U.S. patent application number 09/934383 was filed with the patent office on 2002-07-18 for process for the preparation of macrocyclic esters.
Invention is credited to Klein, Stephan, Mendoza-Frohn, Christine, Muller, Dirk, Ronge, Georg, Surburg, Horst, Verkerk, Kai.
Application Number | 20020095045 09/934383 |
Document ID | / |
Family ID | 7653403 |
Filed Date | 2002-07-18 |
United States Patent
Application |
20020095045 |
Kind Code |
A1 |
Surburg, Horst ; et
al. |
July 18, 2002 |
Process for the preparation of macrocyclic esters
Abstract
Macrocyclic ester compounds can be prepared from oligoesters by
thermal cleavage in the presence of a thermostable benzene
derivative.
Inventors: |
Surburg, Horst; (Holzminden,
DE) ; Muller, Dirk; (Bergisch Gladbach, DE) ;
Klein, Stephan; (Bergisch Gladbach, DE) ;
Mendoza-Frohn, Christine; (Erkrath, DE) ; Ronge,
Georg; (Dusseldorf, DE) ; Verkerk, Kai; (Koln,
DE) |
Correspondence
Address: |
BAYER CORPORATION
PATENT DEPARTMENT
100 BAYER ROAD
PITTSBURGH
PA
15205
US
|
Family ID: |
7653403 |
Appl. No.: |
09/934383 |
Filed: |
August 21, 2001 |
Current U.S.
Class: |
549/266 ;
549/267 |
Current CPC
Class: |
C07D 321/00 20130101;
C07D 315/00 20130101 |
Class at
Publication: |
549/266 ;
549/267 |
International
Class: |
C07D 315/00; C07D
321/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 23, 2000 |
DE |
10041198.3 |
Claims
What is claimed is:
1. A process for the preparation of macrocyclic ester compounds
comprising the steps of condensating difunctional compounds to give
linear oligoesters and subsequently, thermal depolymerization with
or without the addition of catalysts, wherien the depolymerization
is carried out in thermostable benzene derivatives at a pressure of
less than 100 hPa and at temperatures of from 200.degree. C. to
350.degree. C., 0.1 to 1000 parts by weight of solvent being used
per part by weight of the oligoester.
2. The process according to claim 1, wherein thermostable benzene
derivatives of the formula 7in which R.sup.1 is 8and R.sup.2 is H
or CH.sub.3, are used.
3. The process according to claim 2, wherein isomeric
dibenzyltoluenes are used as thermostable benzene derivatives.
4. The process according to claim 1, wherein said catalysts are the
alkali metals or alkaline earth metals or salts thereof, or salts
or organometallic compounds of the elements manganese, cadmium,
iron, cobalt, tin, lead, aluminium, zirconium or titanium.
5. The process according to claim 4, where dibutyltin oxide,
dioctyltin oxide, dibutyltin dilaurate, dioctyltin dilaurate,
dibutyltin bis-2-ethylhexanoate, butyltin tris-2-ethylhexanoate,
butyltin hydroxide oxide or cyclic dibutyl stannoxane are used as
catalyst.
6. The process according to claim 1, wherein the catalyst is
replenished in portions or continuously in order to achieve
constant concentrations of the active form of the catalyst.
7. The process according to claim 1, wherein a rectification
column, from the top of which the macrocyclic ester formed is
removed, is placed on top of the reaction container.
8. The process according to claim 1, wherein the thermostable
benzene compound is freed from high-boiling reaction residues in an
amount of more than 50 percent by weight by partial evaporation,
and is then reused as reaction medium in the oligoester
depolymerization.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a process for the
preparation of macrocyclic ester compounds from oligoesters by
thermal cleavage in the presence of thermostable benzene
derivatives. For the purposes of the present invention,
thermostable refers to compounds which behave mostly inert during
the oligoester cleavage at temperatures between 200.degree. C. and
350.degree. C.
BACKGROUND OF THE INVENTION
[0002] Musk fragrances are present in many perfume oils in not
inconsiderable amounts. Accordingly, the annual worldwide
requirement for musk fragrances is several thousand tons. By far
the largest part is provided by the so-called polycyclic aromatic
musk fragrances. It has become known that polycyclic aromatic musk
fragrances can only be biodegraded with difficulty and
consequently, being extremely lipophilic compounds, exhibit
bioaccumulative behavior, i.e. they are able to accumulate in the
fatty tissue of organisms. In the perfume industry, there is
therefore, a pressing need for biodegradeable musk fragrances which
are suitable both in terms of the odiferous properties and also in
terms of price as replacements for the polycyclic aromatic
compounds. In contrast to the polycyclic aromatic compounds,
macrocyclic musk fragrances are regarded as biodegradeable (U.S.
