Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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TITLE
BLl~D OF TE~TIL~3 STAPL~
TECHNICAL FIELD
This invention concerns improvements in and relating to textile staple fiber of the
polyester type, such as is commonly referred to as polyester staple fiber, and including
precursor polyester tows that are cut or otherwise converted to staple fiber, and to textile
articles such as spun yarns prepared from such staple, and fabrics and garments containing
such yarn or fiber, and to processes for obtaining the same.
BACKGROUND OF THE INVENTION
Synthetic polyester yarns have been known and used commercially for several
decades, having been first suggested by W.~I. Carothers, U.S. Patent No. 2,071,251, and
then by Whinfield and Dickson, U.~. Patent No. 2,465,319. In particular, polyester staple
fiber has been an industrial commodity that has been manufactured and used in such textile
yarns on a very large scale, primarily in blends with natural fibers, especially cotton, such
blends having been spun (twisted) into spun yams that have been made into textile fabrics,
and eventually into garments and other textiles. A typical textile yarn is of cotton count 25,
containing a cross-section of about 140 fibers of 1-1/2 denier and 1-1/2 inches cut length, for
example, but the denier and cut length can vary up to about 3 and down to about 1. Because
of the sophistication of the textile industry, both ~f the polyester fiber manufacturing industry
and of downstream consum~rs of textiles, and because of the commercial interest in providing
apparel and fabrics that will perform well during actual use by the ultimate consumer
(wearer), much attention has been devoted to analyzing appropriate requirements. Many
technical papers, for example, have been published on various aspects, and patents have been
issued with the objective
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of improving the "comfort" that can be obtained from
textile articles, and their constituent , and the
literature ha6 been replete with these ~uggestions for
6ev~ral years. so it ha~ long been considered desirable
to improve the ~omfort properti~e~ obtainable from textile~
prepared from yarns of polyester staple fiber, and much
effort has been devoted in the textile indu~try toward6
this objective.
An important objective of my invention i6 to
provide such polyester staple f:iber, or its precur~or tow,
in a new form ~uch that it can be formed into spun yarns,
which can then be formed into fabric~ and garments that
can show i~proved comfort properties, as discus6ed
hereinafter.
Polye6ter 6taple fiber ha6 generally been
manufactured commercially by a process of ~elt ~pinning
~i.e. extruding molten polyester polymer) into ~ bundle of
~ilaments, collecting such filament~ into a tow, which can
be relatively small and converted directly, e.g. by
stretch-breaking, into a spun yarn, but has ~ore often
been extremely large, amounting to many thou6and ~nd even
~ome million(s) of ilaments, and thi~ tow has then been
processed by drawinq, and possibly ~nnealing, and
crimping, before the crimped filaments have been converted
into ~tapl~ fiber by cutting, or otherwi6e, to the de6ired
lenqth~. AS indicated, most polye~ter çtaple flber has
then been blended, e.g. with cotton, and converted into
yarn, which is generally referred to as ~ ~pun yarn, to
distinguish it from a continuous filament yarn. ~he
natural fiber~, such a~ cotton, with whish the polyester
staple has been blended have not been uniform. For
instance, they vary in 6ize, ~hape and surface properties
to some extent. The natural characteristic~ of cotton
have long been believed to be responsible for the
~ttractive qualities of the spun yarn~, and of the
articles, such as fabrics and garment~, prepared
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therefrom, and much effort has been devoted to duplicating
various characteristics of cotton. Nevertheless, 60 far
as I know, polyester staple has been sold commerci~lly as
of uniform nominal denier (denier being the weight in
grams of 900 meters of a 6taple fiber, continuou~ il~ment
or yarn, ~nd thus being a measure in effect of the
thickness of the fiber, filament or yarn; in fact, since
6taple fiber is, by definition, of short cut length, about
1 to 3 inches, the denier must be calculated by
extrapolation or mu~t be measured on the precur~or tow or,
more precisely, on random extracts of ~ ~pecified number
of continuous filaments from the tow). When one refers to
uniform denier, the nominal denier, i.e. averaye denier,
i6 referred to, since there is inevitable variation
along-end and end-to-end. ~owever for co~modity fibers,
as opposed to some specialty fibers, it har. generally been
the objective of fiber producers to achieve a~ much
uniformity as possible when melt-spinning and drawing, and
thus to minimize variations between individual filaments
(i.e. end-to-end) and along the individual filaments (i.e.
along-end), so as to produce a polyester fiber product of
as uniform denier as practical. This is the pre6ent
commercial practice. Polyester fiber producer~ 6ell tow
or staple fiber of various nominal deniers. ~t would have
been pos~ible for anyone to buy polyester staple fiber (or
tow) of various different denier~, and to blend them
together, if desired with natural fiber , ~uch as cotton.
I do not know that anyone has actually done thi~, but it
would have been ~uite possible. I believe that polyester
staple fiber of intentionally ~ixed denier ha6 not
previously been ~old ~ an article o~ commerce.
By way of contrast, there has certainly been a
~uggection that continuous filament yarns be prepared of
mixed filament denier, e.g. by Jamieson and Reese, U.S.
