U.S. patent number 3,929,542 [Application Number 05/195,427] was granted by the patent office on 1975-12-30 for non-woven webs of filaments of synthetic high molecular weight polymers and process for the manufacture thereof.
This patent grant is currently assigned to BASF Farben and Fasern A.G.. Invention is credited to Heinz Gehrig, Hermann Linge, Sepp Wagner.
United States Patent |
3,929,542 |
Gehrig , et al. |
December 30, 1975 |
Non-woven webs of filaments of synthetic high molecular weight
polymers and process for the manufacture thereof
Abstract
Apparatus and process for the manufacture of a non-woven web.
The web consists of filaments of strands of filaments which show
helical crimping with alternating directions of turn of the helices
within the filament. Preferred outlets are floor coverings, cover
materials and filter mats.
Inventors: |
Gehrig; Heinz (Buerstadt,
DT), Linge; Hermann (Carlsberg, DT),
Wagner; Sepp (Weinheim, DT) |
Assignee: |
BASF Farben and Fasern A.G.
(Ludwigshafen (Rhine), DT)
|
Family
ID: |
5786974 |
Appl.
No.: |
05/195,427 |
Filed: |
November 3, 1971 |
Foreign Application Priority Data
Current U.S.
Class: |
156/167; 28/271;
264/168; 264/289.6; 425/72.2; 428/371; 156/181; 264/210.8; 428/357;
428/910 |
Current CPC
Class: |
D04H
3/007 (20130101); D04H 3/105 (20130101); D04H
3/16 (20130101); Y10T 428/29 (20150115); Y10S
428/91 (20130101); Y10T 428/2925 (20150115) |
Current International
Class: |
D04H
3/16 (20060101); D04H 003/16 () |
Field of
Search: |
;264/168,177F,21F
;161/150,170,173 ;156/167,180,181,183 ;428/225,288,296,371,910,357
;28/72.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
4,515,803 |
|
Feb 1970 |
|
JA |
|
4,512,546 |
|
Jul 1970 |
|
JA |
|
Primary Examiner: Lesmes; George F.
Assistant Examiner: Bell; James J.
Attorney, Agent or Firm: Johnston, Keil, Thompson &
Shurtleff
Claims
We claim:
1. A process for the manufacture of a non-woven web of spun
filaments, consisting of filaments or strands of filaments of
synthetic high molecular weight polymeric material, by extrusion of
filament-forming melts through spinnerets having a plurality of
spinning holes arranged in circles, ellipses or lines, wherein:
a. cooling air is caused to impinge on the extruded filaments from
one side at an angle of from 0.degree. to 90.degree. to the
direction of travel of the filaments, all or at least part of which
air is deflected to a direction of flow parallel to the filaments,
by which means the filaments are asymmetrically cooled and a
primary take-up of the filaments is effected;
b. at the end of the cooling zone substantially all of the cooling
air is allowed to escape from or is sucked away from the
filaments;
c. the filaments, substantially free from cooling air, are
subjected to the main take-up forces in a take-up zone which is
immediately downstream of the cooling zone and is in the form of a
single-stage or, preferably, multi-stage pneumatic jet;
d. the filaments being thereby stretched by the action of said
primary and main take-up forces upon them;
e. after stretching, the partially plastic filaments are helically
crimped by periodic alteration of the position of one or more
annular or cylindrical vortices of gaseous medium along the
filaments at a high frequency with partial flow-off and
replenishment of the vortex or vortices in conjunction with said
asymmetrical cooling of the filaments whereby the diameter of the
helices is from 1 to 10 mm and a change in direction of turn occurs
after every 1 to 50 times;
f. the crimped filaments are discharged through flexibly mounted
mouthpieces, which describe a transverse motion with superimposed
rotating motion, onto a moving belt preferably provided with
suction means at the point at which the said filaments initially
contact the belt; and
g. the laid-down web is bonded.
2. A process as claimed in claim 1, wherein the filaments are
relaxed and simultaneously cooled after the crimping stage, such
that the crimping is fixed as the filaments solidify.
3. A process as claimed in claim 2, wherein the pneumatic jets are
operated with hot gas or steam or both in order to modify the
filament characteristics.
4. A process as claimed in claim 3, wherein the strength properties
and elongation of the filaments and in some cases the type of
crimping obtained are influenced by feeding steam to the cooling
zone.
Description
The present invention relates to a non-woven web of filaments or
strands of filaments of synthetic high molecular weight polymers,
in which the filaments or strands of filaments -- hereinafter
referred to as the filaments -- are laid down in looped
configurations. The invention also relates to a process and
apparatus for the manufacture of such webs.
It is well known that a filament, a group of filaments or a bundle
of filaments coming from a conventional or specially designed
spinneret may be taken up by a pneumatic jet or aspirator jet of a
variety of types and transported to a lay-down area where a tangled
web is produced by turbulent air.
