Note: Descriptions are shown in the official language in which they were submitted.
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DETERGENT COMPOSITIONS
TECHNICAL FIELD
The present invention relates to a product for
treating fabrics in the washing machine in the form of a
tablet containing a particulate bleaching composition
which may optionally include detergent ingredients.
BACKGROUND AND PRIOR ART
Detergent compositions in tablet form have been
known for many years although the form has never achieved
great popularity on the market. In principle, tablets
offer several advantages over powder products: they do
not require measuring and are thus easier to handle and
dispense into the the washload, and they are more
compact, hence facilitating more economical packaging and
storage.
One difficulty that has been experienced in the
formulation of detergent tablets is the incorporation of
bleaching ingredients, especially when the presence of
bleach-sensitive ingredients such as enzymes is also
desired: in a compressed tablet, the ingredients are
r
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much more intimately a6sociated with one another than in
a powder, and any adverse interactions and instability
will be exacerbated. Worse stability problems would be
expected if bleach activators (bleach precursors) were
present.
US 4 099 912 (Ehrl~ch) discloses a plurality of
separate units of different detergent composition
components which may be used in combination to obtain the
required detergent formulation. Tablets are the
preferred unit. A separate tablet containing sodium
perborate or sodium percarbonate is suggested. Bleach
activators are not mentioned.
GB 911 204 (Unilever) discloses layered detergent
tablets containing persalt bleach, for example, sodium
perborate, and certain bleach activators, for example,
sodium acetoxybenzene sulphonate and phthalic anhydride.
To avoid destabilisation, the bleach activator is
segregated from the remaining tablet ingredients,
including the persalt bleach, in a separate section or
layer.
In contrast, EP 395 333A (Unilever) discloses a
detergent tablet containing sodium perborate in
conjunction with one or more bleach-sensitive ingredients
- tetraacetylethylenediamine or similar bleach
activator, enzyme, fluorescer, or any combination of
these - as well as detergent-active compounds,
detergency builders and optionally other ingredients.
The persalt is not segregated from the bleach-sensitive
ingredients but, surprisingly, the tablet is stable with
no more loss of bleach, enzyme or fluorescer performance
on storage than in a powder of the same composition.
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It has now been discovered that tablets containing
persalt bleaches and defined bleach activators together,
in conjunction with detergent ingredients which are
either present in the same tablet or in a separate
S tablet, or powder/liquid form, can give better bleaching
performance than detergent powders of the same
formulation. The benefits are especially evident when
the persalt is sodium percarbonate and when the bleach
activator is tetraacetylethylenediamine.
DEFINITION OF THE INVENTION
The present invention provides a tablet of
compressed particulate bleaching composition comprising:
( i) a persalt selected from the group consisting of
percarbonate and perborate tetrahydrate;
(ii) a bleach activator having an observed
pseudo-first order perhydrolysis rate constant
(KobS) of from l.S x 10 4 to 350 x 10 4 sec 1;
(iii) optionally a detergent-active compound;
(iv) optionally a detergency builder; and
(v) optionally other detergent ingredients;
with the proviso that if the persalt is sodium perborate
and the bleach activator is a N-diacylated or
N,N'-polyacylated amine, the persalt is segregated from
the bleach activator.
Tablets in which sodium perborate and an
N-diacylated or N,N'-polyacylated amine bleach activator
are together without se~le~ation are disclosed and
claimed in the aforementioned EP 395 333A (Unilever) and
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2053~3~
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are specifically disclaimed from the scope of the present
invention.
DETAILED DESCRIPTION OF TH~ INVENTION
The tablet of the invention is characterised by the
presence of both a persalt and a defined bleach
activator. The interaction between the two bleaching
components, to give better bleaching than the persalt
alone can give, appears to be improved by tabletting.
Bleach activators work by reacting in the wash
liquor with hydrogen peroxide from the persalt
(perhydrolysis of the activator) to generate a peracid
which is a more efficient bleach than is hydrogen
peroxide itself. Without limiting in any way the scope
of the invention, it is hypothesised that in a porous
tablet there is an opportunity for the activator to react
with hydrogen peroxide from the persalt within the pores
of the tablet itself, when the tablet first comes into
contact with the wash liquor. In this confined space,
the concentration of both hydrogen peroxide and precursor
will be greater than in the bulk wash liquor, and the
rate of perhydrolysis will be increased.
This can only occur, of course, if the tablet
remains intact in the wash liquor for long enough for the
reaction to take place to a significant degree. However,
the peracid generated needs to be released into the wash
liquor in order to reach the stain to be bleached, which
requires the tablet to dissolve. A rate of tablet
dissolution that represents an ideal compromise between
these conflicting requirements is therefore desirable. A
further requirement would appear to be that the tablet
should remain porous enough under wash conditions to
allow water to penetrate in sufficient quantity and with
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sufficient speed for reaction to take place. Rate of
dissolution and tablet porosity will depend partly on
formulation and may be al~o be controlled to some extent
by choice of tabletting precsure.
