Note: Descriptions are shown in the official language in which they were submitted.
CA 02297458 2000-O1-28
ABRASION-RESISTANT DETERGENT TABLETS WITH A HIGH
NONIONIC SURFACTANT CONTENT
FIELD OF THE INVENTION
This invention relates generally to compact shaped bodies having
detersive properties. Detersive shaped bodies include, for example,
laundry detergent tablets, tablets for dishwashing machines or for cleaning
hard surfaces, bleach tablets for use in washing or dishwashing machines,
water softening tablets or stain remover tablets. More particularly, the
present invention relates to laundry detergent tablets which are used for
washing laundry in domestic washing machines and which are referred to
in short as detergent tablets.
BACKGROUND OF THE INVENTION
Detergent tablets are widely described in the prior-art literature and
are enjoying increasing popularity among consumers because they are
easy to dose. Tabletted detergents have a number of advantages over
powder-form detergents: they are easier to dose and handle and, by virtue
of their compact structure, have advantages in regard to storage and
transportation. As a result, detergent shaped bodies are also
comprehensively described in the patent literature. One problem which
repeatedly arises in the use of detergent tablets is the inadequate
disintegrating and dissolving rate of the tablets under in-use conditions.
Since sufficiently stable, i.e. dimensionally stable and fracture-resistant,
tablets can only be produced by applying relatively high pressures, the
ingredients of the tablet are heavily compacted so that disintegration of the
tablet in the wash liquor is delayed which results in excessively slow
release of the active substances in the washing process. The delayed
disintegration of the tablets has the further disadvantage that typical
detergent tablets cannot be flushed into the washing process from the
dispensing compartment of domestic washing machines because the
tablets do not disintegrate sufficiently quickly into secondary particles
which are small enough to be flushed from the dispensing compartment
into the drum of the washing machine. Another problem which occurs with
detergent tablets in particular lies in the friability of the tablets and
their
CA 02297458 2000-O1-28
2
often inadequate resistance to abrasion. Thus, although sufficiently
fracture-resistant, i.e. hard, detergent tablets can be produced, they are
often not strong enough to withstand the loads encountered during
packaging, transportation and handling, i.e. impact and friction effects, so
that broken edges and signs of abrasion spoil the appearance of the tablet
or even lead to the complete destruction of its structure.
So far as the prior art is concerned, solutions to the problem of the
friability or abrasion resistance of detergent tablets are disclosed solely in
earlier German patent application DE 198 41 146.6 (Henkel KGaA). The
solution proposed in this document is to incorporate liquid, non-surfactant
binders in the premixes to be tabletted.
The use of surfactants in detergent tablets is the subject of
numerous publications. Formulations rich in nonionic surfactants are
described in particular in the following documents.
European patent application EP 355 626 (Henkel KGaA) discloses
a process for the production of phosphate-free or low-phosphate detergent
tablets in which at least two powder-form or granular components (A) and
(B) are prepared, mixed and tabletted. Component (A) contains the total
quantity of anionic surfactants while component (B) contains 75 to 100% of
the total quantity of nonionic surfactants.
European patent application EP 466 485 (Unilever) also describes
detergent tablets which contain builders and anionic and nonionic
surfactants. The premix to be tabletted consists of particles, of which 20 to
100% consist of anionic surfactant, and of particles which are preferably
free from anionic surfactants and which may contain nonionic surfactant.
There is no reference in this document to any particular ratio to be
maintained between the nonionic and anionic surfactants. The problem of
inadequate abrasion resistance is not mentioned either.
Detergent tablets which contain potassium carbonate as a
compulsory component besides large quantities of nonionic surfactant are
described in European patent application EP 482 627 (Kao Corp.).
According to the teaching of this patent specification, the solubility of the
tablets is improved by a special ratio by weight between nonionic
CA 02297458 2000-O1-28
3
surfactant and potassium carbonate. This is also no mention in this
document of anionic surfactant/nonionic surfactant ratios, nor any
discussion of the problem of abrasion resistance.
The use of ethoxylated alcohols with an average C chain length
below 12 (because at least 25% of the alkyl chains have a length of less
than 12 carbon atoms) is disclosed in EP 598 586 (Unilever). Detergent
tablets containing anionic surfactant in addition to nonionic surfactant are
not explicitly described in this document. There is no mention of a
particular ratio to be maintained between nonionic and anionic surfactants,
nor any reference to the problem of abrasion.
Now, the problem addressed by the present invention was to
provide tablets which, for predetermined hardness, would be distinguished
by short disintegration times which and, accordingly, could even be
flushed into the washing process from the dispensing compartment of
commercially available washing machines. In addition to meeting these
requirements, the tablets would have increased resistance to impact and
friction, i.e. would show improved, i.e. reduced, friability and would exhibit
reduced abrasion behavior. As far as possible, the advantageous
properties would be achieved through the making-up of detergent
ingredients in order to be able to dispense with the addition of auxiliaries
that are "foreign" to the formulation, i.e. do not develop a detersive effect.
From this point of view, suitable active ingredients were, above all, the
washing-active or detersive substances.
BRIEF DESCRIPTION OF THE INVENTION
It has now been found that the ratio by weight of nonionic to anionic
surfactants in the formulation as a whole has a critical influence on
friability.
The present invention relates to detergent tablets of compacted
particulate detergent containing builders, anionic and nonionic surfactants
and optionally other detergent ingredients in which the ratio of nonionic to
anionic surfactants is in the range from 0.4:1 to 3:1.
In one aspect of the present invention provides a detergent tablet
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comprising compacted detergent granules containing builders, anionic and
nonionic surfactants and optionally other detergent ingredients, wherein
the ratio of nonionic to anionic surfactants in the tablet is in the range
from
0.4:1 to 3:1.
In another aspect, the invention provides a process for the
production of detergent tablets which comprises: mixing surfactant-
containing granules with fine-particle after treatment components to form a
mixture and subsequently forming/shaping the mixture to form a tablet the
ratio of nonionic to anionic surfactants in the tablet is in the range from
0.4:1 to 3:1.
In yet another aspect, there is provided a method for improving the
abrasion resistance of detergent tablets which comprises compressing a
mixture comprising granules containing nonionic and anionic surfactants
with a ratio of nonionic surfactants to anionic surfactants of from 0.4:1 to
3:1 and fine particle aftertreatment components.
In the context of the present invention, the term "ratio" characterizes
the quotient of the percentages by weight of nonionic and anionic
surfactants, the percentages by weight being based on the tablet as a
whole. It does not matter whether the anionic and nonionic surfactants
have been introduced into the detergent tablets in various ways or whether
they are present in various phases or regions of the tablet. In preferred
embodiments, the ratio is in an even narrower range so that detergent
tablets in which the ratio of nonionic to anionic surfactants is in the range
from 0.45:1 to 2.5:1, preferably in the range from 0.5:1 to 2:1 and more
preferably in the range from 0.75:1 to 1.5:1 are preferred.
The detergent tablets according to the invention contain builders
and anionic and nonionic surfactants as compulsory ingredients. These
ingredients are described in the following.
DETAILED DESCRIPTION OF THE INVENTION
Suitable anionic surfactants are, for example, those of the sulfonate
and sulfate type. Suitable surfactants of the sulfonate type are preferably
C9_~3 alkyl benzenesulfonates, olefin sulfonates, i.e. mixtures of alkene and
hydroxyalkane sulfonates, and the disulfonates obtained, for example,
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5
from C~2_~$ monoolefins with an internal or terminal double bond by
sulfonation with gaseous sulfur trioxide and subsequent alkaline or acidic
hydrolysis of the sulfonation products. Other suitable surfactants of the
sulfonate type are the alkane sulfonates obtained from C~2_~8 alkanes, for
example by sulfochlorination or sulfoxidation and subsequent hydrolysis or
neutralization. The esters of a-sulfofatty acids (ester sulfonates), for
example the a-sulfonated methyl esters of hydrogenated coconut oil, palm
kernel oil or tallow fatty acids, are also suitable.
Other suitable anionic surfactants are sulfonated fatty acid glycerol
esters. Fatty acid glycerol esters in the context of the present invention
are the monoesters, diesters and triesters and mixtures thereof which are
obtained where production is carried out by esterification of a
monoglycerol with 1 to 3 moles of fatty acid or in the transesterification of
triglycerides with 0.3 to 2 moles of glycerol. Preferred sulfonated fatty acid
glycerol esters are the sulfonation products of saturated fatty acids
containing 6 to 22 carbon atoms, for example caproic acid, caprylic acid,
capric acid, myristic acid, lauric acid, palmitic acid, stearic acid or
behenic
acid.
