摘要
采用红外光谱和化学分析方法 ,对天然胶乳的氯化反应进行了跟踪分析 ,其反应历程应与溶液法工艺氯化历程相似 :1)取代氯化和环化 ,由Cl+ 进攻天然橡胶分子 ,产生的最初取代 ,伴随环化 ,导致二个异戊二烯单元中一个CC双键转化为C—C单键 ;2 )加成 消除 ,伴随C—C基团的转移 ;3)纯粹取代 .但胶乳法在第三步“纯粹取代”的同时 ,生成了一定量的叔碳C—Cl键 ;红外光谱还跟踪纪录了胶乳法CNR中ClCCO和ClC—COOH基团的生成 ,此二点为胶乳法CNR和溶液法CNR结构上最大的不同之处 ,也是导致胶乳法CNR稳定性差于溶液法CNR的主要因素 .从1 3C NMR对胶乳法CNR分析得出样品中含有的伯、仲、叔碳C—Cl键的比例 ,结合IR光谱和裂解色谱 质谱分析 ,得出胶乳法CNR氯化反应的历程 ,氯原子的取代与加成顺序 ;并由结果分析可知 ,胶乳法CNR的结构不如溶液法CNR规整 ,其主要原因为氯化起始阶段有HOCl加成、生成了较多的叔碳C—Cl键以及氯化后期有一定量的ClCCO和ClC—COOH基团生成 .此外 ,还得出结论 :胶乳法制备CNR的氯化反应在所有的NR分子上均匀发生 .
Fourier transform infrared spectroscopy and chemical analysis were applied to study the chlorination reaction mechanism of latex. The results showed that the chlorination mechanism of latex is similar to that from solution:(1) substituted chlorination and cyclization (The initial substitution was created by that chlorine attacked natural rubber molecules with concomitant cyclization reaction) (2) addition-elimination accompanied by a shiftiog of the C=C group and (3) pure substitution. Furthermore, the production of CIC-C=O and RCIC-COOH groups was recorded by Fourier transform infrared spectroscopy. This is the largest difference between CNR prepared from latex and from solution. From the ratio of primary, secondary and tertiary C-Cl bands analyzed by C-13-NMR, combined with IR spectrometry and high resolution pyrolysis gas chromatography-mass spectrometry, the chlorination mechanism of CNR from latex and the sequence of -Cl substitution and addition could be introduced. The structure of CNR from latex is not as regular as CNR from solution. The main reason was that HOCl formed at the initial stage of chlorination, and RCIC-COOH produced at the later stage of chlorination. Furthermore, a conclusion could be deduced that the chlorination reaction takes place evenly on all NR molecules in the chlorination process in latex.
出处
《高分子学报》
SCIE
CAS
CSCD
北大核心
2003年第4期489-494,共6页
Acta Polymerica Sinica
基金
国家自然科学基金 (基金号 5 9863 0 0 2
5 0 2 63 0 0 2 )资助项目
农业部天然橡胶加工重点开放实验室开放基金 (基金号 2 0 0 0 8)资助项目
关键词
天然胶乳
氯化反应
反应历程
氯化天然橡胶
红外光谱分析
chlorinated natural rubber
chlorination mechanism
infrared spectroscopy analysis
C-13-NMR