Pat. No. 6,034,052). The known processes cannot be carried out
economically in a satisfactory manner.
[0003] It is known that macrocyclic ester compounds can be prepared
by depolymerization of linear oligoesters of the corresponding
aliphatic hydroxycarboxylic acids or dicarboxylic acids and
alkylene glycols. The thermal depolymerization is usually carried
out without a diluent under vacuum (<100 hPa) and at high
temperatures (200-300.degree. C.) in the presence of a catalyst. A
codecisive factor for the cleavage yield achieved here is the
molecular weight of the oligoester used. For this reason, control
of this parameter during the oligoester formation is important. The
condensation reaction must, accordingly, be terminated at almost
complete conversions before the onset of the molar mass build-up
typical of the polyester reaction. A measure which can be used here
is, for example, the monitoring of the product viscosity.
Alternatively, the condensation and thus, the oligoester formation
can be carried out in the solvent chosen for the cleavage in order
to avoid high molecular weights. EP A 0 260 680 has already
indicated that it may be advantageous to control the molecular
weight and the viscosity of the oligoesters used by targeted
termination with monocarboxylic acids and/or monofunctional
alcohols. Polyesters with acid and OH numbers below 20 or below 10,
respectively, may be particularly advantageous.
[0004] During the depolymerization, the desired cyclization
reaction is accompanied by a further polycondensation of the linear
polyester and a further intermolecular crosslinking reaction. The
yield of product decreases significantly as a result. Moreover, the
crosslinking reactions lead to an increase in the viscosity and to
adhesion of the product to the wall of the reactor. This favors the
onset of decomposition reactions of the product; the decomposition
products may considerably impair the odiferous properties.
[0005] These disadvantages in the case of depolymerization without
a diluent can be overcome by carrying out the reaction in an inert
reaction medium with a high boiling point. The choice of reaction
medium here is decisive for the reaction yield which can be
achieved and the quality of the product and thus also for the
economic efficiency of the process. For example, EP A 0 260 680 has
proposed olefin polymers, JP A 55-120 581 has proposed polyesters,
polyether glycols, polyether glycol esters or only polyglycols, DE
A 3225431 has proposed paraffins, and EP A 0 739 889 has proposed
polyethylene glycol dialkyl ethers as high-boiling medium.
[0006] Although the use of these auxiliaries can increase the
product yield relative to a cleavage without a diluent, said
auxiliaries have the disadvantage that they mostly have a high
melting point, which makes handling difficult. This disadvantage is
all the more serious since one important requirement in the art is
that the thermostable reaction medium which is left behind in the
distillation still can be removed from the reactor easily when the
reaction is interrupted or complete, which is virtually impossible
in the case of the known processes with the traditional reaction
media.
[0007] In the case of the polyether glycols used and in the case of
the polyether glycol esters (JP-A 55-120 581), there is another
significant disadvantage in that they have functional groups which
participate in the polymerization in an undesired manner, possibly
leading to significant yield losses. In addition, in the case of
the paraffins, the difficulty also arises that they have relatively
high vapor pressures compared with the reactants and therefore also
convert to the vapor phase. For this reason, in the case of these
paraffins, isolation of the product, which follows the
depolymerization of the oligoester, is associated with
significantly higher expenditure.
[0008] Moreover, high-boiling reaction media such as, for example
paraffins (DE-A 32 25 341) or olefin polymers (EP-A 0 260 680) are
less suitable solvents for all linear poly- or oligoesters. In many
cases they only disperse said esters, and the particles may
coagulate to form blocks. A remedy is achieved in most cases by
further dilution, as a result of which the space-time yield is
significantly reduced, as is the case with known processes.