Preferred alk(en)yl sulfates are the alkali metal salts and, in
particular, the sodium salts of the sulfuric acid semiesters of C~2_~8 fatty
alcohols, for example cocofatty alcohol, tallow fatty alcohol, lauryl,
myristyl,
cetyl or stearyl alcohol, or C~o_2o oxoalcohols and the corresponding
semiesters of secondary alcohols with the same chain length. Other
preferred alk(en)yl sulfates are those with the chain length mentioned
which contain a synthetic, linear alkyl chain based on a petrochemical and
which are similar in their degradation behavior to the corresponding
compounds based on oleochemical raw materials. C~2_~s alkyl sulfates,
C~2_~5 alkyl sulfates and C~4_~5 alkyl sulfates are preferred from the point
of
view of washing technology. Other suitable anionic surfactants are 2,3-
alkyl sulfates which may be produced, for example, in accordance with US
3,234,258 or US 5,075,041 and which are commercially obtainable as
products of the Shell Oil Company under the name of DAN~.
The sulfuric acid monoesters of linear or branched C~_2~ alcohols
CA 02297458 2000-O1-28
6
ethoxylated with 1 to 6 moles of ethylene oxide, such as 2-methyl-
branched C9_» alcohols containing on average 3.5 moles of ethylene oxide
(EO) or C~2_~8 fatty alcohols containing 1 to 4 EO, are also suitable. In
view of their high foaming capacity, they are only used in relatively small
quantities, for example in quantities of 1 to 5% by weight, in dishwashing
detergents.
Other suitable anionic surfactants are the salts of alkyl sulfosuccinic
acid which are also known as sulfosuccinates or as sulfosuccinic acid
esters and which represent monoesters and/or diesters of sulfosuccinic
acid with alcohols, preferably fatty alcohols and, more particularly,
ethoxylated fatty alcohols. Preferred sulfosuccinates contain C8_~$ fatty
alcohol residues or mixtures thereof. Particularly preferred sulfosuccinates
contain a fatty alcohol residue derived from ethoxylated fatty alcohols
which, considered in isolation, represent nonionic surfactants (for a
description, see below). Of these sulfosuccinates, those of which the fatty
alcohol residues are derived from narrow-range ethoxylated fatty alcohols
are particularly preferred. Alk(en)yl succinic acid preferably containing 8 to
18 carbon atoms in the alk(en)yl chain or salts thereof may also be used.
Other suitable anionic surfactants are, in particular, soaps. Suitable
soaps are saturated fatty acid soaps, such as the salts of lauric acid,
myristic acid, palmitic acid, stearic acid, hydrogenated erucic acid and
behenic acid, and soap mixtures derived in particular from natural fatty
acids, for example coconut oil, palm kernel oil or tallow fatty acids.
The anionic surfactants, including the soaps, may be present in the
form of their sodium, potassium or ammonium salts and as soluble salts of
organic bases, such as mono-, di- or triethanolamine. The anionic
surfactants are preferably present in the form of their sodium or potassium
salts and, more preferably, in the form of their sodium salts.
According to the invention, preferred detergents tablets are those
which contain more than 5% by weight, preferably more than 7.5% by
weight and more preferably more than 10% by weight of anionic
surfactants, based on the weight of the tablet.
So far as the choice of anionic surfactants is concerned, there are
CA 02297458 2000-O1-28
7
no basic requirements to restrict the freedom of formulation. However,
preferred surfactant granules do have a soap content in excess of 0.2% by
weight, based on the total weight of the detergent tablet. Preferred anionic
surfactants are alkyl benzenesulfonates and fatty alcohol sulfates,
preferred detergent tablets containing 2 to 20% by weight, preferably 2.5
to 15% by weight and more preferably 5 to 10% by weight of fatty alcohol
sulfate(s), based on the weight of the detergent composition.
Preferred nonionic surfactants are alkoxylated, advantageously
ethoxylated, more especially primary alcohols preferably containing 8 to 18
carbon atoms and, on average, 1 to 12 moles of ethylene oxide (EO) per
mole of alcohol, in which the alcohol component may be linear or,
preferably, methyl-branched in the 2-position or may contain linear and
methyl-branched residues in the form of the mixtures typically present in
oxoalcohol residues. However, alcohol ethoxylates containing linear
residues of alcohols of native origin with 12 to 18 carbon atoms, for
example coconut oil, palm oil, tallow fatty or oleyl alcohol, and on average
2 to 8 EO per mole of alcohol are particularly preferred. Preferred
ethoxylated alcohols include, for example, C~2_~a alcohols containing 3 EO
or 4 EO, C9_~~ alcohol containing 7 EO, C~3_~5 alcohols containing 3 EO, 5
EO, 7 EO or 8 EO, C~2_~$ alcohols containing 3 EO, 5 EO or 7 EO and
mixtures thereof, such as mixtures of C~Z_~4 alcohol containing 3 EO and
C~2_~8 alcohol containing 5 EO. The degrees of ethoxylation mentioned
represent statistical mean values which, for a special product, can be a
whole number or a broken number. Preferred alcohol ethoxylates have a
narrow homolog distribution (narrow range ethoxylates, NRE). In addition
to these nonionic surfactants, fatty alcohols containing more than 12 EO
may also be used, examples including tallow fatty alcohol containing 14
EO, 25 EO, 30 EO or 40 EO.
Another class of preferred nonionic surfactants which may be used
either as sole nonionic surfactant or in combination with other nonionic
surfactants are alkoxylated, preferably ethoxylated or ethoxylated and
propoxylated, fatty acid alkyl esters preferably containing 1 to 4 carbon
atoms in the alkyl chain, more especially the fatty acid methyl esters which
CA 02297458 2000-O1-28
8
are described, for example, in Japanese patent application JP 581217598
or which are preferably produced by the process described in International
patent application WO-A-90113533.
Another class of nonionic surfactants which may advantageously be
used are the alkyl polyglycosides (APGs). Suitable alkyl polyglycosides
correspond to the general formula RO(G)Z where R is a linear or branched,
more particularly 2-methyl-branched, saturated or unsaturated aliphatic
radical containing 8 to 22 and preferably 12 to 18 carbon atoms and G
stands for a glycose unit containing 5 or 6 carbon atoms, preferably
glucose. The degree of glycosidation z is between 1.0 and 4.0, preferably
between 1.0 and 2.0 and more preferably between 1.1 and 1.4.
Linear alkyl polyglucosides, i.e. alkyl polyglycosides in which the
polyglycosyl component is a glucose unit and the alkyl component is an n-
alkyl group, are preferably used.
The surfactant granules may advantageously contain alkyl
polyglycosides, APG contents of more than 0.2% by weight, based on the
tablet as a whole, being preferred. Particularly preferred detergent tablets
contain APGs in quantities of 0.2 to 10% by weight, preferably in quantities
of 0.2 to 5% by weight and more preferably in quantities of 0.5 to 3% by
weight.
Nonionic surfactants of the amine oxide type, for example N-
cocoalkyl-N,N-dimethylamine oxide and N-tallowalkyl-N,N-dihydroxyethyl-
amine oxide, and the fatty acid alkanolamide type are also suitable. The
quantity in which these nonionic surfactants are used is preferably no
more than the quantity in which the ethoxylated fatty alcohols are used
and, more preferably, no more than half that quantity.
Other suitable surfactants are polyhydroxyfatty acid amides
corresponding to formula (I):
R'
R-CO-N-Z (I)
in which RCO is an aliphatic acyl group containing 6 to 22 carbon atoms,
CA 02297458 2000-O1-28
9
R' is hydrogen, an alkyl or hydroxyalkyl group containing 1 to 4 carbon
atoms and Z is a linear or branched polyhydroxyalkyl group containing 3 to
10 carbon atoms and 3 to 10 hydroxyl groups. The polyhydroxyfatty acid
amides are known substances which may normally be obtained by
reductive amination of a reducing sugar with ammonia, an alkylamine or
an alkanolamine and subsequent acylation with a fatty acid, a fatty acid
alkyl ester or a fatty acid chloride.
The group of polyhydroxyfatty acid amides also includes
compounds corresponding to formula (II):
R'-O-R2
R-CO-N-Z (I I)
in which R is a linear or branched alkyl or alkenyl group containing 7 to 12
carbon atoms, R' is a linear, branched or cyclic alkyl group or an aryl
group containing 2 to 8 carbon atoms and R2 is a linear, branched or cyclic
alkyl group or an aryl group or an oxyalkyl group containing 1 to 8 carbon
atoms, C» alkyl or phenyl groups being preferred, and Z is a linear
polyhydroxyalkyl group, of which the alkyl chain is substituted by at least
two hydroxyl groups, or alkoxylated, preferably ethoxylated or
propoxylated, derivatives of that group.
Z is preferably obtained by reductive amination of a reduced sugar,
for example glucose, fructose, maltose, lactose, galactose, mannose or
xylose. The N-alkoxy- or N-aryloxy-substituted compounds may then be
converted into the required polyhydroxyfatty acid amides by reaction with
fatty acid methyl esters in the presence of an alkoxide as catalyst, for
example in accordance with the teaching of International patent application
WO-A-95107331.
According to the invention, preferred detergent tablets contain more
than 2% by weight, preferably more than 5% by weight and more
preferably more than 7.5% by weight of nonionic surfactants, based on the
weight of the tablet.
