Aqueous dispersion of a biodegradable polyester and its use thereof

The aqueous dispersion of a biodegradable aliphatic-aromatic polyester is useful as a binder for nonwovens and for coating paper.

The present invention relates to a polyester dispersion comprising water 
and a biodegradable, aliphatic-aromatic copolyester, a process for its 
preparation and its use as a binder for nonwovens and for coating paper. 
The present invention further relates to the nonwoven produced using the 
polyester dispersion of the invention, a process for its production and 
its use. 
The biodegradable copolyesters used in the aqueous polyester dispersion of 
the invention contain repeat units derived both from aromatic carboxylic 
acids or derivatives thereof and from aliphatic carboxylic acids and 
derivatives thereof and are known per se. 
For instance, U.S. Pat. No. 5,446,079 and the parallel international 
application WO 92/09654 describe a linear, random, semicrystalline 
aliphatic-aromatic copolyester having a limiting viscosity number of about 
0.5 to 1.8 dl/g, measured in 60/40 w/w phenol/tetrachloroethane at a 
concentration of 0.5 g/100 ml and at a temperature of 25.degree. C., the 
proportion of units derived from aromatic carboxylic acids being from 5 to 
65 mol % and the proportion of repeat units derived from aliphatic 
carboxylic acids being from 95 to 35 mol %, in each case based on the 
total amount of repeat units derived from carboxylic acids. Not only the 
biodegradability of such polyesters also their use as moldings, films, 
etc. are described. 
DE-A-44 32 161 describes biodegradable polyesters which are degraded in the 
natural environment and under the action of microorganisms which are 
condensed (a) from an aliphatic polyol and an aromatic polyol and an 
aliphatic polycarboxylic acid or (b) from an aliphatic polyol, optionally 
alongside an aromatic polyol, and an aromatic polycarboxylic acid as well 
as simultaneously aliphatic polycarboxylic acid, or (c) from an aromatic 
hydroxymonocarboxylic acid and an aliphatic hydroxymonocarboxylic acid as 
monomer components, the units derived from the monomer components being in 
random or alternating arrangement. 
In addition, the biodegradable polyesters used herein are likewise 
described per se in a number of commonly assigned applications (DE-A-44 40 
858, DE-A-44 40 850, DE-A-44 40 837, DE-A-44 40 836, DE-A-195 00 757, 
DE-A-195 00 756, DE-A-195 00 755, DE-A-195 00 754, DE-A-195 00 185, 
DE-A-195 05 186). 
However, none of these references describe polyester dispersions utilizing 
these polyesters. 
Polyester dispersions and their preparation are likewise known per se (see 
inter alia U.S. Pat. No. 3,546,008, EP-A-0 332 980 and EP-A-0 498 156). 
For instance, U.S. Pat. No. 3,546,008 describes fibrous products treated 
with a size comprising a linear polyester which disperses in water. This 
polyester is prepared starting from at least one carboxylic acid, at least 
one diol, provided at least 20% of the diol is polyethylene glycol, and a 
monomer having an SO.sub.3 M group, where M is hydrogen or a metal ion. 
Copolyesters of the type contemplated herein are not mentioned in this 
reference. Polyesters derived from carboxylic acid mixtures comprising 
hexahydroisophthalic acid and from a diol are exemplified. Such polyesters 
are not biodegradable, however. 
EP-A-0 332 980 relates to a process for preparing aqueous polyester 
dispersions by condensing aromatic dicarboxylic acids or esters with at 
least one diol to form prepolymers having an acid number from 2 to 8. 
These prepolymers are subsequently reacted with at least one molecular 
weight enhancer compound to form polyesters having acid numbers of 40 to 
60 and the polyester is dispersed by addition of aqueous mixtures of 
ammonia and amines in a molar ratio of 10:1 to 1:10 to a polyester melt 
having a temperature within the range from 150 to 210.degree. C. The 
reference further relates to the use of these polyester dispersions as 
sizes for sizing filament warp yarns. The polyesters used in this 
reference, which are based on aromatic dicarboxylic acids, have excellent 
mechanical properties, but virtually no biodegradability. 
EP-A-0 498 156 describes aqueous polyesters for high solids baking finishes 
wherein the urethane-, carboxyl- and hydroxyl-functional polyester resin 
described has a hydroxyl number of 40 to 110 and a urethane group content 
of 6.5 to 11% by weight. Such polyesters have relatively high tackiness 
and unsatisfactory mechanical strength and are therefore unsuitable for 
the applications contemplated in this invention. 
Nonwovens suitable for composting are known. 
For instance, EP-A-0 591 821 describes a compostable nonwoven bonded with 
from 5 to 100% by weight, based on the weight of the fiber used, of an 
addition polymer which has a glass transition temperature of -70 to 
+40.degree. C. and which is preparable by free-radical polymerization of 
ethylenically unsaturated monomers comprising 0.5 to 15% by weight of 
N-alkylolamides of .alpha.,.beta.-monoethylenically unsaturated carboxylic 
acids having 3 to 10 carbon atoms, acrylamidoglycolic acids, 
methacrylamidoglycolic acid and/or their ethers, esters or ether-esters 
with alcohols having up to 12 carbon atoms in an aqueous medium in the 
presence of a saccharide, and also its preparation and use. 
DE-A-41 21 085 describes a biodegradable film or molded article prepared 
from a composition comprising 100 parts by weight of cellulose fibers 
having a length of 3 mm or less and a diameter of 50 mm or less, 10 to 600 
parts by weight of a thermoplastic resin and 2 to 100 parts by weight of 
chitosan. Thermoplastic resins mentioned are polyvinyl alcohols, 
polyurethanes and aliphatic polyesters. Here too the resulting 
biodegradable articles generally lack mechanical strength, owing to the 
thermoplastic resins used, and, what is more, are frequently tacky. 
