Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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METHOD AND APPARATUS FOR COOLING MOLTEN
FILAMENTS IN SPINNING APPARATUS
BACKGROUND OF THE INVENTION
1. Field of the Inventlon
The present lnventlon relates to a method for -~
coollng a plurallty of molten fllaments comprlsed of a
thermoplastlc resln extruded from dle and to an apparatus for ;
carrylng out the method.
2. Descriptlon of the Related Art
In t~e cooling of molten filaments, if the
temperature of the coollng alr 1~ lowered or the alr flow rate ls
lncreased so as to rapldly cool the fllaments, only the surface of ~ -
the fllaments wlll be cooled and solldlfled. If a draft ls
applled to the fllaments ln that state, the fllaments wlll melt --
and break or the elastlclty, tenslle strength, and other physlcal
propertles of the yarn wlll be lowered. Conversely, lf the - ~-
fllaments are gradually cooled, the fllaments tend to adhere to
each other and, further, the coollng zone must be made longer, and
thus the slze of the apparatus 18 necessarlly lncreased.
Even lf the spinnlng speed ls lncreased or changed,
lf the coollng ls carrled out wlthout changlng the length of the
coollng zone, a rapld coollng becomes necessary, and thus the --
problems dlscussed above wlll arise.
SUMMAR~ OF THE INVENTION
Accordlngly, an ob~ect of the present lnventlon 18 to
obvlate the above-mentloned problems, caused by a too rapld or
gradual coollng of the fllaments. -
Other ob~ects and advantages of the present inventlon
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wlll be apparent from the followlng descrlptlon.
In accordance wlth the present lnventlon, there ls
provlded a method of coollng molten fllaments ln a splnnlng
apparatus, where a plurallty of molten fllaments extruded from a
dle are cooled by coollng alr blown out from a coollng apparatus
and are taken up wlth a draft, comprlslng controlllng the
temperature of the coollng alr blown from the coollng apparatus so
that the coollng effect 18 made weaker ln the upstream (top)
reglon and stronger ln the downstream ~bottom) reglon, ln stages
or contlnuously.
In accordance wlth the present lnventlon, there ls also
provlded a coollng apparatus ln a splnnlng apparatus where a
plurallty of molten fllaments extruded from B dle are cooled by
coollng alr blown from a coollng apparatus and are taken up wlth a
draft, and whereln a plurallty of coollng apparatuses with
dlfferent temperatures or temperatures and volume~ of the coollng
alr are connected ~o that the coollng ls performed stronger ln the
downstream stages.
In a further embodlment, the lnventlon resldes ln a
coollng apparatus ln a splnnlng apparatus where a plurallty of
molten fllaments extruded from a dle are cooled by coollng alr
blown from a coollng apparatus and are taken up wlth a draft,
whereln there ls provlded a heater ln the flow path of the cooling
alr wlth the pltch sf the heatlng wlres ls made closer upstream 80
as to gradually lncrease t~e amount of heat generated.
In a stlll further embodlment, the lnventlon resldes in
a coollng apparatus ln a splnnlng apparatus where a plurallty of
molten fllaments extruded from a dle are cooled by coollng alr
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blown from a coollng apparatus and are taken up wlth a draft,
whereln the flow path of the coollng alr ls formed so as to be
gradually narrower ln the upstream dlrectlon or ls formed so as to ~ -
gradually lncrease the pressure loss.
BRIEF DESCRIPTION OF THE DRAWINGS
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The present invention will be better understood
from the description set forth below with reference to
the accompanying drawings, in which:
Figure 1 is a schematic view of a spinning
apparatus provided with a cooling apparatus according to
a first embodiment of the present invention;
Fig. 2 is a schematic view of a spinning
apparatus provided with another cooling apparatus; and
Fig. 3 i5 a schematic view of a conventional
1~ spinning apparatus.
DESCRIPTION OF THE PREFERRED ENBODIMENTS
According to the present invention, the above-
mentioned problems can be solved by controlling the
temperature and/or volume of the cooling air 90 that the
cooling is performed stronger, in stages or ~ -
continuously, from upstream to downstream of the
filament flow.
The easiest way to change the cooling in stages and
the easiest in terms of control is to divide the cooling
zone into several sections, a cooling apparatus is
provided for each section, and the cooling by the
apparatus is made stronger in the downstream direction.
To change the cooling continuously, it is possible
to adopt, for example, a method of arranging a heater in
the flow path of the cooling air, and the pitch of the
heating wires is made closer in the upstream direction
so as to gradually increase the amount of heat
generated, whereby the cooling air is warmed by contact
with the heater and then blown or a method of forming
the flow path of the cooling air is gradually narrowed
in the upstream direction or the pressure loss is
gradually increased to gradually reduce the amount of
air upstream of the filament flow.
Further, when changing the spinning speed is
changed, the degree of strength of the cooling can be
changed.
Although the temperature and volume of air for -~
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coollng largely depend upon the materlals to be extruded, the
temperature of the molten fllaments, and the extruslon rate, the
temperature of the coollng alr ls preferably -20C to 140C, more
preferably 0 to 100C, and the volume of the coollng alr to be
blown ls preferably 2 to 40 m3/kg, more preferably 5 to 25 m3/kg. ;-
The materlals to be extruded lnclude, for example, polyethylene,
polypropylene and other thermoplastlc reslns.