[0009] In addition, JP-B 55-120581 describes a process for carrying
out the depolymerization and cyclization in the presence of
polyoxyalkylene glycol and derivatives thereof, monohydric alcohols
and derivatives thereof or monobasic fatty acids and derivatives
thereof which in each case have a high boiling point. According to
this process, ether bonds in the polyoxyalkylene glycol added are
broken and, as a result, various degradation products or gases are
formed and, consequently, the vacuum is lower or the quality of the
resulting macrocyclic ester compound is impaired. In addition, the
odor of the monohydric alcohol or of the monobasic acid or of
derivatives thereof mix with the distillate and as a result the
scent of the macrocyclic ester compound is impaired and its use as
a perfume is impeded. These phenomena are regarded as disadvantages
of these customary processes.
[0010] Finally, the use of polyethylene glycol dialkyl ethers (EP A
0 739 889) is associated with the disadvantage that the desired
effect of an increase in the yield is achieved only at sufficiently
great dilution ratios; for example, in EP A 0 739 889, dilution
ratios between 5 and 1000 parts by weight of polyethylene glycol
dialkyl ether to 1 part by weight of oligomer are given. A further
important disadvantage of the use of polyethylene glycol dialkyl
ethers is also that a work-up of the solvent is not readily
possible and therefore, by-products which contaminate the solvent
considerably limit the suitability of the solvent.
SUMMARY OF THE INVENTION
[0011] The object of the present invention was, therefore, to find
a preparation process for macrocyclic ester compounds with which as
high a reaction yield as possible can be achieved and with which,
the solvent costs can also be reduced, by using a solvent which
restricts the formation of by-products which prevent use of the
macrocyclic ester compounds as a fragrance, which has a low melting
point and thus, good handling properties, which simplifies product
separation by virtue of having a high boiling point, and which can
be worked-up readily for reuse in the process without relatively
large losses as a result of residue formation.
[0012] We have now found a process for the preparation of
macrocyclic ester compounds obtainable from linear oligoesters by
thermal depolymerization with or without the addition of catalysts,
which is characterized in that the depolymerization is carried out
in thermostable benzene derivatives at a pressure of less than 100
hPa, and at temperatures of from 200.degree. C. to 350.degree. C.,
0.1 to 1000 parts by weight of solvent being used per part by
weight of the oligoester.
DETAILED DESCRIPTION OF THE INVENTION
[0013] Macrocyclic ester compounds which can be prepared by the
process according to the present invention are generally 14- to
17-member ring systems. They can be described by the following
general formula 1
[0014] in which
[0015] x and y produce in total a number of at least 10 and at most
13;
[0016] A may be a methylene group or a heteroatom, such as oxygen
or sulfur;
[0017] B may be a methylene group or a carbonyl group or
[0018] A and B taken together may be a carbon double-bond.
[0019] Preferably, the process according to the present invention
may be used to prepare macrocyclic lactones of co-hydroxycarboxylic
acids which may optionally comprise a double bond and/or a further
heteroatom, e.g. oxygen, or macrocyclic lactones of dicarboxylic
acids and diols.
[0020] Particularly preferably, the process according to the
present invention can be used to prepare 1,15-pentadecanolide,
cis-/trans-1,15-pentadec-11-enolide,
cis-/trans-1,15-pentadec-12-enolide or mixtures thereof,
1,16-hexadecanolide or trans-1,16-hexadec-9-enolide or ethylene
tridecadioate, ethylene dodecadioate or ethylene undecadioate or
mixtures thereof.
[0021] The linear oligoesters for the process according to the
present invention can be described by the following general
formula: 2
[0022] in which
[0023] x and y produce in total a number of at least 10 and at most
13;
[0024] A may be a methylene group or a heteroatom, such as oxygen
or sulfur;
[0025] B may be a methylene group or a carbonyl group or
[0026] A and B taken together may be a carbon double-bond.
[0027] For the process according to the present invention,
oligoesters of aliphatic hydroxycarboxylic acids or oligoesters of
dicarboxylic acids with diols are preferred.
[0028] Linear oligoesters as starting compounds for the process
according to the present invention can be prepared by condensation
of difunctional compounds of the formula 3
[0029] in which
[0030] x and y produce in total a number of at least 10 and at most
13;
[0031] A may be a methylene group or a heteroatom, such as oxygen
or sulfur;
[0032] B may be a methylene group or A and B taken together may be
a carbon double-bond;
[0033] R.sup.1 may be a hydrogen atom or a lower alkyl group, such
as, for example, methyl or ethyl,
[0034] or of the formula 4
[0035] in which
[0036] x and y produce in total a number of at least 10 and at most
13;
[0037] R.sup.1 may be a hydrogen atom or a lower alkyl group, such
as, for example, methyl or ethyl,
[0038] in a manner known per se (DE B 2731543; Houben-Weyl,
Methoden der Organischen Chemie [Methods of Organic Chemistry]
Vol.4/2, p. 787ff. and Vol. 6/2, p. 738f.).
