Protection of metal with a novel waterborne acrylic/urethane hybrid technology

Coatings are often required to provide multiple properties that seem to be opposed to one another, or at least difficult to obtain at the same time. One key example for waterborne acrylic coatings is the desire for lower volatile organic compounds (VOC) without the loss of hardness properties. Coupling these seemingly conflicting properties with other high performance needs, such as excellent corrosion resistance and weatherability, can present a serious challenge for raw material suppliers and coatings manufacturers alike. A new waterborne technology that satisfies these many requirements will be introduced. This paper describes a unique acrylic/urethane hybrid technology which couples a hard acrylic dominant phase with a soft polyurethane minor phase, and the development of a new self-crosslinking hybrid polymer which combines the low VOC/fast hardness development balance with excellent corrosion resistance and weatherability in a single-component waterborne system. In the hybrid, the soft polyurethane phase acts as a conduit for the rapid diffusion and release of coalescent from the film, leading to improved hardness development relative to a hard acrylic alone. The soft polyurethane phase also contributes to good film formation at reduced VOC levels. The mechanism of the faster coalescent release will be discussed, along with application data showing improvements in block, print and dirt pickup resistance. The excellent corrosion resistance and durability are a consequence of the formation of polymer–pigment composite particles and a film formation process that offers improved pigment distribution in the dry film. Details of the mechanism will be discussed, along with performance properties of the new acrylic/urethane hybrid polymer in corrosion-resistant coatings for the protection of metal.