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Claims  |
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I claim:
1. A process for the generation of a peroxyacid species comprising the step
of bringing into contact hydrogen peroxide or an adduct thereof or some
other compound which develops hydrogen peroxide, with a peroxyacid
generator having the general formula (I)
##STR9##
in which R.sub.1 R.sub.2 and R.sup.6 are each selected from hydrogen and
lower alkyl groups, and R.sub.3 is selected from hydrogen, lower alkyl and
aryl groups and groups of formula (II) or (III)
##STR10##
in which R.sub.7 represents a carbon-carbon bond or an alkylene diradical,
R.sub.4 and R.sub.5 each represent hydrogen or a lower alkyl, or an aryl,
aralkyl or alkaryl group and R.sub.5 can also be a from group of formula
(IV) --R.sub.8 --CO--O--R.sub.9 in which R.sub.8 represents an alkylene
diradical and R.sub.9 represents a vinyl or alkyl substituted vinyl group
or group of formula (V)
##STR11##
2. A composition comprising (a) hydrogen peroxide or an adduct thereof or a
compound which develops hydrogen peroxide and (b) a peroxyacid generator
having the general formula (I) as described in claim 1.
3. A composition according to claim 2 in which R.sub.1 and R.sub.2 in
Formula I each represent hydrogen and R.sub.3 and R.sub.6 each represent
hydrogen or a lower alkyl group.
4. A composition according to claim 2 in which R.sub.3 represents a group
of formula II or III in which R.sub.7 represents a diradical comprising 1,
2 or 3 linear carbon atoms, unsubstituted or further substituted by one or
more C.sub.1 -C.sub.4 alkyl groups.
5. A composition according to claim 4 in which R.sub.1, R.sub.2 and R.sub.6
represent hydrogen.
6. A composition according to claim 2 in which R.sub.4 represents hydrogen
or a lower alkyl or phenyl or substituted phenyl group.
7. A composition according to claim 2 in which R.sub.5 represents a lower
alkyl or phenyl or substituted phenyl group.
8. A composition according to claim 2 in which R.sub.5 represents an
alkylene diradical containing from 2 to 10 linear carbon atoms,
unsubstituted or substituted by one or more C.sub.1 -C.sub.4 alkyl groups.
9. A composition according to claim 8 in which R.sub.5 represents a C.sub.4
to C.sub.8 polymethylene diradical.
10. A composition according to claim 3, in which R.sub.4 represents a
methyl or phenyl group.
11. A composition according to claim 2 in which the peroxyacid generator is
selected from 1,1,4-triacetoxy but-3-ene, 1,1,4,4-tetraacetoxybutane,
1,1,5-triacetoxypent-4-ene and 1,1,5,5-tetraacetoxypentane.
12. A composition according to claim 3 in which the peroxyacid generator is
selected from ethylidene diacetate, ethylidene dibenzoate, ethylidene
benzoate acetate, and the three corresponding isopropylidene esters.
13. A composition according to claim 10 in which the peroxyacid generator
is selected from ethylidene adipate diacetate and ethylidene azelate
diacetate.
14. A composition according to claim 2 in which either of R.sub.4 and
R.sub.5 represents a C.sub.5 -C.sub.9 chain length alkyl or cycloalkyl
group and the other represents a C.sub.1 -C.sub.4 alkyl or phenyl group.
15. A composition according to claim 14 in which the one of R.sub.4 and
R.sub.5 is selected from cyclohexyl, pentyl hexyl or heptyl groups
unsubstituted or alkyl substituted to provide C.sub.5 to C.sub.9 atoms in
the group.
16. A composition according to claim 15 in which the peroxyacid generator
is selected from ethylidene cyclohexane carboyxlate acetate, ethylidene
heptanoate acetate, ethylidene octanoate acetate and ethylidene
2-ethylhexanoate acetate.
17. A composition according to claim 2 in which the peroxyacid generator
and hydrogen peroxide or generator thereof are brought into contact in an
equivalent mole ratio of from 2:1 to 1:2.
18. A composition according to claim 2 which is in the form of aqueous
acidic emulsion of hydrogen peroxide, the peroxyacid generator and an
emulsifying amount of an emulsifier.
19. A composition according to claim 18 in which the aqueous phase has a pH
of from 2 to 5.
20. A composition according to claim 18 in which the peroxyacid generator
and hydrogen peroxide are present in an equivalent ratio of from 1:1 to
2:3.
