聚对苯二甲酸丁二醇酯在超临界甲醇中降解机理的研究

在高压间歇无搅拌反应器中研究了聚对苯二甲酸丁二醇酯(PBT)在高温甲醇溶液中的降解行为,通过对降解产物的各种定性和定量的分析,提出了超临界甲醇降解PBT的机理为在甲醇的作用下聚合物分子链的随机断裂和酯交换反应双重作用下发生的降解反应,建立了降解-反应模型.PBT在甲醇溶液中的降解可分为超临界区、非超临界区和中间过渡区三个区域.通过分子量测定考察了PBT在不同的区域中降解规律.在非临界区PBT在溶剂中处于溶胀状态,其数均分子量Mn下降缓慢,解聚程度低;在过渡区PBT的溶解性能提高,聚合物大分子发生断裂,降解速率加快;在超临界区,Mn随反应的进行而迅速下降,聚合物很快完全降解.在超临界区中PBT可实现完全降解,其主要产物为单体对苯二甲酸二甲酯(DMT)和丁二醇(BG),它们的收率可分别可达98.1%和72.3%.     

有色废弃PET材料化学回收新工艺

为了解决有色废弃PET材料回收难的问题,促进资源循环利用,研究了有色PET以超临界甲醇技术进行解聚,并脱色提纯得到对苯二甲酸二甲酯的工艺流程。探讨了有色PET在超临界甲醇中的降解规律,并对脱色方案进行了筛选。探索了不同级别的PET材料解聚条件的差异。结果表明：纤维级材料在265 ℃,11 MPa下,超临界甲醇解聚30 min后,用溶解-热过滤-沉析的方法脱色提纯,对苯二甲酸二甲酯的产率可达到85%,纯度达到99.9%以上,白度达到87.5%;瓶片级材料呈现的解聚规律与纤维级变化趋势相同,但达到相同的解聚率,明显需要更长的反应时间。     

Depolymerization of poly(ethylene terephthalate) wastes using ethanol and ethanol/water in supercritical conditions

Chemical recycling of poly(ethylene terephthalate) (PET) in supercritical ethanol has been investigated. In the presence of water, under supercritical conditions (temperature and pressure above 516 K and 6,384 kPa, respectively) excess ethanol reacts with PET to form diethyl terephthalate (DET) as the main product. A laboratory‐made 0.1 L ‐batch reactor was used at 528 K under pressures from 7,600 and 11,600 kPa. After the required reaction times, the reaction products were analyzed by reverse phase high pressure liquid chromatography and nuclear magnetic resonance. It was found that PET is completely depolymerized into monomers in about 5 h. The influences of water, pressure, ethanol/PET weight ratio, PET sources, as well as depolymerization time were investigated. Maximum DET recovery yield was 98.5%. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2009–2016, 2006     

Depolymerization of poly(butylene terephthalate) using high‐temperature and high‐pressure methanol

Poly(butylene terephthalate) (PBT) was depolymerized in excess methanol at high‐temperature (473–523 K) and high‐pressure (4–14 MPa) conditions. Considering the critical point of methanol (512.6 K, 8.09 MPa), the reaction pressure was varied over the range of 6–14 MPa at the reaction temperature of 513 K. As a result, ca. 20 min was required to recover dimethyl terephthalate and 1,4‐butanediol, quantitatively, at any pressure, indicating that the supercritical state of methanol is not a key factor of degradation of PBT and that the effect of pressure is little. On the contrary, when the reaction temperature was varied over the range of 473–523 K at the pressure 12 MPa, the decomposition rate constant of PBT at the reaction temperatures (503–523 K) higher than the melting temperature of PBT (500 K) was much higher than that at 473–483 K. This result indicates that melting of PBT is an important factor for the short‐time depolymerization of PBT. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 3228–3233, 2000     

