Note: Descriptions are shown in the official language in which they were submitted.
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DETERGENT COMPOSITIONS
TECHNICAL FIELD
The present invention relates to particulate
detergent compositions, particularly those of high bulk
density, containing primary alcohol sulphate (PAS), built
with alkali metal aluminosilicate, and optionally
containing sodium carbonate.
BACKGROUND AND PRIOR ART
Detergent compositions built with zeolite and
containing both alkylbenzene sulphonate and PAS are
disclosed in JP 62 240 397A (Kao), JP 62 273 300A (Kao),
EP 219 314A (Procter & Gamble) and EP 220 024A (Procter &
Gamble).
JP 01 142 000A (Nippon Gosen Senzai) discloses a
high bulk density detergent composition prepared by
neutralising PAS acid with sodium carbonate and zeolite.
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EP 342 917A (Unilever) discloses detergent
compositions containing PAS having a specific chain
length distribution.
Our copending Canadian Patent Application No. 2,034,666
filed on January 21, 1991 discloses detergent compositions containing
zeolite, sodium carbonate, and branched-chain PAS.
EP 340 013A (Unilever) relates to high-bulk-density
detergent powders containing a moderate to high
proportion of surfactant (particularly anionic
surfactant) and a relatively high proportion of zeolite
builder. The preferred and exemplified anionic
surfactant is alkylbenzene sulphonate. The powders are
preferably prepared by processes involving granulation
and densification of a spray-dried powder in a high-speed
mixer/granulator having both a stirring action and a
cutting action.
The present invention is based on the observation
that, in detergent compositions of the general type
disclosed in EP 340 013A (Unilever), when PAS is used
partially or wholly in place of alkylbenzene sulphonate,
surprisingly improved detergency can be achieved by
adjustment of the amount of sodium carbonate present.
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DEFINITION OF THE INVENTION
The present invention accordingly provides a
particulate detergent composition which comprises:
(a) from 17 to 35 wt% of non-soap detergent-active
material consisting essentially of:
(i) from 5 to 35 wt% of an anionic surfactant
component consisting of primary alcohol sulphate
[10-100 wt% of (i)] optionally together with
alkylbenzene sulphonate [0-90 wt% of (i)],
(ii) optionally from O to 10 wt% of nonionic
surfactant,
(iii) optionally from O to 10 wt% of anionic
surfactant other than primary alcohol sulphate or
alkylbenzene sulphonate,
(b) optionally from O to 10 wt% of fatty acid soap,
(c) from 25 to 45 wt% (anhydrous basis) of crystalline
or amorphous alkali metal aluminosilicate,
(d) from O to 10 wt% of sodium carbonate if the anionic
surfactant component (a)(i) contains 10-60 wt% of primary
alcohol sulphate, from O to 20 wt% of sodium carbonate if
the anionic surfactant component (a)(i) contains 60-80
wt% primary alcohol sulphate, and from 10 to 20 wt% of
sodium carbonate if the anionic surfactant component
(a)(i) contains 80-100 wt% primary alcohol sulphate,
(e) optionally other detergent ingredients to 100 wt%.
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DETAILED DESCRIPTION OF THE INVENTION
The subject of the invention is a detergent
composition in particulate form characterised by a
moderate to high content of anionic surfactant, including
or consisting of primary alcohol sulphate; a relatively
high level of aluminosilicate builder; and a suitably
chosen level of sodium carbonate ranging from zero to
moderately high.
Preferably the weight ratio of aluminosilicate
builder (c) to total non-soap surfactant (a) is within
the range of from 0.9:1 to 2.6:1, more preferably from
1.2:1 to 1.8:1.
These amounts and ratios have been found to give
excellent detergency and, in the preferred embodiment of
the invention according to which the composition is of
high bulk density, improved processability and powder
properties.
