Biodegradable ester diquaternary compounds and compositions containing them

Disclosed are compounds of the formula (I) ##STR1## useful as fabric softening compounds which exhibit enhanced biodegradability.

BACKGROUND OF THE INVENTION 
Fabrics can be treated to impart softness, static control and antistatic 
properties by addition of fabric softening compositions to the rinse 
cycle, as part of the detergent system, or in the automatic clothes drying 
cycle of the standard washing and drying routine. Treatment in the rinse 
cycle of washing machines and in clothes dryers has been shown to be an 
effective means for applying softening compositions to textiles. 
Various chemical compositions have been used commercially for softening 
fabrics when applied during the laundering operation. This softening or 
conditioning is normally understood and results in a smooth, fluffy feel 
to the touch. The most common softening compositions include one or more 
quaternary ammonium salts. Among the most commercially attractive are 
imidazolinium sales, imadizoline salts, dimethyl dialkyl quaternary salts, 
and diamidoamine quaternary salts. The majority of these compounds are 
derived from fatty raw materials, and these cationics have been the 
subject of many innovations. See, for example, U.S. Pat. Nos. 3,634,947; 
3,686,025; 3,095,373 and 3,442,692. Disclosures specifically for 
dryer-added fabric softeners include U.S. Pat. No. 3,676,199. In all of 
the commercially used dryer-softener systems there is included from 10-30% 
of a release agent to accomplish the transfer of the active softener to 
the textile being dried. This requirement for the release agent results in 
additional handling and manufacturing costs. 
It is, therefore, an object of the present invention to provide a material 
for the treatment of textiles in a washing machine or in an automatic 
dryer to provide softness and static control to the fabric with improved 
transfer properties to the fabric. 
It is an additional objective of the present invention to provide a 
softening system for use in washers and/or in dryers comprising a softener 
exhibiting faster biodegradation than currently available systems. 
The present invention relates to certain diquaternary diesters to provide 
good softening and antistatic properties while exhibiting excellent 
transfer to the clothes, combined with a high degree of biodegradability.

BRIEF SUMMARY OF THE INVENTION 
One aspect of the present invention is a composition of the formula (I): 
##STR2## 
wherein A.sup.1, A.sup.2 and A.sup.3 are the same or different and each is 
alkyl containing up to 3 carbon atoms, benzyl, or H--(Alk--O).sub.1-3 
--Alk-- wherein Alk signifies --CH.sub.2 CH.sub.2 --, 
--CH(CH.sub.3)CH.sub.2 --, or --CH.sub.2 CH(CH.sub.3)--, provided further 
that A.sup.1 can be --(CH.sub.2).sub.1-3 COO.sup.-, and A.sup.3 can be 
hydrogen; 
R.sup.b is --(CH.sub.2).sub.b -- or --Alk--(O--Alk).sub.2-6 --; 
R.sup.c is --(CH.sub.2).sub.c -- or --Alk--(O--Alk).sub.2-6 --; 
a is 2 to 6; 
b is 2 to 4; 
c is 2 to 4; 
D is methyl, ethyl, propyl, --(CH.sub.2).sub.1-3 COO.sup.-, benzyl or 
hydrogen; 
i is 0 or 1 and j is 0 or 1, provided that the sum of (i+j) is 1 or 2; 
X.sup.1 and X.sup.2 are independently YC(O)O-- or YOC(O)-- wherein Y is a 
straight or branched saturated or unsaturated aliphatic group containing 
up to 3 carbon-carbon double bonds and containing 11 to 23 carbon atoms; 
n is (two minus the number of --(CH.sub.2).sub.1-3 COO.sup.- substituents 
present); and 
Z is an anion. 
Another aspect of the present invention is a method of imparting softening 
or antistatic properties to fabric by contacting the fabric with an 
effective amount of one or more compounds corresponding to the above 
formula (I). 
Additional aspects of the present invention include articles and 
compositions containing one or more compounds of formula (I) in a form 
useful in imparting softening and/or antistatic to fabrics. For instance, 
compounds of this invention can be disposed in an effective manner into an 
automatic dryer under conditions which provide for release of an effective 
amount of the composition onto the fabrics. Normally, softening 
compositions are deposited on an absorbent substrate as an impregnate or 
as a coating. Alternatively, compounds of this invention can be formulated 
into liquid preparations, optionally also including one or more of 
detergents, optical brighteners, and soil release agents, and the like, 
whereupon the softening compound or compounds of formula (I) can be added 
into an automatic clothes washing machine, generally in the rinse cycle. 
