ZIRCONIUM COMPOUNDS IN ADHESION AND ABHESION

Zirconium compounds can act as adhesion promoters and adhesion prevent ers, and they can improve the cohesive properties of adhesives. They a re used as adhesion promoters for printing inks on polyolefins, and th e mechanism has been investigated by measurements of peel adhesion, vi scosity of nitrocellulose solutions, surface energies and X-ray photoe lectron spectroscopy (XPS). Zirconium compounds can crosslink polymers which contain suitable functional groups, such as carboxyl and hydrox yl. This has been investigated for an emulsion polymer by swelling mea surements in water, and by mechanical testing of wet and dry materials . During the reclamation of waste paper, adhesives present on the pape r (termed 'stickies') cause problems in that they adhere to the proces sing machinery and can cause unsightly spots on the final product. An approach to reducing the first of these problems has been the addition of zirconium chemicals during the repulping process. The process has been studied by measurements of adhesion, permeation and xps spectra. The investigations show that zirconium compounds affect the adhesion p roperties of polymers by acting at surfaces rather than altering bulk properties. Two types of interaction are indicated, these are the atta chment of carboxylic groups to zirconium polymers and hydrogen bonding .