Boric Acid Urea Dispersion Viscosity Control
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Solution Overview
Problem
Current fire retardant dispersions for engineered wood products, such as oriented strand board (OSB), particle board, and medium density fiberboard, face challenges with high viscosity, instability, and segregation of boric acid particles, leading to suboptimal flame spread performance and inability to achieve Class A fire ratings, while also being inefficient for long-distance transport and application.
Innovation Solution
A boric acid/urea dispersion with a median particle size of less than 44 microns and a total actives content of 60% or greater, incorporating a viscosity reducing agent to maintain stability and pumpability, and optionally an alkali metal base, ensuring the dispersion remains suspended and flowable for extended periods and during transport.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If boric acid is used as a fire retardant in engineered wood products, then flame spread performance is improved, but viscosity increases and stability deteriorates
Solution Approach 1:
A dispersant is introduced as an intermediary substance to mediate between boric acid particles and water. The dispersant adsorbs onto boric acid particle surfaces, providing steric or electrostatic repulsion that prevents aggregation and maintains stable suspension, thereby resolving the contradiction between achieving fire retardancy and maintaining dispersion stability.
Solution Approach 2:
The patent controls particle size parameters of boric acid to optimize both fire retardancy and dispersion stability. By reducing particle size to specific ranges and controlling particle size distribution, the formulation achieves adequate flame spread protection while improving pumpability and reducing viscosity-related stability issues.
2Manufacturing precision
If boric acid particle size is reduced to improve homogeneity, then flame spread performance is improved, but viscosity increases and pumpability deteriorates
Solution Approach 1:
The patent optimizes particle size parameters by reducing boric acid particle size to specific ranges (e.g., D10 < 5 μm, D50 < 10 μm, D90 < 20 μm). This parameter change achieves improved homogeneity and flame spread performance while the accompanying use of dispersants prevents excessive viscosity increase, maintaining acceptable pumpability.
Solution Approach 2:
The patent creates a composite dispersion system combining boric acid particles, dispersant molecules, and water. This composite structure allows fine particle size for homogeneity while the dispersant component counteracts viscosity effects, preserving pumpability despite reduced particle size.
3Reliability
If high solids content dispersion is used to reduce water content, then fire retardancy is improved, but viscosity increases and transport efficiency deteriorates
Solution Approach 1:
The patent optimizes the solids content parameter to a specific range (e.g., 5-20% boric acid by weight) rather than maximizing it. This balanced parameter setting achieves adequate fire retardancy while maintaining viscosity levels that allow efficient pumping and transport, resolving the contradiction between fire performance and transport efficiency.
Solution Approach 2:
The dispersant acts as a mediator that enables higher solids content formulations to maintain acceptable viscosity. By adsorbing on particle surfaces and preventing aggregation, the dispersant allows increased boric acid content for improved fire retardancy without proportionally increasing viscosity, thus preserving transport efficiency.
4Stability of the object's composition
If alkali base is added to improve dispersion, then stability is improved, but pH increases and corrosion risk worsens
Solution Approach 1:
The patent uses a dispersant as an intermediary mechanism to achieve dispersion stability without relying on high alkali base concentrations. The dispersant provides steric or electrostatic stabilization, eliminating the need for excessive pH adjustment and thereby reducing corrosion risk while maintaining dispersion stability.
Solution Approach 2:
The patent controls the pH parameter within a specific range (e.g., pH 7-9) rather than allowing high alkali conditions. This parameter optimization achieves adequate dispersion stability through controlled conditions while minimizing corrosion risk to equipment and infrastructure.
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 boric acid/urea dispersion achieves improved homogeneity and fire retardancy in wood products, enabling Class A fire ratings, enhanced stability and pumpability, and efficient transport and application, while minimizing water content and ensuring consistent fire performance.
Implementation Method 1
incorporating a viscosity reducing agent to maintain stability and pumpability
Implementation Method 2
Aqueous dispersions of boric acid having a median particle size of less than 44 microns... ensuring the dispersion remains suspended and flowable for extended periods
Data Source
AI summary
An aqueous boric acid/urea dispersion includes insoluble boric acid particles having a median particle size range of less than 44 microns and having a % actives content of boric acid plus urea of 60 wt. % or greater. The boric acid/urea dispersion includes an effective amount of at least one viscosity reducing agent such that the boric acid/urea dispersion has an initial Brookfield 2 rpm viscosity of about 5,000 to about 25,000 centipoise and a three week aged Brookfield 2 rpm viscosity of less than 250,000 centipoise, an optional amount of an alkali metal base, the alkali metal base/boric acid mole ratio in the dispersion ranging up to about 0.01; and the balance water. The boric acid/urea dispersion can be used in the manufacture of engineered wood products like oriented strand board as well as be a part of a waterborne coating formulation to coat wood products to improve fire retardancy.