Ahlstrom Paper Group Research & Competence Center

Raimo Piittala

Kay Rokman

Andrea Grosso

Jonathan George

Kaj Back

A non-woven web of fibrous material containing a reactive particulate material is made using the wet laid, or preferably foam, process. First and second fibrous webs are made using the wet laid or foam process, and a liquid or foam slurry including reactive particulate material is provided between the webs so as to provide a composite web. Liquid, or foam and liquid, are withdrawn from the composite web and then the composite web is dried so as to produce a final non-woven web with reactive material having substantially optimum reactivity (that is the reactive material loses a minimum amount reactivity during the web production process). The webs and slurry may be made using substantially pure water, and the particulate part of the reactive material is mixed with the foam or liquid slurry no more than about ten seconds before the liquid and/or foam are withdrawn from the composite web. Activated carbon and titanium dioxide are two particularly desirable reactive particulates; the reactive loading is at least 0.01 g/cm , and the air permeability of the final web is at least 3000 liters per square meter per second.

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Raimo Piittala