Note: Descriptions are shown in the official language in which they were submitted.
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WO 01/38479 PCT/EP00/11816
DETERGENT COMPOSITIONS
This invention relates to detergent compositions in the form
of tablets for cleaning, and in particular tablets for
fabric washing and tablets for machine dish washing. It is
known to make such tablets by compressing or compacting a
quantity of detergent composition in particulate form.
It is desirable that tablets should have adequate mechanical
strength when dry, before use, yet disintegrate and
disperse/dissolve quickly when added to wash water. It has
not proved simple to achieve both properties simultaneously.
As more pressure is used when a tablet is compacted, so the
tablet density and strength rise, but the speed of
disintegration/dissolution when the tablet comes into contact
with wash water goes down.
Our European published application EP-A-839906 describes
tablets of a compacted, particulate detergent composition
intended for fabric washing in which the tablet comprises
particles containing sodium tripolyphosphate with a
substantial content of the phase I form, and this
tripolyphosphate is partially hydrated so as to contain water
of hydration in an amount between to and 5o by weight of the
sodium tripolyphosphate in those particles.
It is demonstrated by examples in that patent application
that tablets incorporating particles with a substantial
content of the Phase I form of sodium tripolyphosphate and
with some partial hydration of the tripolyphosphate
disintegrate and dissolve in use much more quickly than
comparative tablets using sodium tripolyphosphate with a
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2
higher content of the Phase II form. Consequently, it is
possible to achieve tablets which disintegrate rapidly at the
time of use.
Typically these tablets will contain base powder particles
which incorporate organic detergent-active surfactant
together with some tripolyphosphate detergency builder,
separate particles containing sodium tripolyphosphate which
is rich in the Phase I form and also partially hydrated, and
thirdly particles of other ingredients. A substantial
proportion of the other ingredients is constituted by
peroxygen bleach which may be sodium perborate tetrahydrate.
Such tablets have been marketed commercially. For use one or
two tablets are placed in a net bag, closed with a
drawstring. The bag containing these tablets is placed in
the washing machine, with fabrics to be washed.
Our co-pending WO01/02524 discloses machine dish washing
tablets comprising less than 5wt$ of surfactant and
particles of solid tripolyphosphate as described above. The
examples in this appJ_ication also demonstrate an
improvement in dissolution time for tablets containing
sodium tripolyphosphate rich in Phase I and partially
hydrated rather than sodium tripolyphosphate with a higher
content of Phase II form. The tablets exemplified in this
co-pending application contain a considerable amount of
sodium disilicate as a detergency builder, as well as a
peroxygen bleach, sodium perborate, and sodium carbonate.
EP-A-957159 (D1) discloses multilayered detergent tablets
comprising sodium tripolyphosphate in one layer and also
salts present in the tablet.
AMENDED SHEET
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3
We have now surprisingly found that it is beneficial to
partially or completely separate any salts which are fully
hydrated ('fully hydrated salts') in a tablet, from the
sodium tripolyphosphate which is rich in the Phase I form
and which may also be partially hydrated. By this
separation, it has been found possible to increase the
dissolution speed of the detergent tablets containing these
components.
This separation of ingredients can be accomplished by
isolating most, if not all, of the fully hydrated salts, in
a region of the tablet which may be a layer, core or
insert, while the sodium tripolyphosphate which is rich in
the Phase I form is in another region of the tablet.
Therefore, according to the present invention, there is
provided a detergent tablet of compressed particulate
composition comprising a detergent-active compound, a
detergency builder, particles which contain sodium
tripolyphosphate with a content of the Phase I form which
is more than 40o by weight of the sodium tripolyphosphate
in the said particles, at least one salt which is fully
hydrated, and optionally other detergent ingredients, where
the tablet comprises a plurality of discrete regions,
characterised in that in one or more of the discrete
regions containing said particles which contain sodium
tripolyphosphate there is less than 10% by weight of that
region of fully hydrated salts, and there is at least one
discrete region containing at least loo by weight of that
region of fully hydrated salts.
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4
It is envisaged that all of the discrete regions containing
said particles which contain sodium tripolyphosphate will
contain less than 10~ by weight of that region of fully
hydrated salts. However, this may not be the case,
particularly if there is a very small discrete region
containing said particles which contain sodium
tripolyphosphate, or the discrete regions contain a minor
amount of sodium tripolyphosphate, for example Less than 5$
by weight.
The region containing at least 10~ by weight of fully
hydrated salts may also contain a disintegrant system which
does not comprise said particles which contain said sodium
tripolyphosphate.
It is further preferred that there is less than 5$ by
weight, or even no fully hydrated salts in the regions of
the tablet containing said particles of sodium
tripolyphosphate.
Preferably the sodium tripolyphosphate in the said
particles has a content of the Phase I form which is at
least 50~ by weight of the sodium tripolyphosphate in the
said particles. It is also preferred that the amount of
water of hydration in the sodium tripolyphosphate particles
lies in a range from 0.5~ to 5~ by weight, preferably
between 2 and 9 ~, of the sodium tripolyphosphate in those
particles.
Features of this invention, suitable materials and further
preferences will now be described in more detail.
AMENDED SHEET
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Sodium Tripolyphosphate with High Phase I Content
As discussed in EP-A-839906, sodium tripolyphosphate can be
converted to the phase I form by heating to above the
transition temperature at which phase II anhydrous sodium
5 polyphosphate is transformed into the phase I form. A
process for the manufacture of particles containing a high
proportion of the phase I form of sodium tripolyphosphate
by spray drying below 420°C is given in US-A-4536377.
Suitable material is commercially available. Suppliers
include Rhone-Poulenc, Courbevoie, France and Albright &
Wilson, Warley, West Midlands, UK. The sodium
tripolyphosphate is preferably partially hydrated, but the
phase I anhydrous form should also be present. Thus, the
sodium tripolyphosphate in the particles may incorporate
from 0.5% up to, at least, 5% (by weight of the sodium
tripolyphosphate in these particles) of water of hydration.
