Direct Bonding Rubber Foam Composite Sole
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Solution Overview
Problem
The complexity and operation difficulties in the sole-making process of footwear, particularly in bonding the midsole and outsole using adhesive layers, hinder efficient mass production due to labor-intensive coating processes and challenges with manually placing adhesive films.
Innovation Solution
A composite comprising a cured rubber layer with optional carboxyl group-containing copolymers and a crosslinked ethylene vinyl acetate foam layer, where the foam layer adheres directly to the rubber layer without glues or adhesive films, achieved through curing and foaming processes followed by hot pressing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If adhesive layers (glues or adhesive films) are used to bond the midsole and outsole, then bonding strength is improved, but the process complexity and operation difficulty increase significantly
Solution Approach 1:
The patent removes the adhesive layer (glue or adhesive film) from the bonding process entirely. Instead of using separate adhesive materials, the invention creates direct bonding between the foam layer and rubber layer through chemical crosslinking reactions initiated by peroxide during hot pressing, thereby eliminating the complexity of adhesive application processes while maintaining bonding strength
Solution Approach 2:
The patent merges the bonding function with the curing process. The peroxide crosslinking agent serves dual purposes: it crosslinks the foam layer to provide structural integrity and simultaneously creates chemical bonds between the foam layer and rubber layer, combining structural formation and bonding into a single integrated process
2Strength
If adhesive layers are used to bond the midsole and outsole, then bonding strength is improved, but production efficiency decreases due to labor-intensive coating processes
Solution Approach 1:
By removing the adhesive layer and its associated application processes (washing, drying, coating primer, coating glues, removing chemical waste), the patent eliminates multiple labor-intensive steps, thereby significantly improving production efficiency while maintaining bonding strength through direct chemical crosslinking
Solution Approach 2:
The bonding process is made self-service through the in-situ generation of radicals from peroxide during hot pressing. The system automatically creates the bonding conditions through thermal decomposition of peroxide, eliminating the need for external adhesive application operations and enabling automated processing
3Strength
If adhesive films are used for laminating, then bonding is achieved, but positioning accuracy and appearance quality deteriorate due to difficulty in manual placement and adhesive film squeeze-out
Solution Approach 1:
The patent removes adhesive films from the process, eliminating the problems of difficult manual positioning and adhesive film squeeze-out. Direct bonding through peroxide crosslinking allows for better positioning control and prevents appearance defects associated with adhesive film extrusion
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
This solution enhances bonding strength and simplifies the sole-making process, eliminating the need for adhesives and improving production efficiency by achieving high peel strength and structural integrity in articles like footwear soles, carpets, and acoustic panels.
Implementation Method 1
The peroxide crosslinks the foam layer and bonds the foam layer to the rubber layer
Implementation Method 2
hot pressing the assembly to obtain the composite; hot pressing is produced at a temperature of about 120-180°C and with a pressure of 1-10 MPa
Data Source
Figure 1
AI summary
Disclosed is a composite comprising (a) a rubber layer comprising a cured rubber and optionally a first copolymer having carboxyl groups or anhydride groups; and (b) a foam layer comprising a crosslinked ethylene vinyl acetate and optionally a second copolymer having carboxyl groups or glycidyl methacrylate groups; wherein the foam layer has at least one surface adhering to the rubber layer directly, and provided that either the first copolymer or the second copolymer is present, and the composite is free of glues or adhesive films in the interface between the rubber layer and the foam layer.