Heat Shrink Tubing: Flexographic Printing
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Today, flexo label printers face increasing competition, so they are all moving into the shrink label market. The shrink label market is new and has great growth potential. It is also different from the label market, which is generally relatively limited and easy to join, thus preventing new companies from joining the competition. Traditional flexo printers have begun to purchase shrink-label technology devices, including: bonders and new presses, which are expected to grow at a rate of seven to ten percent per year, which is a general standard of only four to five percent growth. The market is high.
Area-based products and patents rely on packaging design to attract customers' attention, which opens the door to the small and medium-sized label market. The market development of ethnic foods, organic foods, and health foods, as well as the labeling regulations of the US Food and Drug Administration, have increased business opportunities in the label market.
According to industry statistics from the Bethesda Business Development Association in Maryland, the total amount of film used in the local shrink label market in 2003 was 49 to 53 million (about 300 million US dollars). Gravure printing occupies this market, and it is estimated that only 15% of the shrink labels are printed in flexo.
When to enter the label market
Patented food and regional product projects are now increasing, which increases the diversity of market management items. This emerging phenomenon has made the shrink label work seamlessly with the flexographic printing industry, which is still short-lived. The quality of flexographic printing has not only improved, but its pre-press cost is also lower than that of gravure printing, which is an important factor for flexographic printing in the label market.
If you are planning to enter the flexo label market, please refer to the recent industry research report. It is estimated that the volume of printing is 40 million square inches or less, winning with a narrow roll; if the volume is more than 40 million square inches, it will win with a wide roll. (see picture 1)
If a 40-inch wide reel is used, the profit and loss balance of flexographic wide-format web printing and gravure printing is about 500,000 meters. This number depends on many factors, including capital equipment costs and cost of relocation.
Two distinct markets
The shrink label industry is divided into two distinct markets: heat shrink tubing and loop cans. Both can be printed in flexo and the quality is just as good.
The transverse shrinkage characteristics of the film are referred to as TD. First, the shrink film is traversed across the wide side of the roll to form a tubular shape that fits over the container. The film then heats up and shrinks laterally, and the film adheres to the container.
The characteristics of the longitudinal positioning of the ring-shaped film are referred to as MD, which means that the film shrinks longitudinally when heated. Heat shrink tubing technology requires bottling companies to purchase expensive shrink-label labeling equipment for matching, while ring-and-can technology does not.
Film and casing equipment
In general, when printing with an unsupported film, tension control is done better than with a pressure sensitive film. Some old-fashioned printers or companies that are determined to run a pressure-sensitive label business will not normally switch to operating shrink labels.
In order to print high-quality labels, in addition to tension problems, thermal control is also an important factor. The printing press must have a high heat dissipation capacity to prevent the film from shrinking during printing. Thermal power is the biggest enemy of shrink film, so take all measures to prevent the film from overheating. A new generation of presses mixes the freezing drums to dissipate heat during the printing process.
The set of labels requires the joining of equipment. The bonding equipment forms a flat printed paper roll into a tubular shape and then bonds the overlapping portions (forming the interface). Next, put the flattened sleeve back in place.
Manufacturing interfaces and monitoring interface manufacturing require labor intensive. In the process of joining, if an important step is wrong, the resulting error will delay the subsequent process. The parts that need to be joined must be cleaned of the ink and contaminants so that the adhesive can properly bond. The manufacturing process of the joint must be monitored 100% to prevent the film from blasting as it shrinks on the container.
The bonding equipment is from 40,000 to more than 200,000 US dollars, and the price is higher with the monitoring system. If the monitoring device is purchased separately, an additional 30,000 to 50,000 US dollars will be required.
Label equipment
In casing production, the next process for label printing is packaging. Although sometimes the packaging of commercial hand-labels, but generally the use of special labeling equipment to label the label on the utensils. Advanced labeling equipment can cost up to $500,000.
The labeling device opens the bonding film, punctures the hole (if needed), then crosses the label and places it on the container. The heat is then transferred through a vapor, infrared or pressurized gas flow incubator to hold the film against the container.
The loop-type film is a conventional device that holds the label against the container. Different technologies require different adhesives and thermostats. Since the pressure is applied to the adhesive of the film to the film contact point during the shrinkage process, a hot melt adhesive is required (in some cases, a solvent type adhesive is required). In the past, it was good to use low-shrinkage UV adhesives when low shrinkage was needed, but so far there have been few successful examples.
Presumably, the only substrate that can be used as a ring-shaped film today is polypropylene. Because of its 20% shrinkage limit, hot-melt adhesives work well, while solvent-based adhesives wrinkle polypropylene. Due to the high shrinkage temperature profile of polypropylene, the pressurized gas flow shrinking thermostat is the type of thermostat that it mainly uses because it can reach higher temperatures than steam incubators.
More shrinkable films enter the market, and solvent-based adhesives will need to resist the high shrinkage of the interface.
Shrinking ink chemicals
The coefficient of friction of the ink plays an important role in the label. The efficiency with which the casing slides on the container depends on the coefficient of friction. Very few ink chemicals are suitable for flexographic printing.
