聚氨酯用二聚酸聚酯二醇的合成

研究了以辛酸亚锡为催化剂、二聚酸（DA）与乙二醇（EG）为原料、制备聚氨酯用二聚酸聚酯二醇的方法,讨论了催化剂的类型和用量、反应温度、原料醇酸比、反应时间等对酯化率的影响,并用红外光谱对合成产物进行了表征。结果表明,DA与EG摩尔配比为1：2．4,催化剂辛酸亚锡用量为原料总质量的0．3％,反应温度在1h内缓慢升温到190℃,然后保温反应4h,并在130℃、2．66kPa下减压3h,酯化率可达99．7％,产品羟值为95mgKOH／g,酸值0．26mgKOH／g。     

Polyester polyols for polyurethanes from pet waste: Kinetics of polycondensation

The kinetics of polyesterification of the glycolyzed PET waste with adipic acid is reported. Glycolysis of PET waste was carried out with ethylene glycol at three different ratios of PET waste to glycol. The glycolyzed products could be readily polyesterified by reacting with adipic acid, to give polyester polyols with low acid number. Kinetics of polyesterification of the glycolyzed product made from 62.5% ethylene glycol (EG) and 37.5% waste were investigated further at different hydroxyl to carboxyl ratios. Reaction conditions were nonisothermal, comparable to the industrial process scheme consisting of two isothermal regions at 170° and 200°C. The kinetic results of the polyesterification of glycolyzed PET waste are compared to the polyesterification of pure diols, namely ethylene glycol and bis(hydroxyethyl) terephthalate (BHET) with adipic acid. The reactions follow second-order kinetics at 170°C and the rate of polyesterification of the mixed diol system from PET waste lies intermediate between those of the pure diols, namely, EG and BHET. Ethylene glycol exhibited the highest reactivity. At 200°C the kinetic plots of the mixed diols from PET waste were nonlinear, and thus the reaction may not follow second-order kinetics. The nonlinearity is explained in terms of the different reactivities of the different diol species in the reaction mixture. The polyester polyols, when cured with polymeric 4,4′ diphenyl methane diisocyanates, gave polyurethane rigid foams and elastomers.     

Application of a mathematical model for the polyesterification process based on mixtures of fumaric acid and adipic acid without catalyst

The production of unsaturated polyesters based on mixtures of fumaric acid and adipic acid for different proportions without added catalyst was studied. The progress of the polyesterification was followed by determining the amount of water produced during the reaction. The kinetic parameters (reaction order n, activation energy E, frequency factor k₀) of the polyesterification were determined and it was found out that n = 3 in all cases, while E and k₀ increased by increasing amount of fumaric acid in the initial mixture of the reaction. A mathematical model for the polyesterification based on the production parameters (e.g. the heating program) and on the kinetic parameters was used and very good correlation was found between the corresponding pair of curves of water produced during the polyesterification, which were determined experimentally and theoretically (by calculating). With regard to the properties of the final product it was found out that its viscosity and its slight yellow colour increased by increasing the amount of fumaric acid in the initial mixture of raw materials. General prospects for practical application of this method were also discussed.     

Structural effects in oxidative dehydrogenation of hydrocarbons over a vanadia–molybdena–niobia catalyst

The oxidative dehydrogenation of ethane, propane and n-butane over a vanadia–molybdena–niobia catalyst has been compared with propane substituted in the 2 position with a methyl (isobutane) or a benzyl (isopropylbenzene) group. In the normal paraffins, selectivity to the olefin was found to decrease as the chain length increased. Substitution at the propane 2 position increased selectivity, particularly in the case of isopropylbenzene. The results are explained partially in terms of over oxidation of the product olefin and partially in terms of structural effects in the parent hydrocarbon influencing the olefin-producing oxidative dehydrogenation reaction. © 1998 SCI     

A kinetic investigation of polyurethane polymerization for reactive extrusion purposes

The effects of the reaction conditions on the kinetics of two different polyurethane systems were investigated. To do so, three different kinetic methods were compared: adiabatic temperature rise (ATR), measurement kneader, and high‐temperature measurements. For the first polyurethane system, consisting of 4,4‐diphenylmethane diisocyanate (4,4‐MDI), butane diol, and a polyester polyol, the reaction conditions did not seem to matter; a kinetically controlled reaction was implicated for all reaction conditions. The reaction was second order in isocyanate concentration and 0.5th order in catalyst concentration and had an activation energy of 52 kJ/mol. The second polyurethane system consisted of a mixture of 2,4‐diphenylmethane diisocyanate and 4,4‐MDI, methyl propane diol, and a polyester polyol. For this system, each of the three measurement methods showed different behavior. Only at a low catalyst concentration did the ATR experiments show catalyst dependence; at higher catalyst levels and for the other two measurement methods, no catalyst dependence was present. Furthermore, the ATR experiments proceeded much faster. Presumably, for this system, the rapid diffusion interfacial of the species present was hindered by the presence of bulky oligomer molecules. The result was a diffusion limitation reaction at low conversions and an inhomogeneous distribution of species at higher conversions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 370–382, 2006     

Polyesterification and isomerization of maleic anhydride and 1,6-hexane diol as studied by 1H and 13C n.m.r.

