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丙交酯作为合成聚乳酸(PLA)的中间体, 其化学及光学纯度决定着PLA的品质。本文阐述了以乳酸为原料, 两步法制备丙交酯过程中温度、压力、反应时间、催化剂种类及用量等工艺条件对最终产品收率及纯度的影响。针对高温裂解所引起的问题, 提出采用新技术、新型反应设备及开发高效均相催化剂等方法使反应在较温和的条件下进行。同时, 对溶剂重结晶法、萃取法、精馏法及熔融结晶法在丙交酯提纯上的应用及特点作了介绍, 指出综合各种精制技术的耦合法精制工艺路线将具有较好的发展前景, 而将熔融结晶技术与其他方法相耦合则是一种更为绿色可行的技术路线。最后, 指出不断研发新的绿色提纯工艺技术, 仍是丙交酯合成技术的关键所在。 相似文献
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考察了两种绿色无毒溶剂乙酸乙酯和乙醇在D,L-丙交酯提纯过程中的使用情况. 以熔点为指标表征重结晶后D,L-丙交酯的纯度,考察了重结晶温度、时间及D,L-丙交酯/溶剂比例对D,L-丙交酯重结晶收率的影响. 结果表明,在不同重结晶温度、时间及溶剂用量下,两种溶剂提纯3次后D,L-丙交酯的熔点均能达到聚合的要求. 使用两种溶剂提纯的经济性对比表明,乙醇较适宜作为D,L-丙交酯扩大生产中的提纯溶剂,其最佳的提纯条件为温度4℃或更低,重结晶时间在1 h以上,乙醇使用量为2.5 mL/g. 在此条件下,提纯3次后D,L-丙交酯的收率约为63%. 对重结晶所得物质进行了元素分析、FT-IR分析及1H-NMR分析,结果表明所得产物为环状D,L-丙交酯结构. 相似文献
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为了提高D,L-丙交酯的收率,研究了D,L-乳酸为单体,低真空条件下使乳酸单体先缩聚后解聚制备D,L-丙交酯的工艺条件。考察了制备过程中脱水温度、脱水率、催化剂量、聚合温度和解聚温度对丙交酯产率的影响。结果表明,以ZnO为催化剂,用量为1.2%,在全程低真空条件下,乳酸分别在120~160℃脱水和220~250℃解聚,以无水乙醇和乙酸乙酯作为溶剂改进了粗产品的提纯方法,可得到产率达40.2%的丙交酯。毛细管熔点法测定了产物的熔点,并用红外光谱、差示扫描量热法、X-射线衍射分析对产物进行了分析表征。所得产物为高纯的环状丙交酯。 相似文献
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丙交酯单体的回收和表征 总被引:1,自引:1,他引:0
为减少在提纯粗丙交酯时的大量耗损,采用不同方法对粗丙交酯在重结晶过程中产生的乙酸乙酯母液进行回收,并比较了各种方法的回收率。最后用紫外光谱和红外光谱对回收的丙交酯进行表征,测试结果表明产物为环状丙交酯结构,采用辛酸亚锡作催化剂是一种高产率的回收方法。 相似文献
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《精细化工原料及中间体》2019,(1)
<正>一、项目简介聚乳酸是生物可降解的高分子合成材料之一,被美国FDA批准进入临床应用,主要应用于药物控制释放材料、骨材料、手术缝合线、暂时性支架、眼科材料以及通用可降解塑料等领域。但作为生物医用材料聚乳酸的中间体-L-丙交酯,制约了聚乳酸在相关领域的大规模应用。本技术开发了连续精馏提纯丙交酯技术,采用三塔高真空带返料的精馏技术,把含L-丙交酯为75%~80%的丙交酯粗液提纯到99.5%的产品,以实现L-丙交酯的大规模生产。二、技术特点采用高真空精馏技术,为降低塔的压力降,选用 相似文献
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Optically pure poly(lactic acid) (PLA) was obtained from lactic acid via purification of the corresponding lactide. The optical purity of PLA was determined using polarimetry and NMR. In the depolymerization
process, the effect of the reaction conditions and catalysts on optical purity of the lactide was examined with temperature
having a significant effect. In addition, the degree of racemization increased with increasing molecular weight of the oligomeric
PLA. The effects of temperature, time, solvent, and stirring speed (RPM) on the lactide purification process were examined
in order to improve optical purity. Optical purity was maximized when separation was carried out at 25 °C. The optical purity
of PLA was significantly affected by that of lactide used. 相似文献
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丙交酯是制备高分子质量聚乳酸的重要原料,其光学纯度和化学纯度的高低决定了高分子质量聚乳酸的品质和价格。对乳酸及丙交酯的结构特点进行了论述,介绍了两步法合成丙交酯的工艺以及影响乳酸低聚物分子质量和丙交酯产率的因素,提出了两步法合成丙交酯的研究方向。 相似文献
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Linear poly(d ‐lactide) (PDLA) with various molecular weights is synthesized and incorporated into commercial poly(l ‐lactide) (PLLA) with different optical purities. And then, the crystallization, mechanical and thermal properties of the PLLA and PLLA/PDLA cast films are investigated. In the PLLA and PDLA/PLLA specimens with lower optical purity, few homochiral crystallites (HC) form in all the specimens and only a small amount of PLA stereocomplex crystallites (SC) are observed in the blends. The elongation at break of all the specimens is extraordinary high, >300%. Dynamic mechanical analyses indicate that the destruction temperature increases at first, and then depresses as enlarging the molecular weight of PDLA in these blends. For the PLLA and PLLA/PDLA with higher optical purity, more content of HC develops in neat PLLA, and both SC and HC produce in the PLLA/PDLA specimens. However, the strains of neat specimens and binary blends are much lower than that of specimens with lower optical purity. The specimens with higher optical purity exhibit higher destruction temperatures and lower loss factors. The high content of crystals (SC and HC) would act as the physical cross‐linking points and provide a key factor to impede the deformation of neat PLLA and binary blends during stretching, which should result in the fragile behavior of the PLLA and PLLA/PDLA blends with higher optical purity. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44730. 相似文献
