Method for the production of fibers and materials having enhanced characteristics

A method and apparatus for forming artificial fibers and a non-woven web therefrom includes generating a substantially continuous fluid stream along a primary axis, at least one extrusion die located adjacent to the continuous fluid stream for extruding a liquified resin into fibers, injecting the fibers into the primary fluid stream, and selectively perturbing the flow of fluid in the fluid stream by varying the fluid pressure on either side of the primary axis to produce crimped fibers for forming the non-woven web. The inventive manufacturing method finely tunes non-woven web material characteristics such as tensile strength, porosity, barrier properties, absorbance, and softness by varying the fluid stream perturbation frequency and amplitude. Finally, the inventive method and apparatus may be implemented in combination with melt-blown, spunbond and coform techniques for producing non-woven webs.

FIELD OF THE INVENTION 
This invention relates generally to the production of man-made fibers, and 
particularly, to the field of production of man-made fibers using 
melt-blown, coform and spunbond techniques. 
BACKGROUND OF THE INVENTION 
The production of man-made fibers has long used melt-blown, coform and 
spunbond techniques to produce fibers for use in forming non-woven webs of 
material. FIGS. 1a through 3b illustrate prior art machines which 
manufacture non-woven webs from melt-blown and spunbond techniques. 
Additionally, prior art coform techniques are discussed in greater detail 
hereinafter. 
FIGS. 1a-1c illustrate a typical approach for producing melt-blown fibers. 
Referring to FIG. 1a, a hopper 10 contains pellets of resin. Extruder 12 
melts the resin pellets by a conventional heating arrangement to form a 
molten extrudable composition which is extruded through a melt-blowing die 
14 by the action of a turning extruder screw (not shown) located within 
the extruder 12. As shown in FIG. 1c, the extrudable composition is fed to 
the orifice 18 through extrusion slot 28. The die 14 and the gas supply 
fed therethrough are heated by a conventional arrangement (not shown). 
FIG. 1b illustrates the die 14 in greater detail. The tip 16 of die 14 
contains a plurality of melt-blowing die orifices 18 which are arranged in 
a linear array across the face 16. Referring now to FIG. 1c, inlets 20 and 
21 feed heated gas to the plenum chambers 22 and 23. The gas then exits 
respectively through the passages 24 and 25 to converge and form a gas 
stream which captures and attenuates the polymer or resin threads extruded 
from orifices 18 to form a gas borne stream of fibers 26 as is seen in 
FIG. 1a. 
The melt-blowing die 14 includes a die member 36 having a base portion 38 
and a protruding central portion 39 within which an extrusion slot 28 
extends in fluid communication with the plurality of orifices 18, the 
outer ends of which terminate at the die tip. The gas borne stream of 
fibers 26 is projected onto a collecting device which in the embodiment 
illustrated in FIG. 1a includes a foraminous endless belt 30 carried on 
rollers 31 and which may be fitted with one or more stationary vacuum 
chambers (not shown) located beneath the collecting surface on which a 
non-woven web 34 of fibers is formed. The collected entangled fibers form 
a coherent web 34, a segment of which is shown in plan view in FIG. 2. The 
web 34 may be removed from the belt 30 by a pair of pinch rollers 33 
(shown in FIG. 1a) which press the entangled fibers together. The prior 
art melt-blowing apparatus of FIGS. 1a-1c may optionally include 
pattern-embossing means as by patterned calender nip or ultrasonic 
embossing equipment (not shown) and web 34 may thereafter be taken up on a 
storage roll or passed to subsequent manufacturing steps. Other embossing 
means may be utilized such as the pressure nip between a calender and an 
anvil roll, or the embossing step may be omitted altogether. 
FIG. 3a illustrates a prior art apparatus 44 for producing spunbond fibers. 
The spunbond apparatus typically contains a fiber draw unit 46 positioned 
above an endless belt 78 which is supported on rollers 76. FIG. 3b 
illustrates the fiber draw unit in greater detail. Fiber draw unit 46 
includes upper air regions 48 and 50 and a longitudinal air chamber which 
contains an upper portion 52, a mid-portion 54, and a lower portion or 
tail pipe 56. The fiber draw unit also includes a first air plenum 58 and 
an air inlet 60 leading from the first air plenum 58 to mid-portion 54 of 
the fiber draw unit. Additionally, a second air plenum 62 also 
communicates with mid-portion 54 of the fiber draw unit via air inlet 64. 
The spunbond apparatus 44 also includes standard equipment for melting an 
extruding resin through dies to create fibers 68. Typically, this 
equipment feeds resin fed from a supply to a hopper extruder, through a 
filter, and finally through a die to create the fibers 68. 
High velocity air is admitted into the fiber draw unit through plenums 58 
and 62 via inlets 72 and 74, respectively. The addition of air to the 
fiber draw unit through inlets 60 and 64 aspirates air through inlets 50 
and 48. The air and fibers then exit through tail pipe 56 into exit area 
70. Generally, air admitted into the fiber draw unit through inlets 50 and 
48 draws fibers 68 as they pass through the fiber draw unit. The drawn 
fibers are then laid down on endless belt 78 to form a non-woven web 80 as 
is seen in FIG. 3a. Rollers 82 may then remove the non-woven web from the 
endless belt 78 and further press the entangled fibers together to assist 
in forming the web. The web 80 is then bonded, such as by embossing by 
calender and anvil, ultrasonic embossing, or other known technique, to 
form the finished material. 
It is well known in the art to vary a number of processing parameters in 
both melt-blown and spunbond fiber forming processes to obtain fibers of 
desired properties in order to form fabrics with desired characteristics. 
However, the majority of prior art techniques for varying fiber 
characteristics required more time consuming changes in machinery or 
process, such as changing dies or changing the resins. Therefore, those 
techniques required that the production line be halted while the necessary 
changes were made, which resulted in inefficiency when a new material was 
to be run. 
The prior art has previously taught that various effects can be obtained by 
the manipulation of air flow near the fiber exit in melt-blown and 
spunbond fiber producing equipment. For example, Shambaugh, U.S. Pat. No. 
5,405,559, teaches that the air flow provided in the melt-blown process 
can be alternately turned on and off on both sides of the die, thus 
reducing the energy required to produce melt-blown fibers. However, this 
teaching of Shambaugh has several drawbacks. Under some conditions, the 
complete shutting off of the air on either side will tend to blow the 
liquefied resin onto the air plates on the other side of the die, thereby 
clogging the machinery for typical production airflow rates (especially 
with high MFR polymers or other polymers normally used in non-woven web 
production). Further, such techniques would likely result in the 
deposition of resin globs or "shot", on the production web since the resin 
would be affected only minimally during the transition from airflow on one 
side of the die to the other. Finally, while the Shambaugh reference 
teaches switching air on and off for the purposes of reducing fiber size 
for a given flow, its main emphasis is that such switching saves energy by 
reducing the overall airflow requirements in the melt-blown process. 
Moreover, the low frequencies taught by Shambaugh would result in poor 
formation on a high speed machine. Fibers produced as given in the 
examples are coarser, e.g. larger diameters than typically found in 
non-woven commercial production. Finally, Shambaugh teaches no 
applicability of selective alteration of airflow characteristics for 
varying fiber parameters in a spunbond fiber production environment. 
U.S. Pat. No. 5,075,068, teaches the use of a steady state shearing air 
stream near the exit of the die in the melt-blown process for the purpose 
of increased drag on fibers exiting the die. The steady state air stream 
therefore draws the fibers further and enhances the quenching of the 
fibers. However, this patent teaches a steady state airflow for producing 
a better fiber, but does not teach that airflow characteristics may be 
selectively altered to vary the characteristics of fibers in a desired 
manner. 
Finally, U.S. Pat. No. 5,312,500, teaches alternating airflows at the exit 
of a spunbond fiber draw unit for laying a continuous fiber down in an 
elliptical fashion to form a non-woven web. This patent teaches that, 
among other techniques, varying airflows may direct fibers onto a 
foraminous forming surface to form a non-woven web. By varying the manner 
in which the fibers are deposited using airflow variation, this reference 
states that the characteristics of the web may be enhanced. However, this 
reference does not teach that the airflows may be used to enhance or vary 
the characteristics of the fibers themselves. 
Therefore, it is an object of the present invention to provide novel 
methods for the production of fibers. 