Depolymerization of poly(trimethylene terephthalate) in supercritical methanol

The depolymerization of poly(trimethylene terephthalate) (PTT) in supercritical methanol was carried out with a batch‐type autoclave reactor at temperatures ranging from 280 to 340°C, at pressures ranging from 2.0 to 14.0 MPa, and for reaction time of up to 60 min. PTT quantitatively decomposed into dimethyl terephthalate (DMT) and 1,3‐propaniol (PDO) under the designed conditions. The yields of DMT and PDO greatly increased as the temperature rose. The yields of the monomers markedly increased as the pressure increased to 10.0 MPa, and they leveled off at higher pressures. The final yield of DMT at 320°C and 10.0 MPa reached 98.2%, which was much closer to the extent of the complete reaction. A kinetic model was used to describe the depolymerization reaction, and it fit the experimental data well. The dependence of the forward rate constant on the reaction temperature was correlated with an Arrhenius plot, which gave an activation energy of 56.8 kJ/mol. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2363–2368, 2004     

The synthesis of poly(butylene terephthalate) from terephthalic acid,part II: Assessment of the first stage of the polymerization process

The production of poly(butylene terephthalate) (PBT) struggles with the formation of substantial amounts of tetrahydrofuran (THF). When PBT is synthesized from terephthalic acid (TPA) instead of dimethyl terephthalate (DMT), even more THF is formed, mainly during the first stage of the melt polymerization process. Although a lot of literature reports on the existence of this side reaction in both processes, to the best of our knowledge, a comparison, which reveals the importance of the acidity and insolubility of TPA on the THF formation, was never described. Finally, an interesting study was performed on the THF formation during the synthesis of PBT from mixtures of DMT and TPA as well as from the completely soluble monomethyl terephthalate (MMT). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Depolymerization of polyethyleneterephthalate in supercritical methanol

The depolymerization of polyethyleneterephthalate (PET) in supercritical methanol was carried out using a batch-type autoclave reactor. The total conversion and the yield of dimethylterephthalate (DMT) increased with rising temperature. The final yield of DMT at 300°C and 310°C reached 97.0% and 97.7%, respectively. The yield of DMT was markedly increased when the methanol density was 0.08 g/cm³, and leveled off at higher densities. A kinetic model to describe the depolymerization of PET in supercritical methanol was proposed, where the scission of one ester linkage in PET by a methanol molecule produces one carboxymethyl group and one hydroxyl group. The values of the forward reaction rate constant at different temperatures were determined by comparing the observed time dependence of carboxymethyl group concentration with that calculated by the proposed model. The activation energy was evaluated to be 49.9 kJ/mol, a value close to a literature value (55.7 kJ/mol). © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2102–2108, 2001     

PET and aluminum recycling from multilayer food packaging using supercritical ethanol

Different properties, such as barriers to gas, light, flavor and water vapor, as well as flexibility, are necessary for the production of food packages. These properties may be obtained by combining different polymers. In spite of the advantages achieved with the use of multilayer films, the recycling process of such material is a challenging task. This study presents an alternative for recycling of a quite common food packaging kind, which contains polyethylene (PE), aluminum and poly(ethylene terephthalate) (PET) as a multilayer film. The multilayer packages were delaminated with acetone. PET was depolymerized by ethanol in supercritical conditions. The diethyl terephthalate (DET) was obtained as the main product, presenting high purity and yield of 80%. Also, metallic aluminum was obtained by the PET-depolymerizing process. The optimal reaction time was 120 min. The products were characterized by FTIR, ¹H NMR and ¹³C NMR spectroscopies, DSC and TGA.     

