Foamed Polyurethane Shoe Sole with Solid Particles
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Solution Overview
Problem
Existing foamed polyurethanes used in shoe soles lack improved slip resistance, especially wet slip resistance, and long-term bending properties at low temperatures, while also not replicating the feel of rubber.
Innovation Solution
A foamed polyurethane is created by mixing polyisocyanates with higher molecular weight compounds having reactive groups, solid particles, blowing agents, and optional chain extenders and catalysts, where the chain extender content is less than 4% and solid particles exceed 15% by weight, and the average functionality of these compounds is less than 2.5, resulting in a product with enhanced mechanical properties and feel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional foamed polyurethanes are used with higher chain extender content, then mechanical strength can be improved, but slip resistance and bending properties deteriorate
Solution Approach 1:
The invention changes the key parameter of chain extender content from conventional levels (typically 5-15% or higher) to a reduced level of less than 4% by weight. This parameter change fundamentally alters the foam structure and molecular network formation, resulting in improved slip resistance and bending properties while maintaining adequate mechanical strength through the optimized balance of other components including polyol, polyisocyanate, and solid particle content.
Solution Approach 2:
The invention creates a composite foam structure by incorporating 15-30% by weight solid particles (such as silica, glass beads, or metal oxides) into the polyurethane matrix. These solid particles act as reinforcing fillers that improve mechanical properties without requiring high chain extender content, thereby enabling the formulation to achieve both strength and improved slip resistance/bending properties through the synergistic combination of reduced chain extenders and added solid particles.
2Weight of moving object
If polyurethane density is reduced to achieve lower weight, then mechanical properties such as tensile strength can be improved, but slip resistance and feel deteriorate
Solution Approach 1:
The invention optimizes the density parameter to a specific range of 200-500 kg/m³, which is lower than conventional shoe sole foams. Within this reduced density range, the invention adjusts the chain extender content to less than 4% and solid particle content to 15-30%, creating a optimized formulation that maintains slip resistance and rubber-like feel despite the lower density, achieving a better balance between weight reduction and performance.
Solution Approach 2:
By incorporating 15-30% solid particles into the low-density polyurethane foam matrix, the invention creates a composite material that compensates for the potential loss of mechanical properties due to reduced density. The solid particles provide structural reinforcement and surface characteristics that maintain slip resistance and bending properties even at the lower density of 200-500 kg/m³, enabling weight reduction without sacrificing performance.
3Strength
If solid particle content is increased to improve mechanical properties, then strength can be improved, but processing difficulty and cost increase
Solution Approach 1:
The invention optimizes the solid particle content to a specific range of 15-30% by weight, which provides sufficient reinforcement to improve mechanical properties while avoiding the excessive processing difficulties and costs associated with higher solid particle loadings. This optimized concentration range ensures adequate dispersion and distribution of solid particles during the foaming process, maintaining ease of manufacture while achieving the desired strength improvements.
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 foamed polyurethane exhibits improved slip resistance, both dry and wet, and superior long-term bending properties, providing a rubber-like feel and mechanical performance suitable for shoe soles and other applications.
Implementation Method 1
foamed polyurethane, obtainable by mixing a) polyisocyanates, b) higher molecular weight compounds with groups reactive towards isocyanate groups
Implementation Method 2
d) blowing agent
Data Source
AI summary
The invention relates to a foamed polyurethane which is obtainable by mixing a) polyisocyanates, b) high-molecular compounds carrying groups that are reactive to isocyanate groups, c) solid particles, d) propellants, e) optionally chain extenders, cross-linking agents or mixtures thereof, f) optionally a catalyst and g) optionally other additives, to give a reaction mixture and allowing said mixture to react, the percentage of chain extenders being less than 6% by weight, based on the overall weight of components a) to f), the solid particle content being more than 15% by weight, based on the overall weight of components a) to f), and the average functionality of the high-molecular compounds carrying groups that are reactive to isocyanate groups being less than 2.5. The invention further relates to a molded body which contains a foamed polyurethane of the invention, to a method for producing the foamed polyurethane and to the use of a molded body according to the invention as a shoe sole.