It is a further object of the present invention to provide techniques 
whereby desired characteristics of fibers may be selected through process 
control. 
It is an additional object of the present invention to provide non-woven 
webs having desired characteristics through the production of fibers using 
perturbed airflows during fiber formation. 
It is yet another object of the present invention to provide a process and 
apparatus for the formation of fibers having specific, desired 
characteristics by the simple, selective variation of the frequency and/or 
amplitude of perturbation of air flow during the production of the fibers. 
It is yet a further object of the present invention to provide processes 
and apparati, using selective variation of the frequency and/or amplitude 
of a perturbing airflow in the formation of fibers, which allow for the 
production of non-woven webs and fabrics having desired characteristics. 
SUMMARY OF THE INVENTION 
The above and further objects are realized in a process and apparatus for 
the production of fibers in accordance with disclosed and preferred 
embodiments of the present invention and resulting non-woven webs. 
Generally, the present invention relates to an apparatus for forming 
artificial fibers from a liquefied resin and for forming a non-woven web. 
The apparatus may include means for generating a substantially continuous 
airstream for entraining fibers along a primary axis, at least a first 
extrusion die located next to the airstream for extruding the liquefied 
resin, and perturbation means for selectively perturbing the air stream by 
varying the air pressure on either side or both sides of the primary axis. 
The apparatus may also include a substrate disposed below the first die 
and substrate translation means for moving the substrate relative to the 
die, wherein the entrained fibers are deposited on the substrate to form a 
non-woven web. 
The apparatus may include a first supply of air connected to first and 
second air plenum chambers located on opposite sides of the axis, wherein 
plenum chambers outlets provide a substantially continuous air stream for 
fiber attenuation. The perturbation means may include a valve for 
selectively varying the airflow rate to the first and second plenums, 
thereby providing airflow perturbation to the entrained fibers. 
Additionally, airstream perturbation may be achieved by superimposing a 
perturbed secondary air supply on the first air supply within the plenum 
chambers. Alternatively, the perturbation means may include first and 
second pressure transducers adjacent or attached to the first and second 
plenum chambers and means for selective activation of the first and second 
pressure transducers for selectively varying the pressure in the first and 
second plenum chambers. Generally, the perturbation means varies a steady 
state pressure in the first and second plenum chambers at a perturbation 
frequency of approximately less than 1000 Hertz and varies an average 
plenum pressure in the first and second plenum chamber up to about 100% of 
the total average plenum pressure in the absence of activation of the 
perturbation means. 
The apparatus may also include a fiber draw unit disposed below the first 
die and adapted to channel the primary air flow therethrough. The fiber 
draw unit may include a fiber inlet at a top portion thereof for receiving 
fluid flow and fibers entrained therein and an outlet for dispensing the 
air entrained fibers onto the substrate. The apparatus may also include a 
multiple die arrangement for extruding several types of resin 
simultaneously, as well as means for adding other fibers or particulates 
(coform). 
The apparatus may also include first and second secondary perturbing air 
supplies disposed on opposite sides of said axis and near the die or fiber 
draw unit for alternatingly perturbing the substantially continuous flow 
of air. 
The present invention also relates to a method for forming artificial 
fibers from a liquefied resin and forming a non-woven web thereby, 
comprising the steps of generating a substantially continuous air stream 
along a primary axis, extruding the liquefied resin through a first die 
located adjacent to the air stream, entraining the liquefied resin in the 
air stream to form fibers, and selectively perturbing the flow of air in 
the airstream by varying the air pressure on either side of the primary 
axis.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The following techniques are applicable to the melt-blown, spunbond and 
coform fiber forming processes. For the sake of clarity, the general 
principles of the invention will be discussed with reference to these 
techniques. Following the general description of the techniques, the 
specific application of these techniques in the melt-blown, spunbond, and 
coform fields will be described. For ease in following the discussion, 
sub-headings are provided below; however, these sub-heading are for the 
sake of clarity and should not be considered as limiting the scope of the 
invention as defined in the claims. As used herein, the term 
"perturbation" means a small to moderate change from the steady flow of 
fluid, or the like, for example up to 50% of the steady flow, and not 
having a discontinuous flow to one side. Furthermore, as used herein, the 
term fluid shall mean any liquid or gaseous medium; however, in general 
the preferred fluid is a gas and more particularly air. Additionally, as 
used herein the term resin refers to any type of liquid or material which 
may be liquefied to form fibers or non-woven webs, including without 
limitation, polymers, copolymers, thermoplastic resins, waxes and 
emulsions. 
General Description of the Air Flow Perturbation Process 
As was described previously, the production of fibers having various 
characteristics has been known in the prior art. However, the preferred 
embodiments of the present invention provide for a much greater range of 
variation in fiber characteristics and provide for a greater range of 
control for forming various non-woven web materials from such fibers. 
These techniques allow one to "tune in" the characteristics of the 
non-woven web formed thereby with little or no interruption of the 
production process. The basic technique involves perturbing the air used 
to draw the fiber from the die. Preferably, the airflow in which the fiber 
travels is alternately perturbed on opposite sides of an axis parallel to 
the direction of travel of the fiber. Thus, the airstream carrying the 
forming fiber is perturbed, resulting in perturbation of the fiber during 
formation. Airstream perturbation according to the methods and apparati of 
the present invention may be implemented in melt-blown and spunbond 
manufacturing, but is not limited to those processes. 
In general, the airflow may be perturbed in a variety of ways; however, 
regardless of the method used to perturb the airflow, the perturbations 
have two basic characteristics, frequency and amplitude. The perturbation 
frequency may be defined as the number of pulses provided per unit time to 
either side. As is common the frequency will be described in Hertz (number 
of cycles per second) throughout the specification. The amplitude may also 
be described by the percentage increase or difference in air pressure 
(.DELTA.P/P).times.100 in the perturbed stream as compared to the steady 
state. Additionally, the perturbation amplitude may be described as the 
percentage increase or difference in the air flow rate during perturbation 
as compared to the steady state. Thus, the primary variables which may be 
controlled by the new fiber forming techniques are perturbation frequency 
and perturbation amplitude. The techniques described below easily control 
these variables. A final variable which may be changed is the phase of the 
perturbation. For the most part, a 180.degree. phase differential in 
perturbation is described below (that is, a portion of the airflow on one 
side of an axis parallel to the direction of flow is perturbed and then 
the other side is alternately perturbed); however, the phase differential 
could be adjusted between 0.degree. to 180.degree. to achieve any desired 
result. Tests have been conducted with the perturbation being symmetric 
(in phase) and with varying phase relationships. This variation allows for 
still more control over the fibers made thereby and the resulting web or 
material. 
The perturbation of the air stream and fibers during formation has several 
positive effects on the fiber formed thereby. First, the particular 
characteristics of the fiber such as strength and crimp may be adjusted by 
variation of the perturbation. Thus, in non-woven web materials, increased 
bulk and tensile strength may be obtained by selecting the proper 
perturbation frequency and amplitude. Increased crimp in the fiber 
contributes to increased bulk in the non-woven web, since crimped fibers 
tend to take up more space. Additionally, preliminary investigation of the 
characteristics of meltblown fibers made in accordance with the present 
invention, as compared to those made with prior art techniques, appears to 
indicate that fibers made in accordance with the present invention exhibit 
different crystalline and heat transfer characteristics. It is believed 
that such differences are due to heat transfer effects (including 
quenching) which result from the movement of fibers in a turbulent 
airflow. It is further believed that such differences contribute to the 
enhanced characteristics of fibers and non-woven materials made in 
accordance with the techniques of the present invention. Additionally, the 
perturbation of the airflow also results in improved deposition of the 
fibers on the forming substrate, which enhances the strength and other 
properties of the web formed thereby. 
Furthermore, since the variables of frequency and amplitude of the 
perturbation are easily controlled, fibers of different characteristics 
may be made by changing the frequency and/or amplitude. Thus, it is 
possible to change the character of the non-woven web being formed during 
processing (or "on the fly"). By this type of adjustment, a single machine 
may manufacture non-woven web fabrics having different characteristics 
required by different product specifications while eliminating or reducing 
the need for major hardware or process changes, as is discussed above. 
Additionally, the present invention does not preclude the use of 
conventional process control techniques to adjust the fiber 
characteristics. 
