Process for applying hydrophobic coating to fibrous substrates
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Solution Overview
Problem
Current methods for applying hydrophobic or oleophobic coatings to fibrous substrates face challenges such as textile shrinkage, inconsistent application, high energy consumption, chemical incompatibility, and environmental concerns due to water-based or solvent-based processes, while requiring coatings that provide excellent water repellency with minimal impact on air permeability and durability against laundering and abrasion.
Innovation Solution
A method involving the application of a curable coating composition with free-radical-curable monomers and crosslinking monomers, cured in a low oxygen environment with atmospheric pressure plasma, allowing for rapid and uniform penetration and polymerization, resulting in a durable, low-weight coating that is resistant to removal by laundry or abrasion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a water-based chemical bath is used to apply hydrophobic coating, then the coating can be applied to fibrous substrates, but textile shrinkage occurs and chemical waste water is generated
Solution Approach 1:
The patent uses supercritical carbon dioxide as an inert fluid medium to replace water-based chemical baths. The coating composition is applied in a supercritical state, eliminating water waste and preventing textile shrinkage while maintaining effective coating application. The supercritical CO2 penetrates the fibrous substrate without causing the shrinkage associated with aqueous treatments.
2Reliability
If a long air-operated oven is used to dry and cure the wet fabric, then the coating can be cured, but large amounts of energy are consumed
Solution Approach 1:
The patent utilizes the phase transition properties of supercritical carbon dioxide. After coating application, the supercritical CO2 is depressurized and transitions back to gaseous state, automatically removing the need for long drying ovens. The curing process occurs during the phase transition itself, significantly reducing energy consumption compared to traditional air-operated ovens.
3Ease of manufacture
If water-based finishing solution is used, then coating can be applied, but inconsistent application of active ingredients occurs
Solution Approach 1:
The patent changes the physical state parameters of the coating medium from liquid (water-based) to supercritical fluid state. This parameter change allows for more uniform distribution and penetration of active ingredients throughout the fibrous substrate, eliminating the inconsistent application problems associated with water-based solutions. The supercritical state provides enhanced solubility and uniformity.
4Shape
If low coating weight is used to maintain good drape, then water repellency can be achieved, but durability against laundry and abrasion is reduced
Solution Approach 1:
The patent employs a composite coating composition containing fluorinated compounds, crosslinking agents, and initiators that work synergistically. This composite formulation achieves durable water repellency at low coating weights by creating a crosslinked network structure that resists laundry and abrasion while maintaining fabric drape. The combination of hydrophobic fluorinated chains with crosslinked polymer matrix provides both lightness and durability.
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 method achieves a durable, hydrophobic or oleophobic coating with excellent water repellency and breathability, maintaining performance through multiple laundry cycles without significant water or oil absorption, while reducing environmental impact and energy usage.
Implementation Method 1
curing the curable coating composition on the porous fabric in the presence of free radicals and in a low oxygen environment... step 3) includes a step of contacting the coated fabric with an atmospheric pressure plasma to initiate polymerization
Implementation Method 2
the curable coating composition comprises at least one free-radical-curable monomer... at least one crosslinking monomer having at least two free-radical-curable polymerizable groups
Implementation Method 3
curing the curable coating composition on the porous fabric in the presence of free radicals and in a low oxygen environment characterized by a partial pressure of oxygen of no greater than 0.1 kPa and/or an atmosphere containing no greater than 0.1 mole percent oxygen
Data Source
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AI summary
Fabrics are treated with a hydrophobic treatment that includes at least one hydrophobic monomer and a crosslinker. The treatment is low in volatile organic compounds and water. It is a liquid at 22°C or a suspension having a phase that is liquid at 22°C. The monomer and crosslinker are cured in a free radical polymerization to form a hydrophobic coating on a fibrous substrate. The curing is performed by removing interstitial air from the fabric and then curing the fabric in a low oxygen environment without allowing it contact with oxygen or air from the time the interstitial air is removed until conversion of monomers reaches at least 50%.