DE1929550A1 - Process for the preparation of cyclic esters of dicarboxylic acids - Google Patents

Description

She Teohni-Chem Company, 524 South Cherry Street, Wallingiord, Conn. 06492 (Y.St.A.)

Process for the preparation of cyclic esters of

Dicarboxylic acids

Carother and coworkers have already proposed the preparation of macrocyclic esters of acyclic diacids or of diacids of an oarbocyclic nature with at least one carbon atom between the acid groups in the ring. The manufacturing process is the formation of a high molecular weight polymer of the diacid and a "diol and the depolymerization at erhb ^ fceil ^ 'li ^ turi" ilnter * INEM eSark reduced brucine ^ teetli m * l ^ lfteerlalttiöfc went dibÄsi- ^ see SWf> iöfn Äinjütoiufi »it dew diol a / uii it formed- '| i | 9ft;: 4 # * iewüiischte wakroöyciieche ester.

and 'aie ^v pointed' iin iaig "m" in "n" in linear: or im

ORIGINAL INSPECTED

on. Typical representatives of polymers after were treated in the manner described above are those from polymethylene glycols, e.g. tetramethylene, heptamethylene, octamethylene, Nonamethylene, decamethylene and tetradecamethylene glycol, and dibasic acids such as succinic acid, glutaric acid ,. Adipic acid, suberic acid and sebacic acid. The polymer made from ethylene glycol and brassylic acid had also been described. There were metal catalysts, such as the chlorides of tin, manganese, iron, cobalt, lead, antimony and the like, as well as the Manganese and magnesium carbonates are also used. Magnesium oxide has also been proposed as a catalyst. To the depolymerization and cyclization you not only have acyclic high molecular weight polymers made from dicarboxylic acids, but also above in addition, polymers made from glycols and diacetic acids of aromatic diols, such as resorcinol and Hydroquinone. These latter aromatic compounds had at least one carbon atom between acid groups, in other words, they represent m- or p-compounds.

Even if the processes were completely feasible in practice, they nevertheless presented certain difficulties for implementation on an industrial scale, where the very high vacuum required to remove the oil monomers from the film melt, which was necessary for stirring greatly aggravating the high viscosity of the molten polymer, the somewhat to be desired yield as well as the formation of hard, cross-linked and out

Hard-to-remove byproduct resins belong in the still.

The present invention now discloses a new method which, through certain modifications, can be regarded as an improvement on the prior art, ooe-ii mentioned working methods. It has not mentioned above, in practical operation occurring disadvantages "So it does not require high vacuum, although a slight vacuum, zBein such can be up ^l j0 mrn, benefit from the 10th A homogeneous reaction phase can be achieved with a suitable choice of catalyst. In the process according to the invention it is not necessary to produce high molecular weight polymers or to isolate any intermediate products, and also the difficulties in terms of the formation of hard, crosslinked by-product resins are largely eliminated. In the present invention, the formation of the macrocyclic ester is essentially carried out in a high-boiling, inert oil, preferably a high-boiling paraffin oil -ionsmedium created and made the implementation of the process on an industrial scale more economical.

The special, inert, high-boiling oil is not from critical importance, although - as already mentioned above - high-boiling ones with particular advantage

0 9 8 81/16 0 3 BAD ORIGINAL

Paraffin oils are used because they are cheap and effective. The boiling point of the oil is in no way of decisive importance. It must, however, be high enough that volatile products that arise in the reaction, such as water, alcohols, glycols, and at least some of the macrocyclic ester can be distilled off. However, it is not necessary that the oil in such high boiling that the entire makrocyclieche ester can be distilled out without the oil evaporated is ψ. On the contrary, the desired macrocyclic ester can be distilled out together with the high-boiling oil. This presents no problem as the cyclic ester can easily be extracted with inexpensive solvents, e.g. B, with low molecular weight alcohols, which can then be distilled off from the ester, so that the latter is obtained in pure form. The losses of the high-boiling oil are only slight, and the high-boiling paraffin oil which is preferably used is comparatively inexpensive, so that the process can be made very economical overall.

