Note: Descriptions are shown in the official language in which they were submitted.
2 1 6 4 8 0 5 AGW2409
Process for the preparation of
polyesters and copolyesters
Akzo Nobel nv, Arnhem
Description:
Polyesters and copolyesters are in general
prepared by a two-stage process, regardless of their
structure, which can extend from aliphatic to completely
aromatic via numerous possible variations. In the first
stage, in particular, dicarboxylic acid esters are
transesterified or dicarboxylic acids are esterified with
excess dialcohols to prepare the esters to be subjected
to polycondensation or a polyester precondensate which
comprises a mixture of oligoesters and can have an
average relative molecular weight, depen~ing on the molar
ratio of the starting compounds, of as a rule between 100
and 2000. Limited amounts of starting components of
higher functionality, such as glycerol, pentaerythritol
and trimellitic acid, can also be employed for any
desired branching modification. Equivalent procedures for
the first stage are the reaction of dicarboxylic acid
chlorides with diols, the addition of ethylene oxide onto
dicarboxylic acids, the esterification of an anhydride
with a dialcohol, the reaction of anhydrides with
epoxides and the reaction of dicarboxylic acids or
dicarboxylic acid esters with the diacetate of a diol.
The second reaction stage is the actual polycondensation,
in which the desired high molecular weight of the
polyesters or copolyesters must be achieved, alcohol
and/or water being split off. As well as applying vacuum,
passing through an inert gas and increasing the reaction
temperature, the polycondensation is accelerated, in
particular, by specific polycondensation catalysts.
A legion of polycondensation catalysts for accele-
ration of the polycondensation reaction has already been
- 2 - 2 1 6 4 8 05 AGW2409
proposed for the preparation of film- and fibre-forming
polyesters. Since the overwhelming majority of compounds
mentioned in numerous patents have an inadequate
catalytic activity or other disadvantages, almost
exclusively sb23 has become accepted as the
polycondensation catalyst in the art. Unfortunately, this
catalyst has recently met objections in terms of
environmental policy, so that its replacement generally
seems desirable.
Attempts are continuously being made to provide
substitute catalysts for Sb2O3. In particular, alkoxy
titanates, specifically tetrabutyl titanate, have already
been proposed, these compounds being used either only for
the transesterification (JA Patent 74 11 474), for the
transesterification and polycondensation (JA-A 77 86 496)
or only for the polycondensation (JA-A 80 23 136), since
they are catalytically active for both stages. Since the
use of titanium compounds causes discolorations in the
polycondensed polyesters, according to JA-A 78 106 792,
it is necessary to pretreat titanium compounds with
various organic substances, for example amines, or to
combine them with other polycondensation catalysts, in
particular with Sb2O3 (JA-A 78 109 597).
It is known from DE P 947 517 to employ metal
oxides, such as zinc oxide, boron trioxide, lead oxide
and titanium oxide, as polycondensation catalysts for the
preparation of polyethylene terephthalate. However, the
polycondensation time with these metal oxides is
disproportionately long and, from the examples therein,
lasts 7-14 hours. For this reason, in BE P 619 210, Sb2O3
is used as a further polycondensation catalyst when Tio2
is used for preparation of the polyesters therein (cf.
Example 1), as a result of which the speed of the
polycondensation increases immensely. These circumstances
of course resulted in the expediency of using only Sb2O3
or titanium tetrabutylate as the polycondensation
catalyst (cf. the other examples of BE P 619 210).
3 2 1 6 4 8 0 5 AGW2409
The object of the present invention is to provide,
for the general synthesis of polyesters and copolyesters,
new polycondensation catalysts as a replacement for Sb2O3
which offer increased safety for the ecosystem and are
distinguished in particular by a higher catalytic
activity than that of Sb2O3, Tio2 and titanium tetra-
butylate each in the same concentration.
The invention relates to a process for the
preparation of polyesters and copolyesters by polyconden-
sation of polyester-forming starting components, esters
or oligoesters being prepared in a first reaction stage
and subjected to polycondensation in a second reaction
stage in the presence of titanium catalysts, which is
characterized in that, in the polycondensation stage, a
titanium dioxide precipitate and/or a titanium dioxide/
silicon dioxide coprecipitate having a composition of
TiO2:SiO2 of > 90:10 mol/mol and/or a titanium dioxide/
zirconium dioxide coprecipitate having a composition of
TiO2 : ZrO2 of > 95:5 mol/mol, which have been obtained
by hydrolytic precipitation of the corresponding metal
alcoholates formed from mono- or polyhydric alcohols, is
employed as the polycondensation catalyst for polyconden-
sation of the esters or oligoesters.
On the basis of the fact that TiO2 is a poor
polycondensation catalyst for the synthesis of polyesters
(cf. Comparison Examples la and lb), it is surprising
that the titanium dioxide precipitates, titanium
dioxide/silicon dioxide coprecipitates and titanium
dioxide/zirconium dioxide coprecipitates employed
according to Claim 1 are highly active polycondensation
catalysts at all, in particular for the preparation of
thread-forming high molecular weight polyesters and
copolyesters, and moreover even in the very small amounts
preferably used.
For the use according to the invention as a
polycondensation catalyst, it is preferable for the
titanium doxide [sic] precipitates, titanium dioxide/
silicon dioxide coprecipitates and titanium dioxide/
- 4 - 2 1 64 8 05 AGW2409
zirconium dioxide coprecipitates to have been obt-ained by
hydrolytic precipitation of the corresponding metal
alcoholates formed from monohydric alcohols having 1-6 C
atoms. A titanium dioxide precipitate or a titanium
dioxide/silicon dioxide coprecipitate from the required
composition range, like a corresponding titanium dioxide/
zirconium dioxide coprecipitate, can be employed as the
polycondensation catalyst by itself or as a mixture with
the other particular type of precipitate or, in the case
of the coprecipitates mentioned, as a mixture with its
own type having a different composition within the
required composition ranges.