21. A composition according to claim 18, in which the concentration of
hydrogen peroxide therein is from 1 to 20% by weight thereof.
22. A composition according to claim 21 in which the concentration of
hydrogen peroxide therein is from 4 to 8% by weight thereof.
23. A composition according to claim 18 in which the proportion of
peroxyacid generator therein is from 1 to 35% by weight thereof.
24. A composition according to claim 23 in which the amount of emulsifier
employed is from 10 to 70% by weight of the peroxyacid generator.
25. A composition according to claim 18 comprising 3 to 20% hydrogen
peroxide, 30 to 85% water, 10 to 30% peroxyacid generator, and from 10 to
70 parts by weight of emulsifier per 100 parts by weight of peroxyacid
generator, the aqueous phase having a pH of from 2 to 5.
26. A composition according to claim 23 which contains a water soluble
emulsifier in at least the weight of the activator.
27. A composition according to claim 26 in which the proportion of
activator is from 1 to 15% w/w and the proportion of emulsifier is
selected in the range of 5 to 30%.
28. A composition according to claim 18 which contains sufficient
emulsifier for the emulsion to be visually clear.
29. A composition according to claim 18, in which the emulsifier is
selected from water-soluble alcohol ethoxylates, alkyl phenol ethoxylates,
elcohol sulphates, linear alkyl benzene sulphonates and alkyl esters of
sulphosuccinates.
30. A composition according to claim 18, which contains an aliphatic
alcohol having a C.sub.4 -C.sub.8 carbon chain in a weight ratio to the
emulsifier of up to 2:1.
31. A composition according to claim 18 which, when plotted on triangular
coordinate graph paper for respectively weight percent of aqueous hydrogen
peroxide, activator and emulsifier is within the quadrilateral having apex
coordinates of 65,10,25; 45,30,25; 25,15,60; 30,10,60.
32. A composition according to claim 2 in which the composition is in the
form of a solution of aqueous acidic hydrogen peroxide and of the
peroxyacid generator in a solvent comprising a glycol, or glycerol or
oligomer of short chain glycols, or short chain aliphatic ether or ester
derivatives, said solvent having a molecular weight of from 125 to 450.
33. A composition according to claim 32 in which the solvent is selected
from polyethylene glycol of average molecular weight 200-400, di or
triethylene glycol and their monoacetate or monopropionate derivatives and
the monopropyl or monobutyl ether of ethylene glycol diethylene glycol or
propylene glycol or mixtures of two or more thereof.
34. A composition according to claim 32 in which the solvent contains up to
twice its weight of an anionic or nonionic surfactant.
35. A composition according to claim 32 which comprises at least 55% w/w
solvent/surfactant, and up to 35% w/w activator and up to 40% w/w aqueous
hydrogen peroxide.
36. A composition according to claim 32 in which the concentration of
hydrogen peroxide based on the aqueous hydrogen peroxide component is from
10 to 30% w/w.
37. A composition according to claim 32 which when plotted on triangular
coordinate paper as respectively weight percent of aqueous hydrogen
peroxide, activator, solvent/surfactant are in the pentagonal area defined
by the points 30,15,55, 20,25,55; 10,20,70; 10,10,80; 30,10,60.
38. A washing composition comprising a substantially non-aqueous liquid
component containing at least one surfactant in which is dissolved a
peroxyacid generator as described in claim 1 and in which is suspended a
hydrogen peroxide developing persalt.
39. A composition according to claim 38 in which from 5 to 95% w/w of the
liquid component comprises a solvent selected from liquid alcohols,
polyols, polyglycols, aminoalcohols, ester or ether derivatives of the
hydroxyl groups, or amines, or N-acyl or N-alkyl derivatives of
aminoalcohols.
40. A composition according to claim 38 in which the liquid component
contains at least one non-ionic surfactant and at least one anionic
surfactant.
41. A composition according to claim 38 in which the persalt is sodium
perborate monohydrate.
42. A composition according to claim 38 containing from 5 to 30 parts by
weight activator, from 5 to 20 parts by weight persalt, from 0 to 30 parts
by weight builder and 0 to 10 parts by weight auxiliaries, the solids
comprising from 5 to 15% by weight of the composition and the
solvent/surfactant mixture provides the balance.
43. A process for washing an article or surface in which the latter is
brought into contact with a composition as described in claim 2, in the
presence of a surfactant.
