Heat shrinkable plastic labels can be used in the packaging of food, beverages and other consumer goods. Every merchant hopes that their products can be distinguished by consumers on an assortment of shelves, and this demand has stimulated the rapid development of the heat shrinkable film label market. Everyone who buys coffee creamer, flavored milk, and yogurt is familiar with the heat shrink film label, which covers almost the entire outer surface of the bottle. Heat shrinkable film labels are widely used in the decoration of various products, such as juice, pet food, bottled water, pharmaceuticals, cosmetics, lawn care products, and automotive accessories.
The latest research shows that the global market for heat shrink film labels is growing at an average annual rate of 10% -15%. Behind the strong demand is the many advantages of heat shrinkable film labels. Heat shrinkable labels add eye-catching, improved quality and 360 ° decoration to blown plastic bottles or containers. Heat shrinkable labels can fit tightly on any irregularly shaped bottle body, especially when the fit is extended to the bottleneck, bottle cap or bottle cap, the label can obviously change the characteristics of the container. In addition, if a UV absorber is added to the formula of the heat shrinkable film label, the shelf life of the packaged article can be extended.
The heat shrink film label market is facing competition from older paper labels, heat transfer decoration and in-mold labeling technologies. It is reported that the material cost of heat shrinkable film labels is at least twice that of traditional methods. But at the same time, many consumer goods packaging manufacturers also said that the advantages of heat shrink film labels will exceed their excessive expenditure costs.
There are two ways to use process heat shrink film labels: full-body shrinkage method and roll-fed method. A common feature of these two methods is that the plastic film with an average thickness of 50 microns is first wrapped around a bottle body and then heated, and the heat generated causes the film to shrink along the contour of the bottle body. The sleeve shrinking method is a more commonly used process, and the rolling method is rapidly developing. The extrusion process of the overall sleeve shrink film usually includes a horizontal orientation process. After the film is printed, it is made into a cylindrical label, and then the processing machine cuts the cylindrical label into a sleeve label with a certain length. Then the bottle is placed inside the sleeve label, and then the bottle and the sleeve label are passed through a steam or Infrared light is the drying tunnel that heats the medium. The heat causes the sleeve label to shrink and generate a label close to the bottle body. The typical shrinkage of the film ranges from 50% to 80%. Bottles with irregular geometries are suitable for this sleeve labeling system with high shrinkage. The most commonly used resin materials for sleeve shrink film are PVC, polyethylene glycol modified polyester (PETG) and oriented polystyrene (OPS). The rolling process must first have a pre-printed film, and the film material is wrapped around the bottle body to form a closed structure through the picking process and the bonding and supporting effect of the hot melt adhesive, and then the packaged bottle body is sent into a hot baking The heat in the drying tunnel causes the film to shrink tightly against the surface of the bottle. Biaxially oriented polypropylene (OPP) is the most commonly used resin material for rolling systems. Since the OPP heat shrinkable film has an orientation effect on the machine, the final shrinkage of the shrink film by the rolling method is smaller than that of the sleeve method, in the range of 5% -20%. Common bottle materials are PET, PP, HDPE or glass. Rolling method is generally suitable for bottle structure with low shrinkage and less complicated structure.
There are various forms of printing on heat shrinkable film labels, from low-cost flexographic printing to 10-color, photo paper-quality gravure printing.
PVC (polyvinyl chloride) film
Because PVC has a lower cost advantage than other competing materials (such as PETG and OPS materials), this advantage has become one of the important reasons for its widespread use in the development of heat shrinkable sleeve material. PVC has a large shrinkage rate and a wide temperature shrinkage range, which does not require high heat sources, and does not require careful control of heating equipment. But environmental issues, especially in Europe, have begun to change the market for PVC shrink labels. In addition, because the proportions of the two resin materials, PVC and PET, are equal, the flotation separation technology used in recycling cannot function well, which makes it difficult to separate the PVC label from the PET bottle body. The maximum shrinkage of PVC material is about 65%.
PVC film also began to appear in the roll-to-roll heat shrink film. The American PVC heat shrinkable film supplier Klockner Pentaplast Company introduced that the maximum shrinkage of roll film of other materials can only reach 20%, and the shrinkage of PVC roll film made on its five-color label film printing production line can be as high as 45%.
