Formaldehyde-releasing compounds ethyleneglycol-hemiformals

Formaldehyde, as such, is often too volatile and too reactive to be used as a microbiodde for the protection of white minerals. It additionally produces unwelcome side-effects such as an increase in viscosity, and has an insufficiently balanced range of activity. One, therefore, continually searches for formaldehyde-releasing compounds which do not exhibit the disadvantageous formaldehyde effects but maintain or even improve the antimicrobial action of formaldehyde. However, the environmental limitations on released formaldehyde still apply. 

5- Dimethyl-tetrahydro-l,3,5-2H-thiadiazine-2-thione has a broad spectrum of high activity which covers bacteria, fungi and yeast, indicating that the substance is a specialised formaldehyde-releasing compound. 

The spectrum of activity is attractive for application in a number of industrial systems, e.g. as a broad spectrum microbidde which prevents fungal blooms in metal working fluid systems. However, there are limitations, including the finding that 3,5-Dimethyl-tetrahydro-l,3,5-2H-thiadiazine-2-thione is very unstable at increased temperatures. Under alkaline conditions it is found that more decomposition products are formed than under pH neutral conditions (e.g. wet-end system). 

The intermediate breakdown products formed under alkaline conditions have a strong smell. The preservation of filler and pigment slurries with thione has a high risk for bad smelling slurries and end product, such as paper, especially when heated in a humid environment. 

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