DETAILED DESCRIPTION OF THE INVENTION 
With reference to formula (I), the substituents A.sup.1, A.sup.2 and 
A.sup.3 may be the same or different and are preferably the same for ease 
of synthesis. Each of A.sup.1, A.sup.2 and A.sup.3 can be alkyl containing 
up to 3 carbon atoms, such as methyl, ethyl, n-propyl or isopropyl. 
Preferably, A.sup.1, A.sup.2 and A.sup.3 are each methyl. One or more of 
these three substituents may be benzyl or may correspond to the formula 
H--(Alk--O).sub.1-3 --Alk-- wherein Alk signifies ethylene or 
isopropylene, that is, --CH.sub.2 CH.sub.2 --, --CH(CH.sub.3)CH.sub.2 --, 
or --CH.sub.2 CH(CH.sub.3)--. 
The substituent A.sup.1, that is, one of the substituents on the nitrogen 
to which A.sup.1, A.sup.2 and A.sup.3 are attached, can also be a 
betaine-type substituent of the formula --CH.sub.2 COO.sup.-, 
--(CH.sub.2).sub.2 COO.sup.- or --(CH.sub.2).sub.3 COO.sup.-. In 
addition, the substituent A.sup.3 can be hydrogen, as can the substituent 
D. 
It will be recognized from the definitions of the subscripts i and j that 
one or both of the nitrogen atoms in the compounds of formula (I) are 
tetra-substituted and will, therefore, carry a positive charge. The 
positive charge, whether +1 or +2, is balanced by the presence of anions 
X.sup.-, by the "internal salt" afforded by the presence of 
--(CH.sub.2).sub.1-3 COO.sup.- substituents, or by any combination of 
X.sup.- and --(CH.sub.2).sub.1-3 COO.sup.- presence. 
Referring again to formula (I), the chain lengths defined by the subscripts 
a, b and c are selected to optimize the fabric softening properties of the 
compound. Thus, a is 2 to 6, and preferably 2, 3 or 4. Likewise, b and c 
are each 2, 3 or 4, and each is preferably 2. The substituent D can be a 
substituent, such as hydrogen, methyl, ethyl, n-propyl, isopropyl, benzyl, 
or --(CH.sub.2).sub.1-3 COO.sup.-. Preferably, D is hydrogen or methyl or 
ethyl. 
The substituents X.sup.1 and X.sup.2 are derived from natural or synthetic 
long-chain fatty acids preferably containing 12 to 24 carbon atoms. Such 
fatty acids can be straight or branched and saturated or unsaturated. 
Typically, when unsaturated fatty acids are used, they may contain one, 
two or three carbon-carbon double bonds. The chain lengths of the 
substituents X.sup.1 and X.sup.2 are selected with reference to the 
desired final properties, including solubility, melting point and ease of 
application onto a fabric substrate in the preparation of a fabric 
softening sheet for use in a clothes dryer. 
The anion Z can be any conventional organic or inorganic anion compatible 
with the fabric softening properties of the compound and with the other 
components with which the fabric softener may be used, such as detergent, 
bleach and so forth. Preferably, Z is chloride, bromide, methylsulfate, or 
ethylsulfate. The anion can be monovalent or divalent and is preferably 
monovalent for solubility purposes. There must be a sufficient amount of 
the anion present to balance the net charge of the rest of the compound. 
Thus, the number of moles of anion per mole of diquaternary is two minus 
the number of betaine-type substituents --(CH.sub.2).sub.1-3 COO.sup.-. 