The preparation of the titanium dioxide
precipitates and titanium dioxide/silicon dioxide and
titanium dioxidetzirnonium [sic] dioxide coprecipitates
used according to the invention is known in principle
(cf., for example, B.E. Yoldes, J. Non-Cryst. Solids, 38
and 39, 81 (1980); E.A. Barringer, H.K. Bowen,
J.Am.Ceram. Soc., 65 C 199 (1982); E.A. Barringer, Ph. D.
Thesis, MIT (1982); B. Fegley jr., E.A. Barringer,
H.K. Bowen, J.Am.Ceram. Soc., 67, C 113 (1984)). The
starting substances are metal alkoxides of the formula
M(OR)m, wherein M is Ti, Si and Zr, according to the
desired oxide or mixed oxide, and m is the integer 4,
which are subjected to hydrolysis. The oxide network is
formed by polymerization reactions during this process.
Suitable alcohols for the preparation of the metal
alkoxides by methods known per se are, for example,
monohydric alcohols, such as methyl alcohol, ethyl
alcohol, propyl alcohol, isopropyl alcohol, n-butanol,
propyl alcohol, isobutyl alcohol, n-amyl alcohol,
3-methyl-1-butanol, n-hexanol, 2-hexanol, 2-heptanol,
n-octanol and n-decanol, which can be used individually
or as a mixture. However, it is also possible to use
polyhydric alcohols, if appropriate as a mixture with
monohydric alcohols, such as ethylene glycol,
1,2-propanediol, 1,4-butanediol, 1,6-hexanediol,
2 1 64 805 AGW2409
1,10-decanediol, glycerol, trimethylolpropane and
pentaerythritol.
The organometallic compounds, in the case of
preparation of a titanium dioxide precipitate, for
example, titanium tetraisopropylate, are subjected to a
hydrolysis which can be effected in various ways. Thus,
for example, the titanium tetraalkoxide, dissolved in
absolute alcohols, for example ethanol, can be hydrolysed
by means of addition of water or an aqueous alcohol
within a period of about 20 minutes to 2 hours at 0 to
50C. However, the hydrolysis can also be effected by
adding water or an aqueous alcohol solution dropwise to
the undissolved pure titanium tetraalkoxide under the
conditions mentioned above. The water required for the
hydrolysis, however, can also be contained in a gas phase
as moisture, for example by passing damp nitrogen into
the titanium tetraalkoxide at 0 to 50C for 3 to 30
hours. The as it were "in situ formation of a dispersion
of TiO2 precipitate in glycol suitable for use in the
reactor can also be advantageous. In this case, the
undissolved pure titanium tetraalkoxides can be
precipitated as TiO2 precipitate under the above
conditions by addition of glycol which contains the
amount of water needed for the hydrolysis. If the glycol
contains smaller amounts of water, the hydrolysis can
additionally be carried out by passing, for example, damp
nitrogen into the reaction vessel.
The preparation of the TiO2/SiO2 and TiO2/ZrO2
coprecipitates is carried out in an analogous manner,
except that in each case two tetraalkoxides of titanium
and silicon or of titanium and zirconium, of which the
alkoxides otherwise can be identical or different, are in
each case used for their precipitation. Advantageous
forms of the preparation, at room temperature, of the
precipitates and coprecipitates used according to the
invention are described in the experimental part A in
Examples 1 to 6. Under the hydrolytic conditions therein,
gel formation, which is to be avoided, is excluded, and,
- 6 - 21 64805 AGw24ag
during this precipitation of the TiO2 and the Ti/Si and
Ti/Zr mixed oxides takes place.
The amounts added of the precipitates and
coprecipitates according to the invention which are used
as the polycondensation catalyst can be varied within
wide limits and include a total amount of about 5 to
500 ppm, based on the esters or oligoesters to be
subjected to polycondensation. Their upper limit can
therefore in principle be of the same order of magnitude
as in the case where Sb2O3 is used, which is as a rule
employed as a polycondensation catalyst in an amount of
about 300 to 400 ppm.
If attention must be paid to achieving good colour
values for certain fields of use of the polyesters and
copolyesters prepared, however, it is preferable to use
the titanium dioxide precipitate and/or the titanium
dioxide/silicon dioxide coprecipitate and/or the titanium
dioxide/zirconium dioxide coprecipitate in a total amount
of only 10 to 100 ppm, based on the esters or oligoesters
to be subjected to polycondensation. The increased
catalytic activity of the precipitates and coprecipitates
used according to the invention allows the use of added
amounts which are considerably lower than in the case
where Sb2O3 is used, the same polycondensation time and a
completely acceptable b* value of 3.0 to 8.0 then being
achieved with the polyesters thus prepared. This b* value
range corresponds in particular to the values which are
likewise obtained in the preparation of polyethylene
terephthalate using 400 ppm of Sb2O3 as the polycondensa-
tion catalyst. The titanium dioxide precipitates and
titanium dioxide/silicon dioxide and titanium dioxide/
zirconium dioxide coprecipitates used according to the
invention are preferably added in the form of a 5 to 20%
strength suspension in glycol to the esters or oligo-
esters synthesized in the first reaction stage, for
example the bisglycol ester of the dicarboxylic acid(s)
to be subjected to polycondensation and/or the preconden-
sate of one or more such bisglycol esters, before their
7 2 1 6 4 8 0 5 AGW2409
polycondensation. However, it is in principle also
possible for the precipitates and coprecipitates even to
be added at any point in time during the first reaction
stage, and in the case of transesterification, if appro-
priate together with one or more transesterification
catalysts. In the case of transesterification in the
first reaction stage, it may sometimes be advantageous to
block the transesterification catalysts after the tran-
sesterification by addition of phosphorus compounds in a
manner known per se. Suitable phosphorus compounds are,
for example, carbethoxymethyldiethyl phosphonate,
ditpolyoxyethylene)hydroxymethyl phosphonate, tetra-
isopropyl methylenediphosphonate and H3P04, an added P
concentration of 30-50 ppm in general being adequate.
