Лако-красочные материалы — производство

While packaging needs remain a major concern of the appliance industry, one other cause for concern with pressure-sensitive adhesives is the potential for staining on painted sur­faces. A pressure-sensitive adhesive system may come into contact with a painted surface, either temporarily during the manufacturing process or for prolonged periods of storage, following which, on removal of the adhesive tape, slight discoloration may be observed. This may be either apparent immediately or it may not become apparent until some time later.

One suitable test to evaluate staining [26] is to use freshly painted test panels using the paint under consideration, and to these are applied strips of the tape being considered in precise locations, plus a control known to be satisfactory, marking the reverse side of the panels as to the exact location and type of each sample under evaluation. Sufficient areas of the panels are left exposed to provide a good comparison later. These panels are then aged. For the evaluation of in-process adhesive systems, the temperatures which the system can encounter during processing are used, at double the exposure time. For long­term storage evaluation, 1 week at 65°C (150°F) is usually sufficient. The adhesive tapes are then removed and any adhesive residue cleaned off with a suitable solvent ensuring that the solvent chosen does not also affect the paint. This can be a low-boiling-point aliphatic hydrocarbon, but isopropyl alcohol may be adequate. The panels are then exam­ined carefully under both daylight and artificial light for signs of color change. A Macbeth light box can be a useful source of light. For latent staining [27] using these same stripped and clearly identified panels, one half of the previous location of each adhesive tape is obscured with small metal plates or other suitable coverings. The panels are then exposed to UV light for several hours, 4h being typical, then examined for any latent staining. The UV set-up can be as previously outlined on aging, taking care to prevent any temperature build-up from the heat of the light source.