PAPPER MED LAOG VIKT OCH GOD STYVHET

摘要

Light-weight paper can be made as stiff as paper of 50% greater weight or more without loss of folding endurance by coating its surfaces with a freshly prepared mixture of polyvinyl alcohol or an analogous polyol or polyamine and a source of formyl groups such as a water-soluble precondensate of formaldehyde with melamine or urea in an aqueous solution viscous enough to prevent full penetration of the paper. The product has a core layer of low bulk density and surface layers of much greater density and toughness and can be processed successfully in xerographic and like copying equipment not normally capable of handling very light paper.