Note: Descriptions are shown in the official language in which they were submitted.
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C.3210
DE~ERGENT COMPOSITIONS
The present invention relates to detergent
compositions. In particular, it relates to liquid
machine dishwashinq detergent compositions suitable for
use in cleansing food soils from cooking utensils, dishes,
glasses and similar ware.
More particularly, the present invention relates to a
stable, pourable, aqueous system comprising at least
partially undissolved builder salts and a dissolved alkali
silicate, the composition being essentially free of
conventional structuring agents. The system is
characterlsed by its thixotropic nature.
; 15
Detergents for use in domestic machine dishwashers
are generally available in powdered or granular forms.
However, such solid compositions exhibit a number of
disadvantages for the producer and user. In manufacture,
the compositions cannot generally be spray-dried~ and thus
separate manufacturinq facilities to those generally used
for powdered detergents must be built. The powders often
incorporate large lumps caused by caking durinq storage at
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high humidity. This can cause difficulties in
dispersion. Powdered forms of the product are often very
dusty, which can affect dispensing as well as causing
irritation~
The use of liquid forms of detergent for machine
dishwashing eliminates many of the above disadvantaqes
solely attributable to powders. However, liquid
detergents must meet certain requirements. Firstly, the
liquid must be a uniform mixture of ingredients in order
to deliver the optimum combination of active components to
the wash with each dose. By active components, we mean
those components which actually take part in the cleaning,
rather than those acting as fillers. In many
formulations described in the art, this requires that the
liquid be shaken before each use in order to re-mix the
different components.
A preferred product should be stable against physical
separation and segregation of the active components during
storage. Particulate solids, for example de~ergency
builders r should remain suspended in liquid detergents.
To keep the solids in suspension, some kind of structuring
system is necessary. In aqueous detergent liquids this
may be achieved either by "external structuring", ie
adding an additional component such as a polymer or clay,
or using the interaction of the water in the liquid and
the detergent actives themselves, $o form an "internal
structurea to support the solids (eg secondary alkane
sulphonates and phosphonates). In all cases, microscopic
investigation indicates that some type of suspending
- ~ network is formed.
Accordingly, it should be understood that the phrase
'structuring agent' as used herein is taken to mean any
component, e.g. clay, polymer or biocellulosic, which at
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suikable amounts within a liquid imparts a structure to
said liquid, usually by network formation. The use of
such agents, particularly clay, in lower amounts is not to
be taken as being excluded from compositions. Such low
amounts may act as builders or rinse aids. The critical
amount of the component in question may only be determined
by reference to experiments or the prior art.
For use with machine dishwashers, the detergent must
be compatible with the dishwashing equipment presently
; available. Home dishwashing machines use a deter~ent cup
which has been designed to house powdered or granular
solid detergent and deliver it to a specific wash cycle.
The cups are usually held vertically on ~he dishwasher
door and are not designed to contain low viscosity
liquids. Consequently, liquids for use as machine
dishwashing detergents must possess sufficient viscosity
to be effectively retained in the cup and avoid leakage
into the machine during cycles which precede the wash.
Excessive leakage will lead to under-dosing in the wash
cycle and may affect cleaning perfonnance. ~lowever, they
must not be so viscous that they cannot be washed out of
the dispensing cup at the appropriate time.
The prior art has disclosed a number of methods for
thickening liquid machine dishwashing compositi$n~ and for
providing some degree of stability. /~ ~ 5~7 706
discloses a slurry structured by the addition of synthetic
polymers. However, it is thought that the low yield
point in liquids containing, eg polyacrylate as the only
tr~c2t2u~ agent, causes poor cup retention.
/6B ~ ~40 454 discloses liquids structu~ed with clay. The
clay lowers the amount of active component which can be
delivered in each dose. Furthennore, the presence of
insoluble clay minerals can negatively affect glass
spotting and filming perfo~nance. The use of biopolymers
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or cellulosics within a liquid detergent base has also
been proposed to provide thickened systems, eg
US 4 226 736 and US 4 260 528. Since most biopolymers
react readily with hypochlorite, these systems are
unstable and exhibit a gradual loss in vis~osity if
P~,lbl lshed J~ 7
r-~ ''" hypochlorite is present. GB 2 185 03y has disclosed the
use of long chain fatty acids to provide a thickening
effect.
The systems described in the prior art are all, in
principle, structured by the use of external,
network-forming structurants and, in general, these
liquids possess a shear thinning character, ie they
exhibit a high viscosity at low shear rate and a low
viscosity at high shear rate. Furthermore, and this
illustrates the thixotropic nature of the liquids) the
viscosity of these liquids is time-dependent after
distortion has taken place.
