Note: Descriptions are shown in the official language in which they were submitted.
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DETERGENT COMPOSITIONS
This invention relates to detergent tablets for use in the
washing of fabrics. These tablets are intended to disintegrate
completely when placed in water and thus to be consumed in a
single use.
Detergent compositions in tablet form and intended for fabric
washing have been described in a number of patent documents
including, for example EP-A-711827, WO-98/42817 and WO-99/20730
(Unilever) and are now sold commercially. Tablets have several
advantages over powdered products: they do not require
measuring and are thus.easier to handle and dispense into the
washload, and they are more compact, hence facilitating more
economical storage.
Tablets of a detergent composition have frequently been made by
compressing or compacting a composition in particulate form;
tablets of the present invention are also made this way.
Although it is desirable that tablets have adequate strength
when dry, yet disperse and dissolve quickly when brought into
contact with water, it can be difficult to obtain both
properties together.
Tablets formed using a low compaction pressure tend to crumble
and disintegrate on handling and packing; while more forcefully
compacted tablets may be sufficiently cohesive but then fail to
disintegrate or disperse to an adequate extent in the wash.
Tableting will often be carried out with enough pressure to
achieve a compromise between these desirable but antagonistic
properties. However, it remains desirable to improve one or
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other of these properties without detriment to the other so as
to improve the overall compromise between them.
Organic surfactants function as a binder in tablets and help to
plasticise the tablets. However, they can also retard
disintegration of the tablet by forming a viscous gel when the
tablet comes into contact with water. Thus, the presence of
surfactant can make it more difficult to achieve both good
strength and speed of disintegration: the problem has proved
especially acute with tablets formed by compressing powders
comprising organic surfactant and built with insoluble
detergency builder such as sodium aluminosilicate (zeolite).
It is already known to make tablets from compositions which
consist of (i) base-powder particles which comprise organic
surfactant and other materials and (ii) various other
ingredients, including water-soluble salts.
It is well known that detergent tablets, like detergent
compositions generally, can be made using water-soluble or
water-insoluble detergency builder. The water-soluble builder
which is commonly used is sodium tripolyphosphate. However it
may be necessary to restrict the amount of this material in
order to meet regulatory constraints on the amount of phosphate
in detergent composi~ions.
The alternative of using a water-insoluble detergency builder,
such as zeolite, also encounters problems in that it can be
even more difficult to make tablets with satisfactory strength
and speed of disintegration.
Furthermore, it has been found that the storage stability of
some ingredients is not yet optimised in detergent tablets so
that the ingredients degrade over time resulting in the tablets
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being less effective. Examples of such ingredients include
bleaching agents and their activators, and, enzymes.
Current practice in the commercial market in Europe is that
when zeolite is used as the detergency builder, some expedient
is adopted to assist disintegration. One possibility, is to
use a tablet core which is not very strong, but dissolves
rapidly, and enclose it in a soluble coating to strengthen the
weak tablet core.
Other tablets which have been sold commercially and are
exemplified in EP-A-838,519 contain a highly soluble salt to
promote disintegration. They also utilise zeolite MAP which
aids disintegration because it swells on Contact with water.
However, zeolite MAP is not used by all detergent manufacturers
in Europe, and it is not always readily available outside
Europe.
WO-A-00/32741, WO-A-98/55590 and WO-A-00/32740 (all Unilever)
disclose highly soluble materials such as sodium
tripolyphosphate having at least 50% by weight thereof in the
phase I form with surfactant granules comprising high levels of
organic surfactant which surfactant granules may comprise
zeolite.
US 4,543,204 (Colgate Palmolive) discloses extruded detergent
bars which may comprise sodium tripolyphosphate having a high
content of the phase 1 material.
WO-A-00/53716 (Henkel) discloses washing tablets comprising
non-ionic surfactants, phosphate builders and low levels of
zeolite of the Faujasite type, wherein the ratio of non-ionic
surfactants: zeolite is between 1:20 and 1:1.
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WO-A-01/04256 published 18 January 2001(Henkel
Kommanditgesellschaft Auf Atkien) discloses an auxiliary
disintegration agent comprising 20 to 95o wt phosphate and 0.1
to 9%wt zeolite for shaped bodies.
The use of sodium tripolyphosphate having a high content of
phase I form in detergent tablets is disclosed in EP-A-839,906
and WO-A-00/77153 (both Unilever). The use of the
predominantly phase II form of sodium tripolyphosphate is
disclosed in GB-A-2,321,466 (Procter & Gamble) and EP-A-
126, 963.
~It is an aim of the present invention to address one or more of
the aforementioned technical problems.
We have now discovered how to provide a detergent tablet which
comprises a mixture of aluminosilicate builder and organic
surfactant and which exhibits good strength and dissolution
characteristics. Additionally we have discovered how to
provide detergent tablets which provide good storage stability
for ingredients which are prone to degradation over time.
Broadly we have found that detergent tablets incorporating base
particles which comprise a mixture of aluminosilicate
detergency builder and organic~surfactant can be made to
disintegrate more readily by incorporating in the composition
sodium tripolyphosphate having at least 500 of said sodium
tripolyphosphate in the phase I form.
Thus according to a first aspect of this invention, there is
provided a detergent tablet of compacted particulate material
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wherein the tablet or a region thereof is compacted from a
particulate composition which comprises;
a) 25% to 1000 by weight of the composition of base particles,
which particles comprise by weight of themselves:
5 from 15% to 40owt organic surfactant comprising no more than
5% by weight primary alkyl sulphate,
from 20o to 60owt aluminosilicate detergency builder, and
from 0 to 60%wt other ingredients, and
b) 0 to 75o by weight of the composition of other materials
mixed with these particles, and
wherein the composition comprises from 5a to 60% by weight of
the composition of sodium tripolyphosphate having at least 500
by weight thereof in the phase I form.