Under customary reaction conditions, the
precipitates and coprecipitates used according to the
invention are in principle suitable as polycondensation
catalysts for the preparation of the most diverse
polyesters and copolyesters for which Sb203 has been
employed to date as the polycondensation catalyst, if
appropriate also in combination with one or more other
polycondensation catalysts. The most diverse fields of
use also correspond to the various types of polyesters
and copolyesters.
If alkyd resins and saturated polyester resins
(hydroxy-polyesters) having a relative molecular weight
of < 10,000 are prepared with the precipitates and
coprecipitates used according to the invention, these can
be used as binders in varnishes and paints. In modern
usage, alkyd resins here are understood as meaning oil-
or fatty acid-modified polyesters of polycarboxylic acids
and polyalcohols and reaction products thereof with, for
example, vinyl compounds, epoxy resins, silicones,
diisocyanates and organometallic compounds ("modified"
alkyd resins). Polycarboxylic acids which are employed
for alkyd resins are essentially phthalic acid,
isophthalic acid, malonic acid, succinic acid, adipic
acid, azelaic acid, sebacic acid, dodecanedioic acid,
21 64805
- 8 - AGW2409
dimerized fatty acids, hexahydrophthalic- acid,
hexahydroterephthalic acid, maleic acid, fumaric acid
and, for the purpose of flameproofing, halogen-cont~;n;ng
dicarboxylic acids, such as tetrachlorophthalic
anhydride. Polyols which are used are in general
glycerol, pentaerythritol, dipentaerythritol,
trimethylolpropane, trimethylolethane, sorbitol and
difunctional polyols, such as ethylene glycol, propylene
1,2-glycol, butane-1,3- and -1,4-diol, diethylene glycol,
dipropylene glycol and neopentylglycol. The third compon-
ent for the preparation of alkyd resins are long-chain
fatty acids, either synthetic fatty acids, such as
pelargonic acid, abietic acid and synthetic fatty acid
mixtures (C7-Cg), or naturally occurring fatty acids,
which are used almost exclusively in the form of their
fats and oils, for example linseed oil, castor oil,
coconut oil, soya oil and cottonseed oil. In contrast, no
longer-chain fatty acids are employed in the polyconden-
sation for the preparation of saturated polyester resins,
which are defined in DIN 55 945, while otherwise the
saturated polycarboxylic acids and polyalcohols used are
essentially the same as those employed for the prepara-
tion of alkyd resins.
If (co)polyesters are synthesized as precursors
for polyurethanes having a relative molecular weight of
< 10,000 using the precipitates and coprecipitates in
question, this leads, depending on their further
processing on the basis of known procedures, not only to
polyurethane varnishes, but also to a diversity of
different types of plastics having variable useful use
properties (thermosets, thermoplastics, casting
elastomers, rigid and flexible foams, compression
moulding compositions, rigid and flexible coatings,
adhesives). The low molecular weight polyesters and
copolyesters as precursors for polyurethanes are in
general prepared from saturated aliphatic or aromatic
dicarboxylic acids and difunctional or di- and
trifunctional alcohols and are linear or slightly to
2 1 64 805 AGW2409
severely branched. With the coprecipitates used according
to the invention, it is possible to prepare the entire
wide range of hydroxy-polyesters known for this, having
hydroxyl numbers of 28-300 mg of KOH/g and acid numbers
of usually less than 1 mg of KOH/g. The highly branched
polyesters among them, which are chiefly obtained on the
basis of aromatic or hydroaromatic dicarboxylic acids,
are used mainly as binders for polyurethane varnishes.
The precipitates and coprecipitates used according
to the invention are particularly suitable, under
customary reaction conditions, as polycondensation
catalysts for the preparation of the known high-melting
fibre- and film-forming polyesters, such as polyethylene
terephthalate, polybutylene terephthalate, poly(ethylene
2,6-naphthalenedicarboxylate), poly(butylene 2,6-
naphthalenedicarboxylate), poly(1,4-dimethylenecyclo-
hexane terephthalate) and copolyesters thereof based on
high homopolyester contents of at least 80 mol per cent,
which belong to the class of thermoplastic polyesters.
Such polyesters and copolyesters in principle have a
molecular weight of > 10,000. The polyalkylene
terephthalates preferably subjected to polycondensation
with the coprecipitates, in particular polyethylene
terephthalate and polybutylene terephthalate, can, as
copolyesters, comprise up to 20 mol per cent of units
which are derived from at least one other polyester-
forming component. Furthermore, it is of course of no
significance for the use of the polycondensation
catalysts according to the invention whether the
bisglycol esters of the dicarboxylic acid(s) to be
subjected to polycondensation and/or the precondensates
of one or more such bisglycol esters have been prepared
by a transesterification process or by a direct
esterification process.
