The present invention relates to a laundry detergent formulation incorporating
an activated bleaching system.
Laundry detergent formulations containing an activated bleaching system are
well known. The bleaching system generally comprises a compound (referred to
herein for convenience as a hydrogen peroxide precursor compound) which provides,
releases or generates hydrogen peroxide under the aqueous conditions of the wash and
a bleach activator reacts with the hydrogen peroxide to generate a peracid which is a
more effective bleach (particularly for low temperature washing operations) than
hydrogen peroxide. Specific examples of hydrogen peroxide precursor compounds
which are known for use in the art include inorganic persalts and specific examples of
bleach activator include tetraacetylethylene diamine (TAED) and acetylated sugars
such as acetylated sorbitol and acetylated mannitol. All of these specific bleach
activators are capable of reacting with hydrogen peroxide to generate peracetic acid
which is an active bleaching species for low temperature washes.
The bleaching properties of a laundry detergent need to meet two requirements
which may be considered to be in conflict with each other. On the one hand, the
bleaching system must be sufficiently active to "bleach out" a range of different types
of stain with which garments being washed may be soiled. Secondly, the bleaching
system should not be so "powerful" that it causes a significant degree of damage to
dye present in the garments being laundered.
Prior art laundry detergent formulations incorporating a bleaching agent and a
bleach activator do however suffer from the disadvantage that a relatively large
amount of damage may be caused to dyes (particularly to the widely used dye
Immedial Black) by the action of the bleaching system. As such, the use of activated
bleaching systems is inadvisable for washing some coloured garments.
It is an object of the present invention to obviate or mitigate the
abovementioned disadvantage.
According to the present invention there is provided a laundry detergent
formulation comprising at least one surfactant, a clay having fabric softening
properties, and an activated bleaching system which includes at least one bleach
activator which is an ester of a polyhydric alcohol having at least 5 carbon atoms and
at least 3 hydroxyl groups esterified with C2-5 acyl groups, the polyhydric alcohol
residue of said activator not having any substituents with six or more carbon atoms.
We have found in accordance with the invention that the combined use, in a
laundry detergent formulation, of a clay having fabric softening properties and
bleaching system whereof the activator is an ester as defined above gives rise to a
formulation having good bleaching activity with reduced damage to dyes, e.g.
Immedial Black, as compared to prior art activated bleach systems particularly those
incorporating TAED as the activator. Performance of the detergent formulation for
bleaching of hydrophobic stains may be improved by incorporation in the formulation
of an enzyme of the type frequently used in laundry detergent formulations, e.g. a
protease and/or an amylase. We have found that the activity of enzymes in the wash
is inhibited to a lower degree (than in the case where TAED is the activator) for a
similar level of bleachable stain removal.
The activator used in the invention will generally have an HLB value of at
least 16.
As used herein, the HLB ("Hydrophobic Lipophilic Balance") of a molecule is
calculated according to the formula:
HLB = 20 x Molecular weight of hydrophilic part Molecular weight of molecule
The hydrophilic part of the molecule is that which is not hydrophobic. For the
purposes of the present application, the hydrophobic part of the molecule is the
hydrocarbon portion consisting of CH3, CH2, and C groups (the latter being carbon
atoms attached to four other carbon atoms) in alkyl and alkenyl chains. The
molecular weights of the hydrophilic part and of the hydrophobic part of the
molecular may be calculated accordingly. On this basis, hexa acetyl sorbitol which is
a preferred activator for use in the invention has a HLB value of 11.8.
Preferably the activator has an HLB value of at least 7, more preferably at least
9, and even more preferably at least 11. The HLB value may be as high as 14 or 15.
The laundry detergent formulation in accordance with the present invention is
preferably a powdered or granular formulation but may also be a liquid.
The alcohol residue of the activator preferably has a maximum of 12 carbon
atoms and a minimum of five hydroxyl groups esterified with C2-5 acyl groups.
Examples of suitable alcohols are sugar and sugar derived alcohols such as sorbitol,
glucitol, mannitol, glucose and sucrose.
For preference, the acyl groups in the activator are aliphatic acyl groups. It is
preferred that the acyl group has two or three carbon atoms and is most preferably the
acetyl group.
Specific examples of bleach activator which may be used in the detergent
formulations of the invention include hexa acetyl sorbitol, hexa acetyl mannitol, penta
acetyl glucose and octa acetyl sucrose. Particularly preferred are hexa acetyl sorbitol
and hexa acetyl mannitol which may be used in admixture, e.g. as disclosed in EP-A-0
525 239. Further examples are compounds having nitrogen atoms in the basic
carbohydrate skeleton, e.g. the peracetylated forms of N-methyl gluxconamide, N-methyl
glucamine and glucopyronosyl amine.
