PET低聚物有机溶剂溶解性能的探讨

通过高分子稀溶液法实验得到PET低聚物的溶解度参数大概在9.8左右,根据溶解度参数相近以及相似相溶原则,测试了低聚物在各种有机溶剂中的特性黏度及溶解性能。结果表明:四氢呋喃、二甲亚砜、吡啶等是PET低聚物的良溶剂,也可用溶解度参数不同的溶剂配合使用作为PET低聚物的良溶剂,如苯酚/四氯乙烷等,综合考虑溶剂的挥发性能,实际生产中可以使用四氢呋喃作为PET低聚物的去除剂。     

PET中环状低聚物的表征及控制方法的研究进展

鉴于环状低聚物的诸多危害,归纳了PET中环状低聚物的表征方法,具体介绍了低聚物的分离方法及其性能的研究方法,重点总结了目前减少环状低聚物含量的一些新的措施和方法,以期为今后的相关研究提供参考,并提出应该建立工业上简便易行的环状低聚物含量检测方法。     

用超临界CO_2技术进行聚合物(PET)纯化和改质

正产品和技术简介:聚合物生产过程中常含有少量低聚物和反应杂质。它们的存在往往影响到聚合物产品的性能(如存在异味、高温下易变色等)。以PET生产为例,固相缩聚合前有70×10-6的AA和约1.5×10-6的低聚物产生。另外,在固相缩聚合后会因少量催化剂的存在而影响产品性能的稳定性。因此在生产过程中要求将这部分杂质或残留物去除,以提高产品质量。本课题利用超临界CO2能够使聚合物溶胀的特性,添加适当的共溶剂,能够溶解其中的低聚物等杂质。经由萃取将其中的杂质分离,实现聚合物的纯化。     

PET切片低聚物的萃取工艺及其表征

采用索氏萃取法从PET切片中提取低聚物,考察了切片尺寸、萃取时间与萃取量的关系;运用分子质量分布、紫外光谱、红外光谱、DSC进行了表征。结果表明：采用氯仿做萃取剂,80℃下连续回流提取18h可作为常规PET切片低聚物萃取终点的定量方法;提取出的低聚物是混合物,其主要成分为环状三聚物;环状低聚物在PET熔融结晶过程中起到了结晶成核剂的作用。     

PET膜用UV固化涂料的配制及涂层性能研究

以聚氨酯甲基丙烯酸酯(PUA)为主体,进行了PET膜用UV固化涂料配制及涂层性能研究。对PUA低聚物进行了筛选,探讨了低聚物结构对涂层附着力、硬度、柔韧性等性能的影响,以及活性稀释剂、光引发剂的种类、配比、用量等因素对涂层性能的影响。获得了较适宜的PET膜用UV固化涂料配方:低聚物采用5#树脂,其用量为总量的48.0%;活性稀释剂组成为m(TMPTA)∶m(TPGDA)=1∶1,其用量为总量的48.0%;光引发剂组成为m(Darocur1173)∶m(Irgacure 184)=2∶1,其用量为总量的3.2%。经测试,制得的涂膜附着力达100%,硬度3H,柔韧性2 mm,耐酒精擦拭大于150次,可满足PET保护膜硬化处理应用要求。     

聚酯纤维染整加工中低聚物问题的研究

PET和PTT纤维中低聚物对染整加工有较大影响。实验结果表明:纤维表面低聚物的浓度与吸光度呈线性关系;高温热定型和高温高压染色,有利于低聚物从纤维内部向外部扩散;聚氧乙烯酯链化合物对除去纤维表面的低聚物效果显著;超声波/碱处理可完全除去纤维表面低聚物。染色结果证明:PET和PTT在除去低聚物后的上染率、表观颜色深度有明显提高。     

水性聚氨酯在PET薄膜上附着力影响因素的探究

采用不同分子结构的低聚物二醇和二异氰酸酯为原料制备了一系列水性聚氨酯(WPU)树脂,对比分析了低聚物二醇、异氰酸酯和扩链剂种类对WPU在PET薄膜上附着力的影响;同时也探讨了低聚物二醇分子量、异氰酸酯指数(R值)以及交联剂用量对其在PET薄膜上附着力的影响.结果表明:采用间苯二甲酸聚酯二醇(PIA)、甲苯二异氰酸酯(T...     

N-乙基乙二胺与乙二胺体系萃取精馏溶剂选择

基于改进的UNIFAC模型,以MATLAB语言开发了萃取精馏过程相对挥发度的计算程序。依据萃取精馏溶剂选择的基本原则、溶解性能评价、相对挥发度比较和溶剂再生性能等,对乙二胺和N-乙基乙二胺共沸体系萃取精馏溶剂进行筛选。研究结果表明:较为合适的萃取精馏溶剂为丙三醇和乙二醇,其中丙三醇更好,此时N-乙基乙二胺成为易挥发组分;溶剂比是重要的影响因素之一,溶剂比越大,被分离体系的相对挥发度越大,且溶剂比的影响主要集中在溶剂比15以下;原料组成对相对挥发度的影响较弱。     