According to the invention, nonionic surfactants from all of the
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groups mentioned above may be used. Irrespective of the chemical
nature of the nonionic surfactants used, the nonionic surfactants present in
the detergent tablets preferably have a melting point below 40°C,
preferably below 30°C and more preferably below 20°C.
As mentioned above, the nonionic and anionic surfactants can be
incorporated in the detergent tablets according to the invention in various
ways. The may be added to the premix to be tabletted, for example, in
solid form or may be sprayed onto the premix in liquid form. It has been
found to be of advantage to produce surfactant granules which are mixed
with other powder-form components to form the premix to be tabletted.
According to the invention, preferred detergent tablets contain the
surfactants in the form of surfactant-containing granules which are present
in the tablets in quantities of 40 to 95% by weight, preferably 45 to 85% by
weight and more preferably 55 to 75% by weight, based on tablet weight.
In order to incorporate the required amount of detersive substance
in the detergent tablets, preferred detergent tablets contain surfactant
granules with surfactant contents of 5 to 60% by weight, preferably 10 to
50% by weight and more preferably 15 to 40% by weight, based on the
weight of the surfactant granules. According to the invention, detergent
tablets containing surfactant granules with anionic surfactant contents of 5
to 45% by weight, preferably 10 to 40% by weight and more preferably 15
to 35% by weight, based on the weight of the surfactant granules, and
surfactant granules with nonionic surfactant contents of 1 to 30% by
weight, preferably 5 to 25% by weight and more preferably 7.5 to 20% by
weight, based on the weight of the surfactant granules, are particularly
preferred.
In order to obtain storage-stable free-flowing granules, carriers
which contain the surfactant granules, i.e. builders, are preferably added in
the production of the surfactant granules. Other detergent ingredients,
more particularly so-called minor components, such as optical brighteners,
polymers, defoamers, phosphonates, dyes and perfumes, may also form
part of the surfactant granules. The substances are described in the
following.
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11
Besides the detersive ingredients, builders are the most important
ingredients of detergents. Any of the builders normally used in detergents
may be present in the detergent tablets according to the invention,
including in particular zeolites, silicates, carbonates, organic co-builders
and also - providing there are no ecological objections to their use -
phosphates.
It has been found that the effect of improving abrasion resistance is
greater if the surfactant granules contain only small quantities of
carbonates. Accordingly, preferred detergent tablets have a potassium
carbonate content of less than 10% by weight, preferably less than 7.5%
by weight and more preferably less than 5% by weight, based on the
weight of the tablet, tablets free from potassium carbonate being
particularly preferred.
Crystalline layer-form sodium silicates suitable as builders
correspond to the general formula NaMSixOZX+~A y H20, where M is
sodium or hydrogen, x is a number of 1.9 to 4 and y is a number of 0 to 20,
preferred values for x being 2, 3 or 4. Crystalline layer silicates such as
these are described, for example, in European patent application EP-A-0
164 514. Preferred crystalline layer silicates corresponding to the above
formula are those in which M is sodium and x assumes the value 2 or 3.
Both ~3- and 8-sodium disilicates Na2Si205A y H20 are particularly
preferred, ~-sodium disilicate being obtainable, for example, by the
process described in International patent application WO-A- 91108171.
Other useful builders are amorphous sodium silicates with a
modulus (Na20:Si02 ratio) of 1:2 to 1:3.3, preferably 1:2 to 1:2.8 and more
preferably 1:2 to 1:2.6 which dissolve with delay and exhibit multiple wash
cycle properties. The delay in dissolution in relation to conventional
amorphous sodium silicates can be obtained in various ways, for example
by surface treatment, compounding, compacting or by overdrying. In the
context of the invention, the term Aamorphous- is also understood to
encompass AX-ray amorphous-. In other words, the silicates do not
produce any of the sharp X-ray reflexes typical of crystalline substances in
X-ray diffraction experiments, but at best one or more maxima of the
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12
scattered X-radiation which have a width of several degrees of the
diffraction angle. However, particularly good builder properties may even
be achieved where the silicate particles produce crooked or even sharp
diffraction maxima in electron diffraction experiments. This may be
interpreted to mean that the products have microcrystalline regions
between 10 and a few hundred nm in size, values of up to at most 50 nm
and, more particularly, up to at most 20 nm being preferred. So-called X-
ray amorphous silicates such as these, which also dissolve with delay in
relation to conventional waterglasses, are described for example in
German patent application DE-A-44 00 024. Compacted amorphous
silicates, compounded amorphous silicates and overdried X-ray-
amorphous silicates are particularly preferred.
If desired, more zeolite besides the quantity of zeolite P and/or X
introduced through the surfactant granules may be incorporated in the
premix by adding zeolite as an aftertreatment component. The finely
crystalline, synthetic zeolite containing bound water used in accordance
with the invention is preferably a zeolite of the A, P, X or Y type. However,
zeolite X and mixtures of A, X and/or P are also suitable. Suitable zeolites
have a mean particle size of less than 10 ~m (volume distribution, as
measured by the Coulter Counter Method) and contain preferably 18 to
22% by weight and more preferably 20 to 22% by weight of bound water.
The generally known phosphates may of course also be used as
builders providing their use should not be avoided on ecological grounds.
The sodium salts of the orthophosphates, the pyrophosphates and, in
particular, the tripolyphosphates are particularly suitable.
Preferred detergent tablets contain less than 5% by weight,
preferably less than 2% by weight and more preferably less than 1 % by
weight of silica(s), based on the weight of the tablet.
Organic cobuilders which may be used in the detergent tablets
according to the invention include, in particular, polycarboxy-
lates/polycarboxylic acids, polymeric polycarboxylates, aspartic acid,
polyacetals, dextrins, other organic cobuilders (see below) and
phosphonates. Substances belonging to these classes are described in
CA 02297458 2000-O1-28
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the following.
Useful organic builders are, for example, the polycarboxylic acids
usable, for example, in the form of their sodium salts (polycarboxylic acids
in this context being understood to be carboxylic acids carrying more than
one acid function). Examples include citric acid, adipic acid, succinic acid,
glutaric acid, malic acid, tartaric acid, malefic acid, fumaric acid, sugar
acids, aminocarboxylic acids, nitrilotriacetic acid (NTA), providing its use
is
not ecologically unsafe, and mixtures thereof. Preferred salts are the salts
of the polycarboxylic acids, such as citric acid, adipic acid, succinic acid,
glutaric acid, tartaric acid, sugar acids and mixtures thereof.
The acids per se may also be used. Besides their builder effect, the
acids typically have the property of an acidifying component and,
accordingly, are also used to establish a lower and more mild pH value in
laundry or dishwashing detergents. Citric acid, succinic acid, glutaric acid,
adipic acid, gluconic acid and mixtures thereof are particularly mentioned
in this regard.
Other suitable builders are polymeric polycarboxylates such as, for
example, the alkali metal salts of polyacrylic acid or polymethacrylic acid,
for example those having a relative molecular weight of 500 to 70,000
g/mole.
The molecular weights mentioned in this specification for polymeric
polycarboxylates are weight-average molecular weights MW of the
particular acid form which, basically, were determined by gel permeation
chromatography (GPC) using a UV detector. The measurement was
carried out against an external polyacrylic acid standard which provides
realistic molecular weight values by virtue of its structural similarity to
the
polymers investigated. These values differ distinctly from the molecular
weights measured against polystyrene sulfonic acids as standard. The
molecular weights measured against polystyrene sulfonic acids are
generally far higher than the molecular weights mentioned in this
specification.
Suitable polymers are, in particular, polyacrylates which preferably
have a molecular weight of 2,000 to 20,000 g/mole. By virtue of their
CA 02297458 2000-O1-28
14
superior solubility, preferred representatives of this group are the short-
chain polyacrylates which have molecular weights of 2,000 to 10,000
g/mole and, more particularly, 3,000 to 5,000 g/mole.
Also suitable are copolymeric polycarboxylates, particularly those of
acrylic acid with methacrylic acid and those of acrylic acid or methacrylic
acid with malefic acid. Acrylic acid/maleic acid copolymers containing 50 to
90% by weight of acrylic acid and 50 to 10% by weight of malefic acid have
proved to be particularly suitable. Their relative molecular weights, based
on the free acids, are generally in the range from 2,000 to 70,000 g/mole,
preferably in the range from 20,000 to 50,000 g/mole and more preferably
in the range from 30,000 to 40,000 g/mole.
The (co)polymeric polycarboxylates may be used either in powder
form or in the form of an aqueous solution. The content of (co)polymeric
polycarboxylates in the compositions is preferably between 0.5 and 20%
by weight and more preferably between 3 and 10% by weight.
In order to improve their solubility in water, the polymers may also
contain allyl sulfonic acids, for example allyloxybenzenesulfonic acid and
methallyl sulfonic acid as monomer.
