Blended Polyvinyl Acetal Resins for Low Haze Interlayers
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Solution Overview
Problem
Polymer interlayers used in safety glass and solar panels often exhibit optical defects like mottle and high haze due to incompatible poly(vinyl acetal) resins, which compromise clarity and mechanical performance, necessitating the development of compositions that balance optical and mechanical properties.
Innovation Solution
A resin interlayer comprising a blend of two poly(vinyl acetal) resins with different residual hydroxyl contents and a blending agent, where the blending agent is more compatible with one resin than the other, to enhance optical clarity and mechanical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If multilayered polymer interlayers with different glass transition temperatures are used to achieve both acoustic performance and impact resistance, then mechanical and acoustic properties are improved, but optical defects such as mottle and high haze occur due to incompatible resins with different refractive indices
Solution Approach 1:
The patent changes the chemical composition parameters of the poly(vinyl acetal) resins by controlling the residual hydroxyl content to be at least 2 weight percent different between resins. This parameter change allows the resins to remain compatible while achieving different mechanical properties, thereby resolving the optical defects caused by refractive index mismatches in multilayered structures
Solution Approach 2:
The patent creates a composite resin system by blending at least two incompatible poly(vinyl acetal) resins with different residual hydroxyl contents. This composite approach allows the interlayer to exhibit both the acoustic performance of softer resins and the impact resistance of stiffer resins, while maintaining optical clarity through proper composition design
2Ease of manufacture
If resins with different residual hydroxyl contents are blended to achieve desired mechanical properties, then processability and strength are improved, but optical clarity deteriorates due to high haze from incompatible polymer phases
Solution Approach 1:
The patent systematically varies the residual hydroxyl content parameter of the poly(vinyl acetal) resins used in the blend. By maintaining a difference of at least 2 weight percent in residual hydroxyl content between blended resins, the invention achieves compatible mixing that improves processability while preventing phase separation that would cause haze
Solution Approach 2:
The patent achieves homogeneous mixing of incompatible resins by carefully controlling the composition parameters. The blended resin composition maintains uniform distribution of components at the molecular level, preventing macroscopic phase separation and ensuring optical clarity while benefiting from the combined properties of different resins
Data Source
AI summary
Resin compositions, layers, and interlayers comprising two or more poly(vinyl acetal) resins and at least one blending agent or haze reducing agent are provided. Such compositions, layers, and interlayers exhibit enhanced optical properties while retaining other properties, such as impact resistance and acoustic performance.