By David Reed, UT EditorWyandotte, Michigan-BASF's Polyurethanes business in North America has launched a modified MDI (methylene diphenyl diisocyanate) grade with improved low-temperature stability, clarity and shelf life compared to similar polyurethane raw materials. Designated Lupranate 5143, the material is suitable for use in coatings, adhesives, sealants, and elastomers (CASE) applications, a 7 Nov. statement from BASF suggests.Pure MDI, monomeric 4,4'-MDI, has an expected lifetime of 14 days at a storage temperature of 40-50°C. It has a tendency to form uretidione, commonly known as dimer, which can alter the appearance and performance of finished products, the statement added. Inappropriate temperatures during storage and handling can exacerbate the problem, BASF says, explaining that manufacturers commonly use carbodiimide chemistry to control the dimer formation rate and solubility level, stabilising the monomeric isocyanate and maintaining its clarity.Using this carbodiimide modification in conjunction with some manufacturing improvements, BASF's Lupranate 5143 material has a lower freeze point than some traditional, carbodiimide-modified isocyanates based on 4,4'-MDI. Better low-temperature stability helps ease the handling concerns of field formulators, the firm claims. Lupranate 5143 complements and expands the property range of BASF's isocyanates, sharing the low temperature stability of unmodified MDI-based isocyanates with the good physical properties of 4,4'-MDI-based carbodiimide-modified isocyanates," said Kevin Kilkenny, manager of BASF's Urethane Chemicals-CASE business unit in North America. Chemical formulators in the CASE market have long desired an isocyanate with these performance attributes," he added. Our new isocyanate is formulated to produce flexible elastomers with high elongation, good impact and tensile strength, low hardness, higher heat-distortion temperatures and good tear resistance. Lupranate 5143 also has a longer gel time than typical materials, which allows more formulating flexibility for systems requiring sufficient open-time," Kilkenny concluded."