According to a second aspect of this invention, there is
provided a detergent tablet of compacted particulate material
wherein the tablet or a region thereof is compacted from a
particulate composition comprising;
a) 25o to 1000 by weight of the composition of base particles,
which particles comprise by weight of themselves:
from 15% to 40%wt organic surfactant comprising,alkylbenzene
sulphonate,
from 20% to 60%wt aluminosilicate detergency builder, and
from 0 to 60owt other ingredients,
2 5 and
b) 0 to 75o by weight of the composition of other materials
mixed with these particles, and
wherein the composition comprises from 5% to 60o by weight of
the composition of sodium tripolyphosphate having at least 500
by weight thereof in the phase I form.
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The aluminosilicate preferably comprises maximum aluminium
zeolite P or zeolite A, more preferably maximum aluminium
zeolite P or zeolite 4A, and especially maximum aluminium
zeolite P.
In especially preferred forms of the invention, the tablet or a
region thereof is compacted from a particulate composition
which comprises 25o to 95o by weight of the base particles a),
maximum aluminium zeolite P as the aluminosilicate and 5 to 750
by weight of the said other materials b).
According to a third aspect of the invention there is provided
a method of making a detergent tablet of compacted particulate
material, the method comprising the steps of;
(1) forming detergent base particles comprising (by weight of
themselves) 15 to 40owt organic surfactant with either (i) no
more than 5%wt by weight primary alkyl sulphate or (ii)
comprising alkylbenzene sulphonate, 20 to 60%wt aluminosilicate
detergency builder and 0 to 60%wt other materials, and
(2) mixing the base particles with other materials as
necessary to form a particulate composition comprising 25 to
1000 by weight of the base particles a)~ and 0 to 75o by weight
of the other materials b); and wherein the particulate
composition comprises from 5o to 60% by weight thereof sodium
tripolyphosphate having at least 50% by weight thereof is in
the Phase I form, and
(3) compacting the composition into tablets or regions
thereof.
In an especially preferred method, the base particles a) are
prepared by a granulation method and mixed with other materials
b) to form a composition comprising 25 to 95% by weight of the
base particles and 5 to 75% by weight of the other materials,
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with maximum aluminium zeolite P or zeolite A as the
aluminosilicate. Preferably the other materials b) comprise
from 5o to 60% by weight of the overall composition of sodium
tripolyphosphate having at least 50% by weight thereof is in
the Phase I form.
These tablets exhibit a good combination of disintegration and
strength properties. Furthermore they exhibit good storage
stability especially at 37°C, 70o relative humidity for
ingredients which are prone to degradation upon tablet storage,
especially bleaching agents and their activators, and, enzymes.
This may be utilised to provide tablets comprising zeolite, but
without restriction to zeolite MAP as the only form of zeolite
WhlGh can be used.
Except in the operating and comparative examples, or where
otherwise explicitly indicated, all numbers in this description
indicating amounts of material or conditions of reaction,
physical properties of materials and/or use are to be
understood as modified by the word "about." All amounts are by
weight, unless otherwise specified.
A detergent tablet may be made from one or more compositions
and so may be either homogeneous or heterogeneous. In the
present specification, the term "homogeneous" is used to mean a
tablet produced by compaction of a single particulate
composition, but does not imply that all the particles of that
composition will necessarily be of identical composition. The
term "heterogeneous" is used to mean a tablet consisting of a
plurality of discrete regions, for example layers, inserts or
coatings, each derived by compaction from a particulate
composition. In a heterogeneous tablet each discrete region of
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the tablet will preferably have a mass of at least 10% of the
whole tablet, which may be a mass of at least 4 gram.
V~h.ere a tablet is a heterogeneous tablet having more than one
discrete region, for example a tablet with two layers of
different composition, it is possible that one region will be
provided by a composition in accordance with this invention
while another region will be provided by some other
composition. It is also possible that two regions would be
provided by different compositions both of which however,
embody the present invention.
Base particles
The detergent tablets of the invention comprise compacted
particulate material which comprises 25 to 1000 by weight of
base particles a) and 0 to 75% by weight of other material b)
mixed therewith.
Preferably the compositions comprise 300, 330 or 40% to 60% or
70% by weight of base particles a) and 300 or 40% to 600, 67%,
or 70o by weight of other material b). The compositions may
comprise for example from 35% to 98%wt of the base particles a)
and from 2% to 65%wt of the other materials b).
The base particles may be made by spray-drying as described in
EP 839906 and WO 98/42819. Alternatively they may be made by a
granulation process. For example, EP 838519 and WO 99/20730
describe tablets containing granulated particles in which
detergent active (i.e. organic surfactant) is mixed with
zeolite A24. This form of zeolite, also known as zeolite MAP,
is a special form of zeolite which is the subject of EP-A-
384070.
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Tf the base particles a) do not comprise the sodium
tripolyphosphate, they can be made by a spray-drying process.
However, granulation is the most appropriate method of
preparation and is preferred whether the particles comprise
sodium tripolyphosphate or not. A suitable method of
granulating is disclosed in WO 00/77147 (Unilever).
Organic surfactant
One or more organic detergent surfactants are present in the
base particles a) and preferably provide from 7 to 40o by
weight of the total composition, more preferably from 8, 10 or
12o by weight of the overall composition up to 40o by weight.
Organic surfactant may be present solely in the base particles
a), or some may additionally be present as part of the other
material b). Preferably at least 800, better 90%wt of the
organic surfactant in the composition is present in the base
particles.