Patent No. 2,980,492, and there ~ay have been other
~uggestions and, indeed, continuous filament polyester
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yarns of mixed filament denier ~ay po~sibly have been
sold. The objectiv~ of Jamieson and Reese was to prepare
a bulky yarn by making 6uch continuou6 filament yarn of
mixed shrinkage. In other words, the component ilament6
of the mixed filament yarn have indiv~dually different
~hrinkages, ~o that upon ~ub~ecting the yarns, preferably
in fabric or garment for~, to conditions under which the
yarns will ~hrink, the ~omponent filament~ will ~hrink to
differing extents with the result that the high ~hrinkage
filaments will become load-bearing filament6 in the
resultiny articles or yarns, and consequently the lower
shrinkage filament6 will become longer than the higher
shrinkage filaments and so impart a bulky texture. ~his
i6 an entirely different objective from the objective of
the present invention, which is to provide textile
articles from fitaple fiber having improved comfort
properties. This invention i~ not concerned with
continuous filament yarns, but with ~pun yarn~ from staple
fiber. However, all 6ynthetic fiber is prepared initially
in the form of extruded filaments, and 60 all synthetic
6taple fiber is formed from precursor ilament~ in bundles
which are referred to 2s tow~, as opposed to ~arn~.
SUM~RY OF THE INVENTION
According to the present invention, there are
provided new blends, or inst~nce in the ~orm of bales of
such blends, of polye~ter ~taple fiber of larger denier
and o~ ~maller denier, the larger denier being about twice
the 6maller denier, and of cut length about 1 to about 3
inches ~nd of average denier up to about 3, ~uch ac are
suitable for conversion into epun yarn, ~nd spun yarns
prepared ~rom such new blends, optionally with other
fibers, And textile fabricc and garments consisting wholly
or partially of ~uch yarn~. In other words, the yarns
(and precursors thereof and textile~ therefrom) are
characterized by the mixed denier of the ~taple ~iber,
i.e. the polyester ~taple is intentionally not of uniform
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nominal denier, but is intentionally of ~ixed denier,
larger and ~maller.
It is believed that it is thi6 mixed denier of
the 6taple fiber in the new art;icle~ of the invention that
provides ~dvantage6 over articles from polyester staple
fiber that h~s been available heretofore commercially.
Only comparisons in fabrics or gar~ent~ are considered
truly meaningful, and these will be di6cussed hereinafter.
As indicated in the Examples, the mixed denier
staple fiber and the precursor tows were obtained by a
preferred process sf melt 6pinning filament~ Df mixed
denier on the same ~pinning machine. In other word6,
filament6 of different denier~ were 6pun from the 6ame
spinning machine ~nd were collected and mixed together in
the same bundle, ~s cvntrasted with mixing 6eparate
batches of uniform fibers (i.e. o the ca~e 6ingle denier)
made by ~pinning on different maehines and collecting into
ceparate bundles and processing ~eparately before they are
6ubsequently mixed.
Accordingly, there i6 provided also, according
to the invention, a proce~s for preparing a blend of
polyester staple fiber of different denier~, wherein a
bundle of filaments of deniers that differ by the desired
ratio i~ prepared by 6pinning through capillarie~ of
differing size and/or throughput on the ~ame ~pinning
machine, and the~e filament6 of different denier~ are
collected together in the same bundle, and ~uch bundles
are then converted into staple ~iber. According to
present conventional technology for preparing polyester
staple fibers, generally ~everal ~uch bundles will be
collected toyether ~nd ~ubjected to the ~tep~ of drawing,
and po~sibly annealing, before crimping and conver~ion to
6taple fiber. ~owever, it has been 6ugge~ted and is known
to be possible to prepare polyester filament~ directly by
winding at high ~peeds (of the order of several km/~in.
and thereby avoid the need for drawing. A~ explained,
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however, the filament~ are preferably mixed by ~nitially
spinning the filaments of different deniers on the ~ame
spinning machine, than by spinning ~eparately filaments of
the same 6ingle denier followed by later mixing cut fibers
of different deniers. Furtherlmore, although thi~ i8 not
yet certain, there may be ~ttendant advantages in the
properties of the actual filamlents by co~pinning the ~ame
¦ bundle in the 6ame cell or 6pimning position through
I capillaries of different diameter~ and/or throughput, and
advancing this bundle of intimately mixed ~ilaments of
; different deniers together from the ~ame cell.
~ccordingly, there i~ al60 provided, according to the
present invention, a proeess for preparing a blend of
polyester ~taple fiber of different denier6, wherein
bundles of filament6 of denier6 that differ by the desired
ratio are prepared by co pinning each bundle rom the same
spinneret through capillaries of differing ~ize ~nd/or
throughput at the same spinning position, whereby the6e
; filaments of different deniers are collected and mixed
together in the same bundle, and such bundles are then
converted into 6taple fiber.
