Polyurethane adhesives and coatings: manufacture, applications, markets, and trends
ADHESIVE AND COATING INDUSTRIES: SIMILARITIES AND DIFFERENCES
Coatings and adhesives are commonly associated in polyurethane (PU) technology due to the commonality of how systems are manufactured and many of the technology trends. In both cases, a film must be applied to a surface, wet the surface, form an integral film, and adhere to the surface. In terms of raw material, applications, and markets, they are as different as people commonly understand their separate uses. More so than any other PU-based technology, coatings and adhesives are formulated systems of which the PU may represent a significant volume, but is often serving as a binder for all the other components put into the system. These additional components are often things such as solvents, solid fillers, pigments and dyes, antioxidants, tougheners, surfactants, coupling agents, coalescing agents, catalysts, defoamers, moisture scavengers, water, plasticizers, and numerous hybridizing polymers.
The technologies for producing both adhesives and coatings can be simplified into variations of reactive and unreactive systems (Fig. 10.1). The ratio of PU sold into the two markets is roughly 2:1 (Fig. 10.2). The market position of PU adhesives, sealants, and coatings is important to their overall industries, but they are by no means volume leaders (Fig. 10.3) [1-6].
Because of the highly formulated and often diluted nature of adhesive and coating products, it is challenging to obtain an accurate measure of total PU consumption for
FIGURE 10.1 Technology structure of polyurethane coatings and adhesives by format. This commonality of product offerings is the reason for grouping these technologies.
FIGURE 10.2 Relative volume of polyurethane used in adhesive and sealants versus coatings.
FIGURE 10.3 Relative market position of polyurethane in (a) adhesives and sealants market and (b) coatings market. Percentages are based on dry volume.
FIGURE 10.4 Distribution of global consumption of polyurethane coatings by region.
these technologies. An analysis of the available market literature suggests that PU represents about 7-8% of all adhesive and sealant binders used with about a total of 800-900 million pounds used globally. Between the years 2005 and 2012, the annual growth rate was about 1% by volume. The coatings market accounts for about 1.5 billion pounds of PU consumption. For adhesives and sealants, the major markets are in order: construction > packaging > transportation > furniture > footwear.
Consumption of PU coatings is global and reflective of finished goods manufacturing that use PU coatings (Fig. 10.4). The global uniformity of consumption reflects the convolution of industrial, architectural, and protective applications that use PU coatings. The prominence of Japan's consumption reflects the use of PU coatings in automotive assembly and architectural coatings in that order.
There are numerous applications consuming similar volume including automotive coatings, wood coatings, artificial leathers, and protective industrial coatings. This versatility is in part responsible for the global breadth of PU that does not favor consumption based on any single manufacturing center. Further, because of highly formulated and customized solutions, each particular customer requires local technical service and production, again favoring a broad distribution of geographical consumption. For this reason, the general appearance of geographical consumption of PU adhesives would have a qualitatively similar appearance to Figure 10.4 with a smaller participation by Japan and a larger participation by the rest of the world.
The similarities in product format and global utilization belie the very different uses of adhesives and coatings and the resulting needs for specific polymer design and requirements [7-9]. In Sections, 10.2 and 10.3, adhesives and coatings will be treated separately to more fully reflect this reality.