Aqueous Body Coating Composition for Low-Temperature Curing Stability
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Solution Overview
Problem
Coating compositions with high curability at low heating temperatures exhibit insufficient storage stability and inadequate film performance, particularly in terms of hardness and water resistance, especially for inner plates in automobile body coatings.
Innovation Solution
An aqueous coating composition comprising a hydroxyl group- and carboxyl group-containing resin, a blocked polyisocyanate compound, a phosphate group-containing compound, and a basic compound with a specific pH range of 7.0 to 8.2, which includes a basic compound with an acid dissociation constant (pKa) of 7.0 to 8.5 and a boiling point of 100 to 200°C, along with a content ratio of 50 to 100% based on the mass of the basic compound, is used to form coating films at low temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If coating compositions with high curability are used to achieve low heating temperature curing, then energy consumption is reduced, but storage stability becomes insufficient
Solution Approach 1:
The patent changes the chemical parameters of the coating composition by introducing a specific basic compound with controlled pKa (6.5-9.0) and boiling point (100-200°C), along with phosphate group-containing compounds, to optimize the curing reaction at lower temperatures while maintaining storage stability through precise parameter control
Solution Approach 2:
The patent creates a composite coating system combining multiple components: hydroxyl group-containing resin, carboxyl group-containing resin, blocked polyisocyanate compound, phosphate group-containing compound, and specific basic compound, where each component contributes to both low-temperature curability and storage stability
2Temperature
If coating compositions with high curability are used to achieve low heating temperature curing, then energy consumption is reduced, but film performance such as hardness and water resistance becomes inadequate
Solution Approach 1:
The patent optimizes the chemical composition parameters including the use of blocked polyisocyanate compounds with specific NCO content (1-5 mmol/g), phosphate group-containing compounds with controlled phosphorus content (0.1-10%), and basic compounds with specific pKa ranges, enabling adequate film performance at reduced curing temperatures
Solution Approach 2:
The patent employs a composite coating formulation combining hydroxyl group-containing resin, carboxyl group-containing resin, blocked polyisocyanate, phosphate compounds, and basic compounds, where the synergistic interaction of these components ensures both hardness and water resistance are achieved even at lower curing temperatures
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The composition achieves excellent storage stability and high film performance, including hardness and water resistance, even when cured at relatively low temperatures, suitable for both outer and inner plates of automobile bodies.
Implementation Method 1
a blocked polyisocyanate compound... a hydroxyl group- and carboxyl group-containing resin
Implementation Method 2
a phosphate group-containing compound... excellent storage stability
Data Source
AI summary
Provided is an aqueous coating composition which has excellent storage stability and whereby high coating film performance in terms of hardness, water resistance, etc., can be exhibited even when the aqueous coating composition is cured at a relatively low temperature. Disclosed is an aqueous coating composition which contains (A) a resin containing hydroxyl groups and carboxyl groups, (B) a blocked polyisocyanate compound, (C) a phosphate-group-containing compound, and (D) a basic compound, and which has a pH in the range of 7.0-8.2, wherein the basic compound (D) contains a specific quantity of (D1) a basic compound which has an acid dissociation constant (PKa) in the range of 7.0-8.5 and a boiling point in the range of 100-200° C.