* The amount of high-boiling oil used is not critical. As a rule, it is used in quite a substantial excess, and amounts on the order of about ten times the amount of the reactants are practical and useful. An excess is necessary, but not critical. If the high-boiling oil is used in too small an amount, the high concentrations of the reaction components can lead to the formation of high polymers and to a loss of

90 9 881/1603

Result in homogeneity and yield. In addition, stirring becomes more difficult if too little oil is present.

In general, any known metal catalyst, such as those set forth above in connection with the description of the prior art, may be used. It has been found, however, that optimal results are obtained with alkyl-tin-alkanoates, for example dibutyltin dilaurate. The amount of catalyst to be used is not of critical importance and it can be in the order of magnitude of -j to 10 % . In many cases it is advisable to add the catalyst in stages, but again this is not of critical importance, and it is an advantage of the present invention that no critical amounts of the metallic catalyst are required *, '

Even if an important advantage of the present invention is that the yields are higher than in the known high vacuum depolymerization processes , the yields are nevertheless often not 100 %. Occasionally a small amount of a low molecular weight polymer can be formed, for example a dimer, and the unreacted material can be recycled together with such a low molecular weight by-product polymer if this appears appropriate for economic reasons. The starting materials used in the process according to the invention are preferably not high molecular weight polymers. In individual rare

909881/1603

In some cases, however, high molecular weight polymers are commercially available at low prices, for example as scrap or waste, and it is an advantage that the process according to the invention can also be carried out with polymeric starting materials, although in its preferred embodiment such a material is not used.

One of the most important operational advantages of the present invention is that they are in one

fc single reaction medium is carried out and the invention is accordingly not limited to any particular i'ol · --ge of mechanisms. Thus, a very simple procedure can use the ester of the dibasic acid and the diol to be used, where 'the latter is preferably in a moderate excess of, for example, 2'; 1 is used »The ratio is in no way critical. A very recommendable starting material for the process according to the invention is a bis-hydroxyalkyl ester eg. the bis-hydroxyethyl brassylate. Dialkyl esters are used as starting material, they will be in the first stages of the reaction by conventional environmental

) Esterification processes using the desired diol, which is to be a part of the finished cyclic ester, is converted into the dihydroxyalkyl ester. Since the metal compounds which are used as catalysts in the final cyclization are usually also good transesterification catalysts, it is possible to effect the transesterification with a smaller amount of catalyst in the preceding or first stage of the reaction, and then to add more catalyst and the reaction conditions to the optimum for the final cyclization

909881/1603

to adjust. If dialkyl esters are used as the starting material for the process according to the invention, then the special nature of the alkyl radical is irrelevant. It can ester with any low molecular weight Alkyl group, e.g., the methyl, ethyl, propyl, butyl and the like group, which are easy to transesterify with the .Diolen are accessible, can be used. As far as this transesterification in the following specific Examples are explained, get esters with the simplest and cheapest alkyl groups, namely die.Diäthylester, for use, but the procedure according to the invention is self-evident not limited to that.

Dialkyl esters are used as starting materials and interesterified, a bis (hydroxyalkyl) ester is of course obtained in this stage, and at the end When the ring closure takes place, half of the diol in question is freed and recovered. It it should be pointed out that this corresponds to the moderate excess of diol that was recommended above, " if not as absolutely necessary, - -toeT'solchen Modifications have been described in which the diol and the acid are the starting materials. In In such a case, of course, water is formed during the reaction, whereas when dialkyl esters are used are transesterified, the corresponding alcohols are produced .. In any case, these volatile constituents easily distilled out at the reaction temperatures. Since the transesterification of something lower temperatures than the final cyclization can be carried out, it is at With these modifications, it is often desirable to carry out the transesterification to essentially complete completion and then the low molecular weight alcohols formed

909881/1603 ■ ORIGINAL BATHROOM

to remove before the temperature is increased, and then usually an additional amount of catalyst for admit the final cyclization. While this is not critical, it is in this embodiment to achieve smooth operation and the best yields, it is desirable.

The process of the present invention is practicable with essentially any conventional acyclic Dicarboxylic acids, and it provides end products that conform to the following general formula:

, COO 1

^C n ^H 2n? M ^H 2m

-COO-r-

In this formula, η means the number of carbon atoms between the acid groups in the dibasic Acid, and m is the number of carbon atoms between the two hydroxyl groups of the diol, where η and m same or different integers between 2 and can be. Even if it's not essential is that the hydrocarbon radical that connects the two carboxylic acid groups is straight-chain, so correspond Yet many of the practically interesting compounds of this condition, and they can go through the formula below can be reproduced.

