Note: Descriptions are shown in the official language in which they were submitted.
~ WO95/10588 PCT~P94/03322
21 7131~
DETERGENT COMPOSITIONS CONTAINING SILVER ANTI-TARNISHING
AGENTS
~.
FIELD OF THE INVENTION
This invention relates to bleaching detergent compositions
which include silver anti-tarnishing agents. More
particularly, the invention relates to detergent
compositions based on peroxygen and/or hypohalite bleaching
agents and which include one or more particular organic
heterocyclic species as a silver anti-tarn;~hing agent.
BACKGROUND OF THE INVENTION AND PRIOR ART
Silver is chemically the most reactive element among the
noble metals and tarnishes readily on exposure to sulphur
bearing atmospheres. Because of its electronic state,
silver exhibits a drastically different chemical behaviour
from, for instance, copper, although both metals are in the
same group of the Periodic Table. Thus, silver tarnishing
is very different from corrosion of other metals.
Tarn;~h;ng, sometimes referred to as discolouring, is
caused by a silver oxidation process in which sulphide is
formed. Food such as onions, mustard and eggs which contain
organic sulphur compounds are also known to tarnish silver.
See Singh et al., "Silver Tarnishing and its Prevention - A
Review" Anti-corrosion Methods and Materials, Vol. 30 (July
1983), pp. 4-8.
Silver tarn;~h;ng is also known to occur when an oxygen
bleaching agent used in detergent compositions oxidizes the
silver to silver oxide. This oxidation process causes
surface-blackening of the silver, leaving undesirable
tarnishing of silverware when machine-dishwashed, for
example.
The use of organic compounds to enhance the resistance of a
silver surface to tarnishing has been described in Singh et
PCT~P94/03322
WO95/10588
~ 2
al, su~ra pp. 5-6. Certain triazoles, particularly
benzotriazole and its variations, are useful as corrosion-
inhibiting agents in detergent compositions as described in
CH 673033 (1990) and U.S. 4,321,166 (Procter & Gamble,
1982).
U.S. Patents Nos. 2,618,606 (Procter & Gamble) and
2,618,608 (Procter & Gamble) disclose the use of
derivatives of triazole, including 1,2,3-triazole,
imidazole and pyrazole, as discolouration inhibitors used
in detergent compositions for non-ferrous metals, such as
copper and brass. The detergents described do not, however,
contain a bleaching agent which complicates silver tarnish
inhibition. The patents further state that a mixture of
copper inhibitors are required to prevent tarnishing over a
broad pH range.
Conventional detergents, particularly automatic machine
dishwashing detergents, are generally formulated with
chlorine bleaching agents in a high alkaline pH range.
During washing, certain such chlorine bleaches (e.g.
chloroisocyanurate) react to form isocyanuric acid and thus
do not greatly effect silver discolouration.
2S Detergent compositions are, however, increasingly being
based on peroxygen bleaching agents and are being
formulated to be milder to produce more environmentally-
friendly products. The problem of tarnishing of silver and
silver-plated articles has thus become more severe.
It is thus a primary object of the present invention to
provide a peroxygen and/or hypohalite bleach-based
detergent composition containing one or more compounds
which prevent or ameliorate the problem of silver
tarnishing, particularly in the context of a machine
dishwashing environment, especially in an alkaline washing
medium.
~ 3 ~ 31 2
It is a further object of the invention to provide an
environmentally-friendly detergent composition which
prevents or inhibits tarnishing of silver or silver-plated
articles.
S ,.
Another object of the invention is to provide a method for
washing silver or silver-plated articles without
discolouring them.
A further object of the invention is to protect a silver or
silver-plated article against tarnishing from organic
foodstuffs with which it comes into contact.
Silver anti-tarnishing bleaching detergent compositions
lS formulated for use in automatic dishwashing machines or
fabric washing machines which are stable in a variety of
physical forms, including liquid, powder, flakes, etc., is
another object of the invention.
.
SUMM~RY OF THE INVENTION
Accordingly, in a first aspect the present invention
provides a bleaching detergent composition comprising:
(a) from about 1 to about 20~ by weight of a bleaching
agent selected from a peroxygen or peroxvgen-yielding
compound, a hypohalite or hypohalite-yielding compound, or
a salt thereof, or mixtures thereof;
(b) from about 0.05 to about 10% by weight of an anti-
tarnishing agent selected from:
(i) a purine class compound of the following formula (I)~:
'r~.'' jr=~ _T
' V ~ 7
i7~312
N~X~ (I)
wherein X~ is ni~rogen or C-R3, Y~ is nitrogen or C-R~,
and Rl, R~, R3 and R~ are each independently hydrogen,
hydroxy, zlkoxy, amine, straight or branched chain
alkyl having 1 to 20 carbon atoms, amido, amidoalkyl,
alkylthio, alkenyl or hydroxyalkyl;~r~ ~G~
(ii) cyanuric acid or isocyanuric acid or a salt thereof;
.
(iii~ a 1,3-N azole compound of the following formula
` (II);
2 H
~ \x2 (II)
R
wherein X' is C-R? or nitrogen provided Y' is also
nitrogen, Y- is nitrogen or C-Rh, and Rs, R~ and R7 are
each independently hydrogen, amine, amido, straight or
branched chain alkyl having from 1 to 20 carbon atoms,
an amino- or carboxylic-containing chain, alkoxy,
alkylthio, hydroxy, hydroxyalkyl, alkenyl, or Rs and R6
.D ~ S~EET
~ . 5 ~ 2~71312
taken together form an unsubstituted or substituted
aryl group; or a salt thereof;
(iv) a mixture of any of the above compounds (i), (ii) or
(iii);
(c) optionally from about 1 to about 75~ by weight of a
detergency builder; and
(d) optionally, from about 0.01 to about 40% by weight of
a surfactant;
~ ~ l~7~ ~ ~
wherein the composition exhibits a pH value ~ln the range
from about 7 to about 13, especially from about 7 to about
at lel2s~ C.~L u~
11, and wherein the anti-~arnishing agent has a pKa value~
below the pH value of ~laqueous solution of the
composition.
In a second aspect, the invention provides a method of
. 20 washing a silver or silver-plated article whilst preventing
or inhibiting tarnishing thereof during or as a result of
the washing process, the method comprising washing the said
article with a bleaching detergent composition according to
the first aspect of the invention defined above.
In a third aspect, the invention provides the use of a
compound selected from any of (i) to (iv) defined above in
accordance with the first aspect of the invention, as a
silver anti-tarnishing agent in 2 peroxygen- and/or
~0 hypohalit7 based bleaching detergent composition ~aving a
pH value ~in ~ an ~ rom about 7 to about 13~ L
a~ h~ ~ pk ~a~ c~ (Q~ ~t ~ pu ~c.l~ ~a 17,
~;C~J S ~ b pG'~
The various aspects of the invention, and preferred
embodiments thereof, will now be described in detail.
Al~\rfi~i~-E
~ ' ~` ~6 ' 2I71312
~ETAILED DESCRIPTION OF T~E INVENTION AND PREFERRED
EM~30DIMENTS
Anti-tarnishin~ a~ent
The silver anti-tarnishing agent of compositions of the
invention is a compound or a mixture of two or more
compounds selected from any of the following:
(i) a purine class compound of the following
formula (I) or ~
; ~ ~ ~ ' Y (I)
wherein X' is nitrogen or C-R3, yl is nitrogen or C-R4,
and R~, R2, R3 and R4 are each independently hydrogen,
hydroxy, alkoxy, amine, straight or branched chain
alkyl having 1 to 20 carbon atoms, amido, amidoalkyl,
alkylthio, alkenyl or hydroxyalkyl~,~ R
~ ~ c~ ,2 ~ ~ X' ~ g~ ~ L;
(ii) cyanuric acid or isocyanuric acid or a salt
thereof;
(iii) a 1,3-N azole compound of the following
formula (II);
\ 2 (II)
~ ~X
s~/ N
R
AMEN~D S~ET
- 2 1 7 1 3 ~ 2
wherein X7 is C-R7 or nitrogen provided Y7 is also
nitrogen, Y- is nitrogen or C-R6, and R5, R6 and R7 are
each independently hydrogen, amine, amido, straight or
branched chain alkyl having from 1 to 20 carbon atoms,
an amino- or carboxylic-containing chain, alkoxy,
alkylthio, hydroxy, hydroxyalkyl, alkenyl, or Rs and R6
taken together form an unsubstituted or substituted
aryl group; or a salt thereof;
with the proviso that the compound(s) have a pK~ value
which is ~bcl~ ~fc.~bl~ at least 1 unit below~
~c3~cci~11y in ~hc cc~c of .hc ~ a~ d~
preferably at least 2 units below, a pH value of ~
~ c~ r~ ^f~ a 1% aqueous solution~ of the
composition in which the compound(s) is/are incorporated.
