Thermoplastic Polyurethane Styrene Bead Foams
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Solution Overview
Problem
There is a need for bead foams with improved processability at low temperatures to produce molded bodies with enhanced mechanical properties, particularly in the shoe sector, where adequate adhesive bonding and fusion are crucial for achieving desirable tensile, flexural, and compression properties while minimizing density and production time, and preventing material instability or collapse during large-scale industrial production.
Innovation Solution
A composition comprising 70-95% thermoplastic polyurethane and 5-30% styrene polymer is used to create bead foams, which are processed to produce molded bodies for shoe components, such as intermediate soles and cushioning elements, with specific molar ratios of isocyanates and polyols, and chain extenders to achieve optimal mechanical properties and reduced density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If bead foams are processed at high temperatures to improve adhesive bonding and fusion, then mechanical properties are improved, but energy consumption increases and material degradation occurs
Solution Approach 1:
The patent modifies the chemical composition parameters of the foam beads by incorporating thermoplastic polyurethane (70-95 wt%) and styrene polymer (5-30 wt%) in specific ratios, along with controlled amounts of crosslinking agents and blowing agents. This compositional parameter change enables the material to achieve adequate adhesive bonding at reduced processing temperatures, thereby lowering energy consumption while maintaining bond strength
Solution Approach 2:
The invention creates a composite foam structure combining thermoplastic polyurethane matrix with styrene polymer domains and crosslinked networks. This multi-phase composite architecture provides both the adhesive bonding capability and the thermal stability needed to process at lower temperatures without material degradation, resolving the contradiction between bond strength and energy efficiency
2Strength
If bead foams are processed at high temperatures to improve adhesive bonding, then mechanical properties are improved, but material degradation and foam structure impairment occur
Solution Approach 1:
The patent adjusts the chemical composition parameters including the ratio of thermoplastic polyurethane to styrene polymer (70:30 to 95:5), the amount of crosslinking agent (0.1-5 wt%), and blowing agent content (1-20 wt%). These parameter optimizations enable adequate adhesive bonding at moderate temperatures while preventing material degradation and maintaining foam structure integrity, thus improving reliability
Solution Approach 2:
The invention incorporates volatile blowing agents that decompose at relatively low temperatures to generate foam expansion, and crosslinking agents that form stable networks upon mild heating. These components perform their functions at low processing temperatures and then effectively 'disappear' or stabilize, preventing further degradation and ensuring material reliability during and after processing
3Productivity
If production time is reduced to maximize throughput, then productivity is improved, but material quality decreases and instability occurs
Solution Approach 1:
The patent modifies the thermal and rheological parameters of the foam composition by selecting thermoplastic polyurethane with specific melt flow characteristics and glass transition temperature, and styrene polymer with appropriate viscosity. These parameter changes enable rapid melting and processing at high throughput while maintaining material stability and preventing collapse, thus resolving the contradiction between productivity and material quality
Solution Approach 2:
The invention incorporates pre-dispersed crosslinking agents and blowing agents within the foam bead matrix during manufacturing, along with nucleating agents for controlled cell formation. This preliminary preparation ensures that when the beads are rapidly processed through the molding machine, the chemical reactions proceed uniformly and quickly without material instability, enabling high throughput while maintaining reliability
4Weight of stationary object
If density is reduced to minimize material usage, then weight is improved, but compression properties deteriorate
Solution Approach 1:
The patent creates a hierarchical composite structure where thermoplastic polyurethane forms the continuous matrix, styrene polymer creates dispersed rigid domains, and crosslinked networks provide three-dimensional reinforcement. This multi-scale composite architecture maintains high compression resistance even at low densities (achieved through controlled foam cell structure), resolving the contradiction between lightweight and mechanical strength
Solution Approach 2:
The invention utilizes a controlled porous foam structure with specific cell size distribution and wall thickness, achieved through optimized blowing agent selection and processing parameters. The porous architecture provides low density for weight reduction while the interconnected cell walls and crosslinked networks maintain compression resistance, enabling lightweight design without sacrificing 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 resulting molded bodies exhibit improved tensile strength, elongation at break, compressive stress, and rebound resilience, with densities between 75-375 kg/m3, suitable for shoe applications, while maintaining low production time and minimizing material instability.
Implementation Method 1
a composition (Z) comprising a) from 70 to 95% by weight of thermoplastic polyurethane as component I and b) from 5 to 30% by weight of styrene polymer as component II
Implementation Method 2
the energy for the fusion of the bead foams is introduced via an auxiliary medium such as steam
Implementation Method 3
there is a relationship between density and compression property, because the compression property is a measure of the minimal achievable density in a molding for the requirements of the application
Data Source
AI summary
The present invention relates to bead foams made of thermoplastic polyurethane and polystyrene produced moldings, to processes for the production of the bead foams and moldings, and also to the use of the moldings for shoe intermediate soles, shoe insoles, shoe combisoles, or cushioning elements for shoes.