[0039] The process according to the present invention is based on a
thermal cleavage of oligoesters to the desired macrocyclic esters.
The cleavage reaction is carried out in a vacuum and at very high
temperatures in an inert, high-boiling reaction medium with or
without the addition of catalysts, a rectification column being
placed on top of the container in which the chemical reaction takes
place and used to separate off and concentrate the macrocyclic
esters formed. Here, the thermal cleavage is carried out in
thermostable, high-boiling alkylbenzene or benzene derivatives,
e.g. of the formula 5
[0040] in which
[0041] R.sup.1 is 6
[0042] and
[0043] R.sup.2 is H or CH.sub.3
[0044] as reaction medium. By using these thermostable benzene
derivatives, the yield is significantly increased compared with a
cleavage without a diluent. The derivatives of type a) are
essentially isomeric dibenzyltoluenes, b) refers to the group of
diarylalkyls, c) represents the bi- or triaryl oxides, d) includes
the group of terphenyls and their partially hydrogenated analogues
and, finally, e) represents the alkylated or non-alkyl-substituted
benzyltoluenes.
[0045] Preferred thermostable benzene derivatives are
dibenzyltoluenes and isomer mixtures thereof, and terphenyls and
their partially hydrogenated analogues. A more preferred embodiment
is dibenzyltoluenes and isomeric mixtures thereof.
[0046] The thermostable benzene derivatives for the process
according to the present invention have a low melting point and a
high boiling point at the same time. However, despite the high
boiling point, they are very vaporizable and can, therefore, be
separated readily from high-boiling impurities. Their use as
reaction medium is therefore advantageous both with regard to
handling and also with regard to product separation. For example
separation of the product from the reaction medium is possible in a
rectification column with only a few separation stages, the number
of separation stages required and the reflux ratio to be set being
governed by the difference in boiling points between the
macrocyclic ester formed and the solvent used.
[0047] If benzene derivatives are used, reaction yields of more
than 90% can be achieved. In this connection, it is essential for
the economic efficiency of the process that the high reaction
yields can be achieved at low solvent costs. This is possible, in
particular, by setting low dilution ratios of solvent to oligomer
during the depolymerization and, moreover, working-up the spent
solvent for recycle and reuse in the process.
[0048] It was surprising that the benzene derivatives used as
reaction medium for the thermal depolymerization are stable. This
was unexpected since alkyl- and benzyl-substituted benzene
derivatives in the presence of the catalysts suitable for the
depolymerization and at the high reaction temperatures are able to
undergo transalkylation reactions, in the course of which
high-boiling and low-boiling components are formed as a result of
disproportionation. As well as a solvent loss, this would also
permanently impair the suitability of the solvent since low-boiling
solvent constituents accumulate in the product, and the
high-boiling constituents can lead to resinification of the
distillation bottoms.
[0049] In particular, dibenzene toluene, which is available in
technical-grade form as an isomer mixture, has an excellent profile
of properties for the process according to the present invention,
since it permits particularly effective separation from the product
which distills off, as a result of its high, comparatively narrow
boiling range.
[0050] For reasons of simplicity, the condensation of the
difunctional compounds to give the linear oligoesters is connected
upstream of the process according to the present invention.
[0051] Implementation of the process is, therefore, first started
with the condensation, which can be carried out in accordance with
known methods at elevated temperatures with or without catalyst. In
this process, hydroxycarboxylic acids, or hydroxycarboxylic esters
are heated, or the dicarboxylic acids or esters thereof are reacted
with a glycol. The water which forms in the process or the alcohol
is distilled off or removed using an entrainer or with the help of
a slight vacuum. The removal of some or all of the excess glycol
can also be carried out in the subsequent process step, i.e. from
the cleavage reactor.
[0052] The oligomer is then transferred to the cleavage reactor,
into which the high-boiling medium has been introduced together
with the catalyst component. The catalysts used are customary
catalysts known per se (EP A 0 739 889), such as, for example,
alkali metals and alkaline earth metals and salts thereof, and
salts and organometallic compounds of the elements manganese,
cadmium, iron, cobalt, tin, lead, aluminium, zirconium and
titanium. The amount of catalyst is in the range from 0.1 to 20% by
weight, preferably in the range from 0.5 to 10% by weight, based on
100% by weight of oligoester, depending on the corresponding type
used.