44. A process according to claim 43 which is effected at a pH of 7.5 to 10.
45. A process for disinfecting a medium in which a composition according to
claim 1 is brought into contact with that medium.
46. A process according to claim 45 which is effected at a pH of from 3 to
9. |
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Claims |
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Description |
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The present invention relates to peroxygen compounds and more particularly
to the generation of organic peroxyacids from activators, and in addition
to compositions containing such activators and the use of such activators
and compositions containing them inter alia for cleaning, bleaching or
disinfection.
For many years, it has been common for many washing or disinfecting
compositions for the European market to contain a peroxygen compound,
which can act as an oxidising agent, a bleach and to at least some extent
a disinfectant. Particularly for washing or bleaching compositions, the
peroxygen compound has typically been a particulate alkali metal persalt
such as sodium perborate tetrahydrate or sodium percarbonate which
generates hydrogen peroxide in aqueous solution. Similarly, in America,
peroxygen compound-containing additives are widely available for use in
conjunction with other washing compositions. Persalts function more
effectively at temperatures in excess of 80.degree. C., but in recent
years there has been a trend towards the use of synthetic fibres for
apparel and household textile wares which may themselves, or their
finishes or dyes, be adversely affected by exposure to high washing
temperatures, and accordingly, increasing interest is being shown in
washing at lower temperatures, for example in the range of ambient to
60.degree. C. Interest has been further intensified by substantial
increases in the cost of energy since the mid 1970's. For a peroxygen
compound to be effective at such lower temperatures, it is necessary for
it to be more active than aforementioned persalts, and accordingly
considerable research effort has been directed by many organisations to
locate either more active peroxygen compounds or compounds which can be
added to persalts in order to activate them, i.e. activators. Both
approaches suffer from their own disadvantages. The use of activators can
be hindered by segregation of them from persalt during storage or
transportation thereby leading to inconsistent washing performance, the
need for both components to be dissolved simultaneously during the washing
performance can lead to incomplete development of the active system during
the restricted washing period available in most washing machines, and many
can interact destructively with various other components in washing
compositions. On the other hand, the more active peroxygen compounds are
not without problems. First, many of them are comparatively unstable, even
when stored alone, and this instability is compounded by the formulation
with the rest of the washing compositions and many of such compounds are
somewhat hazardous to handle, being sensitive to thermal shock, impact or
other disturbance. In view of the problems associated with the existing
active systems, there is a continuing need for alternatives having
advantageous combinations of properties to be located.
One class of compound to which some attention was given during the early
days of finding activators is that of carboxylic acid esters. One of the
earliest of these is the British Pat. No. 836988 and the corresponding
U.S. Pat. No. 2,955,905 which proposes the use of esters giving a titre of
above a predetermined value of 1.5 mls in an arbitrary test. Surprisingly
the instant inventor has found that certain esters described herein fail
the aforementioned test, often providing titres of below half the pass
value but can act as effective activators, thereby indicating that the
test cannot be applied indiscriminately, requiring additional information
that is not provided in the specification to validate the test. In
addition to the test, the specification discloses that the esters should
not yield easily oxidisable hydrolysis products such as unsubstituted
lower aliphatic aldehydes. Subject to the foregoing directive, the
specification lists seven various named sub-classes of esters which can be
employed, naming examples within each and of course those examples do not
include any reference to esters that might yield unsubstituted lower
aliphatic aldehydes. One of the seven sub-classes of compounds, sub-class
(e), is a sub-class not given undue prominence, and which comprise
compounds containing two ester groups attached to the same carbon atom as
may be obtained by acylation of aldehydes and five examples were given,
including benzaldehyde diacetate and glycolic aldehyde triacetate. The
inventor of the instant invention tested the aforementioned compounds in
the course of his investigations into activators, and found that though
they were initially solid products, exposure to ambient air led rapidly to
the evolution of an unpleasant odour and liquefaction of the solids
indicating that the compounds were particularly unstable upon storage or
exhibited unpleasant storage characteristics. Accordingly, it will be
recognised that the aforementioned patent specification does not give
clear guidance as to the practical value or otherwise of various ester
compounds except to discourage the use of those derivable from
unsubstituted lower aliphatic aldehydes.