The present invention makes use of diferent
principles to obtain pourable and stable liquid systems.
In contrast to the prior art the present invention does
not involve the use of a network-forming structurant.
Due to the absence of such a structurant, which in the
current state of the art is judged to be essential for
keeping the solid particles well suspended, the present
invention involves liquid systems (dispersions) which are
Newtonian ~eg not shear thinning) over a broad range of
shear rate values: l-100 sec l, It appears that at
extremely low shear rates, which require special equipment
~controlled stress Deer rheometerl for measurement, the
deviation from Newtonian behaviour becomes more
pronounced, which is in line with a theory ~"Inleiding in
de Reologie, Reometrie, Disperstereologie en
Polymeerreologie", Blom C, Jongschaap RJJ, Mellema J,
Technische Hogeschool Twente Kluwer Technische Boeken, 1
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Druk 1986) developed to describe the rheological behaviour
of concentrated dispersions. Bence, it could not be
expected according ~o the current state of art that these
dispersions would be physically stable. Rapid
sedimentation should occur.
Without being bound ~o any theory we assume that in
compositions of the present invention the solids are ~
present as individual particles and not as flocculates.
By selecting a water-soluble alkali-metal silicate with a
suitable ratio SiO2/M2O (M - ~, Na~ this phenomenon, a
deflocculated system as indicated by pseudo-Newtonian
behaviour, can be obtainedc Addition of an electrolyte
may broaden the range in which the desired rheological
behaviour is observed. The deflocculation effect can be
illustrated by the following observation: the addition of
40~ zeolite 4A to a 20~ sodium disilicat~ (ratio 3.6)
solution results in the formation of a ~iscous, shear
thinning unusable paste outside the scope of the
invention. Adjusting the silicate ratio with NaOH or KOH
. ~ the visoosity will drop considerably and a thin, pourable,
pseudo-New~onian system is obtained by deflocculation of
the particles.
According to the present invention there i5 provided a
stable, non-phosphate pseudo-Newtonian liquid cleaning
composition, especially adapted for use in machine
dishwashers, comprising:
(a) from 5 - 60% by weight of a detergent builder
selected from the group of zeolites and amorphous
silica/alumina builders;
~b) from 3 - 40% by weight of a water-soluble
alXalimetal silicate having a (silica-to-alkali)
ratio between 0~6 and 1.9; and
(c) water,
113~2~
-- 6 ~
which composition is not shear-thinning over the range
of 1 - 100 æec~1 and has a Thixotropic Index of from 0.5 to
2.5, without the use of ex~ernal thickening agents.
The preferred rheological behaviour is identified by
the Thixotropic Index (TI) which has to be between 0.5 and
2.5. The ~hixotropic Index i6 herein defined as the
ratio of the apparent LVT Brookfield viscosity of a sample
after 3 minutes at room temperature using a No 4 spindle
at (a) 3 rpm and (b) 30 rpm.
To explain the surprisingly good physical stability
of the liquid systems according to the present invention,
it might be speculated that by selecting the proper
concentration and ratio of alkali-metal silicate, the
electrostatic Eorce between the particles, which causes
them to flocculate, are more than compensated ~y repulsion
forces. Hence, the individual particles sediment out
slowly at a rate determined by Stokes' law, whereby at
high solids levels (>20%) the phenomenon of ~indered
settling will result in even lower settling rates.
Overall this will lead to liquid systems with a good
physical stability.
The compositions according to the present invention
may be used in formulating detergent liquid cleaning
products. These may be formulated in a very wide range
of specific forms, according to the intended use. They
may be formulated as cleaners for hard surfaces (with or
without abrasive) or as agents for ware washing (cleaning
of dishes, cutlery etc3 either by hand or mechanical
means, as well as in the form of specialised cleaning
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products, such as for cleanin~ surgical apparatus or
artificial dentures.
Products formulated for ware washing, in particular
for use in machine ~ishwashers, const:itute a preferred
form of the present invention.
The composition according to the present invention
has improved rheology and stability in comparison to
compositions of the prior art and can deliver a high and
uniorm dosage of active ingrediQnts to the machine wash
cycle.
The detergent builder material is selected from
zeolite and amorphous silica/alumina builder3.
Aluminosilicates of the zeolite type may be prepared as
described in US 2 882 243 tUnion Carbide) or of the
amorphous type as described in CA 1,189,859 (Unilever).
The aluminosilicate is preferably of the formula 0.8-1.5
20 NazO; ~12O3; 1.7 - 3. a SiO2; 2 - 6 H2O.
Examples of other suitable builders are NTA, EDT~,
CNOS and DPA.
