Solid state polymerization in a micro‐reactor: The case of poly(tetramethylene terephthalamide)

The aim of this work was to develop and optimize a direct solid state polymerization (DSSP) process on a micro scale for alkyldiammonium‐terephthalate salts. This was successfully demonstrated for the first time by the case of tetramethylenediammonium‐terepththalate salt (4T salt). The derived polymer (PA4T) presents interesting properties, but the temperature‐favored acid catalyzed cyclization of tetramethylenediamine (TMD) to mono‐functional pyrrolidine and ammonia inhibits a high polymerization conversion. DSSP was performed in a thermogravimetrical analysis (TGA) chamber, and the continuously monitored weight loss was correlated to polymerization conversion via the release of water, excluding any mass and heat transfer limitations. It was found that the conditions under which the DSSP is performed and the morphology of the starting material affect both the reaction rate and the product quality. The effect of the critical process parameters, namely vent size, heating rate to reach SSP temperature, and reaction temperature were quantified by the observed mass loss and by ¹H NMR analysis. It was noticed that, besides the water formed by amidation, other volatile compounds were also released during the DSSP reaction, with main component, the TMD. In particular, it was observed that conditions favoring the evaporation of TMD also favored a higher reaction rate. The TMD loss was minimized by optimization of the aforementioned process conditions, leading to a more thermally stable and a higher molecular weight final product. The thermal stability of the PA4T was found to be inversely correlated to the concentration of carboxylic end groups present in the formed polymer. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43271.     

半芳香尼龙PA12T的微波辅助聚合与表征

半芳香尼龙具有优异的力学强度、耐热性能和耐溶剂性能,在电子电器、汽车、轨道交通、特种装备中具有重要应用,受到了国内外学者和产业界的广泛关注。然而,传统聚合方法存在的制备周期长、分子量分布宽等技术难题长期得不到有效解决。本文利用微波能够使吸波材料快速、均匀升温的特点,首次在微波辅助条件下制备了耐高温半芳香尼龙PA12T,研究了在密闭条件下,以水作为吸波介质,水的用量、反应温度以及反应时间等条件对聚合产物特性黏数的影响,并对产物结构及热性能进行了表征。结果表明,微波辅助聚合与传统聚合方法相比,反应时间缩短三分之一以上,且产物分子量分布较窄,为解决传统半芳香尼龙聚合方法存在的问题进行了有价值的探索。     

生物法制造丁二酸研究进展

丁二酸因其C₄分子结构在化工领域的潜在价值，被认为是一种具有广阔应用前景的生物基平台化合物。结合生物基丁二酸的产业现状，综合分析了丁二酸生产菌种及菌株改造、生物过程优化和丁二酸分离纯化这三个方面的研究现状。重点介绍以大肠杆菌、产琥珀酸放线杆菌、解脂耶氏酵母为代表的主要生产菌株及其改造策略；低值生物质利用及控制发酵过程中CO₂ 供给和pH 调节等生物过程优化策略；包括钙盐法、电渗析法、直接分离法等方法在内的丁二酸分离工艺。同时指出未来的研究重点将综合考虑经济性与能耗问题，将菌株与发酵和分离全过程整合，提高丁二酸产量，降低发酵及分离成本，进一步拓展生物基丁二酸市场应用领域。     

过硫酸铵引发丙烯腈／衣康酸铵的共聚合工艺研究

选择衣康酸铵[(NH4)2IA)]作为共聚单体,以过硫酸铵[(NH4)2S2O8]为引发剂,采用水相沉淀聚合工艺合成高分子质量的丙烯腈／衣康酸镀[AN／(NH4)2IA)]共聚物。研究了引发剂浓度、单体浓度、单体配比、聚合温度和聚合时间对共聚反应的影响。结果表明:该体系的聚合反应速率较快,且制得了粘均分子质量高达(38-75)×104的AN／(NH4)2IA共聚物。     

ICAR ATRP of methyl methacrylate catalyzed by FeCl3·6H2O/succinic acid

In this work, methyl methacrylate (MMA) was polymerized by initiator for continuous activator regeneration (ICAR) atom transfer radical polymerization (ATRP) method to obtain low molecular weight living polymers. The ATRP initiator was ethyl 2‐bromoisobutyrate, the catalyst ligand complex system was FeCl₃·6H₂O/succinic acid, and the conventional radical initiator 2,2′‐azobisisobutyronitrile was used as a thermal radical initiator. Polymers with controlled molecular weight were obtained with ppm level of Fe catalyst complex at 90°C in N,N‐dimethylformamide. The polymer was characterized by nuclear magnetic resonance (NMR). The molecular weight and molecular weight distribution of the obtained poly (methyl methacrylate) were measured by gel permeation chromatography method. The kinetics results indicated that ICAR ATRP of MMA was a “living”/controlled polymerization, corresponding to a linear increase of molecular weights with the increasing of monomer conversion and a relatively narrow polydispersities index. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

