Note: Descriptions are shown in the official language in which they were submitted.
- 1 - 20~3~7
EFF~RVESCE~T D~TeRGENT TABLETS
-
FIELD OF THE INVENTION
-
This invention relates to detergent compositions and
more particularly to effervescent detergent compositions
in the form of tablets.
BACKGROUND OF THE INVENTION
Laundry detergents are presently provided in the form
of granular powders or concentrated aqueous solutions.
These formulations constitute additional bulk due, in the
case of free flowing granular powders, to entrapped air,
or in the case of aqueous solutions to significant amounts
of water. Further, in the latter case, such water also
results in a significant weight increase over the amount
of detergent active ingredient to be handled.
Yet further, each of the above two forms of
formulations requires a measurement to be made, by the
consumer, of the amount of detergent to be added to the
laundry wash,~which measurement requires a measuring cup
and action which is prone to error.
Yet still ~urther, household detergent formulations
in the form of powders and, particularly, liquids,
constitute a health safety hazard in being in an
available, readily ingestable form. Accidental ingestion
by small children is possible should good housekeeping
precautions by the consumer not be taken or inadvertently
lapse.
,
, ' : . . ' '
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20403~7
Thus, there is a demand to provide laundry detergent
to the trade and/or consumer in a form which minimizes the
bulk and weight of the detergent and its packaging,
obviates the need for measurement and with enhanced safety
features.
Detergent compositions in the form of tablets and the
like are well known in the art. U.S. Pate~t No.
4.370,250, issued January 25, 1983, however, sets out a
detailed description, of the problems associated with
providing a detergent in tablet form.
For a cleaning tablet to be commerically acceptable,
it must be of sufficient strength so that it will not
break under normal production, packaging and handling
conditions, yet it must also be readily dispersed in cold
water so as to provide the desired function comparable to
that of granular or liquid products, which are, because of
their physical nature, readily dispersable in the washing
medium. A disintegration time for a detergent tablet of
about three minutes or less is considered to be a highly
desirable rate from both the viewpoint of the detergent
being dispersed in the water and the minimization of
spotting of the clothes by local concentrations of
detergent. Additionally, overcoming these problems is
further complicated by the need today for cleaning
products which are egually suitable for both hot water and
cold water applications. Cold water washing, in
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- ~- 20~307
particular, is especially important because of the need to
conserve energy and it is imp~rtant that the tablets may
be used interchangeably for either cleaning application.
Cold water, in terms of cleaning products, usually means
tap water, which has a temperature range of about 70F.
The art has attempted to resolve the dichotomy
between a cleaning tablet having sufficient physical
strength and satisfactory water-dispersability, as well as
other associated problems normally encountered with such
tablet products, by using very specialized cleaning
formulations and processing techniques. The solution to
these problems is beset with many difficulties. While
handling of the tablet without breakage normally requires
the tablet to have a high strength, cleaning tablets
normally disintegrate much more slowly as the tablet
strength is increased. These competing forces, coupled
with the inherent nature of cleaning tablets to be much
more readily disintegrated in hot water than in cold
water, present the manufacturer with formidable problems
to be overcome to provide tablets having the desired
characteristics.
Further, the operation of a conventional tablet press
is hampered drastically if the ~ase powder beads to be
compressed into tablet form are (a) not free flowing (b)
sticky and tacky (c) light in density with correspondingly
high bulk and (d) weak and fragile when compressed.
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Surprisingly, we have discovered that a detergent
composition can be formulated in the form of a tablet and
the like, which has sufficient stabili~y to withstand
normal tablet packaging and transportation and yet which
dissolves satisfactorily in a laundry wash. ~e have found
that the detergent tablets of the present in~ention when
placed in contact with water are, surprising'y, adequate
to result in rapid disintegration of the tablels to enable
the detergent to dissolve in the water.
It is an object of the present invention ~o provide a
laundry detergent formulation in tablet form which has
improved disintegration and solubility properties on
addition to water.
S~MMARY OF THE INVENTION
.
In view of the need in the art explained hereinabove,
the present invention provides a stable laundry detergent
tablet which, when added to the laundry water, dissolves
to form a foaming cleansing solution.
