Complex N-hydroxyimide compounds and their use as detergent additives

Complex N-hydroxyimide compounds and carboxy hydroxamic acid-functional derivatives thereof are prepared from organic amines reacted with maleate esters and maleic anhydride. The compounds exhibit strong metal ion chelating properties and are useful as detergent additives to improve stain removal.

The present invention relates novel N-hydroxyimide compounds exhibiting 
strong metal cation chelating properties, which can be used, e.g., to 
enhance the stain removing power of detergent compositions, particularly 
fabric-washing detergent compositions. In particular it relates to complex 
N-hydroxyimide compounds useful as detergent additives and to detergent 
compositions comprising at least one detersive surfactant and an effective 
amount of such N-hydroxyimide compounds. 
BACKGROUND OF THE INVENTION 
Detergent compositions have long employed materials, known as "builders", 
to improve the detergency of soaps and synthetic detergents by actively 
chelating alkali metal cations which are normal components of "hard" tap 
water. Such builders have been found to affect, for instance, soil 
suspension, emulsification of soil particles, solubilization of 
water-insolubles, and inactivation of various mineral constituents present 
in a detergent system. Many materials useful as builders have been 
proposed, and there effects are known. See, e.g., U.S. Pat. Nos. 
3,852,213, 3,950,260, 4,182,718, and 4,440,646 (all incorporated herein by 
reference). 
Recently, however, the attention of detergent manufacturers and researchers 
has turned to the role of heavier metal cations, i.e., transition metal 
cations and particularly iron, in the formation of stain complexes on 
fabrics and other surfaces. It has been observed that these multivalent 
transition metal cations, particularly iron (Fe.sup.+++), enhance the 
binding of the components of many stains to substrates, and breaking up 
the cation-enhanced bonds is an effective approach to stain removal. 
Therefore, there is a strong need for the discovery of new materials that 
are effective as chelating agents for transition metal cations, are easy 
to prepare, and can be added to detergent compositions in economical 
amounts to boost stain-removing power. 
It has now been discovered that complex N-hydroxyimide compounds derived 
from organic amine compounds and maleic acid esters are active transition 
metal ion chelants, particularly with respect to iron (Fe.sup.+++). The 
N-hydroxyimides of the present invention are water-soluble and are active 
in stain removal. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to provide a new class 
of compounds which are strong metal ion chelating agents. 
It is a further object of the present invention to provide new compounds 
useful as detergent additives for stain removal. 
It is a further object of the present invention to provide novel detergent 
compositions. 
It is a further object of the present invention to provide a fabric-washing 
detergent composition that is effective in stain removal. 
It is a further object of the present invention to provide a method for 
preparing complex N-hydroxyimide chelating agents. 
These and other objects are achieved, according to the present invention, 
by compounds of the formula 
##STR1## 
wherein X is 
##STR2## 
Y is hydroxyl or --O.sup.- M.sup.+, where M.sup.+ an alkali metal cation 
(e.g., Na.sup.+, K.sup.+, Li.sup.+, etc.) or ammonium (NH.sub.4.sup.+); 
one of A and A' is hydrogen and the other is 
##STR3## 
R is an organic radical of 2-20 carbon atoms; and n is an integer equal to 
the valency of R. 
Also contemplated herein are detergent compositions comprising one or more 
detersive surfactants and one or more detergent additives consisting 
essentially of N-hydroxyimide compounds of the formula 
##STR4## 
wherein X is 
##STR5## 
Y is hydroxyl or --O.sup.- M.sup.+, where M.sup.+ is an alkali metal or 
ammonium cation; 
one of A and A' is hydrogen and the other is 
##STR6## 
R is an organic radical of 2-20 carbon atoms; and n is an integer equal to 
the valency of R. 
A method for preparing the complex N-hydroxyimide compounds according to 
the present invention is also contemplated. 
