BLEACHING COMPOSITION

COMPOSITION DE BLANCHIMENT

English Abstract

Solutions of hydrogen peroxide which are alkaline,
can be thickened with a combination of surfactant and
electrolyte without unacceptable loss of stability.
Surfactant may be alkyl ether sulphate:
R(OC2H4)n OSO3M
or a combination of amine oxide R(CH3)2NO with alkane
sulphonate RSO3M or alcohol sulphate ROSO3M where any R is
C8 to C20 alkyl and any M is a solubilising cation and n is
0.5 to 5. Stabiliser is present and may be colloidal
hydrous stannic oxide or may be a phosphonate as specified
in EP-B-9839.

Claims

- 12 -
THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A liquid bleaching composition comprising an aqueous alkaline solution
of pH 8.0-10.5, containing:
a) 1-15% by weight hydrogen peroxide,
b) a stabilizer for hydrogen peroxide,
c) 0.05-0.30 Molar electrolyte other than surfactant, and,
d) 0.75-3% by weight of a combination of:
i) an amphoteric surfactant, and,
ii) an anionic surfactant which is either a C8-C20 alkane
sulphonate or a C8-C20 alcohol sulphate.
2. A composition according to claim 1 wherein the surfactant is a
combination of (i) a trialkyl amine oxide having one C8-C20 alkyl group and two
C1 to C4 alkyl groups and (ii) a said anionic surfactant.
3. A composition according to claim 1 wherein the amount of electrolyte in
solution is such that the total quantity of salts other than surfactant in the
composition does not exceed 5% by weight based on the whole composition.
4. A composition according to claim 1 wherein the surfactant is a said alkyl
ether sulphate and the electrolyte concentration is in the range from 0.75 to 10%
by weight.

- 13 -
5. A composition according to claim 1, claim 2 or claim 3 wherein the
stabiliser is colloidal hydrous stannic oxide.
6. A composition according to claim 1, claim 2 or claim 3 wherein the
stabiliser is a compound of the formula:
<IMG>
wherein n = 1-4; and X is H or a water-soluble cation selected from the group
consisting of alkali metals, ammonium, substituted ammonium and alkaline
earth metals.
7. A composition according to claim 1, claim 2 or claim 3 having a pH in the
range from 8.5 to 10.

Description

2006531.
C3290
BLEACHING COMPOSITION
This invention relates to thickened liquid bleach
compositions which may be suitable for sale and use as a
domestic bleach. Pourable domestic bleach is frequently
thickened by including one or more surfactants which, in the
presence of electrolyte, act to thicken the solution
rendering it more viscous than water. Thickening of a
pourable domestic bleach helps the user to control
dispensing of the composition and retards drainage from
surfaces to which it is applied. This invention relates to
such compositions which include surfactant and electrolyte
to increase the viscosity. The compositions of the
invention may be pourable or may be even more viscous so as
not to be poured easily.
A domestic bleach needs to be adequately stable so
that a substantial proportion of the bleaching agent
survives during storage between manufacture and use. Prior
to this invention commercial liquid bleach products have
frequently utilised hypochlorite as bleaching agent.
It is well known that hydrogen peroxide is
unstable unless stabilising agents are present. These
counteract decomposition catalysed by transition metal
ions. Hydrogen peroxide gives better bleaching action if
used under alkaline conditions. However, stabilisation of
hydrogen peroxide under alkaline conditions is difficult and
in consequence commercial solutions of hydrogen peroxide

