Packaging printing
The packaging printing is a segment of the printing industry that deals with the printing of various packaging materials employed. The offset and flexographic printing processes are mainly used.
Types of packaging
The forms and types of packaging are varied. A wide variety of materials are used here. Tin cans , plastic containers , cardboard boxes and outer packaging made of corrugated cardboard are probably the most common types of packaging.
Technical requirements
Different printing and processing machines are used in packaging printing than in conventional printing. With offset printing, the machines have to take into account the thicker printing material and the higher material weight. As a result, different feeders and deliverers, gripper bridges and guide cylinders can be found in the printing machines than in "normal" paper printing machines. A specialty are tin printing machines in offset. With these machines, the stress caused by the printing material is even more pronounced. These printing machines also have a different “inner workings” than paper machines. Folding machines, gluing machines and window gluing machines are required for further processing.
meaning
In the crisis-ridden printing industry, packaging printing is still one of the few stable sectors. Regardless of the product quality, the need for packaging in all branches of industry is a guarantee for this.
Cardboard processing
There are different ways to refine packaging. These would be, for example, various paint applications as well as hot foil stamping , blind stamping and cold foil stamping . In offset printing, printing varnishes ( varnishes that are applied in the printing unit - like a color) and flexo varnishes ( applied via a special varnishing unit) are used. The printing varnishes can be both conventional ( drying by oxidation and absorption ) and UV-curing (drying by means of UV radiation ). The same applies to flexo varnishes; they can also be conventional ( dispersive ) or UV-curing. Flexo varnishes , however, have a completely different viscosity than printing varnishes. They are very fluid, that is to say with a low viscosity . For printing machines with a double coating unit, both systems (conventional and UV-curing) can be coated in one printing pass. Varnishes can be applied over the entire area or only certain areas of the product can be varnished ( spot varnishing ). In offset printing, the coating units also have the option of applying metallic paints over the entire area or in parts. Text, logos and fonts can be printed with metallic lacquers by using photopolymer plates . These photopolymer plates are not required for flat applications.
Hot foil stamping is divided into different techniques (e.g. relief stamping , deep stamping ). Colored foils are used for this (most often silver or gold foils ). Relief embossings are very detailed embossings that can be made e.g. B. can be used for a logo or company logo. With blind embossing, no foils are used, but a specific pattern is created using a die and male die . Cold foil stamping is relatively new in packaging printing. They are flat (without elevation or depression) and can be technically integrated in offset printing with a special device in a printing machine. Cold foil stamping is often overprinted with colors.
Colors in packaging printing
There are three types of inks used in offset printing: conventional inks (drying oxidative and absorbing), UV inks (inks that dry using UV radiation) and hybrid inks (a mixture of conventional and UV inks that use UV Radiation must be dried). Solvent-based inks are mainly used in gravure printing, but UV inks are also possible. Flexographic printing is a letterpress printing process that uses photopolymer plates. Solvent-based inks and UV inks are usually used in packaging printing.
Folding boxes
Folding boxes are subject to special requirements. Depending on the quality and area of application of the product, cardboard boxes have to meet different quality requirements. Common customer requirements are abrasion resistance , good adhesion / friction values and the closing strength of the folding box . A folding box should have good inherent stability, as the construction is subject to high loads. When printing , the color may later burst at the creased edges . This is called creased edge breakage. Food packaging is also subject to special statutory provisions. It must be avoided that pollutants migrate from the packaging into the food . These pollutants can migrate through certain types of cardboard, wrong colors and varnishes. A distinction is made between primary and secondary packaging. Primary packaging has direct contact with food. Secondary packaging does not have this. If there is primary packaging, it is possible to avoid possible migration through barrier varnishes or foil embossing on the inside of the packaging. When it comes to paints and varnishes, you should make sure that you use products that are not harmful to migration. This also applies to the box. For cardboard, too, there are types of material that are specified for this use.
Special paintwork
Metallic paints that are applied over the coating unit are a specialty. This can be planar and partial. These metallic lacquers can be lacquered conventionally and with UV curing (depending on the type of printing machine). The gloss pigment coatings are a specialty. In these applications, luster pigments (very similar to the pigments in auto-metallic paints) are mixed into a dispersion or UV paint in offset printing. Better results are achieved with regard to the pigment size and the amount of pigment in gravure printing . In the case of particularly high-quality folding boxes, screen printing is also used less often , since it is possible to apply the largest pigments in screen printing.
Another specialty of packaging printing is calender painting . With calender coatings you can achieve the most beautiful gloss application in terms of gloss and feel . Here you first print with conventional colors and a final primer varnish . The calender paint is applied in a second production run. During calendering, the varnish is transferred to the sheets, heated, pressed smooth using a very large cylinder and then dried.
Packaging development
If there is a special requirement in terms of stability, design or the inlet for packaging, this must be worked out in advance by the packaging development department of the production company. The weight of the printing material and the inner construction of the packaging are important here . Particularly with cosmetic flacons, very complex developments in the interior of the folding box come into play.
Osh
In packaging printing, there is a risk of inhalation exposure to hazardous substances . The concentration of substances in the air you breathe can fluctuate greatly. Naturally, peak loads are to be expected when activities involving solvents are carried out openly, e. B. with manual cleaning work.
The recommendations of the risk assessment of the accident insurance institutions (EGU) serve as a non-measuring process when carrying out the exposure assessment. They relate to work processes and activities with organic solvents and solvent inks in packaging gravure and flexographic printing (roll width> 500 mm) in various work areas. This EGU is based on comprehensive workplace measurements in 22 member companies of the Employer's Liability Insurance Association for Energy, Textile, Electrical, Media Products . If the protective measures described are observed , the occupational exposure limit values and other assessment criteria are observed. A dermal exposure is not given if the protective measures are observed.
Individual evidence
- ↑ a b German Statutory Accident Insurance e. V. (DGUV): DGUV Information 213-718 - Packaging gravure and flexographic printing with solvent inks. Accessed January 2, 2020 .