Furthermore, Canadian Patent Application CA 2 057 669 describes 
biodegradable aliphatic polyesters useful as binders for impregnating or 
coating fibrous fabrics. These polyesters are admittedly, as briefly 
mentioned above, very readily biodegradable, but generally they possess 
inadequate mechanical properties and relatively poor processibility. 
It is an object of the present invention to provide aqueous biodegradable 
polyester dispersions possessing excellent mechanical properties combined 
with good processibility. In addition, the biodegradability, i.e. the time 
to essentially complete degradation, of the copolyesters used and of the 
nonwovens treated therewith shall be variable within a considerable time 
span. 
We have found that this object is achieved by a polyester dispersion 
comprising 
(A) from 20 to 90% by weight of water, and 
(B) from 10 to 80% by weight of a biodegradable copolyester (B) containing 
structural units derived from both aliphatic and aromatic carboxylic acids 
or derivatives thereof, obtainable by reaction of a mixture comprising 
(a1) a mixture comprising 
(a11) from 20 to 95 mol % of adipic acid or of an ester-forming derivative 
thereof or of a mixture of two or more thereof, 
(a12) from 5 to 80 mol % of terephthalic acid or of an ester-forming 
derivative thereof or of a mixture of two or more thereof, 
(a13) from 0 to 10 mol % of a sulfonate compound or of a mixture of two or 
more thereof, 
the sum total of the individual mol %ages being 100, 
(a2) a dihydroxy compound or an aminoalcohol or a mixture of two or more 
thereof, 
the molar ratio of (a1) to (a2) being within the range from 0.4:1 to 2.5:1, 
(a3) from 0.01 to 10% by weight, based on mixture (a1), of a chain extender 
from the group consisting of the diisocyanates, divinyl ethers and the 
2,2'bisoxazoline of the 
##STR1## 
where R.sup.1 is a single bond, a (CH.sub.2).sub.q alkylene group, where q 
is 2, 3 or 4, or a phenylene group, or of a mixture of two or more 
thereof, and 
(a4) from 0 to 20% by weight, based on mixture (a1), of a compound having 
at least three groups capable of ester formation or of a mixture of two or 
more thereof, 
wherein 
the repeat units derived from (a11) and (a12) carboxylic acid form a random 
distribution, the copolyester has a viscosity number within the range from 
5 to 450 ml/g (measured in 50/50 w/w o-dichlorobenzene phenol at a 
concentration of 0.5% by weight of copolyester at 25.degree. C.), and the 
proportions of components (a13) and (a4) are not zero at the same time. 
As used herein "biodegradable" describes the fact that the copolyesters are 
broken down over a suitable and verifiable period by environmental 
effects. Degradation is in general hydrolytic and/or oxidative, but 
predominantly due to the action of microorganisms such as bacteria, 
yeasts, fungi and algae. Degradation can also take place enzymatically, as 
described for example by Y. Tokiwa and T. Suzuki in Nature 270 (1977), 
76-78. The present invention makes it possible, through appropriate 
selection of the ratio between repeat units derived from aliphatic 
carboxylic acids and repeat units derived from aromatic carboxylic acids, 
to vary the rate of the biological degradation process, i.e. the time to 
essentially complete degradation of the polyesters used in accordance with 
this invention. The rule of thumb is that the rate of biodegradation of 
the copolyesters increases with the proportion of repeat units derived 
from aliphatic carboxylic acids. Furthermore, the rate of bio-degradation 
of the copolyesters increases with the proportion of segments having an 
alternating sequence of repeat units derived from aliphatic and aromatic 
carboxylic acids or derivatives thereof. 
The polyester dispersion of the invention comprises from about 10 to about 
80, preferably from about 20 to about 60, in particular from about 20 to 
about 40,% by weight of solids, i.e. of the copolyester used according to 
this invention. 
The aliphatic dicarboxylic acid which is useful for the purposes of the 
present invention is adipic acid. 
Suitable ester-forming derivatives for the adipic acid are in particular 
the di-C.sub.1 -C.sub.6 -alkyl esters, for example the dimethyl, diethyl, 
dipropyl, dibutyl, dipentyl and dihexyl esters. 
The adipic acid or ester-forming derivatives thereof can be used alone or 
as a mixture of two or more thereof. 
The proportion of adipic acid or its ester-forming derivatives is generally 
within the range from about 20 to 95, preferably from about 30 to about 
70, in particular from about 40 to about 60, mol %, based on the total 
amount of components (a11) to (a13). 
The aromatic dicarboxylic acid used according to the invention is 
terephthalic acid or an ester-forming derivative thereof. Especially the 
di-C.sub.1 -C.sub.6 -alkyl esters, for example the dimethyl, diethyl, 
dipropyl, dibutyl, dipentyl and dihexyl esters, are suitable. 
The terephthalic acid or its ester-forming derivatives (a12) can be used 
individually or as a mixture of two or more thereof. 
The proportion of terephthalic acid or ester-forming derivatives thereof is 
generally within the range from about 5 to about 80, preferably from about 
30 to about 70, in particular from about 40 to about 60, mol %, based on 
the total amount of components (a11) to (a13). 
The sulfonate compound (a13) used in this invention is customarily an 
alkali metal or alkaline earth metal salt of a sulfonate-functional 
dicarboxylic acid or its ester-forming derivatives, preferably alkali 
metal salts of 5-sulfoisophthalic acid or mixtures thereof, especially the 
sodium salt. The proportion of sulfonate compound (a13) is within the 
range from 0 to about 10, preferably from 0 to about 5, in particular from 
about 3 to about 5, mol %, based on the total amount of components (a11) 
to (a13). 
