- A flame-retardant-free and thermo-cross-linkable copolyester: Flame-retardant and anti-dripping mode of action
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Flame-retardant-free and thermo-cross-linkable copolyesters have been synthesized, and their flame retardation and anti-dripping behavior as a consequence of cross-linking during combustion were investigated in detail. TG-DSC simultaneous thermal analysis, rheological analysis, and TGA established the extent and rate of the cross-linking reaction. The extent of cross-linking depends on the content of cross-linkable monomer, PEPE, and the higher the extent of the cross-linking, the better the flame retardance and anti-dripping performance of copolyesters. The large melt viscosity caused by cross-linked networks at high temperature played the most important role in anti-dripping of copolyesters. TG-FTIR results confirmed that the flame-retardant activity of copolyesters mainly took effect in the condensed phase, and XPS results indicated that the carbonization process was aromatization-dominant. SEM and Raman analysis suggested that the char layers were constituted mainly of polyaromatic species with small and uniform microstructures at the surface. Consequently, both the large melt viscosity and the formation of an especially compact char with fine microstructure resulting from cross-linking were considered as the key to the flame retardance and anti-dripping performance of the polymer when subjected to the flame.
- Zhao, Hai-Bo,Liu, Bo-Wen,Wang, Xiao-Lin,Chen, Li,Wang, Xiu-Li,Wang, Yu-Zhong
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- Fe-containing magnetic ionic liquid as an effective catalyst for the glycolysis of poly(ethylene terephthalate)
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The depolymerization of poly(ethylene terephthalate) (PET) in ethylene glycol could be catalyzed by imidazolium-based Fe-containing ionic liquid, 1-butyl-3-methylimidazolium tetrachloroferrate ([bmim]FeCl4). This magnetic ionic liquid exhibits
- Wang, Hui,Yan, Ruiyi,Li, Zengxi,Zhang, Xiangping,Zhang, Suojiang
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- Superparamagnetic γ-Fe2O3 nanoparticles as an easily recoverable catalyst for the chemical recycling of PET
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There have been numerous studies to develop catalysts for the chemical recycling of poly(ethylene terephthalate) (PET) via glycolysis. However, in the field of PET glycolysis, only a few have attempted to recover and reuse the catalysts. This research utilized easily recoverable superparamagnetic γ-Fe2O3 nanoparticles as a reusable catalyst for PET glycolysis. γ-Fe2O3 nanoparticles were produced by calcining Fe3O4 nanoparticles prepared by the co-precipitation method. The produced γ-Fe2O3 nanoparticles had an average size of 10.5 ± 1.4 nm, and a very high surface area reaching 147 m2 g-1. Its superparamagnetic property was also confirmed. Glycolysis reactions were carried out, and the γ-Fe2O3 catalysts were recovered after the reactions by simple magnetic decantation. The use of magnetic iron oxide allowed the easy recovery of the catalyst from the glycolysis products. At 300 °C and a 0.05 catalyst/PET weight ratio, the maximum bis(2-hydroxyethlyl) terephthalate (BHET) monomer yield reached more than 90% in 60 min. At 255 °C and a 0.10 catalyst/PET weight ratio, the BHET yield reached more than 80% in 80 min. The catalyst was reused 10 times, giving almost the same BHET yield each time.
- Bartolome, Leian,Imran, Muhammad,Lee, Kyoung G.,Sangalang, Arvin,Ahn, Jeong Keun,Kim, Do Hyun
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- (Mg-Zn)-Al layered double hydroxide as a regenerable catalyst for the catalytic glycolysis of polyethylene terephthalate
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(Mg-Zn)-Al layered double hydroxide (LDH) was prepared by the coprecipitation method at low super saturation conditions. The prepared (Mg-Zn)-Al LDH was analyzed using XRD, FTIR, N2 adsorption-desorption, TGA and DSC, confirming the formation of pure LDH phase. The extent of polyethylene terephthalate (PET) degradation by the glycolysis process was studied using the prepared (Mg-Zn)-Al LDH. The glycolysis process was optimized in terms of catalyst concentration, temperature, time, ethylene glycol dosage. Under the optimal conditions of 1.0 wt.% of catalyst with 20 g of ethylene glycol (EG) in the presence of 2.0 g of PET at 196 °C after 3 h of glycolysis, complete PET conversion was achieved and the yield of bis (2-hydroxyethyl) terephthalate (BHET) reached 75%.
