To expand on Henning's comments:
In 1981-82, prior to T-Max Film, we (Kodak) did some experimentation with chromogenic B&W films. Much of this was done in the Kodak Ltd. Research Lab in Harrow, England. We had a 400 speed b&w Process C-41 film with grain that was much better than TRI-X or the other B&W C-41 films on the market. The film provided an image that was a hybrid dye-and-silver image. This was achieved by using a bleach restrainer in the emulsion. We had limited resources so we chose to pursue T-MAX Films. Even in retrospect this was the best decision. This technology was never commercialized. A major factor in never pursuing this was it was not reasonable to place future constraints on Process C-41 in order to make a performance improvement in a very small volume product.
Later, after higher priority projects were completed , T 400 CN was commercialized using more conventional dye-only technology. This was intended to be printed on BW Paper using enlargers etc. It competed successfully with Agfa VARIO PAN and ILFORD XP1 and XP2.
Later various b&w films for C-41 process were sold that could be printed to color papers producing almost monochrome prints. This required a special printing channel on automatic color printers. It could also be printed on b&w paper but required long exposure times.
Another attempt at monochrome prints was EKTAMAX Paper. This was an RC paper for RA-4 paper process. Rather than producing CMY dye image
from respective RGB records the print dyes were " mixed" to produce a near neutral print image. This was used in the school picture and commercial lab business. It allowed making b&w prints from color negatives using existing printers and RA-4 paper process. It allowed the labs to provide and additional product using existing printers and processes.
The next generation was PORTRA 400 BW. One of the advantages of PORTRA Films was that all the PORTRA Films could be printed using the same analysis and printing channels. This allowed labs to handle all PORTRA Films the same no need to segregate films. This was a major driver in making PORTRA Films a huge success for Kodak. PORTRA 400 BW had the same color characteristics as otehr PORTRA Films so it could be analyzed and printed with other PORTRA Films. This allowed prolabs to make monochrome prints on RA-4 paper. From a prolab point of view it provided additional products using existing printers and processes.
BW films for Process C-41 was not a big volume or success for any of the film manufacturers. However, it was another product that met a need that could be provided with little cost.
Bob Shanebrook
www.makingKODAKfilm.com