Lignin-Reinforced Wood Composite Adhesion Without Premature Polymerization
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Solution Overview
Problem
Existing methods for incorporating lignin into lignocellulosic materials for wood composites face issues such as high viscosity, premature polymerization, and non-uniform application, leading to manufacturing challenges and inefficiencies.
Innovation Solution
A process involving blending lignin with wood materials at various stages of production, followed by compression, steam cooking, refining, and blending with isocyanate without pre-reacting lignin with adhesives, allowing for uniform distribution and adhesion during elevated temperature pressing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lignin is incorporated into wood composites to improve adhesion and reduce chemical usage, then environmental sustainability and bonding strength are improved, but viscosity increases and premature polymerization occurs
Solution Approach 1:
The patent applies preliminary action by pre-blending lignin with wood materials at specific stages of production (such as during drying or before pressing) rather than mixing it later. This controlled preliminary incorporation ensures uniform distribution and prevents premature polymerization by timing the mixing at the optimal moment when the wood material is most receptive to lignin absorption, thereby improving adhesion while managing viscosity issues.
Solution Approach 2:
The patent utilizes parameter changes by controlling the moisture content of the wood material (maintaining it between 6-15%) and adjusting the temperature during the blending and pressing stages. These parameter adjustments optimize the absorption of lignin by the wood material, improve adhesion strength, and prevent premature polymerization by keeping the temperature below the lignin gelation point while still enabling effective bonding.
2Object-generated harmful factors
If lignin is added to enhance adhesion and reduce adhesive chemical usage, then formaldehyde emissions are reduced, but uniform distribution becomes difficult to achieve
Solution Approach 1:
The patent applies preliminary action by incorporating lignin into the wood material at an early stage, such as during the drying phase or before the pressing operation. This timing allows the lignin to be uniformly absorbed and distributed throughout the wood structure before final assembly, preventing clumping and ensuring consistent adhesion properties across the entire panel while minimizing formaldehyde emissions from synthetic adhesives.
Solution Approach 2:
The patent utilizes parameter changes by controlling the moisture content (6-15%) and temperature during the lignin incorporation process. These controlled parameters optimize the absorption kinetics of lignin by the wood material, ensuring uniform distribution throughout the structure. The temperature is maintained below the gelation point to prevent premature polymerization that would cause non-uniform distribution, while still enabling effective adhesion.
3Reliability
If resin viscosity is increased to improve lignin incorporation, then adhesion strength improves, but application evenness deteriorates
Solution Approach 1:
The patent applies preliminary action by incorporating lignin into the wood material before the pressing stage, allowing the lignin to be absorbed and distributed uniformly throughout the wood structure in advance. This preliminary incorporation means that during the final pressing operation, the lignin is already evenly distributed within the wood matrix, so the resin does not need to have low viscosity to achieve even application - the uniform distribution is already established through the preliminary lignin incorporation process.
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
This method enables the production of lignin-based wood composites with improved adhesion and reduced chemical usage, enhancing properties like water resistance and dimensional stability without the need for additional adhesives.
Implementation Method 1
this lignin is expected to associate with water molecules (e.g. through hydration of ionic groups or hydrogen bonding) to form some kind of a lignin-water complex
Implementation Method 2
this lignin is expected to associate with water molecules (e.g. through hydration of ionic groups or hydrogen bonding) to form some kind of a lignin-water complex
Implementation Method 3
the glass transition temperature, Tg, is the temperature at which a polymer changes from a rigid plastic (below Tg) to a flexible, rubbery material (above Tg). As also known, when lignin is in the moist form and/or in the presence of other wood components (e.g. cellulose, hemicellulose), the glass transition temperature decreases significantly by as much as 100° C.
Implementation Method 4
lignin associates with different resin systems (e.g. isocyanates, phenolic resins, and/or urea-formaldehyde resins with wax) via different mechanisms (e.g. chemical reaction) to reinforce the adhesion among lignocellulosic materials
Data Source
AI summary
It is provided a process to modify lignocellulosic materials with lignin, and incorporating lignin and isocyanates or other wood adhesive in wood products compositions, and their composition, preparation and application for bonding wood products are disclosed. The compositions comprise lignin, derived from a variety of natural resources, isocyanate compounds containing two or more isocyanate functional groups, or other wood adhesives.