共查询到20条相似文献,搜索用时 61 毫秒
1.
2.
α,ω-双(2,6-二甲基羟苯基)聚苯醚树脂 总被引:1,自引:0,他引:1
论述了α,ω-双(2,6-二甲基羟苯基)-聚(2,6-二甲基-1,4-酚氧)(PPO-2OH)型聚苯醚的通用及新型合成方法。这些方法是以2,6-二甲基苯酚通过铜铵络合催化的氧化聚合为基础。通过合成方法的改性可以得到低分子质量双端羟基聚苯醚(PPO-2OH)。概述了各种合成PPO-2OH的方法,例如2,6-二甲基苯酚(DMP)同四甲基双酚A(TMBPA)氧化共聚;单官能团PPO和3,3,5,5-四甲基联苯二醌(TMDPQ)反应;单官能团PPO同甲醛缩合反应,论述了PPO-2OH的改性方法,如引入烯丙基基团,同其他热固性树脂共混改性和互穿聚合物网络如环氧树脂等。还介绍了此种分子质量端羟基聚苯醚的工业应用。 相似文献
3.
4.
祁世宇 《合成材料老化与应用》2019,48(3)
以2,6-二甲基苯酚为基本结构单元,对橡胶助剂中间体2,6-二甲基-4-亚硝基苯酚进行合成研究。结果表明,最佳反应条件为:亚硝酸钠水溶液滴加时间2h,保温反应时间2h,反应温度20℃,反应原料摩尔比n(2,6-二甲酚)∶n(浓硫酸)∶n(亚硝酸钠)=1∶1.2∶1.2。该条件下,产物收率达到了92.3%,熔点167℃~170℃。 相似文献
5.
6.
7.
8.
9.
以米氏酸和香叶醇为原料,采用钯催化的一锅串联反应为关键步骤,通过5步反应,高效率地合成了Amorfrutin B的关键中间体——(E)-7-羟基-2,2-二甲基-8-(3,7-二甲基-2,6-辛二烯-1-基)-5-苯乙基-4H-苯并[d][1,3]二噁英-4-酮(Ⅹ)。各中间体和产物的结构通过FTIR和1HNMR得以确认。中间体(E)-3-(3,7-二甲基-2,6-辛二烯-1-氧基)-3-丙二酸酯(Ⅲ)、(E)-3,7-二甲基-2,6-辛二烯-1-基-4-(2,2-二甲基-4-氧代-4H-1,3-二氧六环-6-基)-3-氧代丁酸(Ⅵ)的反应条件得以优化,提高了产率,降低了成本,使合成路线更加经济合理。对关键串联反应的机理进行了解释,即中间体(E)-3,7-二甲基-2,6-辛二烯-1-基-4-(2-(2,2-二甲基-4-氧代-4H-1,3-二氧六环-6-基)乙酰基)-3-氧代-5-苯基戊酯(Ⅸ)通过两次卡罗尔重排、脱羧后分子内Aldol缩合及脱水后芳构化等一系列转变形成了具有苯酚结构的关键中间体Ⅹ。Ⅹ的成功合成为Amorfrutin B的完全合成奠定了重要基础。 相似文献
10.
11.
12.
Objective: To define the prevalence of variants in collagen VI genes through a next-generation sequencing (NGS) approach in undiagnosed patients with suspected neuromuscular disease and to propose a diagnostic flowchart to assess the real pathogenicity of those variants. Methods: In the past five years, we have collected clinical and molecular information on 512 patients with neuromuscular symptoms referred to our center. To pinpoint variants in COLVI genes and corroborate their real pathogenicity, we sketched a multistep flowchart, taking into consideration the bioinformatic weight of the gene variants, their correlation with clinical manifestations and possible effects on protein stability and expression. Results: In Step I, we identified variants in COLVI-related genes in 48 patients, of which three were homozygous variants (Group 1). Then, we sorted variants according to their CADD score, clinical data and complementary studies (such as muscle and skin biopsy, study of expression of COLVI on fibroblast or muscle and muscle magnetic resonance). We finally assessed how potentially pathogenic variants (two biallelic and 12 monoallelic) destabilize COL6A1-A2-A3 subunits. Overall, 15 out of 512 patients were prioritized according to this pipeline. In seven of them, we confirmed reduced or absent immunocytochemical expression of collagen VI in cultured skin fibroblasts or in muscle tissue. Conclusions: In a real-world diagnostic scenario applied to heterogeneous neuromuscular conditions, a multistep integration of clinical and molecular data allowed the identification of about 3% of those patients harboring pathogenetic collagen VI variants. 相似文献
13.
简要分析了 RL PG数据库系统中建立液体药参数模块的必要性。着重介绍了该模块的构成及其各子模块功能的设计实现。该模块在 Visual Fox Pro3.0环境下编制完成。它的编制对于液体发射药火炮的研究工作具有重要意义和实用价值。 相似文献
14.
15.
16.
湿法磷酸降低过滤系统结垢方法初探 总被引:1,自引:0,他引:1
湿法磷酸生产中过滤系统结垢严重,利用同离子效应的有关原理,在混酸中加入H2SiF6可减少Na2SiF6和K2SiF6的结晶量,有效降低真空抽滤时Na2SiF6和K2SiF6的结垢量。 相似文献
17.
介绍了 17dtex/5f锦纶 66弹力丝的生产过程 ,从切片干燥、纺丝温度、组件、侧吹风、集束位置、上油几个方面对工艺作了粗浅的探讨。 相似文献
18.
19.
20.
Kun Cao Yan Li Zhen Yao Guang‐da Zhou Changchun Zeng Zhi‐ming Huang 《应用聚合物科学杂志》2012,124(2):1447-1455
The morphology evolution of miscible blends of a semicrystalline polyamide 6 (PA6) and an amorphous polyamide 6Ico6T (PA6IcoT) was investigated using an internal Brabender mixer at a temperature range 220–260°C. Morphology of the blends was characterized by scanning electron microscopy (SEM) and laser particle analysis. Temperature rising dissolution was used to separate the different phases of the blends and the phase compositions were determined by Fourier transform infrared (FTIR) spectroscopy. The particle size evolution of the dispersed phase (PA6) was calculated and agreed well with experimental observation. It was found that the particle size was quickly reduced to nanometer scale after several minutes of processing. A convection‐diffusion model was adopted to study the phase evolution during melt–melt mixing stage and compute the dimension of each phase. The results strongly support the notion of existence of distinct phases during blending, whose development can be well described by the model. The dispersed phase is reduced mainly by stretching of flow, while the broadening of the blending phase can be primarily attributed to molecular diffusion. The study also suggests the possibility to prepare novel polymer blends with nanometer sized domain of high uniformity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献