Polyurethane Foam Curing via Composite Polyol Blends
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Solution Overview
Problem
Polyurethane and polyisocyanurate foams used in construction exhibit poor curing performance, leading to defects such as shrinkage and deformation in cored sandwich panels.
Innovation Solution
Formulations and methods involving a specific blend of aromatic polyester polyol, Novolac-type polyether polyol, and sucrose- or sorbitol-initiated polyol, combined with a polyisocyanate and blowing agent, to achieve an isocyanate index above 270, enhancing curing properties and processability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polyol formulations are used, then manufacturing simplicity is maintained, but curing performance deteriorates leading to shrinkage and deformation
Solution Approach 1:
The patent applies composite materials by formulating a polyol blend comprising multiple specific polyol components (aromatic polyester polyol, aliphatic polyester polyol, and polyether polyol) with defined functionality ranges (2.0-4.0, 2.0-3.0, and 2.0-3.0 respectively) and hydroxyl number ranges. This composite polyol formulation resolves the contradiction by achieving superior curing performance and dimensional stability through synergistic material combinations while maintaining formulation manageability through established compositional guidelines.
2Reliability
If polyol functionality is increased to improve crosslinking, then curing performance improves, but viscosity increases making processing difficult
Solution Approach 1:
The patent applies parameter changes by precisely controlling the functionality distribution across different polyol components rather than using a single high-functionality polyol. The aromatic polyester polyol contributes 2.0-4.0 functionality, aliphatic polyester polyol contributes 2.0-3.0, and polyether polyol contributes 2.0-3.0, with each component's hydroxyl number and molecular weight also optimized. This distributed parameter approach achieves adequate crosslinking density for curing performance while maintaining lower overall viscosity and improved processability compared to using high-functionality polyols alone.
3Reliability
If isocyanate index is increased above 270 to improve curing, then crosslinking density increases, but foam stability deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-establishing an optimized polyol blend composition before the foaming reaction, where the specific combination of aromatic polyester polyol, aliphatic polyester polyol, and polyether polyol with defined functionality and hydroxyl number ranges creates a formulation that can tolerate and effectively utilize high isocyanate indices (above 270). This preliminary formulation optimization ensures that when high isocyanate index is applied, the polyol blend's structured composition provides inherent stability to the expanding foam while enabling enhanced crosslinking, thus resolving the contradiction between curing performance and foam stability.
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 improves curing performance and reduces defects like shrinkage and deformation, resulting in enhanced green compressive strength and processability of polyurethane and polyisocyanurate foams, particularly beneficial for sandwich panel production.
Implementation Method 1
The foaming compositions, being liquids, may be used in pour-in-place applications to form rigid foam boards or panels
Implementation Method 2
typically these foams are closed-cell, rigid foams containing a low-conductivity gas in the cells, such as a hydrocarbon like pentane
Data Source
AI summary
Embodiments of the invention provide for polyurethane or polyisocyanurate foam formulations. The formulations include a formulated polyol, a polyisocyanate, and a blowing agent such that the stoichiometric index of the polyisocyanate to the formulated polyol is above 250. The formulated polyol includes (i) from about 20 to about 60 percent by weight of an aromatic polyester polyol, (ii) from about 10 to about 30 percent by weight of a Novolac-type polyether polyol, and (iii) from about 5 to about 40 percent by weight of a polyether polyol including a sucrose- or sorbitol-initiated polyol. Components (i), (ii), and (iii) are selected so that the formulated polyol as a whole has an average functionality of at least about 2.4.