Most preferably, the pK~ value of the anti-tarnishinq
compound(s) is at least 2 and up to 6 units below the pH
value of the aqueous solution of the composition.
As used herein, the term l'pKall means a pH value at-which
50% of the heterocyclic ring moieties of the compound
(particularly the five-membered rings in the case of the
l~ic,
purine class compounds) are in anion~c form.
As used herein, the term "purine class compound~ includes
not only compounds of formula (I) above, but also
tautomeric forms of these compounds.
Preferred compounds of formula (I) include those wherein X~
is nitrogen and Y~ is C-R~ and R', R7 ~ and R~ are each
independently hydrogen, hydroxy, alkoxy,~oxygcn,3 alkylthio,
amine, amido or lower alkyl having from 1 to 6 carbon
atoms~h~ ' ~ Q~ ~ Q~7 ~c~ ~,~
~ h~ 5~ SHL~
- 2171~1~
Especially preferred compounds of formula (I) include
purine, adenine, guanine, 6-mercaptopurine, xanthine,
hypoxanthine, uric acid, and allopurinol.
The above purine class compounds are available
commercially, for example from Aldrich Chemical Co. of
Milwaukee, Wisconsin, USA.
As used herein, the term "cyanuric acid" means 1,3,5-
triazine-2,4,6(lH,3H,5H)-trione, normal cyanuric acid, sym-
triazinetriol, 2,4,6-trihydroxy-1,3,5-triazine, tricyanic
acid or trihydroxycyanidine. Corresponding possibilities
apply to the term "isocyanuric acid" as used herein, and
within the scope of both terms are salts thereof.
Preferably, the cyanuric acid or isocyanuric acid, or a
salt thereof, as an anti-tarnishing agent in the present
invention, is an unsubstitu~ed such species.
Cyanuric acid is available commercially, for example also
from Aldrich Chemical Co. of Milwaukee, Wisconsin, USA.
Preferred 1,3-N azole compounds of formula (II) above
include those wherein x2 is C-R7, Xx is nitrogen provided Y
is nitrogen, y2 is C-R6 and R5 and R6 taken together form an
aryl or a substituted aryl group. Other preferred compounds
of formula (II) include those wherein y2 is C-R6 and Rs and
R6 are each independently hydrogen, amine, amido, straight
or branched chain alkyl having from 1 to 6 carbon atoms,
alkoxy, alkylthio, hydroxy, alkenyl or an amino- or
carboxylic-containing moiety.
Especially useful compounds of ormula (II) include
imidazole, benzimidazole, tetrazole, ~-aminotetrazole,
1,2,4-triazole, 3-amino-1,2,4-triazole and histidine.
~ ,r~ n~ S~EEf
~ WO951105~8 PCT~P94/03322
9 2171~12
1,3-N azole compounds of formula tII) above useful in the
invention are commercially available, for example also from
Aldrich Chemical Co. of Milwaukee, Wisconsin, USA.
In the above formulae (I) and (II), a group defined as
being "alkyl" preferably means a group having from 1 to 20
carbon atoms, more preferably from 1 to about 6 carbon
atoms, most preferably from 1 to about 4 carbon atoms.
In formulae (I) and (II) above, those defined groups which
are substituted alkyl groups preferably have an alkyl chain
length of from 1 to about 5 carbon atoms, more preferably
from 1 to about 3 carbon atoms. The term "aryl" includes
aryl groups containing one or more heteroatoms such as S, N
or 0, preferably N. The term "substituted aryl" includes an
aryl group substituted with one or more of the following
groups: straight or branched chain alkyl having from 1 to
20 carbon atoms, hydroxy, alkoxy or alkenyl.
In the making of the present invention, it was surprising
to discover that the above defined compounds (i) to (iii)
provide beneficial anti-tarnishing properties to silver and
silver-plated articles in the context of the subject active
oxygen- or active halogen-based bleaching detergent
compositions. In contrast, compositions containing certain
1-N azoles (e.g. pyrrole), 1,2-N azoles (e.g. indazole,
pyrazole) and pyrimidine have been observed to be
substantially ineffective in preventing heavy tarnishing of
similar silver and silver-plated articles. This observation
was particularly surprising in view of the fact that most
of the 1-N and 1,2-N azole compounds did prevent copper
tarnishing under similar conditions. Without being limited
by theory, it is proposed that the compounds used in the
present invention form a complex with the silver molecules
at the surface of the article to form a protective film
which prevents or diminishes its tendency to tarnish in an
oxidative environment.
t
21713I~
In the anti-tarnishing b eaching detergent compositions of
the invention, ~he one or more compounds forming the anti-
tarnishing agent are presen~ in a (total) amount of from
about 0.05 to about 10% by -~eight, preferably from about
0.25 to about 2.5% by weign~, most preferably from about
0.75 to about 2% by ~eiah~.
~H a l~
The pH of ~ aqueous solution ~p ~ , 7~ of
the compositions in accordance with the invention should be
from about 7 to about 13, more preferably from about 7 to
- about 11, most preferably from about 7 or 8 to about lO.
PeroxY bleachinq aaent
Peroxygen or peroxygen-yielding bleaching agents for use in
the compositions of the invention include organic peroxy
acids and diacylperoxides. Typical monoperoxy acids useful
herein include alkyl peroxy acids and aryl peroxy acids
such as:
(i) peroxybenzoic acid and ring-substituted
peroxybenzoic acids, e.g., peroxy-alpha-naphthoic acid, and
magnesium monoperphthalate;
(ii) aliphatic and substituted aliphatic monoperoxy
acids, e.g., peroxylauric acid, peroxystearic acid,
epsi~on-phthalimido peroxyhexanoic acid, o-carboxybenzamido
peroxyhexanoic acid, N-nonenylamidoperadipic acid and N-
nonenylamidopersuccinic acid.
Typical diperoxy acids useful herein include alkyl diperoxy
acids and aryldiperoxy acids, such as:
(iii) 1,12-diperoxydodecanedioic acid
(iv) 1,9-diperoxyazelaic acid
(v) diperoxybrassylic acid; diperoxysebacic acid and
35 diperoxyisophthalic acid
(vi) 2-decyldiperoxybutane-1,4-dioic acid
(vii) N,N-terephthaloyl-di(6-aminopercaproic acid).
WO9S/105~8 11 21 713 I ~ PCT~P94J03322
A typical diacylperoxide useful herein includes
dibenzoylperoxide.
Inorganic peroxygen compounds are also suitable for use in
the present invention. Examples of such useful materials
include salts of monopersulphate, perborate monohydrate,
perborate tetrahydrate, and percarbonate.
Preferred organic oxygen bleaching agents include epsilon-
phthalimidoperoxyhexanoic acid, o-carboxybenzamidoperoxy
hexanoic acid, and mixtures thereof.
When an oxygen bleaching agent is used as the bleaching
agent in compositions of the invention, it is present
therein in an amount from about 1 to about 20% by weight,
preferably from about 1 to about 15% by weight, most
preferably from about 2 to about 10% by weight.
The oxygen bleaching agent may be incorporated directly
into the formulation or may be encapsulated by any suitable
encapsulation technique known in the art to produce stable
capsules in alkaline liquid formulations.
A preferred encapsulation method is described in U.S.
Patent No. 5,200,236 (Lang et al), the disclosure of which
is incorporated herein by reference. In the patented
method, the bleaching agent is encapsulated as a core in a
paraffin wax material having a melting point from about
40C to about 50C. The wax coating has a thickness of from
100 to 1500 microns.
Oxygen bleaching agent systems which may be employed in the
present invention may if desired or if necessary employ one
or more peroxyacid bleach precursors.
Suitable peroxygen peracid precursors for peroxy bleach
compounds have been amply described in the literature,
WO95/10588 PCT~P94/03322 ~
~3~ 12
including United Kingdom Patents Nos. 836,988; 855,735;
907,356; 907,3S8; 907,950; 1,003,310 and 1,246,339; and
U.S. Patents Nos. 3,332,882 and 4,128,494.
Typical examples of precursors are polyacylated alkylene
diamines, such as N,N,N',N'-tetraacetylethylene diamine
(TAED) and N,N,N',N'-tetraacetylmethylene diamine (TAMD);
acylated glycolurils, such as tetraacetylglycoluril (TAGU);
triacetylcyanurate, sodium sulphophyl ethyl carbonic acid
ester, sodium acetyloxybenzene sulphonate (SABS), sodium
nonanoyloxybenzene sulphonate (SNOBS) and choline
sulphophenyl carbonate. Peroxybenzoic acid precursors are
known in the art, e.g., as described in GB-A-836,988.
Examples of suitable precursors are phenylbenzoate; phenyl
p-nitrobenzoate; o-nitrophenyl benzoate; o-carboxyphenyl
benzoate; p-bromo-phenylbenzoate; sodium or potassium
benzoyloxy benzenesulphonate; and benzoic anhydride.