- Accordingly, the invention provides in its broadest
aspect a water-disintegratable dry laundry detergent
tablet having a composition comprising a syn~hetic organic
detergent compound and an effervescence-generating agent
in intimate admixture therewith.
The tablet may contain from about 5% w/Y to about 25%
w/w of detergent compound.
2 ~ 4 ~
Preferably, the tablet comprises from about 10 to
about 20% of detergent compound, and more preferably, from
about 15 to about 18~ of detergent compound.
In addition to the detergent tablets and the like
according to the invention, also included are processes
for manufacturing such tablets and methods for washing
laundry using such tablets.
The synthetic organic detergent compound of use in
the practice of the invention is generally an anionic
synthetic organic detergent, preferably of the water
soluble sulfated and/or sulfonated lipophile type, but in
some instances, different synthetic organic detergents ~ay
be employed, usually as mixtures of anionic and nonionic
detergents.
Of the synthetic anionic oeganic detergents those
preferred are higher alkyl (preferably linear alkyl)
benzene sulfonates, higher fatty alcohol sulfates, higher
fa-tty alcohol ethoxylate or polyethoxylate sulfates,
olefin sulfonates and paraffin sulfonates. Usually such
compounds are water soluble alkali metal salts, such as
sodium salts, and include higher fatty alkyl or other
aliphatic moieties, which serve as lipophilic moieties,
and which increase detergency. Such higher alkyl or
higher aliphatic moieties will normally be of 8 to 20
carbon atoms, preferably 12 to 18 carbon atoms and more
preferably, especially for the alkylbenzene sulfonates, 12
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to 14 carbon atoms. As representatives of such detergents
there may be mentioned sodium linear tridecylbenzene
sulfonate, sodium linear dodecylbenzene sulfonate, sodium
lauryl al~oho1 sulfate, sodium coco alcohol triethoxylate
sulfate, sodium Cl6 paraffin sulfonate and sodium olefin
sulfonate derived from Cl4 olefin.
Althouyh nonionic detergents are not preferred
detersive co~ponents of the present compositions and
products, they may be employed, usually in relatively
minor proportions, and normally in conjunction with an
anionic detergent. Among the nonionic detergents, those
which are most preferred are ethylene oxide condensates
with higher fatty alcohols or with alkyl phenols, such as
condensation products of 3 to 12 moles of ethylene oxide
with highec fatty alcohols of lO to 15 carbon atoms or
with alkyl phenols of 7 to 10 carbon atoms in the alkyl
groups, e.g. Neodol~ 257.
_ In addition to the described anionic and nonionic
detergents, in some instances, amphoteric, ampholytic and
zwitterionic detergents may be present, normally in
relatively minor proportions. In some instances, cationic
detergents may be utilized, also normally in relatively
minor proportions, e.g., less than 10%, but in some
circumstances, as when such cationic detergent or surface
active agent is intended to be the fabric softener in a
composition or product to be blended with or to be used
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20~03~7
with such detergent composition, so as in that way to
produce a "softergent", uQ to 20 to 30~ may be employed.
~xtensive listings of detergents that are useful for
practicing the present invention may be found in standard
textbooks relating to synthetic organic detergents, of
which there may be mentioned herein, as representative,
Surface Active Agents (Their Chemistry and Technology) by
Schwartz and Perry, and the various annual editions of
John W. McCutcheon's Detergents and Emulsifiers, e.g. that
of 1980.
Hydratable builder salts may be used with the
synthetic organic detergent. Sodium salt of ethylene
diaminetetracetic acid (EDTA), trisodium salt of
nitriloacetic acid (NTA) and sodium tripolyphosphate are
preferred, but other such salts may also be employed,
either alone or in admixture with such salts, such as, for
example, tetrasodium pyrophosphate and other
pyrophosphates, sodium carbonate, sodium sesquicarbonate,
sodium silicate, sodium sesquisilicate or borax. In some ~
instances, it may be desirable to mix with such salts
builders which are not hydratable. Hydratable filler
salts may be employed in some instances but normally will
desirably be omitted from the compositions because they
add only bulk, and do not contribute to detergency. Of
the builders the polyphosphates are highly preferred, and
of those, particularly, sodium tripolyphosphate.
