PROCESS FOR PREPARATION OF ALKYL AND ALCOXYALKYL-ALPHA -CYANOACRYLATES BY DEPOLYMERISATION OF POLY(ALKYL-ALPHA CYANOACRYLATES) OR POLY(ALCOXYALKYL-ALPHA -CYANOACRYLATES) AND ITS USAGE AS TECHNICAL AND/OR MEDICAL ADHESIVE

This invention is related to the preparation of alkyl or alkoxyalkyl-alpha-cyanoacrylates in monomeric form by depolymerisation of the corresponding poly(alkyl-alpha-cyanoacrylates) or poly(alkoxyalkyl-alpha-cyanoacrylates) (PCA). The PCA's are obtained preferably by base-catalyzed condensation of a cyanoacetate with formaldehyde (or a polymer of the latter). According to the invention, the poly(alkyl-alpha-cyanoacrylate) or poly(alkoxyalkyl-alpha-cyanoacrylate), the condensation product, is mixed with a depolymerisation system comprising phosphorus pentoxide P2O5, hydroquinone, ortho-phosphoric acid and para-toluenesulfonic acid. This process is realized in a batch reactor fitted with a condenser, heated at a temperature in the range of 100-300° C., under a vacuum of 0.5-50 Torr (7.10-5-7.10-3 MPa) and gives rise to monomeric alkyl-alpha-cyanoacrylates or monomeric alkoxyalkyl-alpha-cyanoacrylates, being stable in both gaseous and liquid phase. After an additional purification by vacuum distillation, these cyanoacrylates can be used as fast setting technical or medical adhesives.