ZIRCONIUM COMPOUNDS IN ADHESION AND ABHESION

Zirconium compounds can act as adhesion promoters and adhesion preventers, and they can improve the cohesive properties of adhesives. They are used as adhesion promoters for printing inks on polyolefins, and the mechanism has been investigated by measurements of peel adhesion, viscosity of nitrocellulose solutions, surface energies and X-ray photoelectron spectroscopy (XPS). Zirconium compounds can crosslink polymers which contain suitable functional groups, such as carboxyl and hydroxyl. This has been investigated for an emulsion polymer by swelling measurements in water, and by mechanical testing of wet and dry materials. During the reclamation of waste paper, adhesives present on the paper (termed 'stickies') cause problems in that they adhere to the processing 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 properties of polymers by acting at surfaces rather than altering bulk properties. Two types of interaction are indicated, these are the attachment of carboxylic groups to zirconium polymers and hydrogen bonding.