Referring now to FIGS. 4 and 5, magnified photographs of melt-blown webs 
made in accordance with prior art techniques (FIG. 4) and according to the 
present invention (FIG. 5) may be compared. As is seen in FIG. 4, the 
individual fibers of the web are relatively linear. However, as is seen in 
FIG. 5, the fibers in the web made in accordance with the perturbation 
techniques of the present invention are much more crimped and are not 
predominantly aligned in the same direction. Thus, as will be seen in the 
results described below, webs made in accordance with the present 
invention tend to exhibit greater bulk for a given weight and frequently 
have greater machine and cross direction strengths (the machine direction 
is the direction of movement, relative to the forming die, of the 
substrate on which the web is formed; the cross direction is perpendicular 
to the machine direction). It is believed that the increased crimp will 
provide many more points of contact for the fibers of the web which will 
enhance web strength. As a note, at first glance it would appear that many 
more and larger voids are present in the web of FIG. 5 as compared to that 
of FIG. 4; however, in fact, the web of FIG. 5 does not contain more or 
larger voids than that of FIG. 4. Since the SEM photographs of these 
Figures present views of the top surface of the material, the increased 
bulk of the web of FIG. 5 is not seen in the photograph and the bulk 
manifests in a manner to make it appear that there are a greater number of 
larger voids. Conversely, since the web of FIG. 4 has less bulk, a greater 
number of fibers of that web are located in the plane of the photograph, 
giving the appearance of fewer and smaller voids. As is seen below, the 
barrier properties of webs made in accordance with the present invention 
can be selected to be superior to those made in accordance with the prior 
art, thus demonstrating that the appearance of voids in the photograph of 
FIG. 5 is misleading. 
Melt-Blown Applications 
FIGS. 6a through 6d illustrate various embodiments of the present invention 
which utilize alternating air pulses to perturb air flow in the vicinity 
of the exit of a melt-blown die 59. Each melt-blown embodiment of the 
present invention includes diametrically opposed plenum/manifolds 22 and 
23 and air passages 24 and 25 which lead to a tip of the melt die 59 to 
create a stream of fibers in a jet stream 26. The function of the present 
invention is to maintain a steady flow and to superimpose an alternating 
pressure perturbation on that steady flow near the tip of melt die 59 by 
alternatingly increasing or reducing the pressure of the manifolds 22 and 
23. This technique assures controlled modifications in the gas borne 
stream of fibers 26 and therefore facilitates regularity of pressure 
fluctuations in the gas borne stream of fibers. Additionally, the 
relatively high steady state air flow with respect to pertubation air flow 
amplitude also serves to prevent the airborne stream of fibers from 
becoming tangled on air plates 40 and 42. The jet structure air 
entrainment rate (and therefore quenching rate) and fiber entanglement are 
thus modified favorably. 
FIGS. 7a through 7d illustrate a few examples of valves that alternatingly 
augment the pressure in plenum chambers 22 and 23 shown in FIGS. 6a-6d. 
Referring to FIG. 7a, perturbation valve 86 is essentially comprised of a 
bifurcation of main air line 84 into inlet air lines 20 and 21. In the 
immediate vicinity of the bifurcation, a pliant flapper 98 alternatingly 
traverses the full or partial width of the bifurcation. This provides a 
means for alternatingly restricting air flow to one of air inlet lines 20 
and 21 thereby superimposing a fluctuation in air pressure in manifolds 22 
and 23. Alternatively, an activator may mechanically oscillate the flapper 
across the bifurcation to produce the appropriate fluctuation in air 
pressure in plenums 22 and 23. Flapper valve 98 may traverse the 
bifurcation of mainline 84 in an alternating manner simply by the 
turbulence of air in mainline 84 using the natural frequency of the 
flapper. Oscillation frequency of valve 86 as disclosed in FIG. 7a may be 
varied mechanically by an activator which reciprocates the flapper, or by 
simply adjusting the length of the flapper 98 to change its natural 
frequency. 
FIG. 7b illustrates a second embodiment of the perturbation valve 86. This 
embodiment may include a motor 100 which rotates a shaft 102. The shaft 
102 may be fixed to a rotation plate 109 which has a plurality of 
apertures 108 disposed thereon. Behind rotation plate 109 is a stationary 
plate 104 containing a plurality of apertures 106. Both disks may be 
mounted so that flow is realized through fixed disk openings only when 
apertures from the rotation plate 109 are aligned with apertures in the 
stationary plate 104. The apertures on each plate may be arranged such 
that a steady flow may be periodically augmented when apertures on each 
plate are aligned. The frequency of the augmented flow may be controlled 
through a speed control of motor 100. 
FIG. 7c illustrates yet another embodiment of perturbation valve 86. In 
this embodiment a motor 100 is rotatingly coupled to a shaft 112 which 
supports a butterfly valve 110 having essentially a slightly smaller 
cross-section than main air line 84. Turbulence created downstream from 
rotating butterfly 110 may then provide an alternatingly augmented air 
pressure in air inlet lines 20 and 21 and also in air plenums 22 and 23 to 
achieve the flow conditions in accordance with the present invention. 
FIG. 7d represents yet another embodiment of a perturbation valve 86 in 
accordance with the present invention. There, a motor 100 is coupled to a 
shaft 112 and butterflies 110 and 114 within inlet air lines 20 and 21 
respectively. As is seen from FIG. 7d, butterflies 110 and 114 are mounted 
on shaft 112 approximately 90.degree. to each other. Additionally, each of 
the butterflies 110 and 114 may include apertures 111 so as to provide a 
constant air flow to each of the plenums while alternatingly augmenting 
pressure in each of the plenums 22 and 23 when the appropriate butterfly 
is in an open position. 
FIG. 7e represents still another embodiment of the perturbation valve 86. 
In this embodiment an actuator 124 is coupled to a shaft 122 which in turn 
is mounted to a spool 123. Spool 123 includes channels 118 and 120 which 
communicate with air inlet lines 20 and 21 respectively, depending on the 
longitudinal position of the spool 123. Each of the channels 118 and 120 
is fluidly connected to main channel 116 which is fluidly connected to 
main air line 84. In this embodiment, perturbation valve 86 may achieve 
alternatingly augmented air pressures in each of the plenums by 
reciprocation of rod 122 from actuator 124. Additionally, channels 118 and 
120 may simultaneously be connected to main air line 84 while activator 
124 reciprocates spool 123 to vary an amount of overlap, and thus air flow 
restriction, between channels 118 and 120 with lines 20 and 21, 
respectively, to achieve alternating augmented pressures in the plenum 
chambers 22 and 23, respectively. Actuator 124 may include any known means 
for achieving such reciprocation. This may include but is not limited to 
pneumatic, hydraulic or solenoid means. 
FIGS. 8a-8d illustrate, respectively, plenum air pressures in both the 
prior art melt-blown apparatus and in the melt-blown apparatus according 
to the present invention. As is seen in FIG. 8a, a prior art air pressure 
in the plenum chambers is essentially constant over time whereas in FIGS. 
8b and 8c the air pressure in the plenum chambers is essentially augmented 
in an oscillatory manner. As an example, the point at which the mean 
pressure intersects the ordinate can be about 7 psig. FIG. 8d illustrates 
a prior art air pressure in the vicinity of a prior art extrusion die 
where air is turned on and off. In this case, the mean pressure meets the 
ordinate at about 0.5 psig, for example. The on/off control of prior art 
air flow as illustrated in FIG. 8d is conducive to die clogging due to the 
intermittent flow, as explained above. Additionally, the prior art on/off 
air flow control illustrated in FIG. 8d (implemented by Shambaugh) 
utilizes a lower average pressure, a lower frequency and less pressure 
amplitude than the present invention. Although the airflow characteristic 
illustrated in FIG. 8a is not conducive to die clogging, no control may be 
implemented over fiber crimping or web characteristics, since the flow is 
virtually constant with respect to time. 
Perturbation valve 86 may be placed in a multitude of arrangements to 
achieve the alternatingly augmented flow in plenum chambers 22 and 23 of 
the melt-blown apparatus according to the present invention. For example, 
FIG. 6b shows another embodiment according to the present invention. In 
this embodiment, main air line 84 bifurcates constant air flow to inlet 
air lines 20 and 21 while bleeding an appropriate flow of air to 
perturbation valve 86 via bleeder valve 88 and line 90. Therefore, in this 
embodiment plenum chambers 23 and 22 each include two inlets. The first 
inlet introduces essentially constant flow from air inlet lines 20 and 21. 
