Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Description
The present ;nvention reLates to cordage, i.e.
lines, ropes, hawsers etc., which has been produced pre-
dominantly or exclusively from meltable polymer tila-
ments, fibers and/or yarns.
Cordage of this type has high tensile strengths
and moduli in its longitudinal direction, wh;le these
properties decrease in directions other than the long-
itudina! direction and are at their minimum in the dir-
ection perpendicular to the longitud;nal direction. This
decrease ;n strengths and moduli is adversely apparent
for example when, for fastening purposes~ cordage is pro-
vided at one end with an eye by knotting, splicing or
thimbling or, for joining to other cordage, is joined
with the aid of the same measures~ In the contact areas,
where tensile forces occur in a direction other than the
longitudinal direction of the cordage to an appreciable
extent, the tensile strengths and moduli of the cordage
are then appreciably reduced (down to about 55~ of the
strength/modulus values of the longitud;nal d;rect;on).
Accordingly, cordage which features knots, splices and
thimbles cannot be stressed to the full values of the
tensile strengths and moduli in the longitudinal direc-
tion.
It ;s an object of the present invention to eli-
m;nate the d;sadvantages descr;bed above by providing
cordage which, in the event of knottings, splicings,
thimblings and similar measures, has in the particula
contact areas tensile strengths and moduli which are no
longer reduced by as much as with prior art cordage.
This object is achieved according to the invention
with cordage which has been produced predominantly or ex-
clusively from meltable polymer filaments~ fibers and/or
yarns and which has been subjeGted to a heat treatment,
to br;ng about partial melting o~ the copolymer constitu-
ents without significant loss in molecular orientation,
;n those areas at its ends where, ;n use, stresses occur
;n a direction other than the lon~itudinal direction~
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These areas at the ends are in part;cular those
areas where, to form eyes or to join together with other
cordage, cordage parts are brought into contact, in part-
icular by knotting, splicing or thimbling or similar meas~
ures which have the effect that tensile stresses exerted
on the cordage in th~e longitudinal d;rection result in
those areas in stresses wh;ch no longer act in the longi-
tudinal direction of the cordage but in the least favor-
able case act in a direction perpendicular to the longi-
tudinal direction, as a consequence of ~hich the cordagecan no longer be loaded with the maximum tensile stress
possible in the longitudinal direction.
The heat treatment is carried out by partially
melting, in particular at the surface, of the polymer
constituents of which the cordage is made without sign,f-
icant loss in molecular orientation, thereby enhancing
the tensile strength and modulus ~alues.
The term "partial melting" as used herein is to
be understood as meaning that the polymer filaments,
fibers and/or yarns which predominantly or exclusively
form the cordage become converted at the surface into a
softened or melted state without at the same time incurr-
ing a significant loss in molecular orientation.
The heat treatment can be carried out by heating
the cordage in the areas where cordage parts come into
contact in the course of knotting, spliGing or thimbling
to a temperature above the melting point of polymers of
~hich the cordage is made, with or without pressure be-
ing employed, prior to the step of knotting, splicing
or thimbling. The heating can also be carried out after
knotting, splicing or thimbling has been carried out and
advantageously should be carried out only for such a
length of time, and to such an extent, as to maintain a
good balance between strength enhancement and adequate
flexibility of cordage.
As regards thimbling~ which can be done for ex-
ample using metal rings or resin sheaths, a possible
procedure comprises heating the metal rings or the resin
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before the steP of thimbling to a temperature above
the melting point of the polymer const;tuents of the
cordage, so that in the course of and after the appli-
cation of the thimble, the metal rings or the resin
transfer their heat to the polymer constituents to
effect partial melting of the latter.
The cordage according to the invention can be
produced in any desired conventional manner from poly-
mer filaments, fibers and/or yarns or from mixtures
of such polymer components with natural fibers such
as hemp, manilla, sisal, coconut or cotton, including,
if desired, metal wires. However, the important thing
is that polymer components suitable for partial melt-
ing are present at the surface of the cordage.
The polymer filaments, fibers and yarns used
for producing the cordage according to the invention
can consist of any desired polymer material suitable
for cordage production, although particular preference
is given to polyolefins and polyamides of, in particu-
lar, high molecular weight, particularly preferably of
ultra-high molecular weight af more than 600,000 g/mol
(weight average of moLecular ~eight). To enhance the
orientation and hence the strength properties, these
filaments and fibers have preferably been highly dra~n,
in particular to draw ratios of more than Z0, in part-
icular more than 30.
Suitable filaments and fibers are made in partic-
ular of polyethylene, in particular linear polyethylenes
of ultrahigh molecular weight. These polyethylenes may
contain minor amounts, preferably not more than 5 mol %
of one or more other alkenes copolymeri~able therewith,
such as propylene, butylene, pentene, hexene, 4-methyl-
pentene, octene etc. and have 1 to 10, in particular 2
to 6, methyl or ethyl groups per 1,000 carbon atoms. It
is of course also possible to use other polyolefins, for
example polypropylene homopolymers and copolymers; fur-
thermore, the polyolefins used may also contain minor
amounts of one or more other polymers~ in particular
i
1 3 0 7 9 2 2
alkene-1 polymers.
Of the polyamides, preference is given in par-
ticular to the polyaramids and the nylons, such as
nylon-6 and nylon-6.6.
The filaments or fibers are preferably produced
by the gel process, which is described for example in
G9-A-2,û4Z,414 and -Z,û51,667 and also in DE Offenlegung-
sschrift 3,724,434, and comprises essentially dissolving
the particular polymer used for filament production in a
solvent, molding the solution into a filament at a temp-
erature above the dissolving temperature of the polymer,
cooling the filament, for gelling, down to a temperature
belo~ the dissolving temperature, and drawing the fila-
ment with solvent removal.
In an embodiment of the invention it is also
possible to provide one or more polymers which have lower
melting points than the polymer filaments, fibers and/or
yarns which predominantly or exclusively form the cord-
age, in particular in the areas subject to a stress on
the cordage, in which case the heat treatment is carried
out at a temperature which is above the melting Point of
the low-melt;ng polymers and belo~ the melting point of
polymer filaments, fibers and/or yarns. These lo~-melt~
ing polymers, which preferably have melting points of
less than 135C can be present in the form of filaments,
fibers and/or yarns and be incorporated in the cordage
from the start of the production of the cordage or, how-
ever, be introduced into the cordage, preferably in the
stressed areas, for example by splicing, only before the
heat treatment. It is also possible to introduce these
polymers into the cordage by dipping the stressed areas
of the cordage into a melt of the lo~-melting polymers.
Preferably, the low-melting poly~ers used are polyole-
fins, in particular polyethylenes, in particular (L)LDPE.
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