Faced with the increasingly fierce label printing market, many manufacturers who use flexographic printing labels pay attention to shrink film labels, not only because of its development potential as a new technology, but also as opposed to those technical requirements are not very high. , The cost of investment is not a big label printing market, the threshold for the introduction of shrink film label is higher, so it can block the new company to join the competition. Traditional flexographic printing plants have begun to purchase some shrink film technology equipment, such as: adhesive devices and new printing equipment. It is expected that the shrink film label will have an annual growth of 7% to 10%, which is significantly higher than the 4% to 5% growth rate of the general label market. The reason for this result is the increasing emphasis on the theme of packaging design: how to quickly seize the customer's eyes. It is this demand that opens the door to the small and medium label market. Of course, the introduction of personalization, ethnicity, and health foods, together with the new FDA (United States Food and Drug Administration) labeling regulations, has provided the label market with opportunities for growth and profitability.
According to the statistics of the Maryland State Business Development Association, the use of shrink film labels in the United States was 49 million to 53 million pounds (about 300 million U.S. dollars) in 2003. However, gravure printing accounted for most of the market, leaving only 15% to be completed by flexographic printing.
When to enter the label market
Nowadays, all kinds of patented foods and some regional specialties need different packaging. This just provides a good opportunity for shrink film labeling, combining the characteristics of flexographic printing to fulfill customer requirements. With the development of flexo printing technology, the printing accuracy has been continuously improved, and the pre-press production cost is lower than that of gravure printing. This has enabled flexo printing to play an important role in the label printing market.
If you decide to enter the shrink film label market, it is necessary to refer to the current situation of flexo printing. At present, narrow-web flexographic printing presses are the most competitive ones that have printed less than 40 million square meters of film, while those with more than 40 million square meters are wide-format machines.
For a 40-inch wide reel, 500,000 square meters is the demarcation point between the wide-format flexo and gravure machines. This number depends on many factors, including the cost of the machine and the cost of installation.
Two very different markets
Shrink film labels are divided into two distinct markets due to different processes: shrink tube packaging and wrap packaging. But both technologies can be done with flexo. The general term "TD" refers to shrink tube packaging, which relies mainly on the transverse shrinkage of the film. The printed film is made into the shape of a tube and fits over the container, and the film is then heated, causing the film to contract laterally and tightly engage the container.
Wrapped packaging is oriented according to the direction of operation of the machine. When the film is heated, it shrinks according to the direction of mechanical movement. We call it MD. Packaging technology does not require expensive label printing equipment, while shrink tube packaging (TD) requires high equipment.
Film and casing equipment
Relative to the pressure sensitive film, the tension control of the unsupported film is generally better. Some old label printing companies or companies that are obliged to make pressure-sensitive films generally do not sell shrink film labels.
In addition to pressure control, thermal control also plays an important role in label printing. The printer must have sufficient heat dissipation to prevent film shrinkage during printing. For the shrink film, the heat source is the biggest enemy; we must always pay attention to the contact of the film with an overheated heat source. A new generation of presses are equipped with a heat roller in the printing process to help eliminate heat.
Bonding site, which is a joint part of the tube, forms the film into a tube in one step after printing, and glues (forms a tube) at the places where the two sides overlap; and then puts the flattened sleeve back in place. .
Forming and inspecting seams is a labor-intensive activity and it is the most important step in the casing process. The ink and dirt on the seam must be removed so that the adhesive bonds better. When the film is heat-shrinked in the container, be sure to check for cracks when the connector shrinks.
Bonding equipment costs from $40,000 to $200,000. The higher price configuration has a monitoring system. If you buy a separate monitoring system, the price will range from $30,000 to $50,000.
Labeling equipment
In the manufacturing process of the sleeve, the next step after label printing is packaging. In general, this process uses special equipment to attach the label to the container, although some manufacturers do it manually.
High-end labeling equipment can be sold for $500,000.
Labeling equipment, first open the film, punch (if necessary), cut to the appropriate length, and then put it on the container, heat the film by steam, infrared or hot air, make it tightly fit the container.
The wrap products use conventional equipment to apply adhesive labels to the containers. Different technologies require different adhesives and heating pipes. During the shrinking process, hot melt adhesives are needed because the pressure is applied to the film at the film contact point adhesive (in some cases, solvent adhesives are required). Although UV adhesives have a bright future in the era of low shrinkage, there are not many successful cases.
In general, polypropylene is currently the only material that can be used for wrapping printing. It only applies to a material with a maximum shrinkage of 20%. Hot-melt adhesives are more suitable for this material, while solvent-based adhesives make polypropylene wrinkle. Because of the higher starting temperature of heat shrinkage of polypropylene. A pressurized air-shrinking oven is generally chosen to serve as a constriction.
