SURFACE TREATMENT AGENT FOR USE ON A PRE-COATED METAL SHEET, COATED AND SURFACE TREATED METAL SHEET WHEREON THE SURFACE TREATMENT AGENT HAS BEEN APPLIED, AND PRE-COATED METAL SHEET WITH EXCELLENT FILM ADHESION DURING PROCESSING AND WHICH USES THE SURFACE TREATMENT AGENT

摘要

A PRIMER-TREATING AGENT FOR A PRECOATED METAL SHEET, COMPRISING EACH IN TERMS OF A SOLID CONTENT IN WATER: A POLYESTER RESIN HAVING A PARTICLE SIZE OF 50 TO 150 NM, A GLASS TRANSITION TEMPERATURE (TG) OF 0 TO 30°C AND A HYDROXYL VALUE OF 5 TO 13, IN ADDITION TO TANNIN OR TANNIC ACID, A SILANE COUPLING AGENT AND FINE PARTICULATE SILICA; WHEREIN THE PH VALUE AS THE TREATING AGENT IS 2.0 TO 6.5. THERE IS PROVIDED A STABLE PRIMER-TREATING AGENT FOR A PRECOATED METAL SHEET SUCH THAT NO PRECIPITATE IS FORMED IN THE PRACTICAL LONG-TERM OPERATION OR PRODUCING A PRECOATED METAL SHEET IN A STEADY STATE.