EP1315713A2

EP1315713A2 - Method for the production of macrocyclic esters

Info

Publication number: EP1315713A2
Application number: EP01974158A
Authority: EP
Inventors: Horst Surburg; Dirk MÜLLER; Stephan Klein; Christine Mendoza-Frohn; Georg Ronge; Kai Verkerk
Original assignee: Haarmann and Reimer GmbH; Symrise AG
Current assignee: Symrise AG
Priority date: 2000-08-23
Filing date: 2001-08-10
Publication date: 2003-06-04
Also published as: WO2002016345A2; US20020095045A1; AU2001293753A1; DE10041198A1; JP2004524265A; DE10041198B4; US6458972B1; WO2002016345A3

Abstract

Macrocyclic ester compounds may be produced from oligoesters by thermal cleavage in the presence of a thermostable benzene derivative.

Description

Process for the production of macrocyclic esters

The present invention relates to a ner 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 invention, compounds which are largely thermally stable are those which are largely inert during the oligoester cleavage at temperatures between 200 ° C. and 350 ° C.

Musk fragrances are present in many perfume oils in considerable quantities. Accordingly, the global annual demand for musk fragrances is several thousand tons. The vast majority is provided by the so-called polycyclic aromatic musk fragrances. It has become known that polycyclic aromatic musk fragrances are difficult to biodegrade and consequently behave as extremely lipophilic compounds in a bioaccumulative manner, i.e. can accumulate in the adipose tissue of living beings. There is therefore an urgent need in the perfume industry for biodegradable musk fragrances which are suitable both in terms of their olfactory properties and their price level to replace the polycyclic aromatic compounds. In contrast to the polycyclic aromatic compounds, macrocyclic musk fragrances are seen as biodegradable (US Pat. No. 6,034,052). The known methods cannot be carried out economically in a satisfactory manner.

It is known that macrocyclic ester compounds can be prepared by depolymerizing linear oligoesters of the corresponding aliphatic hydroxycarboxylic acids or dicarboxylic acids and alkylene glycols. The bulk thermal depolymerization is usually carried out under vacuum (<100 hPa) and at high temperatures (200-300 ° C) in the presence of a catalyst. The molecular weight of the oligoester used is decisive for the cleavage yield achieved. Therefore, the control of this size during the oligoester education important. The condensation reaction must therefore be stopped before the onset of the molecular weight build-up, which is typical for the polyester reaction, with almost complete conversions. The tracking of the product viscosity can be used as a measure. Alternatively, the condensation and thus the formation of oligoesters to avoid high molecular weights can already be used for

Cleavage selected solvents are carried out. Already in EP A 0 260 680 it was pointed out that it can 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 and below 10 are particularly advantageous.

In depolymerization, the desired cyclization reaction is accompanied by a further polycondensation of the linear polyester and a further intermolecular crosslinking reaction. As a result, the yield of product decreases significantly. In addition, the crosslinking reactions lead to an increase in

Viscosity and wall adhesion of the product in the reactor. As a result, decomposition reactions of the product set in, the decomposition products being able to significantly impair the olfactory properties.

These disadvantages of bulk depolymerization can be overcome by carrying out the reaction in an inert reaction medium with a high boiling point. The selection of the reaction medium is decisive for the achievable reaction yield and the quality of the product and thus also for the economy of the process. In EP A 0 260 680, for example, olefin polymers, in JP A 55-120 581 polyesters, polyether glycols, polyether glycol esters or only polyglycols, in DE A 3225431 paraffins, in EP A 0 739 889 polyethylene glycol dialkyl ethers are proposed as high-boiling medium.

The use of these auxiliaries can increase the product yield compared to a cleavage in bulk. However, the additives mentioned have the

Disadvantage that they usually have a high melting point, which makes handling difficult. This disadvantage is all the more serious since an important requirement in the art is that the thermostable reaction medium remaining in the distillation bottom can be conveniently removed from the reactor when the reaction is interrupted or ended, which is hardly possible in the known processes with the conventional reaction media ,

Another major disadvantage of the polyether glycols used and of the polyether glycol esters (JP-A 55-120 581) is that they have functional groups which participate in the polymerization in an undesirable manner, which can lead to significant losses in yield. The paraffins also have the difficulty that they have relatively high vapor pressures compared to the reactants and therefore pass into the vapor phase. Therefore, when using paraffins, the preparation of the product in pure form, which follows the depolymerization of the oligoester, is associated with a significantly higher outlay.