The amount of bleach activator incorporated in the detergent formulation of
the invention will generally be in the range of 0.5% to 10% by weight of the total
formulation, more preferably 1% to 8% and even more preferably 2% to 4% on the
same basis.
The preferred bleaching system for use in the invention comprises a hydrogen
peroxide precursor compound and the bleach activator as defined above which is
capable of reacting with the hydrogen peroxide to generate a peracid. The hydrogen
peroxide precursor compound may, for example, be an inorganic persalt e.g. a
perborate (in the monohydrate and/or tetrahydrate form), a percarbonate or a
persulphate. The alkali metal salts of these compounds are preferred, particularly
sodium and potassium salts. Alternatively in the case where the detergent formulation
is in solid form, the bleaching agent may be a urea-hydrogen peroxide complex. In
the case of a liquid formulation the hydrogen peroxide precursor compound may be
hydrogen peroxide per se.
The amount of hydrogen peroxide precursor compound present in the
formulation of the invention is preferably such as to provide 0.5% to 3% by weight
active oxygen.
The clay which is used in the formulation of the invention may be any one of
the fabric softening clays having fabric softening properties used in laundry detergent
formulations. Such clays are generally of the "lamellar type" and are such that the
layers "separate" to become deposited on the garments being washed. The clay may
for example be a smectite such as a Laponite, Bentonite, Montmorrillonite, Hectorite
or Saponite. For example, the clay may be a Sodium Montmorrillonite, a Sodium
Hectorite, a Sodium Saponite, a Calcium Montmorrillonite or a Lithium Hectorite.
Generally the amount of clay in the detergent formulation of the invention will
be 5% to 20% by weight.
The clay may be used in conjunction with a cationic and/or amide surfactant to
help delamination of the clay and absorption thereof onto the garments being
laundered. The cationic surfactant may for example be a quaternary ammonium salt
having one long chain (e.g. C8-22) alkyl group and three short chain (e.g. C1-4) alkyl
groups. A suitable cationic surfactant is coco trimethyl ammonium chloride. The
amide surfactant may contain at least one long chain (e.g. C8-22) alkyl group and may
for example be stearyl stearamide. A suitable clay formulation may contain 20-30%
by weight of the formulation (i.e. clay plus surfactants) of amide surfactant and 1-2%
cationic surfactant.
As indicated above, it is preferred to incorporate an enzyme in the
formulations of the invention. The enzyme may, for example, be a protease, amylase,
lipase or cellulase (or mixtures thereof) such as commonly used in detergent
formulations. Examples of suitable enzymes are available under the names Opticlean,
Savinase, Esperase; Termamyl, Maxamayl, Lipomax, Lipolase; Celluzyme and
Carezyme. The amount of enzyme incorporated in the formulation will depend on
activity but will typically be 0.1 to 3%. This level is particularly suitable for Savinase
6.0T, Termamyl 60T, Celluzyme 0.7T and Lipomax.. We have found that the activity
of enzymes is inhibited to a lower degree, for a similar level of bleachable stain
removal, using the activators employed in the invention as compared to TAED.
The detergent formulation in accordance with the invention will include at
least one surface active agent which may, for example, be an anionic, cationic, non-anionic
or amphoteric surface active agent. Any of the surface active agents widely
used in detergent formulations may be employed in the present invention.
If an amphoteric surface active agent is used it may be present in the
formulation in an amount of 0.1 to 10% by weight, more preferably 0.5 to 5%, even
more preferably 1 to 4% on the same basis.
The amphoteric surface active agent may be betaine surface active agent.
Preferred betaines may be either of the formula (I) or (II).
In the above formula, R1 and R2 may be the same or different C1-4 alkyl groups
whereas R3 is an alkyl group having 8-22 carbon atoms, more preferably 12 to 18
carbon atoms e.g. mixed C10 to C14.
The preferred betaine for use in the formulation of the invention is
cocoamidopropyl betaine (also known as cocodimethyl acetic acid betaine (CAS
Registry No.66455-29-6). Further betaines which may be used are lauryl dimethyl
betaine (CAS Registry No. 683-10-3), cocoa dimethyl amidopropyl betaine (CAS
Registry No. 61789-40-0) and the products identified as CAS Registry Nos. 70851-07-09
and 4292-10-8.
An alternative amphoteric surface active agent for use in the formulation of the
invention is a glycinate of the formula
R3NHCH2CO2H
where R3 is as defined above.
A further glycinate which may be used is of the formula
In which R3 is as defined above and n is 1 to 3.