The organic surfactant in the base particles preferably
comprises anionic surfactant, either alone or mixed with
nonionic surfactant.
Anionic surfactant may be present in an amount from 0.5 to 400
by weight, preferably from 20 or 4% up to 300 or 40% by weight
of the total composition.
Synthetic (i.e. non-soap) anionic surfactants are well known to
those skilled in the art. Examples include alkylbenzene
sulphonates, olefin sulpl~onates, alkane sulphonates, dialkyl
sulphosuccinates, and fatty acid ester sulphonates.
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Linear alkyl benzene sulphonate of the formula:
R ~ _ +
S03 M
5 where R is linear alkyl of 8 to 15 carbon atoms and M+ is a
solubilising ration, especially sodium, is also a commercially
significant anionic surfactant.
It is preferred that the organic surfactant comprises
10 alkylbenzene sulphonates,~ particularly sodium linear
alkylbenzene sulphonates having an alkyl chain length of C$-C15.
Such linear alkyl benzene sulphonates are usually the desired
anionic surfactant and may provide 75 to 100 wto of any anionic
non-soap surfactant in the composition.
Further anionic surfactants which may be used are fatty aryl
I ester sulphonates of formula:
R CH - C02 2M-~-
S03
in which R is an alkyl or alkenyl chain of 8 to l8 carbon. atoms
and M+ is a solubilising ration.
Various other anionic surfactants are available and can be
used. Examples include olefin sulphonates of formula:
R CH-R' M+
S03
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in which R is alkyl of 6 to 18 carbon atoms R1 is methyl or
ethyl and M+ is a solubilising ration.
The amount of non-soap anionic surfactant preferably lies in a
range from 5 or 10o to 20 or 25 %wt ~of the overall tablet
composition. The amount of non-soap anionic surfactant in the
base particles a) preferably lies in a range from 10 to 40%wt
of the weight of the particles themselves, preferably 15 to
35%wt, more preferably 18 to 30wt%.
Primary alkyl sulphate having the formula;
ROS03- M+
in which R is an alkyl or alkenyl chain of 8 to 18 Carbon atoms
especially 10 to 14 carbon atoms and M+ is a solubilising
ration, is also commercially significant as an anionic
surfactant.
In the first aspect of the invention, it is preferred that the
base particles a) are substantially free of primary alkyl
sulphate. In the second aspect, it is preferred that the base.
particles a) comprise no more than 5owt of primary alkyl
sulphate based on the weight of these particles and especially
that they are substantially thereof. Primary alkyl sulphate
may still be added to the composition as part of the other
material b). If added, it may be present in an amount as
specified above for the non-soap anionic surfactant.
It has been found that detergent tablets comprising protease
enzyme and low levels, or no, primary alkyl sulphate in the
base particles a) exhibit improved stability of protease upon
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storage compared to detergent tablets which comprise higher
amounts of this type of surfactant in the base particles a).
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.
Suitable non-ionic surfactant 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.
Specific non-ionic surfactant compounds are alkyl (C$_~2) phenol-
ethylene oxide condensates, the condensation products of linear
or branched aliphatic C$_ao primary or secondary alcohols with
ethylene oxide, and products made by condensation of ethylene
oxide with the reaction products of propylene oxide and
ethylene-diamine.
Especially preferred are the primary and secondary alcohol
ethoxylates, especially the Cg_11 and C1~_15 primary and secondary
alcohols ethoxylated with an average of from 2 to 20 moles of
ethylene oxide per mole of alcohol, preferably 5 to 9 moles. Of
these the C9_11 and Cl~_15 primary and secondary alcohols
ethoxylated with an average of from 5, 6, 7 or 8 moles of
ethylene oxide per mole of alcohol are especially preferred.
Preferably the compositions comprise less than 2o by weight,
based upon the total weight of the composition, more preferably
less than 1 owt, of C9_1z and/or C12-15 primary and secondary
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alcohols ethoxylated with an average of 4 or less moles of
ethylene oxide per mole of alcohol. Most preferably the
compositions are substantially free of said primary and
secondary ethoxylated alcohols.
The amount of non-ionic surfactant may lie in a range of from 2
to 400, better 2.5 or 3% up to 20%wt of the composition. Many
non-ionic surfactants are liquids and may be absorbed onto
particles of the composition prior to compaction into tablets.
V~hen both anionic and nonionic surfactants are used as the
organic surfactant, the weight ratio of anionic surfactant:
nonionic surfactant is preferably in the range from 4:1 to 1:2,
more preferably 3:1 to 1.1.5, most preferably 2.5:1 to 1:1.2.
A mixture of a linear alkylbenzene sulphonate having an alkyl
chain length Of Cg-C15, especially sodium, with a C9_1~ or C12-i5
primary or secondary alcohol ethoxylated with an average of
from 5 to 9 moles of ethylene oxide per mole of alcohol is
especially preferred.
Amphoteric surfactants which may be used jointly with anionic
or non-ionic surfactants or both include amphopropionates of
the formula:
O CH2CH20H
RC-NH-CH2CH2-N-CH2CH2C02Na
where RCO is a aryl group of 8 to 18 carbon atoms, especially
coconut aryl.
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The category of amphoteric surfactants also includes amine
oxides and also zwitterionic surfactants, notably betaines of
the general formula:
R2
i H2
R4-Y-N~=CH2-Z
/CH2
R3
where R4 is an aliphatic hydrocarbon chain which contains 7 to
17 carbon atoms, R~ and R3 are independently hydrogen, alkyl of
1 to 4 carbon atoms or hydroxyalkyl of 1 to 4 carbon atoms such
as CH20H,Y is CHZ or of the form CONHCH~CH~CH2 (amidopropyl
betaine); Z is either a C00- (carboxybetaine), or of the form
CHOHCH~S03 - (sulfobetaine or hydroxy sultaine) .
