Fabric care
The hypochlorite anion (OCl-) is a strong oxidizing bleach and can contribute to fabric and dye damage during washing. Even
the low concentrations of chlorine bleach encountered in domestic water supplies can, over many washes, cause significant
fading of colored fabrics. However, the inclusion of about 1wt.% sodium perborate in laundry detergent powders results in
destruction of the chlorine bleach.
Additionally, cotton and some synthetic fabrics like polyamide-elasthanes have free hydroxyl groups. It is thought that
damage may also occur from the oxidation of these groups when hypochlorite is used as the bleaching agent.
The hypochlorite decomposes to form hypochlorous acid and free radicals (species having an unpaired electron) which are
reactive with, and oxidize, the fabric’s hydroxyl groups. At lower pH the hydroxyl groups can oxidize to aldehyde groups
which are responsible for yellowing.
In order to prevent this, a borate system has been developed which, in the presence of a catalyst, forms an ester with
the fabric so protecting the hydroxyl groups from oxidation. Borates, that yield boric acid or the tetrahydroxy borate
anion, will be effective in this application.
The catalyst can be any Lewis acid, but particularly suitable are organic and inorganic salts of zinc, aluminum, titanium,
magnesium, tin, antimony and bismuth. One compound embodies both esterification and catalytic actions – zinc borate.
The borate also helps buffer the solution, and reduces the conversion of hypochlorite to hypochlorous acid.
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| Fig F1: cotton fibers can fray badly after many wash cycles |
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| Fig F2: fabric / fabric dye transfer; the effect of borax on the dye transfer inhibiting properties of a test detergent |
Dye protection
Low levels (1 - 4 wt.%) of borax in bleach-free 'color' detergent formulations allow the use of less polyvinylpyrrolidine
(PVP) dye transfer inhibitor, while maintaining its efficacy.
Anti-static properties
Boron-based surfactants have been used to confer anti-static finishes to synthetic polymer fabrics.
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| Fig F3: loss of color and discoloration in a black tee-shirt after multiple washes |
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