Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
  • C08G63/78—Preparation processes
  • C08G63/82—Preparation processes characterised by the catalyst used
  • C08G63/823—Preparation processes characterised by the catalyst used for the preparation of polylactones or polylactides

Definitions

• the present invention relates to the polymerization of molten lactide (either S or R) using an yttrium or lanthanide series rare earth metal based catalyst.
• Lactides are presently polymerized to high molecular weight plastics using stannous 2-ethylhexanoate (tin octanoate) as the catalyst by ring opening polymerization of the cyclic ester:
• the present process relates to a process for the polymerization of lactide and optionally up to 20 mole % based on lactide of one or more lactones selected from
• each R is independently selected from hydrogen or hydrocarbyl containing up to 20 carbon atoms or substituted hydrocarbyl containing up to 20 carbon atoms
• M is chosen from yttrium or a lanthanide series rare earth metal
• Z is -OCR', where R' is independently chosen from hydrogen, hydrocarbyl and substituted hydrocarbyl.
• up to two Zs may be other herein below defined materials.
• the present invention relates to a process for the ring opening polymerization of molten lactide and up to 20 mole % based on lactide of another lactone using as catalysts certain compounds of yttrium or lanthanide series rare earth metal.
• n is 4 or 5
• h, i, k and m are independently one or two and each R is independently chosen from H or hydrocarbyl containing up to 12 carbon atoms.
• Preferred lactones are those in which R is hydrogen or methyl, and especially preferred lactones are epsilon-caprolactone, delta-valerolactone, glycolide (l,4-dioxan-2,5-dione), l,5-dioxepan-2-one and l,4-dioxan-2-one.
• the catalysts, characterized by the formula MZ,, for this polymerization are compounds of yttrium and the rare earth metals.
• Rare earth metals include those elements with atomic numbers 57 through 71, namely lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium.
• Preferred metals are yttrium, lanthanum, cerium, samarium and dysprosium.
• lanthanum and mixtures of yttrium and rare earth metals that are obtained from the mining or smelting of rare earth metal ores.
• the yttrium and rare earth metal are trivalent.
• the catalyst preferably is at least slightly soluble in the molten lactide.
• the group denoted Z bonded to the metal, M, is -OCR' where each -R' is independently chosen from hydrogen, hydrocarbyl of up to 50 carbon atoms and substituted hydrocarbyl of up to 50 carbon atoms. It is to be understood that in the group -OCR the carbon atom bound to the oxygen may be part of a non-aromatic carbocycle or non-aromatic heterocycle formed from that carbon and two of the -R' groups.
• Preferred Z groups contain less than 50 carbon atoms and include isopropoxy, 2-ethoxyethoxy and 2-(N,N-dimethylamino)ethoxy.
• Other highly coordinating ligands include fluoride, chloride, bromide, iodide, carboxylate, tetrasubstituted porphyrinato (-2), phthalcyanato (-2), beta keto ester anions such as methyl acetoacetate, dial ylmalonate ion, cyclopentadienide, pentamethylcyclopentadienide, and aryloxide such as phenoxide.
• one Z is an active catalyst group such as -OCH(CH 3 ) 2 , -OC ⁇ O ⁇ OO ⁇ O ⁇ or -OCI ⁇ CH ⁇ CH ⁇ and two Z groups are highly coordinating ligands, preferably 2,2,6,6-tetramethylheptane- 3,5-dionate or acetylacetonate.
• active catalyst group such as -OCH(CH 3 ) 2 , -OC ⁇ O ⁇ OO ⁇ O ⁇ or -OCI ⁇ CH ⁇ CH ⁇
• two Z groups are highly coordinating ligands, preferably 2,2,6,6-tetramethylheptane- 3,5-dionate or acetylacetonate.
• the formula MZ is also meant to encompass "complex" salts of yttrium and rare earth metals of the formula Me2MZy, where M and Z have the meaning given above and Me is a divalent metal cation such as barium.
• Me is a divalent metal cation such as barium.
• the necessary elements in such compounds are trivalent yttrium or rare earth metal and one or more Z groups bound to them. Examples of such compounds are Ba 2 Y[OCH 2 CH 2 N(CH 3 ) 2 3 7 and Ba 2 Y(OC ⁇ CTI 2 OCH 2 CH 3 ) 7 .
• redistribution reactions may take place.
