Expanded Thermoplastic Polyurethane Foaming Process
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for producing expanded thermoplastic polyurethane (eTPU) suffer from temperature control issues, anisotropy, and sticking problems during processing, and require longer charging times, making them inefficient and unsuitable for demanding applications like footwear.
Innovation Solution
A method involving an autoclave process where non-expanded TPU is initially saturated with a gaseous fluid at controlled pressure and temperature, then submerged in a liquid before depressurization to expand, using environmentally friendly gases like N2 and CO2, and additives to prevent sticking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If non-expanded TPU particles are introduced into an autoclave and put under high pressure using gaseous fluids to saturate the TPU particles, then the TPU particles can be expanded, but the obtained eTPU particles suffer from temperature control issues and sticking problems
Solution Approach 1:
The patent introduces a liquid medium as an intermediary between the gaseous blowing agent and the TPU particles. The liquid serves as a heat transfer medium that mediates thermal energy distribution throughout the autoclave, enabling uniform temperature control during the foaming process while allowing gas saturation to proceed effectively
Solution Approach 2:
The patent changes the physical state parameters of the system by introducing a liquid phase into the autoclave environment. This creates a three-phase system (gas, liquid, solid particles) where the liquid's incompressibility and high heat capacity provide stable thermal parameters, preventing temperature fluctuations that cause sticking
2Reliability
If non-expanded TPU particles are saturated with gaseous fluids in an autoclave, then expansion can occur, but the process requires longer charging periods when liquids are used
Solution Approach 1:
The patent combines pneumatic principles (gas saturation) with hydraulic principles (liquid medium) to create a hybrid system. The liquid medium provides rapid and uniform heat distribution through its hydraulic properties, reducing the time required for thermal equilibration during the charging phase compared to gas-only systems
3Productivity
If TPU particles are expanded using conventional autoclave methods, then eTPU can be produced, but the obtained particles exhibit anisotropy issues
Solution Approach 1:
The liquid medium acts as an intermediary that transmits pressure and thermal energy uniformly from all directions to the TPU particles during saturation and expansion. This omnidirectional uniformity prevents preferential expansion in certain directions, maintaining isotropic cellular structure in the final foam product
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 process improves thermal control, reduces anisotropy and sticking, and minimizes charging time, resulting in high-quality eTPU suitable for shock-absorbing materials and other applications.
Implementation Method 1
Increasing the pressure in the autoclave by introducing at least one gaseous fluid (27) at a temperature within the autoclave below the melting temperature of the thermoplastic polymer, and then allowing the non-expanded TP material to reach a saturation state (charging step)
Implementation Method 2
Placing the non-expanded TP in an autoclave, said autoclave being partly filled with a liquid and the material being not in contact with said liquid, and then increasing the pressure in the autoclave by introducing at least one gaseous fluid at a temperature within the autoclave below the melting temperature of the thermoplastic polymer
Implementation Method 3
Decreasing the pressure in the autoclave such that the submerged TP material expands to form eTPU material (expansion step)
Data Source
AI summary
An improved process for fabricating expanded thermoplastic polymers (eTP) starting from non-expanded TP is disclosed whereby said process has improved thermal control, uses preferably environmentally friendly foaming gasses, avoids anisotropy and sticking of the eTP during the processing and minimises the duration of the charging step.