- Eshaq, Gh.,Elmetwally
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- Dielectric relaxation in amorphous poly(ethylene terephthalate) and poly(ethylene 2,6-naphthalene dicarboxylate) and their copolymers
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The dielectric loss spectra of poly(ethylene 2,6-naphthylene dicarboxylate) (PEN) and several copolymers of 2,6-naphthylene dicarboxylic acid and terephthalic acid with ethylene glycol have been studied over a wide range of frequency and temperature. Previously, Ezquerra, Balta-Calleja, and Zachmann have reported the presence, in isochronal temperature scans of dielectric loss, of a subglass process (β*) in PEN homopolymer in addition to the subglass process (β) similar to that in poly(ethylene terephthalate) (PET). In the present work both the β and β* processes in PEN and PET/PEN copolymers are resolved and characterized in isothermal frequency scans. It was found that the lower temperature β loss peak in PEN and the copolymers has a complex or composite frequency domain structure requiring two Cole-Cole processes in its representation. The β* process in the copolymers is found to shift to higher frequency isothermally (or lower temperature isochronally) with increasing terephthalic acid content. Analysis of previous dielectric data for PET shows that its β subglass process is also complex in the log frequency axis but must be represented by three Cole-Cole processes. The two higher frequency components are essentially identical to the two Cole-Cole processes making up the β process in PEN. The third and lowest frequency component is interpreted as of the same origin as the β* process in PEN and the copolymers but shifted to higher frequency isothermally (or lower temperature isochronally) to where it overlaps with the β process.
- Bravard, Shelly P.,Boyd, Richard H.
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- Effective catalysts derived from waste ostrich eggshells for glycolysis of post-consumer PET bottles
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Herein, we report an effective chemical recycling of poly(ethylene terephthalate) (PET) using sustainable sources of catalysts, calcium oxide (CaO) derived from ostrich eggshells. The active catalysts were demonstrated in the chemical depolymerization of post-consumer PET bottles. Beverage bottles were proceeded with 1 wt% catalyst derived from ostrich eggshells in the presence of ethylene glycol at 192?°C under atmospheric pressure to give the major product as bis(2-hydroxyethyl terephthalate) (BHET) which was confirmed by melting point, IR spectroscopy, 1H-, 13C-NMR spectroscopy and mass spectrum. The catalyst could fully depolymerize PET within 2?h, producing a good yield of highly pure BHET monomer. The catalysts were successfully characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy with energy dispersive X-ray spectroscopy analysis (FE-SEM), and thermo-gravimetric analysis (TGA). Furthermore, catalysts derived from chicken eggshells, geloina, mussel, and oyster shells were run to compare the catalytic activities. For better understanding of catalytic parameters, effects of calcination temperatures of catalyst, weight ratio of catalyst, ratio of weight of solvent, and time of depolymerization for the ostrich eggshells catalyst were also investigated.
- Yunita, Isti,Putisompon, Siraphat,Chumkaeo, Peerapong,Poonsawat, Thinnaphat,Somsook, Ekasith
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- Organocatalysed depolymerisation of PET in a fully sustainable cycle using thermally stable protic ionic salt
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The world's plastic production is continuously and exponentially increasing, creating millions of tons of short-lived items that end as waste and accumulate in the environment. Poly(ethylene terephthalate) (PET) provides one of the best examples as it is a non-biodegradable polymer that is mainly used as raw material for a wide range of packaging applications, making degradation of PET a subject of great interest for researchers. Herein we report a sustainable process for the chemical recycling of PET from waste to a new polymer using an innovative protic ionic salt. Using a simple solvent-free process, post-consumer PET bottles are degraded into bis(2-hydroxyethyl) terephthalate (BHET) monomer. The catalyst, formed by an equimolar quantity of triazabicyclodecene (TBD) and methanesulfonic acid (MSA), completely depolymerises PET in less than 2 h, producing 91% of highly pure BHET. Due to the unusual thermal stability of the TBD:MSA salt, the catalyst can be recycled at least 5 times to depolymerise more PET waste. In addition, we demonstrate that the monomer obtained from the degradation reaction can be used to synthesise new PET with similar thermal properties to that produced using a conventional polycondensation method. The protic ionic salt catalyst combines the excellent catalytic ability of organocatalysts with the thermal stability of metal catalysts, resisting degradation up to >400 °C, thus for the first time presenting an industrially-relevant organocatalyst for high-temperature polymer degradation and recycling.