The sulfonate compounds can be used individually or as a mixture of two or 
more thereof. 
Component (a2) of this invention is a dihydroxy compound or aminoalcohol or 
a mixture of two or more thereof. In principle, any diols or aminoalcohols 
known in ester-making can be used. 
In general, however, component (a2) is selected from (a21) alkanediols 
having from 2 to 12 carbon atoms, preferably 4 to 6 carbon atoms, or 
cycloalkanediols having from 5 to 10 carbon atoms, (a22) polyetherdiols, 
i.e. dihydroxy compounds containing ether groups, and (a23) aminoalcohols 
having from 2 to 12 carbon atoms, preferably from 2 to 4 carbon atoms, and 
also aminocycloalcohols having from 5 to 10 carbon atoms. 
Specific examples are ethylene glycol, 1,2-propanediol, 1,3-propanediol, 
1,2-butanediol, 1,4-butanediol, 1,5-pentanediol, 
2,4-dimethyl-2-ethylhexane-1,3-diol, 2,2-dimethyl-1,3-propanediol, 
2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl-1,3-propanediol, 
2,2,4-trimethyl-1,6-hexanediol, especially ethylene glycol, 
1,3-propanediol, 1,4-butanediol and 2,2-dimethyl-1,3-propanediol 
(neopentylglycol); cyclopentanediol, 1,4-cyclohexanediol, 
1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 
1,4-cyclohexanedimethanol and 2,2,4,4-tetramethyl-1,3-cyclobutanediol; 
diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene 
glycol and polytetrahydrofuran, especially diethylene glycol, triethylene 
glycol and polyethylene glycol, or mixtures thereof, or compounds which 
have a differing number of ether units, for example polyethylene glycol 
which contains propylene units and can be obtained for example by 
conventional polymerization of first ethylene oxide and then propylene 
oxide. The molecular weight (Mn) of the polyethylene glycols which can be 
used is generally within the range from about 250 to about 8000, 
preferably within the range from about 600 to about 3000, g/mol; 
4-aminomethylcyclohexanemethanol, 2-aminoethanol, 3-aminopropanol, 
4-aminobutanol, 5-aminopentanol, 6-aminohexanol; aminocyclopentanol and 
aminocyclohexanol; or mixtures thereof. 
The dihydroxy compounds or aminoalcohols can be used individually or as a 
mixture of two or more thereof. 
The molar ratio of (a1) to (a2) is generally chosen within the range from 
about 0.4:1 to about 2.5:1, preferably within the range from about 0.5:1 
to about 1.5:1, more preferably within the range from about 0.5:1 to about 
1.2:1, especially within the range from about 0.5:1 to about 1:1. 
The molar ratio of (a1) and (a2) in the isolated copolyester following the 
removal of the desired amount of excess component (a2) is within the range 
from about 0.4:1 to about 1.5:1, preferably within the range from about 
0.5:1 to about 1.2:1, especially within the range from about 0.5:1 to 
about 1:1. 
The proportion of chain extenders (a3) is within the range from about 0.01 
to about 10, preferably within the range from about 0.05 to about 5, more 
preferably within the range from about 0.07 to about 4, especially within 
the range from about 0.1 to about 1%, by weight, based on mixture (a1). 
Suitable chain extenders (a3) for use herein are diisocyanates, for example 
toluylene 2,4-diisocyanate, toluylene 2,6-diisocyanate, 4,4'- and 
2,4'-diphenylmethane diisocyanate, naphthylene 1,5-diisocyanate, xylylene 
diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate and 
methylenebis(4-isocyanato-cyclohexane), especially hexamethylene 
diisocyanate; divinyl ethers, for example 1,4-butanediol divinyl ether, 
1,6-hexanediol divinyl ether and 1,4-cyclohexane-dimethanol divinyl ether; 
and also 2,2'-bisoxazolines of the general formula (I) 
##STR2## 
The latter are generally obatinable by the process of Angew. Chem. Int. 
Edit. 11 (1972), 287-288. Particularly preferred bisoxazolines are those 
in which R.sup.1 is a single bond, a (CH.sub.2).sub.q -alkylene group 
having q=2, 3 or 4 such as methylene, 1,2-ethanediyl, 1,3-propanediyl, 
1,2-propanediyl, 1,4-butanediyl or a phenylene group. Particular 
preference is given to 2,2'-bis(2-oxazoline), bis(2-oxazolinyl)methane, 
1,2-bis(2-oxazolinyl)ethane, 1,3-bis(2-oxazolinyl)propane, 
1,4-bis(2-oxazolinyl)butane, 1,4-bis(2-oxazolinyl)benzene, 
1,2-bis(2-oxazolinyl)benzene and 1,3-bis(2-oxazolinyl)benzene. 
The chain extenders (a3) can also be used as a mixture of two or more 
thereof. 
This invention further contemplates the use of a compound having at least 
three groups capable of ester formation, (a4), or of a mixture of two or 
more thereof, in an amount, if present at all, within the range from about 
0.01 to about 20, preferably from about 1 to about 10, more preferably 
from about 3 to about 7, especially from about 3 to about 5%, by weight, 
based on mixture (a1). 
The compounds used as compounds (a4) preferably contain from 3 to 10 
functional groups capable of forming ester bonds. Particularly preferred 
compounds (a4) have from 3 to 6 functional groups of this kind in the 
molecule, especially from 3 to 6 hydroxyl groups and/or carboxyl groups. 