909881/160 3

COO ^ ^H 2> m

-coo

If carbocyclic dicarboxylic acids are used in the procedure according to the invention, they can be represented by the following formulas?

-COO

0 (CH ₂ ) -

-COO

and

0 (CH ₀ ) -

-COO

(CH _C

0 (CH,

In the first? The formula below is n-DI ~ oarsonic acids and in the an. 2weit @ r Stell © st®ii @ nden Pöriael p-dicarbonic acids are shown. In general η is a small number, e.g. one in Werfe

■ 909881/1603

-ΙΟ Ι to 4, the most interesting representatives are the diacetic acids of resorcinol or hydroquinone. It is of course not necessary that the benzene ring is unsubstituted, but homologues should be expressly included.

The invention will now be explained in more detail with the aid of the following examples, in which the parts given mean parts by weight, unless otherwise noted.

111 parts of diethyl brassylate _p 46 parts of ethylene glycol and 1 part of dibutyltin cUl & ur-at are in 1000 parts of a high-boiling point. Par-affective solution is dispersed from 300 to 400 ° C. The reaction is poured into a vessel G ₁ , the one capillary for the passage of nitrogen, one mechanical tube and one to a cooling tank and one Template attached distillation attachment is equipped ", The mixture is ^{heated up to 200 0} C for 3 hours, and about 50 parts of ethanol distill over-" At this point in time the transesterification of the diethyl brassylate is essentially complete ", The system is then up Cooled about 100 to 120 ° C and the pressure is now reduced to about J50 in order to remove residual volatile constituents, and then another 5 parts of di-butyl-tin-dilaurate are added ^ and the template is changed. The temperature is gradually increased to about 325 ⁰ C. The pressure is adjusted to about 15 mm and heating is continued until the reaction is essentially complete. During the Anfangsstuf s distill about 20 parts ethylene glycol over _s

909381 / 1-60-3- ■

BATH ORIGINAL

- Ii -

and after that a broad fraction follows, 900 parts that Contains ethylene brassylate and paraffin oil. A small amount of a white solid separates out on standing from the distillate and is filtered off. It consists of dimeric ethylene brassylate and can if desired be used again in the following batch. The filtrate is extracted with methanol and the separated methanol layer is fractionally distilled, to provide about 86 parts of ethylene brassylate.

- * Example 2

100 parts of bis (2-hydroxyethyl) brassylate and 10 parts of lead oxide are dispersed in 1000 parts of the paraffin oil described in Example 1. The mixture is stirred and gradually ^{heated to about 300 °} C., the pressure being set to 20 mm. The distillate obtained is essentially the same as in Example 1, but of course no ethanol distills off. The distillate is worked up as described in Example 1 and provides approximately 67 parts of ethylene brassylate.

Example 3

100 parts of polyethylene brassylate and 5 parts of dibutyltin diacetate are dispersed in 1000 parts of the paraffin oil described in the preceding examples. The mixture is gradually heated to 315 ° C. with stirring at a pressure of 10 mm. As in example 1 about 900 parts of distillate are obtained Contain paraffin oil and ethylene brassylate, which the latter is extracted with methanol, whereupon the methanol

909881/1603

Extract is separated and gives about 85 parts of ethylene brassylate when the methanol is evaporated. This product has a purity of over 90 % .

Example k »

115 parts of dimethyl sebacate and II8 parts of 1,6-hexamethylene glycol are mixed with 10 parts of dibutyl tin di-octanoate in I5OO parts of paraffin oil as described in the preceding examples with each other W mixes. The heating is carried out as in Example 1. The distillation, carried out at 15 mm pressure, gives 100 parts of distillate which, after extraction with methanol and distilling off the methanol, gives 120 parts of hexamethylene sebacate from the extract.

