Coating method and hardener for polyurethane paint

Patent metadata

Field	Value
Publication number	US-9567485-B2
Application number	US-201314412714-A
Country	US
Kind code	B2
Filing date	Jul 3, 2013
Priority date	Jul 9, 2012
Publication date	Feb 14, 2017
Grant date	Feb 14, 2017

Abstract

[Problem] To increase adhesive strength between an aqueous base coat layer and a clear coat layer in a coating method by a two-coat one-bake system where an aqueous base coat paint is coated, then a clear coat paint is coated, and these two coated films are simultaneously hardened, in comparison with the conventional method.
[Solution] Provided is a coating method using a specific hardener in a clear coat paint. Namely, the hardener is characterized in that (1) it includes a reaction product of (i) a derivative of 1,6-hexamethylene diisocyanate including a trimer and virtually not including a diisocyanate monomer, and (ii) a compound having both an active hydrogen and a hydrophilic group; and (2) viscosity at 23° C. is not more than 1,000 mPa·s. The compound having both an active hydrogen and a hydrophilic group herein is a compound having an active hydrogen-containing group and a sulfo group represented by formula (I), and preferably the sulfo group in a hardener is neutralized with a tertiary amine.

X—R—SO 3 H  Formula (I)

(in the formula, X is an amino group, alkylamino group, cycloalkylamino group, or hydroxyl group, R is an aliphatic and/or alicyclic hydrocarbon group.)

First claim

The invention claimed is:

1. A coating method comprising applying an aqueous base coat paint, without hardening the aqueous base coat paint by cross-linking, subsequently coating a clear coat paint comprising a hardener and an active hydrogen-containing resin on the base coat paint, hardening the base coat paint and the clear coat paint simultaneously by cross-linking, wherein the clear coat paint is a two-component polyurethane paint with a mole ratio of 0.9 to 2.0 in NCO/H (active hydrogen), wherein
(1) the hardener comprises a reaction product of (i) a derivative of 1,6-hexamethylene diisocyanate comprising a trimer, wherein the amount of trimers of 1,6-hexamethylene diisocyanate in the derivative of 1,6-hexamethylene diisocyanate is 55 weight % or more and wherein the amount of diisocyanate monomers included in the derivative of 1,6-hexamethylene diisocyanate is 1 weight % or less, and (ii) a compound having both an active hydrogen and a hydrophilic group; and
(2) viscosity of the hardener when it is not diluted with any organic solvent is not more than 1,000 mPa·s/23° C.

2. The coating method of claim 1 , wherein the compound having both an active hydrogen and a hydrophilic group is a compound having an active hydrogen-containing group and a sulfo group represented by formula (I), and the sulfo group in a hardener is neutralized with a tertiary amine
X—R—SO 3 H  formula (I)

wherein
X is an amino group, alkylamino group, cycloalkylamino group, or hydroxyl group, and
R is an aliphatic and/or alicyclic hydrocarbon group.

3. The coating method of claim 2 , wherein the compound represented by formula (I) is 2-(cyclohexylamino)-ethane sulfonic acid and/or 3-(cyclohexylamino)-propane sulfonic acid.

4. The coating method of claim 1 , wherein the aqueous base coat paint is an aqueous baking type paint comprising an active hydrogen.

5. A multilayer coated film comprising a base coat layer and a clear coat layer obtained by the method of claim 1 .

Assignees

• Bayer Materialscience Ag
• Covestro Deutschland Ag

Inventors

• Shigemori Tomokazu
• Morita Hiroshi

Classifications

• C08G18/8061

  masked with compounds having only one group containing active hydrogen · CPC title

• C08G18/6254

  Polymers of alpha-beta ethylenically unsaturated carboxylic acids and of esters of these acids containing hydroxy groups · CPC title

• C08G18/7818

  containing ureum or ureum derivative groups · CPC title

• B05D7/53

  Base coat plus clear coat type · CPC title

• C08G18/79

  characterised by the polyisocyanates used, these having groups formed by oligomerisation of isocyanates or isothiocyanates · CPC title