Particular preference is given to using tri- and/or tetrafunctional 
carboxylic acids or derivatives thereof. Specific examples are tartaric 
acid, citric acid, malic acid, trimethylolpropane, trimethylolethane, 
pentaerythritol, polyethertriols, glycerol, trimesic acid, trimellitic 
acid, trimellitic anhydride, pyromellitic acid, pyromellitic dianhydride 
and hydroxyisophthalic acid. 
By including the chain extenders (a3) and/or the compounds (a4) it is 
possible for example to modify the melt viscosity, the limiting viscosity 
number or the molecular weight in a desired manner compared with 
polyesters without added chain extenders (a3) and/or compounds (a4), to 
raise the limiting viscosity number and the molecular weight accordingly 
and so vary the mechanical properties of the polyesters in accordance with 
the particular application. 
Here it has to be noted that, according to the invention, at least one 
component (a13) and/or (a4) has to be present at all times in order that 
the copolyester may have free acid groups. 
If desired, the copolyesters (B) can have as further component 
trifunctional isocyanate compounds which comprise isocyanurate and/or 
biuret groups having a functionality of not less than 3. 
In a further embodiment, the present invention relates to a polyester 
dispersion comprising 
(A) from 20 to 90% by weight of water, and 
(B) from 10 to 80% by weight of a biodegradable copolyester (B1) containing 
structural units derived from both aliphatic and aromatic carboxylic acids 
or derivatives thereof, 
obtainable by reaction of a mixture comprising 
(a1) a mixture comprising 
(a11) from 20 to 95 mol % of adipic acid or of an ester-forming derivative 
thereof or of a mixture of two or more thereof, 
(a12) from 5 to 80 mol % of terephthalic acid or of an ester-forming 
derivative thereof or of a mixture of two or more thereof, 
(a13) from 0 to 10 mol % of a sulfonate compound or of a mixture of two or 
more thereof, 
the sum total of the individual mol %ages being 100, 
(a2) a dihydroxy compound or an aminoalcohol or a mixture of two or more 
thereof, 
the molar ratio of (a1) to (a2) being within the range from 0.4:1 to 2.5:1, 
(a3) from 0 to 10% by weight, based on mixture (a1), of a chain extender 
from the group consisting of the diisocyanates, dinvinyl ethers and the 
2,2'-bisoxazolines of the 
##STR3## 
where R.sup.1 is a single bond, a (CH.sub.2).sub.q alkylene group, where q 
is 2, 3 or 4, or a phenylene group, or of a mixture of two or more 
thereof, 
(a4) from 0 to 20% by weight, based on mixture (a1), of a compound having 
at least three groups capable of ester formation or of a mixture of two or 
more thereof, 
(b1) from 0.01 to 100% by weight, based on mixture (a1), of a 
hydroxycarboxylic acid (b1) defined by the following formula IIa or IIb 
##STR4## 
where p is an integer from 1 to 1500, r is 1, 2, 3 or 4, and G is 
phenylene, --(CH.sub.2).sub.n --, where n is 1, 2, 3, 4 or 5, --C(R)H-- or 
--C(R)HCH.sub.2 --, where R is methyl or ethyl, 
or of a mixture of two or more thereof, 
wherein the repeat units derived from the (cyclo)-aliphatic and aromatic 
carboxylic acid form a random distribution, the copolyester has a 
viscosity number within the range from 5 to 450 ml/g (measured in 50/50 
w/w o-dichlorobenzene/phenol at a concentration of 0.5% by weight of 
copolyester at 25.degree. C.), and the proportions of components (a13) and 
(14) are not zero at the same time. 
In the above formula, p is preferably from 1 to about 1000, r is preferably 
1 or 2, and n is preferably 1 or 5. 
The level of hydroxycarboxylic acid (b1) in the reaction mixture is 
preferably within the range from about 0.1 to 80% by weight, based on 
mixture (a1). 
Hydroxycarboxylic acid (b1) is preferably glycolic acid, D-lactic acid, 
L-lactic acid, D,L-lactic acid, 6-hydroxy-hexanoic acid, their cyclic 
derivatives such as glycolide (1,4-dioxane-2,5-dione), D- or L-dilactide 
(3,6-dimethyl-1,4-dioxane-2,5-dione), p-hydroxybenzoic acid and also their 
oligomers and polymers such as 3-polyhydroxybutyric acid, 
polyhydroxyvaleric acid, polylactide (obtainable for example as 
EcoPLA.RTM. (fr. Cargill)) and also a mixture of 3-polyhydroxybutyric acid 
and polyhydroxyvaleric acid (the latter is obtainable from Zeneca under 
the name of Biopol.RTM.), and the above-defined low molecular weight and 
cyclic derivatives are used. 
It is of course also possible to use mixtures of two or more of the 
above-defined hydroxycarboxylic acids. 
In a further embodiment, the use of cyclic derivatives of the 
above-described hydroxycarboxylic acids (b1) in the reaction with the 
biodegradable copolyester used according to the invention results, through 
a conventional ring-opening polymerization, in copolyesters of the 
above-defined type which contain block structures consisting of the 
copolyester (B) used according to this invention which are in each case 
linked together by at least one hydroxycarboxylic acid unit (b1) (re 
ring-opening polymerization see Encyclopedia of Polymer Science and 
Engineering, Vol. 12, 2nd Ed., John Wiley & Sons, 1988, pages 36-41). 
