safety. This requires that the raw materials of the ink must meet strict food safety standards.
Ingredients such as pigments, resins, solvents, and additives in the ink should not contain heavy metals such as lead, mercury, and cadmium, as well as harmful organic compounds to the human body such as aromatic amines and polycyclic aromatic hydrocarbons.
The National Food Safety Standard of China, GB 4806-2016 "National Food Safety Standard - Inks for Food Contact Materials and Products", has made detailed provisions on the use of raw materials and migration limits of inks for food contact. The U.S. Food and Drug Administration (FDA) has also formulated strict regulations to supervise the inks used for food packaging to ensure that they meet food safety requirements.
| Region/Country |
Regulatory Standard |
Key Detection Items |
| United States |
FDA 21 CFR 175.300 |
Total migration ≤ 0.01mg/dm², benzene not detected |
| European Union |
EU 10/2011 |
NIAS (non-intentionally added substances) analysis, heavy metals < 0.5ppm |
| China |
GB 4806-2016 |
Phthalates < 0.1mg/kg |
| Japan |
JHOSPA Standard |
Fluorescent whitening agents prohibited, polycyclic aromatic hydrocarbons < 1ppm |
(2) Good Printing Adaptability
In order to be able to transfer smoothly and form high-quality printing effects during the flexographic printing process, food-grade inks need to have good printing adaptability. This includes appropriate viscosity, fluidity, and drying speed, etc.
In terms of viscosity, the ink needs to be able to adhere evenly to the raised part of the printing plate during the ink transfer process of the anilox roller and be able to transfer smoothly onto the substrate during impression.
In terms of fluidity, the ink needs to flow smoothly in the ink transfer system of the printing equipment to ensure the stability of ink supply.
The drying speed is also crucial. An excessively fast drying speed may cause the ink to dry on the printing plate, affecting the continuity of printing; while an excessively slow drying speed will lead to insufficient drying of the printed products, and problems such as smudging and sticking are likely to occur, affecting production efficiency and product quality.
(3) Compatibility with Packaging Materials
There are a wide variety of food packaging materials, and different materials have different surface properties and chemical characteristics. Food-grade inks need to have good compatibility with various packaging materials to ensure that the ink can adhere firmly to the surface of the packaging material and that there will be no phenomena such as ink peeling and discoloration during subsequent processing, storage, and use.
For plastic film packaging materials, due to their low surface energy, it is usually necessary to design a special formula for the ink or pre-treat the plastic surface to improve the adhesion of the ink.
For paper packaging materials, the ink needs to be able to penetrate into the fibers of the paper to form a good bond, and at the same time, it is necessary to ensure that it will not have an adverse impact on the physical properties of the paper.
Classification and Characteristics of Food-grade Inks for Flexographic Printing
- Water-based Inks (Mainstream Choice)
Water-based inks use water as the main solvent and have the environmental protection advantage of low volatile organic compounds (VOCs) emissions, which is in line with the current global requirements for environmental protection. In flexographic printing, the application of water-based inks is becoming more and more widespread. Their resins usually use water-based acrylic resins, water-based polyurethane resins, etc. These resins are dispersed in water to form a stable emulsion, and the pigments are evenly dispersed in it.
• Advantages: VOCs < 5%, certified by ISO 14001 environmental protection standard, suitable for paper and cardboard.
• Key Points of the Formula:
o Resin: Styrene-acrylic copolymer (recognized by FDA)
o Pigment: Inorganic mineral pigments (such as iron oxide red, titanium dioxide)
o Additive: Wetting agent without APEO (alkylphenol ethoxylates)
- UV Inks (for High Resistance Scenarios)
UV inks, that is, ultraviolet curing inks, also have important applications in flexographic printing. The curing process of UV inks is that under the irradiation of ultraviolet light, the photoinitiators in the ink absorb the energy of ultraviolet light and decompose to generate free radicals, which initiate the polymerization reaction of monomers and oligomers, thus enabling the ink to cure rapidly.
• Advantages: Instant curing (200mJ/cm²), resistant to boiling water and freezing.
• Safety Key Points:
o The photoinitiator needs to be of a low-migration type (migration amount < 0.01ppb)
o Avoid using high-risk substances such as ITX (isopropylthioxanthone)
The food-grade water-based ink of Zhongzhixing complies with the certification requirements of international food safety organizations such as the U.S. Food and Drug Administration (FDA), ensuring food safety from the source.
In terms of performance, it has the characteristics of standard color, good gloss, and high color intensity, which can make the printed patterns bright and eye-catching. Moreover, the printed dots are clear, and the printed products have a strong three-dimensional sense of layers, adding attractiveness to food packaging.
The ink has good transfer and leveling performance, a stable printing process, is easy to clean, and is convenient to operate. In addition, it has no irritating odor, a fast drying speed, and good printing adaptability, and can be directly used on the machine.
Whether it is paper food packaging such as paper cups, paper plates, and cake papers, or personal contact product packaging such as sanitary napkins and disposable diapers, the food-grade water-based ink of Zhongzhixing can meet the requirements with its excellent performance and is a reliable choice for food packaging printing.
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