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WO1993018021A1 - Oligomerisation d'acides alpha-hydroxycarboxyliques catalysee par des metaux de terres rares et conversion en esters cycliques dimeres - Google Patents

Oligomerisation d'acides alpha-hydroxycarboxyliques catalysee par des metaux de terres rares et conversion en esters cycliques dimeres Download PDF

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Publication number
WO1993018021A1
WO1993018021A1 PCT/US1993/002299 US9302299W WO9318021A1 WO 1993018021 A1 WO1993018021 A1 WO 1993018021A1 US 9302299 W US9302299 W US 9302299W WO 9318021 A1 WO9318021 A1 WO 9318021A1
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WIPO (PCT)
Prior art keywords
acid
alpha
compound
catalyst
ester
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Application number
PCT/US1993/002299
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English (en)
Inventor
Neville Everton Drysdale
Kang Lin
Thomas Walter Stambaugh
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E.I. Du Pont De Nemours And Company
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
Application filed by E.I. Du Pont De Nemours And Company filed Critical E.I. Du Pont De Nemours And Company
Priority to AU38070/93A priority Critical patent/AU3807093A/en
Publication of WO1993018021A1 publication Critical patent/WO1993018021A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D319/00—Heterocyclic compounds containing six-membered rings having two oxygen atoms as the only ring hetero atoms
    • C07D319/10—1,4-Dioxanes; Hydrogenated 1,4-dioxanes
    • C07D319/12—1,4-Dioxanes; Hydrogenated 1,4-dioxanes not condensed with other rings

