Composite film packaging

In everyday life, we can see composite film packaging everywhere. Technically demanding foils are often used for color printing. In order to produce composite films with different robustness requirements, it is necessary to interact with various materials—the interaction between the composite film, the drilling compound and the printing oil.

A market that continues to grow

In recent years, the total amount of flexible packaging has been increasing, which also fully shows the trend of flexible packaging alternatives such as glass bottles and metal cans. This is not only because of its cost advantage, but also because it can adapt to changes in market demand more quickly and better. More and more complex multi-layer composite processes (three-layer and four-layer composite) make it adapt to the ever-expanding application fields and the growing variety of related requirements. The composite film market can be divided into three categories, namely, the off-the-shelf market for packaged liquid goods: the middle market for packaging cheese and fresh meat, and the low-end market for goods such as instant noodles and instant noodles.

Composite film barrier characteristics

Through the interaction of different materials in the composite film, the advantages of each layer are accumulated. The following are the functions of the composite film:

1. Water vapor barrier to prevent dry wet goods plus cool wipes: Protect dry goods from moisture, such as baked products, powdered products.
2. Acid barriers. Prevent oxidation such as for fats and fresh products.
3. Carbon dioxide barrier. Prevent carbon dioxide loss in MAP packaging to achieve a stable package gas composition plus carbonated beverages.
4. Fragrance barrier. Protects the fragrance from loss from the packaging and loses it like coffee.
5. Smell barrier. Prevent the absorption of external odors or the loss of fragrance.
6. Light blocking. Prevent light oxidation such as dairy products.
7, seal firmly. For the sealing of composite films, hot press seals are used.

Aluminized films have the best barrier properties. Vaporization of metal onto PET plastic film can also achieve characteristics close to that of aluminized sheet metal. The vaporization of aluminum oxide or silicon oxide to PET or OPP plastic crucibles also provides good barrier properties. However, there is no good light blocking ability.

Composite film formation

Films formed from two or more layers must be inseparable like a film. This involves not only the drilling compound between the two films but also the ink film. Drilling compound is a synthetic product. Most of the drilling compounds are two-component poly-nitro-carbonate (PU) drilling compounds. The chemical reaction during the drilling process solidifies the drilling compound. The drilling compound on the surface of the substrate is mainly a physical process. Only a small part is a chemical process. At this time, the composition of the drilling compound is drilled together with the components in the plastic film and further cured.

If a film is already printed during the drilling process, then the drilling compound and the ink must meet more requirements. The most basic requirement is to have good adhesion and thorough drying in the inner layer before compounding. This is even more so. Residues of solvent are not allowed in the printed film. However, solvents or alcohol often remain in the ink's binder. For this reason, the properties of the drilling compound must be able to combine with free radicals (-OH groups). Otherwise, the drilling compound and the curing agent will spontaneously undergo a drilling reaction and lose their cat's character. For example, in the compounding process, PVB ink is printed on the film, and the acid salt is left in the ink. The chemical group “NCO group” of the salt reacts with the free radical-OH combination of alcohol and water. No residue causes the drill mixture to not react adequately. What comes afterwards is an insufficient cure and drilling force.

In drill mixes, solvent-based drill mixes and solvent-free drill mixes such as UV drill mixes are distinguished. Solvent-based drilling compounds require a drying tunnel to volatilize the dopant. When using a UV drill mix, UV light passes through the membrane to the drill mix to polymerize the paste together.

Ink for composite film

The inks suitable for composite membranes not only have good adhesion on a variety of films (OPA, OPP, PET-ALOX, PET-SiOX, PE, Alu), but also fully drilled with the drilling compound, strong Cohesion (ink cohesion) and non-toxic safety are also very important. Further requirements for composite film printing oils are the ability to print long-lasting patterns, sterility and simple stamping with pasteurization and perfect color handling, as well as rapid solvent evaporation performance.

For composite film printing, nitrocellulose (NC), polybutene (PVC), polyvinyl butyral (PVB) nitrocellulose (N/N) vinegar (NC/PU) dish systems are the first considerations. It can be seen that the more plastic the system is adjusted, the more firmly the oil is attached to the substrate, and the better the composite fastness is. The PVB ink system is suitable for almost all drilling applications. This system is currently the most widely used.

The NC/PU oil star system appears later but has better performance in stamping, color processing, and cleaning. It is a "universal" oil-in-place system for flexo and gravure printing that is very environmentally friendly, rarely fails at high-speed printing, solvents evaporate quickly, sterilizes and pasteurizes. No plasticizer component. Its current market position is still relatively low but it has already shown a growing trend. The widely used PU ink system in Asia has similar characteristics and trends as the NC/PU ink system. It needs to be printed with a layer of white ink first.

The market share of PVC ink systems is gradually decreasing. Because the ink it uses contains 'class' ingredients, it cannot be used in packaging. In addition, the "vinegar" component contained therein attenuates the photopolymerization performance, so this ink system has not been considered in flexo printing. So at present it is only applied in gravure.

Defect handling

Because of the turbulence and easy environmental pollution caused by the infiltration and transfer of components in oil and drilling fluids, relevant laws and regulations have imposed restrictions on this, especially with regard to the composite film packaging of foods and medicines.

In daily life, consumers should be especially vigilant when purchasing foods with laminated membranes, because the environmental protection of food packaging is related to their own health. If juice, soy sauce, olives, vinegar, alcoholic beverages, skin care products, detergents, disinfection Agents, bleaches, etc. If unsuitable inks and drill mixes are used, it is possible that these inks or drill mixes will be incorporated into beverages or food products, which will affect the health of consumers.

Monomer plasticizers, also from oil tar or drill mixes, may also penetrate (migrate) into the product. In addition, the durability of pasteurization, pasteurization, heat sealing, and composite membrane drilling can be reduced if unsuitable oil systems and drill mixes are used.

Conclusion

When producing a variety of composite films that not only meet legal requirements but also meet customer requirements, it is of great interest to integrate the advantages of different materials into composite films. However, the production process of such a composite film is also very complicated. It requires the manufacturer to have a comprehensive understanding of the relevant tomb materials, oil systems, and drilling fluids. The effect of these materials on the interaction should also be well-understood in order to avoid problems with the post-processing of composite membranes.