2006531.
have generally been acidic for the sake of stability.
Certain phosphonates able to stabilise hydrogen peroxide in
alkaline solution are disclosed in EP-B-9839 (Unilever).
The presence of electrolyte tends to cause
decomposition of alkaline hydrogen peroxide solution. For
instance, we have found that a 4% by weight solution of
hydrogen peroxide, made alkaline to pH 10 and containing
0.25% of ethylene diamine tetramethylene phosphonic acid as
stabiliser (which is not as effective as the phosphonates
in accordance with EP-B-9839) was found to retain 95% of its
hydrogen peroxide after two weeks storage at 37C. By
contrast, 85% or less of the hydrogen peroxide was retained
if the solution also contained 1% by weight of sodium
chloride, while only about 50% of the hydrogen peroxide was
retained if the solution contained 10% by weight of sodium
chloride. Similar results were observed using sodium
tripolyphosphate rather than sodium chloride as the added
electrolyte. Doubling the quantity of the phosphonate
stabiliser had little effect on the rate of decomposition.
Thus, any attempt to make a surfactant-thickened,
alkaline domestic liquid bleach product using hydrogen
peroxide as the bleaching agent would encounter the
potential problem that the thickening of the solution would
require the presence of some electrolyte but that this
electrolyte would serve to accelerate decomposition of the
peroxide.
We have now found, however, that it is possible to
formulate an aqueous alkaline solution of hydrogen peroxide

3 20~6531
which is thickened with surfactant and electrolyte yet does have sufficient
stability to be useful as a commercial product.
According to the present invention there is provided a liquid bleaching
composition comprising an aqueous alkaline solution of pH 8.0-10.5, containing:
a) 1-15% by weight hydrogen peroxide,
b) a stabilizer for hydrogen peroxide,
c) 0.05-0.30 Molar electrolyte other than surfactant, and,
d) 0.75-3% by weight of a combination of:
i) an amphoteric surfactant, and,
ii) an anionic surfactant which is either a Cg-C20 alkane
sulphonate or a Cg-C20 alcohol sulphate.
We have found that use of a surfactant as specified above is advantageous
in achieving thickening with a fairly low electrolyte concentration. This may
make it possible for the electrolyte to be provided by ions which are in the
15 composition for other reasons, without deliberate addition of salt for the sole
purpose of enhancing ionic strength. Apart from considerations of peroxide
stability, a benefit of a low electrolyte concentration is a reduced tendency for the
product to leave streaks on a surface which is cleaned with it.
When the surfactant is a combination, in accordance with the alternative
2 0 (b) above, a preferred
B

4 2006~31
possibllity for the nonionic/amphoteric surfactant is an
amine oxide surfactant, preferably a trialkyl amine oxide
with one long chain alkyl of 8 to 20 carbon atoms and two
alkyl groups of 1 to 4 carbon atoms. Then, if primary
alcohol sulphate is the anionic surfactant the weight ratio
of amine oxide:alcohol sulphate is preferably in the range
from 82:18 to 65:35, better 80:20 to 65:35, even better
80:20 to 70:30.
Alkane sulphonate is preferred over alcohol
sulphate because the viscosity is less sensitive to changes
in the composition, so making it easier to produce an end
product with repeatable viscosity. The weight ratio of
amine oxide to alkane sulphonate (when this is used) is
preferably in the range from 80:20 to 50:50 or better 65:35,
and preferably in the narrower range from 70:30 to 65:35.
One or more further surfactants may also be
included, within the scope of this invention.
The electrolyte concentration in a composition of
this invention may be such that the total amount of salts
other than surfactant is not more than 7~ by weight, better
not more than 5~ or 3~. The electrolyte level may be such
as to give a concentration of electrolyte in the range 0.05
to 0.30 molar, preferably 0.1 to 0.2 molar. Once again
,
, ..~,
.