The surfactant s~stem
The detergent composition of the invention comprises
from 17 to 35 wt% of non-soap detergent-active material,
of which a specified anionic surfactant component is an
essential ingredient. The specified anionic surfactant
component, which constitutes from 5 to 35 wt% of the
whole composition, consists either of primary alcohol
sulphate (PAS) alone, or of PAS in admixture with linear
alkylbenzene sulphonate (LAS). If both LAS and PAS are
present, PAS must constitute at least 10 wt%, and
preferably at least 20 wt%, of the two together, while
LAS can constitute up to 90 wt%, and preferably up to
80 wt%, of the two together.
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As explained in more detail below, the amount of LAS
present and the relative proportions of LAS and PAS
determine the amount of sodium carbonate, if any,
present.
The primary alcohol sul~hate
An essential ingredient of the surfactant system is
a primary alcohol sulphate (PAS), also known as alkyl
sulphate. PAS constitutes from 10 to 100 wt% of the
essential anionic surfactant component in the
compositions of the invention, which itself constitutes
from 5 to 35 wt% of the whole composition.
These anionic surfactants have received much
attention recently as potential replacements for
alkylbenzene sulphonates on environmental grounds, but
have shown some deficiencies in all-round detergency
performance under a wide range of wash conditions.
Alcohol sulphates may be derived from both synthetic
and natural alcohols containing from about 8 to 22 carbon
atoms. Examples of suitable alcohols that can be used
for PAS manufacture include decyl, lauryl, myristyl,
palmityl and stearyl alcohols, and the mixture of fatty
alcohols derived by reducing the glycerides of tallow and
coconut oils. Natural alcohols, for example, tallow or
coconut alcohol, give rise to straight-chain (linear)
PAS, while synthetic alcohols, for example those produced
by the Oxo process, can give rise to either linear or
branched-chain PAS. Both linear and branched PAS are
suitable for use in the present invention.
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Most commercially available PAS is a mixture
containing a spread of chain lengths. The PAS used in
the compositions of the present invention is preferably
of relatively short chain length, that is to say, it
consists wholly or predominantly of material having an
alkyl chain length of C16 or below, and more preferably
consists wholly or predominantly of material having an
alkyl chain length of C14 or below. Short-chain PAS is
especially suitable for products intended solely or
predominantly for low-temperature (<25~C) washing
conditions.
Preferred PAS of natural origin is derived from
coconut oil, palm kernel oil, babassu oil, or macauba
oil.
Especially preferred is coconut alcohol PAS
(cocoPAS), either as the natural material consisting
predominantly of linear C12 and C14 alcohols with smaller
amounts of shorter- and longer-chain material, or as a
"narrow-cut" material enriched in C12 and C14 alcohols by
fractionation. CocoPAS exhibits good low-temperature
detergency, is of renewable natural origin, and is
biodegradable.
In products intended solely or predominantly for use
in low-temperature wash conditions, longer-chain PAS such
as tallow PAS is preferably absent, or present in a
relatively low proportion, because its low-temperature
performance is poor.
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The linear alkylbenzene sul~honate
As previously indicated, the main anionic surfactant
component, which constitutes 5 to 35 wt% of the
composition, may comprise linear alkylbenzene sulphonate
(LAS) in addition to PAS, provided that PAS constitutes
at least 10 wt%, and preferably at least 20 wt%, of the
two together.
Linear alkylbenzene sulphonates are exceedingly
well-known ingredients of fabric washing detergent
compositions. The alkyl chain length is generally in the
C8-C15 range. These materials are fully described in the
literature, for example, in "Surface-Active Agents and
Detergents", Volumes I and II, by Schwartz, Perry and
Berch.
Optional nonionic surfactant
The compositions of the invention may also contain
up to 10 wt% of nonionic surfactant. Nonionic
surfactants that may be used include the primary and
secondary alcohol ethoxylates, especially the aliphatic
C12-C15 primary and secondary alcohols ethoxylated with
an average of from 3 to 20 moles of ethylene oxide per
mole of alcohol; and alkylpolyglycosides.