According to one aspect of the present invention, there is provided a
process for the generation of a peroxyacid species comprising the step of
bringing into contact hydrogen peroxide or an adduct thereof or some other
compound which develops hydrogen peroxide with a peroxyacid generator
having the general formula (I)
##STR2##
in which R.sub.1 R.sub.2 and R.sub.6 are each selected from hydrogen and
lower alkyl groups, and R.sub.3 is selected from hydrogen, lower alkyl and
aryl groups and groups of formula (II) or (III)
##STR3##
in which R.sub.7 represents a carbon-carbon bond or an alkylene diradical,
R.sub.4 and R.sub.5 each represent hydrogen or a lower alkyl, or an aryl,
aralkyl or alkaryl group and R.sub.5 can also be selected from groups of
formula (IV) --R.sub.8 --CO--O--R.sub.9 in which R.sub.8 represents an
alkylene diradical and R.sub.9 represents a vinyl or alkyl substituted
vinyl group or group of formula (V)
##STR4##
By so bringing the two aforementioned reagents into contact, it has been
found that peroxyacid having the formula R.sub.4 CO.sub.3 H or R.sub.5
CO.sub.3 H can readily be obtained. These peroxyacid species being more
active than hydrogen peroxide are particularly useful for bleaching,
oxidising or for disinfecting/sanitisation.
According to a second aspect of the present invention there is provided a
composition comprising (a) hydrogen peroxide or an adduct thereof or a
compound which develops hydrogen peroxide and (b) a peroxyacid generator
having the general formula (I) described hereinbefore. In certain
embodiments, the composition is formed at the point of use, and in other
embodiments the composition is formed as a storable solid or liquid.
In the peroxyacid generators, R.sub.1, R.sub.2 and R.sub.3 can be the same
as each other except where R.sub.3 is selected from the additional groups
or can differ and similarly R.sub.4 and R.sub.5 can be the same as each
other except when one is selected from the additional groups or be
different. Commonly, at least one of R.sub.1, R.sub.2, R.sub.3 and R.sub.6
is hydrogen. In many desirable embodiments, R.sub.1, R.sub.2 and R.sub.3
each represent hydrogen, R.sub.6 represents hydrogen or methyl or ethyl
and R.sub.4 and R.sub.5 are selected from lower alkyl, particularly
C.sub.1 to C.sub.3 and aryl, in particular phenyl and lower alkyl
substituted phenyl. Expressed differently, one of R.sub.4 and R.sub.5, in
some desirable embodiments, comprises a C.sub.1 -C.sub.3 alkyl group and
the other represents a C.sub.6 -C.sub.10 alkyl or aryl group, including
the aforementioned phenyl and substituted phenyl groups and C.sub.6,
C.sub.7, C.sub.8 chain length alkyl groups, optionally substituted by an
ethyl or methyl groups. Where R.sub.4 differs from R.sub.5 two different
peroxyacids are produced. Thus, advantageously, such gem diesters enjoy
the advantage of being able to generate two different types of peroxyacid
simultaneously thereby to cater for a broader range of stains without any
problems associated with incorporating a mixture of activators, such as a
mixture of hydrophilic and hydrophobic stains. Especially desirable
peroxyacid generators include ethylidene diacetate, ethylidene dibenzoate
and ethylidene acetate benzoate and the corresponding isopropylidene
esters. Other generators include ethylidene or isopropylidene gem diesters
in which one of the ester groups is acetate or propionate and the other is
cyclohexanecarboxylate, hexanoate, heptanoate, octanoate,
2-ethyl-hexanoate or 3,5,5-trimethylhexanoate.
In other desirable embodiments in which R.sub.3 represents a group of
formula (II) or (III), the diradical terminates in a gem-diester or
alternatively in an enol ester. In such compounds, R.sub.7 often contains
up to 8 and particularly 1, 2 or 3 linear carbon atoms. Suitably, groups
R.sub.4 and R.sub.5 can be selected as before. Consequently, highly
desirable peroxyacid generators include 1,1,4,4-tetra acetoxybutane and
1,1,5,5-tetra acetoxypentane together with 1,1,4,-triacetoxy but-3-ene and
1,1,5,-triacetoxypent-4-ene. In yet further embodiments, in which at least
one of R.sub.4 and R.sub.5 represents a dibasic aliphatic ester group,
R.sub.8 normally comprises from 2 to 10 linear carbon atoms, that is to
include succinate, glutarate, adipate, suberate, azelate and
dodecanedioate, in respect of unbranched diradicals and trimethyladipate
in respect of branched diradicals. Alkyl substituents of R.sub.8, if
present, are often C.sub.1 to C.sub.4. It is particularly desirable for
the ester grouping in such di-functional esters that is distant from the
gem ester to form part of an enol ester linkage, particularly with a
phenyl group. Alternatively, it is possible for that distant group not to
be esterified, allowing it to remain as a free carboxylic acid.
