Vehicle Window Adhesive Composition with Crystallizing Polyester Polyol
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Solution Overview
Problem
Existing adhesives used for bonding glass in vehicles and buildings face challenges in providing fast strength development and sag resistance, often requiring additional fixturing and compromising on physical properties due to high thermoplastic content.
Innovation Solution
A composition comprising isocyanate functional polyether polyurethane prepolymers and capped polyester polyols, which crystallizes upon cooling to provide rapid strength and resistance to sagging, allowing for bonding without additional fixturing and maintaining excellent long-term properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If crystalline thermoplastic polymers are included in the adhesive to provide initial green strength, then the adhesive can hold glass in place without additional fixturing, but the adhesive cures too slow and does not provide enough green strength to prevent movement of glass
Solution Approach 1:
The patent modifies the chemical composition parameters by using specific polyester polyols with controlled molecular weights (2,000-10,000 g/mol) and isocyanate indices (105-130), along with catalysts and extenders, to achieve both fast cure and adequate green strength simultaneously
Solution Approach 2:
The adhesive forms a composite structure combining crystalline polyester polyol domains (providing green strength through sag resistance) with crosslinked polyurethane matrix (providing fast cure and final strength), creating a multi-phase material that delivers both rapid setting and structural support
2Strength
If high amounts of thermoplastic component are used to provide green strength, then the adhesive can hold glass in place, but the physical properties of the cured adhesive are negatively impacted
Solution Approach 1:
The patent optimizes the thermoplastic component content to a specific range (5-30 parts by weight per 100 parts polyol) and controls the crystallization temperature (40-80°C) to balance green strength provision with maintenance of cured adhesive physical properties
Solution Approach 2:
The adhesive creates localized crystalline domains of polyester polyol within the adhesive matrix that provide green strength only where needed during application, while the bulk material maintains its cured physical properties through the crosslinked polyurethane structure
3Stability of the object's composition
If the adhesive is applied at ambient temperature, then the adhesive maintains high viscosity for sag resistance, but the adhesive does not spread well and requires heating to become low viscous for proper application
Solution Approach 1:
The adhesive exploits the phase transition of polyester polyol from solid (crystalline) at ambient temperature to liquid at elevated temperature. During storage and application, the adhesive is heated to melt the crystalline domains, reducing viscosity for easy spreading. Upon cooling, the polyester polyol recrystallizes, providing sag resistance and green strength
Solution Approach 2:
The adhesive undergoes periodic heating during application to reduce viscosity for spreading, then cooling during curing to increase viscosity for sag resistance. This temperature cycling enables the adhesive to switch between application-friendly and structurally-stable states
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 adhesive demonstrates rapid strength development and excellent sag resistance, preventing glass movement during installation and maintaining strong bonding over time, thus eliminating the need for additional fixturing and enhancing the physical properties of the adhesive.
Implementation Method 1
As the adhesive cools the thermoplastic portion crystallizes and provides initial green strength to hold the glass in place
Implementation Method 2
the composition is a low viscous paste at temperature of from about 40 to about 80° C. and is high viscous paste at a temperature of from about 40° C. or less
Data Source
AI summary
In one embodiment, the invention is an composition comprising:a) one or more isocyanate functional polyether polyurethane prepolymers; andb) one or more prepolymers of one or more polyisocyanates and one or more polyesterswherein the terminal groups on the polyester polyol polyurethane prepolymer are the residue of a monofunctional polyalkylene glycol (hereinafter capped polyester polyurethane prepolymer) or one or more polyester polyols which are capped with the residue of one or more monofunctional isocyanates (hereinafter isocyanate capped polyesters); wherein the composition is a low viscous paste at temperature of from about 40 to about 80° C. and is high viscous paste at a temperature of from about 40° C. or less. In a preferred embodiment the composition further comprises c) one or more catalysts for the reaction of isocyanate moieties with hydroxyl groups. In another embodiment the invention is a method of bonding two or more substrates together which comprise contacting the two or more substrates together with a composition according to this invention disposed along at least a portion of the area wherein the substrates are in contact wherein the composition is a low viscous paste. In a preferred embodiment the composition is heated to about 40° C. to about 80° C. and converted to a low viscous paste prior to contacting it with the one or more substrates.