Note: Descriptions are shown in the official language in which they were submitted.
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MULTI LAYER DETERGENT TABLET WITH DIFFERENT HARDNESS
The present invention relates to detergent tablets, especially those adapted
for
use in washing.
Although cleaning compositions in tablet form have often been proposed, these
have not (with the exception of soap bars for personal washing) gained any
substantial success, despite the several advantages of products in a unit
dispensing form. One of the reasons for this may be that detergent tablets
usually dissolve slower than the constituent powders from which they are made,
simply because the constituent powders are forced close together in the
tablet,
with comparatively little opportunity for water to permeate between them. This
gives rise to the problem that slow dissolving tablets cause residues which
may
for example be visible through the door of the washing machine during the wash
cycle, or which stick to the fabrics at the-end of the wash cycle, or both.
This
may be compensated by using low compression forces to keep high porosity
and good dissolution profile. However, such tablets are typically softer and
have
mechanical characteristics such that breakage is likely to occur during
production or handling.
DE-A-2 207 633, published on the 30'" of August 1973, discloses tablets having
three layers, the middle layer being sandwiched between two end layers, the
two end layers being made so as to protect the middle layers from mechanical
shocks, while allowing tablet dissolution in less than a minute.
However, particularly in certain front loading washing machines, problems of
tablet residues appearing visibly at the window of the washing machine have
still been encountered. indeed, in particular for detergent tablets, the
dissolution
problems are particularly acute, due for example to the tendency of gelling of
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the surfactant materials, or to low level of water used for environmental
reasons,
or due to dissolution at low temperature, etc...
The object of the present invention is to provide detergent tablets typically
formed by compressing a particulate material, the tablet being suitable for
storing, shipping and handling without breakage while dissolving easily and
rapidly in wash solution, releasing the active ingredients into the wash
solution
and completely disintegrating and dispersing in alkaline or surfactant-rich
solutions such as the wash liquor.
Summary of the Invention
The object of the invention is achieved by providing a detergent tablet having
at
least a first and a second layer, whereby the first layer is softer than the
second
layer, and if said tablet has more than two layers, the tablet is such that a
softer
layer is situated at an end of the tablet.
Detailed Description of the Invention
Figure 1 represents two typical profiles for measuring the elasticity of a
layer or
of a tablet, the profile representing the load applied to the tablet or layer,
corresponding to the resistance of the tablet or layer, in function of the
displacement of the load along the main axis of the tablet or layer. A curve
corresponding to a more elastic and to a less elastic tablet or layer are
shown,
together with schematics showing the structural changes to which the tablet or
layer is submitted during the measurement.
Figure 2 represents a typical profile for measuring the elasticity of a layer
or of a
tablet, the profile representing the load applied to the tablet or layer,
corresponding to the resistance of the tablet or layer, in function of the
displacement of the load along the main axis of the tablet or layer. The
breaking
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point giving the maximum height H of the curve is marked, as well as the area
A
under the curved taken from the breaking point, whereby the elasticity is
deduced from this by dividing A by H.
The invention relates to a detergent tablet. By detergent, it is meant that
the
tablet comprises surfactants. A tablet is defined as having a height along a
main
axis and a cross section normal to the main axis, the cross section being
preferably substantially constant when travelling along the main axis, the
tablet
having two ends, each end being situated at each end of the main axis and
having a surface area substantially equal to the cross section of the tablet.
The tablet is such that it comprises at least a first and a second layer.
Normally,
these layers are produced by compression of particulate materials. Composition
of these layers may be similar or different, and compression force used for
forming these layers may also be similar or different. It should be noted that
a
preferred embodiment of a tablet according to the invention comprises only two
layers, but tablets with more layers may be considered.
According to the invention, a layer is preferably a part of a tablet made from
compressing particulate materials, this part of the tablet having a height
along
the main axis of the tablet and a cross section corresponding to the cross
section of the tablet, such that the composition or the physical and
mechanical
characteristics of this part differs from the rest of the tablet. In other
words, a
tablet according to the invention is made by piling up layers along the main
axis
to form the tablet, this layers adhering to each other to form the tablet,
adhesion
befinreen layers being provided by mechanical or chemical means. ~ aKen
independently, each layer may be considered as a mono-layer tablet, as far as
composition is concerned, for example.
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According to the invention, the first layer is softer than the second layer.
By
softer, it should be understood that the tensile strength is lower than the
tensile
strength of the second layer. When more than two layers are present in the
tablet, a softer layer is simply a layer such that there is another layer in
the
tablet which is less soft. In other words, if three layers are present with
gradual
and different softness, there are two softer layers. According to the
invention,
the softest layer is the layer most soft among all layers in the tablet. Same
applies for harder, i.e. less soft, or hardest, i.e. least soft. Typically,
the softer
layer has a tensile strength 10% lower than the tensile strength of a .harder
layer
part of the same tablet, preferably 20°~ lower, more preferably
30°~ lower, even
more preferably 40% lower and most preferably 50% lower. According to the
invention, the softness-hardness scale is measured by the tensile strength of
the tablet.
According to the invention, if said tablet has more than two layers, the
tablet is
such that a softer layer is situated at an end of the tablet. The softer layer
is not
necessarily the softest layer. In a preferred embodiment, the softest layer is
situated at one end. This is beneficial to dissolution because the surface
activity
of this soft layer is high because it is exposed as it is situated at one end.
Indeed, according to the invention, the mechanical properties and the
dissolution properties of a single tablet can be rendered more independent the
ones from the others, so that a harder layer will more specifically provide
mechanical integrity and protection while a softer layer will more
specifically
favour fast and efficient dissolution.
The level of softness of different layers may be set using different
parameters,
such as different chemical composition, or different compression force. In
particular, if using different compositions, a layer may comprise more binders
than another one to be made harder, i.e. less soft. It should be noted that it
is
preferred that a softer layer comprises higher leveis of surfactant per
weight.
indeed, a softer layer will more readily dissolve, and therefore will
compensate
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gelling of surfactants by its softness. Indeed, gelling of surfactant is
hindering
fast and effective dissolution, which can be compensated by concentrating such
surfactants in a softer layer. This can be advantageously combined with use of
highly soluble compounds, hydrotrope compounds, and compounds providing
high cohesive effect at lower compression force, for example.
In another preferred embodiment and in a two layer tablet according to the
invention, the tablet is such that the less soft layer is situated at an end
of the
tablet. Indeed, it was found sufficient to obtain good mechanical
characteristics
to have one harder layer at one end of the tablet. This particularly applies
to the
method for making a tablet according to the invention, whereby the less soft
layer of the tablet is placed at the bottom end of the tablet during
production.
Even more preferably, the least soft layer is placed at the bottom end of the
tablet during production. Indeed, mechanical stress is particularly high
during
production, and almost only the bottom end of the tablet is exposed to
mechanical constraints at this stage. Furthermore, this allows to obtain good
mechanical resistance while allowing to place a softer layer at the other end
of
the tablet, whereby this softer layer will benefit of a higher surface of
contact
with solution when dissolving the tablet in solution.
Such mechanical resistance was found to be improved when using a tablet
having a substantially rectangular cross section. Indeed, solidity of the
tabtet
could be improved at constant compression value by using a rectangular tablet.
At equal weight, equal compression force, equal composition, equal height and
equal volume, rectangular tablet have a mechanical resistance significantly
improved when compared to round tablets. This particularly applies to square
tablets.
A layer may preferably have a height varying between 5 and 95°~ of
the total
tablet height. More preferably, the harder the layer is, the thinner it is to
have a
minimum impact on the overall dissolution of the entire tablet.
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Typically, a two layer tablet according to the invention will comprise a soft
layer
having a tensile strength between 5 and 100 kPa, whereas the hard layer is
having a tensile strength comprised between 5.5 and 150 kPa.
Elasticity
In a preferred embodiment according to the invention, the tablet comprises at
least two layers having a different elasticity, the more elastic layer being
more
resistant to mechanical shocks, the more brittle layer having better
dissolution
characteristics. Indeed, a less elastic layer, thereby more brittle, will
disperse
readily in solution. In a most preferred embodiment, according to the
invention,
a softer layer is also a more brittle layer, and a harder layer is also more
elastic.
However, this may not be the case.
The elasticity of a tablet or of a layer from a tablet is evaluated as
follows:
1- A load is pressed flat onto one end of the tablet or layer for which the
elasticity is tested, the load being pressed along the direction of the main
axis of
the tablet or layer.
2- The force by the load is measured in function of the displacement of the
load.
3- Two possible curves obtained by this method are illustrated in Figure 1.
