An Overview of Emulsion Polymers Used in the Adhesives Industry

Adhesive Emulsions by Type

PVA and EVA predominate, but acrylics are steadily expanding their market share. General-purpose adhesives may be based on any one of a range of emulsions, including vinyl acetate polymers (encompassing polyvinyl acetate [PVA] and ethylene vinyl acetate [EVA]), acrylics and styrene-butadiene (SB) latex. Smaller volume types include emulsions based on polyvinyl chloride, latex nitrile and acrylonitrile copolymers. PVAs are among the least expensive materials available, while acrylics generally are the most costly, with SB latex typically falling in between.

Vinyl acetate polymers will remain the largest segment of the market, where polyvinyl acetate, ethylene vinyl acetate and other polymers serve as moderately priced, nontoxic glues. Most prominently, PVA is used as the base for both white glue and carpenter's wood glue, two versatile, general-purpose products with broad use in the consumer segment. Vinyl acetate polymer adhesives are amenable to high-speed production processes and function best in the bonding of paper and wood. In particular, PVA and EVA adhesives are widely used in paperboard packaging, particularly the side seaming of lightweight board used for small cartons or boxes. These adhesives also find use in bookbinding, on-site construction, textiles, envelopes, bags and sacks, and labels. Furniture uses include wood veneer, edge gluing and general assembly. Global demand for vinyl acetate polymer emulsions in adhesives is forecast to approach one million metric tons by 2005.

Acrylics (encompassing pure acrylics as well as styrene acrylics and vinyl acrylics) are gaining market share in adhesives, particularly in pressure-sensitive tapes and labels, such as envelopes, decal and label applications, as well as medical tapes. In these applications, acrylics function well in both removable and permanent pressure sensitive adhesives. In permanent pressure sensitive applications, acrylics offer good mechanical stability and provide the necessary high tack and peel strength. For removable applications, acrylics offer good mechanical stability and good cohesive strength. Acrylic emulsions can also be used to join a variety of substrates including metals, plastics, ceramics, wood, leather and textiles. Global demand for acrylic emulsions in adhesives markets is forecast to exceed 600,000 metric tons by 2005.

SB latex is used as the polymeric base for pressure sensitive adhesives, where SB latex tackifiers compete primarily with higher performance acrylics and specialized butyl rubber compounds. In adhesives, SB emulsions provide good resistance to water and solvents, good low-temperature properties, high tensile strength and good adhesion to a variety of substrates. Global demand for SB latex used in adhesives is forecast to exceed 400,000 metric tons by 2005.
 

Adhesive Emulsions by Market

Paper and paperboard packaging markets stable, slower growing; strongest gains forecast for tapes and labels. Emulsion-based adhesives are used primarily in packaging applications, particularly paperboard products such as boxes (corrugated, solid, folding and set-up), sanitary food containers, tubes, cans and drums. Paper packaging includes shipping sacks, along with paper bags and sacks, envelopes and associated materials. Other packaging markets include laminations such as paper/foil, foil/film and film/film. The most rapid annual gains in this segment are forecast for pressure sensitive adhesives used in the production of tapes and labels, where demand for emulsion polymers is forecast to exceed 400,000 metric tons in 2006.

One major factor behind gains in demand for tapes and labels will be the improved cost and performance characteristics of pressure sensitive tapes, which are allowing these materials to replace and/or supplement cold-set glues and, in certain circumstances, mechanical fasteners in the manufacture and assembly of durable goods. Intense functional competition for emulsions will continue to arise from various elastomer-based hot melt adhesives, particularly hot melts based on thermoplastic elastomers (TPEs) (such as Kraton styrenic block copolymers), which have carved out a strong position in tapes and labels over the last decade in United States and West European markets. The nonwovens market encompasses emulsions used in the production of various disposables, which includes diapers, feminine-hygiene products and adult-incontinence products, along with medical products. Major applications include binding together the absorbent fibers, as well as bonding the absorbent portion to the outer layer. In these uses, emulsion polymers act as binders and provide solvent resistance, wet and dry strength, and a soft-hand feel in disposable products such as towels, wipes, diaper-cover stock, feminine-hygiene products and surgical packs.