Silver gray metal repair primer

1、 Customer background:

Domestic repair paint factory, 1K silver gray metal base paint, thermoplastic acrylic system; Feedback from the sheet metal spraying store: The base color spraying is normal, but after applying the two-component PU varnish, there are localized undercutting, wrinkling, and color spots, especially in the thin spray joint area, with a high rework rate.

2、 Original formula issue:

The original formula did not include CAB and relied solely on acrylic resin; The density of the base film is poor, and the strong solvent of PU varnish swells and dissolves the base film; If the flash drying time is insufficient, apply clear varnish to enlarge the defect.

3、 Adjustment plan:

Introduce CAB-381-0.5 and add 4 parts (by mass); To balance flexibility, 0.8 parts of CAB-551-0.2 were compounded.

CAB is pre prepared with 18% solid mother liquor (50% butyl acetate+35% xylene+15% isobutanol), and dry powder is prohibited from being directly fed into the large tank. Stir at 300-500rpm for 100 minutes until completely transparent and particle free.

Production feeding: Mix resin, solvent, and CAB mother liquor evenly, and then add aluminum silver paste at low speed. It is forbidden to grind and crush aluminum sheets at high speed.

Construction guidance: Spray 2-3 thin layers of base color, with an interval of 3-4 minutes between each layer. After the base color is completely dry and non stick to the hands, apply clear varnish. It is forbidden to apply clear varnish directly when wet.

4、 Effect verification

MEK wiping base film: significantly improved solvent resistance; The varnish no longer bites the bottom and wrinkles.

Aluminum powder orientation improvement, reducing color difference between positive and negative surfaces; The speed of flash drying has increased, and the risk of dust accumulation in the paint booth has decreased.

Cold and hot cycling -50 times between 20 ℃ and 80 ℃, with no cracking in the paint film; Interlayer adhesion level 0.