Processes for producing a multilayer coating

Patent metadata

Field	Value
Publication number	US-9631281-B2
Application number	US-201414560372-A
Country	US
Kind code	B2
Filing date	Dec 4, 2014
Priority date	Dec 4, 2014
Publication date	Apr 25, 2017
Grant date	Apr 25, 2017

Abstract

A process for multilayer coating of a metal substrate includes pretreating the metal substrate with an acidic aqueous composition comprising phosphate ions and/or a water-soluble titanium and/or zirconium compound, and water. The pretreated metal substrate optionally is flashed off and a surfacer layer of an organic-solvent based surfacer coating composition is applied. The organic-solvent based surfacer coating composition includes a polyaspartic acid ester, a polyisocyanate cross-linking agent with free isocyanate groups, a pigment and/or extender, and an organic solvent. The surfacer layer is cured.

First claim

The invention claimed is:

1. A process for multilayer coating of a metal substrate, the process comprising the steps of:
pretreating the metal substrate to be coated with an acidic aqueous composition comprising:
a) phosphate ions comprising ammonium hydrogen phosphate, b) a water-soluble titanium compound selected from the group consisting of: a hexafluoro titanium acid or a hexafluoro titanate, and optionally c) a zirconium compound selected from the group consisting of: a hexafluoro zirconium acid or a hexafluoro zirconate, wherein the acidic aqueous composition comprises about 1 to about 16% by weight, relative to the total amount of the acidic aqueous composition, of phosphate ions and about 0.5 to about 1% by weight, relative to the total amount of the acidic aqueous composition, of the water-soluble titanium and, if present, zirconium compound, calculated as elemental titanium and zirconium, and wherein the acidic aqueous composition has a pH value of about 1 to about 4; and
water in an amount of about 30% to about 99% by weight, relative to the total amount of the acid aqueous composition;

subjecting the metal substrate to a flash-off phase to form a metal oxide conversion layer on the metal substrate, said flash-off phase being performed for a time period of about 1 minute to about 2 minutes at a temperature of about 20 to about 23 degrees Celsius;
applying a surfacer layer of an organic-solvent based surfacer coating composition comprising:
a polyaspartic acid ester of formula I:

wherein X represents an n-valent organic group, obtained by removal of the amino groups from a primary polyamine or polyetheramine; R 1 and R 2 are the same or different organic groups which are inert towards isocyanate groups, R 3 , R 4 and R 5 are the same or different and represent hydrogen or organic groups which are inert towards isocyanate groups, and n represents an integer with a value of at least 2, wherein the organic-solvent based surfacer coating composition comprises about 5 to about 60% by weight, relative to the total amount of the organic-solvent based surfacer coating composition, of the polyaspartic acid ester;
a polyisocyanate cross-linking agent with free isocyanate groups, wherein the cross-linking agent consists of aliphatically and/or cycloaliphatically bound isocyanate groups with an average NCO functionality of about 2 to about 6;
at least one epoxy-functional silane compound chosen from (3-glycidoxypropyl)trimethoxysilane, (3-glycidoxypropyl)triethoxysilane, (3-glycidoxypropyl)triisopropoxysilane, beta-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and beta-(3,4-epoxycyclohexyl) ethyltriethoxysilane
at least one aldimine and/or ketimime;
pigments and/or extenders, wherein the organic-solvent based surfacer coating composition has a pigment volume concentration (PVK) of about 20% to about 65%; and
an organic solvent, wherein the surfacer layer is applied such that it has a resulting dry film thickness of about 25 to about 400 μm;

curing the surfacer layer;
applying a top coat layer overlying the cured surfacer layer; and
curing the top coat layer.

2. The process of claim 1 , wherein the acidic aqueous composition is applied by wiping.

3. The process of claim 2 , wherein the acidic aqueous composition is applied by wiping with a cloth soaked in the acidic aqueous composition.

4. The process of claim 1 , wherein the metal substrate comprises vehicle bodies or vehicle body parts.

Assignees

• Axalta Coating Systems Ip Co

Inventors

• Wissing Klaus

Classifications

• B05D7/52

  Two layers · CPC title

• C23C22/82

  After-treatment · CPC title

• C23C22/361 Primary

  containing titanium, zirconium or hafnium compounds · CPC title

• C23C28/00

  Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D · CPC title

• C23C22/83

  Chemical after-treatment · CPC title