[0053] At high temperatures between 200.degree. C. and 350.degree.
C., preferably between 220.degree. C. and 290.degree. C., and at a
vacuum of less than 100 hPa, the depolymerization then takes place.
The cleavage products preferably rise during the process in the
form of vapors and are thus, withdrawn directly from the reaction
in the liquid phase. The product components can be separated from
the components of the reaction medium in a rectification column
placed on top of the reaction container, at the upper end of the
column the product components being withdrawn, and at the lower end
of the column the components of the reaction mixture being taken
off for recycling to the reaction container. The column is operated
for this purpose at pressures of <100 hPa, the pressure range
preferably being from 5 to 95 hPa, particularly preferably from 10
to 80 hPa. At the top of the column, a reflux ratio between 0.1 and
100, preferably between 10 and 80, is to be set.
[0054] The process can either be carried out either batchwise or
continuously. In the case of a batchwise procedure, the oligomer is
introduced in one portion together with the solvent and cleaved in
one batch. By contrast, in the case of the continuous procedure,
the oligomer is metered into the reaction medium during the
cleavage in portions or with a constant material stream. Preference
is given to carrying out the continuous procedure since in this
case the product can be removed from the top of the column with a
constant composition.
[0055] The solvent is recovered by partial evaporation, for example
in a thin-layer evaporator at pressures of less than 100 hPa,
preferably at pressures of less than 50 hPa.
[0056] A very wide variety of macrocyclic ester compounds can be
prepared by this process. It is particularly suitable for the
preparation of macrocyclic esters having 6 to 20, preferably 13 to
16, carbon atoms, since they can be prepared in particularly pure
form by the process according to the present invention, which is
highly beneficial to their use as fragrances. In particular, using
the process according to the present invention, it is also possible
to prepare the mixtures of ethylene dodecanedioate and ethylene
undecanedioate described in U.S. Pat. No. 6,034,052.
EXAMPLES
Example 1
[0057] Preparation of Ethylene Tridecanedioate
[0058] a) Preparation of ethylene glycol tridecanedioic polyester
500 g of a dimethyl tridecanedioate, 250 g of ethylene glycol and 3
g of tetrabutyl titanate are heated slowly under a vacuum of 300
hPa in a reaction distillation apparatus. As soon as a reaction
temperature of 140.degree. C. has been reached, methanol starts to
be eliminated. The heating is continued until methanol is no longer
eliminated; in this connection, the still temperature is slowly
increased to 185.degree. C. The vacuum is let down to 1 hPa, and
the excess ethylene glycol is distilled off. 510 g of polyester are
obtained as residue.
[0059] b) Depolymerization of the Ethylene Glycol Tridecanedioc
Polyester
[0060] A molten mixture comprising 2 parts by weight of
dibenzyltoluene (isomer mixture), 1 part by weight of ethylene
glycol tridecanedioic polyester and 0.02 parts by weight of
dibutyltin dilaurate is metered into a reaction container with
attached rectification column, which contains a mixture of 2 parts
by weight of dibenzyltoluene (isomer mixture) and 0.02 parts by
weight of dibutyltin dilaurate, which is heated to about
280.degree. C. and refluxed at a pressure of 55 hPa. The formation
of monomeric ethylene tridecanedioate becomes evident from a
reduction in the temperature at the distillation head. The
distillate is removed at the rate which polyester is replenished.
Depending on the separation efficiency of the attached
rectification column and the chosen reflux ratio, the distillate
removed comprises between 30 and 98% ethylene tridecanedioate,
which is obtained in pure form in a subsequent fine distillation.
By this method, the yield is about 90%, based on the dimethyl
tridecanedioate used.
[0061] By distilling the reaction residue, more than 90% of the
dibenzyltoluene used are recovered.
Example 2
[0062] Preparation of a Mixture of Ethylene Dodecanedioate and
Ethylene Undecanedioate
[0063] a) Preparation of the Polyester
[0064] 225 g of a technical-grade mixture comprising between 40 and
60% of dodecanedioic acid and 30-50% of undecanedioic acid are
admixed with 105 g of ethylene glycol and slowly heated to
150.degree. C.; at about 130.degree. C. to 140.degree. C., water
starts to be eliminated. When water elimination is complete, to
remove excess ethylene glycol, the temperature is increased to
170.degree. C. and the reaction apparatus is slowly evacuated to a
pressure of 1 hPa.
