Field of the Invention
[0001] This invention relates to aqueous liquid dishwashing detergent compositions and especially.to
substantially unbuilt hand dishwashing detergent compositions incorporating alkane
sulphonate surfactant together with a source of magnesium ions.
Background of the Invention
[0002] The use of magnesium salts and magnesium surfactants such as alkyl sulphates, alkyl
ether sulphates and'alkyl benzene sulphonates in dishwashing detergent formulations
is known, and British Patent Specification Nos. 1,524,441, 1,551,074 and 2,010,893A
are representative disclosures of the state of the art. The art teaches that these
formulations have enhanced performance, particularly when used in water of low mineral
hardness. Liquid detergent compositions containing alkane sulphonate surfactants are
also known in the art. Compositions primarily intended for fabric washing are described
in B.P. 1,054,217, 1,329,508 and 1,291,163, the last named of which discloses a mixture
of an alkane sulphonate, an ethoxylated alkyl sulphate, and a proteolytic enzyme together
with an enzyme-stabilising agent in the form of a calcium or magnesium salt, specifically
the acetate or the chloride.
[0003] Enzymes are not however customary components of hand dishwashing liquid detergent
formulations, particularly in formulations where skin mildness is an important in-use
requirement.
[0004] Dishwashing liquid detergent compositions containing alkane sulphonates are also
known, examples of such disclosures including those in B.P. 1,339,069, 1,382,295,
1,451,228 and 1,567,421. However products made in accordance with these teachings
have all been found to be non-optimal in one area of performance or another eg. raw
material cost, phase stability on storage, sudsing in water of high or low mineral
hardness, effect on hands, suds profile, physical stability under cyclic temperature
conditions etc.
[0005] The present invention is concerned with an aqueous hand dishwashing detergent composition
that is enzyme-free. More particularly, it concerns an enzyme-free dishwashing detergent
composition containing alkane sulphonate surfactant, the sudsing performance of which
has been enhanced by the incorporation of specific levels of magnesium ion.
[0006] According to the present invention there is provided a clear single-phase enzyme-free
dishwashing liquid composition comprising 20-40% of a C
14-C
17 alkane sulphonate, 5-15% of an anionic surfactant selected from water soluble C
10-C
16 alkyl ethoxy sulphates containing from 1-6 ethoxy groups per mole of alkyl sulphate,
and mixtures thereof with water soluble C
10-C
16 alkyl benzene sulphonates, 0-5% of a suds booster selected from C
10-C
16 alkyl amides, C
10-C
16 alkyl C2-C
3 alkanolamides,
C10-
C16 alkyl di C
1-C
3 alkyl or di C
2-C
3 hydroxyalkyl amine oxides and from 0.35%-0.7% magnesium ion, the composition containing
no more than 1.75% by weight of chloride ions or more than 0.35% by weight of inorganic
sulphate ions provided that where chloride ions are also present the level of sulphate
ions should not exceed 0.25% by weight, the counter ions other than magnesium necessary
to provide . a pH of 6.0-7.5 being selected from sodium, potassium, ammonium and alkanolammonium.
[0007] Preferably the composition comprises 22-3
6% C16-17 alkanesulphonate, 6-12% C
12-14 alkyl ethoxy sulphate and 0.5% magnesium ion with a maximum of 0.5% inorganic salt
anions.
[0008] Secondary alkane sulphonates useful in the present invention preferably have from
13 to 18 carbon atoms per molecule, and most desirably 13 to 15, and are characterised
by a high solubility in water compared to alkyl aryl sulphonates and other sulphuric
acid reaction products used for dishwashing detergent compositions. These sulphonates
are preferably prepared by subjecting a cut of paraffin, corresponding to the chain
lengths specified above, to the action of sulphur dioxide and oxygen in accordance
with the well-known sulphoxidation process.
