Oleophilic Polyrotaxane Coating for Hardness and Adhesion
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Solution Overview
Problem
Conventional UV curable and EB curable paints, as well as silica-based hard coating agents, face issues with paint adhesion and cracking due to high hardness and increased crosslinkage density, while two-package type acrylic urethane-based soft paints lack weatherability and stain resistance.
Innovation Solution
A curable solvent-based coating material utilizing oleophilic polyrotaxanes with hydrophilic modification groups, comprising cyclic and linear molecules with blocking groups and hydrophobic modifications, is developed to enhance marring resistance and prevent cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If UV curable paint or EB curable paint or silica-based hard coating agent is used to achieve high hardness, then marring resistance is improved, but adhesion to material deteriorates and cracking occurs due to increased crosslinkage density
Solution Approach 1:
The patent changes the chemical composition parameters by using a specific polyester resin with controlled hydroxyl value (30-70 mg KOH/g) and acid value (15-30 mg KOH/g), along with a polyisocyanate crosslinking agent in specific ratios. This parameter optimization allows achieving high hardness while maintaining adhesion and preventing cracking, resolving the contradiction between strength and reliability.
2Strength
If UV curable paint or EB curable paint or silica-based hard coating agent is used to achieve high hardness, then marring resistance is improved, but cracking occurs due to increased crosslinkage density
Solution Approach 1:
The patent optimizes the molecular weight and functional group content of the polyester resin, specifically controlling the hydroxyl value and acid value within specific ranges. This creates a balanced crosslinkage density that provides hardness while maintaining composition stability and preventing crack formation.
Solution Approach 2:
The patent creates a composite coating system combining polyester resin, polyisocyanate crosslinking agent, and various additives in specific proportions. This composite formulation achieves both high hardness and crack resistance through synergistic interactions between components, resolving the contradiction between strength and composition stability.
3Reliability
If two package type acrylic urethane-based soft paint is used to prevent chipping and cracking, then adhesion is maintained, but weatherability and stain resistance deteriorate due to tack feeling
Solution Approach 1:
The patent changes the chemical parameters by using a polyester resin with specific hydroxyl value (30-70 mg KOH/g) and acid value (15-30 mg KOH/g), which provides both adhesion and weatherability. The controlled crosslinking with polyisocyanate eliminates tack feeling while maintaining strong adhesion and improving resistance to weathering and stains.
Data Source
Figure 1
Figure 2(A)~2(B)
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AI summary
[Object] To provide a coating material for a curable solvent-based topcoating material, having excellent marring resistance, chipping resistance, producing no crack and excellent in performances such as weatherability, stain resistance, adhesion and the like, and a curable solvent-type topcoating material using such a material. [Solving means] A coating material is blended preferably in an amount of 60 to 90 % by mass relative to paint film forming components thereby to form a curable solvent-based topcoating material. The coating material includes an oleophilic polyrotaxane which includes a cyclic molecule, a linear molecule including the cyclic molecule with piercing through the cyclic molecule, and blocking groups which are placed at both end terminals of the linear molecule to prevent the cyclic molecule from leaving from the linear molecule, at least one of the above-mentioned liner molecule and the cyclic molecule having hydrophobic modification group.