Preferred peroxygen bleach precursors are sodium p-
benzoyloxybenzene sulphonate, N,N,N',N'-tetraacetylethylene
diamine, sodium nonanoyloxybenzene sulphonate and choline
sulphophenyl carbonate.
Haloqen bleachinq aqent
Hypohalite or hypohalite-yielding bleaching agents for use
in the compositions of the invention include hypohalite
salts per se or compounds which yield hypohalite anions in
aqueous alkaline conditions. Such materials are preferably
incorporated into compositions of the invention in the form
of dry, particulate, water-soluble anhydrous inorganic
salts.
Examples of suitable hypohalite salts for use in the
invention include lithium, sodium or calcium hypochlorite
and hypobromite, and halogenated (e.g. with chlorine or
bromine) trisodium phosphate. Sodium hypochlorite is
particularly preferred for liquid compositions in
WO95/10588 PCT~P94103322
13
X171.~1~
accordance with the invention.
Hypohalite-yielding compounds suitable for use in the
invention include, for example, chloramines, chloramides,
chlorimines, chlorosulphonamides, and chlorohydantoins
(though preferably not N-chloro imides which are harsher
and less environmentally friendly than oxygen bleaching
agents and other hypohalite bleaching agents such as those
above), and active halogen compounds corresponding to any
of these but which contain bromine instead of chlorine, or
contain a mixture of chlorine and bromine.
Also suitable for use in the invention as a bleaching agent
are halogenated isocyanuric acids, such as
trichloroisocyanuric acid, dichloroisocyanuric acid, and
salts thereof, especially the sodium salts. Commercial
sources of chlorinated isocyanuric acids include, for
example, ACL-59 (trade mark) supplied by Mansanto Company,
and Clearon CDB-56 (trade mark) supplied by Olin
Corporation.
When a halogen-based bleaching agent such as those
described above is used as the bleaching agent in
compositions of the invention, it is present therein in a
similar amount to that when an oxygen-based bleaching agent
is used, namely in an amount of from about 1 to about 20%
by weight, preferably from about 1 to about 15% by weight,
most preferably from about 2 to about 10% by weight.
In embodiments where a mixture of oxygen and halogen
bleaching agents are optionally employed, each component is
used in an appropriate amount, such that the total amount
of bleaching agent present also falls within the essential
and preferred narrower ranges defined above with respect to
each type of bleaching agent separately.
WO95/10588 PCT~P9~103322
2 i~ ~3 ~2 14
Deterqent Builder Materials
The compositions of this invention may contain all manner
of detergent builders commonly taught for use in automatic
dishwashing or other cleaning compositions. The builder
component can include any of the conventional inorganic and
organic water-soluble builder salts or mixtures thereof
and, when present, is included in the composition
preferably in an amount of from about 1 to about 75% by
weight, preferably from about 5 to about 70% by weight.
Typical examples of phosphorus-containing inorganic
builders include water-soluble (especially alkali metal)
pyrophosphates, orthophosphates and polyphosphates.
Specific examples of inorganic phosphate builders include
sodium and potassium tripolyphosphates, phosphates,
pyrophosphates and hexametaphosphates.
Suitable examples of non-phosphorus-containing inorganic
builders include water-soluble (especially alkali metal)
carbonates, bicarbonates, sesquicarbonates, borates,
silicates, metasilicates, and crystalline and amorphous
aluminosilicates. Specific examples include sodium
carbonates (with or without calcite seeds), potassium
carbonate, sodium and potassium bicarbonates, silicates and
zeolites.
Particularly preferred inorganic builders may be selected
from the group consisting of sodium tripolyphosphate,
potassium pyrophosphate, sodium carbonate, potassium
carbonate, sodium bicarbonate, sodium silicate and mixtures
thereof. When present in the compositions of the invention,
sodium tripolyphosphate builder concentrations may range
from about 2 to about 40~ by weight, preferably from about
5 to about 30~ by weight of the composition. Sodium
carbonate and bicarbonate, when present, may range from
about 5 to about 50~ by weight, preferably from about 10 to
about 30~ by weight of the composition. Sodium
-
WO 95/10~88 15 2 PCT~P94/03322
tripolyphosphate and potassium pyrophosphate are preferred
builders in gel formulations, where they may be used in an
amount of from about 3 to about 30% by weight, preferably
from about 10 to about 20% by weight.
S
Organic detergent builders may also be used in the
compositions of the invention. Examples of organic builders
include alkali metal citrates, succinates, malonates, fatty
acid sulphates, fatty acid carboxylates,
nitrilotriacetates, phytates, phosphonates,
alkanehydroxyphosphonates, oxydisuccinates, alkyl and
alkenyl disuccinates, oxydiacetates, carboxymethyloxy
succinates, ethylenediamine tetraacetates, tartrate
monosuccinates, tartrate disuccinates, tartrate
monoacetates, tartrate diacetates, oxidized starches,
oxidized heteropolymeric polysaccharides,
polyhydroxysulphonates, polycarboxylates such as
polyacrylates, polymaleates, polyacetates,
polyhydroxyacrylates, polyacrylate/polymaleate and
polyacrylate/polymethacrylate copolymers,
aminopolycarboxylates and polyacetal carboxylates such as
those described in U.S. Patents Nos. 4,144,226 and
4,146,495.
Alkali metal citrates, oxydisuccinates, polyphosphonates
and acrylate/maleate copolymers are especially preferred
organic builders. When present, they are preferably
included in an amount of from about 1 to about 35% by
weight of the composition.
The foregoing detergent builders are intended to illustrate
by way of example only, and not to limit, the types of
builders which may be employed in the compositions of the
~ present invention.
-
W095/10S88 ~ ~3 ~ 16 PCT~P94/03322
Surfactants
The compositions of this invention may contain one or more
surfactant materials. Useful surfactants include anionic,
nonionic, cationic, amphoteric and zwitterionic types, and
mixtures thereof. Such surfactants are well known in the
detergent art and are described at length in "Surface
Active Agents and Detergents", Vol. II, by Schwartz, Perry
& Birch, Interscience Publishers, Inc. 1959, incorporated
herein by reference.
Anionic synthetic detergents can be broadly described as
surface-active compounds with one or more negatively
charged functional groups. Soaps are included within this
category. A soap is a CR_C2~ alkyl fatty acid salt of an
alkali metal, alkaline earth metal, ammonium, alkyl-
substituted ammonium or alkanolammonium salt. Sodium salts
of tallow and coconut fatty acids and mixtures thereof are
most common. Another important class of anionic compounds
are the water-soluble salts, particularly the alkali metal
salts, of organic sulphur reaction products having in their
molecular structure an alkyl radical containing from about
8 to 22 carbon atoms and a radical selected from the group
consisting of sulphonic and sulphuric acid ester radicals.
organic sulphur-based anionic surfactants include the salts
of C~0-C~6 alkylbenzene sulphonates, C,0-C22 alkane
sulphonates, C~-C22 alkyl ether sulphates, C,0-C22 alkyl
sulphates, C4-C~o dialkylsulphosuccinates, C~0-C22 acyl
isethionates, alkyl diphenyloxide sulphonates, alkyl
napthalene sulphonates, and 2-acetamido hexadecane
sulphonates. Organic phosphate-based anionic surfactants
include organic phosphate esters such as complex mono- or
diester phosphates of hydroxyl- terminated alkoxide
condensates, or salts thereof. Included in the organic
phosphate esters are phosphate ester derivatives of
polyoxyalkylated alkylaryl phosphate esters of ethoxylated
linear alcohols and ethoxylates of phenol. Also included
are nonionic alkoxylates having a sodium
~ WO95/10588 21 71 31 2 l7 PCT~P94103322
alkylenecarboxylate moiety linked to a terminal hydroxyl
group of the nonionic through an ether bond. Counterions to
the salts of all the foregoing may be those of alkali metal
(especially sodium), alkaline earth metal, ammonium,
alkanolammonium and alkylammonium types.
Nonionic surfactants can be broadly defined as surface-
active compounds with one or more uncharged hydrophilic
substituents. A major class of nonionic surfactants are
those compounds produced by the condensation of alkylene
oxide groups with an organic hydrophobic material which may
be aliphatic or alkyl aromatic in nature. The length of the
hydrophilic or polyoxyalkylene radical which is condensed
with any particular hydrophobic group can be readily
adjusted to yield a water-soluble compound having the
desired degree of balance between hydrophilic and
hydrophobic elements. Illustrative, but not limiting,
examples of various suitable nonionic surfactant types are:
(a) polyoxyethylene or polyoxypropylene condensates of
aliphatic carboxylic acids, whether linear- or branched-
chain and unsaturated or saturated, containing from about 8
to about 18 carbon atoms in the aliphatic chain and
incorporating from about 2 to about 50 ethylene oxide
and/or propylene oxide units. Suitable carboxylic acids
include "coconut" fatty acids (derived from coconut oil)
which contain an average of about 12 carbon atoms, "tallow"
fatty acids (derived from tallow-class fats) which contain
an average of about 18 carbon atoms, palmitic acid,
myristic acid, stearic acid and lauric acid;
(b) polyoxyethylene or polyoxypropylene condensates of
aliphatic alcohols, whether linear- or branched-chain and
unsaturated or saturated, containing from about 6 to about
24 carbon atoms and incorporating from about 2 to about 50
ethylene oxide and/or propylene oxide units. Suitable
alcohols include coconut fatty alcohol, tallow fatty
WO95/10~88 PCT~P9~/03322 ~
~3~ 18
alcohol, lauryl alcohol, myristyl alcohol and oleyl
alcohol. Particularly preferred nonionic surfactant
compounds in this category are the "Neodol"-type products,
a registered trademark of the Shell Chemical Company.