Another example of amphoteric surfactant is amine oxide of the
formula;
R2
R C-N CHl -NCO
1 ~ 21n
R4 Rs
where R1 is C1o to Coo alkyl or alkenyl; R2, R3 and R4 are each
hydrogen or C1 to C4 alkyl, while n is from 1 to 5.
Cationic surfactants may possibly be used. These frequently
have a quaternised nitrogen atom in a polar head group and an
attached hydrocarbon group of sufficient length to be
hydrophobic. A general formula for one category of cationic
surfactants is;
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R
Rh N~ R X
R
where each R independently denotes an alkyl group or
hydroxyalkyl group of 1 to 3 carbon atoms and Rh denotes an
5 aromatic, aliphatic or mixed aromatic and aliphatic group of 6
to 24 carbon atoms, preferably an alkyl or alkenyl group of 8
to 22 carbon atoms and X- is a counterion.
The amount of amphoteric surfactant, if any, may be from 3o to
20 or 30o by weight of the tablet or region of a tablet, the
amount of cationic surfactant, if any, may be from 0.5o to 10
or 20% by weight of the tablet or region of a tablet.
Granulated base particles a) may provide at least 50% or even
15 more such as at least 52 or at least 55% of the tablet or
tablet region. In such a case the concentration of surfactant.
j in the tablet or region may be substantial such as from 15% to
40o by weight of the tablet or tablet region. It is preferred
that the amount of total organic surfactant in the tablet or
20 region thereof is at least 100 or 12% by weight in any event.
Aluminosilicate detergency builder
The base particles comprise 20 to 60o by weight of
aluminosilicate detergency builder.
Alkali metal aluminosilicates are strongly favoured as
environmentally acceptable water-insoluble softening agents
(detergency builders) for fabric washing. Alkali metal
(preferably sodium) aluminosilicates may be either crystalline
or amorphous or mixtures thereof, having the general formula:
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0 . 8 - 1. 5 Na20 . A1~03 . 0 . 8 - 6 SiO~. xH20
These materials contain some bound water (indicated as xH20) and
are required to have a calcium ion exchange capacity of at
least 50 mg Ca0/g. The preferred sodium aluminosilicates
contain 1.5-3.5 Si02 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. They remove calcium ions
from water by ion exchange.
The aluminosilicate detergency builder may zeolite P, A, X or Y
and mixtures thereof, with zeolite P and zeolite A being
preferred.
Zeolite A is one, well known, form of crystalline sodium
aluminosilicate. Zeolite A may be used even though it does not
assist disintegration and it is readily available. Zeolite 4A
has been found to be especially suitable.
Zeolite P is especially preferred. A type of zeolite P known
as zeolite MAP, or maximum aluminium zeolite P (e.g. DOUCIL A24
ex Ineos Silicas, UK), has been found to be especially
effective.
The base particles a) preferably comprise aluminosilicate
detergency builder in an amount from 20, 30 or 35o to 40 or 55o
by weight of these particles.
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Sodium Tripolyphosphate
The detergent tablet compositions comprises from 5o to 60% by
weight of the composition of sodium tripolyphosphate having at
least 50% by weight thereof in the phase I form.
Sodium tripolyphosphate is very well known as a sequestering
builder in detergent compositions. It exists in a hydrated
form and two crystalline anhydrous forms. These are the normal
crystalline anhydrous form, known as phase TI which is the low
temperature form, and phase I which is stable at high
temperature. The conversion of phase II to phase I proceeds
fairly rapidly on heating above the transition temperature,
which is about 420°C, but the reverse reaction is slow.
Consequently phase I sodium tripolyphosphate is metastable at
ambient temperature. The resulting product is generally a
mixture of the Phase I and Phase II forms.
Phase I material is known to hydrate to the hexahydrate more
rapidly than phase II material. It is also known to dissolve
somewhat more rapidly when there is no obstacle to dispersion
in the solution. However, during dissolution, this phase I
material can form a viscous or solid mass which, in a confined
space can hinder dissolution. For instance when making a slurry
0
for spray drying, phase I tripolyphosphate can form so-called
"grit", which is a mass of interlocked crystals.
Preferably at least 70%wt, more preferably at least 80%wt, most
preferably substantially all of said sodium tripolyphosphate is
in the phase I form.
It is preferred that the sodium tripolyphosphate which is at
least partially in the Phase I form, is also partially
hydrated. The extent of hydration is desirably at least 0.5owt
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e.g., 1 to 4o by weight, preferably 2 to 4o by weight of the
tripolyphosphate. The extent of hydration may extend up to at
least 5% or at least 10% by weight.
Suitable sodium tripolyphosphate is commercially available.
Suppliers include Courbevoie, France and Rhodia, UK.
A process for the manufacture of particles containing a high
proportion of the Phase I form sodium tripolyphosphate by spray
drying below 420°C is given in US-A-4536377.
The sodium tripolyphosphate in the tablet or region thereof may
consist partly of sodium tripolyphosphate which comprises the
Phase I form and partly of some other form of sodium
tripolyphosphate provided the overall amount of
tripolyphosphate complies with the requirement that at least
50% of it is in the Phase I form. For instance, the base
particles might comprise sodium tripolyphosphate in which the
content of Phase I form was well above 50o by weight of that
tripolyphosphate while the composition of the tablet or region
also comprises additional sodium.tripolyphosphate which is in
the anhydrous Phase II form.
The sodium tripolyphosphate is preferably hydrated by a process
which leads to a homogenous distribution of the water of
hydration within the tripolyphosphate. This can be
accomplished by exposing anhydrous sodium tripolyphosphate to
steam or moist air.
