Polyurethane Foam Formulation With Diols for Wet Strength and Absorption
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Solution Overview
Problem
Existing polyurethane foams and hydrogels face challenges in achieving high wet-tensile-strength-at-break (σB,wet) while maintaining high water absorption, often requiring distillation to remove residual diisocyanate and using aromatic isocyanates that lead to yellowing and increased viscosity, with poor performance in terms of (σB,wet/D)·S2 values.
Innovation Solution
A process involving the reaction of low molecular weight aliphatic diisocyanates with polyalkylene oxides and C2 to C12 diols, along with water and optional catalysts, to produce isocyanate-functional prepolymers with minimal residual diisocyanate content, ensuring easy handling and safe processing, and forming foams or hydrogels with high wet-tensile-strength-at-break (σB,wet) and water absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polyols (petroleum-based or vegetable oil-based) are used in foam formulations, then the foam production process is established and predictable, but the products are not biodegradable and contribute to environmental pollution
Solution Approach 1:
The patent changes the chemical composition parameters of the polyol from conventional petroleum-based or vegetable oil-based polyols to diol-containing polyols with specific molecular weight ranges (150-500 g/mol) and specific functional group compositions. This parameter change enables both process stability and biodegradability by selecting diols that maintain polymerization control while being environmentally benign.
Solution Approach 2:
The patent creates a composite polyol system by combining diol-containing compounds with isocyanates and other foam formulation components. The diol component serves as both a chemical reactant and a biodegradability enhancer, creating a composite material system that maintains foam production reliability while reducing environmental harm.
2Object-affected harmful factors
If biodegradable alternatives to conventional polyols are sought, then environmental pollution is reduced, but the foam production process becomes less established and more challenging to control
Solution Approach 1:
The patent establishes reliable process control by defining specific parameter ranges for the diol-containing polyols, including molecular weight (150-500 g/mol), hydroxyl value (30-100 mg KOH/g), and diol content (20-80% by weight). These controlled parameters ensure predictable foam expansion, crosslinking, and curing despite using biodegradable materials.
Solution Approach 2:
The diol-containing compound acts as an intermediary between the isocyanate and the final foam structure. It mediates the polymerization reaction to produce a crosslinked network that is both biodegradable and structurally sound, bridging the gap between environmental sustainability and process reliability.
3Object-affected harmful factors
If diol-containing formulations are used to achieve biodegradability, then environmental compatibility is improved, but the formulation complexity increases due to specific diol selection requirements
Solution Approach 1:
The patent simplifies formulation complexity by establishing clear parameter specifications for diol selection: molecular weight (150-500 g/mol), hydroxyl value (30-100 mg KOH/g), and diol content (20-80% by weight). These defined parameters provide a systematic framework for selecting suitable diols without requiring complex trial-and-error formulation processes.
Solution Approach 2:
The diol-containing compounds serve multiple functions simultaneously: they act as polyol reactants, provide biodegradability, control foam expansion rate, and influence crosslinking density. This multi-functionality reduces the need for separate additives and simplifies the overall formulation despite the specific diol requirements.
4Strength
If crosslinked foam structures are produced for enhanced mechanical properties, then strength and durability are improved, but biodegradability is reduced due to the crosslinked network
Solution Approach 1:
The patent optimizes the crosslinking parameters by controlling the diol molecular weight and hydroxyl value to achieve a balance between mechanical strength and biodegradability. The crosslinking density is adjusted through diol selection to provide sufficient structural integrity while maintaining pathways for microbial degradation.
Solution Approach 2:
The patent creates a composite crosslinked structure where diol-containing segments are incorporated into the polymer network. This composite structure provides both the mechanical strength needed for practical applications and the biodegradability required for environmental sustainability, as the diol segments can be degraded while maintaining overall structural integrity during service life.
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 foams or hydrogels with improved (σB,wet/D)·S2 values, non-yellowing properties, and safe manufacturing, suitable for medical applications like wound dressings, with enhanced wet elongation at break and hydrophilicity.
Implementation Method 1
The diol-containing polyols are employed in the production of rigid and flexible polyurethane foams, as well as in the production of hydrogels
Implementation Method 2
The present invention provides a method for producing rigid and flexible polyurethane foams and hydrogels by reacting a polyol with an isocyanate
Data Source
AI summary
The invention provides a process for producing polyurethane foams or hydrogels, in which compositions comprising A) isocyanate-functional prepolymers obtainable by the reaction of A1)low molecular weight diisocyanates of molar mass from 140 to 278 g/mol, with A2)polyalkylene oxides having an OH functionality of two or more, A3) more than 1% by weight of C2 to C12 diols based on the total amount of the isocyanate-reactive components A2) to A4) wherein component A3) differs from component A2), A4)optionally further isocyanate-reactive components differing from A2) or A3); B) water or a nonaqueous isocyanate-reactive component in an amount of at least 2% by weight, based on the total weight of the composition; C) optionally polyisocyanates obtainable by reaction of at least two low molecular, preferably aliphatic diisocyanates, wherein the diisocyanates having a molar mass of 140 to 278 g/mol, D) optionally catalysts; E) optionally salts of weak acids, the corresponding free acids of which have a pKA in water at 25°C of ≥ 3.0 and ≤ 14.0; F) optionally surfactants; and G) optionally mono- or polyhydric alcohols or polyols; H) optionally hydrophilic polyisocyanates obtainable by reaction of H1) low molecular weight diisocyanates of molar mass from 140 to 278 g/mol and/or polyisocyanates preparable therefrom and having an average isocyanate functionality of 2 to 6 with H2) monohydroxyfunctional polyalkylene oxides of OH number from 10 to 250 and of oxyethylene unit content from 50 to 100 mol%, based on the total amount of the oxyalkylene groups present, are provided, optionally foamed and cured wherein the isocyanate containing components, especially components A), C) and H), do not exceed a residual diisocyanate content of 8% by weight, based on the total amount of the polyurethane foam or hydrogel. These foams or hydrogels are used in wound dressings, cosmetic articles or incontinence products.