The polyesterification and isomerization reaction of 1,6-hexane diol and maleic anydride in a melt without catalyst was studied by ¹³C and ¹H n.m.r. spectroscopy. The structure and concentration of oligoester species during the polyesterification and isomerization were determined depending on the reaction temperature and time. According to the number and configuration of repeating units determined from ¹H n.m.r. spectra kinetics of both reactions were also considered. The degree of isomerization is continuously increasing in the investigated reaction range.     

Effect of the reaction conditions on the photopolymerization of methyl methacrylate by diethyl dithiocarbamato‐(1,2)‐propane diol

The photopolymerization of methyl methacrylate (MMA) through the use of diethyl dithiocarbamato‐(1,2)‐propane diol (DCPD) was studied. The photoinitiator was synthesized from 3‐chloro‐1,2‐propane diol and sodium diethyl dithiocarbamate in a solvent mixture of acetone and anhydrous ethanol. The photopolymerization was carried out in a Heber multilamp photochemical reactor (COMPACT‐LP‐MP88) (Heber Scientific, Chennai, India) at 254 nm. The effects of the reaction conditions on the polymerization of MMA were studied. The conversion and molecular weight increased with an increase in the monomer concentration and reaction time. However, for the DCPD‐to‐MMA molar ratio, a critical value was found for maximum conversion. The results suggested the living radical nature of the photoinitiator, which was further investigated by the preparation of a block copolymer with styrene. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2320–2328, 2005     

Should the removal of water be taken into account in the analysis of kinetic data of polyesterification reactions?

Summary In most polyesterification reactions, the concentrations of acid, alcohol and catalyst (if present) are expressed in moles per unit mass of the charge, denoted as moles/kg. In this paper, a general kinetic equation that takes water removal into account has been derived. It has been shown that (i) when the progress of reaction is followed by titration of acid, the removal of water affects the concentrations of alcohol and catalyst; and (ii) the ratio of the rate constants that do and do not account for water removal is smaller than unity, and it varies with the degree of reaction. On the other hand, it has been found that the rate constant obtained using moles/kg as the unit of concentration is not a real constant but a function of the charge density. Treating it as a constant may lead to appreciable error or misinterpretation.     

Model esterification of neopentyl glycol and trimethylol propane with 1,4-tert-butyl benzoic acid

The esterification kinetics of difunctional neopentyl glycol and trifunctional trimethylol propane with monofunctional 1,4-tert-butyl benzoic acid was studied in the melt phase at 200°C in the presence of a metal catalyst. The rate of conversion was monitored via titrations and by determination of the relative concentrations of products and reactants using HPLC with a UV detector. A small but significant positive substitution effect was found for neopentyl glycol (K_DA = 1.15) and none was found for trimethylol propane. The reaction rate constant of neopentyl glycol with the acid is about 40% higher than that of trimethylol propane with the acid. A second-order overall reaction order was used to compute the rate constants.     

Synthesis of polyesters as binders for deinkable inks. II. Kinetics and mechanism of polyesterification between o-phthalic anhydride and neopentyl glycol in bulk at 200°C

The kinetics of the polyesterification in bulk at 200°C between o-phthalic anhydride and neopentyl glycol (2,2-dimethyl-1,3-propanediol) in a nonequimolecular ratio and in the absence of an external catalyst was investigated. The formation of the monoester and two dimeric compounds by uncatalyzed heating of o-phthalic anhydride with neopentyl glycol was virtually complete after dissolution of the anhydride. The data were analyzed statistically by a mathematical method due to Fradet and Maréchal for the estimation of the orders of reaction. This statistical adjustment of the data analysis supports the assumption that the kinetics of polyesterification in the absence of both the solvent and catalyst may be fitted to several orders of reaction over all the conversion. At first, our experimental data may be fitted to 3, or , or 2, etc., overall orders. The results establish that the overall kinetic order of the polyesterification depend upon the goodness of the experimental results and cannot be only selected by means of a correlation coefficient. If this last criterium is adopted, the polyesterification at low, medium, as well as at high conversions may be 3 as the most probable one, order one with respect to acid group concentration, and order two with respect to alcoholic group concentration, in agreement with Flory's predictions. A mechanism consistent with the most plausible kinetic results (I_m,n = 0.9990 and m, n = 1, 2) is proposed. It consists of a dimerization of the alcoholic groups followed by an attack of the acid to the dimer. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 2409–2431, 1997     