Copolyesters whose use is particularly preferred in the present invention 
have the following composition as regards components (a11), (a12) and 
(a2), although it has to be taken into account that these copolyesters can 
not only have sulfonic acid groups but also contain the chain extenders 
and/or compounds defined as components (a3) and (a4). The parenthetical 
values following the respective component correspond to the proportion of 
this component, expressed in mol %: 
terephthalic acid (40)--adipic acid (60)--butanediol (100), 
terephthalic acid (30)--adipic acid (70)--butanediol (100). 
The copolyesters used according to the invention are characterized by the 
following features: 
They have a viscosity number within the range from about 5 to 450 ml/g, 
preferably within the range from about 50 to about 350 ml/g, more 
preferably within the range from about 100 to about 350 ml/g, especially 
within the range from about 200 to about 350 ml/g, in each case measured 
in 50/50 w/w o-dichlorobenzene/phenol at a concentration of 0.5% by weight 
of copolyester at 25.degree. C. 
The copolyesters used according to the invention further possess both 
hydroxyl and carboxyl end groups. 
The hydroxyl number of the copolyesters used according to the invention is 
within the range from 0 to about 30, preferably within the range from 0 to 
about 20, in particular within the range from 0 to about 10. 
For further details of the (cyclo)aliphatic dicarboxylic acids, aromatic 
dicarboxylic acids, diols and/or amino-alcohols usable in this invention 
and also of the further components (a3), (a4) and (b1) reference is made 
to the commonly assigned patent applications mentioned at the beginning in 
the discussion of background art and to U.S. Pat. No. 5,446,079, or the 
parallel Application WO92/09654, incorporated herein by reference for the 
copolyesters and their preparation described therein. 
None the less, the preparation of the copolyesters used according to the 
invention will now be briefly described. 
This preparation of polyesters is known in principle (Sorensen and 
Campbell, Preparative Methods of Polymer Chemistry, Interscience 
Publishers, Inc., New York, 1961, pages 111-127; Encyclopedia of Polymer 
Science and Engineering, Vol. 12, 2nd Ed., John Wiley & Sons, 1988, pages 
1-75; Kunststoffhandbuch, Vol. 3/1, Carl Hanser Verlag, Munich, 1992, 
pages 15-23 (Herstellung von Polyestern); and also the aforementioned 
patent applications. 
For instance, the reaction of (a1)-comprised dimethyl esters of 
dicarboxylic acids (a11/a12) with component (a2) ("transesterification") 
and optionally components (a13) and/or (b1) can be carried out at 
temperatures within the range from about 160 to about 230.degree. C. in 
the melt at atmospheric pressure, preferably under an inert gas 
atmosphere. 
It is advantageous to prepare the biodegradable copolyester used according 
to the invention using a molar excess of component (a2), based on the 
dicarboxylic acids used, for example up to an excess of not more than 
about 2.5-fold, generally up to about 1.5-fold. 
The preparation of the abovementioned copolyester is customarily effected 
in the presence of suitable conventional catalysts such as metal compounds 
based on the following elements such as Ti, Ge, Zn, Fe, Mn, Co, Zr, V, Ir, 
La, Ce, Li and Ca, preferably organometallic compounds based on these 
metals such as salts of organic acids, alkoxides, acetylacetonates and the 
like, especially on the basis of Zn, Sn and Ti. 
The reaction of components (a1), (a2) and optionally (b1) is generally 
carried out under reduced pressure or in an inert gas stream, for example 
under nitrogen, and under continued heating to a temperature within the 
range from 180 to 260.degree. C. until the desired molecular weight having 
regard to the desired molar ratio of carboxyl end groups to hydroxyl end 
groups. Subsequently, (a3) and/or (a4) can generally be added at 
atmospheric pressure at a temperature within the range from about 50 to 
about 200.degree. C., preferably under an inert gas, to continue the 
reaction. 
To avoid undesirable degradation and/or side reactions, this process step 
can, if desired, also be carried out in the presence of stabilizers, the 
amount of which should be kept as low as possible and is generally within 
the range from 0.1 to 200 ppm, based on the copolyester. Examples of such 
stabilizers are phosphorus compounds as described for example in EP-A 13 
461, U.S. Pat. No. 4,328,049 and the abovementioned commonly assigned 
patent applications. 
The present invention accordingly further provides a process for preparing 
the aqueous polyester dispersion of the invention, which comprises 
(i) preparing a copolyester (B) in a conventional manner by reacting a 
mixture comprising 
(a1l) a mixture comprising 
(a11) from 20 to 95 mol % of adipic acid or of an ester-forming derivative 
thereof or of a mixture of two or more thereof, 
(a12) from 5 to 80 mol % of terephthalic acid or of a mixture of two or 
more thereof, 
(a13) from 0 to 10 mol % of a sulfonate compound or of a mixture of two or 
more thereof, the sum total of the individual mol %ages being 100 mol %, 
(a2) a dihydroxy compound or an aminoalcohol or a mixture of two or more 
thereof, 
the molar ratio of (a1) to (a2) being within the range from 0.4:1 to 2.5:1, 
(a3) from 0.01 to 10% by weight, based on mixture (a1), of a chain extender 
from the group consisting of the diisocyanates, dinvinyl ethers and the 
2,2'-bisoxazolines of the 
##STR5## 
where R.sup.1 is a single bond, a (CH.sub.2).sub.q alkylene group, where q 
is 2, 3 or 4, or a phenylene group, or of a mixture of two or more 
thereof, and 
(a4) from 0 to 20% by weight, based on mixture (a1), of a compound having 
at least three groups capable of ester formation or of a mixture of two or 
more thereof, 
and performing the reaction in such a way that 
the repeat units derived from (a11) and (a12) form a random distribution, 
the copolyester has a viscosity number within the range from 5 to 450 ml/g 
(measured in 50/50 w/w o-dichlorobenzene/phenol at a concentration of 0.5% 
by weight of copolyester at 25.degree. C.), and the proportions of 
components (a13) and (a4) are not zero at the same time; 
(ii) neutralizing and dispersing the resulting copolyester (B) in an 
aqueous medium using a suitable neutralizer. 