Example 5

143 parts Diäthyldodecandioat, J6 parts of trimethylene glycol and 2 parts of dibutyl tin dilaurate are the paraffin oil described in the preceding examples is mixed in 1500 parts together and heated at atmospheric pressure to 200 ⁰ C. The ethanol distilled over essentially quantitatively. The mixture is then cooled, and a further 10 parts of the catalyst are added, and the mixture is ^{distilled analogously to the manner described in Example 1 at 150 to 320 °} C. under a pressure of 13 mm. 1410 parts of distillate are obtained which, after extraction with methanol and distillation, are carried out in the manner described in the preceding examples

909881/1603

BATH ORIGINAL

yielded about 160 parts of trimethylene dodecandloate.

Example 6

113 parts of resorcinol diacetic acid, 10 parts of hexamethylene-1,6-diol and 10 parts of dibutyltin dilaurate are mixed with 2000 parts of the paraffin oil described in the preceding examples. The mixture is heated under atmospheric pressure gradually to 200 ⁰ G, and distilled water over. The mixture is then cooled and a further 10 parts of catalyst are added, followed by vacuum distillation at 10 mm and a temperature rising from 150 ° to 30 ° C., which is carried out analogously to the manner described in Example 1. 1700 parts of distillate are obtained which, after extraction with methanol and evaporation, give about 90 parts of hexamethylene resorcinol diacetate »

The working cycle of Example 6 is repeated with the difference that hydroquinone diacetic acid is used instead of resorcinol diacetic acid. It will be corresponding hexamethylene hydrochloride acetate obtained «.

BATH ORIGINAL

909881/1603

Claims (1)

Claims 1. Process for the preparation of cyclic esters of Dicarboxylic acids of the general formula -COO- ^C n ^H 2n ^C m ^H 2m COO- in egg η the number of between the acid groups of the two acid based carbon atoms and m is the number of between the two hydroxyl groups Definite carbon atoms of the diol mean b2w. "^ ori esters of the general formula 0 (CH.,) 0 (CH ₂ ). coo ^C m ^H 2m COO in etc. in the number of carbon atoms located between the two hydroxyl groups of the diol, y is an integer from 1 to H- and X is a mononuclear aromatic carbocyclic ring with at least one carbon atom between the two oxygen atoms, thereby: 909881/1603 indicates that the corresponding dicarboxylic acids or the alkyl esters or hydroxyalkyl esters the same in which the hydroxyalkyl group the formula ^HOC m ^H 2m corresponds, and polymers in a high-boiling, inert oil containing reaction medium in which the oil is present in a large excess that essentially suppresses the formation of hard, crosslinked resins, to a temperature between 20O ⁰ C and 525 ⁰ C in the presence of catalytic amounts a metal compound are heated, and the reaction mixture is then subjected to a reduced pressure sufficient to ensure the distillation of a mixture of the high-boiling oil and the cyclic ester formed in the reaction mixture, whereupon the ester is extracted from the distillate and isolated from the extract will. 2. The method according to claim 1, characterized in that the hydrocarbon chain in the dibasic The alcohol group of the ester consists of a straight-chain polymethylene chain. 3>. Method according to claims 1 and 2, characterized characterized in that said ester is the ester of a straight-chain, aliphatic dibasic Acid is. BATHROOM ΟΒΙΘ1ΝΑ1 0 9 8 8 1/16 01 «# ♦ t ' ψ W * f * f 1S29550 - 16 - K. Process according to Claims 1, 2 and 3 *, characterized in that the high-boiling oil consists of a high-boiling paraffin oil. 5. Process according to claims 1 to 4, characterized in that the cyclic ester consists of one cyclic brassylate, preferably ethylene brassylate. 6. The method according to claims 1 to 5 * thereby "marked that a low molecular weight dialkyl ester the dicarboxylic acid is transesterified with an amount of at least one sufficient for transesterification Diols of the formula H0C _m H _Om
m 2m at a temperature, but which is so high at 200 ⁰ C but that it is sufficient to bring about the transesterification stand, and the resulting ester then located on a higher, between 200 ⁰ C and ^ 25 ° C temperature is heated to a mixture of the high-boiling oil and the cyclic ester. distill. 7. Process according to claim S _9, characterized in that a low molecular weight dialkyl ester of brassylic acid is heated with ethylene glycol. 9 0 988 1/1 en-3