Patent ID: 9115440
Filing Date: 2015-08-25
Classification: C08G,C08L,C09D,C23C,C25D

Abstract:
1. A method for forming a multilayer coating film in a coating line comprising a chemical conversion treatment coating film (F 1 ) and an electrodeposition coating film (F 2 ), the method comprising the following steps: Step 1: immersing a metal substrate in a coating film forming agent ( Step 2: without water washing, electrodepositing a coating film forming agent ( wherein the cationic electrodeposition coating composition (I) contains 40 to 80 mass % of an amino group-containing modified epoxy resin (A) based on the total solid content of the resin component constituting the cationic electrodeposition coating composition, and the amino group-containing modified epoxy resin (A) contains 3 to 50 mass % of a poly (oxyalkylene) chain represented by Formula (1) based on the resin content of the resin (A) where Rs in the b-number of repeating units may be the same or different, each R represents a hydrogen atom or a C 1-6 alkyl group, a represents an integer from 1 to 8, and b represents an integer from 1 to 50, and wherein the amino group-containing modified epoxy resin (A) is produced by reacting an epoxy resin (a2) having an epoxy equivalent of 170 to 500 and a bisphenol (a3) with at least one poly(oxyalkylene)compound (a1) selected from the group consisting of poly(oxyalkylene) diglycidyl ethers (a13), at a ratio of 5 to 30 mass % of the compound (a1), 15 to 75 mass % of the epoxy resin (a2), and 20 to 50 mass % of the bisphenol (a3) based on the total solid content mass of the compound (a1), epoxy resin (a2) and bisphenol (a3), to obtain a modified epoxy resin (a4); and then reacting the modified epoxy resin (a4) with an amine compound (a5).