Transesterification of dimethyl terephthalate with ethylene glycol

Conclusion For the first time, data are given on the quantitative composition of the transesterification products of dimethyl terephthalate with ethylene glycol at various molar ratios of the starting materials.During the transesterification process, oligomerization reactions take place rather intensively. Thereupon the linear oligomers are formed both in the transesterification process of carbomethoxy groups and also as a result of the interaction of carbohydroxyethoxy groups. The ethylene glycol formed in the latter case ensures further transesterification of the carbomethoxy groups.It is possible in principle to reduce the molar ratio of ethylene glycol to dimethyl terephthalate in the transesterification stage. Thereupon a polyethylene terephthalate can be obtained which has properties similar to the serially produced product.Translated from Khimicheskie Volokna, No. 5, pp. 18–20, September–October, 1983.     

Unsaturated polyesters based on bis(2-hydroxyethyl)terephthalate

A series of unsaturated polyesters based on bis(2-hydroxyethyl)terephthalate, ethylene glycol, propylene glycol, diethylene glycol, maleic anhydride and styrene were prepared. Properties of these castings were investigated and compared with those analogues based on dimethyl terephthalate or polyester oligomers formed by depolymerization of poly(ethylene terephthalate). It is found that properties of castings based on bis(2-hydroxyethyl)terephthalate are superior to those based on polyester oligomer. When compared with those based on dimethyl phthalate, the castings have higher hardness and heat distortion temperature, but lower tensile strength and elongation; other properties are very similar.     

The characterisation of dope dyed poly (ethylene terephthalate)

By analysing the polycondensation of ethylene glycol with dimethyl terephthalate, the influence of 1,4-aminoanthraquinone dyestuffs on the chemical and molecular properties of dope dyed poly(ethylene terephthalate) has been determined. The results show that dope dyed poly(ethylene terephthalate) differs from the uncoloured polymer by a possession of a higher amount of -COOH end groups and diethylene glycol units. The shape and the position of molecular weight distribution curves determined by gel permeation chromatography are also influenced by the soluble dyestuffs used.     

Effect of antimony trioxide on corrosivity of volatile polycondensation distillates in synthesis of polyethylene terephthalate

Conclusions The effect of Sb₂O₃ on the corrosivity of volatile polycondensation distillates has been studied. Inhibiting action of the antimony which separates on metallic constructional materials thereupon has been shown. It has been found that separation of antimony on apparatus walls takes place due to reduction of Sb₂O₃ by the metal of the contact surface.It has been established that the formation of noncontinuous coatings of antimony on the surface of carbon steel leads to an intensification of local corrosion. Recommendations have been given on the use of constructional materials of the system for trapping and collecting volatile distillates.Translated from Khimicheskie Volokna, No. 3, pp. 12–14, May–June, 1988.     

Infra-red and Raman spectra of poly(m-methylene terephthalate) polymers

A detailed comparison of the infra-red and Raman spectra of poly(trimethylene terephthalate) (3GT), poly(tetramethylene terephthalate) (4GT) and poly(ethylene terephthalate) (2GT) is reported. Particular attention has been given to the changes in the spectra which occur on crystallization. Additionally, the spectra of oriented 4GT samples have been examined under applied stress, because this produces a change in the structure of the crystalline regions. It is shown that the differences between the spectra of these polymers can be satisfacorily accounted for by changes in the conformation of the molecular chains involving both trans/gauche isomerism in the glycol sequence and the planarity of the terephthalate residue.     

Transesterification of dimethyl terephthalate with ethylene glycol. A kinetic model of the process

Conclusions The possibility of calculating and obtaining the values of the rate constants of reactions (4)–(6) in the process of transesterifying DMT with ethylene glycol over various catalytic systems at a 1.8 molar ratio of the starting components, EG:DMT, has been shown.The results presented permit one to solve the problem of optimizing the process of transesterifying DMT with ethylene glycol with the objective of reducing the molar ratio of the starting materials and cutting down energy outlays and starting material norms.Translated from Khimicheskie Volokna, No. 6, pp. 10–13, November–December, 1983.     

Synthesis of organic boron compounds and their use to stabilize polyethylene terephthalate

Conclusions The possibility of using aromatic esters of boric acid as thermostabilizers for polyethylene terephthalate has been investigated.It has been found that the use of borates containing a naphthyl or p-hydroxyphenyl group as thermostabilizers makes it possible to obtain a polyethylene terephthalate with improved mechanical properties and an increased thermal stability.Translated from Khimicheskie Volokna, No. 6, pp. 24–26, November–December, 1986.     

