Note: Descriptions are shown in the official language in which they were submitted.
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STABILISED QUATERNARY AMMONIUM COMPOSITIONS
Technical Field
The present invention relates to the stability of quaternary
ammonium materials, in particular it relates to maintaining
stable quaternary ammonium materials containing at least one
ester group in the raw material form or as a solution in a
suitable solvent.
Background and Prior Art
Quaternary ammonium materials both solid or liquid are used
extensively in fabric softener compositions. Typically such
compositions contain a water insoluble quaternary ammonium
fabric softening agent dispersed in water at a level of
quaternary ammonium softening agent up to 8% by weight in
which case the compositions are considered dilute or at
levels from 8 to 50~ in which case the compositions are
considered concentrates.
A problem associated with quaternary ammonium materials
containing at least one ester group is their instability on
storage.
The problem is particularly noticeable in the storage of
these materials at variable temperatures over time.
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The instability of both such solid and liquid quaternary
ammonium material manifests itself by the discolouration of
such material during storage at various temperatures. The
amount of discolouration is generally an indication of the
level of decomposition occurring over time. This
decomposition is of greatest concern when quaternary
ammonium material is stored at temperatures above their
melting points.
In the past, stability of quaternary ammonium compounds has
been improved by the storage of compounds at low
temperatures, i.e. temperatures well below the melting
points of the compounds being stored. Also, the addition of
anti-oxidants have been used to counteract decomposition.
BP 299 176 (Kao) discloses soft-finishing agents comprising
a di-long chained quaternary alrnnonium salt containing a
single ester group and a decyldimethyl amine.
US 4 937 008 (Kao) discloses concentrated fabric softening
agents comprising one or more quaternary ammonium salts and
a di or tri-valent polyol with 2 to 3 carbon atoms.
Surprisingly, we have found that low and high temperature
stability of solid or liquid quaternary ammonium compounds
containing at least one ester group may be improved by the
addition of one or more of a select group of stabilising
agents which act to prevent the extent of decomposition of
the quaternary ammonium material.
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Definition of the Invention
Thus according to one aspect of the invention there are
provided improved stable compositions comprising quaternary
ammonium material containing at least one ester group
characterised in that they further comprise one or more
stabilising agent, wherein the one or more stabilising
agents) are strong hydrogen bond donors.
In a second aspect of the present invention there is
provided a process of stabilising quaternary ammonium
material containing at least one ester group via the steps
of adding at least one stabilising agent to the quaternary
amanonium material, wherein the stability agent is a strong
hydrogen bond donor.
In a third aspect of the present invention, the composition
as defined is incorporated into a solid and/or liquid rinse
conditioner.
Also provided is a method of reducing the level of
discolouration of quaternary ammonium material containing at
least one ester group over time by the addition of a
stabilising agent as defined herein.
As used herein the term 'ester group' in the quaternary
ammonium material includes an ester group which is a linking
group in the molecule. References herein to quaternary
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ammonium material are to those having at least one ester
group in their structure.
It has surprisingly been found that compounds which readily
donate hydrogen bonds to the aforementioned quaternary
ammonium material assist in maintaining a high level of
quaternary ammonium material and avoiding high levels of the
decomposition products.
Detailed Description of the Invention
Preferably the stabilising agents) are chosen from one or
more of the following group comprising,
a) urea
b) urea derivative
c) primary or secondary amides, and/or
d) polyhydric alcohols.
Such compositions show improved stability at varying
temperatures.
The quaternary ammonium compounds containing at least one
ester group are referred to herein as ester-linked
quaternary ammonium compounds.
It is preferred if the quaternary ammonium compounds contain
two or more ester groups. In both the monoester and the
diester quaternary ammonium compounds of the invention it is
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preferred if the ester groups) is a linking group between
the nitrogen atom and an alkyl group. The ester groups(s)
are preferably attached to the nitrogen atom via another
hydrocarbyl group.