Biodegradable polymers of more than two different monomer units
are also particularly preferred, examples including those which contain
salts of acrylic acid and malefic acid and vinyl alcohol or vinyl alcohol
derivatives as monomers or those which contain salts of acrylic acid and
2-alkylallyl sulfonic acid and sugar derivatives as monomers.
Other preferred copolymers are those described in German patent
applications DE-A-43 03 320 and DE-A-44 17 734 which preferably
contain acrolein and acrylic acid/acrylic acid salts or acrolein and vinyl
acetate as monomers.
Other preferred builders are polymeric aminodicarboxilic acids, salts
or precursors thereof. Polyaspartic acids or salts and derivatives thereof
which, according to German patent application DE-A-195 40 086, have a
bleach-stabilizing effect in addition to their co-builder properties are
particularly preferred.
Other suitable builders are polyacetals which may be obtained by
CA 02297458 2000-O1-28
15
reaction of dialdehydes with polyol carboxylic acids containing 5 to 7
carbon atoms and at least three hydroxyl groups. Preferred polyacetals
are obtained from dialdehydes, such as glyoxal, glutaraldehyde,
terephthalaldehyde and mixtures thereof and from polyol carboxylic acids,
such as gluconic acid and/or glucoheptonic acid.
Other suitable organic builders are dextrins, for example oligomers
or polymers of carbohydrates which may be obtained by partial hydrolysis
of starches. The hydrolysis may be carried out by standard methods, for
example acid- or enzyme-catalyzed methods. The end products are
preferably hydrolysis products with average molecular weights of 400 to
500,000 g/mole. A polysaccharide with a dextrose equivalent (DE) of 0.5
to 40 and, more particularly, 2 to 30 is preferred, the DE being an
accepted measure of the reducing effect of a polysaccharide by
comparison with dextrose which has a DE of 100. Both maltodextrins with
a DE of 3 to 20 and dry glucose syrups with a DE of 20 to 37 and also so-
called yellow dextrins and white dextrins with relatively high molecular
weights of 2,000 to 30,000 may be used.
The oxidized derivatives of such dextrins are their reaction products
with oxidizing agents which are capable of oxidizing at least one alcohol
function of the saccharide ring to the carboxylic acid function. Dextrins
thus oxidized and processes for their production are known, for example,
from European patent applications EP-A-0 232 202, EP-A-0 427 349, EP-
A-0 472 042 and EP-A-0 542 496 and from International patent
applications WO 92118542, WO 93108251, WO 93116110, WO 95107303,
WO 95112619 and WO 95120608. An oxidized oligosaccharide according
to German patent application DE-A-196 00 018 is also suitable. A product
oxidized at C6 of the saccharide ring can be particularly advantageous.
Other suitable co-builders are oxydisuccinates and other derivatives
of disuccinates, preferably ethylenediamine disuccinate. Ethylenediamine-
N,N'-disuccinate (EDDS) is preferably used in the form of its sodium or
magnesium salts. Glycerol disuccinates and glycerol trisuccinates are
also particularly preferred in this connection. The quantities used in
CA 02297458 2000-O1-28
16
zeolite-containing and/or silicate-containing formulations are from 3 to 15%
by weight.
Other useful organic co-builders are, for example, acetylated
hydroxycarboxylic acids and salts thereof which may optionally be present
in lactone form and which contain at least 4 carbon atoms, at least one
hydroxy group and at most two acid groups. Co-builders such as these
are described, for example, in International patent application WO-A-
95/20029.
Another class of substances with co-builder properties are the
phosphonates, more particularly hydroxyalkane and aminoalkane phos-
phonates. Among the hydroxyalkane phosphonates, 1-hydroxyethane-
1,1-diphosphonate (HEDP) is particularly important as a co-builder. It is
preferably used in the form of a sodium salt, the disodium salt showing a
neutral reaction and the tetrasodium salt an alkaline ration (pH 9).
Preferred aminoalkane phosphonates are ethylenediamine tetramethylene
phosphonate (EDTMP), diethylenetriamine pentamethylene phosphonate
(DTPMP) and higher homologs thereof. They are preferably used in the
form of the neutrally reacting sodium salts, for example as the hexasodium
salt of EDTMP and as the hepta- and octasodium salt of DTPMP. Within
the class of phosphonates, HEDP is preferably used as builder. The
aminoalkane phosphonates also show a pronounced heavy metal binding
capacity. Accordingly, it can be of advantage, particularly where the
detergents also contain bleaching agents, to use aminoalkane
phosphonates, more especially DTPMP, or mixtures of the phosphonates
mentioned.
In addition, any compounds capable of forming complexes with
alkaline earth metal ions may be used as co-builders.
The production of surfactant-containing granules is widely
described in the prior art literature, including many patents and numerous
synoptic articles and books. Thus, W. Hermann de Groot, I. Adami and
G.F. Moretti describe various spray drying, mixing and granulation
processes for the production of detergents in "The Manufacture of
Modern Detergent Powders", Hermann de Groot Academic Publisher,
CA 02297458 2000-O1-28
Wassenaar, 1995.
17
On energy grounds, the surfactant-containing granules are
preferably produced by a granulation process and not by spray drying
according to the invention. Besides conventional granulation and
agglomeration processes, which may be carried out in various mixer-
granulators and mixer-agglomerators, press agglomeration processes, for
example, may also be used. Accordingly, processes in which the
surfactant-containing granules are produced by granulation,
agglomeration, press agglomeration or a combination of these processes
are preferred.
The granulation process may be carried out in a number of
machines typically used in the detergent industry. For example, the
spheronizers widely used in the pharmaceutical industry may be
employed. In rotary machines such as these, the residence time of the
granules is normally less than 20 seconds. Conventional mixers and
mixer-granulators are also suitable for granulation. The mixers used may
be both high-shear mixers and also normal mixers with lower rotational
speeds. Suitable mixers are, for example, Series R or RV Eirich~ mixers
(trademarks of Maschinenfabrik Gustav Eirich, Hardheim), the Schugi~
Flexomix mixer, the Fukae~ FS-G mixers (trademarks of Fukae Powtech,
Kogyo Co., Japan), Lodige~ FM, KM and CB mixers (trademarks of
Lodige Maschinenbau GmbH, Paderborn) and Series T or K-T Drais~
mixers (trademarks of Drais-Werke GmbH, Mannheim). The residence
times of the granules in the mixers is less than 60 seconds, the residence
time also depending on the rotational speed of the mixer. The residence
times are shorter, the higher the rotational speed of the mixer. The
residence times of the granules in the mixer/spheronizer are preferably
under one minute and more preferably under 15 seconds. In low-speed
mixers, for example a Lodige KM, residence times of up to 20 minutes are
adjusted, residence times of under 10 minutes being preferred in the
interests of process economy.
In the press agglomeration process, the surfactant containing
granules are shear-compacted under pressure and, at the same time,
CA 02297458 2000-O1-28
18
homogenized and are then discharged from the machine via a
shaping/forming stage. Industrially the most important press
agglomeration processes are extrusion, roll compacting, pelleting and
tabletting. Press agglomeration processes preferably used in accordance
with the invention for producing the surfactant-containing granules are
extrusion, roll compacting and pelleting.
In a preferred embodiment of the invention, the surfactant-
containing granules are preferably delivered continuously to a planetary
roll extruder or to a twin-screw extruder with co-rotating or contra-rotating
screws, of which the barrel and the extruder/granulation head may be
heated to the predetermined extrusion temperature. Under the shearing
effect of the extruder screws, the premix is compacted under pressure
(preferably at least 25 bar or - with extremely high throughputs - even
lower, depending on the machine used), plasticized, extruded in the form
of fine strands through the multiple-bore die in the extruder head and,
finally, chopped by means of a rotating blade into preferably substantially
spherical or cylindrical granules. The bore diameter of the multiple-bore
extrusion die and the length to which the extruded strands are cut are
adapted to the size selected for the granules. In this embodiment, it is
possible to produce granules with a substantially uniform predetermined
particle size, the absolute particle sizes being adaptable to the particular
application envisaged. Important embodiments comprise the production of
uniform granules in the millimeter range, for example in the range from 0.8
to 5 mm and, more particularly, in the range from about 1.0 to 3 mm. In
one important embodiment, the length-to-diameter ratio of the primary
granules formed by cutting the extruded strands is between about 1:1 and
about 3:1. In another preferred embodiment, the still plastic primary
granules are subjected to another shaping or forming step in which the
edges present on the crude extrudate are rounded off so that spherical or
substantially spherical granules can ultimately be obtained. Alternatively,
extrusion/ compression can also be carried out in low-pressure extruders,
in a Kahl press or in a Bextruder.
