Note: Descriptions are shown in the official language in which they were submitted.
CA 02347430 2001-04-17
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Thickened Liauid Hydrogen Perozide
Bleach Compositions
This invention relates to alkaline thickened liquid hydrogen peroxide
bleaching
compositions. More particularly, this invention relates to such alkaline
thickened bleaching
compositions which are highly stable in terms of providing a uniform and
thickened viscosity
which remains stable over time, concomitant with the ability to maintain a
stable bleaching
activity during extended periods of storage prior to use by the consumer.
Hydrogen peroxide compositions have been the focus of much attention in the
patent
literature in recent years as replacements for or as alternatives to halogen-
containing bleaches,
often motivated by environmental considerations. In particular, interest has
focused on
alkaline hydrogen peroxide bleaches because of their greater reactivity and
enhanced bleaching
efficacy as compared to acidic hydrogen peroxide compositions.
One of the prime requirements of a bleach intended for domestic use is that
the
bleaching species remain sufficiently stable to insure good efficacy of the
bleach product upon
use by the consumer, typically many months after the products manufacture.
Hydrogen
peroxide solutions are known to provide enhanced bleaching efficacy when used
under alkaline
conditions. However, stabilization of hydrogen peroxide is particularly
troublesome at such
alkaline conditions.
Further, the problem of bleach stability is often exacerbated when formulating
a
thickened bleach product. Thickening of a pourable liquid bleach is intended
to provide an
enhanced aesthetic appearance of the product as well as assist the consumer to
control
dispensing of the liquid bleach product. A thickened composition also serves
to limit the rate
at which the composition flows or drains from the surfaces to which it is
applied. However,
the use of a thickening agent or thickening system in the bleach composition
presents problems
in formulation: it is often incompatible with peroxide bleach stabilizers
which are otherwise
effective in non-thickened compositions, or the thickening agents themselves
may provide an
uneven viscosity to the liquid bleach product and, in general, adversely
affect product
appearance and flow characteristics depending on variables such as product pH
or the non-
bleach ingredients, such as electrolyte, present in the composition.
EP 376 704 describes hydrogen peroxide aqueous solutions which contain a
combination of surfactant and electrolyte to provide thickening and bleach
stability.
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UK patent application GB 2 273 721 describes a thickened bleach composition
which
comprises an alkaline aqueous solution of hydrogen peroxide containing as the
thickening
system a mixture of a quaternary long chain alkyl ammonium compound together
with a salt of
an aromatic sulphonic acid hydrotrope.
U.S. Patent 5,736,498 is concerned with alkaline hydrogen peroxide
compositions
which are thickened with a polymeric thickener having a polyethylene backbone.
U.S. Patent 4,900,469 describes a thickened laundry composition comprising a
surfactant thickening system, a hydrogen peroxide bleach and a stabilizing
system consisting of
a chelating agent and an antioxidant. A C6-C~g soap is optionally included to
increase
viscosity.
Notwithstanding the above-mentioned patent literature and the availability of
numerous
commercial thickeners intended for liquid compositions, there remains a need
in the art for a
thickened alkaline liquid bleach composition containing a hydrogen peroxide
bleach which is
capable of providing long-term bleaching efficacy, and which also contains an
effective,
environmentally safe and economical thickening system which does not adversely
affect the
bleaching performance and stability of hydrogen peroxide.
Summary of the Invention
The present invention provides an alkaline thickened liquid bleaching
composition
comprising, by weight:
(a) from about 0.1 % to about 10% of hydrogen peroxide;
(b) from about 1.5% to about 8% of a surfactant mixture comprising
(i) alkyl dimethylamine oxide; and
(ii) soap formed by the in-situ neutralization of a C6-C~g fatty acid with an
alkali metal hydroxide; the weight ratio of (i) and (ii) being from about
1.5:1 to about 6:1;
(c) from about 0.5% to about 5% of an electrolyte comprising an alkali metal
sulfate;
(d) from about 0.4% to about 1% of a phosphonate stabilizer for the hydrogen
peroxide;
(e) an alkali metal hydroxide in an amount sufficient to effect the in-situ
neutralization of the aforesaid C6-C,g fatty acid to form the soap defined in
(b)
(ii), and also provide a pH in the range of from about 8 to about 9.5 for the
thickened bleaching composition;
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(f) from about 0% to about 2% of sodium benzoate; and
(g) balance water.