Compounds in accordance with formula (I) are made by straightforward 
techniques employing readily available starting materials. For instance, a 
compound of the formula (A.sup.1)(A.sup.2)N--(CH.sub.2).sub.a --NH.sub.2 
is di-alkoxylated on the unsubstituted nitrogen by reaction with one molar 
equivalent each of compounds of the formula L--(CH.sub.2).sub.b --OH and 
L--(CH.sub.2).sub.a --OH (or two molar equivalents of L--(CH.sub.2).sub.b 
OH where it is desired that b and c are to be equal) where L is a suitable 
leaving group such as chloro. Alternatively, the compound of the formula 
(A.sup.1)(A.sup.2)N--(CH.sub.2).sub.a --NH.sub.2 is reacted on the 
unsubstituted nitrogen with a total of 2 moles or more of one or more 
compounds of the formula L--Alk--(O--Alk).sub.2-6 --OH. The resulting 
bis(hydroxyalkylene)-substituted or bis(hydroxy-polyalkoxy)-substituted 
diamine is then reacted with two molar equivalents of fatty acid, that is, 
a total of two molar equivalents of one or more fatty acids of the formula 
Y--COOH wherein Y is as described above. The resulting diester compound 
can then be quaternized or protonated at one or both nitrogens by reaction 
under conventional quaternization conditions with quaternization agents 
such as methyl chloride, dimethyl sulfate, and the like, or by protonation 
with a suitable strong acid of the formula HX. 
In the case where the desired compounds are substituted with YOC(O)--groups 
instead of long chain acyloxy radicals, the synthesis proceeds through the 
formation of a diacid intermediate which is subsequently esterified with 
the corresponding fatty alcohol Y--OH. 
The preferred compounds of the present invention are disubstituted as 
YC(O)O--. 
When it is desired to provide one or two substituents of the formula 
--CH.sub.2 COO.sup.-, --(CH.sub.2).sub.2 COO.sup.- or --(CH.sub.2).sub.3 
COO.sup.-, the appropriate intermediate is reacted after esterification 
with a reactive acid L--CH.sub.2 COOH, L--(CH.sub.2).sub.2 COOH or 
L--(CH.sub.2).sub.3 COOH where L is a suitable leaving group. Preferred 
reactants for this step are chloroacetic acid or chloropropionic acid. 
Compounds of the present invention exhibit a number of advantages making 
them particularly advantageous for use in the fabric softening 
applications. For instance, the synthesis of these compounds does not 
generate byproduct salts, thereby alleviating the need to remove 
byproducts during manufacture and thereby alleviating the burdens of waste 
disposal. In addition, the compounds can be synthesized in a 
straight-forward manner not requiring extra steps or posing any unusual or 
difficult reaction conditions. In particular, avoiding the need to recover 
byproduct salts affords rapid attainment of product in high yield, without 
the additional steps that would be entailed if salts were present that had 
to be removed. 
In addition, the compounds of formula (I) would exhibit enhanced 
biodegradability, thereby permitting the use of fabric softening 
compositions and articles even under circumstances where relatively 
stringent controls need to be implemented on the volume and content of 
waste water effluent streams. This biodegradability also contributes to 
the lessening of the burden on household and municipal waste water 
treatment facilities. 
The compounds of the present invention are preferably used by providing 
them to the fabric to be softened in amounts effective to afford softening 
or antistatic properties to the fabric. Satisfactory amounts typically 
range from 1 to 2 grams of softening compound(s) per load of laundry. When 
the mode in which the compound is to be provided is a solid article, it is 
typically prepared by coating the compound or compound(s) per se onto a 
solid carrier such as a suitably sized swatch of woven or non-woven fabric 
such as spun, bonded polyester sheet. The sheets are provided in any of 
the conventional means such as a pop-up dispenser or a roll of perforated 
sheets, whereby the user can remove a single sheet and add it to the load 
of laundry in the automatic clothes dryer. Alternatively, the fabric 
softening compounds of the present invention can be provided in a liquid 
or solid formulation. In the liquid formulation, the softener compound is 
suspended and/or dissolved in water optionally containing as well other 
ingredients and diluents such as detergents, viscosity builders, optical 
brighteners, salt release agents, water, fragrance, and so forth, in 
relative amounts effective to provide about 1 to about 2 grams of fabric 
softening compound in the dose of the liquid composition which is added to 
the load of fabric being washed. In the solid formulation, the product 
comprises small flowable solid particles or beads on a water-soluble 
carrier such as solid detergent optionally compounded with builders, 
brighteners, fragrance, and the like as is known in the art. 
Preferred compounds within the scope of the present invention include the 
following: 
##STR3##