Note: Descriptions are shown in the official language in which they were submitted.
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The inven~ion relates to a novel fibrous structure ~ ~
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of coherent film fibres having a square or nearly square
cross-seGtion. The invention also relates to a process
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for the manufacture of such fibrous structures.
It is known to manufacture fibres of thermoplastic
polymeric material by spinning~ i.e., by extruding a
melt of the thermoplastic polymer through a spinneret.
Such spun fibres have, generally speaking, a transverse
cross-section of non-angular shape and in most cases
even a circular cross-section. It is also known to manu-
facture thermoplastic polymeric fibres from the base
material by routes involving film splitting. In such
routes the molten thermoplastic polymer is extruded
through a linear or annular slit to form a film which is
thereafter converted into a fibrous product of fibres with
or without interconnectionO In order to carry out such
conversion the film may, for instancel be subjected to
a process known in the art as mechanical fibrillation, i.e.,
the film is ~irst stretched to effect molecular orientation
and subsequently subjected to a mechanical treatment, such i
as passing it over a rotating cylinder provided on its
surface with needles~
The above-mentioned known process of mechanical
fibrillation yields a fibrous product which is composed of
flat fibres~ i.e., the cross-section of such fibres is not
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only trapezoidal and t~refore angular in shape but their
width, being referred to as the longest side of the cross-
sectional quadrangle, is several times longer than their
thickness, which latter term indicates the cross-sectional
dimension perpendicular to that longest side. Many
mechanical fibrillation methods, however, yield fibres t
having a rectangular or substantially rectangular cross-
- section and it will be clear that in such instances the
terms width and thickness simply denote the longest and
the shortest side of the rectangle, respectively.
Although in many cases the known mechanical fibrillation
process and other known methods involving film splitting
offer important advantages over spinneret-extrusion and
~hilst f'ilm fibres (i.e., f'ibres made from film) may be
useful and sometimes even preferable for certain end-use
applications, commercial acceptance of such fibres,
particularly in the low denier range, has in some cases -
been hampered by properties which to a certain extent seem
inherent to the flat cross-sectional shape of the fibres,
such as gloss, less constant crimp, and moderate resilience.
It will be clear that these disadvantages are circumvented
or at least considerably reduced by film fibres having a
high degree of cross-sectional "squareness", but so far
such fibres have not been made available or described. : ~
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Accordingly, the invention provides a fibrous structure of . `
coherent film fibres, in which at least 70% of the fibres have a width/ ; ;
thickness ratio of 1.5 or less and in which each of the fibres has a
denier of 10 or less.
The term "dimensional ratio" as used in this specification
indicates the ratio between width and thickness, both used in the meaning
as explained above.
Preferably, at least 70% of the fibres contained in the fibrous
structure according to the invention have a dimensional ratio o~ 1.5 or
less.
The advantages of the fibrous structure as now proposed are
most evident in the lower fibre denier range. Accordingly, fibrous
structures consisting of fibres having a denier per filament (dpf~ of 10
or less are preferred. In most cases an average dpf of 6 or less is found
to be advantageous with respect to further processing the fibrous structures,
whilst an average dpf of 4 or less is particularly preferred.
A particular advantage of the presently proposed fibrous
structure in the lower fibre denier range is the absence of even small
amounts of heavy denier fibres. The latter have been known to occur in
some of the film fibrillates produced by previously descrlbed film splittine
methods, and this phenomenon has been regarded in the past as one of the
main disadvantages of film fibres as compared with spun fibres.
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In view of the narrow denier distribution combined with
- the low fibre denier in the presently proposed fibrous
structure the latter is particularly suitable for blend- `
ing with cotton and/or wool. Such blending may be effected
in any of the known systems of staple fibre processing.
Open-end spinning may advantageously be applied for that
purpose.
The invention also encompasses articles comprising
the novel fibrous structures as hereinbefore described.
Such articles not only include yarns and other textile !~'
materials (such as woven, knitted or non-woven fabric,3)
as well as ropes, cordage, upholstery, and floor oovering,
but also materials beyond the textile field, e.g., cellulosic
0:? synthetic paper and fibre-reinforced concrete. Parti-
~cularly preferred articles of the sald type are yarns
comprising the novel fibrous structur~sblended with cotton
and/or wool, and textile materials comprising such yarns.
