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
  • C08G63/85—Germanium, tin, lead, arsenic, antimony, bismuth, titanium, zirconium, hafnium, vanadium, niobium, tantalum, or compounds thereof
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2531/00—Additional information regarding catalytic systems classified in B01J31/00
  • B01J2531/40—Complexes comprising metals of Group IV (IVA or IVB) as the central metal
  • B01J2531/46—Titanium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
  • B01J31/16—Catalysts comprising hydrides, coordination complexes or organic compounds containing coordination complexes
  • B01J31/22—Organic complexes
  • B01J31/2204—Organic complexes the ligands containing oxygen or sulfur as complexing atoms
  • B01J31/2208—Oxygen, e.g. acetylacetonates
  • B01J31/2226—Anionic ligands, i.e. the overall ligand carries at least one formal negative charge
  • B01J31/2243—At least one oxygen and one nitrogen atom present as complexing atoms in an at least bidentate or bridging ligand

Definitions

• Polyesters such as, for example, polyethylene terephthalate, polytrimethylene terephthalate and polybutylene terephthalate, are a class of important industrial polymers. They are widely used in thermoplastic fibers, films, and molding applications.
• Polyesters can be produced by esterification of an acid such as terephthalic acid (TPA) with a glycol followed by polycondensation.
• a catalyst is used to catalyze the polycondensation and may be used to catalyze the esterification.
• Antimony is often used as a catalyst for the esterification and polycondensation reaction.
• antimony-based catalysts are coming under increased environmental pressure and regulatory control, especially in food contact and fiber applications.
• Antimony-based catalysts may also cause problems with grey discoloration.
• Tin compounds can also be used in the esterification and polycondensation reactions.
• tin-based catalysts have similar toxicity and regulatory concerns.
• Titanium-based catalysts either alone or in combination with other compounds, have been described for use in the preparation of polyesters in US Patent No. 4,482,700, 4,131,601, 5, 302, 690, 5,744,571, 5, 905, 136, and in WO 97/45470.
• US Patent Publication 2005/0009687 describes the use of titanium alkoxide catalyst for the polymerization of cyclic esters in particular. There has been some concern that titanium catalysts, if used in the esterification and polycondensation reactions, tend to hydrolyze on contact with water forming glycol-insoluble oligomeric species, which lose catalytic activity, as described in US 2005/0215425.
• Esters and polyesters produced using certain titanium compounds as catalysts may also suffer from yellow discoloration, as described in US 4,131,601 and 4,482,700.
• a catalyst system for the synthesis of polyesters, in particular polyethylene terephthalate and its copolyesters having increased catalytic activity, no or only minimal effect on the properties of the polyester, and reduced toxicity concerns.
• the present invention is a method for producing a polyester comprising esterifying a polyacid and a polyol to produce an oligomer; and polymerizing the oligomer by way of polycondensation in the presence of an atrane containing catalyst to form an acyclic polyester.
• the present invention is a catalyst comprising a titanium atrane for use in acyclic ester polycondensation.
• the present invention is a method for making a titanium atrane catalyst comprising: (a) contacting a solution comprising a titanium (IV) alkoxide compound and a first solvent with an organic acid; (b) contacting the solution formed in step (a) with a substituted or unsubstituted trialkanolamine to form an impure catalyst; and(c) purifying the impure catalyst to form the titanium atrane catalyst.
• An example of byproduct formation is the formation of acetaldehyde that is formed during resin production and regenerated during processing. Most titanium catalysts have high acetaldehyde regeneration rates compared to antimony, but the catalysts of the present invention provide a solution to the problem of regenerated acetaldehyde.
• acyclic polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), and polyethylene naphthalate (PEN).
• PET polyethylene terephthalate
• PBT polybutylene terephthalate
• PTT polytrimethylene terephthalate
• PEN polyethylene naphthalate
• the first one is an esterif ⁇ cation reaction, in which a polyacid and a polyol are esterified.
• Suitable polyacids include terephthalic acid, isophthalic acid, cyclohexanedicarboxylic acid, naphthalenedicarboxylic acid; and long chain branching polyacids like trimesinic acid, trimellitic acid, and its anhydride.
