Wood preservative formulations

Wood preservative compositions can be most easily distinguished based on either the presence of heavy metals in the formulation, such as copper, zinc and tin, or their absence in metal-free (organic) formulations. This applies equally to both fungicide and insecticide based compositions. Many authors also consider Tar Oil preservatives such as creosote as a separate class of compounds. However, for consistency, these are discussed under organic wood preservatives in the following sections. 

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Indoor household dust samples gathered by a vacuum cleaner from rooms with furniture treated with a wood-preserving formulation were analyzed for CDDs (Christmann et al. 1989b). The wood-preserving... 

Christmann W, Kloeppel KD, Partscht H, et al. 1989b. PCDD/PCDF and chlorinated phenols in wood preserving formulations for household use. Chemosphere 18 861-865. 

Biocidal applications. The use of quaternary ammonium salts in disinfecting systems for household and industrial cleaners has been known for many years [95, 96]. Alkyl-benzyldimethyl quaternaries, alkyltrimethyl quaternaries, and dialkyldimethyl quaternaries are the more commonly used biocidal quaternary ammonium salts [16]. Recently, dialkyldimethyl quaternary ammonium salts have received renewed attention as potential wood preservatives to replace the heavy metal types [97]. Metal-free wood preservative formulations containing dialkyldimethyl ammonium salts with non-halide anions, such as carboxylates, borates, and carbonates, have been developed [98, 99]. 

Table 4. The amount of PCDEs in technical chlorophenols and chlorophenol-based wood preservative formulations...

Copper has been a primary ingredient in wood preservative formulations for over a eentury because of its excellent broad-speetrum fungieidal properties, low... 

In many respects a ground contact or fresh water immersion environment represents a very consistent and high exposure hazard the same cannot necessarily be said of all above ground applieations. In certain situations, for example where moisture or organic debris ean colleet, the above ground environment may present a deterioration hazard similar to a ground contact exposure. This can be particularly problematic to the wood preservative formulator and treater. Here, the heavy duty preservatives discussed in the previous section may be more appropriate for such applications, especially in critical structural members. 

Xyligen . [BASF AG] Active ingredients for wood preservative formulations additives to glues for wood applic. 

Polychlorinated diphenyl ethers (PCDE) were found in the ng/g range in cod liver oils [138]. The PCDE profiles were compared with those of PCDEs in chlorinated phenols, wood preserving formulations, and fly ash. The primary source of PCDEs are chlorophenols but sources other than those investigated appear to be involved as well. The majority of PCDEs found in cod liver oil are mono- or di-ortho- substituted and also have chlorines in the meta and para positions. 

The use of quaternary ammonium compounds as biocides in wood preservation formulations is increasing rapidly. Their low toxicity and biodegradable properties, combined with their favourable adsorption characteristics, have led to an increase in the popularity of these products as an alternative to other wood preservative formulations such as pentachloraphenate (PCP) and chromated copper arsenate (CCA). Due to growing environmental pressure, the use of these latter products is declining and the development of alternative wood preservatives is gaining momentum. 

Used by themselves, or in combination with other modem biocides - such as systematic fungicides, bactericides or insecticides - the long-alkyl-chain quaternary ammonium compounds offer a useful tool in the development of new environmentally acceptable wood preservative formulations. The most commonly used quaternary ammonium compounds are coco(fractionated) benzyldimethylammonium chloride and didecyldimethylammonium chloride. 

This chapter aims to summarise this subject area, focussing on the most commonly encountered types of wood degrade, their recognition and the range of wood preservative formulations used to prevent degrade. 

A similar system based upon use-category is also described in the American Wood Preservers Association Standard (2002). In addition, consideration is being given to a Hazard Class 6 specifically for the application of formulations to freshly felled timber (anti-sapstain treatments). Table 1 provides clear insight into the properties that a wood preservative formulation must possess in order to be effective. 

Basidiomycete fungi. The performance of a wood preservative formulation against a range of individual wood decaying basidiomycetes can be determined using a simple wood block exposure method. 

Phenylsulphamide fungicides II, 16.]. There are two phenylsulphamide preservatives that have been evaluated and used as components of wood preservative formulations dichlofluanid [II, 16.5.] and tolylfluanid [II, 16.6.]. Both of these active ingredients target the mould and stain fungi, and have been used as components to control stain and mould in organic solvent-based systems, and in particular, for joinery (millwork) applications. However, they have very limited stability in water-based systems. 

Benzimidazole fungicides. Of the benzimidazole fungicides, both thiabendazole [II, 15.9.] and carbendazim [II, 11.4.] have been evaluated as components of wood preservative formulations. Of these, carbendazim has been valued for its activity towards stain and mould fungi, particularly in combination with chlorothalonil as noted above. Carbendazim (a breakdown product of benomyl [II, 11.5.]) has very low solubility in most solvents and therefore is most commonly applied as a dispersion in antisapstain treatments. Carbendazim is however soluble at lower pH (as an acid salt), and has been used as a mould control agent in CCA treatment solutions. Acid salts of carbendazim (hydrochloride and phosphate) have been used in the treatment of Dutch elm disease. 

Pyrethroids. More accurately described as the synthetic pyrethroids, this group of compounds has been used extensively in wood preservation for control of both beetles and termites. Activity, cost and performance characteristics vary depending upon the specific compound but most readily accepted for use in wood preservative formulations are permethrin, cypermethrin, deltamethrin, bifenthrin and cyfluthrin. In terms of activity against wood boring beetles, cyfluthrin is estimated to be 20 times more effective than permethrin, 10 times as effective as cypermethrin and twice as effective as deltamethrin when compared in laboratory evaluative procedures. However, in practice other factors need to be considered, particularly the relative vapour pressures (and therefore evaporative loss) and, in wood in soil contact, the rate of biotransformation by colonising bacteria. The pyrethroids are effective as neurotoxins, and are axonic poisons. 

From the global perspective, each country, each state or member state (in the European Community) may apply similar protocols for the regulation in use of the active substances used in a wood preservative formulation. The complexity of these requirements is certainly not a subject for this section, but it is clear that whilst the time frame for major change may be different on a global basis, the trends are the same. Put most simplistically, these changes have impacted on the wood protection industry in the following areas ... 

The science of wood protection is becoming increasingly complex from all aspects including product formulation, application, efficacy and health, safety and the environment. In addition, aesthetic properties such as colour, water repellency and long-term surface appearance are becoming as important to the consumer of treated wood products as wood preservative performance and service life. This in turn has led to a change within the wood protection industry with greater focus on the individual performance requirements for specific commodities and end uses. The selection of the most appropriate microbicides to meet these needs has become a critical part of the development process for new wood preservative formulations. 

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