Aqueous surface treatment agent, surface-treated galvanized steel sheet and method of manufacturing the same

Abstract

This invention provides an aqueous surface treatment agent, a surface-treated galvanized steel sheet, and a method for manufacturing the same. By controlling the molar ratio of an aminosilane coupling agent to an epoxysilane coupling agent, an organosilicone compound with a specific structure can be generated, allowing the aqueous surface treatment agent to cure into a film at a lower temperature. This results in a surface-treated galvanized steel sheet with excellent solvent resistance and corrosion resistance.

Claims

1. An aqueous surface treatment agent, comprising: An organosilicone compound (A), wherein the organosilicone compound (A) is obtained by reacting an aminosilane coupling agent (A1), an epoxysilane coupling agent (A2), and an acidic solution (A3), wherein the molar ratio (A1 / A2) of the aminosilane coupling agent (A1) and the epoxysilane coupling agent (A2) is 0.9 to 1.5, and the organosilicone compound (A) comprises: a monocondensed silicon atom (T1), wherein the monocondensed silicon atom (T1) has a silicon-oxygen bond (Si-O-Si); A bis-condensation silicon atom (T2), wherein the bis-condensation silicon atom (T2) has two silicon-oxygen bonds; and a fully condensation silicon atom (T3), wherein the fully condensation silicon atom (T3) has three silicon-oxygen bonds; and a polycarbonate-based cationic polyurethane resin (B).

2. The water-based surface treatment agent as claimed in claim 1, wherein the content ratio (T1 / T3) of one of the monocondensed silicon atoms (T1) and the fully condensed silicon atoms (T3) is not greater than 0.

07.

3. The water-based surface treatment agent as claimed in claim 1, wherein the content ratio (T1 / T3) of one of the monocondensed silicon atoms (T1) and the fully condensed silicon atoms (T3) is 0.05 to 0.

07.

4. The water-based surface treatment agent as claimed in claim 1, wherein the content ratio (T2 / T3) of one of the biscondensation silicon atoms (T2) and the whole condensation silicon atoms (T3) is not greater than 0.

42.

5. The aqueous surface treatment agent as claimed in claim 1, wherein the content ratio (T2 / T3) of one of the dicondensation silicon atoms (T2) and the fully condensation silicon atoms (T3) is 0.34 to 0.

42.

6. The aqueous surface treatment agent as claimed in claim 1, wherein the molar ratio (a3 / A1) of the hydrogen ions (a3) ​​dissociated from the acidic solution (A3) to one of the aminosilane coupling agents (A1) is 0.9 to 1.

1.

7. The water-based surface treatment agent as claimed in claim 1, wherein the total solid content of the water-based surface treatment agent is 100 wt%, and the organosilicone compound (A) is 45 wt% to 55 wt%.

8. The aqueous surface treatment agent as claimed in claim 1, wherein the total solids content of the aqueous surface treatment agent is 100 wt%, and the polycarbonate cationic polyurethane resin (B) is 25 wt% to 35 wt%.

9. A method for manufacturing a surface-treated galvanized steel sheet, comprising: coating a surface of a galvanized steel sheet with an aqueous surface treatment agent as described in any one of claims 1 to 8; and performing a drying step on the aqueous surface treatment agent to obtain a dried coating film, wherein a peak metal temperature (PMT) of the drying step is 40°C to less than 50°C, and the dried coating film is formed on the galvanized steel sheet.

10. A surface-treated galvanized steel sheet, which is produced by the method of manufacturing the surface-treated galvanized steel sheet described in claim 9, wherein the film weight of the surface-treated galvanized steel sheet is from 0.5 g / m2 to 1.2 g / m2.