[0009] The product of this reaction is a secondary sulphonic acid which is then neutralized
with a suitable base to provide a water-soluble secondary alkyl sulphonate. Similar
secondary alkyl sulphonates may be obtained by other methods, e.g. by the sulphochlorination
method in which chlorine and sulphur dioxide are reacted with paraffins in the presence.of
actinic light, the resulting sulphonyl chlorides being hydrolyzed and neutralized
to form the secondary alkyl sulphonates. Whatever technique is employed, it is normally
desirable to produce the sulphonate as the monosulphonate, having no unreacted starting
hydrocarbon or'having only a limited proportion thereof present and with little or
no inorganic salt by-product. Similarly, the proportions of disulphonate or higher
sulphonated material will be minimized but some may be present. The monosulphonate
may be terminally sulphonated or the sulphonate group may be joined on the 2-carbon
or other carbon of the linear chain. Similarly, any accompanying disulphonate, usually
produced when an excess of sulphonating agent is present, may have the sulphonate
groups distributed over different carbon atoms of the paraffin base, and mixtures
of the monosulphonates and disulphonates may be present.
[0010] Mixtures of monoalkane sulphonates wherein the alkanes are of 14 and 15 carbon atoms
are particularly preferred wherein the sulphonates are present in the weight ratio
of
C14-to C
15 paraffins in the range from 1:3 to 3:1, preferably 1:2 to 2:1. Surprisingly, this
particular mixture produces detergents which clean dishes better and which suds longer,
especially in hard water, than other mixtures of paraffin sulphonates, e.g. those
of 13 to 17 carbon atoms. This is also true, to a lesser extent, of the individual
components of the Cl4 and C
15 mixture.
[0011] The alkane sulphonates are used at a level of from 20% to 40%, more generally at
a level of from 22% to 36%, preferably from 24% to 34% and most preferably from 26%
to 32% by weight of the composition.
[0012] The alkyl ethoxy sulphates used in the compositions of the present invention can
be represented by the formula
RO(C
2H
4O)
nSO
3X where R is a C
10-C
16 preferably 12-15 linear or branched chain, primary alkyl group, n is a value from
1 to 6 preferably 2-5 and X is a water soluble cation. C
10-C
16 alcohols, derived from natural fats or Zie
gler olefin build-up or OXO synthesis form suitable sources for the alkyl group. Examples
of synthetically derived materials include Dobanol 23 (RTM) sold by Shell Chemicals
(UK) Ltd., Ethyl 24 sold by the Ethyl Corporation, a blend of C
13-C
15 alcohols in the ratio 67% C13, 33% C
15 sold under the trade name Lutensol by BASF GmbH and Synperonic (RTM) by ICI Ltd,
and Lial 125 sold by Liquichimica Italiana. Examples of naturally occuring materials
from which the alcohols can be derived are coconut oil and palm kernel oil and the
corresponding fatty acids.
[0013] The alkyl ethoxy sulphates are used in an amount of from 5% to 15% by weight of the
composition, and, where they constitute the only anionic surfactant species other
than the alkane sulphonate, are normally used at from 10% to 15% by weight.
[0014] The alkyl ethoxy sulphates can also be used in admixture with water soluble linear
or branched C
10-C
16 alkyl benzene sulphonates. In such alkyl benzene sulphonates, the alkyl group.is
preferably linear and contains 11-13 carbon atoms,-a material with an average carbon
chain length of 11.8 being most preferred. The phenyl isomer distribution, ie. the
point of attachment of the alkyl chain to the benzene nucleus, is not critical but
alkyl benzenes having a high 2-phenyl isomer content are preferred.
[0015] Where mixtures of the alkyl ethoxy sulphates and alkyl benzene sulphonates are used
the levels of alkyl benzene sulphonate should be such that the ratio of the combined
weight of alkane sulphonate and alkyl benzene sulphonate to the weight of alkyl ethoxy
sulphate should not exceed 10:1 and preferably should not exceed 5:1. In practice
the level of alkyl benzene sulphonate will not usually exceed 12% by weight of the
composition and will normally be in the range 4%-10% by weight. Correspondingly, the-overall
alkyl ethoxy sulphate level will be reduced where such mixtures are employed.
