Note: Descriptions are shown in the official language in which they were submitted.
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CLEANING COMPOSITIONS
This invention relates to cleaning compositions in the form
of tablets. These tablets are intended to disintegrate
when placed in water and thus are intended to be consumed
in a single use. The tablets may be suitable for use in
machine dishwashing, the washing of fabrics or other
cleaning tasks.
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 containing bleach for use as an
additive to a fabric washing liquor have been disclosed in
US-A-4013581 (Huber/Procter and Gamble). Tablets
containing a water softening agent, for use as an additive
in cleaning, are sold commercially and are one form of
tablet disclosed in EP-A-838519 (Unilever). Tablets of
composition suitable for machine dishwashing have been
disclosed in EP-A-318204 and US-A-5691293 and are 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 cleaning composition are generally made by
compressing or compacting a composition in particulate
form. 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
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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 other of these properties without detriment
to the other so as to improve the overall compromise
between them.
If a tablet contains organic surfactant, this functions as
a binder, plasticising the tablet. However, it 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 containing surfactant and built with
insoluble detergency builder such as sodium aluminosilicate
(zeolite).
In our published applications WO 98/46719 and WO 98/46720
we have taught that the speed of disintegration of tablets
can be improved by stamping with dies (also known as
punches) which bear a surface of an elastomeric material.
This leads to an improved porosity at the tablet surface.
It is known to include materials whose function is to
enhance disintegration of tablets when placed in wash
water. For example, our EP-A-838519 mentioned above
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teaches the use of sodium acetate trihydrate for this
purpose.
A number of documents have taught that the disintegration
of tablets of cleaning composition can be accelerated by
incorporating in the tablet a quantity of a water-insoluble
but water-swellable material serving to promote
disintegration of the tablet when placed in water at the
time of use. Such documents include EP-A-466484,
EP-A-482627 and WO-98/40463.
EP-A-979,863 (filing date 13 August 1998, but only
published 16 February 2000) discloses the inclusion of
water swellable disintegrants in tablet coatings. WO
98/55583 discloses tablets with the concentration of a
water-swellable polymeric material varying in different
regions of the tablet to cause them to disintegrate at
different rates.
WO 98/55590 discloses a cleaning tablet composition
comprising a water-swellable polymer in a concentration
greater in at least one other region of a tablet to promote
disintegration of the regions at different rates. The
region may be a layer or a core or inset (or shell or
coating around such inset).
In the present invention, such a disintegration-promoting
material is incorporated within a tablet but is not
distributed uniformly. We have found that the speed of
disintegration of a tablet can be increased by
concentrating water-swellable disintegrant adjacent to one
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or more tablet surfaces, even when the tablets have been
stamped using elastomeric-surfaced dies.
So, according to a first aspect of this invention, there is
provided a tablet of compacted particulate cleaning
composition containing at least one cleaning ingredient
which is an organic surfactant, a water softening agent or
a bleach, wherein a water-swellable disintegration-
promoting material is present at a greater concentration in
at least one zone adjacent a tablet surface than in an
interior zone which is more remote from any surface of the
tablet.
According to a particularily preferred form of the first
aspect, the water swellable disintegration-promoting
material is in a form of particles with a mean particle
size in a range from 250 - 1,500 micrometers.
The water-swellable material may be cellulose or a material
which contains cellulose mixed with other materials.
However, other materials including starch are known to be
effective as water-swellable disintegration-promoting
materials, and these may also be used in accordance with
this invention.
This invention is particularly applicable when the tablets
contain both surfactant and detergency builder, as in
tablets for fabric washing.
In a second aspect this invention provides a process for
making a tablet by placing a quantity of a particulate
cleaning composition within a mould and compacting that
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composition within the mould, characterised by placing a
smaller quantity of a water-swellable disintegration-
promoting material, or a composition incorporating such a
material, in the mould before, after, or both before and
5 after the said quantity of cleaning composition, so that
this disintegration-promoting material lies in one or more
zones of the tablet adjacent to one or more mould surfaces.
This quantity of disintegration promoting material will
then be absent from a further zone of the tablet formed
from the quantity of cleaning composition.
Forms of this invention, preferred and optional features,
and materials which may be used, will now be discussed in
greater detail.
