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|標題:||The Study of Preparing Liquid MDI|
|摘要:||Methylene diphenylene diisocyanate (4, 4'-MDI) is one of the most important raw materials for making polyurethane (PU) polymers. MDI being a crystalline solid with melting point of 38~40oC is generally refrigerated under -10 C to prevent it from undergoing dimerization. In the plant scale production, the work involved heating up and thawing of the MDI solid before its utilization has been a cumbersome process. The technology to liquefy 4, 4'-MDI has been sought for decades, and has been the target of my research.
Our research group at NCHU has been worked in the chemistry of isocyanate for the last five years, and particularly on the conversion of isocyanate into carbodiimide (CDI) derivatives. My research has attempted to liquefy 4, 4'-MDI by converting small portion of isocyanate groups of MDI into branched or unsymmetrical structures consisting of either acylurea, amide or urea derivatives so that they could depress the melting point of pure MDI. The formation of acylurea and amide derivatives could be easily accomplished by the partial introduction of carbodiimide groups into MDI followed by the addition of di-carboxylic acids at various temperatures. When no heat was applied to the CDI-Diacid reaction, the product was essentially acylurea whereas amide derivative became the product if heated to 120 and above. Special ether-imide diacid (EI Diacid) have been prepared for this research from trimellitic acid (TMA) and Jeffamines of different chain lengths and ethoxylated/propoxylated ratios in the ether chains. In yet another approach, MDI with partial functionalized biuret groups has also been prepared for screening.
Among the three approaches attempted, it was found that the partial amide fuctionalizations of MDI with EI Diacids prepared from Jeffamine ED series have been the most successful. The best liquefied MDI product has the initial viscosity of 45.6 cps at NCO% of 29.56% and the viscosity of 56.7 cps at NCO% of 28.61 after 2 months .|
二苯基甲烷二異氫酸鹽（4,4’-MDI）是最重要的聚胺酯原料之一，其熔點約38~40℃，在室溫下儲存為固體結晶。此外4,4’-MDI還有自身二量化之特性易形成二量體，對於產品會有不良影響，因此須冷凍儲存以減少二量體的產生。工業製程中在使用前就必須先將它加熱融化後才能夠使用。鑒於工業製程上處理不易的缺點，本研究以嘗試製備液態4,4’-MDI為主要目標。 以我們實驗室對於異氰酸鹽近五年來的化學研究為基礎，特別是對異氰酸鹽轉化成碳二醯胺的化學。本研究嘗試將部分MDI轉化成部分的醯脲(Acylurea)、醯胺(Amide)或是縮二脲(Biuret)衍生物，利用這些不對稱、含支鏈結構的分子降低MDI的熔點來製備液態MDI。Acylurea衍生物及Amide衍生物可由二苯基甲烷二異氫酸鹽(4,4’-MDI)轉化部分少量的碳二醯胺(CDI)後，再與有機二元酸在不同溫度下反應部份生成得到，前者不須加熱可得到，後者經加熱120℃裂解後可得到。特殊的醚基-醯亞胺二元酸(EI-Diacid)是由不同鏈長及乙烷氧基/丙烷氧基比例的Jeffamine與偏苯三甲酸酐(TMA)合成得。另一種方法則是製備含縮二胺液態MDI。 在本研究主要嘗試三種的方式中，以使用Jeffamine ED series的IE-Diacid所製備出來含部份Amide的液態MDI表現較為佳。表現最好的液態MDI最初黏度為45.6 cps，NCO%為29.1 %，且在存放兩個月之後的黏度變化為56.7 cps，NCO%為28.61%。
|Appears in Collections:||化學工程學系所|
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