Advantageously, many of the aforementioned peracid generators are liquid
at or near ambient temperature which means, for example, they can be
readily dispersed in aqueous media during use in for example sanitising or
washing or bleaching, thereby minimising the possibility of localised
concentrations of peracid, and also avoiding the problems of irritancy and
the like caused by powders in which it is necessary to employ solid
peroxygen generators.
It will further be understood that where the gem-diester product is derived
from an alpha-omega dialdehyde, one method of pre-production of the
dialdehyde can obtain some material terminating at one end of the molecule
in a vinyl ether group and at the other end in an aldehyde group. For the
avoidance of doubt, the vinyl ether and gem-diester-containing product
obtainable from such a process is contemplated within the scope of the
instant invention.
It will be recognised that hitherto there have been various compounds
proposed which are liquid at ambient temperatures and which can act as
peroxyacid generators. An example of such a compound is vinyl acetate.
Unfortunately, although vinyl acetate has various commendable features,
its availability for widespread use is hampered by its rather low flash
point as is in consequence the flashpoint of liquid compositions
containing a substantial proportion of it. Advantageously, by comparison
with such compounds, the peroxyacid generators according to the instant
invention have a substantially comparable activity with respect to
peroxyacid generation, but a substantially higher flashpoint. This means
that the invention compounds and liquid compositions containing a
substantial proportion of them are correspondingly safer to store and
transport. Moreover, the instant invention compounds also retain the
advantage of ready biodegradability, low toxicity and freedom from
nitrogen and phosphorus.
The esters according to the recent invention can be made by one or other of
the following general routes described herein, the selected method
depending upon the functionality of the component moieties. The first
method can readily be applied to the manufacture of gem-diesters having
the formula
##STR5##
in which R.sub.1, R.sub.2 and R.sub.3 are all monofunctional and at least
one of which represents hydrogen and in practice preferably all three,
R.sub.6 represents hydrogen or alkyl and R.sub.4 and/or R.sub.5 represent
mono or difunctional moieties. Expressed at its broadest, method 1
comprises reacting an enol ester having the formula
##STR6##
with a carboxylic acid having the formula
R.sub.5 --CO.sub.2 H
in the presence of an acid catalyst. It will further be recognised that
compounds terminating at each end with an enol ester or with a carboxylic
acid group can be substituted for the monofunctional compounds described
herein above, and the mole ratios of the reactants adjusted
correspondingly.
In the presence of a strong acid such as a strong organic acid, that is
soluble in the reaction medium, such as methane sulphonic acid or
paratoluene sulphonic acid, and/or a strong inorganic acid such as
sulphuric acid or perchloric acid, the reaction is carried out at a
temperature desirably of at least 40.degree. C. and preferably at least
60.degree. C. and conveniently at up to 100.degree. C. For reaction
mixtures having a boiling point of below 100.degree. C. it is often most
convenient to employ a temperature at or within 5.degree. C. of the reflux
temperature.
In the case of vinyl acetate as the liquid starting material, the mixture
refluxes at around 80.degree. C., but naturally, for other enol esters,
the reflux temperature will be different. A temperature in excess of
100.degree. C. can be used for some enol esters, with an increasing risk
of polymerisation. Reaction is normally carried out for several hours
until a substantial proportion of the enol ester has been converted to
form a gem diester, or a mixture of diesters in some cases, which can be
determined for example by periodically measuring the residual
concentration of carboxylic acid in a sample. It is usual for a reaction
period of at least 11/2 and often at least 3 hours, typically up to 12
hours and often from 4 to 8 hours to be employed.
The sulphonic acid catalyst is normally separated out, subsequently, in
practice though not essentially after the reaction mixture has cooled to
at or near ambient temperature, the separation is effected by washing the
reaction mixture with water and/or a mildly alkaline aqueous solution, for
example of sodium acetate or sodium bicarbonate and the aqueous and
organic phases separated.