As mentioned above, the invention also relates to a
process for the manufacture of the novel fibrous structures
as hereinbefore described, in which a film material of
a molecularly orientable thermoplastic polymer having a `
thickness of 100 microns or less is longitudinally stretched, -
transported in the longitudinal direction, and contac~ed
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with a plurality of needles bf which the points rotate in
the same direction as the movement of the film at the area
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of contact, with a circumferential spee~ of 10~60 times
the linear speed of the film material, the axis of
rotation being in transverse direction and at least some
o~ the said needles being arranged in rows having a needle
density of at least 15 per cm.
The product obtained after the contacting of the film
material with the needles in the manner as described may
be collected as such for further processing but in many
cases it is preferred to subject it to a stretch-breaking
treatment subsequent to the contacting with the needles
in order to reduce the length of the fibres contained
in the structure to the ~esired staple length. Although other
methods to reduce the fibre length, i.e., cutting with suit-
able means, can also be employed before or during the further
processing, stretch-breaking can be effected without destroy-
ing cohesion between the fibres in the fibrous structure.
The film material as used in the process according to
the invention may be a single film, the term film including
tape, ribbon or the like, or it may be a multiple film, -
i.e., a film consisting of two or more layers in overlying
relationship, each layer being connected to the adjacent
layer or layers. In both instances a number of single or
multiple films may be simultaneously processed in side-by-
side andior overlying relationship, and particularly-in
~5 -~e oommercial operation of the present process to manu-
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facture fibrous products composed of low denier fibres
it is found to be advantageous to use, as the film
material, 2-6 films in overlying relationship by con-
tacting them simultaneously with the needles, the use
in such manner of 4 films being particularly preferred ~ -
in some cases. ~ i
The needles may comprise, for example, needles, pins
teeth of pointed or bladed strips, wires, or wire bristles.
In most cases the needles are positioned in such a way
that they have a rearward inclination with respect to the
direction of the rotation, which inclination facilitates
the disengagement of the needles from the film material
after their contact therewith. Suitable needle inclination ;~
angles are within the range of 10-40 degrees, an angle of
3 degrees being generally satisfactory. ~ ~
A suitable method of carrying out the process of the in-
vention is to pass the stretched film material under tension
over a rotating cylinder, for instance a roller or drum,
provided with needles disposed on its surface in rows.
The rows of needles may be straight or bent and may extend
to the whole width of the film material to be processed
or may be considerably shorter, although in the latter
event they should, of course, be present in sufficient
number to ascertain contact with needles over the whole
width of the film material. Helical rows extending over the `~
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cylindrical surface or axial bands of short non-axial rows
are suitably employed in some cases. Particularly preferred
is the use of a cylinder having axial or substantially
axial rows of needles, and under the required process
conditions as indicated hereinbefore such use yields a
fibrous structure of attractive appearance, being composed
of fibres having only a limited number of highly irregular
interconnections whilst complying with the above-mentioned ~ -
- dimensional requirements.
The operating conditions Or the present process may be
varied in many other respects. A speed ratio, i.e., the
ratio between the circumferential speed of the needle
points and the linear speed of the film material, within
the range of 25-40 is advantageously used ln many cases,
~a speed ratio of 30-35 being particularly preferred.
Suitable linear speeds of the film material are normally
within the range of 3-20 m/min. and preferably within the ;
range of 5-15 m/min. It has been found that rows having
a needle density (i.e., the number of needles per cm) ;
of 20-40 may favourably affect the performance of the ~
present process, whilst generally a needle density of ~ '
25-35 is most preferred. Particularly advantageous are
rows of oval or flat needles arranged with their longest
cross-sectional dimension in longitudinal direction, i.e.,
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in the same or substantially the same ùirection as the
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movement Or the film material. In certain cases two co~
operating contra-rotating rollers with intermeshing
straight axial rows of needles and the same rotational
speed are suitably used.
