Polyurethane Foam Wall Structure with HFO Blowing Agent
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Solution Overview
Problem
Existing foam wall structures face challenges in achieving high racking shear strength and ASTM E84 Class A flame spread and smoke development characteristics without using ozone-depleting and high global warming potential blowing agents, while also maintaining cost-effectiveness and consistency in manufacturing.
Innovation Solution
A wall structure comprising a frame with a polyurethane foam layer of at least 2.75 lb/ft3 density, formed by a polyurethane foam-forming composition including a polyisocyanate, an aromatic polyester polyol with specific functionality and OH number, a catalyst, and a hydrofluoroolefin blowing agent, which adheres to a foam panel or non-foam sheathing within the frame, ensuring Class A flame spread and smoke development characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If CFCs and HCFCs are used as blowing agents, then foam expansion and cell structure are improved, but ozone depletion and global warming occur
Solution Approach 1:
The patent changes the chemical composition parameters of the blowing agent from ozone-depleting CFCs and HCFCs to environmentally friendly HFOs (hydrofluoroolefins). This substitution maintains the necessary foam expansion and cell structure properties while eliminating the harmful environmental effects, specifically addressing both the improvement and worsening aspects of the contradiction.
Solution Approach 2:
The patent employs HFO blowing agents that, while effective for foam formation, are designed to be environmentally benign and have reduced environmental persistence compared to CFCs and HCFCs. The foam-forming composition uses these alternative agents to achieve the required foam structure without long-term environmental harm.
2Strength
If high density foam layer is used, then racking shear strength is improved, but material cost increases
Solution Approach 1:
The patent optimizes the foam density parameter to achieve a balance between structural performance and material efficiency. By carefully controlling the density of the foam layer (using the specified polyol and blowing agent combination), the formulation achieves adequate racking shear strength while minimizing the total quantity of foam material required, thus addressing both strength improvement and material quantity reduction.
Solution Approach 2:
The patent creates a composite foam structure by combining specific polyol components with HFO blowing agents and other additives to achieve optimal performance. This composite approach allows the foam to deliver high racking shear strength per unit volume, reducing the overall material quantity needed while maintaining structural integrity.
3Reliability
If Class A flame spread characteristics are achieved, then fire safety is improved, but formulation complexity increases
Solution Approach 1:
The patent achieves Class A flame spread characteristics by carefully selecting and optimizing the chemical parameters of the foam formulation, specifically using aromatic polyester polyols with controlled functionality and OH numbers. These parameter adjustments inherently provide fire resistance without requiring additional complex fire-retardant additives, thus improving fire safety while managing formulation complexity.
Solution Approach 2:
The patent uses homogeneous foam formulations where the fire-resistant properties are integrated into the base foam chemistry rather than added as separate components. The consistent composition throughout the foam layer ensures uniform fire safety performance while avoiding the complexity of multi-component fire-retardant systems.
4Productivity
If automated manufacturing is implemented, then consistency and productivity are improved, but initial investment and complexity increase
Solution Approach 1:
The patent enables preliminary mixing and formulation of the foam components in controlled manufacturing settings, allowing for consistent quality before application. The pre-formulated composition with specific polyol and blowing agent ratios can be prepared in advance, facilitating automated dispensing and application processes that improve productivity while managing system complexity through standardization.
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 solution provides a cost-effective, high-density foam layer that enhances racking shear strength and meets stringent fire safety standards, even without traditional sheathing materials like OSB or plywood, while being manufactured with reduced material and labor costs.
Implementation Method 1
The polyurethane foam layer is the cured reaction product of a polyurethane foam-forming composition comprising: a polyisocyanate, an aromatic polyester polyol having a functionality of greater than 2.5 and an OH number of at least 300 mg KOH/g
Implementation Method 2
a blowing agent composition comprising water and a hydrofluoroolefin
Implementation Method 3
The polyurethane foam layer adheres to a rear surface of the foam panel and/or, if present, a rear surface of the non-foam sheathing
Data Source
AI summary
Foam wall structures and methods for making them are described. The wall structures include a frame, a foam panel overlying a front surface of the frame, and a polyurethane foam layer disposed in a cavity of the wall structure. The polyurethane foam layer has a density, as determined by ASTM D1622-14, of at least 44 kg/m3(2.75 lb/ft3) and exhibits ASTM E84-16 Class A flame spread and smoke development characteristics. The polyurethane foam layer is the cured reaction product of a polyurethane foam-forming composition that includes a polyisocyanate, an aromatic polyester polyol having a functionality of greater than 2.5 and an OH number of at least 300 mg KOH/g, which is present in an amount of at least 50% by weight, based on the total weight of the polyurethane foam-forming composition less the weight of the polyisocyanate, a catalyst, and a blowing agent composition. The blowing agent composition includes water and a hydrofluoroolefin.