(54) FILTERING EQUIPMENT WITH MICROBICIDAL FILTER MATERIALFOR SUSPENDED SUBSTANCES(71) We, DRAGERWERK AKI1ENGESELL- scEtAFr, a German company, of MoislingerAllee 53/55, 2400 Lübeck, Federal Republic of Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to filtering equipment which includes a microbicidal fibrous filter material. In the description and claims, the term "filtering equipment" is used to denate equipment which comprises not only a filter element but also means for guiding the flow of a fluid being filtered.
Filtering equipment with high separating power for separating particles from a gas stream can be used for, for example the purification of the air supplied to sterile rooms, by removing bacteria, fungus spores and viruses. Such filtering equipment contains, as a filter element, papers or masses of fibres which comprise a mixture of relatively coarse and relatively fine fibres.
Fibrous materials used include cellulose, linters, asbestos, glass fibre and plastics material fibres. A common feature of all these filter elements or materials is that the micro-organisms, cells and spores, are precipitated on the fine fibres on enary into the filter material. Particles of inanimate matter remain at the place where they were first precipitated, but bacteria can multiply provided that there are nutrients and moisture at the place where they are deposited.
Bacillus endospores and fungus spores may germinate and then grow or become propagated in the filter material.
In order to prevent micro-organisms from spreading through filtering equipment, filter materials have been used which cannot form a nutrient base for the growth of such micro-organisms, for example glass fibre material. However, it has been found that, for example, the outside air drawn in for air supplies to hospital rooms practically always contains so many dust particles of an organic origin that a nutrient base is formed on the surface of the glass fibre material for micro-organisms. Even at the air discharge side of filtering equipment the deposition of organic substances and micro-organisms from the air on the filtering equipment must be expected, especially after the installations have been switched off. Consequently, even in the case of filter materials which do not contain a nutrient base at the time of production, it is expected that there will be a growth of micro-organisms in the filter element after a certain length of working life.
What is required is a filtering equipment including a filter element for particles in which filter element the filtered-out microorganisms and viruses are killed. The necessary level of separating capacity and the other properties should also be retained.
According to the present invention there is provided filtering equipment intended for filtering off particles suspended in a gas, the filtering equipment including, as a filter ele ment, a fibrous filter material on the surface of the fibres of which is/are elemental copper and/or elemental silver deposited by vapour coating under a subatmospheric pressure.
The present invention also provides a method of producing filtering equipment according to the invention which method includes the step of forming the fibrous filter material which constitutes the filter element by depositing, on the surface of a mass of fibres, elemental copper and/or elemental silver, by vapour coating at a subatmospheric pressure.
After the fibres have been vapour coated with copper and/or silver the or each metal is present in a finely divided form on the fibres. An extremely large surface area of copper and/or silver is produced. As a result the possibility of germs coming into contact with the metal(s) is high and a good microbicidal effected is obtained. The structure of the filter material can remain substantially unaltered. Thus the separating capacity, the air throughflow resistance and the mechanical properties are similar to these of untreated fibres.
For a better understanding of the present invention and to show more clearly how it may be carried into effect, description will now be given of two exemplary embodiments of the present invention; the examples describe only the production of the fibrous filter material which is to be incorporated in known manner in filtering equipment.
Example 1A filter paper consisting of glass microfibres with an air throughflow resistance of 2 mbar at an incident flow speed of 2 cm/s and a separating power of 99.997% according to DIN 24184 is vapour coated on both sides under a subatmospheric pressure either with a silver or copper layer or a mixed silver and copper layer of 600 A thickness.
After vapour coating there is no substantial alteration in the air througliflow resistance, separating power or mechanical properties of the filter paper. In microbiological testing the vapour coated filter paper exhibits effective inhibiting action on the growth of microorganisms in comparison to non-coated paper, and also extensively kills microorganism cells and fungus spores which are filtered off in the paper.
Example 2A mass of irregular fibres is vapour coated under a vacuum on both sides with a copper layer, silver layer or a mixed copper-silver layer of' 500 A thickness. The air throughflow resistance, separating power and mechanical properties are not substantially effected.
Microbiological testing shows a strong inhibiting effect on the growth of microorganisms and that micro-organism cells and fungus spores absorbed by the material are killed.
WHAT WE CLAIM IS:- 1. Filtering equipment intended for filtering off particles supended in a gas, the filtering equipment including, a a filter element, a fibrous filter material on the surface of the fibres of which is/are elemental copper and/or elemental silver deposited by vapour coating under a subatmospheric pressure.
2. A method of producing filtering equipment as claimed in claim 1, which includes the step of forming the fibrous filter material which constitutes the filter element by depositing, on the surface of a mass of fibres, elemental copper and/or elemental silver, by vapour coating at a subatmospheric pressure.
3. A method of producing filtering equipment, wherein the formation of the fibrous material is substantially as described in the foregoing Example 1 or Example 2.
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