In another preferred embodiment of the present invention, the
CA 02297458 2000-O1-28
19
surfactant-containing granules are produced by roll compacting. In this
process, the surfactant-containing granules are introduced between two
rollers - either smooth or provided with depressions of defined shape -
and rolled under pressure between the two rollers to form a sheet-like
compactate. The rollers exert a high linear pressure on the premix and
may be additionally heated or cooled as required. Where smooth rollers
are used, smooth untextured compactate sheets are obtained. By
contrast, where textured rollers are used, correspondingly textured
compactates or individual pellets, in which for example certain shapes can
be imposed in advance on the subsequent granules, can be produced.
The sheet-like compactate is then broken up into smaller pieces by a
chopping and size-reducing process and can thus be processed to
granules which can be further refined and, more particularly, converted
into a substantially spherical shape by further surface treatment processes
known per se.
In another preferred embodiment of the present invention, the
surfactant-containing granules are produced by pelleting. In this process,
the surfactant-containing granules are applied to a perforated surface and
forced through the perforations by a pressure roller. In conventional pellet
presses, the surfactant-containing granules are compacted under
pressure, plasticized, forced through a perforated surface in the form of
fine strands by means of a rotating roller and, finally, are size-reduced to
granules by a cutting unit. The pressure roller and the perforated die may
assume many different forms. For example, flat perforated plates are
used, as are concave or convex ring dies through which the material is
pressed by one or more pressure rollers. In perforated-plate presses, the
pressure rollers may also be conical in shape. In ring die presses, the dies
and pressure rollers) may rotate in the same direction or in opposite
directions. A press suitable for carrying out the process according to the
invention is described, for example, in DE-OS 38 16 842 (Schliiter GmbH).
The ring die press disclosed in this document consists of a rotating ring die
permeated by pressure bores and at least one pressure roller operatively
connected to the inner surface thereof which presses the material
CA 02297458 2000-O1-28
20
delivered to the die space through the pressure bores into a discharge
unit. The ring die and pressure roller are designed to be driven in the
same direction which reduces the shear load applied to the premix and
hence the increase in temperature which it undergoes. However, the
pelleting process may of course also be carried out with heatable or
coolable rollers to enable the premix to be adjusted to a required
temperature.
The surfactant granules are then mixed with other aftertreatment
components to form a premix which may then be compressed to detergent
tablets. In addition to the ingredients already mentioned, the premix to be
compressed may contain other typical detergent ingredients as
aftertreatment components, more particularly from the group of builders,
disintegration aids, bleaching agents, bleach activators, enzymes, pH
regulators, fragrances, perfume carriers, fluorescers, dyes, foam inhibitors,
silicone oils, redeposition inhibitors, optical brighteners, discoloration
inhibitors, dye transfer inhibitors and corrosion inhibitors. However, the
substances mentioned, either wholly or in part, may already form part of
the surfactant granules.
Accordingly, the present invention also relates to a process for the
production of detergent tablets by mixing surfactant-containing granules
with fine-particle aftertreatment components and subsequent
forming/shaping in known manner, characterized in that the ratio of
nonionic to anionic surfactants in the tablets is in the range from 0.4:1 to
3:1.
In a preferred variant of the process according to the invention, the
ratio of nonionic to anionic surfactants in the tablets is in the range from
0.45:1 to 2.5:1, preferably in the range from 0.5:1 to 2:1 and more
preferably in the range from 0.75:1 to 1.5:1.
As mentioned above, the surfactants can be introduced into the
tablets in various ways, their incorporation via surfactant granules being
particularly advantageous. In this case, process-related advantages can
arise from the separation of anionic and nonionic surfactants so that
processes in which two batches of surfactant-containing granules are
CA 02297458 2000-O1-28
21
mixed with fine-particle aftertreatment components and the resulting
mixtures are subjected to subsequent forming/shaping in known manner,
one batch of granules containing the anionic surfactants and the other
batch containing the nonionic surfactants, represent preferred
embodiments of the invention.
It is of course also possible to use only a single batch of surfactant-
containing granules, i.e. to carry out a variant of the process in which one
batch of surfactant granules is mixed with fine-particle aftertreatment
components and the resulting mixture is subjected to subsequent
forming/shaping in known manner, the surfactant granules containing both
anionic and nonionic surfactants.
In this variant of the process, the surfactant-containing granules
preferably have total surfactant contents of 5 to 60% by weight, preferably
10 to 50% by weight and more preferably 15 to 40% by weight, based on
the weight of the surfactant granules, the surfactant granules having
anionic surfactant contents of preferably 5 to 45% by weight, more
preferably 10 to 40% by weight and most preferably 15 to 35% by weight
and nonionic surfactant contents of preferably 1 to 30% by weight, more
preferably 5 to 25% by weight and most preferably 7.5 to 20% by weight,
based on the weight of the surfactant granules.
Besides the surfactant granules, the detergent tablets according to
the invention may contain other detergent ingredients, for example
disintegration aids, bleaching agents, bleach activators, dyes and
perfumes, etc. These substances, which may also be part of the
surfactant granules, are described in the following.
In order to facilitate the disintegration of heavily compacted tablets,
disintegration aids, so-called tablet disintegrators, may be incorporated in
them to shorten their disintegration times. According to Rompp (9th
Edition, Vol. 6, page 4440) and Voigt "Lehrbuch der pharma-
zeutischen Technologie" (6th Edition, 1987, pages 182-184), tablet
disintegrators or disintegration accelerators are auxiliaries which promote
the rapid disintegration of tablets in water or gastric juices and the release
of the pharmaceuticals in an absorbable form.
CA 02297458 2000-O1-28
22
These substances, which are also known as "disintegrators" by
virtue of their effect, are capable of undergoing an increase in volume on
contact with water so that, on the one hand, their own volume is increased
(swelling) and, on the other hand, a pressure can be generated through
the release of gases which causes the tablet to disintegrate into relatively
small particles. Well-known disintegrators are, for example,
carbonate/citric acid systems, although other organic acids may also be
used. Swelling disintegration aids are, for example, synthetic polymers,
such as polyvinyl pyrrolidone (PVP), or natural polymers and modified
natural substances, such as cellulose and starch and derivatives thereof,
alginates or casein derivatives.
Preferred detergent tablets contain 0.5 to 10% by weight, preferably
3 to 7% by weight and more preferably 4 to 6% by weight of one or more
disintegration aids, based on the weight of the tablet.
According to the invention, preferred disintegrators are cellulose-
based disintegrators, so that preferred detergent tablets contain a
cellulose-based disintegrator in quantities of 0.5 to 10% by weight,
preferably 3 to 7% by weight and more preferably 4 to 6% by weight. Pure
cellulose has the formal empirical composition (C6H~o05)~ and, formally, is
a ~-1,4-polyacetal of cellobiose which, in turn, is made up of 2 molecules
of glucose. Suitable celluloses consist of ca. 500 to 5000 glucose units
and, accordingly, have average molecular weights of 50,000 to 500,000.
According to the invention, cellulose derivatives obtainable from cellulose
by polymer-analog reactions may also be used as cellulose-based
disintegrators. These chemically modified celluloses include, for example,
products of esterification or etherification reactions in which hydroxy
hydrogen atoms have been substituted. However, celluloses in which the
hydroxy groups have been replaced by functional groups that are not
attached by an oxygen atom may also be used as cellulose derivatives.
The group of cellulose derivatives includes, for example, alkali metal
celluloses, carboxymethyl cellulose (CMC), cellulose esters and ethers
and aminocelluloses. The cellulose derivatives mentioned are preferably
not used on their own, but rather in the form of a mixture with cellulose as
CA 02297458 2000-O1-28
23
cellulose-based disintegrators. The content of cellulose derivatives in
mixtures such as these is preferably below 50% by weight and more
preferably below 20% by weight, based on the cellulose-based
disintegrator. In one particularly preferred embodiment, pure cellulose free
from cellulose derivatives is used as the cellulose-based disintegrator.
The cellulose used as disintegration aid is preferably not used in
fine-particle form, but is converted into a coarser form, for example by
granulation or compacting, before it is added to and mixed with the
premixes to be tabletted. Detergent tablets which contain granular or
optionally co-granulated disintegrators are described in German patent
applications DE 197 09 991 (Stefan Herzog) and DE 197 10 254 (Henkel)
and in International patent application WO 98140463 (Henkel). Further
particulars of the production of granulated, compacted or co-granulated
cellulose disintegrators can also be found in these patent applications.
The particle sizes of such disintegration aids is mostly above 200 Nm, at
least 90% by weight of the particles being between 300 and 1600 pm in
size and, more particularly, between 400 and 1200 Nm in size. According
to the invention, the above-described relatively coarse-particle cellulose-
based disintegrators described in detail in the cited patent applications are
preferably used as disintegration aids and are commercially obtainable, for
example under the name of Arbocel~ TF-30-HG from Rettenmaier.
Microcrystalline cellulose may be used as another cellulose-based
disintegration aid or as part of such a component. This microcrystalline
cellulose is obtained by partial hydrolysis of the celluloses under
conditions which only attack and completely dissolve the amorphous
regions (ca. 30% of the total cellulose mass) of the celluloses, but leave
the crystalline regions (ca. 70%) undamaged. Subsequent de-aggregation
of the microfine celluloses formed by hydrolysis provides the
microcrystalline celluloses which have primary particle sizes of ca. 5 Nm
and which can be compacted, for example, to granules with a mean
particle size of 200 Nm.
