Preservative formulations solvent-based

Zinc in contact with wood Zinc is not generally affected by contact with seasoned wood, but oak and, more particularly, western red cedar can prove corrosive, and waters from these timbers should not drain onto zinc surfaces. Exudations from knots in unseasoned soft woods can also affect zinc while the timber is drying out. Care should be exercised when using zinc or galvanised steel in contact with preservative or fire-retardant-treated timber. Solvent-based preservatives are normally not corrosive to zinc but water-based preservatives, such as salt formulated copper-chrome-arsenic (CCA), can accelerate the rate of corrosion of zinc under moist conditions. Such preservatives are formulated from copper sulphate and sodium dichromate and when the copper chromium and arsenic are absorbed into the timber sodium sulphate remains free and under moist conditions provides an electrolyte for corrosion of the zinc. Flame retardants are frequently based on halogens which are hygroscopic and can be aggressive to zinc (see also Section 18.10). 

Butanolhemiformal may be used as a preservative for water based products with the advantage that the affinity of formaldehyde to w-butanol is stronger than in formalin to water. Additionally -butanolhemiformal can serve as a formulation aid (e.g. solvent) with antimicrobial effectiveness, for example, when a microbidde has to be formulated to a preservative. 

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. 

Historically, wood preservatives have been thought of in terms of their solubility in either water or oil-type solvents (Ibach, 1999). Thus we have so called oil-bome and water-borne preservative systems. More recently that classification has become less relevant, because, with advances in formulation chemistry active ingredients can be formulated with either type of solvent, while others may be emulsions or suspensions. Water-based preservatives often include some type of co-solvent such as an amine or ammonia to keep one or more of the active ingredients in solution. Each solvent has advantages and disadvantages depending on the application. 

Fillers (calcium carbonate, calcium sulfate, aluminum oxide, bentonites, wood flour) increase the solid content of the dispersion, and they are added up to 50%, based on PVAc. The purpose of their addition is the reduction of the penetration depth, a thixotropic behavior of the adhesive, gap filling properties, and the reduction of the adhesive costs. Disadvantages can be the increase of the white point and possibly the more marked tool wear rate due to greater hardness of the adhesive. Other components in PVAc formulations are defoamers, stabilizers, filler dispersants, preservatives, thickeners (hydro-xyethylcellulose, carboxymethylcellulose), poly(vinyl alcohols), starch, wetting agents, tackifiers, solvents (alcohols, ketones, esters), flame retardants, and others. 

In solvent-borne rubber adhesives, a variety of solvents can be chosen to control drying rate, adjust viscosity and dissolve important ingredients. Resins can be added to improve tack, wetting properties, heat resistance, bond strength and oxidation resistance. The most common resins nsed in rubber-based adhesives are rosins, rosin esters, and terpene, coumarone-indene, hydrocarbon and phenobc resins. Plasticizers and softeners reduce hardness, enhance tack and decrease cost of rubber adhesive formulations. Paraffinic oils, phthalate esters and polybutenes are typical plasticizers. Fillers are not often added to rubber adhesive formulations because they reduce adhesion. However they are sometimes used because they decrease cost and increase solution viscosity. Carbon black and titanium dioxide are also used to provide colour to the adhesives. Clays, calcium carbonate and silicates are also common fillers in rubber adhesive formulations. For water-borne adhesives, typically protective colloid, preservative, defoamers, wetting agents and emulsifiers are included in the formulations. 

Filled adhesives typically are designed for the construction and do-it-yourself trade. Filled adhesives consist primarily of the base polymer, fillers such as calcium carbonate or clay, solvents, surfactants, dispersants, preservatives, and thickeners. Formulations are specifically tailored for numerous end uses including brick mastics, carpet tile and continuous carpet adhesives, floor tile adhesives, ceramic tile, subflooring, and panel adhesives. 

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