溶液聚合法合成聚乳酸

研究了以L-乳酸为单体,以二苯醚和十氢萘为溶剂,用溶液聚合法合成聚乳酸。采用逐步减压、逐渐升温的工艺路线,二苯醚做溶剂,所得产物相对分子质量较高。探讨了反应过程中原料的干燥预处理、溶剂、反应时间、反应温度等因素对聚合产物相对分子质量的影响。结果表明,最佳的反应条件为:乳酸／二苯醚体积比2／3,氯化亚锡为催化剂,催化剂的质量分数0．5％(相对单体),在160℃下反应24 h。     

New kinetic model for polymerization process of nylon 66 salt solution based on functional group non-isoactivity

The polymerization process of nylon 66 salt solution is a dynamically controlled process. Based on the assumption of unequal activity of functional carboxyl and amido groups, a new nylon 66 salt solution polymerization kinetic model was established by introducing the nylon salt dehydration reaction to the acid-catalyzed third-order reaction kinetic model and fitted to obtain the corresponding key kinetic parameters. The fitted salt dehydration reaction rate constant was 8.17×10^-3 kg?mol^-1?h^-1, while the activation energy was 19859 cal?mol^-1, respectively. Compared with Mallon model, the new developed model has a better fitting effect and can accurately predict the change of the polymerization process in a wider range of temperature and water content. Simulation results showed that salt dehydration reaction has an important effect on the polymerization process and the polymerization efficiency was relatively lower with higher concentration of nylon salt, especially under low temperature and high water content. Appropriately increase the reaction temperature or reduce the initial water content can accelerate the nylon salt dehydration reaction, thereby increasing the polymerization reaction efficiency. New nylon salt polymerization kinetics modeling method is not only applicable to nylon 66, but also to nylon 1212 and other salt solution polymerization systems.     

基于官能团非等活性假设的尼龙66盐溶液聚合动力学模型

尼龙66盐溶液聚合过程属于动力学控制过程。基于官能团非等活性假设，在Mallon酸催化3阶反应动力学模型基础上，引入尼龙盐脱水反应，建立了新的尼龙66盐溶液聚合反应动力学模型，拟合得到了关键反应动力学模型参数，其中盐脱水反应速率常数为8.17×10^-3 kg?mol^-1?h^-1、活化能为19859 cal?mol^-1。与Mallon模型相比，新模型拟合效果更优，可在更宽的温度和水含量范围内准确预测聚合过程的变化。模拟仿真发现，盐脱水反应对聚合过程有重要影响，低温和高水含量下尼龙盐浓度高，聚合效率低；适当提高反应温度或降低初始水含量可以加快尼龙盐脱水反应，从而提高聚合反应效率。新的尼龙盐聚合动力学建模方法不仅适用于尼龙66，也可应用于尼龙1212等盐溶液聚合体系。     

尼龙6固相聚合模型及计算机模拟研究

根据尼龙6固相聚合反应机理,建立了由可逆化学反应和小分子扩散共间控制的尼龙6固相聚合动力学模型,并确定了其动力学和热力学参数。通过计算机模拟实验表明,聚合反应温度越高,预聚体尺寸越小,预聚体初始相对分子质量越高,越有利于固相增粘反应,有利于固相聚合尼龙6相对分子质量的增加。     

水溶性偶氮引发剂AIBA引发AN-MA-IA水相沉淀共聚合的研究

以含有亲水基团的偶氮二异丁脒盐酸盐（AIBA）为引发剂,以丙烯腈（AN）、丙烯酸甲酯（MA）和衣康酸（IA）为单体,β-巯基乙醇（β-ME）为分子量调节剂,采用水相沉淀聚合法制备了不同分子量的AN-MA-IA共聚物,研究了AIBA浓度、单体浓度和β-ME浓度对聚合过程的影响。根据AIBA分解半衰期和单体竞聚规律确定了聚合温度70℃和pH=4.7为较优反应条件。结果表明,AIBA浓度是影响聚合转化率的决定因素,通过调整AIBA浓度可以得到分子量60000~500000的PAN共聚物,较高的AIBA浓度会由于聚合场所的改变而造成分子量分散度小幅上升;浓度在0.2%（质量）以内时,分子量调节剂β-ME可以调控PAN共聚物的分子量,并使其分布变窄。     

