Percarbonate
Sodium percarbonate is an effective oxygen bleaching agent, but suffers from relatively fast degradation which results
in diminishing effectiveness during storage. Several borate-based coatings have been described showing that this degradation
can be reduced to acceptable levels.
In powder formulations, sodium percarbonate can be stabilized by coatings containing borates such as boric acid and sodium
metaborate. Several patents describe such coatings, which typically also comprise other sodium or potassium salts such as
chlorides, sulfates, carbonates, silicates or even polyhydroxycarboxylates. These additional salts can enhance the solubility
of boric acid, and produce a thicker coat, which is easier to apply.
Boric acid’s ability to function as a highly efficient exotherm control agent makes it particularly effective as a stabilizer
for reactive peroxygen bleaches. Aside from its use with percarbonate, boric acid is highly effective as a stabilizer for
several pre-formed peroxyacid bleaches, and furthermore helps buffer wash liquor pH in the range which is optimum for peroxyacid
bleaching performance.
Hydrogen peroxide
There is interest in the use of hydrogen peroxide as a replacement for chlorine compounds in liquid laundry pretreatment and
cleaning products.
Several stabilizers (essential for hydrogen peroxide) have been described, including calcium or magnesium orthophosphates,
cyclohexane-1,2-diamino tetramethylene phosphonic acid, and other phosphonates. The factor which links the effectiveness of
each of these is the use of borates as a buffer.
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Borate-surfactant interaction
Polyhydroxy fatty acid amide surfactants have recently gained prominence and perform exceptionally well in modern detergent
systems. They are derived from renewable raw materials and have the advantage of being crystalline solids, which enables them
to be readily processed in dry mixing, non-tower powder production operations.
However, precipitation and/or gelling may occur with solutions of these surfactants during storage, and at higher temperatures
they are susceptible to degradation as the amide bond hydrolyzes.
A storage-stable, pumpable fluid composition with a high concentration of the surfactant is made possible by the presence of
borax, sodium metaborate or monoethanolamine borate (see Solubilization section). In the context of stabilization, borate
prevents chemical degradation of the surfactant at elevated temperatures.
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