Japanese Pat. No. 45-5057 describes a process for the manufacture
of non-woven fabrics which uses conventional single-stage pneumatic
jets having a circular cross-section and adapted to take up the
filaments immediately after spinning or after mechanical
stretching. These simple pneumatic jets are moved transversely
across a moving belt, which procedure clearly leads to a web in
which the filaments are predominantly transversely oriented. Such
transverse orientation is inconvenient in most cases, as it
produces variations in the properties of the web in the different
directions in its plane. Another drawback of this process is that,
the filament being uncrimped, only webs of a low specific volume
can be obtained.
U.S. Pat. No. 3,117,055 describes non-woven fabrics consisting of
crimped filaments which have been bonded together with a bonding
agent by a special procedure. The fabrics are produced by causing a
single-stage aspirator jet to take up filaments issuing from the
spinneret. The aspirator jet is charged with static electricity so
that the filaments are also charged and repel each other on leaving
the aspirator jet. As a result, some of the suction medium can
escape laterally and there is a reduction in the axial speed
producing only slight compression of the filaments. Consequently,
the filaments passing to the web are crimped only slight and
irregularly. The use of electrostatic charges in this process adds
to its cost.
The disadvantages and shortcomings discussed above with reference
to the cited prior art may be added to by the following drawbacks
which occur in some cases:
Some of the filaments form fused lumps while still hot, due to
insufficient cooling;
Operational safety is inadequate;
The melt and air distribution over the length or width of the
nozzles and channels are very uneven;
The specific gas or energy consumption is uneconomically high; the
degrees of stretch obtained (strength properties and elongation)
are inadequate, or
Only smooth filaments can be obtained.
It is an object of the invention to provide an economical process
for the manufacture of a non-woven material which is superior to
known non-woven materials as regards specific volume, resilience
and recovery, damping properties and yield or slip characteristics
of the filaments during, for example, needle punching or tufting
operations.
In accordance with the present invention, this object is achieved
by providing each filament forming the fabric with helical crimping
showing alternating directions of turn along the length of the
filament, even if the latter is in a strand, the diameter of the
helices being from 1 to 10 mm and the changes in the direction of
turn thereof occurring after every 1 to 50 and preferably after
every 5 to 15 turns.
According to a preferred embodiment of the invention, the filaments
forming the web are laid down in the form of perfect or imperfect
trochoids, which trochoids show regular or random variations of
orientation.
Preferably, the web-formung filaments are of polypropylene,
polyester, polyamide, polyethylene or polyurethane. They may be
needle-punched, thermally bonded or bonded by means of dispersions
of bonding agents such as polyacrylates.
It is a further object of the invention to provide a process for
the manufacture of the non-woven webs of the invention from
filaments of synthetic high molecular weight polymers by extrusion
of filament-forming melts through spinnerets having a plurality of
holes in a circular, eliptical or linear arrangement, which process
is characterized in that
a. cooling air is caused to impinge on the extruded filaments from
one side at an angle of from 0.degree. to 90.degree. to the
direction of travel of the filaments, all or at least part of which
air is deflected to a direction of flow parallel to the filaments,
by which means the filaments are cooled and a primary take-up of
the filaments is effected;
b. at the end of the cooling zone, substantially all of the cooling
air is allowed to escape from or is sucked away from the
filaments;
c. the filaments, substantially free from cooling air, are
subjected to the main take-up forces in a take-up zone which is
immediately downstream of the cooling zone and is in the form of a
single-stage or, preferably, multi-stage pneumatic jet;
d. after stretching, the partially plastic filaments are crimped by
periodic alteration of the position of one or more annular or
cylindrical vortices of gaseous medium along the filaments at a
high frequency with partial flow-off and replenishment of the
vortex or vortices;
e. if desired, the laid-down web is bonded by mechanical, thermal
or chemical means by known methods.
During crimping, the filaments are normally partially plastic,
which means that the pneumatic jets may be operated with cold air.
If the filaments are over-cooled in the cooling zone, crimping may
be achieved by using hot air or steam in the pneumatic jet. The
crimps may be fixed by allowing the crimped filaments to relax
under conditions of cooling to below their softening point. The use
of steam in the cooling zone can influence the strength properties
and resilience of the filaments and also the type of crimping
obtained.
