Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
2001-08-21
2002-10-01
Owens, Amelia (Department: 1625)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C549S010000, C549S267000
Reexamination Certificate
active
06458972
ABSTRACT:
FIELD OF THE INVENTION
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° C. and 350° C.
BACKGROUND OF THE INVENTION
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.
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° 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.
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.
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.
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.
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.
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.
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.
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
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.
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° C. to 350° C., 0.1 to 1000 parts by weigh
Klein Stephan
Mendoza-Frohn Christine
Müller Dirk
Ronge Georg
Surburg Horst
Cheung Noland J.
Gil Joseph C.
Haarmann & Reimer GmbH
Owens Amelia
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