• Suitable polyols include diethylene glycol, cyclohexanedimethanol, 1,3- propanediol, 2,2-dimethylpropanediol-l,3, 1,4-butanediol, isosorbide; aromatic polyols such as resorcinol, hydroquinone; and long chain branching polyols such as trimethylolpropane and pentaerythritol.
• the polyacid is terephthalic acid and the polyol is typically ethylene glycol.
• the esterification step can be carried out without any catalyst (autocatalysis), but typically, antimony compounds are able to catalyze the esterification reaction.
• the esterification step is typically conducted at a temperature of above 200 0 C, more preferably at a temperature of from 240 0 C to 270 0 C, and at a pressure of from 1 to 10 bar.
• water is formed as a reaction product.
• vinyl alcohol which isomerizes extremly fast to acetaldehyde, is formed as a byproduct.
• the second main reaction is referred to as polycondensation, which is extremly important for molecular weight build-up of the polyester.
• the polycondensation reaction may include two phases, a melt phase and a solid state phase.
• the melt phase of the polycondensation step is conducted at a temperature of from 240 0 C to 290 0 C and under vacuum between 3 and 0.1 mbar.
• the solid state phase of the polycondensation step is conducted at a temperature of from 190 0 C to 230 0 C and may be conducted either under nitrogen flow or under vacuum between 3 and 0.1 mbar.
• titanium atrane catalysts of the present invention retain significant catalytic activity during both of the polycondensation reactions, (melt and solid state)
• Atranes are comprised of two bridgehead atoms bridged by three atom moieties.
• the bridgehead atoms interact, a (3.3.3.0) tricyclic system is produced (Vercade et al.; Coordination Chemistry Reviews (1994), 137, 233-295).
• the atrane is a titanium atrane having the following structure:
• the first ligand is a substituted or unsubstitued trialkanolamine, and is preferably triethanolamine, tri-isopropanolamine, or a substituted triethanolamine.
• the second ligand is an organic acid. Any acid may be used, but preferably the acid is a carboxylic acid, and even more preferably the second ligand is acetic acid or propionic acid.
• the titanium atrane catalysts of the present invention only contain one titanium atom per molecule, such that no significant bridging with other molecules occurs.
• the titanium atrane catalysts of the present invention are used in both the melt phase and the solid state phase of the polycondensation step at a concentration of from 5 to 250 ppm.
• the catalyst may be added in the form of a powder, in which case it may be added to the polyacid and polyol (the mixture of these referred to herein as "paste") before the esterification reaction.
• a catalyst-containing solution may be prepared comprising the catalyst and a suitable polyol such as ethylene glycol.
• the catalyst-containing solution may be added to the paste, directly to the esterification reaction, or directly to the polycondensation reaction.
• the manner of addition is not critical, so long as direct contact with water, especially at higher temperatures, is avoided before the catalyst is added to the reaction mixture.
• the catalyst works at the same temperatures and pressures as antimony catalysts typically described in the prior art.
• the titanium atrane catalysts of the present invention may be synthesized using the following steps: First, an alcohol solution is prepared by adding a titanium (IV) alkoxide to a first solvent.
• the first solvent is the alcohol corresponding to the alkoxide in the titanate.
• titanium n-butylate is the titanate used, then preferably the first solvent is n-butanol.
• titanium n-propylate is the titanate, then 1-propanol is the preferred first solvent; if titanium iso-propylate is the titanate, then iso-propyl alcohol is the preferred first solvent; if titanium t-butylate is the titanate, then t-butanol is the preferred first solvent; if titanium ethylate is the titanate, then ethylalcohol is the preferred first solvent; and so forth.
• the alcohol solution is prepared under nitrogen.
• an organic acid is added slowly under nitrogen to the alcohol solution in an amount such that the molar ratio of titanate to organic acid is 1 : 1.
• a solution of an acid- substituted titanate results.
• the acid is a carboxylic acid. More preferably, the carboxylic acid is acetic acid.