The precur~or polyester tow~ of intimately mixed
filament6 of different deniers are ~lso believed new, ~6
are the processe6 for their preparation. Accordingly,
there is also provided, according to the pre~ent
invention, a process for preparing a tow of polye~ter
filaments for conversion into polyester ~taple fiber,
wherein the tow is a mixture of polyester filament~ of
different deniers, ~uch proce6~ comprising the 6tep of
forming bundles of filament~ of denier~ that differ by the
de6ired ratio by ~pinning through capillarie6 of differing
size and/or throughput on the same ~pinning machine, and
such filaments of different denier are collected together
in the ~ame bundle, optionally combining together 6uch
bundle~ into a larger tow, and optionally subjecting the
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filament~ to drawing, annealing and/or crimping operations
in the form of such tow.
Furthermore, there is provided a proces~ for
preparing a tow of polyester filaments for conver~i~n into
polyester staple fiber, ~herein the t~w is a ~ixture of
polyester filament~ of different deniers, such proc~ss
comprising the ~tep of forming bundles of fil~ment~ of
denler that differ by the desired ratio by co~pinning each
bundle from the same spinneret through capillaries of
differing size and/or throughput into the same 6pinning
position, whereby such filaments of different denier are
collected and mixed together in the ~ame bundle,
optionally combining together such bundles into a larger
tow, and optionally ~ubjectiny the filaments to drawing,
annealing and/or crimping operation6 in the for~ of such
tow.
The textile yarns, fabrics and gar~ents
containing fiber of mixed denier referred to herein are
also believed new, according to the invention.
BRIEF DSSC~IPTION OF DRAWINGS
FIGURES 1 and 2 show, in cross-section,
~ssemblie6 of ~ome 140 fibers to demonstrate the
difference between how the fiber6 pack together in a mixed
denier yarn in contr~st to a unifor~ denier yarn, as
explained hereinafter.
FIGURE 3 is a block diagram to ~how typical
process teps by which a 6taple fiber blend of the
invention ~ay be prepared.
FIGURE 4 6hows schematically a part of a
spinning machine with a piddler can, whereby a bundle of
filaments of mixed denier according to the invention may
be prepared.
FIGURE 5 6hows denier histograms for yarns, as
explained hereinafter.
DETAILED DESCRIPTION OF INVENTION
Assemblies of 140 fibers are shown as circles in
Figures 1 and 2, to represent ~chematically the difference
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between the packing together of fibers in a 6pun yarn
consisting of an intimate mixture of fibers of tw~
different denier~, i.e. according to the inv~ntion, as
shown in cross-section in Figure 1, ~nd a ~imilar as~embly
but of uniform denier, a~ shown in cross-~ectlon in Figure
2, i.e. accordin~ to the prior ~rt. It will be noted
that, in Figure 2, the filaments of uniform denier are
closely packed, and that this does not permit ~uch ~pace
between the filament~. In cGntr~st, in Figure 1, defipite
the random arrangement ~i.e. the filaments are not
arranged in a uniformly alternating pattern),
~ignificantly larger ~paces are provided between the
filament I believe that this ~ay be a signific~nt
factor in increa6ing the comfort of fabrics and garments
incorporating polyecter fibers of mixed denier according
to the present invention, although this may not explain
all the advantages of the invention, as will be apparent,
hereinafter.
The degree of mixing of the fibers of mixed
denier in the cross-section of ~uch yarn as represented in
Figure 1 can be measured by a DFI test. DFI means degree
of filament intermingling, and i~ described, in relation
to continuous filament yarns (referred to as heather
yarns) in Reese U.S. Patent No. 3,593,513. The same
general technique, i.e. measurement of intermingling, i6
applicable herein to polyester staple fiber in a ~pun
yarn. However, unlike heather continuou~ filament yarn~,
for which the filaments must be colored to distinguish
them, the DFI relates to the degree of intermingling of
fibers of differing deniers. Sin~e the ~iber of 6maller
denier i~ distinctly smaller (about half the size) of the
fiber of larger denier, the difference will be immediately
apparent, and there is no need to cclor the fiber6. As
will be appreciated from looking ~t Figure 1, even a
comparatively random degree of mixing provides a
significant increase in the interstitial ~pa~es, because
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the presence of fibers of ~ignificantly differing deniers
prevents close packing, even if the fibers of one denier
tend to pack together to some extent. What i~ ~o~t
~ignificant i6 that the use of iEiber~ of mixed denier has
S shown a perceptible increase in comfort propertie~ in
wholly polyester fabric~. Po6sibly, the improvement may
be because of the inevitable packing tsgether of the prior
3rt polyester fibers, of uniforDn denier, especially when
they are subjected to the later~ pressure~ involved in
spinning (twisting) into yarn~, and in ~ubsequent fabric
formation.
~he advantaqes of using the intimate ~ixture6 of
polyester ~taple fiberfi acc~rding to the invention are
better described hereinafter in relation to the Examples.
These advant~ges ~hown hitherto ~re significantly
~urprising, especially if such advantages can be
confirmed by perceived comfort improvements in fabrics
prepared from yarns prepared from blends with cotton.