In accordance with the method aspect of the invention there is provided a
method of
bleaching fabrics comprising the step of contacting the fabrics to be bleached
with an ei~ective
amount of the above-described alkaline thickened liquid bleaching composition.
The present invention is predicated on the discovery that thickening of a
hydrogen
peroxide bleach solution can be effectively provided with a surfactant mixture
of alkyl
dimethylamine oxide and soap as herein described in combination with a weak
electrolyte such
as an alkali metal sulfate, such that a stable commercially desirable
viscosity in the range of
from about 80 to 500 cps can be readily achieved, preferably from about 100 to
300 cps,
without adversely affecting the stability of the peroxide bleach.
Detailed Description of the Invention
The amount of hydrogen peroxide bleach present in the composition of the
invention
may vary from about 0.1% to about 10%, by weight, of the total composition.
Preferred
compositions comprise from about 2% to about 6%, by weight.
The surfactant mixture which forms part of the thickening system is comprised
of an
alkyl dimethylamine oxide and a neutralized C6-C1g fatty acid, such mixture
being present in an
amount of from about 1.5 to 8%, by weight, preferably from about 2% to 4%, by
weight. The
alkyl group in the dimethylamine oxide surfactant contains from about 11 to 16
carbon atoms.
A preferred alkyl group is comprised of a mixture of carbon chain lengths
comprising 33% to
43% of C12; from 42% to 52% of C14; and from 4% to 14% of C16. Lauryl is a
particularly
preferred alkyl group.
The second component of the surfactant mixture is a C6-C~8 fatty acid which is
neutralized in-situ by the alkali metal hydroxide in the liquid composition to
form a C6-C,g
soap. Typical fatty acids include capric acid, lauric acid, any myristic acid,
but most preferred
is coconut fatty acid which after neutralization forms the coconut lauryl
soap.
The ratio of the described amine oxide surfactant to the fatty acid soap is
generally
from about 1.5:1 to about 6:1, and preferably from about 2:1 to about 4:1.
The third component of the thickening system which serves to stabilize the
increased
viscosity provided by the surfactant mixture is an alkali metal sulfate such
as sodium or
potassium or magnesium sulfate. Sodium sulfate is preferred as a source of
weak electrolyte
which serves to stabilize the viscosity of the composition without adversely
affecting the
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stability of the hydrogen peroxide in solution. It has been found that the
presence of strong
electrolyte in solution at a level to compliment the surfactant thickening
such as Na2C03,
NaOH, NaHC03 cause decomposition of alkaline hydrogen peroxide solution and
is, therefore,
to be avoided in the present liquid bleaching compositions.
The peroxide bleach stabilizer used herein is a polyphosphonate sequestrant.
Examples
of suitable phosphonate stabilizers include sodium or potassium salts of HEDP'
and EDTMP2.
Most preferred is the pentasodium salt of diethylenetriamine penta (methylene
phosphoric
acid), which is available commercially under the trademark bequest 2066 from
the Monsanto
Company.
An essential ingredient in the present bleaching composition is an alkali
metal hydroxide
such as sodium or potassium hydroxide, in an amount sufficient to neutralize
in-situ the fatty
acid ingredient present in the surfactant mixture so as to form the soap. The
alkali metal
hydroxide also serves to provide an alkaline pH in the liquid bleach
composition of from 8 to
9.5, and preferably from 8.2 to 9.2. The amount of alkali metal hydroxide in
the composition
is generally from about 0.10 to 0.5%.
The liquid bleach compositions may preferably include a pH buffer such as
sodium
benzoate which serves to stabilize the pH of the composition and thereby
assists in stabilizing
the peroxide bleach.
Other materials, such as colorants, perfumes, germicides may also be added in
minor
amounts, if desired.
' HEDP= 1,1,1-hydroxyethylenediphosphonic acid
2 EDTMP = ethylene diamine tetramethylenephosphonic acid
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