[0065] b) Depolymerization
[0066] The dicarboxylic acid/ethylene glycol polyester resulting as
residue is admixed, per part by weight of polyester, with 3 parts
by weight of dibenzyltoluene (isomer mixture) and 0.05 parts by
weight of dibutyltin dilaurate and heated in a reaction container
with attached rectification column at a pressure of 55 hPa at about
280.degree. C. and refluxed. In the process, the monomeric cleavage
products distil over. At the start, the distillate comprises,
depending on the composition of the starting material, between
40-60% of ethylene dodecanedioate and 30 to 50% of ethylene
undecanedioate, and in the further course of the reaction,
increasingly also small amounts of dibenzyltoluenes, which are
separated off in a subsequent fine distillation. Overall, a
reaction yield of about 91% is achieved in the
depolymerization.
[0067] By distilling the reaction residue, more than 90% of the
dibenzyltoluene used are recovered.
Example 3
[0068] Preparation of a Mixture of Ethylene Dodecanedioate and
Ethylene Undecanedioate
[0069] a) Polymerization
[0070] 250 g of ethylene glycol, 500 g of a technical-grade mixture
consisting of 40 to 60% of dimethyl dodecanedioate and 30-50% of
dimethyl dodecanedioate, and 3 g of tetrabutyl titanate are heated
slowly under a vacuum of 300 hPa in a reaction distillation
apparatus. At a reaction temperature of between 130-140.degree. C.,
methanol starts to be eliminated, which is distilled off over a 30
cm packed column. Heating is continued until methanol is no longer
eliminated; here, the still temperature is slowly increased to
185.degree. C. The vacuum is then let down to 1 hPa, and the excess
ethylene glycol is distilled off. 500 g polyester are obtained as
residue.
[0071] b) Depolymerization
[0072] A molten mixture comprising 500 g of dibenzyltoluene (isomer
mixture), 250 g of the diacid ethylene glycol polyester mixture
obtained as in a) and 5 g of dibutyltin dilaurate is metered into a
reaction container with attached rectification column which
contains a mixture of 500 g of dibenzyltoluene (isomer mixture) and
5 g of dibutyltin dilaurate, which is heated to about 280.degree.
C. and is refluxed at a pressure of 55 hPa. The formation of
monomeric esters becomes evident from a reduction in the
temperature at the distillation head. As soon as the head
temperature has dropped below 220.degree. C., the distillate is
taken off and polyester mixture is continuously replenished.
Depending on the separation efficiency of the attached
rectification column and the chosen reflux ratio, the distillate
taken off comprises between 30 and 98% of a mixture of the monomers
ethylene dodecanedioate and ethylene undecanedioate. In the present
case, at a head temperature of 220-225.degree. C. and a reflux
ratio of 15:1 490 g of distillate with a weight fraction of 225 g
of ethylene dodecanedioate and ethylene undecanedioate mixture were
obtained, which corresponds to a yield of 90%, based on
dicarboxylic acid dimethyl ester mixture used. The mixture of
ethylene dodecanedioate and ethylene undecanedioate was separated
off from the dibenzyltoluene in a subsequent fine distillation and
thus obtained in pure form.
[0073] By distilling the reaction residue, more than 90% of the
dibenzyltoluene used are recovered.
Example 4
[0074] Preparation of 1,15-pentadecanolide
[0075] a) Preparation of the Polyester
[0076] 260 g of 15-hydroxypentadecanoic acid are slowly heated to
170.degree. C. under a slight vacuum (650 hPa). As soon as the
elimination of water has subsided, the mixture is stirred for a
further 1 h at a vacuum of 20 hPa and for 30 min at a vacuum of 1
hPa. The polyester of 15-hydroxypentadecanoic acid is left behind
as residue.
[0077] b) Depolymerization
[0078] A molten mixture comprising 1 part by weight of the
15-hydroxy-pentadecanoic polyester left behind as residue, 2 parts
by weight of dibenzyltoluene (isomer mixture) and 0.02 parts by
weight of dibutyltin dilaurate is metered into a reaction container
with attached rectification column which contains a mixture of 2
parts by weight of dibenzoyltoluene (isomer mixture) and 0.02 parts
by weight of dibutyltin dilaurate, which is heated to about
280.degree. C. and is refluxed at a pressure of 55 hPa. The
formation of monomeric 1,15-pentadecanolide becomes evident from a
reduction in the temperature at the distillation head. Distillate
is taken off at the rate at which polyester is replenished.