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The effervescence producing agents of use in the
practice of the invention comprise an acid and a compound
which reacts with the acid in water to generate gas
bubbles to effect disintegration and agitation when the
tablet is added to water.
Preferably, the effervescence producing agent is a
carbon dioxide generating mixture comprising a carbonate
compound and an acid. By ~carbonate compound" is meant an
alkali metal carbonate or bicarbonate, such as for example
carbonate or bicarbonate of sodium or potassium. The acid
component is preferably citric or tartaric acid or_
mixtures thereof but may be other water soluble acids
including mixtures thereof such as, for example, sodium or
potassium acid phosphates, gluconic acid, malic acid, and
the like. The acid and the carbonate compound are
generally employed in approximately stoichiometric
amounts, although a very slight excess of acid may be
employed to effectively generate the potential carbon
dioxide. Large excesses of acid are generally not
desirable.
The tablets may have as an additional or alternative
effervesence producing agent one or more peroxygen or
active oxygen compounds such as sodium perborate
monohydrate, sodium perborate tetrahydrate, potassium
persulfate, sodium carbonate peroxide and the like, which
cause the tablets to evolve microbubbles of nascent or
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active oxygen as they are dissolved in water and provi~e
an additional oxidizing, cleansing action, including a
bleaching effect on the laundry. A hypochlorite ion
forming oxidizing agent may, optionally, be included to
provide an additional oxidizing, cleansing action.
The effective amount of the effervescence producing
agent in the tablet will depend on the nature and amounts
of the remaining ingredients present in the composition of
the tablet. This amount can be readily determined by the
skilled man without the exercise of his inventive
faculty. Accordingly, the effervescence_producing agent
will be present in the tablet in an effervescent effective
amount to effect the required disintegration in a laundry
wash.
The synthetic organic detergent compositions of use
in the invention preferably further comprise conventional
detergent composition additives. For instance, in
addition to the aforesaid builder salts, which are hard
water softeners, generally chelating agents, used to
enhance the cleaning ability of the detergent surfactant,
alkali, such as granular sodium hydroxide and/or sodiu~
metasilicate is very preferably also present to provide an
increase in the pH tOr at least, the neutral level.
We have found that the presence of salts, alkali and
bu1lders which are readily soluble in water also enhance
the disintegration process. We have, further, found that,
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lO - 2~ ~0~ ~
surprisingly, the gas bubbles generated by the
effervescent action provides an additional agitation
action to the detergent and enhances the desirable foaming
effect sought in a laundry wash.
Thus, we have found that the disintegration times of
the de~ergent tablets according to the invention are also
dependent upon the choice and amounts of salts, alkali and
builders. However, the amount of alkali used to increase
the p~ of the laundry wash solution in the practice of the
present invention can be kept to a minimum and well below
that conventionally used. The ~referred composition of
use provides an approximate neutral solution of pH 7.
Enzymes and fluorescent whitening agents are further
optional additives. The tablet compositions may thus
additionally comprise detergent enzymes such as amylases
and proteases. Examples include ESPERASETM and SAVINASETM
protease enzymes. (Novo Nordisk Bioindustries,
Netherlands) and BANTM and MAXATASETM amylase enzymes.
The detergent tablets may be made with relatively
inexpensive, easy-to-operate and trouble-free standard
mixing and tablet-forming equipment. In view of the sticky
and tacky nature of the majority of built synthetic
organic detergents having the desired detergency
proper~ies, we have found that the presence of a de-
tackifier compound, such as talc, titanium dioxide,
magnesium stearate, in an amount of from about 0.05 to
20403~7
about 5% w/w in the ?reparation of the tablet, assists the
mixing and tabletting by reducing the tackiness of the
detergent compound. The amount of such de-tackifer will
be dependent on the detergent composition, but can be
readily determined by the skilled man.
Thus, in a further feature the invention provides a
process for the manufacture of a detergent tablet as
hereinbefore defined which process comprises intimately
mixing said detergent compound and said effervescence-
generating agent to provide an admixture thereof, and
compacting said admi~ure in the form of a tablet.