The present invention further provides a process for preparing the 
polyester dispersion of the invention, which comprises 
(i) preparing a copolyester (Bl) in a conventional manner by reacting a 
mixture comprising 
(a1) a mixture comprising 
(a11) from 20 to 95 mol % of adipic acid or of an ester-forming derivative 
thereof or of a mixture of two or more thereof, 
(a12) from 5 to 80 mol % of terephthalic acid or of a mixture of two or 
more thereof, 
(a13) from 0 to 10 mol % of a sulfonate compound or of a mixture of two or 
more thereof, 
the sum total of the individual mol %ages being 100, 
(a2) a dihydroxy compound or an aminoalcohol or a mixture of two or more 
thereof, 
the molar ratio of (a1) to (a2) being within the range from 0.4:1 to 2.5:1, 
(a3) from 0 to 10% by weight, based on mixture (a1), of a chain extender 
from the group consisting of the diisocyanates, divinyl ethers and the 
2,2'bisoxazoline of the 
##STR6## 
where R.sup.1 is a single bond, a (CH.sub.2).sub.q alkylene group, where q 
is 2, 3 or 4, or a phenylene group, or of a mixture of two or more 
thereof, and 
(a4) from 0 to 20% by weight, based on mixture (a1), of a compound having 
at least three groups capable of ester formation or of a mixture of two or 
more thereof, 
(b1) from 0.01 to 100% by weight, based on mixture (a1), of a 
hydroxycarboxylic acid (b1) defined by the following formula IIa or IIb 
##STR7## 
where p is an integer from 1 to 1500, r is 1, 2, 3 or 4, and G is 
phenylene, --(CH.sub.2).sub.n --, where n is 1, 2, 3, 4 or 5, --C(R)H-- or 
--C(R)HCH.sub.2 --, where R is methyl or ethyl, or of a mixture of two or 
more thereof, 
and performing the reaction in such a way that the repeat units derived 
from the (cyclo)aliphatic and aromatic carboxylic acid form a random or 
alternating distribution, the copolyester has a viscosity number within 
the range from 5 to 450 ml/g (measured in 50/50 w/w 
o-dichlorobenzene/phenol at a concentration of 0.5% by weight of 
copolyester at 25.degree. C.), and the proportions of components (a13) and 
(a4) are not zero at the same time; 
(ii) neutralizing and dispersing the resulting copolyester (B1) in an 
aqueous medium using a suitable neutralizer. 
In the two processes of the invention, the preparation of copolyester B or 
copolyester B1 in step (i) is carried out as extensively discussed above. 
Thereafter the copolyester obtained as per step (i), generally as a hot 
melt having a temperature within the range from about 150 to about 
230.degree. C., is admixed with an aqueous solution or dispersion of a 
neutralizer. The amount of neutralizer added is chosen so that the 
neutralizer is able to effect partial or complete neutralization of the 
acid groups, "partial neutralization" in the context of the present 
invention meaning a degree of neutralization within the range from about 
at least 70% of the carboxyl groups present in the copolyester. Water is 
generally added in such an amount as to produce an aqueous polyester 
dispersion having a polyester content within the range from about 10 to 
about 80% by weight, preferably within the range from about 20 to about 
60% by weight. The neutralizer can also be added in excess. 
As stated above, the mixture of water and a neutralizer is added to the 
polyester melt at temperatures of the melt within the range from about 150 
to about 230.degree. C., preferably at temperatures from about 150 to 
about 200.degree. C. However, the temperature should not be below 
150.degree. C., since otherwise there is a risk of not obtaining a fine 
dispersion of the polyester in water. The aqueous polyester dispersion can 
also be prepared from the melt by first slowly adding up to about half the 
amount of water required, then adding the neutralizer and finally adding 
the rest of the water. As the water, or mixture of water and neutralizer, 
is added to the melt, the temperature thereof decreases. 
On completion of the addition of the neutralizer/water mixture, the 
temperature of the resulting polyester dispersion is generally within the 
range from about 70 to about 100.degree. C. The polyester dispersion 
obtained in this way is then stirred for from 2 to 12, preferably from 4 
to 6, hours, optionally at an elevated temperature of up to 95.degree. C., 
and then cooled down to ambient temperature. 
The neutralizer used can in general be a traditional neutralizer. Specific 
examples are ammonia, triethylamine, triethanolamine, monoethanolamine, 
diethanolamine, N-methyldiethanolamine, morpholine, N-methylmorpholine, 
2-amino-2-methyl-1-propanol and mixtures of two or more thereof. 
Preference is given to using monoethanolamine, diethanolamine, 
N-methylmorpholine, methyldiethanolamine and ammonia. Alkali metal 
hydroxides such as, for example, sodium hydroxide of potassium hydroxide 
can also be used, but are less preferable. 
It is further possible, on completion of the dispersing, to distil some of 
the water back out in order that the solids content may be maximized. 
Furthermore, on completion of step (i), the resulting melt can first be 
admixed with a suitable organic solvent, for example methyl ethyl ketone, 
tetrahydrofuran or acetone, and the polymer dissolved therein, then, as 
per step (ii), admixed with a neutralizer and water to neutralize and 
disperse and subsequently subjected to a vacuum distillation to distil the 
organic solvent, which should be water-miscible or at least 
water-dispersible, back out, if desired together with excess water. 