The second inlet of each plenum chamber introduces the alternating flow to 
the chamber, thereby superimposing oscillatory flow on the constant flow 
from lines 20 and 21. The amount of air bled from bleeder valve 88 will 
control the amplitude of the pressure augmentation for precise adjustment 
of fiber characterization, as explained in greater detail below, while 
perturbation valve 86 controls frequency. 
FIG. 6c represents yet another embodiment of the present invention. In this 
embodiment, main air line 84 bifurcates into air lines 21 and 20 to supply 
air pressure to plenum chambers 22 and 23. Additionally, an auxiliary air 
line 92 bifurcates at perturbation valve 86. The perturbation valve 86 
then superimposes an alternatingly augmented air pressure onto plenum 
chambers 22 and 23 to achieve the oscillatory flow conditions in 
accordance with the present invention. Here, pressure on the air line 92 
controls the amplitude of air pressure perturbation, while perturbation 
valve 86 controls perturbation frequency, as explained above. 
FIG. 6d represents yet another embodiment of the present invention. In this 
embodiment, main air line 84 bifurcates into inlet air lines 20 and 21 
which lead to plenum chambers 22 and 23 respectively. The alternatingly 
augmented pressure in plenum chambers 22 and 23 may be provided by 
transducers 94 and 96 respectively. Transducers 94 and 96 are actuated by 
means of an electrical signal. For example, the transducers may actually 
be large speakers which receive an electrical signal to pulsate 
180.degree. out of phase in order to provide the alternating augmented 
pressures in plenum chambers 22 and 23. However, any type of appropriate 
transducer may create an augmented air flow by using any means of 
actuation. This may include but is not limited to electromagnetic means, 
hydraulic means, pneumatic means or mechanical means. 
As was discussed previously, all of the described embodiments allow for the 
precise control of the perturbation frequency and amplitude, preferably 
without interrupting the operation of the fiber forming machinery. As will 
be described below, this ability to precisely control the perturbation 
parameters allows for relatively precise control of the characteristics of 
the fibers and web formed thereby. Typically, there are a wide variety of 
fiber parameters and while a particular set of parameters may be desired 
for making one type of non-woven material, such as filter material, a 
different set of fiber parameters may be desired for making a different 
type of material, such as for disposable garments. 
For example, in filter applications, the material is preferably made of 
small diameter fibers. However, larger diameter fibers may be desired for 
other materials. Furthermore, many end products consist of layers of 
material having a variety of characteristics. For example, disposable 
diapers generally consist of a wicking layer designed to move moisture 
away from contact with the skin of an infant and to keep such moisture 
away. A middle, absorbent layer is used to retain the moisture. Finally, 
an outer, barrier layer is desired to prevent the absorbed moisture from 
seeping out of the diaper. The fiber characteristics for each layer of the 
diaper are different in order to achieve the specific functions of each 
type of material. With the present techniques, various portions of the web 
can be formed by varying the perturbation parameters with respect to time 
so that each layer of the diaper is formed sequentially in one non-woven 
web. Then the single web may be folded to provide the layered finished 
material. 
Thus, with precise control of the fiber and material characteristics by 
control of the perturbation characteristics, a great degree of flexibility 
is possible in the formation of non-woven webs. This control, in turn, 
allows for greater efficiency and the ability to design a greater range of 
materials which may be produced with little interruption of the production 
process. 
One shortcoming of prior art melt-blown equipment is the relative inability 
to precisely control the diameter of fibers produced thereby. The 
formation of materials with particular characteristics often requires 
precise control over the diameter of the fibers used to form the non-woven 
web. With the perturbation technique of the present invention, it is 
possible to provide for much less variation in fiber diameter than was 
previously possible with prior art techniques. 
FIGS. 9 and 10 illustrate fiber diameter distribution for samples taken 
from prior art melt-blown techniques and the melt-blown fiber producing 
technique according to the melt-blown apparatus embodiment of FIG. 6c. 
FIG. 9 shows a diameter distribution in accordance with the prior art. 
FIG. 10 represents a fiber diameter distribution chart for melt-blown 
fibers made in accordance with the inventive technique. The fiber 
distribution in FIG. 10 illustrates a fiber diameter sample which has a 
distribution that is centered on a peak between about 1 and 2 microns. 
Here, the narrow band of fiber distribution achieved by the perturbation 
method and apparatus illustrates the great extent to which fiber diameter 
may be controlled by only varying perturbation frequency or amplitude. 
FIG. 11 represents the Frazier porosity of a non-woven melt-blown web made 
in accordance with the present invention as a function of perturbation 
frequency in the plenum chambers 22 and 23. The Frazier Porosity is a 
standard measure in the non-woven web art of the rate of airflow per 
square foot through the material and is thus a measure of the permeability 
of the material (units are cubic feet per square foot per minute). For all 
samples the procedure used to determine Frazier air permeability was 
conducted in accordance with the specifications of method 5450, Federal 
Test Methods Standard No. 191 A, except that the specimen sizes were 8 
inches by 8 inches rather than 7 inches by 7 inches. The larger size made 
it possible to ensure that all sides of the specimen extended well beyond 
the retaining ring and facilitated clamping of the specimen securely and 
evenly across the orifice. 
As is illustrated in FIG. 11, the Frazier porosity generally falls first to 
a minimum and then increases with perturbation frequency from a steady 
state to approximately 500 hertz. Thus, one can observe that to make a 
material with a desired Frazier porosity with the present invention, it is 
only necessary to vary the oscillation frequency (and/or the amplitude). 
With prior art techniques, changes in porosity often required changes to 
the die or starting materials or the duplication of machinery. Thus, with 
the present techniques, it is possible to easily change the porosity of a 
material once a run is completed; it is only necessary to adjust the 
perturbation frequency (or amplitude), which can easily be done with 
simple controls and without stopping production. Therefore, the 
melt-blowing apparati according to the present invention may quickly and 
easily manufacture filtering materials of varying porosity by simply 
changing perturbation frequency. 
FIG. 12 illustrates a plot of hydrohead as a function of perturbation 
frequency. The Hydrohead Test is a measure of the liquid barrier 
properties of a fabric. The hydrohead test determines the height of water 
(in centimeters) which the fabric will support before a predetermined 
amount of liquid passes through. A fabric with a higher hydrohead reading 
indicates it has a greater barrier to liquid penetration than a fabric 
with a lower hydrohead. The hydrohead test is performed according to 
Federal Test Standard No. 191A, Method 5514. Generally, hydrohead first 
increases and then decreases with increasing perturbation frequency in a 
frequency range of approximately 75 hertz to 525 hertz. Since perturbation 
frequency directly affects hydrohead, an appropriate adjustment of the 
perturbationvalve 86 provides the type of barrier to liquid required by a 
particular application. Perturbation frequency may be used to vary 
hydrohead to suit the particular use for the material. 
EXAMPLES 
The following examples provide a basis for demonstrating the advantages of 
the present invention over the prior art in the production of melt-blown, 
coform and spunbond webs and materials. These examples are provided solely 
for the purpose of illustrating how the methods of the present invention 
may be implemented and should not be interpreted as limiting the scope of 
the invention as set forth in the claims. 
Example 1 
Process Condition 
Die Tip Geometry: 
Recessed Die Width=20" 
Gap=0.090"30 hpi 
Primary Airflow: 
Heated (.apprxeq.608.degree. F. in heater) 488 scfm 
Pressure P.sub.T =6.6 psig 
Auxiliary Airflow: 
Unheated (ambient air temp.) 60 scfm 
Inlet Pressure=20 psig 
Polymer: Copolymer of butylene and propylene 
polypropylene*--79% 
polybutylene--20% 
blue pigment--01% 
FNT *800 MFR polypropylene coated with peroxide--final MFR.apprxeq.1500 
Polymer Throughput: 0.5 GHM 
Melt Temperature: 470.degree. F. 
Perturbation Frequency: 0 Hz, 156 Hz, 462 Hz 
Basis Weight: 0.54 oz/yd.sup.2 
Forming Height: 
TABLE 1-1 
______________________________________ 
Test Results 
Barrier 
Perturbation Frequency 
0 Hz 156 Hz 462 Hz 
______________________________________ 
Frazier Porosity 
45.18 35.70 65.89 
(cfm/ft.sup.2) 
Hydrohead (cm) 86.40 103 74.60 
______________________________________ 
In this example, the melt-blown process was configured as described above 
and corresponds to the embodiment shown in FIG. 6c, in which the primary 
airflow is supplemented with an auxiliary airflow. In the example, the 
unit hpi characterizes the number of holes per inch present in the die. 