Structural and thermal properties of modified poly(ethylene terephthalate)

High-molecular-weight copolyesters based on ethylene glycol, tetraphthalic and 4,4′-biphenyl dicarboxylic acids containing up to 10.3 mole % of a second component were synthesized in the presence of homo- and heterogeneous catalysts. It was found that synthesis of these copolymers with a heterogeneous catalyst yields polymers with a higher molecular weight. The thermochemical properties of the copolyesters obtained were investigated. The thermostabilizing effect on addition of up to 10.3 mole % ethylene-4,4′-biphenyl dicarboxylic acid units to the PET polymer substrate was demonstrated. It was hypothesized that this modifier is a mesogen with respect to poly(ethylene terephthalate). Translated from Khimicheskie Volokna, No. 1, pp. 21-23, January-February, 2009.     

Adsorption of moisture from the air in polyethylene terephthalate dryers

Conclusions Results of a study of the operation of air drying adsorbers for polyethylene terephthalate dryers have been given.It has been shown that overloading the adsorbers with air to be dried which has a reduced moisture content as a result of mixing fresh air and circulating air adversely affects the adsorbent activity.It has been proposed to replace the existing scheme of connecting up adsorbers with two seasonal variants which eliminate drying of the circulating air.Translated from Khimicheskie Volokna, No. 5, pp. 43–45, September–October, 1985.     

Synthesis of Urethane Oil Varnishes from Waste Poly(ethylene terephthalate)

Waste poly(ethylene terephthalate) was depolymerized by glycolysis to obtain hydroxyl‐terminated oligomers. The effect of depolymerization temperature, the type of glycol and the amount of catalyst on the yield and the composition of the products were studied. The hydroxyl‐terminated oligomers obtained from the glycolysis of poly(ethylene terephthalate) were used in the synthesis of urethane oils. The physical properties of urethane oils were compared with a commercial product.     

Effect of alkali on filaments of poly(ethylene terephthalate) and its copolyesters. II. Presence of quaternary ammonium salt in the alkali-bath

Influence of alkyl (C₁₂–C₁₄)-dimethyl-benzyl ammonium chloride in the solution of sodium hydroxide on the hydrolysis of poly(ethylene terephthalate) (PET), anionically modified poly(ethylene terephthalate) copolyster (CDP), and block polymer of poly(ethylene terephthalate)-poly(ethylene glycol) (EDP), has been studied under a variety of proportions, concentrations, time and temperature of reaction, M : L ratio, etc. Mechanical properties of treated polymeric materials are evaluated. Hydrolysis of two polymers in the same bath is compared with that in separate baths.     

PET缩聚催化剂乙二醇盐的合成与应用技术进展

介绍了聚对苯二甲酸乙二醇酯(PET)缩聚反应用催化剂乙二醇盐的合成与应用进展;详述了乙二醇锑、乙二醇钛、乙二醇铝催化剂的合成和应用,以及应用各种催化剂的优缺点;指出乙二醇锑催化剂活性高,但污染严重,乙二醇铝催化剂毒性低,催化活性也低。综合考虑,绿色环保的乙二醇钛及其复合催化剂将是聚酯的良好催化剂,将替代现有锑系催化剂,前景看好。     

A study of molecular orientation in one-way drawn poly(ethylene terephthalate) films by means of polarized infra-red spectroscopy and birefringence measurements

Summary Polarized infrared spectroscopy and birefringence measurements have been used to study the changes in molecular orientation which occur on homogeneous hot (T=80°C) and cold (T=20°C) drawing of poly(ethylene terephthalate) (PET) sheets. Excellent agreement was obtained between the infrared orientation functions for absorption bands associated with 1507 cm^–1, 1580 cm^–1 and 1615 cm^–1, C-C stretching mode of the benzene ring, and average orientation functions obtained from optical birefringence. It was confirmed that the Gauche conformer of the ethylene glycol residue in the amorphous phase could be oriented perpendicularly to the draw direction (_p<4). The development of molecular orientation along the specimen axis in the necked sample confirms the entangled nature of the polymer chains in which the natural draw-ratio corresponds to the response of a network stretched up to its maximum of extensibility.     

Activation of catalysts for the transesterification of dimethylterephthalate with ethylene glycol

Conclusions A possibility has been demonstrated of shortening the duration of the transesterification reaction between dimethyl terephthalate and ethylene glycol by preliminary treatment of the catalysts or by introducing investigated lower alcohols or acetone into the reaction mixture.Translated from Khimicheskie Volokna, No. 3, pp. 49–50, May–June, 1990.     