The polycondensation catalysts according to the
invention are thus suitable both for the preparation of a
fibre-forming polyethylene terephthalate having an
intrinsic viscosity [~] of 0.65-0.75, which as a rule is
lo - 21 6 4 8 0 5 AGW2409
further processed to staple fibres for textile purposes,
and for the preparation of fibre-forming polyethylene
terephthalates having an intrinsic viscosity [~] of
0.75-0.80 and 0.95-1.05, from which filament yarns are
prepared for industrial purposes. The increased molecular
weights can be achieved by continuous polycondensation
with direct spinning or, preferably, by post-condensation
in the solid phase. For post-condensation in the solid
phase, it is advantageous to block any transesterifica-
tion catalysts present by phosphorus compounds in a
manner known per se. Phosphorus compounds which are
suitable for this are, for example, di(polyoxyethylene)-
hydroxymethyl phosphonate, tetraisopropyl methylene-
diphosphonate and H3PO4, an added P concentration of
30-50 ppm being sufficient.
The fibre- and film-forming thermoplastic
polyesters prepared with the polycondensation catalysts
according to the invention, in particular polyethylene
terephthalate and polybutylene terephthalate, can of
course also be processed, for example, to all types of
shaped articles and profiles by means of injection
moulding and extrusion. For example, if a polyethylene
terephthalate prepared with the polycondensation cata-
lysts according to the invention is processed to PET
bottles, these have a high transparency and a lower
acetaldehyde content.
The other polyester-forming components for fibre-
and film-forming copolyesters can be an aliphatic diol,
such as ethylene glycol, propylene glycol, tetramethylene
glycol, pentamethylene glycol, hexamethylene glycol,
polyethylene glycol, polypropylene glycol and poly(tetra-
hydrofuran)diol, an aromatic diol, such as pyrocatechol,
resorcinol and hydroquinone, an alicyclic diol, such as
1,4-cyclohexanedimethanol and cyclohexanediol, an
aliphatic dicarboxylic acid, such as adipic acid, sebacic
acid and decanedicarboxylic acid, an aromatic dicarb-
oxylic acid, such as isophthalic acid, 5-sodium-sulpho-
isophthalic acid, sodium-sulphoterephthalic acid and 2,6-
- 11 - 21 64805 AGW2409
naphthalenedicarboxylic acid, and an alicyclic dicarboxy-
lic acid, such as hexahydroterephthalic acid and 1,3-
cyclohexanedicarboxylic acid. The analogous polyester-
forming components for copolyester formation are also
possible for the thread-forming homopolyesters, some of
which have already been mentioned above, which do not
belong to the class of polyalkylene terephthalates.
The film- and fibre-forming polyesters can of
course also comprise, as customary modifying agents,
known branching agents, such as pentaerythritol, tri-
mellitic acid, pyromellitic acid and trimesic acid or
esters thereof, in the small amounts customary for this
purpose of, for example, 1 to 15 micro-equivalents per g
of polymer, these guaranteeing high-speed spinning at
3000 to 4000 m/min or more, and also draw-texturing at a
rate of at least 1000 m/minute. These branching agents
are advantageously added as a solution in ethylene glycol
to the bisglycol ester of the dicarboxylic acid(s) to be
subjected to polycondensation.
The term copolyester also includes the extensive
class of polyether-esters. As is known, the thermoplastic
polyether-esters are block copolymers which are syn-
thesized from mutually incompatible rigid crystalline and
flexible amorphous segments. The rigid and short-chain
segments generally chiefly comprise an aromatic poly-
ester, for example ethylene terephthalate units or
butylene terephthalate units, while the flexible and
long-chain segments comprise, in particular, the reaction
product of an aliphatic polyether, for example
poly(butylene glycol) or poly(ethylene glycol) with an
aliphatic, cycloaliphatic or aromatic dicarboxylic acid.
Both the long-chain and the short-chain ester units are
often copolyesters which result from the limited co-use
of one or more other dicarboxylic acid and glycol compon-
ents. Thermoplastic polyether-esters, for the preparation
of which the titanium dioxide precipitates and titanium
dioxide/silicon dioxide and titanium dioxide/zirconium
dioxide coprecipitates employed according to the
- 12 - 2 1 6 4805 AGW2409
invention as polycondensation catalysts are also
suitable, are described, for example, in US-A 3,023,192,
GB-B 682 866, DE-C 23 52 584, EP-A-0 051 220 and EP-A-
0 109 123.
The titanium dioxide precipitates and titanium
dioxide/silicon dioxide and titanium dioxide/zirconium
dioxide coprecipitates used according to the invention
are also suitable for the preparation of completely
aromatic or liquid-crystalline polyesters if this is
carried out on the basis of customary polycondensation
catalysts, such as Sb2O3 and titanium alkoxides. Thus,
for example, completely aromatic polyesters of 10-90 mol
per cent of a hydroxy-naphthalene-carboxylic acid,
5-45 mol per cent of at least one other aromatic
dicarboxylic acid, for example terephthalic acid, and
5-45 mol per cent of at least one aromatic diol, for
example hydroquinone, are known from US-A 4,421,908.
According to EP-A-0 472 366, completely aromatic
polyesters are prepared from (A) isophthalic acid, (B)
hydroquinone and (C) from 4,4-dihydroxybiphenyl and/or
p-hydroxybenzoic acid and/or 2-hydroxy-6-naphtha-
lenecarboxylic acid and (D) a phenol. And EP-A-0 496 404
describes completely aromatic polyesters which are
obtained by reaction of at least one dialkyl ester of an
aromatic dicarboxylic acid, for example DMT, with at
least one aromatic polycarbonate, for example poly(4,4'-
isopropylidene-diphenylene carbonate) and/or an aromatic
dialkyl dicarbonate. In these processes, mentioned by way
of example, for the preparation of completely aromatic
polyesters, the polycondensation catalysts used therein,
such as Sb2O3, titanium alkoxides and zirconium
alkoxides, can be replaced in an advantageous manner by
the specific precipitates and coprecipitates according to
the invention, quite irrespective of whether they are
added as early as in the first reaction stage or in the
subsequent actual polycondensation stage.
