Cyclic N-hydroxyimide compounds derived from tartaric acid are provided which exhibit strong metal ion chelating ability, making them useful as detergent additives, in boiler water systems, as reaction intermediates, etc. A detergent composition containing N-hydroxyimide compounds as detergent additives is also disclosed.

The present invention relates to chelating agents useful, e.g., as 
adjuvants for detergent compositions, particularly fabric-washing 
detergent compositions. In particular it relates to novel cyclic 
N-hydroxyimides useful as detergent additives and to detergent 
compositions comprising at least one detersive surfactant and an effective 
amount of an N-hydroxyimide detergent additive. 
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 constitutents 
present in a detergent system. Many materials useful as builders have been 
proposed, and their effects are known. See, e.g., U.S. Pat. Nos. 
3,852,213, 3,950,260, 4,182,718, and 4,440,646 (all incopporated herein by 
reference). 
Recently, however, the attention of detergent manufacturers and researchrrs 
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 certain cyclic N-hydroxyimides add their 
salts derived from tartaric acid esters are active chelants of metal ions, 
particularly Fe.sup.+++, and are useful as detergent additives because of 
their stain-removing ability. As an additional advantage, the 
N-hydroxyimides of the present invention are believed to be broken down in 
freshwater systems to tartaric acid, which is well known to be 
biodegradable. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to provide a new class 
compounds which are useful as transition metal ion chelating agents. 
It is a further object of the present invention to provide detergent 
additives effective in stain removal. 
It is a further object of the present invention to provide a detergent 
additive that is biodegradable. 
It is a further object of the present invention to provide a novel 
detergent composition. 
It is a further object of the present invention to provide a fabric-washing 
detergent composition that is effective in stain removal. 
These and other objects are achieved, according to the present invention, 
by cyclic N-hydroxyimide compounds having the formula 
##STR1## 
where X is --OH or --O.sup.- M.sup.+, where M.sup.+ is an alkali metal or 
ammonium cation. 
Also contemplated herein are detergent compositions comprising one or more 
detersive surfactants and one or more detergent additives consisting 
essentially of cyclic N-hydroxyimide compounds having the formula 
##STR2## 
where X has the same meaning as above. 
DETAILED DESCRIPTION OF THE INVENTION 
The N-hydroxyimide compounds of the present invention are advantageously 
prepared from tartaric acid, e.g., by first reacting it with an alkanol to 
form a tartrate ester, then reacting the tartrate ester with hydroxylamine 
or a salt thereof to obtain the N-hydroxyimide compounds of the present 
invention. A typical reaction scheme for the preparation of detergent 
compounds according to the present invention is as follows: 
##STR3## 
Tartaric acid, especially L-tartaric acid or "natural" tartaric acid 
(L-2,3-dihydroxybutanedioic acid), is widely distributed in nature and 
occurs in many fruits. In modern processes it is obtained as a byproduct 
of the wine-making industry from potassium tartrate, a crystalline deposit 
from fermentation, which is converted to the calcium salt, then hydrolyzed 
to tartaric acid and calcium sulfate. 
In order to prepare the dialkyl tartrate esters which are the preferred 
starting materials in preparing the N-hydroxyimide compounds of the 
present invention, dehydrated tartaric acid is reacted with an alkanol of 
from 1 to 6 carbons, e.g., methanol, ethanol, propanol, isopropanol, 
butanol, isobutanol, etc. The amount of alkanol employed will normally be 
a large stoichiometric excess in order to ensure esterification of both 
carboxyl groups of the dicarboxylic acid substrate. Most advantageously, 
the tartaric acid is simply dissolved in a suitable quantity of the 
alkanol, e.g., 2-20 moles alkanol per mole of tartaric acid. 
Reaction of the dialkyl tartrate ester to obtain N-hydroxyimide products 
may be accomplished by contacting the ester with at least a substantially 
equimolar quantity of hydroxylamine. A hydroxylamine salt, preferably 
hydroxylamine hydrochloride, can be used, and it will be necessary to 
neutralize the salt (which is unreactive toward the esters) and generate 
free hydroxylamine for the reaction to proceed. The reaction will 
therefore normally be carried out in the presence of about 1-5 moles per 
mole of hydroxylamine of a basic agent, preferably an organic base such as 
sodium ethoxide, pyridine, triethylamine, or quinoline. Most preferably, 
the reaction will be carried out in an alcoholic solvent, such as ethanol. 