Also included within this category are nonionic surfactants
having the following formula (III):
R-(CH2CH0)x(CH2CH20)y(CH2CHO)zH (III)
Rl R2
wherein R is a linear alkyl hydrocarbon radical having an
average of 6 to 18 carbon atoms, Rl and R2 are each linear
alkyl hydrocarbons of about 1 to about 4 carbon atoms, x is
a integer of from 1 to 6, y is an integer of from 4 to 20
and z is an integer from 4 to 25.
one preferred nonionic surfactant of formula I is Poly-
Tergent SLF-18 (trade mark), from the Olin Corporation, New
Haven, Connecticut, USA, having a composition of the above
formula where R is a C6-C~, linear alkyl mixture, Rl and R2
are methyl, x averages 3, y averages 12 and z averages 16.
Also suitable are alkylated nonionics as are described in
U.S. Patent No. 4,877,544 (Gabriel et al.), incorporated
herein by reference.
Another family of nonionic surfactants included within this
category are compounds of the following formula (IV):
R3-(CH2CH2o)DH (IV)
wherein R3is a C6-C7~ linear or branched alkyl hydrocarbon
radical and q is a number from 2 to 50; more preferably R3
is a Cg-C~g linear alkyl mixture and q is a number from 2 to
15;
~ WO95/10588 21 71~2 19 PCT~P94/03322
(c) polyoxyethylene or polyoxypropylene
condensates of alkyl phenols, whether linear- or branched-
chain and unsaturated or saturated, containing from about 6
to 12 carbon atoms and incorporating from about 2 to about
25 moles of ethylene oxide and/or propylene oxide;
(dj polyoxyethylene derivatives of sorbitan
mono , di-, and tri-fatty acid esters wherein the fatty
acid component has from 12 to 24 carbon atoms. The
preferred polyoxyethylene derivatives are of sorbitan
monolaurate, sorbitan trilaurate, sorbitan monopalmitate,
sorbitan tripalmitate, sorbitan monostearate, sorbitan
monoisostearate, sorbitan tripalmitate, sorbitan
monostearate, sorbitan monoisostearate, sorbitan
lS tristearate, sorbitan monooleate, and sorbitan trioleate.
The polyoxyethylene chains may contain between about 4 and
30 ethylene oxide units, preferably about 20. The sorbitan
ester derivatives contain 1, 2 or 3 polyoxyethylene chains
dependent upon whether they are mono-, di- or tri-acid
esters;
(e) polyoxyethylene-polyoxypropylene block
copolymers having the following formula (V):
25 HO(cH2cHzo)u(cH(cH3)cH2o) b ( CH2CH2 ) CH ( V )
or the following formula (VI):
HO(CH(CH3)CH2O)~(CH~CH2O)c(CHCH3CH20)fH (VI)
wherein a, b, c, d, e and f are integers from 1 to 350,
reflecting the respective polyethylene oxide and
polypropylene oxide blocks of said polymer. The
polyoxyethylene component of the block polymer constitutes
at least about 10~ of the block polymer. The material
preferably has a m~lecular weight of between about 1,000
and 15,000, more preferably from about 1,500 to about
WO95/10588 ~ PCT~P9~/03322
6,000. These materials are well known in the art. They are
commercially available for example under the trademarks
"Pluronic" and "Pluronic R" from BASF corporation;
5(f) Alkyl glycosides having the following formula
(VII):
R4O(RsO)n(ZI)p (VII)
wherein R4 is a monovalent organic radical (e.g., a
monovalent saturated aliphatic, unsaturated aliphatic or
aromatic radical such as alkyl, hydroxyalkyl, alkenyl,
hydroxyalkenyl, aryl, alkylaryl, hydroxyalkylaryl,
arylalkyl, alkenylaryl, arylalkenyl, etc.) containing from
about 6 to about 30 (preferably from about 8 to 18, more
preferably from about 9 to about 13) carbon atoms; Rs is a
divalent hydrocarbon radical containing from 2 to about 4
carbon atoms such as ethylene, propylene or butylene (most
preferably the unit (RsO) n represents repeating units of
ethylene oxide, propylene oxide and/or random or block
combinations thereof); n is a number having an average
value of from 0 to about 12; Z' represents a moiety derived
from a reducing saccharide containing 5 or 6 carbon atoms
(most preferably a glucose unit); and p is a number having
an average value of from 0.5 to about 10, preferably from
about 0.5 to about 5.
Examples of commercially available materials from Henkel
Kommanditgesellschaft Aktien of Dusseldorf, Germany
include: APG (trade mark) 300, 325 and 350, with R4 being
C9-CII ~ n is 0 and p is 1.3, 1.6 and 1.8-2.2, respectively;
APG 500 and 550 with R~ is Cl7-cl3, n is 0 and p is 1.3 and
1.8-2.2, respectively; and APG 600 with R4 being Cl2-C~4, n
is 0 and p is 1.3. Particularly preferred is APG 600;
WO9S/10~88 I ~t~ ~ ~ PCT~P94/03322
21
(g) Amine oxides having the following formula (VIII):
R5R6R7N = o (VIII)
wherein R5, R6 and R7 are saturated aliphatic radicals or
substituted saturated aliphatic radicals. Preferable amine
oxides are those wherein R5 is an alkyl chain of about lO
to about 20 carbon atoms and R6 and R7 are methyl or ethyl
groups or both Rs and R6 are alkyl chains of about 6 to
about 14 carbon atoms and R7 is a methyl or ethyl group.
Amphoteric synthetic detergents can be broadly described as
derivatives of aliphatic and tertiary amines, in which the
aliphatic radical may be straight or branched chain and
wherein one of the aliphatic substituents contain from
about 8 to about 18 carbons and one contains an anionic
water-solubilizing group, i.e., carboxy, sulpho, sulphato,
phosphato or phosphono. Examples of compounds falling
within this definition are sodium 3-dodecylamino propionate
and sodium 2-dodecylamino propane sulphonate.
Zwitterionic synthetic detergents can be broadly described
as derivatives of aliphatic quaternary ammonium,
phosphonium and sulphonium compounds in which the aliphatic
radical may be straight or branched chain, and wherein one
of the aliphatic substituents contains from about 8 to
about 18 carbon atoms and one contains an anionic water-
solubilizing group, e.g., carboxy, sulpho, sulphato,
phosphato or phosphono. These compounds are frequently
referred to as betaines. Besides alkyl betaines, alkyl
amino and alkyl amido betaines are encompassed herewithin.
The one or more surface active materials forming the
surfactant component of compositions of the invention, when
present, constitute from about O.Ol to about 40% by weight
of the composition. The amount of surfactant, if present,
will generally be within this range, but the actual amount
PCT~P9~/03322 _
WO95/lOS88 2~ ~3~2 22 ~
used may depend upon the type of surfactant(s) employed.
For instance, anionic and/or nonionic surfactants making up
the total surfactant concentration may typically be present
in an amount of from about 1 to about 40% by weight of the
composition, more preferably from about 2 to about 35% by
weight, even more preferably from about 5 to about 30% by
weight. Alkyl polyglycosides as the surfactant component,
however, may typically be present in lower concentrations,
such as in an amount from about 0.01 to about 20~ by
weight, preferably from about 0.5 to about 10~ by weight,
optimally between about 1 and about 5~ by weight of the
composition.
OPTIONAL ADDITIONAL INGREDIENTS
Silicates
The compositions of this invention may optionally contain
sodium or potassium silicate in an amount of from about 1
to about 40%, preferably from about 1 to about 20~ by
weight of the composition. When present, this material is
employed as a cleaning ingredient, source of alkalinity,
metal corrosion inhibitor and protector of glaze on china
tableware. Especially effective is sodium silicate having a
ratio of SiO~:Na2O of from about 1.0 to about 3.3,
preferabIy from about 2 to about 3.2. Some of the silicate
may be in solid form.
Filler
An inert particulate filler material which is water-soluble
may optionally also be present in the compositions of the
invention which are in powder form. This material should
not precipitate calcium or magnesium ions at the filler use
level. Suitable for this purpose are organic or inorganic
compounds. Organic fillers include sucrose esters and urea.
