Glycolysis of poly(ethylene terephthalate) wastes in xylene

To reclaim the monomers or prepare intermediates suitable for other polymers zinc acetate catalayzed glycolysis of waste poly(ethylene terephthalate) (PET) was carried out with ethylene or propylene glycol, with PET/glycol molar ratios of1 : 0.5–1 : 3, in xylene at 170–245°C. During the multiphase reaction, depolymerization products transferred to the xylene medium from the dispersed PET/glycol droplets, shifting the equilibrium to glycolysis. Best results were obtained from the ethylene glycol (EG) reaction at 220°C, which yielded 80 mol % bis-2-hydroxyethyl terephthalate monomer and 20 mol % dimer fractions in quite pure crystalline form. Other advantages of employment of xylene in glycolysis of PET were improvement of mixing at high PET/EG ratios and recycling possibility of excess glycol, which separates from the xylene phase at low temperatures. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2311–2319, 1998     

Studies of glycolysis of poly(ethylene terephthalate) recycled from postconsumer soft‐drink bottles. I. Influences of glycolysis conditions

The glycolysis of recycled poly(ethylene terephthalate) flakes by ethylene glycol (EG) is investigated. Bis‐2‐hydroxyethyl terephthalate (BHET) and oligomers are predominately glycolysis products. The influences of glycolysis temperature, glycolysis time, and the amount of catalyst (cobalt acetate) are illustrated. The BHET, dimer, and oligomers are predominately glycolysis products. The optimum glycolysis temperature is found to be 190°C. If a 190°C glycolysis temperature, 1.5‐h glycolysis time, and 0.002 mol glycolysis catalyst (cobalt acetate) are used, the glycolysis conversion is almost 100%. The glycolysis conversion rate increases significantly with the glycolysis temperature, glycolysis time, and the amount of cobalt acetate. Thermal analyses of glycolysis products are examined by differential scanning calorimetry. In addition, the chemical structures of glycolysis products are also determined by a Fourier transform IR spectrophotometer. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 943–948, 2001     

Recycling of PET and PVC wastes

A method for recycling mixed PET and PVC wastes is described. Glycolysis of PET leads to oligomers that are polycondensed with caprolactone. The obtained diols are extended with hexamethylene diisocyanate. In certain conditions the polyurethanes are totally miscible with PVC, leading to acceptable mechanical characteristics for the blend. A relation between the structure of the polyurethane and miscibility with PVC is described. The mechanical characteristics of the blend depends on the polyurethane chemical structure. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 657–665, 1998     

Kinetic and catalytic aspects of the formation of poly(ethylene terephthalate) (PET) investigated with model molecules

Kinetic and catalytic aspects of the formation of poly(ethylene terephthalate) (PET) have been studied in this work using model molecules such as 2-hydroxyethyl 4-methylbenzoate (MP), 2-hydroxyethyl 4-benzoate (MB), and 2(-hydroxyethyl 4-methylbenzoate) 4-methylbenzoate (DP), synthesized and purified in our laboratories. The methods to obtain these molecules have been described in detail. Many kinetic runs have been performed using different catalysts, such as compounds of Sb, Ti, Zr, Al, Mo (VI), Mn, Zn, Sn (IV), and Ge. We have made kinetic runs on some catalysts under different operative conditions to evaluate the effect of catalyst concentration and temperature on the reaction rate. We have observed that a second-order kinetic law is suitable for both condensation and reverse reaction. All kinetic runs have been interpreted and kinetic parameters determined. Activity can depend on catalyst concentration in a different way for each type of catalyst. Bivalent metals activity is affected by the presence of a substituent in the aromatic ring, unlike tri- and tetravalent metals. Suggestions on the reaction mechanisms conclude the work. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2423–2433, 1998     

New Motivation for the Depolymerization Products Derived from Poly(Ethylene Terephthalate) (PET) Waste: a Review