In terms of weight percentage of the total
composition, the builder most preferably constitutes from
; ~0-40%.
Tha second essential component of ~he present
invention is a silicate material. Nhen in combina~ion
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C.3210
with an alkali material, disill~c~t~2 ~a~ particularly
preferred, although metasilicates may also be included.
The alkali-metal silicates which are used serve a~
anti-corrosion agents, protecting metal and china surfaces
against harshly alkaline environments present during a
dishwashing cycle.
. In terms of weight percentage of the total
composition; the silicate-based materia:L may constitute
10 from 3-40~, most preferably from 5-20~.
Jn its broadest sense, the present invention
comprises compositions which do not necessarily contain
any detergent surfactantsO In the absence of such
surfactants, the compositions may be used for the delivery
of caustic agents to the wash liauor during mechanical
dishwashina operations. However, lt is generally
preferred to include one or more detergent surfactant
; agents. In general, these may be selected from one or
20 more of nonionic, anionic, cationic, zwitterionc and
amphoteric agents. Such agents are commercially
available and will be well kno~n by those skilled in the
art; for instance, they are fully described in the
literature, such as in "Surface Active Agents and
Detergents", Volumes I and II by Schwarz, Perry and Berch.
Preferably, any detergent active material comprises one or
more nonionic agents, for example the condensation
products of alcohols having from 8-16 carbon atoms, and
alkyl phenols with alkylene oxides including ethylene
oxide, propylene oxide, butylene oxide and mixtures
thereof. Preferably the alcohols are linear, having from
12-15 carbon atoms, and are condensed with 2-10 mols of
ethylene oxide. Most preferred are those compounds which
are generally regarded as "low-foaming", especially those
where the alkylene oxide chain is terminated by a moiety
other than hydrogenO
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The compositions according to the present invention
may be prepared by admixture of the various components.
Conventional additives such as colourants and
perfumes may be present in the composition in conventional
amounts.
An alkali-metal hypochlorite may be present in the
formula as an agent for removing tea, coffee and other
food stains from cups, dishes, flatware, etc. The b~each
source may be present in the mixture at from 0.1-10 wt ~,
with the most preferred range being from 0.1-2 wt %
(percentages as active chlorine).
Electrolytes such as NaCl, NaI, Na2SO4 may be
inc]uded in the composition at from 0.1 to 10 wt %.
Defoamers may be included in the composition. These
defoamers may be of the general type of slightly soluble
alkyl carboxylates, alkyl phosphates, hydrophobic silicas,
silicone defoamers, or many others. In addition to being
an effective defoamer, the species should be stable to
hypochlorite. The defoamer may optionally be present in
the composition at from 0-5 wt %, more preferably from
0.1-1 wt ~, and most preferably from 0.1-0.5 wt %.
The products according to the present in~ention
exhibit a high degree of stability at room temperature, in
comparison to other systems. Unlike known liquids, the
products produced in accordance with the present in~ention
do not require shaking in order to redisperse the
ingredients. Furthermore, compositions formulated in
accordance with the present invention exhibit a higher
den~ity (1.7-1.8) than comparable products of the prior
art. This is particularly important when considerin~
transportation. A more concentrated liquid benefits from
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lower packing and transport c05ts. Also, a unit dose
will deliver more active ingredients per unit dose than
products produced in accordance with the artO
The absence o network formation, due to the
deflocculation forces within the system, has also
important consequences for the nature of the product
hefore dosing. Liquid systems according to the present
invention are not susceptible to setting after storage.
Even after prolonged storage the product does not solidify
and no s~tting has been observed. The inference is that
the product can be dosed without shaking or ~queezing the
bottle which i5 required for the current liquids with an
external structurant. Dealing with hottles of 1.5-2.5 kg
this benefits the com~enience aspect of the product.
The compositions of the present invention provide a
liquid system which is very convenient for consumers
whilst being also perfectly suitable for an aut~matic
dosing application. The automatic dosing principle can
be used for domestic as well as industrial dishwashing
machines,
Unlike compositions of the prior art, comp~sitions
according to the present invention are pourable from rest
without need for shear thinning. Dispenser behaviour is
strongly determined by the rheological properties of the
liquid. In the prior art, ~lewtonian liquids are not
considered to be suitable. Some of the liquids according
to the present invention have been tested to measure
dispenser cup leakage in a number of c~mmercially-
available dispenser types. It was found that the degree
of dispenser cup leakage was acceptable if the liquid had
a viscosity of at least 2000 mPAS.
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The dosing of the machine dishwashing liqu1ds which
are currently available on the market makes use of bottles
with a small aperture to realise high shear rates to break
down the network. Because the liquid system according to
the present invention is pseudo-Newtonian this high shear
rate regime is not required during dosing so that a
selection can be made out of a wide range of bott,les.