DETAILED DESCRIPTION OF THE INVENTION 
The complex H-hydroxyimide compounds of the present invention may be 
advantageously prepared from dialkyl maleate esters and organic amine 
compounds, preferably organic diamines having the general formula H.sub.2 
N--R--NH.sub., wherein R is a divalent organic radical of from 2-20 carbon 
atoms. The organic amine/polymaleate reaction products are further reacted 
with maleic anhydride to obtain tertiary amine compounds having maleic 
anhydride substituents as well as maleate ester substituents. These 
tertiary amine compounds are further reacted with hydroxylamine (H.sub.2 
NOH) to obtain N-hydroxyimide compounds according to the present 
invention. The N-hydroxyimide compounds may be further reacted with a base 
to provide poly(carboxy hydroxamic acid) compounds. The latter 
N-hydroxyimide and poly(carboxy hydroxamic acid) products are 
water-soluble and exhibit strong metal ion chelating properties. 
While the precise chemistry of the present detergent builders is not 
completely understood, it is believed that on treatment with base, ring 
opening reactions occur on the N-hydroxyimide molecule, adding carboxylic 
acid and hydroxyamic acid functions to the compound. Thus, a typical 
reaction scheme for the preparation of the compounds contemplated by the 
present invention is as follows: 
##STR7## 
The organic amine starting materials suitable for use in the present 
invention are organic compounds having from 2 to about 20 carbon atoms and 
at least one amino substituent group. Diamines, for example, will have the 
general formula H.sub.2 N--R--NH.sub.2, in which the two amino groups are 
bridged by a divalent organic radical having 2-20 carbon atoms, which 
divalent organic radicals include, e.g., aliphatic, alicyclic and aryl 
radicals such as straight chain or branched alkylene, alkenylene, 
cycloalkylene, arylene, alkarylene, and the like, and also divalent hetero 
radicals including hydrocarbon chains interrupted by one or more atoms of 
oxygen, nitrogen or sulfur and saturated or unsaturated divalent cyclic 
radicals containing one or more atoms of oxygen, nitrogen or sulfur. 
Examples of diamines contemplated herein include ethylenediamine, 
trimethylenediamine, propylenediamine, tetramethylenediamine, 
t-butylenediamine, pentamethylenediamine, hexamethylenediamine, o-, m- and 
p-phenylenediamine, biphenylenediamine, naphthylenediamine, 
styrenediamine, xylylenediamine, etc. 
Organic mono-amines are also suitable. These compounds will have the 
formula R--NH.sub.2, in which R is a monovalent organic radical of 2-20 
carbon atoms. Such radicals will include, e.g., aliphatic, alicyclic and 
aryl radicals such as straight chain or branched alkyl, alkenyl, 
cycloalkyl, aryl, alkaryl radicals, and the like, and also hetero radicals 
including hydrocarbon chains interrupted by one or more atoms of oxygen, 
nitrogen or sulfur and saturated or unsaturated cyclic radicals containing 
one or more atoms of oxygen, nitrogen or sulfur. 
Preferred among organic mono-amines will be those in which R is a long, 
straight-chain saturated hydrocarbon radical. That is, in mono-amines of 
the formula R--NH.sub.2, R will preferably be --(CH.sub.2).sub.8-19 
CH.sub.3, most preferably --(CH.sub.2).sub.12-19 CH.sub.3. Special mention 
is made of the organic mono-amine, H.sub.2 N--(CH.sub.2).sub.17 
--CH.sub.3. 
Also contemplated are more complex organic polyamines such as triamines, 
R(NH.sub.2).sub.3 ; tetraamines, R(NH.sub.2).sub.4 ; pentaamines, 
R(NH.sub.2).sub.5, and the like, in which 3, 4, 5 or more amino groups, 
respectively, are bridged by trivalent, tetravalent, pentavalent, etc. 
organic radicals of 2-20 carbon atoms. The chemical structure of the 
organic radicals, e.g., in terms of chain length degree of branching, 
degree of unsaturation, steric hindrance, and other structural properties 
will affect the flexibility of the final product and the spacing between 
chelating groups, which, in turn, affects the chelating efficiency and the 
types of cations which are strongly sequestered by the final compound. 