PBT/PEG/LA可降解聚醚酯的合成及纺丝研究

采用对苯二甲酸二甲酯(DNT)、1,4-丁二醇(BDO)、聚乙二醇(PEG)和乳酸(LA)合成了聚对苯二甲酸丁二醇酯(PBT)/PEG/LA可降解聚醚酯,通过纺丝制备了PBT/PEG/LA共聚物纤维。结果表明:红外光谱和核磁共振分析所得聚合物为PBT/PEG/LA。PBT/PEG/LA共聚物在50℃真空预干燥5 h,80℃干燥5 h,控制纺丝温度高于聚醚酯熔点15～30℃可顺利纺丝,纤维质量良好。随着拉伸倍数、热定型温度或时间的增加,纤维的断裂强度提高.断裂伸长率下降。LA摩尔分数高,有利于纤维降解,但纤维熔点和断裂强度相应下降。     

Synthesis and characterization of copolymers based on poly(butylene terephthalate) and ethylene oxide‐poly(dimethylsiloxane)‐ethylene oxide

A series of thermoplastic elastomers based on ethylene oxide‐poly(dimethylsiloxane)‐ethylene oxide (EO‐PDMS‐EO), as the soft segment, and poly(butylene terephthalate) (PBT), as the hard segment, were synthesized by catalyzed two‐step, melt transesterification reaction of dimethyl terephthalate (DMT) with 1,4‐butanediol (BD) and α,ω‐dihydroxy‐(EO‐PDMS‐EO). Copolymers with a content of hard PBT segments between 40 and 90 mass % and a constant length of the soft EO‐PDMS‐EO segments were prepared. The siloxane prepolymer with hydrophilic terminal EO units was used to improve the miscibility between the polar comonomers, DMT and BD, and the nonpolar PDMS. The molecular structure and composition of the copolymers were determined by ¹H‐NMR spectroscopy, whereas the effectiveness of the incorporation of α,ω‐dihydroxy‐(EO‐PDMS‐EO) into the copolymer chains was verified by chloroform extraction. The effects of the structure and composition of the copolymers on the melting temperatures and the degree of crystallinity, as well as on the thermal degradation stability and some rheological properties, were studied. It was demonstrated that the degree of crystallinity, the melting and crystallization temperatures of the copolymers increased with increasing mass fraction of the PBT segments. The thermal stability of the copolymers was lower than that of PBT homopolymer, because of the presence of thermoliable ether bonds in the soft segments. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis of Poly(butylene terephthalate) Nanocomposite by <Emphasis Type="Italic">In-situ</Emphasis> Interlayer Polymerization and Characterization of Its Fiber (I)

Summary The nanocomposites with poly(butylene terephthalate)(PBT) incorporated between the montmorillonite (MMT) layers were synthesized from dimethyl terephthalate (DMT) and butane diol (BD) by using an in-situ interlayer polymerization approach. The PBT nanocomposites were melt spun at different organoclay contents to produce monofilaments. The existence of clay layers in the PBT was confirmed by using X-ray diffraction and transmission electron microscopy, and those layers were found to be disperse on a nanometer scale. The thermal properties of the layered structures of the hybrids were found to be more stable than those of pure PBT. These improved thermal properties of the nanocomposites might arise from an extensive and strongly bonded interface between the organic and the inorganic components. Moreover, the addition of only a small amount of organoclay was enough to improve the mechanical properties of the PBT hybrid fibers.     

DMT甲醇溶液结晶介稳区性质的研究

研究了对苯二甲酸二甲酯（ＤＭＴ）甲醇溶液的结晶特性。测定了ＤＭＴ在甲醇中的溶解度、ＤＭＴ甲醇溶液于不同降温速率、搅拌转速下的结晶介稳区宽度以及不同过饱和度下的结晶成核诱导期。结果表明：ＤＭＴ在甲醇溶液中的溶解度随温度升高而增加;溶液的结晶介稳区随降温速率的增加变宽,随搅拌转速的增加而变窄,且ＤＭＴ甲醇溶液的结晶诱导期随相对过饱和度的增加而缩短。     

