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.     

Miscible binary blends containing the polyhydroxy ether of bisphenol-a and various aliphatic polyesters

Blends of the polyhydroxy ether of bisphenol-A, Phenoxy, with the polyesters poly(1,4-butylene adipate), poly(ethylene adipate), poly(2,2-dimethyl-1,3-propylene succinate), poly(2,2-dimethyl-1, 3-propylene adipate), poly(1,4-cyclohexane-dimethanol succinate), and poly(?-caprolactone), are found to exhibit the single, composition-dependent glass transition temperatures characteristic of miscible systems. Phenoxy blends containing poly(ethylene succinate), poly(hexamethylene succinate), or poly(pivaloactone) were found to be immiscible. Blend interaction parameters, obtained from analysis of the melting-point depressions observed for miscible blends containing crystallizable polyester components, are found to vary with polyester chemical structure so as to suggest an optimum density of ester groups in the polyester chain for achieving maximum interaction with Phenoxy. Too many or too few ester groups lead to immiscible polyester–Phenoxy blends.     

Degradative transesterification of terephthalate polyesters to obtain DOTP plasticizer for flexible PVC

It has been found that dioctyl terephthalate (DOTP), a plasticizer for polyvinyl chloride (PVC), can be made from scrap terephthalate polyesters such as polyethylene terephthalate (PET) by a method known as degradative transesterification. It is recognized that this plasticizer is as good as plasticizer as commercial DOTP, and that it may potentially replace dioctyl phthalate (DOP). The production of DOTP from scrap PET is shown to be cost effective. The use of this technology may provide a solution to a part of our solid-waste problem.     

反应挤出酯交换法制备r-PET/PC合金

使用反应型挤出机研究了在乙酸铈催化作用下回收聚对苯二甲酸乙二酯饮料瓶片（r－PET）和聚碳酸酯（PC）的挤出反应情况、产物的特性黏数、熔体流动速率和力学性能变化。结果表明,加入少量的乙酸铈可使部分大分子链发生酯交换反应．促进了高结晶性PET和非晶性PC间的相容性,使两者可以任意比例混合而正常地挤出。酯交换使产物的特性黏数提高,最高达0．82dL／g;加入质量分数为0．045％的乙酸铈,挤出反应产物r-PET／PC的力学性能比纯r-PET有明显提高,简支梁无缺口冲击强度比纯r-PET提高4．7倍,实现了利用PC增韧r-PET的目的。     

Photoluminescent enhancement of polyesters via photocrosslinking

A homologous series of soluble photoluminescent polyesters, namely poly{bis(4‐hydroxybenzylidene)acetone‐5‐(m‐alkyloxyisophthalate)}, PAI1‐PAI5 were designed and synthesized via polycondensation reaction. The branches of these polyesters consisted of flexible alkyloxy chains with different chain lengths in order to investigate their influence toward thermal stability as well as the photocrosslinking property. It was found that increasing length of the flexible chain would reduce the thermal stability of the polyesters. Irradiation of these polyesters under UV light induced photocrosslinking and showed fascinate enhancement in their photoluminescence property with greater emission intensity. This was evidenced visually from the transformation of a weak greenish blue emission to highly intense cloudy blue emission. The photocrosslinking system was further confirmed using spectroscopic methods. Morphology analysis using SEM showed that the photocrosslinked polyesters have a fiber‐like or thread‐like texture with more voids as compared to the virgin polyesters. This was because of the formation of cyclobutanes through photodimerization involving 2π + 2π cycloaddition. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41504.     

酯交换缩聚法合成聚碳酸酯的研究进展

聚碳酸酯的酯交换缩聚工艺具有绿色环保的特性,符合当今世界可持续发展的主题,相对于传统的光气法工艺更具有发展前途。综述了国内外在酯交换缩聚工艺的机理以及催化剂选择和工艺条件上取得的进展。指出碳酸二苯酯与双酚A酯交换反应是四面体机理,正反应是二级反应,逆反应是三级反应;以La(ACAC)_3作催化剂,得到的产品不但粘均分子量较高,而且热稳定性非常好;利用酯交换熔融聚合工艺可以解决传统光气法的环境问题,而固相聚合可以得到超高分子量的产品。     

酯交换法合成碳酸二甲酯研究进展

从催化剂体系和反应条件等方面,综述了酯交换法合成碳酸二甲酯的研究新进展。介绍了硫酸二甲酯法、环烷基碳酸酯法和甲醇、环氧烷、CO2一步合成法,并评价所用催化剂的性能,分析了这些合成方法的优缺点。     

The transesterification of bisphenol-a polycarbonate (PC) and polybutylene terephthalate (PBTP): A new route to block copolycondensates

In this work, the exchange reaction taking place in molten blends of bisphenol-A polycarbonate and polybutylene terephthalate was studied. A direct transesterification mechanism catalyzed by titanium residues, present in commercial PBTP, was deduced. The transesterification reaction can be -stopped at various levels by additives capable of complexing the titanium catalyst. This work enhances the possibility of a new approach in macromolecular engineering by directly combining polycondensates in a processing machine such as an extruder.     