Depending on the separation efficiency of the attached
rectification column and the reflux ratio chosen, the distillate
taken off comprises between 30 and 95% of 1,15-pentadecanolide.
[0079] In the present case, at a head temperature of
215-220.degree. C. and a reflux ratio of 10:1, a distillate with a
weight fraction of about 60% of 1,15-pentadecanolide was obtained,
which is obtained in pure form in a subsequent fine distillation.
The yield of the 1,15-pentadecanolide obtained in this way is 85%,
based on 15-hydroxypentadecanoic polyester used.
[0080] By distilling the reaction residue, more than 90% of the
dibenzyltoluene used are recovered.
Example 5
[0081] Preparation of cis-/trans-1,15-pentadec-11/12-enolide
[0082] a) Preparation of the Polyester
[0083] 260 g of cis-/trans-15-hydroxy-11/12-pentadecenoic acid are
slowly heated to 170.degree. C. under a slight vacuum (650 hPa). As
soon as the elimination of water subsides, the mixture is stirred
for a further 1 h at a vacuum of 20 hPa and for 30 min at a vacuum
of 1 hPa. The polyester of 15-hydroxypentadecanoic acid is left
behind as residue.
[0084] b) Depolymerization
[0085] A molten mixture comprising 1 part by weight of the
cis-/trans-15-hydroxy-11/12-pentadecanoic polyester which is left
behind as residue, 2 parts by weight of dibenzyltoluene (isomer
mixture) and 0.02 parts by weight of dibutyltin dilaurate is
metered into a reaction container with attached rectification
column which contains a mixture of 2 parts by weight of
dibenzyltoluene (isomer mixture) and 0.02 parts by weight of
dibutyltin dilaurate, which is heated to about 280.degree. C. and
refluxed at a pressure of 55 hPa. The formation of monomeric
cis-/trans-1,15-pentadec-11/12-enolide is evident from a reduction
in temperature at the distillation head. The distillate is taken
off at the rate at which the polyester is replenished. According to
the separation efficiency of the attached rectification column and
the reflux ratio chosen, the distillate taken off comprises between
30 and 90% of 1,15-pentadecanolide. In the present case, at a head
temperature of 210-215.degree. C. and a reflux ratio of 10:1, a
distillate with a weight fraction of about 60%
cis-/trans-1,15-pentadec-11/12-enolide is obtained, which is
obtained in pure form in a subsequent fine distillation.
[0086] The yield of cis-/trans-1,15-pentadec-11/12-enolide obtained
in this way is about 85%, based on 15-hydroxypentadecanoic
polyester used.
[0087] By distilling the reaction residue, more than 90% of the
dibenzyltoluene used are recovered.
Example 6
[0088] Preparation of 1,1 6-hexadecanolide
[0089] a) Preparation of the Polyester
[0090] 140 g of 16-Hydroxyhexadecanoic acid are slowly heated to
170.degree. C. under a slight vacuum (650 hPa). As soon as the
elimination of water subsides, the mixture is stirred for a further
1 h at a vacuum of 20 hPa and for 30 min at a vacuum of 1 hPa. The
polyester of 16-hydroxyhexadecanoic acid is left behind as
residue.
[0091] b) Depolymerization
[0092] A molten mixture of 1 part by weight of the
16-hydroxyhexadecanoic polyester which is left behind as residue, 2
parts by weight of dibenzyltoluene (isomer mixture) and 0.02 parts
by weight of dibutyltin dilaurate is metered into a reaction
container with attached rectification column which contains a
mixture of 2 parts by weight of dibenzyltoluene (isomer mixture)
and 0.02 parts by weight of dioctyltin dilaurate, which is heated
to about 280.degree. C. and refluxed at a pressure of 55 hPa. The
formation of monomeric 1,16-hexadecanolide is evident from a
reduction in the temperature at the distillation head. Distillate
is taken off at the rate at which polyester is replenished.