In order further to improve their mechanical properties, for example
their abrasion resistance, the tablets may also be provided with a coating
CA 02297458 2000-O1-28
24
which covers the entire tablet. Coated detergent tablets such as these
may be produced by spraying the tablets with or dipping them in a melt or
solution of the coating material. In preferred embodiments of the
invention, however, the detergent tablets are not provided with a coating
that covers the entire tablet.
Among the compounds yielding HZ02 in water which serve as
bleaching agents, sodium perborate tetrahydrate and sodium perborate
monohydrate are particularly important. Other useful bleaching agents
are, for example, sodium percarbonate, peroxypyrophosphates, citrate
perhydrates and H202-yielding peracidic salts or peracids, such as
perbenzoates, peroxophthalates, diperazelaic acid, phthaloiminoperacid or
diperdodecane dioic acid. Even where the bleaching agents are used,
there is no need for surfactants and/or builders so that pure bleach tablets
can be produced. If pure bleach tablets are to be used in the washing of
laundry, a combination of sodium percarbonate and sodium sesqui-
carbonate is preferred irrespective of the other ingredients present in the
tablets. If detergent or bleach tablets for dishwashing machines are being
produced, bleaching agents from the group of organic bleaches may also
be used. Typical organic bleaching agents are diacyl peroxides, such as
dibenzoyl peroxide for example. Other typical organic bleaching agents
are the peroxy acids, of which alkyl peroxy acids and aryl peroxy acids are
particularly mentioned as examples. Preferred representatives are (a)
peroxybenzoic acid and ring-substituted derivatives thereof, such as alkyl
peroxybenzoic acids, but also peroxy-a-naphthoic acid and magnesium
monoperphthalate, (b) aliphatic or substituted aliphatic peroxy acids, such
as peroxylauric acid, peroxystearic acid, E-phthalimidoperoxycaproic acid
[phthaloiminoperoxyhexanoic acid (PAP)], o-carboxybenzamidoperoxy-
caproic acid, N-nonenylamidoperadipic acid and N-nonenylamidoper-
succinates. and (c) aliphatic and araliphatic peroxydicarboxylic acids, such
as 1,12-diperoxycarboxylic acid, 1,9-diperoxyazelaic acid, diperoxysebacic
acid, diperoxybrassylic acid, diperoxyphthalic acids, 2-decyldiperoxy-
butane-1,4-dioic acid, N,N-terephthaloyl-di(6-aminopercaproic acid).
Other suitable bleaching agents in dishwasher tablets are chlorine-
CA 02297458 2000-O1-28
25
and bromine-releasing substances. Suitable chlorine- or bromine-
releasing materials are, for example, heterocyclic N-bromamides and N-
chloramides, for example trichloroisocyanuric acid, tribromoisocyanuric
acid, dibromoisocyanuric acid and/or dichloroisocyanuric acid (DICA)
and/or salts thereof with cations, such as potassium and sodium.
Hydantoin compounds, such as 1,3-dichloro-5,5-dimethyl hydantoin, are
also suitable.
In order to obtain an improved bleaching effect where washing is
carried out at temperatures of 60°C or lower, bleach activators may be
incorporated in the detergent tablets according to the invention. The
bleach activators may be compounds which form aliphatic
peroxocarboxylic acids containing preferably 1 to 10 carbon atoms and
more preferably 2 to 4 carbon atoms and/or optionally substituted
perbenzoic acid under perhydrolysis conditions. Substances bearing O-
and/or N-acyl groups with the number of carbon atoms mentioned and/or
optionally substituted benzoyl groups are suitable. Preferred bleach
activators are polyacylated alkylenediamines, more particularly tetraacetyl
ethylenediamine (TAED), acylated triazine derivatives, more particularly
1,5-diacetyl-2,4-dioxohexahydro-1,3,5-triazine (DADHT), acylated
glycolurils, more particularly tetraacetyl glycoluril (TAGU), N-acylimides,
more particularly N-nonanoyl succinimide (NOSI), acylated phenol
sulfonates, more particularly n-nonanoyl or isononanoyloxybenzene-
sulfonate (n- or iso-NOBS), carboxylic anhydrides, more particularly
phthalic anhydride, acylated polyhydric alcohols, more particularly
triacetin, ethylene glycol diacetate and 2,5-diacetoxy-2,5-dihydrofuran.
In addition to or instead of the conventional bleach activators
mentioned above, so-called bleach catalysts may also be incorporated in
the tablets. Bleach catalysts are bleach-boosting transition metal salts or
transition metal complexes such as, for example, manganese-, iron-,
cobalt-, ruthenium- or molybdenum-salen complexes or carbonyl
complexes. Manganese, iron, cobalt, ruthenium, molybdenum, titanium,
vanadium and copper complexes with nitrogen-containing tripod ligands
and cobalt-, iron-, copper- and ruthenium-ammine complexes may also be
CA 02297458 2000-O1-28
used as bleach catalysts.
26
Suitable enzymes are, in particular, those from the classes of
hydrolases, such as proteases, esterases, lipases or lipolytic enzymes,
amylases, cellulases or other glycosyl hydrolases and mixtures thereof.
All these hydrolases contribute to the removal of stains, such as protein-
containing, fat-containing or starch-containing stains, and discoloration in
the washing process. Cellulases and other glycosyl hydrolases can
contribute towards color retention and towards increasing fabric softness
by removing pilling and microfibrils. Oxidoreductases may also be used
for bleaching and for inhibiting dye transfer. Enzymes obtained from
bacterial strains or fungi, such as Bacillus subtilis, Bacillus licheniformis,
Streptomyces griseus, Coprinus cinereus and Humicola insolens and from
genetically modified variants are particularly suitable. Proteases of the
subtilisin type are preferably used, proteases obtained from Bacillus lentus
being particularly preferred. Of particular interest in this regard are
enzyme mixtures, for example of protease and amylase or protease and
lipase or lipolytic enzymes or protease and cellulase or of cellulase and
lipase or lipolytic enzymes or of protease, amylase and lipase or lipolytic
enzymes or protease, lipase or lipolytic enzymes and cellulase, but
especially protease- and/or lipase-containing mixtures or mixtures with
lipolytic enzymes. Examples of such lipolytic enzymes are the known
cutinases. Peroxidases or oxidases have also been successfully used in
some cases. Suitable amylases include in particular a-amylases,
isoamylases, pullanases and pectinases. Preferred cellulases are
cellobiohydrolases, endoglucanases and ~i-glucosidases, which are also
known as cellobiases, and mixtures thereof. Since the various cellulase
types differ in their CMCase and avicelase activities, the desired activities
can be established by mixing the cellulases in the appropriate ratios.
The enzymes may be adsorbed to supports and/or encapsulated in
shell-forming substances to protect them against premature
decomposition. The percentage content of the enzymes, enzyme mixtures
or enzyme granules in the tablets according to the invention may be, for
example, from about 0.1 to 5% by weight and is preferably from 0.1 to
CA 02297458 2000-O1-28
about 2% by weight.
27
In addition, the detergent tablets according to the invention may
also contain components with a positive effect on the removability of oil
and fats from textiles by washing (so-called soil repellents). This effect
becomes particularly clear when a textile which has already been
repeatedly washed with a detergent according to the invention containing
this oil- and fat-dissolving component is soiled. Preferred oil- and fat-
dissolving components include, for example, nonionic cellulose ethers,
such as methyl cellulose and methyl hydroxypropyl cellulose containing 15
to 30% by weight of methoxyl groups and 1 to 15% by weight of hydroxy-
propoxyl groups, based on the nonionic cellulose ether, and the polymers
of phthalic acid and/or terephthalic acid known from the prior art or
derivatives thereof, more particularly polymers of ethylene terephthalates
and/or polyethylene glycol terephthalates or anionically and/or nonionically
modified derivatives thereof. Of these, the sulfonated derivatives of
phthalic acid and terephthalic acid polymers are particularly preferred.
The tablets may contain derivatives of diaminostilbenedisulfonic
acid or alkali metal salts thereof as optical brighteners. Suitable optical
brighteners are, for example, salts of 4,4'-bis-(2-anilino-4-morpholino-
1,3,5-triazinyl-6-amino)-stilbene-2,2'-disulfonic acid or compounds of
similar composition which contain a diethanolamino group, a methylamino
group, an anilino group or a 2-methoxyethylamino group instead of the
morpholino group. Brighteners of the substituted diphenyl styryl type, for
example alkali metal salts of 4,4'-bis-(2-sulfostyryl)-diphenyl, 4,4'-bis-(4-
chloro-3-sulfostyryl)-diphenyl or 4-(4-chlorostyryl)-4'-(2-sulfostyryl)-diphen-
yl, may also be present. Mixtures of the brighteners mentioned above may
also be used.