In addition, high-boiling reaction media such as paraffins (DE-A 32 25 341) or olefin polymers (EP-A 0 260 680) are unsuitable solvents for all linear polyesters or oligoesters. They often only disperse them, whereby the particles can coagulate into blocks. Remedy is usually achieved by further dilution, which significantly reduces the space-time yield, as is the case according to known methods.

JP-B 55-120581 also describes a process for carrying out the depolymerization and cyclization in the presence of polyoxyalkylene glycol and its derivatives, monohydric alcohols and their derivatives or monohydric fatty acids and their derivatives, each of which has a high boiling point. According to this process, ether bonds of the added polyoxyalkylene glycol are broken down and various degradation products or gases are formed, and as a result the vacuum is reduced or the quality of the macroeylics obtained

Ester compound deteriorated. Furthermore, the smell of the monovalent mix Alcohol or the monohydric acid or its derivatives with the distillate and thereby the fragrance of the macrocyclic ester compound is adversely affected and its use as a perfume is difficult. These phenomena are reported as disadvantages in these conventional processes.

Finally, the use of polyethylene glycol dialkyl ether (EP A 0 739 889) has the disadvantage that the desired effect of increasing the yield is only achieved with sufficiently high dilution ratios; For example, EP A 0 739 889 shows dilution ratios between 5 and 1000 parts by weight of polyethylene glycol dialkyl ether to 1 part by weight of oligomer. Another major disadvantage of using polyethylene glycol dialkyl ether is that it is not easy to work up the solvent and therefore by-products which contaminate the solvent considerably restrict the usability of the solvent.

The object of the present invention was therefore to find a production process for macrocyclic ester compounds with which the highest possible reaction yield can be achieved and with which the solvent costs can also be reduced by using a solvent which prevents the formation of by-products which prevent the use of the macrocyclic ester compounds as a fragrance, which has a low melting point and is therefore easy to handle, which simplifies product separation due to a high boiling point and which can be worked up well for recycling in the process without major losses due to residue formation.

A process for the preparation of macrocyclic ester compounds, obtainable from linear oligoesters by thermal depolymerization with or without the addition of catalysts, has been found, which is characterized in that the depolymerization in thermostable benzene derivatives at a pressure of less than 100 hPa and at temperatures of 200 ° C to 350 ° C is carried out, with each Parts by weight of the oligoester 0.1 to 1000 parts by weight of solvent are used.

Macrocychic ester compounds which can be prepared by the process according to the invention are generally 14 to 17-membered ring systems. They can be described by the following general formula

wherein

x and y add up to a number of at least 10 and at most 13;

A can represent a methylene group or a hetero atom such as oxygen or sulfur;

B may represent a methylene group or a carbonyl group or

A and B taken together can represent a carbon double bond.

Macrocych lactones of ω-hydroxycarboxylic acids, which optionally have a double bond and / or a further heteroatom, e.g. May contain oxygen, or macrocychic lactones of dicarboxylic acids and diols.

In particular, 1,15-pentadecanolide, cis / trans-l, 15-pentadec-l 1-enolide, cis / trans-l, 15-pentadec-12-enolide or mixtures thereof, 1 , 16-hexadecanolide or trans-l, 16-hexadec-9-enolide or Ethylene tridecadioate, ethylene dodecadioate or ethylene undecadioate or mixtures thereof.

The linear oligoesters for the process according to the invention can be described by the following general formula:

embedded image in which

x and y add up to a number of at least 10 and at most 13;

A can represent a methylene group or a hetero atom such as oxygen or sulfur;

B may represent a methylene group or a carbonyl group or

A and B taken together can represent a carbon double bond.

Oligoesters of aliphatic hydroxycarbon acids or olio esters of dicarboxylic acids with diols are preferred for the process according to the invention.