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…     

木质素在超临界甲醇和乙醇溶剂中液化过程分析

通过研究木质素分别在超临界甲醇和乙醇溶剂中的液化过程，分析反应温度（260～340℃）及反应时间（0～120min）对木质素在两种溶剂中的转化率、生物油收率及其组分差异的影响。实验表明，木质素在超临界乙醇中的转化率及产物收率均高于甲醇。当反应温度340℃，反应时间60min，木质素在超临界乙醇中的转化率和生物油收率比在甲醇中分别提高了16.23%和11.54%，残渣收率降低了16.23%。通过GC-MS和FTIR对生物油和残渣分析，发现生物油组分中芳香族化合物相对含量较高，在甲醇和乙醇溶剂中分别达到66.13%和58.84%；随着反应时间的延长，甲醇溶剂中残渣的醚键官能团逐渐增强，而在乙醇溶剂中则先增强后减弱。分析认为在木质素降解过程中，超临界乙醇和甲醇均可产生氢自由基作为供氢体，攻击木质素及其大分子片段中的官能团，同时使液化产物中的活性片段减活，减弱重聚合反应，从而更利于芳烃产物的生成。而甲醇在液化过程中容易与木质素断键产生的苯酚中间体发生脱氢缩合反应，通过醚键聚合产生长链芳香族化合物，形成残渣，降低生物油收率。     

Recycling of waste PET‐bottles using dimethyl sulfoxide and hydrotalcite catalyst

The degradation of PET bottles has been successfully achieved using hydrotalcite as catalyst and dimethyl sulfoxide (DMSO) as solvent. The reaction was carried out at boiling point of DMSO (190°C) and degradation was complete in 10 min. The oligomer (tetramer) obtained was treated with NaOH at room temperature in methanol to get dimethyl terephthalate (DMT) and ethylene glycol (EG). Thus, it is a safe and cleaner process. Oligomer was characterized by MS, 13 C‐NMR, X‐ray diffractometric, and thermogravimetric analysis. DMT and EG were characterized by GC‐MS. DMT was also characterized by FT‐IR. GC‐MS analysis shows that the purity of DMT was 99%. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2012     

Effects of co‐hard segments on the microstructure and properties thermoplastic poly(ether ester) elastomers

A thermoplastic poly(ether ester) elastomer (TPEE) is composed of polyester hard segments and polyether soft segments. Polyester and polyether segments are often homopolymer segments. This work aims at incorporating poly(butylene phthalate (PBP) as co‐hard segments in the hard segments of poly(butylene terephthalate) (PBT)‐b‐poly(tetramethylene oxide) (PTMO) thermoplastic elastomer, and investigating structures and properties of the resulting materials, denoted as (PBT‐co‐PBP)‐b‐PTMO. (PBT‐co‐PBP)‐b‐PTMO was synthesized from dimethyl terephthalate (DMT), dimethyl phthalate (DMP), PTMO (M_n = 1000 g/mol), and 1,4‐butanediol (BDO). The crystallinity of (PBT‐co‐PBP)‐b‐PTMO first decreased and then increased with increasing PBP content from 5% to 10% due to a decrease in the average sequence length of the PBT hard segments. Its elongation at break was increased by 200–350%. When the mass fractions of PBT and PBP were 42% and 8%, respectively, the (PBT‐co‐PBP)‐b‐PTMO showed the best performance in terms of permanent deformation, strength, and hardness whose values were 30%, 25 MPa, and 37 D, respectively. All the synthesized copolymers had good thermal stability with a decomposition temperature of 400°C or so. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43337.     

Synthesis of biodiesel from edible and non-edible oils in supercritical alcohols and enzymatic synthesis in supercritical carbon dioxide

Biodiesel is an attractive alternative fuel because it is environmentally friendly and can be synthesized from edible and non-edible oils. The synthesis of biodiesel from edible oils like palm oil and groundnut oil and from crude non-edible oils like Pongamia pinnata and Jatropha curcas was investigated in supercritical methanol and ethanol without using any catalyst from 200 to 400 °C at 200 bar. The variables affecting the conversion during transesterification, such as molar ratio of alcohol to oil, temperature and time were investigated in supercritical methanol and ethanol. Biodiesel was also synthesized enzymatically with Novozym-435 lipase in presence of supercritical carbon dioxide. The effect of reaction variables such as temperature, molar ratio, enzyme loading and kinetics of the reaction was investigated for enzymatic synthesis in supercritical carbon dioxide. Very high conversions (>80%) were obtained within 10 min and nearly complete conversions were obtained at within 40 min for the synthesis of biodiesel in supercritical alcohols. However, conversions of only 60–70% were obtained in the enzymatic synthesis even after 8 h.     

