Two-Component Clear Coating Balancing Sandability and Scratch Resistance
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Solution Overview
Problem
Existing clear coating films in automobile repair are difficult to sand without generating scratches, compromising their physical properties.
Innovation Solution
A two-pack type clear coating composition comprising a base agent with first and second hydroxy group-containing acrylic resins and a curing agent with a polyisocyanate compound, optimized to achieve a coefficient of dynamic friction of 0.35 or more, ensuring easy sandability and superior scratch resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a clear coating film is formed for automobile repair, then the coating film has lowered physical properties and is difficult to sand, but sanding is required to remove foreign matters without stopping the manufacture line
Solution Approach 1:
The patent changes the physical and chemical parameters of the coating composition by specifying precise hydroxyl value ranges for the acrylic resins (first resin: 120 mg KOH/g or less, second resin: more than 120 mg KOH/g) and controlling the ratio W1/W2 between the two resins. These parameter adjustments optimize the coating film's friction coefficient to 0.35 or more, enabling easy sanding while maintaining scratch resistance.
Solution Approach 2:
The patent uses a composite coating system combining a base agent containing two different hydroxy group-containing acrylic resins with a curing agent containing an isocyanate compound. This composite material approach creates a coating film with balanced properties: the specific resin combination provides both sandability (friction coefficient ≥0.35) and mechanical strength (scratch resistance).
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 forms a clear coating film that is easily sanded while maintaining high scratch resistance, preventing scratches during sanding and car washes.
Implementation Method 1
a base agent (A) and a curing agent (B), wherein the base agent (A) contains: a first hydroxy group-containing acrylic resin having a hydroxyl value of 120 mg KOH/g or less; and a second hydroxy group-containing acrylic resin having a hydroxyl value of more than 120 mg KOH/g, the curing agent (B) contains: an isocyanate compound
Implementation Method 2
a coefficient of dynamic friction of a surface of a coating film obtained from the two-pack type clear coating composition is 0.35 or more under a load of 50 g
Data Source
Figure 1~2
AI summary
Provided is a two-pack type clear coating composition capable of forming a clear coating film that is easily sanded while being superior in scratch resistance. A two-pack type clear coating composition including a base agent (A) and a curing agent (B), wherein the base agent (A) includes a first hydroxy group-containing acrylic resin having a hydroxyl value of 120 mg KOH/g or less and a second hydroxy group-containing acrylic resin having a hydroxyl value of more than 120 mg KOH/g, the curing agent (B) includes an isocyanate compound, and a coefficient of dynamic friction of a surface of a coating film obtained from the two-pack type clear coating composition is 0.35 or more under a load of 50 g.