The ~ersalt
The most preferred per~alt for use in the present
invention is sod~um percarbonate.
Sodium percarbonate, Na2C03.1.5H2O2, unlike sodium
perborate, is a perhydrate rather than a true persalt,
and it can release hydrogen peroxide of crystallisation
without requiring dissolution. However, sodium
percarbonate dissolves more slowly than sodium perborate
monohydrate in water so that the tablet structure is
maintained in the wash liquor for a sufficient length of
time for the effect described above to operate.
Very little benefit has been observed with sodium
perborate monohydrate, which dissolves very rapidly in
water so that the tablet breaks up more quickly, but
which requires an inherently slower reaction (hydrolysis)
to release hydrogen peroxide.
Some benefit has been observed with sodium perborate
tetrahydrate which is slower to dissolve than the
monohydrate, but the effect is smaller than with sodium
percarbonate.
The total amount of persalt in the tabletted
composition as a whole is preferably within the range of
from 5 to 60 wt%. In fully formulated detergent tablets
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the amount of persalt is preferably from 10 to 40 wt%,
more preferably 10 to 30 wt%.
The bleach activator
The tablet of the invention also contains a defined
bleach activator.
The extent to which the effect described above will
operate will depend on the choice of bleach activator as
well as on the choice of persalt. Preferably the
activator is one having moderate reactivity, where the
greatest improvement will be observed. Very fast
reacting bleach activators will already perform so well
that no further significant improvement is possible;
while very slow reacting bleach activators will be
improved but not necessarily to a sufficient extent to
render them useful in practice.
It is thus an essential feature of the present
invention for the bleach activator to have an observed
pseudo-first order perhydrolysis rate constant (KobS) of
from 1.5 x 10 - 350 x 10 sec . This rate constant
provides a measure as to how reactive the bleach
activator will be.
The best known bleach activators are peracetic acid
precursors and perbenzoic acid precursors. The peracetic
acid precursor, tetraacetylethylenediamine (TAED), is
especially preferred for use in the tablets of the
present invention because its reactivity is such that a
particularly worthwhile improvement over loose powder can
be demonstrated (KObs 2.3 x 10 sec ).
The peracetic acid precursor, glycerol triacetate,
has also shown some benefit, but its reactivity is still
20~3433
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rather low (K b = 1.9 x 10 4 sec 1). Other peracetic
acid precursors that would be expected to benefit from
tabletting in accordance with the present invention
include glucose pentaacetate and xylose tetraacetate.
An example of a perbenzoic acid precursor that may
benefit from tabletting in accordance with the present
invention is sodium benzoyloxybenzene sulphonate,
although since this is already a fast-reacting precursor
(KobS = 3 x 10 2 sec 1) the benefit is less substantial
than with TAED.
Further examples of suitable precursors that may
benefit from tabletting in accordance with the present
invention are monosaccharide esters as disclosed in
EP 0 380 437A (Procter & Gamble; Novo), and sugar
ester-based precursors as disclosed in WO91/10719 (P&G;
Novo) preferred compounds are l-O-(long-chain acyl)-2,3,
4,6-tetra-O-acetyl-glucose in ~ or ~ form where the long
chain acyl is one of the following: octanoyl, nonanoyl,
decanoyl, undecanoyl, dodecanoyl, 10-undecanoyl,
3,5,5-trimethylhexanoyl or 2-ethylhexanoyl. The most
preferred compound is where the long chain acyl is
octanoyl: l-O-octanoyl-2,3,4,6-tetra-O-acetyl-glucose
(OTAG).
Bleach activators are suitably present in an amount
of from 1 to 30 wt%. In fully formulated detergent
tablets the bleach activators are preferably present in
an amount of from 1 to 10 wt%, more preferably from 2 to
5 wt%.
Bleach stabiliser
If desired, the tablet of the invention may also
include a small amount of a bleach stabiliser (heavy
metal sequestrant) such as ethylenediamine tetraacetate
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(EDTA), ethylenediamine tetramethylene phosphonate
(EDTMP) or diethylenetriamine pentamethylene phosphonate
(DTPMP).
Other inqredients
As well as persalt and bleach activator, the tablet
of the invention may optionally contain at least one
detergent-active compound, at least one detergency
builder, and other ingredients. Tablets of the
invention may therefore pro~ide a fully formulated, high
performance detergent composition within a single tablet.
It is preferred, however, that a detergent composition
consists of at least a two-tablet system; one, a tablet
of the invention, containing the bleaching composition,
the other containing the detergent base composition.
