Isocyanurate Silane Curable Polyurethane for Primerless Adhesion
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Solution Overview
Problem
Existing polyurethane compositions face challenges in achieving adequate adhesion on various substrates without mechanical or chemical pre-treatment, particularly on modern automotive materials, and contain harmful monomeric diisocyanates exceeding 0.1% by weight, necessitating costly and time-consuming pretreatments and posing health risks.
Innovation Solution
A curable polyurethane composition with isocyanate group-containing polymers, featuring a low monomeric diisocyanate content of less than 0.5% by weight, utilizing isocyanurate silanes and specific reaction conditions to enhance adhesion on metals, plastics, and paint coatings, eliminating the need for pre-treatment and reducing health hazards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyurethane compositions are formulated to achieve good adhesion on difficult substrates like automotive paint, then adhesion performance is improved, but extensive pre-treatment (mechanical sanding or chemical primers) is required which increases process complexity and cost
Solution Approach 1:
The patent introduces silane coupling agents as intermediary substances that mediate between the polyurethane composition and the substrate surface. These silanes form chemical bonds with both the substrate and the polyurethane, creating a bridge that enables adhesion without requiring mechanical or chemical pre-treatment of the substrate.
Solution Approach 2:
The patent modifies the chemical composition parameters of the polyurethane system by incorporating specific silane compounds and adjusting the isocyanate index. This chemical parameter change enables the composition to chemically interact with difficult substrates like automotive paint, achieving adhesion through molecular-level interaction rather than mechanical anchoring.
2Stability of the object's composition
If monomeric diisocyanates are used in excess during polymer production to ensure complete reaction, then polymerization completeness is improved, but residual monomeric diisocyanate content increases above the 0.1% safety threshold
Solution Approach 1:
The patent carefully adjusts the isocyanate index (NCO/OH ratio) and reaction parameters to optimize the balance between complete polymerization and residual monomer content. By controlling the isocyanate index within a specific range and optimizing reaction conditions, the process achieves sufficient polymerization completeness while keeping residual monomeric diisocyanate below 0.1%.
Solution Approach 2:
The patent uses a model approach where the polymerization process is optimized based on established kinetic models and previous experimental data. This allows prediction and control of residual monomer content while ensuring complete reaction, avoiding the need for excessive isocyanate that would lead to harmful residuals.
3Ease of operation
If one-component polyurethane compositions are used to simplify application, then ease of operation is improved, but curing control becomes dependent on atmospheric moisture diffusion which may affect curing consistency
Solution Approach 1:
The silane coupling agents act as intermediaries that facilitate more uniform curing by creating a controlled reaction pathway. The silanes can react with both moisture and isocyanate groups, providing an additional curing mechanism that complements moisture-curing and ensures more consistent results across different atmospheric conditions.
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 composition exhibits excellent adhesion performance on diverse substrates, including metals and plastics, with overpaintability, low odor emissions, durability, and resistance to aging, while being safe to handle without special protective measures.
Implementation Method 1
One-component polyurethane compositions cure by reacting the isocyanate groups with moisture, usually atmospheric moisture
Implementation Method 2
crosslink by reaction of isocyanate groups with moisture and cure to form elastomers
Implementation Method 3
at least one isocyanurate silane IS
Data Source
AI summary
The invention relates to a curable polyurethane composition comprising at least one isocyanate group-containing polyurethane polymer with a maximal content of 0.5 wt.-% of monomeric diisocyanate obtained from the reaction of at least one diisocyanate monomer with at least one polyether polyol in an NCO/OH molar ratio of at least 3/1 and by subsequent removal of the majority of the monomer diisocyanate using a suitable separation method and furthermore comprising at least one isocyanurate silane. The curable polyurethane composition can be formulated to show excellent properties for primerless adhesion on metals, plastic and paint coatings and other industrial substrates. Further advantages of the inventive composition include generally good performance characteristics, particularly overpaintability, low emissions of odor, durability and resistance to ageing and weathering. Furthermore, the inventive composition is safe to handle without special protective measures.