Copolymers derived from polyamino acids with at least 75% of the units present selected from the group consisting of structural units having the general formulas (I) and (II) in which the structural elements A are identical or different trifunctional hydrocarbon radicals with 2 or 3 C atoms, wherein the copolymer contains at least three units of formula (I).

BACKGROUND OF THE INVENTION 
Polyamino acid derivatives, particularly polyaspartic acid, have aroused 
interest very recently because of their properties. One advantage of the 
polyaspartic acid skeleton is its very good environmental compatibility 
and biological degradability. The biological degradability of polymeric 
aspartic acids is a result of the basic structure, which is similar to a 
natural one and which has been derived from polyamino acids. The 
advantageous properties of polyaspartic acids with respect to the 
biological degradability in comparison to polymers with C-C skeletons (for 
example, polyacrylates) have been described (Abstracts of papers of the 
ACS, 1994, V208, 423-4; M. B. Freeman, Y. H. Paik, G. Swift, R. 
Wilczynski, S. K. Wolk, K. M. Yocom). The applications proposed are, 
primarily, use as biologically degradable complexing agents, softeners and 
detergent builders. 
The immediate synthetic precursor in most cases is polysuccinimide, the 
cyclic imide of polyaspartic acid, or derivatives of monoethylenically 
unsaturated carboxylic acids, such as maleic acid. 
EP-A-0578449 describes the synthesis of polysuccinimide by the heating of 
aspartic acid in polyalkylene glycols, alone or in a mixture with 
additional amino acids. WO 92/14753 describes the synthesis of 
polysuccinimide and polyaspartic acid by the thermal condensation of 
aspartic acid. U.S. Pat. No. 5,219,952 describes the synthesis of 
polysuccinimide from maleic acid anhydride and ammonia, and the hydrolysis 
of the product to form polyaspartic acid. EP-A-0578448 describes the 
synthesis of polysuccinimide by the heating of amino acids and 
monoethylenically unsaturated dicarboxylic acids or their ammonium salts. 
These compounds present numerous advantageous properties, but they have no 
surface active properties. In order to obtain compounds which combine the 
positive properties of polyaspartic acid with surfactant properties, it is 
necessary to introduce hydrophobic, oil-compatible molecule parts into the 
predominantly hydrophilic polyaspartic acid skeleton. 
The reaction of polysuccinimide with amines to form polyaspartic acid 
amides is also known in the state of the art (for example, DE-A-2253190). 
U.S. Pat. No. 5,292,858 describes the synthesis of copolymeric polyamino 
acid amides by the hydrolysis of polysuccinimide derivatives, prepared by 
reacting maleic acid semiesters with ammonia or amines. 
In accordance with these teachings, copolymers with free carboxylic acid 
groups and alkylamide groups can be prepared. These copolymers however 
present serious drawbacks. Thus, as a result of the preparation, the 
products contain more or less small amounts of free alkylamines, which are 
undesired in many applications and whose use can also entail toxicological 
and ecological drawbacks. The alkylamines can additionally be released, 
for example, by hydrolytic cleavage, during the use of such copolymers. 
BRIEF SUMMARY OF THE INVENTION 
Copolymeric polyaspartic acid derivatives, in which a portion of the 
carboxyl groups are esterified with alcohols, particularly fatty alcohols, 
are not known so far. Such novel ester derivatives are made available by 
the invention: since the preparation of the compounds in accordance with 
the invention is not based on the use of amines, and since the copolymers 
also do not contain amines in bound form, the compounds in accordance with 
the invention do not present the above-mentioned drawbacks. 
An additional advantage of the copolymers in accordance with the invention 
is their very good environmental compatibility, which is the result of the 
fundamental structure, which is close to the natural one, and derived from 
polyamino acids, and the linkage of the alkyl side chains by means of 
ester groups. 
The copolymers in accordance with the invention can be adapted to a very 
great variety of application-technological requirements by the type and 
density of the alkyl side chains and by their molecular weights. Thus, 
short-chain alkyl-substituted derivatives can be suitable as sequestrants 
or they can be used in corrosion-protecting paints, particularly since 
they can be soluble in polar organic solvents. 
