Preservatives for the Market Preservatives?
- or the Market for
C.R. Coggins RENTOIUL LTD.. FELCOURT, EAST GRINSTEAD. WEST SUSSEX RH19 UY,UK
INTRODUCTION The need for effective wood preservatives has always existed. Accounts exist of methods employed, for example, by the ancient Greeks, the Romans, the Chinese and Alexander the Great in ancient Persia. These efforts were almost Inevitably in vain becauee the ancients did not understand the causes of wood decay and their use of sea water and various oils was doomed to failure. The industrial revolution brought demands for the effective preservation of poles, sleepers and mine timbers, providing Its own answers in the form of creosote oil as a by-product of the processing of coal tar and the beginnings of the metal salt Preservatives In the form of zinc or mercuric chloride. The remarkable extent of early research and development of wood Preservatives is reflected in a treatise on wood preservation of timber by W.Chain which he said:
"Almost every chemical compound of any plausibility has been suggested and submitted but the multiplicity of opinions forms nearly an inextricable labyrinth" Treatise on the Preservation of Timber, W Chapman, 1817. Simple soaking and hot-and-cold open tank methods were used alongside the vacuum-pressure method patented by Brbant in 1831 and utilised by Bethel1 in his famous 1838 patent covering the impregnation of timber with creosote oil by the full-cell process. Also in 1838 Boucherie developed his process for the treatment with copper sulphate of freshly-felled trees for use as poles using a simple but effective sap-displacement process. Upon these foundations was built the wood preservation industry we know today. THE EMPIRICAL AGE The shortcomings of the main metal salt preservatives zinc and mercuric chloride and copper sulphate were recognized early this century.
-
Zinc chloride has fungicidal properties but it is easily leached from timber. Furthermore, it decomposes in water releasing hydrochloric acid which destroys the wood and any metal fittings. Treated sleepers were found to have a life of less than five years.
Preservatives for the Marker
- or the Market for heservatives?
Mercuric chloride-treated timber suffered from failures in ground contact and its highly poisonous nature and other drawbacks led to its demise. Copper sulphate cannot be used in steel plants because of its corrosive nature and failures of treated wood in contact with chalky soils a160 led to its demise. Nevertheless its use on a huge scale reflected the need for even partly effective preservatives between 1860 and 1910 around 5,500,000 poles were treated with copper sulphate by the Boucherie process.
-
Of course right up to the present day creosote has continued in extremely effective use. refined and produced in accordance with strict specifications. Its oily nature and odour, however, tends to limit its use to heavy duty industrial components such as sleepera and poles. This has helped to maintain the pressure to develop cheap and effective water-borne metal salt preservatives for many end-uses. One of those who responded to that need was a young German engineer, K.H.Wolman who had gone to Silesia in 1900 where major collieries were being exploited. His attention was drawn to the problem of preservation of pit timber and he set his mind to the development of impregnating salts or compounds which would not harm wood or iron and which would resist leaching from the wood. The history of the company which Wolman founded and which still bears h i s name is in the main the history of wood preservation at least up to the period from 1900 to the second world war.
2S9
260
The Chemi.stty of Wood Preservation
sequence of patents granted to Wolman shows how he exploited first the fungicidal properties of fluorides and nitrated phenols. He then identified 5% of chromates and dichromates could that 2% advantageously be added to these substances to prevent corrosion of iron. In 1921 the need for preservation of timber in termite-infested areas led to the addition of arsenic and in the 1930's perhaps the most significant development - the increase of the chromium content to 35% to achieve fixation of the water-soluble salts in the treated wood.
A
-
Meanwhile outside Germany in the 1930's similar important developments were taking place. Gilbert Gunn patented several variants on the copper/chromium theme which he called Celcure. Kamesan in 1933 patented a new preservative in which he added copper sulphate to a previously patented mixture of arsenic the first CCA which he and chromium compounds called 'Ascu'. The standard set by this and, particularly, the later CCA formulations, of performance, cost-effectiveness, ease of use and lack of collateral problems show what a serendipitous development Kamesan made. 40 years of subsequent intensive research have failed to produce another waterborne preservative with benefits approaching those of CCA.