The extent of hydration is desirably from 1% to 4%, 5% or
7% by weight.
The sodium tripolyphosphate in these particles is
preferably hydrated by a process which leads to a
homogeneous distribution of the water of hydration within
the tripolyphosphate.
This can be accomplished by exposing anhydrous sodium
tripolyphosphate to steam or moist air. The particles
preferably consist solely of sodium tripolyphosphate with a
high content of the phase I form. However, it may be
preferred that only at least 80% or 90% by weight of the
particles is sodium tripolyphosphate. It is possible that
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only at least 50% by weight of the particles are sodium
tripolyphosphate.
The particles preferably contain sodium tripolyphosphate in
a porous form so as to have high surface area. This can be
achieved by spray drying the tripolyphosphate as a mixture
with a blowing agent, 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 porous
structure, with higher surface area than hollow beads of
tripolyphosphate obtained without blowing agent.
The bulk density of the sodium tripolyphosphate particles
is preferably 0.75 kg/m3 or less, more preferably from 0.52
to 0.72 kg/m3.
The particles which contain or consist of sodium
tripolyphosphate may have a small mean particle size, such
as not over 300~m, better not over 250,um. Small particle
size can if necessary be achieved by grinding.
Uniform prehydration and high phase I content 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 Rhone-Poulenc which has been found to be particularly
suitable. It consists of porous particles of small particle
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size (mean size below 250 Vim) with 70% phase I and
prehydrated with 3.5% water of hydration.
Preferably the said particles containing sodium
tripolyphosphate with more than 40% of phase I material
provide sodium tripolyphosphate, including the phase I
tripolyphosphate, in a quantity which is from 20o up to 45%
or 50%, or even 60% by weight of the whole tablet. A
quantity of at least 30% has been found useful in some
tablets. The amount of these particles in any one region of
the tablet may be higher then these limits, in order to
provide a suitable level of particles in the whole tablet.
The remainder of the tablet composition may include
additional sodium tripolyphosphate not in the form
discussed above, such as anhydrous sodium tripolyphosphate
with a high content of the phase II form, hydrated sodium
tripolyphosphate or some combination of the two.
The total quantity of sodium tripolyphosphate, in all
forms, present in the tablet composition of a laundry
tablet will generally lie in a range up to 70% by weight of
the tablet. This may also be the case for a machine dish
wash tablet, although a range of up to 60% by weight of the
tablet is preferred for this type of tablet. Therefore it
will be appreciated that the overall quantity of sodium
tripolyphosphate may be provided at least partially by
other material in addition to the said particles.
Salts which are fully hydrated
These salts are those which are in their maximum
thermodynamically stable hydration state at ambient
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temperature. This maximum hydration state may be the
highest possible for the salt, or may be lower than the
highest possible for the salt, but where the higher
hydration states are thermodynamically unstable at ambient
temperature. These fully hydrated salts include perborates,
citrates, acetates, sulphates, carbonates and
thiosulphates. Preferably the fully hydrated salt is a
sodium salt or persal.t.
Perborates may exist in a range of hydration states, and
have at least one hydrogen peroxide present instead of, or
in addition to, water of hydration. For example, sodium
perborate exists in a manohydrated or tetrahydrated form
both of which are suitable for use in detergent
formulations. Therefore it can be seen that sodium
perborate tetrahydrate is a fully hydrated salt. Perborates
are used as bleaches in detergent tablets (see below).
Many carbonates naturally display a range of hydration
states. For example, sodium carbonate may be anhydrous, or
may have one, seven or ten water molecules present as water
of hydration. Both potassium and magnesium carbonates also
have a variety of hydration states. Thus, as long as some
of the carbonate present is in its maximum
thermodynamically stable hydration state, the salt will be
fully hydrated. Carbonates (in particular sodium and
potassium carbonates) are often included in detergent
tablets in order to control the pH of the composition when
it dissolves. They also function, to some extent, as
detergency builders, particularly in machine dish washing
tablets.
AMENDED SHEET
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Sulphates can have different hydration states. Sodium
sulphate may be anhydrous, heptahydrated or decahydrated,
whilst magnesium sulphate may be anhydrous or
heptahydrated. Sulphates may be included in detergent
tablets as fillers. Sodium thiosulphate may be anhydrous or
pentahydrated.
Sodium acetate may exist in a range of hydration states
from 0 (anhydrous) to 3 (trihydrate). Sodium acetate
trihydrate may be present as a disintegration aid (see
below).
Sodium citrate has two hydration states, 2 (dehydrate) and
5 (pentahydrate). However, the pentahydrate state is not
thermodynamically stable at temperatures between 20°C and
60°C, and therefore sodium citrate dehydrate is a fully
hydrated salt. Sodium citrate also functions as a
disintegration aid (see below).
It is preferred that the fully hydrated salts have a
solubility at 20°C of at least 50 gms per 100 gms of water.
Discrete Regions
The discrete regions may be in the form of layers, and a
tablet with two layers is one preferred embodiment of the
present invention. One layer of this two-layer tablet
contains granules of sodium tripolyphosphate rich in Phase
I form and also partially hydrated, whilst the other layer
contains fully hydrated salts and/or persalts and
optionally another disintegrant.
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Each layer of such a tablet is preferably substantially
homogeneous, that is to say, is the compaction product of a
single particulate composition, although that particulate
composition may have been prepared by mixing a number of
5 components and all its particles will not necessarily be
identical. Typically, such a two-layer tablet is made on a
tableting press by part filling the die with the
composition of the first layer, pressing this layer, and
then adding the composition of the second layer before
10 pressing the tablet for a second time. It is preferred that
the two layers of this tablet are not equal in size - a
weight ratio range of 10:90 to 40:60 is preferable, and a
ratio range of 20:80 to 30:70 is mare preferred, with a
ratio of 25:75 being most preferred. A discrete region
typically has a minimum weight of 5g.