Preparation of nanometer‐sized poly(methacrylic acid) particles in water‐in‐oil microemulsions

A water‐in‐oil microemulsion, water‐in‐cyclohexane stabilized by poly(ethylene glycol) tert‐octylphenyl, was developed to prepare poly(methacrylic acid) (PMAA) particles. Up to 100% conversion of the amphiphilic monomer, methacrylic acid (MAA), which could not be converted to the polymer efficiently in a dioctylsulfosuccinate sodium salt/toluene microemulsion, was achieved. The viscosity‐average molecular weight of the PMAA prepared was 1.45 × 10⁵ g/mol. The effects of some polymerization parameters, including the reaction temperature and the concentrations of the initiator and the monomer, on the polymerization of MAA were investigated. The results showed that the polymerization rate of MAA was slower than that of acrylamide in the microemulsions reported in the literature. The degree of conversion increased with the initiator concentration, reaction temperature, and monomer concentration. However, the stable microemulsions became turbid during the polymerization when the reaction temperature was at 70°C or at a high monomer concentration (40 wt %) The synthesized PMAA particles were spherical and had diameters in the range of ～50 nm. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2497–2503, 2006     

ATRP of acrylonitrile catalyzed by FeCl2/succinic acid under microwave irradiation

A single‐pot atom‐transfer radical polymerization (ATRP) under microwave irradiation was first used to successfully synthesize polyacrylonitrile. This was achieved by using FeCl₂/succinic acid as the catalyst and 2‐chloropropionitrile as the initiator. Using the same experimental conditions, the apparent rate constant under microwave irradiation was found to be higher than that under conventional heating. The FeCl₂/succinic acid ratio of 1 : 2 not only gives the best control of molecular weight and its distribution but also provides rather rapid reaction rate. When FeCl₂ was replaced with CuCl, ATRP of AN does not show an obvious living characteristics. To demonstrate the active nature of the polymer chain end, the polymers were used as macroinitiators to proceed the chain‐extension polymerization. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1598–1601, 2006     

Nylon 66, Nylon 46, and Pet Phase-Transfer-Catalyzed Alkaline Depolymerization at Atmospheric Pressure

The depolymerization of PET, nylon 66, and nylon 46 at high temperatures in an autoclave is well known in the patent literature. We sought to invent processes for the depolymerization of PET, nylon 66, and nylon 46 in alkaline solutions at low temperatures and atmospheric pressure. A method was developed for the depolymerization of polyethylene terephthalate (PET) which involved the use of quarternary ammonium salt phase-transfer catalysts in saponification processes at atmospheric pressure and temperatures as low as room temperature. Phenyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, trioctylmethylammonium chloride, and trioctylmethylammonium bromide were found to be effective catalysts for the depolymerization of PET in 5% aqueous sodium hydroxide solutions at temperatures as high as 80°C and atmospheric pressure to form terephthalic acid in yields as high as 93%. The catalyst could be recycled. The alkaline phase-transfer-catalysis approach was then successfully applied for the depolymerizations of nylon 66 and nylon 46. Benzyltrimethylammonium bromide was discovered to be an effective phase-transfer catalyst in 50 wt.% sodium hydroxide solution for the conversion of nylon 46 to oligomers. The collected nylon 46 oligomers were repolymerized using solid-state polymerization techniques to form high-molecular-weight nylon 46. Nylon 66 fibers were depolymerized in the presence of benzyltrimethylammonium bromide in 50% sodium hydroxide to form oligomers and a monomer. Adipic acid was isolated.     

