Paper 3: The Future of Packaging Adhesives

Abstract

Varying requirements necessitate numerous assembly processes, although all need fluidity which is achieved by a solid being dissolved or dispensed in fluid, or melted. A common adhesive base is a polymer, and more general dispersions are based on polyvinyl acetates; but where speed of assembly and special surfaces are needed, hot melt adhesives are used. Starch pastes and dextrines being ‘natural’ aqueous adhesives are used mainly for bonding non-synthetic porous materials. With the development of cellulose acetates, plastics, polythene, etc., and the introduction of improved machinery, synthetic adhesives became necessary. In view of the fact that hot-melt application appears to be the norm for modern packaging, applications of this type only have been enlarged upon in this paper. As it is essential that adhesive be applied with minimum waste and at a speed regulated to the packaging line there are two main types of applicator, namely, the nozzle type which applies a continuous bead of cement on to a moving web of material and the wheel type which applies a line or pattern of adhesive on to intermittently passing articles by means of a rotating transfer wheel. To arrive at the monetary expenditure it is usual to estimate in terms of milage of seam inches of bond per pound or cost per package unit. Whereas the actual amount of hot melt purchased is usable as an adhesive because it is all solid (although it does yield varying milage), in liquid adhesives the solid content, expressed as a percentage of the total volume, can be quite low. A more important cost factor is the effect of the adhesive system on the production rate of the packaging line—greater efficiency and output offset slightly higher costs. Speed packaging by fully automatic cartoning machines has been introduced and there is a trend for the package to be built around the product, involving joint activities of converter, machinery manufacturer, and adhesive manufacturer all at the same time. This era necessitates high-speed packaging machines together with complete adhesive systems for bonding natural and synthetic materials at high speed. It can be concluded that future packaging adhesives must be fast-setting, have the ability to bond synthetic materials, be automatically fed and applied, be able to withstand exacting service conditions, and adhesive systems must be introduced at the design stage of a new package.