Definitions

  • This invention relates to an improved process for preparing oligomers of alpha-hydroxycarboxylic acids and their thermolysis to dimeric cyclic esters in the presence of a rare earth metal or a compound thereof.
  • the invention relates to such a process as above for the preparation of lactic acid oligomers and their conversion to lactide.
  • oligomers of alpha-hydroxycarboxylic acids and the dimeric cyclic esters produced from them such as glycolide (l,4-dioxane-2,5-dione) and lactide (l,4-dioxane-3,6-dimethyl-2,5-dione), are intermediates to high molecular weight polyhydroxycarboxylic acids which are useful in biomedical and other applications because of their ability to be degraded biologically and hydrolytically to form physiologically and environmentally acceptable by-products.
  • Grater et al. U. S. Patent 1,095,205, discloses that the addition of small amounts of a suitable catalytic substance to a polylactyllactic acid (oligomer) derived from lactic acid facilitates the conversion to lactide and enables the reaction temperature to be lowered.
  • Suitable Grater et al. substances include metal oxides such as zinc oxide, magnesium oxide and aluminum oxide; also, carbonates such as zinc carbonate and phosphates such as aluminum phosphate.
  • Lowe U. S. Patent 2,668,1622, discloses the conversion of relatively low molecular weight polyglycolic acid to glycolide by heating with a catalytic amount of antimony trioxide, i.e.
  • German Patent Application 1,083,275 describes the production of lactide in which the depolymerization (thermolysis) of an oligomeric polylactic acid to lactide is carried out in the presence of a metal or compound of a metal of Group IV, V or VJQI of the Periodic Table.
  • a metal or compound of a metal of Group IV, V or VJQI of the Periodic Table Specifically exemplified catalysts are zinc oxide, lead oxide, stannous oxide, antimony oxide, ferrous lactate and ferric acetate.
  • U. S. Patent 3322,791 discloses the use of titanium tetraalkylates as catalysts for the production of lactide from lactic acid.
  • British Patent 1,108,720 discloses metals of Group IV of the Periodic Table or compounds thereof, e.g., lead (II) stearate as oligomerization and depolymerization catalysts.
  • German Patent Application 3,708,915 discloses that particularly suitable as catalysts for the production of optically active lactide from optically active lactic acid are tin powder or an organic tin compound derived from a carboxylic acid having up to 20 carbon atoms.
  • Stannous (2-ethyIhexanoate) commonly referred to as stannous dioctoate is particularly preferred.
  • East German Patent 261,362 discloses the oligomerization of alpha-hydroxycarboxylic acids in the presence of antimony oxide or titanium tetrabutylate and the subsequent thermolysis of the oligomer in the presence of a manganese (II) salt, preferably manganese (II) acetate.
  • the divalent tin carboxylates of the art notably stannous octoate
  • suitable catalysts for the production of lactide and other cyclic esters since the same material may be used in both the oligomerization and depolymerization steps.
  • the tin catalysts suffer the drawback that they produce relatively viscous oligomers, and the viscosity of the molten state tends to increase with time. This would be disadvantageous in commercial use where it may be necessary to hold the ohgomer molten at elevated temperatures for an extended period of time before feeding it to the depolymerization step.
  • viscous oligomers produce even more viscous "heels” of unconverted oligomer in the depolymerization step. These "heels” are slow draining which tends to limit the overall production rate. Also, they are inefficiently converted to the desired cyclic ester when it is attempted to increase process productivity by recycling them to the depolymerization reactor.
  • the present invention provides an improved process involving the use of a catalytically effective amount of a rare earth metal or process-compatible compound thereof.
  • the catalyzed process is a process for oligomerizing the alpha-hydroxycarboxylic compound.
  • the catalyzed process is a process for depolymerizing the depolymerizable oligomer to a dimeric cyclic ester.
  • the invention process comprises sequential oligomerization and depolymerization steps conducted in the presence of the novel lanthanoid catalytic substance.
  • the alpha-hydroxy compound is the acid, preferably glycolic or lactic acid, more preferably is lactic acid, in particular L-lactic acid.
  • rare earth (or lanthanoid) metal is meant, for purposes of this invention, yittrium, lanthanum or other metal having an atomic number of from 58 through 71 as defined by Rose and Rose, The Condensed Chemical Dictionary, 7th Ed., Reinbold Publishing Corporation, New York, at pages 309-310.
  • a process-compatible compound of lanthanum or other rare earth metal is meant a compound of such metal wherein the constituent groups attached to the metal moiety are so constituted that they are compatible with the other components of the reaction system and do not interfere with the intended transformations.
  • the compounds may be pre-formed derivatives of the metals or may be formed in situ, for example, by reaction of the metal with an alpha-hydroxycarboxylic acid starting material.
  • Preferred catalytic metals include lanthanum and mixtures thereof with other rare earth metals having atomic number 58 through 64, i.e. encompassing lanthanum through gadolinium.
  • the catalysts of this invention offer several advantages over the art. They are generally regarded as non-toxic.
  • the uncracked heels produced in accordance with the present invention are sufficiently fluid and operationally active to be recycled to the depolymerization step for the production of additionally quantities of the desired cyclic ester.
  • Still another object is to provide such a catalyzed process that enables the depolymerization heels to be recycled to the depolymerization step for further conversion into cyclic ester with attendant increase in process productivity.
  • the lanthanum (lanthanoid) catalysts of this invention include yttrium, lanthanum, other rare earth metals having an atomic number of 58 to 71 and mixtures thereof, including commercially available mixtures such as bastnaesite and didymium oxide, especially the latter, which is obtained from monazite sand and consists essentially of oxides of lanthanum, praseodymium, neodymium, samarium, yttrium, cerium and gadoliriurn.
  • Lanthanum and the other lanthanoids may be employed as the free metals, in view of their reactivity with water and acids, or as process-compatible compounds thereof.
  • Representative compatible compounds are the hydroxides, oxides, carbonates, nitrates, sulfates, halides and carboxylates, preferably the hydroxides, oxides, carbonates and carboxylates, more preferably the carboxylates, notably such carboxylates as the acetates and their homologs, oxalates, benzoates, glycolates, lactates, citrates and other hydroxycarboxylates.
  • the compounds of lanthanum (La) and didymium (sometimes given the "atomic" designation Di) are preferred, in particular their carboxylates.
  • the catalyst is employed in catalytically effective amounts, which can vary widely depending upon the particular feed material (e.g. hydroxycarboxylic acid, ester or amine salt as defined) and the reaction conditions.
  • the optimum catalytically-effective amounts are readily determined through trial runs.
  • lanthanum acetate as the catalyst, its quantity is generally such that the reaction mass contains from about 0.01 to about 5% by weight, more usually from about 0.5 to 3% by weight
  • the oligomerizable hydroxycarboxylic acid composition may be an alpha-hydroxycarboxylic acid, an ester of an alpha-hydroxycarboxylic acid or a heat-dissociable nitrogen base salt thereof.