Therefore, in practice, it may be possible by judicious selection of 
starting materials to tailor to some extent the detergent additives of the 
present invention to a particular detersive system or to work upon a 
particular type of stain complex. For the fabric-washing detergent systems 
contemplated in the present invention, diamine starting materials will be 
preferred. Substantially linear alkylenediamines are most preferred, 
especially those having the general formula H.sub.2 N--(CH.sub.2).sub.m 
--NH.sub.2, where m is 5 or more. Hexamethylenediamine is most preferred. 
The organic amine is reacted with a dialkyl maleate ester of the formula 
R'OOC--CH.dbd.CH--COOR', where R' is lower (C.sub.1 -C.sub.6) alkyl. 
Examples include dimethyl maleate, diethyl maleate dipropyl maleate, 
diisopropyl maleate, di-t-butyl maleate, etc. Dimethyl maleate is 
preferred. 
The maleate ester is reacted with the organic amine in a suitable solvent. 
Toluene is preferred. Approximately 1 amine equivalent of the dialkyl 
maleate ester will be used, since a secondary amine reaction product is 
desired. Thus, where an organic diamine is used, preferably about 2-2.5 
moles of a dialkyl maleate ester will be used, per mole of the diamine 
compound, in order to obtain an N,N'-substituted organic diamine 
intermediate. (See Formula III, supra, where n=2.) 
The maleate ester-substituted organic amine is further reacted, in 
accordance with the invention, with maleic anhydride. Typically, the 
maleic anhydride is added to the dialkyl maleate ester/organic amine 
reaction mixture, after allowing sufficient time for the initial ester 
substitution (producing the secondary amine intermediate) to be 
substantially completed. Preferably, approximately 1 amine equivalent of 
maleic anhdyride will be used for this reaction as well, although use of 
excess amounts is also contemplated in order to ensure complete reaction 
of free amine moieties or to speed the rate of reaction. Most preferably, 
in the case where diamine starting materials are used, about 2-3 moles of 
maleic anhydride, per mole of maleate ester-substituted organic diamine 
intermediate, will be employed. The tertiary amine product of this second 
stage reaction exhibits an N-substituted butenedioic acid residue, i.e., 
--CO--CH.dbd.CH--COOH, in addition to the maleate ester substituent; and 
this second stage product will be referred to herein as a maleic 
anhydride/ maleate ester-substituted organic amine. (See Formula IV, 
supra.) 
Reaction of the maleic anhydride/maleate ester organic amine to obtain the 
complex N-hydroxy-substituted maleimide compounds of this invention may be 
accomplished by contacting the maleic anhydride/maleate ester-substituted 
organic amine with hydroxylamine, i.e., H.sub.2 NOH, or a salt thereof. 
Preferably, hydroxylamine hydrochloride will be used. Any amount of 
hydroxylamine may be employed which is effective to react with the maleate 
ester or vinylene moieties of the maleic anhydride/maleate ester organic 
polyamine to obtain an effective proportion of N-hydroxy or hydroxylamino 
substituent groups. Preferably, at least approximately 2 amine equivalents 
of the hydroxylamine compound will be used. Thus, where organic diamine 
starting materials are used, it is preferred that about 3-6 moles of 
hydroxylamine per mole of maleic anhydride/maleate ester-substituted 
organic diamine be used, and most preferably, about 3.5-4.5 moles 
hydroxylamine per mole of diamine intermediate will be used. 
Where a salt of hydroxylamine is used, the reaction will normally be 
carried out in the presence of about 1-5 moles (per mole of hydroxylamine 
compound) of a basic agent, preferably an organic base such as sodium 
ethoxide, pyridine, triethylamine or quinoline. 