Kinetics of glycolysis of poly(ethylene terephthalate) melts

The reaction of poly(ethylene terephthalate) (PET) melts with ethylene glycol was examined in a pressure reactor at temperatures above 245°C. The reaction rate was found to depend on temperature and on the concentrations of liquid ethylene glycol and of ethylene diester groups in the polymer. A kinetic model proposed for the initial period of the reaction was found to be consistent with experimental data. It was found that internal catalysis by ethylene glycol does not play an important role in the glycolytic depolymerization of PET. The rate constants for glycolysis were calculated for three different temperatures, yielding an activation energy of 92 kJ/mol. Zinc salts, which have a catalytic effect on glycolysis of PET below 245°C, do not appear to influence glycolysis rates above that temperature. © 1994 John Wiley & Sons, Inc.     

An adaptive system of automatic control of the quality indices in the process of polyethylene terephthalate

Conclusions -- Principles for constructing an adaptive control system for qualitative indices of the polyethylene terephthalate synthesis process have been examined.-- A mathematical assurance of a control system for the basic technological stages has been developed.-- A control algorithm has been realized in the esterification stage of the synthesis process of an industrial unit, which ensures a degree of completion of the process within assigned limits.Translated from Khimicheskie Volokna, No. 5, pp. 48–49, September–October, 1990.     

Effects of pH and Neutral Salts on the Adsorption of the Poly(ethylene glycol terephthalate) Condensates Toward Poly(ethylene terephthalate) Fiber

This study deals with the effects of pH and neutral salts on the adsorption of PET fiber with four kinds of poly(ethylene glycol terephthalate) condensated from dimethyl terephthalate (DMT) and poly(ethylene glycol) (PEG). The surface properties of the aqueous solution, the contact angle of polyol‐treated PET fabrics, and its parameters were also discussed. The pH of the solution or the adding of neutral salt in the polyol solution largely affected the contact angle of polyol‐treated PET fabrics as well as the surface tension of the solution. A lower pH of the polyol solution or adding neutral salts in the solution showed a lower surface tension and a lower contact angle that resulted in a better adsorption between polyol and poly(ethylene terephthalate) fibers. The lower pH of the solutions and a higher valence of the added neutral salt in the solution showed a largely positive effect on the adsorption parameters, and the order of effectiveness is Al₂(SO₄)₃ > MgSO₄ > Na₂SO₄.     

Light-stability of Lavsan dyes in bulk with aroylene-benzimidazole derivatives

Conclusions Naphthoylenebenzimidazole derivatives have been found which are able to dye polyethylene terephthalate fibres in bulk.It has been shown that the dyes reduce the thermal degradation which takes place in melt-spinning polyethylene terephthalate fibres.The sorption properties of the fibres obtained have been evaluated.Translated from Khimicheskie Volokna, No. 3, pp. 38–39, May–June, 1988.     

Effect of alkali on filaments of poly(ethylene terephthalate) and its copolyesters

The alkali hydrolysis of poly(ethylene terephthalate), anionic copolymer of poly(ethylene terephthalate), and block copolymer of poly(ethylene terephthalate)–poly(ethylene glycol) is investigated under a variety of conditions of alkali concentration in aqueous bath, additives, time, and temperature. Measurements of loss in weight, linear density, breaking load, tenacity, elongation to break apart from intrinsic viscosity, fiber density, COOH-end group content, diameter of filaments, and scanning electron micrographs have been analyzed to identify the differences in the action of alkali on these polymer materials.     

Modelling of reversible poly(ethylene terephthalate) reactors

The second stage of batch poly(ethylene terephthalate) (PET) reactor with bis(2-hydroxyethyl) terephthalate (BHET) as the feed has been simulated. In this stage, the overall polymerization is not diffusion limited and is known to be a complex reaction. In this work it has been assumed to consist of polycondensation, reaction with monofunctional compounds (cetyl alcohol), redistribution, and cyclization reactions. The forward and reverse steps of each of these have been modelled in terms of the rate constants involving functional groups and the reacted bonds. The equations for the calculation of the molecular weight distribution (MWD) in batch reactors have been written and solved numerically. The MWD reported in this work is assumed to include the monofunctional products only, and, for the case where ethylene glycol is not removed from the reaction mass, it was found to be unaffected by the choice of the redistribution rate constant (k_r). Since the removal of ethylene glycol is not mass transfer controlled, its concentration in the reaction mass is assumed be given by the vapor–liquid equilibrium existing at the pressure applied on the reactor. In this work, the level of ethylene glycol concentration, y_g (?[G]/[P₁]₀), has been taken as a parameter, and, on application of vacuum, the MWD results were found to vary with k_r with the sensitivity increasing with y_g. It was then shown that the importance of the redistribution reaction is enhanced when the cyclization reaction also occurs. The effect of vacuum on the performance of the reactor has been studied by varying y_g. For y_g less than 0.01, the change in the MWD of the polymer becomes very small. The effects of polymerization temperature and initial concentration of monofunctional compounds on MWD were found to be small.