PETG (modified polyester) film
Although PETG film is more expensive than PVC film, it has the largest shrinkage (up to 80%) in heat shrink sleeve material. Therefore, PETG material is often selected as the label material for bottles with complex geometric shapes. In addition, PETG resin is environmentally friendly. Its bulk resin shrinks at a lower temperature than PVC and OPC. Compared with other competing materials, the temperature-shrink change of PETG is relatively flat. These properties make it possible to more precisely control the thermal shrinkage of the label in a hot drying tunnel. In this way, it is possible to obtain a PETG shrink label film with a specific gravity less than 1.0, thereby ensuring that during the recycling process of the bottle, the heat shrinkable film can be sufficiently separated from the denser material such as PET.
OPS (oriented polystyrene) film
OPS is conducive to environmental protection, and its shrinkage performance is as high as 80%, which makes OPS gain market share of heat shrinkable film labels based on the cost of PVC and is one of the reasons for its rapid development. OPS material is slightly cheaper than PETG, it has very good clarity and gloss. OPS material is particularly suitable as a label material for squeezeable bottles. Because OPS has a relatively small shrinkage in the longitudinal direction, it can produce a consistent product. In the past, OPS films had the disadvantage of being easily deformed during shipment, but now heat shrink film manufacturers have developed many relatively stable grades.
OPP (oriented polypropylene) film
OPP is a standard film material for roll-to-roll labeling systems. It is the most commonly used heat-shrinkable film label for bottles such as carbonated soft drinks and water, and it shrinks between 5% and 20%. Through the action of hot melt adhesive, OPP labels have good container adhesion properties, good anti-wear or friction properties, and high-level gloss and sharpness. The density of the rolling method OPP process is lower than that of the sleeve method. Therefore, the rolling method OPP only needs to perform a moderate label shrinking process, which can be used as a more economical alternative to the shrinkable sleeve method. The 4-layer ion-exchange polymer membrane is first thermoformed, and then placed in a basic injection mold cavity containing polypropylene or TPO material. They form an integrated structure in the membrane cavity. According to Mayco, the membrane system of this structure is suitable for producing Class A finished products on the surface of automobiles. Films can be made in monochrome or metallic colors, as well as different textures and gloss levels.
Other materials
SBC (styrene-butadiene) copolymer film is comparable to PVC. PETG and OPS are generally used for sleeve labeling. Chevron (R) Phillips Chemical launched the heat shrinkable film market under the trade name K-Resin (RK54) (SBC). The density of SBC material is lower than that of standard sleeve film material. As a result, it is said that the shrinkage rate of SBC heat shrinkable film is between 20% and 30%, which has advantages over PVC, PETG and OPS. At about 60 ° C, the K-resin product begins to shrink; it reaches a maximum of 75% at 95 ° C. According to the supplier, the shrinkage control of SBC heat shrinkable film in the hot drying tunnel is easier than other types of heat shrinkable film. The recyclable polyolefin copolymer (COC) sold under the name Topas has been promoted by its former owner, Ticona, as an alternative to heat-shrinkable label films for PVC, PETG and OPS materials. (Topas's business is managed by Topas Advanced Polymers, a joint venture between Daicel Chemical Industries and Polyplastics, effective date: January 1, 2006). In addition to having a surprisingly high shrinkage of 90%, COC materials are also reported to have the advantages of being smaller than PET and being easier to separate from PET bottles. A film material based on polylactic acid (PLA) can meet the requirements of packaging manufacturers who expect the appearance of biodegradable heat shrinkable labels. It is an aliphatic polyester obtained from the fermentation of agricultural products such as corn starch. According to Seal-It, the company's heat-shrinkable film labels made with PLA can degrade in the environment after 47 days. The company also said that high transparency, printability and machinability are another advantage of PLA films.
in conclusion
Although heat shrinking is not the most economical method of plastic labeling, it can bring extraordinary visual effects to packaging products, which can also be translated into higher sales. The heat shrink film label market is growing at a double-digit rate, and a variety of different materials and processes are intensifying market competition. How to choose a suitable and special packaging system for product labeling depends on the shape of the container, the appearance to be achieved, the composition of the container, and the cost constraints faced by the product manufacturer.
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