Formaldehyde release biocides

Formaldehyde release biocides are perhaps the most commonly used biocides in metalworking fluids. One of die best know examples of this chemistry is hexahedron -l,3,5-tris(2-hydroxyethyl)-s-triazine, (see Figure 2). 

It does have a number of draw backs. It has poor thermal stability (a property common to most formaldehyde release biocides) and, in some instances, may cause blackening of metalworking fluid concentrates if heated above 50°C for a period of time. Recently, this active ingredient was placed on Annex 1 of the Dangerous Substances Directive having been identified as a potential skin sensitiser. This means that formulations containing efficacious levels of this class of triazine in them would have to be labelled with R43 - may cause sensitisation by skin contact. This is unacceptable to many UK customers. As this material is only bactericidal, it needs to be co-formulated with a fungicide to provide complete protection for a product. 

Another class of formaldehyde release biocide are the oxizolidines. 

Secondly, customers are applying ever greater pressures on formulators to make less use of some chemistries, for example formaldehyde release biocides. Customers would prefer preservatives that are good for die environment and possess no adverse mammalian toxicity characteristics. This would require that new actives are developed. This is unlikely considering the new regulatory frameworks. 

The pH of a metalworking fluid must be kept above neutrality in order to prevent acid corrosion of the metal In vitro, acid catalyzed nitrosation is optimized at pH 3.5 (4 0) however, it has been shown that In the presence of other catalysts, aqueous solutions of amines and nitrite leads to significant yields of nitrosamines at room temperature over the pH range of 6.4 to 11.0 (41). Furthermore, C-nitro-containing, formaldehyde-releasing biocides, such as bronopol or tris nitro, exert their potential catalytic effect in alkaline solution. It would thus be desirable to determine the optimum pH for a metalworking fluid that would lead to the lowest concentration of nitrosamine possible. 

Fransway AF, Schmitz NA. The problem of preservation in the 1990s. II. Formaldehyde and formaldehyde-releasing biocides Incidence of cross-reactivity and the significance of the positive response to formaldehyde. Am J Contact Dermatitis 1991 2 78-88. 

Geier J, Lessmann H, Schnuch A, et al. 1997. [Contact allergy due to formaldehyde-releasing biocides]. Allergologie 20 215-224. (German). 

Another possibility of cross reaction is found with formaldehyde-releasing biocides (Tables 8 and 9), which may cause positive test reactions (and clinical reactions) in persons sensitized to formaldehyde to a certain, varying extent (Geier et al. 1997). It is not yet clear whether the reaction to formaldehyde in patients sensitized to a formaldehyde releaser can be interpreted as a cross or as a concomitant reaction (Geier et al. 1997). 

Non-formaldehyde-releasing-biocide reactions occur slightly less frequently than reactions to formaldehyde releasers but are still potentially significant. They include ... 

Fransway AF (1991) The problem of preservation in the 1990s. I. Statement of the problem, solution(s) of the industry, and the current use of formaldehyde and formaldehyde releasing biocides. Am J Contact Dermat 2 6-23... 

Biocides that function as formaldehyde-releasers comprise about 60 % of total sales of antimicrobials (29). Thus, such antimicrobials are expected to be common additions to metalworking fluids. Examples of formaldehyde-releasing antimicrobials are tris(hydroxy methyl) nitromethane, trivially called tris nitro, 4,4 -(2-ethyl-2-... 

In addition to the chemicals evaluated in this volume, some synthetic and soluble fluids may contain chlorinated paraffins, formaldehyde (see lARC, 1995a)-releasing biocides, microbial contaminants and metal and metal alloy contaminants (National Institute for Occupational Safety and Health, 1998). 

Richardson, C.R., Styles, J.A. Burlinson, B. (1983) Evaluation of some formaldehyde-release compounds and other biocides in the mouse mieronueleus test. Mutat. Res., 124, 241-246... 

Formaldehyde is released by numerous agents, such as paraformaldehyde, dichlorophene, Dowicil 75 and Dowicil 200 (c/s-l-(3-chloroalkyl)-3,5,7-triaza-l-azonia-adamantane chloride), bronopol. Biocide DS 52-49 (1,2-benzoisothiazoline-3-one plus a formaldehyde releaser), and Bakzid (cyclic aminoacetal). Formalin is an alternative name for an aqueous solution of formaldehyde, but the latter name is preferred, since formalin is also used as a brand name in some countries. 

Chem. Descrip. 1,2-Benzisothiazolin-3-one aq. sol n. in propylene glycol Uses Biocide effective against bacteria, yeast, and fungi for use in latexes, emulsion paint, aq. slurries, adhesives, tape joint compds., o/w emulsions, paper coating compositions, pesticides, water-based inks, hides and skins USDA approved for paints used in Federally inspected plants and packing adhesives having min. contact with meat or poultry food prods. food pkg. adhesives, paper food-contact slimicide Features Heat-stable, readily degradable In environment low corrosivity no formaldehyde released... 

Empirical C7H12N2O4 Properties M.w. 188.21 Toxicology LD50 (oral, rat) 2 g/kg primary irritant TSCA listed Precaution May release formaldehyde Uses Biocide antimicrobial, preservative for cosmetics, pharmaceutical topicals intermediate... 

Some biocides are formaldehyde-releasing agents, and this may sometimes be the basis of their biocidal properties. Those described as sensitisers include ... 

Aza-5-ethyl-3,7-dioxabicyclo(3,3,o)octane (Bioban CS 1246), 1% pet [biocide, formaldehyde releaser use in metal-working fluids forbidden in Germany (Geier et al. 1996)]... 

Bromo-2-nitro-i,3-propandiol (Bronopol), 0.5% pet (biocide, formaldehyde releaser)... 

Chloroacetamide, 0.2% pet (biocide) i,3,5-tris(2-Hydroxyethyl) -hexahydrotriazine (Grotan BK), 1% pet (biocide, formaldehyde releaser) 4-Aminoazobenzol (solvent yellow 1), 1% pet (color) Triclosan (Irgasan DP 300), 2% pet (biocide) Benzotriazole, 1% pet (corrosion inhibitor) Benzylhemiformal (Preventol D2), 1% pet (biocide, formaldehyde releaser) p-tert-Butylcatechin, 1% pet... 

As the continuing trend away from solvent-based paints in favor of aqueous products accelerates, the variety of available preservatives has kept pace. These can be generically deseribed as nitrogen and/or sulfm-containing organic biocides. Many of these are actually formaldehyde releasers, which largely accounts for their effeetiveness, but in some cases limits their use. 

Isothiazolinones are a class of broad-spectrum biocides used as preservatives in many household and industrial products. They are used in cosmetics and shampoos as a biocide to kill fungi and bacteria. Unlike the preservatives DMDM hydantoin and imidazolidinyl urea, also commonly used in these products, isothiazolinones do not release formaldehyde, to which some people are sensitive. On the other hand, some people are sensitive to isothiazolinones. 

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