These two curves are showing the type of curves obtained for two different
tablets or layers, one of the tablet being more elastic than the other, which
in
tum is more brittle (=less elastic). The elasticity value corresponding to the
tablet or layer tested is deduced from this experimental curve as follows:
The area under the curve and beyond the breaking point is calculated by
integrating the curve from its top value up to large displacement values. This
area A is then divided by the height H of the curve at the breaking point for
normalising the elasticity of the tablet or layer, E. This is illustrated in
Figure 2.
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High values for E represent high elasticity, while low value represent highly
brittle layers or tablets.
In order to achieve this test, the following equipment was used:
Instron 4444 series machine tester with a standard load cell of 2kN linked to
a normal PC computer. The program used to make the calculations was a
Series IX version 7.49.00 provided by the equipment supplier.
A Plexiglas cylinder of 25 mm diameter, 30 mm height and a weight of 18 gr.
was used to crush the tablet or layer
A standard dye to make tablets or layers, this dye having a of 54 mm
diameter.
~ the tablet or layer is placed between the plates of the Instron 4444 and the
Plexiglas cylinder is placed in the middle of the tablet or layer end.
~ The cross head of the load cell moves at a constant speed of 10 mmlmin and
the computer starts to record the force of resistance of the tablet versus the
displacement of the cylinder into the tablets.
~ The elasticity is calculated by dividing the area under the slope after the
breakage point by its maximum height (see figures and explanations above).
~ The elasticity is hereby measured in JIkN (Joules for the area and kN for
the
maximum height used to normalise the area curves).
Typically, the elasticity value for a preferred embodiment of tablets
according to
the invention and more particularly adapted for laundry use is comprised
between 0.5 and 5 JIkN, and more preferably between 1 and 4 JIkN. It is
preferred that a more elastic layer or tablet for laundry use, for example,
has an
elasticity comprised between 3 and 4JIkN, more preferably between 3.1 and 3.5
J/kN. It is preferred that a more brittle layer or tablet for laundry use,
.for
example, has an elasticity comprised between 1.5 and 2.5JIkN, more preferably
between 1.7 and 2.1 JIkN.
Highly soluble Compounds
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In a preferred embodiment, the tablet preferably comprises a highly soluble
compound. More preferably, this compound is comprised or is present at higher
levels per weight in the relatively hard layer of the tablet, i.e. the less
soft layer,
in order to further favour dissolution. Indeed, it may be preferred to aid
dissolution of the harder layer, as this layer will for example be more
compressed than a softer layer. Such a compound could be formed from a
mixture or from a single compound. A highly soluble compound is defined as
follow:
A solution is prepared as follows comprising de-ionised water as well as 20
grams per litre of a specific compound:
1- 20 g of the specific compound is placed in a Sotax Beaker. This beaker is
placed in a constant temperature bath set at 10°C. A stirrer with a
marine
propeller is placed in the beaker so that the bottom of the stirrer is at 5 mm
above the bottom of the Sotax beaker. The mixer is set at a rotation speed of
200 turns per minute.
2- 980 g of the de-ionised water is introduced into the Sotax beaker.
3- 10 s after the water introduction, the conductivity of the solution is
measured,
using a conductivity meter.
4- Step 3 is repeated after 20, 30, 40, 50, 1 min, 2 min, 5 min and 10 min
after
step 2.
5- The measurement taken at 10 min is used as the plateau value or maximum
value.
The specific compound is highly soluble according to the invention when the
conductivity of the solution reaches 80°~ of its maximum value in less
than 10
seconds, starting from the complete addition of the de-ionised water to the
compound. Indeed, when monitoring the conductivity in such a manner, the
conductivity reaches a plateau after a certain period of time, this plateau
being
considered as the maximum value. Such a compound is preferably in the form of
a flowable material constituted of solid particles at temperatures comprised
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between 10 and 80°Celsius for ease of handling, but other forms may be
used
such as a paste or a liquid.
Example of highly soluble compounds include Sodium di isoalkyibenzene
sulphonate or Sodium toluene sulphonate.
Cohesive Effect
In a preferred embodiment of this invention, the tablet preferably comprises a
compound having a Cohesive Effect on the particulate material of a detergent
matrix forming the tablet. More preferably, this compound is comprised or is
present at higher levels per weight in the relatively hard layer of the
tablet, i.e.
the less soft layer, in order to obtain satisfactory hardness without need for
high
compression. The Cohesive Effect on the particulate material of a detergent
matrix forming the tablet or a layer of the tablet is characterised by the
force
required to break a tablet or layer based on the examined detergent matrix
pressed under controlled compression conditions. For a given compression
force, a high tablet or layer strength indicates that the granules stuck
highly
together when they were compressed, so that a strong cohesive effect is taking
place. Means to assess tablet or layer strength (also refer to diametrical
fracture
stress) are given in Pharmaceutical dosage forms : tablets volume 1 Ed. H.A.
Lieberman et al, published in 1989.
The cohesive effect is measured by comparing the tablet or layer strength of
the
original base powder without compound having a cohesive effect with the tablet
or layer strength of a powder mix which comprises 97 parts of the original
base
powder and 3 parts of the compound having a cohesive effect. The compound
having a cohesive effect is preferably added to the matrix in a form in which
it is
substantially free of water (water content below 10% (pref. below 5%)). The
temperature of the addition is between 10 and 80C, more pref. between 10 and
40C.
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A compound is defined as having a cohesive effect on the particulate material
according to the invention when at a given compacting force of 3000N, tablets
with a weight of 50g of detergent particulate material and a diameter of 55mm
have their tablet tensile strength increased by over 30°~ (preferably
60. and
more preferably 100%) by means of the presence of 3°r6 of the compound
having a cohesive effect in the base particulate material.
An example of a compond having a cohesive effect is Sodium di
isoalkylbenzene sulphonate.
When integrating a highly soluble compound having also a cohesive effect on
the particulate material used for a tablet or layer formed by compressing a
particulate material comprising a surfactant, the dissolution of the tablet or
layer
in an aqueous solution is significantly increased. In a preferred embodiment,
at
least 1 °~ per weight of a tablet or layer is formed from the highly
soluble
compound, more preferably at feast 2%, even more preferably at lest 3°~
and
most preferably at least 5% per weight of the tablet or layer being formed
from
the highly soluble compound having a cohesive effect on the particulate
material.
It should be noted that a composition comprising a highly soluble compound as
well as a surfactant is disclosed in EP-A-0 524 075, this composition being a
liquid composition.
A highly soluble compound having a cohesive effect on the particulate material
allows to obtain a tablet having a higher tensile strength at constant
compacting
force or an equal tensile strength at lower compacting force when compared to
traditional tablets. Typically, a whole tablet will have a tensile strength of
more
than SkPa, preferably of more than lOkPa, more preferably, in particular for
use
in laundry applications, of more than lSkPa, even more preferably of more than
30 kPa and most preferably of more than 50 kPa, in particular for use in dish
washing or auto dish washing applications; and a tensile strength of less than
300 kPa, preferably of less than 200 kPa, more preferably of less than 100
kPa,
even more preferably of less than 80 kPa and most preferably of less than 60
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kPa. Indeed, in case of laundry application, the tablets should be less
compressed than in case of auto dish washing applications for example,
whereby the dissolution is more readily achieved, so that in a laundry
application, the tensile strength is preferably of less than 30 kPa.
This allows to produce tablets or layers which have a solidity and mechanical
resistance comparable to the solidity or mechanical resistance of traditional
tablets while having a less compact tablet or layer thus dissolving more
readily.
Furthermore, as the compound is highly soluble, the dissolution of the tablet
or
layer is further facilitated, resulting in a synergy leading to facilitated
dissolution
for a tablet according to the invention.
Tablet Manufacture
For the purpose of manufacture of a single layer, the layer may be considered
as a tablet itself.
Detergent tablets of the present invention can be prepared simply by mixing
the
solid ingredients together and compressing the mixture in a conventional
tablet
press as used, for example, in the pharmaceutical industry. Preferably the
principal ingredients, in particular gelling surfactants, are used in
particulate
form. Any liquid ingredients, for example surfactant or suds suppressor, can
be
incorporated in a conventional manner into the solid particulate ingredients.
In particular for laundry tablets, the ingredients such as builder and
surfactant
can be spray-dried in a conventional manner and then compacted at a suitable
pressure. Preferably, the tablets according to the invention are compressed
using a force of less than 100000N, more preferably of less than 50000N, even
more preferably of less than 5000N and most preferably of less than 3000 N.
indeed, the most preferred embodiment is a tablet suitable for laundry
compressed using a force of less than 2500N, but tablets for auto dish washing
may also be considered for example, whereby such auto dish washing tablets
are usually more compressed than laundry tablets.
