Organosilanes and EVO75’s Improvements
There is a significant difference between water-stable QACs and products where companies mix a methanol-based QAC into water. Unlike EvoTek75, these products cannot bond to surfaces, maintain stability in the container, or remain active. Additionally, the composition of these methanol-based products results in a much more toxic substance that requires more careful handling.
DOW Corning 5700 is a notable example of an organosilane that experiences undesirable self-condensation in water. In the presence of water, the propyl trimethoxysilane portion of the molecule transforms into a propyl trihydroxysilyl moiety, which then polymerizes by forming Si--O bonds with hydroxylated surfaces of the substrate and intermolecular O--Si bonds.
The C18 hydrocarbon chain quaternary ammonium part of the molecule offers long-lasting antimicrobial properties and initially associates with the substrate surface through ionic bonds and/or electrostatic interactions. To achieve this, a dilute solution of 3-(trimethoxysilyl)propyl-dimethyloctadecyl ammonium chloride in methanol is added to water.
This addition rapidly converts the --Si(OCH3)3 portion of the molecule into a reactive --Si(OH)3 group, thereby activating the dimethyloctadecyl ammonium chloride. However, this mixture is typically unstable and prone to self-condensation, leading to a gradual loss of effectiveness. Consequently, the activated 3-(trimethoxysilyl/trihydroxysilyl)propyl-dimethyloctadecyl ammonium chloride system must be used within a short timeframe—typically within a few hours, and at most about 12 hours—to effectively treat a surface or fabric and create a permanent surface coating.
Unfortunately, as noted above, organosilanes in water, such as the activated mixture of 3-(trihydroxysilyl)propyl in as little as four to eight hours, a gel formation in this and similar silane formulations in the water begins to occur in even shorter times. Moreover, such products are notorious for agitation difficulty during the addition of the silane to water.
While quaternary ammonium silicon compounds have been used to sanitize, sterilize, or disinfect various surfaces, their use remains limited due to several challenges. These include toxicity, often stemming from the solvent systems used for delivery, the necessity for a solvent solution (e.g., Dow Corning antimicrobial agents contain 50% methanol), short-term stability (aqueous silane solutions remain stable for only a few hours to several weeks), and poor water solubility. For example, although 3-(trimethoxysilyl)propyl-dimethyloctadecyl ammonium chloride is water-soluble, it is unstable in water and, due to its 50% methanol content, highly toxic. Similar issues arise with other antimicrobial organosilanes, especially quaternary ammonium silicon compounds, which present significant physical health hazards. These hazards include the need for precautions to avoid skin and eye contact, the risk of accidental spills, flammability, and the additional manufacturing steps required to incorporate these antimicrobial agents into products, all of which substantially increase manufacturing costs.
Therefore, there was a clear need for organosilane compounds, products, and compositions that offer extended shelf life and water stability, ensuring the active component remains effective for the intended application. Additionally, there was a demand for water-stable organosilane compounds that are essentially non-toxic, non-flammable, uniformly dispersible, and easy and cost-effective to use.
To accomplish the water stable objective a polyol containing at least three hydroxy groups, wherein all of the hydroxy groups are separated by at least three intervening atoms, must be employed in the manufacturing of the organosilane formula or the self-condensation of the formula will occur. This stabilizing compound is used in the EVO75 organosilanes.
It is important to highlight that numerous substrate compositions have been developed or adopted since the original DOW formulas were introduced. Many of these are inert materials lacking bonding sites and therefore offer no bonding capabilities. Other substrates exhibit varying degrees of interfacial surface tension, which must be reduced to enable non-polar covalent bonding, ultimately enhancing substrate coverage. This behavior is largely due to the presence of nonionic inert compounds in the EVO75 formulations.
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As a result, I recommend that organosilanes be classified differently based on their composition and, more importantly, their performance. They should not be grouped or identified broadly under the same category as trimethoxysilyl quaternary ammonium compounds. Instead, they should be more accurately referred to as "silane quats." Specifically for EVO75, its unique features of water stability and surface penetration should be emphasized, as these characteristics lead to improved efficacy.