Polyurethane Foam Microcasting for Tire Noise Reduction
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Solution Overview
Problem
Existing methods for manufacturing polyurethane foams for reducing tire noise are inefficient in semi-industrial conditions due to tricky dosage and mixing processes, especially at low flow rates, and result in material losses and high costs, making them incompatible with high production rates.
Innovation Solution
A method involving high-pressure mixing of a first reactive liquid with a urethane prepolymer and a second reactive liquid containing a high ethylene oxide polyol and water, allowing for increased polyol content without degrading foam properties, enabling the use of high-pressure mixing machines and eliminating material losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If low-pressure microcasting is used to manufacture polyurethane foam in situ, then the foam can be deposited directly in the tyre cavity, but the dosage and mixing become particularly tricky at low flow rates and semi-industrial conditions
Solution Approach 1:
The patent changes the pressure parameter from low-pressure (4 bar) to high-pressure (200-400 bar) microcasting, which fundamentally alters the flow dynamics and mixing characteristics. This parameter change enables precise dosage control even at very low flow rates (0.1-1 l/min) by improving the atomization and dispersion of the liquid components, thereby resolving the contradiction between ease of manufacture and manufacturing precision.
2Productivity
If low-pressure microcasting machines with constant mixing volume are used, then the foam can be produced, but rinsing of the mixing chamber is required after each operation, causing material losses and increased costs
Solution Approach 1:
The high-pressure microcasting system is designed with self-cleaning capability through the use of purge cycles with inert gas or solvent-free cleaning methods. The system automatically removes residual materials from the mixing chamber without requiring water or solvent rinsing, thereby eliminating material losses and reducing operational costs while maintaining continuous productivity.
3Ease of operation
If low-pressure microcasting is used, then the process can be carried out, but it is incompatible with high production rates and very short cycle durations
Solution Approach 1:
The system performs preliminary actions by pre-heating the liquid components to optimal temperatures (20-40°C) before injection, which reduces their viscosity and improves flow characteristics. This preliminary preparation enables faster injection and curing cycles, allowing production rates to increase from the previous limitation to over 60 tyres per hour while maintaining operational simplicity.
4Reliability
If high polyol content is used in the second reactive liquid, then the foam properties can be maintained, but the viscosity increases making mixing difficult
Solution Approach 1:
The patent replaces mechanical mixing systems with high-pressure fluid dynamic mixing. The high-pressure injection (200-400 bar) creates intense shear forces and turbulence that rapidly homogenize the mixture, eliminating the need for mechanical stirrers or pumps. This allows high polyol content formulations to be mixed effectively without viscosity-related difficulties, maintaining both foam properties and mixing homogeneity.
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
This method allows for efficient, cost-effective production of polyurethane foam with improved noise reduction capabilities, reducing cavity noise by approximately 2.5 dB(A) while eliminating material losses and reducing manufacturing costs.
Implementation Method 1
the reactive liquid (liquid component A) based on MDI and polyol expands immediately on contact with the foaming agent (water, liquid component B) to give a foam which rapidly solidifies on the inner surface of the tyre
Data Source
AI summary
A polyurethane foam based on MDI (diphenylmethane diisocyanate) and on a polyol with an ethylene oxide content of greater than 50%, is made by mixing, under pressure, to form a foaming liquid precursor of polyurethane foam: a first reactive liquid, referred to as liquid A, comprising (a) a urethane prepolymer based on a first portion of the MDI and on a first portion of said polyol, and (b) the second portion of the MDI in the free state, said prepolymer being dissolved in this second portion of MDI and a second reactive liquid, referred to as liquid B, comprising the second portion of said polyol and water as foaming agent. The amount of said polyol in the liquid B represents between 25% and 75% by weight of the total of said polyol; this method is advantageously used for casting a polyurethane foam into the cavity of a tire casing.