Styrene Elastomer Injection Molding for Wrinkle-Free Shoe Surfaces
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Solution Overview
Problem
Injection molded articles often fail to accurately reflect the molding surface conditions of the forming mold, resulting in fine wrinkles and a compromised appearance, particularly in shoe parts intended for transparency and smoothness.
Innovation Solution
Incorporating a styrene-based thermoplastic elastomer with a high mass average molecular weight and a specific molecular structure, along with a plasticizer, to adjust the melting characteristics and improve the retention capacity, ensuring the elastomer composition exhibits suitable viscosity and loss tangent values for smooth injection molding and transparency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional elastomer composition is used for injection molding, then the material can be processed, but fine wrinkles are generated on the surface and the molding surface conditions are not accurately reflected
Solution Approach 1:
The patent changes the molecular weight parameter of the styrene-based thermoplastic elastomer to a specific range (mass average molecular weight: 100,000-500,000, number average molecular weight: 50,000-200,000) to optimize the melting characteristics and eliminate surface wrinkles during injection molding
Solution Approach 2:
The patent creates a composite elastomer composition by combining styrene-based thermoplastic elastomer with specific molecular weight characteristics and plasticizer in controlled ratios, achieving both processability and wrinkle-free surface quality
2Illumination intensity
If the elastomer composition is made transparent, then the internal structure is visible, but surface wrinkles compromise the appearance and transparency
Solution Approach 1:
The patent optimizes the molecular weight parameters of the elastomer to achieve appropriate melting characteristics that prevent surface wrinkles while maintaining the transparent property of the elastomer composition
Solution Approach 2:
The patent achieves uniform distribution of plasticizer throughout the elastomer composition through controlled mixing, ensuring consistent transparency and surface quality without localized defects
3Reliability
If high molecular weight elastomer is used, then the retention capacity of plasticizer is improved, but the viscosity may increase affecting processability
Solution Approach 1:
The patent precisely controls both mass average molecular weight (100,000-500,000) and number average molecular weight (50,000-200,000) parameters to achieve the optimal balance between plasticizer retention capacity and injection molding processability
Solution Approach 2:
The patent utilizes the dynamic melting characteristics of the elastomer composition during injection molding, where the material transitions from a solid state with high plasticizer retention to a molten state with appropriate flowability for molding
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 results in injection molded articles with a smooth surface that accurately reflects the molding surface, enhancing the appearance and transparency of shoe parts, while maintaining mechanical strength and cushioning performance.
Implementation Method 1
the elastomer composition has a maximum value of loss tangent obtained by dynamic viscoelasticity measurement at 200 °C in a frequency range of from 1 Hz to 50 Hz being 1 or more, at least one of the one or more styrene-based thermoplastic elastomers of the elastomer composition is a block polymer that comprises a soft segment and hard segments at both terminals of the soft segment in a molecular structure
Implementation Method 2
the injection molding, products are produced by injecting the elastomer composition in a heated and molten state into a cavity of a forming mold
Implementation Method 3
followed by allowing the elastomer composition filled in the cavity to cool and set
Implementation Method 4
the elastomer composition has a maximum value of viscosity obtained by dynamic viscoelasticity measurement at a temperature of 200 °C in a frequency range of from 1 Hz to 50 Hz being 10,000 Pa -s or less, the elastomer composition has a maximum value of loss tangent obtained by dynamic viscoelasticity measurement at 200 °C in a frequency range of from 1 Hz to 50 Hz being 1 or more
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
In order to provide an injection molded article that is able to be easily produced so that a molding surface of a forming mold is accurately reflected on the injection molded article, and, in order to provide a shoe having a shoe part excellent in appearance, the shoe part is formed of an elastomer composition showing a certain heat melting characteristics.