Water-Swellable 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 PrimojelT", carboxymethyl starch
and ExplotabTM, sodium starch glycolate; celluloses, for
example, Arbocel~-B and Arbocel~-BC (beech cellulose),
Arbocel~-BE (beech-sulphite cellulose), Arbocel~-B-SCH
(cotton cellulose), Arbocel~-FIC (pine cellulose) as well
as further Arbocel~ types from Rettenmaier and cellulose
derivatives, for example CourloseT" and Nymcel''", sodium
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carboxymethyl cellulose, Ac-di-SolT" cross-linked modified
cellulose, and Hanfloc''" microcrystalline cellulosic fibres;
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
but not all of the original lignin.
Suppliers of water-swellable disintegrant materials include
Rettenmaier in Germany and FMC Corporation in USA.
The overall quantity of water-swellable disintegration-
promoting material in the tablet is preferably between 0.1
and 20o by weight, especially between 0.5 and 5o by weight.
The water-insoluble, water-swellable material which is
incorporated into a tablet composition preferably has a
mean particle size in a range from 250/.cm to l, 500/.cm, more
preferably from 700,um to 1,100,um.
Surfactant Compounds
Compositions which are compacted to form tablets or tablet
regions of this invention may contain one or more organic
detergent surfactants. In a fabric washing composition,
these preferably provide from 5 to 50o by weight of the
overall tablet composition, more preferably from 8 or 9% by
weight of the overall composition up to 400, 490 or 50o by
weight. Surfactant may be anionic (soap or non-soap),
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cationic, zwitterionic, amphoteric, nonionic or a
combination of these.
Anionic surfactant may be present in an amount from 0.5 to
50o by weight, preferably from 20 or 4o up to 300 or 40o by
weight of the tablet composition.
In a machine dishwashing composition, organic surfactant is
likely to constitute from 0.5 to 80, more likely from 0.5
to 9.50 of the overall composition and is likely to consist
of nonionic surfactant, either alone or in a mixture with
anionic surfactant.
Synthetic (i.e. non-soap) anionic surfactants are well
known to those skilled in the art. Examples include
alkylbenzene sulphonates, particularly sodium linear
alkylbenzene sulphonates having an alkyl chain length of
C8-C15; olefin sulphonates; alkane sulphonates; dialkyl
sulphosuccinates; and fatty acid ester sulphonates.
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 cation, is commercially significant as an
anionic surfactant.
Linear alkyl benzene sulphonate of the formula
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R ~ _ +
S03 M
where R is linear alkyl of 8 to 15 carbon atoms and M+ is a
solubilising cation, especially sodium, is also a
commercially significant anionic surfactant.
Frequently, such linear alkyl benzene sulphonate or primary
alkyl sulphate of the formula above, or a mixture thereof
will be the desired anionic surfactant and may provide 75
to 100 wto of any anionic non-soap surfactant in the
composition.
In some forms of this invention the amount of non-soap
anionic surfactant lies in a range from 5 to 20 or 25 wto
of the tablet composition.
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 nonionic 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.
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Specific nonionic surfactant compounds are alkyl (CB-2z)
phenol-ethylene oxide condensates, the condensation
products of linear or branched aliphatic C$-2o 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 C9-11 and C12_ls primary and
secondary alcohols ethoxylated with an average of from 5 to
moles of ethylene oxide per mole of alcohol.
In certain forms of this invention the amount of nonionic
surfactant lies in a range from 4 to 400, better 4 or 5 to
15 30o by weight of the composition. Many nonionic
surfactants are liquids. These may be absorbed onto
particles of the composition, prior to compaction into
tablets.
20 Amphoteric surfactants which may be used jointly with
anionic or nonionic surfactants or both include
amphopropionates of the formula:
2 5 O CH2CH20H
RC-NH-CH2CH2-N-CH2CH2C02Na
where RCO is a acyl group of 8 to 18 carbon atoms,
especially coconut acyl.
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The category of amphoteric surfactants also includes amine
oxides and also zwitterionic surfactants, notably betaines
of the general formula
R2
5 ~CH2
R4-Y-N~ CH2-Z
/CH2
R3
10 where R4 is an aliphatic hydrocarbon chain which contains 7
to 17 carbon atoms, R2 and R3 are independently hydrogen,
alkyl of 1 to 4 carbon atoms or hydroxyalkyl of 1 to 4
carbon atoms such as CHZOH,
Y is CHZ or of the form CONHCHZCH2CH2 (amidopropyl betaine) ;
Z is either a C00- (carboxybetaine), or of the form
CHOHCHzS03 - (sulfobetaine or hydroxy sultaine).
