Aqueous Coating Composition for Low-Temperature Glass Adhesion
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Solution Overview
Problem
Existing coating materials struggle to achieve high coating film performance, such as hardness and water resistance, while maintaining storage stability and glass adhesiveness, especially when cured at lower temperatures, which is desirable for energy conservation in automotive manufacturing.
Innovation Solution
An aqueous coating material composition comprising a hydroxyl group- and carboxyl group-containing resin, a blocked polyisocyanate compound, a polycarbodiimide compound, and a basic compound with a specific pH range of 8.0 to 11.5, including a basic compound with a PKa of 7.0 to 8.5 and a boiling point of 100 to 200°C, is used to form a multilayer coating film at a temperature of 60 to 110°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a coating material composition with high reactivity is used to achieve high curability at low heating temperature, then coating film performance such as hardness and water resistance is improved, but storage stability deteriorates
Solution Approach 1:
The patent applies preliminary action by using a blocked polyisocyanate compound where the polyisocyanate groups are预先 blocked with a blocking agent. This prevents premature reaction and maintains storage stability, while allowing the reaction to proceed when heated to the curing temperature range of 60-110°C, thus achieving both storage stability and curability at low temperature.
Solution Approach 2:
The patent employs parameter changes by selecting a blocking agent with a specific blocking temperature that matches the desired curing temperature range. The blocking agent releases the polyisocyanate groups at temperatures between 60-110°C, transforming the material from a stable blocked state during storage to an active curing state during application, thereby resolving the contradiction between storage stability and curability.
2Strength
If the intermediate coating film is softened to improve chipping resistance, then chipping resistance is improved, but adhesion to member deteriorates due to cohesive failure or peeling
Solution Approach 1:
The patent applies local quality by creating different functional zones within the intermediate coating film through the use of multiple resins with different properties. The hydroxyl group-containing resin provides flexibility and chipping resistance in certain regions, while the carboxyl group-containing resin ensures strong adhesion to the electrodeposition coating film and member in other regions, thus achieving both chipping resistance and adhesion simultaneously.
Solution Approach 2:
The patent uses composite materials by combining multiple resins (hydroxyl group-containing resin, carboxyl group-containing resin) with different functional properties in the intermediate coating composition. This composite approach allows the coating film to exhibit both flexibility for chipping resistance and strong bonding capability for adhesion, resolving the contradiction between these two properties.
3Use of energy by stationary object
If a three-coat one-bake (3C1B) technique is used instead of three-coat two-bake (3C2B) to conserve energy, then energy consumption is reduced, but coating film performance and storage stability become difficult to achieve simultaneously
Solution Approach 1:
The patent applies universality by designing an intermediate coating composition that performs multiple functions simultaneously: it provides storage stability through the blocked polyisocyanate system, achieves curability at low temperature (60-110°C) matching the base coat curing conditions, ensures strong adhesion through carboxyl and hydroxyl groups, and delivers excellent chipping resistance through the resin combination. This multi-functional composition enables the 3C1B process to achieve all performance requirements while reducing energy consumption by eliminating the separate intermediate coat curing step.
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 forms a coating film with good glass adhesiveness, high hardness, and water resistance even when cured at relatively low temperatures.
Implementation Method 1
an aqueous coating material composition including (A) a hydroxyl group- and carboxyl group-containing resin, (B) a blocked polyisocyanate compound
Implementation Method 2
an aqueous coating material composition including (A) a hydroxyl group- and carboxyl group-containing resin, (B) a blocked polyisocyanate compound, (C) a polycarbodiimide compound
Implementation Method 3
the aqueous coating material composition has a pH in a range from 8.0 to 11.5
Data Source
AI summary
An object of the present invention is to provide an aqueous coating material composition that has excellent storage stability and that demonstrates high coating film performance and strong glass adhesiveness even when cured at a relatively low temperature. The present invention discloses an aqueous coating material composition including (A) a hydroxyl group- and carboxyl group-containing resin, (B) a blocked polyisocyanate compound, (C) a polycarbodiimide compound, and (D) a basic compound. The basic compound (D) includes (D1) a basic compound having an acid dissociation constant (PKa) in a range from 7.0 to 8.5 and a boiling point in a range from 100 to 200° C. A content ratio of the basic compound (D1) is in a range from 30 to 100 mass % based on the mass of the basic compound (D). The aqueous coating material composition has a pH in a range from 8.0 to 11.5.