It is preferred that the layer or layers containing the
particles of sodium tripolyphosphate make up at least 50
wtg of the tablet, and that the layer (or layers) which
contain the fully hydrated salts and/or persalts make up at
least 15~ by weight of the whole tablet.
An alternative preferred embodiment of the invention is a
tablet which has a pair of opposite faces spaced apart from
each other and joined by a peripheral surface of the
tablet, wherein the tablet is subdivided into at least two
regions which are each visible at a said face. One such
tablet is one having a central core passing through the
whole tablet. One particular method of manufacturing such
tablets is described in our co pending application,
W000/44869.
AMENDED SHEET
r --
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Other forms of discrete regions are known for detergent
tablets and are included in the present invention, and
include cores which do not pass all the way through the
tablet and a central region completely enclosed by an outer
region.
Detergent-active compounds
In laundry detergent tablets, detergent-active compounds
are suitably present in an amount of from 20 or 5o up to 50
wto, more preferably from 50 or 8o up to 40 wto of the
whole tablet. These will most usually be anionic and
nonionic surfactants and mixtures of the two. Amphoteric
(including zwitterionic) and less commonly cationic
detergents can also be used.
Anionic Surfactant Compounds
Synthetic (i.e. non-soap) anionic surfactants are well
known to those skilled in the art. The anionic surfactant
may comprise, wholly or predominantly, linear alkyl benzene
sulphonate of the formula
R\ _ +
S03 M
where R is linear alkyl of 8 to 15 carbon atoms and M+ is a
solubilising cation, especially sodium.
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
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solubilising cation, is also commercially significant as an
anionic surfactant and may be used in this invention.
Frequently, such linear alkyl benzene sulphonate or primary
alkyl sulphate of the formula above, or a mixture thereof
will be the desired non-soap anionic surfactant and may
provide 75 to 100 wt% of any anionic non-soap surfactant in
the composition.
Examples of other non-soap anionic surfactants include
olefin sulphonates; alkane sulphonates; dialkyl
sulphosuccinates; and fatty acid ester sulphonates.
One or more soaps of fatty acids may also be included in
addition to non-soap anionic surfactant. Examples are
sodium soaps derived from the fatty acids from coconut oil,
beef tallow, sunflower or hardened rapeseed oil.
Nonionic surfactant compounds
Nonionic surfactant compounds 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 nonionic surfactant compounds are alkyl (Ca-zz)
phenol-ethylene oxide condensates, the condensation
products of linear or branched aliphatic CB-zo 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.
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Especially preferred are the primary and secondary alcohol
ethoxylates, especially the C9_11 and C12-is primary and
secondary alcohols ethoxylated with an average of from 3 to
20 moles of ethylene oxide per mole of alcohol.
Amphoteric surfactants
Amphoteric surfactants which may be used jointly with
anionic or nonionic surfactants or both include
amphopropionates of the formula:
oII c~c~oH
C-NH-CHzCki2-N-CHzCHz~z~
where RCO is a acyl group of 8 to 18 carbon atoms,
especially coconut acyl.
The category of amphoteric surfactants also includes amine
oxides and also zwitterionic surfactants, notably betaines
of the general formula
R2
~I Hi
Ra-Y- ~~ CH2-Z
/CH2
R
3
where RQ is an aliphatic hydrocarbon chain which contains 7
to 17 carbon atoms, RZ and R3 are independently hydrogen,
alkyl of 1 to 4 carbon atoms or hydroxyalkyl of 1 to 4
carbon atoms such as CHZOH,
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Y is CHZ or of the -form CONHCHZCHZCHZ (amidopropyl betaine);
Z is either a COO- (carboxybetaine), or of the form
CHOHCHZS03 - (sulfobetaine or hydroxy sultaine).
Another example of amphoteric surfactant is amine oxide of
the formula
Rz
1 O R1-CON ( CH2 ) n-N->O
R9 R3
where R1 is Clo to CZO alkyl or alkenyl
R2, R3 and R4 are each hydrogen or C1 to Cq alkyl while n is
from 1 to 5.
In machine dish washing tablets, detergent-active compounds
are preferably present in an amount of 5 wt% of the total
composition or less.
Typically the detergent-active compound is a low to non
foaming nonionic surfactant, which may be an alkoxylated
nonionic surface-active agent wherein the alkoxy moieties
are selected from the group consisting of ethylene oxide,
propylene oxide and mixtures thereof. This nonionic
surfactant is used to improve the detergency without
excessive foaming, however, an excessive proportion of
nonionic surfactant should be avoided. Preferably the level
of nonionic surfactant is at least O.lo by weight, more
preferably at least 0.5o by weight.
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Examples of suitable nonionic surfactants for use in
machine dish washing tablets of the invention are the low-
to non-foaming ethoxylated straight-chain alcohols.
Preferred nonionic surfactants are Plurafac LF series ex
5 BASF, the Synperonic series ex ICI; Lutensol~ LF series, ex
BASF Company and the Tritons DF series, ex Rohm & Haas
Company.
Other surfactants such as anionic surfactant may be used
10 but may require the additional presence of an antifoam to
suppress foaming. If an anionic surfactant is used it is
advantageously present at levels of 2 wt% or below.
Detergency builder
15 The detergent tablets of the invention contain one or more
detergency builders, in addition to the sodium
tripolyphosphate builder of the invention. These builders
may be either water-soluble or water-insoluble, and a
mixture of the two is also included within the scope of the
present invention.