Long-chain alkyl substituted copolymers present surface-active properties. 
By the variation of different parameters, such as chain length of the 
long-chain components, degree of polymerization of the copolymer, ratio of 
hydrophobic side chains to free carboxylic acid groups, etc., 
environmentally safe surfactants with excellent application properties can 
be obtained. They can be used in multiple applications, for example, as 
W/O or O/W emulsifiers. The foam-stabilizing properties allow an 
application as foam strengthener, for example, in mild cosmetic cleaning 
agents or in household detergents. Other fields of application of the 
surfactant materials with the ability to complex bivalent metal ions, such 
as Ca.sup.2+, which is characteristic for polyaspartic acids, are 
detergent auxiliary agents and builders, dispersants and conditioners for 
cosmetic applications. 
At least 75% of the units present in the copolymers in accordance with the 
invention consist of structural units selected from the group consisting 
of units having the general formulas (I) and (II) 
##STR1## 
in which each structural element A is the same or different and each is a 
trifunctional hydrocarbon radical with 2 or 3 C atoms, provided that a 
copolymer contains at least three units having the formula (I), in which 
R.sup.1 can have the meaning of R.sup.2, R.sup.3 and R.sup.4, where 
R.sup.2 represents one or more residues selected from the group consisting 
of alkali metals, alkaline earth metals, hydrogen, and ammonium, i.e. 
NR.sup.5 R.sup.6 R.sup.7 R.sup.8 !.sup.+ where R.sup.5 -R.sup.8 
represent, independently of each other, hydrogen, alkyl or hydroxyalkyl, 
each preferably containing 1 to 4 carbon atoms, 
R.sup.3 represents identical or different, straight or branched, saturated 
or unsaturated alkyl residues R.sup.9 with 6-24 C atoms or radicals having 
the structure --X--R.sup.9, where X represents an oligo- or 
polyoxyalkylene chain with 1-100 oxyalkylene units, 
R.sup.4 represents identical or different, straight or branched, saturated 
or unsaturated alkyl residues with 1-5 C atoms, 
and in each case at least one residue R.sup.1 must have the meaning of 
R.sup.2 and at least one residue R.sup.1 must have the meaning of R.sup.3 
or R.sup.4, and 
the units --NH--B--CO! are residues selected from the group consisting of 
protein-forming and nonprotein-forming amino acids, and constitute not 
more than 20 wt. % of the copolymer. 
The copolymer is terminated on the terminal nitrogen seen in formulas (I) 
and (II) with --H or with the acyl residue of, e.g., maleic, fumaric, or 
succinic acid or of a salt or monoester thereof with an R.sup.2, R.sup.3 
or R.sup.4 group. The copolymer is terminated at the terminal carboxyl 
group seen in formulas (I) and (II) --OR.sup.1, with --OH or --NH.sub.2. 
As will be seen below, in a preferred form the copolymer is comprised 
between the aforementioned terminal nitrogen and carboxyl groups entirely 
of units of the formulas (I) and (II). 
DETAILED DESCRIPTION OF THE INVENTION 
Amino acid components --NH--B--CO! from the group of protein-forming amino 
acids which can be used include, for example, residues of glutamine, 
asparagine, lysine, alanine, glycine, tyrosine, tryptophan, serine and 
cysteine as well as their derivatives; the nonprotein-forming amino acid 
residues can be, for example, residues of .beta.-alanine, 
.omega.-amino-1-alkanoic acids, etc. 
Compounds in accordance with the invention include those which contain at 
least one free carboxylate group (R.sup.1 is H, metal such as alkali 
metal, or ammonium).sub.1 a residue R.sup.4 from the group of straight or 
branched chain, saturated or unsaturated alkyl residues with 1-5 C atoms 
(for example, methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, 
s-butyl, n-pentyl) and a residue R.sup.3, identical or different radicals 
with the structure R.sup.9 --X--, where R.sup.9 originates from the group 
of straight or branched, saturated or unsaturated alkyl residues with 6-24 
C atoms (for example, branched or linear octyl, decyl, dodecyl, 
tetradecyl, hexadecyl, octadecyl, docosyl residues, and also unsaturated 
or polyunsaturated species such as, for example, oleyl) and X, a 
polyoxyalkylene chain of 0-100 alkylene glycol units, is preferably 
derived from ethylene oxide, propylene oxide or mixtures thereof. A 
preferred form of the copolymer in accordance with the invention contains 
alkyl residues R.sup.10 with 8-24 C atoms without alkylene glycol spacer 
(alkylene glycol chain length=0). 