  • the invention includes converting an oligomerizable alpha-hydroxycarboxylic acid composition having the formula I, below, to an ohgomer having the formula ⁇ , below: n HOCR 1 R 2 C0 2 X ⁇ H(OCR 1 R 2 CO) n OX + (n-1) HOX (1)
  • n is an integer of 2 to 50;
  • X is independently H, R ⁇ or a cationic group HA R- , R ⁇ and R, are independently H or a C ⁇ to C 6 hydrocarbyl radical; and
  • A is a volatile nitrogen base.
  • R j , R2 and R ⁇ when other than H in the above formula, are alkyl groups.
  • the cationic group is derived from a nitrogen base such as ammonia or alkyl amine, and preferably is ammonia or a tertiary amine such as trimethylamine, triethylamine, memyldiethylamine, tripropylamine, tributylamine or the like.
  • n is not greater than about 20, more preferably not greater than about 12. The value of n defines the average number of monomenc units in the ohgomer, the value n-1 the average degree of polymerization.
  • the by-products would correspond to HLO and the nitrogen base, A.
  • the starting material I is an alkyl ester
  • X in oHgomer ⁇ is an alkyl group
  • the by-product, HOX is the alcohol, ROH.
  • X is H throughout, for reasons of economy, and by-product HOX is water.
  • X is so constituted that condensation by-product, HOX, whether water, alcohol or a nitrogen base, is more volatile than the oligomer, and distills away from it during the course of the reaction.
  • the oligomerization and depolymerization embodiments of the invention may be conducted batchwise or in a semi-continuous or continuous manner in accordance with any of such processes disclosed in the art.
  • a hydroxycarboxylic starting material, as described above, containing an oUgomerizing concentration of a lanthanoid catalyst, as defined above is heated at temperatures and pressures effective to produce an ohgomer along with by-product HOX, per equation
  • Suitable temperatures for oHgomerization generally range upwards from an initial 20° to 30°C up to about 230°C depending on the particular hydroxycarboxylic compound employed and the degree of polymerization/condensation desired.
  • the temperature is usually in the range from about 20° through about 185°C and, for glycolic acid oHgomer from about 20° through 210°C.
  • the oligomerization process can be carried out under sub-atmospheric to atmospheric pressures consistent with the vapor pressures of the volatile by-products and the oHgomers being recovered at the operating (polymerizing) temperature.
  • the by-product HOX (e.g. 1 ⁇ .0) may be removed in a stream of N 2 or other inert gas at ambient pressures, as more fully disclosed and taught, for example, in U.S. Patents 4,727,163, 4,835,293 and 5,023,349, which are also incorporated herein by reference.
  • Heating of the oHgomers produced by any of the above methods wherein, however, the catalyst is a lanthanum or other rare earth metal compound described above may be continued to convert them to the corresponding dimeric cyclic esters, that is, cyclic esters having the formula:
  • concentration of catalyst employed in the oHgomerization step is normally sufficient for the depolymerization step as well although if desired the concentration may be augmented by the addition of a further charge of the same or different lanthanum or other rare earth metal compound.
  • the depolymerization conditions in terms of temperature, pressure and reaction mode can vary widely, as described in the art, with continuous operation preferred.
  • the temperature of the depolymerization mass is in the range of about 180° to 270°C depending on the chemical constitution of the ohgomer and the cychc ester being produced.
  • the temperature is normally in the 190° to 230°C range, preferably in the 200° to 220°C range. Somewhat higher temperatures, in the 220°-250°C, are normally employed for preparing glycolide from ohgomeric glycohc acid.
  • reaction pressure may vary widely from subatmospheric to atmospheric pressure and above, and the mode of operation can vary from batch to continuous, as disclosed in U.S. Patents 1,095,205, 2,668,162, 3,597,450, 4,727,163, 4,835,293 and 5,023349 referenced and incorporated above.
  • the catalysts of this invention may also be employed in the process of European Patent AppUcation 0264 926 A2 wherein the depolymerization of a polyhydroxycarboxyHc acid (ohgomer) to a dimeric cyclic ester is conducted under reduced pressure and forced feed in an extruder having an increased temperature gradient along its length, a vapor port at its end for the volatile cychc ester and a drain for the unconverted oHgomeric reaction heel.
  • the catalyst of this invention may also be used in the thin film depolymerization of oHgomers of alpha-hydroxycarboxylic acids to dimeric cychc esters desribed in copending patent apphcation U. S. serial number 07/734,977, filed July 25, 1991.
  • the foUowing examples are intended to illustrate, not Hmit, the scope of the appended claims. Unless specified otherwise, the materials described are reagent grade, temperatures are in degrees Celsius and pressures in pounds per square inch (psi).
  • the ohgomeric material in the flask is held at 185° for another hour, then analyzed for its degree of polymerization by titration with 0.1 N sodium methoxide in methanol containing phenolphthalein indicator, and is found to have an average value of n equal to 11, where n is defined in equation (1) above.
  • the oUgomer is a readily pourable fluid, and retains its high degree of fluidity on being held molten for extended periods of time at 185°.
  • the reactor for this step is a heated 3-inch diameter 5-sieve tray glass Oldershaw column surmounting a 2 Hter flask heated at 200° to prevent depolymerization residue from sohdifying.
  • the column is equipped with an electrically-heated mantle whose heating temperature is controlled by means of a thermocouple situated at the third tray from the top of the column.
  • the flask is fitted with an inlet for N 2 gas.
  • Cracking of the ohgomer to lactide is effected by pumping the molten (185°) oUgomer of Example 1 to the top tray of the column, which is heated to 210° as measured at the third tray.
  • the ohgomer feed rate is adjusted to allow the entire Example 1 charge to be fed over a period of about 3 hours.
  • N 2 gas preheated to about 200° is fed to the column via the flask at a rate of 22.4 gr /min countercurrent to the downfiow of the oligomer.
  • the oligomer cracks as it moves down the heated column and lactide and other volatile products of cracking are vaporized and swept out of the column in the N 2 gas flow. Unvaporized material exits the column at its lower end and accumulates as heel in the unheated flask.
  • the gas stream exiting the column at its top end is passed through a 1000 gm body of methyl isobutyl ketone (MIBK) as scrubbing solvent contained in a 2 Hter receiver.
  • MIBK methyl isobutyl ketone
  • the gas leaves the scrubbing flask and is vented after first passing through cold traps cooled at about -80°C with soHd C0 2 .
  • the MIBK solution Upon completion of the run, the MIBK solution is cooled to about 5°, held at that temperature for about 16 hours and filtered to recover 501 gms of the L-lactide product. Evaporation of the filtrate yields an additional 285 grams of somewhat less pure L-lactide. The 786 grams total amount of lactide corresponds to a yield of 56%. In yield and quahty the L-lactide product is comparable to that of the product obtained using stannous octoate as the catalyst.
  • the heel of unconverted ohgomer coUected at the bottom of the column is relatively fluid and is recyclable to the cracking column for the production of additional quantities of lactide. This is in marked contrast to the highly viscous heels obtained using stannous octoate as the catalyst, which heels on being recycled to the depolymerization column yield Uttle or no additional lactide.