It is a further object of the invention to provide an apparatus for
carrying out the process of the invention, which apparatus is
characterized by:
a. one or more spinnerets of a circular, oval or rectangular shape,
each having a plurality of holes;
b. a cooling channel immediately downstream of said spinnerets and
comprising means for feeding and appropriately distributing the
cooling air and optionally means for deflecting the air to a
direction of flow parallel to the filaments, and a passageway
immediately downstream of said cooling channel, the lower end of
said passageway having means for allowing the cooling air to escape
or be sucked off and, if desired, flaps for partially closing the
outlet cross-section of the passageway;
c. pneumatic jets downstream of the passageway, preferably of the
two-stage or multi-stage type, and consisting of an outer housing
having air-feed connections, an equalizing chamber with damming
elements and inlet chambers downstream thereof, which inlet
chambers communicate with an inner channel via inlets, slots or
ducts at an angle of from 5.degree. to 30.degree., which inner
chamber is provided, in its wall, with a screw-adjustable suction
nozzle and, in the case of a multistage injector, increases in
cross-section from stage to stage, optionally via a diffusor;
d. a crimping device downstream of the pneumatic jet and consisting
of an inlet channel to which there is mounted via means for axial
displacement such as a screw-thread connection a member of greater
cross-section, for example a tube, the increase in cross-section
starting with an undercut and continuing irregularly to form a
chamber which ends in an irregular reduction of cross-section
leading to sharp edges defining the commencement of a short outlet
channel;
e. flexible connecting members, e.g. flexible tubes, which are
connected to the crimping device and are fitted with mouthpieces of
constant cross-section or, preferably, of enlarged
cross-section;
f. a moving device to which the mouthpieces are secured;
g. a moving belt optionally provided with suction means at the
point where the filaments initially contact the belt;
h. optionally, a device for effecting mechanical, thermal or
chemical bonding of the web.
The filaments are normally spun by means of spinnerets having a
circular, oval, rectangular or similar shape and containing a
plurality of spinning holes. Spinnerets may also be used which have
free spaces in their central region, through which cooling air may
be blown into the bundles of filaments, which cooling air may be
thermally screened from the spinnerets if necessary. It has been
found convenient, for the purposes of the process of the invention,
to pre-orientate the melt before it is extruded by subjecting it to
strong shearing strains. The first-mentioned spinning method has
the advantage that spinnerets of simple design may be used. The
second method using spinnerets with free spaces in the central
region still utilizes relatively simple designs compared with
complicated spinnerets of special design. Consequently, further
advantages of the process of the invention are as follows:
a. cold air may be used;
b. the point of impingement of the pneumatic force is not close to
the spinning hole but at a distance of at least about 10 mm
therefrom, this giving rise to a longer primary take-up zone;
and
c. the ratio of the cross-sectional areas of the melt and air at
their respective nozzles is more advantageous, with the result that
the specific air consumption is reduced for a given working
pressure.
Furthermore, the process of the invention differes from other
processes from the manufacture of non-woven webs, for example the
processes described in U.S. Pat. No. 3,117,055 and Japanese Pat.
No. 45-5057, in that a definite cooling zone is provided, this
being divided into sections for the introduction of cooling air and
its deflection (if necessary), for parallel air-flow, and for the
removal of the cooling air by suction or escape means. The process
of the invention differes from conventional spinning processes
which also make use of a definite cooling zone in that the cooling
air, which is caused to impinge on the filaments at an angle of
from 0.degree. to 90.degree. thereto, is deflected so that a
substantial proportion thereof flows parallel to the filaments. The
various cooling methods have the common feature of impingement of
the cooling air on the filaments from one side and, at least in the
second section, strong air flow parallel to the filaments at an
independent velocity.
Another important distinguishing feature of the present invention
as compared with prior art processes for the manufacture of
non-woven webs is evident at the end of the cooling zone, where the
cooling air is removed from the process and not transported through
the following main take-up means with the filaments. The primary
advantage of this embodiment of the process of the invention is
that the spatial density of energy is very high for a given
consumption of air energy and remains high over the length of the
pneumatic jet because only a very small amount of air and not the
entire stream of cooling air is sucked into the air jet. Whereas
the air used for taking up the filaments in the known processes
must also, to a considerable extent, carry out the function of
cooling the filaments, cooling is effected in a much more
economical manner in the present invention using air at a pressure
of from approximately 50 to 200 mm of water, since the air pressure
required to take up the filaments must be at least some thousands
of mm of water to some atmospheres if satisfactory filament
properties are to be achieved. Another advantage resulting from the
removal of the cooling air from the system is that when the web is
laid down, the amount of air which has to be sucked off is several
times (from 5 to 10 times) the amount of air impinging on the
moving belt, this being necessary to prevent the web from being
dislodged by the blast of air. In the present case therefore, only
the relatively small amount of air used for taking up the filaments
determines the suction power required, while the generally larger
volume of cooling air has already been removed from the filaments
before they are taken up.
In the process of the invention, the filaments are taken up by
means of, preferably, two-stage or multi-stage pneumatic jets
operated by an external air jet. The type of pneumatic jet proposed
by the invention makes it possible to operate all stages at an
equally high pressure, by which means highly efficient filament
take-up is achieved without the apparatus becoming blocking up. The
filament take-up apparatus of the invention increases in
cross-section from stage to stage in order to accommodate the added
volumes of working air. Another distinguishing feature of the
single-stage or multi-stage take-up apparatus as compared with
prior art devices is that after the air has passed into the outer
housing it initially flows into an antechamber where it is
uniformly distributed before passing over damming elements and
through inlet chambers to the inlet slots or ducts leading to the
inner channel containing the filaments.
