Methanolysis of Poly（ethylene terephthalate）in Supercritical Phase

1 INTRODUCTIONPoly(ethylene terephthalate), commonly known as PET polyester, is extensively used for making synthetic fibers and package containers. The volume of PET consumed is rising by year, and thus the chemical recycling and reuse of waste PET are drawing much attention for the preservation of resources and the protection of environment. Through chemical recycling, waste PET is depolymerized into its valuable monomers such as dimethyl terephthalate (DMT), bis (hydroxyethyl) ter…     

Unsaturated Polyester Resins Obtained from Glycolysis Products of Waste PET

Abstract

Waste polyethylene terephthalate (PET) flakes were depolymerized by using ethylene glycol (EG), propylene glycol (PG), diethylene glycol (DEG), and triethylene glycol (TEG) in the presence of zinc acetate as catalyst. All glycolysis products were reacted with maleic anhydride and mixed with styrene monomer to get unsaturated polyester (UP) resins. Molecular weights of all synthesized UP resins were determined by end-group analysis. The curing characteristics such as gel time and maximum curing temperatures, and mechanical properties such as hardness, tensile strength, and elastic module of these resins were investigated. The waste PET resins were compared with the reference resins prepared with the same glycols and the properties of the resins were found to be compatible with the properties of the reference resins.     

聚酯废丝的化学回收研究

使用乙二醇(EG)对有色聚酯(PET)废料解聚,经分离提纯,得到对苯二甲酸二乙二醇酯(BHET)。研究了物料比、反应温度、反应时间、催化剂对醇解率的影响。结果表明,在m(乙二醇)∶m(PET)=2∶1,反应温度196℃,反应时间3 h,催化剂用量为PET质量的0.5%条件下,聚酯解聚很彻底,产物羟值可达434 mg/g以上,主要成分是BHET单体及其低聚物。并通过IR,DSC,HPLC验证了产物的组成,BHET单体纯度可达96.457%。     

Correlation of acidity of metal ion with catalytic activity for the formation of poly(ethylene terephthalate)

For the transesterification of DMT (dimethyl lerephthalate) and polycondensation of BHET [bis(2-hydroxyethyl) terephthalate)], catalytic activity of various metal complex can be correlated with acidity of metal ion, which is expressed as modified electronegativily. Based on correlations mode of catalysis for the formation of PET [poly(ethylene terephthalate] was suggested.     

第三单体SIPM对改性PET的热性能及染色性的影响

以间苯二甲酸二甲酯－５－磺酸盐（ＳＩＰＭ）为第三单体，合成了可染母粒（ＰＥＩ）。将ＰＥＩ和ＰＥＴ在真空中熔融共混，用ＤＳＣ和ＴＧＡ测定改性ＰＥＴ的热性能，并熔融纺丝测定它的染色饱和值。与无规共聚改性ＰＥＴ相比，共混改性ＰＥＴ的熔点高，热稳定性好，染色饱和值优良。     

涤棉织物化学回收工艺研究

以废旧涤棉织物为原料,乙二醇(EG)为醇解剂,通过改变醇解时间、醇解温度、EG/废旧涤棉织物中聚对苯二甲酸乙二醇酯(PET)质量比(mEG/mPET)、催化剂种类及用量等研究了蓬松态下废旧涤棉织物的醇解工艺,以及醇解过程对涤棉织物中棉纤维性能的影响。结果表明:随着醇解时间、醇解温度的提高,mEG/mPET的增大,涤棉织物的醇解程度增大,各参数达到一定程度后醇解程度基本不变;最佳醇解工艺为涤棉织物中mEG/mPET为2/1,催化剂用量为涤棉织物中PET质量的0.30%,醇解温度196℃,醇解时间1 h;在乙酸锌、碳酸钠、乙酸钾、氯化镁4种催化剂中,碳酸钠综合催化效果最佳;经醇解过程后涤棉织物中棉纤维表面变得粗糙,力学性能有较大下降。     

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.     

