Low VOC Polyurethane Deck Membrane Formulations
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Solution Overview
Problem
Current polyurethane deck membrane products contain high levels of volatile organic compounds (VOCs), which are subject to increasingly stringent regulations, and reducing VOC content often compromises viscosity, cost, and surface properties.
Innovation Solution
Development of high-solids, high-performance polyurethane coating formulations using VOC-exempt solvents, such as methyl formate and parachlorobenzotrifluoride, with specific molecular weight ranges and NCO/OH ratios to achieve low VOC content while maintaining performance criteria, including the use of aromatic and aliphatic polyurethane pre-polymers and a combination of solvents to balance properties and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If VOC-type solvents are removed or significantly reduced from the formulation, then VOC content is reduced, but viscosity, cost, and surface properties of the coating are negatively affected
Solution Approach 1:
The patent changes the chemical parameters of the solvent system by replacing VOC-type solvents with VOC-exempt solvents (water, esters, ethers, glycols). This substitution maintains the necessary viscosity and surface properties while achieving VOC content below 97 g/L. The formulation uses specific combinations of these alternative solvents to match the performance characteristics of traditional VOC-based systems.
Solution Approach 2:
The patent creates a composite solvent system combining multiple VOC-exempt solvents (water, esters, ethers, glycols) in specific proportions. This composite approach allows the formulation to achieve the desired balance between low VOC content and maintained performance properties including viscosity, cost, and surface characteristics that would be difficult to achieve with a single alternative solvent.
2Object-generated harmful factors
If VOC content is reduced in polyurethane deck membrane products, then environmental compliance is improved, but performance features and formulation cost are compromised
Solution Approach 1:
The patent modifies the formulation parameters by incorporating VOC-exempt solvents and adjusting the polyol to polyisocyanate ratio to between 85-95% by weight. These parameter changes enable the coating to achieve VOC content below 97 g/L while maintaining essential performance features such as tensile strength, modulus, and hardness required for deck membrane applications.
Solution Approach 2:
The patent utilizes a high solids content formulation (greater than 84% solids) which creates a dense, low-porosity cured membrane. This high solids approach reduces the need for VOC solvents while ensuring the coating provides sufficient film thickness and structural integrity for protective deck membrane applications, thereby maintaining reliability despite reduced VOC content.
3Object-generated harmful factors
If VOC content is reduced in polyurethane deck membrane products, then environmental compliance is improved, but formulation cost is compromised
Solution Approach 1:
The patent adjusts the formulation parameters to use VOC-exempt solvents and optimizes the polyol to polyisocyanate ratio to 85-95% by weight. These changes reduce VOC content below 97 g/L while controlling formulation cost through efficient use of raw materials and avoidance of expensive specialty solvents, achieving a balance between environmental compliance and manufacturing economics.
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 formulations achieve VOC levels below 97 g/L for basecoats and 95 g/L for topcoats, maintaining performance characteristics like tensile strength, modulus, and hardness, while being environmentally safer and more cost-effective than conventional products.
Implementation Method 1
the pre-polymer being the reaction product of about 51 wt % to about 100 wt % aromatic polyisocyanate, 0 wt % to about 49 wt % aliphatic polyisocyanate, and a polyol selected from the group consisting of polyalkylene polyols, polyester polyols, and polycarbonate polyols
Data Source
AI summary
A basecoat coating composition includes an aromatic polyurethane pre-polymer having isocyanate terminal end groups, a first solvent and optionally a second VOC-exempt solvent, in which the total composition formulation has a VOC content of less than 97 g/L. A topcoat coating composition includes an aliphatic polyurethane pre-polymer having isocyanate terminal end groups, a first solvent and optionally a second VOC-exempt solvent, in which the total composition formulation has a VOC content of less than or equal to 95 g/L. The total composition formulations of the basecoat and/or topcoat may have a VOC content of less than 50 g/L. A membrane system may include an optional primer coating, and the above described basecoat and topcoat coating compositions.