It is particularly advantageous to use copolymers in accordance with the 
invention which are compounds derived from polyaspartic acid, where A is a 
trifunctional radical with 2 C atoms having the structure (A1) or (A2) 
##STR2## 
The manufacture of the copolymers can be carried out by the sequential 
reaction of polyaspartic acid imide (polysuccinimide, prepared, for 
example, in accordance with U.S. Pat. No. 5,219,952) with alcohols R.sup.4 
OH in a first step and, should the situation arise, following with partial 
reaction with alcohols R.sup.3 OH. Here R.sup.3 and R.sup.4 have the 
above-indicated meanings. It is preferred that R.sup.4 is a straight or 
branched alkyl residue with 1-4 C atoms. Preferably R.sup.3 is a straight 
or branched, saturated or unsaturated alkyl residue with 8-24 C atoms. If 
polyoxyalkylene chains X are to be present, they are preferably derived 
from ethylene oxide, propylene oxide or mixtures thereof. In a third step, 
the ester groups derived from R.sup.4 OH can be partially or completely 
hydrolyzed under mild conditions, with the release of the carboxylic acid 
or carboxylic groups which are characteristic for the copolymers in 
accordance with the invention. In this process, the ester groups of the 
long chain alcohols, which continue to characterize the copolymers in 
accordance with the invention, preferably remain intact. 
As alcohols with formula R.sup.4 OH, it is possible to use, for example, 
compounds with R.sup.4 =methyl, ethyl, n-propyl, i-propyl, n-butyl, 
i-butyl, s-butyl and n-pentyl. Methyl and ethyl alcohol are used 
particularly preferably. 
As the residue R.sup.3 it is possible to use, for example, linear or 
branched decyl, dodecyl, tetradecyl, hexadecyl, octadecyl, docosyl 
residues or unsaturated alkyl residues such as oleyl. 
A preferred method consists of reacting the aspartic acid imide with an 
excess of the alcohol at 1-20 bar and 65-200.degree. C. for 6-48 h, with 
or without the addition of additional solvent, such as dimethyl sulfoxide, 
dimethylformamide, ethylene glycol, oligoethylene glycol, mono- and 
oligoethylene glycol alkyl ether with or without the presence of an acidic 
or basic catalyst, preferably a mineral acid, organic acids, acidic ion 
exchangers, alkali or alkaline earth salts of organic or mineral acids, 
alkali and alkaline earth hydroxides, alkoxylates, particularly preferably 
alkali or alkaline earth alkoxylates of the alcohols used. 
An additional method for the preparation of the copolymers in accordance 
with the invention is characterized in that one or more monoesters of 
monoethylenically unsaturated dicarboxylic acids is reacted with ammonia 
or the ammonium salts of these acids are thermally transformed into the 
polymer. It is possible to use derivatives of maleic acid, fumaric acid, 
itaconic acid, alkenylsuccinic acid, alkylmaleic acid, citraconic acid or 
their ammonium salts, preferably derivatives of maleic acid, fumaric acid 
or itaconic acid, and particularly preferably maleic acid derivatives 
having the formulas (III) and (IV) 
##STR3## 
where Z denotes hydrogen and/or ammonium, and R.sup.3 and R.sup.4 denote 
the above-mentioned residues. These maleic acid derivatives can in each 
case be used separately or in a mixture. 
Preferably used residues R.sup.3 are alkyl residues with 8-24 C atoms 
without a polyalkylene glycol portion, for example, linear or branched 
decyl, dodecyl, tetradecyl, hexadecyl, octadecyl or docosyl residues as 
well as unsaturated alkyl residues, such as, for example, oleyl. Residues 
R.sup.4 which are preferably used are alkyl residues with 1-4 C atoms 
without a polyalkylene glycol portion, preferably methyl, ethyl, n-propyl, 
i-propyl, n-butyl, i-butyl, or b-butyl. The ratio of components (III) and 
(IV) is preferably between 100:0 and 10:90, particularly preferably 
between 75:25 and 25:75. 