Solubility determination and thermodynamic modeling of bis-2-hydroxyethyl terephthalate (BHET) in different solvents

Studies on the degradation process of waste polyethylene terephthalate (PET) have become increasingly mature, but there are relatively few studies on the separation of degradation products. The products contain many components and the separation of which is difficult. Therefore, the study on phase equilibrium thermodynamics of bis-2-hydroxyethyl terephthalate (BHET) is of great theoretical significance and practical value to provide basic data for the BHET crystallization separation. In this work, the degraded products were purified and characterized. The solubility of BHET in methanol, ethanol, ethylene glycol, water and the mixture of ethylene glycol + water were determined by static method. The experimental results were correlated with different models, such as ideal solution (IS) model, λh equation, Apelblat equation and NRTL model. Based on the van't Hoff equation, the mixing Gibbs energy, enthalpy and entropy were calculated. From this work, the basic data which can be used to guide the crystallization process of BHET were obtained, including solubility data, correlation model and thermodynamic properties.     

Unsaturated polyester based on poly(ethylene glycol)

Unsaturated polyesters were prepared by one-stage melt condensation of maleic anhydride, phthalic anhydride, propylene glycol, and poly(ethylene glycol)s with different molecular weight, and the properties of their castings from styrenated resins were investigated. Tensile and flexural properties decrease with the increase of molecular weight of poly(ethylene glycol), but impact strength, elongation, and water absorption have an inverse effect. This study improves the understanding of the effect of chain length of poly(ethylene glycol) in unsaturated polyester on the properties of its castings.     

Glycolysis of polyethylene terephthalate waste fibers

Glycolysis of polyethylene terephthalate waste fibers was carried out using excess ethylene glycol in the presence of different simple chemicals, namely, glacial acetic acid, lithium hydroxide, sodium sulfate, and potassium sulfate. Good yields (> 60%) of the monomer bis(2‐hydroxyethylene terephthalate) were obtained using these chemicals as depolymerization catalysts. The purified monomer was characterized by elemental analysis, melting point, IR spectroscopy, and nuclear magnetic resonance. The qualitative and quantitative yields of the monomer obtained using these catalysts are most comparable with the conventionally used heavy metal catalysts such as zinc acetate and lead acetate. The chemicals used, being cheap and comparatively less harmful to the environment, offer further advantages in chemical recycling of polyester waste fibers. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 513–517, 2005     

Preparation and hydrolytic degradation of sulfonated poly(ethylene terephthalate) copolymers

A series of poly(ethylene terephthalate-co-ethylene 5-sodiosulfoisophthalate) copolyesters containing from 1 up to 50 mol% of sulfonated units was prepared by melt polycondensation from ethylene glycol and mixtures of dimethyl terephthalate and dimethyl 5-sodiosulfoisophthalate. The resulting copolymers had a random microstructure and contained oligo(ethylene glycol) units in amounts increasing with the content in sulfonated isophthalate units. Copolyesters with more than 20 mol% of 5-sodiosulfoisophthalic units were amorphous and easily soluble in water. The hydrodegradability of the copolyesters was very high as compared to poly(ethylene terephthalate), and increased with the content in sulfonated units. It was demonstrated that the susceptibility to acidic hydrolysis of these copolymers is mainly due to the presence of the sodium sulfonate groups, the influence of the oligo(ethylene glycol) units in this regard being noticeable but limited.     

聚酯及共聚酯化学组成分析

介绍用甲醇醇解法把聚酯或共聚酯解聚成二元酸二甲酯和二元醇。用差示扫描量热 (DSC)、气相色谱及气相色谱 质谱联用仪对醇解液进行检测分析 ,得到聚酯的化学组成。     

新型共聚酯-PETG

PETG(聚对苯二甲酸乙二醇酯-1,4-环己二甲醇酯)是一种结晶度很低甚至是完全不结晶的共聚酯,具有优异的韧性、透明度、易加工和耐化学性能。它是由DMT(对苯二甲酸二甲酯)、EG(乙二醇)、CHDM(1,4-环己二甲醇)在通N2条件下发生酯交换反应,然后在高真空度下发生缩聚反应而制得。本文就PETG的制备、性能和应用等方面作一论述。     

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     

Crystallization behavior and crystal structure of poly(ethylene‐co‐trimethylene terephthalate)s

A series of random copolymers were synthesized by the bulk polycondensation of dimethyl terephthalate with ethylene glycol (EG) and propane‐1,3‐diol (PDO) in various compositions. Their composition and thermal properties were investigated. The copolymers with 57.7 mol % or more PDO or 14.4 mol % or less PDO were crystallizable, but those with 36–46.2 mol % PDO were amorphous. The nonisothermal crystallization behavior was investigated with varying cooling rates by DSC. Poly(ethylene terephthalate) (PET) and poly(trimethylene terephthalate) (PTT) homopolymers have relatively lower activation energy than their copolymers. PET‐rich copolymers (EG > 85.9%) exhibited PET crystal structure, and exhibited no PTT crystal structure; and PTT‐rich copolymers (PDO > 41.7%) exhibited PTT crystal structure, and exhibited no PET crystal structure. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