Water-insoluble builders
Alkali metal aluminosilicates are strongly favoured as
environmentally acceptable water-insoluble builders for
fabric washing. Alkali metal (preferably sodium)
aluminosilicates may be either crystalline or amorphous
or mixtures thereof, having the general formula:
0 . 8 - 1. 5 Na20 . A1203 . 0 . 8 - 6 SiOz . xH20
These materials contain some bound water (indicated as
"xH20") and are required to have a calcium ion exchange
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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.
Suitable crystalline sodium aluminosilicate ion-exchange
detergency builders are described, for example, in
GB 1429143 (Procter & Gamble). The preferred sodium
aluminosilicates of this type are the well known
commercially available zeolites A and X, the zeolite P
described and claimed in EP 384070 (Unilever) which is also
referred to as zeolite MAP and mixtures thereof. Zeolite
MAP is available from Crosfields under their designation
Zeolite A24.
Conceivably, water-insoluble detergency builder could be a
crystalline layered sodium silicate as described in
US 4664839.
NaSKS-6 is the trademark for a crystalline layered silicate
marketed by Hoechst (commonly abbreviated as "SKS-6").
NaSKS-6 has the delta-Na2Si05 morphology form of layered
silicate. It can be prepared by methods such as described
in DE-A-3,417,649 and DE-A-3,742,043. Other such layered
silicates, which can be used have the general formula
NaMSiXOZX+i. yH20 wherein M is sodium or hydrogen, x is a
number from 1.9 to 4, preferably 2, and y is a number from
0 to 20, preferably 0.
Crystalline layered silicate may be used in the form of
granules which also contain citric acid.
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Water-soluble builders
Suitable organic builders include the carboxylate or
polycarboxylate builders containing from one to four
carboxy groups, particularly selected from monomeric
polycarboxylates or their acid forms, homo or copolymeric
polycarboxylic acids or there salts in which the
polycarboxylate comprises at least two carboxylic radicals
selected from each other by not more than two carbon atoms.
Preferred carboxylates include the polycarboxylate
materials described in US-A-2,264,103, including the water-
soluble alkali metal salts of mellitic acid and citric acid
(citrate), gluconic acid, dipicolinic acid, oxydisuccinic
acid and alkenyl succinates, glycerol mono- di- and
trisuccinates, carboxymethyloxysuccinates,
carboxymethyloxymalonates, dipicolinates and
hydroxyethyliminodiacetates.
The water-soluble salts of polycarboxylate polymers and
copolymers, such as are described in US-A-3,308,067 are
also be suitable for use with the invention. Of the builder
materials listed in the above paragraph, the preferred
polycarboxylates are hydroxycarboxylates containing up to
three carboxy groups per molecule, especially citric acid
or its salt, particularly sodium citrate.
Further soluble detergency builder salts which can be used
with the present invention are poly-valent inorganic and
poly-valent organic builders, or mixtures thereof. Non-
limiting examples of suitable water-soluble, inorganic
alkaline detergency builder salts include the alkali metal
(generally sodium) carbonates (see above), bicarbonates,
borates, phosphates, and polyphosphates, phosphono
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18
carboxylates. Specific examples of such salts include the
sodium and potassium tetraborates, carbonates,
bicarbonates, orthophosphates and hexametaghosphates.
Other suitable detergency builders include organic alkaline
compounds such as water-soluble amino polyacetates, e.g.
nitrilotriacetates and N-(2-hydroxyethyl)nitrilodiacetates;
and water-soluble salts of phytic acid, e.g. sodium and
potassium phytates.
Preferably, the total amount of builders in the composition
including the particles containing sodium tripolyphosphate
(having a water of hydration in an amount from 1~ to 5~ by
weight and wherein at least 50~ by weight of the sodium
tripolyphosphate within the particles is of a phase I form)
for fabric laundry tablets is from 5 or 30 to 70~ by
weight, whereas for machine dish washing tablets is from 5
or 40 to about 80~ by weight.
Bleach Material
Bleach material may preferably be incorporated in
composition for use in processes according to the present
invention. These materials may be incorporated in solid
form or in the form of encapsulates and less preferably in
dissolved form.
The bleach material may be a chlorine- or bromine-releasing
agent or a peroxygen compound. Peroxygen based bleach
materials are however preferred for use in detergent
tablets of the invention.
AMENDED SHEET
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Inorganic peroxygen bleaches
Inorganic peroxygen-generating compounds are most
preferably used as the bleaching material of the present
invention, and salts (especially sodium salts) of perborate
monohydrate and tetrahydrate and percarbonate have been
mentioned above, and of these, sodium perborate
tetrahydrate is a fully hydrated salt.
Organic peroxy acids
Organic peroxy acids can be used as the bleach material.
The peroxyacids suitable for use in the present invention
are solid and, preferably, substantially water-insoluble
compounds. By "substantially water-insoluble" is meant
herein a water-solubility of less than about to by weight
at ambient temperature. In general, peroxyacids containing
at least about 7 carbon atoms are sufficiently insoluble in
water for use herein.
Monoperoxy acids useful herein include alkyl peroxy acids
and aryl peroxyacids such as peroxybenzoic acid and
ring-substituted peroxybenzoic acids (e. g. peroxy-alpha-
naphthoic acid); aliphatic and substituted aliphatic
monoperoxy acids (e. g. peroxylauric acid and peroxystearic
acid); and phthaloyl amido peroxy caproic acid (PAP).
Typical diperoxy acids useful herein include alkyl diperoxy
acids and aryldiperoxy acids, such as 1,12-di-peroxy-
dodecanedioic acid (DPDA); 1,9-diperoxyazelaic acid,
diperoxybrassylic acid, diperoxysebacic acid and diperoxy-
isophthalic acid; and 2-decyldiperoxybutane-1,4-dioic acid.
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Chlorine & Bromine bleaches
Among suitable reactive chlorine- or bromine-oxidizing
materials are heterocyclic N-bromo and N-chloro imides such
as trichloroisocyanuric, tribromoisocyanuric,
5 dibromoisocyanuric and dichloroisocyanuric acids, and salts
thereof with water-solubilising cations such as potassium
and sodium. Hydantoin compounds such as 1,3-dichloro-5,5-
dimethyl-hydantion are also quite suitable.