Because cotton i5 a natural product, cotton is it~elf a
variable product, in the sense that there i6 no uniform
length, diameter, or sur ace, and in this respect, quite
apart from chemical differences, there are ~ignificant
physical differenc~ between a natural ~iber, such as
cotton, ~nd a ~ynthetic fiber, where every effort has
generally been made by a ~ynthetic fiber manufacturer to
achieve uniformity to the extent ~f practical identity
between different fibers. Because of the 6ignificant
content of cotton (which is nece~sarily of varying
dimension~) it would be extremely ~urpri~ing if garments
formed ~rom yarns of blends of cotton with mixed denier
polyester staple according to the ~nvention 6hould provide
confirmed comfort advantages, ~s compared with garments
prepared from prior art blends, involving only single
nominal denier polyester staple fiber.
Although the reasons for these advantages are
not fully understood, and the invention is not limited by
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any theory of operation, the following ~peculations may be
of assistance. Conventionally, most polyester staple has
been of round cros~ ~sction. This is becau~e a round
cross ~ection ha~ proven, ~o far, to be the most
economical tc produce, and cost ha6 been an extremely
important consideration in the manufacture o~ polyester
staple fiber, which has long been ~ comm~dity, and has
been ~vailable in ~bundant quantities (~enerally in exce~s
of demand) in many industrial countries, and ha6 been
easily transportable at relatively low cost6 from
countries where costs of manufacture are already low, and
are often 6ubsidized ~o a~ to facilitate the export of
polyester staple fiber ~nd imprDve the balance of trade of
the country of manufacture 85 part of that country' 5
government policy. As already indicated, conventionally,
polyester staple fiber i~ manufactured from polye~ter
filament tow which, in turn, is generally prepared by
assembly from individual bundles of polye~ter continuous
filaments formed by spinning in individual cell6, in a
manner comparable to that conventionally u~ed for
polyester continuous filament yarns. These bundle~ of
filaments are ~ssembled into a tow, which may amount to
~ome ~illion or 50 polyester filament~. The filament~ in
these bundles ~ay have 60me oohesion, depending on their
hi6tory and mode of preparation, possibly resulting from
the applic~tion of ini~h to the freshly-6pun bundle, from
any other r~ason for the filaments in the initial bundle
to stick together, and from any ~light degree of twist
that may be introduced as the filament bundle is advanced
past various rolls and guides. Consequently, depending on
the particular history of making the individual bundles
and the tow, and on the particular conditions of mixin~,
any 6uch ~ubsequent mixing or blending operation may
appear to achieve intimate admixture with cotton, but may
not achieve a degree of mixing of the individual fibers as
great as can be obtained by cospinning or 6pinning on the
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same machine according to the preferred proce~s of the
invention. If filaments of the 6ame denier and round
cross section are closely packed into small bundles, it is
believed that certain results may follow, such as reduced
air permeability between the fibers, difficultie~ in
dyeing, reduced moisture transport (wicking ~ction) and
other characteristics that may, in retrospect, also be
attributable to the close packing of the individual
filament~. In contrast, if the filaments ~re of
distinctly different deniers, this close packing
arrange~ent become~ more difficult, if not impossible, and
probably account~ for improved air permeability, ease of
access of dye molecules, ~oisture tran~port, for example,
and alco an ability of the filaments to move past each
other readily and take up different positions, which could
be of great advantage in a comfort sen~e and in improving
processability of the staple fibers and possibly even of
precursor tows. These results and consequent advantayes
may be enhanced by varying the cross ~ection of the
individual filaments, in addition to varying the denier,
and this i~ why, from technical considerations, different
cross sections for the polyester ~taple fiber and
precursor filaments may be preferred, as well a6 ~ixed
deniers. However, 60me cro~s-6ections (~uch as ~ertain
trilobal filament~) may tend to give a harsher feel in
fabric~, whereas ~ ~calloped-oval cros~-~ection or other
les~ harsh configuration may be preferred.
For convenience, the discussion herein is
directed to mixtures of fibers of two different deniers,
with the perceived objective being to minimize the
possibility of close packing, and maximize the spaces
between adjacent fibers. Taking this simple combination
of two different deniers, from theoretical considerations,
we have calculated that the percentage of space between
such elosely packed fibers increases through a maximum, at
a ratio of small to large diameters of about 0.7,
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corresponding to a small to large denier ratio of about O.S. It will be understood that
essentially the same effect can, however, be obtained with different diameter or denier ratios
within a range on either side of this approximate optimum. For instance, almost as much
5 beneflt can be obtained when the small to large flber diameter ratio is from 0.5 to 0.9,
corresponding to a denier ratio of 0.25 to 0.8. In other words, it is believed possible to
obtain essentially as much advantage by providing m;xed denier staple of such small to large
denier ratios, and it is not necessary to provide mixed denier fibers only in the exact 0.5 ratio
of small to large denier. The above calculations have been made on the basis that essentially
10 only 2 fiber diameters are involved, which would be the case in a wholly polyester yarn of
only 2 deniers mixed together. When blended with cotton, however, assuming that the
polyester blend is of, for example, 1-1/2 nominal denier, i.e., the lower denier fibers are of
average denier about 1, and the higher denier fibers are of average denier about 2, and that
the polyester is blended with cotton also of matching average denier 1-1/2, then the resulting
15 yarn will involve such cotton hbers of this intermediate average denier, which may have the
effect of reducing the void content, so that it may be advantageous to further widen the
difference between the average deniers of the polyester fibers, so as to increase the void
content in the resulting blend, because it is this blend with cotton, rather than the polyester
blend of mixed deniers, that will be used in the yarns, and so in the ultimate garments and
20 fabrics that must be worn.