The invention is most useful for quaternary ammonium
compounds containing at least one ester group, preferably
two, wherein at least one higher molecular weight group
containing at least one ester group and two or three lower
molecular weight groups are linked to a common nitrogen atom
to produce a cation and wherein the electrically balancing
anion is a halide, acetate or lower alkosulphate ion, such
as chloride or methosulphate. The higher molecular weight
substituent on the nitrogen is preferably a higher alkyl
group, containing 12 to 28, preferably 12 to 22, eg 12 to 20
carbon atoms, such as coco-alkyl, tallowalkyl, hydrogenated
tallowalkyl or substituted higher alkyl, and the lower
molecular weight substituents are preferably lower alkyl of
1 to 4 carbon atoms, such as methyl or ethyl, or substituted
lower alkyl. One or more of the said lower molecular weight
substituents may include an aryl moiety or may be replaced
by an aryl, such as benzyl, phenyl or other suitable
substituents.
Preferably the quaternary ammonium material used in the
invention is a compound having two C12-C22 alkyl or alkenyl
groups connected to a quaternary ammonium head group via at
least one ester link, preferably two ester links or a
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compound comprising a single long chain with an average
chain length equal to or greater than C2o.
More preferably the invention is useful for quaternary
amomonium material comprising a compound having two long
chain alkyl or alkenyl chains with an average chain length
equal to or greater than C14. Even more preferably each
chain has an average chain length equal to or greater than
C16. Most preferably at least 50% of each long chain alkyl
or alkenyl group has a chain length of C18. It is preferred
if the long chain alkyl or alkenyl groups are predominantly
linear.
The problems referred to above have found to be particularly
associated with quaternary ammonium compounds having an
ester link and wherein the compound has two or three
electron withdrawing groups connected to the quaternary
nitrogen atom by one or two carbon atoms on different
substituents, and, a methyl group also attached to said
nitrogen atom. This arrangement is shown in the following
formula (A). Such compounds having a chloride counterion
have been found to particularly benefit from the present
invention in terms of stability.
Without wishing to be bound by theory the applicant believes
that the problems of discolouration/instability are most
common in quaternary ammonium compounds containing an ester
linking group and having a methyl group attached to the
nitrogen and a chloride counter-ion and two or three
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electron withdrawing groups separately attached to the
quaternary nitrogen atom.
Whilst the quaternary ammonium compounds of general formula
(B) below may suffer from discolouration and instability
these problems have found to be most prevalent in the
compounds of type (A) below and especially in those
compounds referred to immediately above.
Thus especially preferred ester-linked quaternary ammonium
material for use in the invention can be represented by the
formula:
R1
(A) R1 N+ ( ,CHZ) n-T-RZ X_
( CHZ ) n-T-R2
wherein each Rl group is independently selected from Cl_4
alkyl, hydroxyalkyl or C2_4 alkenyl groups; and wherein each
R2 group is independently selected from C8_ZB alkyl or alkenyl
groups; X- is any suitable counterion, i.e. a halide,
acetate or lower alkosulphate ion, such as chloride or
methosulphate.
0 O
T is -O-C- or -C-O-; and
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n is an integer from 1-5 or is 0
It is especially preferred that each R' group is methyl and
each n is 2 as such compounds are found to be particularly
susceptible to the stability problems referred to above.
Di (tallowyloxyethyl) dimethyl ammonium chloride, available
from Hoechst, is especially preferred, also Di(hardened
tallowyloxyethyl) dimethyl ammonium chloride, ex Hoechst.
Another preferred type of ester-linked quaternary ammonium
material that can be used according to the invention is
represented by the formula:
OOCR2
(B) (R1)3N+ - (CH2)n CH X-
CH20CORz
wherein Rl, n R2 and X- are as defined above.
However it has been found that these materials do not show
such a tendency to instability, particularly at high
temperatures eg 60-70°C, as the compounds of the preceding
f orrnula .
It is advantageous for environmental reasons if the
quaternary ammonium material is biologically degradable.
