UV-Resistant Lignin PU Elastomer via Selective Acylation
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Solution Overview
Problem
Current methods for synthesizing lignin-based polyurethane (PU) elastomers often require modifications that increase production costs and environmental impact, while lacking UV resistance and transparency, and do not fully utilize natural lignin's potential for green and sustainable materials.
Innovation Solution
A method involving the direct use of natural lignin as an end-capping agent with isophorone diisocyanate and 2,2-dimethylolbutyric acid, combined with polyether chain polyols, to produce a UV-resistant, transparent, and colored lignin-based PU elastomer through a series of reactions and processing steps, including dissolving and reacting components in DMF, followed by rotary evaporation, drying, and thermoplastic molding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If lignin is modified by enzymatic hydrolysis or alkali digestion to improve reactivity and processability, then the reprocessability and molecular weight control are improved, but the UV resistance and transparency are lost, and additional production steps increase environmental impact
Solution Approach 1:
The patent extracts only the necessary functional groups (hydroxyl groups) from lignin through selective acylation, rather than completely depolymerizing the lignin structure. This preserves the aromatic ring structures that provide UV resistance while obtaining sufficient reactivity for PU synthesis. The mild acylation treatment maintains the integrity of lignin's chromophoric structures unlike harsh enzymatic or alkali methods.
Solution Approach 2:
The patent changes the chemical parameters of lignin by controlling the degree of acylation (DS value) to optimize the balance between reactivity and UV resistance. By adjusting the acylation degree rather than complete depolymerization, the method maintains lignin's inherent UV-absorbing properties while achieving adequate reaction activity for elastomer synthesis.
2Reliability
If additional polyol or lignin modifications are performed to improve reactivity, then the synthesis activity is improved, but the synthesis procedure becomes complicated and production costs increase
Solution Approach 1:
The patent performs preliminary acylation of lignin to introduce reactive acyl groups before the main PU synthesis reaction. This preliminary modification ensures sufficient reactivity for the subsequent isocyanate reaction without requiring complex multi-step modifications during the main synthesis process, thereby simplifying the overall procedure while maintaining high synthesis activity.
Solution Approach 2:
The patent uses acyl groups as intermediary functional groups that bridge the gap between natural lignin's low reactivity and the high reactivity requirements of isocyanate reactions. These acyl groups serve as reactive intermediaries that facilitate urethane bond formation while maintaining the underlying lignin structure's beneficial properties.
3Ease of manufacture
If natural lignin is used directly as polyol to simplify the synthesis procedure, then the production cost and environmental impact are reduced, but the reactivity and cross-linking degree are insufficient
Solution Approach 1:
The patent applies preliminary acylation treatment to natural lignin to enhance its reactivity before use in PU synthesis. This preliminary modification introduces more reactive acyl groups that can effectively participate in isocyanate reactions, achieving sufficient cross-linking density without requiring complex subsequent modifications or higher lignin loading.
Solution Approach 2:
The patent changes the chemical reactivity parameters of natural lignin through controlled acylation, transforming it from a low-reactivity natural polymer to a highly reactive precursor suitable for efficient PU elastomer synthesis with adequate cross-linking, all while maintaining the simplicity of using naturally sourced lignin.
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 resulting lignin-based PU elastomer exhibits excellent high elasticity, elastic recovery, mechanical properties, UV resistance, and reprocessability, with potential applications in films, fabric coatings, and biomass materials, maintaining a simple and environmentally friendly synthesis process.
Implementation Method 1
the lignin-based PU elastomer exhibits excellent high elasticity, elastic recovery, mechanical properties, UV resistance
Data Source
AI summary
The present disclosure discloses a preparation method of an ultraviolet (UV)-resistant and transparent lignin-based polyurethane (PU) elastomer. During the synthesis process, natural lignin-based polyols are directly used as an end-capping agent, isophorone diisocyanate and 2,2-dimethylolbutyric acid are used as a hard segment and polyether chain polyols are used as a soft segment, to synthesize a PU elastomer with a transparent brown appearance, excellent high elasticity and elastic recovery performance, as well as excellent mechanical properties, excellent UV resistance and repeatable processability. The lignin-based PU elastomer has a simple preparation process, and has great potential values for use in the fields such as PU elastomer film, fabric coating, and elastic fiber and biomass polymer materials.