[0016] An essential component of the formulation is a source of magnesium ions at a level
to provide 0.35% to 0.70% by weight of magnesium ion in the product, preferably 0.40%
to
0.60% by weight. Subject to the requirement that the final product is a clear single-phase
liquid, the magnesium ion can be provided either by addition of a water soluble magnesium
salt such as the chloride:or acetate to the formulation, or by the use of magnesium
oxide or hydroxide slurry as a component of the neutralising medium for one or other
of the anionic surfactants during manufacture.
[0017] The requirement that the final product is a clear, single phase liquid creates a
constraint on the level of dissolved inorganic salts that can be tolerated by the
formulation without phase separation or crystallisation occurring. By 'tolerated'
is meant the ability of a formulation to withstand storage without the formation of
other solid or liquid phases. A minimum requirement is that storage at ambient temperature
(viz 20°C) should not result in such phase separation but preferably the temperature
at which phase separation or crystal deposition occurs should necessitate cooling
of the composition to a sub-ambient temperature. This sub-ambient temperature is conventionally
known as the chill point temperature of a liquid detergent composition and is defined.as
that temperature below which solid inorganic crystals separate from the composition
on storage. It has been found that, in order to achieve acceptable chill point temperatures,
the composition of the present invention should not contain more than 1.75% by weight
of chloride ions or more than 0.35% of sulphate ions, provided that where chloride
ions are also present the level of sulphate ions should not exceed 0.25% by weight
and preferably should not exceed 0.15% by weight. Formulations having low chill point
temperatures, i.e. < 5°C, have sulphate levels.at the lower end of this range.
[0018] The tolerance of the formulations to inorganic salt level has been found to be dependent
on the inorganic salt type and also on the counter ion types present in the formulations.
Thus formulations in which the counter ions (other than the magnesium) are mainly
or exclusively ammonium or potassium are more tolerant to inorganic salts than those
where the counter ions are mainly or exclusively sodium ions. Furthermore chloride
ions can be tolerated at much higher levels than sulphate ions.
[0019] It has been found, for example, that in a formulation comprising
30% MC15-C17 paraffin sulphonate
15% MC12 (EO) 3 sulphate
10% ethyl alcohol solvent
with 0.475% Magnesium ion added as magnesium
[0020] hydroxide forming part of the counter ion M, when M is ammonium, the level of sulphate
ion that the formulation can tolerate without precipitation is 0.35% by weight of
the formulation whereas when M is sodium, the level of sulphate ion that can be tolerated
is no more than 0.20
% by weight. By contrast in the same system, 1.75% chloride ion can be tolerated, irrespective
of the counter ion employed, although at this level of chloride ion the presence of
sulphate ions in excess of about 0.15% by weight will lead to deposition of a crystalline
precipitate.
[0021] The commercial production of paraffin sulphonates, alkyl benzene sulphonates and
alkyl ether sulphates uses techniques that are well known in the art and involves
the use of sulph(on)ating agents such as S0
3, oleum, chlorosulphonic acid or SO
2, all of which give rise to residues of sulphates and/or chlorides in the active materials.
The levels of sulphates and/or chlorides can be minimised by careful control of the
sulph(on)ation conditions, and by air, or inert gas, sparging of the acid sulph(on)ate
products but in general at least 0.1% by weight of inorganic sulphate (on a finished
product basis) arise from this source,even under ideal conditions. Thus, little or
no sulphate ion can be added to these systems if precipitation is to be avoided, and
the addition of the magnesium ion as magnesium sulphate, is not feasible from a product
stability standpoint.
[0022] Indeed, the low tolerance of the compositions of the present invention to inorganic
sulphates, produced as a by-product of the sulph(on)ation process frequently results
in a 'desalting' step being necessary to provide acceptable product stability on storage.
Where appreciable levels of inorganic sulphate are present, such as the 4-6% by weight
of sulphate found in-commercially available paraffin sulphonates, this 'desalting'
step is essential in order to avoid precipitation and deposition of inorganic sulphate
from compositions in accordance with the invention. This desalting step is normally
carried out on the surfactant concerned prior to mixing with other formulation components
and can be performed by adding a lower aliphatic alcohol such as ethanol or isopropanol
to the neutralised surfactant in order to precipitate the sulphate as a crystalline
solid. The precipitated sulphate is then removed by filtration or centrifugation.
