Liquid doctor-blade coating

Interference pigments based on liquid crystalline materials are prepared by a doctor-blade coating of the polymers in the liquid or liquid crystalline state on an even surface. The doctor-blade process leads to a thin film wherein a homogeneous orientation of the molecules takes place. It is only after this orientation process that the film shows an interference color. The films are then cured and crushed by special techniques to yield platelets of liquid crystalline polymers showing interference effects. 

Methods which enploy liquid phase treating liquors (spray, transfer rolls and belts, etc.) share a cannon difficulty stemming from the lew volume of liquor in relation to the large surface area of the fibers conprising the substrate to be treated. This difficulty is acerbated when aqueous liquors are to be applied to hydrophilic fibers. Foam coating methods enploy stable foams which allow the thickness of the liquid-air mixture to be controlled by a doctor blade or roll. Conparatively low add-ons can be achieved by virtue of the low density of the foam layer, but the stable nature of such foam, and its immobile liquid phase, inhibit rapid, uniform distribution through the substrate. 

In drum dryers, the surface of a pair of rotating hot drums is coated with the liquid or smii-liquid form of the product. Drums are heated by steam or by direct firing inside the drum. The drums rotate slowly and over the course of about 300 of rotations the product is dried. The dried product is scraped off with doctor blades in flakes or sheets. 

Saab et al. [92, 93] developed a doctor-blade spreading technique for preparing the catalyst layers in a faster and highly reproducible fashion. The ink was coated onto laser jet transparency material wifli a doctor blade device driven by an X-Y chart recorder time base. The chart recorder time base is a highly accurate mechanical drive with a broad range of selectable speeds (20-0.05 cm/s), which is useful when compensating for liquids of varying viscosity. Machined aluminum... 

Usually, just the ink viscosity and particle size are limiting parameters at doctor blade processes. At not absorbing materials, liquids with viscosities between 100 and 50,000 mPa s can get applied with ink loadings from 10 up to 1250 g m GDL. By coating of porous materials... 

This manufacturing process can be used for coating of whole MEA rolls. This fits continuous production in best way. Via the CCM process, the catalyst ink is applied directly via a spray or doctor blade process on the polymeric membrane. Due to the swelling and shrinking behavior of the membrane when in contact with liquids, this process causes high mechanical stress during the application of the catalyst ink on the membrane, in special... 

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