Other suitable materials are as given in chapter 1 of "Amphoteric Surfactants",
e.g. Lomax Ed, Marcel Decker, New York 1996.
It is highly preferred that a cationic surface active agent is employed in
conjunction with the amphoteric surface active agent. The cationic surface active
agent is preferably used in an amount of up to 2% by weight of the formulation and is
conveniently added in conjunction with the clay. Examples of suitable cationic
surface active agents include quaternary ammonium salts having three lower (C1-4)
alkyl groups (preferably methyl groups) and a long chain (C8-20) alkyl group, e.g. coco
trimethyl ammonium chloride. Further examples include alkyl pyridinium salts and
other compounds in which the nitrogen atom of the pyridine assumes a quaternary
form, e.g. as in an alkyl pyridinium bromide.
Further examples of cationic surface active agents which may be used include
amine and imidazoline salts.
If an anionic surface active agent is used then it is preferably present in the
formulation in an amount of up to 20%, more preferably up to 10%, even more
preferably up to 5% by weight of the formulation. Examples of anionic surface active
agents which may be employed include alkylaryl sulphonates, alkyl sulphates, ether
sulphates and ether carboxylates all as conventionally employed in laundry detergent
formulations.
If a non-ionic surface active agent is used then it is preferably present in an
amount of up to 20% by weight of the formulation, more preferably 2 to 10% on the
same basis. Examples of non-ionic surface active agent which may be used include
alkoxylates, ethylene oxide/propylene oxide block copolymers, alkanolamides (e.g.
monoethanolamides and diethanolamides), esters and amine oxides.
The formulation may include at least one builder salt in a total amount of 10%
to 50% by weight of the formulation. The builder may be for example be an alkali
metal phosphate or alkali metal carbonate. A particularly preferred builder is sodium
triphosphate.
It will be appreciated that the formulation may incorporate additional
components as conventionally included in laundry detergent formulation. One
example of such an additional component is a soap which may be used in an amount
up to 5% by weight as a processing aid. Further examples include anti-foam agents,
sequestrants (e.g. of the phosphonate type), whiteness maintenance agents (e.g. CMC,
polyoxyethylene terephthalate, polyethylene terephthalate), colourants (e.g. dyestuffs),
perfume, flow control agents (e.g. a sulphate) flow enhancer (e.g. a zeodite), pH
regulators (e.g. a carbonate or bicarbonate), anti-corrosion agents, dye transfer
inhibitors (e.g. PVP) and optical brighteners (e.g. Tinopal CBS-X and Tinopal DMS-X).
These components may, for example, each be present in amounts up to 1% by
weight of the formulation.
The invention will be further described with reference to the following nonlimiting
Examples.
Example 1
The following laundry detergent formulation A (see Table 1) in accordance
with the invention was produced using standard procedures
| % by weight |
Sodium Triphosphate | 29.23 |
Granular Sodium Carbonate | 9.81 |
Sodium Perborate Tetrahydrate | 9.00 |
Sodium Perborate Monohydrate | 9.00 |
Hexaacetyl Sorbitol | 3.10 |
WA Powder (clay incl cationic and amide surfactants) | 11.5 |
Ampholak X07/SD80
(Betaine Surfactant) | 3.00 |
Synperonic 87k | 4.50 |
Synperonic A3 | 1.50 |
Trepalbe Veg. Soap | 4.92 |
Opticlean M375 Plus (Proteolytic Enzyme) | 1.14 |
Maxamyl 2900 (Amylolytic Enzyme) | 0.80 |
CMC | 2.06 |
C-Sol (disilicate) | 4.47 |
Wessalith P (zeolite) | 3.43 |
Dequest 20160 (Diphosphonate Sequestrant) | 0.69 |
Colour | 0.75 |
Optical Brightners | 0.30 |
Antifoam | 0.41 |
Perfume | 0.40 |
The surfactants included in the WA powder are stearyl stearamide and
cocotrimethyl ammonium chloride.
A comparative formulation B was prepared exactly as for A save that the
hexaacetyl sorbitol was replaced by tetraacetyl ethylene diamine (TAED).
Formulations A and B were used to launder standard pre-stained Red Wine,
Tea, Blackcurrant, Enzyme Sensitive, Cocoa) or pre-dyed (Immedial Black) cotton
swatches so as to test the bleaching activity of the formulations and the extent to
which they caused dye damage. These laundering operations were carried out using a
Hoover Ecologic Autowasher 100 de Luxe set on its "Main Wash" wash cycle.
Laundering was carried out at 40°C and 60°C using 75 g of the formulations. Water
hardness was 290 ppm calcium.