Particulate, water-soluble anhydrous inorganic salts are
10 likewise suitable for use herein such as lithium, sodium or
calcium hypochlorite and hypobromite. Chlorinated
trisodium phosphate and chloroisocyanurates are also
suitable bleaching materials.
15 Encapsulation techniques are known for both peroxygen and
chlorine bleaches, e.g. as described in US-A-4,126,573, US-
A-4,327,151, US-A-3,983,254, US-A-4,279,764, US-A-3,036,013
and EP-A-0,436,971 and EP-A-0,510,761. However,
encapsulation techniques are particularly useful when using
20 halogen based bleaching systems.
For chlorine bleaches, the compositions of the invention
may comprise from about 0.5o to about 3% AvCl (available
Chlorine). For peroxygen bleaching agents a suitable range
are also from 0.5% to 3% AvOx (available Oxygen).
Preferably the amount of bleach material in the wash liquor
is at least 12.5 x 10-9o and at most 0.030 AvOx by weight
of the liquor.
Bleach activator
Detergent tablets of the present invention which contain an
inorganic peroxygen bleaching material such as sodium
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percarbonate or sodium perborate preferably also contain a
bleach activator. Bleach activators have been widely
disclosed in the art. Preferred examples include peracetic
acid precursors, for example tetraacetylethylene diamine
(TAED), and perbenzoic acid precursors. 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.
It is preferred that the bleach activator is present in a
different region of the tablet to the bleach, and in
particular alkali metal percarbonate/perborate monohydrate
(if present). Thus it may be present in the region
containing the particles of sodium tripolyphosphate which
is rich in Phase I form, especially if the tablet has only
two discrete regions, e.g. layers.
In terms of tablet composition, bleach activator is usually
present in an amount from 1 to loo by weight of the tablet,
possibly less in the case of a transition metal catalyst
which may be used as O.lo or more by weight of the tablet.
Heavy Metal Chelating Agent
A detergent tablet of the invention may also include a
heavy metal chelating agent, which may also act as a bleach
stabiliser. Such components will also chelate non-heavy
metals to a limited extent, and similarly builders such as
tripolyphosphate will chelate heavy metals to a limited
extent.
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22
Preferred chelating agents include organic phosphonates,
amino carboxylates, polyfunctionally-substituted compounds,
and mixtures thereof.
Particularly preferred chelating agents are organic
phosphonates such as ethylenediamine tetramethylene
phosphonate; --hydroxy-2 phenyl ethyl diphosphonate;
methylene diphosphonate; ethylene diphosphonate; hydroxy
1,1-hexylidene; vinylidene 1,1 diphosphonate; 1,2
dihydroxyethane 1,l diphosphonate; and hydroxy-ethylene 1,1
diphosphonate. Most preferred is hydroxy-ethylene 1,1
diphosphonate; 2 phosphono-1,2,4 butanetricarboxylic acid
or salts there of.
Another possible chelating agent is ethylenediamine
disuccinate (EDDS).
If present it is preferable if the level of chelating agent
is from 0.5 to 3 wto of the total composition.
Disintecrrant Systems
As mentioned above, the region of the tablet which does not
include the sodium tripolyphosphate rich in Phase I form
may contain a further disintegrant system. This is
particularly preferred in discrete regions which contain
more than 5o detergent active compounds, which is generally
the case for laundry detergent tablets. The further
disintegrant system helps such regions to disperse quickly,
which counters the binding effect of the detergent active
compound.
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23
The fully hydrated salt may in fact be a disintegrant
itself, or be part of a disintegrant system.
Suitable disintegrants may preferably be present in the
region as at least 15 or 20o by weight of the region,
possibly at least 25% up to 50 or 600.
Suitable disintegrants ma y be grouped into the following
classes: swelling (physical) disintegrants; effervescent
disintegrants; and materials of high solubility.
Swelling disintegrant
Swelling disintegrants include organic materials such as
starches, for example, corn/ maize, rice and potato
starches and starch derivatives, such as PrimojelT"~,
carboxymethyl starch and ExplotabT"~, sodium starch
glycolate; celluloses, for example, Arbocelo-B and
Arbocel~-BC (beech cellulose), Arbocelo-BE (beech-sulphite
cellulose), Arbocel~-B-SCH (cotton cellulose), Arbocel~-FIC
(pine cellulose) as well as further Arbocelo types
(Arbocel~-TF-30-HG) from Messrs Rettenmaier and cellulose
derivatives, for example CourloseT"' and NymcelTM, sodium
carboxymethyl cellulose, Ac-di-SolTM, cross-linked modified
cellulose, and HanflocTM, microcrystalline cellulosic
fibres; and various synthetic organic polymers, notably
polyethylene glycol and cross-linked polyvinyl pyrrolidone,
for example PolyplasdoneTM, XL or KollidonTM CL.
Inorganic swelling disintegrants include bentonite clay.
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Effervescent disintegrants
Effervescent disintegrants include weak acids or acid
salts, for example, citric acid (preferred), malic acid or
tartaric acid, in combination with alkali metal carbonate
or bicarbonate; these may suitably be used in an amount of
from 1 to 25 wto, preferably from 5 to 15 wto. Further
examples of acid and carbonate sources and other
effervescent systems may be found in Pharmaceutical Dosage
Forms: Tablets, Volume l, 1989, pages 287-291 (Marcel
Dekker Inc, ISBN 0-8247-8044-2).
Materials of High Solubility
Highly water soluble materials, which are one of the two
possibilities are compounds, especially salts, with a
solubility at 20°C of at least 50 gms per 100 gms of water.