Another example of amphoteric surfactant is amine oxide of
the formula
C- i-(CH2)~ i
R4 R3
where R1 is Clo to Czo alkyl or alkenyl; R2, R3 and R9 are
each hydrogen or C1 to CQ 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
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 possibly
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
possibly be from to to 10 or 20o by weight of the tablet or
region of a tablet.
The particles of water-swellable material may be mixed with
surfactant, so that they do not end up floating on top of
the wash liquor. It is suitable for this purpose to spray
them with a liquid anionic surfactant such as Aerosil OT,
which is the sodium salt of sulphosuccinic acid (2-
ethylhexyl) ester.
Such a surfactant may be sprayed on in a quantity which is
from 0.01 to l00 of the weight of the water-swellable
particles, preferably from 0.01 to 0.5% of their weight.
Water-softening agent
A composition which is compacted to form tablets or tablet
regions may contain a so-called water-softening agent which
serves to remove or sequester calcium and/or magnesium ions
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in the water. In the context of a detergent composition
containing organic surfactant, a water-softening agent is
more usually referred to as a detergency builder.
When a water-softening agent (detergency builder) is
present, the amount of it is likely to lie in a broad range
from 50, preferably 15 wto up to 980 of the tablet
composition. In detergent tablets the amount is likely to
be from 15 to 800, more usually 15 to 60% by weight of the
tablet.
Water-softening agents may be provided wholly by water
soluble materials, or may be provided in large part or even
entirely by water-insoluble material with water-softening
properties.
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:
0.8 - 1.5 NazO.A1203. 0.8 - 6 Si02, 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.
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Suitable crystalline sodium aluminosilicate ion-exchange
materials 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 newer zeolite P described and claimed
in EP 384070 (Unilever) and mixtures thereof. This form of
zeolite P is also referred to as "zeolite MAP". One
commercial form of it is denoted "zeolite A24".
Conceivably a water-insoluble water-softener (detergency
builder) could be a 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, such as those having the general formula
NaMSiXO2x+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 can be used.
The category of water-soluble phosphorus-containing
inorganic softeners includes the alkali-metal
orthophosphates, metaphosphates, pyrophosphates and
polyphosphates. Specific examples of inorganic phosphate
detergency builders include sodium and potassium
tripolyphosphates, orthophosphates and hexametaphosphates.
Non-phosphorus water-soluble water-softening agents may be
organic or inorganic. Inorganics that may be present
include alkali metal (generally sodium) carbonate; while
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organics include polycarboxylate polymers, such as
polyacrylates, acrylic/maleic copolymers, and acrylic
phosphonates, monomeric polycarboxylates such as citrates,
gluconates, oxydisuccinates, glycerol mono- di- and
trisuccinates, carboxymethyloxysuccinates,
carboxymethyloxymalonates, dipicolinates and
hydroxyethyliminodiacetates.
Tablet compositions preferably include polycarboxylate
polymers, more especially polyacrylates and acrylic/maleic
copolymers which have some function as water-softening
agents and also inhibit unwanted deposition onto fabric
from the wash liquor.
The water-soluble builders may be present in the amount
srated above, in particular in amounts of from 10 - 80o by
weight.
Bleach System
Tableted compositions according to the invention may
contain a bleach system. This preferably comprises one or
more peroxy bleach compounds, for example, inorganic
persalts or organic peroxyacids, which may be employed in
conjunction with activators to improve bleaching action at
low wash temperatures. If any peroxygen compound is
present, the amount is likely to lie in a range from 10 to
85o by weight of the composition. If the tablet contains
surfactant and detergency builder, the amount of peroxygen
compound bleach is unlikely to exceed 250 of the
composition.
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Preferred inorganic persalts are sodium perborate
monohydrate and tetrahydrate, and sodium percarbonate,
advantageously employed together with an activator. Bleach
activators, also referred to as bleach precursors, have
5 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. The quaternary ammonium and
10 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-
15 549272. A bleach system may also include a bleach
stabiliser (heavy metal sequestrant) such as
ethylenediamine tetramethylene phosphonate and
diethylenetriamine pentamethylene phosphonate.
Water-Soluble Disintegration-Promoting Particles
A tablet or a region of a tablet may contain water-soluble
particles to promote disintegration. These would be in
addition to the water-swellable, water-insoluble particles
concentrated in surface zones of the tablet as required by
this invention.
