Isocyanate‐Derived Polymers

Ulrich, H.

doi:10.1002/0471440264.pst174

Cited by 1 publication

(1 citation statement)

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“…2 The reactions between MDI and various species including phosgene and MDA are detailed elsewhere. 2,3 HCl is present during the first separation stages in MDI production and increases corrosion and potentially etching of the stainless steel surface, which can result in greater adhesion of organic species. Because of this, HCl was used in keeping with the aim of replicating initial plant conditions by accelerating fouling on the lab scale.…”

Section: ■ Materials and Methodsmentioning

confidence: 99%

Interfacial Chemistry Investigation of Initial Fouling Conditions in Isocyanate Production: The Antifouling Performance of AISI 316L Stainless Steel

Bevas

Abel

Jacobs³

et al. 2021

ACS Omega

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The fouling of AISI 316L stainless steel during themanufacture of polymeric methylene diphenyl diisocyanate (pMDI) has been investigated. Studies have been carried out using a laboratory-based rig that simulates the process chemistry of the production plant. A variety of solution concentrations and treatment times have been employed to represent different stages in the production process. Following exposure, steel coupons have been removed and studied by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The thickness of the fouling layer, determined by XPS, is found to vary inversely with exposure time and solution concentration. This is a result of the solubility of the different pMDI derivatives that have been formed at different stages, and a reaction scheme is developed to explain these inverse relationships. ToF-SIMS indicates the formation of metal chlorides as a result of the initial treatment of the steel in the reaction vessel with hydrogen chloride. Fragment ions characteristic of reacted and unreacted pMDI (at m/z = 106 and 132 au, respectively) were used as an indicator of the degree of reacted isocyanate groups within the fouling layer and show a decrease with increasing exposure time, as a result of the formation of intermediates such as amines, ureas, carbodiimides, and uretonimines. The ToF-SIMS data was also processed by principal component analysis (PCA). This generally reinforced the conclusions reached by XPS and ToF-SIMS but, in addition, gave confidence in the repeatability of the analyses with the repeat data (of four analyses) clustering very tightly in the PCA score plots.

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Section: ■ Materials and Methodsmentioning

confidence: 99%