The sodium tripolyphosphate is preferably in a porous form so
as to have high surface area. This can be achieved by spray
drying the tripolyphosphate. Porosity can be enhanced by spray
drying the tripolyphosphate as a mixture with a blowing agent,
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that is a compound such as ammonium carbonate which decomposes
to yield a gas during the course of the spray drying. This
gives the dried material a higher surface area than porous
beads of tripolyphosphate obtained without blowing agent.
Particles of sodium tripolyphosphate preferably have a small
mean particle size, such as not over 300pm, preferably 280pm or
less. Small particle size can, if necessary, be achieved by
grinding.
Uniform prehydration, high Phase I content, porosity and small
particle size all promote rapid hydration when the
tripolyphosphate comes into contact with water. A standard
test for the rapidity of hydration is the Olten test. It is
desirable that in such a test the tripolyphosphate reaches 90%
of the final value (i.e.. 90% of complete hydration when exposed
to water at 80°C) within 60 seconds.
"Rhodiaphos HPA 3.5" is a grade of sodium tripolyphosphate from
Rhodia-Chemie (previously from Rhone-Poulenc) which has been
found to be particularly suitable. It consists of porous
particles of small particle size (mean size below 250~m) with
70o Phase I and prehydrated with 3.5% water of hydration.
If the base particles a) include some of the sodium
tripolyphosphate then it is typically in an amount of from 7-
400 of their own weight. However in some aspects of the
invention it is preferred that the base particles a) comprise
less than 10% of the sodium tripolyphosphate, more preferably
less than 5%wt of their own weight, especially less than 2%wt
and most especially are substantially free thereof. The
remainder of the sodium tripolyphosphate is present in the
other particles b).
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In some aspects of the invention the other material b)
preferably comprises at least 60o by weight, more preferably at
least 80o by weight, and especially substantially all of the
5 sodium tripolyphosphate present in the whole composition of the
tablet or region thereof.
Preferably the total amount of the sodium tripolyphosphate in
the total composition is at least 15% by weight, better in a
10 range from 20 or 25 to 50% by weight.
The preferred weight ratio of the sodium tripolyphosphate:
aluminosilicate builder is in the range of from 3:1 to 2:5,
better 2.5:1 to 1:1.5, especially 2.2:1 to 1:1.
Materials which may be used in tablets or regions of tablets
will now be discussed in greater detail, and specific
possibilities will be mentioned by way of example.
All detergent tablets according to the invention may comprise
disintegrant materials to aid in the disintegration of the
tablets. If present, the amount is preferably in the range of
from 2% to 10o by weight of the composition. These materials
are preferably added as part of the other materials (b).
Optional water soluble material
In certain forms of the invention, the tablet or region thereof
comprises from 35% to 98% by weight of granulated base
particles mixed with 2 to 10o by weight of further disintegrant
materials (and optionally other ingredients up to 100%wt as
appropriate).
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The tablets of this, invention optionally comprise from 2o to
10% of a material, such as a salt, which has a solubility in
deionised water at 20°C of at least 50 grams per 100 grams of
water. Preferably amounts of from 2 to 5 or 7% by weight are
used. The highly soluble material may be included in the base
particles a) or as part of the material b).
A solubility of at least 50 grams.per 100 grams of water at
20°C is an exceptionally high solubility: many materials which
are classified as water soluble are less soluble than this.
Some suitable highly water-soluble materials are listed below,
with their solubilities expressed as grams of solid to form a
saturated solution in 100 grams of water at 20°C:-
Material Water Solubility (g/100
Sodium citrate dehydrate 72
Potassium carbonate 112
Sodium acetate 119
Sodium acetate trihydrate 76
Magnesium sulphate 7H20 71
Urea >100
By.contrast the solubilities of some other common materials at
20°C are:-
Material Water Solubility (g/100g)
Sodium chloride 36
Sodium sulphate decahydrate 21.5
Sodium carbonate anhydrous 8.0
Sodium percarbonate anhydrous 12
Sodium perborate anhydrous 3.7
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Sodium tripolyphosphate anhydrous 15
Preferably this highly water soluble material is incorporated
as particles thereof in a substantially pure form (i.e. each-
such particle contains over 95% by weight of the material).
However, the said particles may comprise material of such
solubility in a mixture with other material, provided that
material of the specified solubility provides at least 40o by
weight of these particles.
Preferred materials are sodium acetate in a partially or fully
hydrated form, urea or sodium citrate dehydrate.
Optional water-swellable disintegrant
Another material which may be present is a water-swellable but
dispersible material.
A number of water-insoluble, water-swellable materials are
known to be useful as tablet disintegrants, in particular for
pharmaceutical tablets. Although insoluble, these materials
are generally dispersible in water. A discussion of such
materials is found in "Drug Development and Industrial
Pharmacy", Volume 6, pages 511-536 (1980). Such materials are
mostly polymeric in nature and many of them are of natural
origin. Such disintegrants include starches, for example,
maize, rice and potato starches, and starch derivatives, such
as PrimojelTM, and ExplotabT"", which are both forms of sodium
carboxymethyl starch also known as sodium starch glycolate;
celluloses, for example Arbocel~-B and Arbocel~-BC (beech
cellulose), Arbocel~-BE (beech-sulphite cellulose), Arbocelo-B-
SCH (cotton cellulose), Arbocelo-FIC (pine cellulose) as well
as further Arbocel~ types from Rettenmaier and cellulose
derivatives, from example CourloseTM and NymcelTM, sodium
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carboxymethyl cellulose, Ac-di-SolTM cross-linked modified
cellulose, and HanflocTM microcrystalline cellulosic fibers; and
various synthetic organic polymers.