Alternatively the detergent composition may consist of a
tablet of the invention, containing the bleaching
composition, and a power/liquid containing the detergent
base composition.
Percarbonate segregation
If sodium percarbonate is present, it is preferably
separated from any other ingredient likely to destabilise
it by segregation in a discrete region of the tablet, as
described and claimed in our copending Canadian Application No.
2,053,434 (Unilever PLC). This is particularly important when
tablets which contain a full detergent composition within a single
table are formulated.
According to Canadian Application No. 2,053,434, at
least one discrete region comprising sodium percarbonate
and optionally other ingredients compatible with sodium
percarbonate is present. Other components such as
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detergent-active compound, detergency builder and any
other ingredients of doubtful compatibility with sodium
percarbonate are excluded from the discrete region(s) in
which the sodium percarbonate is segregated.
A preferred embodiment of the invention which is
simple in structure and simple to manufacture is a tablet
consisting of two layers: the first layer containing the
percarbonate, and the second layer containing other
ingredients. The percarbonate may be segregated alone,
or together with one or more other ingredients that are
fully compatible with it. It is generally preferred that
a major proportion of the non-percarbonate ingredients
should be separated from the percarbonate.
However, the stability of the percarbonate may
actually be increased by segregating it together with a
diluent in the form of a compatible inorganic salt. The
salt is preferably in a finely divided or highly porous
form, having a preferred surface area, as measured using
nitrogen absorption, of 5-15 m2/g. It is believed that
it contributes to percarbonate stability by acting as a
moisture sink. One especially preferred inorganic salt
is sodium carbonate, which of course also plays a useful
role in the detergent composition as a whole, as a
detergency builder and provider of alkalinity. It is
believed that sodium carbonate may also contribute to
percarbonate stability by reabsorption of any liberated
hydrogen peroxide.
According to one especially preferred embodiment of
the invention, the diluent is in the form of a
spray-dried composition comprising the compatible
inorganic salt, more preferably sodium carbonate, and a
polymeric binder.
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The binder must itself be stable to oxidation.
Preferred binders are acrylic and/or maleic polymers, for
example, the acrylic/maleic copolymer sold commercially
as Sokalan (Trade Mark) CP5 ex BASF. As well as their
binder function which improves tablet integrity and
allows tabletting without having to wet the percarbonate
to any significant degree, polycarboxylate polymers of
this type also have a useful detergency building and
antiredeposition action.
In this embodiment of the invention, the discrete
tablet region or layer is the compaction product of a
particulate composition prepared by mixing sodium
percarbonate with the spray-dried salt/polymeric binder
granules. This particulate starting composition
suitably contains from 30 to 70 wt% of sodium
percarbonate, from 30 to 70 wt% of the inorganic salt
(preferably sodium carbonate), and from 0.5 to 5 wt% of
the polymeric binder.
Deterqent-active comPounds
In a tablet intended to provide a fully-formulated
bleaching detergent composition, detergent-active
compounds are suitably present in an amount of from 2 to
50 wt%, more preferably from 5 to 40 wt%.
Detergent-active material present may be anionic (soap or
non-soap), cationic, zwitterionic, amphoteric, nonionic,
or any combination of these.
Anionic detergent-active compounds may be present in
an amount of from 2 to 40 wt%, preferably from 4 to
30 wt%.
Synthetic anionic surfactants are well known to
those skilled in the art. Examples include alkylbenzene
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sulphonates, particularly sodium linear alkylbenzene
sulphonates having an alkyl chain length of C8-Cl5;
primary and secondary alkyl sulphates, particularly
sodium Cl2-C15 primary alcohol ~ulphates; olefin
sulphonates; alkane sulphonates; dialkyl
sulphosuccinates; and fatty acid ester sulphonates.
It may also be desirable to include one or more
soaps of fatty acids. These are preferably sodium soaps
derived from naturally occurring fatty acids, for
example, the fatty acids from coconut oil, beef tallow,
sunflower or hardened rapeseed oil.
Anionic surfactants are preferably concentrated in
discrete domains as described and claimed in our
copending Canadian Patent Application No. 2,046,483
(Unilever PLC).
Suitable nonionic detergent compounds which may be
used include in particular the reaction products of
compounds having a hydrophobic group and a reactive
hydrogen atom, for example, aliphatic alcohols, acids,
amides or alkyl phenols with alkylene oxides, especially
ethylene oxide either alone or with propylene oxide.
Specific nonionic detergent compounds are alkyl
(C6 22) phenol-ethylene oxide condensates, the
condensation products of linear or branched aliphatic
C8 20 primary or secondary alcohols with ethylene oxide,
and products made by condensation of ethylene oxide with
the reaction products of propylene oxide and
ethylenediamine. Other so-called nonionic detergent
co~ou-lds include long-chain tertiary amine oxides,
tertiary phosphine oxides, and dialkyl sulphoxides.