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The particulate material used for making the tablet of this invention can be
made
by any particulation or granulation process. An example of such a process is
spray drying (in a co-current or counter current spray drying tower) which
typically gives low bulk densities 600811 or lower. Particulate materials of
higher
density can be prepared by granulation and densification in a high shear batch
mixerlgranulator or by a continuous granulation and dens~cation process (e.g.
using Lodige~ CB andlor Lodige~ KM mixers). Other suitable processes
include fluid bed processes, compaction processes (e.g. roll compaction),
extrusion, as well as any particulate material made by any chemical process
like
flocculation, crystallisation sentering, etc. Individual particles can also be
any
other particle, granule, sphere or grain.
The components of the particulate material may be mixed together by any
conventional means. Batch is suitable in, for example, a concrete mixer, Nauta
mixer, ribbon mixer or any other. Alternatively the mixing process may be
carried
out continuously by metering each component by weight on to a moving belt,
and blending them in one or more drums) or mixer(s). Non-gelling binder can
be sprayed on to the mix of some, or all of, the components of the particulate
material. Other liquid ingredients may also be sprayed on to the mix of
components either separately or premixed. For example perfume and slurries of
optical brighteners may be sprayed. A finely divided flow aid (dusting agent
such as zeolites, carbonates, silicas) can be added to the particulate
material
after spraying the binder, preferably towards the end of the process, to make
the
mix less sticky.
The tablets may be manufactured by using any compacting process, such as
tabletting, briquetting, or extrusion, preferably tabletting. Suitable
equipment
includes a standard single stroke or a rotary press (such as Courtoy~, Korch~,
Manesty~, or Bonals~). The tablets prepared according to this invention
preferably have a diameter of between 20mm and 60mm, preferably of at least
35 and up to 55 mm, and a weight between 25 and 100 g. The ratio of height to
diameter (or width) of the tablets is preferably greater than 1:3, more
preferably
greater than 1:2. The compaction pressure used for preparing these tablets
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need not exceed 100000 kNlm2, preferably not exceed 30000 kNlm2, more
preferably not exceed 5000 kN/m2, even more preferably not exceed 3000kNlmZ
and most preferably not exceed 1000kNImZ. in a preferred embodiment
according to the invention, the tablet has a density of at least 0.9 glcc,
more
preferably of at least 1.0 glcc, and preferably of less than 2.0 glcc, more
preferably of less than 1.5 glcc, even more preferably of less than 1.25 glcc
and
most preferably of less than 1.1 glcc.
Multi layered tablets are typically formed in rotating presses by placing the
matrices of each layer, one after the other in matrix force feeding ftasks. As
the
process continues, the matrix layers are then pressed together in the pre-
compression and compression stages stations to form the multilayer layer
tablet.
With some rotating presses it is also possible to compress the first feed
layer
before compressing the whole tablet.
Hydrotrope compound
In a preferred embodiment of the invention, a highly soluble compound having a
cohesive effect is integrated to the tablet of the invention, whereby this
compound is also a hydrotrope compound. Such hydrotrope compound may be
generally used to favour surfactant dissolution by avoiding gelling, so that
they
may be for example advantageously comprised in a softer layer. A specific
compound is defined as being hydrotrope as follows (see S.E. Friberg and M.
Chiu, J. Dispersion Science and Technology, 9(5&6), pages 443 to 457, (1988-
1989)):
1. A solution is prepared comprising 25% by weight of the specific compound
.and 75% by weight of water.
2. Octanoic Acid is thereafter added to the solution in a proportion of 1.6
times
the weight of the specific compound in solution, the solution being at a
temperature of 20°Celsius. The solution is mixed in a Sotax beaker with
a
stirrer with a marine propeller, the propeller being situated at about 5mm
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above the bottom of the beaker, the mixer being set at a rotation speed of
200 rounds per minute.
3. The specific compound is hydrotrope if the the Octanoic Acid is completely
solubilised, i.e . if the solution comprises only one phase, the phase being a
liquid phase.
It should be noted that in a preferred embodiment of the invention, the
hydrotrope compound is a flowable material made of solid particles at
operating
conditions between 15 and 60° Celsius.
Hydrotrope compounds include the compounds listed thereafter:
A list of commercial hydrotropes could be found in McCutcheon's Emuls~ers
and Detergents published by the McCutcheon division of Manufacturing
Confectioners Company. Compounds of interest also include:
1. Nonionic hydrotrope with the following structure:
R ~ O - (CH2CH20~ CH -CH20~H
CH3
where R is a C8-C10 alkyl chain, x ranges from 1 to 15, y from 3 to 10.
2. Anionic hydrotropes such as alkali metal aryl sulfonates. This includes
alkali
metal salts of benzoic acid, salicylic acid, bezenesulfonic acid and its many
derivatives, naphthoic acid and various hydroaromatic acids. Examples of these
are sodium, potassium and ammonium benzene sulfonate salts derived from
toluene sulfonic acid, xylene sulfonic acid, cumene sulfonic acid, tetralin
sulfonic
acid, naphtalene sulfonic acid, methyl- naphtalene sulfonic acid, dimethyl
naphtalene sulfonic acid, trimethyl naphtalene sulfonic acid=
Other examples include salts of dialkyl benzene sulfonic acid such as salts of
di-
isopropyl benzene sulfonic acid, ethyl methyl benzene sulfonic acid, alkyl
benzene sulfonic acid with an alkyl chain length with 3 to 10, (pref. 4 to 9),
linear
or branched alkyl sulfonates with an alkyl chain with 1 to 18 carbons.
3. Solvent hydrotropes such as alkoxylated glycerines and alkoxylated
glycerides, esters slakoxylated glycerines, alkoxylated fatty acids, esters of
glycerin, polyglycerol esters.,Preferred alkoxylated glycerines have the
following
structure:
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R
rp~~H~OI~
R
CHiO(-CH~H-dlnH
R
CN=.O(-CH~CH~O~,H
where I, m and n are each a number from 0 to about 20, with I+m+n = from about
2 to about 60, preferably from about 10 to about 45 and R represents H, CH3 or
CZHs
Preferred alkoxylated glycerides have the following struture
-H
where R1 and R2 are each C"C00 or -(CH2CHR3-Oy~-H where R3 = H, CH3 or
CZHs and l is a number from 1 to about 60, n is a number from about 6 to about
24.
4. Polymeric hydrotropes such as those described in EP636687:
R Rt
-(CHr y,~ - (Cllr )r'
E Rz
where E is a hydrophilic functional group,
R is H or a C1-C10 alkyl group or is a hydrophilic functional group;
R1 is H a lower alkyl group or an aromatic group,
R2 is H or a cyclic alkyl or aromatic group.
The polymer typically has a molecular weight of between about 1000 and
1000000.
5. Hydrotrope of unusual structure such as 5-carboxyl-hexyl-2-cyciohexene-1-
yl octanoic acid (Diacid~)
Use of such compound in the invention would further increase the dissolution
rate of the tablet, as a hydrotrope compound facilitates dissolution of
surfactants, for example. Such a compound could be formed from a mixture or
from a single compound.
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Coating
Solidity of the tablet according to the invention may be further improved by
making a coated tablet, the coating covering a non-coated tablet according to
the invention, thereby further improving the mechanical characteristics of the
tablet while maintaining or further improving dissolution.
This very advantageously applies to multi-layer tablets according to the
invention, whereby the mechanical characteristics of a harder layer can be
transmitted via the coating to the rest of the tablet, thus combining the
advantage of the coating with the advantage of the harder layer. Indeed,
mechanical constraints will be transmitted through the coating, thus improving
mechanical integrity of the tablet.
In one embodiment of the present invention, the tablets may then be coated so
that the tablet does not absorb moisture, or absorbs moisture at only a very
slow
rate. The coating is also strong so that moderate mechanical shocks to which
the tablets are subjected during handling, packing and shipping result in no
more than very low levels of breakage or attrition. Finally the coating is
preferably brittle so that the tablet breaks up when subjected to stronger
mechanical shock. Furthermore it is advantageous if the coating material is
dissolved under alkaline conditions, or is readily emulsified by surfactants.
This
contributes to avoiding the problem of visible residue in the window of a
front-
loading washing machine during the wash cycle, and also avoids deposition of
undissolved particles or lumps of coating material on the laundry load.
Water solubility is measured following the test protocol of ASTM E1148-87
entitled, "Standard Test Method for Measurements of Aqueous Solubility".
Suitable coating materials are dicarboxylic acids. Particularly suitable
dicarboxylic.acids are selected from the group consisting of oxalic acid,
malonic
acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid,
azeiaic
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acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic
acid
and mixtures thereof.
The coating material has a melting point preferably of from 40 °C to
200 °C.
The coating can be applied in a number of ways. Two preferred coating
methods are a) coating with a molten material and b) coating with a solution
of
the material.