O~tional anionic surfactant
The composition may alternatively or additionally
contain up to 10 wt% of one or more anionic surfactants
other than LAS and PAS. Examples of suitable anionic
surfactants are alkyl ether sulphates, alkyl xylene
sulphonates, olefin sulphonates, dialkyl sulphosuccinates
and fatty acid ester sulphonates.
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These lists are not intended to be exhaustive and
for further examples the reader is referred to the
standard literature, for example, "Surface-Active Agents
and Detergents", Volumes I and II, by Schwartz, Perry and
Berch.
Optional soap
As well as non-soap detergents, the composition of
the invention may contain up to 10 wt% of fatty acid
soap, to provide foam control and additional detergency
and builder power. Soap, if present, is not included
within the total of 17 to 35 wt~ which refers only to
non-soap surfactant.
The aluminosilicate deterqencY builder
The alkali metal (preferably sodium) aluminosilicate
builder present in the composition of the invention may
be crystalline or amorphous or a mixture thereof. The
sodium salts have the general formula
2 2 3 2
These materials contain some bound water and are
required to have a calcium ion exchange capacity of at
least about 50 mg Cao/g. The preferred aluminosilicates
contain 1.5-3.5 SiO2 units (in the formula above) and
have a particle size of not more than about 100 microns,
preferably not more than about 20 microns. Both
amorphous and crystalline aluminosilicates can be made
readily by reaction between sodium silicate and sodium
aluminate, as amply described in the literature.
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Crystalline aluminosilicates (zeolites) are
preferred for use in the present invention. Suitable
materials are described, for example, in GB 1 473 201
(Henkel) and GB 1 429 143 (Procter ~ Gamble). The
preferred sodium aluminosilicates of this type are the
well-known commercially available zeolites A and X, and
mixtures thereof. Especially preferred for use in the
present invention is Type 4A zeolite.
Also of interest is the novel zeolite - maximum
aluminium zeolite P - described and claimed in
EP 384 070A (Unilever).
The aluminosilicate detergency builder is present in
an amount of from 25 to 45 wt% (anhydrous basis),
and preferably at the relatively high level of 28 to 45
wt%. This has been found to give processing advantages
for high-bulk-density compositions (see below) as well as
good cleaning performance.
O~tional sup~lementarY deterqency builder
If desired, a supplementary builder may also be
present. Preferred supplementary builders are organic
sequestrant builders. Examples include polycarboxylate
polymers such as polyacrylates, acrylic/maleic
copolymers, and acrylic phosphinates; monomeric
polycarboxylates such as citrates, gluconates,
oxydisuccinates, glycerol mono-, di- and trisuccinates,
carboxymethyloxysuccinates, carboxymethyloxymalonates,
dipicolinates, hydroxyethyliminodiacetates.
Alternatively, organic precipitant builders such as
alkyl- and alkenylmalonates and succinates, and
sulphonated fatty acid salts, may be used.
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Especially preferred supplementary builders are
polycarboxylate polymers, more especially polyacrylates
and acrylic/maleic copolymers, suitably used in amounts
of from 0.5 to 15 wt%, especially from 1 to 10 wt%; and
monomeric polycarboxylates, more especially citric acid
and its salts, suitably used in amounts of from 3 to 20
wt%, more preferably from 5 to 15 wt%.
The composition of the invention preferably does not
contain more than 5 wt% of inorganic phosphate builders,
and is desirably substantially free of phosphate
builders.
Sodium carbonate
The amount of sodium carbonate present is a key
feature of the invention.
If the main anionic surfactant component (a)(i)
consists of 80-100 wt% PAS and 0-20 wt% LAS, the
composition of the invention contains, as an essential
ingredient, sodium carbonate in an amount of from 10 to
20 wt~. It has surprisingly been found that the presence
of sodium carbonate at this level gives a detergency
advantage over similar compositions containing lower
amounts of, or no, carbonate; while the amount of
carbonate has no significant effect on a similar LAS-only
system.