For conven;ence, about equal numbers of small and large denier fibers have been
used, but this is not essential, especially if mixed cross-sections are used in addition to mixed
deniers, bearing in mind the perceived objective of maximizing spaces between fibers, and
minimizing close packing. Indeed, from a theoretical
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stan~point, in a yarn of some 140 fibers in cross-section,
a major improvement in loose packing can be ~btained, in
theory, from arran~ing only a relatively 5~all number of
fibers of different denier, provided they are
5 strategically located ~o as to ~aximize the packing
dislocation, i.e. prevent clo~e packing. ~ow~ver, the u6e
of minimally 6mall proportions of fibers of di~ferent
denier will not necessarily achieve uni~orm ~dvantageç,
and so it is pre$erred to use more equal proportions and
obtain more reliable re6ult~. This will al60 depend on
the number of fibers, 6ince ~he u~e of mixed denier~ will
probably provide little difference in the packing of
fibers in yarns having only a very ~mall number of fibers
in each cross-section.
A process or preparing the blends according to
the invention will be described with reference to Figure
3, which is a block diagram showing a typical processing
sequence th~t may be used. Thus, the fir6t 6tage i~ to
- melt spin the filaments of higher denier ~nd the filament~
of lower denier and form them into a bundle of filaments
of mixed denier, and this will be descr~bed in further
detail. However, in other respects, the preparation of
the staple fiber may be conventional. The preci~e de~ails
will generally depend on the intended use of the polyester
fiber and, accordingly, the prspertie~ desired. For
$nst~nce~ for textile processing, e~pecially spin~ing
(twisting) to form 6pun yarns, polyester tow6 are
conventionally crimped mechanically, e.g. by a
~tufer-box. ~or some purposes, especially where 6trength
is desirable, the tows are annealed. At present, it is
believed that all polyecter ~taple fiber or textile u6e
is prepared from filaments that have been withdrawn from
the spinneret at relatively low speeds, followed by a
drawing operation to increase the orientation and
3~ crystallinity. ~owever, it has been known for many years,
e.g. as disclosed by Hebeler, U.S. Patent No. 2,604,667,
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that 60mewhat similar properties can be obtained, without
drawing, merely by withdrawing polyester filament~ at
extremely high speeds, although ~uch a process requires
high capital investment. Conventionally, ~n appropriate
finish is applied to the polyester filaments to facilitate
further proce~sing, and the particular finish selected
will depend on the 0nd use intended. For some end u~e
applicati~ns, a tran~ient finish is desired, i.e. one that
is easily re~oved, e.g. by washing. For other
applications, it ~ay be de~ir~ble to apply a permanent
finish, or a combination of a plermanent and transient
~inish, according to the desired end u~e.
The preparation of an intimate mixture of
filaments of mixed denier in the same bundle by 6pinning
on the ~ame spinning machine will now be desçribed in
greater det~il with reference to Figure 4, which
represents part of ~ conventional 6pinning ~achine
prov~ding a bundle of polyester continuous filaments which
are collected in a piddler can, Dnd which can be adapted
for preparing a tow of filaments of mixed denier for use
according to the pre~ent invention. The piddler can 1 is
6hown on the left and is ~ed with a l~rge bundle ~ of
filament~ obtained fro~ the ~pinning ~achine 3 on the
right of the Figure. ~t the top are ~hown a ~eries of
spinneret~ 4, ~tretching away to the right, it being
under~tood that only part of the cpinning machine 16
6hown, with only two of the spinneret~, but it being
conventional ts arrange a much larger number of ~pinnerets
in a bank on either &ide of the spinning machine, only one
side of which is shown in the Figure. Molten polymer i5
~pun through orifices in each ~pinneret 4 to form
filaments 5 which are cooled by air conventionally by
means not ~hown, ~nd are converged by passing between
guides 6, before the solid filaments pass a ~ini~h
applicator, 6hown as a roll 7, before contacting feed
rolls 8, which are driven at a speed (the withdrawal
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speed, ~r ~pinning speed) which deter~ines the orientation
of the freshly-extruded filaments. Thereafter, each
filament bundle 9 rom each individual ~jpinneret ~, or
~pinnin~ po~ition, or ~pinning cell, is advanced by
rolling guides 10 ~nd combined ~ith bundles from the other
~pinning position~ to form larger bundle 11 that emerge6
from the front of the spinning machine and i~ co~bined
with a ~imilar bundle 11' that has been provided from
cpinnerets and spinning positions (not shown) on the ~ack
of the spinning ~achine and advanced by rolling guides
10~. Thus the larger bundles 13 and 11' are ~upeeimposed
and so combined into large bundle 2 which i6 further
advanced by rolling guide or guides 10'' ~nd fed into air
jet 12 and through lay-down ~pout 13 into piddler can 1,
which i5 used for transporting the freshly-spun ~ilaments
in large bundle 2 to the next ~tage. The next ~tage is
conventionally a drawing machine, assuming that large
bundle 2 consists of conventional undrawn polyester
filaments, which are subjected to the conventional ~teps
of drawing, annealing if desired, crimping, relaxing and
converting to staple fiber. Hitherto, the process
described has been conventional.