Immediately downstream of the take-up apparatus there is a crimping
device which is distinctly different from prior art devices for
crimping filaments, for example for effecting aerodynamic
compression crimping, aerodynamic false-twist crimping or crimping
in a zone of a medium showing a high degree of irregular
turbulence. In the present case, crimping is effected by
periodically applying to and removing from the filaments, at a high
frequency, one or more annular or cylindrical vortices of a gaseous
medium with partial flow-off and replenishment of the vortex or
vortices. Crimping is assisted by the previous one-sided cooling of
the filaments under the action of the take-up forces.
When the filaments have been crimped, they pass to a diffusor zone
where the crimped effect is fixed as the filaments solidify in a
relaxed state. To obtain the crimping effect, it is first of all
essential to effect proper temperature control in the cooling zone.
If the filaments are over-cooled, they can no longer be shaped in
the crimping zone unless hot gas or steam is used in the working
stream of the aspirator jet. If the filaments are insufficiently
cooled, they will adhere to each other in the take-up and crimping
zones. If it is desired to open up the bundle of crimped filaments
such that the individual crimps are not in phase with each other
and the filaments are well separated from each other, it is
convenient to operate the final stage of the multi-stage pneumatic
jet not with a laminar flow of air but preferably with a plurality
of individual air jets emeging from appropriately arranged
bores.
The bundles of filaments leaving the pneumatic jets and their
associated crimping devices pass through movable elements, for
example flexible tubes, to mouthpieces which are moved according to
certain kinematic rules so as to describe perfect or imperfect
trochoids. In this way, webs are formed on the moving belt and have
a structure complying to the said lay-down movements.
The kinematics of the lay-down movements are composed of two
superimposed swinging motions, preferably a rotating motion and a
linear reciprocating motion effected transversely of the belt and
referred to as the transverse motion, the ratio of the frequencies
of the rotating and transverse motions being from 2:1 to 100:1 and
preferably from 4:1 to 50:1. The amplitudes of the linear
transverse motion are advantageously many times greater than the
diameter of the rotating motions. The reciprocating transverse
motion may cover the entire width of the belt or it may be effected
to cover a number of overlapping zones. Depending on the degree to
which the bundles of filaments have been opened up, the resulting
webs show structures composed of strands of filaments or individual
filaments.
The main advantages of the process of the invention are as
follows:
1. it involves a simple procedure and uses relatively small
units,
2. it is economical and very safe in opertion,
3. it produces good filament qualities with relatively uniform
thicknesses,
4. it provides the possibility of producing voluminous non-woven
webs of crimped filaments having excellent elastic and damping
properties.
The various parameters of the process are dimensioned as
follows:
Temperature of the melt: depending on the thermoplastic material
used, the melts may be spun within various temperature ranges, the
upper and lower limits of which may be anywhere in the range
defined by the commencement of melting and the maximum temperature
possible without the occurrence of chemical changes.
Pressure of melt: the pressures applied to the melt are between
about 1 and 150 atmospheres and preferably between 20 and 80
atmospheres gage.
Melt throughput: the throughput through each spinning hole is from
0.1 to 10 g/min and mainly from 1 to 6 g/min. Thus the rate of
extrusion of the melt is generally between 0.5 and 15 m/min and
preferably between 2 and 10 m/min.
Gas temperature: the temperature of both the cooling air and the
take-up air is conveniently in the range of normal room
temperatures, that is from 20.degree. to 30.degree.. However, the
take-up air may have a temperature of up to about 150.degree.C. if
desired, in order to achieve certain crimping characteristics for
example. For the same reason, steam or a mixture of air and steam
may be used.
Gas pressure: the pressures applied to the cooling air are normally
between 20 and 5,000 mm of water and preferably between 50 and 500
mm of water. The take-up air is usually under a pressure of between
0.5 and 50 atmospheres and preferably between 1 and 10 atmospheres
gage.
Gas velocities: the velocity of the cooling air is between 1 and 50
and preferably between 2 and 8 m/sec. In the suction tube of the
pneumatic jet velocities of from 10 to 500 and preferably from 50
to 200 m/sec may occur. The velocity of the take-up air on entering
the inner tube of the pneumatic jet is generally approximately
equal to the speed of sound or just below, after which the air
undergoes expansion with local supersonic velocities being
possible. Subsequent mixture of the take-up air with air drawn in
from the atmosphere reduces it velocity to below that of sound and
it achieves values between about 100 and 300 m/sec. In the crimping
zone this velocity is further reduced the values between 10 and 100
m/sec.
Specific gas consumption (defined as the ratio of amount of gas to
amount of melt in kg/kg or m.sup.3 /kg (STP): in the case of the
main take-up air, this ratio is approximately within the limits 1
to 50 and preferably 5 to 20.
