Removable Polyurethane Hot Melt Adhesive for Reusable Substrates
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Solution Overview
Problem
Traditional polyurethane (PU) hot melt adhesives offer high bonding strength but are difficult to detach at elevated temperatures, limiting their reuse and efficiency in structural assembly applications, where low bonding strength at elevated temperatures and high strength at room temperature are needed.
Innovation Solution
A reactive hot melt adhesive comprising a (meth)acrylate polymer and an isocyanate-functional polyurethane prepolymer, with a melting point of 90-140°C and molecular weight of 20,000-80,000 g/mol, which allows for easy removability and high bonding strength at room temperature, achieved by reacting with moisture to form a crosslinked adhesive with urea and urethane groups.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional PU hot melt adhesives are used, then high bonding strength at room temperature is achieved, but bonding strength at elevated temperature remains too high for easy removal
Solution Approach 1:
The patent changes the chemical composition parameters of the adhesive by incorporating specific polymers (polyester polymer, polyether polymer, and carboxylic acid) to create a system where bonding strength becomes temperature-dependent. This allows high strength at room temperature while enabling easy removal at elevated temperatures through controlled chemical interactions.
Solution Approach 2:
The patent uses a composite adhesive system combining multiple polymer types (polyester, polyether, and carboxylic acid components) to achieve dual functionality: strong bonding at room temperature and easy removal at elevated temperatures. The composite nature allows different components to contribute different properties that resolve the contradiction.
2Strength
If adhesive bonding is used for structural assembly, then strong bonding is achieved, but substrate reuse becomes difficult due to strong adhesion
Solution Approach 1:
The patent changes the thermal parameters of the adhesive system to enable controlled debonding. By formulating the adhesive with specific polymers that respond to elevated temperatures, the bonding strength can be reduced on demand, allowing substrate separation and reuse while maintaining strong initial bonding.
Solution Approach 2:
The patent introduces dynamic properties to the adhesive system where bonding characteristics can change based on temperature conditions. The adhesive transitions from a strong-bonding state at room temperature to a easy-removal state at elevated temperatures, enabling both strong assembly and substrate reuse.
3Reliability
If high bonding strength adhesive is used, then assembly reliability is improved, but assembly efficiency decreases due to difficulty in separation
Solution Approach 1:
The patent changes the thermal and chemical parameters of the adhesive to create a system with high reliability during assembly but low resistance during separation. The specific polymer composition allows the adhesive to maintain strong bonding under normal conditions while enabling efficient separation when heated, thus improving both reliability and productivity.
Solution Approach 2:
The patent enables periodic switching between bonding and separation states through temperature control. The adhesive provides strong bonding during assembly operations, then can be easily separated during removal operations by applying heat, allowing repeated assembly cycles and improving overall productivity.
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 adhesive exhibits significantly low bonding strength at elevated temperatures, enabling easy removal without residue, while maintaining high bonding strength at room temperature, thus improving assembly efficiency and allowing for the reuse of expensive substrates.
Implementation Method 1
reacting with moisture to form a crosslinked adhesive with urea and urethane groups
Implementation Method 2
The adhesive exhibits significantly low bonding strength at elevated temperatures, enabling easy removal without residue
Data Source
AI summary
The invention relates to a polyurethane (PU) reactive hot melt adhesive removable at elevated temperature as well as having a high bonding strength at room temperature.