The product may be isolated in any one of a number of known ways. For 
example, the product can be isolated by precipitation from a non-solvent, 
such as absolute ethanol, and the precipitate filtered, washed and dried 
under vacuum to give the N-hydroxy maleimide product. These hydroxylamine 
reaction products, which will be referred to generally as the 
N-hydroxyimide compounds of the present invention, exhibit N-substituents 
of a cyclic N-hydroxymaleimide and a 2- or 3-hydroxylamino butanedioic 
acid residue, i.e., either a --CO--C(NHOH)--CH.sub.2 --COOH substituent or 
a --CO--CH.sub.2 --C(NHOH)--COOH substituent, depending on the precise 
nature of the hydroxylamine reaction at the unsaturated site. 
The N-hydroxyimide compounds are generally soluble in polar solvents, such 
as dilute sodium hydroxide, ammonium hydroxide or other bases, 
dimethylsulphoxide, N,N-dimethylformamide, N,N-dimethylacetamide. They are 
generally insoluble in non-polar solvents, such as hexane, ethyl ether, 
alcohols, dilute hydrochloric acid, dilute acetic acid. 
In the presence of base, the N-hydroxyimide compounds undergo a 
ring-opening reaction so that the cyclic N-hydroxyimide moiety is cleaved 
to obtain a difunctional carboxy hydroxamic acid moiety. The structure of 
the carboxy hydroxamic acid groups with respect to the polyamine nitrogens 
will be --CH(COOH)--CH.sub.2 --CO--NHOH or --CH(--CO--NHOH)--CH.sub.2 
--COOH, depending upon the precise cleavage of the N-hydroxyimide ring 
during the hydrolysis reaction. Where the reaction takes place in a 
solution of an alkali metal hydroxide, such as NaOH, alkali metal salts of 
the carboxy hydroxamic acid products are also contemplated. 
The N-hydroxyimide compounds and the carboxy hydroxamic acid derivatives 
are active transition metal ion chelating agents and are advantageously 
included in a detergent composition to boost stain-removal properties, in 
accordance with the present invention. A detergent composition of this 
invention will contain at least one detersive surfactant. Such surfactants 
will be present in amounts usually encountered in detergent compositions, 
e.g., from about 1% to about 50% by weight, preferably about 5% to about 
25% by weight for fabric-washing detergents, and most preferably from 
about 10% to about 20% by weight based on the total weight of the 
detergent composition. The surfactants may be anionic, nonionic, cationic 
or amphoteric, and mixtures of different detersive surfactants may be 
used. Non-limiting examples of suitable detersive surfactants include: 
(a) Anionic surfactants: soaps, i.e., alkali metal (preferably sodium or 
potassium) salts of long-chain fatty acids containing from 8 to 20 carbon 
atoms, such as lauric, myristic, oleic, palmitic, capric, caprylic, and 
stearic acids, used singly or in mixtures of differing chain lengths; 
alkali metal salts of organic sulphuric reaction products having long 
hydrocarbon chains of about 8 to about 20 carbon atoms and a radical 
selected from the group consisting of sulphonic acid and sulfuric acid 
ester radicals, such as sodium or potassium alkyl sulphates, preferably 
those obtained by sulphating higher (C.sub.8 -C.sub.18) alcohols; sodium 
or potassium alkyl benzene-sulphonates in which the alkyl group contains 
from about 9 to about 20 carbon atoms, such as sodium linear alkyl 
(C.sub.10 -C.sub.15) secondary benzenesulphonate, 
2-phenyl-dodecanesulphonate, 2-phenyl-octadecanesulphonate and 
3-phenyl-dodecanesulphonate; alkali metal (preferably sodium) olefin 
sulphonates, i.e., the mixture of detersive surfactants obtained from 
sulphonation of C.sub.8 -C.sub.22 olefins, preferably straight-chain 
alpha-olefins; sodium alkyl glyceryl ether sulphonates, including ethers 
of higher alcohols derived from tallow coconut oil and synthetic alcohols 
derived from petroleum; sodium coconut oil fatty acid monoglyceride 
sulphates and sulphonates; sodium or potassium salts of sulfur acid esters 
of the reaction between higher fatty alcohols (e.g., tallow or coconut oil 
alcohols) and ethylene oxide; the esterification products of fatty acids 
with isethionic acid, neutralized with sodium hydroxide; and sodium or 
potassium salts of fatty acid amides of methyl taurine. 
