Flexible packaging, adhesives

Report 122 Flexible Packaging - Adhesives, Coatings and Processes, T.E. Rolando, H.B. Fuller Company. 

Ethylene acid polymer is obtained by the copolymerisation of ethylene with either acrylic or methacrylic acid. These copolymers are somewhat similar to LDPE and are found as ethylene acrylic acid (EAA) and ethylene methacrylic acid (EMA). Both are used in various packaging applications, i.e. flexible packaging, adhesive laminating, hot melts, and heat seal coatings. 

Some flexible packaging is fabricated by converters into bags and pouches. Bag material is either small monolayer or large multiwall with paper as a principal substrate. Pouches are small and made from laminations. Bags usually contain a heat-sealed or adhesive-bonded seam mnning the length of the unit and a cross-seam bonded in the same fashion. 

Water-borne adhesives are preferred because of restrictions on the use of solvents. Low viscosity prepolymers are emulsified in water, followed by chain extension with water-soluble glycols or diamines. As cross-linker PMDI can be used, which has a shelf life of 5 to 6 h in water. Water-borne polyurethane coatings are used for vacuum forming of PVC sheeting to ABS shells in automotive interior door panels, for the lamination of ABS/PVC film to treated polypropylene foam for use in automotive instmment panels, as metal primers for steering wheels, in flexible packaging lamination, as shoe sole adhesive, and as tie coats for polyurethane-coated fabrics. PMDI is also used as a binder for reconstituted wood products and as a foundry core binder. 

Trace Solvent Removal. Several papers were written by Nadeau (4) and by Gilbert (5) and co-workers on gas chromatographic methods for determining solvent traces remaining in flexible packaging films after printing or adhesive lamination. With proper equipment and techniques,... 

This paper describes an irradiation curing method which improves the mechanical, chemical, and thermal properties of multilayered flexible materials, increases the bond strength among the adhesively bonded layers, and provides flexible packages that can withstand the thermo-... 

A specific method of analysis has been developed by Sapici, a manufacturer of PU adhesives for flexible packaging, to... 

Dearborn, Mi., 26th-29th Oct. 1997, p.397-423 EPA AND FDA REGULATIONS AS FACTORS IN THE CONVERSION FROM SOLVENT TO WATERBORNE ADHESIVE SYSTEMS FOR FLEXIBLE PACKAGING Simmons R A Keller Heckman LLP (Adhesive Sealant Council)... 

This paper discusses how tightening environmental regulations in the USA are encouraging a shift from solvent-based to waterborne adhesives for use in flexible packaging applications. It also looks at how new adhesive systems have a relatively easy path to Food Drug Administration clearance for food packaging uses. 

Flexible Packaging Products Pressure-Sensitive Materials Films Adhesives... 

Rolando (2000) has reviewed the adhesives, coatings and processes used for multilayer flexible packaging. The converting processes used, include printing. 

The majority of adhesive laminations in multilayer flexible packaging are manufactured using the dry-bond process. In this technique, a liquid adhesive is applied to one substrate. The adhesive is then dried using hot air. This dried surface can be adhered to a second substrate using heat and pressure at a nip point. The adhesive formulations themselves represent a reactive chemistry (typically urethanes or acrylics) that is chosen to withstand the processing and storage/distribution environment of the filled product. The adhesives polymerise and/or cross-link during production of the laminated product. 

Energy curable adhesives for use in flexible packaging based on ultraviolet or electron beam irradiation are in their infancy. The potential use of these types of adhesive is promising due to the fast cure rate (essentially full cure on irradiation and hence low risk of migratory components) and the potentially... 

The Rapra review report on flexible packaging (Rolando, 2000), provides a large amount of information on lamination and the adhesives used in multilayer packaging. 

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