Representative inorganic fillers include sodium sulphate,
sodium chloride and potassium chloride. A preferred filler
WO95/10588 ~ PCT~P94/03322
is sodium sulphate. Its concentration may range from 0 to
about 60%, preferably from about 10 to about 30% by weight
- of the composition.
Thickeners and Stabilizers
Thickeners are often desirable for inclusion in liquid
cleaning compositions of the invention. Thixotropic
thickeners such as smectite clays including montmorillonite
(bentonite), hectorite, saponite, and the like may be used
to impart increased viscosity to such liquid bleaching
detergent compositions. Silica, silica gel, and
aluminosilicate may also be used as thickeners. Salts of
polyacrylic acid (of molecular weight of from about 300,000
up to 6 million and higher), including polymers which are
cross-linked, may also be used either alone or in
combination with other thickeners. Use of clay thickeners
for automatic dishwashing compositions is disclosed, for
example, in U.S. Patents Nos. 4,431,559; 4,511,487;
4,740,327; and 4,752,409. Commercially available synthetic
smectite clays include Laponite (trade mark) supplied by
Laporte Industries. Commercially available bentonite clays
include Korthix H and VWH ex Combustion Engineering, Inc.;
Polargel T ex American Colloid Co.; and Gelwhite clays
(particularly Gelwhite GP and H) ex English China Clay Co.
Polargel T is preferred as imparting a more intense white
appearance to the composition than other clays.
The amount of clay thickener employed in the compositions,
when it is present, is preferably from about o.l to about
10% by weight, preferably from about 0.5 to about 5% by
weight. Use of salts of polymeric carboxylic acids is
disclosed, for example, in GB-A-2,164,350, and in U.S.
Patents Nos. 4,859,358 and 4,836,948.
For liquid formulations with a gel appearance and rheology,
particularly if a clear gel is desired, a chlorine-stable
polymeric thickener is particularly useful. U.S. Patent No.
W095/10588 PCT~P94/03322 ~
2l7l3~l2
4,260,528 discloses natural gums and resins for use in
clear autodishwashing detergent compositions, which are not
chlorine-stable. Cross-linked acrylic acid polymers
manufactured by, for example, B.F.Goodrich and sold under
the tradename "Carbopol" have been found to be effective
for producing clear gels, and Carbopol 940 and 617, having
a molecular weight of about 4,000,000, are particularly
preferred for maintaining high viscosity with excellent
chlorine stability over extended periods. Further suitable
chlorine-stable polymeric thickeners are described in U.S.
Patent No. 4,867,896, incorporated herein by reference.
When it is present, the amount of thickener employed in the
compositions of the invention is preferably from O to about
5% by weight, preferably from about 0.5 to about 3% by
weight.
Stabilizers and/or co-structurants such as long-chain
calcium and sodium soaps and C~ to C~ sulphates which may
optionally be incorporated in compositions of the invention
are detailed in U.S. Patents Nos. 3,956,158 and 4,271,030
and the use of other metal salts of long-chain soaps is
detailed in U.S. Patent No. 4,752,409. Other co-
structurants include Laponite (trade mark) and metal oxides
and their salts, as described in U.S. 4,933,101,
incorporated herein by reference.
The amount of stabilizer which may be used in liquid
compositions of the invention is preferably from about 0.01
to about 5~ by weight of the composition, preferably from
about 0.01 to about 2~ by weight. Such stabilizers are
optional in gel formulations.
Co-structurants which are found especially suitable for
gels include compounds containing trivalent metal ions
which may be present in an amount of from about 0.01 to
about 4~ by weight of the composition, and Laponite and/or
W09StlOSB8 ~ ~ 25 PCT~P94103322
water-soluble structuring chelants, which may be present in
an amount of from about l to about 60% by weight. These co-
structurants are more fully described in EP-A-0323209, the
disclosure of which is incorporated herein by reference.
Defoamer
Formulations of the cleaning composition of the invention
comprising surfactant may further include a defoamer.
Suitable defoamers include mono- and distearyl acid
phosphate, silicone oil and mineral oil. Even if the
composition includes only defoaming surfactant, the
defoamer may still assist in the minimizing of foam which
food soils can generate. If a defoamer is present, the
compositions may include from about 0.02 to about 2~ by
weight thereof, more preferably from about 0.05 to about
l.O% by weight thereof.
Other adiunct inqredients
Minor amounts of various other optional components may be
present in the cleaning compositions of the invention.
These include: bleach scavengers including (but not limited
to) sodium bisulphite, sodium perborate, reducing sugars,
and short-chain alcohols; solvents and hydrotropes such as
ethanol, isopropanol and xylene sulphonates; flow control
agents (in granular forms of the composition); enzyme-
stabilizing agents; soil-suspending agents; anti-
redeposition agents; anti-tarnish agents; anti-corrosion
agents; colourants; other functional additives; perfumes.
The pH of cleaning compositions of the invention may be
adjusted as desired or as necessary by addition of strong
acid or base. Such alkalinity or buffering agents include,
for example, sodium carbonate and sodium borate.
Enzymes
Enzymes capable of facilitating the removal of soils from a
substrate may also optionally be present in compositions of
WO95110588 PCT~P9~/03322 ~
~ 3~ 26 ~
the invention, preferably in an amount of from 0 to about
10% by weight, preferably from about l to about 5% by
weight. Such enzymes include proteases (e.g., Alcalase
(trade mark), Savinase (trade mark) and Esperase (trade
mark) from Novo Industries A/S), amylases (e.g., Termamyl
(trade mark) from Novo Industries A/S), lipases (e.g.,
Lipolase (trade mark) from Novo Industries A/S), oxidases,
and mixtures thereof.
The following examples more fully illustrate the invention
in its various aspects and preferred embodiments thereof.
All parts, percentages and proportions referred to herein
and in the appended claims are by weight unless otherwise
indicated.
WO95/105~8 131~ 27 PCT~P94/03322
EXAMPLE 1
The following seven machine dishwashing compositions were
prepared as follows:
Table l
Ingredient % by weight
Sodium citrate (2H~0) 30.0
Sodium tetraborate 3.0
lO Glycerol 6.0
Sokalan CP7 (40%)~ 5.0
Sodium hydroxide l.6
(50%)
Bleaching agent2 x
15 Anti-tarnish agent3 y
Water to lO0
An acrylic acid/maleic acid copolymer supplied by BASF
Corporation of Parsippany, New Jersey, USA
2 The following different levels of sodium perborate (H2O)
and TAED (N,N,N',N'-tetraacetylethylene diamine bleach
activator) were used in Example l:
a. 0.0%.sodium perborate (H20) and 0.0% TAED
b. 0.5% sodium perborate (H2O) and 0.3% TAED
c. 0.7% sodium perborate (H20) and 0.5% TAED
d. 0.9% sodium perborate (H2O) and 0.6% TAED
e. l.3~ sodium perborate (H2O) and 0.9% TAED
f. l.7% sodium perborate (H20) and l.1% TAED
g. 6.8% sodium perborate (H2O) and 4.3% TAED
3 No anti-tarnish agent was used in Example l.
Tarnish-monitoring experiments to determine silver
tarnishing were conducted with compositions a, b, c, d, e,
f, and g at a product dosage of 40 grams per run in a
European dishwasher, Bauknecht GSF 3162, with an intake of
of 5 litres deionized water. The wash program consisted of
a pre-wash at 40C, a mainwash at 55C, two intermediate
rinses, and a final rinse at 65C.
The mainwash pH with these compositions was typically about
8.7. Silver-plated spoons (2 per run) were the monitors
WO95/10588 28 PCT~P9~/03322
used in the test. The spoons were supplied by Oneida
Silversmiths, USA. The monitors were washed in a
commercially available hand dishwash liquid and rinsed with
deionized water and acetone before use. In the dishwasher
the monitors were kept apart from each other in the cutlery
basket. At the end of a single-run machine program, the
monitors were visually analyzed for the presence of colours
and the loss of gloss.
The spoons washed with composition a were unchanged after
the dishwashing process, except for a few stain spots. The
stain spots were caused by deposition of non-volatile
materials during the evaporation of undrained wash solution
in the drying step of the machine program and were not
related to a tarnishing (i.e. silver oxidation) process of
the monitors.
However, the spoons washed with compositions b, c, d, e, f,
and g were increasingly tarnished as the levels of
bleaching agent were increased. The spoons washed with
composition g were so heavily tarnished that they lost
their gloss and were turned brown/black. The set of spoons
washed with the compositions a, b, c, d, e, f, and g were
ranked from zero to six, respectively. This ranking of
spoons was used as a reference scale for all subsequent
Examples.
