Silane-Functional Polymer Curing Without Organotin Catalysts
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Solution Overview
Problem
Silane-functional polymers used in construction and industrial applications face challenges with high viscosity, slow curing, and the need for harmful catalysts like organotin compounds and DBU, which are undesirable due to health and environmental concerns.
Innovation Solution
A polymer formulation with a combination of silane end groups of different reactivities, specifically including end groups of formulas (I), (II), and (III), that cure rapidly without harmful catalysts, achieving low viscosity and excellent mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If silane-functional polyurethane polymers with high content of hydrogen bond-forming urethane and/or urea groups are used, then crosslinking speed and mechanical strength are improved, but viscosity increases making them difficult to process
Solution Approach 1:
The patent changes the chemical composition parameters by reducing urea groups and optimizing urethane group content, while adjusting silane group content to achieve a balance between viscosity and crosslinking speed. This allows the polymer to have lower viscosity for easier processing while maintaining adequate mechanical strength through controlled crosslinking.
2Ease of operation
If silane-functional polymers with low viscosity and few urethane groups are used, then processability is improved, but crosslinking speed decreases and they remain tacky for long periods
Solution Approach 1:
The patent optimizes the concentration of reactive end groups (isocyanate or hydroxyl groups) and silane group content to achieve faster crosslinking speed. By carefully controlling these parameters, the polymer maintains low viscosity for good processability while achieving rapid curing and reduced tackiness through enhanced crosslinking reactivity.
3Speed
If highly active catalysts like organotin compounds are used to accelerate crosslinking, then crosslinking speed is improved, but health and environmental hazards increase
Solution Approach 1:
The patent removes harmful organotin catalysts from the composition entirely. Instead, it relies on the inherent reactivity of the polymer end groups and silane groups to achieve rapid crosslinking without requiring toxic catalysts, thus eliminating health and environmental hazards while maintaining fast curing performance.
4Object-affected harmful factors
If organotitanates are used as catalysts instead of organotin compounds, then health hazards are reduced, but catalytic activity decreases requiring very high dosages or combination with strong bases
Solution Approach 1:
The patent eliminates the need for organotitanate catalysts and strong base additives by designing polymer end groups with inherently high reactivity. This simplifies the catalyst system to just organotitanate at low dosage, reducing both health hazards and formulation complexity while achieving rapid crosslinking through optimized molecular structure rather than high catalyst dosage.
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 polymer formulation exhibits rapid curing, low viscosity, and good mechanical properties, maintaining storage stability and thermal stability without the use of hazardous catalysts, making it suitable for elastic adhesives and coatings.
Implementation Method 1
cures surprisingly rapidly with moisture
Implementation Method 2
crosslinking speed
Implementation Method 3
crosslink relatively rapidly and cure to give nontacky materials
Data Source
AI summary
A polymer preparation consisting of silane-functional polymers, including at least one polymer having at least one terminal group of formula (I) and at least one further silane terminal group, a method for producing the polymer preparation and a composition containing it. The polymer preparation has a surprisingly low viscosity, cross-links surprisingly quickly even without the use of EHS-critical catalysts such as organotin compounds or DBU, and hardens into a non-sticky material with good strength and elasticity. It is especially well suited as an elastic adhesive or sealant or as an elastic coating. The invention further relates to a method for lowering the viscosity of a polymer having at least one terminal group of formula (I) by introducing at least one further silane terminal group.