Cellulose-containing fibrous materials originating from timber
may be compacted wood pulps. So-called mechanical pulps
generally incorporate lignin as well as cellulose whereas
chemical pulps generally contain cellulose but little of the
original lignin remains. Pulp obtained by a mixture of
chemical and mechanical methods may retain some by not all of
the original lignin.
Suppliers of water-swellable disintegrant materials include
Rettenmaier in Germany and FMC Corporation in USA.
Other suitable disintegrants include granules based upon water
swellable inorganic materials such as aluminosilicates.
The impregnated swellable material which is incorporated into a
tablet composition may well have a mean particle size in a
range from 250,um to 1, 500,um, more preferably from 700,um to
1, 10 O,um .
Optional bleach system
Tabletted compositions according to the invention may be
bleach-free or may contain a bleach system. If present, this
preferably comprises one or more peroxy bleach compounds, for
i
example, inorganic persalts or organic peroxyacids, which may
be employed in conjunction with activators to improve bleaching
action at low wash temperatures. Preferred inorganic persalts
are sodium perborate monohydrate and tetrahydrate, and sodium
percarbonate, advantageously employed together with an
activator. If any peroxygen compound is present, the amount is
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likely to lie in a range from 5 to 50% by weight of the
composition, preferably 10 to 200.
Bleach activators, also referred to as bleach precursors, have
been widely disclosed in the art. Preferred examples include
peracetic acid precursors, for example, tetraacetylethylene
diamine (TAED), now in widespread commercial use in conjunction
with sodium perborate; and perbenzoic acid precursors. N-alkyl
ammonium acetonotriles as described in WO 96/40061 and US 6 225
274 may be used as may sodium nonanoyloxy benzene sulphonate
(SNOBS) and (6-nonanamidocaproyl)oxy benzene sulphonate
(Na.COBS) as described in US 6 207 632 and EP 170 386. The
quaternary ammonium and phosphonium bleach activators disclosed
in US 4751015 and US 4818426 (Lever Brothers Company) are also
of interest. Another type of bleach activator which may be
used, but which is not a bleach precursor, is a transition
metal catalyst as disclosed in EP-A-458397, EP-A-458398 and EP-
A-549272.
A bleach system may also include a bleach stabiliser (heavy
metal sequestrant) such as ethylenediamine tetramethylene
phosphonate, diethylenetriamine pentamethylene phosphonate or
ethylene diamine di-succinate.
If a bleach system is present, the bleach and/or activator are
is preferably included as the other material b) mixed with the
base particles a).
Other optional materials
Other materials which may be present, typically as 0.5 to 5% of
the composition are one or more polycarboxylate polymers, more
especially polyacrylates and acrylic/maleic copolymers which
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have some function as water-softening agents and also inhibit
unwanted deposition onto fabric from the wash liquor.
Tablets may comprise one of the detergency enzymes well known
5 in the art for their ability to degrade and aid in the removal
of various soils and stains. 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
10 MaxataseTM, as supplied by Gist-Brocades N.V., Delft, Holland
and AlcalaseTM, and SavinaseTM, 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 amount of from about 0.1% to about 3.0o
15 by weight of the composition; and these granules or marumes
present no problems with respect to compaction to form a
tablet.
The compositions of the invention have been found to be
20 particularly advantageous for the storage stability of protease
enzymes. Thus protease enzymes are especially preferred.
Tablets may also comprise a fluorescer (optical brightener),
for example, TinopalTM DMS or Tinopal CBS available from Ciba-
25 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 may be included. Suitable antifoam
materials are usually in granular form, such as those described
in EP 266863A (Unilever). Such antifoam granules typically
comprise a mixture of silicone oil, petroleum jelly,
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hydrophobic silica and alkyl phosphate as antifoam active
material, sorbed onto a porous absorbed water-soluble
carbonate-based inorganic carrier material. Antifoam granules
may be present in an amount up to 5o by weight of the
composition.
It may also be desirable that a tablet includes an amount of an
alkali metal silicate, particularly sodium ortho-, meta- or
disilicate. 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 in manufacture of the
particulate material which is compacted into tablets. A
composition for fabric washing will generally not comprise more
than 15 wto silicate.
Further ingredients which can optionally be employed in fabric
washing detergent tablets of the invention include anti-
redeposition 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; and colorants or coloured speckles.
A number of these further ingredients are typically used in
small amounts such as not more than 5% by weight of the tablet
or tablet region. They may be incorporated amongst the post-
dosed constituents of the composition. Some of them, notably
fluorescer, polycarboxylate polymers and anti-redeposition
agents may be incorporated into the granulated particles. Any
constituents which are liquids such as non-ionic detergents or
perfumes may possibly be incorporated within the granulated
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particles or may be sprayed onto those particles or the overall
mixture. Preferably perfumes are sprayed onto the overall
mixture so that they are the last ingredient added to the
overall composition before tableting.
Granulation of particles
The preparation of detergent compositions in particulate form
by granulation processes is well known. A granulation process
for making particles which comprise surfactant, zeolite and
water-soluble salts is described in EP-A-340013 for example.
Continuous processes for the preparation of granulated
particles containing organic surfactant zeolite and other
ingredients have been described in EP-A-420317 and WO 98/11193.
Processes as described in the above aocuments can be modified
to include sodium tripolyphosphate among the solids supplied to
the granulation process to produce the base particles a).
A suitable method of granulating is disclosed in WO 00/77147
(Unilever) wherein a liquid binder is contacted with a solid
starting material in a high-speed mixer and the resulting
mixture treated in a medium- or low-speed mixer and finally in
a gas fluidisation granulator, where more liquid binder is
added.