The process of the invention affords aqueous polyester dispersions having a 
solids content from about 10 to about 80% by weight, preferably from about 
20 to about 60% by weight. 
In addition, the present invention provides for the use of the 
above-described polyester dispersions as binders for biodegradable 
nonwovens, as coatings for paper and as spray mulch. 
Suitable materials for nonwoven base webs are fibers which are 
biodegradable. These are generally fibers having a diameter from about 
0.002 to about 0.1 mm, preferably from about 0.01 to about 0.05 mm, which 
can usually be ascertained with the aid of electron micrographs. 
In general, the fibers used are natural fibers of cellulosic origin, such 
as viscose fibers or pulp fibers, or synthetic fibers, such as aliphatic 
polyester fibers, for example based on copolymers of 3-hydroxybutyrate, 
3-hydroxyvalerate and 4-hydroxyvalerate, as described in EP-A 466 050, or 
those based on aliphatic dicarboxylic acids, for example adipic acid. In 
addition, it is also possible to use synthetic fibers based on 
aliphatic-aromatic polyesters as described herein. 
Suitable cellulose fibers are fibers obtained from cellulose, hemicellulose 
or lignocellulose, obtained from wood, straw, cotton, jute, bamboo or 
bagasse, and cellulose produced by bacteria. 
The formation of webs from the fibers is common knowledge and described for 
example in Rompp, Chemie Lexikon, Georg Thieme Verlag, Stuttgart--New 
York, 9th Edition, p. 4450. The fiber webs in question can be random fiber 
webs or preferably oriented fiber webs with or without mechanical 
preconsolidation, for example in the form of needling, entangling or 
stitch bonding. 
The fiber webs are bonded using from about 5 to 100, preferably from about 
11 or more, especially from about 15 to about 50, more preferably from 
about 20 to about 35%, by weight, based on the amount of fiber web used, 
of the copolyester. 
The consolidation of the fiber webs using the polyesters is effected 
according to known methods (as described for example in Ullmann's 
Encyklopadie der technischen Chemie, 4th Edition, Vol. 23, 1983, pages 738 
to 742). The fiber web is customarily contacted or saturated with the 
polyester dispersion by bath impregnation, foam impregnation, spraying, 
padding or printing. The dispersion can if necessary be additionally 
diluted with water or else thickened with customary thickeners to obtain 
the desired processing viscosity. The treatment of the web with the 
dispersion is generally followed by an operation of drying and heating the 
resulting nonwoven fabric. The drying conditions depend on the type of 
dryer used; the drying temperature is customarily within the range from 
100 to 230.degree. C., and the drying/heating is carried out for a period 
within the range from about 10 s to about 60 min. 
The present invention accordingly also provides a non-woven comprising as 
binder 5 to 100% by weight, based on the weight of the fibers used, of a 
copolyester as defined above or of a copolyester prepared by a process as 
defined above. 
In a preferred embodiment, this nonwoven further comprises from 2 to 100% 
by weight of chitosan, based on 100 parts by weight of the fiber used. 
Chitosan is a product obtained by deacetylation of chitin present in the 
mycelium or shells of crustaceans such as crabs or lobsters. The molecular 
weight and the final degree of acetylation of chitosan used in the present 
invention are not subject to specific restrictions. However, for reasons 
of solubility, a final degree of acetylation of at least 60% is desirable. 
As observed above, the amount of chitosan is within the range from 2 to 
100% by weight, preferably within the range from 5 to 80% by weight, based 
on 100 parts by weight of the fibers used. An amount of chitosan outside 
the aforementioned range is not advantageous, since the wet strength 
suffers. The at least 5% by weight of binder, based on the weight of the 
fibers used, are necessary to confer the desired flexibility on the web. 
Experimental work on webs coated or bonded with chitosan exclusively has 
shown that such webs are exceedingly rigid and consequently not usable for 
many applications. 
The present invention further provides a process for producing a nonwoven, 
which comprises contacting the fibers with a polyester dispersion as 
defined or a polyester dispersion prepared by a process as defined in such 
an amount that the level of copolyester in the bonded fabric is from 5 to 
100% by weight, based on the weight of the fibers used. Of course, it is 
also possible to use mixtures of two or more of the above polyester 
dispersions. 
To produce the nonwoven of the invention which further comprises chitosan 
as binder, the process of the invention includes a further step of 
preparing an aqueous solution of an acidic salt of chitosan and contacting 
this solution with the fibers before or during or together with the 
aqueous dispersion of the copolyester. 
On completion of the contacting impregnation step, the resulting nonwoven 
is dried. 
Before drying, the nonwoven thus obtained can be additionally shaped, so 
that it is also possible to produce a shaped article from the nonwoven of 
the invention, which is subsequently dried. For example, the as-obtained 
nonwoven can be spread out on a suitable surface such as a glass plate to 
obtain a shaped article in the form of a free or supported film. 
In the practice of the foregoing process for producing the preferred 
embodiment of the chitosan-comprising nonwoven according to the invention, 
it is advisable to use chitosan in the form of an acidic salt such as 
hydrochloride or as a similar inorganic acidic salt or formate, acetate, 
lactate or as a similar organic acidic salt. 
In addition, the nonwoven of the invention may include one or more 
additives, for example a filler or a dye or a mixture of two or more 
thereof, in which case not only organic fillers, for example starch, but 
also inorganic fillers, for example silicon dioxide, are used. 
The nonwovens of the invention are notable for good compostability coupled 
with favorable performance characteristics, especially high mechanical 
strength. They exhibit, inter alia, good dry strength, high wet strength 
and a soft hand. It must be considered surprising, especially in relation 
to the additional use of chitosan as per the preferred embodiment of the 
nonwovens of this invention, that the addition of a polyester dispersion 
greatly increases the flexibility of the resulting nonwoven. 