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Abstract

On décrit un procédé amélioré permettant de préparer de manière catalytique des oligomères d'acides alpha-hydroxycarboxyliques, par polymérisation par condensation, et de produire de manière catalytique des esters d'acides cycliques dimères par thermolyse des oligomères, impliquant l'utilisation d'yttrium, de lanthane ou d'autres métaux de terres rares (de numéro atomique 58 à 71) ou de leur composé compatibles avec ce procédé à titre de catalyseur. Recourir à de tels catalyseurs conduit à des viscosités plus faciles à utiliser et une toxicité moindre.
PCT/US1993/002299 1992-03-13 1993-03-15 Oligomerisation d'acides alpha-hydroxycarboxyliques catalysee par des metaux de terres rares et conversion en esters cycliques dimeres WO1993018021A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU38070/93A AU3807093A (en) 1992-03-13 1993-03-15 Rare earth metal catalyzed oligomerization of alpha-hydroxycarboxylic acids and conversion to dimeric cyclic esters

Applications Claiming Priority (2)

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US81413392A 1992-03-13 1992-03-13
US07/814,133 1992-03-13

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101195678B (zh) * 2006-12-08 2011-05-18 东丽纤维研究所（中国）有限公司 直接缩聚法制备聚乳酸的催化剂
RU2695998C1 (ru) * 2018-04-17 2019-07-30 Федеральное государственное бюджетное учреждение науки "Институт металлоорганической химии им. Г.А. Разуваева Российской академии наук (ИМХ РАН)" Способ каталитического синтеза лактида в присутствии неорганических добавок
US20210347754A1 (en) * 2018-10-29 2021-11-11 Pujing Chemical Industry Co., Ltd. Glycolide Production From Methyl Polyglycolate

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0261572A1 (fr) * 1986-09-20 1988-03-30 Boehringer Ingelheim Kg Procédé de production de lactide

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0261572A1 (fr) * 1986-09-20 1988-03-30 Boehringer Ingelheim Kg Procédé de production de lactide

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101195678B (zh) * 2006-12-08 2011-05-18 东丽纤维研究所（中国）有限公司 直接缩聚法制备聚乳酸的催化剂
RU2695998C1 (ru) * 2018-04-17 2019-07-30 Федеральное государственное бюджетное учреждение науки "Институт металлоорганической химии им. Г.А. Разуваева Российской академии наук (ИМХ РАН)" Способ каталитического синтеза лактида в присутствии неорганических добавок
US20210347754A1 (en) * 2018-10-29 2021-11-11 Pujing Chemical Industry Co., Ltd. Glycolide Production From Methyl Polyglycolate

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