PDI-Based Polyurethane Dispersion Adhesive Low-Temperature Activation
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Solution Overview
Problem
Aqueous polyurethane or polyurea dispersions based on hexamethylene diisocyanate (HDI) exhibit inadequate tack values and strength at low activation temperatures, and these properties are lost after storage at temperatures below 10°C, making them unsuitable for efficient industrial shoe manufacturing processes.
Innovation Solution
The use of aqueous polyurethane or polyurethane-urea dispersions containing pentamethylene diisocyanate (PDI) as the isocyanate component, with a composition that includes a difunctional polyol, isocyanate-reactive components, and specific ratios of components to achieve improved tack and strength at low temperatures, retaining these properties even after cold storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If hexamethylene diisocyanate (HDI) based adhesives are used for bonding, then very good bonds are achieved at activation temperatures around 70°C, but insufficient tack values and inadequate strength are exhibited at lower activation temperatures around 50°C
Solution Approach 1:
The invention changes the chemical composition parameter by replacing HDI with PDI as the isocyanate component, which fundamentally alters the adhesive's thermal and bonding properties to enable effective activation at lower temperatures while maintaining strong tack values
Solution Approach 2:
The invention uses composite material formulation by combining PDI with specific polyol components (polyester polyols with specific molecular weights and melting points) to create a semi-crystalline polymer system that melts at lower temperatures, enabling effective bonding at 50°C
2Reliability
If hexamethylene diisocyanate (HDI) based dispersions are stored at low temperatures below 10°C, then transport and storage requirements are met, but tack values and bonding properties are lost after storage
Solution Approach 1:
The invention changes the chemical structure parameter by using PDI instead of HDI, which fundamentally alters the polymer's behavior during cold storage to prevent crystallization and property loss, while maintaining tack retention after storage
Solution Approach 2:
The invention provides beforehand cushioning by formulating the dispersion with PDI and specific polyol ratios that prevent detrimental crystallization during cold storage, cushioning against the potential loss of tack properties before storage even occurs
3Strength
If traditional adhesive processes are used in industrial shoe manufacturing, then bonding strength is achieved, but significant manual work and energy consumption are required
Solution Approach 1:
The invention changes the activation temperature parameter to 50°C, which enables simultaneous drying and activation in one step, dramatically improving manufacturing efficiency by eliminating separate drying and bonding operations while maintaining bonding strength
Solution Approach 2:
The invention merges the drying and activation steps into a single simultaneous operation by using PDI-based dispersions that can be activated at low temperatures, combining what were traditionally separate process steps into one efficient operation
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 dispersions demonstrate excellent tack values and strength at 50°C activation temperatures, maintaining performance after cold storage, enabling efficient, cost-effective, and energy-saving bonding processes for industrial shoe manufacturing.
Implementation Method 1
the adhesive layer is activated by heating (e.g., with an infrared heater) and melting the semi-crystalline polymer, thus bringing it into a tacky state
Implementation Method 2
the resulting adhesive layer is activated after complete evaporation of the water by heating to at least the activation temperature of the layer
Implementation Method 3
the dispersion is applied to the substrate, and after complete evaporation of the water
Data Source
AI summary
The invention relates to dispersion adhesives on the basis of aqueous polyurethane dispersions or polyurethane urea dispersions, which meet the requirements for industrial shoe manufacture and at the same time can dry and be activated at low temperatures, and to the use of the dispersion adhesives for producing substrate-adhesive composites.