Sales Folder Adhesive Resins - Adhesives & Sealants by Evonik

Dynacoll® 7000Preparation of Reactive Hot MeltsMolten DYNACOLL® grades are charged and heated up to approx. 130 °C. The meltis dried for 45 min. at less than 10 mbar. Water evaporation is important to avoidcrosslinking reactions and to obtain good shelf life and viscosity stability of theRHM.The calculated amount of isocyanate is added under a weak stream of protective gas(dried nitrogen or carbon dioxide) and rapidly homogenized with the melt. Reactiontime is normally 45 min. at 120 – 130 °C.The reaction is finished after the theoretical value of isocyanate content is reached.The isocyanate content is determined by reaction of the RHM with an excess ofdibutylamine and titration with hydrochloric acid. The melt should be degassed untilit is free of bubbles. Afterwards the reactive hot melt is filled into containers andstored in the absence of moisture and light. Depending on the application it isrecommended to filter the melt.For quality control, the following data should be determined: isocyanate content,visosity at elevated temperature, melting point or softening point (R&B), open time.Calculation:Weight (diisocyanate) =(WPES1 . OH1 + WPESn . OHn) . EW . R56110WPES1 = weight of polyester 1OH1 = hydroxyl number polyester 1WPESn = weight of polyester nOHn = hydroxyl number polyester nEW = equivalent weight of diisocyanate usedR = ratio of isocyanate to hydroxyl groupsReactive Hot Melt adhesives based on Dynacoll® 7000• offer excellent bonding to a huge variety of substrates• provide solutions for versatile applications in diverse industries,e.g. wood working, automotive, packaging and textile industry,also for bookbinding applications and sandwich bonding• can be applied with standard hot melt equipment,e.g. roll coaters, bead, spray and melt print applicators etc.27