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首页> 外文期刊>Environmental Science & Technology >Hydrolytic Stability of Toluene Diisocyanate and Polymeric Methylenediphenyl Diisocyanate Based Polyureas under Environmental Conditions
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Hydrolytic Stability of Toluene Diisocyanate and Polymeric Methylenediphenyl Diisocyanate Based Polyureas under Environmental Conditions

机译：甲苯二异氰酸酯和基于亚甲基二苯基二异氰酸酯的聚脲在环境条件下的水解稳定性

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摘要

Polyureas were prepared by reacting toluene diisocyanate (TDI) or polymeric methylenediphenyl diisocyanate (PMDI) with water under prolonged vigorous mixing at room temperature. Hydrolytic degradation of these (powdered) TDI- and PMDI-based polyureas was studied by measuring the rates of formation of free toluenediamine (IDA) or methylenedianiline (MDA) in water as a function of time by utilizing HPLC. The heterogeneous hydrolysis reactions were carried out in glass reaction tubes under nitrogen with initial polyurea loadings of 2 g/L in deionized water or buffer solution. In the case of TDI-polyurea, concentrations of free 2,4- and 2,6-toluenediamine in water were measured after hydrolysis at 120, 140, and 160℃. The hydrolysis of PMDI-polyurea was carried out at 150, 160, and 170℃, and concentrations of 2,4'-methylenedianiline (2,4'-MDA), 4,4'-methylenedianiline (4,4'-MDA), and 2,4-bis(p-aminobenzyl)aniline were measured. In both cases the rate of formation of diamine was well represented by both a pseudo-first-order reaction and a zero-order reaction. The temperature dependence of rate constants fit Arrhenius behavior. The half-time for hydrolysis of TDI-polyurea at 25℃ was calculated to range from about 18 000 to 300 000 years and that of PMDI-polyurea was estimated to range from about 110 000 to 12 million years, depending on the kinetic assumptions made. The half-times for hydrolysis at buffered pH levels of 4, 7, and 9 were within a factor of 2 of those in deionized water. These results are of importance in understanding the fate of polyureas formed in the event of a release of TDI or PMDI into the environment.
机译：通过在室温下长时间剧烈混合下使甲苯二异氰酸酯（TDI）或聚合的亚甲基二苯基二异氰酸酯（PMDI）与水反应来制备聚脲。通过利用HPLC测量水中游离甲苯二胺（IDA）或亚甲基二苯胺（MDA）的形成速率随时间变化，研究了这些（粉状）TDI和PMDI基聚脲的水解降解情况。异质水解反应在玻璃反应管中在氮气下，在去离子水或缓冲液中初始聚脲负载量为2 g / L的条件下进行。在TDI-聚脲的情况下，在120、140和160℃水解后，测量了水中游离2，4-和2，6-甲苯二胺的浓度。 PMDI-聚脲的水解温度分别为150、160和170℃，浓度分别为2,4'-亚甲基二苯胺（2,4'-MDA），4,4'-亚甲基二苯胺（4,4'-MDA）测定了2，4-双（对氨基苄基）苯胺。在两种情况下，假胺一级反应和零级反应都很好地代表了二胺的形成速率。速率常数对温度的依赖性符合Arrhenius行为。根据做出的动力学假设，TDI-聚脲在25℃下水解的半衰期约为18 000至30万年，而PMDI-聚脲的半衰期约为11万至1200万年。 。在缓冲的pH值为4、7和9时，水解的半衰期是去离子水中水解半衰期的两倍。这些结果对于理解在TDI或PMDI释放到环境中时形成的聚脲的命运具有重要意义。

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