聚合条件对P（AN-co—IA）分子质量分布影响的研究

采用凝胶色谱（GPC）法测定了丙烯腈与衣康酸共聚物P（AN—co—IA）的重均分子质量和数均分子质量,并通过已知聚丙烯腈的重均分子质量数据和数均分子质量数据对所测的分子质量进行校正,进一步计算得到共聚物的多分散系数。同时研究了引发剂用量、单体浓度、聚合温度、聚合时间对P（AN—co—IA）分子质量分布的影响。研究结果表明,P（AN-co-IA）分子质量分布随引发剂用量的增大、聚合单体浓度的增加而变宽,与聚合反应温度、聚合反应时间无明显的变化趋势。     

高摩尔质量PBS的合成工艺研究

用丁二酸、丁二醇为原料,以钛酸四丁酯为催化剂,采用直接酯化缩聚的方法合成了聚丁二酸丁二醇酯(PBS)。考察了醇酸比、催化剂用量、聚合温度对PBS的黏度及酸值的影响。实验获得最佳合成条件为:醇酸物质量之比1.3,催化剂质量分数为0.03%,并在酯化后加入,缩聚温度为230℃。用凝胶渗透色谱仪对聚合物的摩尔质量进行了表征,通过工艺优化可得到重均摩尔质量约为12万g/mol的PBS。     

尼龙6固相聚合建模与计算机仿真

在一定假设基础上建立了尼龙６固相聚合过程模，并用实验数据验证了模型的正确性，结果表明随着固相聚合时间的延长，数均聚合度Ｕｎ增加。     

Simulation of molecular weight distribution and cyclic oligomer formation in the polymerization of nylon 6

The reversible polymerization of nylon 6 including ring opening, polycondensation, polyaddition, and cyclization reactions as well as the reaction with monofunctional acids was simulated for an isothermal batch reactor at 235°C. The cyclic oligomer concentrations, the molecular weight distributions, and its moments have been computed using a chain length-dependent equilibrium constant for the cyclization reaction. Even though the cyclization step does not influence the monomer conversion considerably, it does effect the molecular weight distribution and its moments.     

乙丙橡胶新牌号的合成及应用

以乙烯、丙烯为主要原料、氢气为相对分子质量调节剂、改性三氯氧钒-倍半氯化乙基铝为催化剂,采用溶液聚合法进行高门尼粘度乙丙橡胶合成实验,研制了三元乙丙橡胶(EPDM)密封条。考察了催化剂及其用量、相对分子质量调节剂用量、n(Al)/n(V)、反应压力、温度等工艺条件对EPDM性能的影响。实验结果表明,合成的高门尼粘度乙丙橡胶新牌号各项指标满足目标样品要求;制备的EPDM密封条完全满足密封条生产厂家制造工艺要求。     

正交实验优化低分子质量聚丙烯酸钠合成工艺

采用水溶液聚合法,以丙烯酸为单体,过硫酸铵-亚硫酸氢钠为氧化还原引发体系,亚硫酸氢钠为链转移剂制得分子质量为3000～4000的聚丙烯酸钠。采用粘度法测得产物的黏均分子质量,对丙烯酸单体和聚丙烯酸钠聚合物的FTIR图谱进行了分析,通过正交实验研究了各因素对聚丙烯酸钠分子质量的影响趋势和程度。结果表明:影响最显著的因素为单体浓度,其次为反应温度,再次为引发剂用量,反应时间的影响最小。确定了最佳合成工艺条件:反应温度为45℃,反应时间为4h;丙烯酸单体质量分数为25%,引发剂过硫酸铵用量为单体质量的6%,链转移剂亚硫酸氢钠用量为单体质量的3%。FTIR谱图中不含碳碳双键,且有羧酸盐的特征峰出现,验证了聚合物的合成。该工艺节省能源,且制备方法简单,易于工业化生产。     

Synthesis of cationic flocculant by radiation-induced copolymerization of methyl chloride salt of N,N-dimethylaminoethyl methacrylate with acrylamide in aqueous solution

The radiation-induced copolymerization of the methyl chloride salt of N,N-dimethylaminoethyl methacrylate (DMAEM·MC) with acrylamide (AAm) was used to prepare a cationic polymer flocculant. The polymerization rate increased with increasing dose rate, polymerization temperature, monomer concentration and mole fraction of AAm in the monomer mixture. The molecular weight of the copolymer was also found to increase with monomer concentration and mole fraction of AAm, but at high concentration and fraction of AAm, intermolecular crosslinking tends to occur during the polymerization to form water-insoluble copolymer. A water-soluble copolymer having various molecular weights and cationic strengths can be synthesized by selecting suitable reaction conditions; i.e., this radiation process can provide a much higher molecular weight copolymer with a wide range of cationic strength. The flocculation effect was evaluated using sludge from wastewater of sugar manufacture. It was found that the radiation-polymerized copolymer DMAEM·MC–AAm has an excellent flocculation effect.