- Jehanno, Coralie,Flores, Irma,Dove, Andrew P.,Müller, Alejandro J.,Ruipérez, Fernando,Sardon, Haritz
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- Mechanically linked poly(ethylene terephthalate)
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The synthesis, by solid-state copolymerization, and properties of poly(ethylene terephthalate) (PET) copolymers containing various amounts of [2]catenane mechanical linkages are described. Polymers end-capped by the corresponding noninterlocked macrocycle as well as a copolymer with a rigid fluorene monomer unit were also prepared as reference systems. Size exclusion chromatography and 1H NMR indicate that the catenane is quantitatively incorporated during synthesis but that a small fraction ring-opens to form noninterlocked macrocycles, incorporated as either chain ends or branching points. Catenanes induce a smaller increase in the glass transition temperature than the macrocycle at the same weight content. This is probably due to the suppression of interchain hydrogen bonds upon interlocking and points to a specific effect of the mechanical linkage on properties. The crystallization and melting temperatures of catenane copolymers are only slightly depressed compared to those of PET homopolymer, further demonstrating significant flexibility of the catenane rings. SAXS results show that the amorphous interlayer between lamellae increases with increasing catenane content at constant lamellar thickness, confirming that the uncrystallizable catenane units concentrate in the amorphous phase during solid-state polymerization.
- Fustin,Clarkson,Leigh,Van Hoof,Jonas,Bailly
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- DISPERSION AND METHOD AND COMPOSITION FOR PREPARING THE SAME
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A dispersion includes a zinc oxide component, and an aromatic polyol which is represented by Formula (I) and which has terminal hydroxyl groups that form chelating bonds with zinc atoms of the zinc oxide component, wherein p and q are independently integers ranging from 1 to 40. A method for preparing the dispersion includes heating a composition including the aromatic polyol and a zinc-containing salt, so that the zinc-containing salt undergoes nucleophilic reaction and condensation reaction to form the zinc oxide component. A composition for preparing the dispersion is also disclosed.
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Paragraph 0036
(2021/12/03)
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- Preparation method of bis (2-hydroxyethyl) terephthalate
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The invention relates to a preparation method of bis (2-hydroxyethyl) terephthalate. Terephthalic acid and ethylene oxide are used as raw materials to prepare bis (2-hydroxyethyl) terephthalate; a Lewis acid ionic liquid is selected as a solvent and a catalyst; the invention provides the preparation method of bis (2-hydroxyethyl) terephthalate which suitable for industrial production, the conversion rate of terephthalic acid in the preparation method is 90% or above, the selectivity on bis (2-hydroxyethyl) terephthalate is up to 95% or above, and the preparation method is simple in process andsuitable for requirements of industrial production.
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Paragraph 0026; 0030-0032; 0036-0038; 0042-0044; 0047-0050
(2020/04/22)
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- Method for efficiently synthesizing bis(hydroxyethyl) terephthalate without catalysis
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A method for efficiently synthesizing bis(hydroxyethyl) terephthalate without catalysis is disclosed. Terephthalic acid and ethylene glycol are adopted as raw materials. The method comprises the following steps: 1) putting a reaction system formed by mixing the terephthalic acid and the ethylene glycol according to a molar ratio of 1:(10-40) into a reaction vessel; carrying out esterification on the reaction system for 6-12 hours at the esterification reaction temperature of 175-195 DEG C and under atmospheric pressure. In the whole reaction process, inert gas flows through the reaction system; water generated by the reaction and used as a by-product is brought out of the reaction system by the inert gas; and after the reaction is finished, the reaction liquid in the reaction vessel is cooled and filtered, and filter cake is washed and dried to obtain the bis(hydroxyethyl) terephthalate. The bis(hydroxyethyl) terephthalate is efficiently synthesized in the absence of a catalyst, a reaction system is simplified, the cost is reduced, the post-treatment process is shortened, and three-waste emission is reduced.
