A background to the industry
Phenolic resins are the oldest commercially manufactured synthetic polymer. They were first 'invented' by Bakeland in 1907. Although thermosetting by nature, they were the first materials to provide the design values now widely associated with thermoplastics. Accordingly, the growth of phenolic resin use was rapid in the early stages of market development and the trade name 'Bakelite' became synonymous with the product during the 1920s and 1930s. Indeed, such was the impact of the material that the name is still heavily associated with the era to this present day.
As other more colour stable thermosets began to emerge (e.g. melamine and other amino resins), the role of phenolic resins began to become more specialised. This trend was accelerated still further when thermoplastics such as polyethylene, PVC and latterly the engineering thermoplastics began to emerge, since their cost base and ease of processing offered much greater versatility of application.
The main applications for phenolic resins today are in areas where heat resistant binders are required. There is still significant use within moulding powders for items such as cookware, although the bulk of use is now found in commercial and industrial applications. A more recent trend has been the increasing use of phenolic materials because of their excellent fire properties. Developing phenolic technologies in the fields of fibre reinforced composite materials and insulation foams have shown particular potential.
The development of the industry
The original use of phenolic resins in moulding powder formulations was based mostly on novolacs and these could be produced in batch processes without the need for substantial technical innovation. The net result was a plethora of small producers each with reaction vessels with low capacity.
With the introduction of other formaldehyde based thermosets such as those based on urea and melamine (aminos), there was a tendency for resin producers to manufacture all three in order to cover the risk of product substitution. Additionally, this allowed some to back-integrate into formaldehyde manufacture.
As the demand for ‘Bakelite’ began to wane, the industry moved towards greater specialisation and phenolic resins were increasingly taken up for their excellent heat resistance. In the foundry industry they became widely used as sand binders, replacing previous pitch-based formulations. Other applications included binders for refractory equipment and grinding wheels. Additional applications in the growing automotive sector also began to emerge including use as binders for friction materials and as reinforcing agents for rubber. The effect of this activity was to create a substantial diversification of resin type and formulation. This diversification was accelerated further by the increasing use of phenolic resins in adhesives and paint formulations – particularly in the areas of can coating and printing inks.
In parallel, larger volume consumers of phenolic resin began to emerge and new uses were found as wood binders for plywood and, more latterly, as binders for mineral wool insulation. In these high volume areas, there was a tendency for the producers of the end products to back-integrate into phenolic resin manufacture and this remained a pattern throughout the period from the early 1960s to the late 1980s. It is only in recent years that captive resin manufacture has become less prevalent, for the most part because of increasing environmental and other regulatory pressure.
As the global phenolic resin industry stands today, it represents approximately 40% of total phenol consumption. However, few, if any, phenol producers have ever forward integrated into resin manufacture. This is perhaps a measure of the distinction which still exists between the high capital investment culture of the petrochemical sector and the lower capital base yet highly innovative activities of the specialist resin manufacturer.
For most resin producers, the reference to the word ‘specialist’ or ‘speciality’ would come as a welcome encouragement. However, partly because of the age of the industry and partly because of the range of resins produced and applications served, the market has never perceived phenolic resins as a ‘high tech’ speciality material. This has led to a pricing structure which only seldom supports major reinvestment. Nonetheless, existing producers have been keen to raise standards in the industry and much of the work of the European Phenolic Resins Association (EPRA) has been aimed at this task.