Summary: Over the last several decades, the process of recycling polymer waste has been attracting the attention of many scientists working on this issue. Polymer recycling is very important for at least two main reasons: firstly, to reduce the ever increasing volumes of polymer waste coming from many sources: from daily life packaging materials and disposables and secondly, to generate value‐added materials from low cost sources by converting them into valuable materials similar, to some extent, to virgin materials. Poly(ethylene terephthalate) (PET) occupies the top of the list of polymers to be recycled due to its easy recycling by different ways, which, in accordance, give variable products that can be introduced as starting ingredients for the synthesis of many other polymers. PET can by recycled by hydrolysis, acidolysis, alkalolysis, aminolysis, alcoholysis and glycolysis. Glycolysis is the breakdown of the ester linkages by a glycol, resulting in oligomers or oligoester diols/polyols with hydroxyl terminal groups. Oligoesters coming from the glycolysis of PET waste have been well known for a number of decades to be utilized as a starting material in the manufacture of polyurethanes, unsaturated polyesters and saturated polyester plasticizers. But, as a current motivation, we are reporting on a new application for these oligoester diols/polyols by converting the hydroxyl terminals into acrylate/methacrylate groups. These new acrylated/methacrylated oligoesters have been tested as UV curable monomers and gave promising results from the point of view of their curability by UV and their mechanical properties. The new motivations open the potential for the market to apply the depolymerization products of PET waste for UV curable coatings, useful for wood surfaces, paints and other applications.

Recycling of PET polymer by different chemical routes.     

Recycling of PET waste using 3‐amino‐1‐propanol by conventional or microwave irradiation and synthesis of bis‐oxazin there from

There is a growing interest in recycling of post‐consumer poly(ethylene terephthalate) (PET) waste for both environmental and economic reasons. PET in the form of disposable soft drink bottle waste was subjected to depolymerization via aminolysis using excess of 3‐amino‐1‐propanol under soxhlet by conventional heating as well as microwave irradiation using catalyst sodium acetate or potassium sulfate. The product obtained was characterized after purification by using melting point, IR spectroscopy, nuclear magnetic resonance, and differential scanning calorimeter and was found to be bis‐(3‐hydroxy propyl) terephthalamide (BHPTA). The BHPTA thus obtained was subjected to cyclization reaction using thionyl chloride to obtain bis‐oxazin under conditions of ambient temperature. Bis‐oxazin has applications in polymer synthesis as a chain extender or a cross linking agent. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Characterization of poly(trimethylene/butylene terephthalate) copolymer prepared by the copolycondensation of bis(3‐hydroxypropyl terephthalate) and bis(4‐hydroxybutyl terephthalate)

Homopolymers and copolymers were synthesized by polycondensation and copolycondensation, with varying feed ratios of bis(3‐hydroxypropyl terephthalate) (BHPT) and bis(4‐hydroxybutyl terephthalate) (BHBT) at 270°C. In addition, in the mol ratio of 1:1, copoly(trimethylene terephthalate/butylene terephthalate) [P(TT/BT)], with reaction times of 5, 10, 20, 30, and 60 min, was synthesized to identify the chain‐growth process of the copolymers. From differential scanning calorimetry (DSC) data, it was found that a random copolymer might be formed during copolycondensation. The molecular structure of copolymers, formed through the interchange reaction of BHPT and BHBT, was investigated using carbon nuclear magnetic resonance spectroscopy (¹³C‐NMR). We calculated the sequence‐length distributions of trimethylene and butylene sequences and randomness in the copolymers using ¹³C‐NMR data. From the values of the number‐average sequence length calculated, it was determined that a random copolymer was produced: This result coincides with previous DSC data. The lateral spacing of the unit cell of the copolymer increased slowly when the mol percent of one monomer was increased to that of the other monomer, indicating broadening of the unit cell by lateral distortion. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2200–2205, 2003     

