Silane Functional Binder Thiourethane Structure
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Solution Overview
Problem
Existing methods for producing silane-modified polyurethanes face challenges such as high viscosity, contamination with non-isocyanate functional silanes, and instability during thermal processing, making them unsuitable for industrial-scale production and application as binders in adhesives, sealants, and coatings.
Innovation Solution
A process involving the reaction of mercaptosilanes with diisocyanates in a controlled equivalent ratio, followed by thin-film distillation to separate excess monomers, results in low-viscosity, stable isocyanatosilanes that can be effectively combined with polyols to form silane-functional polyurethanes with improved properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If isocyanatoalkylalkoxysilanes are used to modify polyols, then low-viscosity silane-functional polyurethanes can be produced, but the isocyanatosilanes are difficult to access on an industrial scale and have inadequate storage stability
Solution Approach 1:
The patent changes the chemical structure parameter of the isocyanatosilane by using aspartic acid ester derivatives instead of simple alkylaminosilanes. This structural modification enables the formation of stable urea structures during reaction with isocyanates, preventing the blocking agent character that causes instability and storage problems while maintaining low viscosity properties.
Solution Approach 2:
The patent employs a straightforward synthesis route using readily available aspartic acid esters and diisocyanates that can be produced on an industrial scale. The process accepts the formation of some byproducts (doubly silylated compounds) but achieves practical utility through controlled reaction conditions, making the isocyanatosilanes economically viable for industrial production despite the complexity of achieving high monomer purity.
2Productivity
If simple N-alkylaminosilanes are reacted with isocyanates, then isocyanatosilanes can be formed, but the urea structures are unstable and release isocyanate groups at elevated temperatures causing blocking agent character
Solution Approach 1:
The patent modifies the chemical structure by replacing simple N-alkylamino groups with aspartic acid ester-derived amino groups. This structural change creates sterically hindered and electronically stabilized urea structures that resist thermal decomposition, preventing the release of isocyanate groups at elevated temperatures and eliminating the blocking agent character while maintaining reaction efficiency.
3Manufacturing precision
If a large molar excess of isocyanate is used in the reaction, then 1:1 monoadducts can be obtained, but very high proportions of doubly silylated 2:1 bisadducts are always formed
Solution Approach 1:
The patent changes the reactivity parameters by using aspartic acid ester derivatives that form stable urea structures upon reaction with isocyanates. This kinetic stabilization prevents further reaction of the monoadduct with additional isocyanate groups, allowing high selectivity for 1:1 monoadducts even when using large molar excesses of isocyanate, thereby maximizing both precision and yield.
4Stability of the object's composition
If adducts of isocyanates to aspartic acid esters are reacted at mild temperatures, then hydantoin derivatives are formed with loss of NCO functionality
Solution Approach 1:
The patent modifies the molecular structure by introducing specific substituents on the aspartic acid ester framework that sterically protect the NCO groups from intramolecular cyclization. This structural modification raises the activation energy for hydantoin formation, allowing the compound to remain stable at mild temperatures while retaining NCO functionality for subsequent reactions with polyols.
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 process yields polyurethanes with low viscosity and reduced crystallization tendency, maintaining stability under high temperatures, and allows for the production of high-quality binders suitable for various applications, including moisture-curing and thermally curable adhesives, sealants, and coatings.
Implementation Method 1
A process for producing polyurethanes containing silane groups by reacting at least A) a composition containing a) one or more compounds of the general formula (I) containing isocyanate and silane groups
Implementation Method 2
The unreacted monomeric diisocyanates are then separated off by distillation
Implementation Method 3
reacting at least A) a composition containing a) one or more compounds of the general formula (I) containing isocyanate and silane groups. and b) ≤ 1% by weight, based on the total mass of the composition A), of one or more monomeric diisocyanates
Data Source
AI summary
The invention relates to a method for producing polyurethanes containing silane groups by reacting at least A) a composition containing a) one or more compounds containing isocyanate and silane groups of general formula (I) and b) ≤ 1 percent by weight, relative to the total mass of composition A), one or more monomeric diisocyanates with aliphatically, cycloaliphatically, araliphatically and/or aromatically bonded isocyanate groups of general formula (II), where R1, R2 and R3 are the same or different radicals and respectively indicate a saturated or unsaturated, linear or branched, aliphatic or cycloaliphatic or an optionally substituted aromatic or araliphatic radical with up to 18 carbon atoms, which can contain optionally up to 3 heteroatoms from the series oxygen, sulphur, nitrogen, X is a linear or branched organic radical with at least 2 carbon atoms and Y is a linear or branched, aliphatic or cycloaliphatic radical with 4 to 18 carbon atoms or an optionally substituted aromatic or araliphatic radical with 6 to 18 carbon atoms, with B) an at least difunctional polyol with a numerically average molecular weight Mn of 62 to 22000 g/mol, preferably 90 to 12000 g/mol, while maintaining an equivalent ratio of isocyanate groups to hydroxyl groups of 0.7:1 to 1.2:1. The invention further relates to the products which can be obtained using the method according to the invention. Moreover, the invention relates to the use of the products which can be obtained using the method according to the invention as starting components in the production of cross-linkable binders, varnish, and raw materials for sealants or adhesives.