Linear oligoesters as starting compounds for the process according to the invention can be obtained by condensation of difunctional compounds of the formula

embedded image in which x and y add up to a number of at least 10 and at most 13;

A can represent a methylene group or a hetero atom such as oxygen or sulfur;

B can mean a methylene group or A and B together can be one

Can mean carbon double bond; R ^{1 is} a hydrogen atom or a lower alkyl group, such as methyl or

Ethyl can mean i or the formula

wherein

x and y add up to a number of at least 10 and at most 13;

R ^{1 can denote} a hydrogen atom or a lower alkyl group, such as methyl or ethyl,

in a manner known per se (DE B 2731543; Houben-Weyl, Methods of Organic Chemistry Vol. 4/2, pp. 787ff. and Vol. 6/2, pp. 738f.).

The process according to the invention is based on thermal cleavage of oligoesters to the desired macrocyclic esters. The cleavage reaction is carried out in vacuo 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 the container in which the chemical reaction takes place is attached, with which the macrocyclic esters formed are separated off and concentrated. Here, the thermal cleavage in thermostable, high-boiling aikylbenzene or benzene derivatives, for example of the formula

embedded image in which

R ¹

c) \

^{, Q →} /;

and

R ² H or CH ₃

means

is carried out as a reaction medium. By using these thermostable benzene derivatives, the yield becomes clear compared to cleavage in bulk increase. The derivatives of the form a) are essentially isomeric dibenzyltoluenes, b) denotes the group of diarylalkyls, c) represents the bi- or triaryloxides, d) includes the group of terphenyls and their partially hydrogenated analogues, and e) finally represents them alkylated or nonalkyl-substituted benzyltoluenes.

Preferred thermostable benzene derivatives are dibenzyltoluenes and their isomer mixtures, and terphenyls and their partially hydrogenated analogs. Dibenzyltoluenes and their isomer mixtures are particularly preferred.

The thermostable benzene derivatives for the process according to the invention simultaneously have a low melting point and a high boiling point. Despite the high boiling point, however, they are easily evaporable and can therefore be easily separated from high-boiling contaminants. Their use as a reaction medium is therefore advantageous both in terms of handling and in terms of product separation. In this way, the product can be separated from the reaction medium in a rectification column with a few separation stages, the number of separation stages required and the reflux ratio to be set being based on the boiling point difference between the macrocyclic ester formed and the solvent used.

When using the benzene derivatives, reaction yields of more than 90% can be achieved. It is essential for the economy of the process that the high reaction yields can be achieved at low solvent costs. This is achieved in particular by the fact that low depolymerization

Dilution ratios of solvent to oligomer are set and the used solvent is also processed for recycling and recycling in the process.

It was surprising that the benzene derivatives used as the reaction medium for the thermal depolymerization are stable. You couldn't expect that there alkyl- or benzyl-substituted benzene derivatives can undergo transalkylation reactions in the presence of the catalysts suitable for depolymerization and at the high reaction temperatures, in the course of which high and low boilers are formed by disproportionation. In addition to a loss of solvent, this would also have a lasting negative effect on 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.

In particular, dibenzyltoluene, which is technically available as a mixture of isomers, has an excellent profile of properties for the process according to the invention, since its high, comparatively narrow boiling range permits particularly effective separation from the product to be distilled off.

For simplicity, the process according to the invention is preceded by the condensation of the difunctional compounds to the linear oligoesters.

The process is therefore initially carried out with the condensation, which can be carried out according to known processes at elevated temperatures with or without a catalyst. Hydroxycarboxylic acids or hydroxycarboxylic acid esters are heated or the dicarboxylic acids or their esters are reacted with a glycol. The water or alcohol formed is distilled off or removed with the aid of an entrainer or with the aid of a slight vacuum. The removal of excess glycol can also be done in whole or in part in the subsequent process step, i.e. from the cleavage reactor.

The oligomer is then transferred to the cleavage reactor in which the high-boiling medium together with the catalyst component are placed. The catalysts used are conventional catalysts known per se (EP A 0 739 889), such as, for example, alkali and alkaline earth metals and their salts, and also salts and organometallic compounds of the elements manganese, cadmium, iron, cobalt, Tin, lead, aluminum, zircon and titanium. The amount of the catalyst is, depending on the use of the corresponding type, in the range from 0.1 to 20% by weight, but preferably in the range from 0.5 to 10% by weight, based on 100% by weight of oligoester.

