Insulated Twin Pipe Polyurethane Foam Curing for Tube Position Stability
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Solution Overview
Problem
Pre-insulated pipes with twin inner tubes manufactured using the continuous moulding technique face challenges in maintaining adequate compressive strength and axial shear strength, especially when using special additive polyols, which can cause displacement issues due to excessive influence on polymerization.
Innovation Solution
Employing a delayed-action catalyst package instead of special additive polyols, which supports final polymerization and maintains the correct positioning of twin tubes, resulting in improved compressive strength and axial shear strength through a controlled polymerization process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If special additive polyols are used to improve compressive strength, then compressive strength is improved, but twin tubes are displaced due to excessive influence on polymerization
Solution Approach 1:
The patent changes the chemical parameters of the catalyst system by introducing a delayed-action catalyst (e.g., tin octoate) instead of using special additive polyols. This parameter change in the catalytic system allows controlled polymerization that does not displace the twin tubes while still achieving the required compressive strength of at least 0.30 MPa.
Solution Approach 2:
The delayed-action catalyst acts as an intermediary that mediates the polymerization process. It provides a controlled release of catalytic activity, allowing the foam to expand and cure without excessive pressure that would displace the twin tubes, while still achieving adequate compressive strength.
2Productivity
If continuous moulding technique is used for twin inner tubes, then productivity is improved, but positioning accuracy deteriorates due to tube displacement
Solution Approach 1:
The delayed-action catalyst serves as an intermediary that enables the continuous moulding process to proceed without displacing the twin tubes. The controlled catalytic activity allows the foam to expand and cure gradually, maintaining tube positioning while preserving the high productivity of continuous manufacturing.
Solution Approach 2:
By changing the catalytic parameters to use a delayed-action catalyst, the patent enables continuous moulding of twin tube configurations without the tube displacement problem, thus maintaining both high productivity and positioning accuracy.
3Speed
If polymerization is accelerated at the beginning of the process, then production speed is improved, but twin tubes are pushed out of position
Solution Approach 1:
The delayed-action catalyst provides periodic catalytic activity rather than immediate acceleration. The catalyst activates gradually during the foam expansion and curing process, ensuring that polymerization occurs at the appropriate stages without pushing the twin tubes out of position.
Solution Approach 2:
The patent changes the temporal parameters of the polymerization process by using a delayed-action catalyst. This parameter change shifts the polymerization speed profile to occur later in the process, preventing tube displacement while still achieving complete curing and required mechanical 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 use of delayed-action catalysts significantly enhances the compressive strength of the polyurethane foam in pre-insulated pipes, both immediately after production and after post-curing, and increases axial shear strength, meeting or exceeding the required standards of EN 253.
Implementation Method 1
the insulating layer is made of a rigid polyurethane material prepared from a polyol comprising component, a di- or polyisocyanate, and one or more delayed-action catalysts
Implementation Method 2
supports final polymerization and maintains the correct positioning of twin tubes
Data Source
AI summary
The invention relates to an insulated pipe comprising at least one inner pipe, an outer casing, and an insulating layer positioned between the outer casing and the at least one inner pipe. The insulating layer is made of a rigid polyurethane material, which has an increased compressive strength. The present invention further relates to a method of producing the insulated pipe and the use of a delayed-action catalyst for increased compressive strength.