The nonwoven of the invention can be used as a compostable film, 
compostable molding and for manufacturing diapers or wipes. 
The invention will now be more particularly described with reference to 
some examples.

INVENTIVE EXAMPLES 1 TO 3 AND COMATIVE EXAMPLE 
General Method of Polyester Production 
To prepare polyesters Inv. 1, Inv. 2 and Inv. 3, the amounts of aromatic 
dicarboxylic acids, adipic acid and dihydroxy compound specified in Table 
1 were introduced into a reaction vessel together with 100 ppm of 
tetrabutyl orthotitanate (TBOT), the molar ratio between alcohol 
components and acid component being 1.85. The reaction mixture was heated 
to a temperature within the range from 170.degree. C. to 190.degree. C. 
and reacted at that temperature for 3-4 hours. The temperature was then 
raised to 240.degree. C., and excess dihydroxy compound was distilled off 
under reduced pressure. The OH number of the copolyester obtained was 
determined and adjusted to 20 by addition of a dihydroxy compound. 
General Method of Dispersion Production 
The polyesters Inv. 1 to Inv. 3 prepared by the above general method were 
melted in a reaction vessel. The resulting polyester melt was admixed with 
an amount of pyromellitic dianhydride (PMDA) corresponding to the OH 
number and stirred at 50 rpm. The temperature was slowly raised to 
180.degree. C., and hexamethylene diisocyanate (HDI) was added in 0.5 ml 
increments. The torque was measured. As soon as the torque reached 50% 
(measured with an RE162 laboratory stirrer from Janke & Kunkel), 300 ml of 
methyl ethyl ketone (MEK) were added to the melt and the polymer was then 
dissolved in MEK. After the polymer solution had been cooled down to 
40.degree. C., the acid groups of the polyester were neutralized with an 
appropriate amount of ethanolamine. The solution was then admixed with 1 l 
of water and vigorously stirred. 200 ml of acetone were added to the 
resulting dispersion. The acetone and the MEK were then distilled off at 
60.degree. C. under reduced pressure. 
Viscose nonwovens were impregnated with these dispersions in a dip bath 
process, dried at 150.degree. C. for 2 minutes and then tested in respect 
of their application properties. 
The results of these tests and the composition of the copolyester obtained 
(without HDI and PMDA) are shown in Table 1. 
TABLE 1 
__________________________________________________________________________ 
TS IS ADS BD DEG Rkr .multidot. tr 
Rkr .multidot. na.beta. 
mol % mol % mol % mol % mol % N/50 mm Nm 
__________________________________________________________________________ 
Inv. 1 
40 -- 60 100 -- 38 13 
Inv. 2 35 5 60 85 15 33 14 
Inv. 3 30 -- 70 100 -- 29 12 
Acronal .RTM. -- -- -- -- -- 39 13 
DS2331X 
(comp.) 
__________________________________________________________________________ 
Key to abbreviations used in the table: 
TS: terephthalic acid; 
IS: isophthalic acid; 
ADS: adipic acid; 
BD: butanediol; 
DEG: diethylene glycol; 
Acronal .RTM. DS2331X designates a commercially available acrylate 
dispersion marketed by BASF; 
Rkr .multidot. tr: dry breaking strength (measured according to DIN 
53857); 
Rkr .multidot. na.beta.: wet breaking strength (measured according to ISO 
90733). 
In the above inventive examples (Inv. 1 to Inv. 3), the amount of 
copolyester applied as binder was 33% by weight, based on the amount of 
nonwoven used. 
The nonwovens consolidated by treatment with the dispersion of the 
invention had dry and wet strengths similar to those obtained with the 
dispersion Acronal.RTM. DS2331X, which consists of starch and a 
polyacrylate and is accordingly not biodegradable in respect of the 
polyacrylate content. In addition, however, they advantageously exhibited 
biodegradability. 
The biodegradability of the polyester dispersions of the invention was also 
tested. 
The following tests were carried out: 
Film composting test 
Polyester films produced in a thickness of 50 .mu.m from the polyester 
dispersion Inv. 2 by drying at 80.degree. C. were buried in mature compost 
at 58.degree. C. and the degradation of the films was assessed by 
inspection. 
The film prepared from the polyester dispersion Inv. 2 was almost 
completely decomposed after 6 weeks in the compost at 58.degree. C. 
CO.sub.2 evolution test at 58.degree. C. (conforming to ISO 14852) and 
aerobic composting test (conforming to ISO/CD 14855). 
The dispersion Inv. 2 was tested for biodegradability in the CO.sub.2 
evolution test at 58.degree. C. This test measures the carbon dioxide 
produced by the process of biodegradation and the increase in biomass. 
The dispersion Inv. 1 was tested for biodegradability or compostability in 
the aerobic composting test. This test measures the carbon dioxide 
produced in the course of biodegradation. 
The results of the two tests are shown in Table 2. 
TABLE 2 
__________________________________________________________________________ 
TS IS ADS BD DEG Biodegradab- 
mol % mol % mol % mol % mol % ility Method 
__________________________________________________________________________ 
Inv. 2 
35 5 60 85 15 87% (CO.sub.2 + 
CO.sub.2 evolu- 
biomass) tion test 
Inv. 1 40 -- 60 100 -- 76% CO.sub.2 Aerobic 
composting 
test 
__________________________________________________________________________ 
As can be seen from Table 2, almost 90% of the test substance used was 
converted into CO.sub.2 and biomass.