Further purification of the reaction mixture is desirable, and can be
effected either by distilling under a reduced pressure at 40 to 2500 Pa,
and/or by stripping off any low boiling starting material or impurities.
A related alternative route employs the same starting materials but either
a mercury II acetate or palladium II system which include or generate acid
as catalyst. In such a route the reaction temperature is normally greater
than ambient, but below reflux temp and particularly from 40.degree. to
70.degree. C., for a period usually in excess of 3 hours, especially from
5 to 8 hours. Subsequently, and especially after the reaction mixture has
cooled to approximately ambient temperature, the catalyst can be removed
by washing with an aqueous solution of a metal-ion sequestrant, typically
ethylene diamine tetraacetic acid or related amino compounds. Thereafter,
separation and purification of the reaction mixture can follow the
preceding route.
It will be recognised that this technique is especially well adapted to the
production of peracid generators in which the ester groups are different.
Such compounds can have particular advantages, and for example ethylidene
benzoate acetate, which can readily be obtained by reactions between
benzoic acid and vinyl acetate has a remarkably low smell, thereby
rendering it more acceptable to both domestic and commercial users who can
often be substantially off-put especially by acetic acid developed on
storage by and from enol esters.
In a second general method, compounds can be obtained having the general
formula
##STR7##
and the corresponding compound terminating at one end in an enol ester and
the other in gem diesters or at both ends in gem diesters. In this
process, an aldehyde of formula:
##STR8##
or corresponding dialdehyde preferably after dewatering, is reacted with
an anhydride of formula R.sub.4 --CO--O--CO--R.sub.4 or R.sub.4
--CO--O--CO--R.sub.5 or with a mixture of the two anhydrides R.sub.4
COOCOR.sub.4 and R.sub.5 COOCOR.sub.5 in the presence of an alkali or
soluble alkaline earth metal carboxylate, especially an acetate, at a
temperature in excess of 80.degree. C. and preferably in excess of
100.degree. C. and conveniently at or near the reflux temperature of the
reaction mixture. The mixture can be monitored for example by intermittent
sampling, and halted when a desired amount of gem-diester has formed. The
reaction period is normally at least 3 hours and in many instances is from
4 to 6 hours, although at temperatures in the vicinity of 100.degree. C.
somewhat longer periods are preferable.
After the reaction is halted, the mixture is preferably water washed at
below 100.degree. C. to remove the water-soluble carboxylate, and is
preferably dried such as by addition of acetic anhydride. A purer product
can subsequently be obtained by stripping out unreacted aldehyde and
carboxylic acid and further by fractional distillation.
In practice, there is often obtained a mixture of products including that
in which the gem-diester has been formed at each of the dialdehyde groups
and one in which a gem-diester has been formed from one of the aldehyde
groups and an enol ester at the other aldehyde.
The second essential component for carrying out a peracid generating
process according to the present invention is hydrogen peroxide or a
compound which can produce hydrogen peroxide in use. Such compounds
include adducts of hydrogen peroxide with various inorganic or organic
compounds, of which the most widely employed adduct is sodium carbonate
perhydrate, which is often referred to as sodium percarbonate. Other
adducts include sodium phosphate perhydrate, a persalt obtained by
addition of hydrogen peroxide to mixed sodium sulphate and sodium chloride
or sodium sulphate with potassium chloride, adducts of hydrogen peroxide
with zeolites, or urea hydrogen peroxide. Other hydrogen
peroxide-developing compounds which are of a special importance comprise
sodium perborate, often in the form of either the tetrahydrate or the
monohydrate but also usable as the trihydrate. These compounds can either
by introduced as such or in admixture with other components such as
surfactants, sequestrants, builders, pH regulators, buffers, stabilisers,
processing additives or any other known components of washing
compositions, sanitising compositions, disinfecting compositions or bleach
additives.
In order to avoid premature interaction of the hydrogen peroxide or persalt
with the peroxyacid generator, the two components can be introduced
separately into the point of use, but can alternatively be adsorbed into a
substrate or incorporated into liquid formulations.
Liquid formulations demonstrating markedly enhanced storage stability in
comparison with related formulations containing the specified diesters of
subclass (e) in GB No. A-836988 can be obtained by incorporating the
invention gem diester peroxyacid generator in an acidic aqueous emulsion
together with an emulsifying amount of an emulsifier, preferably a
reasonably matched emulsifier. By the term `matching` is meant that the
emulsifier or combination of emulsifiers having an HLB value substantially
the same as that of the activator. The more closely the HLB values of
emulsifier and peroxyacid generator match, the greater the tendency for
the liquid system to be capable of containing in microemulsion form a
comparatively high concentration of generator. However, and by way of
corollary, as the ratio of emulsifier to generator increases, the extent
of matching of HLB values can be relaxed, as will be apparent later
herein.