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Especially preferred are the primary and secondary
alcohol ethoxylates, especially the C12 15 primary and
secondary alcohols ethoxylated with an average of from 5
to 20 moles of ethylene oxide per mole of alcohol.
The nonionic detergent-active compounds are
preferably concentrated in discrete domains. Since the
nonionic detergent compounds are generally liquids, these
domains are preferably formed from any of the well-known
carriers in the detergent business impregnated by
nonionic detergent-active compound. Preferred carriers
include zeolite; zeolite granulated with other
materials, for example, Wessalith CS (Trade Mark),
Wessalith CD (Trade Mark), Vegabond GB (Trade Mark),
sodium perborate monohydrate; Burkeite (spray-dried
sodium carbonate and sodium sulphate as disclosed in EP
221 776A (Unilever)).
Nonionic detergent-active compounds may optionally
be mixed with materials which make the granules slow
wetting and/or prevent the nonionic leaching out into the
main tablet matrix. Such materials may suitably be
fatty acids, especially lauric acid.
Detergency builders
Fully-formulated detergent tablets in accordance
with the invention may suitably contain one or more
detergency builders, preferably in an amount of from 5 to
80 wt%, more preferably from 20 to 80 wt%.
Preferred detergency builders are alkali metal
aluminosilicates. However, these builders have a
particular tendency to destabilise sodium percarbonate:
therefore, in tablets of the invention containing sodium
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percarbonate segregation of these two components is
essential.
Alkali metal (preferably sodium) aluminosilicates
may suitably be incorporated in amounts of from 5 to 60%
by weight (anhydrous basis) of the composition, and may
be either-crystalline or amorphous or mixtures thereof,
having the general formula:
0.8-1.5 Na20. A1203Ø8-6 sio2
These materials contain some bound water and are
required to have a calcium ion exchange capacity of at
least 50 mg CaO/g. The preferred sodium aluminosilicates
contain 1.5-3.5 sio2 units (in the formula above). Both
the amorphous and the crystalline materials can be
prepared readily by reaction between sodium silicate and
sodium aluminate, as amply described in the literature.
Suitable crystalline sodium aluminosilicate
ion-exchange detergency builders are described, for
example, in GB 1 429 143 (Procter & Gamble). The
preferred sodium aluminosilicates of this type are the
well-known commercially available zeolites A and X, and
mixtures thereof. Also of interest is the novel
zeolite P described and claimed in EP 384 070A
(Unilever).
Other builders may also be included in the detergent
tablet of the invention if necessary or desired: suitable
organic or inorganic water-soluble or water-insoluble
builders will readily suggest themselves to the skilled
detergent formulator. Inorganic builders that may be
present include alkali metal (generally sodium)
carbonate; while organic builders include polycarboxylate
polymers such as polyacrylates, acrylic/maleic
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copolymers, and acrylic phosphinates; monomeric
polycarboxylates such as citrates, gluconates,
oxydisuccinates, glycerol mono-, di- and trisuccinates,
carboxymethyloxysuccinates, carboxymethyloxymalonates,
dipicolinates, hydroxyethyliminodiacetates; and
organic precipitant builders such as alkyl- and
alkenylmalonates and succinates, and sulphonated fatty
acid salts.
Especially preferred supplementary builders are
polycarboxylate polymers, more especially polyacrylates
and acrylic/maleic copolymers, suitably used in amounts
of from 0.5 to 15 wt%, especially from 1 to 10 wt%; and
monomeric polycarboxylates, more especially citric acid
and its salts, suitably used in amounts of from 3 to
20 wt%, more preferably from 5 to 15 wt%. As previously
indicated, at least part of any polymer required in the
formulation may be incorporated, as binder, in the region
of the tablet in which the sodium percarbonate is
segregated.
Preferred tabletted compositions of the invention
preferably do not contain more than 5 wt% of inorganic
phosphate builders, and are desirably substantially free
of phosphate builders. However, phosphate-built
tabletted compositions are also within the scope of the
invention.
Enzymes
Fully-formulated tablets in accordance with the
invention may also contain one of the detergency enzymes
well-known in the art for their ability to degrade and
aid in the removal of various soils and stains. Most
enzymes are bleach-sensitive to some extent, and should
20534~
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also be excluded from the region containing the sodium
percarbonate.
Suitable enzymes include the various proteases,
cellulases, lipases, amylases, and mixtures thereof,
which are designed to remove a variety of soils and
stains from fabrics. Examples of suitable proteases are
Maxatase (Trade Mark), as supplied by Gist-Brocades N.V.,
Delft, Holland, and Alcalase (Trade Mark), Esperase
(Trade Mark) and Savinase (Trade-Mark), as supplied by
Novo Industri A/S, Copenhagen, Denmark. Detergency
enzymes are commonly employed in the form of granules or
marumes, optionally with a protective coating, in amounts
of from about 0.1% to about 3.0% by weight of the
composition; and these granules or marumes present no
problems with respect to compaction to form a tablet.