[0023] As noted above, the formulations of the present invention are more tolerant of chloride
ions than sulphate ions and thus where chloride ions are produced by a sulphation
by-product, such as in the chlorosulphation of alkyl ethers, subsequent treatment
of the surfactant is normally unnecessary. The level of chloride ion arising from
this source is normally of the order of 0.5% on a total product weight basis and preferred
formulations, made using S0
3 sulphonation techniques, are essentially free of chloride ions.
[0024] The higher tolerance of the compositions of the invention to chloride ions leads
to the situation that provided the system is substantially free of inorganic salts
prior to the incorporation of the magnesium ion, the latter can be incorporated as
the chloride salts.
[0025] In this context 'substantially free' means no more-than 0.25% by weight of the composition
of inorganic anions. Preferably the compositions contain less than 0.15% by weight
of other inorganic anions when levels of chloride ion in excess of about 1% by weight
are present.
[0026] Nevertheless, the incorporation of a water soluble magnesium salt into the formulation,
whilst being permissible, is not a preferred technique as it increases the risk of
phase separation or crystalline salt deposition, and, in the case of magnesium chloride,
may give rise to corrosion problems in the processing equipment. As noted above, the
addition of magnesium sulphate in an amount sufficient to provide the benefits of
the present invention causes crystalline salt precipitation. Even where a salt such
as magnesium acetate is employed as the source of magnesium ion, its addition to the
formulation may cause sulphate and chloride salts to precipitate, even though these
may only be present at levels which would otherwise be acceptably low. Accordingly
the use of magnesium oxide or hydroxide neutralisation of one or more of the anionic
surfactant'species is a preferred means of introducing the magnesium ion into the
system.
[0027] The other cations used in the neutralisation of the anionic surfactants may be sodium,
potassium, ammonium or alkanolammonium, but ammonium is a preferred cation because
of its depressive effect on the chill point temperature of the compositions. Preferred
compositions have chill points < O°C and in order to achieve this at least 50% of
the surfactant cations should be ammonium ions.
[0028] A desirable component of the invention is a suds boosting agent at a level of up
to 5%, preferably 3-4% by weight.
[0029] The suds-promoting agent can be any of C
12-C
14 mono-and di C
2-C
3 alkanolamide, C12-C14 alkyl amides condensed with up to 15 moles of ethylene oxide
per mole of amide and tertiary amine oxides containing a C
8-C
18 alkyl group.
[0030] Examples of the alkanolamides are coconut alkyl monoethanolamide, coconut alkyl diethanolamide
and coconut alkyl mono and di isopropanolamides.
[0031] Examples of the ethoxylated amides include coconut alkyl amide condensed with six
moles of ethylene oxide, lauryl amide condensed with eight moles of ethylene oxide,
myristyl amide condensed with ten moles of ethylene oxide and coconut amide condensed
with eight moles of ethylene oxide. Amine oxides useful in the present invention have
one alkyl or hydroxyalkyl moiety of 8 to 18 carbon atoms, preferably 8 to 16 carbon
atoms and two moieties selected from alkyl groups and hydroxyalkyl groups containing
1 to 3 carbon atoms. Examples of such amine oxides include dimethyloctylamine oxide,
diethyldecylamine oxide, bis - (2 - hydroxyethyl) dodecylamine oxide, dimethyldodecylamind
oxide, dipropyltetra- decylamine oxide, methylethylhexadecylamine oxide, and dimethyl
- 2 - hydroxyoctadecylamine oxide.
[0032] A highly preferred example of the tertiary amine oxide is a C
12-C
14 alkyl dimethyl amine oxide in which the C
12-C
14 alkyl group is derived from coconut oil.
[0033] The balance of the formula comprises a hydrotrope-water system in which the hydrotrope
may be urea, a C
l-C
3 alkanol, or a lower alkyl benzene sulphonate salt such as toluene, cumene or xylene
sulphonate. The preferred hydrotrope is ethanol which is employed at from 6% to 10%
by weight of the composition preferably at from 7% to 9%.