不同溶剂在无火香薰液中的挥发性能研究

为了探究不同溶剂在无火香薰液中的挥发性能,通过跟踪使用过程中样品的重量变化、气相色谱定量的组分变化以及感观香气变化,研究了不同溶剂、复配溶剂等多种体系样品随使用时间挥发性能的变化,结果表明：单一溶剂在恒温恒湿条件下,每日挥发量为定值,且挥发棒是促进溶剂挥发的重要因素;不同溶剂复配会引起产品使用挥发过程中组分比例的变化,比例变化大小与不同溶剂的挥发性、极性,溶剂间的分子作用力等有关;特定比例下,乙醇或异构烷烃与其他醇醚类溶剂复配时,会促进醇醚类溶剂挥发;醇醚类溶剂复配后可能存在共沸现象,导致比例变化极小,每日挥发量恒定;异构烷烃类溶剂性质相似,可能存在分子作用力,复配后每日挥发量低于理论值。挥发前后组分变化大的双组分溶剂体系会造成前后香气的不一致,从而影响消费者感观体验。     

木器漆用溶剂(续二)

５３硝基纤维素涂料溶剂的挥发速率在设计硝基纤维素涂料溶剂配方时，一定要保证溶剂挥发速率的平衡。只有这样才能给涂料流动创造更好的条件，保证涂料性能更好地发挥。所谓溶剂挥发平衡，就是保证涂膜在干燥过程中，真溶剂和稀释剂的比例保持平衡，绝对不能在涂膜干燥...     

正丙醇-水-复合溶剂体系等压汽液平衡研究

采用新型双循环沸点仪,测定了100 kPa下正丙醇-水-复合溶剂体系的等压汽液平衡数据。实验结果表明:乙二醇与醋酸钾组成的复合溶剂可消除正丙醇-水的共沸点,并显著提高正丙醇-水的相对挥发度;随着复合溶剂质量分数的增加,正丙醇对水的相对挥发度增大;此复合溶剂可作为萃取精馏正丙醇-水体系的溶剂,适宜的质量分数约为60%。用有序双液(NRTL)方程对实验数据进行了关联,关联结果良好,温度标准偏差为0.45 K,气相组成标准偏差为0.008 7。     

Guidelines for dryer design based on results from non‐Fickian model

In polymer solution coatings below the glass transition temperature of the pure polymer, the coating can go undergo a glass transition and develop stresses during drying. When stresses develop, a non‐Fickian model accurately describes solvent mass transport in drying polymer coatings. The non‐Fickian model includes the solvent transport due to both stress and concentration gradients. This article presents a non‐Fickian model, which predicts a lower residual solvent than does the corresponding Fickian model. We showed in an earlier article that the non‐Fickian model predicts trapping skinning (higher residual solvent under more intense operating conditions) at higher drying gas‐flow rates. In this article, the non‐Fickian model was used to investigate how the gas‐flow rate, dry film thickness, and substrate thickness affect the residual solvent for a single‐zone dryer. This work recommends guidelines for choosing gas‐flow rates, gas temperatures, and substrate thickness to minimize the residual solvent. The model predictions show that, at any gas temperature, the residual solvent is minimum at an intermediate gas‐flow rate. The trapping skinning effect is less evident in thicker coatings and substrates. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 477–486, 2003     

纸张表面墨膜蒸发与渗透干燥的耦合建模

油墨干燥速率是影响印品质量的关键因素之一,干燥通常是油墨溶剂渗透和蒸发共同作用的结果。文中建立了考虑纸张和油墨内部导热、油墨内固体骨架等复杂因素的一维油墨干燥模型。渗透部分基于毛细管束模型,引入了蒸发对油墨黏度的影响;蒸发部分引入了油墨溶剂相分数的概念,分析了各界面处应满足的边界条件,实现了渗透和蒸发的耦合计算。模型揭示了孔隙率对蒸发速率的影响、对流换热系数对渗透速率的影响,能很好地再现实验数据。     

利用互溶溶剂交替浸取强化植物提取过程

利用互溶溶剂交替浸取的方法,在室温下对中药大黄进行了浸取实验。实验结果显示,利用水和乙醇对大黄进行交替浸取能够极大的提高提取速率。水和乙醇的浸泡能够可逆的改变大黄颗粒的尺度和微观结构,经过水浸润的大黄颗粒体积增大,且颗粒表面呈现明显的多孔状结构。在使用互溶溶剂进行交替浸取时,微尺度上溶液组成分布的不均会引起局部湍流,从而极大的加强传质过程。     

水复合溶剂体系茴脑臭氧化反应合成茴香醛新工艺

以茴脑为原料,有机溶剂与水复合溶剂为溶剂,室温下通过臭氧化分解反应制取茴香醛,并通过GC-MS、FT-IR和1H-NMR对产品进行了表征.对该溶剂体系与传统溶剂体系下茴香醛的产率进行了对比,并确定了丙酮/水体系为最佳溶剂体系.实验详细考察了溶剂用量、臭氧气流量、混合溶剂中水含量和反应时间等工艺参数.优化的工艺条件为:丙酮和水为溶剂,m(茴脑)∶m(混合溶剂)=1∶3,臭氧气流量0.06 m3·h-1,混合溶剂中水的质量含量为15％,反应时间100 min,茴香醛产率82.70％.该反应在水的存在下实现了室温下一步法合成茴香醛,避免了茴脑臭氧化物的分离及还原步骤,工艺简单,洁净环保.     

