This invention is directed to a membrane contactor for debubbling an ink.
It is known to use hollow fiber membrane contactors to degas liquids. See, for example, the LIQUI-CEL(copyright) SemiPer(trademark) membrane contactor commercially available from Celgard Inc. of Charlotte, N.C. This contactor utilizes a homogeneous, non-skinned, symmetric, polypropylene microporous hollow fiber membrane coated with a fluoropolymer and has been used to remove gases from photoresist developer solutions, lithographic printing plate solutions, and photographic film and paper emulsions. In this contactor, the foregoing liquids flow over the exterior surfaces of the hollow fibers.
Inks, for example, inks for ink jet printers, are sensitive to bubble formation. Formation of the bubbles, as the ink is discharged, can be detrimental to, among other things, quality printing applications or cartridge filling operations. See, for example, European Publication 1,033,162, Paragraph 0014, which is incorporated herein by reference.
Several membrane-based solutions have been proposed for bubble-in-ink problems. See, for example, Japanese Kokai""s 5-17712; 10-60339; 10-298470; European Publications 1,033,162; 1,052,011; and U.S. Pat. No. 6,059,405. Also, please note European Publication 1,033,162, Paragraph 0007 that categorizes additional techniques for removing dissolved gases from chemical liquids by use of a membrane.
Japanese Kokai 5-17712 discloses the use of membranes made from polyethylene, polypropylene, poly(tetrafluoroethylene), polystyrene, or polymethyl methacrylate resins (Paragraph 0008), and the ink flows on the lumen side of the membrane (Paragraph 0007).
Japanese Kokai 10-60339 discloses the use of membranes made from a fluororesin (claim 2), and the ink flows on the lumen side of the membrane (abstract).
Japanese Kokai 10-298470 (and its related case European Publication 1,052,011) discloses the use of composite (or conjugate or multi-layered) membranes with porous and nonporous layers, and suggests, among other things, the use of polymethylpentene (or PMP or poly(4-methylpentene-1)) (Paragraphs 0018-0020), and the ink flows on the lumen side of the membrane (abstract).
European Publication 1,033,162 discloses the use of composite membranes, with porous and nonporous layers and suggests, among other things, the use of PMP (Paragraphs 0026 and 0048) for both layers, and the ink flows on the lumen side of the membrane (Paragraph 0054).
U.S. Pat. No. 6,059,405 discloses the use of a membrane, a hollow fiber membrane, and the ink flows on the lumen side of the membrane (column 3, lines 55-65).
While each of the foregoing had a measured success in accomplishing the debubbling task, there is still a need for a membrane contactor for removing entrained gases from inks in a simple and cost-effective manner.
The present invention is directed to a membrane contactor for debubbling (or degassing) a liquid. The membrane contactor comprises a perforated core tube, a plurality of hollow fiber membranes surrounding the tube and having an end, a tube sheet affixing the end of the plurality of hollow fiber membranes to the core tube, and a shell surrounding the plurality of hollow fiber membranes and the tube sheet. A lumen side is defined by an internal surface of the membranes. A shell side is defined by the perforated core tube, an external surface of said membrane, and the shell. The membrane is a single layered, skinned, polymethylpentene hollow fiber microporous membrane. The skin is on the shell side.