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 highly water-soluble materials which may be used 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/100g)
Sodium citrate dehydrate 72
Potassium carbonate 112
Urea >100
Sodium acetate trihydrate 76
Magnesium sulphate 7H20 71
Potassium acetate >200
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Particularly preferred materials are sodium acetate
trihydrate and sodium citrate dehydrate.
As different disintegrants are found in different regions
of the tablets, the tablets may provide for the sequential
5 release of components of the tablet into the wash liquor.
By placing different types of component in the different
regions, such a tablet may be able to deliver detergent
actives first, and fabric softeners later.
10 Further examples of disintegrants falling into the above
categories, particularly swelling disintegrants, are known
for use in pharmaceutical tablets.
Silica material for Machine Dish Washing Tablet
15 Dish washing tablets may preferably contain silica
material. Suitable forms of silica include amorphous
silica, such as precipitated silica, pyrogenic silica and
silica gels, such as hydrogels, xerogels and aerogels, or
the pure crystal forms quartz, tridymite or crystobalite,
20 but the amorphous forms of silica are preferred. Suitable
silicas may readily be obtained commercially. They are
sold, for example under the Registered Trade Name Gasil 200
(ex Crosfield, UK).
25 Preferably, the silica is in the product in such a form
that it can dissolve when added to the wash liquor.
Therefore, addition of silica by way of the addition of
anti-foam particles of silica and silicone oil is not
preferred.
The particle size of the silica material of the present
invention may be of importance, especially as it is
believed that any silica material that remains undissolved
CA 02389984 2002-05-03
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26
during the washing process, may deposit on the glass at a
later stage. Therefore, it is preferred that silica
material are used that have a particle size (as determined
with a Malvern Laser, i.e. "aggregated" particles size) of
at most 40 Vim, more preferably at most 30~.m, most
preferably at most 20~m provides better results in the
wash. In view of incorporation in a cleaning composition,
it is preferred that the particle size of the silica
material is at least lam, more preferably at least 2~.m,
most preferably at least 5~.m.
Preferably, the primary particle size of the silica is in
general less than about 30nm, in particular less than about
25nm. Preferably, elementary particles size are less than
20nm or even lOnm. There is no critical lower limit of the
elementary particle size; the lower limit is governed by
other factors such as the manner of manufacture, etc. In
general commercial available silicas have elementary
particle sizes of 1 nm or more.
Preferably, the silica material is present in the wash
liquor at a level of at least 2.5x10-4%, more preferably, at
least 12 . 5x10-4 0, most preferably at least 2. 5x10-3~ by
weight of the wash liquor and preferably at most 1x10-1~,
more preferably at most 8x10-Zo, most preferably at most
5x10-2% by weight of the wash liquor.
Preferably, the level of dissolved silica material in the
wash liquor is at least 80 ppm, more preferably at least
100 ppm, most preferably at least 120 ppm and preferably at
most 1,000 ppm. It is noted that for the silica material to
CA 02389984 2002-05-03
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27
be effective, the lower level of dissolved silica material
depends on the pH value, i.e. thus at pH 6.5, the level is
preferably at least 100 ppm; at pH 7.0 preferably at least
110 ppm; at pH 7.5 preferably at least 120 ppm; at pH 9.5
preferably at least 200 ppm; at pH 10 preferably at least
300 ppm; at pH 10.5 preferably at least 400ppm.
Preferably, the silica material is present in the cleaning
composition at a level of at least 0.1%, more preferably at
least 0.50, most preferably at least to by weight of the
cleaning composition and preferably at most 100, more
preferably at most 8%, most preferably at most 5% by weight
of the cleaning composition.
Silicates
The composition of the invention optionally comprises
alkali metal silicates. The alkali metal silicate has some
detergency builder properties, and particularly for machine
dish washing may provide pH adjusting capability and
protection against corrosion of metals and against attack
on dishware, including fine china and glassware benefits.
The presence of such alkali metal silicates in detergent
tablets may be advantageous in providing protection against
the corrosion of metal parts in washing machines, and also
in aiding the detergency builder and in adjusting the
alkalinity of the wash liquor.
If silicates are present in machine dish washing tablets,
they are preferably included at a level of from to to 300,
preferably from 2% to 200, more preferably from 3o to 100,
based on the weight of the composition.
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28
In laundry tablets, preferred amounts of silicate are
between 1 and 6 o by weight, which may be achieved through
the base powder or by post dosing.
The ratio of SiOz to the alkali metal oxide (M20, where
M=alkali metal) is typically from 1 to 3.5, preferably from
1.6 to 3, more preferably from 2 to 2.8. Preferably, the
alkali metal silicate is hydrous, having from 15o to 25%
water, more preferably, from 17o to 200.
The highly alkali metasilicates can in general be employed,
although the less alkaline hydrous alkali metal silicates
having a SiO2:M20 ratio of from 2.0 to 2.4 are, as noted,
greatly preferred. Anhydrous forms of the alkali metal
silicates with a Si02:M20 ratio of 2.O or more are also
less preferred because they tend to be significantly less
soluble than the hydrous alkali metal silicates having the
same ratio.
Sodium and potassium, and especially sodium, silicates are
preferred. A particularly preferred alkali metal silicate
is a granular hydrous sodium silicate having a Si02:Naz0
ratio of from 2.0 to 2.4 available from Ak30 PQ
Corporation, especially preferred is Britesil H20 and
Britesil H24. Most preferred is a granular hydrous sodium
silicate having a SiO2:Na20 ratio of 2Ø While typical
forms, i.e. powder and granular, of hydrous silicate
particles are suitable, preferred silicate particles having
a mean particle size between 300 and 900 microns and less
than 40o smaller than 150 microns and less than 5% larger
than 1700 microns. Particularly preferred is a silicate
particle with a mean particle size between 400 and 700
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29
microns with less than 20% smaller than 150 microns and
less than to larger then 1700 microns. Compositions of the
present invention having a pH of 9 or less preferably will
be substantially free of alkali metal silicate.