The raaction takes place at room temperature and is completed in several 
hours, e.g., 2-20 hours. 
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 hexane, and the precipitate filtered, washed and dried under 
vacuum to give the cyclic N-hydroxyimide product. 
Alternatively, flash or spray drying may be used. The drying step removes 
substantially all of the organic base, and washing with alcoholic hydrogen 
chloride effectively scavenges residual amounts, in cases where complete 
removal of the basic agent is required. 
The cyclic N-hydroxyimide compounds are active chelating agents with 
respect to transition metal cations, especially iron, and are 
advantageously included in a detergent composition, 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 sulfuric 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 benzenesulphonates 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 alkylphenols (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 carbonaatoms; long chain 
tertiary amine oxides corresponding to the following general formula, 
R.sup.1 R.sup.2 R.sup.3 N.dbd.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 dimethyldodecylamine 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.dbd.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-hydroxyethyl)dodecylphosphine oxide, 
2-hydroxypropylmethyltetradecylphosphine oxide, dimethyloleylphosphine 
oxide, and dimethyl-2-hydroxydodecylphosphine oxide; and dialkyl 
sulphoxides corresponding to the following formula, R.sup.7 .sup.8 
S.dbd.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-hydroxytridecyl methyl sulphoxide, 2-hydroxydodecyl methyl sulphoxide, 
3-hydroxy-4-decyloxybutyl methyl sulphoxide, 3-hydroxy-4dodecyloxybutyl 
methyl sulphoxide, 2-hydroxy-3decyloxypropyl 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-dodecylaminopropionate, 
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-(cetylmethylphosphonium) 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 cyclic N-hydroxyimide 
compounds described above. 
In addition to the surfactants and the cyclic N-hydroxyimide chelants, the 
detergent composition may also contain coventional detergent builders such 
as condeneed 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, 36666,664, 3,707,502, 3,839,215 and 4,067,816, which are 
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 comprise 
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. 
Liquid detergent compositions according to the invention will most 
preferably be a concentrated aqueous solution having a basic pH, at least 
about pH 8, most preferably pH 9 or above, comprising one or more of the 
detersive surfactants described above and one or more cyclic 
N-hydroxyimide compounds of this invention. 
The invention is further illustrated by the following examples, which 
should not be contrued as limiting the scope of the invention.

EXAMPLE 1 
An alcoholic hydroxylamine/sodium ethoxide reactant solution was prepared 
as follows: 15 g (0.65 moles) of metallic sodium were added to 300 ml of 
absolute ethanol under nitrogen gas. A separate hydroxylamine solution was 
prepared by adding 22.5g (0.326 moles) of hydroxylamine hydrochloride to 
500 ml of absolute ethanol. The two solutions were mixed at 40.degree. C., 
then cooled to 5.degree. and filtered. 
26.7 g (0.15 moles) of the L-dimethyl tartrate were added to the 
hydroxylamine/sodium ethoxide solution. The reaction mixture was allowed 
to stand at room temperature overnight. 
The ethanol was removed by rotary evaporator at reduced pressure, then 500 
ml water and 200 ml of hexane were added to the reaction mixture, which 
was shaken and allowed to separate into two layers. The aqueous layer was 
freeze dried to give 36.59 g of a light yellow powder. 
Infrared and nuclear magnetic resonance spectra and high pressure liquid 
chromatography (pH 7.0 with UV detector set at 270 nm) indicated that the 
product had the following structure: 
##STR4## 
EXAMPLE 2 
The procedure of Example 1 was carried out in the same manner, except that 
10.0 g of sodium (0.43 moles) were used in preparing the sodium ethoxide 
solution, and 15.0 g of hydroxylamine hydrochloride (0.22 moles) were 
used. The yield was 34.46 g of the sodium salt of 
N-hydroxy-(3R-trans)-3,4-dihydroxy-2,5-pyrrolidinedione. 
EXAMPLE 3 
The performance of the N-hydroxyimide compounds of Examples 1 and 2 as 
fabric-washing detergent additives 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 minutss. 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 0.1 g 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. add 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 Examples 1 and 2 were 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 samples using 
the detergent builders of Examples 1 and 2 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-hydroxyimides in detergent systems, they will 
also find application in boiler water systems and other scale prevention 
uses, polymerization intermediates, and other embodiments where strong 
transition metal ion chelation is required.