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Paragraph 0029-0069
(2020/09/09)
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- MANUFACTURING METHOD OF TEREPHTHALIC ACID BIS(2-HYDROXYETHYL)
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PROBLEM TO BE SOLVED: To provide a manufacturing method of terephthalic acid bis(2-hydroxyethyl) capable of providing a reaction product for manufacturing polyester such as PET without causing time and cost consuming such as solvent removal, at high conversion rate of terephthalic acid, and low monoester/diester ratio. SOLUTION: There is provided a manufacturing method of terephthalic acid bis(2-hydroxyethyl) including a step for reacting ethylene oxide and terephthalic acid at a molar ratio of 2.5:1 to 3.5:1 at a high temperature by 150°C in presence of a solvent mixture containing water and a diol cosolvent at a weight ratio of 0.2:1 to 5:1, to obtain a reaction mixture. SELECTED DRAWING: None COPYRIGHT: (C)2020,JPOandINPIT
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Paragraph 0025-0034
(2020/01/11)
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- PROCESS FOR PREPARING BIS(2-HYDROXYETHYL) TEREPHTHALATE
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A process for preparing bis(2-hydroxyethyl) terephthalate, comprising a step of: subjecting ethylene oxide and terephthalic acid in a molar ratio of from 2.5:1 to 3.5:1 to a reaction at an elevated temperature of up to 150° C. in the presence of a solvent mixture containing water and a diol cosolvent in a weight ratio of from 0.2:1 to 5:1.
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Paragraph 0025-0036
(2020/01/04)
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- Double-(2 - hydroxy ethyl) terephthalate preparation
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A process for preparing bis(2-hydroxyethyl) terephthalate, comprising a step of: subjecting ethylene oxide and terephthalic acid in a molar ratio of from 2:1 to 3:1 to a reaction at an elevated temperature in the presence of a solvent mixture containing water and a C6-C8 hydrocarbon in a weight ratio of from 1:1 to 3:1.
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Paragraph 0019; 0020; 0026
(2018/09/27)
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- Development and Applications of Transesterification Reactions Catalyzed by N-Heterocyclic Olefins
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A novel method to utilize N-heterocyclic olefins (NHOs), the alkylidene derivatives of N-heterocycic carbenes, as organocatalysts to promote transesterification reactions has been developed. Because of their strong Br?nsted/Lewis basicity, NHOs can enhance the nucleophilicity of alcohols for their acylation reactions with carboxylic esters. This transformation can be employed in industrially relevant processes such as the production of biodiesel, the depolymerization of polyethylene terephthalate (PET) from plastic bottles for recycling purposes, and the ring-opening polymerization of cyclic esters to form biodegradable polymers such as polylactide (PLA) and polycaprolactone (PCL).
- Blümel, Marcus,Noy, Janina-Miriam,Enders, Dieter,Stenzel, Martina H.,Nguyen, Thanh V.
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supporting information
p. 2208 - 2211
(2016/06/01)
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- A normal pressure alcoholysis PETG waste film preparation dimethyl terephthalate (by machine translation)
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The invention claims a normal pressure alcoholysis PETG waste film preparation dimethyl terephthalate, includes the following steps: (1) waste PETG thin film pretreatment; (2) the alcoholysis EG PETG film; (3) interchange preparing dimethyl terephthalate; (4) methanol and glycol recovery. The invention under normal pressure can make the high-purity terephthalic acid dimethyl ester, the production process in the apparatus performance requirement is not high, the product yield as high as 97.8% and in the process of production without generating waste, the prepared EG can be 99% recovery, recovery of the methanol 90% or more. Not only in response to the call of the Government clean production, also meets the needs of the rely profits. The invention is also suitable for waste PETG sheet material, the recycling of the plate. (by machine translation)
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Paragraph 0016-0020
(2017/09/16)
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- Unexpected efficiency of cyclic amidine catalysts in depolymerizing poly(ethylene terephthalate)
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This article describes studies on the catalytic activity of several nitrogen-based organic catalysts for the depolymerization of poly(ethylene terephthalate) (PET), in which a few cyclic amidines work more effectively than a potent, bifunctional guanidine
- Fukushima, Kazuki,Coady, Daniel J.,Jones, Gavin O.,Almegren, Hamid A.,Alabdulrahman, Abdullah M.,Alsewailem, Fares D.,Horn, Hans W.,Rice, Julia E.,Hedrick, James L.