Suitable plastics materials for the process described above are as
follows:
1. polyethylene of all densities (0.918 to 0.960 g/cm.sup.3) and
the copolymers of ethylene with l-olefins (e.g. propylene and
butene), with vinyl esters and acrylic esters (e.g. vinyl acetate
copolymers and butyl acrylate copolymers), with additional free
acrylic acid groups (e.g. ethylene/t-butyl acrylate/acrylic acid
copolymers) and with vinyl chloride. Post-chlorinated polyethylene
having a chlorine content of up to 40% is also suitable. The
proportion of comonomers in the total polymer may be up to 30% by
weight. Polymers in a wide range of molecular weights, measured in
terms of melt index (according to ASTM D1238-57 T) are suitable,
melt indices MI.sub.2.16/190.sub..degree.C being from 1 to 100 and
preferably from 5 to 20.
2. Polypropylene and polybutelen-1 and their copolymers with each
other and with other l-olefins (e.g. ethylene). The proportion of
comonomers may be up to 15% by weight, and the range of molecular
weights is as above (melt index range MI.sub.2.16/210.sub..degree.C
being from 0.1 to 50 and preferably from 1 to 20).
3. Polyamides, for example pure polycondensates of caprolactam or
dicarboxylic acids such as adipic and sebacic acids and diamines,
for example hexamethylene diamine. Copolymers, for example
copolymers of the above starting materials, are also suitable. The
molecular weights, expressed in terms of K values, may vary between
K = 50 to K = 90 and preferably between K = 70 to K = 80 (K value
calculated from the relative viscosity .eta./.eta..sub.o as
measured according to German Standard Specification DIN
53,726).
4. Polyesters: particularly suitable are the linear saturated
polyesters having average molecular weights between 10,000 and
50,000, such as polyethylene terephthalate (e.g. from terephthalic
acid diglycol ester), and the polyesters obtainable from
hydroxycarboxyolic acids such as .omega.-hydroxydecanoic acid or
4-(.beta.-hydroxyethoxy)benzoic acid. Apart from this group of
polyesters, which may be prepared from only one component, a
general group of suitable polyesters comprises the linear saturated
polyesters obtainable from glycols and aliphatic or aromatic
dicarboxylic acids, provided they give products having the high
range of molecular weights specified above. Not only the carboxylic
acids but also their anhydrides, esters or acid chlorides may be
used.
5. Polyvinyl chloride: homopolymers and copolymers with vinyl
esters (e.g. vinyl acetate). Before the processing step, suitable
plasticizers should be added, e.g. phthalic esters or adipic esters
with monohydric and dihydric alcohols in proportion of up to 40%
and preferably from 20 to 30% by weight). Molecular weight range
(expressed in K values): 50 to 80.
Before they are converted to filaments, all of the said polymers
may have incorporated therein a variety of auxiliaries as used in
conventional spinning processes, for example heat stabilizers,
light stabilizers, U.V. stabilizers, dyes, flame retardants,
crystallization accelerators, etc.
The process described above is capable of producing filaments
having the following characteristics:
Filament thicknesses between 1 and 200.mu.m and preferably between
10 and 100.mu.m, equivalent to about 1 to 100 g/10,000 m (1 to 100
dtex). The number of helical crimps in the filament is from about 1
to 40 and preferably from 5 to 20 per cm, the diameters of the
helices being from about 1 to 10 mm.
Depending on denier, raw materials and conditions of operation, the
spinning speeds are between 1,000 and 5,000 m/min, tensile
strengths being between between 2 and 6 g/dtex and elongations
being between 20 and 300%.
The webs made from the crimped filaments are particularly suitable,
on account of their favorable elastic and damping properties, for
making carpets and also as filling materials for stuffing
matresses, upholstery, quilts, sleeping bags, anoraks, etc., as
insulating mats, tapestries and as backing materials, e.g. for
artificial leather, or for use in tires. Other applications
include, for example, filters, home furnishings and certain
articles of clothing, and also packaging materials, in which latter
case webs having only weakly crimped filaments are of primary
importance.
Embodiments of the apparatus of the invention are described below
with reference to the accompanying drawings in which
FIG. 1 is a diagram of an apparatus for carrying out the process of
the invention.
FIG. 2 shows special embodiments of a cooling channel with means
for feeding and removing the cooling air.
FIG. 3 illustrates a 2-stage pneumatic jet and a filament crimping
zone downstream thereof.
FIG. 4 is an elevation of a preferred embodiment of the lay-down
means.
FIG. 5 shows diagrammatically a plan view of the lay-down means
shown in FIG. 4 and a non-woven web of the invention.