The depolymerization then takes place at high temperatures between 200 ° C. and 350 ° C., preferably between 220 ° C. and 290 ° C., and under a vacuum of less than 100 hPa. The cleavage products preferably rise in vapor form and are thus removed directly from the reaction in the liquid phase. In a rectification column placed on the reaction vessel, the product components can be separated from the components of the reaction medium, the product components being removed at the upper end of the column and the components of the reaction medium being removed at the lower end of the column for recycling into the reaction vessel. For this purpose, the column is operated at pressures <100 hPa, the pressure range from 5 to 95 hPa, particularly preferably the range from 10 to 80 hPa, being preferred and 80.

The process can be carried out either batchwise or continuously. In the case of a discontinuous procedure, the oligomer is mixed with the

Solvent presented at once and split in one batch. In the case of a continuous procedure, on the other hand, the oligomer is metered into the reaction medium in portions or with a constant stream during the cleavage. The continuous procedure is preferably carried out since the product can be removed with a constant composition at the top of the column.

The solvent is recovered by partial evaporation, for example in a thin-film evaporator at pressures below 100 hPa, preferably at pressures below 50 hPa. A 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 a particularly pure manner by the process according to the invention, which greatly benefits their use as fragrances. In particular, the process according to the invention can also be used to prepare the mixtures of ethylene dodecanedioate and ethylene undecanedioate described in US Pat. No. 6,034,052.

Examples

example 1

Production of ethylene tridecanedioate

a) Preparation of ethylene glycol tridecanedioic acid polyester 500 g of dimethyl tridecanedioate, 250 g of ethylene glycol and 3 g of tetrabutyl titanate are slowly heated in a reaction distillation apparatus under a vacuum of 300 hPa. As soon as a reaction temperature of 140 ° C is reached, methanol begins to split off. The heating is continued until no more methanol is released; the bottom temperature is slowly increased to 185 ° C. The vacuum is then removed to 1 hPa and the excess ethylene glycol is distilled off. 510 g of polyester are obtained as residue.

b) depolymerization of the ethylene glycol tridecanedioic acid polyester

A melted mixture of 2 parts by weight of dibenzyltoluene (mixture of isomers), 1 part by weight of ethylene glycol tridecanedioic acid polyester and 0.02 part by weight of dibutyltin dilaurate is metered into a reaction vessel with a rectification column in which there is a mixture of 2 parts by weight of dibenzyltoluene (mixture of isomers) and 0.02 parts by weight of dibuturate , which is heated to about 280 ° C and is boiled under reflux at a pressure of 55 hPa. The formation of monomeric ethylene tridecadioate is noticeable by a drop in the temperature at the distillation head. Distillate is removed to the extent that polyester is replenished. Depending on the separation efficiency of the rectification column and the chosen reflux ratio, the distillate removed contains between 30 and 98% ethylene tridecadioate, which is obtained in a subsequent fine distillation in pure form. In this way, the yield is about 90%, based on dimethyl tridecanedioate used.

By distilling the reaction residue over 90% of the used

Dibenzyltoluenes recovered. Example 2

Production of a mixture of ethylene dodecanedioate and ethylene undecanedioate

a) Preparation of the polyester

225 g of a technical mixture containing between 40 to 60% dodecanedioic acid and 30 - 50% undecanedioic acid are mixed with 105 g of ethylene glycol and slowly heated to 150 ° C; at about 130 ° C to 140 ° C water splitting begins. After the elimination of water has ended, the temperature is raised to 170 ° C. to remove excess ethylene glycol, and the reaction apparatus is slowly evacuated to a pressure of 1 hPa.

b) Depolymerization The resulting dicarboxylic acid / ethylene glycol polyester is mixed with 3 parts by weight of dibenzyltoluene (isomer mixture) and 0.05 part by weight of dibutyltin dilaurate per part by weight of polyester and heated to about 280 ° C. in a reaction vessel with a rectification column attached at a pressure of 55 hPa and cooked under reflux. The monomeric cleavage products distill over. Depending on the composition of the starting material, the distillate initially contains between 40 to 60% ethylene dodecanedioate and 30 to 50% ethylene undecanedioate, and in the further course of the reaction increasingly 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.

