PET固相缩聚设备的改造

介绍了PET固相缩聚的工艺流程。详述了固相缩聚主要设备如结晶器、固相缩聚塔的结构、工作原理、运行中故障及改造方法。通过改造使安装更加方便,运行可靠,保证连续固相缩聚生产顺利进行。     

PET固相缩聚工艺技术分析

综述了聚酯(PET)固相缩聚过程特点,重点对比分析了Bepex、Buhler、Sinco及Dupont的NG3连续固相缩聚工艺、关键设备构型及主要操作参数。PET固相缩聚过程中结晶增长与缩聚反应共存并互相耦合,因而结晶工序是固相缩聚工艺的重要组成部分,也是各工艺专利商的专利技术之所在。有效的结晶增长、结晶形态与缩聚反应的解耦合是强化固相缩聚技术的科学基础。     

固相缩聚对半芳香族聚酰胺树脂结构和性能的影响

为了研究固相缩聚对半芳香族聚酰胺可纺性能的影响,为半芳香族聚酰胺的纺丝成型提供理论基础,研究了固相缩聚时间对半芳香族聚酰胺树脂的特性黏数、流变行为、结晶性能和热稳定性的影响。结果表明,固相缩聚时间增加,树脂的特性黏数增加;固相缩聚时间增加到一定程度,树脂的特性黏数略有减低。半芳香族聚酰胺的熔体为假塑性流体,固相缩聚使得熔体的非牛顿指数n及熔体黏度对温度的敏感性增大;固相缩聚使得树脂的玻璃化转变温度、熔融温度和结晶度有小幅度增加,但长支链的存在反而使之降低;固相缩聚时间对树脂的热稳定性的影响也呈现相同的趋势。     

固相缩聚对聚酯切片热性能和结晶行为的影响

用差示扫描量热仪(DSC) 和热重分析仪分别对普通聚酯切片和通过固相缩聚增黏的聚酯切片进行了热性能和结晶行为的研究。结果表明,固相缩聚增黏的聚酯切片的DSC第一次升温曲线上观察不到结晶吸热峰,说明固相缩聚使聚酯相对分子质量增大的同时,也使其充分得到结晶;固相缩聚聚酯切片的熔点升高;此外,固相缩聚增黏聚酯切片的结晶度较低、结晶尺寸较小、结晶速率较小,而热稳定性优于普通聚酯切片。     

结晶态双酚A型聚碳酸酯固相缩聚的研究

在自制的反应器中将结晶态、无定形两种双酚A型聚碳酸酯(BAPC)预聚体固相缩聚合成了高摩尔质量的双酚A型聚碳酸酯.采用DSC、IR对双酚A型聚碳酸酯(BAPC)的熔融行为和结构进行了表征.结果表明,BAPC在固相缩聚后,玻璃化转变温度升高,热稳定性增强,其中BAPC为结晶态时固相缩聚的温度低于无定形态BAPC的固相缩聚温度,且结晶态BAPC固相缩聚后为无定形态.     

十四烷辅助下聚酯的固相缩聚

在200～240℃研究了聚对苯二甲酸乙二醇酯(PET)在十四烷辅助下的固相缩聚反应.结果表明,溶剂辅助下的固相缩聚(分散相固相缩聚)的反应速度较传统气相环境中的固相缩聚更快,最佳反应温度为230℃左右.随着反应温度的升高,分散相固相缩聚得到的PET切片的熔点和结晶度也相应提高.分散相固相缩聚前后PET切片的孔隙率并未发生明显变化.用苯酚处理之后的PET孔隙率增加,有利于小分子扩散,使缩聚反应速率加快.聚合物在十四烷中溶胀导致链活动性增强可能是分散相固相缩聚分子量提高的主要原因.     

不同PET切片固相缩聚主副反应规律研究(Ⅲ)

本文接近于工业生产的装置上对几种不同工艺生产的PET切片的固相缩聚进行了对比研究,指出在固相缩聚中,PET的链增长仍符合普通的二级反应动力学方程,且与文献报道一致。用直接酯化工艺生产的有光切片和半消光切片进行固相缩聚时,其动力学行为相似;用酯交换工艺生产的PET切片进行固相缩聚时,难以得到高分子量的产物;直接酯化中不同TPA/EG配比所得到的PET切片的固相缩聚动力学行为相似。实验还发现,在PET切片的固相缩聚中,羧端基含量有所下降,醚键含量基本不变。这些结果对于为满足不同用途而选择固相缩聚所用的PET切片具有重要意义。     

PET连续固相缩聚工艺及主要影响因素

介绍了大连合成纤维研究设计院自主研发的10 kt/a连续式固相缩聚技术的生产工艺。从切片形状、结晶度及结晶形态、缩聚前预热、缩聚时间、氮气的纯度及流量等方面,讨论了固相缩聚主要影响因素。     