In a), the coating material is applied at a temperature above its melting
point,
and solidifies on the tablet. In b), the coating is applied as a solution, the
solvent
being dried to leave a coherent coating. The substantially insoluble material
can
be applied to the tablet by, for example, spraying or dipping. Normally when
the
molten material is sprayed on to the tablet, it will rapidly solidify to form
a
coherent coating. When tablets are dipped into the molten material and then
removed, the rapid cooling again causes rapid solidification of the coating
material. Clearly substantially insoluble materials having a melting point
below
40 °C are not sufficiently solid at ambient temperatures and it has
been found
that materials having a melting point above about 200 °C are not
practicable to
use. Preferably, the materials melt in the range from 60 °C to 160
°C, more
preferably from 70 °C to 120 °C.
By "melting point" is meant the temperature at which the material when heated
slowly in, for example, a capillary tube becomes a clear liquid.
A coating of any desired thickness can be applied according to' the present
invention. For most purposes, the coating forms from 1 % to 10%, preferably
from 1.5% to 5%, of the tablet weight.
The tablet coatings of the present invention are very hard and provide extra
strength to the tablet.
In a preferred embodiment of the present invention the fracture of the coating
in
the wash is improved by adding a disintegrant in the coating. This
disintegrant
will swell once in contact with water and break the coating in small pieces.
This
will improve the dissolution of the coating in the wash solution. The
disintegrant
is suspended in the coating melt at a level of up to 30°r6, preferably
between 5%
and 20%, most preferably between 5 and 10% by weight. Possible disintegrants
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are described in Handbook of Pharmaceutical Excipients (1986). Examples of
suitable disintegrants include starch: natural, modified or pregelatinized
starch,
sodium starch gluconate; gum: agar gum, guar gum, locust bean gum, karaya
gum, pectin gum, tragacanth gum; croscarmylose Sodium, crospovidone,
cellulose, carboxymethyl cellulose, algenic acid and its salts , including
sodium
alginate, silicone dioxide, clay, polyvinylpyrrolidone, soy polysacharides,
ion
exchange resins and mixtures thereof.
Tensile Strength
For the purpose of measuring tensile strength of a layer, the layer may be
considered as a tablet itself.
Depending on the composition of the starting material, and the shape of the
tablets, the used compacting force may be adjusted to not affect the tensile
strength, and the disintegration time in the washing machine. This process may
be used to prepare homogenous or layered tablets of any size or shape.
For a' cylindrical tablet, the tensile strength corresponds to the diametrical
fracture stress (DFS) which is a way to express the strength of a tablet or
layer,
and is determined by the following equation
Tensile strength = 2 FI nDt
Where F is the maximum force (Newton) to cause tensile failure (fracture)
measured by a VK 200 tablet hardness tester supplied by Van Kell industries,
(nc. D is the diameter of the tablet or layer, and t the thickness of the
tablet or
layer. For a non round tablet, nD may simply be replaced by the perimeter of
the
tablet.
(Method Pharmaceutical Dosage Forms : Tablets Volume 2 Page 213 to 217).
A tablet having a diametral fracture stress of less than 20 kPa is considered
to
be fragile and is likely to result in some broken tablets being delivered to
the
consumer. A diametral fracture stress of at least 25 kPa is preferred.
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This applies similarly to non cylindrical tablets, to define the tensile
strength,
whereby the cross section normal to the height of the tablet is non round, and
whereby the force is applied along a direction perpendicular to the direction
of
the height of the tablet and normal to the side of the tablet, the side being
perpendicular to the non round cross section.
Tablet Dispensing
The rate of dispensing of a detergent tablet can be determined in the
following
way:
Two tablets, nominally 50 grams each, are weighed, and then placed in the
dispenser of a Baucknecht~ WA9850 washing machine. The wafer supply to the
washing machine is set to a temperature of 20 °C and a hardness of 21
grains
per gallon, the dispenser water inlet flow-rate being set to 8 Ilmin. The
level of
tablet residues left in the dispenser is checked by switching the washing on
and
the wash cycle set to wash program 4 (whitelcolors, short cycle). The
dispensing percentage residue is determined as follows:
°~ dispensing= residue weight x 100 I original tablet weight
The level of residues is determined by repeating the procedure 10 times and an
average residue level is calculated based on the ten individual measurements.
In this stressed test a residue of 40 % of the starting tablet weight is
considered
to be acceptable. A residue of less than 30% is preferred, and less than 25%
is
more preferred.
It should be noted that the measure of water hardness is given in the
traditional
°grain per gallon" unit, whereby 0.001 mole per litre = 7.0 grain per
gallon,
representing the concentration of Ca2~ ions in solution.
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Effervescent
In another preferred embodiment of the present invention the tablets further
comprises an effervescent.
Effervescency as defined herein means the evolution of bubbles of gas from a
liquid, as the result of a chemical reaction between a soluble acid source and
an
alkali metal carbonate, to produce carbon dioxide gas,
i.e. CgH807 + 3NaHC03 ~ Na3CgH807 + 3C02 ~ + 3H20
Further examples of acid and carbonate sources and other effervescent systems
may be found in : (Pharmaceutical Dosage Forms : Tablets Volume 1 Page 287
to 291 ).
An effervescent may be added to the tablet mix in addition to the detergent
ingredients. The addition of this effervescent to the detergent tablet
improves
the disintegration time of the tablet. The amount will preferably be between 5
and 20 °~ and most preferably between 10 and 20% by weight of the
tablet.
Preferably the effervescent should be added as an agglomerate of the different
particles or as a compact, and not as separated particles.
Due to the gas created by the effervescency in the tablet, the tablet can have
a
higher D.F.S. and still have the same disintegration time as a tablet without
effervescency. When the D.F.S. of the tablet with effervescency is kept the
same as a tablet without, the disintegration of the tablet with effervescency
will
be faster.
Further dissolution aid could be provided by using compounds such as sodium
acetate or urea. A list of suitable dissolution aid may also be found in
Pharmaceutical Dosage Forms: Tablets, Volume 1, Second edition, Edited by
H.A. Lieberman et all, ISBN 0-8247-8044-2.
Detersive surfactants
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Surfactant are comprised in the tablet according to the invention. The
dissolution of surfactants is favoured by the addition of the highly soluble
compound.
Nonlimiting examples of surfactants useful herein typically at levels from
about
1°r6 to about 55°~, by weight, include the conventional C11_C18
alkyl benzene
sulfonates ("LAS") and primary, branched-chain and random C1p_C20 alkyl
sulfates ("AS"), the C1p_C1g secondary (2,3) alkyl sulfates of the formula
CH3(CH2)x(CHOS03_M+) CH3 and CH3 (CH2)y(CHOS03_M+) CH2CH3 where
x and (y + 1 ) are integers of at least about 7, preferably at least about 9,
and M
is a water-solubilizing ration, especially sodium, unsaturated sulfates such
as
oleyl sulfate, the C1p_C1g alkyl alkoxy sulfates ("AEXS'; especiaNy EO 1-7
ethoxy sulfates), C1p_C1g alkyl alkoxy carboxylates (especially the EO 1-5
ethoxycarboxylates), the C10-18 9lY~rol ethers, the C10_C1g alkyl
polyglycosides and their corresponding sulfated polyglycosides, and C12_C~8
alpha-sulfonated fatty ~ acid esters. If desired, the conventional nonionic
and
amphoteric surfactants such as the C12_C1g alkyl ethoxylates ("AE") including
the so-called narrow peaked .alkyl ethoxylates and Cg-C12 alkyl phenol
alkoxylates (especially ethoxylates and mixed ethoxy/propoxy), ~C12_C18
betaines and sulfobetaines ("sultaines"), C10_C1g amine oxides, and the like,
'
can also be included in the overall compositions. The C10-C18 N-alkyl
polyhydroxy fatty acid amides can also be used. Typical examples include the
C12-C1g N-methyiglucamides. See WO 9,206,154. Other sugar-derived
surfactants include the N-alkoxy polyhydroxy fatty acid amides, such as C 10'
C18 N-(3-methoxypropyl) glucamide. The N-propyl through N-hexyl C12-C18
glucamides can be used for low sudsing. C10-C20 conventional soaps may
also be used. If high sudsing is desired, the branched-chain C10-C16 soaps
may be used. Mixtures of anionic and nonionic surfactants are especially
useful. Other conventional useful surfactants are listed in standard texts. In
a
preferred embodiment, the tablet comprises at least 5% per weight of
surfactant,
more preferably at least 15% per weight, even more preferably at least 25% per
weight, and most preferably between 35% and 45°~ per weight of
surfactant.
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Non gelling binders
Non gelling binders can be integrated to the particles forming the tablet in
order
to further facilitate dissolution.