If, on the other hand, the main anionic surfactant
component (a)(i) consists of 10-60 wt% PAS and 40-90 wt%
LAS, the amount of carbonate should be low or zero
from 0 to 10 wt% - for optimum detergency.
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Surprisingly, in this area the detergency performance
obtained from combinations of PAS and LAS is better than
that of either surfactant alone.
A preferred anionic surfactant component within this
area, where low carbonate is preferred, comprises
20-50 wt% PAS and 50-80 wt% LAS, more preferably
30-40 wt% PAS and 60-70 wt% LAS.
At the crossover region of 60-80 wt% PAS and
20-40 wt% LAS, the amount of carbonate appears to have a
less marked effect on the detergency and can therefore
range from nil to 20 wt%. However, a low carbonate
level of nil to 10 wt% is preferred, especially at
60-75 wt% PAS and 25-40 wt% LAS.
Hiqh bulk densitY
According to a preferred embodiment of the
invention, the composition has a bulk density of least
650 g/litre, more preferably at least 700 g/litre.
Particle porosity preferably does not exceed 0.25, and
more preferably does not exceed 0.20.
High-bulk-density compositions in accordance with
the invention may be prepared by a variety of processes,
batch or continuous, some involving post-tower
densification of a spray-dried powder, and others
involving wholly non-tower processing.
One type of process involves subjecting a
particulate starting material (in effect, a particulate
detergent of conventional bulk density) to a
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granulation/densification treatment. The starting
material may itself be prepared by spray-drying or by a
non-tower process such as dry mixing or granulation.
This treatment may be carried out in a high-speed
batch mixer/granulator having both a stirring action and
a cutting action, as described and claimed in EP 340 013A
(Unilever). Preferably the stirrer and the cutter may
be operated independently of one another, and at
separately variable speeds. Such a mixer is capable of
combining a high energy stirring input with a cutting
action, but can also be used to provide other, gentler
stirring regimes with or without the cutter in operation.
It is thus a highly versatile and flexible piece of
apparatus.
A preferred type of batch high-speed
mixer/granulator is bowl-shaped and preferably has a
substantially vertical stirrer axis. Especially
preferred are mixers of the Fukae (Trade Mark) FS-G
series manufactured by Fukae Powtech Kogyo Co., Japan;
this apparatus is essentially in the form of a
bowl-shaped vessel accessible via a top port, provided
near its base with a stirrer having a substantially
vertical axis, and a cutter positioned on a side wall.
The stirrer and cutter may be operated independently of
one another, and at separately variable speeds.
The Fukae mixer may also be used to produce
compositions of the invention directly from raw
materials by high-speed mixing and granulation.
PAS and LAS may be introduced into the mixer in, for
example, powder, flake, noodle or paste form. It is
also possible to use processes in which PAS or LAS or
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both are prepared by neutralisation in situ, for example,
as described and claimed in EP 352 135A (Unilever) and in
our copending Canadian Patent Application No. 2,034,244 filed
January 16, 1991.
As indicated previously, the Fukae mixer requires
batch operation. Alternatively, continuous processes
may be employed, for example, using a continuous
high-speed mixer/granulator such as the Lodige (Trade
Mark) Recycler, optionally followed by a moderate-speed
continuous mixer/granulator such as the Lodige
Plough~h~re. As with the Fukae mixer, this apparatus
can be used for both post-tower and non-tower processes,
including in-situ neutralisation. Suitable processes
are disclosed in EP 367 339A, EP 390 251A and EP 420 317A
(Unilever), and in our copending Canadian Patent Application No.
2,034,244, filed March 26,1992.
The granulate obtained from the mixer/granulator may
be used as a complete detergent composition in its own
right. Alternatively, it may be admixed with other
components or mixtures prepared separately, and may form
a major or minor part of a final product.