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Preferred materials of this class such as 1,2 bis[hardened
tallowoyloxyl-3- trimethylammonium propane chloride and
their method of preparation are, for example, described in
US 4 137 180 (Lever Brothers). Preferably these materials
comprise small amounts of the corresponding monoester as
described in US 4 137 180 for example 1-hardened tallow
oyloxy-2-hydroxy -3-trimethylammonium propane chloride.
Accordingly it is especially preferred that the quaternary
ammonium material according to the invention comprises at
least one methyl group attached to the quaternary nitrogen
atom, with two or three nitrogen atom substituents
containing electron withdrawing groups and having a chloride
counter-ion. It is especially preferred that such compounds
falling within general formula A are used, and even more
preferred that such compounds have two methyl substituents
on the nitrogen and in the remaining radicals n is 1 or 2
and RZ is C12-C22. especially C16-C22 a . g . tallow.
Tt is also preferred that the quaternary ammonium compound
used in the present invention is substantially anhydrous,
meaning containing less than 10% water in the context of the
present invention.
The quaternary ammonium material may contain optional
additional components, as known in the art, in particular,
low molecular weight solvents, for instance isopropanol
and/or ethanol, and co-actives such as nonionic softeners,
for example fatty acid or sorbitan esters.
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The types of stabilising agent that may be used are any that
are strong hydrogen bond donors.
The stabilising agent may be urea or a derivative thereof, a
primary or secondary amide or a polyhydric alcohol, or
mixtures thereof. Two or more stabilising agents may be
used.
The stabilising agent is preferably added to the composition
of the present invention at levels of 0.05 to 10% by weight
of the weight of the quaternary ammonium material. However,
lower amounts than this are preferred, more preferably 0.1
to 7.5% is added based on the weight of the quaternary
ammonium material, especially 0.5 to 6.0% and even more
preferably 0.5 to 4%.
The stabilising agent may be introduced to the quaternary
ammonium material at any stage during the manufacture of the
quaternary ammonium material or after manufacture i.e. on
storage. The stabilising agent may be added in any form, as
a powder direct to the molten quaternary ammonium material
or as a solution in a suitable solvent, for instance iso
propanol.
The addition step can take place during the synthesis of the
quaternary ammonium material, preferably following the
quaternisation step. The addition may take alternatively,
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or additionally, place during storage of the quaternary
ammonium material.
The stabilising agent is most effectively introduced at any
stage following the quaternisation step of the synthesis of
the quaternary ammonium material.
An example of amide to be used in the present invention is
acetomide. Polyhydric alcohols such as glycerol may be used
as stabilising agents. Another preferred stabilising agent
is urea. A combination of glycerol and a quaternary
ammonium compound of general formula (A) is particularly
preferred, especially wherein both R1 are CH3, n is 2 and R2
is tallow.
The stabilised composition may be in a liquid, molten or
semi-solid form containing less than 10% by weight water.
Also provided according to the invention is a solid rinse
conditioner comprising a stabilised composition as defined
above, preferably a composition in a granular or powdered
form. Another type of rinse conditioner provided by the
invention is a liquid rinse conditioner comprising a
stabilised composition as defined above.
The invention will now be illustrated by the following
example. Further examples within the scope of the invention
will be apparent to the person skilled in the art.
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Example
Urea was added to the quaternary ammonium material as a
powder and heated to 82°C. The combined material was stored
for three days.
The reflectance was measured on a datacolor international
Spectraflash SF600 plus reflectometer after 3 days storage
at 82°C.
8540 after 3 days at 82C
DEQ (control) 19.8
DEQ + 3.6% urea 25.1
DEQ + 7.3% urea 27.4
DEQ is di(2-[hardened tallow]oxyl oxyethyl) dimethyl
ammonium chloride ex Hoechst. It includes
approximately 10% mono ester and minor amounts of
unquaternised amine/amine salt as well as approximately
2% fatty acid and 14% isopropanol.
These results show that addition of urea to compositions
comprising a quaternary ammonium compound counteracts
decomposition at high temperature. This is indicated by the
greatly increased 8540 reflectance values found for samples
of quaternary ammonium compound stored in admixture with
urea.