The molten fllaments extruded from the die are cooled
weakly at the upstream portlon of the coollng zone and strongly at
the downstream portlon thereof. When the coollng ls weak, the
temperature dlfference of the fllament surface and lnterlor is
made small and the draft ls applled ln that state to ensure that, -
a unlform draft ls applled, whereby the elastlclty, tenslle
strength, and other physlcal propertle~ of the fllaments are
lmproved, and meltlng and breaklng occur wlth dlfflculty.
Further, at the downstream slde where the fllaments are taken up,
a strong coollng ls performed for solldlflcatlon, so adheslon
between fllaments occurs wlth dlfflculty. Thus, lt ls posslble to
make the coollng zone shorter than wlth gradual coollng of the
whole.
If the splnnlng speed ls lncreased, lt ls posslble to
avold rapld coollng by lncreaslng the ratlo of the weak coollng ln
the coollng zone. Note that when the splnning speed ls reduced,
there ls no problem lf the ratlos of the strength of the coollng
are varled.
Flgure 3 shows a conventlonal splnnlng apparatus for
fllaments comprlsed of polyethylene, polypropylene, or other
thermoplastlc reslns. In thls apparatus, a plurality of molten ;~
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fllaments 2 extruded from a dle 1 are cooled by coollng alr blown
from a coollng apparatus 3 and then taken up with a draft. The
coollng apparatus 3 comprlses a chlmney 4 connected to a dle 1 ln
a manner so as to surround the molten fllaments 2 and a gas
temperature ad~ustment apparatus 5 composed of coolers. The -
apparatus S cools the cooling air to the deslred temperature and
the coollng alr ls fed to the chlmney 4 by a fan 6 and ls blown
from the lnner perlpheral surface thereof through a fllter 7.
Reference numeral 8 ls an exhaust fan. . -
Ernbodlments
Flgure 1 shows a flrst embodlment of two-stage coollng
apparatus accordlng to the present lnventlon, havlng the same
construction as that of the coollng apparatus 3 provlded ln the
splnnlng apparatus as shown ln Flg. 3 except for the fllter at the
bottom of the coollng apparatus 3, l.e., ls comprised of a chlmney
12 and a gas temperature ad~ustment apparatus 13 comprlsed
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of coolers. The said apparatus sends the cooling air,
cooled to a desired low temperature by the top stage gas
temperature adjustment apparatus 13, to the chimney 12
by the fan 14 and connects this to a cooling appa~
ratus 11 so that it is blown out from the inside
peripheral surface. It blows out relatively high
temperature cooling air from the top stage and
relatively low temperature cooling air from the bottom `
stage thus slowly cooling the molten filaments 2 at the
top stage and rapidly cooling them at the bottom stage.
For example, when polyethylene is used, the
preferable cooling conditions are as follows:
Top stage: 30C x 8 m3/kg
Bottom stage: 10C x 8 m3/kg
In the above-mentioned embodiment, the temperature
of the cooling air blown out from the bottom stage is
made lower than that at the top stage, but it is also
possiblé to change the air amounts of the fans 6 and 14
so as to increase the amount of air of the bottom stage
over the top stage and fur~her possible to change both
the temperature and air amount of the top and bottom `
stages.
A typical example of the cooling condition when
polyethlene is used i# as follows:
Top stage: 20~ x 4 m3/kg
Bottom stage: 10C x 8 m3/kg
The embodiment shown in Fig. 2 is comprised in the
same way as the apparatus shown in Fig. 1 outside of the
fact that the fan 6 in the apparatus shown in Fig. 1 is
made an exhaust fan and the cooling air of the bottom
stage is exhausted from the fan 16, heated by the
heater 17, then blown out from the top stage. As a ~ -
result, cooling air of a relatively higher temperature -
is blown out from the top stage and cooling air of a
relatively lower temperature is blown out from the
bottom stage.
The above-mentioned embodiment shows an example
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where two cooling apparatuses are connected for two-
stage cooling, but in another embodiment three or more
cooliny apparatuses may be connected for multi-stage
cooling and in still another embodiment heating wires
ma~ be wound around the internal peripheral surface of
the chimney and the pitch made gradually closer upstream
so as to heat the cooling air and give it a temperature
gradient so that the temperature gradually falls
dowr~stream, whereby the cooling can be made continuously
stronger downstream. Further, in another embodiment,
the flow path of the cooling air can be formed to be
gradually narrower upstream or formed 80 that the
pressure loss gradually increases, thereby gradually
decreasing the amount of the cooling air upstream.
As mentioned above, according to the method of
claim 1, the cooling is made performed weaker at the
upstream side and stronger at the downstream side,
thereby improving the elasticity, tensile strength, and :
other physical properties of the filaments without
enlarging the apparatus and further making molten
brea~age difficult and preventing mutual adhesion of
filaments.
According to the method of claim 2, even if the
spinning speed is changed to make it faster, the ratio
of the weaker portion of the cooling at the cooling zone
can be increased 80 as to avoid rapid cooling or
elongation of the cooling zone.
In the cooling apparatus of claim 3, a plurality of ;
cooling apparatuses are connected so as to strengthen
the cooling in stages downstream. -
In the cooling apparatus of claim 4, the
temperature of the cooling air can be given a
temperature gradient descending in the downstream
direction and the cooling can be made continuously
stronger downstream.
In the cooling apparatus according to claim 5, the
volume of the cooling air can be gradually increased
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downstream and thus the cooling can be made continuously
stronger downstream.
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