Minor ingredients
Fully-formulated tablets in accordance with the
invention may also contain a fluorescer (optical
brightener), for example, Tinopal (Trade Mark) DMS or
Tinopal CBS available from Ciba-Geigy AG, Basel,
Switzerland. Tinopal DMS is disodium
4,4'bis-(2-morpholino-4-anilino-s-triazin-6- ylamino)
stilbene disulphonate; and Tinopal CBS is disodium 2,2'-
bis-(phenyl-styryl) disulphonate.
An antifoam material is advantageously included in
the fully-formulated tablet of the invention, especially
if the tablet is primarily intended for use in
front-loading drum-type automatic washing machines.
Suitable antifoam materials are usually in granular form,
such as those described in EP 266 863A (Unilever). Such
antifoam granules typically comprise a mixture of
silicone oil, petroleum jelly, hydrophobic silica and
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alkyl phosphate as antifoam active material, sorbed onto
a porous absorbent water-soluble carbonate-based
inorganic carrier material. Antifoam granules may be
present in any amount up to 5% by weight of the
composition.
It may also be desirable to include in the
fully-formulated detergent tablet of the invention an
amount of an alkali metal silicate, particularly sodium
ortho-, meta- or preferably neutral or alkaline silicate.
The presence of such alkali metal silicates at levels,
for example, of 0.1 to 10 wt%, may be advantageous in
providing protection against the corrosion of metal parts
in washing machines, besides providing some measure of
building and giving processing benefits.
Further ingredients which can optionally be employed
in the fully-formulated detergent tablet of the invention
include antiredeposition agents such as sodium
carboxymethylcellulose, straight-chain polyvinyl
pyrrolidone and the cellulose ethers such as methyl
cellulose and ethyl hydroxyethyl cellulose;
fabric-softening agents; heavy metal sequestrants such
as EDTA; perfumes; pigments, colorants or coloured
speckles; and inorganic salts such as sodium and
magnesium sulphate. Sodium sulphate may if desired be
present as a filler material in amounts up to 40% by
weight of the composition; however as little as 10% or
less by weight of the composition of sodium sulphate, or
even none at all, may be present.
As well as the functional detergent ingredients
listed above, there may be present various ingredients
specifically to aid tabletting or to aid tablet
dispersion in the wash, for example, binders,
disintegrants, or lubricants. As already indicated,
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some ingredients may give both functional wash benefits
and tabletting benefits.
Tabletting
As previously indicated, the tablets of the
invention are prepared by compaction of particulate
starting material. Any suitable compacting process may
be used, for example, tabletting, briquetting or
extrusion, but tabletting is generally preferred.
For any given starting composition, the time taken
for the tablet to disintegrate in the wash liquor will
vary with the compaction pressure used to form the
tablet. If the compaction pressure is too low, the
tablet will tend to crumble and break up in the dry
state, on handling and packaging; an increase in
compaction pressure will improve tablet integrity, but
eventually at the expense of disintegration time in the
wash liquor.
Using an Instron (Trade Mark) Universal Testing
Machine at constant speed, or a Research and Industrial
screw hand press, to operate a steel punch and die, it
has been found that effective tablets may be produced
using compaction pressures ranging from 0.1 to 500 MPa
(0.01 to 50 kN/cm2), especially from 0.2 to 100 MPa (0.02
to 10 kN/cm2).
The optimum compaction pressure will depend to some
extent on the starting composition; for example, a
tablet containing only the bleach composition of the
invention may require a higher compaction pressure than
that required for a fully formulated detergent
composition tablet; a formulation containing a high
proportion of organic ingredients (for example,
2053433 - 18 - C3390
surfactants) and a low p~o~oL~ion of inorganic salts may
require a compaction pressure lower than that required
for a formulation containing a lower proportion of
organic ingredients and a higher proportion of inorganic
salts; and a dry-mixed formulation will generally
require a higher pressure than will a spray-dried powder.
Preferred tablet forms
Preferred tablets having improved disintegration and
dissolution properties are described and claimed in our
copending Canadian Patent Applications Nos. 2,046,453 and
2,046,483 (Unilever PLC). These preferred tablet forms have
particular relevance for tablets or fully formulated detergent
compositions.
The tablet described and claimed in Application No.
90 15503.7 or a discrete region thereof, consists
essentially of a matrix of particles substantially all of
which have a particle size within a range having upper
and lower limits each lying within the range of from 200
to 2000 ~m and differing from each other by not more than
700 ~m.