Liquefaction of sawdust for liquid fuel

Pressurized liquefaction of sawdust was carried out in an autoclave in the presence of solvent under cold hydrogen pressure ranging from 2.0 to 5.5 MPa at the temperature range of 150C–450°C. The reaction time varied from 5 to 30 min. Investigations were made on the effects of temperature, reaction time, cold hydrogen pressure and solvent on the liquefaction process. Results indicate that liquefaction of sawdust can start at a temperature of 200°C, much lower than that for coal in a hydrogen-donor solvent, e.g., tetralin which was used in this run of experiment. Oil yield increase with the rise either in temperature and in cold hydrogen pressure or with the longer reaction time.     

Effects of thermodynamic models on the predictions of free volume diffusion theory for concentrated polymer solutions

Three thermodynamic models were used to demonstrate the effects of model choice on solvent–polymer binary diffusion coefficients predicted by free volume theory. Poly(vinyl acetate) and four solvents were used as typical solutions for these calculations. Thermodynamic models affect the predictions the most at high solvent weight fractions and for solutions which exhibit positive enthalpic interactions. For solutions dilute in solvent where Henry's law might describe phase equilibria, diffusion coefficients can be estimated without reference to thermodynamic data.     

加盐DMF萃取精馏分离C4

<正>C4组分是由含有4个碳原子的丁烷、丁烯、丁二烯和炔烃等分子所组成的混合物。其中丁二烯是合成橡胶的重要单体,用途十分广泛。由于C4各组分之间的沸点很接近,用普通的精馏方法将丁二烯从中分离出来几乎是不可能的。 文献中报道的分离C4生产丁二烯最具竞争力的方法是萃取精馏法。萃取精馏最大的弱点是溶剂比大,大溶剂量降低了塔的生产能力和塔板效率,抵消了由于加入溶剂后提高相对挥发度使所需塔板数减少的效果。所以降低溶剂比,提高溶剂分离能力,对整个过程的技术经济指标有着重要的影响。目前常用的溶剂是:乙腈（ACN）、N-甲基砒咯烷酮（NMP）、二甲基甲酰胺（DMF）。其中ACN和NMP可以通过加入一定量的水来提高C4各组分之间的相对挥发度,而DMF由于强烈的水解作用,不能与水混用,因此,希望能够找到另一种物质对之进行改性,提高其选择性。     

Effect of interphase mixing on a water–organic solvent two-liquid phase microbial system: ethanol fermentation

Ethanol fermentation by Saccharomyces cerevisiae was investigated in broth-organic solvent two-liquid phase systems with and without interphase mixing. The effect of interphase mixing with aliphatic alcohols as polar solvents and with alkanes as apolar solvents was determined from investigations in three distinct systems: a solvent-saturated broth, a solvent-broth dispersion system and a dispersion-free solvent-broth system. Microbial activities, measured as a function of solvent volume and inoculum size, revealed that a dispersed polar solvent caused a longer growth lag time and a slower growth rate. Viability measurements showed that yeast cells were gradually killed in a dodecanol-water dispersion system and not in a dispersion-free one. This process was believed to be initiated and enhanced by cell adhesion to the solvent interface as observed under a microscope. Yeast activity was also measured as a function of an apolar solvent volume and inoculum size. A full fermentative activity was observed in an initially alkanesaturated broth unlike in an intermixed biphasic system. As a result of these investigations, it was concluded firstly that microbial activity in initially solvent-saturated broths with and without contact with a stagnant solvent phase can be different and secondly that the process efficiency of a biphasic bioreactor, unlike that of a chemical reactor, can be hampered by interphase mixing. The yeast activities in the presence of the various alcohols and alkanes were correlated with ‘log P’ values of the solvents. Full activity was observed at log P > 5 and almost none at log P < 4.     

Effects of Adsorbent Characteristics on Adiabatic Vacuum Swing Adsorption Processes for Solvent Vapor Recovery

The effects of the adsorbent characteristics on the performance parameters and periodic state behavior of the vacuum swing adsorption (VSA) solvent vapor recovery (SVR) processes are examined and optimized. The adsorbent characteristics studied were the adsorbent particle's porosity, density, radius and heat capacity, the packed bed void fraction, the isosteric heat of adsorption, the monolayer saturation limit of the solvent molecules on the adsorbent, the adsorbent's affinity to adsorb the solvent molecules and the mass transfer coefficient for the adsorption of the solvent molecules. It was found that the best VSA‐SVR process performances can be obtained using adsorbents characterized by the minimum possible packed bed void fraction and particle porosity, with the maximum possible adsorbent heat capacity and density, adsorption monolayer saturation capacity and mass transfer coefficient, and at intermediate adsorption affinity and isosteric heat of adsorption of the solvent molecules.