P.sub.T is defined as the total pressure measured in a stagnant area of 
the primary manifold. GHM is defined as the flow rate in grams per hole 
per minute; thus, the GHM unit defines the amount, by weight, of polymer 
flowing through each hole of the melt-blown die per minute. As discussed 
above, Frazier Porosity is a measure of the permeability of the material 
(units are cubic feet per minute per square foot). The hydrohead, measured 
as the height of a column of water supported by the web prior to 
permeation of the water into the web, measures the liquid barrier 
qualities of the web. 
The above configuration and results provide a baseline comparison of a 
typical melt-blown production run with no air perturbation (a frequency of 
perturbation of 0 Hz) with runs conducted with perturbation frequencies of 
156 and 462 Hz. As can be seen from Table 1-1, in general, the barrier 
characteristics of materials made using perturbed airflows improve with 
increasing perturbation frequency. Thus, by merely varying the 
perturbation frequency, a relatively easy process, materials or webs with 
desired barrier characteristics may be made without major changes to the 
process conditions. This ability to adjust barrier properties was not 
previously possible in the prior art without substantial changes to the 
process conditions which required significant time and effort. As can be 
seen there is an initial decrease in Frazier Porosity (which represents an 
decrease in the permeability of the web or material to air) at the 156 Hz 
perturbation frequency. Similarly, at the 156 Hz frequency, there is an 
increase in the supported hydrohead. Thus, at the 156 Hz frequency, the 
web material produced is a more effective barrier. At the 462 Hz 
perturbation frequency, the Frazier Porosity has increased and the 
Hydrohead has decreased from both the 0 Hz (prior art) and 156 Hz 
production runs. Thus, at the higher perturbation frequency, the web 
material is a less effective barrier, but is more suitable for use as an 
absorbent or wicking material. 
The change in barrier properties with respect to change in perturbation 
frequency is also demonstrated in FIGS. 11 and 12 (for different process 
conditions from those of Example 1). As FIG. 11 shows, there is an initial 
drop in Frazier Porosity as the process is changed from no perturbation to 
a perturbation frequency between 1 and 200 Hz. As the perturbation 
frequency is increased above about 200 Hz, the Frazier Porosity increases, 
until the original 0 Hz Frazier Porosity is exceeded between about 300 to 
400 Hz. Above 400 Hz, the Frazier Porosity increases relatively steeply 
with increasing perturbation frequency. Similarly, referring to FIG. 12, 
supported hydrohead initially increases between about 1 to 200 Hz 
perturbation frequency. Then the hydrohead steadily decreases with 
increasing perturbation frequency until the supported hydrohead at between 
about 400 to 500 Hz is less than that at the 0 Hz (steady flow) frequency. 
Thus, as these Figures demonstrate, with no variation in the basic process 
conditions such as polymer type, flow conditions, die geometry, aside from 
a simple change in the frequency of perturbation of the airflow, a wide 
variety of different web materials can be made having desired barrier 
properties. For example, by merely setting the perturbation frequency in 
the 100 to 200 Hz range, with all of the other process conditions 
remaining unchanged, a more effective barrier material can be made. Then, 
if less effective barrier material is desired, the only process change 
necessary would be an increase in the perturbation frequency, which could 
be accomplished with a simple control and without necessitating the 
interruption of the production line. In prior art techniques, alteration 
of the production run barrier properties may require substantial changes 
in the process conditions, thereby requiring a production line shut-down 
to make the changes. In actuality, such changes are not typically made on 
a given machine; multiple machines typically produce a single type of web 
material (or an extremely narrow range of materials) having desired 
properties. 
Example 2 
Process Conditions 
Die Tip Geometry: 
Recessed Die Width=20" 
Gap=0.090"30 hpi 
Primary Airflow: 
Heated (.apprxeq.608.degree. F. in heater) 317 scfm 
Pressure P.sub.T =2.6 psig 
Auxiliary Airflow: 
Unheated (ambient air temp.) 80 scfm 
Inlet Pressure=20 psig 
Polymer: High MFR PP* 
FNT *e.g. 800 MFR polypropylene coated with peroxide--final MFR.apprxeq.1500 
Polymer Throughput: 0.5 GHM 
Melt Temperature: 470.degree. F. 
Perturbation Frequency: 0 Hz (control), 70 Hz 
Basis Weight: 5 oz/yd.sup.2 
Forming Height: 10" 
Test Results 
In this example the bulk of the web made using a 70 Hz perturbation 
frequency was compared to a control web (0 Hz perturbation frequency). 
Control--0.072" (thickness) 
70 Hz--0.103" 
Thus, it can be seen that using a modest 70 Hz perturbation frequency 
results in a 43% increase in bulk over the prior art. Increased bulk is 
often desired in the final web or material because the increased bulk 
often provides for better feel and absorbency. 
Furthermore, with respect to desired texture or appearance, the use of the 
perturbation techniques of the present invention allows for custom texture 
or appearance control. Referring to the photographs of FIGS. 13 and 14, 
FIG. 13 represents the appearance of the web produced with the 0 Hz 
perturbation frequency while the web of FIG. 14 represents that produced 
using the 70 Hz perturbation frequency. As can be seen from the Figures, 
the web of FIG. 14 has a leather like appearance and texture which is not 
present in the web of FIG. 13. Thus, to the extent such appearance and 
texture is desired, the techniques of the present invention allow for 
added control and variety in production of various types of webs having 
such characteristics. 
Example 3 
Process Conditions 
Die Tip Geometry: 
Recessed Gap=0.090"30 hpi 
Primary Airflow: 
Heated (.apprxeq.608.degree. F. in heater) 426 scfm 
Pressure P.sub.T =5 psig 
Auxiliary Airflow: 
Unheated (ambient air temp.) 80 scfm 
Inlet Pressure=20 psig 
Polymer: High MFR PP*, 1% Blue pigment 
FNT *e.g. 800 MFR polypropylene coated with peroxide--final MFR.apprxeq.1500 
Polymer Throughput: 0.16 GHM 
Melt Temperature: 480.degree. F. 
Perturbation Frequency: 0 Hz (control), 192 Hz, 436 Hz 
Basis Weight: 0.54 oz/yd.sup.2 
Forming Height: 10" 
Test Results 
Softness--Cup Crush 
0 Hz--1352 
192 Hz--721 
Cup Crush is a measure of softness whereby the web is draped over the top 
of an open cylinder of known diameter, a rod of a diameter slightly less 
than the inner diameter of the cup cylinder is used to crush the web or 
material into the open cylinder while the force required to crush the 
material into the cup is measured. The cup crush test was used to evaluate 
fabric stiffness by measuring the peak load required for a 4.5 cm diameter 
hemispherically-shaped foot to crush a 22.9 cm by 22.9 cm piece of fabric 
shaped into an approximately 6.5 cm diameter by 6.5 centimeter tall 
inverted cup while the cup shaped fabric was surrounded by an 
approximately 6.5 cm centimeter diameter cylinder to maintain a uniform 
deformation of the cup shaped fabric. The foot and cup were aligned to 
avoid contact between the cup walls and the foot which could affect the 
peak load. The peak load was measured while the foot was descending at a 
rate of about 0.64 cm/s utilizing a Model 3108-128 10 load cell available 
from the MTS Systems Corporation of Cary, N.C. A total of seven to ten 
repetitions were performed for each material and then averaged to give the 
reported values. 
The lower cup crush number achieved by the material made using the 192 Hz 
perturbation frequency indicates that the material made thereby is softer. 
Subjective softness tests such as by hand or feel also confirm that the 
material made by using the 192 Hz perturbation frequency is softer than 
that made using the prior art techniques. 
