Comparative reactivity of glycols in PET glycolysis

The kinetics of poly(ethylene terephthalate) (PET) glycolysis by diethylene glycol (DEG), dipropylene glycol (DPG), glycerol (Gly) and mixtures of these glycols have been studied with two experimental procedures: uncatalysed at 220 °C and catalysed at 190 °C. An experimental device was set up allowing the isothermal kinetics to be monitored. A precise initial reaction time was obtained by separately warming the glycol and the polyester at the temperature of reaction before mixing them.The reactivity order of different glycols varies according to the conditions of temperature and catalysis. Schematically, the global reactivity does depend not only on the chemical reactivity of the glycol but also on its physico-chemical properties: ability to solvate the solid polyesters and polarity of the reaction mixture. Attempts to find synergic effects failed for almost all mixtures, except the mixture DPG + Gly in which the PET is digested more quickly than in pure DPG or Gly.     

Glass transition temperature of polyurethane foams derived from lignin by controlled reaction rate

Sodium ligninosulfonate (LS)-based polyurethane (PU) foams were prepared using three kinds of ethylene glycols, diethylene glycol, triethylene glycol or polyethylene glycol. Two kinds of industrial NaLS, acid-based and alkaline-based NaLS, were mixed with various ratios, and foaming reactions were controlled. Mixing, cream, and rise time were used as an index of foaming reaction. Mixing time was defined as the time interval from adding isocyanate to detection of evolved heat under stirring, cream time as the time interval from termination of stirring to starting of foaming, and rise time as the time interval from starting to completion of foaming. The above reaction time increased with increasing amount of acid base NaLS content in polyols. Apparent density, compression strength and compression modulus of PU foams linearly increased with reaction time. Thermal decomposition temperature was measured by thermogravimetry and glass transition temperature by differential scanning calorimetry. Glass transition temperature can be controlled in a temperature range from 310 to 390 K by changing the mixing rate of two kinds of LS and molecular mass of ethylene glycols. It was found that mechanical and thermal properties of PU foams are controllable through the foaming reaction rate using two kinds of industrial lignin.     

Complexes of Cu(II) with 2,2'-bipyridyl and maleic or phthalic acid

The stability constants of ternary copper(II) complexes with 2,2'-bipyridyl and a dicarboxylic acid (maleic and phthalic) have been determined by means of pH-titrations at 25 +/- 0.1 degrees and an ionic strength of 0.1M (Na,H)ClO(4). The stabilities of ternary complexes are compared with those of similar complexes and related to the size of the chelate rings and the nature of the dicarboxylic ligands.     

Synthesis and Properties of a New Polyesterimide from a Forest Product

Polyesterimide offers a class of resin which combines the advantage of high temperature stability with ease of process-ability. Gum rosin, the exudate of pine trees, has been developed as the raw material for preparation of polyesterimide. Abietic acid of rosin reacts readily with maleic anhydride to form the Diels-Alder adduct, which reacts with p-amino benzoic acid to produce a dicarboxylic acid containing an internal imide group. The dicarboxylic acid reacts with diethylene glycol under melt polycondensation at higher temperature (260–300°C)to produce polyesterimide. The polymer is found to be soluble in highly polar solvents. The polymer is amorphous and of low molecular weight. Thermal stability of the polymer has been characterized, and the polymer was found to be thermostable.     

Polyepichlorohydrin polyurethane/poly(methyl methacrylate) interpenetrating polymer networks

Polyurethane (PU) based on polyepichlorohydrin/poly(methyl methacrylate) (PECH/PMMA) interpenetrating polymer networks (IPNs) was synthesized by a simultaneous method. The effects of composition, hydroxyl group number of PECH, NCO/OH ratio and crosslinking agent content in IPNs were investigated in detail. Some other glycols, such as poly(ethylene glycol), poly(propylene glycol) and hydroxyl-terminated polybutadiene, were also used to obtain PU/PMMA IPNs. The interpenetrating and fracture behaviors of the IPNs are explained briefly.     

