Technology flexes its muscles: the hottest trends in electron beam curable laminating adhesives for flexible packaging

摘要

Recently, there has been significant interest in electron beam (EB) curable laminating adhesives for flexible packaging [1] EB curing offers a number of potential advantages over solvent-based water based and solventless adhesive systems. These advantages include: ·full bond strength achieved immediately upon cure; ·one-component systems; ·adhesive remains unchanged until cured; ·no viscosity adjustments; ·shelf-life at least six months; ·100 percent reactive systems offer near zero VOC's; ·potential for application at room temperature; ·easy clean-up; ·potential for very low misting; ·compatible with multiple ink systems including water-base, solvent-base and UV/EB curable inks; ·no isocyanates; ·and no aromatic amines. The interest in EB-curable laminating adhesives has been driven in part by the availability of new EB-curing equipment. This equipment requires a much lower capital investment compared to the previous generation of equipment. It also offers lower voltage, which allows penetration of outer films while limiting energy applied to the inner heat-seal surface. This is important for preventing EB-induced degradation of heat seal properties of certain films [2]. Although EB laminating of flexible packing materials is a new technology, EB curable inks and topcoats for other types of packaging has been in commercial use more than 20 years [3]. In addition, Uv laminating has been well established for more than 10 years. The primary use of UV adhesives has been the in-line lamination of clear films to printed labels [4]. EB laminating offers several advantages over UV laminating for flexible packaging: ·EB will penetrate printed and opaque films, while UV is limited to clear films, which allow light penetration; ·EB will typically produce higher conversion compared to UV; ·and most EB materials cure without photoinitiators. These advantages are important in order to achieve low odor and low migration to allow use in food packaging applications. One of the challenges associated with any new adhesive technology is the ability to achieve adequate bonding to the wide variety of substrates used in the flexible packaging industry. It is often very desirable to have a single adhesive that will bond to multiple substrates used within manufacturing facility. A goal of this study was to optimize the adhesive compositions for specific packaging film structures. A further goal was to identify adhesive compositions that are suitable for bonding to multiple substrates.