Aqueous Coating Composition for Low-Temperature Hard Film Curing
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Solution Overview
Problem
Existing aqueous base coating materials used in low-temperature bake curing processes for automobile body parts fail to achieve adequate hardness and water resistance, particularly when a clear coating material is not applied on the base layer.
Innovation Solution
An aqueous coating composition comprising a hydroxyl group-containing resin and a blocked polyisocyanate compound with a weight-average molecular weight of 20,000 to 200,000, which can be cured at temperatures between 60 to 110°C, forming a coating film with high hardness and water resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If low heating temperature is used in bake curing step, then energy consumption is reduced, but hardness and water resistance of base coating film deteriorate
Solution Approach 1:
The invention changes the molecular weight parameter of the blocked polyisocyanate compound from conventional ranges to 20,000-200,000, which fundamentally alters the curing behavior and film formation mechanism, enabling adequate film performance at lower curing temperatures while maintaining hardness and water resistance
Solution Approach 2:
The invention creates a composite coating system combining hydroxyl group-containing resin with high molecular weight blocked polyisocyanate compound, where the specific molecular weight range of the polyisocyanate provides both low-temperature curability and sufficient film durability, achieving a balance between energy savings and performance
2Device complexity
If aqueous base coating material is used without clear coating material, then coating process is simplified, but film performance deteriorates
Solution Approach 1:
By adjusting the molecular weight parameter of the blocked polyisocyanate compound to 20,000-200,000, the base coating material achieves self-sufficient film performance with adequate hardness and water resistance, eliminating the need for clear coating while maintaining reliability
Solution Approach 2:
The invention extracts the clear coating step from the traditional multi-layer coating system by enhancing the base coating material's intrinsic properties through molecular weight optimization, allowing the base coating to perform multiple functions alone
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 enables the formation of a coating film with excellent hardness and water resistance even at low curing temperatures, suitable for automobile body parts, thereby enhancing durability and performance.
Implementation Method 1
an aqueous coating composition comprising (A) a hydroxyl group-containing resin and (B) a blocked polyisocyanate compound
Implementation Method 2
heating and curing the uncured colored coating film at a temperature in the range of 60 to 110° C.
Data Source
AI summary
Provided is an aqueous coating composition that can exhibit high coating film performance even when cured at a relatively low temperature. The present invention pertains to an aqueous coating composition comprising (A) a hydroxyl group-containing resin and (B) a blocked polyisocyanate compound. The weight average molecular weight of the blocked polyisocyanate compound (B) is in a range of 20,000-200,000.