A hot melt adhesive from polyester waste

Hot melt adhesives were prepared from polyester waste in three steps: Step I: Polyester waste was degraded to a monomer stage, i.e. bis-(2-hydroxyethyl)terephthalate (BHET) (1) by means of different metal acetates in the presence of ethylene glycol. The reaction in the presence of zinc acetate gave the highest yield of BHET (95%). Step II: Esterification of (I) with isophthalic acid in situ led to the formation of an esterified product (II). Step III: Further esterification of (II) with sebacic acid in situ, followed by polycondensation in the presence of antimony oxide and triphenylphosphate, led to the formation of the hot melt adhesive (III) based on BHET via the intermediate esterified product (IV). The hot melt adhesive, possessing a highest adhesive strength of 620 (psi) was obtained in a total reaction period of five hours. The present paper also details the effect of isophthalic acid and sebacic acid on the adhesive strength of (III).     

水溶性聚酯的溶解性能

研究了由对苯二甲酸二甲酯 (DMT)、间苯二甲酸 (IPA)和间苯二甲酸二甲酯 5 -磺酸钠 (SIPM)与乙二醇 (EG)和聚乙二醇 (PEG)等共缩聚合成的水溶性聚酯的溶解性能。研究结果表明 ,随分子链中间苯二甲酸乙二醇酯 5 -磺酸钠 (SIPE)链节含量的增加 ,聚合物的水溶性增强 ,对外加盐的容忍度提高 ;水溶性聚酯能溶于某些有机溶剂 ,但有时在同一溶剂中不同样品的溶解性表现出明显差异。     

用废PET醇解制墨粉树脂的研究

本实验主要研究了回收PET瓶片在催化剂和二元醇存在下,进行醇解和酯交换转化为各种不同组成具有端羟基低分子链段和二醇,进而醇解产物与反丁烯二酸酯化缩聚为用于墨粉树脂的聚酯。探索了从原料配比到反应工艺条件等多方面因素合成聚酯树脂的条件。利用聚酯回收料为原料醇解后直接合成墨粉用聚酯树脂的工艺简单、产品质量稳定、具有良好的经济效益和环保效应。     

Kinetics of glycolysis of poly(ethylene terephthalate) waste powder at moderate pressure and temperature

The reaction of poly(ethylene terephthalate) waste (PETW) powder with ethylene glycol (EG) was carried out in a batch reactor at 2 atm of pressure and a 220°C temperature. The particle size range of 50–512.5 μm and the reaction time of 40–180 min that are required for glycolysis of PETW were optimized. To avoid the carbonization and oxidation of reactants and reaction products and to reduce corrosion, the reaction was undertaken below 250°C using a lower reaction time. To increase the yield of dimethyl terephthalate and EG, an external catalyst was introduced during the reaction. The degree of depolymerization of PETW was proportional to the reaction time. The reaction rate was found to depend on the concentrations of liquid EG and of ethylene diester groups in the polyester. A kinetic model was used for the reaction was found to be consistent with experimental data. The rate constant was inversely proportional to the reaction time, as well as the particle size, of PETW. The degree of depolymerization of PETW was inversely proportional to the particle size of PETW. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1569–1573, 2003     

Nucleation of crystallization of polyester by catalyst remnants—a review

The antimony catalyst content of poly(ethylene terephthalate) has an appreciable effect on the tendency of the polymer to crystallize upon cooling from the melt. Nucleation density increases significantly as antimony catalyst concentration increases. The crystallization tendency of the polymer at a given molecular weight correlates strongly with both the antimony content and the diethylene glycol comonomer content. The behavioral patterns of nucleation by catalyst remnants are similar in polyester prepared from terephthalic acid or dimethyl terephthalate. The antimony catalyst is deposited in the polyester matrix in a form suitable to nucleate quiescent crystallization. The differences in tendency to crystallize that correlate with catalyst and diethylene glycol comonomer content are reflected in the crystallinity of injection molded samples.