If non gelling binders are used, suitable non-gelling binders include
synthetic
organic polymers such as polyethylene giycols, polyvinylpyrrolidones,
polyacrylates and water-soluble acrylate copolymers. The handbook of
Pharmaceutical Excipients second edition, has the following binders
classification: Acacia, Alginic Acid, Carbomer, Carboxymethylcellulose sodium,
Dextrin, Ethylcellulose, Gelatin, Guar gum, Hydrogenated vegetable oil type f,
Hydroxyethyl cellulose, Hydroxypropyl methylcellulose, Liquid glucose,
Magnesium aluminum silicate, Maltodextrin, Methyfceliulose, polymethacrylates,
povidone, sodium alginate, starch and zein. Most preferable binders also have
an active cleaning function in the laundry wash such as cationic polymers,
i.e.
ethoxylated hexamethylene diamine quaternary compounds, bishexamethylene
triamines, or others such as pentaamines, ethoxylated polyethylene amines,
malefic acrylic polymers.
Non-gelling binder materials are preferably sprayed on and hence have an
appropriate melting point temperature below 90°C, preferably below
70°C and
even more preferably below 50°C so as not to damage or degrade the
other
active ingredients in the matrix. Most preferred are non-aqueous liquid
binders
(i.e. not in aqueous solution) which may be sprayed in molten form. However,
they may also be solid binders incorporated into the matrix by dry addition
but
which have binding properties within the tablet.
Non-gelling binder materials are preferably used in an amount within the range
from 0.1 to 15% of the composition, more preferably below 5°r6 and
especially if
it is a non laundry active material below 2% by weight of the tablet.
It is preferred that gelling binders, such as nonionic surfactants are avoided
in
their liquid or molten form. Nonionic surfactants and other gelling binders
are
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23
not excluded from the compositions, but it is preferred that they be processed
into the detergent tablets as components of particulate materials, and not as
liquids.
Builders
Detergent builders can optionally be included in the compositions herein to
assist in controlling miners! hardness. inorganic as well as organic builders
can
be used. Builders are typically used in fabric laundering compositions to
assist
in the removal of particulate soils.
The level of builder can vary widely depending upon the end use of the
composition.
Inorganic or P-containing detergent builders include, but are not limited to,
the
alkali metal, ammonium and alkanolammonium salts of polyphosphates
(exemplified by the tripolyphosphates, pyrophosphates, and glassy polymeric
meta-phosphates), phosphonates, phytic acid, silicates, carbonates (including
bicarbonates and sesquicarbonates), sulphates, and aluminosiiicates.
However, non-phosphate builders are required in some locales. importantly, the
compositions herein function surprisingly well even in the presence of the so-
called "weak" builders (as compared with phosphates) such as citrate, or in
the
so-called "underbuilt" situation that may occur with zeolite or layered
silicate
builders.
Examples of silicate builders are the alkali metal silicates, particularly
those
having a Si02:Na20 ratio in the range 1.6:1 to 3.2:1 and layered silicates,
such
as the layered sodium silicates described in U.S. Patent 4,664,839, issued May
12, 1987 to H. P. Rieck. NaSKS-6 is the trademark for a crystalline layered
silicate marketed by Hoechst (commonly abbreviated herein as "SKS-6").
Unlike zeolite builders, the Na SKS-6 silicate builder does not contain
aluminum. NaSKS-6 has the delta-Na2Si05 morphology form of layered
silicate. It can be prepared by methods such as those described in German DE-
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24
A-3,417,649 and DE-A-3,742,043. SKS-6 is a highly preferred layered silicate
for use herein, but other such layered silicates, such as those having the
general formula NaMSix02x+1 ~YH20 '~'~erein 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 herein. Various other layered silicates from Hoechst include
NaSKS-5, NaSKS-7 and NaSKS-11, as the alpha, beta and gamma forms. As
noted above, the delta-Na2Si05 (NaSKS-6 form) is most preferred for use
herein. Other silicates may also be useful such as for example magnesium
silicate, which can serve as a crispening agent in granular formulations, as a
stabilizing agent for oxygen bleaches, and as a component of suds control
systems.
Examples of carbonate, builders are the alkaline earth and alkali metal
carbonates as disclosed in German Patent Application No. 2,321,001 published
on November 15, 1973.
Aluminosilicate builders are useful in the present invention. Aiuminosilicate
builders are of great importance in most currently marketed heavy duty
granular
detergent compositions, and can also be a significant builder ingredient in
liquid
detergent formulations. Aluminosilicate builders include those having the
empirical formula:
Mz(zA102)y]~xH20
wherein z and y are integers of at least 6, the molar ratio of z to y is in
the range
from 1.0 to about 0.5, and x is an integer from about 15 to about 264.
Useful aluminosilicate ion exchange materials are commercially available.
These aiuminosilicates can be crystalline or amorphous in structure and can be
naturally-occurring aluminosilicates or synthetically derived. A method for
producing aluminosilicate ion exchange materials is disclosed in U.S. Patent
3,985,669, Krummel, et al, issued October 12, 1976. Preferred synthetic
crystalline aluminosilicate ion exchange materials useful herein are available
under the designations Zeolite A, Zeolite P (B), Zeolite MAP and Zeolite X. In
an especially preferred embodiment, the crystalline aluminosilicate ion
exchange material has the formula:
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Nal2I(A102)12(Si02)121~xH20
wherein x is from about 20 to about 30, especiaNy about 27. This material is
known as Zeolite A. Dehydrated zeolites (x = 0 - 10) may also be used herein.
Preferably, the aluminosilicate has a particle size of about 0.1-10 microns in
diameter.
Organic detergent builders suitable for the purposes of the present invention
include, but are not restricted to, a wide variety of polycarboxylate
compounds.
As used herein, "polycarboxylate" refers to compounds having a plurality of
carboxylate groups, preferably at least 3 carboxyiates. Polycarboxylate
builder
can generally be added to the composition in acid form, but can also be added
in the form of a neutralized salt. When utilized in salt form, alkali metals,
such
as sodium, potassium, and lithium, or alkanolammonium salts are preferred.
Included among the polycarboxylate builders are a variety of categories of
useful materials. One important category of polycarboxylate builders
encompasses the ether polycarboxylates, including oxydisuccinate, as disclosed
in Berg, U.S. Patent 3,128,287, issued April 7, 1964, and Lamberti et al, U.S.
Patent 3,635,830, issued January 18, 1972. See also 'TMS/TDS" builders of
U.S. Patent 4,663,071, issued to Bush et al, on May 5, 1987. Suitable ether
polycarboxylates also include cyclic compounds, particularly alicyciic
compounds, such as those described in U.S. Patents 3,923,679; 3,835,163;
4,158,635; 4,120,874 and 4,102,903.
Other useful detergency builders include the ether hydroxypolycarboxylates,
copolymers of malefic anhydride with ethylene or vinyl methyl ether, 1, 3, 5-
trihydroxy benzene-2, 4, 6-trisulphonic acid, and carboxymethyloxysuccinic
acid,
the various alkali metal, ammonium and substituted ammonium salts of
polyacetic acids such as ethylenediamine tetraacetic acid and nitrilotriacetic
acid, as well as poiycarboxylates such as mellitic acid, succinic acid, oxy-
disuccinic acid, polymaleic acid, benzene 1,3,5-tricarboxylic acid,
carboxymethyloxysuccinic acid, and soluble salts thereof.
Citrate builders, e.g., citric acid and soluble salts thereof (particularly
sodium
salt), are polycarboxylate builders of particular importance for heavy duty
liquid
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26
detergent formulations due to their availability from renewable resources and
their biodegradability. Citrates can also be used in granular compositions,
especially in combination with zeolite andlor layered silicate builders.
Oxydisuccinates are also especially useful in such compositions and
combinations.
Also suitable in the detergent compositions of the present invention are the
3,3-
dicarboxy-4-oxa-1,6-hexanedioates and the related compounds disclosed in
U.S. Patent 4,566,984, Bush, issued January 28, 1986. Useful succinic acid
builders include the C5-C2p alkyl and alkenyl succinic acids and salts
thereof.
A particularly preferred compound of this type is dodecenylsuccinic acid.
Specific examples of succinate builders include: laurylsuccinate,
myristylsuccinate, palmitylsuccinate, 2-dodecenylsuccinate (preferred), 2-
pentadecenylsuccinate, and the like. Laurylsuccinates are the preferred
builders of this group, and are described in European Patent Application
86200690.5J0,200,263, published November 5, 1986.
Other suitable polycarboxylates are disclosed in U.S. Patent 4,144,226,
Crutchfield et al, issued March 13, 1979 and in U.S. Patent 3,308,067, Diehl,
issued March 7, 1967. See also Diehl U.S. Patent 3,723,322.
Fatty acids, e.g., C12-C1g monocarboxylic acids, can also be incorporated into
the compositions alone, or in combination with the aforesaid builders,
especially
citrate andlor the succinate builders, to provide additional builder activity.
