Dielectric Curing of Lignocellulosic Composite Sheets for Uniform Hardening
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Solution Overview
Problem
Existing lignocellulosic composite production processes using carbohydrate-based binders require harsh reaction conditions, multiple curing steps, and result in uneven heating, surface defects, and inhomogeneous material characteristics, posing challenges in efficiency, economy, and quality control.
Innovation Solution
A process involving a heat-curable binder composition with carbohydrate and amino compounds, hardened via dielectric heating and pressing in a single step, eliminating the need for post-curing and ensuring uniform heating across the sheet.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional conductional heating with hot press plates is used, then the binder can be hardened, but the heating is uneven causing surface defects and inhomogeneous material characteristics
Solution Approach 1:
The patent replaces the mechanical conductional heating system (hot press plates) with a dielectric heating system using electromagnetic fields. This substitution enables uniform volumetric heating throughout the sheet material, eliminating the surface-to-core temperature gradient that causes surface defects and inhomogeneous characteristics in conventional heating methods.
Solution Approach 2:
The patent changes the heating parameter from contact-based thermal conduction to electromagnetic field-based dielectric heating. This parameter change allows the energy to penetrate and heat the material uniformly throughout its volume, rather than heating from the surface inward, thus resolving the uneven heating issue.
2Reliability
If multiple curing steps are used, then the binder hardening is more complete, but the production time and process complexity increase
Solution Approach 1:
The patent combines the compacting and curing operations into a single integrated step using dielectric heating. By applying electromagnetic fields during the pressing operation, the binder cures completely in one step rather than requiring separate curing stages, thus reducing production time while maintaining hardening completeness.
Solution Approach 2:
The dielectric heating enables continuous and uniform energy distribution throughout the material during the single curing step, ensuring complete binder hardening occurs continuously throughout the entire sheet volume simultaneously, eliminating the need for multiple sequential curing operations.
3Strength
If high temperatures and long heating periods are used, then the binder hardens sufficiently, but the production efficiency decreases
Solution Approach 1:
The patent replaces slow thermal conduction heating with rapid dielectric heating using electromagnetic fields. This substitution reduces the heating time from long periods to much shorter durations while achieving sufficient binder hardening, thereby significantly improving production efficiency without sacrificing strength development.
Solution Approach 2:
The dielectric heating system applies electromagnetic fields at frequencies that optimize energy absorption and conversion to heat within the material, enabling rapid and efficient heating that achieves complete binder curing in shorter time periods compared to conventional continuous low-frequency thermal conduction.
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
Achieves efficient, one-step hardening of lignocellulosic composites with improved mechanical properties and uniform density, reducing production complexity and time, while using environmentally friendly bio-based materials.
Implementation Method 1
the formed sheet is at least temporarily simultaneously compacted and dielectrically heated so that the heat-curable binder composition hardens
Data Source
AI summary
Described is a process of producing a lignocellulosic composite or a product thereof, wherein the process comprises at least the steps of making a formed sheet by preparing a mixture comprising lignocellulosic particle and a heat-curable binder composition comprising as components for hardening the binder via reaction with each other at least one, two or more carbohydrate compounds and one or two compounds having two or more amino groups, comprising hexamethylenediamine and/or polylysine, and forming a sheet from said mixture, so that the formed sheet results, and of at least temporarily simultaneously compacting and dielectrically heating the formed sheet in a dielectric heating and pressing unit, so that the heat-curable binder composition hardens and the lignocellulosic composite results. Furthermore described is a lignocellulosic composite, which is preparable according to that process, a construction product comprising such lignocellulosic composite and the use of such lignocellulosic composite as a building element in a construction product.