In the method in accordance with the invention, the maleic acid monoesters 
are reacted with 0.5-1.5, preferably 0.8-1.5, equivalents of ammonia (as 
ammonia gas or solution). The reaction can be conducted with or without 
the addition of an organic solvent. Possible solvents are alcohols, 
ethers, oligo- and poly(alkylene) glycols or glycol ethers, dimethyl 
sulfoxide and dimethylformamide. If a solvent is used, it is preferred to 
use a short-chain alcohol R.sup.4 OH. The reaction takes place at 
temperatures of 0-150.degree. C., preferably 40-120.degree. C. A preferred 
process consists, for example, of the reaction of maleic acid monoalkyl 
ester and aqueous or gaseous ammonia at 50-70.degree. C., removal of any 
water originating from the ammonia solution or the reaction water at a 
reduced pressure and 20-120.degree. C., preferably 50-80.degree. C., and, 
still at reduced pressure, at a slowly increasing temperature up to 
90-150.degree. C., preferably 100-120.degree. C., with stirring of the 
reaction mixture, which becomes increasingly viscous. During this time, 
the conversion to copolymer takes place. Under the reaction conditions, a 
portion of the ester groups, preferably those derived from R.sup.4 OH, is 
simultaneously hydrolyzed and the desired carboxylic acid or carboxylate 
groups are released. Under the reaction conditions, the formation of 
cyclic imide structures (V) from the hydrolyzed aspartic acid units (VI) 
occurs to only a secondary degree. 
##STR4## 
In addition, it can be assumed that imide structures (V) present in the 
product are additionally opened under the application conditions in the 
presence of an aqueous medium with release of the acid units (VI). 
By a mild partial or complete hydrolysis, preferably of the ester functions 
derived from the short-chain alcohol R.sup.4 OH, if desired, the 
proportion of free acid groups or carboxylate groups can be further 
increased. For the hydrolysis, solutions or suspensions of the copolymer 
in organic solvents are reacted with water or steam, or the copolymers are 
hydrolyzed in water with or without the addition of organic cosolvents. 
This reaction can take place without catalyst or in the presence of 
organic or mineral acids, acidic ion exchangers or acidic minerals or 
basic compounds such as metal hydroxides or amines. It is preferred to use 
as bases alkali metal hydroxides or alkaline earth metal hydroxides, for 
example, sodium hydroxide and potassium hydroxide, in catalytic or 
stoichiometric quantities. 
By the addition of amino and carboxy functional compounds to the reaction 
mixture, copolymers can be obtained in which the available units are bound 
by amide bonds. Suitable compounds are polyamino acids from the group of 
the 20 protein-forming amino acids, which are contained as monomers in all 
natural proteins, in pure enantiomeric or racemic form, such as, for 
example, glutamine, asparagine, lysine, alanine, glycine, tyrosine, 
tryptophan, serine and cysteine as well as their derivatives, or 
nonprotein-forming amino acids with, in each case, one or more amino or 
carboxy functions such as, for example, .beta.-alanine or .omega.-amino-1 
alkanoic acids. The components, preferably 0-20 wt. %, are added to the 
starting mixture of the maleic acid derivatives or they are reacted for 
the modification of the chain ends after complete synthesis of the polymer 
with the polymer, preferably with the addition of polar solvents, such as, 
for example, alcohols or dimethylformamide. 
The copolymers in accordance with the invention present excellent 
properties as sequestrant, as additives to colors or lacquers and, 
particularly, in the stabilization of O/W or W/O emulsions and as foam 
stabilizers. Because of their structure which is derived from polyamino 
acids, they present a high environmental compatibility. 
Examples of copolymers in accordance with the invention are: 
##STR5## 
For simplification, all the structures given as examples are shown with the 
.alpha.-linkage (VII); this does not represent a statement of the actual 
ratio of .alpha./.beta. structures in the polymers in accordance with the 
invention. 