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p. 1606 - 1611
(2013/08/25)
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- Synthesis and properties of long-chain aromatic telechelic monodispersed diols radical-initiated, addition of 2-mercaptoethanol onto α, ω nonconjugated dienes
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The synthesis of aromatic telechelic mono dispersed diols produced from the radical-initiated addition reaction of a twofold excess of 2-mercaptoethanol onto original α, ω nonconjugated dienes reaction is presented. These novel α, ω nonconjugated dienes were prepared by addition reaction of m-isopropyl α, α' dimethyl benzylisocyanate with mono dispersed telechelic diols obtained by fractionation of oligo(ethylene terephthalate)s. In these cases, the long chain α, ω diols were produced selectively and quantitatively. The products are soluble in most organic solvents in contrast to classical oligo (ethylene terephthlate)s and posses a lower glass transition and melting temperatures. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements for the following free supplemental resource: Figures S1-S3.
- Boutevin, Bernard,Ameduri, Bruno,Elidrissi, Abderrahmane,Touzani, Rachid
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experimental part
p. 482 - 494
(2012/04/17)
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- A simple and efficient synthetic method for poly(ethylene terephthalate): Phenylalkyl pyrrolidinium ionic liquid as polycondensation medium
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A series of phenylalkyl pyrrolidinium ionic liquids (ILs) ([YBPy][X], Y = NO2, CH3, F, H; B = benzyl, phenethyl; X = Tf 2N) were synthesized and found to be environmentally benign reaction media for the preparation of poly(ethylene terephthalate) (PET). ILs with specific functional groups had high thermostabilities and showed interesting properties in synthesizing PET at lower temperature (190-240 °C) and pressure (500 Pa) compared to conventional ILs. PET with Mw up to 1.9 × 104 g mol-1 was obtained. The ILs can be easily separated and reused after simple purification except for the PF 6- ILs. This process provides a valuable and environmentally friendly alternative to the currently available method for the preparation of PET in industry.
- Dou, Junyan,Liu, Zhengping
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experimental part
p. 2305 - 2313
(2012/09/08)
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- METHODS OF DEPOLYMERIZING TEREPHTHALATE POLYESTERS
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A method comprises forming a reaction mixture comprising a terephthalate polyester, a glycol comprising 2 to 5 carbons, and an amidine organocatalyst; and heating the reaction mixture at a temperature of about 120° C. or more to depolymerize the terephthalate polyester, thereby forming a terephthalate reaction product comprising a monomeric dihydroxy terephthalate diester; wherein the terephthalate reaction product contains terephthalate oligomers in an amount less than the amount of terephthalate oligomers that would result from i) substituting the amidine organocatalyst with an equimolar amount of a guanidine catalyst and ii) depolymerizing the terephthalate polyester under otherwise identical reaction conditions.
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Page/Page column 15
(2012/09/11)
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- A novel aromatic-aliphatic copolyester consisting of poly(1,4-dioxan-2one) and poly(ethylene-co-1,6-hexene terephthalate): Preparation, thermal, and mechanical properties
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A novel multiblock aromatic-aliphatic copolyester poly(ethylene-co-1,6- hexene terephthalate)-copoly(1,4-dioxan-2one) (PEHT-PPDO) was successfully synthesized via the chainextension reaction of dihydroxyl teminated poly(ethylene-cohexane terephthalate) (PEHT-OH) with dihydroxyl teminated poly(1,4-dioxan-2-one) (PPDO-OH) prepolymers, using toluene2,4-diisocyanate as a chain extender. To produce PEHT-OH prepolymer with an appropriate melting point which can match the reaction temperature of PEHT-OH prepolymer with PPDOOH prepolymer, 1,6-hexanediol was used to disturb the regularity of poly(ethylene terephthalate) segments. The chemical structures and molecular weights of PEHT-PPDO copolymers were characterized by 1H NMR, FTIR, and GPC The DSC data showed that PPDO-OH segments were miscible well with PEHT-OH segments in amorphous state and that the crystallization of copolyester was predominantly contributed by PPDO segments. The TGA results indicated that the thermal stability of PEHT-PPDO was improved comparing with PPDO homopolymer. The novel aromatic-aliphatic copolyesters have good mechanical properties and could find applications in the field of biodegradable polymer materials.