Reflectance measurements were made on the swatches both before (r1) and
after (r2) laundering using a Harrison Reflectometer. The effect of the formulation as
the swatch was calculated as (r2-r1) which represents the extent to which the fabric had
been bleached by the laundering procedure.
The results are shown in Table 2.
Stain Type and Temperature | | A | B |
Red Wine Stain | 40°C | 21.5 | 21.5 |
| 60°C | 31.4 | 29.3 |
Tea Stain | 40°C | 10.5 | 10.5 |
| 60°C | 16.5 | 14.6 |
Blackcurrant Stain | 40°C | 23.5 | 23.3 |
| 60°C | 35.1 | 33.1 |
Enzyme Sensitive Stain | 40°C | 43.4 | 35.7 |
| 60°C | 52.4 | 44.6 |
Cocoa Stain | 40°C | 36.9 | 36.3 |
| 60°C | 45.8 | 38.2 |
TOTAL | | 316.9 | 287.0 |
Immedial Black Dye Damage | 40°C | 3.1 | 3.2 |
| 60°C | 6.7 | 7.6 |
TOTAL | | 9.8 | 10.8 |
It can be seen from Table 2 that, with regard to stain removal, formulation A
was more effective (i.e. higher value of r2-r1) than formulation B save for Red Wine
and tea stains using the 40°C wash for which A and B gave the same stain removal
properties.
With regard to dye damage, formulation A was superior (lower value of r2-r1)
to B at both 40°C and 60°C.
Example 2
Formulation C in accordance with the invention was formulated as shown in
Table 3.
Raw Material | C
% |
STP L16 | 16.5 |
Light Sodium Carbonate | 21 |
Perborate Tetrahydrate | 11.5 |
Sodium Sulphate | 20.3 |
Al Powder (Pyramid P10) | 1 |
CMC | 1.5 |
Tinopal DMS-X | 0.125 |
Tinopal CBS | 0.03 |
Esperase/Savinase | 0.5 |
Maxamyl 2900 CXT | 0.5 |
Antifoam Rhodersil 20471LV | 0.2 |
STP L16 | 1.645 |
C Sol (Pyramid P40) | 2.5 |
Armosoft WA Powder | 10 |
Blue Beads | 1 |
Green Beads | 1 |
Synperonic A7 | 1.5 |
Nansa SS Acid | 3.4 |
Waterglass C100 | 4.5 |
Perfume White Blossom 2951 | 0.2 |
Hexaacetyl Sorbitol | 1.5 |
Less Evaporation | -0.4 |
TOTAL | 100 |
Comparative formulation D was prepared by replacing the Hexaacetyl Sorbitol
(HAS) with the same amount (1.5%) of TAED. A further comparative formulation E
was prepared by omission of HAS and increasing the sodium sulphate content to
21.8% by weight.
Formulations C-E were tested as described in Example 1 save that the washing
machine used was a Creda 1150 Supaspeed and 150 g of each formulation was used.
The results are shown in Table 4.
Stain Type and Temperature | | C
% | D
% | E
% |
Removal of Coffee from Cotton | 40°C | 39.5 | 34.0 | 34.8 |
| 60°C | 48.2 | 47.2 | 43.0 |
Removal of Blackcurrant from Cotton | 40°C | 24.9 | 23.1 | 28.0 |
| 60°C | 45.5 | 43.7 | 33.2 |
Red Wine Stain removal | 40°C | 21.4 | 15.6 | 14.4 |
| 60°C | 12.4 | 11.9 | 19.8 |
Tea Stain Removal | 40°C | 11.2 | 9.8 | 8.3 |
| 60°C | 37.5 | 37.1 | 13.4 |
Immedial Black Dye Damage | 40°C | 2.5 | 3.1 | 2.0 |
| 60°C | 4.9 | 6.0 | 4.3 |
Enzyme Sensitive Stain Removal | 40°C | 34.0 | 33.3 | 36.9 |
| 60°C | 42.0 | 36.5 | 46.8 |
Cocoa Stain Removal | 40°C | 31.1 | 28.8 | 32.8 |
| 60°C | 42.1 | 37.4 | 39.5 |
OXIDSABLE TOTALS | | 247.9 | 231.4 | 201.1 |
ENZYME TOTALS | | 149.2 | 135.9 | 155.9 |
SUM TOTAL | | 397.06 | 367.3 | 357.02 |
Once again it can be seen that the formulation in accordance with the
invention (i.e. C) gave improved removal of stains (higher value of r2-r1) than
comparative formulation D but gave reduced dye damage (i.e. lower value of r2-r1 in
the case of the swatch dyed with Immedial Black).