After granulation the particles may have average particle size
in the range from 200 to 2000um, more preferably from 250 to
1400~.m. Fine particles, such as those smaller than 180~m or
200um and oversized particles may be eliminated by sieving
before tableting, if desired, although we have observed that
this is not always essential. Sieved out particles may be
returned to the granulation stage if oversized.
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The starting particulate composition may suitably have a bulk
density of at least 500g/litre, preferably at least 600g/litre,
and possibly at least 700g/litre.
Tableting
Tableting entails compaction of a particulate composition. A
variety of tableting machinery is known, and can be used.
Generally it will function by stamping a quantity of the
particulate composition which is confined in a die.
The mould in which the tablet is formed may be provided by an
aperture within a rigid structure and a pair of dies which can
be urged into the aperture towards each other, thereby
compacting the contents of the aperture. A tableting machine
may have a rotary table defining a number of apertures each
with a pair or associated dies which can be driven into an
apertures. Each die may be provided with an elastomeric layer
on its surface which contacts the tablet material, as taught in
WO 98/46719 or WO 98/46720.
Tableting may be carried out at ambient temperature or at a
temperature above ambient which may allow adequate strength to
be achieved with less applied pressure during compaction. In
order to carry out the tableting at a temperature which is
above ambient, the particulate composition is preferably
supplied to the tableting machinery at an elevated temperature.
This will of course supply heat to the tableting machinery, but
the machinery may be heated in some other way also.
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When the sodium tripolyphosphate is present in the base
particles a method of forming the detergent composition
comprises;
(1) forming detergent base particles by mixing together and
granulating 15 to 40% by weight of organic surfactant, 20 to
60o by weight of aluminosilicate detergency builder, 7 to 400
by weight of sodium tripolyphosphate, at least 50% of which is
in Phase I form, and optionally 0 to 580 of other ingredients;
(2) optionally mixing these detergent base particles with
other ingredients which may include sodium tripolyphosphate, so
as to form a composition comprising 33 to 1000 by weight of
base particles and 0 to 67o by weight of other ingredients,
wherein the composition comprises from 5 to 50% by weight of
sodium tripolyphosphate having at least 50o in the Phase I
form, and
(3) compacting that composition into tablets or regions
thereof .
If any heat is supplied, it is envisaged that this will be
supplied conventionally, such as by passing the particulate
composition through an oven, rather than by any application of
microwave energy.
The size of a tablet will suitably range from 10 to 160 grams,
preferably from 15 to 60g, depending on the conditions of
intended use, and whether it represents a dose for an average
load in a fabric washing or dishwashing machine or a fractional
part of such a dose. The tablets may be of any shape.
However, for ease of packaging they are preferably blocks of
substantially uniform cross-section, such as cylinders or
cuboids.
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The overall density of a tablet for fabric washing preferably
lies in a range from 1000 or 1040g/litre up to 1400 or 1450
gllitre. The overall density of a tablet of some other cleaning
composition, such as a tablet for machine dishwashing or as a
5 bleaching additive, may range up to 1700gmllitre and will often
lie in a range from 1300 to 1550gm/litre.
The invention will now be further illustrated with reference to
the following non-limiting examples. Further examples will be
10 apparent to the person skilled in the art.
~zrawr~r.~c
Example 1
Tablets for use in fabric washing were made, starting with a
15 granulated base powder of the following composition:
Ingredient a by weight
Sodium linear alkylbenzene sulphonate 22
C13-15 fatty alcohol 7E0 5
Zeolite 4A 29
Sodium carbonate (light) 27
Sodium tripolyphosphate 12.5
Moisture and minor ingredients 4.5
Total 1000
Particulate compositions were made by mixing this powder with
further ingredients as tabulated below.
Ingredient _ __ o By Weight
Base powder _
56
Sodium tripolyphosphate (HPA 3.5) 35
Primary alkyl sulphate particles 5.5
Coloured speckles 1.5
Enzymes, heavy metal sequestrant and 2
perfume
Total 1000
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In the above composition, the sodium tripolyphosphate in the
granulated base powder was anhydrous sodium tripolyphosphate
consisting predominantly of the Phase II anhydrous form.
The sodium tripolyphosphate which was mixed with the granulated
base powder particles comprised over 750 of its own weight in
the Phase I form and was partially hydrated to contain 3.5% of
its own weight of water of hydration. This sodium
tripolyphosphate was supplied by Rhodia Chemie under their
designation Rhodiaphos HPA 3.5 and it had a porous structure
resulting from the spray-drying procedure employed prior to
partial hydration.
The composition was sieved to remove all particles smaller than
250~m or larger than 1400um. Then 40g portions of the
composition were compacted into tablets of 44mm diameter using
a hand press.
To test dissolution of tablets, a test procedure was used in
which a tablet was placed on a plastic sieve with 2mm mesh size
which was immersed in 9 litres of demineralised water at
ambient temperature of 20°C. The water conductivity was
monitored until it reached a constant value. The time for
dissolution of the tablets was taken as the time (T9o) for
change in the water conductivity to reach 90% of its final
magnitude; and was found to be 3.5 minutes.
The strength of the tablets was measured by compressing them
radially, between the platens of a universal materials testing
machine until fracture of the tablet occurred.
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The force at the fracture was measured. From this measurement
of force a test parameter called diametral fracture stress,
which we have used in the past, can be calculated using the
equation:
a = 2Ff
~Dt
where a is the diametral fracture stress in Pascals, Ff is the
applied force in Newtons to cause fracture, D is the tablet
diameter in meters and t is the tablet thickness in meters.
The value of DFS measured for these tablets was 40 kPa. (It is
desirable that the value of DFS is at least 20 or 25kPa).