2006~31
higher concentrations may be used but are less preferred.
Stabiliser for the hydrogen peroxide may be a
phosphonate sequestrant in accordance with EP-B-9839, which
defines the phosphonate compounds as of the general formula:
(P03 X2 )CH2~ /CH2 ( P03 X2 )
N-CH2 -CH2 ~ ( N~CH2 -CH2 )n -N
( P03 X2 )CH2 CH2 (P03 X2 ) CH2 ( P03 X2 )
wherein n = 1-4; and X is H or a water-soluble cation
selected from the group consisting of alkali metals,
ammonium, substituted ammonium and alkaline earth metals.
Such a sequestering agent may be used in an amount from 0.01
to 1% by weight. This is approximately 1.5 x 10- 4 to
2 x 10-2 molar.
These compounds are effective to counter
decomposition catalysed by iron but are less effective
against manganese. We have found that it may be possible to
prevent contamination by traces of manganese (e.g. by use of
sufficiently pure raw materials) so that a separate
stabiliser against manganese may not be required. However,
if required a separate stabilising agent to counteract
manganese may be a phosphate salt used in an amount from
0.5% up to 4% by weight, preferably 1 to 3% (reckoned as
anhydrous salt). Tetrasodium pyrophosphate may be used as
such a salt.
Another possible stabilising agent which we have
found to be effective in alkaline solution against

200~53~
decomposition caused by transition metals including both
iron and manganese, is colloidal hydrous stannic oxide.
This stabilising agent is preferably formed in-
situ in the solution as the product of hydrolysis of a
soluble tin compound. Various tin compounds can be added to
the solution to undergo hydrolysis to form the stannic
oxide, including tin sulphate, sodium stannate, tin
dichloride and tin tetrachloride.
Suitable concentrations of tin compound in the
composition may lie in the range from 10- 4 molar to lO- 2
molar, preferably 3 x lO- 3 to 6 x lO- 3 molar. The quantity
of tin compound should not be substantially greater than
necessary, since excess of it can itself cause peroxide
decomposition. An optimum concentration of the tin compound
(or any stabiliser) can be determined by making test
solutions with various concentrations of the stabiliser and
analytically determining the amount of hydrogen peroxide
remaining after a period of storage.
An appropriate viscosity for a pourable
composition having the appearance of a thick liquid is a
dynamic viscosity in the range from 40 to 250 centipoise
(0.05 to 0.25 Pa.sec), preferably about 100 centipoise
(0.1 Pa.sec). More viscous liquids for example with
viscosity in the range from 250 to 1000 centipoise or more
are also within the scope of the invention.
Since the compositions of this invention are
generally aqueous, they will usually have specific gravity
close to unity. Consequently values of kinematic

2006531
viscosities (in stokes) will be numerically approximately
the same as values of dynamic viscosity (in poise). Dynamic
viscosities expressed in Pascal.sec will be approximately
1000 times kinetic viscosities expressed in m2.sec~1.
The pH of the solution is preferably in the range
from 8.0 to 10.5, better 8.5 to 9.8 or 10Ø With a
phosphonate stabiliser it is further preferred that the pH
is in the narrower range from 9.2 to 9.8, while with
colloidal stannic oxide as stabiliser it is preferable to
use a slightly lower pH in the range from 8.7 to 9.3. A
buffer may be included to maintain pH at the desired value,
but this may not be necessary. A phosphate, if present,
will give a buffering action. Another compound which may be
used for this purpose is borax.
The concentration of hydrogen peroxide in
compositions of this invention, reckoned as pure H2 2 '
desirably lies in the range from 1 to 15% by weight
preferably 2 to 10% by weight.
Example 1
Formulations were prepared containing the
constituents set out in Table 1 below. The compositions
were stored in plastic bottles at 37C. At intervals
aliquots were removed and titrated with potassium
permanganate to determine the level of hydrogen peroxide
remaining. Results are included in Table 1.
The viscosity of these formulations was measured
using a Ubbelohde capillary viscometer and found to be