Syntheses and properties of halato-telechelic polyurethane-ureas from divalent metal salts of p-aminobenzoic acid,diamine, dialkylene glycols,and diisocyanate

Halato-telechelic polyurethane-ureas were synthesized from divalent metal salts of p-aminobenzoic acid, 4,4′-diaminodiphenylmethane (4,4′-methylenedianiline, MDA), dialkylene glycols, and 2,4-toluylene diisocyanate (TDI). As the divalent metal, Mg and Ca were used, and diethylene glycol and dipropylene glycol were the glycols used. The halatotelechelic polyurethane-ureas obtained showed better solubilities in dimethylformamide (DMF) and dimethylsulfoxide (DMSO) than previously reported halato-telechelic polyureas from the metal salts, MDA, and TDI. The reduced viscosities of the polyurethane-ureas in DMF and DMSO were very low at very low concentrations but increased as the concentration increased. The increase was higher in DMF having lower dielectric constant, due to lower depression of ionic association. Introducing the metal into the urethane-urea backbone resulted in a considerable decrease in decomposition temperature. In dynamic mechanical property measurements, they exhibited no sharp decrease in relative shear modulus and no peak of tan δ, probably due to aggregation of ionic groups in the polymer main chain.     

Interfacial syntheses of polyphosphonate and polyphosphate esters. I. Effects of alkaline medium

The effects on polymer yield and viscosity in the interfacial condensation of hydroquinone with phenylphosphonic dichloride as a function of the pH of the aqueous medium are reported. Reactions competing with polymer formation are discussed. The beneficial advantages in the use of soluble buffers or bases of limited water solubility to control pH are contrasted with results of conventionally used sodium hydroxide. The results of investigations of other comer pairs for which reaction conditions have not been optimized are also reported; desoxyribose and the diols: thymidine, resorcinol, 2,5-dichlorohydroquinone, 1,3-dihydroxyacetone, 1,4-butanediol, tartaric acid, ethylene glycol, and 2,2-dimethyl-1,3-propanediol are tabulated.     

Catalytic Oxidative Deformylation of Polyethylene Glycols with the Participation of Molecular Oxygen

The kinetics of oxidation of diethylene glycol, triethylene glycol, and polyethylene glycols (PEGs) with molecular weights ranging from 400 to 2000 in the presence of Cu(II) ions and bases was studied. It was found that ethylene glycols can be oxidized by molecular oxygen in anhydrous media in a temperature range of 30–60°C at anomalouosly high rates which are higher than the rates of chain-radical PEG autoxidation by several orders of magnitude. Only terminal hydroxyl groups were subjected to oxidation. The reaction occurs with the cleavage of a C–C bond and results in the formation of formic acid and a PEG with the number of –(CH₂CH₂O)– groups lower than that in the parent compound by unity. The rate and selectivity of PEG oxidation were found to strongly depend on the molecular weight of the polymer; from diethylene glycol to PEG 2000, the specific rate of oxidation increased by a factor of 60 in terms of terminal hydroxyl groups. An oxidation mechanism was suggested, which involves the formation of ternary complexes [Cu²⁺···A^–···O₂], which undergo further degradation by a many-electron concerted mechanism to form formic acid and, probably, an unstable hemiacetal {RO–CH₂OH}. The rapid oxidative degradation of the latter leads to the formation of PEG with a lower molecular weight.     

Microscopy and FTIR investigations of the thermal gelation of methylcellulose in glycols

Methylcellulose is a well-known polymer due to its reverse thermal gel formation property in aqueous solutions. Support materials play an important role in the additive manufacturing of three dimensional parts using processes that utilise inkjet technology. This paper presents novel compositions of methylcellulose (MC) in non-aqueous solvents and investigates the thermal gel formation of these compositions. Compositions containing MC in different glycols (ethylene, propylene and butylene glycol) were prepared. Suitability of these compositions as reusable support materials for jetting based three dimensional printing processes have been previously established. In this paper, the mechanism of gelation of MC in three different glycols is explained and compared using experimental techniques such as heating and cooling between 25–150°C, hot stage microscopy and Fourier Transform Infrared (FTIR) spectroscopy. Based on the results, a generalised gel formation diagram for MC in glycols is presented and compared with aqueous MC gel formation. The results showed that MC forms gels in glycols upon cooling and the temperatures of gel formation/melting are different for each glycol. Understanding of the gel formation of these compositions can help in fine tuning these compositions for their performance during three dimensional printing.     