Dissolution/reprecipitation: A model process for PET bottle recycling

A dissolution/reprecipitation route was followed for the recycling of poly(ethylene terephthalate) (PET). Model experiments on virgin material, either in the form of pellets or blow‐molded bottles, are presented. The process proposed comprises dissolution of the plastic in an appropriate solvent, reprecipitation by using a nonsolvent, thorough washing of the material obtained, and drying. The solvent mixtures involved are separated by fractional distillation for further reuse. N‐Methyl‐2‐pyrrolidone (NMP)/n‐octane + n‐hexane proved to be a particularly effective solvent/nonsolvent system. Further investigation was focused on the effect of the sample history through successive recycling cycles. The recycled material was evaluated in terms of molecular weight, crystallinity, and grain‐size analysis, resulting in an excellent quality, competing with the virgin grade. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 91–95, 2001     

Effect of addition of glycolysis products of poly(ethyleneterephthalate) wastes to urea‐formaldehyde resin on its adhesion performance to wood substrates and formaldehyde emission

Recycling of poly(ethyleneterephthalate) waste was achieved through glycolysis using diethyleneglycol (DEG) and poly(ethyleneglycol) (PEG 400), which yielded different fractions that exhibited hydroxyl numbers of 174.41 and 54.86 mg of KOH/g, respectively, whereas GPC profiles revealed bimodality in both cases corresponding to M_n values equivalent to 534 and 1648. The products of glycolysis from both cases were individually incorporated as modifiers during the synthesis of urea‐formaldehyde resins from both the basic as well as acidic stages, respectively. It was found that the free formaldehyde level was remarkably decreased for the modified resins while the gel time was slightly affected indicating some activation of the resins. In addition, the adhesion strength of wood joints bonded with the modified resins improved markedly in the dry state while the moisture resistance was significantly fortified with respect to the comparable joints formulated from unmodified resins where instant failure took place within few hours after immersion in water. The shelf life of the resins did not prolong and lasted maximum for about 2 months which was ascribed to the presence of reasonable amount of carboxyl terminal groups at the ends of a minor portion of the glycolyzed products that could actively act to self‐catalyze the polycondensation and crosslinking reactions during storage leading eventually to vitrification of the resin and shortening of shelf life. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Oligomer production through glycolysis of poly(ethylene terephthalate): effects of temperature and water content on reaction extent

Using ethylene glycol (EG) and post‐consumer poly(ethylene terephthalate) (PET) bottles, monomers and oligomers were obtained through glycolysis catalyzed by zinc acetate. Three reaction temperatures (150, 160 and 170 °C) and water contents (0, 1.0 and 2.0% with respect to the volume of EG) were used as inputs; the extent of depolymerization as the analyzed response formed the basis for a factorial design experiment. The products obtained from PET glycolysis were analyzed using high‐performance liquid chromatography and Fourier transform infrared spectroscopy, and their morphology was evaluated using scanning electron microscopy. The results showed the presence of terephthalic acid, hydroxylated tetramers, bis(hydroxyethyl) terephthalate monomer and dimer, and also oligomers with various molecular weights, water being present in the reaction medium. Statistical analysis (95% confidence) indicated that temperature and water content were significant inputs for glycolysis of PET, with the temperature being much the more important factor. © 2016 Society of Chemical Industry     

A novel catalyst for the glycolysis of poly(ethylene terephthalate)

Poly(ethylene terephthalate) waste materials were depolymerized by ethylene glycol (EG), diethylene glycol (DEG), and propylene glycol (PG) in the presence of a novel catalytic system: titanium (IV)‐phosphate. The new catalyst was synthesized through a reaction of TiCl₄ with triethyl phosphate (C₂H₅O)₃P(O). It was found that the depolymerization of poly(ethylene terephthalate) fiber proceeds faster in the presence of titanium (IV)‐phosphate compared with compounds traditionally used in this process like Zn(OOCCH₃)₂. The oligomer distribution in the glycolysis products was studied by size‐exclusion chromatography. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1148–1152, 2003     

