Propylene-Based Elastomer Footwear Sole Weldability

Solution Overview

Problem

Traditional materials for footwear soles, such as polyurethane or EVA, fail to deliver a targeted combination of desired properties like low density, low compression set, weldability, slip resistance, and abrasion durability, requiring different materials for the upper and sole, which complicates recycling and manufacturing processes.

Innovation Solution

A propylene-based elastomer composition with at least 50 wt% propylene-derived units and 5 to 35 wt% ethylene-derived units, combined with an ethylene copolymer, is used for both the sole and upper, offering improved weldability and maintaining desired properties without the need for adhesives, enabling unified recycling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional materials like polyurethane or EVA are used for footwear soles, then cushioning and comfort are improved, but weldability deteriorates and adhesive bonding is required

Engineering Contradiction:
Core Design Contradiction:
ReliabilityVSEase of manufacture

Solution Approach 1:

The patent changes the material parameter from traditional polyurethane or EVA to a propylene-based elastomer composition with specific molecular weight (10,000-1,000,000 g/mol) and comonomer content (5-35 wt%), which fundamentally alters the material's thermal and mechanical properties to enable both cushioning and weldability

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent uses a composite propylene-based elastomer system comprising multiple components: propylene polymer (50-90 wt%), comonomer (5-35 wt%), and optional additives, creating a material that combines the cushioning properties of elastomers with the weldability of thermoplastics

Inventive Principle:
Principle #40Composite materials

2Adaptability or versatility

If different materials are used for upper and sole, then specific performance requirements are met, but recycling complexity increases

Engineering Contradiction:
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The propylene-based elastomer composition is designed to be universally applicable for both the upper and sole components of footwear, replacing the need for different materials while maintaining or achieving the required performance characteristics for each component

Inventive Principle:
Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent promotes material homogeneity by using the same propylene-based elastomer composition throughout the entire footwear article, which simplifies the recycling process by eliminating the need to separate different material types

Inventive Principle:
Principle #33Homogeneity

3Strength

If adhesive bonding is used to attach upper and sole, then bonding strength is improved, but manufacturing complexity and time increase

Engineering Contradiction:
Core Design Contradiction:
StrengthVSProductivity

Solution Approach 1:

The patent replaces the chemical bonding mechanism (adhesives) with a mechanical/thermal bonding mechanism (welding), where the propylene-based elastomer's thermoplastic properties enable direct welding of the upper and sole components, eliminating the adhesive application, drying, and curing steps

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

4Ease of manufacture

If propylene-based elastomer with high propylene content is used, then weldability is improved, but compression set resistance may deteriorate

Engineering Contradiction:
Core Design Contradiction:
Ease of manufactureVSReliability

Solution Approach 1:

The patent optimizes the compositional parameters of the propylene-based elastomer, specifically controlling the propylene polymer content (50-90 wt%) and comonomer content (5-35 wt%), and adjusting molecular weight (10,000-1,000,000 g/mol) to achieve the optimal balance between weldability and compression set resistance

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent applies different propylene-based elastomer formulations with specific compositional characteristics to different regions or components of the footwear, allowing optimization of local properties such as weldability for the sole attachment areas and compression set resistance for the cushioning regions

Inventive Principle:
Principle #3Local quality

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 propylene-based elastomer composition achieves a balanced set of properties including low density, reduced compression set, and enhanced weldability, allowing for adhesive-free bonding and efficient recycling, thereby simplifying the manufacturing process and improving performance.

Implementation Method 1

improved weldability, allowing for adhesive-free bonding

Methodology Applied
Scientific EffectWelding: Welding

Data Source

PatentUS10548367B2Footwear sole comprising a propylene-based elastomer, footwear comprising said sole, and methods of making them
Publication Date: 2020.02.04

AI summary

Disclosed are footwear soles comprising a propylene-based elastomer. The presence of the propylene-based elastomer provides the footwear sole with a well-balanced combination of desired properties, including low density, low compression set, and weldability.