We have, surprisingly, found that the tablets of the
present invention are advantageously and significantly
more compact than the tablets disclosed in USP 4,933,100,
wherein a density of 0.8 g/cm3 is reported. Such an
enhanced density of the tablets of the present invention
with a concommittent satisfactory disintegration rate
provides for the manufacture of tablets of advantageously
reduced size.
Typically, tablets with greater than 80~
disintegration in the first 3 minutes, very satifactorily
breakdown with the ac~ion of the water, agitation of the
machine and the friction of the clothes. Tablets with
less than 80% disintegration, although of value, do not
breakdown fully when ~sing a short 6 minute wash cycle.
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Thus, in a yet further feature the invention provides
a method of cleaning laundry comprising adding a detergent
tablet as hereinbefore defined to a laundry wash for a
sufficient period of time to effect cleaning of said
laundry.
By the term "tablet'l is meant a compact mass of a
detergent composition according to the invention in the
form of a suitable shape to utilize the concept of the
invention. Preferably, the tablet takes the form of a
disc, cube, square or solid cylinder. It is not necessary
that each individual tablet contains the requisite amount
of detergent for a full laundry wash. Although not
preferred, clearly, such a requisite amount could be
provided by a combined amount from a plurality of tablets.
We have found that the manufacture and shelf
stability of the tablets are dependent on the free water
content of the compositions, i.e. water not bound up as
water of crystallization or in hydrat~d salts. The free
water content should not be greater than 3% w/w of the
composition, preferably ~ O.5% w/w and more
preferably ~ 0.1% w/w i.e. the tablets should be dry.
Thus, in this specification and claims the term "water-
disintegratable dry laundry detergent tablet" means a
ta~let having no more than 3% w/w free water content.
We have further found in shelf-life studies with the
tablets that they may absorb moisture and over a two to
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three-week period show signs of "pitting" with the surface
becoming rough. Although this does not effect th3
performance of the detergent, testing shows that the
initial effervescent reaction upon submergence of t~e
tablets in water is not as violent as compared to fresh"
samples. This, however, changes into aggressive ~bling
after the pitted surface has an opportunity to dissolve
away, generally after about 2-S seconds.
In order to provide an improved tablet resis~nt to
humidity and, thus, a product having an extended shelf-
life, the tablet has been given a humidity resist~nt,
water soluble coating.
Accordingly, in a preferred feature, the inven~ion
provides a water-disintegratable dry laundry deterg~nt
tablet as hereinbefore defined provided with a water-
~oluble coating.
An example of such a coating is provided by spraying
the tablets with an effectiv~ amount of non-aqueo1s
solvent based cellulosic composition sold under the trade
mark OPADRY CLEARCOAT (Colorcon, U.S.A.). As the solvent,
typically an aliphatic alcohol such as ethyl alcohol,
evaporates, a thin glossy cellulosic film forms to protect
the tablet.
Accordingly, in a preferred process, the invention
provides a process for the manufacture of a detergent
tablet as hereinbefore defined further comprising coating
said tablet with a water-soluble coating composition.
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In a further featurer the invention provides a method
ef cleaning laundry as hereinbefore defined wherein said
tablet is coated with a water-soluble coat.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In order that the invention may be better understood
~referred embodiments will now be described with reference
~o the accompanying examples.
The efficacy of a detergent composition in a laundry
wash was measured by a visual noting of the degree of
removal of an artificially induced stainl such as ketchup,
tomato, and the like and of measurement of the brightness.
Example 1
A detergent tablet was made having the following
composition:-
% w/w
Sodium dodecylbenzene sulphonate t90% a.i.;
NANSATM HS85/S-Albright and Wilson Ltd.) - talc (4% w/w) 16
Sodium metasilicate 4.8
Citric acid 18
Sodium bicarbonate 51
Sodium hydroxide (50% granular) 4
rthylene diaminetT~raacetate acid (Kalex ~00TM) 5
Amylase (MAXATASE ) - protease (~AXAMYLT ) enzyme
mixture (1:1) w/w 1.15
Fluorescent whitening agent (TINOPALTM AMS-GX stilbene
type - Ciba-Geigy) 0.05
The above ingredients, totalling 450 kg. were,
sequentially, mixed in a ribbon blender (Britton Machine,
Guelph, Ontario, Canada). Sodium dodecylbenzenesulphonate
surfactant and talc, 4% w/w, de-tackifer, were charged to
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- 15 - 2~4~7
the blender and mixed for 2 minutes. The following
ingredients, namely, sodium metasilicate, sodium
bicarbonate, sodium hydroxide, citric acid, ethylene
diamine tetraacetate acid, enzymes and fl~orescent
whitening agent were, subsequentl~, added, in sequence,
after a respective 2-3 minute blending time between
individual additions. The composition was sufficiently
dry to prevent or significantly reduce any effervescence
reaction between the citric acid and sodium bicarbonate.