In emulsions described herein, the concentration of hydrogen peroxide is
normally at least 1%, desirably at least 3% and conveniently is not more
than 20% and quite often not more than 10%, all by weight of the
composition. In many of the instant compositions, hydrogen peroxide
concentration is in the range of 4 to 8% by weight of the composition. The
balance of the aqueous phase comprises water which in practice is often in
the region of 30 to 85% of the composition weight. It is preferable to
select compositions in which the concentration of hydrogen peroxide in the
aqueous phase is less than 35% w/w in the phase and often is 10 to 35% w/w
on that basis and it will be recognised that such concentrations
correspond often to overall peroxide concentrations of below 10% w/w on
the composition.
The aqueous phase also contains sufficient water soluble-acid to generate
an acidic pH, preferably from pH2 to pH5, and especially pH2 to pH3.5.
Such a pH may often be obtained in the aqueous phase of the emulsion in
practice by dilution with demineralised water of commercially available
hydrogen peroxide solutions which contain a small amount of acidic
stabilisers such as pyrophosphoric acid and/or one or more phosphonic
acids (particularly amino methylene phosphonic acids, such as DTPMP and
EDTMP, and often on emulsification a small proportion of organic acid from
the activator can transfer into the aqueous phase. The pH of the
composition can readily be monitored and if necessary adjusted to the
preferred range by suitable acid or base introduction. The aqueous phase
can additionally contain a small amount of a thickener, such as about 0.5%
by weight of the composition of a xanthan gum, the precise amount being
variable at the discretion of the manufacturer to obtain a desired
viscosity.
The concentration of activator in the composition is normally selected in
the range of from 1 to 35% by weight, is usually at least 3% by weight and
in many embodiments is from 10 to 30% by weight. Many useful compositions
contain activator in the range 3 to 10% w/w. Of course, it will be
recognised that the higher molecular weight activators tend to be present
in somewhat higher concentrations than the lower molecular weight
activators, in order to achieve a similar mole ratio to the hydrogen
peroxide. Thus, in some embodiments for activators having an equivalent
molecular weight of up to 100 the proportion of activator is preferably
from 10 to 20% by weight, for activators having an equivalent molecular
weight of over 100 to 130 the corresponding proportion is preferably from
15 to 25% and for activators having a molecular weight of over 130, the
corresponding proportion is preferably from 20 to 30% by weight.
The amount of emulsifier that can been used can be found over a very wide
range. One convenient way of assessing how much emulsifier to employ is to
relate it to the weight of activator present. Naturally one should also
take into account the extent to which the activator and emulsifier are
matched in the formulation employing low relative amounts of emulsifier
only when they are reasonably matched. With that proviso, the amount of
emulsifier usually employed is at least 5% by weight based on the
activator, and indeed in many desirable compositions is from 10% likewise
based with a reasonably matched emulsifier/activator system, and it is
possible to achieve excellent emulsions, using less than 100% emulsifier
w/w based on the activator, though when around 50% or less emulsifier is
employed there is a marked tendency for it to be a macro-emulsion.
Particularly in the region of at least 70% emulsifier in such a matched
system, it tends to form a micro-emulsion. Naturally, above 100%
emulsifier can be used if desired, but for a matched system, its
justification would often be found in some non-emulsion aspects of the
inventions, for example in order to improve washing performance; however
in a system that is less well matched, it can be beneficial for the
emulsion stabilitity to employ over 100% w/w emulsifier. Normally, the
total weight proportion of emulsifiers in the emulsion is not more than
60% w/w.
The extent to which the matching of HLB values for the activator/emulsifier
can be related in the context of the present disclosure using high amounts
of emulsifier can be gauged from the fact that clear emulsions can be
formed from water soluble anionic emulsifiers such as alkyl benzene
sulphonate, alcohol sulphates or sulphosuccinates provided that the weight
ratio of the emulsifier to activator is generally at least 4:1 and in some
instances from 2:1 to 4:1 also, in the range of activator concentrations
from 1-10% w/w. At ratio of emulsifier to activator below those ranges but
at least 1:1, the emulsion is primarily a macroemulsion, but it will be
seen to comprise two phases only, i.e. does not separate readily to a
three phase system.
