A process is disclosed for preparing a polyurethane or polyurea elastomer by reacting in a closed mold a reaction mixture comprising a polyisocyanate and a relatively high equivalent weight polyether. The process is characterized by employing as said polyether a polymer or copolymer of propylene oxide having at least two hydroxyl groups per molecule, an equivalent weight from about 1000 to about 5000 and a monofunctional species content of about 0.04 milliequivalents/gram of polymer or less.

A process for preparing a polyurea reaction injection molded (RIM) elastomer is described. A hindered polyetherpolyamine is first obtained by reacting a polyol having two or more hydroxyl groups with an effective amount of long chain alkyl epoxide to give an at least partially hindered intermediate having hydroxyl terminations; and then aminating at least one of the hydroxyl terminations on the intermediate to primary amine groups to give an at least partially hindered polyetherpolyamine. The hindered polyetherpolyamine is then reacted with a polyisocyanate in the optional presence of a catalyst to give a polyurea RIM elastomer. The long chain alkyl group provides steric hindrance to the primary aliphatic amine group, which slows down the reactivity of the amine. The slower reactivity of the amine group is useful in RIM and RRIM compositions since it allows for longer shot or flow times, which in turn permit larger parts to be made from existing equipment.

A miniature module emits and focuses a divergent light beam. The focusing module consists of a small-sized light emitter, such as a laser diode, and a micro-optical element seated in a lens holder. The outside diameter of the micro-optical element is 4 mm or less and preferably less than or equal to 2.5 mm. The micro-optical element may be a small conventional lens, a gradient index lens, or one of several types of diffractive optical element. The focal length of the module relative to the light from the emitter is set by sliding the lens holder along its central axis and permanently adhering it in place with respect to the emitter after focusing. During focal adjustment, axial rotation between the lens holder and between the base of the emitter is prevented by a series of notches. The miniature focusing module is smaller, lighter, costs less and may provide a larger relative aperture than the conventional structures currently used for example in solid state laser scanners.