Aqueous Occluded Polymer Dispersion for Blister-Resistant LASD Coatings
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Solution Overview
Problem
Existing liquid applied sound damping (LASD) coatings lack sufficient water resistance, which limits their application and adoption in areas requiring moisture resistance, such as vehicle wheel wells, and they often exhibit blistering and poor damping performance.
Innovation Solution
An aqueous dispersion of multiphase occluded polymer particles is prepared by emulsion polymerization, incorporating a specific ratio of first and second monomers, including a phosphorus acid monomer, to form discrete high Tg domains within low Tg particles, enhancing water resistance and damping performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional LASD coatings are used, then damping performance and ease of application are improved, but water resistance is insufficient
Solution Approach 1:
The patent employs a composite polymer system consisting of a first polymer matrix (with Tg of -30°C to 30°C) containing phosphorus acid monomer units (0.2-5 wt%), and a second polymer phase (at least 90 wt% methyl methacrylate with Tg > 30°C) occluded within the first polymer. This multiphase composite structure creates distinct functional domains: the soft first polymer provides flexibility and adhesion, while the hard second polymer domains provide water resistance and structural integrity, preventing blistering while maintaining damping performance.
Solution Approach 2:
The invention creates local quality differentiation within the coating by forming discrete occluded particles of the second polymer (high Tg, water-resistant) distributed throughout the first polymer matrix (low Tg, flexible). Each occluded particle acts as a localized water-resistant domain, providing water resistance at critical interfaces while the continuous matrix maintains overall coating flexibility and damping characteristics.
2Adaptability or versatility
If water resistance is improved, then application areas are expanded, but coating formulation complexity increases
Solution Approach 1:
The patent segments the coating formulation into two distinct polymer phases that are synthesized separately and then combined. The first polymer is formed by emulsion polymerization of monomers including phosphorus acid monomer (0.2-5 wt%), and the second polymer (at least 90 wt% MMA) is formed separately and then occluded within the first polymer. This segmentation allows independent optimization of each phase's properties and simplifies formulation by using commercially available monomers and standard emulsion polymerization processes.
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 resulting coatings exhibit excellent water resistance, minimal blistering, and maintain high vibration damping performance, suitable for diverse applications including vehicle wheel wells.
Implementation Method 1
contacting, under emulsion polymerization conditions, first monomers and a chain transfer agent to form an aqueous dispersion of first polymer particles
Implementation Method 2
the first monomers comprise from 0.2 to 5 weight percent of a phosphorus acid monomer or a salt thereof
Data Source
AI summary
The present invention relates to a process for preparing an aqueous dispersion of multiphase occluded polymer particles comprising the steps of a) contacting, under emulsion polymerization conditions, first monomers and a chain transfer agent to form an aqueous dispersion of first polymer particles having a Tg in the range of from −30° C. to 30° C.; then b) contacting the aqueous dispersion of first polymer particles with a second monomer under emulsion polymerization conditions to form an aqueous dispersion of second polymer particles occluded within the first polymer particles, wherein the first monomers a phosphorus acid monomer or a salt thereof; and the second monomer comprises at least 90 weight percent methyl methacrylate. The aqueous dispersion of occluded polymer particles arising from the process of the present invention is useful in a formulation that can be used to prepare a water-resistant blister free LASD coating.