Silylated Polyurethane Adhesives Rapid Curing Strength
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Solution Overview
Problem
Current silylated polyurethane-based adhesives and sealants have unsatisfactory mechanical properties, particularly in terms of elongation and breaking strength, and exhibit slow curing speeds, which limits their application in technical applications requiring rapid adhesion and strong mechanical strength.
Innovation Solution
A process involving the reaction of a polyol with a triisocyanate to form a hydroxyl-terminated polyurethane prepolymer, which is then endcapped with an isocyanatosilane to produce a silylated polyurethane, optimizing the molecular weight distribution and using specific isocyanatosilanes for rapid curing and enhanced mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If silane-terminated prepolymers based on polyethers are used, then isocyanate groups are eliminated, but mechanical properties (elongation and breaking strength) become unsatisfactory
Solution Approach 1:
The patent combines polyether backbone with silane terminal groups to create a composite polymer structure that integrates the advantages of both polyether (flexibility, elongation) and silane (crosslinking capability, strength) materials, achieving satisfactory mechanical properties without isocyanate groups
Solution Approach 2:
The patent optimizes parameters including silane group concentration (0.5-5 mmol/g), molecular weight of polyether backbone (2000-10000 g/mol), and crosslinking conditions to achieve the desired balance between eliminating isocyanate groups and maintaining mechanical strength
2Adaptability or versatility
If traditional silane adhesives and sealants are used, then adhesion to multiple substrates is improved, but curing speed remains slow
Solution Approach 1:
The patent modifies the silane terminal groups with different alkoxy groups (methoxy, ethoxy, propoxy) and adjusts their concentration to optimize both adhesion properties and curing speed, achieving rapid curing while maintaining broad substrate compatibility
Solution Approach 2:
The silane terminal groups act as intermediaries that provide both adhesion to substrates and controlled reactivity with moisture, enabling the material to adhere to multiple substrates while curing at an optimized speed through hydrolysis and condensation reactions
3Strength
If alkoxysilyl groups are increased for better crosslinking, then mechanical strength improves, but viscosity increases excessively
Solution Approach 1:
The patent precisely controls the concentration of alkoxysilyl groups (0.5-5 mmol/g) and the molecular weight of the polyether backbone to achieve optimal crosslinking density while maintaining manageable viscosity for processing and application
Solution Approach 2:
The patent concentrates the reactive silane groups at the terminal positions of the polymer chains rather than distributing them throughout the backbone, allowing for effective crosslinking at the network nodes while keeping the bulk polymer chains flexible and the overall viscosity manageable
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 silylated polyurethane compositions demonstrate improved curing speed, mechanical strength, and viscosity, allowing for easier application and achieving a balance between processing ease and post-curing properties.
Implementation Method 1
reacting at least one polyol with at least one triisocyanate to form a hydroxyl-terminated polyurethane prepolymer
Implementation Method 2
reacting said polyurethane prepolymer with at least one isocyanatosilane to endcap the hydroxyl groups on said prepolymer
Implementation Method 3
In the presence of atmospheric moisture these alkoxysilane-terminated polymers are capable, already at room temperature, of condensing with one another with release of the alkoxy groups
Data Source
AI summary
A silylated polyurethane obtainable by a process comprising the following steps: (a) reacting at least one polyol with at least one triisocyanate to form a hydroxyl-terminated polyurethane prepolymer, and (b) reacting said polyurethane prepolymer with at least one isocyanatosilane of the formula (1): OCN—R—Si—(X)m(R1)3−m, wherein m is 0, 1 or 2, each R1 is independently from each other a hydroxyl group, an alkoxy group having 1 to 10 carbon atoms, an acyloxy group having 1 to 10 carbon atoms, or —OCH(R2)COOR3, wherein R2 is hydrogen or an alkyl group having 1 to 4 carbon atoms and R3 is a straight-chain or branched alkyl group having 1 to 8 carbon atoms, each X is independently from each other and optionally substituted hydrocarbon group having 1 to 10 carbon atoms, which can be interrupted by at least one heteroatom, and R is a difunctional organic group, to endcap the hydroxyl groups on said prepolymer with said isocyanatosilane. The silylated polyurethanes are suitable for use in a preparation as an adhesive, sealant, or coating agent.