Timber preservative

Specifications. Tar bulk products are covered by both national specifications and those formulated by the user. For instance, creosote for timber preservation is covered by the American Wood Preserving Association Standards (AWPA) and ASTM D350. 

Creosote oils are by far the most widely used timber preservatives (see Wood). This use dates back to 1850. Eor the treatment of railway ties and marine pilings, the BetheU or fliU-ceU process is preferred. The timber to be treated is charged to a pressure cylinder, which is evacuated to extract the air from the wood ceUs. The cylinder is then filled with hot creosote and the pressure increased to 0.8—1 MPa (ca 8—10 atm) to force the oil into the ceUs. 

Timber-preservation creosotes are mainly blends of wash oil, strained anthracene oil, and heavy oil having minor amounts of oils boiling in the 200—250°C range. Coal-tar creosote is also a feedstock for carbon black manufacture (see Carbon, carbon black). Almost any blend of tar oils is suitable for this purpose, but the heavier oils are preferred. Other smaller markets for creosote were for fluxing coal tar, pitch, and bitumen in the manufacture of road binders and for the production of horticultural winter wash oils and disinfectant emulsions. 

A pesticide is defined, under the Food and Environment Protection Act (1985), as any substance, preparation or organism prepared or used for destroying any pest . Pesticides include herbicides, fungicides, insecticides, molliiscicides, roden-ticides, growth regulators, and masonry and timber preservatives. 

In-situ timber treatment using timber preservatives... 

A few acid woods, such as oak, chestnut and Western red cedar, accelerate surface weathering of aluminium, but do not usually give rise to serious attack . Timber preservatives containing soluble copper compounds should be avoided creosote and zinc napthenate are satisfactory preservatives for wood in contact with aluminium. 

Timber Preservation-, 3rd edn.. Timber Research and Development Association and British Wood Preserving Association (1986)... 

Azaarenes are structural elements of coal and petroleum, and are found in products derived from them by pyrolysis and distillation. They are components of creosote, which has been widely used as a timber preservative. 

Used industrially as a seed fungicide and disinfectant, and as a timber preservative. 

Bardgett, R.D., T.W. Speir, DJ. Ross, G.W. Yeates, and H.A. Kettles. 1994. Impact of pasture contamination by copper, chromium, and arsenic timber preservative on soil microbial properties and nematodes. Biol. Fertil. Soils 18 71-79. 

The presence of chlorine and chlorinated compounds is also the source of dioxins and furans during paper making, and these compounds have been detected in sediments in the vicinity of a pulp and paper mill [53] and in effluents, along with polychlorinated dibenzothiophenes [54]. A recent study found high concentrations of PCDD and PCDF along with PCP in nestling tissue (Tachycineta bicolor) collected downstream of paper pulp mills, suggesting that the primary source of contaminants was the use of PCP for timber preservation [55]. In addition, it has been shown that dioxins bioaccumulate in fish downstream of pulp and paper mills [56]. The levels of chlorinated compounds of different families are shown in Fig. 3. 

All of the above environmental concerns are leading to restrictions being placed upon the use and composition of preservatives used to treat timber. Preservative systems of the future will therefore be selected not simply on the basis of criteria such as efficacy and cost, but also environmental impact, both during service and at the end of product lifetime. This will inevitably have economic implications. 

New Zealand pasture contaminated by runoff from chromated copper arsenate timber preservation facility 1991 control surface soils contained an average of 19 mg Cu/kg DW, low contamination 109 mg/kg, medium contamination 425 mg/kg, and high contamination 835 mg/kg DW soil Vegetation... 

Severe local arsenic pollution can occur adjacent to industrial enterprises producing the various arsenicals used in timber preservation and as agricultural pesticides. Concern expressed by environmental groups has led to a reduction in the use of arsenicals in agriculture over the last decade, and this trend is likely to continue. Waste disposal is the main problem in industrial arsenic production and this problem has been responsible for closing several plants in Western Europe. 

Na-PCP is highly effective in killing snails and is used extensively to kill them in places where schistosomiasis prevails. Na-PCP can kill mature snails, larva, eggs, the larva of a tapeworm, and the cercaria for disease vector control. Na-PCP is also registered as an herbicide and a timber preservative by some enterprises, and it is consumed for these purposes in... 

The majority of phenols, especially those containing chlorine, are too phytotoxic to permit their use as agricultural fungicides. They are widely used as industrial fungicides. Cresols contribute to the fungicidal action of creosote which is used as a timber preservative. Pentachlorophenol, another chlorinated phenol, and its esters are widely used as industrial biocides for the protection of such materials as wood and textiles. 

Robert A.W. Johnstone, Ph.D., is a full professor in the Department of Chemistry at the University of Liverpool, Liverpool, U.K. He possesses a D.Sc., a Ph.D., and a B.Sc. in chemistry. He is also a Fellow of The Royal Society of Chemistry (FRSC). An author and contributor to several books. Dr. Johnstone has published over 200 journal papers in natural product chemistry, catalysis in oxidation and reduction, and spectroscopy. His work has resulted in several new synthetic procedures in organic chemistry that are widely used and have provided some 30 full patents. Part of his research with industry led to a Queen s Award for Technological Achievement, an award not usually given to industrial and business enterprises and not normally given to university staff. The award concerned large-scale manufacture of an important ingredient of timber preservative by a new catalytic method, which produces about 30001 per annum of the product. Apart from his career... 

Some countries, such as New Zealand, have a well established and regulated timber preservation industry and the benefits of construction with treated timber are well appreciated by the public at large. This is not so true of the United States or Europe where treated wood for residential decking and other consumer applications is losing market share to man made materials such as plastics (Clemons, 2002). 

Vinden P and Torgnikov G (2002) Microwave conditioning of woodfor combined drying and preservative treatment. Timber Preservation 2002 technology and product opportunities to improve performance. Forest Industry Engineering Association, Rotorua, New Zealand, 7 p... 

Coal tar creosote is now commonly defined by function, and refers to "the fractions or blends of fractions specifically used for timber preservation" (IARC 1987). Coal tar creosote is referred to as creosote by the U.S. EPA. The substance is a complex mixture typically composed of approximately 85% PAHs and 2-17% phenolics (Bedient et al. 1984). The composition of the mixture may also vary across lots and across manufacturers. Properties of coal tar creosote are shown in Table 4-6. 

The herbicides of this group are mostly superseded and replaced by less toxic chemicals. Pentachlorophenol (PCP, 1) was introduced in 1936 as a timber preservative in the United States. It is produced by catalytic chlorination of phenol (Stoesser, 1937). Other procedure for the synthesis of pentachlorophenol uses the inactive hexachlorocyclohexane isomers as starting material. The isomer mixture is partially hydrolised, then from the polychlorophenol mixture formed pentachlorophenol is obtained by chlorination ... 

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