Kinetic modeling of oxidative dehydrogenation of propane with CO2 over MoOx/La2O3–Al2O3 in a fluidized bed

A 4-step kinetic model of CO₂-assisted oxidative dehydrogenation (ODH) of propane to C₂/C₃ olefins over a novel MoO_x/La₂O₃–γAl₂O₃ catalyst was developed. Kinetic experiments were conducted in a CREC Riser Simulator at various reaction temperatures (525–600 °C) and times (15–30 s). The catalyst was highly selective towards propylene at all combinations of the reaction conditions. Langmuir-Hinshelwood type kinetics were formulated considering propane ODH, uni- and bimolecular cracking of propane to produce a C₁-C₂ species. It was found that the one site type model adequately fitted the experimental data. The activation energy for the formation of propylene (67.8 kJ/mol) is much lower than that of bimolecular conversion of propane to ethane and ethylene (303 kJ/mol) as well as the direct cracking of propane to methane and ethylene (106.7 kJ/mol). The kinetic modeling revealed the positive effects of CO₂ towards enhancing the propylene selectivity over the catalyst.     

Effects of Ga content and reaction pressure upon the aromatization of propane over H–Ga–Al-bimetallosilicate catalysts

Aromatization of propane has been investigated at 540 °C in a reaction pressure range up to 0.686 MPaG over MFI-type H–Ga–Al-bimetallosilicates having various Ga/(Ga + Al) atomic ratios but a constant Si/(Ga + Al) ratio of 15. Both the propane conversion and the aromatic selectivity increased with increasing the Ga/(Ga + Al) ratio up to 0.25. Further increase in the Ga content decreased the propane conversion, although the aromatic selectivity increased. Of the catalysts examined, the H–Ga–Al-bimetallosilicate sample having the Ga/(Ga + Al) ratio of 0.25 showed the highest performance for propane aromatization. The effect of reaction pressure was investigated using this catalyst. With increasing the reaction pressure, the propane conversion increased, but the aromatic selectivity decreased. The reaction pressure was also found to strongly influence the cracking activity and the deactivation rate of the catalyst. From the analysis of the gaseous products, it was concluded that the aromatization reaction was suppressed under high reaction pressure conditions because of the formation of methane and ethane by protolytic cracking and hydrogen transfer from aromatic precursors to olefinic intermediates.     

DSC curing study of catalytically synthesized maleic‐acid‐based unsaturated polyesters

Unsaturated polyesters were synthesized based on ethylene glycol and maleic acid as unsaturated dicarboxylic acid, using a variety of saturated acids in the initial acid mixture, without or with different catalysts. The curing of the polyesters produced with styrene was studied using differential scanning calorimetry (DSC) under dynamic‐ and isothermal‐heating conditions. The FTIR spectra of the initial polyesters and cured polyesters were also determined. Curing is not complete at the end of DSC scan and the unreacted bonds were quantitatively determined from the FTIR spectra and by estimation based on literature data. The value of the mean degree of conversion (α) of all double bonds (styrene unit and maleate unit) was approximately α = 0.40. Using an appropriate kinetic model for the curing exotherm of polyesters, the activation energy (E_a), the reaction order (x) and the frequency factor (k_o) were determined. Because the kinetic parameters (ie E_a, k, x) affect the kinetics in various different ways, the curves of degree of conversion versus time at various isothermal conditions are more useful to compare and characterize the curing of polyesters. The kinetic parameters are mainly influenced by the proportion of maleic acid in the polyesterification reaction mixture and secondarily by the residual polyesterification catalyst. The degree of conversion of already crosslinked polyesters is greatly increased by post‐curing them at elevated temperature and for a prolonged time. © 2002 Society of Chemical Industry     

Concave reagents. 31. A Merrifield bound concave pyridine for the selective acylation of polyols

The concave pyridine 2a has been synthesized in 61% yield in two macrocyclization steps. After deprotection to give 2b , the concave pyridine has been attached to a Merrifield resin, and the resulting polymer 10 containing 0.3 mmol 2 /g has been used as a selective acylation catalyst for the addition of propane‐1,2‐diol ( 11 ) and the glucose derivative 14a to diphenylketene ( 12 ) to form selectively 2‐hydroxypropyl diphenylacetate ( 13a ) (selectivity 13a / 13b : 11:1) and methyl 4,6‐0‐benzylidene‐2‐diphenylacetyl‐α‐D‐gluco‐pyranoside ( 14b ), (selectivity 14b / 13c : 29:1), respectively. After successful applications in batch reactions, the selective addition of 11 to 12 has also been carried out in a flow reactor filled with the polymeric catalyst 10 .     

