Low density attached polyurethane foams made using a combination of frothing and blowing methods
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Solution Overview
Problem
Existing methods for producing polyurethane foam backing for textiles face challenges in achieving low density due to rapid curing and gas escape issues, limiting the production of softer carpet products and increasing costs with the use of containment layers and higher catalyst levels.
Innovation Solution
A process involving a frothed polyurethane-forming composition with specific ratios of polyols, water, physical blowing agents, and fillers, allowing for slow initial cure and subsequent expansion to achieve densities below 11 pounds/cubic foot without a containment layer, using both chemical and physical blowing agents to control viscosity and expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a chemical blowing agent is used to create cellular structure in polyurethane foam, then gas is generated during curing to form foam, but the reaction occurs too quickly allowing time for dispensing and gauging
Solution Approach 1:
The patent segments the blowing process into two distinct phases: (1) mechanical frothing of the formulation before application to create initial air incorporation, and (2) controlled chemical blowing during curing using water-isocyanate reaction. This segmentation allows the rapid chemical reaction to occur after application rather than during mixing and dispensing, resolving the timing conflict between gas generation and process execution time.
Solution Approach 2:
The patent applies preliminary mechanical frothing to the polyurethane formulation before it is applied to the textile. This preliminary action incorporates air into the formulation in advance, creating a headspace layer that will expand during curing. By performing this action before application, the system avoids the need for rapid in-situ gas generation during the critical dispensing and gauging operations.
2Quantity of substance
If a physical blowing agent is used to create cellular structure in polyurethane foam, then gas is formed by volatilization under curing conditions, but elevated temperature increases cure rate making application and gauging difficult
Solution Approach 1:
The patent extracts the physical blowing agent function from the system by eliminating the need for elevated temperature curing. Instead of using volatile liquids that require heat to vaporize, the patent relies on mechanical frothing to incorporate air and the ambient-temperature water-isocyanate reaction to generate carbon dioxide. This extraction removes the conflicting requirement for elevated temperature, allowing slow initial cure for easy application and gauging.
3Quantity of substance
If high levels of blowing agent are used to achieve low density foam, then gas quantity increases, but gas escapes through the exposed surface of the curing mixture reducing blowing efficiency
Solution Approach 1:
The patent applies beforehand cushioning by mechanically frothing the formulation to create a stable headspace layer of air bubbles before application. This pre-formed bubble structure acts as a cushion that traps subsequent gas generation during curing, preventing gas escape. The mechanical frothing creates a template of stable bubbles that confines the carbon dioxide generated during curing, maintaining blowing efficiency without requiring excessive blowing agent quantities.
Solution Approach 2:
The patent utilizes the textile substrate as a flexible barrier that confines the expanding foam formulation during curing. The textile acts as a form that holds the formulation in place, preventing gas escape through the bottom surface. Combined with the mechanical frothing headspace, this creates a confined environment that maintains blowing efficiency.
4Ease of operation
If frothed polyurethane system is used to allow slow initial cure for easy application and gauging, then density cannot be reduced below 11-12 pounds/cubic foot
Solution Approach 1:
The patent merges two blowing mechanisms: mechanical frothing (physical) and water-isocyanate reaction (chemical). The mechanical frothing creates initial air incorporation and headspace that provides the slow initial cure characteristics for easy application and gauging. The chemical reaction then generates additional carbon dioxide during curing to expand the foam and achieve densities below 11-12 pounds/cubic foot. This combination of mechanisms resolves the contradiction between ease of operation and low density achievement.
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
This process enables the production of low-density polyurethane cushions with improved softness and resilience, reducing material and operating costs while eliminating the need for containment layers, allowing for wider product range and better cushioning performance.
Implementation Method 1
A chemical blowing agent reacts under the conditions of the curing reaction to generate a gas. The most commonly used chemical blowing agent is water which, in addition to generating a gas (carbon dioxide) reacts with isocyanate groups to produce urea linkages
Implementation Method 2
Physical blowing agents are low-boiling liquids which volatilize under the curing conditions to form the blowing gas
Implementation Method 3
A gas is whipped into the foam formulation before it is applied to the textile
Data Source
AI summary
Textiles backed with a polyurethane cushion are produced by applying a layer of frothed polyurethane-forming mixture to a surface of the textile. The mixture contains both water and a physical blowing agent. The layer expands due to the action of the water and the physical blowing agent and cures to form an attached cushion having a density of 176 g/L or less.