The effects on the properties of PET bottles of changes to bottle‐base geometry

Poly(ethylene terephthalate) (PET) bottles are commonly used for packaging of carbonated beverages. Stress cracking in the petaloid‐shaped base of the filled bottle has been costly to the beverage industry. This study compares the performance of a standard bottle and a bottle with a base geometry optimized against environmental stress cracking (ESC). The crystallinity of the bottle base is evaluated across the base diameter for both bottles. Moreover, to explain the mechanism of the crack formation and propagation, the cracks in the bottle base are investigated through environmental scanning electron microscopy (ESEM) and optical microscopy. Top‐load strength, burst strength, and thermal stability are also reported. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Chain extension of recycled poly(ethylene terephthalate) with 2,2′‐(1,4‐phenylene)bis(2‐oxazoline)

The present work provides improved recycled high molecular weight poly(ethylene terephthalate) (PET) by chain extension using 2,2′‐(1,4‐phenylene)bis(2‐oxazoline) (PBO) as the chain extender. PBO is a very reactive compound toward macromolecules containing carboxyl end groups but not hydroxyl end groups. In the case of PET, where both species are present, for even better results, phthalic anhydride (PA) was added in the initial sample, before the addition of PBO. With this technique, we succeeded in increasing the carboxyl groups by reacting PA with the hydroxyl terminals of the starting polymer. From this modification of the initial PET sample, PBO was proved an even more effective chain extender. So, starting from a recycled PET with intrinsic viscosity [η] = 0.78, which would be [η] = 0.69 after the aforementioned treatment without a chain extender or M̄_n = 19,800, we prepared a PET grade having [η] = 0.85 or M̄_n = 25,600 within about 5 min. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2206–2211, 2000     

聚酯装置工艺优化与增容工作总结

分析了吉玛工艺的特点,细述了聚酯装置工艺优化和增容的原则、步骤和组织实施,总结了仪化公司10多年的聚酯工艺优化和改造的思路和成功经验,指出了增容改造的根本点,为进一步的工作指明了方向。     

Modeling of glycolysis of flexible polyurethane foam wastes by artificial neural network methodology

The glycolysis process as a useful approach to recycling flexible polyurethane foam wastes is modeled in this work. To obtain high quality recycled polyol, the effects of influential processing and material parameters, i.e. process time, process temperature, catalyst‐to‐solvent (Cat/Sol) and solvent‐to‐foam (Sol/Foam) ratios, on the efficiency of the glycolysis reaction were investigated individually and simultaneously. For the continuous prediction of process behavior and interactive effects of parameters, an artificial neural network (ANN) model as an efficient statistical‐mathematical method has been developed. The results of modeling for the criteria that determine the glycolysis process efficiency including the hydroxyl value of the recycled polyol and isocyanate functional group conversion prove that the adopted ANN model successfully anticipates the recycling process responses over the whole range of experimental conditions. The Cat/Sol ratio showed the strongest influence on the quality of the recycled polyol among the studied parameters, where the minimum hydroxyl value was obtained at a medium amount of the assigned ratio. For the consumed polyurethane foam, a higher value of this ratio led to an increase in the hydroxyl value and isocyanate conversion. © 2015 Society of Chemical Industry     

Studies of glycolysis of poly(ethylene terephthalate) recycled from postconsumer soft‐drink bottles. II. Factorial experimental design

Glycolysis temperature, glycolysis time, and amount of catalyst are important factors affecting the glycolysis of recycled poly(ethylene terephthalate) (PET) flakes. A 2³ factorial experimental design is applied to study the main, two‐factor interaction, and three‐factor interaction effects of glycolysis temperature, glycolysis time, and amount of catalyst on the glycolysis of recycled PET flakes. In this study cobalt acetate is used as the glycolysis catalyst. The sequence of the main effects on the glycolysis conversion of the recycled PET flakes in ascending order is glycolysis time < glycolysis temperature < amount of catalyst. The sequence of the two‐factor interaction effects on the glycolysis conversion of the recycled PET flakes in ascending order is glycolysis temperature versus the glycolysis time < glycolysis time versus the amount of catalyst < glycolysis temperature versus the amount of catalyst. The three‐factor interaction effect is significantly related to the glycolysis conversion of the recycled PET flakes. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 956–962, 2001     