(b) Nonionic synthetic detersive surfactants: compounds formed by 
condensing ethylene oxide with a hydrophobic base formed by the 
condensation of propylene oxide with propylene glycol; the polyethylene 
oxide condensates of alkyl-phenols, e.g., the condensation products of 
alkyl-phenols, having an alkyl group containing from about 6 to 12 carbon 
atoms in either a straight or branched chain, with ethylene oxide, said 
ethylene oxide being present in amounts equal to 5 to 25 moles of ethylene 
oxide per mole of alkyl-phenols (the alkyl substituent in such compounds 
may be derived from polymerised propylene, diisobutylene, octene, 
dodecene, or nonene, for example); compounds derived from the condensation 
of ethylene oxide with the product resulting from the reaction of 
propylene oxide and ethylenediamine, such as compounds containing from 
about 40% to about 80% polyoxyethylene by weight and having a molecular 
weight of from about 5,000 to about 11,000 resulting from the reaction of 
ethylene oxide groups with a hydrophobic base constituted of the reaction 
product of ethylenediamine and excess propylene oxide, said hydrophobic 
base having a molecular weight of the order of 2,500 to 3,000; the 
condensation product of aliphatic alcohols having from 8 to 18 carbon 
atoms, in either straight chain or branched chain configuration, with 
ethylene oxide, e.g., a coconut alcohol-ethylene oxide condensate having 
from 6 to 30 moles of ethylene oxide per mole of coconut alcohol, the 
coconut alcohol fraction having from 10 to 14 carbon atoms; long chain 
tertiary amine oxides corresponding to the following general formula, 
R.sup.1 R.sup.2 R.sup.3 N=O, wherein R.sup.1 is an alkyl radical of from 
about 8 to 18 carbon atoms and R.sup.2 and R.sup.3 are each methyl, ethyl 
or hydroxyethyl radicals, such as dimethyl-dodecylamine oxide, 
dimethyloctylamine oxide, dimethyldecylamine oxide, diethyltetradecylamine 
oxide and dimethylhexadecylamine oxide, N-bis (hydroxyethyl)dodecylamine 
oxide; long chain tertiary phosphine oxides corresponding to the following 
formula R.sup.4 R.sup.5 R.sup.6 P=O, wherein R.sup.4 is an alkyl, alkenyl 
or monohydroxyalkyl radical of 10 to 18 carbon atoms and R.sup.5 and 
R.sup.6 are each alkyl or monohydroxyalkyl groups containing from 1 to 3 
carbon atoms, such as dimethyldodecylphosphine oxide, 
dimethyltetradecylphosphine oxide, ethylmethyltetradecylphosphine oxide, 
cetyldimethylphosphine oxide, dimethylstearylphosphine oxide, 
cetylethylpropylphosphine oxide, diethyldodecylphosphine oxide, 
diethyltetradecylphosphine oxide, bis(hydroxymethyl)dodecylphosphine 
oxide, bis(2-hydroxy-ethyl)dodecylphosphine oxide, 
2-hydroxypropylmethyltetradecyl-phosphine oxide, dimethyloleylphosphine 
oxide, and dimethyl-2-hydroxydodecylphosphine oxide; and dialkyl 
sulphoxides corresponding to the following formula, R.sup.7 R.sup.8 S=O, 
wherein R.sup.7 is an alkyl, alkenyl, beta- or gamma-monohydroxyalkyl 
radical or an alkyl or beta- or gamma-monohydroxyoxyalkyl radical 
containing one or two other oxygen atoms in the chain, the R.sup.7 groups 
ranging from 10 to 18 carbon atoms in chain length, and wherein R.sup.8 is 
methyl, ethyl or alkylol, such as dodecyl methyl sulphoxide, tetradecyl 
methyl sulphoxide, 3-hydroxy-tridecyl methyl sulphoxide, 2-hydroxydodecyl 
methyl sulphoxide, 3-hydroxy-4-decyloxybutyl methyl sulphoxide, 
3-hydroxy-4-dodecyloxybutyl methyl sulphoxide, 2-hydroxy-3-decyloxypropyl 
methyl sulphoxide, 2-hydroxy-3-dodecyloxypropyl methyl sulphoxide, dodecyl 
ethyl sulphoxide, 2-hydroxydodecyl ethyl sulphoxide, dodecyl-2-hydroxy 
ethyl sulphoxide. 
