The Study of Preparing Liquid MDI

• Main Author: 童民政
• Other Authors: Shenghong A. Dai
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/69398621594014268482

碩士 === 國立中興大學 === 化學工程學系 === 92 === 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 .