Depending on the separation efficiency of the attached
rectification column and the reflux ratio chosen, the distillate
taken of comprises between 30 and 90% of 1,16-hexadecanolide. In
the present case, at a head temperature of 220-230.degree. C. and a
reflux ratio of 5:1, a distillate with a weight fraction of about
50% of 1,16-hexadecanolide is obtained, which is obtained in pure
form by subsequent fine distillation. The yield of
1,16-hexadecanolide achieved in this way is about 75%, based on
16-hydroxyhexadecanoic polyester used.
[0093] By distilling the reaction residue, more than 90% of the
dibenzyltoluene used are recovered.
Example 7
[0094] Preparation of trans-1,16-hexadec-9-enolide
[0095] a) Preparation of the Polyester
[0096] 260 g of trans-16-hydroxy-9-hexadecenoic acid are slowly
heated to 170.degree. C. under a slight vacuum (650 hPa). As soon
as the elimination of water has subsided, the mixture is stirred
for a further 1 h at a vacuum of 20 hPa and for 30 min at a vacuum
of 1 hPa. The polyester of trans-16-hydroxy-9hexadecanoic acid is
left behind as residue.
[0097] b) Depolymerization
[0098] A molten mixture comprising 1 part by weight of the
trans-16-hydroxy-9-hexadecenoic polyester which is left behind as
residue, 2 parts by weight of dibenzyltoluene (isomer mixture) and
0.02 parts by weight of dibutyltin dilaurate is metered in to a
reaction container with attached rectification column which
contains a mixture of 2 parts by weight of dibenzyltoluene (isomer
mixture) and 0.02 parts by weight of dibutyltin dilaurate, which is
heated to about 280.degree. C. and refluxed at a pressure of 55
hPa. The formation of monomeric trans-, 16-hexadec-9-enolide is
evident from a reduction in the temperature at the distillation
head. Distillate is taken off at the rate at which polyester is
replenished. Depending on the separation efficiency of the attached
rectification column and the chosen reflux ratio, the distillate
taken off comprises between 30 and 90% of
trans-1,16-hexadec-9-enolide.
[0099] In the present case, at a head temperature of
225-235.degree. C. and a reflux ratio of 10:1, a distillate with a
weight fraction of about 60% of trans-1,16-hexadec-9-enolide was
obtained, which is obtained in pure form in a subsequent fine
distillation. The yield of trans-1,16-hexadec-9-enolide achieved in
this way is about 80%, based on trans-16-hydroxy-9-hexadecenoic
polyester used.
[0100] By distilling the reaction residue, more than 90% of the
dibenzyltoluene used are recovered.
Example 8
[0101] Preparation of a Mixture of Ethylene Dodecanedioate and
Ethylene Undecanedioate
[0102] A molten mixture of 260 g of partially hydrogenated
terphenyl (isomer mixture, trade name Diphyl THT, Bayer AG), 130 g
of the diacid ethylene glycol polyester mixture obtained as in
Example 3a), and 6.4 g of dibutyltin dilaurate is metered into a
reaction container with attached rectification column which
contains a mixture of 500 g of partially hydrogenated terphenyl
(isomer mixture, see above), which is heated to about 280.degree.
C. and refluxed at a pressure of 110 hPa. The formation of
monomeric esters is evident from a reduction in the temperature at
the distillation head. As soon as the head temperature has dropped
below 240.degree. C., distillate is taken off and polyester mixture
is continuously replenished. Depending on the separation efficiency
of the attached rectification column and the reflux ratio chosen,
the distillate taken off comprises between 20 and 90% of a mixture
of the monomers ethylene dodecanedioate and ethylene
undecanedioate. In the present case, at a head temperature of
238-240.degree. C. and a reflux ratio of 10:1, 250 g of distillate
with a weight fraction 95 g of ethylene dodecanedioate and ethylene
undecanedioate mixture were obtained, which corresponds to a yield
of 70%, based on dicarboxylic dimethyl ester mixture used. The
mixture of ethylene dodecanedioate and ethylene undecanedioate was
separated off from the partially hydrogenated terphenyl in a
subsequent fine distillation and thus obtained in pure form.
[0103] By distilling the reaction residue, more than 90% of the
partially hydrogenated terphenyl used are recovered.
[0104] Although the invention has been described in detail in the
foregoing for the purpose of illustration, it is to be understood
that such detail is solely for that purpose and that variations can
be made therein by those skilled in the art without departing from
the spirit and scope of the invention except as it may be limited
by the claims.
* * * * *