Other ingredients
Detergent compositions in accordance with the
invention may if desired or appropriate contain other
functiona~l ingredients. Some of these, for example,
sodium silicate, inorganic salts such as sodium sulphate,
and fluorescers, will be capable of withstanding the
granulation/densification process and any steps that
precede it, while others, for example, bleach
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ingredients, lather control agents, enzymes and perfume,
are more suitably added afterwards. The skilled
detergents worker will have no difficulty in judging when
and how the various ingredients that go to make up a
fully formulated detergent composition should be
incorporated.
EXAMPLES
The following Examples illustrate the invention.
Examples identified by numbers are within the invention,
while those identified by letters are comparative.
Parts and percentages are by weight unless otherwise
stated.
Examples 1 to 5 Comparative Examples A to E
Detergent powders were prepared to the formulations
shown in Tables 1 and 2. The PAS used was Empicol
(Trade Mark) LX, a narrow-cut (C12/C14 enriched) cocoPAS
(Na salt) supplied by Albright & Wilson.
Examples 1, 2, A, B and C in Table 1 were
high-carbonate compositions, and Examples D, 3, 4, 5 and
E in Table 2 were zero-carbonate formulations.
The comparative all-LAS powders C and E were
prepared by spray-drying an aqueous slurry of all
ingredients except sodium carbonate, sodium sulphate and
enzyme, to form a common base powder; densifying the
base powder using the Fukae FS-100 high-speed
mixer/granulator, as described in EP 340 013A (Unilever);
then admixing the relevant inorganic salt (sodium
carbonate or sodium sulphate) and enzyme.
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The all-PAS powders 1 and D were prepared by
dry-mixing the PAS (in powder form) with all other
ingredients except sodium carbonate, sodium sulphate and
enzyme to form a base, in the Fukae mixer; densifying;
then admixing the relevant inorganic salt (sodium
carbonate or sodium sulphate) and enzyme.
The LAS/PAS powders (Examples 2, A, B, 3, 4 and 5)
were prepared by a~miYing the appropriate quantities of
the LAS base powder of Examples C and E and the PAS base
powder of Examples 1 and D, then proceeding as in the
other Examples.
The final powders had bulk densities above
720 g/litre. They were free-flowing and showed no
tendency to cake.
Detergency measurements were carried out using two
different test cloths; Test Cloth 1 carried a mixture of
fatty and particulate soil, and Test Cloth 2 a mixture of
fatty soil, particulate soil and casein. The powders
were dosed at 0.96 g/litre into 35 litres of water (5~
French hard in Ca2 , 2~ French hard in Mg2 ) in a
Japanese (National (Trade Mark) Electronic W100) washing
machine; the test cloths were washed together with a
2.0 kg soiled cotton load, the wash time being 8 minutes
and the rinse time also 8 minutes (running rinse).
Reflectance data at 460 nm of the washed cloths were
measured using a Micromatch (Trade Mark) reflectometer.
The results are also shown in Tables 1 and 2.
Comparison of Examples 1 and D shows that when
cocoPAS was present and LAS absent, detergency was
significantly better in the presence of 15.51 wt% sodium
carbonate than in the absence of sodium carbonate.
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At 75 wt% PAS/25 wt% LAS (Examples 2 and 3), good
detergency was obtained at both high and zero carbonate
levels.
At 50 wt% PAS/50 wt% LAS (Examples A and 4) and at
25 wt% PAS/75 wt% LAS (Examples B and 5), detergency was
significantly better in the absence of carbonate.
When LAS was present and PAS absent (Examples C and
E), the level of carbonate had no effect on detergency.
Comparison of Examples 3, 4 and 5 with Examples D
and E also shows a synergistic benefit: in the absence
of sodium carbonate, the detergency obtained from the
PAS/LAS mixture was better than that obtained from either
surfactant used alone.
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