Can pretreatment for improved coat adhesion

摘要

The invention relates to use of an aqueous composition for pretreating can body stock, whereby an inorganic-organic conversion layer is formed, which effects outstanding sliding behavior of the shaped can body stock and in addition offers an outstanding holding primer for subsequent coating. The invention comprises a process in which can body stock which is deep-drawn to form a half-open can cylinder, before further shaping processes, is contacted with an acidic aqueous composition which contains water-soluble inorganic compounds of Zr, Ti, Si, Hf or Ce, water-soluble polymers having carboxyl groups or hydroxyl groups and also a dispersed wax. Both outer and inner surfaces of metallic can cylinders can be pretreated in the process. The invention also relates to an acidic aqueous composition for use in the pretreatment process, which contains water-soluble polymers selected from condensation products of glycoluril and aldehydes.

主权项

1. A process for surface-treating a can cylinder which is deep-drawn from a metal sheet comprising a tinplate, a steel sheet, or an aluminum sheet and which is open at one end, in which process at least an outer circumferential surface of the can cylinder is contacted with an acidic aqueous composition which contains:
a) at least one water-soluble compound of elements Zr, Ti, Si, Hf, and/or Ce, present in an amount of from 0.01 to 1.0 g/L with respect to a total content of said elements; b) at least one water-soluble organic resin, which comprises at least carboxyl groups or hydroxyl groups, having an acid value and/or a hydroxyl value wherein a sum of the acid value and/or hydroxyl value of the at least one water-soluble organic resin is at least 50 mg KOH/g, and present in an amount of from 0.1 to 50 g/L; and c) at least one dispersed wax, present in an amount of from 0.1 to 10 g/L; wherein said acidic aqueous composition has a pH of not less than 2 and not more than 6.