By distillation of the reaction residue, over 90% of the dibenzyltoluene used is recovered. Example 3

Preparation of a mixture of ethylene dodecanedioate and ethylene undecanedioate

a) polymerization 250 g of ethylene glycol, 500 g of a technical mixture consisting of 40 to 60%

Dodecanedioic acid dimethyl ester and 30-50% undecanedioic acid dimethyl ester, and 3 g of tetrabutyl titanate are slowly heated in a reaction distillation apparatus under a vacuum of 300 hPa. Between 130 - 140 ° C reaction temperature, methanol begins to be split off, which is distilled off via a 30 cm packed column. The heating is continued until no more methanol is released; the bottom temperature is slowly increased to 185 ° C. The vacuum is then removed to 1 hPa and the excess ethylene glycol is distilled off. 500 g of polyester are obtained as a residue.

b) depolymerization

A melted mixture of 500 g of dibenzyltoluene (mixture of isomers), 250 g of the diacid ethylene glycol polyester mixture obtained according to a) and 5 g of dibutyltin dilaurate is metered into a reaction container with a rectification column in which a mixture of 500 g of dibenzyltoluene (mixture of isomers) and 5 g of dilaurutyl is located, which is heated to about 280 ° C and is boiled under reflux at a pressure of 55 hPa. The formation of monomeric esters is noticeable by a drop in the temperature at the distillation head. As soon as the head temperature has dropped below 220 ° C, the distillate is removed and the polyester mixture is continuously added. Depending on the separation performance of the rectification column and the chosen reflux ratio, the distillate removed contains between 30 and 98% of a mixture of the monomers ethylene dodecadioate and ethylene undecadioate. In the present case, 490 g of distillate with a weight fraction of 225 g of ethylene dodecadioate and ethylene undecadioate mixture were obtained at a head temperature of 220-225 ° C. and a reflux ratio of 15: 1, which gives a yield of 90% based on the dicarbonate used. acid dimethyl ester mixture corresponds. The mixture of ethylene dodecadioate and In a subsequent fine distillation, ethylene undecadioate was separated from the dibenzyltoluene and thus obtained in pure form.

By distillation of the reaction residue, over 90% of the dibenzyltoluene used is recovered.

Example 4

Production of 1,15-pentadecanolide

a) Preparation of the polyester

260 g of 15-hydroxypentadecanoic acid are slowly heated to 170 ° C. under a slight vacuum (650 hPa). As soon as the splitting off of water subsides, will

Stirred for 1 h at a vacuum of 20 hPa and 30 min at a vacuum of 1 hPa. The polyester of 15-hydroxypentadecanoic acid remains as a residue.

b) depolymerization

A melted mixture of 1 part by weight of the remaining 15-hydroxypentadecanoic acid polyester, 2 parts by weight of dibenzyltoluene (isomer mixture) and 0.02 part by weight of dibutyltin dilaurate is metered into a reaction container with a rectification column in which a mixture is formed

2 parts by weight of dibenzyltoluene (mixture of isomers) and 0.02 part by weight of dibutyltin dilaurate, which is heated to about 280 ° C and is boiled under reflux at a pressure of 55 hPa. The formation of monomeric 1,15-pentadecanolide is noticeable by a drop in the temperature at the distillation head. Distillate is removed to the extent that polyester is replenished. Depending on the separation performance of the rectification column and the chosen reflux ratio, the distillate removed contains between 30 and 95% 1,15-pentadecanolide. In the present case, a distillate with a weight fraction of approx. 60% 1,15-pentadecanolide was obtained at a top temperature of 215-220 ° C and a reflux ratio of 10: 1, which is obtained in a subsequent fine distillation in pure form. The yield of the 1,15-pentadecanolide obtained in this way is 85% based on the 15-hydroxypentadecanoic acid polyester used.

