High Temperature-Resistant Polyurethane Hot Melt Adhesive via Silane Crosslinking
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Traditional polyurethane hot melt adhesives exhibit poor high temperature resistance, limiting their application above 100 °C due to their linear molecular structure and flexible segments.
Innovation Solution
A method involving the use of isocyanate with high aromatic ring content, silane modifier, and specific polyols to form a three-dimensional network structure, enhancing heat resistance and flexibility through chain extension reactions and the introduction of urea bonds, while balancing the proportion of crystalline and non-crystalline polyols for optimal adhesive performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional linear PUR structure with flexible segments is used, then ease of manufacture and flexibility are improved, but high temperature resistance deteriorates
Solution Approach 1:
The patent introduces silane-modified isocyanate derivatives as a composite component with dual functional groups (NCO and siloxane). The silane modifier reacts with isocyanate to form a compound containing both NCO groups for polyurethane chain extension and siloxane groups for three-dimensional crosslinking. This composite structure enables the adhesive to achieve both flexibility from the polyurethane segments and high temperature resistance from the crosslinked network, resolving the contradiction between ease of manufacture and temperature resistance.
Solution Approach 2:
The patent changes the molecular structure parameters by introducing silane-modified isocyanate derivatives with specific dual functional groups. The functionality balance (NCO to siloxane ratio) is controlled to optimize the balance between linear chain flexibility and crosslinked network rigidity. This parameter change transforms the material from a simple linear structure to a hybrid structure that maintains processability while achieving high temperature resistance above 100°C.
2Temperature
If three-dimensional network structure is formed through silane modification, then high temperature resistance is improved, but molecular flexibility deteriorates
Solution Approach 1:
The patent applies local quality by creating distinct structural zones within the adhesive matrix. The silane-modified isocyanate derivative creates localized crosslinked regions through siloxane group condensation, while the polyol chains maintain flexible linear segments between these crosslinks. This local differentiation allows the material to exhibit both high temperature resistance at the crosslinked nodes and molecular flexibility in the chain segments, resolving the contradiction between network rigidity and overall flexibility.
Solution Approach 2:
The patent segments the molecular structure into distinct functional regions: flexible polyol segments, rigid urethane/urea bonds from chain extension, and crosslinked siloxane nodes. This segmentation creates a hierarchical structure where flexibility and rigidity are distributed at different levels, allowing the adhesive to maintain toughness and impact resistance while achieving high temperature stability through the crosslinked network.
3Strength
If crystalline polyester polyol is increased to improve initial strength, then adhesive strength is improved, but curing speed deteriorates
Solution Approach 1:
The patent introduces silane-modified isocyanate derivatives as an intermediary that facilitates the curing process. The dual functional structure (NCO and siloxane groups) acts as a bridge: NCO groups react with polyol hydroxyls to form polyurethane chains, while siloxane groups undergo condensation to form crosslinks. This intermediary mechanism enables simultaneous achievement of strong adhesive bonds and adequate curing speed, as the crosslinking process is catalyzed by the siloxane functionality without requiring excessive crystalline polyester content.
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 resulting polyurethane hot melt adhesive demonstrates excellent high temperature resistance, toughness, adhesive strength, and resistance to cold and hot shocks, with improved thermal stability and drop resistance, meeting the demands of high-temperature environments.
Implementation Method 1
adding 0.3-3.0 parts of silane modifier to the reactor, and stirring while maintaining a constant temperature of 60-80°C for 1-3 hours to obtain isocyanate derivatives with an average functionality of 1.5-2.0 from a reaction
Implementation Method 2
After bonding and curing, the side chain siloxane is hydrolyzed and dealcoholized, which promotes the curing reaction to form three-dimensional network structure
Implementation Method 3
The heat resistance of urea bond formed by the chain extension reaction of polyether amine and NCO group is higher than that of urethane bond
Implementation Method 4
Its active functional group and isocyanate are subjected to polymerization, which effectively improves the crystallinity of hot melt adhesive
Data Source
AI summary
The present invention relates to a method of preparing polyurethane hot melt adhesive with high temperature resistance. The prepared polyurethane hot melt adhesive is single component moisture cure polyurethane adhesive. The hot melt adhesive made according to the new method has a variety of improved physical and mechanical properties, including improved high temperature resistance, cold and heat shock resistance, drop resistance toughness, high adhesive strength, salt spray resistance and moisture and heat aging resistance, which is of great practical significance to enhance the core competitiveness of domestic polyurethane hot melt adhesive.