酯交换法合成聚碳酸酯二醇的研究进展

综述了酯交换法合成聚碳酸酯二醇(PCDL)的研究进展.通过对碳酸二甲酯、碳酸二乙酯、碳酸乙烯酯、碳酸二苯酯等用于酯交换合成PCDL进行了比较,指出碳酸二苯酯与二元醇合成PCDL是最具工业化前景的方法.对碱金属化合物、有机金属化合物、有机胺类化合物、Mg/Al水滑石、负载型催化剂、酶等催化剂的催化性能作了评述.     

熔融酯交换合成聚碳酸酯预聚体的动力学

研究了双酚A与碳酸二苯酯以氢氧化四丁基铵为催化剂的酯交换反应动力学。根据官能团模型推导出以苯酚浓度表示的积分型速率方程,得到了不同温度下的预聚合反应平衡常数,正、逆反应速率常数,活化能和反应热。酯交换反应的反应级数为二级,反应为放热反应,反应热为-17.45 kJ/mol,反应活化能为77.170 kJ/mol。探讨了不同反应温度、催化剂用量对反应速率的影响。实验数据与官能团模型符合良好,可以为后期的实验设计提供一定的理论指导。     

MgO/NaY催化甲醇与碳酸乙烯酯酯交换合成碳酸二甲酯

以硝酸镁为前体,通过等体积浸渍法制备不同负载量的MgO/NaY催化剂,用CO2-TPD和TEM对催化剂进行了表征,考察MgO负载量、反应温度、反应时间等条件对甲醇与碳酸乙烯酯（EC）酯交换反应合成对碳酸二甲酯（DMC）的影响。实验结果表明：MgO的负载量对催化剂表面的碱量和MgO分散程度有着重要影响。高分散的MgO物种越多,其催化剂碱量越高。采用12%MgO/NaY为催化剂、反应温度70 ℃、n(甲醇)∶n(EC)= 8∶1、反应时间3 h时,EC的转化率和DMC的选择性最佳,DMC收率高达89%。     

Reactive processing of ethylene-vinyl acetate rubber/polyamide blends via a dynamic transesterification reaction

Dynamic vulcanization process of ethylene-vinyl acetate rubber (EVM) and ternary polyamide copolymer (tPA) blends in the presence of tetraethyloxysilane (TEOS) was investigated. The morphology, crosslink density and mechanical properties of the resultant EVM/tPA thermoplastic elastomers (TPEs) were characterized. The dynamically crosslinked EVM phase was distributed homogeneously in the continuous tPA phase for the EVM/tPA (70/30) TPE, and the phase size of EVM decreased further as the TEOS content increased. The crosslink density reached 3.17 × 10^?5 mol cm^?3, and the tensile strength and the elongation at break were up to 10.6 MPa and 296 %, respectively, when the TEOS content was increased to 8 phr, and the heat oil resistance was accordingly enhanced. As compared to dicumyl peroxide-initiated crosslinking reaction of EVM, the crosslinking reaction of EVM through the transesterification reaction between EVM and TEOS presented lower crosslinking rate constant and activation energy, indicating that the transesterification reaction is more suitable for high temperature dynamic vulcanization processing. The optimized dynamic vulcanization process of EVM/tPA TPEs is useful for developing high-performance TPEs for automotive applications.     

Synthesis and properties of bisphenol-Z polycarbonate via melt transesterification

Polycarbonate (PC) is a thermoplastic engineering plastic with excellent properties, and its excellent dielectric properties have broad application prospects in the field of electronics. In this paper, bisphenol Z (BPZ) and diphenyl carbonate (DPC) are used as raw materials to synthesize special polycarbonate (BPZ-PC) by melt transesterification. The effects of catalyst type, catalyst dosage, molar ratio of raw materials, transesterification reaction time and vacuum degree, polycondensation reaction temperature and time on the molecular weight of the product are investigated, and the optimal reaction conditions are obtained. The chemical structure of the product is verified by FTIR, ¹H-NMR and ¹³C-NMR spectra tests. The thermal properties, mechanical properties, optical properties and dielectric properties of BPZ-PC are evaluated. Therefore, due to its excellent performance, BPZ-PC, a high-performance low-dielectric polycarbonate, can be widely used in high-frequency communication, microelectronics, and aerospace industries.     