EXAMPLE 2
Machine dishwashing compositions were prepared as described
in Example l, except that the selected bleaching agent was
epsilon-phthalimido peroxyhexanoic acid incorporated at 4%
by weight. The compound was supplied by Hoechst AG of
Germany. The compositions also contained various anti-
tarnish agents incorporated in an amount of 1% by weight,
as follows:
PCT~P94/03322
W095/10588 71~ 29 -'~
Table 2
SAMPLE ANTI-TARNISHING AGENT
(l wt.%)
A None
B Purine
C Adenine
D Guanine
E 6-mercaptopurine
F xanthine
G uric acid
H allopurinol
The anti-tarnishing agents were supplied by Aldrich
Chemical Co.
Tarnish-monitoring experiments as described in Example l
were conducted with Samples A to H, using two silver-plated
spoons as monitors in each of the experiments. The main
wash pH in this series of experiments was between 8.8 and
8.5.
Anti-tarnish scores ranging from 0 to 6 according to the
level of tarnishing were obtained for samples A to H as
follows:
TABLE 3
Composition Tarnish Score
A 5
B 0
C 0.5
D 0
E
F 0
G
H 0
WO95/10588 ~ ~3 ~ PCT~P9l/03322
It was observed that spoons washed with compositions
containing anti-tarnish agents (Samples B to H) either
remained unchanged or developed a slightly yellowish
appearance during the dishwashing process. In contrast, the
control sample A, which did not contain an anti-tarnish
agent, produced heavy tarnishing.
WO95/10588 PCT~P94/03322
EXAMPLE 3
A detergent base was prepared having the following formula:
Table 4
Ingredient ~ by weight
Sodium citrate (2H20) 42
Sodium disilicate 2.0 35
Sodium perborate (H20) 7
10 Sokalan CP51 5
TAED2 (80%) 4.2
Amylase 1.7
Protease 1.7
Laponite3 1.7
15 Nonionic surfactant 1.7
An acrylic acid/maleic acid copolymer supplied by BASF,
Germany.
2 N,N,N',N'-tetraacetylethylene diamine.
3 A smectite clay supplied by Laporte Industries of
Cheshire, England.
Various amounts of an adenine compound were dosed into 27
gram samples of the foregoing base as follows:
Table 5
SAMPLES ADENINE (% by weight)
0
2 0.05
3 0.1
- 4 0.25
0.5
As described in Example 1, tarnish monitoring tests were
conducted with samples 1 to 5 using two silver-plated
spoons as monitors. However, 1 gram/liter of sodium
chloride was added to the deionized water used in the
WO9S/10588 ~ 3 ~ PCT~P94/03322
experiments. Additionally, 5 grams of egg yolk were dosed
in the dishwasher immediately after water intake at the
start of the main wash of each experiment. The main wash pH
values were typically about 9.8.
Silver-tarnishing scores on a scale of 0 to 6 were observed
for samples 1 to 5 as follows:
TABLE 6
Sample Tarnish Score
1 3
2 1.5
3 1.5
4 0
The control sample containing no anti-tarnishing agent gave
rise to moderately heavy tarnishing. In contrast, samples 2
to 5 exhibited little to no tarnishing. Optimal anti-
tarnishing performance was observed with sample 4
containing 0.25 wt.% adenine.
EXAMPLE 4
Six machine dishwashing compositions were prepared as
described in Example 1, except that the type of bleaching
agent and the amount of purine as the anti-tarnish agent
were varied as follows:
~ WO95/10588 PCT~P94/03322
~ 7~ 33
Table 7
Sample Bleaching Agent (% by wt) Purine (% by wt)
A Peracetic acid~ (4.12%) o%
B Peracetic acid~ (4.12%) 1.0%
C Epsilon-phthalimidoperoxy 0%
hexanoic acid2 (4.0%)
D Epsilon-phthalimidoperoxy 1.0
hexanoic acid2 (4.0%)
E Sodium hypochlorite3 o%
(8.23%)
F Sodium hypochlorite3 1.0%
(8.23%)
' A 32% peracetic acid solution, supplied by Aldrich
Corporation of Milwaukee, USA was used.
7 Supplied by Hoechst AG, Germany.
3 An 8.2% active C17 solution was used, supplied by
Jones Chemicals of Caledonia, NY, USA.
Tarnishing-monitoring experiments were conducted, using
samples A, B, C, D, E, and F at a product dosage of 40
grams per run in a Bauknecht GSF 3162 dishwasher, with an
intake of 5 litres water. The mainwash pH values for
compositions A and B were adjusted to 7.5; the mainwash pH
values for compositions C and D were adjusted to 8.5. Two
experiments (each) were conducted, using compositions E and
F; the mainwash pH values were adjusted to 9.0 and 10.5,
respectively. Silver-plated spoons, knives, and forks
(supplied by Oneida Silversmiths, USA), were used as
monitors for all experiments. The monitors were washed in a
commercially available hand dishwashing liquid and rinsed
with deionized water and acetone before use. At the end of
~ 30 the dishwashing machine program, the monitors were visually
evaluated for the presence of colours and/or loss of shine,
according to the reference scale described in Example 1.
Each sample containing purine (B, D and F) was observed to
reduce the level of tarnishing relative to the samples
WO95/10588 ~ PCT~P94/03322
~ 34
which did not contain purine (A, C and E). While tarnishing
inhibition due to purine occurs through the pH range
described above, this effect was observed to be greatest at
pH values of 7.5, 8.5 and 9Ø Furthermore, the presence of
purine reduced tarnishing regardless of the type of
bleaching agent (chlorine or oxygen) present in the
samples.
EXAMPLE 5
The required association of the pK3 value of purine class
compounds usable in the invention and the pH of the
composition in which they are incorporated to provide
effective silver anti-tarnishing was demonstrated and the
results are reported below.
The pK3 of each compound was determined by preparing a
0.001M solution of inhibitor in deionized water. The pH of
this solution was adjusted to 3.0 with H~SO4. The solution
was then titrated with lN NaOH to pH 11Ø A plot of mls.
NaOH vs. pH for each sample was prepared. The pK~ of the
compound is that point where the maximum change in pH as a
function of mls. NaOH is observed.
A comparison of anti-tarnishing performance of purine class
compounds within the scope of the invention and azole
compounds outside the invention was conducted. The selected
compounds were incorporated in an amount of 1 wt.% in a
machine dishwashing composition containing 4 wt.% epsilon-
phthalimido peroxyhexanoic acid as the bleaching agent.
The pH values of the compositions were adjusted by the
addition of a 50% solution of sodium hydroxide or
concentrated sulfuric acid, as necessary.
Silver plates were then held in each of the compositions
for 25 minutes, removed, rinsed with deionized water and
evaluated for silver tarnishing, and ranked as described in
PCT~P94103322
WO95/10588 1 71 31 ~ 35
Example 1. A tarnish score of 3 or less was considered
effective as a silver anti-tarnishing compound. The
observations were tabulated as presented below:
C 622~(V) , -
217~ 36
Table 8
Invenlive Compounds pK. of pH of Effective Silver
compou. Ids composition Anti-Tarnishing
1 ) Purine . N~ N
~ N ~ N ~ 5;5 8.6 Yes
2) Adenine NH2
0 N~ I ~ 7.2 8.6 Yes
N "'" ~N
3) Adenine 7.2 6.9 No
15 4) Guanine
~ 6.77.0 No
5) Guanine 6.7 8.6 Yes
6) Xanth;ne
7.08.6 Yes
7) Hypoxanthine 0
3 0 H ~ J ~ 6.08.6 Yes
HN
8) Uric Acid
3 5 4.6 8.6 Yes
4 0 0
9) Allopurinol
~ ' "` 6.1 . 8.6 Yes
4 5 ;`~ ' `~ ~
AMt,''~'!r-D ~,EEl`
21 71 3~2
~ ~ 37
J~ ~ r1 Y~!rlhC~_
It was observed that the (c'aimc~ compounds~must exhibit a
pKJ of more than 1 unit less than the pH of an aqueous
solution of the composition in which they are incorporated.
In particular, adenine (pKa = 7.2) and guanine (pKa = 6.7)
prevented silver ~arnishing at pH 8.6, but did not prevent
tarnishing at pH 6.9 and 7.0, respectively.
Azole compounds ou~side the.scope of the invention were
tested and the following silver anti-tarnishing results
were observed.
