Foamed Sole Thermal Shrinkage Control via Viscoelastic Tuning
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Solution Overview
Problem
Foamed soles for shoes undergo significant thermal shrinkage during heat treatment, leading to dimensional changes and poor adherence to the shoe body, while highly foamed versions are lightweight but prone to shrinkage, compromising stability and durability.
Innovation Solution
A foamed sole composition with a rubber component and a resin component, where the maximum loss factor at 10 Hz and 30°C to 80°C is 0.18 or less, and a peak loss factor at 10 Hz lies within 100°C or higher, suppressing thermal shrinkage and allowing for high foaming without weight increase, using a resin with a glass transition point, melting point, and softening point of 90°C or higher.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the expansion ratio of foam molding is increased to reduce weight and improve wearing impression, then the foamed sole becomes lighter and more comfortable, but thermal shrinkage is greatly increased during heat treatment, causing dimensional instability and poor adherence precision
Solution Approach 1:
The patent modifies the chemical composition parameters of the foam molding by incorporating specific rubber components (polyisoprene rubber, polybutadiene rubber) in controlled ratios with thermoplastic polymers. This compositional parameter change enables the foam to achieve high expansion ratios while maintaining resistance to thermal shrinkage, as the specific polymer blend creates a foam structure that is less susceptible to heat-induced dimensional changes
Solution Approach 2:
The patent creates a composite foam material combining rubber components (providing elasticity and foam structure) with thermoplastic polymers (providing thermal stability). This composite structure allows the foam to maintain its expanded shape during heat treatment while remaining lightweight, as the thermoplastic phase restricts the thermal shrinkage tendency of the rubber-based foam matrix
2Stability of the object's composition
If the expansion ratio of foam molding is reduced to decrease thermal shrinkage, then dimensional stability is improved, but the foamed sole becomes heavier and wearing impression deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters by optimizing the ratio of rubber components to thermoplastic polymers and selecting specific polymer types with appropriate glass transition temperatures. This parameter optimization enables the foam to achieve high expansion ratios with controlled thermal shrinkage, simultaneously achieving lightweight properties and dimensional stability
3Manufacturing precision
If thermal shrinkage is suppressed to maintain dimensional precision, then adherence precision to shoe body is improved, but the foam molding becomes heavier
Solution Approach 1:
The patent employs a composite foam material consisting of rubber components (for lightweight foam structure) and thermoplastic polymers (for thermal shrinkage resistance). This composite approach achieves both lightweight properties and dimensional stability during heat treatment, ensuring precise adherence to the shoe body without compromising weight
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 solution prevents thermal shrinkage in the foamed sole, ensuring precise adherence to the shoe body, maintaining lightweight properties, and enhancing durability and stability under varying temperatures.
Implementation Method 1
it is considered that in the case where a resin component is added to the forming material for a foam molding, thermal shrinkage thereof can be suppressed since the resin component resists shrinkage caused by the rubber component
Implementation Method 2
the more the rubber component is greatly stretched, and therefore, the force of going to return to the original state (shrinkage) is generated strongly
Implementation Method 3
the maximum value of a loss factor [tan δ] at a frequency of 10 Hz and at 30°C to 80°C of the foam molding is 0.18 or less, and a peak of a loss factor [tan δ] at a frequency of 10 Hz of the foam molding lies within the range of 100°C or higher
Data Source
Figure 1~2
Figure 3
AI summary
A foamed sole according to the present invention includes a foam molding containing a rubber component and a resin component, wherein the maximum value of a loss factor [tan δ] at a frequency of 10 Hz and at 30°C to 80°C of the foam molding is 0.18 or less, and a peak of a loss factor [tan δ] at a frequency of 10 Hz of the foam molding lies within the range of 100°C or higher. The foamed sole has a feature that it hardly shrinks when it is heated.