The composition was formed into 54 g, disc-shaped
tablets having a density of 1.42 g/cm, a 5.8 cm. diameter
and 1.47 cm. thickness, using a STOKES-RTM tablet press
under a compression ratio of 2.8:1.
Disintegrations tests were conducted by weighing the
tablet before it was placed in water and after it was
submerged for 3 minutes in water and, subsequently,
dried. The disintegration figure is based on the
percentage mass reduction.
The tablets of Example 1 were found to satisfactorily
disintegrate to a 82~ degree within a standard 3 minute
period.
Example 2
A detergent tablet was made having the identical
composition as the tablet of Example 1 but with an
alternative surfactant, namely, the sodium salt of the
linear alkyl benzenesulphonate sold under the trade mark
.
- 16 - 2040~07
NACCONOLTM 90G (Stepan Compan~, Illinois, U.S.A.),
substituted for the surfactant described in Example 1.
The tablets were identical to ~hose of Example 1 in
disintegration characteristics and efficacy.
Example 3
Detergent tablets according to the present invention
were made incorporating a peroxy bleach agent, namely,
sodium perborate (monohydrate) and having the composition:
% w/w
Sodium d~decylbenzene sulphonate (90% a.i.;
NANSAT HS85/S-Albright and ~ilson ~td.) -
(titanium dioxide, 0.5% w/w) 16
Sodium metasilicate 4.8
Citric acid 14
Sodium bicarbonate 36
Sodium hydroxide (50% - granular) 4
NTA
Sodium perborate (Monohydrate) 19
Amylase and Protease (1:1 w/w) 1.1
Fluorescent whitening agent, TINOPALTM AMS-GX stilbene
type (Ciba-Geigy) 0.05
100
These tablets were found to have excellent laundry
cleaning properties and a superb disintegration rate.
Example 4
This example illustrates the effect of detergent
additives, such as salts, alkali or builders on the
disintegration rate of a table~ according to the invention
having constant amounts of the same detergent (surfactant)
and effervescence-producing agent. The enzymes and FWA
were as for Example 1.
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~0~3~7
The resJlts are given in the Table and show that the
disintegration varied from 59-81~.
.
.
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19- ~0~7
Example 5
Comparative tests were carried out on tablets
prepared fr~m three commercially available laundry
detergents.
The granular powders of three commercially available
detergents were individually compacted into the tablet
form as described for the compositions of ~he invention of
Examples 1 to 4. Difficulty was found in ~he preparation
of these tablets in that the press had to ~e modified to
allow for adequate compacting. It is believed that
the ~ 3% w/w water content inherent in the detergent
composition contributed to this difficulty.
The compacted tablets of these commercial detergent
compositions did not disintegrate and produce a readily
soluble cleaning solution when added to water.
One of the commercial powder compositions was mixed
with various amounts of sodium bicarbonate~citric acid
effervescence producing agent and formed into tablets.
The results of the three minute resid~nce
diaintegration tests ~e shown below.
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NaHC03/
citric acid % disintegration
Commercial detergent 20 6.8
12
15.2
The results indicate that disintegration and
cleansing were obtained. The nature of the commercial
composition in being ~ 3% w/w water-containing to effect
undue compacting of the tablet does not produce a
preferred tablet according to the invention.
Although this disclosure has described and
illustrated certain preferred embodiments of the
invention, it is to be understood that the invention is
not restricted to these particular embodiments. Rather,
the invention includes all embodiments which are
functional or mechanical equivalents of the specific
embodiments and features that have been described and
illustrated herein.
