Acrylic-Modified Polyester Resin for Water-Based Coatings
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Solution Overview
Problem
Aqueous coating compositions used in automobile coatings often face issues with insufficient chipping resistance, coating workability, and finished appearance, particularly in shortened coating steps, due to limitations in existing formulations such as PTL 1, PTL 2, and PTL 3.
Innovation Solution
An aqueous coating composition comprising an acrylic-modified polyester resin with a polyoxyalkylene chain and a polyester part where compounds with 6 or more carbon atoms constitute 50 mass% or more, providing enhanced dispersion stability and physical properties for improved chipping resistance and coating workability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If aqueous coating compositions are used to reduce VOCs, then environmental protection is improved, but chipping resistance and coating workability deteriorate
Solution Approach 1:
The patent uses a composite resin system combining polyester resin with graft-polymers of carboxyl-containing monomers and vinyl monomers. This composite structure allows the coating to maintain aqueous formulation (reducing VOCs) while achieving adequate chipping resistance through the synergistic interaction of different polymer components and crosslinking mechanisms.
Solution Approach 2:
The patent optimizes specific parameters including acid value (15-80 mgKOH/g), hydroxy value (20-200 mgKOH/g), and molecular weight (1000-5000) of the polyester resin, along with the ratio of carboxyl-containing to vinyl monomers. These parameter adjustments enable the aqueous coating to achieve proper balance between environmental compliance and mechanical performance.
2Object-affected harmful factors
If aqueous coating compositions are used to reduce VOCs, then environmental protection is improved, but coating workability deteriorates
Solution Approach 1:
The patent adjusts key parameters including viscosity (100-5000 cP), solid content (30-70%), and the specific composition ratios of resin components. These parameter optimizations ensure proper coating flow, leveling, and application characteristics while maintaining aqueous formulation for reduced VOC emissions.
3Object-affected harmful factors
If aqueous coating compositions are used to reduce VOCs, then environmental protection is improved, but finished appearance deteriorates
Solution Approach 1:
The patent optimizes parameters affecting film formation and appearance including hydroxy value (20-200 mgKOH/g), molecular weight (1000-5000), and the ratio of functional groups. These adjustments ensure proper crosslinking density and film uniformity, achieving high-gloss, defect-free appearance while maintaining aqueous formulation.
4Productivity
If heat-curing step is omitted to shorten coating process, then productivity is improved, but chipping resistance deteriorates
Solution Approach 1:
The patent employs a self-crosslinking system where the polyester resin contains both carboxyl groups (from graft-polymerized carboxyl-containing monomers) and hydroxy groups. These functional groups react with each other during film formation to create crosslinked structures, eliminating the need for external heat-curing while achieving adequate chipping resistance.
Solution Approach 2:
The patent balances the acid value (15-80 mgKOH/g) and hydroxy value (20-200 mgKOH/g) to ensure sufficient crosslinking reactivity at ambient or moderate temperatures. This parameter optimization enables the coating to develop adequate mechanical strength without requiring prolonged or high-temperature curing cycles.
Data Source
AI summary
An aqueous coating composition containing an acrylic-modified polyester resin (A) and a reactive-group-containing resin (B), the acrylic-modified polyester resin (A) comprising as a monomer component constituting the acrylic part, a polyoxyalkylene group-containing unsaturated monomer having a weight average molecular weight of 400 or more, and the proportion of compounds having 6 or more carbon atoms of the total amount of the polyester-constituting components being 50 mass% or more.