超临界二氧化碳萃取石菖蒲挥发油

绿色溶剂超临界CO2 被用来提取富含β细辛醚的石菖蒲挥发油。考察了萃取压力、温度、时间、夹带剂及其用量对石菖蒲挥发油提取率和β细辛醚提取选择性的影响。萃取压力10MPa,温度45℃下,挥发油提取率较高,达到3 20%,其中x(β细辛醚) =43 70%。在恒定萃取条件10MPa, 45℃,对不同夹带剂(甲醇,乙醇,己烷,丙酮和乙酸乙酯)对挥发油中β细辛醚提取的影响作了考察,发现甲醇对选择性提取β细辛醚的效果较好,x(β细辛醚)可达56 08%。     

Mechanical and dielectric breakdown properties of PBT/TPE,PBT/PBT/PET,and PBT/antioxidant blends

To improve the thermal aging flexibility of poly(butylene terephthalate) (PBT), PBT was melt‐blended with three type thermoplastic elastomer [poly ether‐ester type (TPE1), polyester‐ester type (TPE2), and poly(buthylene 2,6‐naphthalate)/poly(tetramethylene glycol) block copolymer type (TPE3)], PBT/poly(ethylene terephthalate), (PET) alloy (Alloy), and phosphate type antioxidant (T1). The content of the three type TPEs and Alloy was fixed at 20 parts per 100 g of PBT. The morphology and thermal behavior of these blends have been investigated with scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and thermogravimetry (TG). In the case of PBT/Alloy‐20 and PBT/TPE3–20 blends show clean fractured surface, whereas for PBT/TPE1–20 and PBT/TPE2–20 blends, the elongated pieces or fiber can be seen abundantly which indicates a good compatibility. TG traces show a significant shift of the weight loss toward higher temperature for PBT/Alloy‐20, whereas PBT/TPE1–20, PBT/TPE2–20 and PBT/TPE3–20 blend decrease in thermal stability than PBT. To investigate the applicability for insulation material, the prepared blend samples were extruded an electric wire and flexibility and electric breakdown voltage (BDV) of wire after thermal aging were studied. For PBT/TPE1–20 and PBT/TPE2–20 blends did not show any cracks after flexibility test at 130°C for 6 h and 225°C for 30 min. In contrast PBT, PBT/Alloy‐20, PBT/TPE3–20, and PBT/T1–1 showed a partial crack in the insulation after flexibility test at 130°C for 6 h although its good flexibility at 225°C for 30 min. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and properties of poly(tetramethylene terephthalate-co-ethylene terephthalate)–poly(tetramethylene ether) segmented copolymers

A series of polyether–copolyester segmented copolymers ((PBT–PET)PTMG) based on hard segments of tetramethylene terephthalate–ethylene terephthalate copolyester (PBT–PET) and soft segments of poly(tetramethylene ether)(PTMG) was synthesized. The hard : soft segment weight ratio was 30 : 70 and the mole ratio of PBT : PET was 1 : 10; 1 : 6; 1 : 1; 3 : 1, respectively. Their mechanical properties, morphology, crystallization behavior and optical transparency were investigated and compared with poly(tetramethylene terephthalate)–poly(tetramethylene ether)(PBT–PTMG), as well as with poly(ethylene terephthalate)–poly(tetramethylene ether)(PET–PTMG), consisting of the equivalent composition ratio of hard and soft segments. It was found that the transparency could be improved by introducing a small amount of PBT into PET–PTMG through copolymerization. However, a decrease was observed in the transparency if more PBT was added. This is due to the fact that the copolymerization makes both crystallinity and crystallization rate decrease.