Dyes and fragrances are added to the detergent tablets according
to the invention to improve the aesthetic impression created by the
products and to provide the consumer not only with the required washing
performance but also with a visually and sensorially "typical and
unmistakable" product. Suitable perfume oils or fragrances include
individual fragrance compounds, for example synthetic products of the
CA 02297458 2000-O1-28
28
ester, ether, aldehyde, ketone, alcohol and hydrocarbon type. Fragrance
compounds of the ester type are, for example, benzyl acetate,
phenoxyethyl isobutyrate, p-tert.butyl cyclohexyl acetate, linalyl acetate,
dimethyl benzyl carbinyl acetate, phenyl ethyl acetate, linalyl benzoate,
benzyl formate, ethyl methyl phenyl glycinate, allyl cyclohexyl propionate,
styrallyl propionate and benzyl salicylate. The ethers include, for example,
benzyl ethyl ether; the aldehydes include, for example, the linear alkanals
containing 8 to 18 carbon atoms, citral, citronellal, citronellyloxy-
acetaldehyde, cyclamen aldehyde, hydroxycitronellal, lilial and bourgeonal;
the ketones include, for example, the ionones, a-isomethyl ionone and
methyl cedryl ketone; the alcohols include anethol, citronellol, eugenol,
geraniol, linalool, phenyl ethyl alcohol and terpineol and the hydrocarbons
include, above all, the terpenes, such as limonene and pinene. However,
mixtures of various fragrances which together produce an attractive
fragrance note are preferably used. Perfume oils such as these may also
contain natural fragrance mixtures obtainable from vegetable sources, for
example pine, citrus, jasmine, patchouli, rose or ylang-ylang oil. Also
suitable are clary oil, camomile oil, clove oil, melissa oil, mint oil,
cinnamon
leaf oil, lime blossom oil, juniper berry oil, vetiver oil, olibanum oil,
galbanum oil and labdanum oil and orange blossom oil, neroli oil, orange
peel oil and sandalwood oil.
The detergent tablets according to the invention normally contain
less than 0.01 % by weight of dyes whereas perfumes/fragrances can
make up as much as 2% by weight of the formulation as a whole.
The fragrances may be directly incorporated in the detergents
according to the invention, although it can also be of advantage to apply
the fragrances to supports which strengthen the adherence of the perfume
to the washing and which provide the textiles with a long-lasting fragrance
through a slower release of the perfume. Suitable support materials are,
for example, cyclodextrins, the cyclodextrin/perfume complexes optionally
being coated with other auxiliaries.
In order to improve their aesthetic impression, the detergents
according to the invention may be colored with suitable dyes. Preferred
CA 02297458 2000-O1-28
29
dyes, which are not difficult for the expert to choose, have high stability in
storage, are not affected by the other ingredients of the detergents or by
light and do not have any pronounced substantivity for textile fibers so as
not to color them.
Before the particulate premix is compressed to form detergent
tablets, it may be "powdered" with fine-particle surface treatment materials.
This can be of advantage to the quality and physical properties of both the
premix (storage, tabletting) and the final detergent tablets. Fine-particle
powdering materials have been known for some time in the art, zeolites,
silicates and other inorganic salts generally being used. However, the
compound is preferably "powdered" with fine-particle zeolite, zeolites of
the faujasite type being preferred. In the context of the present invention,
the expression "zeolite of the faujasite type" encompasses all three
zeolites which form the faujasite subgroup of zeolite structural group 4 (cf.
Donald W. Breck: "Zeolite Molecular Sieves" John Wiley & Sons, New
York/London/Sydney/Toronto, 1974, page 92). Besides zeolite X,
therefore, zeolite Y and faujasite and mixtures of these compounds may
also be used, pure zeolite X being preferred.
According to the invention, preferred processes for the production
of detergent tablets are those in which the, or one of the, fine-particle
aftertreatment components subsequently incorporated is a zeolite of the
faujasite type with particle sizes below 100 Nm, preferably below 10 Nm
and more preferably below 5 Nm and makes up at least 0.2% by weight,
preferably at least 0.5% by weight and more preferably more than 1 % by
weight of the premix to be compressed.
In preferred processes according to the invention, the premix to be
compressed has a bulk density of at least 500 g/I, preferably of at least
600 g/I and more preferably above 700 g/I and additionally contains one or
more substances from the group of disintegration aids, bleaching agents,
bleach acivtators, enzymes, pH regulators, fragrances, perfume carriers,
fluorescers, dyes, foam inhibitors, silicone oils, redeposition inhibitors,
optical brigtheners, discoloration inhibitors, dye transfer inhibitors and
corrosion inhibitors.
CA 02297458 2000-O1-28
30
To produce the tablets according to the invention, the premix is
compacted between two punches in a die to form a solid compactate. This
process, which is referred to in short hereinafter as tabletting, comprises
four phases, namely metering, compacting (elastic deformation), plastic
deformation and ejection.
The premix is first introduced into the die, the filling level and hence
the weight and shape of the tablet formed being determined by the
position of the lower punch and the shape of the die. Uniform metering,
even at high tablet throughputs, is preferably achieved by volumetric
metering of the premix. As the tabletting process continues, the top punch
comes into contact with the premix and continues descending towards the
bottom punch. During this compaction phase, the particles of the premix
are pressed closer together, the void volume in the filling between the
punches continuously diminishing. The plastic deformation phase in which
the particles coalesce and form the tablet begins from a certain position of
the top punch (and hence from a certain pressure on the premix).
Depending on the physical properties of the premix, its constituent
particles are also partly crushed, the premix sintering at even higher
pressures. As the tabletting rate increases, i.e. at high throughputs, the
elastic deformation phase becomes increasingly shorter so that the tablets
formed can have more or less large voids. In the final step of the tabletting
process, the tablet is forced from the die by the bottom punch and carried
away by following conveyors. At this stage, only the weight of the tablet is
definitively established because the tablets can still change shape and
size as a result of physical processes (re-elongation, crystallographic
effects, cooling, etc.).
The tabletting process is carried out in commercially available tablet
presses which, in principle, may be equipped with single or double
punches. In the latter case, not only is the top punch used to build up
pressure, the bottom punch also moves towards the top punch during the
tabletting process while the top punch presses downwards. For small
production volumes, it is preferred to use eccentric tablet presses in which
the punches) is/are fixed to an eccentric disc which, in turn, is mounted on
CA 02297458 2000-O1-28
31
a shaft rotating at a certain speed. The movement of these punches is
comparable with the operation of a conventional four-stroke engine.
Tabletting can be carried out with a top punch and a bottom punch,
although several punches can also be fixed to a single eccentric disc, in
which case the number of die bores is correspondingly increased. The
throughputs of eccentric presses vary according to type from a few
hundred to at most 3,000 tablets per hour.
For larger throughputs, rotary tablet presses are generally used. In
rotary tablet presses, a relatively large number of dies is arranged in a
circle on a so-called die table. The number of dies varies - according to
model - between 6 and 55, although even larger dies are commercially
available. Top and bottom punches are associated with each die on the
die table, the tabletting pressures again being actively built up not only by
the top punch or bottom punch, but also by both punches. The die table
and the punches move about a common vertical axis, the punches being
brought into the filling, compaction, plastic deformation and ejection
positions by means of curved guide rails. At those places where the
punches have to be raised or lowered to a particularly significant extent
(filling, compaction, ejection), these curved guide rails are supported by
additional push-down members, pull-down rails and ejection paths. The
die is filled from a rigidly arranged feed unit, the so-called filling shoe,
which is connected to a storage container for the compound. The
pressure applied to the premix can be individually adjusted through the
tools for the top and bottom punches, pressure being built up by the rolling
of the punch shank heads past adjustable pressure rollers.
To increase throughput, rotary presses can also be equipped with
two filling shoes so that only half a circle has to be negotiated to produce a
tablet. To produce two-layer or multiple-layer tablets, several filling shoes
are arranged one behind the other without the lightly compacted first layer
being ejected before further filling. Given suitable process control, shell
and bull's-eye tablets - which have a structure resembling an onion skin -
can also be produced in this way. In the case of bull's-eye tablets, the
upper surface of the core or rather the core layers is not covered and thus
CA 02297458 2000-O1-28
32
remains visible. Rotary tablet presses can also be equipped with single or
multiple punches so that, for example, an outer circle with 50 bores and an
inner circle with 35 bores can be simultaneously used for tabletting.
Modern rotary tablet presses have throughputs of more than one million
tablets per hour.
Tabletting machines suitable for the purposes of the invention can
be obtained, for example, from the following companies: Apparatebau
Holzwarth GbR, Asperg, Wilhelm Fette GmbH, Schwarzenbek, Hofer
GmbH, Weil, KILIAN, Cologne, KOMAGE, Kell am See, KORSCH Pressen
GmbH, Berlin, Mapag Maschinenbau AG, Bern (Switzerland) and Courtoy
N.V., Halle (BE/LU). One example of a particularly suitable tabletting
machine is the model HPF 630 hydraulic double-pressure press
manufactured by LAEIS, D.
