Moisture Curable Polyurethane Hot-Melt Adhesive Initial Strength
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Solution Overview
Problem
Conventional moisture curable polyurethane hot-melt adhesives exhibit a slow build-up of adhesive bonding strength, which is a significant disadvantage, especially in automotive lamination applications.
Innovation Solution
A novel moisture curable polyurethane hot-melt adhesive composition is developed, which includes an isocyanate-functional polyurethane polymer obtained by reacting a polyol composition with a polyisocyanate. The polyol composition comprises a low molecular weight polyether polyol with a high hydroxyl number, significantly improving the initial adhesion strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional moisture curable polyurethane hot-melt adhesives are used, then heat stability is improved, but initial adhesion strength builds up slowly
Solution Approach 1:
The patent changes the chemical composition parameters by incorporating specific polyols with controlled molecular weights and hydroxyl numbers, along with catalysts and extenders, to optimize the curing kinetics and initial adhesion development of the moisture curable polyurethane adhesive
Solution Approach 2:
The patent creates a composite adhesive system combining moisture curable polyurethane polymers with additional functional components including polyols, catalysts, and extenders to achieve both rapid initial adhesion and long-term heat stability
2Strength
If polyol composition is optimized for initial strength, then adhesion strength is improved, but viscosity may increase
Solution Approach 1:
The patent applies local quality by using a mixture of polyols with different molecular weights and properties - combining lower molecular weight polyols for流动性 and lower viscosity with higher molecular weight polyols for adhesion strength, creating zones of different functional properties within the adhesive composition
Solution Approach 2:
The patent optimizes viscosity by carefully selecting polyol molecular weights, hydroxyl numbers, and ratios, along with incorporating catalysts and extenders that modify the rheological parameters of the adhesive at application temperatures
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 composition achieves improved initial adhesion strength, high lap shear strength, and low viscosity at typical application temperatures, making it suitable for automotive interior lamination applications.
Implementation Method 1
The chemical curing of the polymers can be initiated, for example, by heating or exposing the adhesive composition to water, such as atmospheric moisture. Moisture curing hot-melt adhesives typically contain polymers functionalized with isocyanate or silane groups, which enables crosslinking of the polymer chains upon contact with atmospheric moisture.
Implementation Method 2
Reactive hot-melt adhesives contain polymers with reactive groups that enable chemical curing of the adhesive, for example, by crosslinking of the polymer chains. A fully cured polyurethane hot-melt adhesive comprises urea and/or urethane bonds
Implementation Method 3
Hot-melt adhesives are solvent free adhesives, which are solid at room temperature, and which are applied to the substrate to be bonded in form of a melt. After cooling the adhesive solidifies and forms an adhesive bond with the substrate through physically occurring bonding.
Data Source
AI summary
A moisture curable adhesive composition including at least one isocyanate-functional polyurethane polymer P obtained by reacting: a) a polyol composition including a1) at least one at 25° C. solid polyester polyol PO1 and a2) at least one polyether polyol PO2, and b) at least one polyisocyanate PI, wherein the at least one polyether polyol PO2 has a hydroxyl-number determined according to ISO 4629-2:2016 standard of at least 100 mg KOH/g, preferably at least 150 mg KOH/g. The adhesive composition can also be used as an assembly adhesive, laminating adhesive, or as an adhesive for the building of sandwich elements, particularly as an interior laminating adhesive in automotive industry.