Such soluble particles typically contain at least 40% (of
their own weight) of one or more materials selected from
~ compounds with a water-solubility exceeding 50
grams per lOC grams water
~ phase I sodium tripolyphosphate
~ sodium tripolyphosphate which is partially hydrated
J~.-~A.r-JM~n'. 1y yJ' /JIV 1LGVCIC t'tY I CJY I LCf' I r r.. m ~ n
C 25-09-2(~t~1 CA 02385296 2002-03-18 EP00091 ~
is
so as to contain water of hydration in an amount
which is at least 0.5E by weight of the sodium
tripolyphosphate in the particles.
3t is especially preferr~d that said soluble particles are
selected from urea, salts with a water--solubility exceeding
50 g per 100 g water, and mixtures thereof.
As will be explained further below, these disintegration-
promoting particles can also contain other forms of
tripolyphvsphate or other salts within the balance of their
composition.
if the material in such water-soluble disintegration-
promoting particles can function as a detergency. builder,
(aa is the case with sodium tripolyphosphate) then of
course it contributes to the total quantity of detergency
builder in the tablet composition.
2o The quantity of water-soluble disintegration-promoting
particles may be from 3 or 5% up to 30 or 40% by weight of
the tablet or region thereof. The quantity may possibly be
from e% up to 25 or 30% or more. However, it is within
this invention that the amount of such water-soluble
disintegration-promoting particles is low, below 5% of the
tablet or region, reliance being placed on insoluble
swellable particles.
One possibility is that these particles contain at least
40% of their own weight, bettex at least SO%, of a material
which has a solubility in deionised water at 20°C of at
least 50 grams per 100 grams of water.
AMENDED SHEET
E(6Pfd118~tcm r.v~vcr~ Iu~vv
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These particles may provide material of such solubility in
an amount which is at least 7 wto or 12 wto of the
composition of the tablet or discrete region thereof.
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 119
Sodium acetate trihydrate 76
Magnesium sulphate 7H20 71
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
Sodium tripolyphosphate anhydrous 15
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Preferably this highly water soluble material is
incorporated as particles of the material in a
substantially pure form (i.e. each such particle contains
over 95o by weight of the material). However, the said
particles may contain 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.
A preferred material is sodium acetate in a partially or
fully hydrated form.
It may be preferred that the highly water-soluble material
is a salt which dissolves in water in an ionised form. As
such a salt dissolves it leads to a transient local
increase in ionic strength which can assist disintegration
of the tablet by preventing nonionic surfactant from
swelling and inhibiting dissolution of other materials.
Another possibility is that the said particles which
promote disintegration are particles containing sodium
tripolyphosphate with more than 400 (by weight of the
particles) of the anhydrous 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 II 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
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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.
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.
Particles which contain this phase I form will often
contain the phase I form of sodium tripolyphosphate as at
least 500 or 55% by weight of the tripolyphosphate in the
particles.
Suitable material is commercially available. Suppliers
include Rhone-Poulenc, France and Albright & Wilson, UK.
Another possibility is that the particles which promote
disintegration are particles which contain at least 40 wto
(by weight of the particles) of phase I sodium
tripolyphosphate which is partially hydrated. The extent of
hydration should be at least 0.5o by weight of the sodium
tripolyphosphate in the particles. It preferably lies in a
range from 0.5 to 4o by weight of the particles, or it may
be higher. Indeed fully hydrated sodium tripolyphosphate
may be used to provide these particles.
It is possible that the particles contain at least 40 wto
sodium tripolyphosphate which has a high phase I content
but is also sufficiently hydrated so as to contain at least
0.5o water by weight of the sodium tripolyphosphate.
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The remainder of the tablet composition used to form the
tablet or region thereof may include additional sodium
tripolyphosphate. This may be in any form, including
sodium tripolyphosphate with a high content of the
5 anhydrous phase II form.
Other Ingredients
Tablets of the invention may also contain one of the
detergency enzymes well known in the art for their ability
10 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 Maxatase
15 (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,
Denmark. Detergency enzymes are commonly employed in the
form of granules or marumes, optionally with a protective
20 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.
The 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.
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An antifoam material is advantageously included if organic
surfactant is present, especially if a 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.
It may also be desirable that a tablet of the invention
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 wto, 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 contain
more than 15 wto silicate. A tablet for machine
dishwashing will frequently contain at least 20 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
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22
cellulose and ethyl hydroxyethyl cellulose, fabric-
softening agents; heavy metal sequestrants such as EDTA;
perfumes; and colorants or coloured speckles.