固体超强酸SO_4~(2-)/Fe_2O_3催化合成丙酸丙酯

利用制备的固体超强酸SO2-4/Fe2O3代替浓硫酸作催化剂,将正丙酸和正丙醇酯化合成丙酸丙酯,讨论了催化剂的制备及合成丙酸丙酯的条件。实验表明:固体超强酸不仅能减少对生产设备的腐蚀,而且具有很好的催化活性,当催化剂用量为1.0g(正丙酸为0.1mol),醇酸摩尔比为2.5∶1,回流反应3h时,酯收率可达97.2%。     

Melt‐processable and self‐healing poly(vinyl alcohol) elastomer containing diol groups in the side chain

A 3‐amino‐1,2‐propane diol functionalized poly(vinyl alcohol) elastomer (PVA–COO–AP) with melt processability and self‐healing properties was prepared by chemical graft modification, that is, a poly(vinyl alcohol) (PVA) carboxylation and carbodiimide reaction. Unlike that of conventional PVA modifiers, the incorporation of diol groups in the 3‐amino‐1,2‐propane diol molecules onto PVA chains reduced the breaking of intrinsic hydrogen‐bonding interactions of PVA because of the formation of new hydrogen bonds between the diol groups and the hydroxyl groups of PVA. PVA–COO–AP possessed a lower melting temperature and a higher decomposition temperature than PVA; this enabled the melt processing of PVA. The PVA–COO–AP samples prepared by compression molding exhibited excellent flexibility and elasticity, and the samples with a lower glass‐transition temperature below ambient temperature could be self‐healed because of the existence of dynamic hydrogen bonds. AP–COO–AP is believed to have potential applications in the fields of fibers and biomedical membranes. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46050.     

Polybutadiene/polyhedral oligomeric silsesquioxane nanohybrid: investigation of various reactants in polyesterification reaction

Nano‐sized polyhedral oligomeric silsesquioxane (POSS) diol or ethylene glycol (EG) as diol monomer was incorporated into hydroxyl‐terminated polybutadiene (HTPBD) chain in the presence of fumaryl or thionyl chloride as extenders. Using these polyesterification reactions, two fumarate‐based polyesters and two polyester sulfites were synthesized. Each couple of polyesters and polyester sulfites includes a linear (diol:EG) and a nanohybrid macromer (diol:POSS). Full structural characterization was performed using Fourier transform infrared, ¹H NMR and ¹³C NMR spectroscopies. Gel permeation chromatography was undertaken to study polyesterification mechanisms by deconvolution of the obtained traces. Finally, differential scanning calorimetry, thermogravimetric analysis and cell culture were performed to evaluate the structure–property relationship for the synthesized macromers in comparison with unreacted HTPBD. © 2016 Society of Chemical Industry     

C_(36)二聚脂肪酸/聚乙二醇聚酯的制备及动力学研究

以C36二聚脂肪酸和聚乙二醇400为原料,缩聚得到一种新型高分子表面活性剂,适宜的工艺条件:在0.097 MPa下,n(二聚脂肪酸)∶n(聚乙二醇400)为1∶1.2,催化剂SnCl2(相对二聚脂肪酸质量分数为0.3%,反应温度200℃,反应时间6 h,酯化率达到98.11%。建立了SnCl2催化下,二聚脂肪酸与聚乙二醇缩聚反应的动力学模型,并采用改进的遗传算法,对动力学模型参数进行估算。结果显示,二聚脂肪酸与聚乙二醇400缩聚反应级数为0.998级,酯化反应活化能E=97.18 kJ/mol,指前因子A=1.947 9×109L/(mol.min),缩聚反应的Arrhenius方程为lnk=21.39-11.689/T。     

Synthesis and Kinetic Studies on Dimer Fatty Acid/Polyethylene Glycol Polyester

Dimer fatty acid polyethylene glycol polyester, a new kind of non-ionic polymeric surfactant, was synthesized by using dimer fatty acid and polyethylene glycol (400) as materials in this paper. The optimum reaction conditions of esterification were as follows: the molar ratio of dimer fatty acid (DFA)/PEG (400) is 1 / 1.20, the preferable catalyst is stannous chloride and the amount is 0.3% (w/w) of the mass of DFA, reaction temperature is 200°C, reaction time is 6 h. The conversion ratio of polyesterification can reach 98.11%. A new kinetic model of polyesterification reaction catalyzed with stannous chloride was presented. The Genetic Algorithms and Runge–Kutta were used to estimate the parameters of the kinetic model. The results of experiments and computer operations indicated that the reaction order is 0.998 to the carboxyl and 1 order to the hydroxyl. The activation energy obtained from Arrhenius plot is 97.18 kJ mol⁻¹, and the pre-exponential frequency factor is lnA = 21.39 kg² mol⁻² min⁻¹ at temperature range of 160 ∼ 190°C.