• redistribution reactions is meant exchange of Z groups between metal atoms, so that it is possible, in theory, to obtain any combination of Z groups present on any particular metal atom.
• hydrocarbyl is meant any monovalent radical that contains only carbon and hydrogen.
• substituted hydrocarbyl is meant any monovalent hydrocarbyl radical that contains other functional groups that do not substantially interfere with the reaction or react with any of the reactants or products.
• Suitable functional groups include halo, ester, ether, amino, thioether, silyl, hydroxy, carbon-carbon unsaturation (i.e., double or triple bonds) and aldehyde.
• Trivalent yttrium and rare earth compounds will not be stable if they contain a functional group whose pKa is less than that of the pKa of the conjugate acid of the functional group bonded to the yttrium or rare earth metal. A special case may arise when the two pKas are approximately equal. Then an equilibrium may exist as to which group is bound to the yttrium or rare earth metal, and if such groups fit the definition of Z above then both will initiate polymerization.
• the polymerization of the present invention is carried out in the absence of any solvent in the molten lactide at from 100 to 220 °C, preferably from 110 to 200 °C and most preferably from 165 to 180 °C It is preferred to use a diy inert gas such as nitrogen or argon to blanket the reaction. Moisture is deleterious to the stability of the catalyst and can limit the molecular weight of the polymer produced.
• the starting materials should be dry. Drying methods are known to those skilled in the art, and include distillation from calcium hydride passage over molecular sieves or crystallization.
• the preferred catalyst is lanthanum bis(2£6,6- tetrametbylheptane-3 ⁇ -dionato)isopropoxide
• the catalyst must be stable at the reaction temperature which eliminates many of the known yttrium and rare earth metal compounds otherwise available.
• the advantages of the process of the present invention are that it is faster, provides a narrow molecular weight distribution, provides a product with a better thermal stability as determined by weight loss at 200 °C and involves fewer side reactions as observed by color formation than many of the highly active catalysts in the literature.
• Example 5 Lanthanum bis( f 2.2.6.6-tetramethylheptane dionato) isopropoxide catalyst 5g L-lactide, polymer grade, was melted in a flame-dried, nitrogen-flushed glass test tube suspended in a 165 °C vapor bath. 17.5 microliters of 025 M tetrahydrofuran solution was injected via hypodermic syringe to give a monomer to catalyst molar ratio of 8000/1. The clear, colorless mixture increases rapidly in viscosity. After 2 minutes the tube was quenched in ice water to. stop the reaction. Monomer conversion as measured by thermogravimetric analysis was 66%. Gel permeation chromatography in tetrahydrofuran vs.
• Example 8 Yttrium bis(22.6.6-tetramethylheptane dionato) isopropoxide catalyst 5g L-lactide, polymer grade, was melted in a flame-dried, nitrogen-flushed glass test tube suspended in a 166 °C vapor bath. 87 microliters of 02 M solution of yttrium bis (2,2,6,6-tetramethylheptane dionato) isopropoxide in 2-methyl-tetrahydrofuran was injected via hypodermic syringe to give a monomer to catalyst molar ratio of 2000/1. The clear, colorless mixture increases in viscosity, and after an additional 3.5 minutes the tube was quenched in ice water to stop the reaction.
• Example 9 Di-iodo-Samarium-1-benzyl-n-octyloxide 5g L-lactide, polymer grade, was melted in a flame-dried, nitrogen-flushed glass test tube suspended in a 166 °C vapor bath. 864 microliters of 0.04 M solution of Di-iodo-Samarium alkoxide prepared according to J. Org. Chem., 49(11), p. 2045 (1984) from Sml2, n-octanal and benzylbromide, was injected via hypodermic syringe to give a monomer to catalyst molar ratio of 1000/1.

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• Chemical Kinetics & Catalysis (AREA)
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• 1992
  • 1992-03-13 US US07/815,107 patent/US5235031A/en not_active Expired - Fee Related
  • 1992-12-30 WO PCT/US1992/011308 patent/WO1993018080A1/en not_active Ceased
  • 1992-12-30 TW TW081110506A patent/TW222654B/zh active

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