The invention is illustrated in more detail with
the aid of the following examples. The relative solution
- 13 - 2 1 64 805 AGW2409
viscosity stated therein was measured at 25C -as a 1%
strength solution in m-cresol. The number of carboxyl
groups has been stated as carboxyl group
equivalents/106 g or mmol/kg of the polymer. This
parameter was determined by titration of the polymer in
o-cresol with potassium hydroxide.
The L* a* b* colour system was taken as the basis
for evaluation of the colour of the polyesters. This is
one of the colour systems for standardization of colour
measurement and was recommended in 1976 by the CIE
(Commission Internationale de l'Eclairage) because of its
relatively high accuracy in describing perceptible
colours and colour differences. In this system, L* is the
lightness factor and a* and b* are colour measurement
numbers. In the present case, the b* value, which indi-
cates the yellow/blue balance, is important. A positive
b* value means yellow discoloration and a negative b*
value blue discoloration. Polyesters prepared con-
ventionally with antimony trioxide have a b* value of
between 3 and 8. Higher values are also accepted for
products for which colour is not critical.
Preparation of the TiO2 precipitates and TiO2/SiO2 and
TiO2/ZrO2 coprecipitates
Example 1
Catalytically active titanium dioxide precipitate No. 1
10.80 g of titanium(IV) tetraisopropylate
(38 mmol) are dissolved in 263 ml of absolute ethanol
(solution A). 27.02 g of distilled water (1.5 mol) are
mixed with 263 g of absolute ethanol (solution B).
Solution A is initially introduced into the reaction
vessel and solution B is added dropwise at 22C in the
course of 30 minutes. A white precipitate separates out.
The mixture is centrifuged three times for 20 minutes and
the residue is rinsed once with distilled water and once
21 64805
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with ethanol. The resulting titanium dioxide precipitate
is dried at 65C in vacuo.
Example 2
Catalytically active titanium dioxide precipitate No. 2
27.02 g of distilled water (1.5 mol), if
appropriate mixed with 263 g of absolute ethanol, are
added dropwise to 10.80 g of titanium(IV)
tetraisopropylate (38 mmol) in the course of 30 minutes.
A white precipitate separates out. The mixture is
centrifuged three times for 20 minutes and the residue is
rinsed once with distilled water and once with ethanol.
The resulting titanium dioxide precipitate is dried at
65C in vacuo.
Example 3
Catalytically active titanium dioxide precipitate No. 3
80 Nl/hour of nitrogen, saturated with water via a
wash bottle, are passed into 10.80 g of titanium(IV)
tetraisopropylate (38 mmol) for 24 hours. A white
precipitate separates out. The mixture is centrifuged
three times for 20 minutes and the residue is rinsed once
with distilled water and once with ethanol. The resulting
titanium dioxide precipitate is dried at 65C in vacuo.
Example 4
Catalytically active titanium dioxide precipitate No. 4
150 ml of glycol (water content about 0.02 % by
weight) are added to 10.80 g of titanium(IV) tetra-
isopropylate (38 mmol). In addition, 80 l/hour (s.t.p.)
of nitrogen, saturated with water via a wash bottle, are
passed in for a period of 60 minutes. A white precipitate
separates out. The titanium dioxide precipitate
dispersion formed is employed without further processing.
Example 5
Catalytically active titanium dioxide precipitate No. 5
21 64805
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34.04 g of titanium(IV) tetrabutylate (0.1 mol)
are heated to about 120C together with 62.07 g of glycol
(1.0 mol). 32.4 g of dibutylamine (0.25 mol) are added
dropwise at this temperature as a transesterification
catalyst. The butanol formed is distilled off overnight,
while stirring. The residue of the titanium alcoholate
formed from glycol is precipitated by means of water
contA;n;ng hydrochloric acid (pH=3), a white precipitate
separating out. The mixture is centrifuged three times
for 20 minutes and the residue is rinsed once with
distilled water and once with ethanol. The resulting
titanium dioxide precipitate is dried at 65C in vacuo.
Example 6
Catalytically active titanium dioxide precipitate No. 6
34.04 g of titanium(IV) tetrabutylate (0.1 mol)
are heated to about 120C together with 92.09 g of
glycerol (1.0 mol). 32.4 g of dibutylamine (0.25 mol) are
added dropwise at this temperature as a
transesterification catalyst. The butanol formed is
distilled off overnight, while stirring. The residue of
the titanium alcoholate formed from glycerol is
precipitated by means of water contA;n;ng hydrochloric
acid (pH=3), a brownish precipitate separating out. The
mixture is centrifuged three times for 20 minutes and the
residue is mixed once with distilled water and once with
ethanol. The resulting titanium dioxide precipitate is
dried at 65C in vacuo.
Example 7
Catalytically active titanium dioxide/silicon dioxide
coprecipitate (TiO2:SiO2 = 95:5 mol/mol)
11.37 g of titanium(IV) tetraisopropylate
(40 mmol) and 0.44 g of tetraethoxysilane (2.1 mmol) are
dissolved with 100 ml of absolute ethanol (solution A).
10.27 g of distilled H2O (0.57 mol) are mixed with 100 ml
of absolute ethanol (solution B). Solution A is initially
introduced into the reaction vessel, and solution B is
21 64805
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added dropwise at 22C in the course of 30 minutes. A
white precipitate separates out. After the mixture has
been stirred for 1 hour, it is centrifuged and the
residue is washed 3 times with distilled H2O~ The
resulting Tio2/Sio2 coprecipitate is dried at 70C in
vacuo.
