pMDI-PDMS Hybrid Resin for Lignocellulosic Water Resistance
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Solution Overview
Problem
Engineered wood products, such as OSB, face issues with water absorption leading to swelling, aesthetic, and structural problems due to their porous structure, and the use of waxes for water repellency is inefficient, costly, and can reduce internal bond strength, while existing pMDI-PDMS hybrid resins fail to meet criteria for sprayability, curability, stability, and cost-effectiveness.
Innovation Solution
A polymeric methylene diphenyl diisocyanate-polydialkylsiloxane resin is developed by mixing pMDI with a polydialkylsiloxane at controlled temperatures, resulting in a hybrid resin that is sprayable, curable during hotpressing, stable, and cost-effective, with sufficient isocyanate groups for crosslinking, and can be used to improve water repellency and dimensional stability of lignocellulosic composite articles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If waxes are used to improve water repellency of lignocellulosic composite articles, then water absorption is reduced, but internal bond strength is reduced and manufacturing cost increases
Solution Approach 1:
The patent uses a hybrid resin system combining polymeric methylene diphenyl diisocyanate (pMDI) with polydialkylsiloxane (PDMS) to create a composite binding agent that provides both water repellency and bonding strength. The PDMS component contributes hydrophobicity while the pMDI provides adhesive and cohesive strength, resolving the contradiction between water resistance and bond strength that plagues wax-based solutions.
Solution Approach 2:
The patent modifies the chemical composition and molecular structure of the binding agent by incorporating siloxane groups into the polymeric resin. This parameter change in the chemical structure provides inherent water repellency through the hydrophobic siloxane groups while maintaining the crosslinking capability and adhesive strength of the isocyanate-based resin system.
2Object-affected harmful factors
If waxes are used to improve water repellency, then swelling is reduced, but manufacturing cost increases
Solution Approach 1:
The patent changes the chemical parameters of the binding agent by incorporating polydialkylsiloxane, which provides water repellency and swelling resistance as an inherent property of the siloxane structure. This eliminates the need for separate wax additives, thereby reducing manufacturing costs while achieving the desired water resistance and dimensional stability.
Solution Approach 2:
The hybrid pMDI-PDMS resin performs multiple functions simultaneously: it acts as a binding agent for structural integrity, provides water repellency, and prevents swelling. This multi-functionality replaces the need for separate wax additives, reducing both material costs and processing complexity.
3Object-affected harmful factors
If existing pMDI-PDMS hybrid resins are used to improve water repellency, then hydrophobicity is enhanced, but sprayability, curability, stability, and cost-effectiveness are insufficient
Solution Approach 1:
The patent optimizes the molecular weight, viscosity, and functional group content of the polydialkylsiloxane component to achieve the desired balance between hydrophobicity and processability. By carefully controlling these parameters, the hybrid resin maintains adequate sprayability and curability while providing enhanced water repellency.
Solution Approach 2:
The patent incorporates the hydrophobic PDMS component at optimized concentrations within the pMDI matrix, creating a locally enhanced hydrophobic effect without compromising the overall resin's processability. This local quality enhancement provides water repellency while maintaining the bulk resin's sprayable and curable properties.
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 pMDI-PDMS hybrid resin effectively enhances the water repellency and dimensional stability of OSB, reducing swelling and absorption, while maintaining consistent performance and being more cost-effective than traditional pMDI and wax combinations, with improved mechanical properties and reduced manufacturing costs.
Implementation Method 1
The pMDI-PDMS hybrid resin effectively enhances the water repellency and dimensional stability of OSB, reducing swelling and absorption
Implementation Method 2
with sufficient isocyanate groups for crosslinking
Data Source
AI summary
A method of preparing a polymeric methylene diphenyl diisocyanate-polydialkylsiloxane resin by mixing at a temperature between 25° C. and 100° C.: (i) a polymeric methylene diphenyl diisocyanate with (ii) a polydialkylsiloxane selected from hydroxyalkyl dialkyl terminated polydialkylsiloxane having a viscosity of from 5 to 500 000 cSt at 25° C. or (hydroxyalkoxy)alkyl dialkyl terminated polydialkylsiloxane having a viscosity of from 5 to 500 000 cSt at 25° C. in an amount such that from 1 to 99% by weight of the total weight of (i) and (ii) is component (ii), optionally in the presence of a solvent; and subsequently extracting the solvent, if present.