• the organic acid is added to the alcohol solution at a temperature of from 20 0 C to 50 0 C and at normal pressure.
• a substituted or unsubstituted trialkanolamine is added slowly under nitrogen to the acid-substituted titanate solution in an amount such that the molar ratio of titanate to trialkanolamine is 1 :1.
• the trialkanolamine is triethanolamine, tri-isopropanolamine, or a substituted triethanolamine.
• the trialkanolamine is added to the solution of the acid-modified titanate at a temperature of from 20 0 C to 50 0 C and at normal pressure. The result is a mixture comprising impure catalyst in the form of a solid precipitate, liquid alcohol, and impure catalyst dissolved in the liquid alcohol.
• the solid precipitate may be separated from the rest of the mixture, for example, by way of filtration, and the solid precipitated catalyst may then be purified as described below. Preferably, however, the solid precipitate is left to remain with the rest of the mixture and the entire mixture is purified as described below.
• the impure catalyst is then purified.
• the first solvent is removed by way of evaporation under vacuum at temperatures below 50 0 C, leaving a solid precipitate.
• the solid precipitate is then added to a second solvent such as, for example, toluene between 1 and 50 weight% of catalyst, based on the weight of toluene, and boiled to remove residual substances such as alcohol, ester and traces of water.
• the resultant suspension is hot filtered, and the (white) filter cake was dried and stored under vacuum.
• the resulting titanium atrane catalyst may be used for the manufacture of resins used for bottles, films, fibers, and other applications.
• the titanium atrane catalysts of the present invention may also be used for different processes, such as, for example, the so referred to as "high IV processes".
• titanium atrane catalysts described herein it is possible to add small amounts of the titanium atrane catalysts described herein to the conventional catalysts such as antimony or germanium-based catalysts, in order to increase capacity. Even up to 10 ppm titanium atrane catalyst (2 ppm titanium) can increase polycondensation and esterification rates so as to increase capacity.
• Measurement Measurements are performed with a Micro-UBBELOHDE- Viscosimeter Type No. 536 20
• the equipment is used when the reference standards reach the following XYZ values.
• the sample is measured as pellets.
• the cuvette must be clean and is filled to at least % full.
• the sample is measured eight times, and for each measurement the cuvette is filled with new pellets.
• the average value of all 8 measurements is calculated using SPECTRAL QC software
• the resin is processed on an ES 200-50 injection molding machine (Engel Co. ) with a 30 millimeter diameter screw and a lengthrdiameter ratio of 20.
• the dried resin is fed to the material hopper of the injection molding machine, to which a nitrogen curtain is applied.
• the resin is processed at temperature between 270 0 C and 300 0 C.
• the resulting melt is then injected into a cooled mold under pressure. Processing parameters: Drying:
• the acetaldehyde content of the processed resins is determined according to the following method: At first, the various materials are ground with a 1 mm screen in a centrifugal mill by RETSCH Co. (ZMl) in the presence of liquid nitrogen. Approximately 0.1 g to 0.3 g of the ground material is put into a 22 ml sample bottle and sealed with a polytetrafluoroethylene seal. The sample bottles are heated under controlled temperature in a headspace oven (HS-40 XL headspace autosampler by Perkin Elmer) at 150 0 C for 90 minutes, and subsequently analyzed through gas chromatography (XL GC AutoSystem by Perkin Elmer) with an external standard. The calibration curve is prepared through complete evaporation of aqueous solutions of different acetaldehyde contents.
• ZMl centrifugal mill by RETSCH Co.
• Carrier gas nitrogen, 30 ml/min
• the trials are conducted in a 200 L batch reactor (Pisticci Mini Plant).
• This reactor is equipped with a spiral agitator with hydraulic drive (speed control system for constant speed/torque measurement) and an oil heating system (max. temperature 300 0 C) for the reactor and a second heating system (275 0 C) for the outlet valve/hole plate.
• the spiral agitator transports the product from the bottom up on the wall with a space to the wall of 1.5 cm.
• the filling level in the reactor iss approx. 40%.