Effect of glycols used as glycolysis agents on chemical structure and thermal stability of the produced glycolysates

In this study, the influence of glycols on chemical structure and thermal stability of glycolysates as polyurethane intermediates were investigated. The intermediates were obtained by the glycolysis process of waste polyurethane foams in the reaction with different glycols ranging from ethylene glycol to hexane-1,6-diol. The used glycols were not separated from the product after the glycolysis process has been terminated. The effects of different weight ratio of glycols to polyurethane (PU) foam on chemical structure and thermal stability were investigated by FTIR, GPC, and TG/DTG. FTIR analysis of the glycolysates revealed their similar chemical architecture as manifested by the similarity of absorption peaks within the entire wavenumber range of spectra. This may indicate that the glycol has no influence on the chemical composition of glycolysates. GPC analysis showed that the glycolysates were characterized by polydispersity smaller than 2 which is lower as compared to some commercial polyols used for PU synthesis. GPC chromatograms showed that the applied glycols and the conditions of PU glycolysis allowed recreation of the original polyol as documented on the chromatograms by a single, well-formed peak at the beginning of retention time. Based on TG thermograms, it was established that glycol used in transesterification of PUs affected the temperature at which the loss of glycolysate mass by 5 and 10?% occurs. It was also observed that glycol affected the temperature at which the decomposition rate of glycolysates was the highest.     

Lipase-catalyzed polycondensation of dicarboxylic acid–divinyl esters and glycols to aliphatic polyesters

Lipase-catalyzed polymerization of dicarboxylic acid–divinyl esters with glycols has been performed. The vinyl esters used were divinyl adipate and divinyl sebacate. Lipases derived from Candida antarctica, Mucor miehei, Pseudomonas cepacia, and P. fluorescens showed high catalytic activity toward the present polymerization. Effects of solvent, reaction temperature, and enzyme amount were systematically investigated. A combination of divinyl adipate, 1,4-butanediol, and P. cepacia lipase afforded the highest molecular weight (2.1 × 10⁴). The yield of the polymer from divinyl sebacate was higher than that from divinyl adipate, whereas the opposite tendency was observed in the polymer molecular weight. Methylene chain length of α,ω-alkylene glycol also affected the polymerization behavior. The enzymatic polymerization of divinyl sebacate with cis-2-butene-1,4-diol and 2-butyne-1,4-diol resulted in the polymer containing unsaturated group in the polymer backbone. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2737–2745, 1999     

Reactivity of polyesters in glycolysis reactions: Unexpected effect of the chemical structure of the polyester glycolic unit

Kinetic studies of PET glycolysis by diethylene glycol (DEG), dipropylene glycol (DPG), glycerol (Gly) and mixtures of these glycols have shown, in a previous study, that the order of reactivity of the glycols differs according to the conditions of temperature and catalysis. Indeed, their global reactivity depends both on their chemical reactivity and physico-chemical properties.Glycolysis of model polyesters which are liquid at the reaction temperature, which allows us to overcome the problem of the polyesters' solubility, were studied to compare the chemical reactivity of these glycols. Three oligoesters were synthesized from dimethyl terephthalate and three different glycols namely triethylene glycol, ethylene glycol and hexanediol to form, respectively, PE₃T, OET and PTHD.Results showed that the order of reactivity of the glycols is the same for PET, OET and PTHD but different for PE₃T. Indeed, DPG without catalyst has a particular and unexpected behaviour: its reactivity seems to be strongly influenced by the presence of oxygen atoms in the chain.     

