Composite film packaging
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In daily life, we can see composite film packaging everywhere. Technically demanding foil-coated films are commonly used for color printing. In order to produce composite films with different firmness requirements, interactions between multiple materials are required—the interaction between synthetic material films, drills, and printing oils.
A growing market
In recent years, the total amount of flexible packaging has been increasing, which fully demonstrates the tendency of flexible packaging to replace bulky packaging 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 faster and better. The increasingly complex multi-layer composite process (three-layer and four-layer composite) adapts it to ever-expanding applications and a growing variety of related requirements. The composite film market can be divided into three parts: the off-end market for packaging liquid goods: the middle market for packaging cheese, fresh meat, etc., or the low-end market for goods such as 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 wet goods from drying and used for cool wet wipes: to protect dry goods from moisture, such as baked products and powdered products.
2. Acidic barriers. Prevent oxidation such as fat and fresh goods.
3. Carbon dioxide barrier. Preventing carbon dioxide loss in MAP packaging A stable packaging gas constitutes a carbonated beverage.
4. Aroma barrier. The protective scent does not evaporate from the package and loses, such as coffee.
5. Odor barrier. Prevent absorption of external odours or prevent loss of fragrance.
6. Light blocking. Prevent the oxidation of light such as dairy products.
7, the seal is firm. For the sealing of the composite film, heat sealing is used.
Aluminized films have the best barrier properties. Vaporization of the metal onto the PET plastic film also provides properties that are close to that of the aluminum foil. The use of aluminum sulphate or silicon oxide vaporized onto PET or OPP plastic enamel also has a good barrier function. But there is no good light blocking ability.
Composite film formation
A film formed of two or more layers must be as inseparable as a film. This involves not only the drilling agent between the two films but also the ink film. Drilling Agents are Synthetic Products Most drilling agents are two-component polynitrous urethane (PU) drills. The chemical reaction of the drilling process cures the drilling compound. The drilling agent on the surface of the substrate is mainly a physical process. Only a small part is the chemical process. At this time, the components of the drilling agent are drilled together with the components in the plastic film and further cured.
If a film is already printed during the drilling process, the fluxing agent and ink should meet more requirements. The most basic requirement is to have good adhesion and thorough drying in the inner layer before compounding. This is the more delicious. No solvent residue is allowed in the printed film. However, solvents or alcohol often remain in the ink binder. For this reason, the performance of the drilling compound must be able to combine with free radicals (-OH groups). Otherwise, the drilling agent and the curing agent will spontaneously undergo a drilling reaction to lose the cat nature that they should have. For example, in the compounding process, the film has been printed with PVB ink, and the salt is left in the ink, and the chemical base "NCO group" of the salt reacts with the free radical-OH combination of alcohol and water. No residue results in insufficient reaction of the drilling agent. What followed was an insufficient cure and effort.
Among the drilling agents, solvent-based drills are distinguished from solvent-free drills such as UV drills. Solvent-based drills require a drying tunnel to evaporate the agent. When a UV drilling compound is used, UV light passes through the film to reach the drilling agent to cause the bonding agent to polymerize together.
Ink for composite film
The ink suitable for the composite film not only has good adhesion on various films (OPA, OPP, PET-ALOX, PET-SiOX, PE, Alu), but also fully penetrates with the drilling agent and is strong. Internal cohesion (cohesiveness of the ink) and non-toxic safety are also very important. Further requirements for composite film printing oils are: long-lasting pattern printing, sterility and simple stamping and perfect color treatment with fast solvent volatility.
For composite film printing. Nitrocellulose (NC), poly-p-butene (PVC), polyethylene drunk butyral (PVB) nitrocellulose arsenic-polyurethane (NC/PU) oil dish system should be considered first. It can be seen that the more plastic the system is adjusted, the stronger the adhesion in the oil on the substrate, and the better the composite fastness. 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 appeared late, but it performed better in stamping, color processing and cleaning. It is a “universal” oil system for flexo and gravure printing. It is very environmentally friendly, with few failures at high speed printing, rapid solvent evaporation, sterilization and pasteurization. No plasticizer. At present, its market position is still relatively low but it has shown a growing trend. The PU ink system widely used in Asia has similar features and trends as the NC/PU ink system. It first needs to be printed with a layer of white ink.
The market share of PVC ink systems is gradually decreasing. Since the ink used in it contains a 'grade' component, it cannot be used in packaging. In addition, the "vinegar" component contained therein weakens the performance of the photopolymerization plate, so this ink system is not considered in flexo printing. So currently it is only used in gravure.
Defect handling
Due to the environmental pollution caused by the infiltration and transfer of components in the oil and the drilling agent, the relevant laws and regulations have imposed restrictions on this, especially in the packaging of food and drug composite film packaging.
In daily life, consumers should be especially careful when purchasing composite film packaging foods, because food packaging is environmentally friendly and 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 drilling agents are used, it is possible that these inks or drills will be incorporated into beverages or foods, which will affect the health of consumers.
Monomeric plasticizers, also from oil rafts or drills, may also penetrate (migrate) into the product. In addition, the durability of the pasteurization, sterilization or heat sealing and the lamination of the composite film may be reduced if an improper oil system and a drilling agent are used.
Conclusion
It is very meaningful to produce a composite film that not only meets the legal requirements but also meets the customer's requirements. It is important to integrate the advantages of different materials into the composite film. However, the production process of such composite membranes is also very complicated. It is based on the manufacturer's comprehensive understanding of the relevant tombs, oil systems and drilling fluids, and the interaction between these materials should be recognized to avoid problems with the post-processing of composite membranes.