Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Patent
1998-11-05
2000-06-13
Copenheaver, Blaine
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
4282931, 428365, 428379, 428396, D02G 300, B32B 1504
Patent
active
060747528
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a metal fibre agglomerate to be used for example in the production of metal fibre suspensions or in the production of metal fibre webs utilizing the wet method, and to a process for manufacturing the same.
For the production of suspensions containing metal fibres, metal fibre agglomerates are needed which are easy to handle and meter, and in which the metal fibres are entangled as little as possible with one another so that they can go into suspension easily and uniformly. Conventionally, these suspensions are produced starting from loose fibres or fibre granules in which the fibres are held together by a glue that is dissolvable in the suspension medium, such as PVOH (polyvinyl alcohol) in water.
A known method for producing these fibres consists of continuously pickling in nitric acid a composite comprising a bundle of stainless steel fibres in an iron-copper matrix, as described in U.S. Pat. No. 2,050,298. Then the bundle is impregnated, for example, with PVOH. The composite thus obtained is then cut into granules and marketed either as such or as loose fibres after the glue has been dissolved, as described in U.S. Pat. No. 3,977,069, column 4, line 5 through 29.
Loose fibres, however, are difficult to handle and meter.
Moreover, the preparation of a homogeneous fibre suspension starting from loose metal fibres presents major problems. On the other hand, when using the aforementioned granules it is nearly impossible in practice to completely remove the glue, which fact can cause problems in the production of metal fibre webs utilizing the wet method and, more in particular, in the sintering of the metal fibre web afterwards.
The specific terms which are used in the following description will now be explained. "Fe/Cu/SS" composite is understood to mean a bundle of stainless steel fibres which fibers are each enveloped in copper, the bundle itself being enveloped in an iron casing. The "equivalent diameter of the metal fibre agglomerate" is the diameter of an imaginary spherical agglomerate with the same volume as the ellipsoidal agglomerate obtained according to the invention.
The "equivalent diameter of a fibre" is the diameter of an imaginary round fibre with the same cross-sectional surface area as the actual fibre. It is an object of the invention to provide a metal fibre agglomerate which can be handled and metered, and which can be utilized, for example, in the production of homogeneous metal fibre suspensions and in the production of metal fibre webs utilizing the wet method.
In addition, it is an object of the invention to provide a process for manufacturing these metal fibre agglomerates.
More specifically, the invention provides a metal fibre agglomerate comprising fibres with an equivalent diameter of between 1 .mu.m and 30 .mu.m and with a length of between 1 mm and 20 mm, with the feature that the core of the agglomerate contains at least one bundle of fibres oriented substantially parallel to one another, while the casing consists of a network of randomly oriented fibres.
The agglomerates have a relatively high porosity (and thus a low mass density) so that, when immersed in a liquid they settle down slowly, which fact promotes the suspendibility and homogeneity of the suspension obtained.
Since the core consists mainly of small bundles of substantially parallel, non-entangled fibres, these fibres easily separate from one another in order thus to go into suspension.
In addition, it is an object of the invention to provide a process for manufacturing these metal fibre agglomerates starting from a cut Fe/Cu/SS composite, and comprising the following steps: cut composite; the copper casings of the composite; with the substrate continuously subjected to a tumbling movement in steps (a) through (d).
Such a discontinuous process in which the substrate (e.g. fibres, fibre agglomerates, composite) is subjected to a tumbling movement is in general very suitable for carrying out pickling operations and for the leaching, for example, of coatings on these different substrates.
REFERENCES:
patent: 4249918 (1981-02-01), Argo et al.
patent: 4265981 (1981-05-01), Campbell
Copenheaver Blaine
N.V. Bekaert S.A.
Ruddock Ula C.
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