TABLE 3-1 
______________________________________ 
Strength 
Perturbation 
Frequency 0 Hz 192 Hz 436 Hz 
______________________________________ 
MD Peak Load (lbs) 
1.989 2.624 2.581 
MD Elongation (in) 
0.145 0.119 0.087 
CD Peak Load (lbs) 
1.597 1.322 1.743 
CD Elongation (in) 
0.202 0.212 0.135 
______________________________________ 
As can be seen from Table 3-1, the machine direction strength increases for 
runs in which the perturbation frequency is greater than 0 Hz. In the 
production runs of Example 3, the direction of perturbation was generally 
parallel to the machine direction (MD). Applicants believe that the 
increased strength in MD is due to more controlled and regular overlap in 
the laydown of the web on the substrate as the fibers oscillate as a 
result of the perturbation. A similar result is demonstrated in FIG. 15 
which is a graph showing the variation of Peak Load in MD and CD as a 
function of perturbation frequency. As is seen in the FIG. 15, strength in 
the MD increases as the perturbation frequency increases. Typically, CD 
strength remains relatively constant (with slight variations) regardless 
of perturbation frequency. It is applicants' belief that increases in CD 
strength can be achieved by varying the angle of the perturbation relative 
to the MD. Thus, by having the perturbation occur at some angle between 
parallel to MD and perpendicular to MD, CD strength can be improved as 
well as MD strength. 
TABLE 3-2 
______________________________________ 
Barrier 
Perturbation Frequency 
0 Hz 192 Hz 
______________________________________ 
Frazier Porosity 31.5 22.3 
(cfm/ft.sup.2) 
Hydrohead (cm of H.sub.2 O) 
90.8 121.6 
Equiv. Pore Diameter (.mu. 
13.2 10.8 
m) 
______________________________________ 
As Table 3-2 demonstrates, and as was demonstrated in Example 1, at 
relatively low perturbation frequencies (between about 100 to 200 Hz) the 
barrier properties of a web produced thereby increase. This result is 
explained by the measured Equivalent Circular Pore Diameter in the 0 Hz 
case and the 192 Hz case. As is shown in Table 3-2, the pore size for web 
material produced using a 192 Hz perturbation frequency is 2.4 microns 
less than that for a material produced with no perturbation. Thus, since 
the pores in the material are smaller, the permeability of the material is 
less and the barrier properties are greater. 
Example 4 
Process Conditions 
Die Tip Geometry: 
Recessed Die Width=20" 
Gap=0.090"30 hpi 
Primary Airflow: 
Heated (.apprxeq.608.degree. F. in heater) 422 scfm 
Pressure P.sub.T =5 psig 
Auxiliary Airflow: 
Unheated (ambient air temp.) 40 scfm 
Inlet Pressure=15 psig 
Polymer: Copolymer of butylene and propylene 
polypropylene*--79% 
polybutylene--20% 
blue pigment--01% 
FNT *800 MFR polypropylene coated with peroxide--final MFR.apprxeq.1500 
Polymer Throughput: 0.6 GHM 
Melt Temperature: 471.degree. F. 
Perturbation Frequency: 0-463 Hz 
Basis Weight: 0.8 oz/yd.sup.2 
Forming Height: 
TABLE 4-1 
______________________________________ 
Test Results 
Barrier 
Perturbation Frequency 
0 Hz 305 Hz 463 Hz 
______________________________________ 
Frazier Porosity 
46.27 26.85 59.34 
(.paren open-st. cfm/ft.sup.2) 
______________________________________ 
Once again, it can be seen that the porosity of the web material initially 
decreases when the airflow is perturbed. However, as the perturbation 
frequency increases, the porosity also increases. The results in Example 4 
agree with the other barrier property results from the other examples and 
with the results reported in FIGS. 11 and 12. 
Although the above referenced examples utilize a polypropylene or mixture 
of high melt flow polypropylene and polybutylene resins for non-woven web 
production, a multitude of thermoplastic resins and elastomers may be 
utilized to create melt-blown non-woven webs in accordance with the 
present invention. Since it is the structure of the web of the present 
invention which is largely responsible for the improvements obtained, the 
raw materials used may be selected from a wide variety. For example, and 
without limiting the generality of the foregoing, thermoplastic polymers 
such as polyolefins including polyethylene, polypropylene as well as 
polystyrene may be used. Additionally, polyesters may be used including 
polyethylene terepthalate and polyamides including nylons. While the web 
is not necessarily elastic, it is not intended to exclude elastic 
compositions. Compatible blends of any of the foregoing may also be used. 
In addition, additives such as processing aids, wetting agents, nucleating 
agents, compatibilizers, wax, fillers, and the like may be incorporated in 
amounts consistent with the fiber forming process used to achieve desired 
results. Other fiber or filament forming materials will suggest themselves 
to those of ordinary skill in the art. It is only essential that the 
composition be capable of spinning into filaments or fibers of some form 
that can be deposited on a forming surface. Since many of these polymers 
are hydrophobic, if a wettable surface is desired, known compatible 
surfactants may be added to the polymer as is well-known to those skilled 
in the art. Such surfactants include, by way of example and not 
limitation, anionic and nonionic surfactants such as sodium 
diakylsulfosuccinate (Aerosol OT available from American Cyanamid or 
Triton X-100 available from Rohm & Haas). The amount of surfactant 
additive will depend on the desired end use as will also be apparent to 
those skilled in this art. Other additives such as pigments, fillers, 
stabilizers, compatibilizers and the like may also be incorporated. 
Further discussion of the use of such additives may be had by reference 
to, for example, U.S. Pat. No. 4,374,888 issued on Bornslaeger on Feb. 22, 
1983, and U.S. Pat. No. 4,070,218 issued to Weber on Jan. 24, 1978. 
Additionally, a multitude of die configurations and die cross-sections may 
be utilized to create melt-blown non-woven webs in accordance with the 
present invention. For example orifice numbers of 20 to 50 holes per inch 
(hpi) are preferred. Moreover, virtually any appropriate orifice diameter 
may be utilized. Additionally, star-shaped, elliptical, circular, square, 
triangular, or virtually, any other geometrical shape for the 
cross-section of an orifice may be utilized for melt-blown non-woven webs. 
Coform Applications 
Applicants hereby incorporate by reference U.S. Pat. No. 4,818,464, issued 
to Lau on Apr. 4, 1989 which discloses coform methods of polymer 
processing by combining separate polymer melt streams into a single 
polymer melt stream for extrusion through orifices in forming non-woven 
webs. Additionally, applicants hereby incorporate by reference U.S. Pat. 
No. 4,818,464, issued to Lau on Apr. 4, 1989 which discloses the 
introduction of superabsorbent material as well as pulp, cellulose, or 
staple fibers through a centralized chute in an extrusion die for 
combination with resin fibers in a non-woven web. Referring now to FIG. 
16, a description of the coform process is provided. In essence, a coform 
die is basically a combination of two melt-blown die heads 173, 175. Air 
flows 176 and 178 are provided around die 172 and air flows 180 and 182 
are provided around die 174. A chute 184 is provided through which pulp, 
staple fibers, or other material may be added to vary the characteristics 
of the resulting web. Since any of the above described techniques to vary 
the airflow around a melt-blown die may be used in the coform technique, 
specific descriptions of all of the valving techniques will not be 
repeated. However, it will be apparent to one skilled in the art, that to 
vary the four air flows present in the coform die, the equipment used to 
control the perturbation of the air flows will have to be doubled. 
In the coform technique, there are a variety of possible perturbation 
combinations. The most basic is to perturb each side of a given die 172 or 
174 just as described above with respect to the melt-blown techniques 
(basically, air flows 176 and 178 alternating with each other and the same 
for airflows 180 and 182). However, it is also possible to perturb the air 
flows around die 172 relative to those around die 174. Thus, air flows 176 
and 182 could be perturbed in phase with each other, but out of phase with 
air flows 178 and 180 to achieve a desired characteristic in the fibers or 
web. To achieve a different effect it may be desirable for air flows 176 
and 180 to be perturbed in phase with each other, but out of phase with 
air flows 178 and 182. It should be readily apparent that with four air 
flows, many perturbation combinations are possible, all of which are 
within the scope of the present invention. For example, a centralized 
chute may be located between the two centralized air flows for introducing 
pulp or cellulose fibers and particulates. Such a centralized location 
facilitates integration of the pulp into the non-woven web and results in 
consistent pulp distribution in the web. 
Example 5 
As described above with reference to FIG. 16, coform materials are 
essentially made in the same manner as melt-blown materials with the 
addition of a second die. Thus, there are two airflows around each die, 
for a total of four air flows, which may be perturbed as described above. 
Additionally, there is typically a gap between the two dies through which 
pulp or other material may be added to the fibers produced and 
incorporated into the web being formed. The following example utilizes 
such a conforming arrangement, but otherwise, with respect to the airflow 
perturbation, conforms to the previous description of the melt-blown 
process. 
