Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Including a second component containing structurally defined...
Patent
1989-07-13
1991-04-02
Ryan, Patrick J.
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Including a second component containing structurally defined...
4285375, 428908, 427244, 206363, 206438, 206439, B32B 900
Patent
active
050046454
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to barrier products (generally comprising barrier webs) and to a method of producing such barrier materials.
There are many uses for materials which act as a barrier to the passage of air-borne micro-organisms or particulate dispersions whilst still retaining air-permeability.
For example, medical and surgical items are generally supplied in a sterile state enclosed within individual packages fabricated in part from porous material (e.g. paper, polymeric web or other non-woven material). Such porous materials are of necessity permeable to gases and vapours so as to permit sterilisation of the item (after packaging) by means of steam or a gas such as ethylene oxide. Furthermore permeability to air is important to allow the application of a vacuum during sterilisation to facilitate the packaging process and to limit the air volume around the packaged item. However, in spite of this air-permeability, the material must act as an effective barrier to the passage of micro-organisms so that the packaged item remains sterile.
Other examples of air-permeable barrier materials which are used in the medical field include drapes, wrapping materials, clean room clothing, and face masks. Further examples of barrier products are filter media (e.g. HEPA filters) used to provide clean environments in, for example, the pharmaceutical, medical, electronic and energy industries.
Effective barrier materials as described above may be difficult and expensive to produce. Furthermore microbiological barrier materials presently available vary considerably in their ability to stop microorganisms. For example, one commercially available paper used as a packaging material for sterile medical and surgical items shows a level of penetration of around 20% when challenged with a dispersion of bacterial spores flowing at a rate of 6.times.10.sup.-3 dm.sup.3 min.sup.-1 cm.sup.-2 whereas another commercially available paper shows a level of penetration of around 0.001% when challenged under similar conditions.
It is therefore an object of the present invention to provide barrier materials which are highly effective against the passage of micro-organisms or air-borne particulate dispersions and which may be produced comparatively easily and cheaply.
According to a first aspect of the present invention there is provided an air-permeable barrier material comprising porous material having pores with a range of sizes wherein a pore modifying agent is selectively incorporated in the pores at the upper end of the size range, said pores constituting a minor proportion of the total number; said modifying agent being such as to provide zones of high surface area within these pores in such a way as to restrict the passage of air-borne particles through these pores. It can be arranged that the incorporation of the modifying agent has little or no effect on the permeability of the porous material, because the incorporation is effected without substantially reducing the pore sizes and/or because the air-permeability of the material is substantially provided by the smaller pores which incorporate substantially none of the modifying agent.
Preferably the modifying agent is of at least one substantially uniform particle size (as explained below).
The term `pore` is used herein to include any passageway or interstice that extends from one major face to an opposed major face of the material.
Typical air-borne particles against which the barrier material of the invention is effective are microorganisms.
According to a second aspect of the present invention there is provided a method of enhancing the barrier performance of an air-permeable material having a range of pore sizes, the method comprising establishing a pressure differential across the material and treating the higher pressure side of the material with a suspension, dispersion or aerosol of a pore modifying agent under conditions such that the pore modifying agent is selectively incorporated in the pores at the upper end of the size range (said pores constituting a minor
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patent: 4046939 (1977-09-01), Hart
patent: 4084949 (1978-04-01), Biggins
patent: 4099943 (1978-07-01), Fischman et al.
patent: 4522843 (1985-06-01), Kundrat
Sinclair Colin S.
Tallentire Alan
DRG (UK) Limited
Ryan Patrick J.
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