Lipase-catalyzed synthesis of aliphatic polyesters via copolymerization of lactide with diesters and diols

Aliphatic lactate-bearing copolyesters were successfully synthesized via copolymerization of L-lactide (LLA) with diesters and diols using Candida antarctica lipase B (CALB) as the catalyst. The resultant copolymers had a M_w up to 38,000 Da with M_w/M_n between 1.5 and 2.0, and contained L-lactate units (up to 53 mol%), C₆–C₁₂ diester units, and C₄–C₆ alkylene units in the polymer chains. The lactate repeat units were present primarily as lactate–lactate diads in the polymers. The LLA-diester-diol copolymers were purified in good yield (70–85%) and all purified copolymers were optically active. Hydrolytic degradation study shows that LLA-diethyl adipate-1,6-hexanediol (LLA-DEA-HD) copolymers are degradable polymers as the molecular weight (M_w) of the copolymer with 53% lactate units decreased by ∼70% upon incubation in PBS solution under physiological conditions (37 °C, pH of 7.4) for 80 days. The LLA-diester-diol copolymers are thermally stable up to at least 300 °C with the temperature of maximum degradation rate ranging from 380 to 410 °C. The copolymers exhibit a wide range of physical properties (e.g., from white solid to wax and liquid) depending on their structure and composition. In particular, the LLA-DEA-HD and LLA-DEA-1,4-butanediol copolymers with ∼50 mol% lactate units are colorless, viscous liquids at ambient temperature. Biodegradable liquid polymers are potentially useful biomaterials for drug delivery to treat ocular ailments because of their good compatibility with sensitive soft tissues.     

二氧化硅负载甲烷磺酸催化酯交换制备生物柴油

通过溶胶-凝胶-包埋法制备的二氧化硅负载甲烷磺酸固体酸催化剂,用于大豆油与乙醇的酯交换制备生物柴油,考察了催化剂的处理温度、乙醇与大豆油物质的量比、催化剂用量、正庚烷用量和反应时间的影响。结果表明,二氧化硅负载的甲烷磺酸具有较高的酯交换反应活性。制备生物柴油的最佳条件为：催化剂焙烧温度130 ℃、醇油物质的量比6∶1、催化剂用量为大豆油质量的5.0%,溶剂正庚烷用量为大豆油质量的30.0%,反应时间6 h。在此条件下,产品收率可达98.33%。与固体碱催化剂相比,固体酸催化剂对原料的酸度有更强的适应性。     

超声强化酯交换合成蔗糖月桂酸单酯的工艺

以月桂酸甲酯和蔗糖为原料,无水碳酸钾为催化剂,在超声场中合成蔗糖月桂酸酯。考察了糖酯摩尔比、催化剂用量、DMSO试剂量及反应时间对蔗糖月桂酸单酯产率的影响,根据Box-Benhnken试验设计原理,采用三因素三水平的响应面分析法 ,建立了40 kHz 超声场中合成蔗糖月桂酸单酯的二次多项式回归方程,确定了合成蔗糖月桂酸单酯的适宜工艺条件：糖酯摩尔比3.7∶1、催化剂用量占月桂酸甲酯质量的12.8%、DMSO试剂量为7.9 mL。在适宜工艺条件合成的蔗糖月桂酸单酯产率为68.16%。     

酯交换法合成脂肪族聚碳酸酯的研究现状

概述了国内外脂肪族聚碳酸酯生物可降解材料的发展状况,总结了近十多年以脂肪族二元醇与碳酸二烷基酯为原料,经不同催化剂、工艺条件酯交换、缩聚反应合成脂肪族聚碳酸酯的研究进展,和展望了酯交换法合成APC的发展途径和应用前景。     

用棉籽油制备生物柴油

采用棉籽油为原料连续化生产生物柴油,研究了工艺及设备的设计。由棉籽油与甲醇在催化剂NaOH存在下由酯交换反应制得生物柴油。在优化条件下反应50 min,转化率达到99%。生产的生物柴油,各项指标与天然柴油相似。其各项燃烧指标优于或与普通柴油相仿,满足欧洲Ⅱ排放标准。     

Solid state bonding of graphite/thermoset composites via interchain transesterification reaction (ITR)

Thick section composite laminates are expensive and difficult to manufacture because of problems with porosity, large reaction exotherms from epoxies and residual strains. The copolyester thermosets described here can eliminate these problems. Through interchain transesterification reactions, individually cured prepreg plies of graphite reinforced copolyester can be bonded with each other in the solid state. ITR bonding is shown to produce well‐consolidated laminates with less than 2% void volume and mechanical properties comparable to those of current high‐end polymer matrix composites. DMA testing showed the glass transition to begin at 190°C for a 45% fiber volume fraction composite. Tensile testing of 55% fiber volume composites at room temperature showed modulus, strength and elongation to failure averages of 105.4 GPa, 1.02 GPa and 1.0% respectively.