Such a process can easily be adapted for
preparing the mixed denier products of tbe invention in
several ways. It is believed that the most uniform mixing
can be achieved by co~pinning, i.e. by spinning mixed
denier filaments from the same ~pinneret 4 through
capillaries of differing size and/or throu~hput into the
~ame spinning cell, or ~pinning position, and sollecting
these filaments of different deniers into the ~ame bundle
9 at the bottom of each spinning position, and then
collecting several such bundles of mixed denier filaments
forwarding and processing them appropriately. Such a
process may be particularly desirable if the bundles 9 are
provided with 6ignificant bundle integrity, e.g. by
application of twist and/or such amount and/or type of
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finish, or for ~mall tows, e.g. for conversion by
stretch-breahing.
~ owever, provided precauti~ns ~re taken, we have
found that very ~ati~factory re~iults have been obtained by
spinning filaments of uniform denier from each 6pinneret 4
and collecting them in the ~ame bundle 9 at the b~ttom of
each ~pinning position, and then combining 6uch bundle 9
of filament6 of unifDrm denier with other bundles of
filaments of different denier into a large bundle of
filaments of mixed denier. In other words, different
spinning poæitions on the ~a~e spinning machine will each
spin bundles 9 of filaments of uniform denier, but because
the different ~pinnerets 4 Dre spinning filaments of
different denier, the final bundle 2, and possibly the
larger bundles 11 and 11', contain filaments of ~ixed
denier. It i~ important to Avoid the individual bundles 9
having too much bundle integrity Guch as will inhibit
for~ing an intimate ~ixture of mixed denier during later
processing. Thus, it is important to ~void excessive
interlacing, or bundle twist, Ot exces~ive coating of
finish, as will inhibit later intimate mixing.
If the ab~ve theory is correct, namely that
mixed denier fibers provide more comfort in garments
because they do not pack ~o closely in ~pun yarns as
single denier fiberc, then thi6 advantage will be
obtained, regardless of the time of mixing proYided the
distribution of fibers of different denier6 is achieved
~e.g. by obtaining a preferred DFI of at lea~t about 90~)
in the spun yarns in the ultimate garment~. Thu~, in
order to obtain thi~ objective, it may not prove necessary
to mix the filament~ in the precursor tows, a~ described
above for the preferred proces6. Neverthele6s, thi~
process is preferred because of its effectivenes6 and it~
economy. However, alternatively, ~ixing could be achieved
during proce6E;ing of the staple fiber, preferably by
cutter blending tows containing filaments of different
-~7- ~323~
deniers so a6 to produee a mixed denier ~taple, or ~t a
convenient later stage. It will be understood that the
normal staple operations are intended to ~ix the various
fibers together, and to improve the degree 9f mixing of
whatever materials are fed. For instance, if slivers o~
fibers of differing denier are fed into an e~rly stage of
a multi-stage drafting operation, considerable mixing will
be achieved in the l~ter stages and in the resulting spun
yarns. The drafting conditions should not be ~uch as to
6egregate the different deniers to an undesirable extent.
The fibers in ~pun yarns must be twi6ted tightly
together in order to ~aintain the integrity of the yarn.
In contrast in filament yarns, close packing i~ not
necessary to maintain the inteqrity of the yarns. So it
can be understood that the need for interstitial voids
between closely packed fibers is correspondingly greater
if, indeed, such inter~titial voids or pas6age~ promote
greater comfort for the wearer of the garment6. Thus, it
is believed that the garment from spun yarn~ containing
mixed denier fibers are ~ofter and provide more comfort
because of the open space and loose ends, which are
believed to provide soft, dry, cool, and airy ~esthetics,
and more breathability. It i~ p~ssible that the mixture
of deniers also gives better aesthetics for reasons that
are not connected (or only indirectly connected) with the
grsater inters~itial spacing, ~or ~nstance the loose ends
that inevitably protrude from the ~urface of a ~pun yarn
and garment thereof may provide a more pleasant texture,
because of the mixture of denier~. The inter~titial
spacing may, however, be responsible for a greater ability
of the fibers to move and flex, and this could be
responsible, in part, for ~ny greater feeling of comfort
in the garments.
The invention is further illustrated in tbe
following Exa~p~e.
-18 1323~
EXAMPLE
An intimate mixture of appr~ximately equal
numbers of low pilling polyester staple fiber (relative
viscosity 15.4, LRV 11.5) of about 1 and about 2 dpf was
obtained by a proce6s, as described with reference to
Figure 4, involving conventionally ~elt-spinning to ~orm
a bundle of filaments, combining 6everal bundles to form a
large bundle, i.e. ~ small tow, drawing/annealing and
crimping the tow, and converting the tow to 6taple ~iber
by cutting, except that the large bundle (tow) contained
intimately mixed filaments of different dpf made by
~pinning through orifices and capillaries with different
throughput on the same ~pinning machine. The orifices
were circular to provide filaments of round cro~ ~ection.