-
THE MODERN ERA In the period from 1950 to the present day the benefits of the copper/chromium/arsenic mixture coupled with its refinement in the form of the mixtures enshrined in British Standard 4072, Boliden
hservatives for the Market
- or the Marketfor Reservatives?
261
K33 from Sweden (AWPA Type B) and ultimately the Type C version in the USA have led to its domination of the world water-borne wood preservative markets. Other types have had local importance greater than CCA, notably the copper/chromium/boron and copper/chromium/fluoride preservatives in Germany,Switzerland and Austria, but they are part of the same generic group as CCA's, have common roots and essentially do the same job. In the same period there has grown up a market need for preservatives which can be used to treat machined joinery sections and other precision wooden building components without affecting dimensions or surface characteristics. This has been satisfied with the light organic solvent preservatives based on really quite simple mixtures of highly effective organic DDT,dieldrin,lindane,synthetic biocides pyrethroids, PCP, zinc soap8,tributyltin compounds in solvents of the white spirit type.
-
-
The period is well characterised by statistics for production of preservative treated wood in Sweden since 1950. Fig.1 shows the growth of treatments by water-borne preservatives at the expense of creosote and the birth of the organic solvent business. THE MARKET NOW AND THE FUTURE The 1990's finds the manufacturer of wood preservatives facing major difficulties associated with the growth of awareness of the requirements for health, safety and environmental protection.
262
The Chemrstr?,of Wood Pre.yenwron
Legislators are introducing new controls over the marketing and use of chemicals of all types but pesticides in particular. A debate on the background to and relevance of current developments to the wood preservation industry is out of place here but wood preservatives are subject now in some countries to the same controls as those imposed on agricultural pesticides spread directly onto the land and water in great quantity. One particular problem is the 'catching-up' exercise being carried out by product approval authorities on 'old' products like CCA and its variants, creosote and some of the earlier organic solvent preservatives. In this exercise the lists of requirements for characterisation of animal toxicity and eco-toxicity of new products are compared with data available on existing products. Data-gap callins are then implemented which may require the expenditure of millions of pounds to fill. Such matters lead to the question can the old preservatives survive? The present market for wood preservatives is characterised by:
-
an existing population of treatment plants using a very limited range of highly costeffective preservatives in accordance with well established treatment parameters and handling procedures
-
a timber trade on which our industry lives which suffers low profit margins and often
Preservativesfor the Marker
- or the Market for Preservurives?
views preservation as cost-added rather than value-added
-
strong environmental pressures form both regulatory authorities and ginger groups against all of the major preservative groups
The opportunities for research and development groups to bring new preservatives to this market are therefore tremendous today, perhaps mirroring the opportunity facing the young K.H.Wolman in Silesia in 1900. What is not open, however, is the cheap route to developments which he enjoyed. The full gamut of toxicity testing is required before products may be introduced to the market. New active ingredient toxicity testing costs run into millions of pounds against which the costs of registering a formulation based on a new active substance (€30,000 in the UK) seem to pale into insignificance, yet these are greatly in excess of anything seen by our industry before. New performance standards for wood preservatives are about to be introduced in Europe. These are productspecific and mean that the 'type' specifications like BS4072 will no longer have any role. The old or existing products may not have been tested to the new requirements and may therefore need re-testing to the same regime as entirely new preservatives. Treatment companies will have to bring their plants up to standards of health, safety and pollution control which are being both changed and raised by regulators. This is necessary, of course, but it
263
264
The Chemistty of Wood hesenation
raises the cost of staying in or entering this business to a very high level. The prospects €or the sale of new preservatives with more desirable properties are limited by the higher prices demanded by increased raw material costs and high testing costs. Thus what is needed from research and development is a combination of support for the existing products to ensure the continued availability to society of these cost-effective products where they can be used without compromising health and safety or the environment and the bringing forward of new formulations and techniques which provide realistic options for the timber trade, perhaps most importantly offering the opportunity to extend the uses of timber or timber-based materials with the added value of preservation. The old marketing adage that the company which has the right product at the right place at the right time and at the right price will be a successful company will undoubtedly prove true in the 1990's and beyond. In this context the right product will not always be the new product.
P)'
E
x n
.-c