Water Soluble Polymeric Polycarboxylic Compounds
A water soluble polymeric polycarboxylic compound may be
present in the composition, and is advantageously present
in a dish wash composition. They inhibit unwanted
deposition from the wash liquor onto the material being
washed, either laundry or dish ware, and also onto machine
parts.
Preferably these compounds are homo- or co-polymers of
polycarboxylic compounds, especially co-polymeric compounds
in which the acid monomer comprises two or more carboxyl
groups separated by not more than two carbon atoms. Salts
of these materials can also be used.
Particularly preferred polymeric polycarboxylates are co-
polymers derived from monomers of acrylic acid and malefic
acid. The average molecular weight of these polymers in the
acid form preferably ranges from 4,000 to 70,000.
Another type of polymeric polycarboxylic compounds suitable
for use in the composition of the invention are homo-
polymeric polycarboxylic acid compounds with acrylic acid
as the monomeric unit. The average weight of such homo-
polymers in the acid form preferably ranges from 1,000 to
100,000 particularly from 3,000 to 10,000.
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Acrylic sulphonated polymers as described in EP 851 022
(Unilever) are also suitable.
Preferably, this polymeric material is present at a level
5 of at least O.lo, more preferably at levels from 1 wto to 7
wto of the total composition.
Polymer Binder
Tablets of this invention, and in particular laundry
10 tablets, may include an organic water-soluble polymer,
serving as a binder when the particles are compacted into
tablets. This polymer may be a polycarboxylate included as
a supplementary builder, as mentioned earlier. It may be
applied as a coating to some or all of the constituent
15 particles prior to compaction.
As taught in our EP-A-522766, such polymers can function to
enhance tablet disintegration at the time of use, as well
as acting as a binder to enhance tablet strength prior to
20 use.
It is preferred that such a binder material, if present,
should melt at a temperature of at least 35°C, better at
40°C or above, which is above ambient temperatures in many
25 temperate countries. For use in hotter countries it will be
preferred that the melting temperature is somewhat above
40°C, so as to be above the ambient temperature.
For convenience the melting temperature of the binder
30 material should be below 80°C.
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31
Preferred binder materials are synthetic organic polymers
of appropriate melting temperature, especially polyethylene
glycol. Polyethylene glycol of average molecular weight
1500 (PEG 1500) melts at 45°C and has proved suitable.
Polyethylene glycol of higher molecular weight, notably
4000 or 6000, can also be found.
Other possibilities are polyvinylpyrrolidone, and
polyacrylates and water-soluble acrylate copolymers.
The binder may suitably be applied to the particles by
spraying, e.g. so as a solution or dispersion. It may be
applied to particles which contain organic surfactant. As
an alternative, the binder may be provided in a powder
form, and be dispersed into the composition to be tableted.
If used, the binder is preferably used in an amount within
the range from 0.1 to 10% by weight of the tablet
composition, more preferably the amount is at least 1$ or
even at least 3o by weight of the tablets. Preferably the
amount is not over 8% or even 6% by weight unless the
binder serves some other additional function.
Enzymes
The detergent tablets of 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. 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 and dishes. Examples of suitable proteases are
Maxatase (Trade Mark), as supplied by Gist-Brocades N.V.,
Delft, Holland, and Alcalase (Trade Mark), and Savinase
(Trade Mark), as supplied by Novo Industri A/S, Copenhagen,
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32
Denmark. Detergency enzymes are commonly employed in the
form of granules or marumes, optionally with a protective
coating, in amount of from about O.lo to about 3.0o by
weight of the composition; and these granules or marumes
present no problems with respect to compaction to form a
tablet.
Other Laundry Detergent Ingredients
The laundry detergent tablets of 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, especially
if the detergent 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 266863A (Unilever). Such
antifoam granules typically comprise a mixture of silicone
oil, petroleum jelly, 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.
Further ingredients which can optionally be employed in the
laundry detergent tablet of the invention include anti-
redeposition agents such as sodium carboxymethylcellulose,
straight-chain polyvinyl pyrrolidone and the cellulose
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33
ethers such as methyl cellulose and ethyl hydroxyethyl
cellulose, fabric-softening agents; heavy metal
sequestrants such as EDTA; perfumes; and colorants or
coloured speckles.
Other Dish Washing Detergent Ingredients
Anti-tarnishing agents such as benzotriazole and those
described in EP 723 577 (Unilever) may be included in dish
washing detergent tablets of the present invention.
Optional ingredients in dish washing detergents tablets
are, for example, buffering agents, reducing agents, e.g.,
borates, alkali metal hydroxide and the well-known enzyme
stabilisers such as the polyalcohols, e.g. glycerol and
borax; anti-scaling agents; crystal-growth inhibitors,
threshold agents; thickening agents; perfumes and dyestuffs
and the like.
Reducing agents may e.g. be used to prevent the appearance
of an enzyme-deactivating concentration of oxidant bleach
compound. Suitable agents include reducing sulphur-oxy
acids and salts thereof. Most preferred for reasons of
availability, low cost, and high performance are the alkali
metal and ammonium salts of sulphuroxy acids including
ammonium sulphite ( (NHQ) ZS03) , sodium sulphite (Na2S03) ,
sodium bisulphite (NaHS03) , sodium metabisulphite (Na2S203) ,
potassium metabisulphite (K2S205), lithium hydrosulphite
(hi2S204), etc., sodium sulphite being particularly
preferred. Another useful reducing agent, though not
particularly preferred for reasons of cost, is ascorbic
acid. The amount of reducing agents to be used may vary
from case to case depending on the type of bleach and the
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34
form it is in, but normally a range of about O.Olo to about
1.0% by weight, preferably from about 0.020 to about 0.50
by weight, will be sufficient.