PET固相缩聚反应动力学研究进展

目前多种固相缩聚反应动力学模型共存,影响了固相缩聚工艺优化及新工艺的开发。笔者从固相缩聚本征反应出发,对比分析了文献报道的动力学模型：经验模型、反应控制模型、扩散控制模型及反应与扩散共同控制模型及所涉及的反应及活化能,指出固相缩聚过程中扩散与结晶的研究不足是造成固相缩聚反应动力学模型多样性的主要原因。     

PBT固相缩聚工艺优化

介绍了PBT固相缩聚的工艺流程和基本原理,对PBT固相缩聚装置存在的生产周期长、黏度偏差大、粉尘含量高等问题进行了分析,并提出相应的整改措施,将PBT固相缩聚生产周期缩短8 h,产品黏度偏差稳定在±0.015 dL/g范围内,粉尘含量有效降低。     

Microbial degradation of polyesters: Polycaprolactone degraded by P. pullulans

Polycaprolactone is degraded by the mold P. pullulans in the presence of other nutrients. The weight loss from solid polymer films covered by a nutrient agar gel on which colonies are growing is used to establish comparative rates of degradation. There is substantial loss (16 mg/cm² surface area) from a whole polymer of low (2,000) molecular weight in three weeks at 30°C. A high (30,000) molecular weight whole polymer degrades about 0.15 as much in the same time period. A fraction in the same range (38,000) but with a narrower molecular weight distribution shows no significant loss. This indicates that whole polymers of high molecular weight may lose only a portion of their distribution by microbial degradation in short-term tests. This hypothesis is tested by making mixtures of high (61,000) molecular weight with low (2,000) molecular weight polymer. Degradation is directly proportional to the low molecular weight content in these short-term tests with a single species of mold. Other workers have shown previously that in long-term, soil-burial tests, even a high (40,000) molecular weight polycaprolactone is essentially completely degraded after one year.     

Synthesis and characterisation of telechelic poly(2,6-dimethyl-1,4-phenylene ether) for copolymerisation

Telechelic poly(2,6-dimethyl-1,4-phenylene ether) (PPE) segments are interesting starting materials, for example for copolymerisation. A good method to make partly bifunctional PPE-2OH is by redistribution or depolymerisation of high molecular weight commercial PPE with tetramethyl bisphenol A. The product has a bimodal molecular weight distribution because only ∼70-80% of high molecular weight starting material is depolymerised. The phenolic endgroups can be modified easily by a fast and complete reaction with methyl chlorocarbonyl benzoate. The product after endgroup modification is called PPE-2T and has two terephthalic methyl ester endgroups and a molecular weight of 2000-4000 g/mol. The functionality of these PPE-2T products is around 1.8. The bimodal PPE-2OH and PPE-2T products can be separated in a high and low molecular weight fraction by selective precipitation. The low molecular weight fraction has a narrow molecular weight distribution with a polydispersity between 1.2 and 1.5.     

Fiber growth in tubular flow

Data are presented for the seeded growth of polyethylene fibers from solutions undergoing laminar flow in tubular geometry. Radial growth rates are reported for solutions of high and low molecular weight fractions for the second stage fiber thickening process which occurs in the tube entrance region. Results are also shown for high molecular weight growth from fiberglass seeds which indicate an enhanced growth rate at elevated temperatures. A two-stage growth pattern documented earlier for the high molecular weight fraction is shown to occur for the lower molecular weight material. The Discussion includes an analysis for the tapered fiber geometry in the second stage of growth and calculations for stress-induced, diffusion-limited growth in the first stage downstream from the tube entrance.     

超高分子量聚乙烯现状与展望

介绍了超高分子量聚乙烯目前国内外生产及市场情况，展望了其发展前景。     

Kinetic model for short-cycle bulk styrene polymerization through bifunctional initiators

A model describing the kinetics of bulk styrene polymerization through bifunctional initiators has been developed. The diffusion-controlled propagation and termination reactions at high monomer conversions are modeled with the free volume theory for polymer solutions. Three different commercially available bifunctional initiators were experimentally evaluated for a wide range of polymerization conditions to study the effect of the reaction rate on the molecular weight and molecular weight distribution. The model predictions for the same polymerization conditions show excellent agreement with the experimental data, for the whole range of conversions, for both reaction rate and molecular weight distribution development, under all the conditions tested. It is demonstrated throughout this study that high molecular weights, very high reaction rates, and narrow molecular weight distributions can be achieved simultaneously by using bifunctional initiators. A comparison between monofunctionally initiated systems with the bifunctionally initiated ones shows that short-cycle reactions with reductions in polymerization time of up to 75% may be achieved with the bifunctional initiators for a wider range of conditions without significantly affecting the molecular weight and molecular weight distribution of the final product.     