Particle Size and Distribution
A tablet of this invention, or a discrete region of such a
tablet, is a matrix of compacted particles.
Preferably the particulate composition has an average
particle size in the range from 200 to 2000 um, more
preferably from 250 to 1400 um. Fine particles, smaller
than 180 um or 200 um 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 may be
especially relevant to tablets of detergent composition
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 400 g/litre, preferably at least
500 g/litre, and possibly at least 600 g/litre.
A composition which is compacted into a tablet or tablet
region may contain particles which have been prepared by
spray-drying or granulation and which contain a mixture of
CA 02385296 2002-03-18
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23
ingredients. Such particles may contain organic detergent
surfactant and some or all of the water-softening agent
(detergency builder) which is also present in a detergent
tablet.
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
processes described and claimed in EP 367339A (Unilever)
and EP 390251A (Unilever), are inherently suitable for use
in the present invention.
Preferably, separate particles of the water-insoluble,
water-swellable disintegration-promoting material required
for this invention, and any optional water-soluble
particles to promote disintegration, are mixed with the
remainder of the particulate composition prior to
compaction.
Product forms and proportions
The present invention may especially be embodied as a
tablet for fabric washing. Such a tablet will generally
contain, overall, from 5 to 50o by weight of surfactant and
from 5 to 80o by weight of detergency builder which is a
water softening agent. Water-soluble disintegration
promoting particles may be present in an amount from 5% to
25o by weight of the composition. Peroxygen bleach may be
present and if so is likely to be in an amount not
exceeding 25o by weight of the total composition.
25~-09-2Ci01 w yr ~ EP00091 ~
CA 02385296 2002-03-18
24
In another type~of tablet formulation, the tablet may
contain from 0-5% by weight of surfactant, from 0.1-2 0% by
~ weight of said water-swellable disintegration-promoting
particles and either from 50-98% by weight of water-
s softening agent or from 25 to 85% by weight of a bleach.
The invention may be embodied as tablets comprising
water-softening agents, especially water-insoluble
aluminosilicate, in an amount of from 50 to 98 wt % of
the tablet composition. A water-soluble supplementary
builder may well be included, for instance in an amount
from 2%~to 30wt% of the composition, or may be considered
unnecessary and not used.
Water-softening tablets embodying this invention may
include some surfactant.
The invention may be embodied as tablets for machine
dishwashing. Such tablets typically contain a high
proportion of water soluble salts, such as 50 to 95% by
weight, at least some of which, exemplified by sodium
citrate and sodium silicate, have water-softening
properties.
Both water-softening and machine dishwashing tablets may
include nonionic surfactant Which can act as a lubricant
during tablet manufacture and as a low foaming detergent
during use. The amount may be small, e.g. from 0.2 or 0.5%
by weight of the composition up to 3% or 5% by weight.
3~
AMENDED SHEET
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WO 01/21756 PCT/EP00/09191
Tablets for use as a bleaching additive will typically
contain a high proportion of peroxygen bleach, such as 25
to 85o by weight of the composition. This may be mixed
with other soluble salt as a diluent. The composition of
5 such a tablet may well include a bleach activator such as
tetraacetylethylene diamine (TAED). A likely amount would
lie in the range from 1 to 20o by weight of the
composition.
10 The overall quantity of disintegration-promoting water-
swellable material within a tablet may well be from 0.5 to
15o preferably from to to 80 or loo by weight of the whole
tablet.
15 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.
In order to provide water-swellable disintegrant adjacent
to surfaces of the tablet it can be put into a tableting
mould before the remainder of the composition or after the
remainder of the composition, or both, but before the mould
is closed.
In one possible procedure a small quantity of disintegrant-
promoting particulate material is placed in a tableting
mould, the cleaning composition for the bulk of the tablet
is then placed in the mould, a small further quantity of
disintegrant is added to the mould on top of the
composition already in the mould and then the mould is
CA 02385296 2002-03-18
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26
closed and the contents compacted into a tablet. The
resulting tablet will have a greater concentration of
disintegrant adjacent to opposite tablet surfaces than
within the tablet interior.
The surface zone or zones of the tablet in which the water-
swellable disintegrant is concentrated do not need to be
one or more layers with defined boundaries. The water-
swellable disintegrant which is concentrated at one or more
surface zones will generally be mixed at the surface zone
with some of the cleaning composition which also provides
an interior zone where there is less of the water-swellable
disintegrant.