As shown in FIGS. 1 and 2a to 2c, the filaments are extruded
through spinnerets 1 of circular, oval or rectangular shape, or, as
shown in FIG. 2d, through spinnerets 1 having a free space in the
center. The melt is extruded through a number of spinning holes 2
of circular of profied cross-section. The ratio of axial length to
diameter is preferably at least 2.5 and the center-to-center
distance between adjacent holes is at least 5 times and preferably
10 times the diameter of the holes. Depending on the shape of the
spinneret, holes 2 are arranged either in concentric circles or
ellipses or in straight lines, the free space in the embodiment
shown in FIG. 2d being either in the center of the circles or
ellipses or between the lines of holes.
The various possibilities of the direction of feed of the cooling
air between 90.degree. and 0.degree. to the direction to travel of
the filaments are diagrammatically illustrated in FIGS. 1 and 2a to
2d, and the cooling blower (not shown) may operate by suction or by
pressure blowing or by both, i.e. by sucking and blowing
simultaneously. In FIG. 1, the cooling air impinges on the
filaments at right angles to their direction of travel after it has
passed through equalizing wire gauze or grid 12. If pressure
blowing is used, the side opposite the air inlet 11 may be in the
form of, say, a finescreen such that only a small proportion of the
cooling air flows horizontally through cooling channel 10, the
remainder passing vertically down through passageway 14 which may
have a circular or rectangular cross-section. In FIG. 2a, the feed
of cooling air is effected through a Venetian-blind-type baffle
grid 13, by means of which the angle of impingement of the air on
the filaments may be adjusted from 0.degree. to 90.degree.. Here
again, the flow of cooling air may be caused by suction or blowing.
In the embodiment shown in FIG. 2b, the angle of impingement may
again be from 0.degree. to 90.degree., the air inlet 11, which may
be a pressure inlet or a suction inlet, being in the form of an
inclined nipple. In the embodiment shown in FIG. 2c, the cooling
air is fed to the bundle of filaments by an injector effect,
passing in from the ambient atmosphere at small angles down to
0.degree.. It is convenient to place a throttling element 18, for
example a grid or gauze, on the upstream side of inlet slot 17. In
the embodiment shown in FIG. 2d, the cooling air is blown in
parallel to the filaments through a free space in a spinneret 1 or
between two adjacent spinnerets 1. In this case, the filaments are
cooled from the inside of the bundle. In the last two embodiments
it is practically only possible to use pressure blowing. In all of
the aboved described cases, the cooling air, when not already
introduced in a direction parallel to the filaments, is deflected
at least to a major extent so as to continue its flow parallel to
the filaments and thus to effect a primary take-up action in
addition to its cooling action, the point of impingement of this
take-up air not being directly in the outlet plane of the holes 2
but at a distance of at least 3 to 10 cm therefrom.
In all embodiments, the inlet portions of the cooling zones
described above merge into a second zone in the form of a
passageway 14, through which the filaments and air pass in parallel
directions, the velocity of the air being relatively high. The
total length of cooling zone 10, 14 is primarily determined by the
polymer used and by the thicknesses of the filaments and the type
of filament (degree of crimping) desired. Suitable lengths are of
the order of about 1 to 15 m and preferably about 2 to 10 m. At the
end of passageway 14, the cooling air is removed. If the cooling
air is pressure-blown into cooling zone 10, 14, it is allowed to
escape to the atmosphere through perforated section 15 (see FIG.
1). If, on the other hand, the cooling air is sucked into the
cooling zone, a suction chamber surrounds the perforated section 15
and is connected by a suction tube to a suction blower (see FIG.
2a). The cooling zone is closed by adjustable flaps 16, which
reduce the outlet cross-section of passageway 14 and thus prevent
unwanted air from being sucked in from below. Where the cooling air
is applied to the cooling zone by pressure blowing, these flaps 16
may be omitted.
If, in the case of certain raw materials, it is necessary to
condition the cooling air, the air extracted from the perforated
section 15 or from the moving belt by suction means 61 is passed
through an air-conditioning apparatus in which the temperature and
humidity are adjusted and the conditioned cooling air is then
returned to the cooling channel 10 through feed connection 11, with
or without the addition of fresh air.
To the cooling zone 10, 14 there is connected a main take-up
apparatus in the form of a single-stage or, preferably, multi-stage
pneumatic jet 20 operated by an external air jet. The two-stage
embodiment of pneumatic jet 20 shown in FIG. 3 consists of an outer
housing 21 with an air inlet connection 22 and an inner tube or
channel 27 which is located within the housing 21 and forms,
together with damming elements 24, an antechamber or equalizing
chamber 23. A cap nut 31 holds inner tube 27 and outer housing 21
together. On each side of damming elements 24 there is located an
inlet chamber 25 from which the air passes through inlet passages
26 (slots or bores) to the interior of inner tube 27 at an angle of
from 5.degree. to 30.degree., as a result of which the filaments
are drawn in and taken up through the preferably funnel-shaped
suction nozzle 29. The distance between the take-up stages is
adjusted by means of a screw thread 28 or similar means. The length
of the suction nozzle 29 is usually from 5 to 50 times its internal
diameter or internal width. The length of inner channel 27
including a diffusor 30 integral therewith, as measured between the
two inlet points 26, is approximately the same as that of the
suction nozzle 29 and is also approximately the same as that of a
connecting piece 41 adjoining pneumatic jet 20 downstream thereof.
