QUANTUM LEAPS AND PARADIGM SHIFTS: NEW DEVELOPMENTS IN AND INNOVATIVE APPLICATIONS OF PLASTICS IN FLEXIBLE PACKAGING

摘要

Both subtle and dramatic changes in the flexible packaging industry can occur from forces within the industry and also from outside of it. In this regard, flexible packaging is similar to other segments of the overall packaging business. Internally, it is experiencing the same type of consolidation that we have seen in glass, metal cans, and paperboard. The reduction in the number os suppliers by their larger customers and closer relationships with those customers is another industry-wide trend.Externally, the government, the consumer and demographics all indirectly affect flexible packaging. The government with regulations on emissions and waste disposal plus approval of materials and processes that affect the public health; consumers with their desire for certain features in their packaging such as ease of opening with reclosability plus tamper evidence; and demographics in terms of total population sub-divided by age, sex, ethnicity and geography.More direct external factors are the inputs of material and process equipment sources and the needs of the customers of flexible packaging companies. In this category fall plastic resin and film manufacturers. (The latter may either be considered to be part of the flexible packaging industry or a supplier to it. In this paper, I tend to view film companies primarily as suppliers.)Plastics can be incorporated into flexible packaging structures by several processes. These include extrusion coatings, liquid-based coatings (water- or solvent-based) and laminations of films. The larger converters may produce some of their own films, usually polyethylene types, and rely on outside sources for more sophisticated substrates. Film suppliers have not only the opportunity to choose resin type but the film process. This includes cast or blown, mono- or multi-layer, degree and type of orientation, and heat setting.In multi-layer structures, plastics can be found in the outer, inner, or core layers. The outer layer typically carries the graphics and provides strength, temperature resistance and perhaps barrier resistance. The inner layer is the sealant and needs regulatory approval for direct food contact (if food is theproduct to be packaged) and product compatibility. The core layer is usually there as either the gas barrier or for its adhesive characteristics.Not all developments of new plastic materials for use in flexible packaging are necessarily a high priority by the resin producers. In come cases, particularly the more expensive engineering plastics, other markets are the drivers for these materials and packaging is secondary. Even when packaging is their primary focus, it may be for rigid containers such as blow molded bottles, rather than for film or flexible markets. An example here is PEN resin. In other cases, flexible packaging is their main target. In this category would fall metallocene-based polyethylenes.The most common resins and films used in flexible packaging are polyethylene and their copolymers, polypropylene, polyester, nylon, and PVC. Others used to a lesser degree include fluoropolymers, polystyrene, and barrier resins PVDC, EVOH and PAN.In addition to the choice of monomer (or monomers in the case of co- or multi-polymers), resin producers have new polymerization technologies available to them which offer a wider range of potential properties. Also, through the incorporation of additives and/or blending/compounding, resin suppliers (and to a degree the larger film producers and converters) can further modify the base polymer properties to further expand their potential.Among the new or high-growth markets that are helping to drive plastic developments in flexible packaging are pre-cut fresh produce, case-ready fresh meat, and medical/pharmaceutical. The needs of new packaging materials tend to focus on temperature resistance, barrier properties (either high or low), sterilizability, economics, good processability, regulatory approval, and availability. They may also need to be compatible with new sterilization and "smart" or "interactive" film technologies.Among the new plastics materials that can have a significant impact on flexible packaging in the upcoming years are metallocene-catalyzed PE (and cycloolefins, PP and PS), PEN, LCPs, glass-coated films, aliphatic polyketones, and high-respiratory-rate films such as styrenics like K-Resin.The remainder of this paper will review these plastics and their potential in flexible packaging.