JPS6351742B

A process is disclosed for coating the inside surface of a length of tubing comprising the steps of forming at least one loop of tubing with a downwardly inclined portion and an upwardly inclined portion; filling the cavity of the tubing forming the loop with a coating liquid; transporting the tubing along its longitudinal axis in a substantially vertically upward direction to coat the inside of the tubing above the level of the coating liquid with an initial layer of coating liquid; constricting the tubing adjacent to and above the level of the coating liquid along a constriction zone transverse to the longitudinal axis of the tubing, the constriction zone progressively diminishing in width in the direction of travel of the tubing to reduce the thickness of the initial layer and form a thin layer of desired thickness on the inside of the tubing issuing from the constriction zone; filling the cavity of the tubing issuing from the metering device with support gas; and exposing the tubing to heat at a sufficient temperature to fuse the coating layer to the inside of the tubing and form an uninterrupted film of uniform thickness thereon. The coating liquid can comprise an aqueous polymeric dispersion containing at least about 15% by weight of dispersed polymer based on the total weight of the dispersion and preferrably in the range of about 15 to 60% by weight. Also disclosed is an apparatus for carrying out the process of the present invention.