The film material as used in the process O:e the in-
vention may consist of any thermoplastic polymer which,
as indicated hereinbefore, can be molecularly oriented
by stretching. Many polymeric materials may suitably be
used, for example, homo- and copolymers of vinyl chloride,
vinylidene chloride, vinyl acetate, and acrylonltrile, as
well as polyesters, polyamides, and polylactones, such as
polypivalolactone. Preferred polymeric materlals in¢lude
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homo- and copolymers of mono-olefins, such as ethylene
and propylene. Film material containing at least 80%w of
polypropylene, low pressure polyethylene or a blend thereof ;-
is particularly preferred, whilst in some cases additional
advantages are obtained if in addition to the said poly-
olefin(s) the film material contains 2-20%w of a homo-
polymer or block copolymer of butadiene and/or 0.1-~%w
of a slip agent. The indication "%w" as used in this
specification means percentage by weight with respect to
the total composition.
It will be appreciated that two or more different
thermoplastic polymers may suitably be used in embodiments
of the present process already mentioned hereinbefore,
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which involve the processing of a multiple film or of a
plurality of single or multiple films in side-by-side
and/or overlying relationship. In such cases a bi- or
multi-component fibrous structure is obtained. Under
suitable conditions such product is particularly at-
tractive for further processing in view of its bulk~
owing to spontaneous or heat-induced crimping properties
of the fibrous structure or at least a major part of the
fibres thereofO
The invention may be illustrated by the following non-
restrictive Examples.
E;xampïe _l ' '
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A film of a polypropylene having a melt index of 105 j.:-
(expressed in g/10 min.; determined according to ASTM
D 1238-70, condition E) was extruded via the blown film
route in a thickness of 50 microns for each layer of the
lay-flat film. The film was stretched at 135 C at a
stretch ratio of 1:8 after being cut into tapes having a
width of 10 cm.
The stretched film material tdouble layer) was passed
at a linear speed of S m/min. over a roller equipped with
6 equispaced axial rows of needles and rotating at a
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peripheral speed of 200 m/min.~ each row having a needle
density of 32.
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A fîbrous structure was obtained consisting of fibres ~
within the denier range of 3.2-6.5, 60% of the fibres ,.
having a dimensional ratio (DR) between 1 and 1l5 and 80%
of the fibres having a DR bet~een 1 and 200.
Exam~le 2 .
Starting from the extruded film as described in
Example 1~ a 4-layer system was made by cutting and
stretching two lay-flat films under the above-mentioned ~ `
conditions. : ~ .
The stretched film material was fibrillated under the
condit:ions as mentioned in Example 1 except a peripheral
roller speed of 150 m/minO and a needle density of 39. ..
A fibrous product having the same characterizing .:
features as those given in ~xample 1 was obtained.
A film of the polypropylene as used in Example 1 was ..
extruded in a thickness of 40 microns and subsequently
converted into a 4-layer stretched film material and
fibrillated as described in Example 2.
A fibrous product was obtained consisting of fibres within ;.
the denier range of 1~8 and 3.7~ whilst 65% of the fibres ~ .
had a DR between 1 and 1.5 and 83% had a DR between 1 and 2.
Example 4 .:
A blend was made by dry tumble mixing the following
composition:
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87%w of the polypropylene as used in Example 1; :
10%w of granulated "CARIFLEX"-TR 1101 (a styrene-
butadiene block copolymer), and ,~.
~ 3%w of "UNISLIP" (a slip agent).
This blend was extruded into a lay-flat film, cut,
stretched and fibrillated under the conditions as given
-in Example 1 except a peripheral roller speed Or 150 m/min. . .
A fibrous product was obtained consisting of very . :
soft hand fibres within the denier range of 3.2-4.9, ~:
82% of the fibres having a DR between 1 and 1.5.
EXAMPLE 5 ..
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Starting from the blend as used in Example 4, the
procedure of Example 3 was repeated, yielding a fibrous
product consisting of very soft hand fibres within the
denier range of 1.8-2.7, whilst 85% of the fibres had a j~
DR between 1 and 1.5. : ~;
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