Linear Isocyanate Polymer Adhesive for Plastic Substrates
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Solution Overview
Problem
Current polyurethane compositions with low monomeric diisocyanate content struggle with slow curing and low mechanical strength, while those with high monomeric diisocyanate content are complex to produce and pose health hazards, necessitating a solution for adhesives that adhere well to plastic substrates without complex pretreatment and are safe to handle.
Innovation Solution
A linear polymer with an NCO content of 0.3 to 1.5% by weight, based on aromatic monomeric diisocyanates and polyether diols, is developed, allowing for the removal of excess monomeric diisocyanate through distillation, resulting in adhesives with improved adhesion and mechanical properties on plastic substrates like PVC, PMMA, and polycarbonate, even under heat and water exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If monomeric diisocyanate is used in excess during polymer synthesis to ensure complete reaction, then conversion is improved, but residual monomer content increases leading to health hazards and labeling requirements
Solution Approach 1:
The patent applies extraction by removing the harmful residual monomeric diisocyanate from the polymer product through distillation processes. The method specifically removes excess monomer after polymer synthesis while retaining the desired polymer structure, achieving both high conversion and low residual monomer content (below detection limits or <0.1% by weight).
Solution Approach 2:
The patent changes physical parameters (temperature, pressure) during distillation to selectively remove monomeric diisocyanate. By controlling distillation conditions, the process achieves complete monomer removal while preserving the polymer integrity and functional properties.
2Object-affected harmful factors
If excess monomeric diisocyanate is removed by distillation to reduce residual content, then health safety is improved, but curing speed and mechanical strength decrease
Solution Approach 1:
The patent changes the chemical structure parameters of the polyol component (using polyols with specific OH numbers and molecular weights) to compensate for the reduced monomer content. This allows achieving high mechanical strength without relying on excess monomeric diisocyanate, thereby maintaining both safety and performance.
Solution Approach 2:
The patent creates a composite polymer system combining polyether diols with specific properties and controlled amounts of monomeric diisocyanate. This composite approach allows optimizing both the safety (low monomer content) and mechanical properties through synergistic material composition.
3Object-affected harmful factors
If linear polymer with long chain length is used to reduce monomer content, then adhesion to plastic substrates is improved, but viscosity increases making handling difficult
Solution Approach 1:
The patent changes the molecular weight and OH number parameters of the polyether diol to control polymer viscosity. By selecting polyols with specific properties (OH number 5-21 mg KOH/g), the process achieves low viscosity despite using linear polymers with long chain lengths, thereby maintaining both safety and ease of handling.
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 enables label-free, elastic adhesives with high strength and excellent adhesion to plastic substrates, providing superior mechanical properties and storage stability, while reducing health risks associated with monomeric diisocyanate exposure.
Implementation Method 1
obtained from the reaction of at least one monomeric aromatic diisocyanate and a polyether diol with an OH number in the range of 5 to 21 mg KOH/g in an NCO/OH ratio of at least 5/1
Implementation Method 2
subsequent removal of a large part of the monomeric aromatic diisocyanate by means of a suitable separation process
Data Source
AI summary
The invention relates to a linear isocyanate group-containing polymer having an NCO content in the range from 0.3 to 1.5 wt% and a monomeric diisocyanate content of not more than 0.5 wt%, characterized in that the polymer is obtained from the reaction of at least one monomeric aromatic diisocyanate and a polyether diol having an OH number in the range from 5 to 21 mg KOH/g in an NCO/OH ratio of at least 5:1 and subsequent removal of a majority of the monomeric diisocyanate by way of a suitable separation process, and to moisture-curing polyurethane compositions having a monomeric diisocyanate content of less than 0.1 wt% containing said polymer. The polymer according to the invention permits the production of elastic adhesives having high elongation, surprisingly high strength and surprisingly good adhesion to plastic substrates.