- July 01, 1996, Bentley, David J., Jr.
As recently as 15 years ago, in-mold labeling was not a common technology. A desire to reduce costs was the motive for its development. A successful combination of a traditional heat-seal adhesive with some innovations in the blow molding operation led to this novel way to label and decorate containers for detergent and other cleaning and laundry products, liquid and solid foods, health and beauty aids, and miscellaneous articles such as motor oil.
Examination of the items on shelves in any grocery store, chain drug store, or similar point-of-sale location will immediately reveal the multitude of products that are packaged today using this innovative concept. The lack of a ridge at the edge of a label on a plastic container is a certain sign that the package is sporting an in-mold label.
In-mold labels have replaced glued labels, heat transfer labels, and pressure-sensitive labels in many applications because of their many advantages. Besides a lower cost during long runs, these advantages can include various filling and processing benefits and a significantly better appearance.
The first in-mold labels consisted of two-side, clay-coated paper. One side had a heat-seal adhesive, and the other side had an inked surface with an overprint coating to provide protection. Today, such paper labels comprise approximately half the in-mold label market. Labels made with a plastic film form the other portion of the market.
In-mold labels made from film offer better heat, moisture, and chemical resistance than those labels made from paper. There are also recycling advantages with film labels. However, the greatest advantage with the use of film is a decorative consideration designated the "no-label look." This means it is possible to prepare an in-mold-labeled container that actually appears to have no label at all.
All improvements seem to have associated disadvantages. This is certainly the case with film for in-mold label applications. In-mold labels made from film can cost twice as much as paper in-mold labels. There are also handling problems associated with film labels, including dimensional stability and excessive amounts of static electricity.
A common misconception with film in-mold labels is that the film melts and therefore disappears during the blow molding process. Although there is a "no-label look" for the final container, the film does, in fact, not melt. It is an integral part of the wall of the final container. Any degree of film melting would distort the graphics on the label. Instead, the film matches the container so well because it has a polymer or copolymer composition similar to that of the plastic container.
Fusing of the adhesive or special sealant layer on the reverse of the film label during the blow molding operation causes the label to adhere to the container. A clear film will then look the same as a clear container, much as a white film will look the same as a white container. Because only the graphics remain visible, it seems to the consumer that there is no label on the container. This is the obvious origin of the "no-label-look" terminology.
A particularly intriguing package is one that uses a plastic film with reverse printing. This procedure buries the graphics in the final composite wall of the container. It provides an unexcelled degree of protection for the graphics that are used to decorate and distinguish the product.
Today, films have their greatest use for in-mold label applications in those premium-grade products that can justify their higher cost or in those applications in which their resistance characteristics are necessary or desirable.
Future developments and innovations will undoubtedly cause the market share of film in-mold labels to increase further Their advantages are so exemplary that consumer product companies cannot overlook them. Eventually film in-mold labels may displace most paper in-mold labels. Then there will undoubtedly be an entirely new development in this packaging technique to replace film use as the hot item for in-mold labeling.
David J. Bentley Jr. is a recognized industry expert in polymers, laminations, and coatings with more than 30 years of experience in R&D and technical service.