- Gong, Jie,Lou, Xiao-Jie,Li, Wen-Da,Jing, Xin-Ke,Chen, Hong-Bing,Zeng, Jian-Bing,Wang, Xiu-Li,Wang, Yu.-Zhong
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experimental part
p. 2828 - 2837
(2011/03/19)
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- METHOD FOR RECOVERING USEFUL COMPONENTS FROM DYED POLYESTER FIBER
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To establish an efficient and economical useful component recovery method capable of recovering high purity useful components from a dyed polyester fiber. A method for recovering useful components from a dyed polyester fiber, includes a dye extraction step, a solid liquid separation step, a depolymerization reaction step, an ester interchange reaction step, and a useful component separation step, for recovering useful components from the dyed polyester fiber, wherein the dye extraction step includes a step of extracting and removing a dye at the glass transition temperature of the polyester or higher and at 220° C. or less with a xylene extracting solvent and an alkylene glycol extracting solvent in combination.
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Page/Page column 6-8
(2009/06/27)
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- PROCESSES FOR THE PURIFICATION OF BIS(2-HYDROXYETHYL) TEREPHTHALATE
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An object of the present invention is to provide a method of obtaining BHET of high purity efficiently from an EG (ethylene glycol) solution containing crude BHET (bis(2-hydroxyethyl)terephthalate), especially a decomposition product solution obtained by decomposing a polyester containing PET (polyethylene terephthalate) as a main component, by use of EG, while minimizing by-production of impurity components such as DEG (diethylene glycol), DEG ester and oligomers. The present invention is a method of purifying BHET by subjecting the decomposition product solution to crystallization and solid-liquid separation under specific temperature conditions. Further, the present invention is a method of purifying BHET which comprises evaporation steps of evaporating low-boiling-point components from the decomposition product solution under specific conditions so as to obtain a melt solution and a molecular distillation step of distilling the obtained melt solution under specific conditions so as to obtain a specific fraction.
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Page/Page column 29-31
(2010/02/10)
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- Polymeric compositions with embedded pesticidal desiccants
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The invention is a polymeric composition and a method of forming a composition in which a pesticidal desiccant is homogeneously dispersed throughout the polymer. The desiccant is of appropriate size to be incorporated into a polymer melt for eventually forming articles, such as melt spun fibers, from the polymer-desiccant mix. The desiccant may be embedded throughout the body of an article, particularly fibers, produced pursuant to this invention. Silicon dioxide based desiccants that are present within the polymer matrix in an amount between about 0.1 and 2.5 weight percent are useful to provide absorptive properties pursuant to this invention. The desiccant dehydrates the microscopic reservoirs of moisture on which pests, such as a dust mite, survive. In this regard, the invention prevents pests from infesting and thriving on articles formed of the desiccant enhanced polymeric composition.
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Page/Page column 8
(2010/02/14)
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- Catalytic depolymerization of polymers containing electrophilic linkages using nucleophilic reagents
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A method is provided for carrying out depolymerization of a polymer containing electrophilic linkages in the presence of a catalyst and a nucleophilic reagent, wherein production of undesirable byproducts resulting from polymer degradation is minimized. The reaction can be carried out at a temperature of 80° C. or less, and generally involves the use of an organic, nonmetallic catalyst, thereby ensuring that the depolymerization product(s) are substantially free of metal contaminants. In an exemplary depolymerization method, the catalyst is a carbene compound such as an N-heterocyclic carbene, or is a precursor to a carbene compound. The method provides an important alternative to current recycling techniques such as those used in the degradation of polyesters, polyamides, and the like.
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- METHOD OF DEIONIZING SOLUTION YIELDED BY POLYESTER DECOMPOSITION WITH ETHYLENE GLYCOL
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There is provided a method for deionizing a decomposition produced solution resulting from decomposition of a polyester by ethylene glycol.The ester interchange reaction and hydrolysis reaction along with cation removing treatment of a decomposition product resulting from decomposition of a polyester by ethylene glycol are suppressed. Thereby, a method for deionizing the decomposition produced solution with small reductions in yield and purity can be provided.
