Polyurethane Foam Production Using Supercritical CO2 Blowing Agent
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Solution Overview
Problem
Current methods for producing polyurethane foams are limited in achieving a homogeneous cell structure and controlled use of high levels of CO2 as a blowing agent, leading to suboptimal foam density and cell size.
Innovation Solution
A method involving a mixture with a supercritical blowing agent component, an isocyanate-reactive component, and a polyisocyanate component, where the mixture is discharged through a mixing head with increased flow resistance via openings, allowing for counterpressure and subsequent relaxation to ambient pressure, resulting in fine-cell polyurethane hard foams with low density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If CO2 is used as a blowing agent in polyurethane foam production, then foam density can be reduced, but achieving a homogeneous cell structure becomes difficult when high levels of CO2 are used
Solution Approach 1:
The patent applies parameter changes by utilizing supercritical CO2 (changing the physical state parameter) and controlling pressure transitions during the foaming process. The mixture is maintained under supercritical conditions during mixing, then pressure is reduced in a controlled manner to achieve homogeneous nucleation and cell structure while incorporating high levels of CO2.
Solution Approach 2:
The patent exploits phase transitions of CO2 between supercritical, liquid, and gaseous states. The blowing agent is introduced in supercritical state, maintained under pressure during mixing, then undergoes phase transition to liquid and finally to gas during the foaming process, enabling controlled bubble formation and homogeneous cell structure.
2Quantity of substance
If high levels of CO2 are incorporated into the polyol component, then foam density decreases, but expansion control during mixing becomes impossible
Solution Approach 1:
The patent changes the physical state parameter of CO2 to supercritical during mixing, which allows high levels of CO2 to be incorporated while maintaining liquid-like behavior and enabling expansion control. The supercritical state provides unique properties that facilitate both high CO2 content and controlled expansion during the foaming process.
Solution Approach 2:
The patent performs preliminary action by pre-mixing the polyol component with high levels of CO2 under supercritical conditions before adding the isocyanate component. This preliminary mixing under controlled supercritical conditions ensures homogeneous distribution of CO2 and enables subsequent expansion control when the reaction proceeds.
3Speed
If pressure is reduced suddenly to normal pressure, then CO2 release is rapid, but homogeneous cell structure cannot be achieved
Solution Approach 1:
The patent applies periodic action by implementing a multi-stage pressure reduction process rather than a single sudden drop. The pressure is reduced in steps: first from supercritical to subcritical, then to normal pressure, with mixing and nucleation occurring at each stage. This periodic pressure control enables homogeneous cell structure while maintaining efficient CO2 release.
Solution Approach 2:
The patent performs preliminary nucleation and bubble formation at intermediate pressure stages before final pressure reduction to normal pressure. This preliminary action ensures that nucleation sites are established and distributed homogeneously before the final rapid expansion, preventing uncontrolled bubble formation.
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 approach enables the controlled use of higher CO2 levels, achieving a homogeneous cell structure and low-density, fine-cell polyurethane foams, overcoming the limitations of previous processes.
Implementation Method 1
C) a blowing agent component selected from the group comprising linear, branched or cyclic C 1 to C 6 hydrocarbons, linear, branched or cyclic C 1 to C 6 fluorocarbons, N 2 , O 2 , argon and/or CO 2 , wherein the propellant C) is in the supercritical state
Implementation Method 2
the pressure is reduced to a pressure close to the equilibrium solution pressure, whereby in the meantime the equilibrium solution pressure is undershot with the release of small amounts of carbon dioxide and the formation of a bubble microdispersion
Implementation Method 3
The reaction of isocyanate with water produces carbon dioxide, which also acts as a blowing agent
Implementation Method 4
The liquid polyurethane reactive mixture is foamed to release dissolved carbon dioxide, the foamed mixture is applied to a substrate and then cured to form block foam
Implementation Method 5
the carbon dioxide is first completely dissolved in the reactive mixture or at least one of the components polyol and isocyanate at a pressure significantly above the equilibrium solution pressure. The pressure is then reduced to a pressure close to the equilibrium solution pressure, whereby in the meantime the equilibrium solution pressure is undershot with the release of small amounts of carbon dioxide
Data Source
AI summary
The invention relates to a method for producing a polyurethane foam, wherein a mixture having the following is discharged from a mixing head through a discharge line: A) a component reactive toward isocyanates; B) a surfactant component; C) a blowing agent component selected from the group comprising linear, branched, or cyclic C1 to C6 hydrocarbons, linear, branched, or cyclic C1to C6 fluorocarbons, N2, O2, argon, and/or CO2, wherein the blowing agent C) is present in the supercritical or near-critical state; and D) a polyisocyanate component. The component A) has a hydroxyl value = 100 mg KOH/g and = 1000 mg KOH/g. The blowing agent component C) is present at least partially in the form of an emulsion, and means provided with an opening or several openings are arranged in the discharge line in order to increase the flow resistance during the discharge of the mixture comprising A), B), C), and D), wherein the cross-sectional area of the opening or the sum of the cross-sectional areas of all openings is = 0.1% and = 99.9% of the inner cross-sectional area of the discharge line.