Importance

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Abstract

A method and system for continuously preparing a solvent cast film having a secondary component are disclosed. The method includes continuously providing a pressurized stream of polymer solution, continuously combining a fluid stream including a secondary component with the pressurized stream of polymer solution, homogeneously mixing the combination of polymer solution and fluid stream in-line, continuously applying the resulting homogeneous mixture of polymer solution and secondary component to a continuously moving surface, and then evaporating solvent from the mixture to form a polymeric film. The system includes: (i) a continuous polymer solution casting system, including a first pump in fluid communication with a supply of polymer solution, a casting die for continuously depositing polymer solution disposed in proximity to a moving casting surface, and a first conduit providing a flow path for the polymer solution from the pump to the casting die; (ii) a secondary liquid component injection system, including a second reservoir for holding a supply of a secondary liquid component, a variable-speed second pump in fluid communication with the supply of secondary liquid component, a needle valve, and a second conduit providing a flow path for the secondary liquid component from the reservoir, through the second pump, then through the needle valve, and to an outlet; (iii) a conduit junction connecting the outlet of the secondary liquid component injection system to the first conduit of the continuous polymer solution casting system, the junction disposed downstream of the first pump; and (iv) an in-line mixer disposed between the casting die and the conduit junction. An improved method of casting a colored polymer solution onto a traveling belt for evaporating off a solvent and forming a colored film is also disclosed, the improvement including continuously injecting a secondary component into a stream of polymer solution and then mixing the resulting stream of polymer solution with secondary component in-line before casting the resulting polymer solution.

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First Claim