(c) Ampholytic synthetic surfactants: derivatives of aliphatic secondary 
and tertiary amines, in which the aliphatic radical may be straight chain 
or branched chain and wherein one of the aliphatic substituents contains 
from about 8 to 18 carbon atoms and one contains an anionic water 
solubilizing group, such as sodium-3-dodecylamino-propionate, 
sodium-3-dodecylaminopropanesulphonate and sodium 
N-2-hydroxydodecyl-N-methyl-taurate. 
(d) Zwitterionic synthetic surfactants: derivatives of aliphatic quaternary 
ammonium compounds, sulphonium compounds and phosphonium compounds in 
which the aliphatic radical may be straight or branched chain and wherein 
one of the aliphatic substituents contains from about 8 to 18 carbon atoms 
and one contains an anionic water solubilizing group, such as 
3-(N,N-dimethyl-N-hexadecylammonio)propane-1-sulphonate, 
3-(N,N-dimethyl-N-hexadecylammonio)-2-hydroxypropane-1-sulphonate, 
3-(dodecylmethylsulphonium) propane sulphonate, and 
3-(cetyl-methylphosphonium) ethane sulphonate. 
The detergent compositions of the present invention will contain, besides 
one or more detersive surfactants, about 3% to about 12% by weight of the 
composition, preferably about 6% by weight, of the N-hydroxyimide and/or 
carboxy hydroxamic acid detergent compounds described above. The complex, 
alternating structure of the multifunctional compounds of this invention 
may enhance their metal chelating effectiveness by providing a variety of 
spacings between functional chelating groups, which, in turn, allows the 
compounds to sequester a wider variety of cations. 
In addition to the surfactants and the N-hydroxy-imide detergent additives, 
the detergent composition may also contain conventional detergent builders 
such as condensed phosphates, trisodium nitrilotriacetate (NTA), sodium 
carbonate, zeolites, sodium silicates, etc., and organic polymers such as 
polyacrylates, polymaleates and polymethacrylates. See, e.g., U.S. Pat. 
Nos. 3,393,150, 3,666,664, 3,707,502, 3,839,215 and 4.067,816, 
incorporated herein by reference. The combined detergent builders will 
make up from about 10% to about 50% by weight of the detergent 
composition. In addition to the essential detersive surfactants and 
detergent additives, a detergent composition of the invention may also 
include such conventional ingredients as lather boosters (e.g., 
alkanolamides), fillers, antiredeposition agents, fluorescers, pigments, 
germicides, scents, and enzymes. 
A detergent composition according to the invention can be prepared by any 
conventional manufacturing technique used for preparing detergent 
compositions, such as slurry making and spray-drying, and the detergent 
can take anyone of the common physical forms associated with detergents, 
such as powders, flakes, granules, noodles, cakes, bars and liquids.

The invention is further illustrated by the following examples, which 
should not be contrued as limiting the scope of the invention. 
EXAMPLE 1 
72 g (0.50 mole) of dimethyl maleate were added to a solution of 25 g 
(0.215 mole) hexamethylenediamine in 150 ml of toluene. An exotherm 
resulted in which the reaction mixture reached 70.degree. C. After the 
exotherm subsided, the reaction mixture was refluxed for two hours. The 
reaction mixture was cooled and then 49 g (0.50 mole) of maleic anhydride 
were added. Another exotherm resulted. 