Ex~mple 8
Catalytically active titanium dioxide/zirconium dioxide
coprecipitate (TiO2:ZrO2 = 97:3 mol/mol)
25.58 g of titanium(IV) tetraisopropylate
(90.0 mmol) and 0.92 g of zirconium(IV) tetrapropylate
(2.8 mmol) are dissolved in 263 g of absolute ethanol
(solution A). 27.02 g of distilled H2O (1.5 mol) are
mixed with 263 g of absolute ethanol (solution B).
Solution A is initially introduced into the reaction
vessel, and solution B is added dropwise at 22C in the
course of 30 minutes. A white precipitate separates out.
After the mixture has been stirred for 1 hour, it is
centrifuged. The residue is washed once with distilled
H2O and then washed with ethanol and centrifuged for in
each case 20 minutes. The resulting TiO2/ZrO2
coprecipitate is dried at 60-70C in vacuo for 24 hours.
Polycondensation Examples
Example 9
Polyethylene terephthalate was prepared in a two-
stage process. In the first stage, the transesterifica-
tion, the reaction of ethylene glycol and dimethyl
terephthalate (= DMT) in a molar ratio of 2.5:1 was
carried out in the presence of 100 ppm of ZnAc2.2 H2O (Ac
= acetate) and 150 ppm of MnAc2~4 H2O, based on the DMT,
at temperatures in the range from 165 to 265C, the
continuous increase in temperature from 165C to 265C
being carried out not too quickly in order to avoid
sublimation of the DMT. The methanol liberated during the
21 64805
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transesterification is [sic] distilled off over a-column.
When the reaction temperature had reached 240C, 50 ppm
of phosphorus, based on the DMT employed, were added as
ethyl phosphonoacetate in order to block the trans-
esterification catalysts.
As soon as the reaction temperature of 250C was
reached, 100 ppm, based on the bis-(2-hydroxyethyl)
terephthalate present, of the titanium dioxide
precipitate prepared according to Example 1 were added in
the form of a 5% strength by weight suspension in glycol.
The polycondensation reaction was carried out at 290C
under a vacuum of 1.3 mbar. After a reaction time of 96
minutes, a polymer having a relative solution viscosity
of 1.665 was obtained. The b* value was 9.0 and the COOH
end group content was 18.3 equivalents/106 g of polymer.
Example lO
Polyethylene terephthalate was prepared in a two-
stage process. In the first stage, the transesterifica-
tion, the reaction of ethylene glycol and dimethyl
terephthalate was carried out in the presence of 55 ppm
of MnAc2.4 H2O or 75 ppm of MnAc2.2 H2O, based on the
DMT, in a manner otherwise the same as in Example 7
[sic]. However, the transesterification catalysts were
blocked with an equivalent amount of phosphorous acid,
which was added in the form of a 70% strength by weight
solution in glycol.
At 250C, 100 ppm, based on the bis-(2-hydroxy-
ethyl) terephthalate present, of the titanium dioxide
precipitate prepared according to Example 3 were added in
the form of a 5% strength by weight suspension in glycol.
The polycondensation reaction was carried out at 283C
under a vacuum of 0.8 mbar, [sic] After a reaction time
of 88 minutes, a polymer having a relative solution
viscosity of 1.654 was obtained. The b* value was 7.5 and
the COOH end group content was 19.3 equivalents/106 g of
polymer.
- 18 - 21 64805 AGW2409
Example 11
Example 9 was repeated, with the modification that
at 250C 100 ppm, based on the bis-(2-hydroxyethyl)
terephthalate present, of the titanium dioxide
precipitate prepared according to Example 4 were added in
the form of a 5% strength by weight suspension in glycol.
The polycondensation reaction was carried out at 276C
under a vacuum of 0.5 mbar. After a reaction time of 82
minutes, a polymer having a relative solution viscosity
of 1.614 was obtained. The b* value was 7.5 and the COOH
end group content was 20.1 equivalents/106 g of polymer.
Example 12
Example 9 was repeated, with the modification that
at 250C 100 ppm, based on the bis-(2-hydroxyethyl)
terephthalate present, of the titanium dioxide
precipitate prepared according to Example 2 were added in
the form of a 5% strength by weight suspension. The
polycondensation reaction was carried out at 290C under
a vacuum of 1.3 mbar. After a reaction time of 98
minutes, a polymer having a relative solution viscosity
of 1.653 was obtained. The b* value was 6.5 and the COOH
end group content was 14.8 equivalents/106 g of polymer.
Example 13
Example 9 was repeated, with the modification that
at 250C 100 ppm, based on the bis-(2-hydroxyethyl)
terephthalate present, of the titanium dioxide
precipitate prepared according to Example 5 were added in
the form of a 5% strength by weight suspension. The
polycondensation reaction was carried out at 290C under
a vacuum of 1.3 mbar. After a reaction time of 101
minutes, a polymer having a relative solution viscosity
of 1.635 was obtained. The b* value was 8.2 and the COOH
end group content was 17.6 equivalents/106 g of polymer.
19 - 21 64805 AGW2409
Example 14
Example 9 was repeated, with the modification that
at 250C 100 ppm, based on the bis-(2-hydroxyethyl)
terephthalate present, of the titanium dioxide
precipitate prepared according to Example 6 were added in
the form of a 5% strength by weight suspension. The
polycondensation reaction was carried out at 290C under
a vacuum of 1.3 mbar. After a reaction time of 92
minutes, a polymer having a relative solution viscosity
of 1.634 was obtained. The b* value was 10.4 and the COOH
end group content was 17.7 equivalents/106 g of polymer.