Synergistic effects of crosslinking and chitosan molecular weight on the microstructure,molecular mobility,thermal and sorption properties of porous chitosan/gelatin/hyaluronic acid scaffolds

In this study, synergistic effects of crosslinking and chitosan molecular weight on the microstructure, molecular mobility, thermal, and sorption properties of porous chitosan/gelatin/hyaluronic acid hybrid foams are reported. Fourier transform infrared spectroscopy has been utilized to confirm the covalent attachment of hyaluronic acid to gelatin and chitosan, and covalent chemical crosslinking between gelatin and chitosan. Detailed image analysis of scanning electron microscopy images of the porous scaffold hydrids reveal that the pore size of the materials formulated using either low‐ or high‐molecular‐weight chitosan increases significantly upon crosslinking using ethyl(dimethylaminopropyl) carbodiimide/N‐Hydroxysuccinimide. These microstructural changes are even more pronounced for the crosslinked hybrid scaffolds formulated using low‐molecular‐weight chitosan, highlighting a synergistic effect between crosslinking and the use of low‐molecular‐weight chitosan. Results obtained using differential scanning calorimetry demonstrate a significant reduction in molecular mobility reduction in molecular mobility for crosslinked scaffolds formed using high‐molecular‐weight chitosan compared to non‐crosslinked hybrids and crosslinked hybrids formulated using low‐molecular‐weight chitosan. Correspondingly, dynamic vapor sorption evidenced significantly lower water vapor sorption for crosslinked scaffolds formulated using high‐molecular‐weight chitosan. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44772.     

Fractionation of Linear Polyethylene with Gel Permeation Chromatography. Part III

Abstract

Many commercial linear polyethylenes have very broad distributions of molecular weight. The high molecular weight fractions often extend beyond the highest molecular weight calibration standard of GPC. For this reason the reliability of information obtainable from GPC has been examined with attention to the average molecular weights. Calibration range is a serious limitation for the accurate determination of the - weight-average and the higher averages of molecular weight. Uncertainty in the baseline at the high molecular weight region, however, does not produce a significant error. With a four-column GPC having 10³ to 10⁷ A nominal capacity, improved resolution is needed in the high molecular weight range. In order to examine the resolution and to improve the calibration, a polyethylene standard of ca. 3–4 million molecular weight is required. With the present limitation of GPC the greatest amount of information can be obtained by examining and intercomparing the cumulative distribution curves. With this representation ca. 95% or more of the cumulative weight range is free from uncertainty in calibration and resolution. A question is raised as to whether melt index is precisely a function of the weight-average molecular weight. This question is pertinent when significantly different molecular weight distributions are involved. GPC offers an opportunity to resolve the question.     

Optimizing polymer reactivities for the solid-state polycondensation of AA and BB type monomers

A new method is presented to optimize the reactivities of a prepolymer for the solid-state polymerization of AA and BB type monomers to obtain high molecular weight polymers. The proposed method consists of blending the prepolymers of different end group mole ratios to maintain optimal reaction stoichiometry, and developing a computational procedure to calculate the molecular weight of the polymer in the solid-state polymerization. A molecular species model is used to calculate the molecular weight moments of the optimized prepolymer and to calculate the molecular weight development in a solid-state polymerization. The molecular weight moments of different polymer species in the prepolymer mixture are estimated by performing the dynamic simulations of a melt prepolymerization process model in conjunction with a numerical optimizer. The model simulation results show that the proposed method offers a significantly improved process performance to obtain high molecular weight condensation polymers in a solid-state polymerization. Bisphenol A polycarbonate is selected as an example to illustrate the proposed method.     

芳纶1414纺丝过程中聚合体的相对分子质量变化及其控制

芳纶1414是一种高强、高模、耐高温的高性能纤维。聚合体的相对分子质量对纤维的强度有很大的影响。在纺丝过程中,影响聚合体PPTA相对分子质量的因素有很多。在500t/a规模芳纶1414生产线上系统研究了硫酸浓度、溶解温度、溶解方式以及纺程中其它影响PPTA分子质量的因素,并提出合理的控制措施,为1000t/a规模生产线奠定一定的数据基础。     

Interactions in compatible polymer systems

Summary Dynamic mechanical measurements on polystyrene — poly(vinylmethylether) blends are demonstrating that the relaxation processes in the blends are mainly connected with the motions of the poly(vinylmethylether) chain.Concerning the effect of mixing on topological properties of the blends, an increase of the polydispersity of the relaxation processes is detected in blends with high molecular weight polystyrene while low molecular weight polystyrene exerts an effect of dilution upon the relaxation of the high molecular poly(vinylmethylether) chains.From these measurements as well as from thermoanalytical data it results that the energetic interaction is more pronounced in the blends with oligomeric than with high molecular weight polystyrene. The glass transition temperature shows a larger deviation from additivity for blends with high molecular polystyrene than for those with oligomeric polystyrene.Herrn Prof. Dr. M. Kryszewski zum 60. Geburtstag herzlichst gewidmet