Hence a broad conventional spout, eg 0.5-1.0 cms diameter,
optionally equipped with a self-drainirg device, may be
used for a bottle containing the liquid system according
to the present invention. Less spillage, an optimal
dosing and less undesired skin contact result from the
lack of need to shake, saueeze or squirt the bottle.
It has been found that dishwashiny compositions
formulated according to the present invention show less
tendency to cause spot formation on glass than other
conventionally structured (eg by polymers or clays) liquid
detergent systems. This is particularly noticeable after
a number of wash cycles.
A further possible use of the system of the invention
arises when considering systems incorporating zeolite as
the builder. Zeolite slurrys of the prior art are known
to be unstable. The li~uids of the present invention
provide a stable zeolite slurry which does not separate on
standing. The slurry can be spray dried as a basis for
formulating powders for, e,~. fabric or ware washing.
The invention will now be further illustrated by
means of the following non-limiting examples, wherein all
percentages are given by weight unless otherwise stated.
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Examples
1 1-1.3
Using a basic composition of 40~ zeolite and 20%
disilicate, the viscosity of different compositions was
measured as varying amounts of KOH were added. Viscosity
was measured with respect to shear rate for each system.
10 ~ase : 40% zeolite 20% disilicate
Addition : 0% KOH 10~ ROH 20~ KOH
,
Lo~ shear rate log visc loy visc log visc
-0.75 5.0 - -
-0,45 ~v7 4.1
15-0.06 4.3 4.2 3.7
0.25 4.1 4.2 3,7
0.55 3.8 4.1 3.8
0.85 3.4 4.2 3.8
1,15 3.4 4.1 3.8
201.45 3.4 ~.1 3.8
With the addition of KOH to lower the silicate ratio,
the composition exhibits pseudo-Newtonian behaviour.
When no KOH is added, the liquid is shear thinning.
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2.1 2.3
Using a base composition of 20~ disilicate and 10%
KOH, lo~ viscosity was measured as a function of log shear
- 5 rate for varying additions of zeolite to the system.
Base : 20% disilicate 10% KO~T
Addition : 35% zeolite 40~ ~eolite 45% zeolite
Log shear rate lo~ visc log Vi5C log visc
--1.OS -- -- --
-0.75 - _ ~ 5
-~.45 ~ 4.1 4.4
-0.06 - 4.1 4O4
0.25 3.5 4.2 4.5
0.55 3.6 4.2 ~.5
0.85 3.5 4.1 4.5
1.15 3.5 4.1 4.5
1.45 3,5 4~1 4.5
As ~eolite is added, the viscosity increases, but a
pseudo-Newtonian behaviour is exhibited.
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.
The stability of liquid compositions according to the
present invention was measured as the percentage of
separation at 1, 2, 3 and 4 weeks after storage at 20C.
t (weeks) 1 2 3 4
30 Zeolite Disilicate KOH _ _~ Separatio_
13 20 10 3 6 13 12
36 20 10 0
4~ 20 10 0
0 0 0 0
35 32 20 5 1 2 2 2
48 20 5
~3~ 2~
- 14 - C.3210
The build-~up of spots on glasses was measured over a
number of washes using different compositions formulated
,- 5 according to the present invention. Comparisons were
made with a commercially-a~railable pol3~er structured
machine di,shwashing liquid~
Formulation A B C
Zeolite 4A30 10 30
Disilicate20 20 20
~.OH 10 10 5
Hypochlorite
Water ~ to 100% -----------
The build-up of spots over 4 washes is measured as
the number of spots on a glass tumbler:
0
~-5 2
6-10 3
11 20
>20 5
Washing was carried out in a Bauknecht GS ~70 S
machine on a normal 55C programme, dosing at
30 g/machine. (Water 15~ French hardness.)
An average score for 20 glasses was made.
Spot Score
Wash No A B C ComPariSOn
l 1.0 1.6 2.~ 5.0
2 3.4 1.4 4.0 5.0
,3 3.9 2.4 4.9 5.0
4 4.0 3.2 5.0 5.0
.
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It can be seen that spot build-up is considerably
reduced using compositions formulated in accord~nce with
the present invention in comparison to composikions which
are "externally" structured.
The following composition was prepared:
wt~
Zeolite 4A 42
Sokalan Polymer 120% slurry~ 5
Disilicate (ratio 2.0) 20
; 15 R O~ (85~ soln) 5
HOCl (as Cl2)
Water to l00
The composition was found not to have separated over
a period of weeks and was suitable for cleaning dishes in
a machine dishwasher.
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