Aqueous Polyurethane Dispersion for High Initial Bonding Force
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Solution Overview
Problem
Existing aqueous polyurethane dispersions do not provide sufficient initial bonding force for adhesive applications, particularly in the shoe-glue industry.
Innovation Solution
An aqueous polyurethane dispersion with anionic groups, a fusion enthalpy of 3J/g-100J/g, weight-average molecular weight of 31,000-95,000, and an acid value of 0.5 mg KOH/g-8.5 mg KOH/g, prepared by reacting a polyisocyanate mixture with an isocyanate-reactive group-containing mixture, and incorporating emulsifiers and stabilizers to enhance bonding properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If existing aqueous polyurethane dispersions are used, then the adhesive composition is simple and easy to manufacture, but the initial bonding force is insufficient
Solution Approach 1:
The patent creates a composite adhesive system by combining aqueous polyurethane dispersion with specific additives including carboxylic acid compounds (0.1-5 wt%), compounds containing elements from groups V and VIB (0.1-5 wt%), and polyisocyanates (1-20 wt%). This composite approach enhances the initial bonding force by integrating multiple functional components that work synergistically, where the carboxylic acid compounds provide initial adhesion, the group V/VIB compounds facilitate crosslinking reactions, and polyisocyanates enable further reinforcement of bonds.
Solution Approach 2:
The patent optimizes specific parameter ranges to achieve excellent initial bonding force: carboxylic acid compounds at 0.1-5 wt%, group V/VIB compounds at 0.1-5 wt%, polyisocyanates at 1-20 wt%, and polyurethane weight-average molecular weight at 20,000-250,000. By precisely controlling these compositional parameters and the polyurethane's molecular weight, the adhesive achieves optimal balance between initial bonding strength and composition complexity.
2Strength
If the polyurethane molecular weight is increased, then the adhesive strength is improved, but the viscosity and applicability are worsened
Solution Approach 1:
The patent specifies a weight-average molecular weight range of 20,000-250,000 for the polyurethane, with optimal performance observed in the 50,000-150,000 range. This parameter optimization ensures that the polyurethane chains are sufficiently long to provide strong adhesive bonds while remaining short enough to maintain manageable viscosity for practical application. The balanced molecular weight range allows the adhesive to flow properly during application yet form strong bonds upon curing.
3Reliability
If crystalline or semi-crystalline polyurethane is used, then the bonding layer properties are improved, but the manufacturing complexity increases
Solution Approach 1:
The patent utilizes the inherent crystalline or semi-crystalline structure of polyurethane formed through controlled polymerization of polyols and isocyanates. By optimizing the polyurethane synthesis parameters (molecular weight 20,000-250,000, specific polyol-to-isocyanate ratios), the patent achieves reliable bonding layer properties with crystalline structure without requiring additional complex manufacturing steps. The crystalline structure develops naturally during the adhesive formulation and curing process.
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 dispersion achieves excellent initial bonding force, suitable for adhesive applications, particularly in the shoe-glue industry.
Implementation Method 1
the first polyurethane and/or polyurethane-polyurea polymer is capable of attaining an at least partially crystalline state with a final degree of crystallinity and wherein during and/or after the application the first polyurethane and/or polyurethane-polyurea polymer is present in an amorphous state
Implementation Method 2
the polyurethane has a fusion enthalpy of 3J/g-100J/g at 20°C-100°C of the first temperature rising curve measured with the DSC
Data Source
AI summary
The present invention relates to an aqueous polyurethane dispersion and a process for preparing the same, an adhesive containing the same, and an adhesion article obtained by bonding with the adhesive. The aqueous polyurethane dispersion comprises a polyurethane having an anionic group dispersed therein, the polyurethane has a fusion enthalpy of 3J/g - 100J/g at 20°C-100°C of the first temperature rising curve measured with the DSC according to DIN 65467, a weight-average molecular weight of 31,000 - 95,000, and the aqueous polyurethane dispersion has an acid value of 0.5 mg KOH/g - 8.5 mg KOH/g. The adhesive comprising the aqueous polyurethane dispersion of the present invention has an excellent initial bonding force.