The formation of polyethylene terephthalate in the presence of dicarboxylic acids

The process of polyethylene terephthalate (PET) formation in the presence of dicarboxylic acids has been studied. Certain amounts of terephthalic acid (TPA) have two- to threefold accelerating efficiency in the polycondensation process. To elucidate the causes of the acceleration the main reactions leading to PET formation in the presence of dicarboxylic acids have been investigated by the use of models. The evaluation of kinetic and equilibrium parameters obtained for model reactions made it possible to conclude that the influence of carboxyl-containing additives on the apparent rate of polycondensation manifests itself in accelerating direct reactions and facilitating the liberation of the eliminated by-product; that is, ethylene glycol (EG) from the polymer melt. Carboxylic acid acts as a catalyst on the ester interchange of 2-hydroxyethyl ester end groups and thus increases the rate of polymer formation in this reaction 10–40 times. The parallel interaction between the 2-hydroxyethyl ester end group and the carboxyl group of the added acid is also catalyzed by the acid and its rate constant is four times larger than that of the catalytic polycondensation of 2-hydroxyethyl ester end groups. Unlike EG, the reaction water formed in the process is more readily removed from the reaction system and thus promotes the intensification of the process. In addition, the carboxyl groups react with the eliminated EG to decrease its amount and shift the equilibrium toward polymer formation. The investigation of the consequent parallel reactions on models made it possible to draw a conclusion about the higher reactivity of 2-hydroxyethyl esters in the esterification processes. This fact has been explained by strengthening the nucleophilicity of the oxygen atom in the hydroxyl of a 2-hydroxyethyl ester group compared with that of EG; for example, by the formation of an intramolecular cycle involving a hydrogen bond. Simultaneously, it has been found that in the system simulating PET polycondensation in the presence of dicarboxylic acids the reaction mechanism involves the catalysis by a proton formed during the carboxyl group dissociation and accepted by the 2-hydroxyethyl ester group.     

Copolymerization of 2,2-diallyl-1,1,3,3-tetraethylguanidinium chloride and alkyl methacrylates

Radical copolymerization of 2,2-diallyl-1,1,3,3-tetraethylguanidinium chloride with methyl methacrylate and allyl methacrylate in the bulk and methanol solution in the presence of azobis-isobutyric acid dinitryle at 70–90°C has been studied. Copolymerization of 2,2-diallyl-1,1,3,3-tetraethylguanidinium chloride with methyl methacrylate or allyl methacrylate in the bulk proceeds with formation of random copolymers enriched in methacrylate units; in the copolymerization of 2,2-diallyl-1,1,3,3-tetraethylguanidiny chloride with methyl methacrylate in methanol, the copolymerization constants of the monomers become close. The kinetic parameters of the reaction have been studied, the relative activities of the monomers have been determined. It has been found that 2,2-diallyl-1,1,3,3-tetraethylguanidinium chloride is copolymerized with allyl methacrylate or methylmethacrylate to form pyrrolidinium structures in the cyclolinear polymer chain. At high degrees of conversion of the copolymerization of 2,2-diallyl-1,1,3,3-tetraethylguanidinium chloride with allyl methacrylate, the viscosity increases and the side polymer chains are crosslinked by “allyl bonds” to form insoluble copolymers, swelling in benzene and DMSO.     

Reaction of diisocyanates with alcohols. I. Uncatalyzed reactions

Because diisocyanates are widely used raw materials in the production of urethane elastomers and foams, it is of particular interest, to know the contribution of secondary reactions to the overall reaction between diisocyanates and polyether glycols, because of the well known influence of crosslinks on the physicochemical properties of polyurethanes. A mathematical method is suggested to calculate rate constants for the primary and secondary reactions, the hypothesis being that the allophanate group is the main secondary product. The method has been verified with experimental data obtained by reacting models. In addition, the influence of the [NCO]/[OH] ratio and of temperature on the formation of the allophanate group has been studied. The method has been applied to the reaction of 4,4′-diphenylmethane diisocyanate with poly(oxytetramethylene) glycol, a polyether glycol specifically designed for use in preparing polyurethanes. The results are in complete agreement with the experimental data.     

