Rigid Polyurethane Foam Viscosity and Flame Resistance
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Solution Overview
Problem
Existing rigid polyurethane foams face issues with high brittleness, dimensional instability, surface defects, and unsatisfactory fire behavior, along with challenges in mixing due to high viscosity, which affect their performance and visual acceptability in sandwich elements.
Innovation Solution
A process involving the reaction of polyisocyanates with polyetherester polyols derived from aromatic dicarboxylic acids, fatty acids, and polyether polyols, where the mass ratio of total polyetherester and polyester polyols to polyether polyols is less than 1.6, enhancing self-reactivity, solubility, and dimensional stability, while reducing brittleness and toxic compound formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyester polyols based on aromatic carboxylic acids are used to produce rigid polyurethane foams, then flame resistance is improved, but viscosity increases and mixing with isocyanate becomes difficult
Solution Approach 1:
The patent modifies the chemical composition parameters of the polyester polyol by incorporating specific aromatic dicarboxylic acids (terephthalic acid, isophthalic acid, phthalic anhydride) in controlled amounts (5-50 mol%) combined with aliphatic dicarboxylic acids and diols. This parameter optimization maintains flame resistance while controlling viscosity to enable proper mixing with isocyanate
Solution Approach 2:
The invention creates a composite polyol system combining polyester polyols with specific aromatic acid content, polyether polyols, and chain extenders. This composite approach balances the flame resistance benefits of aromatic polyesters with the lower viscosity characteristics of polyether components, achieving both fire safety and processability
2Strength
If high-functionality alcohol components like glycerol are used in rigid PU foam production, then crosslinking is improved, but dimensional stability deteriorates due to significant foam distortion
Solution Approach 1:
The patent carefully controls the functionality and amount of high-functionality alcohol components (glycerol, trimethylolpropane, pentaerythritol) within specific ranges (5-30 mol%, 2-20 mol% respectively). This parameter control enables sufficient crosslinking for mechanical strength while preventing excessive crosslinking that would cause foam distortion and dimensional instability
Solution Approach 2:
The invention distributes different alcohol components with varying functionalities throughout the polyol blend to achieve uniform crosslinking density. This local quality control ensures consistent crosslinking throughout the foam structure, preventing localized stress concentrations that would lead to distortion
3Productivity
If conventional polyol blends are used, then basic foam formation is achieved, but self-reactivity is insufficient requiring high catalyst amounts
Solution Approach 1:
The patent incorporates polyols with inherent self-reactivity characteristics, including specific functional groups and molecular structures that naturally promote reaction with isocyanate. The polyol blend composition (components B and C totaling 20-80 parts per 100 parts polyisocyanate) is designed to provide sufficient self-reactivity to reduce catalyst requirements while maintaining productive foam formation
4Reliability
If polyol components with high viscosity are used, then flame resistance and mechanical properties are improved, but meterability and mixability deteriorate
Solution Approach 1:
The patent optimizes the viscosity parameters of individual polyol components and their blends by selecting specific molecular weights, functional group densities, and compositional ratios. The polyether polyol component (20-60 parts) with lower viscosity balances the higher viscosity polyester components, achieving optimal flow characteristics for metering and mixing while maintaining flame resistance and mechanical properties
Solution Approach 2:
The invention uses polyether polyols as intermediary components that facilitate mixing between high-viscosity polyester polyols and polyisocyanate. These intermediary polyols with moderate viscosity and compatible chemical structure act as carriers that enable uniform distribution of all components during mixing while maintaining the beneficial properties of the higher viscosity components
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 process results in rigid polyurethane foams with improved brittleness, dimensional stability, and reduced surface defects, offering better fire protection and visual quality, along with enhanced self-reactivity and solubility of blowing agents, thus addressing the limitations of prior art.
Implementation Method 1
polyetherester polyols obtainable by esterification of b1) 10 to 70 mol % of a dicarboxylic acid composition comprising b11) 50 to 100 mol %, based on the dicarboxylic acid composition, of one or more aromatic dicarboxylic acids or derivatives thereof
Data Source
AI summary
The present invention relates to a process for preparing rigid polyurethane foams or rigid polyisocyanurate foams by using certain polyetherester polyols B) based on aromatic dicarboxylic acids, optionally further polyester polyols C), which differ from those of component B), and polyether polyols D), wherein the mass ratio of total components B) and optionally C) to component D) is less than 1.6. The present invention also relates to the rigid foams thus obtainable and to their use for producing sandwich elements having rigid or flexible outer layers. The present invention further relates to the underlying polyol components.