Such
use of fatty acids will generally result in a diminution of sudsing, which
should
be taken into account by the formulator.
In situations where phosphorus-based builders can be used, and especially in
the formulation of bars used for hand-laundering operations, the various
alkali
metal phosphates such as the well-known sodium tripolyphosphates, sodium
pyrophosphate and sodium orthophosphate can be used. Phosphonate builders
such as ethane-1-hydroxy-1,1-diphosphonate and other known phosphonates
(see, for example, U.S. Patents 3,159,581; 3,213,030; 3,422,021; 3,400,148 and
3,422,137) can also be used.
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Bleach
The detergent compositions herein may optionally contain bleaching agents or
bleaching compositions containing a bleaching agent and one or more bleach
activators. When present, bleaching agents will typically be at levels of from
about 1 °r6 to about 30°~, more typically from about 5% to about
20°~, of the
detergent composition, especially for fabric laundering. If present, the
amount
of bleach activators will typically be from about 0.1 °~ to about 60%,
more
typically from about 0.5% to about 40°~ of the bleaching composition
comprising
the bleaching agent-plus-bleach activator.
The bleaching agents used herein can be any of the bleaching agents useful for
detergent compositions in textile cleaning, hard surface cleaning, or other
cleaning purposes that are now known or become known. These include
oxygen bleaches as well as other bleaching agents. Perborate bleaches, e.g.,
sodium perborate (e.g., mono- or tetra-hydrate) can be used herein.
Another category of bleaching agent that can be used without restriction
encompasses percarboxylic acid bleaching agents and salts thereof. Suitable
examples of this class of agents include magnesium monoperoxyphthaiate
hexahydrate, the magnesium salt of metachloro perbenzoic acid, 4-nonylamino-
4-oxoperoxybutyric acid and diperoxydodecanedioic acid. Such bleaching
agents are disclosed in U.S. Patent 4,483,781, Hartman, issued November 20,
1984, U.S. Patent Application 740,446, Burns et al, filed June 3, 1985,
European Patent Application 0,133,354, Banks et al, published February 20,
1985, and U.S. Patent 4,412,934, Chung et al, issued November 1, 1983.
Highly preferred bleaching agents also include 6-nonylamino-6-
oxoperoxycaproic acid as described in U.S. Patent 4,634,551, issued January 6,
1987 to Burns et al.
Peroxygen bleaching agents can also be used. Suitable peroxygen bleaching
compounds include sodium carbonate peroxyhydrate and equivalent
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"percarbonate" bleaches, sodium pyrophosphate peroxyhydrate, urea
peroxyhydrate, and sodium peroxide. Persulfate bleach (e.g., OXONE,
manufactured commercially by DuPont) can also be used.
A preferred percarbonate bleach comprises dry particles having an average
particle size in the range from about 500 micrometers to about 1,000
micrometers, not more than about 10°r6 by weight of said particles
being smaller
than about 200 micrometers and not more than about 10°r6 by weight of
said
particles being larger than about 1,250 micrometers. Optionally, the
percarbonate can be coated with silicate, borate or water-soluble surfactants.
Percarbonate is available from various commercial sources such as FMC,
Solvay and Tokai Denka.
Mixtures of bleaching agents can also b~e used.
Peroxygen bleaching agents, the perborates, the percarbonates, etc., are
preferably combined with bleach activators, which lead to the in situ
production
in aqueous solution (i.e., during the washing process) of the peroxy acid
corresponding to the bleach activator. Various noniimiting examples of
activators are disclosed in U.S. Patent 4,915,854, issued April 10, 1990 to
Mao
et al, and U.S. Patent 4,412,934. The nonanoyloxybenzene sulfonate (NOES)
and tetraacetyl ethylene diamine (TAED) activators are typical, and mixtures
thereof can also be used. See also U.S. 4,634,551 for other typical bleaches
and activators useful herein.
Highly preferred amido-derived bleach activators are those of the formulae:
R1 N(R5)C(O)R2C(O)L or R1 C(O)N(R5)R2C(O)L
wherein R1 is an alkyl group containing from about 6 to about 12 carbon atoms,
R2 is an alkylene containing from 1 to about 6 carbon atoms, R5 is H or alkyl,
aryl, or alkaryl containing from about 1 to about 10 carbon atoms, and L is
any
suitable leaving group. A leaving group is any group that is displaced from
the
bleach activator as a consequence of the nucleophilic attack on the bleach
activator by the perhydrolysis anion. A preferred leaving group is phenyl
sulfonate.
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29
Preferred examples of bleach activators of the above formulae include (6-
octanamido-caproyl)oxybenzenesulfonate, (6-nonanamidocaproyl)oxybenzene-
sulfonate, (6-decanamido-caproyl)oxybenzenesulfonate, and mixtures thereof
as described in U.S. Patent 4,634,551, incorporated herein by reference.
Another class of bleach activators comprises the benzoxazin-type activators
disclosed by Hodge et al in U.S. Patent 4,966,723, issued October 30, 1990,
incorporated herein by reference. A highly preferred activator of the
benzoxazin-type is:
O
11
CEO
o .,~ o
'N
Still another class of preferred bleach activators includes the acyl lactam
activators, especially acyl caprolactams and acyl valerolactams of the
formulae:
O
O
O C-C H2-C H2 O C-C HZ-C H2
Rs-C-Nw iCH2 R6-~-N~ -- H
CHZ-CH2 CH2 2
wherein R6 is H or an alkyl, aryl, alkoxyaryl, or alkaryl group containing
from 1
to about 12 carbon atoms. Highly preferred lactam activators include benzoyl
caprolactam, octanoyl caprolactam, 3,5,5-trimethylhexanoyl caprolactam,
nonanoyl caprolactam, decanoyl caprolactam, undecenoyl caprolactam, benzoyl
valerolactam, octanoyl valerolactam, decanoyl vaierolactam, undecenoyl
valerolactam, nonanoyl valerolactam, 3,5,5-trimethylhexanoyl valeroiactam and
mixtures thereof. See also U.S. Patent 4,545,784, issued to Sanderson,
October 8, 1985, incorporated herein by reference, which discloses acyl
caprolactams, including benzoyl caprolactam, adsorbed into sodium perborate.
Bleaching agents other than oxygen bleaching agents are also known in the art
and can be utilized herein. One type of non-oxygen bleaching agent of
particular interest includes photoactivated bleaching agents such as the
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sutfonated zinc andlor aluminum phthalocyanines. See U.S. Patent 4,033,718,
issued July 5, 1977 to Holcombe et al. If used, detergent compositions will
typically contain from about 0.025°~ to about 1.25%, by weight, of such
bleaches, especially sulfonate zinc phthalocyanme.
If desired, the bleaching compounds can be catalyzed by means of a
manganese compound. Such compounds are well known in the art and include,
for example, the manganese-based catalysts disclosed in U.S. Pat. 5,246,621,
U.S. Pat. 5,244,594; U.S. Pat. 5,,194,416; U.S. Pat. 5,114,606; and European
Pat. App. Pub. Nos. 549,271 A1, 549,272A1, 544,440A2, and 544,490A1;
Preferred examples of these catalysts include MnlV2(u-0)3(1.4,7-trimethyl-
1,4,7-triazacyclononane}2(PF6)2, Mnlll2(u-0)1(u-OAc)2(1,4,7-trimethyl-1,4,7-
triazacyclononane)2-(C104)2, MnlV4(u-O)6(1,4,7-triazacyclononane)4(CI04)4,
MnllIMnlV4(u-O)1 (u-OAc)2_(1,4,7-trimethyl-1,4,7-triazacyclononane}2(CI04)3,
MnIV(1,4,7-trimethyl-1,4,7-triazacyclononane)- (OCH3)3(PF6), and mixtures
thereof. Other metal-based bleach catalysts include those disclosed in U.S.
Pat. 4,430,243 and U.S. Pat. 5,114,611. The use of manganese with various
complex ligands to enhance bleaching is also reported in the following United
States Patents: 4,728,455; 5,284,944; 5,246,612; 5,256,779; 5,280,117;
5,274,147; 5,153;161; and 5,227,084.
As a practical matter, and not by way of limitation, the compositions and
processes herein can be adjusted to provide on the order of at least one part
per ten million of the active bleach catalyst species in the aqueous washing
liquor, and will preferably provide from about 0.1 ppm to about 700 ppm, more
preferably from about 1 ppm to about 500 ppm, of the catalyst species in the
laundry liquor.