##STR6##

EXAMPLE 1 
In a 200-mL flask with an agitator producing high shear forces, a 
thermometer and a distillation attachment, 710 g maleic acid monododecyl 
ester (2.5 mol), 360 g maleic acid monoethyl ester (2.5 mol) and 100 mL 
n-butanol were heated to 50.degree. C. Over 20 min, 340 g 25% aqueous 
ammonia solution (5 mol) was added dropwise at a maximum temperature of 
70.degree. C. After a reaction time of 30 min, with slow pressure 
reduction to 30 mbar and at a maximum temperature of 80.degree. C., water 
and butanol were separated by distillation over 2 h. As soon as no water 
visibly condensed in the condenser, the preparation was slowly heated to 
110.degree. C. under a vacuum within 6 h. Then a yellow-brown, 
caramel-like composition was obtained. Analysis by .sup.13 C-NMR showed 
the composition was a partially esterified polyaspartic acid, with a ratio 
of --COOH:--COOC.sub.12 H.sub.25 of approximately 1:1. The ethyl ester and 
the dodecyl alcohol portion were less than 1 mol %. The gel chromatogram, 
measured in a solution of tetrahydrofuran, showed an average molecular 
weight of approximately 900 (corresponding to a chain length of 
N=approximately 4.5; calibration against polystyrene). 
EXAMPLE 2 
500 g of the product of Example 1 was heated in an evacuable kneader heated 
to 100.degree. C. and heated slowly to 120.degree. C. within 6 h at 30 
mbar. The resulting product had a mean molecular weight of approximately 
2400 (N=approximately 12) as shown by GPC. 
EXAMPLE 3 
As described in Example 1, 422 g of maleic acid monostearyl ester (1.2 
mol), 826 g maleic acid monobutyl ester (4.8 mol), 100 mL n-butanol and 
408 g 25% ammonia solution (6 mol) were reacted. The resulting solid, 
slightly tacky product showed by .sup.13 C-NMR a ratio of the groups 
--COOH:--COOC.sub.4 H.sub.9 :--COOC.sub.18 H.sub.37 of approximately 750 
(N=approximately 4.3). 
EXAMPLE 4 
500 g of the product of Example 3 was further processed as described under 
Example 2 to increase the molecular weight. The resulting solid product 
had a mean molecular weight of approximately 2000 (N=approximately 11.5) 
as shown by GPC. 
EXAMPLE 5 
As described in Example 1, 1098 g maleic acid monooleyl ester (3 mol), 316 
g itaconic acid monoethyl ester (2 mol) and 100 mL n-butanol were reacted 
with 340 g 25% ammonia solution (5 mol). The resulting highly viscous 
product showed by .sup.13 C-NMR a ratio of --COOH:--COOC.sub.18 H.sub.35 
of approximately 0.7:1. GPC showed a mean molecular weight of 
approximately 1100 (N=approximately 4.1). 
EXAMPLE 6 
485 g polyaspartic acid imide (mean MW 1500), 800 g methanol and 17.8 g 
sodium methylate were heated to 170.degree. C. in a pressure apparatus at 
18 bar. These conditions were maintained for over 8 h. After cooling, the 
residue (35 g) was separated by filtration, and the excess methanol was 
separated by distillation at 100.degree. C. and 30 mbar. GPC of the 
remaining residue showed a mean molecular weight of approximately 1400. 
The degree of esterification was 78% as shown by .sup.13 C-NMR. The 
product was dissolved in 2000 g dimethylformamide. In a 400-mL apparatus 
with agitator, thermometer, column, reflux condenser and cold trap, 535 g 
oleyl alcohol and 9 g tetraisopropyl titanate were added under nitrogen to 
the solution of the product. The preparation was heated (approximately 
125.degree. C.) at approximately 300 mbar until reflux of the 
dimethylformamide was obtained. The performance of the column was adjusted 
in such a manner that only methanol condensed in the cold trap. After 5 h 
reaction time, the column was separated and the dimethylformamide was 
removed by distillation at 30 mbar. .sup.13 C-NMR showed a 
transesterification degree of 88% of the theoretical. The product was 
heated with 400 g water and 5 g sodium hydroxide for 1 h at 60.degree. C. 
