Waterborne Soft Touch Coatings Resolving VOC and Hardness Trade-offs
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Solution Overview
Problem
Existing soft touch coatings face a challenge in achieving both good chemical and mechanical resistance while maintaining a soft touch feel, as increasing crosslink density and hardness often compromises the soft touch properties, and most coatings are solvent-based, which raises environmental concerns due to VOC emissions.
Innovation Solution
A waterborne coating composition comprising an aqueous polyurethane resin with urethane linkages, hydrazinecarboxamide linkages, and reactive hydrazide functional groups, combined with a reactive silicone component and crosslinker, which provides a balance between chemical and mechanical resistance and soft touch feel, and is predominantly water-based to minimize VOC emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If crosslink density and hardness are increased to improve chemical and mechanical resistance, then chemical and mechanical resistance is improved, but soft touch properties deteriorate
Solution Approach 1:
The patent uses a composite coating system combining polyurethane resin with silicone components and crosslinkers to achieve both soft touch feel and chemical/mechanical resistance. The silicone-modified polyurethane acrylate resin creates a composite structure that provides tactile softness while the crosslinking network delivers durability and chemical resistance.
Solution Approach 2:
The patent optimizes the glass transition temperature (Tg) of the polyurethane resin to be less than 25°C, which is a critical parameter change that enables soft touch properties. Additionally, the crosslink density is controlled within specific ranges (0.5-5 mol/L) to balance softness and mechanical resistance, demonstrating parameter optimization to resolve the contradiction.
2Ease of operation
If solvent-based coatings are used to achieve soft touch properties, then soft touch feel is achieved, but VOC emissions increase causing environmental damage
Solution Approach 1:
The patent transitions from solvent-based to waterborne coating chemistry, changing the fundamental parameter of the coating vehicle from organic solvent to water. This allows the coating to maintain soft touch properties through resin chemistry (silicone-modified polyurethane acrylate with controlled Tg < 25°C) rather than relying on solvent plasticization, thereby eliminating VOC emissions while preserving tactile properties.
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 waterborne coating composition achieves a soft touch feel with enhanced chemical and mechanical resistance, reducing VOC emissions and avoiding the limitations of solvent-based coatings, while maintaining a pleasant tactile experience and improved durability.
Implementation Method 1
the aqueous polyurethane resin comprises urethane linkages, hydrazinecarboxamide linkages, and reactive hydrazide functional groups
Implementation Method 2
combining the mixture of the reactive silicone component and aqueous polyurethane resin with a crosslinker
Data Source
AI summary
A waterborne coating composition includes an aqueous polyurethane resin, a reactive silicone component, and a crosslinker. The aqueous polyurethane resin can have urethane linkages, hydrazinecarboxamide linkages, and reactive hydrazide functional groups. The polyurethane resin can have a glass transition temperature of less than 25°C. Methods of preparing waterborne coating compositions and substrates at least partially coated with waterborne coating compositions are also disclosed.