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- A general and versatile approach to thermally generated N-heterocyclic carbenes
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The synthesis of N-heterocyclic carbene (NHC) adducts by condensation of diamines with appropriately substituted benzaldehydes is described. This simplified approach provides the NHC adduct without first having to generate the carbene followed by its protection. These adducts undergo thermal deprotection to generate N-heterocyclic carbene in situ. Adduct decomposition temperatures were investigated as a function of catalyst structure by using thermal analysis and spectroscopic techniques. Importantly, unlike adducts derived from chloroform, the new pentafluorobenzene-based adducts are more readily prepared and are stable at room temperature. The utility of these adducts as organic catalyst precursors for living ring-opening polymerization (ROP) of lactide, transesterification reactions, and the synthesis of N-heterocyclic carbene ligated organometallic complexes is also described.
- Nyce, Gregory W.,Csihony, Szilard,Waymouth, Robert M.,Hedrick, James L.
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p. 4073 - 4079
(2007/10/03)
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- Bredereck's reagent revisited: Latent anionic ring-opening polymerization and transesterification reactions
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The ring-opening polymerization of lactide with commercially available Bredereck-type reagents in the presence or absence of alcohol initiators was carried out affording polylactide with controlled molecular weight and narrow polydispersities. An anionic mechanism involving heterolytic cleavage to alkoxides is proposed, where these reagents function as latent anionic initiators for the ring-opening polymerization of lactide.
- Csihony, Szilard,Beaudette, Tristan T.,Sentman, Alan C.,Nyce, Gregory W.,Waymouth, Robert M.,Hedrick, James L.
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p. 1081 - 1086
(2007/10/03)
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- Expanding the catalytic activity of nucleophilic N-heterocyclic carbenes for transesterification reactions
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(graph presented) Currently, there is a renewed interest in reactions that are catalyzed by organic compounds. Typical organic catalysts for acylation or transesterification reactions are based on either nucleophilic tertiary amines or phosphines. This communication discusses the use of nucleophilic N-heterocyclic carbenes as efficient transesterification catalysts. These relatively unexplored and highly versatile organic catalysts were found to be mild, selective, and more active than traditional organic nucleophiles.
- Nyce, Gregory W.,Lamboy, Jorge A.,Connor, Eric F.,Waymouth, Robert M.,Hedrick, James L.
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p. 3587 - 3590
(2007/10/03)
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- Process for the preparation of bis(amidocarboxylic acids)
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A process is reported for the preparation of bis(amidocarboxylic acid) involving reacting an ester with an aminocarboxylate compound, the latter being formed from lactams or aminocarboxylic acids and salts thereof. The ester and aminocarboxylate compound are present in a weight ratio of about 1:1 to about 1:4, and reaction is conducted in a mono- or polyhydric alcohol solvent.
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- SYNTHESIS OF AROMATIC MONODISPERSED TELECHELIC DITHIOLS
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The synthesis of aromatic monodispersed telechelic dithiols performed from the esterification of thioglycolic acid with aromatic monodispersed telecholic diols is presented.The diols were prepared from the transesterification of ethylene glycol with the dimethyl terephthalate .In all cases the yields are high and the products are carefully characterized by 1H and 13C-NMR.Key words: Dithiol; telechelic oligomers; ethylene terephthalate derivatives; monodispersity; aromatic compounds.
- Ameduri, Bruno,Khamlichi, Mohamed,Robin, Jean-Jacques,Idrissi, A. el,Ramdani, A.
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p. 109 - 116
(2007/10/02)
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- Chromium salt catalysts
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This patent describes the catalytic promotion of the reaction of oxirane-containing compounds with carboxylic acid compounds at high, ambient, and low temperature. Specifically, this patent describes the method of reacting oxirane-containing compounds with carboxyl-containing compounds, preferably at temperatures at or around ambient, in the presence of active chromium III tricarboxylate salts which have unoccupied coordination sites. More specifically this patent describes the preparation of catalytically active chromium III-tricarboxylates from normally catalytically inactive chromium III tri-carboxylate hydrates. These compounds are powerful catalysts for the reactions of oxirane compounds with both organic carboxylic acids and cyclic primary imides.
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