• Example 1 Titanium Atrane Catalyst Preparation 0.4 moles of titanium n-butylate are added under stirring to 500 mL n-butanol in a nitrogen atmosphere at room temperature. After this, 24 g glacial acetic acid(0.4 moles) are added at room temperature slowly to the solution of titanium n-butylate in n-butanol. The color of the solution changes to slightly yellow. It is stirred for additional 10 minutes. 59.67 g triethanolamine are added dropwise to the stirred solution. The temperature increases by about 2 K during the addition of the amine. The mixture is stirred at room temperature. During this time a white precipitate forms. The mixture is stirred for a certain period of time (between 0.5 and 50 h).
• n-butanol is evaporated under vacuum at temperatures below 50 0 C.
• the resulting off-white to amber solid is added to 500 ml toluene. It is boiled in this solvent to remove alcohol, ester and water traces. The resultant suspension is hot filtered, and the (white) filter cake was dried and stored under vacuum. The resulting atrane has a melting point of greater than 200°C. The yield is in the range of 60 to 90% (based on titanium).
• Example 2 PET produced using Titanium atrane catalyst
• Monoethylene glycol (29.5 kilograms), 34.65 grams of an aqueous solution of tetramethylammonium hydroxide (TMAH, used to inhibit formation of diethylene glycol) (50 ppm), 15 parts per million (ppm) titanium as catalyst (added as 5.9 g titanium atrane), and a colorant comprising Polysynthren RBL (0.288 g or 4 ppm) and Polysynthren GFP (4 ppm), are fed into the paste mixer.
• TMAH tetramethylammonium hydroxide
• a paste mixer which is a vessel used to mix the raw materials before being fed into a reactor.
• the reactor is purged with nitrogen for approximately 5 minutes.
• the MEG/PTA paste is then fed into the reactor.
• esterification the pressure is decreased to 1.5 bar (absolute) in 10 minutes; followed by the addition of a phosphorous compound which is added as a stabilizer (2.675 g phosphoric acid or 10 ppm phosphorous.)
• Esterification The set points for reactor temperature and pressure for the first step of esterification are approximately 235 0 C and 2.6 bar (absolute). The stirrer speed is 80 min "1 . In the column the gas phase is separated into ethylene glycol (EG) and water. The EG is recycled back to the reactor. The condensed water (at the top of the column) is collected in a tank. During the esterification time the product temperature increases to 270 °C. The esterification run lasts approximately 200 minutes.
• EG ethylene glycol
• the phosphorous compound is given into the reactor from a separate catalyst tank.
• the catalyst tank is purged with nitrogen before adding the solution of phosphoric acid in ethylene glycol.
• the stirrer speed is decreased to 35 min '1 .
• the product temperature increased to
• the polycondensation is finished at a fixed value for the hydraulic pressure of the hydraulic drive.
• the highly viscous polyester is cooled in a water bath, and the thus formed strands are pelletized.
• the SSP reactor is a fluidized bed reactor (pulse bed) from the BUHLER company.
• the reactor has a batch capacity of 3 kilograms.
• the PET pellets are treated in a hot nitrogen stream (125 Nm3/h) at normal pressure. Crystallization, drying and SSP are batch processes with the same nitrogen flow. Approximately 10 % of the nitrogen is removed from the stream after passing the pellets and is replaced with fresh nitrogen. The dew point of the nitrogen is -55 0 C. Table 1 shows the results.
• Example 3 PET produced using conventional antimony-based catalyst The procedures described for Example 2 are followed, except the following recipe substituted for that in Example 2:
• MEG (9.5 kilograms), 34.65 grams TMAH (50 ppm), 230 ppm antimony (added as 40.25 g antimony acetate, used as the catalyst), and 10 ppm cobalt (added as 3.035 g cobalt acetate, used as a colorant) are fed into the paste mixer. Under stirring (2 stirrers at 3,600 min 1 ), 60.675 kilograms PTA and 1.44 kilograms IPA are added into the paste mixer. The reactor is purged with nitrogen for approximately 5 minutes. The MEG/PTA paste is fed into the reactor.

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• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Polyesters Or Polycarbonates (AREA)
• Catalysts (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

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