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Poly(D ,L ‐lactide) (PDLLA) was synthesized by microwave‐irradiated ring‐opening polymerization catalyzed by stannous octoate (Sn(Oct)2) under atmosphere. The effects of heating medium, monomer purity, catalyst concentration, microwave irradiation time, and vacuum level were discussed. Under the appropriate conditions such as carborundum (SiC) as heating‐medium, 0.15% catalyst, lactide with purity above 99.9%, 450 W microwave power, 30 min irradiation time, and atmosphere, PDLLA with a viscosity–average molecular weight (Mη) over 2.0 × 105 and a yield over 85% was obtained. The dismission of vacuum to ring‐opening polymerization of D ,L ‐lactide (DLLA) under microwave irradiation simplified the process greatly. The temperature under microwave irradiation and conventional heating was compared. The largely enhanced ring‐opening polymerization rate of DLLA under microwave irradiation was the coeffect of thermal effects and microwave effects. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2244–2247, 2006 相似文献
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Amorphous‐made poly(L ‐lactide) [i.e., poly(L ‐lactic acid) (PLLA)], poly(L ‐lactide‐co‐D ‐lactide)[P(LLA‐DLA)](77/23), and P(LLA‐DLA)(50/50) films and PLLA films with different crystallinity (Xc) values were prepared, and the effects of molecular weight, D ‐lactide unit content (tacticity and optical purity), and crystallinity of poly(lactide) [i.e., poly(lactic acid) (PLA)] on the water vapor permeability was investigated. The changes in number‐average molecular weight (Mn) of PLLA films in the range of 9 × 104–5 × 105 g mol?1 and D ‐lactide unit content of PLA films in the range of 0–50% have insignificant effects on their water vapor transmission rate (WVTR). In contrast, the WVTR of PLLA films decreased monotonically with increasing Xc from 0 to 20%, while leveled off for Xc exceeding 30%. This is probably due to the higher resistance of “restricted” amorphous regions to water vapor permeation compared with that of the “free” amorphous regions. The free and restricted amorphous regions are major amorphous components of PLLA films for Xc ranges of 0–20% and exceeding 30%, respectively, resulting in the aforementioned dependence of WVTR on Xc. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006 相似文献
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Wanqing Han Jianhao Zhao Mei Tu Rong Zeng Zhengang Zha Changren Zhou 《应用聚合物科学杂志》2013,128(3):1332-1338
A biomimetic nanofibrous poly(L ‐lactide) scaffold strengthened by nanohydroxyapatite particles was fabricated via a thermally induced phase separation technique. Scanning electron microscopy results showed that nanohydroxyapatite particles uniformly dispersed in the nanofibrous poly(L ‐lactide) scaffold (50–500 nm in fiber diameter) with slight aggregation at a high nHA content, but showed no influence on the interconnected macroporous and nanofibrous structure of the scaffold. The nanofibrous poly(L ‐lactide) scaffold presented a specific surface area of 34.06 m2 g?1, which was much higher than that of 2.79 m2 g?1 for the poly(L ‐lactide) scaffold with platelet structure. Moreover, the specific surface area of the nanofibrous scaffold was further enhanced by incorporating nanohydroxyapatite particles. With increasing the nanohydroxyapatite content, the compressive modulus and amount of bovine serum albumin adsorbed on the surface of the nanofibrous composite scaffold were markedly improved, as opposed to the decreased crystallinity. In comparison to poly(L ‐lactide) scaffold, both the nanofibrous poly(L ‐lactide) and poly(L ‐lactide)/nanohydroxyapatite scaffolds exhibited a faster degradation rate for their much larger specific surface area. The culture of bone mesenchymal stem cell indicated that the composite nanofibrous poly(L ‐lactide) scaffold with 50 wt % nanohydroxyapatite showed the highest cells viability among various poly(L ‐lactide)‐based scaffolds. The strengthened biomimetic nanofibrous poly(L ‐lactide)/nanohydroxyapatite composite scaffold will be a potential candidate for bone tissue engineering. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献
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开展了20 t/a规模工业双戊烯连续气相催化脱氢反应放大试验装置的设计和测试统计。在温度280~300℃、氮气流速2.0 L/min、工业双戊烯进料速度4.0 L/h时,上述催化脱氢反应可连续进行,工业双戊烯原料与脱氢粗产物的平均质量比为1.11。经真空精馏装置处理,脱氢粗产物极易被提纯精制。工业双戊烯原料与对伞花烃成品的质量比(即工业双戊烯单耗)分别为1.81(纯度99.0%以上)、1.69(98.0%以上)、1.54(96.0%以上)和1.45(90.0%以上)。纯度99.5%对伞花烃成品的沸点、相对密度和折光指数分别为177.1℃、0.857 g/mL和1.490。该放大统计可为工业双戊烯生产对伞花烃的工程化或工业化开发提供服务。 相似文献