Shrink ink chemical composition
The coefficient of friction of the ink plays an important role in the application of the sleeve label, which determines the efficiency of the label sliding across the container. There are few inks that are generally suitable for flexographic printing.
Environmentally friendly water-based inks are not only highly elastic, but also have a shrinkage rate of more than 40%. It costs less than UV inks and is less affected by the movement of atoms in chemical molecules.
Similar to water-based inks, solvent-based inks are also very elastic, with shrinkage exceeding 40%. The drying of a solvent-based ink is also less affected by moisture, but it is affected by the movement of atoms in chemical molecules.
UV radical ink can be instantly cured. This ink is affected by oxygen rather than moisture. Generally, the shrinkage of UV radical ink is less than 20%. On some printing materials, its adhesion is limited. Two types of free radical inks have now been introduced to the market.
1. UV inks use a sensitizer to absorb UV light and start the hard curing process.
2. The electron beam produces polymerization, eliminating the need for photosensitizer.
For most printing materials, UV cationic inks are suitable, and its shrinkage capability can exceed 40%. This ink is also very elastic. In addition, this ink can be cured almost instantly, but the price is much more expensive than UV radical ink.
Advice on prepress design
For prepress designers who shrink labels, be sure to consider the shape of the container, and try not to place the key image in a highly constricted place. The other is to consider where to place the barcode.
Bar codes are generally printed vertically to prevent image distortion and affect scanning.
Many computer programs can interpret distorted images, but in some cases (especially for low-shrinkage applications), distorted images are considered waste.
Knowledge about shrink film
A typical shrink film has a thickness of 50 μm and has been relatively thin in the past few years, with a thickness of approximately 40 μm to 45 μm. The thickness of the film used is determined by the type of label printer. It is generally recommended that label printers purchase some of the more expensive shrink films, which have a higher shrinkage.
Although the shrink film is designed to shrink in a certain direction, there is also a slight contraction in the opposite direction. Since the shrink film is sensitive to heat, extreme care must be taken in the storage, printing, and transportation of the shrink film. Most film manufacturers recommend that the film be stored in an easily controllable environment. The temperature should be maintained at 21°C to 32°C immediately before the label is affixed to the container.
By calculating the minimum contraction rate required for the container, the value obtained is used as a reference for the shrinkage requirements of the film. The shrinkage of the film must not be lower than this value. If the diameter of a container suddenly changes, you must choose a film with a stronger contraction force.
In order to calculate the printing width of the label, two overlapping widths can be added to the maximum width of the container. The sleeve is to be added 4mm, so that the sleeve can slide on the container.
PVC (polyvinyl chloride), now used in the shrink film, 2/3 of PVC shrink film. The reason why PVC is valued in the industry is that its shrinkage capacity is maintained at 40% to 60%, while its cost is low, and its strength is very high. It is suitable for multiple-sealing and anti-theft device edge strips.
However, the environmental pollution caused by PVC cannot be ignored. Plastic container recyclers generally do not accept PVC in the recycling process. In particular, they must be separated from PETG (ethylene glycol polyester) containers. Because the proportions of PVC and PETG are close to 1.33, today's technology is very difficult to separate the two in the recycling process.
PETG (ethylene glycol polyester), its high shrinkage rate of 78%, previously considered to be PVC substitutes, the market share of about 15% to 20%. Now that the PETG market is growing, PVC is regressing. However, due to the high cost of PETG raw materials, it has hindered further development, especially when newer, more competitive materials are entering the market.
OPS (Oriented Polystyrene) has become a printing material that many countries in the world like to choose. OPS is more environmentally friendly than PVC and economical than PETG. The OPS's ability to shrink up to 65% is comparable to other high shrinkage films. The proportion of OPS is 1.025, and the profit advantage is 20% higher than PVC and PETG. Another advantage of using OPS is that it shrinks little in the opposite direction and does not even shrink.
Although OPP (Oriented Stretched Polypropylene) is not good in shrinkage, it has a place in the market of wrapping shrink film, and its market share reaches 18% to 20%. OPP is suitable for containers that require low shrinkage and are near cylindrical. The proportion of OPP is 0.90. The price is competitive, and the output is large, successfully blocking the entry of other printing materials.
Printing on a white OPP surface requires adding something else to stop the friction. OPP is different from the printing materials mentioned earlier. It is designed specifically for wrapping.
Future film
Nowadays, several companies are researching environmentally friendly films that have potential for non-petrochemicals.
This film was even tried as a basic material for the container. This material is a PLA (resin) that can be used as a compost and can be decomposed by living things. Due to the rising prices of petrochemical products relied on by industry, PLA can naturally become another kind of printing materials.