Example 5

Production of cis- / trans-l, 15-pentadec-l 1/12-enolide

a) Preparation of the polyester

260 g of cis- / trans-15-hydroxy-1 l / 12-pentadecenoic acid are slowly heated to 170 ° C. under a slight vacuum (650 hPa). As soon as the elimination of water subsides, the mixture is stirred for a further 1 h under a vacuum of 20 hPa and for 30 min under a vacuum of 1 hPa. The polyester of 15-hydroxypentadecanoic acid remains as a residue.

b) depolymerization

A melted mixture of 1 part by weight of the residual cis / trans-15-hydroxy-ll / 12-pentadecenoic acid polyester, 2 parts by weight of dibenzyltoluene (mixture of isomers) and 0.02 part by weight of dibutyltin dilaurate is mixed into one

Reaction vessel with attached rectification column, in which there is a mixture of 2 parts by weight of dibenzyltoluene (mixture of isomers) and 0.02 part by weight of dibutyltin dilaurate, which is heated to approx. 280 ° C. and is boiled under reflux at a pressure of 55 hPa. The formation of monomeric cis- / trans-l, 15-pentadec-l 1/12-enolide is caused by a drop in temperature

Distillation head noticeable. Distillate is taken off to the extent that Polyester is added. Depending on the separation performance of the rectification column and the chosen reflux ratio, the removed distillate contains between 30 and 90% 1,15-pentadecanolide. In the present case, at a head temperature of 210-215 ° C and a reflux ratio of 10: 1, a distillate with a weight fraction of approx. 60% cis / trans-l, 15-pentadec-ll / 12-enolide was obtained, which in a subsequent fine distillation is obtained in pure form.

The yield of cis- / trans-l, 15-pentadec-ll / 12-enolide achieved in this way is approximately 85%, based on the 15-hydroxypentadecanoic acid polyester used.

Example 6

Preparation of 1,16-hexadecanolide

a) Preparation of the polyester

140 g of 16-hydroxyhexadecanoic acid are slowly heated to 170 ° C under a slight vacuum (650 hPa). As soon as the splitting off of water subsides, will

Stirred for 1 h at a vacuum of 20 hPa and 30 min at a vacuum of 1 hPa. The polyester of 16-hydroxyhexadecanoic acid remains as a residue.

b) Depolymerization A melted mixture of 1 part by weight of the remaining residue

16-hydroxyhexadecanoic acid polyester, 2 parts by weight of dibenzyltoluene (mixture of isomers) and 0.02 part by weight of dibutyltin dilaurate is metered into a reaction vessel with a rectification column in which a mixture is formed

2 parts by weight of dibenzyltoluene (mixture of isomers) and 0.02 parts by weight of dioctyltin dilaurate, which is heated to about 280 ° C and at a pressure of

55 hPa is boiled under reflux. The formation of monomeric 1,16-hexa- decanolide is noticeable when the temperature at the distillation head drops. Distillate is removed to the extent that polyester is replenished. Depending on the separation performance of the rectification column and the chosen reflux ratio, the distillate removed contains between 30 and 90% 1,16-hexadecanolide.

In the present case, at a top temperature of 220-230 ° C and a reflux ratio of 5: 1, a distillate with a weight fraction of approx. 50% 1,16-hexadecanolide was obtained, which is obtained in a subsequent fine distillation in pure form. The yield of 1,16-hexadecanolide achieved in this way is approximately 75% based on the 16-hydroxyhexadecanoic acid polyester used.

Example 7

Preparation of trans-l, 16-hexadec-9-enolide

a) Preparation of the polyester

260 g of trans-16-hydroxy-9-hexadecenoic acid are slowly heated to 170 ° C. under a slight vacuum (650 hPa). As soon as the elimination of water subsides, the mixture is stirred for a further 1 h under a vacuum of 20 hPa and for 30 min under a vacuum of 1 hPa. The polyester of trans-16-hydroxy-9-hexadecenoic acid remains as a residue.

b) depolymerization

A melted mixture of 1 part by weight of the remaining trans-16-hydroxy-9-hexadecenoic acid polyester, 2 parts by weight of dibenzyltoluene (mixture of isomers) and 0.02 part by weight of dibutyltin dilaurate is mixed into one

Dosed reaction vessel with attached rectification column in which a Mixture of 2 parts by weight of dibenzyltoluene (isomer mixture) and 0.02 part by weight of dibutyltin dilaurate, which is heated to about 280 ° C and is boiled under a reflux of 55 hPa. The formation of monomeric trans-1,16-hexadec-9-enolide is noticeable by a drop in the temperature at the distillation head. Distillate is removed to the extent that polyester is replenished. Depending on the separation performance of the rectification column and the chosen reflux ratio, the distillate removed contains between 30 and 90% trans-l, 16-hexadec-9-enolide.

