In addition, the formation of this complex is responsible for the observed substantial increase in the dissolution
rate of perborate in solutions containing saccharate. This builder system also assists in the removal of many stains.
Red wine stain is particularly susceptible.
In terms of performance in washing tests against a range of stains and soils, sodium perborate-saccharate acts as a
powerful bleach and builder combination, at least rivalling sodium perborate-zeolite andsodium perborate-STPP systems.
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| Fig B6: stain removal using a PBS-saccharate-based aqueous detergent and two commercial liquids (built and unbuilt) |
Perborate-GLS (2-Gluconoxysuccinate)
HOCH2[CH(OH)]3 - CH - O - CH - CH2CO2Na
\\
CO2Na CO2Na
Research by Borax and Surface Chemists of Florida, Inc. shows that the perborate-GLS builder system performs as an
effective partial or total replacement for zeolite in powder formulations. Also, borate-GLS is an effective replacement
for citrate in liquid formulations. It is a strong calcium ion sequestrant (pKCa = 4.4) and good dispersant of certain
soils in the wash.
While GLS is by itself a reasonable sequestrant, it becomes more powerful when there is borate in solution. It is now
believed that a proportion of the boron exists in several types of ester complexes which it forms with the polyol. This
is indicated by peaks at 1, 5, 6 and 10 ppm in the 11B nuclear magnetic resonance spectra compared to the free boron at 2ppm.
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| Fig B7: 11B nmr spectra; borate, borate-saccharate and borate-GLS Intensity (arbitrary units) |
In a range of washing tests using different powder and liquid detergent formulations simulating European and U.S.
conditions, the sodium perborate-GLS and borate-GLS systems show performance equal to zeolite and consistently better than citrate.
Keeping the pH under control
The ability to buffer wash liquor in the range pH 9 - 10.5 is an essential feature of soluble detergent builders, and
borates have this property.
Although borates are less alkaline than many detergent builders, they function particularly well as pH buffers in this
range. A more comprehensive description of this property is included in the pH effects section. This lower pH particularly
favors bleaching by the peracid formed from the reaction between perborate and activator.
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| Fig B8: detergency of liquid detergent formulations (described in colour-coded table) with partial or total replacement
of citrate by borate-GLS |
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