Abstract:
A METHOD FOR PREPARING POLYURETHANE RESINS IN PARTICULATE FORM WHICH COMPRISES REACTING TOGETHER IN FINELY DISPERSED FORM IN AN INERT LIQUID MEDIUM, TWO COMPOUNDS WHICH ARE SUBSTANTIALLY INSOLUBLE IN THAT MEDIUM, AT LEAST ONE OF THE REACTIVE COMPOUNDS BEING LIQUID FOR REACTIVE ENGAGEMENT WITH THE OTHER COMPOUND, ONE OF SAID COMPOUNDS HAVING ISOCYANATE GROUPS AND ANOTHER OF THE COMPOUNDS HAVING GROUPS WITH REACTIVE HYDROGEN ATOMS SUCH AS HYDROXYL, AMINO OR CARBOXYL GROUPS AND COMBINING WITH SAID COMPOUND HAVING ISOCYANATE GROUP TO FORM A REACTION PRODUCT INSOLUBLE IN THE LIQUID MEDIUM AND RECOVERING THE REACTION PRODUCT.
Abstract:
A continuously operative coating machine electrostatically deposits heat activatable powdered polymers, for example polyurethane, on a release carrier which progressively passes through a heating zone. The powder is applied from an electrostatic fluidized bed employing a microporous wire cloth as both bed and charging grid. Deposited powder is transformed to a film which is brought into adhering relation to flexible sheet material such as a fabric to be coated. The carrier and the sheet material then pass over a cooling means where the film is solidified and bonded to the material and the unloaded carrier is returned for receiving further powder deposits. The powder bed may include compartments for successive application of different types of powder particles. An ionized zone preferably insures that the recirculated carrier is free from any residual positive or negative charge which might affect the charged powder particles to be deposited by the electrostatic fluidized bed. An alternative arrangement employs a reuseable release paper backed by a metallic flexible strip for transfer of the film to the sheet material. When either arrangement is operated without supplying sheet material, it may with slight modification be used to produce plastic sheeting per se.