The end of connecting piece 41 remote from the pneumatic jet is
connected to a crimping device 40 which consists of said connecting
piece 41 acting as inlet channel, to which there is fitted via
axial displacement means, for example a screw thread 42, a member
43 of enlarged cross-section, the increase in cross-section
commencing in an undercut and continuing irregularly until a
chamber is formed, at the end of which the cross-section again
diminishes irregularly, to a final point 45 at which a sharp edge
44 is formed, from which point 45 a short outlet channel 46 extends
in the downstream direction. The axial length of the crimping zone
40 is adjusted by means of a setting device 42 in such a manner
that the annular or cylindrical vortices formed at point 47 move
away from point 47 at a high frequency, drift to point 48 and
spring back to point 47 with partial flow-off and
replenishment.
The crimping zone 40 is directly connected to a flexible connecting
piece 50, for example a plastic hose, which is fitted with a
mouthpiece 51 and is adapted to carry out lay-down motions. The
mouthpiece 51 may be a simple tube, a tube which increases in
cross-section regularly or irregularly, or a slotted nozzle for
fanning out the strand of filaments. Fanning of the filaments may
be alternatively effected by directing two of the filament-laden
air nozzles at an angle to each other.
An apparatus 59 suitable for the subsequent step of laying down
structured non-woven webs is shown diagrammatically in FIG. 4. It
is composed of the aforementioned mouthpiece 51, which are
connected to the flexible connecting pieces 50 and are also secured
to a strip 52 via bearings which permit a tilting movement, for
example self-aligning ball bearings, the said strip 52 being in the
form of a connecting rod extending between rotating discs 53. The
discs 53 are mounted in a frame 54 which also carries the driving
unit 55 for the said discs. The frame 54 is suspended for linear
reciprocating motion on hanging bars 56 and is hingedly connected
to a connecting rod 57 which is in turn pivotally connected,
eccentrically, to a driven disc 58. Alternatively, this
reciprocating motion may be effected by means of a pneumatic or
hydraulic cylinder and piston combination.
Non-woven webs produced by the above combination of superimposed
motions have the structure shown in FIG. 5 resulting from the
rotating motion with superimposed linear reciprocating motion and
the movement of belt 60. Lay-down is preferably effected with
overlapping of at least 50%. Such overlapping is not shown in FIG.
5 for the sake of clarity. The spirals drawn in FIG. 5 represent
either single crimped filaments or bundles of crimped filaments. To
obtain a uniform web, it is recommended to operate a number of the
aforementioned spinning units in parallel and to cause the groups
of filaments to be laid down in overlapping relationship. The
moving belt 60 is preferably provided with suction means 61, this
being particularly necessary with webs of high specific weights.
The reference numeral 70 indicates a device for effecting
mechanical, thermal or chemical bonding of the web, for example by
needle punching, steaming, calendering, impregnation (spraying or
dipping), followed by drying. To improve the quality of the
filaments, a conventional mechanical stretching device having
take-up godets and stretching godets may be provided between
passageway 14 and pneumatic jet 20.
Threads, yarns and fibers, for example staple fibers, having the
features of the filaments produced by the process of the invention
and products made therefrom also come within the scope of the
present invention.
EXAMPLE 1
Polypropylene having a density of 0.91 g/cm.sup.3 and a melt index
MI.sub.2.16 kg/190.sub..degree.C of 2.5 as measured according to
ASTM D 1238 - 52 T and provided with a finely divided pigment was
fed to a spinneret at a temperature of 280.degree.C and a pressure
of 75 atmospheres gage and extruded through a number of holes
having a diameter of 0.8 mm. The throughput of melt through each
hole was 5 g/min. The filaments were cooled by air blown against
them from the side at a pressure of 70 mm of water, in the manner
illustrated in FIG. 1. The total cooling zone 10, 14 had a length
of 6.5 m and was provided with suction means 15 at its lower end.
The two-stage pneumatic jet 20 as illustrated in in FIG. 3 had an
internal inlet diameter of 5 mm. An adjacent crimping zone 40 had a
diameter of 12 mm and a length of 30 mm. The pneumatic jet was
operated at 1 atmospherere gage of air and a speccific air
consumption of 10 kg/kg of melt. The filaments were passed through
a flexible connecting piece 50 and emerged from a mouthpiece 51
which, guided by a moving mechanism 59, executed a rotating motion
of 3 c/s and a superimposed linear reciprocating motion of about
0.5 c/s. On moving belt 60 of wire netting, which had suction means
61 below the point where the filaments initially contact the belt,
there was formed a web of non-woven fibrous material having a width
of about 0.5 m. The weight constancy of the web in its central test
area was better than .+-. 5%.