After the exotherm had subsided, the reaction mixture was refluxed for two 
hours and then cooled. The toluene was removed in a rotary evaporator at 
reduced pressure. Excess dimethyl maleate and maleic anhydride were 
removed with a Kugelrohr still at 100.degree. C. at 1 mm Hg pressure, 
yielding 121.3 g of a yellowish thick oil which later solidified into a 
glass. 
Infrared (IR) and nuclear magnetic resonance (NMR) spectrometry confirmed 
the presence of both the expected N-substituents, resulting from 
cis-dimethyl maleate and maleic anhydride (having intact --CH=CH= moiety) 
residues. 
An ethanolic solution of hydroxylamine was prepared by adding 15 g (0.65 
mole) of sodium to 300 ml absolute ethanol. This solution was then 
combined with a solution of 22 g (0.317 mole) of hydroxylamine 
hydrochloride in 350 ml absolute ethanol at 40.degree. C. The reaction 
mixture was cooled to 0.degree. C. and filtered. 
50 g (0.083 mole) of the maleate ester/maleic anhydride intermediate were 
added in 50 ml of ethanol to the ethanolic solution of hydroxylamine. The 
reaction mixture was allowed to stand at room temperature for two days, 
with formation of a white precipitate. 
400 ml of hexane were added to the reaction mixture, which was then 
filtered. The white solid obtained was dissolved in 300 ml of water and 
the pH adjusted to 8.0 with concentrated HCl. The solution was then freeze 
dried to give 56.9 g of an orange solid. 
IR, NMR and ultraviolet spectra were obtained, indicating an 
N-hydroxyimide/2- or 3-hydroxylamino butanedioic acid-substituted product 
of about 80% purity. 
EXAMPLE 2 
The performance of the N-hydroxyimide compound Example 1 as a 
fabric-washing detergent additive was examined in a tea stain removal 
test: 
Swatches of white cotton cloth were boiled in very strong tea (10 tea 
bags/1 liter dionized water), brewed 10 min.) for 15 minutes. The tea 
solution and swatches were removed from the heat and cooled to 115.degree. 
F. with continued stirring. The swatches were thereafter wrung and air 
dried between paper towels. 
Deionized water was heated to 40.degree. C. and 100 mg of CaCl.sub.2 were 
added per each liter of water, followed by 1.5 g per liter of water of a 
commercial fabric-washing detergent (Tide.RTM.; Procter & Gamble). 
To 1-liter aliquots of this detergent solution were added 100 mg of the 
detergent additives to be tested, which were stirred until dissolved. The 
wash solutions were maintained at about 35.degree. C. and a stirring speed 
of 100 rpm. The pH was adjusted to 10 if necessary with sulfuric acid or 
sodium hydroxide. Tea stained swatches of cloth were added to each test 
solution and stirred rapidly for 10 minutes, after which the solution was 
poured off and the swatches squeezed out and rinsed for 2 minutes in 
deionized water containing the same proportion of CaCl.sub.2. The swatches 
were then air dried overnight and compared against a control and a 
commercial detergent additive. 
The detergent additives of Example 1 was compared against a control (no 
additive) and a commercial detergent additive (Dequest.RTM. 2041; 
Monsanto). After the complete wash cycle, the swatches of the control 
solution appeared darkest, and the comparison sample and the sample using 
the detergent additive according to the invention appeared visibly 
lighter. 
It will be understood that the foregoing description of the invention is 
susceptible to modifications, changes and adaptations, all of which are 
intended to be comprehended within the meaning and range of equivalents of 
the appended claims. For instance, though the foregoing description is 
directed to the use of the N-hydroxyimide compounds and their carboxy 
hydroxamic acid derivatives in detergent systems, they will also find 
application in boiler water systems and other scale prevention uses, 
polymerization intermediates, and other embodiments where strong metal ion 
chelation is required.