Enzymes
Enzymes can be included in the formulations herein for a wide variety of
fabric
laundering purposes, including removal of protein-based, carbohydrate-based,
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or triglyceride-based stains, for example, and for the prevention of refugee
dye
transfer, and for fabric restoration. The enzymes to be incorporated include
proteases, amylases, lipases, cellulases, and peroxidases, as well as mixtures
thereof. Other types of enzymes may also be included. They may be of any
suitable origin, such as vegetable, animal, bacterial, fungal and yeast
origin.
However, their choice is governed by several factors such as pH-activity
andlor
stability optima, thermostability, stability versus active detergents,
builders and
so on. In this respect bacterial or fungal enzymes are preferred, such as
bacterial amylases and proteases, and fungal cellulases.
Enzymes are normally incorporated at levels sufficient to provide up to about
5
mg by weight, more typically about 0.01 mg to about 3 mg, of active enzyme per
gram of the composition. Stated otherwise, the compositions herein will
typically
comprise from about 0.001 % to about 5°~6, preferably 0.01 °~-1
°~ by weight of a
commercial enzyme preparation. Protease enzymes are usually present in such
commercial preparations at levels sufficient to provide from 0.005 to 0.1
Anson
units (AU) of activity per gram of-composition.
Suitable examples of proteases are the subtiiisins which are obtained from
particular strains of B. subtilis and B. licheniforms. Another suitable
protease is
obtained from a strain of Bacillus, having maximum activity throughout the pH
range of 8-12, developed and sold by Novo Industries AIS under the registered
trade name ESPERASE. The preparation of this enzyme and analogous
enzymes is described in British Patent Specification No. 1,243,784 of Novo.
Proteolytic enzymes suitable for removing protein-based stains that are
commercially available include those sold under the tradenames ALCALASE
and SAVINASE by Novo Industries AIS (Denmark) and MAXATASE by
International Bio-Synthetics, Inc. (The Netherlands). Other proteases include
Protease A (see European Patent Application 130,756, published January 9,
1985) and Protease B (see European Patent Application Serial No. 87303761.8,
filed April 28, 1987, and European Patent Application 130,756, Bott et al,
published January 9, 1985).
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Amylases include, for example, a-amylases described in British Patent
Specification No. 1,296,839 (Novo), RAPIDASE, International Bio-Synthetics,
Inc. and TERMAMYL, Novo Industries.
The cellulase usable in the present invention include both bacterial or fungal
cellutase. Preferably, they will have a pH optimum of between 5 and 9.5.
Suitable cellulases are disclosed in U.S. Patent 4,435,307, Barbesgoard et al,
issued March 6, 1984, which discloses fungal cellulase produced from Humicola
insoiens and Humicola~ strain DSM1800 or a cellulase 212-producing fungus
belonging ~ to the genus Aeromonas, and cellulase extracted from the
hepatopancreas of a marine mollusk (Dolabella Auricula Solander), suitable
cellulases are also disclosed in GB-A-2.075.028; GB-A-2.095.275 and DE-OS-
2.247.832. CAREZYME (Novo) is especially useful.
Suitable lipase enzymes for detergent usage include those produced by
microorganisms of the Pseudomonas group, such as Pseudomonas stutzeri
ATCC 19.154, as disclosed in British Patent 1,372,034. See also lipases in
Japanese Patent Application 53,20487, laid open to public inspection on
February 24, 1978. This lipase is available from Amano Pharmaceutical Co.
Ltd., Nagoya, Japan, under the trade name Lipase P "Amano," hereinafter
referred to as "Amano-P." Other commercial lipases include Amano-CES,
lipases ex Chromobacter viscosum, e.g. Chromobacter viscosum var. lipolyticum
NRRLB 3673, commercially available from Toyo Jozo Co., Tagata, Japan; and
further Chromobacter viscosum lipases from U.S. Biochemical Corp., U.S.A. and
Disoynth Co., The Netherlands, and lipases ex Pseudomonas gladioli. The
LIPOLASE enzyme derived from Humicola lanuginosa and commercially
available from Novo (see also EPO 341,947) is a preferred lipase for use
herein.
Peroxidase enzymes are used in combination with oxygen sources, e.g.,
percarbonate, perborate, persulfate, hydrogen peroxide, etc. They are used for
"solution bleaching," i.e. to prevent transfer of dyes or pigments removed
from
substrates during wash operations to other substrates in the wash solution.
Peroxidase enzymes are known in the art, and include, for example, horseradish
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peroxidase, ligninase, and haloperoxidase such as chloro- and bromo-
peroxidase. Peroxidase-containing detergent compositions are disclosed, for
example, in PCT International Application WO 891099813, published October
19, 1989, by O. Kirk, assigned to Novo Industries AIS.
A wide range of enzyme materials and means for their incorporation into
synthetic detergent compositions are also disclosed in U.S. Patent 3,553,139,
issued January 5, 1971 to McCarty et al. Enzymes are further disclosed in U.S.
Patent 4,101,457, Place, et al, issued July 18, 1978, and in U.S. Patent
4,507,219, Hughes, issued March 26, 1985, both. Enzyme materials useful for
liquid detergent formulations, and their incorporation into such formulations,
are
disclosed in U.S. Patent 4,261,868, Hora et al, issued April 14, 1981. Enzymes
for use in detergents can be stabilized by various techniques. Enzyme
stabilization techniques are disclosed and exemplified in U.S. Patent
3,600,319,
issued August 17, 1971 to Gedge, et al, and European Patent Application
Publication No. 0 199 405, Application No. 86200586.5, published October 29,
1986, Venegas. Enzyme stabilization systems are also described, for example,
in U.S. Patent 3,519,570.
Other components which are commonly used in detergent compositions and
which may be incorporated into the detergent tablets of the present invention
include chelating agents, soil release agents, soil antiredeposition agents,
dispersing agents, brighteners, suds suppressors, fabric softeners, dye
transfer
inhibition agents and perfumes.
Method of Washing
It is known to place traditional laundry detergent tablets in the washing drum
together with the laundry. However, this method tends to result in unsightly
residues appearing visibly at the window, especially in certain types of
washing
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machine which have been designed to operate with a lower water consumption.
In extreme cases visible residues can also be left on clothes at the end of
the
wash cycle due to non complete dissolution.
The tablet according to the invention may be used according to a method of
washing which significantly avoids this problem. The new method comprises
preparing an aqueous solution of a laundry detergent for use in a washing
machine, wherein the aqueous solution of laundry detergent is formed by
dissolving in water a tablet according to the invention.
A preferred method more specifically relates to the preparation of an aqueous
solution of a laundry detergent for use in a front-loading washing machine,
the
front-loading washing machine having a dispensing drawer and a washing drum,
wherein the aqueous solution of laundry detergent is formed by dissolving a
detergent tablet according to the invention in water, characterised in that
the
detergent tablet is placed in the dispensing drawer and water is passed
through
the dispensing drawer so that the tablet is dispensed as an aqueous solution
of
a laundry detergent, the aqueous solution subsequently being passed in the
washing drum.
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EXAMPLES
Example 1
i) A detergent base powder of composition C (see tables under) was prepared
as follows: all the particulate material of base composition were mixed
together in a mixing drum or spray drum to form a homogenous particulate
mixture. During this mixing the spray-on of the binder system was carried
out. After this stage, the matrix was separated in two different samples. The
DIBS sticky hydrotope was added .to only one of the samples and then
processed independently in a Loedige KM 600~. The layer with DIGS was
used for a harder bottom layer and the layer without DIGS was used for a
softer top layer of a dual layer tablet.
ii) Using a Bonals~ rotary press both matrices were filled in two independent
force feeding flasks. The matrix with DIBS is consecutively filled first in
the
turret stations, followed by the second matrix (the without DIBS matrix). Both
layers are compressed together in the pre-compression and compression
stations to form a dual layer tablet with a harder bottom layer.
iii) tn this particular example, the tablets have a rectangular cross section
of
62.5 by 38.5 mm, a height of 20.5 mm and a weight of 48 gr. The height of
the bottom layer corresponded to 25°r6 of the total height of the
tablet. If a
round tablet is made of the bottom layer matrix with the same density as in
the rectangular tablet (983 gll), the tensile strength of the layer is 7.8
kPa.
Using the same experiment (for a density of 991 gll), the top layer of the
tablet has an equivalent tensile strength of 5.1 kPa. Elasticity measurements
gave values of 1.8 JIkN for the top layer and 3.3 JIkN for the bottom layer.
iv) In order to have a reference for the trials, tablets were made running the
press with the same press settings but using the matrix without DIGS for both
layers. This tablet has exactly the same density (991 911) and strength as the
top layer of the dual layer tablets. The only difference between the dual
layer
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tablet and the reference tablet is that the dual layer tablet has a bottom
layer
made with the matrix that has D1BS in its composition.
v) In order to prove the fact that a stronger bottom layer improves the
resistance in the line, reference and dual layer tablets were conducted
trough a series of roller belts of the line and then analysed separately for
breakage grades. More than one hundred tablets of each series were made
and analysed for the tests.
vi) In order to prove that the dispensing properties are not affected by the
harder bottom layer, 10 tablets of each kind were tested with the standard
dispensing tests described before.
vii) A difference was found between the dual layer tablets and the reference
tablets. Most of the reference tablets were severely damaged in the bottom
(the part of the tablets in contact with the roller belts and the belts in
general)
while the dual layer tablets with a harder bottom layer were almost not
damaged. A clear difference in the amount of split tablets was also
significantly reduced. The dispensing properties of the dual layer tablet were
not affected by the harder bottom layer. The following table summarises the
results of the conducted tests.