According to Application No. 90 15504.5, a tablet of
compacted particulate detergent composition comprises a
minor proportion (2-40 wt%) of a first component (a)
which contains 20-100 wt% anionic surfactant, the rest of
the composition containing only 0-3 wt% anionic
surfactant.
The tablet described and claimed in our British
application filed on 1 July 1991, or a discrete region
thereof, consists essentially of a matrix of particles
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substantially all of which have a particle size >200~m,
at least the particles of detergent-active compound and
detergent builder are coated with binder/disintegrant
before tablet compaction.
Dosage forms
The tablet of the invention may provide a bleaching
composition for treating fabrics in the washing machine.
lo This tablet may preferably be used as one of two or more
tablets within a two-tablet or multi-tablet detergent
system. Especially preferred is a two-tablet system in
which the second tablet containing the detergent base
system.
Alternatively, the detergent tablet of the invention
may be formulated for use as a complete heavy-duty fabric
washing composition. The consumer does not need to use
a mix of tablets having different compositions.
Although one fully-formulated or bleach-only tablet
may contain sufficient of all the components to provide
the correct amount required for an average washload, it
is convenient if each tablet contains a submultiple
quantity of the composition required for average washing
conditions, so that the consumer may vary the dosage
according to the size and nature of the washload. For
example, tablet sizes may be chosen such that two
fully-formulated or bleach-only tablets are sufficient
for an average washload; one or more further tablets may
be added if the washload is particularly large or soiled;
and one only tablet may be used if the load is small or
only lightly soiled.
Alternatively, larger subdivisible full-formulated
or bleach-only tablets representing a single or multiple
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dose may be provided with scorings or indentations to
indicate unit dose or submultiple unit dose size to the
consumer and to provide a weak point to assist the
consumer in breaking the tablet if appropriate.
The size of the tablet will suitably range from 5 to
160 g, depending on the wash conditions under which it is
intended to be used; whether it is a bleach-only tablet
or contains other ingredients; and whether it represents
a single dose, a multiple dose or a submultiple dose.
Bleach-only tablets preferably range from 5 to 50 g in
size. Fully formulated tablets preferably range from 10
to 160 g in size, more preferably from 15 to 60 g in
size.
The tablet may be of any suitable shape, but for
manufacturing and packaging convenience is preferably of
uniform cross-section, for example, circular (preferred)
or rectangular.
EXAMPLES
The following non-limiting Examples illustrate the
invention. Parts and percentages are by weight unless
otherwise stated. Examples identified by numbers are in
accordance with the invention, while Examples identified
by letters are comparative.
Examples 1 to 3
Measurement of the observed pseudo-first order
perhydrolysis rate constant
A 4.lmM solution of sodium perborate tetrahydrate
was prepared at 30C and buffered to pH 10 with (25mM)
sodium carbonate buffer.
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2.1/n mM of activator, where n is the number of
perhydrolysable groups on the activator, was added neat
(ie not in solution) to the predissolved perborate.
5The peracid yields were measured using a sodium
thiosulphate titration at 0C (standard acid/ice method).
The observed pseudo-first-order perhydrolysis rate
constant (KObs) was measured for the following
10 activators:
sodium benzoyloxy benzenesulphonate (SBOBS) - Example 1;
TAED - Example 2;
glycerol triacetate (GTA) - Example 3.
Results are shown in Table 1.
Table 1
Example Activator Kobs (s
1 SBOBS 3.0 x 10
2 TAED 2.3 x 10 3
3 GTA 1.9 x 10 4
Examples 4 to 6. Comparative Examples A to C
(i) Pre~aration of bleach compositions
A 40 wt% solution of Analar sodium carbonate was
prepared. Acrylic/maleic copolymer in sodium salt form
- Sokalan (Trade Mark) CP5 ex BASF - was admixed in an
amount of 2 wt% based on the sodium carbonate (dry
weight), and the solution was stirred at 50C for
20~3433
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2 hours. The solution waC then spray-dried using
laboratory equipment (inlet temperature 275C, feed rate
10 ml/min through a 0.75 ~m jet) to give granular
anhydrous sodium carbonate of high specific surface area.
Bleach compositions were then prepared by dry-mixing
the spray-dried sodium carbonate composition with sodium
percarbonate and bleach sctivator to give the
formulations shown in Table 2. The bleach activators
used were TAED (in granule form), glycerol triacetate
(GTA), and sodium benzoyloxy benzenesulphonate (SBOBS),
used in amounts chosen to give equivalent weights of
peracid (assuming 100% peracid generation efficiency).
The GTA, being a liquid, was preabsorbed in the
spray-dried sodium carbonate.
(ii) Preparation of deterqent base composition
A detergent base composition was prepared to the
formulation shown in Table 2, by spray-drying an aqueous
slurry of all ingredients except the nonionic surfactant
7EO which was subsequently sprayed on.
