Syntheses of novel acetal-based formaldehyde-free crosslinkers

Crosslinking of polymers is a fundamental process applied in industry to enhance mechanical and physical properties of polymeric materials. Wide variety of crosslinkers are available to be used for this purpose whose structures depend on functionalities of the polymers and desired characteristics of the products. Crosslinkers can be in the form of polymeric or small molecule. As polymeric crosslinkers, formaldehyde based resins and latex binders may be given as examples of commonly used ones in coatings, adhesives and textile. N-Methylol acrylamide is one of the most commonly used monomer in latex binder composition to have crosslinkable system since it has good chemical, physical properties and self-crosslinking ability. However, it emits formaldehyde to the environment during the handling and crosslinking reaction as a side product. Formaldehyde based resins also release formaldehyde by degradation or during condensation as a side product. Formaldehyde is known as a human carcinogen compound and is harmful to the human health and the environment. Therefore there is a general tendency to limit or completely eliminate formaldehyde based chemical goods. Previous studies performed in our research group involved the syntheses of novel formaldehyde-free crosslinkers that are free radically polymerizable and their incorporation into latex binders by incorporating them into the polymer chains. This manuscript focuses on the synthesis of new formaldehyde-free crosslinkers in the form of small molecules. New crosslinkers will contain cyclic acetals as functional groups and have tetra- or tri- functional analogues. They will be used to crosslink –NH2 and -OH containing polymer chains through trans-acetalization reactions, and their crosslinking ability at different temperatures will be investigated.