Polyamide Foams for Mining Cavities Using Reactive Diluents
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Solution Overview
Problem
Existing cavity fillers used in mining and civil engineering are often flammable and require high temperatures for production, making them unsuitable for mining applications and posing occupational hygiene concerns due to phenol content, while lacking alternatives that are non-flame-propagating and maintain suitable mechanical strength.
Innovation Solution
A process involving a liquid isocyanate component with a high molar ratio of aromatic isocyanate groups and a liquid isocyanate-reactive component containing reactive diluents, such as aliphatic and alicyclic polycarboxylic acids, to produce non-fire-propagating polyamide foams at ambient temperatures, ensuring mechanical strength and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If phenol-formaldehyde resin-based foams are used as cavity fillers, then fire propagation is prevented, but occupational hygiene concerns arise due to phenol content
Solution Approach 1:
The invention changes the chemical composition parameters by using aromatic polycarboxylic acids instead of phenol-formaldehyde resins, maintaining fire safety while eliminating phenol content. The specific parameter change involves selecting carboxylic acids with at least two carboxyl groups per molecule (e.g., adipic acid, phthalic acid, terephthalic acid) to react with polyisocyanates, creating non-flame-propagating foams without phenolic compounds.
Solution Approach 2:
The invention replaces expensive and hazardous phenol-formaldehyde resin systems with simpler, safer aromatic polycarboxylic acid systems that achieve the same fire safety function without the harmful phenol content, making the material both safer and potentially more cost-effective.
2Reliability
If aromatic dicarboxylic acids are used to produce non-flammable polyamide foams, then fire safety is improved, but high temperatures (180-320°C) are required for production
Solution Approach 1:
The invention changes the processing temperature parameter by selecting aromatic polycarboxylic acids that remain liquid or can be easily handled at lower temperatures. Instead of requiring 180-320°C to melt solid aromatic dicarboxylic acids, the patent uses acids like adipic acid, phthalic acid, terephthalic acid, and their anhydrides that can react with polyisocyanates at ambient or mildly elevated temperatures, thus maintaining fire safety while eliminating high-temperature processing requirements.
Solution Approach 2:
The invention applies local quality by selecting specific aromatic polycarboxylic acids with appropriate melting points and reactivities for the application. The patent identifies and uses acids that have favorable thermal properties for low-temperature processing while still providing the desired fire-resistant characteristics in the final foam product.
3Temperature
If solid aromatic dicarboxylic acids are dissolved in diluents or solvents to enable ambient temperature processing, then processing temperature is reduced, but mechanical properties of the foams deteriorate
Solution Approach 1:
The invention extracts the problematic diluents and solvents from the system entirely. Instead of dissolving solid aromatic dicarboxylic acids in external diluents that compromise mechanical strength, the patent uses aromatic polycarboxylic acids that are inherently suitable for direct reaction with polyisocyanates, eliminating the need for compromising diluents while maintaining both low processing temperature and high mechanical strength.
Solution Approach 2:
The invention creates a composite chemical system where aromatic polycarboxylic acids react with polyisocyanates to form polyamide linkages within the foam structure. This composite approach at the molecular level (forming amide bonds) provides both the low-temperature processing capability and the mechanical strength, without requiring separate diluents that would weaken the final product.
4Ease of operation
If classic cavity fillers are used, then ease of application is maintained, but fire propagation cannot be prevented
Solution Approach 1:
The invention changes the chemical composition parameters of the cavity filler by using aromatic polycarboxylic acids with specific properties (liquid or easily handleable state, appropriate reactivity with isocyanates) that enable both easy application and fire safety. The patent specifies acids like adipic acid, phthalic acid, terephthalic acid, and their anhydrides that can be applied similarly to conventional two-component systems while providing non-flame-propagating properties.
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 yields foams that are non-flame-propagating, maintain mechanical strength, and can be used in mining and civil engineering applications without the need for high-temperature processing or phenol-based materials, addressing safety and regulatory concerns.
Implementation Method 1
a process for producing non-fire-propagating polyamide foams by mixing (i) a liquid isocyanate component containing at least one polyisocyanate with (ii) at least one liquid isocyanate-reactive component which contains a reactive diluent
Implementation Method 2
Carboxyl groups develop carbon dioxide when reacting with isocyanates; the resulting carbon dioxide acts as a blowing agent for foam formation
Implementation Method 3
the resulting carbon dioxide acts as a blowing agent for foam formation
Implementation Method 4
An amide bond forms from the carboxyl group and the isocyanate group
Data Source
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Figure 2
AI summary
Polyamide foams which inhibit the spread of fires are obtained by mixing (i) a liquid isocyanate component which contains at least one polyisocyanate, wherein the molar ratio of aromatic isocyanate groups to the sum of aromatic and aliphatic isocyanate groups is at least 60 mol.%, with (ii) at least one liquid isocyanate-reactive component which contains a reactive diluent that comprises (a) a chain-extending and/or crosslinking reactive diluent selected from aliphatic branched C24-66-polycarboxylic acids, alicyclic C24-66-polycarboxylic acids, and partial esterns of polycarboxylic acids with at least two unesterified carboxyl groups and/or b) a chain-terminating reactive diluent selected from aliphatic branched C24-66-monocarboxylic acids, alicyclic C24-66-monocarboxylic acids, and partial esters of polycarboxylic acids with an unesterified carboxyl group, and (iii) optionally a solid isocyanate-reactive component. The liquid isocyanate-reactive component and/or the solid isocyanate-reactive component comprises an aromatic C8-18-polycarboxylic acid and/or an anhydride thereof. Reactive diluents are dimeric fatty acids or trimeric fatty acids which are optionally hydrogenated. The foams are suitable for filling cavities in mining, tunnel construction, underground engineering or for obtaining oil and gas as a fire protection foam, heat damping, or acoustic damping.