Example 2
A spray-dried base powder of the following composition was
prepared:
Ingredients % By Weight
_
_ 22
Linear alkyl benzene sulphonate
Nonionic detergent 5
(C13-15 fatty alcohol 7E0)
Soap 3
Zeolite 4A 35
Sodium carbonate 20
Sodium tripolyphosphate (fully hydrated) 10
Moisture and other minor ingredients 5
Total 100%
This powder was mixed with other materials as follows:
Ingredients % by weight
Base powder 66
Sodium tripolyphosphate 31
(Rhodiaphos HPA 3.5)
Blue speckles 1.5
Sequestrant, enzymes and perfume 3.5
Total 100%
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The resulting compositions was sieved and made into tablets as
in Example 1.
Example 3
Tablets for use in fabric washing were made, starting with a
granulated base powder of the following compositions. Example
3A is a comparative example where the base powder particles do
not comprise aluminosilicate detergency builder. Example 3 is
an example according to the invention.
Ingredients o by weight % by weight
Ex 3A E_x 3
Sodium linear alkyl 23.7 20.8
benzene sulphonate
Nonionic detergent 5.1 9.2
(C13-15 fatty alcohol 7E0)
Nonionic detergent 5.3 -
(c13-15 fatty alcohol 3E0)
soap 0.7 1.6
zeolite A24 (anhydrous) - 46.5
70130 AA/MA co-polymer 3.1 -
salt (1000)
Sodium tripolyphosphate 40.6 -
Na acetate 3H20/ zeolite - 5.9
A24 (99:1wt mix)
light soda ash 6.9
sodium disilicate 8.7 -
SCMC (68o active) 0.5 0.9
Moisture, salts, NDOM 12.3 8.2
Total 1000 1000
Particulate compositions were made by mixing this powder with
further ingredients as tabulated below.
Ingredients % by weight % by weight
Ex 3 A Ex 3
__ _ 42.4
Base powder 41.4
Antifoam granules 2.6 2.1
Sodium tripolyphosphate 34.5 32.7
(Rhodiaphos HPA 3.5)
Granular Na-disilicate - 2.5~
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(80o active granules)
TAED (83% active 2.8 2.8
I granules )
I Coated sodium 14.00 14.0
Percarbonate
Savinase 12.0T 3250 GU/mg 0.4 0.4
Perfume, heavy metal 2.8 3.1
sequestrant, fluorescer
granule
Blue Speckles 1.5 -
Total 1000 100%
The sodium tripolyphosphate in the base powder of Example 3A
was a mixture of about 55 parts of anhydrous sodium
tripolyphosphate phase II and about 45 parts of anhydrous
sodium tripolyphosphate phase I. The 70/30 AA/MA co-polymer
salt (100%) was Sokalan CP5 (ex BASF).
Comparative example 3B
A further comparative laundry detergent tablet was made from a
granulated base powder with the other ingredients added
thereto. The amounts are given for the base powder on the basis
of the amount of each ingredient present in the final
composition.
Example 3B o b
y weight
_
BASE POWDER
Na Primary alkyl sulphate 8
Nonionic detergent 4
(C13-15 fatty alcohol 7E0)
soap 1
zeolite A24 (anhydrous) 16
Na acetate 3H20/ zeolite A24 3
(99:1wt mix)
light soda ash 4
SCMC (68% active) 1
ADDED INGREDIENTS
Sodium tripolyphosphate 31
(Rhodiaphos HPA 3.5)
sodium citrate 2H~0 2
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TAED (83% active granules) 6
o_dium Percarbonate 16
Coated s
_ 1
Savinase 12.0T 3250 GU/mg
Perfume, heavy metal 7
sequestrant, polymers, other
enzymes, Granular Na-disilicate
(80% granules), antifoam
granules
Total 100 0
The resulting compositions were sieved and made into tablets as
in Example 1.
5 A quantity of the tablets were packaged in flow-wrap packaging
arid stored in normal carton packs at 37°C/70 o relative
humidity for up to 8 weeks. At the intervals given in the
tables below, a tablet was selected and tested for the presence
of TAED, protease and percarbonate. The results are given in
10 the table below. The numbers in the (results) column show the
initial level of the ingredient detected in the tablet and the
level after the given storage time. The numbers in the (o)
column show the percentage of the ingredient remaining after
the given storage time, expressed as a percentage of the
15 original level detected in the tablet. The percarbonate
results are expressed as o available oxygen. The protease
result is expressed as enzyme activity GU/mg.
TAED storage stability
storage 3A 3A 3 3
(wks) (o) (result) (o) (result)
37C 0 100 2.3 100 2.7
70% RH
2 83 1.9 89 2.4
4 74 1.7 78 2.1
8 57 1.3 78 2.1
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Percarbonate storage stability
storage 3A 3A 3 3
(wks) (o) (result) (%) (result)
37C 0 100 2.0 100 2.0
70o RH
2 87 1.74 92 1.84
4 85 1.7 90 1.8
8 70 1.4 85 1.7
Protease (as savinese) storage stability
storage 3A 3A 3B 3 3
(wks) (%) (result) (%) (%) (result)
37C 0 100 14.9 100 100 14.4
70% RH
2 77 11.5 - 94 13.6
4 65 9.7 - 85 12.3
8 30 4.4 50 90 13.0
The tablets of the invention show better storage stability at
37°C, 70o relative humidity for TAED, percarbonate and
especially for protease enzyme (savinese) than do the tablets
comprising no aluminosilicate builder (Ex 3A). They also show
better stability for protease than do tablets comprising
,conventional amounts of primary alkyl sulphate and no linear
alkyl benzene sulphonate (Ex 3B).