The smaller filaments (spun denier 2.72, natural draw
ratio 1~68) were ~pun on one ~ide, on 18 po6ition5, ~ach
having 2400 orifices of diameter 15 x 30 ~il (about
0.38 x 76 mm) under a pack pressure of 1500 psig at a
throughput of 0.0625 lbs. per hour. The larger filaments
(spun denier 4.89, natural draw ratio 1.69) were ~pun
through similar orifice6, but under a pack pressure of
1900 psig at a throughput of 0.1195 lbs. per hour, on the
other side, on 24 po6itions, each having 1590 orifices.
~ll these filamen~ were 6pun ~t a withdrawal ~peed o~
1,800 ypm. The tow, ~mounting to ~bout 80,000 filaments,
was drawn at a draw ratio of 3.1X, cr~mped to give drawn
filaments of 9 crimps per inch and crimp take-up 31.5, and
cut to a cut length of 1-1~2 inches, to give taple ~iber
with tenacity of 3.4 g/d and a dry heat shrinkage of about
5.5% and a fini6h level of 0.07% by weight of the
filament~. The nominal denier was 1.5, but about half the
filaments were of 1 denier and the other half of 2 denier.
It wa~ ~urprising that it was possible to spin
on the same ~pinning machine undrawn filaments of
different denler that could be assembled into a tow and
then be drawn satisfactorily at the same draw ratio in the
--18--
... . . ... .. . . . . .
1~23~ ~
--19--
~ame t~w, i.e. to give ~atisfactory drawn filament~ and
eventually cut fiber (of intentionally ~ignificantly
different denier). ln other words, it was ~urprising that
it was possible to spin undrawn filaments of 6ubstantially
S the same natural draw ratio, but of ~ignificantly
different denier, on the ~ame ~pinning ~achine. These
filament~ and cut fiber have alEio ~hown good
processability through to spun yarns, and eventually
fabric~ and garments, which ~ay be 2 re~ult of their
relatively sharply deined denie!r distribution, as shown
hereinafter in Figure 5 for Yarn A. The tensile
properties of the drawn filaments (and cut ~iber~) were
~ignificantly different, the tenacities of the 6~aller
denier filaments being significantly higher than those of
the filaments Df higer denier.
The staple fiber was formod into yarns of
singles tcotton) count 16 (corresponding to ~bout 330
denier, or about 220 fibers of nominal denier 1-1/2) and
knit by an outside evaluator into fabrics which were
tested in comparison with co~parable fabrics, except from
a competitive co~mercial polyester 6taple fiber (Fabric
K). The details are shown in Table 1.
--lg--
... . .. , . . . " , .
~323~ ~
-20-
TABLE 1
Yarn Types
Par~meter A R
Fabric Wt., oz./sq. yd. 4.93 5.36
~abric Count, w x c 25x27 26x26
Fabric Thickness, mil 19.0 20.0
Moisture Vapor,
gm./sq.m./24 hrs.987.3 953.0
Air Permeability-Dry,
cu . ft ./sq . ft./min. 576.4 479.3
Air Permeability-Wet,
cu.ft./sq.ft./min.613.0 50~.5
Random Pilling, 0 min.4.9 4.9
3 min.4.3 2.9
5 min.3.1 l.9
10 ~in.2.1 1.3
20 min.1.5 1.0
30 ~in.1.2 l.0
Cover/Thickness 4.53 4.40
Tenacity, gm/den 1.75 2.39
Elongation, ~ 17.30 27.50
~/S ~ 460 nm 0.0061 0.0053
~ -20-
... .. . .. .. .. . . . .. . .
-21- ~323~
Fabric A prepared fro~l staple fiber of the
invention showed the foll~wing differences, which
translate into a ~ignificant sverall ~dvantage, ~s rated
by the outside evaluator;
1. 17% deeper dyed in competitive dyeing;
2. 20~ higher air-permeability in dry fabric,
and 12% higher in wet fabric;
3. 4% higher moisture vapor tran6port;
4. 27% lower tenacit:y;
5. 37% lower elongat:ion;
6. ~ignificantly 6uperior pilling performance;
7. 3% higher cover per thickne6s.
The i~proved results obtained with the polyester
~taple fiber of the invention prepared in thi~ Example
over the prior art fiber are believed to result from the
~ixed denier feature, which may provide ~ore open ~pace
between the tightly packed fibers, and possibly other
advantages, which cannot yet be fully explained,, and are
not yet therefore under6tood.
The distribution of the denier~ in
representative samples of ~taple fiber compri lng yarns A
and R was counted, by taking 200 ~uch staple fibers from
each yarn, measuring their deniers and plotting the
frequency of such denier~ as histograms that are ~hown in
Figure 5 of the accompanying drawings. Thus, the
histogram for yarn R, at the bottom, is typical in that it
it monomodal, i.e. ha~ a distribution about a single peak
at the nominal denier of about 1.5, whereas the histogram
for yarn ~ is bimodal, i.e. has distribution about two
~eparate peaks at the approximate nominal deniers of the
two component fibers of about 1 and about 2.