[0034] Optional ingredients of the liquid detergent compositions of the invention include
thickeners such as guar gum, antibacterial agents such as glutaraldehyde and Bronopol
(RTM), antitarnish agents such as benzoxytriazole, heavy metal chelating agents such
as EDTA or EDTMP, perfumes and dyes. The pH of the compositions may-be anywhere within
the range 6-7.5 but as manufactured the compositions normally have a pH in the range
6.6-7.3 preferably 6.6-6.9 in order to maintain colour stability.
[0035] The technique of incorporation of the magnesium ions is not thought to be critical
and the compositions can be made in a number of ways.
[0036] The individual anionic surfactants can be made as aqueous solutions of alkali metal
or ammonium salts which are < then mixed together with the hydrotrope, and the suds
booster, if this is included, following which the mag-
' nesium ion can be introduced as a water soluble salt such as the chloride or acetate.
Optional minor ingredients are then added after which the pH and viscosity is adjusted.
This method has the advantage of utilising conventional techniques and equipment but
results in the introduction of additional chloride or acetate ions which can increase
the chill point temperature (the temperature at which inorganic salts precipitate
as crystals in the liquid).
[0037] An alternative method is to neutralise the alkyl ether sulphuric acid or the alkane
sulphonic acid with a magnesium oxide or hydroxide slurry which avoids the introduction
of additional inorganic anions. Although not essential, it is convenient to carry
out the neutralisation of the alkyl ether sulphate in a 'heel' formed by a dispersion
of the magnesium oxide or hydroxide slurry in a mixture of the hydrotrope and the
other surfactant. Any alkyl benzene sulphonate present in the formulation can be neutralised
separately or in the same 'heel', and the neutralised sulphonate and sulphate surfactants
together with the hydrotrope are then added to the final mixing tank and the suds
booster and any optional ingredients added before the pH is adjusted as above.
[0038] The invention is illustrated in the following examples in which the percentage of
the components are by weight on the finished composition.
Example 1
[0039] The following composition was made up

[0040] The C
14-C
15 s-alkane sulphonate, available as a paste of the ammonium salt containing 60% active
and 4% ammonium sulphate was desalted by treating 58.33 parts paste with 9 parts ethanol
and filtering off the precipitated ammonium sulphate to leave 65.23 parts of desalted
paste containing 0.23 parts ammonium sulphate. This desalted paste was then used as
a heel for the neutralisation of the alkyl ether sulphuric acid. The latter was prepared
by sulphation of an ethoxylated linear C
12-C
13 alcohol using an S0
3-air mixture and contained 0.46% H
2SO
4. 2.12 parts of a 50% slurry of magnesium hydroxide in water was added to the paste
heel and then the alkyl ether sulphuric acid was added with agitation. After the neutralisation
of the alkyl ether sulphuric acid the remaining components were added and the pH was
trimmed to 6.8 using ammonium hydroxide or citric acid. The resulting liquid detergent
was a stable clear liquid with a sulphate content, expressed as (NH
4)
2SO
4, of 0.32% by weight of the composition.
Example 2
[0041]

A similar procedure is followed as for Examgle 1. The ammonium alkane sulphonate surfactant
is desalted to leave 57.2 parts of paste containing ammonium sulphate and 0.20 parts
ammonium sulphate and the alkyl benzene sulphonic acid (produced by S0
3 sulphonation and containing 0.11 parts H
2SO
4) is added to this desalted paste. The magnesium hydroxide slurry is then mixed in
followed by the alkyl ether sulphuric acid. When neutralisation of the latter is complete
the pH is brought up to pH 6.8 with ammonium hydroxide and the remainder of the ingredients
added to complete the formulation. The final product is a clear stable liquid with
a sulphate content, expressed as (
NH
4)
2 SO
4 of 0.43% by weight of the composition.
Example 3
[0042]

[0043] The product is made up using the procedure of Example 2 to give a clear liquid having
a sulphate content expressed as (NH
4)
2SO
4 of 0.40% by weight of the composition.