AM,"'?. -; ~'~'E;~
PCT~P94/03322
WO9S/10588 ~
38
Table 9
Compound plC. of pH ofEffective Silver
compoundscompositionAnti-Tarnishing
H 6.8 8.5 No
1 ) 6-Nitroindazole O~N
2) 6-Nitroindazole 6.8 11.0 No
3) 2-Phenylimidazole ~
/N ~J 8.8 8.5 No
1~,
4) 2-Phenylimidazole 8.8 11.0 No
5) Arginine 9.1 8.6 No
6) Pyrrole ¢~3 11.0 8.6 No
H
s~i
7) Pyrazole _~N 11.5 8.6 No
It was observed that compounds having pK1 values greater
than the pH values of the compositions in which they were
incorporated did not exhibit anti-tarnishing effects.
sf~~ r
WO95/10588 ~ 39 - ~ PCT~P94/03322
EXAMPLE 6
To demonstrate the ineffectiveness of known copper anti-
tarnishing compounds on silver plates, machine dishwashing
compositions having a pH of both 8.5 and ll were prepared
containing 4% by weight epsilon-phthalimido peroxyhexanoic
acid as the bleaching agent and 1% by weight of three
copper anti-tarnishing compounds listed below. Samples of
the compositions were adjusted to both a pH of 8.5 and ll
by the addition of sodium hydroxide. Copper plates and
silver plates were held in each of the compositions for 25
minutes, removed, rinsed with deionized water and evaluated
for tarnishing. The following results were observed.
Table lO
Copper Anti-
tarnishing Copper Plates Silver Plates
Compounds'
206-nitroindazole +
2-phenylimidazole +
pyrazole +
~Described as effective copper anti-tarnish
compounds in US 2,618,608 (Schaeffer)
It was observed that anti-tarnishing compounds which
prevented tarnishing on copper plates had no effect on
preventing silver tarnishing. The oxidation behaviour of
copper versus silver is very different and compounds which
affect one type of metal may be drastically different from
those compounds which affect the other. The compounds
exhibiting copper anti-tarnishing effects do not possess a
structure within the scope of the anti-tarnishing compounds
which are useful in the invention.
WO95/10588 ~ PCT~P94/03322
EXAMPLE 7
Three machine dishwashing compositions were prepared as
described in Example l, except that a chlorine bleaching
agent and cyanuric acid as anti-tarnish agent were combined
as follows:
Table 11
Bleaching agent Cyanuric acid3
Sample (% by wt.) (% by wt.)
lo A Sodium 0%
dichloroisocyanurate
(2.2%)
B Sodium hypochlorite2 0%
(8.23%)
C Sodium hypochlorite2 1%
(8.23%)
~ CDB, supplied by Olin Corporation of Stamford,
Connecticut, USA
2 An 8.29~ active C11 solution, supplied by Jones
Chemicals of Caledonia, New York, USA
3 Supplied by Aldrich Chemical Co., of Milwaukee,
Wisconsin, USA
Tarnish monitoring experiments as described in Example l
were conducted with compositions A to C using two silver-
plated spoons as monitors in each of the experiments. The
mainwash pH in this series of experiments was typically
about 8.7.
The influence of the compositions A, B and C on silver
tarnishing are shown in the following Table 12. The anti-
tarnish scale ranks from 0 to 6, according to the levels of
tarnishing obtain with the compositions a to g of Example
1.
W095/10588 21 713 41 . PCT/EP94/03322
TABLE 1 2
Composition Tarnish Score
A 1.5
B 5.5
C 0
It was observed that spoons washed with composition C,
containing 1~ cyanuric acid, remained unchanged during the
dishwashing process. In contrast, composition B, in which
hypochlorite was incorporated without cyanuric acid,
produced quite heavy tarnishing. Composition A containing
sodium dichloroisocyanurate but no anti-tarnishing agent
exhibited little silver tarnishing. It is believed that
isocyanurate is formed during a wash in which sodium
15 dichloroisocyanurate is used. Isocyanurate can be formed
upon dissociation of dicholoroisocyanurate, producing
hypochlorite as the active bleaching species. This is also
believed to explain why chloroisocyanurate bleach systems
generally do not cause many problems in terms of silver
20 tarnishing.
EXAMPLE 8
Six machine dishwashing compositions were prepared as
25 described in Example 1, except that the bleaching agent and
anti-tarnish agent were varied as follows:
WO95/10588 PCT~P94/03322
Q ~'~
42
Table 13
Bleaching Agent
Composition (% by wt.)Cyanuric Acid4
A Peracetic acid1 0%
(4. 1 2%)
B Peracetic acid1 1.0%
(4. 1 2%)
C Epsilo~- 0%
phthalimidoperoxy-
hexanoic acid2
(4.0%)
D Epsilon- 1.0%
phthalimidoperoxy-
hexanoic acid2
(4.0%)
E Sodium 0%
hypochlorite3
(8.23%)
F Sodium 1.0%
hypochlorite3
(8.23%)
A 32% peracetic acid solution supplied by Aldrich
Corp. of Milwaukee, Wisconsin, USA
2 Supplied by Hoechst AG of Germany
3 A 8.2~ active C12 solution supplied by Jones Chemicals
of Caledonia, New York, USA
4 Supplied by Aldrich Corp.
Tarnish monitoring experiments were conducted using
compositions A, B, C, D E and F at a product dosage of 40
grams per run in a Bauknecht GSF 3162 dishwasher, with an
intake of 5 litres water. The mainwash pH values for
compositions A and B were adjusted to 7.5; the mainwash pH
values for compositions C and D were adjusted to 8.5. Two
experiments (each) were conducted using compositions E and
F; the mainwash pH values were adjusted to 9.0 and 10.5,
respectively. Silver-plated spoons, knives, and forks
(supplied by Oneida Silversmiths, USA), were used as
monitors for all experiments. The monitors were washed in a
WO9S/10588 1 71312 PCT~P94/03322
43
commercially available dishwashing li~uid and rinsed with
deionized water and acetone before use. At the end of the
dishwashing machine program, the monitors were visually
evaluated for the presence of colours and/or loss of shine,
according to the reference scale described in Example l.
In each case, the presence of cyanuric acid reduced the
level of tarnishing relative to the case where no anti-
tarnish agent was present. While tarnishing inhibition due
to cyanuric acid occurred throughout the pH range described
above, this effect was greater at higher alkalinity. At pH
7.5, the introduction of cyanuric acid led to a reduction
of l.5 units of tarnishing; at pH lO.5 the reduction in
tarnishing was 3.0 units. Furthermore, cyanuric acid
reduced tarnishing irrespective of the type of bleaching
agent present in the composition; inhibition was noted for
both chlorine and oxygen bleaches.
EXAMPLE 9
Five machine dishwashing compositions were prepared as
described in Example l, except that epsilon-
phthalimidoperoxyhexanoic acid was used as a peroxygen
bleaching agent and cyanuric acid was used at five
different amounts as follows:
Wo 95/10588 ~, PCTIEP94/03322
TABLE 1 4
Epsilon-
phthalimidoperoxy Cyanuric
hexanoic acidl Acid2
Composition (% wt) (% wt)
A 4.0% 0%
B 4.0% 0.25%
C 4.0% 0.75%
D 4.0% 1.0%
E 4.0% 2.5%
Supplied by Hoechst AG, Germany
~ Supplied by Aldrich Co.
As described in Example 1, tarnish monitoring tests were
conducted with compositions A to E using two silver-plated
spoons as monitors in each of the experiments. The mainwash
pH in this series of experiments was typically between 8.8
and 8.5.
The effects of compositions A to E on silver tarnishing are
shown in Table 15 below. The anti-tarnish scale ranks from
0 to 6, according to the levels of tarnishing obtained with
the compositions a to g of Example 1.
WO 95/10588 2 PCT/EP94/03322
t 7131~ 45
TABLE 1 5
Composition Tarnish Score
A 5
B 4.5
C 3
D 0.5
E 0.8
It can be seen from this table that the level of cyanuric
acid which gives optimum anti-tarnish performance is about
1%. The monitors had a slightly yellow appearance after
using cyanuric acid at a 2.S% level.
EXAMPLE 10
The following machine dishwashing compositions were
prepared according to Example 1, except that 4% by weight
of epsilon-phthalimidoperoxyhexanoic acid was incorporated
as the bleaching agent and various azole-compound anti-
tarnishing agents (both within and outside the scope of thedefinition of the 1,3-N azole compounds characteristic of
the present invention) were incorporated in an amount of 1%
by weight, as follows:
Wo95/10~88 3~ 46 PCT~P9~/03322 ~
c~
TABLE 16
Sample 1% wt Agent
A None
B Pyrrole
C Indazole
D Pyrazole
E Benzimidazole
F Imidazole
G 1, 2, 3-triazole
lo H Benzotriazole
1, 2,4-triazole
J Pyrimidine
K Histidine
~ Compounds supplied by Aldrich Chemical Co. of
Milwaukee, Wisconsin, USA
Tarnish monitoring experiments were conducted as described
in Example 1, using two silver-plated spoons as monitors in
each of the experiments. The main wash pH in the
experiments was between 8.8 and 8.5.
The control composition (Sample A) produced heavy
tarnishing on the spoons. Samples E, F and K (within the
scope of the invention) exhibited only a slightly tarnished
appearance on the washed spoons. Compositions G and H also
exhibited only a slightly tarnished appearance on the
washed spoons. In contrast, compositions B, C, D and J
(outside the scope of the invention) exhibited heavy
tarnishing on the washed spoons.
