Waterborne Polyurethane Coating with Microfibers for Sag Elimination
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Solution Overview
Problem
Existing coating formulations for vertical surfaces, such as walls, often result in aesthetically unacceptable roller lines and streaks due to thickness differences and curing mechanisms, and existing solutions do not adequately address these issues while maintaining desirable physical properties.
Innovation Solution
Incorporating very short thermoplastic microfibers, specifically polyolefin microfibers with lengths of 1 mm or less and diameters of 0.025 mm or less, into a waterborne two-pack polyurethane coating composition comprising a polyol and an isocyanate crosslinker, which improves surface characteristics by reducing or eliminating lines and sag.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional coating formulations are applied to vertical surfaces, then the coating can be applied using common spreading techniques, but roller lines and streaks appear due to thickness differences and curing mechanisms
Solution Approach 1:
The patent modifies the rheological parameters of the coating by adding very short thermoplastic fibers (1 mm or less in length, 0.025 mm or less in diameter). These fibers change the flow characteristics and sag resistance of the coating, allowing it to maintain uniform thickness during application and curing without requiring specialized application equipment
Solution Approach 2:
The patent creates a composite coating formulation by combining very short thermoplastic fibers with the base coating matrix. This composite structure provides both the ease of application of conventional coatings and the sag resistance needed to eliminate roller lines and streaks on vertical surfaces
2Strength
If fillers or fibers are added to improve physical properties of coating, then tensile strength and chemical resistance improve, but viscosity increases and film appearance deteriorates
Solution Approach 1:
The patent carefully controls the size parameters of the added fibers (1 mm or less in length, 0.025 mm or less in diameter) to optimize the balance between reinforcement benefits and appearance maintenance. This precise parameter control allows the fibers to provide tensile strength without creating visible defects in the film appearance
Solution Approach 2:
The patent uses very short fibers that are distributed uniformly throughout the coating matrix, providing localized reinforcement throughout the film rather than concentrated reinforcement. This uniform distribution maintains consistent physical properties and appearance across the entire coating surface
Data Source
AI summary
Waterborne polyurethane coating compositions comprising a polyol, an isocyanate crosslinker, and a small amount of thermoplastic microfibers, e.g., polyolefin microfibers, having a length of less than 1 mm, exhibit a much less sag, roller lines and other surface imperfections upon application to a substrate, in particular a vertical substrate such as a wall, than analogous water borne polyurethane compositions that lack the microfibers.