Consequently, water-swellable disintegrant which is to be
concentrated adjacent a tablet surface could be put into a
tableting mould concurrently with some of the cleaning
composition but before the majority of it. It could be put
into a tableting mould after the majority of the cleaning
composition but concurrently with the last part of the
cleaning composition. Furthermore both methods of addition
can be used concurrently.
This invention can be utilised in tablets made with two
separate layers of respective different cleaning
compositions.
The sequence of addition to the mould might then be
(i) a small quantity of swellable disintegrant,
(ii) cleaning composition for one layer of the tablet,
(iii) cleaning composition for the second layer of the
tablet,
CA 02385296 2002-03-18
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27
(iv) a small additional quantity of water-swellable
disintegrant.
Although the surface zones) containing water-swellable
disintegrant do not need to be distinct layers of the
tablet, this is nevertheless possible. So a further
possibility is that the water-swellable disintegrant is
incorporated in a cleaning composition used to form a layer
of the tablet adjacent to a surface or two layers adjacent
two opposite surfaces of the tablet, while a further layer
which provides the tablet interior contains a lesser
concentration of the disintegrant or none at all.
The mould in which the tablet is formed may be provided by
an aperture within a rigid structure and a pair of punches
movable towards each other within the aperture to compact a
composition within 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.
._-...r.- ..,...., yp, ,uJ v~yl~,yvW . w.rw vu i
C 25-09-20tD1 ~ ~ EP00091 ~
CA 02385296 2002-03-18
2a
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 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
ZO 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. The overall density
of a tablet for fabric washing preferably lies in a range
from 1040~or 1050g/litre preferably at least 1100g/litre up
to 140og/litre. The tablet density may well lie in a range
up to no more than 1350 or even 1250g/litre. The overall
density of a tablet of some other cleaning composition,
such as a tablet for machine dishwashing or as a bleaching
additive, may range up to 1700g/litre and will often lie in
a range from 1300 to 1550g/litre.
The accompanying drawings illustrate the formation of a
tablet in accordance with this invention.
Figure 1 is a diagrammatic section of a tableting mould
Fig. 2 is a crass-sectional view of a tablet formed in such
a mould.
Figs. 3, 4 and 5 illustrate the filling of the mould so as
to form a three-layer tablet.
Fig. s is a cross-sectional view of a tablet formed by the
procedure shown in Figs. 3, 4 and 5.
AMENDED SHEET
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29
Referring to Fig. l, the mould is defined by a cylindrical
aperture 10 in a rotary tablet 12 of a tableting machine.
Associated with the aperture 10 are a lower punch 14 and an
upper punch 16 which can be driven into the aperture 10 so
as to compress between them any composition placed in the
aperture. A tablet in accordance with this invention can
be made by placing a small quantity of water-swellable
disintegrant within the aperture 10 so that it lies on the
upper face of the lower punch 14. The mould is then filled
with a composition for the tablet, a further small quantity
of water-swellable disintegrant is placed onto the upper
surface of the composition within the aperture 10, the
punch 16 is then driven down to close the mould and the two
punches are driven together to compact the contents of the
mould into a tablet as shown in Fig. 2 which has flat upper
and lower faces 22 where the water-swellable disintegrant
will be concentrated.
The interior of the tablet and its cylindrical surface 28
are formed solely by the cleaning composition, but at the
flat faces 22 the cleaning composition is mixed with the
water-swellable disintegrant which was put in the mould
before and after the cleaning composition.
Figs. 3 onwards illustrate a slightly different procedure,
also embodying the invention. At a first station shown in
Fig. 3 the lower punch 14 is raised to be slightly below
the upper surface of the rotary table 12. The space above
the lower punch 14 is filled with a composition 24
containing water-swellable disintegrant together with other
constituents.
CA 02385296 2002-03-18
WO 01/21756 PCT/EP00/09191
At a subsequent station the lower punch I4 is lowered to
the position shown in Fig.4 creating a space above the
composition 24 which is filled with a further composition
26 in which either the water-swellable disintegrant is
5 absent or it is present at a lesser concentration than in
composition 24.
Next at a third station shown by Fig. 5 the lower punch 14
is lowered further and more of the composition 24 is filled
10 into the top of the cavity within the rotary table 12.