2006531
approximately lOOcS.
TABLE 1
% by weight
5 Constituent A B C
Hydrogen peroxide 5 5 5
(reckoned as anhydrous)
Tallow dimethylamine oxide 1.0 1.0 1.0
Sodium alkane sulphonate 0.5 0.5 0.5
Perfume 1.0 1.0 1.0
15 Tetrasodium pyrophosphate 1.8 - -
(reckoned as anhydrous)
Phosphonate stabiliser 0.15
according to EP 9839
Borax (reckoned as anhydrous) - 1.6 1.6
Sodium stannate trihydrate - 0.5 0.1
Sodium hydroxide to give: pH 9.6pH 9.6 pH 9.0
Water ----- balance to 100% -----
H202 remaining after 50 days: 85% 79%
H202 remaining after 100 days: 96%
Example 2
The procedure of Example 1 was repeated, using
formulations with the same amounts of hydrogen peroxide,
surfactant, perfume and dye. Various tin compounds were
used at a concentration of 6 x 10- 3 molar, both with and
without 3.0% borax decahydrate. Glass bottles were used,
which are somewhat detrimental to stability. In every case
pH was 9.6 initially. Proportions of hydrogen peroxide
remaining after 28 days were:-

2(:)~)653~.
SnCl2 with borax 68%
Na2SnO3 with borax 47%
SnS0~ with borax 45%
Na2SnO3 without borax 96%
SnCl4 without borax 68%
Example 3
A range of formulations were prepared, all
containing:
Hydrogen peroxide 5.0% reckoned as anhydrous
Tetrasodium pyrophosphate 3.0% (approx 1.8% reckoned as
decahydrateanhydrous)
Phosphonate stabiliser
according to EP 9839 0.3%
Perfume 0.1%
Sodium hydroxideto pH 9.6
25 Thickening systemvariable
Water --- balance to 100% ---
The thickening systems used various constituents
and varied both in the properties and total amounts of
materials employed.
The thickening systems contained tallow
dimethylamine oxide (A0) together with sodium lauryl
sulphate (SLS), or sodium alkane sulphonate (SAS), which was
a secondary alkane sulphonate derived from an n-alkane

10 201~6~1
mixture which i8 principally Cl 3 to Cl fl .
Vlscosities of the formulations were measured
using a Ubbelohde capillary viscometer. The results
obtained are shown in the accompanying Figures.
Figure 1 shows variation ln viscosity with the
proportion of SLS ln an A0/SLS mixture, while the total
amount of A0 plus SLS is varied from 1.1% to 1.9% by weight
of the composition.
Figure 2 shows variation in viscosity for A0/SAS
mixtures while the total of A0 plus SAS is varied from 1.2%
to 2.6% of the composition. It can be seen that the
viscosity maxima are broader peaks, while the maximum
viscosity is less sensitive to variation in the total amount
of A0 plus SAS. For instance in Figure 1 the concentration
of surfactant to give a viscosity of lOOcS is 1.2%, and an
increase from this of 0.2%, up to 1.4%, would double the
viscosity to 200cS. In Figure 2 1.4% total surfactant gives
a viscosity of lOOcS. Increasing by 0.2% increases the
viscosity to 150cS and a larger increase, to 1.8%, is
required to achieve 200cS.
~3 ''

2~06531
Example 4
An alkaline solution of hydrogen peroxide was prepared containing
surfactant, sodium chloride and stannic chloride which hydrolysed to colloidal
hydrous stannic oxide.
The quantities of surfactant and sodium chloride were such as to give
viscosities well in excess of that preferred for a pourable "thick liquid" type of
bleach product. Smaller quantities could be used to give a "thick liquid" type of
bleach product.
The initial concentration of hydrogen peroxide, reckoned as anhydrous,
1 0 was 4% by weight. The solution was made alkaline to pH 10 with sodium
hydroxide.
Stannic chloride was used at a concentration of 2.3 x 10-3 molar.
The surfactant system consisted of 4.5% by weight of Cl2-Cl4 alkyl
dimethyl amine oxide and 4.5% by weight sodium lauryl sulphate. This was
used with a sodium chloride concentration of 9% by weight.
The solution was stored at 40 C and the amount of hydrogen peroxide
remaining was determined at intervals. It was found that the amounts of
hydrogen peroxide remaining was between 80 and 85%.
B
.