Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Patent
1998-07-14
2000-05-09
Edwards, Newton
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
428373, 139420A, D01F 604, D01F 806
Patent
active
060601612
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a pintle wire, particularly but not exclusively for use in joining the ends of industrial fabrics, such as papermachine clothing, for example press felts and dryer fabrics.
2. Description of the Related Art
It is known to join the ends of an industrial fabric using a monofilament pintle wire so as to provide an endless belt. Each end of the fabric is provided with outwardly extending loops, the two sets of loops being interdigitatable and capable of union by a pintle wire.
These known monofilament pintle wires have a low tensile strength. The wires may additionally have flaws in the monofilament structure. As a result the wires often break on insertion through the tunnel defined by the interdigitated loops. More importantly, the wires may break while the belt is in operation. This may lead to belt damage and necessitate the disposal of the belt before the end of its expected working life. As these belts, particularly those for use in papermaking, are extremely expensive this problem is of considerable importance.
Another problem with these known monofilament pintle wires is that the diameter of the wires are such that they do not fill the loop area and as such result in a high degree of localised permeability. This, once again, is of particular importance in the field of papermaking, where variations in permeability in the belt result in marking of the paper produced on the belt.
As an alternative to monofilament pintle wires multifilament pintle wires comprising polyamide have been used which are resin-treated. The resin treatment involves impregnation with phenolic or epoxy polymer resin which is then cured. Alternatively multifilament pintle wires have been used which comprise polyamide multifilaments wrapped around a polyamide monofilament core. Both of these known structures serve to give the polyamide multifilament a stiffness akin to a monofilament. Resin treatment processes are a burden in terms of increased material costs and production times, as well as being increasingly environmentally unsound due to the fact that treatment with these resins requires a considerable amount of organic solvent. Furthermore polyamides are generally lacking in abrasion resistance.
For dryer fabrics the aramid NOMEX (trade mark) and NOMEX (trade mark)/polyester blends have been used but neither can withstand the high loads present in the nips of a press section.
BRIEF SUMMARY OF THE INVENTION
The present invention has been made from a consideration of these problems.
According to the present invention there is provided a multifilament pintle wire comprising a polyolefin material, optionally in combination with another material, said pintle wire being free of a resin coating.
DETAILED DESCRIPTION OF THE INVENTION
The multifilaments of the invention provide excellent pintle wires (due to the high degree of molecular orientation in the polymer) without the need for any conventional stiffening treatment such as resin-coating or impregnation, or combination with a monofilament, as is the case with prior art multifilament pintles. The individual filaments of the wires of the present invention are generally of the same diameter. However, the multifilament still retains a reasonable degree of flexibility.
Ideally the material which may optionally be combined with the polyolefin does not comprise polyamide.
This polyolefin may be gel-spun, giving a preferred weight average molecular weight of 500000-8000000, especially 1500000-4000000, or melt-spun, giving a preferred weight average molecular weight of 50000-3000000, especially 750000-2000000. The yarns preferably have a tenacity greater than 10 g/denier.
The polyolefin is typically a homo- or copolymer of ethylene or propylene. It may also contain other polyolefin additives (preferably no more than 2 wt. %) having an average molecular weight less than that of the host polyolefin material. Examples of such additives include linear polyethylene; isotactic polypropylene; polybut-1-ene;
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Research Disclosure; vol. 386 No. 036, Jun. 10, 1996, Emsworth, GB.
Research Disclosure; vol. 382 No. 011, Feb. 10, 1996 Emsworth, GB.
Edwards Newton
Scapa Group PLC
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