These histograms seem to indicate that the
significant advantages in fabrics of mixed denier yarn A
over yarn K may not result entirely or directly only from
~he fact that fibers of mixed denier do not pack together
so olosely, because the variation in denier for the fibers
.
.
.
-22- ~3~3~
6ampled fro~ yarn ~ ~fro~ a ~in~mum of abo~t l dpf t~
maximum of more th~n 2 dpf) ~ ~ignificant ~ough ln
theory to allow for 1006e packinq unle6~ the f~ber6 o
6imilar denier ~n yarn ~ happen to or tend to conqeqrAte
together in practice.
A further comp~rison i~ ~Dde by ~king spun y~rn
of 27/1 cc from 1003 of the same mixed denier y~rn A, and
from 50/50 polyester/cotton blonds, and knitting 18-cut
$nterl~ck fabric6 therefrom an~d comp~ring with ~lm1lar
fabric~ ~r~ a commerclal ~taple flber ~ (of the ~ame
polymer as used for yarn A) anld from a c~mercial
competiti~e ~taple fiber C, both of un$form den~er 1.5 .
The fabrics were ~ll Jawatex 6coured at 205F, pressure
dyed, dried, Tubetex~6teamed tw~ce and he~t set at 350Dr
for l minute. No re~ins or 60ftener6 were u6ed. ~he
breathability of these fabric6 w~c tested by mea~ur$ng
their air permeability ~n cfm ~average cubic ~eet per
~inute), for both the lO0~ polye~t~r and the blends. The
results are ~hown in ~ble 2.
TAaLE 2
Sample A ~ C
Air Permeability in CFM
100% Polye~ter 393 3~1 363
50f50 Blend 300 291 237
These re6ult6 6how an lmprove~ent ln alr
permeab$1ity for Sample A (~ixed den~er ~t~ple of ~y
invention) over two commercial flber~ of the ~a~e nomin~l
denier, but of uni~orm denier. The ~mprovement 18
~ignificant, and is ~hown b~th for 100~ polyester and for
50/50 blends with ootton. Intere6tingly, the ~ir
permeability for the blends i~ in~erisr to that ~or the
lO0~ polyester, ~nd the difference ~r A ~nd C, ~t least,
is far gre~ter in the blend than ~or the lO0~ polye~ter,
which ~eems to indic~te that any 6peculation based on
~heoretical calculations o~ 6pacinq between fiberE ~ay not
; * denotes trade mark
' ' . . .
' ' .
-23- 13~3~
be sufficient to account for the differences obtained in
practice.
Si~ilar yarns of other cotton counts can be
made, and formed into fabrics and garments, from 100%
polyester and/or blends containing variou~ percentages of
other fibers, ~uch ~s cotton. An advantage of the
perception that the mixed denier staple fiber provides
better perceived comfort, is that the proportion of
polyester in such blends can be improved over that
preferred today by the wearer, e.g. back to 60/40
polyester-cotton, or sven higher, e.g. to 75/25, or 80/20
or 100% polyester. The cut length of the polyester has
generally been 1-1/2 inches to match the average length of
the cotton. Conventionally, cut lengths range from about
1 to ~bout 3 inche~. The denier of the polyester 6taple
has conventionally matched the cut length ~pproximately,
i.e. a 1-1/2 nominal denier for a ~ut length of 1-1/2
inches. Vsing mixed denier poly~ster staple according to
the invention, therefore, a mixed denier (1 and 2 denier)
blend would match 1-1/2 inches in cut length, as in the
Example, although use of the mixed deniers may enable some
variation in this hitherto-accepted rule of thumb. Thus
nominal deniers of up to about 3 (mixed deniers of about 2
and about 4 denier) and generally down to ~bout 1 (~ixed
deniers to about ~/4 and ab~ut 1-1/2) ~an be expected to
be used, althouqh there has been a tendency to use finer
deniers in recent years, and thi~ could be of advantage,
e.g. in pilling performance. Furthermore, as indicated,
especially when blending with cotton, there ~ay be an
advantage in widening the difference between the average
denier6 of the polyester fibers beyond the value~
indicated.
The invention has been described hereinbefore
with particular reference to yarns and other articles
consisting of polyester staple fiber of ~ixed denier
prepared from poly~ethylene terephthalate), which i6 u~ed
. . ~ . . - ~
-24- 1323~ ~
commercially on a very large ~cale. Other polyester
polymer may be used alternatively, or in addition, of
course, e.g. cationic-dyeable polyesters, ~uch as are
already used commercially, or other copolymer~ that are
mentioned in the literature. IE desired, the polyester
may include ingredients and/or additives, a6 i6
conventional, e.g. a content of delustrant, r~uch as
titanium dioxide, and/or be treated so ~s to modify the
surface or other characteristic~s, as desired, to improve
the properties of the ~ubstrate polyester during filament
formation or subsequently, e.g. in fabric form. Such
changes or modifications in the nature of the polyester
polymer do not affect the essence of the invention, which
is ba~ed on the intentional u~e of mixed denier ~taple
$nstead of uniform denier staple to form the ~pun yarns.
.
-24-