Thermophysical characterization of aqueous ternary system containing n-tris-[hydroxymethyl]methyl-3-amino propanesulfonic acid and glycol (PG or DPG or TPG)

In this present work, a thermophysical property characterization of aqueous ternary system containing n-tris-[hydroxymethyl]methyl-3-aminopropanesulfonic acid (TAPS) and glycol was done. Thermophysical properties, including refractive index, density, and electrolytic conductivity, measurements were considered. The glycols considered are propylene glycol (PG), dipropylene glycol (DPG), and tripropylene glycol (TPG). The measurements were done over a temperature range of 298.15 K to 343.15 K and at normal atmospheric pressure. Different concentrations (4% to 16% by weight TAPS or 56% to 44% water, in a fixed amount of glycol – 40%) were used. The effects of temperature and compositions on the measured properties were discussed and then correlated based on the equation proposed for aqueous salt–glycol systems. Calculation results show that the applied model was satisfactory in representing the measured properties in the aqueous ternary systems containing TAPS and considered glycols.     

对环芳烷二氯化产物组成的GC-MS表征

对环芳烷([2,2]Paracyclophane,简称PCP）是指苯环对位桥联的化合物,PCP及其氯代PCP的重要用途是通过升华、裂解、聚合等步骤沉积于物体表面形成聚合膜,该聚合膜具有透湿和透气小、抗化学腐蚀和抗辐射等优良性能[1,2].     

Novel approaches for the prediction of density of glycol solutions

Two new approaches for the accurate prediction of densities of the commonly used glycol solutions in the gasprocessing industry are presented in the article. The first approach is based on developing a simple-to-use polynomial correlation for an appropriate prediction of density of glycol solutions as a function of temperature and weight percent of glycols in water, where the obtained results show very good agreement with the reported experimental data. The second approach, however, is based on the artificial neural networks （ANN） methodology, wherein the results demonstrate the ability of the introduced method to predict reasonably accurate densities of glycols under operating conditions. Comparisons of the two novel approaches indicated that the simple-to-use correlation appears to be superior owing to its simplicity and clear numerical background, wherein the relevant coefficients can be retuned if new and more accurate data are available in the future. The average deviation of the new proposed polynomial correlation results from reported data is 0.64 kg/m^3 whereas the average deviation of artificial neural networks （ANN） methodology from reported data is 1.1 kg/m^3.     

Meso-substituted [34]octaphyrin(1.1.1.0.1.1.1.0) and corrole formation in reactions of a dipyrromethanedicarbinol with 2,2'-bipyrrole

The reaction of a dipyrromethanedicarbinol with 2,2'-bipyrrole leading to meso-substituted [34]octaphyrin(1.1.1.0.1.1.1.0) and/or corrole was investigated to determine the effect of key reaction parameters on the distribution of the two macrocycles. Solvent, acid catalyst, acid quantity, oxidant, oxidant quantity, and reaction time were surveyed for a model reaction affording 5,10,19,24,29,38-hexaphenyl[34]octaphyrin(1.1.1.0.1.1.1.0) (HPO) and/or meso-triphenylcorrole (TPC). HPO was found to be a fairly ubiquitous product, produced in yields as high as 23% (UV-vis), while TPC was observed infrequently, in yields up to 10% (UV-vis). A preparative-scale reaction provided HPO in an isolated yield of 25%. The methodology was extended to the synthesis of an octaphyrin bearing two different substituents in defined locations and to an octaphyrin possessing electron-withdrawing pentafluorophenyl substituents. Preferential formation of octaphyrin instead of corrole suggests that the anti conformation of 2,2'-bipyrrole is the relevant form under the reaction conditions surveyed. The spectral properties of the novel meso-substituted [34]octaphyrin(1.1.1.0.1.1.1.0) species are similar to those of the known beta-substituted analogue, including spectra consistent with the absence of macrocycle aromaticity despite a main conjugation path of 34 pi-electrons. Key to the overall study was the development of a refined synthesis of 2,2'-bipyrrole.     

Reactivation of CoMo/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> hydrotreating catalysts with chelating agents

Effect of various chelating components, multibasic carboxylic acids and glycols, used to prepare hydrotreating catalysts on the activity regeneration of calcined hydrotreating catalysts was studied. Reactivated catalyst samples were tested in a model reaction of hydrodesulfurization of dibenzothiophene. It was shown that the treatment of calcined catalysts with the chelating components leads to an increase in the catalytic activity. The best catalytic characteristics are observed for the catalyst reactivated with a solution containing citric acid and triethylene glycol.