Polyurea Mine Seal Adhesive Strength
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Solution Overview
Problem
Current mine seals, formed by cementing concrete blocks, have limitations in resisting explosive forces and static loads, particularly in moist underground environments, as the mortar portion is less resistant than the concrete blocks, necessitating improved structural properties for enhanced safety and durability.
Innovation Solution
The development of a mine seal using novel polymer materials, specifically castable polyurea polymers with a long pot life, which join concrete or other structure-forming materials to create a seal capable of withstanding forces greater than 400 psi, comprising a mixture of isocyanates, polyols, and an amine functional resin, along with a water scavenger and colorant for improved adhesion and mixing indication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional cement mortar is used to join concrete blocks in mine seals, then the construction process is simple and familiar, but the structural strength and resistance to explosive forces are insufficient
Solution Approach 1:
The patent changes the chemical composition and physical properties of the bonding material from traditional cement mortar to a polyurea-based polymer adhesive. This polymer adhesive has significantly higher tensile and shear strength, allowing it to resist explosive forces and static loads that would exceed the capacity of conventional mortar. The material parameter change directly addresses the strength deficiency while maintaining ease of application through pumpable consistency.
Solution Approach 2:
The patent employs a composite material system consisting of polyurea polymer adhesive combined with concrete blocks. The polyurea itself is a composite formed by reacting isocyanate with amine, creating a material with superior mechanical properties. This composite approach allows the seal to achieve strength levels greater than 400 psi, far exceeding traditional mortar-capped blocks.
2Reliability
If cement mortar is used to form mine seals, then the construction process is straightforward, but the durability in moist underground environments deteriorates
Solution Approach 1:
The patent changes the material parameters by selecting polyurea polymer, which has inherent resistance to moisture, chemicals, and degradation. Unlike cement mortar that can crack and deteriorate in moist environments, the polyurea adhesive maintains its bonding properties, providing long-term reliability. The material's cross-linked polymer structure prevents water penetration and chemical attack, ensuring durability in underground mine conditions.
Solution Approach 2:
The patent introduces a water scavenger component as an intermediary substance within the adhesive composition. This additive actively absorbs and removes moisture from the environment and from within the adhesive matrix, preventing water-related degradation. The colorant serves as a visual intermediary to monitor the adhesive's condition and ensure proper mixing ratios, adding complexity to the composition but significantly improving reliability.
3Strength
If traditional concrete blocks with mortar are used, then the construction method is well-established, but the overall seal strength is limited by the weak mortar portion
Solution Approach 1:
The patent changes the strength parameter of the bonding material from mortar (typically 300-500 psi compressive strength) to polyurea adhesive (exceeding 400 psi tensile and shear strength). This parameter change ensures that the adhesive becomes the strong link in the system rather than the weak point. The concrete blocks can now be joined with full utilization of their inherent strength, achieving overall seal strength greater than 400 psi as required by safety regulations.
Solution Approach 2:
The patent applies the adhesive in a pre-mixed, pumpable formulation that is ready for immediate application. The adhesive is pumped directly onto the blocks and bonds rapidly, eliminating the need for on-site mortar mixing and curing wait times. This preliminary preparation of the adhesive in optimal working condition accelerates construction while maintaining superior strength properties throughout the sealing process.
4Reliability
If polymer adhesives are used to join concrete blocks, then the strength and durability are improved, but the complexity of the adhesive composition increases
Solution Approach 1:
The patent introduces several intermediary components into the adhesive formulation to manage complexity: a water scavenger that mediates moisture control, a colorant that mediates visual monitoring, and a foam that mediates gap filling and bonding. These intermediaries simplify the overall system by handling specific functions (moisture removal, visual inspection, void filling) that would otherwise require separate processes, thereby improving reliability while containing formulation complexity.
Solution Approach 2:
The polyurea-based adhesive serves multiple functions simultaneously: it provides structural bonding strength, resists moisture and chemicals, accommodates movement and settling, and can be applied in varying conditions. This multi-functionality reduces the need for separate materials or processes, managing formulation complexity by consolidating multiple requirements into a single universal adhesive system that enhances structural integrity.
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 polymer-based mine seal achieves a sheer strength of at least 350 psi, effectively adhering rigid blocks together to form a robust barrier that exceeds the resistance of traditional concrete mortar seals, ensuring enhanced safety and durability in underground mining applications.
Implementation Method 1
preparing a first prepolymer by mixing an isocyanate having an NCO content of between 15% and 35%... with a polyol
Implementation Method 2
a second prepolymer is prepared by mixing the first prepolymer and an aliphatic isocyanate such as HDI
Implementation Method 3
The second prepolymer is then mixed with providing an amine functional resin comprising a secondary amine in order to form a flowable adhesive composition
Implementation Method 4
the amine functional resin is admixed with a water scavenger, preferably a molecular sieve
Data Source
AI summary
A mine seal constructed from blocks adhered with a polyurea adhesive, the adhesive being formed by reacting a first prepolymer comprising an aromatic isocyanate with a second prepolymer comprising an aliphatic isocyanate, thereby forming an A-side mixture, and then reacting this mixture with a B-side mixture comprising an amine functional resin that includes a secondary amine.