The speed of travel of the belt was adjusted so that a web having a
weight of 750 g/m.sup.2 was formed. Some slight needlepunching of
the very voluminous, colored web (specific volume 25 cc/g) was
carried out and the web was finished by subjection to two further
needle-punching operations. There was obtained a needleloom
material which, after usual impregnation and provision of backing
in the form of waffle foam, was eminently suitable as a floor
covering.
EXAMPLE 2
Propylene was fed to a spinneret 1 under the same conditions as
mentioned in Example 1, which spinneret had a free space in its
center, as illustrated in FIG. 2d, the melt being spun through
holes 2 having a diameter of 0.5 mm. The cooling air fed to the
center of the assembly was under a pressure of 0.1 atmosphere gage,
and the cooling air was sucked off at the end of the cooling zone
10, 14, which had a length of 4 m. Pneumatic jet 20 was of the
single-stage type and was connected to a crimping zone 40. The
resulting crimped filaments, after passing through the flexible
connecting piece 50 and the moving mouthpiece 51, as described in
Example 1, were laid down to form a web weighing 400 g/m.sup.2. The
diameter of the filaments was 20.mu. m and they possessed from 8 to
10 crimps per cm. Their tensile strength was 3 g/dtex and their
elongation was 180%. The web was slightly needle-punched and was
then in a condition suitable for use as backing for a further layer
of carpet material to be secured thereto by needle-punching in the
manufacture of needle-punched floor coverings.
EXAMPLE 3
Polypropylene containing pigment and having a melt index
MI.sub.2.16 kg/190.sub..degree.C of 5.5 was fed to a spinneret 1
having 100 holes 2 with a diameter of 0.5 mm, at a temperature of
260.degree.C and under a pressure of 40 atmospheres gage. Cooling
air was fed to the filaments as described in Example 1. The cooling
zone 10, 14 was 4 m long and had merely a grid 15 at its lower end
to enable the cooling air to escape. Using a two-stage pneumatic
jet 20 connected to a crimping chamber 40 and operated at a
pressure of 1.8 atmospheres gage, filaments were obtained which had
a diameter of 60.mu. m and a very fine crimping effect consisting
of about 18 to 20 helices of a diameter of about 2 mm in every cm
of unstretched filament. Tensile strenghts were at 4.5 g/dtex and
elongations were below 100%. The filaments were laid down as
described in Example 1 to form a web weighing 400 g/m.sup.2. The
web was needle-punched twice and it was given a surface texture by
needle-punching in order to give it the appearance of a textile
fabric. It was eminently suitable for use as cover material for
upholstery, automobile seats, cushions, etc.
EXAMPLE 4
Polypropylene was fed, under the same conditions described in
Example 3, to a spinneret 1 of the kind described in Example 2. The
filaments were taken up by a four-stage pneumatic jet 20 having
inlet bores 26 of a diameter of 1 mm in its first stage 4, its
second stage 6, its third stage 8 and its fourth stage 12. The
interal diameter of the pneumatic jet increased by 1 mm from stage
to stage. The resulting filament characteristics were approximately
the same as obtained in Example 3. The filaments could be laid down
to form a web of the same type as that described in Example 3 and
having the same applications.
EXAMPLE 5
Polyester having a K value of 61 was fed, at 40 atmospheres gage
and 300.degree.C, to a spinneret 1 having bores 2 of 1 mm in
diameter. The filaments were cooled by means of a suction fan
connected to the bottom end of cooling zone 10, 14 having a length
of 3 m. The filaments were taken up by a two-stage pneumatic jet 20
operating at a pressure of 2 atmospheres gage. The resulting
filaments were slightly crimped and had a diameter of about 10.mu.
m and comprised from 3 to 4 helices of 2 mm in diameter per cm of
filament. The filaments were laid down to form a voluminous web
having a weight of 450 g/m.sup.2. During the laying down process,
the web was sprayed with an aqueous dispersion of a curable acrylic
ester such that after drying and curing the web consisted of 90% of
filaments and 10% of binder. The coherent, resilient non-woven web
thus obtained was highly suitable for use as stuffing in quilts and
winter clothing.
EXAMPLE 6
Polycaprolactam having a K value of 72 and a melt viscosity of
3,500 poises at 250.degree.C was fed to a spinneret 1 containing
holes 2 having a diameter of 0.6 mm. The cooling system operated by
pressure blowing at a pressure of 70 mm of water, the cooling air
being blown out to the side at the lower end of the 4 m long
cooling zone 10, 14. The two-stage pneumatic jet 20 and crimping
zone 40 as used in Example 1 produced filaments having a diameter
of 18.mu. m and containing from 4 to 5 helices of from 1.5 to 2.0
mm in diameter per cm of filament. The voluminous web produced from
these filaments and having a weight of 300 g/m.sup.2 was lightly
powdered with an adhesive, which was cured at 130.degree.C to bond
the web. The web was suitable for making air filter mats.
* * * * *