Process conditions 
Die Tip Geometry: 
Recessed Gap=0.070" 
Die Width=20" 
Primary Air Flow: 350 scfm per bank (20" bank) 
Primary Air Temperature: 510.degree. F. 
Auxiliary Air Flow: 40 scfm per MB bank 
Polymer: PF-015 (polypropylene) 
Poly/Polymer Ratio: 65/35 
Basis Weight: 75 gsm (2.2 osy) 
TABLE 5-1 
______________________________________ 
Test Results 
Perturbation 
Frequency 0 Hz 67 Hz 208 Hz 320 Hz 
______________________________________ 
MD Peak Load 1.578 1.501 1.67 2.355 
MD Elongation (%) 
23.86 22.48 24.21 20.23 
CD Peak Load 0.729 0.723 0.759 0.727 
CD Elongation (%) 
49.75 52.46 58.08 71.23 
Cup Crush (gm/mm) 
2518 2485 2434 2281 
______________________________________ 
From table 5-1, it can be seen that the results generally agree with those 
shown in the melt-blown examples. Generally, with increasing perturbation 
frequency, aligned along the MD, MD strength increased while CD strength 
remains about the same. Similarly, the softness, measured as cup crush, 
generally increases as the perturbation frequency increases (a lower cup 
crush value indicates increased softness). Thus, this example shows that 
the techniques previously described can be applied to coform-forming 
technology to achieve the process and material control by simple 
adjustment of the perturbation frequency in the same manner as they were 
applied to the melt-blown process. 
Spunbond Applications 
FIGS. 17a through 17d represent various embodiments which utilize 
alternatingly augmented air pressure in plenum chambers 58 and 62 of a 
standard fiber draw unit, as illustrated in FIG. 3b. In a manner similar 
to that of the valving arrangements for the melt-blown unit, the fiber 
draw unit may receive alternatingly augmented air pressure into plenum 
chambers 62 and 58 via lines 74 and 72, respectively, through the 
bifurcation of main air lines 66 via perturbation valve 86. Alternatively, 
as is illustrated in FIG. 17b, main air line 66 may be bifurcated by valve 
86 into supply lines 130 and 128 with a third bleeder portion supplying 
perturbation valve 86. While lines 128 and 130 receive air from bleeder 
valve 88 at a relatively constant pressure, perturbation valve 86 receives 
bleed air from bleeder valve 88 and perturbs that air to create an 
oscillatory pressure which is then superimposed onto supply lines 128 and 
130 to create alternatingly augmented pressure in lines 74 and 72 for 
supply to plenum chambers 62 and 58, respectively. In yet another 
embodiment illustrated in FIG. 17c, main supply line 66 bifurcates into 
lines 128 and 130. This embodiment utilizes an auxiliary air supply 92 
which is perturbed by valve 86 superimposed onto the constant air pressure 
of lines 128 and 130 to create an alternatingly augmented air flow supply 
in lines 72 and 74 so as to supply air plenum chambers 62 and 58 of the 
fiber draw unit, respectively. Finally, FIG. 17d represents still another 
embodiment of the present invention which utilizes a perturbation valve 86 
which provides an alternatingly perturbing air flow prior to the 
bifurcation of the main air supply line. 
FIGS. 18a through 18f illustrate various locations for secondary 
perturbation jets which may be used with a standard prior art fiber draw 
unit such as the one illustrated in FIG. 3b to create the proper flow 
conditions for increasing desirable properties of fibers made in 
accordance with the present invention. For example, FIG. 18a illustrates 
the tail pipe 56 of a fiber draw unit which utilizes secondary 
perturbation jets 132 and 134. As described above, these secondary 
perturbation jets impose alternating augmented flow in a direction which 
is perpendicular to the main air flow through the tail pipe 56 of the 
present invention. This orthogonal relationship between primary and 
secondary air flow increases both the degree and order of turbulence of 
the air flow in the vicinity of the tail pipe 56. 
As illustrated in FIG. 18b, tail pipe 56 may also include alternatingly, or 
otherwise activated, co-flowing jets 136 and 138 to create turbulent flow 
in accordance with the present invention near the tail pipe of the fiber 
draw unit. FIG. 18c illustrates secondary perturbing jets 142 and 140 
disposed near a top portion of the fiber draw unit upstream of plenum 
chamber inlets 60 and 64. FIG. 18d represents yet another embodiment of 
the present invention that utilizes alternatingly augmented flow through 
Coanda nozzles 144 and 146 at an exit of tail pipe 56 to create turbulent 
air flow in the vicinity of tail pipe 56. Additionally, FIG. 18e 
illustrates Coanda-like nozzles 190 and 192 disposed at mid portion 54 of 
the fiber draw unit. Finally, FIG. 18f illustrates jets at inlet portions 
48 and 50 of the fiber draw unit. Each of those jets illustrated in FIGS. 
18a through 18f may alternatingly perturb air flow through the fiber draw 
unit in addition to any perturbation which may be implemented upstream of 
the jets. Additionally, each of the jets illustrated in FIGS. 18a-18f may 
also be implemented without additional perturbation means upstream 
therefrom. 
FIG. 19 represents yet another embodiment of the present invention. The 
alternatingly augmented pressure in plenum chambers 147 and 150 may be 
provided by transducers 148 and 152 via inlets 150 and 154, respectively. 
Transducers 148 and 152 are preferably actuated by means of an electrical 
signal. For example, the transducers may actually be large speakers which 
receive an electrical signal to activate 0.degree. to 180.degree. out of 
phase in order to provide the alternating augmented pressures in plenum 
chambers 147 and 150. However, any type of appropriate transducer may 
create an augmented air flow by using any means of actuation. This may 
include but is not limited to electromagnetic means, hydraulic means, 
pneumatic means or mechanical means. 
FIGS. 20a and 20b illustrate yet another embodiment of the present 
invention wherein hot and cold jets are alternatingly used to increase 
fiber crimp. Referring to FIG. 20a, fiber draw unit 69 includes secondary 
perturbation jets 156 and 158. Oscillatory jet 156 supplies hot air 
whereas oscillatory air jet 158 supplies cold air. Alternatively, FIG. 20b 
illustrates perturbation air jets 164, 166, which alternatingly supply hot 
air to the primary air flow and fiber bundle exiting from the tail pipe of 
the fiber draw unit. Both FIGS. 20a and 20b illustrate the fiber bundle 
deflection upon application of secondary perturbation. This secondary 
perturbation creates fiber bundle deflection and heating or cooling 
effects which lead to added crimp of the fibers being distributed within a 
web on an endless belt. The temperature varied perturbation provides for 
additional parameters which may be varied and controlled during 
production. The jets may be symmetrically or asymmetrically oriented to 
achieve desired fiber characteristics, namely fiber crimp. As with 
perturbation frequency and amplitude, the temperature of the air may be 
controlled without interruption of the production process, although this 
control is more complex. Thus, materials having different properties can 
be made without requiring the line to be substantially delayed and without 
the need for additional equipment. This technique may be applied to 
processes utilizing the homopolymer fibers as well as to multi-component 
fibers and materials. 
FIGS. 21(a) through 21(d) represent yet another embodiment of the present 
invention, wherein a standard fiber draw unit includes secondary 
perturbation jets at an exit of the tail pipe thereof wherein at least one 
bank of perturbation jets is rotated with respect to the machine direction 
to create a crimp or fiber movement in a cross direction with respect to 
travel of the belt within the fiber draw unit apparatus to increase 
tensile strength in the cross direction of the non-woven web. For example, 
as shown in FIG. 21(a), jet bank 162 is disposed at an angle with respect 
to the machine direction while jet bank 160 is essentially parallel to the 
machine direction. FIG. 21(b) illustrates jet banks 202 and 200 which are 
both disposed at an angle with respect to the machine direction but oppose 
one another. Furthermore, FIG. 21(c) illustrates yet another configuration 
for jet orientation. There, jet banks 202 and 204 are each rotated with 
respect to the machine direction and face in the same direction. Finally, 
FIG. 21(d) illustrates opposing jet banks 208 and 210. 