(iii) Tabletting
Tablets were prepared using an Instron (Trade Mark)
Model 4202 Materials Testing Machine fitted with a 10KN
load ,cell.
For Examples 4 to 6 (the invention), bleach
compositions (10 g) was added to the die, the die was
tapped gently to level the powder, and detergent base
composition (30 g) was added on top of the bleach
composition, before tabletting.
2~S:3433
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The tablets each weighed 40 g, and were 53 mm in
diameter and 22 mm in thickness.
Comparative Examples A, B and C were loose powders
of the same composition, prepared by mixing the bleach
composition and the detergent base composition in the
same proportions as in Example 4.
(iv) Bleaching performance
Bleaching performance was assessed by measuring the
increase in reflectance at 460 nm (with incident light
<400 nm filtered out) (~R460*) of standard tea-stained
test cloths after washing in a Miele (Trade Mark) 756
front-loading automatic washing machine, using a standard
heat-up to 40C wash in the presence of a 1 kg ballast
washload. For each wash two tablets (Examples 4 to 6)
or 80 g of powder (Comparative Examples A to C) were
used. The results are shown in Table 3.
20~343~
- 24 - C3390
Table 2 Deterqent Base and Tablet Compositions
% (base) % (tablet)
Deterqent base composition
Linear alkylbenzene sulphonate 9.60 7.20
Nonionic surfactant (7EO) 4.10 3.08
Soap 2.60 1.95
Zeolite 4A (anhydrous basis)40.50 30.38
Polymer (acrylic/maleic) 6.10 4.58
Sodium alkaline silicate 0.70 0.53
Sodium carbonate 14.80 11.10
Sodium carboxymethylcellulose0.90 0.68
Minor ingredients 2.70 2.03
Moisture 18.00 13.50
_____ _____
100.00 75.00
Tablet and Powder Compositions
4,A 5,B 6,C
Detergent base composition 75.0 75.0 75.0
Sodium percarbonate 12.5 12.5 12.5
Spray-dried sodium carbonate 10.25 9.5 7.65
TAED granules (82~ active) 2.25
GTA ~ 3-0
SBOBS - - 4.85
100. 0 100 . O 100. 0
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Table 3 Bleach Performance Results
Example Activator Reflectance increase
t~R460*)
Tablet Powder
4 TAED 9.3
A TAED 5.4
GTA 7.1
B GTA 5.9
6 SBOBS 13.6
C SBOBS 11.0
Example 7, Comparative Example D
(i) Preparation of bleach compositions
A spray-dried sodium carbonate composition was
prepared as described for Examples 4 to 6. Bleach
compositions were then prepared by dry-mixing the
spray-dried sodium carbonate composition with sodium
percarbonate, 1-O-octanoyl-2,3,4,6-tetra-O-acetyl glucose
(OTAG) and glycerol as shown in Table 4.
20~3~33
- 26 - C3390
Table 4
Component ~(wt) (tablet)
OTAG 9 4
Sodium percarbonate 42.9
Spray-dried sodium carbonate composition 42.9
Glycerol 4.8
100. 0
(ii) Tabletting
Tablets were prepared using an Instron (Trade Mark)
Model 4202 Materials Testing Machine fitted with a 5KN
load cell.
The tablets each weighed 25.62 g and were 40 mm in
diameter and 13 mm in thickness.
Comparative Example D was a loose powder of the same
composition.
(iii) Bleaching performance
Bleaching performance was assessed by measuring the
increase in reflectance at 460 nm (with incident light
<400 nm filtered out) (~R460*) of st~n~rd tea-stained
test cloths after washing in a Miele (Trade Mark) 756
front-loading washing machine, in 10 litres of soft water
in the presence of a buffer containing 10g/l sodium
metaborate and 5g/l sodium bicarbonate at pH 9.85 at 20C
for 30 minutes. For each wash one tablet (Example 7) or
25.8g of powder (Comparative Example D) were used. The
results are shown in Table 5.
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Table 5
Reflectance Increase
Example ( 460*)
7 3.8
D 2.4
Example 8, Com~arative Examples E and F
(i) Preparation of bleach compositions
A spray-dried sodium carbonate composition was
prepared as described for Examples 4 to 6. Bleach
compositins were then prepared by dry-mixing the
spray-dried sodium carbonate composition with sodium
percarbonate and OTAG as shown in Table 6.
20534~3
- 28 - C3390
Table 6
Component ~(wt) (tablet)
OTAG 10.6
Sodium percarbonate 44.7
Spray-dried sodium carbonate composition44.7
100. 0
(ii) Tabletting
Tablets were prepared as described for Example 7.
Comparative Examples E and F were loose powders of
the same composition.
