Silane-Functional Polyurethane Sealant for Isocyanate-Free High Strength
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Solution Overview
Problem
Existing silane-modified amorphous polyalphaolefin-based sealant compositions have lower tensile strength and slower curing profiles compared to polyurethane-based sealants, and they often contain isocyanate monomers, which is a concern.
Innovation Solution
A moisture curable hot melt sealant composition is developed, comprising 1-12% silane-functional polyurethane without isocyanate groups, combined with 10-30% thermoplastic elastomer, 10-40% tackifying agents, and a liquid butene component, which provides improved green strength and curing speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If silane-modified amorphous polyalphaolefin-based sealant compositions are used, then the sealant is free of isocyanate monomers, but the tensile strength is lower and curing profile is slower
Solution Approach 1:
The patent combines silane-modified amorphous polyalphaolefin (providing isocyanate-free formulation) with silane-functional polyurethane (providing high tensile strength and fast curing). This composite approach allows the sealant to achieve both isocyanate-free status and high mechanical performance by leveraging the complementary strengths of each polymer system
Solution Approach 2:
The patent optimizes the molecular weight of the silane-functional polyurethane to be 10,000-100,000 g/mol and controls its content at 1-20% by weight. These parameter adjustments ensure the polyurethane provides sufficient tensile strength enhancement without compromising the isocyanate-free characteristic or causing excessive viscosity
2Object-affected harmful factors
If silane-modified amorphous polyalphaolefin-based sealant compositions are used, then the sealant is free of isocyanate monomers, but the curing profile is slower
Solution Approach 1:
The patent combines silane-modified amorphous polyalphaolefin with silane-functional polyurethane, where the polyurethane component provides faster moisture curing kinetics. The silane groups on both polymers react with atmospheric moisture to form crosslinked networks, with the polyurethane contributing to accelerated cure development
Solution Approach 2:
The patent controls the silane content in the polyurethane component and optimizes its molecular weight to balance reactivity and processing. The silane-functional polyurethane contains sufficient hydrolyzable alkoxy groups to drive rapid crosslinking while maintaining appropriate viscosity for application
3Strength
If silane-functional polyurethane is added to improve green strength and curing speed, then the tensile strength and curing profile improve, but the composition complexity increases
Solution Approach 1:
The patent creates a multi-component composite system combining silane-modified amorphous polyalphaolefin, silane-functional polyurethane, and tackifying resin. Each component serves a specific function: the polyalphaolefin provides isocyanate-free base polymer, the polyurethane enhances strength and curing speed, and the tackifying resin ensures adhesion. This functional division allows optimization of each component
Solution Approach 2:
The patent optimizes the weight ratio of components, specifically limiting silane-functional polyurethane to 1-20% and tackifying resin to 5-40%. These parameter controls prevent excessive viscosity and processing difficulties while ensuring sufficient green strength and adhesion performance
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 composition exhibits enhanced initial green strength, faster curing, and excellent adhesion properties, including high peel strength and shear adhesion failure temperature, while being free of isocyanate monomers.
Implementation Method 1
moisture curable hot melt sealant composition
Implementation Method 2
silane-functional polyurethane
Data Source
AI summary
A moisture curable hot melt sealant composition that includes a silane-functional polyurethane that is free of isocyanate groups, a thermoplastic elastomer having a weight average molecular weight of at least 100,000 grams per mole and being derived from 0% by weight to no greater than 30% by weight styrene, based on the weight of the thermoplastic elastomer, the thermoplastic elastomer being selected from the group consisting of butyl rubber, ethylene-propylene rubber, ethylene-propylene diene rubber, thermoplastic polyolefin elastomer, styrene block copolymer, and combinations thereof, a first tackifying agent that includes from 0% by weight to less than 15% by weight aromaticity based on the weight of the tackifying agent, the first tackifying agent being selected from the group consisting of aliphatic tackifying agent, aromatic-modified aliphatic tackifying agent, cycloaliphatic tackifying agent, aromatic-modified cycloaliphatic tackifying agent, and combinations thereof, a liquid butene component selected from the group consisting of polyisobutylene, polyisobutene, polybutene, and combinations thereof, and optionally a second rosin-based tackifying agent.