Tablet type % of tablets % of broken % of
with damaged tablets Dispensing
bottom residues
Reference 98% 18°~ 1.8°r6
Dual layer 10% 5% I 2.5%
Presented below are Examples for base particulate material composition for
making laundry detergent tablets according tot he invention, whereby a harder
layer may be more compressed than a softer layer, or whereby diifferent
compositions may be used or adapted for each layer.
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nposition A
per weight)
iionic Agglomerates 1 21.45
Bionic Agglomerates 2 13.00
ationic Agglomerate 5.45
~yered Silicate 10.8
odium percarbonate 14.19
leach activator agglomerates 5.49
odium carbonate 13.82
DDSISulphate particle 0.47
etrasodium salt of Hydroxyethane Diphosphonic0.73
acid
.oil Release Polymer 0.33
'luorescer 0.18
'.inc Phthalocyanide sulphonate encapsulate0.025
;oap powder 1.40
iuds Suppressor 1.87
~itric acid 7.10
0.79
protease
Lipase 0.28
Cellulase 0.22
_ , 1.08
Binder Spray-on-system 1.325
OTAL 1100.00
Anionic agglomerates 1 comprise of 40% anionic surfactant, 27% zeolite and
33% carbonate.
Anionic agglomerates 2 comprise of 40% anionic surfactant, 28°~
zeolite and
32°~ carbonate.
Cationic agglomerates comprise of 20°~ cationic surfactant,
56°~ zeolite and
24°~ sulphate.
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Layered silicate comprises of 95°~ SKS 6 and 5°~ silicate.
Bleach activator agglomerates comprise of 81 °~ TAED, 17°~
acryliclmaleic
copolymer (acid form) and 2°~ water.
Ethylene diamine N,N-disuccinic acid sodium saItISulphate particle comprise of
58°~6 of Ethylene diamine N,N-disuccinic acid sodium salt, 23°~
of sulphate and
19°~6 water.
Zinc phthalocyanine sulphonate encapsulates are 10°r6 active.
Suds suppressor comprises of 11.5% silicone oil (ex Dow Coming);
59°~ of
zeolite and 29.5°~ of water.
Binder spray-on system comprises of 50°~ Lutensit K-HD 96 and
50°~ PEG
(polyethylene glycol).
nposition B
per weight)
Bionic Agglomerates 1 21.45
iionic Agglomerates 2 13.00
~tionic Agglomerate 5.45
iyered Silicate 10.8
odium percarbonate 14.19
peach activator agglomerates 5.49
12.645
odium carbonate
DDSlSulphate particle 0.47
etrasodium salt of Hydroxyethane Diphosphonic0.73
acid
soil Release Polymer 0.33
l 0.18
Phthalocyanide sulphonate encapsulate0.025
1.40
~ powder
1.87
s Suppressor
7.10
c acid
0.79
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Anionic agglomerates 1 comprise of 40% anionic surfactant, 27% zeolite and
33°~ carbonate.
Anionic agglomerates 2 comprise of 40°~ anionic surfactant, 28%
zeolite and
32°~ carbonate.
Cationic agglomerates comprise of 20°~ cationic surfactant,
56°~ zeolite and
24°~ sulphate.
Layered silicate comprises of 95°~ SKS 6 and 5°r6 silicate.
Bleach activator agglomerates comprise of 81 % TAED, 17% acryliclmaleic
copolymer (acid form) and 2% water.
Ethylene diamine N,N-disuccinic acid sodium saItISulphate particle comprise of
58% of Ethylene diamine N, N-disuccinic acid sodium salt, 23% of sulphate and
19% water.
Zinc phthalocyanine sulphonate encapsulates are 10% active.
Suds suppressor comprises of 11.5% silicone oil (ex Dow Coming);
59°~ of
zeolite and 29.5% of water.
Binder spray-on system comprises of 50% Lutensit K-HD 96 and 50% PEG
(polyethylene glycol).
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Composition C
~o~~
Anionic agglomerates 1 9'1
Anionic agglomerates 2 22.5
Nonionic agglomerates 9.1
Cationic agglomerates 4.6
9'7
Layered silicate
Sodium percarbonate 12.2
lomerates 6.1
Bleach activator agg
Sodium carbonate 7.27
EDDSISulphate particle 0.5
Tetrasodium salt of Hydroxyethane 0.6
Diphosphonic acid
Soil Release Polymer 0.3
0.2
Fluorescer
Zinc Phthalocyanine sulphonate encapsulate0.03
1.2
Soap powder
2.8
Suds suppressor
5.5
Citric acid
I 11
Protease
0.35
Lipase
0:2
Cellulase
1.1
Amylase
3.05
Binder spray-on system
0.5
Perfume spray-on
DIGS
Anionic agglomerates 1 comprise of 40°~ anionic surfactant, 27%
zeoiite and
33% carbonate
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Anionic agglomerates 2 comprise of 40°r6 anionic surfactant,
28°~ zeolite and
32°~ carbonate
Nonionic agglomerate comprise 26°~ nonionic surfactant, 6°~6
Lutensit K-HD 96,
40°~ Sodium acetate anhydrous, 20°~ carbonate and 8°~
zeolite.
Cationic agglomerates ~ comprise of 20°~ cationic surfactant,
56°~ zeolite and
24°~ sulphate
Layered silicate comprises of 95°~ SKS 6 and 5°~ silicate
Bleach activator agglomerates comprise of 81 °r6 TAED, 17°~
acryliclmaleic
copolymer (acid form) and 2% water.
Ethylene diamine N,N-disuccinic acid sodium saItISulphate particle comprise of
58°~ of Ethylene diamine N,N-disuccinic acid sodium salt, 23% of
sulphate and
19°r6 water.
Zinc phthalocyanine sulphonate encapsulates are 10°~ active.
Suds suppressor comprises of 11.5°~ silicone oil (ex Dow Coming);
59°r6 of
zeolite and 29.5°~ of water.
Binder spray-on system comprises of 0.5 parts of Lutensit K-HD 96 and 2.5
parts of PEGs
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Composition D
~o~~
Anionic agglomerates 1 32
Cationic agglomerates 5
11.5
Layered silicate
Sodium percarbonate 16.2
Bleach activator agglomerates 4.7
Sodium carbonate 3.76
Sodium bicarbonate 2.0
2.4
Sodium sulphate
EDDSISulphate particle 0.5
Tetrasodium salt of Hydroxyethane 0'8
Diphosphonic acid
Soil Release Polymer 0.3
0.1
Fluorescer
Zinc Phthalocyanine sulphonate encapsulate0.02
2.1
Suds suppressor
2
Citric acid
0.7
Protease
0.2
Lipase
0.2
Cellulase
0.6
Amylase
0.2
Perfume encapsulates
3
Polymer particle
0.35
Perfume spray-on
5.17
Nonionic spray-on system
6.2
Zeolite
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Anionic agglomerates 1 comprise of 40°~ anionic surfactant,
27°~ zeolite and
33°~ carbonate
Cationic agglomerates comprise of 20°~ cationic surfactant,
56°~ zeolite and
24°~ sulphate
Layered silicate comprises of 95°~ SKS 6 and 5°~ silicate
Bleach activator agglomerates comprise of 81 °~6 TAED, 17°r6
acryliGmaleic
copolymer (acid form) and 2°~ water.
Ethylene diamine N,N-disuccinic acid sodium saltlSulphate particle comprise of
58% of Ethylene diamine N,N-disuccinic acid sodium salt, 23°~ of
sulphate and
19°~6 water.
Zinc phthalocyanine sulphonate encapsulates are 10% active.
Suds suppressor comprises of 11.5% silicone oil (ex Dow Coming);.
59°r6 of
zeolite and 29.5°~6 of water.
Perfume encapsulates comprise 50°~ perfume and 50% starch.
Polymer particle comprises 36°~, 54°~ zeolite and
10°~ water
The Nonionic spray-on system comprises of 67°~ C12-C15 AE5 (alcohol
with an
average of 5 ethoxy groups per molecule), 24°~ N-methyl glucose amide
and
9°~6 water.