Finally, FIG. 15 illustrates the peak load of a non-woven web sample as a 
function of perturbation frequency of secondary perturbation jets for the 
embodiment utilized in Example 6. As is illustrated in the chart, machine 
direction strength of the non-woven web increases with increasing 
perturbation frequency. In the process run used to generate the data for 
FIG. 15, the direction of perturbation was parallel to the machine 
direction, as illustrated in FIG. 21(d). Furthermore, by varying the 
direction of the perturbation jets or airstreams relative to the machine 
direction, it is possible to increase cross-direction strength. 
The following examples show the application of the techniques of the 
present invention to the production of fibers and non-woven webs in the 
spunbond process. The processes and apparati are described using terms and 
units well known in the prior art. The initial example describes fibers 
and a web formed using prior art techniques to provide a basis for 
comparison for fibers and webs formed using the techniques of the present 
invention. 
Example 6 
The following examples show the application of perturbing airflows to the 
spunbond process. In this particular example, the perturbing airflows were 
applied to the air stream carrying the fibers at the exit of the fiber 
draw unit (FDU), which corresponds to the embodiment shown in FIG. 21(d). 
However, as was previously described, the process is equally applicable to 
perturbing the airflow in the FDU itself, or by application of auxiliary 
air, or bleeding airflow, at the manifolds prior to the FDU. 
Prococess Conditions 
FDU Draw Pressure: 
4 psi 
Draw unit width=14" 
Polymer Throughput: 0.5 GHM 
Polymer: 3445 Polypropylene* 
FNT *Exxon brand 3445 polymer, peroxide coated 
Melt Temperature: 430.degree. F. 
Auxiliary Flow: 40 scfm 
Basis Weight: 0.5 osy (17 gsm) 
TABLE 6-1 
______________________________________ 
Test Results 
Perturbation Frequency 
(Hz) 0 67 227 338 463 
______________________________________ 
MD Peak Load (lb) 
0.921 1.687 1.844 2.108 2.452 
CD Peak Load (lb) 
0.824 0.645 0.462 0.586 0.521 
MD Elongation (%) 
23.85 52.79 18.03 11.08 23.05 
CD Elongation (%) 
60.84 46.5 42.31 38.76 57.10 
Total Tensile 
1.24 1.81 1.90 2.19 2.51 
(MD.sup.2 + CD.sup.2).sup.1/2 
______________________________________ 
As can be seen from the Table, the use of perturbing airflows in the 
spunbond process provides substantially increased MD strength (in this 
example, the perturbing airflows were aligned with the machine direction). 
As was the case with the melt-blown process with perturbed airflows, the 
CD strength remained relatively constant after a slight decrease. As the 
total tensile strength calculation indicates, however, the overall 
strength of the web is increased by the application of the perturbing 
airflows. Once again, as was demonstrated with the use of perturbation of 
airflow in the melt-blown process, the use of airflow perturbation 
provides for a range of selectable characteristics in the final web 
material, merely by adjusting the perturbation frequency. This ease of 
process control is not currently available in the spunbond art. Typically, 
to prepare spunbond web materials with varying properties, the processing 
equipment must be completely shut down and the process conditions changed, 
such as by changing the die or other substantial change to the equipment. 
Though the present invention does not preclude those processes, with the 
present process, such changes to the web material may be accomplished on 
the fly by merely changing the perturbation frequency while the other 
process conditions remain constant. This feature of the present invention 
allows for much greater flexibility and efficiency in the operation of 
spunbond equipment. 
Example 7 
In this example, the spunbond process was adapted, using the techniques 
disclosed herein to provide for perturbing airflows disposed at the exit 
of the FDU. For the purposes of this example, the perturbing airflows were 
not disposed immediately opposite each other, as was the case in Example 
6, but rather one bank of auxiliary air nozzles was directed parallel to 
the machine direction, while the other was directed at an angle with 
respect to the cross direction to provide a slight cross direction 
trajectory (as shown schematically in FIG. 21(a)). 
Process Conditions 
Fiber Draw Pressure: 9 psi 
Polymer Throughput: 0.75 GHM 
Basis Weight: 1.0 oz/yd.sup.2 
Polymer: 3445 Polypropylene* 
FNT *Exxon brand 3445 polymer, peroxide coated 
Melt Temperature: 450.degree. F. 
Auxiliary Air Flow: 75 scfm 
TABLE 7-1 
______________________________________ 
Test Results 
Perturbation Frequency 
(Hz) 0 115 195 338 500 
______________________________________ 
MD Peak Load (lb) 
12.00 19.96 21.00 21.13 20.00 
MD Elongation (%) 
34.75 37.36 38.36 39.77 37.48 
CD Peak Load (lb) 
8.965 11.30 10.53 10.34 12.69 
CD Elongation (%) 
40.10 49.78 52.84 43.18 47.94 
______________________________________ 
Once again, it can be seen that by simply varying the perturbation 
frequency of the airflow, a variety of changes can be effectuated in the 
final non-woven web. Thus, to the extent that a material having different 
characteristics is desired, varying the perturbation frequency of the 
perturbing airflow can result in substantial changes in the final 
non-woven material. This change represents a substantial departure from 
prior art spunbond techniques in which other process conditions, which are 
much more difficult to achieve, must be varied to vary the characteristics 
of the final material. 
As is seen from the above Examples 1-7 of meltblown, coform and spunbond 
non-wovens made in accordance with the present invention, the techniques 
of the present invention allow for the formation of a non-woven webs of 
various characteristics with relatively simple adjustments to process 
controls. While some of the differences can be attributed to the lay-down 
of the fibers on the forming surface, preliminary investigation indicates 
that the present inventive techniques also result in fundamental changes 
to the fibers formed thereby. Referring now to FIGS. 22 and 23, there are 
shown X-Ray diffraction scans of a meltblown fiber made according to prior 
art techniques (FIG. 22) and a meltblown fiber made in accordance with the 
present invention (FIG. 23) both otherwise under identical processing 
conditions and polymer type. As can be seen from comparison of FIGS. 22 
and 23, the X-Ray scan of the meltblown fiber made with the inventive 
techniques has two peaks, while that of the prior art meltblown fiber has 
several peaks. It is believed that the differences observed in FIG. 23 
result from the presence of smaller crystallites in the fiber, which 
possibly result from better quenching of the fiber during formation. In 
summary, these X-Ray diffraction scans indicate that the fibers made in 
accordance with the present technique are more amorphous than prior art 
fibers and may have a broader bonding window than fibers made in 
accordance with prior art techniques. 
Additional evidence of the believed characteristic differences between 
fiber made in accordance with the present invention and those made in 
accordance with the prior art are shown in FIG. 24. FIG. 24 is a graph 
showing the results of a Differential Scanning Calorimetry (DSC) test 
conducted on a prior art meltblown fiber (indicated by the dashed line on 
the graph) and with a fiber made in accordance with the present techniques 
(the solid line). The test basically observes the absorbance or emission 
of heat from the sample while the sample is heated. As can be seen from 
FIG. 24, the DSC scan of the prior art fiber is significantly different 
from that of the present fiber. A comparison of DSC scans shows two main 
features in the present fiber that do not appear in the prior art fiber: 
(1) heat is given off from 80.degree.-110.degree. C. (apparent exotherm) 
and (2) a double melting peak. It is believed that these DSC results 
confirm that the present formation techniques produce fibers having 
significant differences from fibers produced with prior art techniques. 
Once again, it is believed that these differences relate to crystalline 
structure and quenching of the fiber during formation. 
While preferred embodiments of the present invention have been described in 
the foregoing detailed description, the invention is capable of numerous 
modifications, substitutions, additions and deletions from the embodiments 
described above without departing from the scope of the following claims. 
For example, the teachings of the present application could be applied to 
the atomizing of liquids into a mist (or entraining a liquid in a fluid 
flow such as air). An apparatus for entraining such liquids is very 
similar, in cross section, to the melt-blown apparatus shown in FIGS. 
6A-6D. In this embodiment, the apparatus simply would not have the typical 
melt-blown width of several inches to several feet. Additionally, the 
components of an atomizer would typically be several orders of magnitude 
smaller. In any event, the perturbation techniques in an atomizing 
embodiment provide for narrow droplet size distribution and more even 
distribution of the small liquid droplets in the entraining air flow. This 
embodiment could be employed in many applications such as creating 
fuel/air mixtures for engines, improved paint sprayers, improved pesticide 
applicators, or in any application in which a liquid is entrained in an 
airflow and an even distribution of the liquid and narrow particle size 
distribution in the airflow is desired.