Then as before the upper punch 16 which has not been shown
in Figs. 3 to 5 is lowered to close the cavity and the
punches 14, 16 are driven together to form a three layer
tablet as illustrated diagrammatical in Fig. 6.
In the tablet of Fig. 6 as in the tablet of Fig. 2 there is
a greater concentration of water-swellable disintegrant
adjacent to surfaces 22 of the tablet than in the interior
of the tablet which has the same composition as regions
adjacent to the cylindrical surface 28 of the tablet.
Example
A detergent base powder, incorporating organic surfactants,
a small percentage of crystalline sodium acetate
trihydrate, and zeolite MAP detergency builder was made
using known granulation technology. It had the following
composition, which is shown both as weight percentages of
the base powder and as parts by weight.
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WO 01/21756 PCT/EP00/09191
31
Ingredient ~ by Parts by
Weight Weight
Sodium linear alkylbenzene 23.65 11.12
sulphonate
nonionic surfactant (C13-15 2.47 i 1.16
branched fatty alcohol 3E0)
nonionic surfactant (C13-15 4.63 2.16
branched fatty alcohol 7E0)
Soap 1.25 0.59
zeolite A24 45.82 21.54
Sodium acetate trihydrate 6.17 2.90
Sodium carbonate 6.63 3.12
sodium carboxymethyl cellulose 0.96 0.45
(SCMC)
Sodium sulphate, moisture and 8.42 3.96
minor ingredients including
soil-release polymer
Total 100 47.00
The amount of zeolite MAP (zeolite A24) in the table above
is the amount which would be present if it was anhydrous.
Its accompanying small content of moisture is included as
part of the moisture and minor ingredients.
The base powder and other ingredients were mixed together
as set out in the following table, to form compositions
indicated as A and B.
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WO 01/21756 PCT/EP00/09191
32
Parts by
Weight
A B
Base powder, as above 44.6 44.6
Fluorescer on sodium carbonate 1.24 1.24
Soil release polymer (18o active) 1.09 1.09
sodium acetate trihydrate 23.5 23.5
Acrylate-maleate copolymer 1.19 1.19
Na-silicate (granular) 800 3.18 3.18
TAED granules (83% active) 5.06 5.06
Percarbonate (coated) 15.0 15.0
Sequestrant granules (bequest 2047) 0.74 0.74
Enzymes 0.88 0.88
Minor ingredients 1.77 1.77
Arbocel Al 8 7.5
TOTAL 100.00 99.5
Arbocel Al is a water-insoluble cellulosic disintegrant
obtained from wood pulp. It was sieved before use and the
fraction which was used had a particle size in the range
500-710 micrometers.
Formulation A was compacted in a laboratory press to
produce cylindrical tablets with a weight of approximately
40 grams. The moveable dies had elastomer on their faces
which contacted the composition placed in the mould.
Formulation B was also used to make tablets using the same
press and mould parts. However, the procedure followed was
that a quantity of Arbocel equal to 0.250 of the
formulation was sprinkled into the empty mould so as to lie
on the upper surface of the lower punch as described
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WO 01/21756 PCT/EP00/09191
33
earlier with reference to Fig. l, then the formulation B
was placed in the mould cavity and finally a further
quantity of Arbocel A1 again in a quantity equivalent to
0.250 of the total composition was sprinkled on top of the
composition before the upper punch was driven into the
mould to compact the composition to a tablet. Thus tablets
of formulation A and tablets from formulation B had
identical overall composition but in the case of the
tablets from formulation B there was a greater
concentration of Arbocel A1 adjacent the upper and lower
surfaces of the tablets than in the tablet interior.
The tablets were tested by placing two previously weighed
tablets of each type in a washing machine dispenser. The
dispenser was of a type used in Philips washing machines.
Water at 10°C flowing at a rate of 5 litres per minute was
passed through the dispenser for a period of one minute,
the residue of the tablets remaining in the dispenser was
then removed, re-weighed, dried at 100°C for 24 hours to
give constant weight and weighed again.
With tablets of formulation A, residue collected from the
dispenser tray and dried to constant weight was found to be
more than 80o of the original weight of the tablet placed
in the dispenser tray.
By contrast with tablets from formulation B where a small
quantity of the Arbocel was concentrated adjacent the upper
and lower surfaces of the tablets, the residue recovered
from the tray and dried to constant weight was less than
150 of the original weight of the tablets. Thus, under
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34
identical conditions, tablets in accordance with the
invention disintegrated to a much greater extent.
