Silylated Polyurethane Synthesis via Controlled NCO Ratios
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Solution Overview
Problem
Current processes for synthesizing silylated polyurethanes are economically inefficient, have high crosslinking times, and result in unstable viscosity in adhesive and surface coating compositions, requiring large amounts of expensive silanes and leading to potential toxicity issues from residual diisocyanate monomers.
Innovation Solution
A process involving sequential stages of polyaddition with a diisocyanate and polyol, followed by reaction with aminosilanes or mercaptosilanes, and then with compounds containing alcohol, amine, or thiol functional groups, to achieve a composition of silylated polyurethanes with controlled NCO functional group ratios, reducing the need for expensive silanes and eliminating residual diisocyanates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large amounts of aminosilanes are used to react with 100% of NCO functional groups, then complete reaction of NCO groups is achieved, but the cost increases due to expensive starting materials
Solution Approach 1:
The patent applies partial action by reacting NCO functional groups with aminosilanes in a ratio less than 1:1 (specifically 0.9:1 to 1.05:1), allowing some NCO groups to remain unreacted. This partial reaction approach reduces the quantity of expensive aminosilane needed while maintaining acceptable product performance, directly resolving the contradiction between complete reaction and material cost.
Solution Approach 2:
The patent changes the reaction parameter by adjusting the molar ratio of NCO groups to aminosilane from complete stoichiometric ratio (1:1) to a controlled excess ratio (0.9:1 to 1.05:1). This parameter modification optimizes the balance between reaction completeness and material efficiency, reducing costly silane consumption while maintaining product quality.
2Adaptability or versatility
If the amount of NCO functional groups is made greater than the amount of amine or thiol functional groups, then more versatile silylated polyurethane can be obtained, but the crosslinking time becomes high
Solution Approach 1:
The patent optimizes the NCO to aminosilane ratio parameter within the range of 0.9:1 to 1.05:1, which is slightly less than the 1:1 stoichiometric ratio. This parameter adjustment accelerates the crosslinking reaction by creating a more balanced functional group ratio, thereby reducing crosslinking time while still producing versatile silylated polyurethane with adequate reactivity.
3Ease of manufacture
If residual diisocyanate monomers are present in the composition, then the synthesis process is simpler, but toxicity issues arise
Solution Approach 1:
The patent converts the potential harm of residual diisocyanate into a benefit by controlling the NCO to aminosilane ratio to be slightly less than 1:1. This ensures that aminosilane is in excess, completely consuming all NCO groups and eliminating residual diisocyanate monomers. The excess aminosilane reacts to form additional silylated polyurethane chains, transforming what would be a harmful residue into a beneficial component that enhances product performance and safety.
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 results in a composition with high crosslinking rates, stable viscosity over time, and reduced toxicity, while minimizing the use of expensive starting materials, thus enhancing the performance and safety of silylated polyurethane-based adhesive and surface coating compositions.
Implementation Method 1
polyaddition of at least one polyol (B) with at least one diisocyanate (C)
Implementation Method 2
reaction of said polyurethane prepolymer having NCO endings with an aminosilane, where each of the NCO functional groups reacts with an amine functional group of the aminosilane
Implementation Method 3
reaction of said polyurethane prepolymer having NCO endings with a mercaptosilane
Implementation Method 4
the crosslinking of the coated composition (P), by heating the coated carrying surface
Data Source
AI summary
The present invention provides a process for the synthesis of silylated polyurethanes, comprising three sequential steps, a step (i) of preparing NCO-terminated polyurethane, a step (ii) of partial grafting of the NCO functions with silane functions and a step (iii) of total grafting of the residual NCO functions with functions that react with the NCO functions by means of polyfunctional compounds. The present invention also provides a silylated polyurethane composition that can be obtained by means of the process according to the invention, an adhesive composition comprising said silylated polyurethane composition and a self-adhesive item obtained from the adhesive composition according to the invention.