Filtering material for fluidic media and a method and device...

Gas separation: apparatus – Solid sorbent apparatus – Layered or laminated

Reexamination Certificate

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C210S506000, C055S524000, C055S527000, C055SDIG005, C055SDIG007, C442S058000, C442S417000

Reexamination Certificate

active

06423123

ABSTRACT:

This application is a 371 of PCT application No. PCT/DE99/03162, filed on Oct. 1, 1999.
BACKGROUND OF THE INVENTION
The present invention concerns a filter material, in particular in the form of a flat article, for fluid media, comprising a carrier layer and an adsorption layer, as well as a process and an apparatus for producing such a flat article. A particularly area of use for such adsorption filters is in particular use thereof in motor vehicles as a filter for the passenger compartment air. Other areas of use are for example use in relation to the production of protective clothing and insoles or the use as exhaust air or ventilation filters in the domestic section.
A series of various adsorption filters and processes for the production thereof are known from the state of the art. These adsorption filters which are known from the state of the art can be basically subdivided into those in which adsorber particles are arranged within a fleece or non-woven cloth or fiber or foam layer and those in which adsorber particles are arranged on a layer of a particle filter or between two such layers.
DE 37 19 415 A1 discloses for example a filter element with an open-pore foam carrier and adsorber particles. Apart from the complicated and expensive manner of manufacture involved here, a filter element of that kind suffers from the disadvantage that the amount of adsorber which can be applied and thus the capacity is restricted by the pore size of the foam carrier. A higher weight in relation to surface area of the filter can only be achieved by way of a greater thickness for the foam matrix, which results in worsened air permeability, that is to say an increased pressure drop at the filter. Uniform introduction of the adsorber particles also represents a certain problem, in which respect DE 37 19 415 A1 also discloses the use of binding agents for the immobilization of the adsorber particles. A further great disadvantage of filters of the described kind is that pleating which is imperative in the production of combination filters is only possible with difficulty by virtue of the thickness of the foams used.
German published specification (DE-AS) No 25 02 096 discloses an adsorption filter, in the production of which adsorber particles are introduced into the fleece or non-woven cloth during the operation of laying same, and are held exclusively mechanically, that is to say without binding agent or adhesive, between the intersection points of the fibers used for production of the non-woven cloth. Adsorption filters produced in that way however suffer from a series of disadvantages. On the one hand, the non-woven cloth must involve a certain minimum density in order substantially to prevent the adsorber particles from falling out, in which respect it is not possible entirely to prevent adsorber particles from falling out when a mechanical loading is involved, for example due to vibration, or, when used to produce protective clothing, when the clothing is being worn. In particular the required thickness of the non-woven cloth gives rise to a pressure drop at the filter which as far as possible is to be avoided.
German published specification (DE-AS) No 125 41 27 discloses a filter layer in which adsorber particles are fixed in the non-woven cloth or fleece by a suitable binding agent which can possibly be hardened. For that purpose a suitable web of non-woven cloth is sprayed with a binding agent and subsequently the adsorber particles are applied to the nonwoven cloth and distributed in the layer of non-woven cloth by the action of a vibrating sieve. A disadvantage in that respect is that uniform distribution of the adsorber particles within the layer of non-woven cloth can only be achieved at the cost of high effort and expenditure, if at all, because the adsorber particles which first impinge on the non-woven cloth provided with the binding agent immediately adhere to the non-woven cloth fibers and at least greatly prevent further penetration of adsorber particles into the non-woven cloth. It is also not impossible that the adsorption capability of a filter of that kind is comparatively severely restricted because a large part of the surface of the adsorber particles is wetted with binding agent and is thus no longer available for adsorption.
A similar filter to that described above is known from U.S. Pat. No. 5, 124,5, 177. In production of the filter in accordance with U.S. Pat. No. 5, 124, 177, a web of non-woven cloth is firstly sprayed with a binding agent and then adsorber particles are applied to the non-woven cloth and mechanically incorporated thereinto. Optionally, thereafter the procedure involves a further spray coating operation using a binding agent. Accordingly that filter suffers from the same disadvantages as that described hereinbefore, but in this case the adsorption capability is further reduced in the operating procedure which involves a second application of binding agent. Furthermore, in comparison with the mass of adsorber particles, a large amount of binding agent is required for durably fixing the adsorber particles.
A flat textile filter with adsorption properties, which does not include additional binding agent of the kind set forth hereinbefore, is the subject-matter of DE 32 00 959 A1. In that filter, adsorber particles are introduced into a non-woven cloth which contains fibers which at elevated temperature become temporarily sticky without melting. The fibers of that kind, which are disclosed in that respect, are heterophilic fibers comprising two coaxially arranged components of which the outer has a lower melting point, and undrawn amorphous polyester fibers. In the production of that filter, firstly a non-woven cloth is formed from the appropriate fibers, then the adsorber particles are incorporated into the non-woven cloth, and finally the adsorber particles are fixed to the fibers by heating the non-woven cloth and subsequently cooling it. A disadvantage in that respect is both the expensive production of the filter and also the comparatively high degree of wetting of the surface of the adsorber particles at the contact locations with the fixing fibers, with an adsorber particle generally being fixed to a plurality of fibers. In addition the binding fibers used are comparatively costly.
Finally the state of the art also includes GB 2 077 141 A, DE 38 13 564 A1, DE 40 34 798 C2 and EP 0 818 230 A1 which each relate to filters with adsorption properties in which at least one layer of adsorber particles is fixed on the surface of a substrate, for example a non-woven cloth, with a binding agent. Those filters suffer in particular from the disadvantage that a relatively large amount of binding agent is required, while at the same time the adsorption capacity leaves something to be desired by virtue of wetting of the surface of the adsorber particles with the respective binding agent. In terms of practical use moreover the provision of a further layer of a non-woven cloth material is generally required so that adsorber particles do not come loose from the substrate when a mechanical loading is involved.
In consideration of the filter materials known from the state of the art, with adsorption properties, and the disadvantages that they entail, there is still a need for an improved filter material which as far as possible eliminates the disadvantages known from the state of the art and which is economical to produce. The provision of a flat article of that kind, for example for use as a filter, a process for the production thereof and an apparatus for carrying out that process are therefore the object of the present invention.
SUMMARY OF THE INVENTION
That object is attained by a filter material of the kind described in the opening part of this specification, in that the adsorption layer is formed by melt adhesive threads loaded with adsorber particles.
DETAILED DESCRIPTION OF THE INVENTION
The filter according to the invention is distinguished in particular by a high level of adsorption capacity, spontaneity and a high level of air permeability. That

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