Environmentally friendly water-based inks can shrink more than 40%, are very flexible, and cost less than UV inks. Moreover, the surface of the ink is less affected by the movement of atoms in the chemical molecules.
Solvent inks are similar to water-based inks and have a high elasticity and can shrink more than 40%. The drying time required for solvent-based inks is less affected by moisture, but it is somewhat affected by the movement of atoms in the chemical molecules. Solvent inks have the greatest adhesion for most films.
UV free radical inks cure instantly, and are inks that are inhibited by oxygen rather than moisture. In general, its shrinkage is less than 20%. In some substrates, the adhesion is limited. Atomic movement in the chemical may occur on the surface of the ink. Two free radical inks are now available in the market:
UV uses a sensitizer to absorb ultraviolet light to initiate the hardening process.
The electron beam produces a polymerization that eliminates the use of sensitizers.
UV cationic inks produce adhesion in a wide variety of substrates, with shrinkage rates exceeding 40%. This ink tends to be more elastic. In addition, the ink hardens almost instantly, and the atomic movement of the chemical molecules is less, but the price is also more expensive than UV radical inks.
Graphic design advice
The flat design of the shrink label needs to take into account the shape of the container. Try not to place the key image in a place with high shrinkage. Another factor to consider is where to place the barcode. Bar codes are generally printed vertically to prevent image distortion and affect sketching.
A series of computer programs can interpret distorted images, but remember that in some cases (especially low-shrink printing), distorted images are useless.
About shrink film
Typical shrink film thicknesses are within fifty microns (one thousandth of an inch). In the past few years, a thinner shrink film of only 40-45 microns has been introduced. The label processing properties of the equipment used by the label manufacturer determine the acceptable shrink film thickness. In general, label manufacturers can expect higher shrinkage shrinkage films at higher prices.
Although the shrink film is designed to shrink in a particular direction, there is a slight shrinkage in the opposite direction. Since the shrink film is sensitive to heat, care should be taken to keep the temperature of the shrink film stored, printed, and transported. Most film manufacturers recommend that the film be stored in a controlled environment, approximately 75-85 degrees Fahrenheit, until it needs to be labeled on the container.
The mathematical program is used to determine the minimum shrinkage required for a particular container. The resulting value is used to determine the shrinkage requirement for the film. The shrinkage of the film must not be lower than this value. If the diameter of a container suddenly changes, the need for a substrate with a high shrinkage force is greatly increased.
To calculate the width required to print the label, add the width of the overlapping position of the container to the width of the overlapping interface twice; the sleeve is added four millimeters to allow the sleeve to slide over the container.
PVC (polyvinyl chloride) - Two-thirds (about 34 million pounds) of the shrink film used today is a PVC shrink film. PVC is gaining weight in the industry. The shrinkage of PVC shrink film is maintained at 40% to over 60%. The shrinkage rate is high and the cost is low. It is the choice of many companies in the United States. The strength of PVC makes it suitable for multiple packaging and anti-theft device edge strips.
However, PVC continues to create environmental problems. Plastic container recyclers prefer to exclude PVC during the recycling process, especially to separate them from PETG (polyester) containers. However, since the proportion of PVC and PETG is close to 1.33, with today's technology, it is impossible to separate the two in the recycling process.
PETG (polyester film) has a shrinkage rate of 78%, which was previously considered a substitute for PVC. The market share of polyester film is about 15 to 20 percent. The PETG market is growing, but the PVC market is not. PETG has a specific gravity of 1.28, making it comparable to PVC. However, due to the high raw material cost of PETG, it hinders its market growth, especially the existing updated and more competitive materials entering the market.
OPS (polystyrene film) - relatively new in the US domestic market, but has become a favorite material for many users around the world. OPS is environmentally friendly than PVC and is more economical than PETG. OPS currently has a 5 percent market share in the US, and its apparent growth rate is just around the corner.
Because OPS shrinks by as much as sixty-five percent, it rivals other high-shrinkage products. OPS has a specific gravity of 1.025 and a yield advantage of 20% higher than PVC and PETG. Another benefit of using OPS is that it shrinks little or not in the opposite direction.
OPP (polyvinyl chloride), although not shrinkable, has a share of the ring-shaped shrink film market, with a market share of 18 to 20. OPP is suitable for containers that require low shrinkage and are close to cylindrical. The proportion of OPP is 0.90, the price is competitive, and the output is too much, which hinders other printing materials from entering this targeted market.
Printing on a white OPP surface requires a film to resist abrasion. OPP differs from the other substrates mentioned above in that it is designed for ring-and-loop applications.
Future film
Today, several companies are studying the potential of non-petrochemical environmentally friendly films. This film was even used as a basic material for containers. This material is PLA (resin) and is completely used as a compost and is biodegradable. Due to the rising production prices of petrochemical products that the industry relies on, the PLA substrate is naturally another option. Although this kind of printing material is a bit ultra-modern, it should be introduced to the market earlier than expected.
It is necessary to enter the shrink film market in time, and it will take time. In the long run, investment in this market should be profitable. However, important technical issues cannot be solved independently, so your production team must include printer manufacturers, ink and film suppliers.