A list of suitable emulsifiers is given in European Patent Specification
No. 92932A, on pages 10 and 11 which is incorporated herein by reference.
It will be recognised that there are other and closely related emulsifiers
to one or more of the listed emulsifiers which will have similar
characteristics or characteristics having a predictable difference. For
example, the PEG 400 monostearate has an HLB value approximately 1.4 units
lower than the PEG 400 monolaurate emulsifier listed and the POE(20) cetyl
alcohol (ether) has an HLB value 2.8 higher than the corresponding POE(10)
cetyl alcohol (ether). It is often desirable to match unsaturated
emulsifiers with unsaturated activators and vice versa.
In addition, mixtures of the emulsifiers, such as a mixture of one or more
alkyl benzene sulphonates and/or alcohol sulphates and/or sulphosuccinates
with one or more water-soluble alkyl phenol and/or ethoxylated fatty
alcohol or acid, alkanolamine or other ethoxylated nonionic emulsifier,
can be used. The ratios of the mixtures can be selected within wide
limits, with the ratio of anionic to nonionic emulsifier usually in the
range 10:1 to 1:10. In the preferred range of 3:1 to 1:3 and by so doing
it is often possible to extend the area within which the compositions are
clear rather than being strictly macroemulsions. In many instances such
co-operation between the two types of emulsifiers could enable clear
compositions to be formed containing 1 part activator per 2 to 3 parts by
weight of the emulsifier system. An excellent example comprises a 2:1 to
1:2 ratio of a nonylphenol ethoxylate with a sulphosuccinate.
Some, or the major part or all of the emulsifiers is often premixed with
the activator before subsequent dispersion in the aqueous hydrogen
peroxide, such amount in many cases comprising 100% to 50% of the weight
of the activator. However, it is possible for some of the emulsifier
combination to be pre or post mixed in the aqueous phase, especially in
respect of an anionic emulsifier, in which case for example up to 50% and
typically at least 5% of such emulsifiers by weight based on the activator
can be so added to the aqueous phase. Advantageously, it has been found in
some embodiments that transparent emulsions can be obtained, such as by
including an anionic emulsifier as well as a nonionic emulsifier and
employing at least about half as much emulsifier as activator. All or part
of the anionic emulsifier can in the main be added in either phase at the
discretion of the formulator.
It is possible also to employ an intermediate weight aliphatic alcohol
having a C.sub.5 to C.sub.8 chain length to co-operate with especially the
anionic emulsifiers, in a weight ratio thereto often of up to 2:1.
In addition to the foregoing components, the composition can also contain
one or more dyes or perfumes, preferably those which have demonstrable
resistance to attack by peroxygen compounds, usually in an amount of less
than 0.5% by weight. Since the composition may be used for the bleaching
of absorbent materials, it may also be advantageous to add an optical
brightening agent to the formulation. This would usually be employed in an
amount not greater than 2% by weight, often from 0.5 to 1%, and should
also be resistant to attack by peroxygen compounds.
It will be recognised that when high ratios of emulsifier to activator are
used, it is possible to obtain bleach activator compositions which
establish their own balance of nonionic to anionic surfactants when used
in conjunction with conventional amounts of a base washing composition and
therefore can minimise the risk of impaired cleansing of
surfactant-sensitive soils which can occur if relatively low ratios of
emulsifier to activator are employed.
It will be recognised, furthermore, that an alternative approach is
facilitated by the use of the type of compositions described herein. In
this latter approach, the bleach activator composition can be tailored for
use in conjunction with a selected washing composition so that the
benefits of the bleach augment the performance of that washing composition
without interfering markedly with the cleansing of surfactant-sensitive
stains. This can be achieved by matching the emulsifier system of the
bleach composition to the surfactant mixture in the washing composition
and then employing a high concentration of the emulsifier system into
which is introduced the selected activator in a relatively low ratio
thereto.
Normally, the aqueous phase comprises at least 25% and the organic phase
not more than 75% of the emulsion. In many emulsions described herein, the
aqueous hydrogen peroxide comprises from 40 to 95% by weight of the
composition and correspondingly the organic phase, mainly the activator
and emulsifier comprises the balance of from 60 to | | |
