Processing Polyurethane

Bayer MaterialScience AG, Business Unit Polyurethanes, Process Research Isocyanates, Building R79, D-47812 Krefeld, Germany. Fax 4-49 215 188 3228 e-mail ... 

There are three main infrared bands, namely, the near, mid-, and far infrared zones. The most commonly used band is the mid-range band covering 50 to 2.5 pm or, in wave numbers, 200 to 4000 cm4. The near infrared band that covers the range of 0.8 to 2.5 pm (wave numbers 12500 cm1 to near 4000 cm4) has overtones that have some importance to polyurethane processing. In this region, real-time studies have been carried out to follow the course of a reaction. (Wave numbers (in cm4) = 10000/wavelength (in pm).) The far infrared range does not have information that is relevant to polyurethane studies. 

Inert gas A gas that exhibits great stability and extremely low reaction rates under normal temperature and pressure conditions, for example, nitrogen, argon, and helium. Nitrogen is commonly used in polyurethane processing. 

PTMEG PU (R) Purging Polytetramethylene glycol. An abbreviation for polyurethane. Process of expelling an unwanted gas or vapor from a system through the introduction of a different gas or vapor until all traces of unwanted gas or vapor have been removed. 

Currently, raw material suppliers are the sole providers of polyurethane processing information. In most cases, they give instruction only on how to mix products and do not always include an explanation of the accompanying logic as to why these recommendations are being made. 

The preceding sections have shown the effect of changes in structure of isocyanate and hydroxyl compound, solvent and temperature on the isocyanate/hydroxyl reaction, and have indicated the role of basic catalysts. The largest commercial polyurethane processes utilize catalysed reactions, especially the preparation of foams. For this reason the catalysis of the isocyanate/hydroxyl reaction has been the object of extensive research. 

While tertiary amines are adequate catalysts for many reactions, a variety of metal catalysts has been found to be far more powerful. Organotin compounds are now used commercially in many polyurethane processes. The discovery of these catalysts was made independently by Hostettler and Cox [145] and by Britain and Gemeinhardt [146], all of whom were searching for more effective catalysts for foam formation. 

With use of appropriate catalysts, mixtures of dianhydrides and diisocyanates were directly converted to rigid foam products without use of foaming agents [105,106]. In situ formation of imide forms like the polyurethane process, was developed by Riccitiello et al. [107]. The system contains a unique furfuryl alcohol-acid mixture which generates heat to initiate the isocyanate-anhydride reaction. 

A knowledge of the mould-filling process in polyurethane processing thus makes it possible to recognize back at the mould design stage areas of the mould that are at risk from air bubbles and to do something about it by... 

SCCO2 is largely used to process food (extraction or fractionation), but other applications, such as the fluoropolymer synthesis by DuPont, hydrogenation or alkylation by Thomas Swan, coatings by Union Carbide, and polyurethane processing by Crain Industries, are still in development [111]. The application of supercritical fluids (SCFs) as reaction media with homogeneous catalysts has been mainly investigated on a laboratory scale. 

Y.C.Yen and T.S. Tsao, Polyols for Polyurethanes, Process Economic Program Report No.45A, Stanford Research Institute, Menlo Park, CA, USA, 1982, p.119. 

Dynasolve CU-5 is a unique solvent that was cleaning urethane residues and crystallized types of polyurethane processing equipment. 

A recent analysis (internal Cannon Report) of the antomotive seat-manufacturing market segment, to identify the future needs and trends of this group highlighted a number of interesting considerations for a producer of polyurethane processing equipment. 

Mould cleaning is required because of the chemical nature of the polyurethane process. The objective in developing the Foam Film technology was to eliminate the tedious, time-consuming manual operations, which must be performed on the moulds as part of a discontinuous polyurethane foaming process. 

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