In the present case, a head temperature of 225-235 ° C and a

Reflux ratio of 10: 1 a distillate with a weight fraction of about 60% trans-l, 16-hexadec-9-enolide obtained, which is obtained in a subsequent fine distillation in pure form. The yield of trans-1,16-hexadec-9-enolide thus obtained is approximately 80% based on the trans-16-hydroxy-9-hexadecenoic acid polyester used.

Example 8:

Preparation of a mixture of ethylene dodecadioate and ethylene undecadioate

A melted 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 according to Example 3a) and 6.4 g of dibutyltin dilaurate is metered into a reaction container with a rectification column attached, in which there is a mixture of 500 g of partially hydrogenated terphenyl (isomer mixture, see above) which is heated to about 280 ° C. and is boiled under reflux at a pressure of 110 hPa. The formation of monomeric esters becomes apparent

Noticeable drop in temperature at the distillation head. As soon as the head temperature has dropped to below 240 ° C, the distillate is removed and the polyester mixture is continuously added. Depending on the separation performance of the rectification column and the chosen reflux ratio, the distillate removed contains between 20 and 90% of a mixture of the monomers ethylene dodecanedioate and ethylene undecanedioate. In the present case, at a top temperature of 238-240 ° C. and a reflux ratio of 10: 1, 250 g of distillate with a weight fraction of 95 g of ethylene dodecanedioate and ethylene undecanedioate mixture were obtained, which corresponds to a yield of 70% based on the dicarboxylic acid dimethyl ester used. Mixture corresponds. The mixture of ethylene dodecanedioate and ethylene undecadioate was separated from the partially hydrogenated terphenyl in a subsequent fine distillation and thus obtained in pure form.

By distillation of the reaction residue, over 90% of the partially hydrogenated terphenyl used is recovered.

Claims

claims

Process for the preparation of macrocyclic ester compounds, obtainable by condensation of difunctional compounds to linear oligoesters and subsequent thermal depolymerization with or without the addition of catalysts, characterized in that the depolymerization in thermostable benzene derivatives at a pressure of less than 100 hPa and at temperatures of 200 ° C to 350 ° C is carried out, 0.1 to 1000 parts by weight of solvent being used per part by weight of the oligoester.

Method according spoke 1 characterized in that thermostable benzene derivatives of the formula

embedded image in which

R ¹

and

R ^z H or CH ₃

means be used.

3. The method according to claim 2, characterized in that isomeric dibenzyltoluenes are used as thermostable benzene derivatives.

4. The method according to any one of claims 1 to 3, characterized in that alkali or alkaline earth metals or their salts, or salts or organometallic compounds of the elements manganese, cadmium, iron, cobalt, tin, lead, aluminum, zirconium or titanium are used as catalysts ,

5. The method according to any one of claims 1 to 4, characterized in that dibutyltin oxide, dioctyltin oxide, dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin bis-2-ethylhexanoate, butyltin tris-2-ethylhexanoate, butyltin hydroxide oxide or cyclic doxutyl are used as dibutyldanutyl.

6. The method according to any one of claims 1 to 5, characterized in that the catalyst is metered in portions or continuously in order to achieve constant concentrations of the active form of the catalyst.

7. The method according to any one of claims 1 to 6, characterized in that a rectification column is placed on the reaction vessel, at the top of which the macrocychic ester formed is removed.

8. The method according to any one of claims 1 to 7, characterized in that the thermostable benzene compound by partial evaporation to more than 50 percent by weight of high-boiling reaction residues and then used again as a reaction medium in the oligoester depolymerization.