The tablets can be made in certain shapes and certain sizes.
Suitable shapes are virtually any easy-to-handle shapes, for example
slabs, bars, cubes, squares and corresponding shapes with flat sides and,
in particular, cylindrical forms of circular or oval cross-section. This last
embodiment encompasses shapes from tablets to compact cylinders with
a height-to-diameter ratio of more than 1.
The portioned pressings may be formed as separate individual
elements which correspond to a predetermined dose of the detergent.
However, it is also possible to form pressings which combine several such
units in a single pressing, smaller portioned units being easy to break off in
particular through the provision of predetermined weak spots. For the use
of laundry detergents in machines of the standard European type with
horizontally arranged mechanics, it can be of advantage to produce the
portioned pressings as cylindrical or square tablets, preferably with a
diameter-to-height ratio of about 0.5:2 to 2:0.5. Commercially available
hydraulic presses, eccentric presses and rotary presses are particularly
suitable for the production of pressings such as these.
The three-dimensional form of another embodiment of the tablets
according to the invention is adapted in its dimensions to the dispensing
compartment of commercially available domestic washing machines, so
CA 02297458 2000-O1-28
33
that the tablets can be introduced directly, i.e. without a dosing aid, into
the
dispensing compartment where they dissolve on contact with water.
However, it is of course readily possible - and preferred in accordance with
the present invention - to use the detergent tablets in conjunction with a
dosing aid.
Another preferred tablet which can be produced has a plate-like or
slab-like structure with alternately thick long segments and thin short
segments, so that individual segments can be broken off from this "bar" at
the predetermined weak spots, which the short thin segments represent,
and introduced into the machine. This "bar" principle can also be
embodied in other geometric forms, for example vertical triangles which
are only joined to one another at one of their longitudinal sides.
In another possible embodiment, however, the various components
are not compressed to form a single tablet, instead the tablets obtained
comprise several layers, i.e. at least two layers. These various layers may
have different dissolving rates. This can provide the tablets with favorable
performance properties. If, for example, the tablets contain components
which adversely affect one another, one component may be integrated in
the more quickly dissolving layer while the other component may be
incorporated in a more slowly dissolving layer so that the first component
can already have reacted off by the time the second component dissolves.
The various layers of the tablets can be arranged in the form of a stack, in
which case the inner layers) dissolve at the edges of the tablet before the
outer layers have completely dissolved. Alternatively, however, the inner
layers) may also be completely surrounded by the layers lying further to
the outside which prevents constituents of the inner layers) from
dissolving prematurely.
In another preferred embodiment of the invention, a tablet consists
of at least three layers, i.e. two outer layers and at least one inner layer,
a
peroxy bleaching agent being present in at least one of the inner layers
whereas, in the case of the stack-like tablet, the two cover layers and, in
the case of the envelope-like tablet, the outermost layers are free from
peroxy bleaching agent. In another possible embodiment, peroxy
CA 02297458 2000-O1-28
34
bleaching agent and any bleach activators or bleach catalysts present
and/or enzymes may be spatially separated from one another in one and
the same tablet. Multilayer tablets such as these have the advantage that
they can be used not only via a dispensing compartment or via a dosing
unit which is added to the wash liquor, instead it is also possible in cases
such as these to introduce the tablet into the machine in direct contact with
the fabrics without any danger of spotting by bleaching agent or the like.
Similar effects can also be obtained by coating individual
constituents of the detergent composition to be compressed or the tablet
as a whole. To this end, the tablets to be coated may be sprayed, for
example, with aqueous solutions or emulsions or a coating may be
obtained by the process known as melt coating.
After pressing, the detergent tablets have high stability. The
fracture resistance of cylindrical tablets can be determined via the
diametral fracture stress. This in turn can be determined in accordance
with the following equation:
2P
a=
~Dt
where a represents the diametral fracture stress (DFS) in Pa, P is the
force in N which leads to the pressure applied to the tablet that results in
fracture thereof, D is the diameter of the tablet in meters and t is its
height.
The present invention also relates to the use of surfactant granules
which, after mixing with fine-particle aftertreatment components, are
compressed in known manner to form detergent tablets and in which the
ratio of nonionic to anionic surfactants is in the range from 0.4:1 to 3:1 for
improving the abrasion resistance of detergent tablets.. Through the use of
the surfactants in a defined ratio by weight, the physical properties of the
tablets can be improved, as shown by the following Examples:
CA 02297458 2000-O1-28
Examples
Various surfactant granules differing in their nonionic and anionic
surfactant contents were produced by wet granulation in a 130-liter Lodige
plowshare mixer. After granulation, the granules were dried in an
Aeromatic fluidized bed dryer for 30 minutes at an inflowing air
temperature of 60°C. After drying, the granules were sieved to remove
the
fine particles (< 0.06 mm) and coarse fractions (> 1.6 mm).
The surfactant granules E1 to E4 and V1 and V2 were then mixed
with other components to form a compressible premix which was then
tabletted in a Korsch eccentric press (tablet diameter 44 mm, height 22
mm, weight 37.5 g). The measured tablet hardnesses and disintegration
times are the mean values of a double determination, the individual values
varying by at most 2 N and 2 s, respectively, according to the type of
tablet. The composition of the surfactant granules is shown in Table 1
while the composition of the premixes to be tabletted (and hence the
tablets) is shown in Table 2.
Table 1: Composition of the surfactant granules [% by weight]
E1 E2 E~ E4 1f1' lt2
Cg~3 alkyl benzenesulfonate7.5 12.7 15.0 15.5 18.0 18.0
C,z_~8 fatty alcohol 2.5 4.3 5.0 5.5 6.0 6.0
sulfate
C,z_~8 fatty alcohol 21.0 14.0 11.0 10.0 7.0 7.0
sulfate + 7E0
Soap 1.3 1.3 1.3 1.3 1.3 1.3
Sodium carbonate 10.0 10.0 10.0 10.0 10.0 10.0
Sodium sulfate 5.0 5.0 5.0 5.0 5.0 5.0
Zeolite A - 34.8 34.9 35.0 35.0 -
Zeolite X 34.8 - - _
- 35.0
Na hydroxyethane-1,1- 1.0 1.0 1.0 1.0 1.0 1.0
diphosphonate
Acrylic acid/maleic acid6.0 6.0 6.0 6.0 6.0 6.0~
copolymer
CA 02297458 2000-O1-28
36
NaOH, water-free active 0.1 0.1 0.1 0.1 0.1 0.1
substance
Water, salts Rest Rest Rest Rest Rest Rest
Sum of nonionic surfactant21.0 14.0 11.0 10.0 7.0 7.0
Sum of anionic surfactants11.3 18.3 21.3 22.3 25.3 25.3
Ratio of nonionic to 1.86:10.77:10.52:10.45:10.28:10.28:1
anionic
surfactant
Table 2: Composition of the premixes [% by weight]
Surfactant granules (Table 62.05
1)
Sodium perborate monohydrate 17.4
TAED 7.3
Foam inhibitor 3.5
Enzymes 1.7
Repel-O-Tex~ SRP 4* 1.1
Perfume 0.5
Wessalith~ P (zeolite A) 1.0
Disintegration aid (cellulose)5.0
* Terephthalic acid/ethylene glycol/polyethylene glycol ester (Rhodia,
Rhone-Poulenc)
The hardness of the tablets was measured after two days' storage
by deforming a tablet until it broke, the force being applied to the sides of
the tablet and the maximum force withstood by the tablet being
determined.
Dissolvability was tested in a Miele Novotronic W918 washing
machine (main wash cycle, 60°C). After the flushing in phase (three
tablets, cold mains water with a hardness of 16° dH), the residues were
dried and weighed out.
Abrasion resistance was determined by placing a tablet on a 1.6
CA 02297458 2000-O1-28
37
mm mesh sieve. The sieve was then placed in a Retsch analytical sieving
machine and stressed at an amplitude of 2 mm for 120 seconds. The
abrasion in % can be calculated by weighing the tablet on the sieve before
and after stressing. The experimental data are shown in Table 3:
Table 3: Detergent tablets [physical data]
Tat~~et E1 E~ E3 E4 V1: V2
Tablet hardness 39 40 38 41 41 40
[N]
Residue [g] 3 7 7 4 6 6
Abrasion [%] 12 3 10 15 23 38
Whereas the hardnesses and residue values of tablets E and V are
of the same order, the tablets E according to the invention show far better
resistance to the friction effect of the vibrating sieve. A nonionic to
anionic
surfactant ratio below 0.4:1 (V1, V2) leads to tablets which lose a quarter
(v1 ) and two fifths (V2) of their weight. With such drastic losses of weight,
the original form of the tablet is no longer visible. The performance
properties are thus further improved by the ratio of nonionic to anionic
surfactant according to the invention.
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