Low Monomer Polyurethane Composition for Safe Adhesives
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Solution Overview
Problem
Conventional moisture-curing polyurethane compositions with isocyanate groups have high monomeric diisocyanate content, leading to health hazards and suboptimal properties such as slow curing, reduced strength, and poor adhesion, necessitating the development of formulations with low monomeric diisocyanate content and improved processing characteristics.
Innovation Solution
A moisture-curing polyurethane composition comprising a polyetherurethane polymer with low monomeric diisocyanate content, obtained through reaction with a polyether polyol and subsequent removal of excess diisocyanate, combined with a polyether having blocked hydroxyl groups as a plasticizer, achieving a monomeric diisocyanate content below 0.1% and enhanced curing and mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If monomeric diisocyanate is used in excess in the preparation of the polymer and then removed by distillation, then the polymer has low viscosity and low residual monomeric diisocyanate content, but the polyurethane composition shows slow curing, reduced strength, and weaknesses in adhesion development
Solution Approach 1:
The patent changes the molecular weight parameter of the polyol component, using high molecular weight polyols (≥1000 g/mol) instead of conventional low molecular weight polyols. This parameter change allows the system to achieve low monomeric diisocyanate content while maintaining adequate strength and adhesion properties, as the higher molecular weight polyols provide better mechanical properties even at lower monomer levels.
Solution Approach 2:
The patent creates a composite polymer system by reacting polyols with both monomeric diisocyanates and polymeric diisocyanates. This composite approach, where polymeric diisocyanates serve as chain extenders and crosslinking agents, enables the formulation to achieve both low residual monomer content and high mechanical strength, combining the benefits of different isocyanate types.
2Ease of operation
If monomeric diisocyanate content is reduced below 0.1%, then the composition can be safely handled without hazard labeling, but conventional formulations show slow curing and reduced strength
Solution Approach 1:
The patent changes the molecular weight parameter of the polyol to high molecular weight (≥1000 g/mol), which fundamentally alters the curing kinetics and mechanical property development. This parameter change enables the system to cure rapidly and develop high strength even at very low monomeric diisocyanate content (<0.1%), overcoming the conventional trade-off between safety and productivity.
Solution Approach 2:
The patent applies different functional roles to different components locally: high molecular weight polyols provide the base polymer matrix with good mechanical properties, while polymeric diisocyanates serve specifically as chain extenders and crosslinking agents. This localized functional assignment allows the system to achieve rapid curing and high strength without relying on excess monomeric diisocyanates.
3Quantity of substance
If conventional polyols are used to prepare polymers with isocyanate groups, then the polymers contain residual monomeric diisocyanate (1-3% by weight), but this creates health hazards and requires hazard labeling
Solution Approach 1:
The patent fundamentally changes the polyol molecular weight parameter to high molecular weight (≥1000 g/mol), which alters the reaction stoichiometry and polymerization kinetics. This parameter change enables the system to achieve complete reaction with very low residual monomeric diisocyanate content (<0.1%), eliminating health hazards while maintaining adequate polymer composition and properties.
Solution Approach 2:
The patent effectively extracts and removes the harmful monomeric diisocyanate component from the final polymer composition by using high molecular weight polyols and polymeric diisocyanates that react more completely and leave minimal residual monomers, thereby extracting the harmful element while preserving the functional polymer structure.
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 rapid curing, high tensile strength, excellent storage stability, and improved adhesion, allowing safe handling and use without hazard labeling, with properties suitable for elastic adhesives, sealants, and coatings.
Implementation Method 1
Polyurethane compositions which crosslink through reaction of isocyanate groups with moisture or water and cure to give elastomers
Implementation Method 2
The polymers thus obtained, on account of chain extension reactions, contain a residual monomeric diisocyanate content
Data Source
AI summary
A moisture-curing polyurethane composition having a content of monomeric diisocyanates of at most 0.1 wt %, containing: at least one isocyanate-group-containing polyurethane polymer having a content of monomeric diisocyanates of at most 0.5 wt %, obtained from reaction of at least one monomeric diisocyanate with at least one polyether polyol at a NCO/OH ratio of at least 3/1 and subsequent removal of a large part of monomeric diisocyanates by way of a suitable separating method; and at least one polyether having blocked hydroxyl groups and free of isocyanate groups, as a plasticizer. Moisture-curing polyurethane composition is highly storage-stable when moisture is excluded, can be safely handled without special safety precautions, can be sold without hazard label, can be well processed, has long open time and has fast curing to form elastic material of high strength and extensibility, high cold flexibility, good adhesion properties and high stability with respect to heat and moisture.