Example 15
Example 9 was repeated, with the modification that
at 250C 100 ppm, based on the bis-(2-hydroxyethyl)
terephthalate present, of the titanium dioxide/zirconium
dioxide coprecipitate having the composition TiO2:ZrO2 =
97:3 mol/mol prepared according to Example 8 were added
in the form of a 5% strength by weight suspension in
glycol. The polycondensation reaction was carried out at
290C under a vacuum of 1.3 mbar. After a reaction time
of 80 minutes, a polymer having a relative solution
viscosity of 1.634 was obtained. The b* value was 7.3 and
the COOH end group content was 16.9 equivalents/106 g of
polymer.
Example 16
Example 9 was repeated, with the modification that
at 250C 100 ppm, based on the bis-(2-hydroxyethyl)
terephthalate present, of the titanium dioxide/silicon
dioxide coprecipitate having the composition of TiO2:SiO2
= 95:5 mol/mol prepared according to Example 7 were added
in the form of a 5% strength by weight suspension in
glycol. The polycondensation reaction was carried out at
290C under a vacuum of 1.3 bar. After a reaction time of
97 minutes, a polymer having a relative solution
viscosity of 1.646 was obtained. The b* value was 9.2 and
- 20 - 2 1 64 8 05AGW2409
the COOH end group content was 17.5 equivalentstl06 g of
polymer.
Example 17
Polyethylene terephthalate was prepared in a two-
stage process, a direct esterification of terephthalic
acid with ethylene glycol to give bis-(2-hydroxyethyl)
terephthalate being carried out in the first stage. In
the second reaction stage, the polycondensation was
carried out using a) 400 ppm of Sb2O3, b) 100 ppm of
Tio2/SiO2 (95:5 mol/mol) and c) TiO2/ZrO2 (97:3 mol/mol)
as polycondensation catalysts.
a) Sb2O3 as the polycondensation catalyst
1707 g (10.3 mol) of terephthalic acid are heated up
in the esterification autoclave together with 1020 g
of glycol (16.4 mol) and 1 ppm of defoamer M 10
(from Dow Corning) until an increased pressure of
7 bar has been established by the water split off
(235C batch temperature). The time this pressure is
reached is evaluated as the starting time of the
reaction. The increased pressure is maintained for
60 minutes, during which the internal temperature is
increased to about 250C. The water vapour thereby
discharged is condensed in the condenser and
collected in a measuring cylinder. After a total of
60 minutes, the internal pressure is reduced step-
wise to normal pressure in the course of a further
60 minutes (temperature between 250 and 260C). The
product is then drained into the polycondensation
autoclave. Immediately after draining, 50 ppm of
phosphorus are added as ethyl phosphonoacetate (EPA)
at 240C. 400 ppm of Sb2O3, based on the bis-(2-
hydroxyethyl) terephthalate present, are then added
in the form of a 1.1% strength solution in glycol at
an internal temperature of 250C (after about 5
minutes). A vacuum programme which reduces the
internal pressure to about 1 torr in the course of
21 64805
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25 minutes is then started, with further -heating.
The internal temperature is regulated by the peak
procedure (peak temperature: 298C). The reaction
end point is determined by measuring the power
consumption of the stirrer. After 95 minutes, a
product having a solution viscosity of 1.681 is
obtained. The carboxyl end group content was
20.1 mmol/kg.
- b) TiO2/SiO2 (95:5 mol/mol) as the polycondensation
catalyst
Example 17 a) was repeated, with the modification
that at 250C 100 ppm of TiO2/SiO2 (95:5 mol/mol),
based on the bis-(2-hydroxyethyl) terephthalate
present, were added as the polycondensation catalyst
in the form of a 5% strength dispersion in glycol.
After 94 minutes, a product having a solution vis-
cosity of 1.669 is obtained. The carboxyl end group
content was 12.2 mmol/kg, and is thus significantly
better than in experiment 17 a).
c) TiO2/ZrO2 (97:3 mol/mol) as the polycondensation
catalyst
Example 17 a) was repeated, with the modification
that at 250C 50 ppm of TiO2/ZrO2 (97:3 mol/mol),
based on the bis-(2-hydroxyethyl) terephthalate
present, were added as the polycondensation catalyst
in the form of a 5% strength dispersion in glycol.
After 84 minutes, a product having a solution vis-
cosity of 1.682 is obtained. The carboxyl end group
content was 13.4 mmol/kg, and is thus likewise more
favourable than in experiment 17 a).
Example 18
Post-condensation in the solid phase
a) Polycondensation catalyst Sb2O3
About 2 g of polyethylene terephthalate having a
relative solution viscosity (SV) of 1.681 and a
carboxyl end group concentration of 20.1 mmol/kg,
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prepared using 400 ppm of Sb2O3 as the polycondensa-
tion catalyst in accordance with Example 17 a), are
introduced into a glass tube immersed in a metal
bath. Under a continuous stream of nitrogen, the
polymer is first kept at 140C for one hour (pre-
crystallization) and then kept at 231C for a
further 4 hours. After the post-condensation, the SV
was 1.880 and the carboxyl end group content was
11.0 mmol/kg.
b) Polycondensation catalyst TiO2 precipitate
About 2 g of polyethylene terephthalate having a
relative solution viscosity (SV) of 1.654 and a
carboxyl end group content of 19.3 mmol/kg, prepared
using 100 ppm of TiO2 precipitate as the
polycondensation catalyst in accordance with Example
9, are introduced into a glass tube immersed in a
metal bath. Under a continuous nitrogen atom [sic],
the polymer is first kept at 140C for one hour
(pre-crystallization) and then kept at 231C for a
~urther 4 hours. After the post-condensation, the SV
was 1.982 and the carboxyl end group content was
10.6 mmol/kg.
