2K-PU Adhesive Low-Temperature Elasticity via Isocyanate Shape
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Solution Overview
Problem
Existing two-component polyurethane adhesives fail to provide sufficient elasticity and bond stability at low temperatures, leading to brittleness and reduced adhesion when exposed to temperature changes and humidity.
Innovation Solution
A 2-component polyurethane adhesive system comprising an OH polyurethane prepolymer and a crosslinker component, where polyisocyanate A has an elongated or angled shape and polyisocyanate B has an opposite structure, with a specific NCO:OH ratio, ensuring a modulus of elasticity less than 4000 MPa across a -60 to +30°C temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional polyurethane adhesives are used to bond substrates, then adhesion is achieved at room temperature, but the bond becomes brittle and loses elasticity at low temperatures
Solution Approach 1:
The patent changes the chemical composition parameters of the adhesive by incorporating specific polyols (polyester polyol, polyether polyol, or poly silicone oxide) with defined molecular weights and hydroxyl numbers. This parameter modification enables the adhesive to maintain elasticity at low temperatures while preserving bond strength, resolving the contradiction between strength and elasticity stability.
Solution Approach 2:
The patent creates a composite adhesive system combining multiple components: polyol component (with specific polyols), isocyanate component, and optional additives. This composite formulation allows the adhesive to achieve both strong bonding and temperature-stable elasticity by leveraging the complementary properties of different materials working together.
2Stability of the object's composition
If plasticizers are added to improve elasticity, then low-temperature flexibility increases, but the plasticizers sweat out at temperature changes and worsen adhesion
Solution Approach 1:
The patent modifies the chemical parameters of the adhesive formulation by selecting specific polyols with controlled molecular weights (200-10,000 g/mol) and hydroxyl numbers (50-400 mg KOH/g). This parameter optimization enables the adhesive to achieve adequate elasticity without requiring plasticizers that would migrate and compromise adhesion stability.
Solution Approach 2:
The patent eliminates the need for plasticizers by incorporating the elasticizing function directly into the adhesive formulation through carefully selected polyols. This removes the harmful element (plasticizer migration) while maintaining the desired elasticity, effectively replacing a temporary fix with a permanent solution.
3Ease of operation
If the adhesive is designed for room temperature bonding, then ease of application is improved, but performance deteriorates under temperature gradients and humidity
Solution Approach 1:
The patent adjusts the chemical parameters of the adhesive by incorporating polyols with specific molecular weights and hydroxyl numbers, along with controlled NCO:OH ratios. These parameter changes enable the adhesive to maintain its bonding properties across a wide temperature range (-60 to +30°C) and under humid conditions, while still remaining easy to apply at room temperature.
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 achieves stable and flexible bonding at low temperatures, maintaining adhesion and elasticity even under varying conditions, including humidity and temperature gradients, with improved cohesion due to the alternating isocyanate structures.
Implementation Method 1
a 2-component polyurethane adhesive consisting of an OH polyurethane prepolymer, possibly further polyols and additives, produced by reacting an oleochemical 2 to 5 functional polyol and 5 to 75% by weight, based on the polyol component, of further polyols with a polyisocyanate A
Data Source
AI summary
A two-component polyurethane adhesive consisting of a polyol component containing an OH polyurethane prepolymer, optionally further polyols and additives, produced by reacting at least one oleochemical 2 to 5 functional polyol with a polyisocyanate A having an NCO:OH ratio of 1:2 to 1:5 and a crosslinking component consisting of a polyisocyanate B, wherein the polyisocyanate A has an elongated or angular shape and the polyisocyanate B is selected from isocyanates with an opposite shape, wherein 20 to 85 mol% of the sum of A and B must have an elongated shape, the elongated isocyanates are contained in only one component, and the crosslinked adhesive exhibits a change in the modulus of elasticity of less than 4000 MPa in the temperature range between -60 and +30°C.