(iii) PreParation of detergent base ~owder composition
A detergent base composition was prepared to the
formulation shown in Table 7, by spray-drying an aqueous
slurry of all ingredients except the nonionic surfactant
7EO which was subsequently sprayed on.
2~53Q33
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Table 7, Deterqent Base Powder Composition
Detergent base composition % (base)
Linear alkylbenzene sulphonate 10.00
Nonionic surfactant (7EO) 4.58
Soap 2.76
Zeolite 4A (anhydrous basis) 41.79
Polymer (acrylic/maleic) 4.47
Sodium alkaline silicate 0.68
Sodium carbonate 18.13
Sodium carboxymethylcellulose 0.84
Fluorescer 0.33
Moisture 16.42
100.00
(iv) Bleaching performance
Bleaching performance was assessed by measuring the
increase in reflectance at 460 nm (with incident light
>400 nm filtered out) (~R460) of both standard
tea-stained test cloths and EMPA wine stained cloths
after washing in a Miele (Trade Mark) 756 front-loading
machine, in 10 litres of water at 40C. For each wash
one tablet (Example 8) or 25.8g of bleach composition
powder (Comparative Examples E and F) were used in
conjunction with 50g of the described detergent base
powder. For Comparative Example E the bleach
composition powder was added to 20 ml of water in a
bottle and shaken vigorously for one minute for adding to
the wash, thus enabling some perhydrolysis to take place
under conditions of high concentration and pH prior to
the bleach performance test described above. The
results are shown in Table 8.
2~3~133
~ 30 - C3390
Table 8
Reflectance increase (~R460*)
Example Tea stain Wine stain
8 6.2 17.9
E 3.8 12.8
F 2.0 11.3
Examples 9 to 13, Comparative Example G
The effect of tabletting pressure on peracid yield
using the bleach composition of Example 3 (containing
TAED as bleach activator) was investigated. The results
are shown in Table 9.
For this work, separate bleach and detergent tablets
were prepared, so that the bleach composition could be
tabletted at a series of different pressures (0.4 to
8 KN/cm2) while the detergent base powder was always
tabletted at the same pressure (0.4 KN/cm2), thus
avoiding complications that would have arisen if the
detergent base powder had dissolved at different rates in
the different experiments.
In each experiment, two bleach composition tablets
(each 10 g) and two detergent base composition tablets
(each 30 g) were used.
Wash conditions, selected to obtain maximum
reproducibility, were a long (45 minute) wash at ambient
temperature in the Miele 756 washing machine in the
absence of a ballast load.
Peracid yields, expressed as a percentage of the
theoretical yield, were measured by a stAn~rd
iodine/thiosulphate titration at 0C at intervals
~3~33
- 31 - C3390
throughout the wash: the maximum yield, and the time
(TmaX) taken to reach that maximum, were recorded.
The integrated yield (arbitrary units) was also
calculated, by numerical integration of the peracid yield
over the whole wash time: this is a measure of the
peracid level available over the whole of the wash
period.
Table 9: Peracid Yield Results (Sodium Percarbonate)
Example Tabletting Maximum Tmax Integrated
pressure yield yield
(kN/cm2) (mole %) (min) (arbitrary
units)
G 0 (powder) 83 5 2965
9 0.4 80 10 2907
0.8 86 8 3060
11 1.6 88 12 3252
12 4.8 94 12 3458
13 8 86 14 3058
It may be seen that at the optimum (a tabletting
pressure of 4.8 KN/cm) the integrated yield was just over
115% of that for the powdered formulation.
26353433
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Examples 14 to 18, Comparative Exam~le H
The procedure of Examples 9 to 13 and G was repeated
using a bleach formulation containing sodium perborate
tetrahydrate and TAED.
The formulation was adjusted slightly in order to
maintain the same levels of available oxygen as in
Examples 9 to 13 and G, since commercial sodium perborate
tetrahydrate contains about 10% available oxygen while
sodium percarbonate contains about 13.5%. This
adjustment increased the weight of the bleach tablets
from 10 g to 11.75 g, while the weight of the detergent
tablets remained at 30 g. The bleach formulation was as
follows:
Detergent base composition 71.9
Spray-dried sodium carbonate 9.8
Sodium perborate tetrahydrate 16.1
TAED granules (82% active) 2.2
100. 0
Again, two bleach tablets and two detergent tablets
were used per wash.
The results are shown in Table 10. Some benefit
was observed at higher tabletting pressures, but it was
smaller than the benefit observed with sodium
percarbonate.
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- 33 - C3390
Table 10: Peracid Yield Results (Sodium Perborate
Tetrahydrate)
Example Tabletting Integrated
pressure yield
(kN/cm2) (arbitrary units)
H 0 (powder) 2069
14 0.4 2180
0.8 2045
16 1.6 2097
17 4.8 2269
18 8 2251