WO95/10588 PCT~P94/03322
71 ~? 47
EXAMPLE 11
Six machine dishwashing compositions were prepared as
described in Example 1, except that the type of bleaching
S agent and the amount of 1,2,4-triazole as anti-tarnishing
agent were varied as follows:
TABLE 17
Sample Bleaching Agent (% by weight) 1,2,4-Triazole
lo A Peracetic acid' (4.12%) o%
B Peracetic acidl (4.12%) 1.0%
C Epsilon-phthalimidoperoxyhexanoic acid2 0%
(4.0%)
D Epsilon-phthalimidoperoxyhexanoic acid2 1.0%
(4.0%)
E Sodium hypochlorite3 (8.23%) 0%
F Sodium hypochlorite3 (8.23%) 1.0%
A 32% peracetic acid solution, supplied by Aldrich
corporation of Milwaukee, Wisconsin, USA was used.
2 Supplied by Hoechst AG, Germany.
3 A 8.2~ active Cl2 solution was used, supplied by Jones
Chemicals of Caledonia, New York, USA.
Tarnish monitoring experiments were conducted using
compositions A, B, C, D, E and F at a product dosage of 40
grams per run in a Bauknecht GSF 3162 dishwasher, with an
intake of 5 litres water. The mainwash pH values for
compositions A and B were adjusted to 7.5; the mainwash pH
values for compositions C and D were adjusted to 8.5. Two
experiments (each) were conducted using compositions E and
F; the mainwash pH values were adjusted to 9.0 and 10.5.
respectively. Silver-plated spoons, knives and forks
(supplied by Oneida Silversmiths, USA), were used as
monitors for all experiments. The monitors were washed in a
commercially available dishwashing liquid and rinsed with
deionized water and acetone before use. At the end of the
WO95/10588 ~ PCT~P9~/03322
~ ~ 48
dishwashing machine program, the monitors were visually
evaluated for the presence of colours and/or loss of shine,
according to the reference scale described in Example 1.
In each case, the presence of 1,2,4-triazole reduced the
level of tarnishing relative to the case where no anti-
tarnishing agent was present. While tarnishing, inhibition
due to 1,2,4-triazole occurred throughout the pH range
described above, this effect was greater at higher
alkalinity. At pH 7.5, the introduction of 1,2,4-triazole
led to a reduction of 1.5 units of tarnishing; at pH 10.5
the reduction in tarnishing was 3.0 units. Furthermore,
1,2,4-triazole reduced tarnishing irrespective of the type
of bleaching agent present in the composition; inhibition
was noted for both chlorine and oxygen bleaches.
EXAMPLE 12
The following machine dishwashing compositions were
prepared as described in Example 1, except that epsilon-
phthalimido peroxyhexanoic acid was included as the
bleaching agent at a level of 4% by weight and various
levels of 1,2,4-triazole as anti-tarnish agent were
incorporated as follows:
W095/lOS88 t ~ 2 49 - PCT~P94/03322
TABLE 18
Sample 1,2,4-Triazole (Wt. %)
A none
B 0.05
C 0.25
D 0.75
E 1.0
As described in Example l, anti-tarnish monitoring tests
were conducted using two silver-plated spoons as monitors.
The main wash pH in these experiments was between 8.8 and
8.5.
The effect of samples A to E on silver tarnishing was
observed and is shown in Table 19 below:
TABLE 19
Sample Tarnish Score
A 5.0
B 0.5
C 0.5
D 0.5
E 0
WO95/10~88 ~ PCT~P94/03322
~ 50
It was thus observed that at amounts of 0.05 ~ by weight,
the anti-tarnish agent l,2,4-triazole effectively reduced
silver tarnishing. Optimum performance of the agent was
achieved at levels of about l % by weight.
EXAMPLE l3
The required association of the pK~ value of l,3-N azole
compounds usable in the invention and the pH of the
composition in which they are incorporated to provide
effective silver anti-tarnishing was demonstrated and the
results are reported below.
A comparison of anti-tarnishing performance of l,3-N azole
compounds within the scope of the invention and azole
compounds outside the invention was conducted. The selected
compounds were incorporated in an amount of l wt.% in a
machine dishwashing composition containing 4 wt.% epsilon-
phthalimido peroxyhexanoic acid as the bleaching agent.
The pH values of the compositions were adjusted by the
addition of a 50% solution of sodium hydroxide or
concentrated sulfuric acid, as necessary.
The pK~ of each compound was determined by preparing a
0.00lM solution of inhibitor in deionized water. The pH of
this solution was adjusted to 3.0 with H2SO4. The solution
was then titrated with lN NaOH to pH llØ A plot of mls.
NaOH vs. pH for each sample was prepared. The pK~ of the
compound is that point where the maximum change in pH as a
function of mls. NaOH is observed.
Silver plates were then held in each of the compositions
for 25 minutes, removed, rinsed with deionized water and
evaluated for silver tarnishing, and ranked as described in
Example l. A tarnish score of 3 or less was considered
effective as a silver anti-tarnishing compound. The
observations were tabulated as presented below:
1 71~i2
Table 20
Inventive Compounds pK, of pH of Et~ecllve Silver Anti-
comDounds composltlon Tarnlshlnç
1) tTotrazole N~N 8.4 8.= No
. ¦ NH
, 7, 3,s- ? b~N/
2) ilfetrazole ~/ ~, t~ 8.4 9.5 Yes
3) fTetrazole 8.4 10.5 Yes
10 4) Eetrazole ~ ,3,S- J 8.4 11.0 Yes
7 ,~,S~
5) ;0~amino~,etraZole 8.1 8.8 No
~ \
1S L , ~
~LO
6) 1,2,4-triazolef~ \ 5.4 8.8 Yes
NH
~/
7) 3-amino-1,2.4-triazole 7.3 8.3 Yos
2 5 8) Benzlmid~lzoie o~ 5 8.6 Yes
9) Imidazole N
/ \ 6.9 8.6 Yes
~ 11
6.0 8.6 Yes
3 5 10) Histidine
A~,~t~ D S~EE~
W095/10588 ~3~ PCT~P94/03322
~ 52
It was observed that tetrazole was not effective as a
silver anti-tarnishing at a pH of 8.5 but was effective at
a pH of 9.5 and greater. Tetrazole with a pK~ of 8.4 is
effective only in compositions having a pH of greater than
9.4. 5-aminotetrazole having a PKa of 8.l was not effective
at a pH of 8.8. The other compounds exhibited effective
anti-tarnishing effects because their pK~ values were more
than l unit less than the pH of an aqueous solution of the
composition in which they were incorporated.
Azole compounds outside the scope of the invention were
tested and the following silver anti-tarnishing results
were observed.
~ 7 PCT~Ps~/03322
~ WO95/10588 13f~
53
Table 21
Compound pK. of pH of Effective Silver
compoundscompositionAnti-Tarnishing
H 6.8 8.5 No
1 ) 6-Nitroindazole ~
2) 6-Nitroindazole 6.8 11.0 No
10 3) 2-Phenylimidazole ~
~ 8.8 8.5 No
15 4) 2-Phenylimidazole 8.8 11.0 No
5) Arginine 9.1 8.6 No
6) Pyrrole ~3 9.5 8.6 No
~j
2 5 7) Pyrazole ~
N~ 1 1.5 8.6 No
3 0 It was observed that compounds having pKa values greater
than the pH values of the compositions in which they were
incorporated did not exhibit anti-tarnishing effects. 2-
Phenylimidazole did not prevent silver tarnishing at a pH
ll.0, possibly because of hindrance from the phenyl group
35 attached to the imidazole ring.
W095/10588 ~ ~ PCT~P94/03322
54
EXAMPLE 14
To demonstrate the ineffectiveness of known copper anti-
tarnishing compounds on silver plates, machine dishwashing
compositions having a pH of both 8.5 and 11 were prepared
containing 4% by weight epsilon-phthalimido peroxyhexanoic
acid as the bleaching agent and 1% by weight of three
copper anti-tarnishing compounds listed below. Samples of
the compositions were adjusted to both a pH of 8.5 and 11
by the addition of sodium hydroxide. Copper plates-and
silver plates were held in each of the compositions for 25
minutes, removed, rinsed with deionized water and evaluated
for tarnishing. The following results were observed.
Table 22
Copper Anti-
tarnishing Copper Plates Silver Plates
Compoundsl
2 o6-nitroindazole +
2-phenylimidazole +
pyrazole +
l Described as effective copper anti-tarnish compounds
in US 2,618,608 (Schaeffer)
It was observed that anti-tarnishing compounds which
prevented tarnishing on copper plates had no effect on
preventing silver tarnishing. The oxidation behavior of
copper versus silver is very different and compounds which
affect one type of metal may be drastically different from
those compounds which affect the other. The compounds
exhibiting copper anti-tarnishing effects do not possess a
structure within the scope of the anti-tarnishing compounds
which are useful in the invention.