and then, for the conversion to the salt, was converted into the free acid 
by means of a column with a highly acidic ion exchanger (LEWATIT SPC 108, 
Bayer AG). Then the water and the methanol produced were drawn off in a 
rotary evaporator at approximately 30 mbar. The resulting product had a 
--COOH:--COOC.sub.18 H.sub.35 ratio of approximately 1:0.8 and a mean 
molecular weight of 1200 (N=approximately 5.3). 
EXAMPLE 7 
485 g polyaspartic acid imide (mean MW 1500), 1480 g n-butanol and 31.1 g 
sodium n-butyrate were heated to 180.degree. C. in a pressure apparatus at 
5 bar for 10 h. After cooling, the mixture was filtered and excess 
n-butanol was removed by distillation to 100.degree. C. and 30 mbar. GPC 
of the remaining residue showed a mean MW of approximately 1200. The 
degree of esterification was 69% as shown by .sup.13 C-NMR. 
EXAMPLE 8 
As described in Example 1, 710 g maleic acid monododecyl ester (2.5 mol), 
860 g maleic acid monobutyl ester (5.0 mol), 300 mL n-butanol and 510 g 
25% ammonia solution (7.5 mol) and 36 g (0.4 mol) DL-alanine were reacted. 
The resulting, slightly tacky product showed by 13C-NMR a ratio of the 
groups --COOH:--COOC.sub.4 H.sub.9 :--COOC.sub.12 H.sub.25 :Ala of 
approximately 1.6:0.5:1.0:1.5. GPC showed a mean molecular weight of 
approximately 645 (N=approximately 3.7). 
EXAMPLES 9 TO 12 
Using the products of Examples 1,3,5 and 6, the following preparation with 
sodium lauryl ether sulfate solution (28% in water, subsequently called 
NaLES) were prepared: 
______________________________________ 
Amount 
(g) of 
Product Amount 0.1M Amount 
of (g) of NaOH (g) of Water 
Example 
Example Product solution 
NaLES (g) 
______________________________________ 
9 1 10 23 40 0 
10 3 10 0 40 23 
11 5 10 0 40 23 
12 6 10 11 40 12 
______________________________________ 
0.07 g of each preparation was dissolved separately in 200 mL water. For 
comparison, 0.1 g of a preparation of 40 g NaLES and 31.2 g of an acylated 
protein hydrolysate solution were dissolved in 200 mL. In a 1000-mL 
graduated cylinder these solutions were agitated to generate foam, using a 
turbine. Then the decrease in the volume of the foam was observed. The 
results are presented in the following table (values in mL): 
______________________________________ 
Time after 
turbine Comparison 
shutoff Ex. 9 Ex. 10 Ex. 11 Ex. 12 example 
______________________________________ 
Immediately 
160 200 170 180 150 
30 Min. 150 180 160 170 120 
60 Min. 140 180 160 170 120 
3 Hrs. 130 160 150 160 110 
6 Hrs. 120 150 130 150 100 
24 Hrs. 100 120 100 110 70 
______________________________________ 
EXAMPLE 13 
7.5 g of the product Example 2 was dissolved at 50.degree. C. in 67.5 g of 
low viscosity paraffin oil (5.degree. Engler). In an agitator set at high 
speed, 75.0 g water was added. An O/W emulsion was obtained which remained 
stable over a test period of 3 weeks. 
EXAMPLE 14 
15.0 g of the product of Example 4 was stirred with 100.0 g water. During 
this time, the pH value was adjusted to 7 by the slow addition of 29 mL 
diluted NaOH (0.1 mol/L). 114 g paraffin oil (5.degree. Engler) was added 
to the resulting slightly turbid solution in a high-speed agitator. The 
resulting W/O emulsion was still stable after 2 weeks. 
EXAMPLE 15 
Example 13 was repeated except for using isopropyl myristate instead of 
paraffin oil. The resulting O/W emulsion was still stable after 3 weeks.