Example 19
Preparation of a malonate resin
a) Catalyst: dibutyl-tin oxide
A 2000 ml five-necked flask which was equipped with
a metal stirrer, dropping funnel, nitrogen inlet
tube, thermocouple for the internal temperature, a
300 mm long Vigreux silver-jacketed column and a
distillation column head was used as the apparatus
for this example. The reaction batch comprised the
following components:
312.45 g (3 mol) of pentane-1,5-diol as component A,
560.60 g (3.5 mol) of diethyl malonate as component
B,
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0.87 g (= 0.1% by weight, based on A -+ B) of
dibutyl-tin oxide as component C,
43.5 g (15% by weight, based on A + B) of m-xylene
as component D,
130.5 g (15% by weight, based on A + B) of xylene as
component E.
The dibutyl-tin oxide customary for this reaction
was used as the catalyst. Components A, B, C and D
were weighed into a flask and the flask was flushed
with nitrogen. The mixture was then heated slowly
and the first drops of ethanol were distilled off at
an internal temperature of 115C. At a falling rate
of distillation, the internal temperature was
increased to 200C. Component E was then addition-
ally added dropwise as an entraining agent for the
distillation and removal of the ethanol/m-xylene
distillate continued. When the conversion had
reached 99.5%, the polycondensation was interrupted.
This conversion was achieved after 16 hours.
The total amount of distillate at this point in time
was 378.03 g. The amount of ethanol distilled off
was 274.92 g ttheoretical total amount = 276.42 g).
The Gardner colour number was 13.
b) Catalyst: TiO2 precipitate
The experiment under a) was repeated with the cata-
lyst according to the invention. The reaction batch
comprised the following components:
312.45 g (3 mol) of pentane-1,5-diol as component A,
560.60 g (3.5 mol) of diethyl malonate as component
B,
0.87 g (0.1% by weight, based on A + B) of TiO2
precipitate as component C as in Example 3,
43.5 g (5% by weight, based on A + B) of m-xylene
as component D,
87.0 g (10% by weight, based on A + B) of m-xylene
as component E.
Components A, B, C and D were weighed into the flask
and the flask was flushed with nitrogen. The mixture
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was then heated slowly and the first drops of
ethanol were distilled off as a mixture with
m-xylene at an internal temperature of 142C. At a
falling rate of distillation, the internal tempera-
ture was increased to 200C. Component E was then
additionally added dropwise as an entraining agent
for the distillation and removal of the ethanol/
m-xylene distillate continued. When the conversion
reached 99.8%, the polycondensation was dis-
continued. This conversion was reached after only 6
hours.
The total amount of distillate at this point in time
was 342.28 g. The amount of ethanol distilled off
was 276.04 g (theoretical total amount of ethanol =
276.42 g). The Gardner colour number was 10.
Comparison Examples
Comparison Examples la and lb
a) An attempt was made to prepare a polyethylene tere-
phthalate analogously to Example 7, in which commer-
cially available titanium dioxides were to function
as polycondensation catalysts. For this purpose,
after the transesterification carried out in accord-
ance with Example 7 and after blocking of the trans-
esterification catalysts when the reaction tempera-
ture reached 250C, 500 ppm of Hombitec KO 3 TiO2 (a
titanium dioxide from Sachtleben), based on the bis-
(2-hydroxyethyl) terephthalate present, were added
to the reaction batch as the polycondensation cata-
lyst in the form of a 10% strength by weight
suspension in glycol. The polycondensation reaction
was carried out at 290C under a vacuum of 1.3 mbar.
After a reaction time of 180 minutes, the experiment
was discontinued, since no adequate melt viscosity
and therefore no ade~uate relative viscosity either
- 25 - 2 1 64 805 AGW2409
had been established because the molecular weight of
the polycondensation product was too low.
b) A second attempt carried out under the same reaction
conditions, in which 500 ppm of Tilcom HPT 3 TiO2
(titanium dioxide from Tioxide), based on the bis-
(2-hydroxyethyl) terephthalate present, were added
as the polycondensation catalyst in the form of a
10% strength by weight suspension in glycol, pro-
ceeded with the same negative result.
Comparison Example 2
Example 8 was repeated with the modification that
at 250C, 340 ppm of Sb2O3, based on the bis-(2-hydroxy-
ethyl) terephthalate present, were added. The polyconden-
sation reaction was thus carried out at 283C under a
vacuum of 0.8 mbar. After a reaction time of 180 minutes,
a polymer having a relative solution viscosity of 1.590
was obtained. The b* value was 4.8 and the COOH end group
content was 22.5 equivalents/106 g of polymer.
This comparison example shows in particular that
the catalytic activity of the catalysts used according to
the invention is considerably higher than that of Sb2O3,
and with the former it is therefore possible to achieve
the same polycondensation times as when Sb2O3 is used by
considerably reducing the amount of catalyst employed,
and - if the colour values of the thread-forming
polyesters are important for certain uses - also to
achieve practically the same b* values (Examples 7, 8,
and 9).
Comparison Example 3
Example 7 was repeated with the modification that
at 250C, 213 ppm of titanium tetrabutylate, based on the
bis-(2-hydroxyethyl) terephthalate present, were added as
the polycondensation catalyst in the form of a 5%
strength by weight solution in glycol. The
polycondensation reaction was carried out at 290C under
a vacuum of 3.5 mbar. After a reaction time of 134
21 64805
- 26 - AGW2409
minutes, a polymer having a relative solution viscosity
of 1.633 was obtained. The b* value was 15.5 and the COOH
end group content was 20.2 equivalents/106 g of polymer.
This comparison example shows in particular
that, although titanium tetrabutylate has a higher
catalytic activity than Sb2O3 at a significantly poorer
b* value, it has to be employed in a higher concentration
than the catalysts used according to the invention to
achieve comparably short polycondensation times.