Aspects of the chemistry of poly(ethylene terephthalate): 5. Polymerization of bis(hydroxyethyl)terephthalate by various metallic catalysts

Bis(hydroxyethyl)terephthalate (BHET) was polymerized to poly(ethylene terephthalate) (PET) in the presence of various metallic catalysts. The influence of the nature and concentration of these catalysts on the rate of polymerization has been investigated. The effect of the reaction temperature has also been studied. The order of decreasing catalytic influence of various metal ions, on the polymerization of BHET was found to be: Ti>Sn>Mn>Zn>Pb>No.     

Glycolyzed PET waste and castor oil‐based polyols for two‐pack coating systems

Useful coating products may be obtained by chemical valorization (glycolysis) of post‐consumed poly(ethylene terephthalate) (PET) wastes. Glycolysis of PET waste was carried out using poly(ethylene glycol) (PEG) of various molecular weights (200, 400, 600). The depolymerized oligoesters obtained were transesterified with castor oil which results in the formation of saturated hydroxyl‐functional polyester polyols. Two‐pack coating systems were formulated using these resins as base component and melamine formaldehyde resins as hardener component. Cured films were tested for their mechanical and chemical performances. The glycolysis of PET using PEG and polyester polyol formation was characterized using Fourier transform infrared spectroscopy and the molecular weights were determined using gel permeation chromatography. Copyright © 2006 Society of Chemical Industry     

Utilization of some oligomers based on poly(ethylene terephthalate) wastes as modifiers for polyvinyl chloride

Two glycolyzed products, PET-TEG and PET-BD, were prepared by depolymerization of PET wastes using 30 wt % triethylene glycol (TEG) and 40 wt % 1,4-butanediol (BD). In this work we investigated how the mechanical and electrical properties of PVC and PVC/EPDM blend were affected by mixing them with different concentrations of the two obtained glycolyzed products. Dynamic mechanical, DSC, and dielectric behaviors of PVC containing various amounts of the two modifiers were studied. The present data confirm that the α-relaxation dynamic of PVC at constant frequency shifts to a lower temperature with increasing modifier content. PVC samples containing 5 phr of the two modifiers show the highest impact strength at −30°C. It was noted that addition of PET-TEG to PVC or PVC/EPDM blend led to end products with enhanced insulating properties, which makes them suitable for industrial applications. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2501–2509, 2002     

Chemical Recycling of PET by Glycolysis: Polymerization and Characterization of the Dimethacrylated Glycolysate

Summary: In the framework of chemical recycling of polymers, leading to the generation of secondary value‐added products, PET flakes taken from post‐consumer soft drink bottles, were glycolyzed with DEG. The oligomers obtained were analyzed for their molecular weight and characterized by FT‐IR and POM. Subsequently, dimethacrylated oligoesters of PET glycolysate (PET‐GLY‐DMA) were synthesized by methacrylation of the glycolyzed PET product. The resulted monomer PET‐GLY‐DMA was studied by FT‐IR, POM and DSC. Thermal polymerization of this monomer was carried out at 80 °C in the presence of benzoyl peroxide as initiator. A UV‐curable formulation was also prepared on the basis of neat PET‐GLY‐DMA, as well as by mixing PET‐GLY‐DMA with styrene, using DMPA as photoinitiator. Nanoparticles of SiO₂ were dispersed into PET‐GLY‐DMA/styrene copolymers as reinforcing agents and the mechanical properties of resins formed were studied.

Preparation of methacrylated PET glycolysate.