Particle Size and Distribution
The discrete regions of a detergent tablet of this
invention are each a matrix of compacted particles.
Preferably the particulate composition has an average
particle size in the range from 200um to 2000um, more
preferably from 250um to 1400um. Fine particles, smaller
than 180um or 200um may be eliminated by sieving before
tableting, if desired, although we have observed that this
is not always essential.
While the starting particulate composition may in principle
have any bulk density, the present invention is especially
relevant to tablets made by compacting powders of
relatively high bulk density, because of their greater
tendency to exhibit disintegration and dispersion problems.
Such tablets have the advantage that, as compared with a
tablet derived from a low bulk density powder, a given dose
of composition can be presented as a smaller tablet.
Thus the starting particulate composition may suitably have
a bulk density of at least 400g/litre, preferably at least
500g/litre, and advantageously at least 700g/litre.
Granular detergent compositions of high bulk density
prepared by granulation and densification in a high-speed
mixer/granulator, as described and claimed in EP 340013A
(Unilever), EP 352135A (Unilever), and EP 425277A
(Unilever), or by the continuous granulation/densification
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processes described and claimed in EP 367339A (Unilever)
and EP 390251A (Unilever), are inherently suitable for use
in the present invention.
5 A spray-dried base powder may also be used, and this can
results in a powder to be tableted having a bulk density of
600 to 700 g/litre.
Porosity
10 The step of compacting the particles reduces the porosity
of the composition. Porosity is conveniently expressed as
the percentage of volume which is air.
The air content of a tablet or region of a tablet can be
15 calculated from the volume and weight of the tablet or
region, provided the air-free density of the solid content
is known. The latter can be measured by compressing a
sample of the material under vacuum with a very high
applied force, then measuring the weight and volume of the
20 resulting solid.
The percentage air content of a tablet or region of a
tablet varies inversely with the pressure applied to
compact the composition while the strength of the tablet or
25 region varies with the pressure applied to bring about
compaction. Thus the greater the compaction pressure, the
stronger the tablet or region becomes but the smaller the
air volume within.
30 The invention may be applied when compacting particulate
detergent composition to give tablets with a wide range of
porosities. Specifically included among possible
27-12-2001 EP00118'
CA 02389984 2002-05-03
36
porosities is a porosity of up to 38~ air volume, e.g. from
or 15 better 25$ up to 35~ air by volume in the tablet.
Tablet Size and Density
5 The size of a tablet will suitably range from 10 to 160
grams, preferably prom 15 to 60 g, 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. In particular,
10 a machine dish wash tablet is preferably from 15 to 30 g.
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. The
overall density of a tablet preferably lies in a range from
1040 or I050gm/litre, possibly 1100gm/litre, up to
1450gmilitre or 1700gm/litre, or more. The tablet density
may well lie in a range up to 1350 to 1400gm/litre for a
laundry tablet and in a range from 1300 to 1600gm/litre for
a machine dish wash tablet.
Embodiments of the present invention will now be described
by way of example only.
Example 1
42g cylindrical detergent tablets having the following
formulations were prepared on a rotating table tableting
machine from Fette. Two tablets of the invention were made
with two layers, the thicker of which contained the
Rhodiaphos HPA 3.5, the other sodium perborate or sodium
acetate trihydrate. The thicker layer was 75~ of the
tablet (31.5g), the thinner layer 25$ (9.2g). Two
comparative tablets were made having a single layer, but
AMENDED SHEET
CA 02389984 2002-05-03
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37
having the same composition as the two two-layer tablets.
All the tablets contained the same base powder, which had
the following formulation:
Component $ wt
Na-LAS 23.55
Nonionic surfactant 10.42
Soap 0.72
AA/MA copolymer (70:30) 3.22
Sodium tripolyphosphate (builder) 40.63
Sodium silicate 8.63
Sodium carboxy methyl cellulose 0.67
Moisture 12.15
Total 100.00
CA 02389984 2002-05-03
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38
O O O O O ~ ~ O ODM
r-I ~ I ~ O ~ u7 I~I~O ~ O
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~ M M ~ O O M r-IO
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H W W u W H fxC.,x Ll t H
U n '-' 7
CA 02389984 2002-05-03
WO 01/38479 PCT/EP00/11816
39
The strength of the tablets, in their dry state, as made on
the press, was determined as the force, expressed in
Newtons, needed to break the tablet, as measured using an
Instron type universal testing instrument to apply
compressive force on a diameter (i.e. perpendicular to the
axis of a cylindrical tablet).
The rate of disintegration of the detergent tablet was
assessed by means of the "still water grid test": the
tablet is placed on a 10 x 9 cm metal grid with a mesh size
of 1.2 x 1.2 cm and placed into a beaker containing 1 litre
of still water at 20°C. The disintegration time was the
time taken for 10% residue to be left on the grid. The
test was repeated 3 times. The results are shown in the
tablet below:
Tablet A I B II
Strength (N) 35 35 35 35
Disintegration Time 28956 45733 1176 173f2
(s)
Example 2
25g cuboid machine dish wash detergent tablets having the
following formulations were prepared on a rotating table
tableting machine from Fette. Two tablets of the invention
were made with two layers, the thicker of which contained
the Rhodiaphos HPA 3.5 and optionally a minor proportion of
sodium perborate tetrahydrate, the other the major
proportion (or all) of this salt. The thicker layer was
750 of the tablet, the thinner layer 250.
CA 02389984 2002-05-03
WO 01/38479 PCT/EP00/11816
A comparative tablet was made having a single layer, but
having the same composition as the respective two-layer
tablets.
CA 02389984 2002-05-03
WO 01/38479 PCT/EP00/11816
41
H
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rtf(s ~ ~ ~ M
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O 'O b O W ~ .~GC3''~ ~1 N l~
O O .~ FC ~ ~ O O O N O
cn U7 OG H LL W cn Ca v~ LL .~ H
H
