Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~Z~
-- 1 --
The present invention relates to a method and
apparatus for making microfilament~ from organic film
forming materials or compositions and particularly for
making plastic microfilaments.
The presen~ invention also relates ~o plastic
microfilaments spun into fiber~ for ~he manufacture of
woven plastic fabrics or rope and for the manufacture of
matted fabrics.
The present invention also relates to plastic
lo microfilaments used to make an improved reinforcing and
filler material.
The present invention also relates to plastic
microfilaments suitable for use a~ filler material and
reinforcing m~tcri~l in rubber, plastics ! concr~te and
asphalt co~posit~ons.
$~
` ' ,
~s
The present inven~ion particularly relates to a
method and apparatus for using a coaxial blowing nozzle
to blow plastic microfilaments from liquid plastic
compositions comprising forming an elongated hollow tube or
cylinder of said plastic composition and subjecting the
tube or cylinder during its formation to an external
pulsating or fluctuating pressure field having periodic
oscillations. The pulsating or fluctuating pressure field
produces a laminar flow o entraining fluid in the vicinity
o of the forming elongated tube or cylinder which laminar
flow assists in the formation of the tube or cylinder and
in detaching the microfilaments from the blowing nozzle.
The invention more particularly relates to a method
and apparatus for blowing microfilaments from plastic film
forming compositions.
Means are provided for forming a thinned wall or
weakened portion of the forming elongated hollow plastic
tube or cylinder. The thinned wall or weakened portion of
the elongated plastic tube or cylinder causes a longitudinal
break along the length of the elongated plastic tube or
cylinder. The pulsating or fluc~uating pressure field
causes the broken elongated tube or cylinder to flap and to
form a multiplicity of small diameter plastic microfilaments.
The continued feeding of liquid plastic to the coaxial
nozzle stabilizes the longitudinal break in the elongated
tube or cylinder a short distance below the coaxial nozzle.
The plastic microfilaments are entrained in the entraining
fluid, increase in length, are stretched and pulled and
break away from the portion of the elongated cylinder
attached to the coaxial nozzle.
A transverse jet is used ~o induce the external
pulsating or fluetuating pressure fîeld by directing the
entraining fluid over and around the blowing nozzle at an
angle to the axis of the blowing nozzle. The entraining
fluid as it passes over and around the blowing nozzle
envelops and acts on the liquid plastic as it is being
2003S~i
1 blown to form the elongated plastic t~be or cylinder and
the plastic microfilaments and to detach the plastic
microfilaments from the coaxial blowing nozzle.
Quench or heating means may be disposed close to
and below the blowing nozzles to direct a quench or heating
fluid onto the microfilaments to rapidly cool or heat and
cure, solidify and harden the microfilaments.
BACKGROUND OF THE INVENTION
In recent years, the substantial increases in costs
o of basic materials such a~ metals, metal alloys, plastics,
cement, asphalt, rubbers and the like has encouraged
development and use of light weigh~ structural materials,
reinforcing materials and of filler materials to reduce the
amount and cost of the basic materials used and the weight
of the finished materials. One of the suggested filler
materials utilizes plastic fibers. The present invention
which produces relatively long plastic micr~filaments at an
economical low price provides an improved plastic micro-
filament material for use as a filler and reinforcing
material.
The known methods of making plastic filaments
and fibers suffer from the disadvantages of requiring the
use of relatively large amounts of energy to manufacture a
given amount of filaments or fibers and/or requiring large
capital investments in filament or fiber drawing apparatus.
The known methods of producing plastic filaments and
fibers also suffer the disadvantage of relatively low
production rates.
The known methods of producing plastic filaments and
fibers are also believed to suffer the disadvantage of not
being able to produce filaments and fibers of relatively
small uniform diameters and uniform lengths at economical
costs.
-
~LZ~
--4--
1 The process and apparatus of the present invention
are believed to overcome the disadvantages of the prior art
processes and are capable of producing microfilaments of
uniform diameter and relatively uniform length of
controlled and predictable physical and chemical character-
istics, quality and strength at economical low costs.
OBJECTS OF THE INVENTION
It is an object of the present invention to provide
a process and an apparatus for making relatively long plastic
lo microfilaments of uniform small diameters.
It is another object of the present invention to
provide plastic microfilaments that are useful in the
manufactuxe of improved structural materials.
It is another object of the present invention to
produce plastic microfilaments having relatively long
lengths and relatively uniform diameter size distribution.
It is another object of the presen~ invention to
provide plastic microfilaments for use in producing fibers,
ropes and wo~en and matted fabrics~
It is another object of the present invention to
produce in an economical simple manner plastic micro-
filaments which are substantially uniform in diameter, length
and strength characteristics.
BRIEF DESCRIPTION OF THE INVENTION
The present invention relates to plastic micro-
filaments and to a process and apparatus for making the
microfilaments.
The microfilaments are preferably made from -thermo-
setting or thermoplastic compositions.
The plastic microfilamen~s of the present invention
are made by forming a liquid film of thermoplastic or
thermosetting plastic composition across a coaxial blowing
nozzle, applying a blowing gas or an inert blowing gas at a
~U~355
- s -
positive pressure on the inner surface of the plastic film
to blow the ilm and form an elongated hollow tube or
cylinder shaped liquid film o:E liquid plastic. The
elongated tube or cylinder is initially closed at its outer
end and is attached at its inner end to the coaxial blowing
nozzle. Means are provided in the coaxial blowing nozzle
for forming a thinned wall or weakened por~ion of the
forming elongated tube or cylinder. A transverse jet
is used ~o direct an entraining fluid over and around the
o blowing nozzle. The entraining fluid as i~ passes over and
around the blowing nozzle fluid dynamically induces a
pulsating or fluctuating pressure field at the opposite or
lee side of the blowing nozzle in the wake or shadow of the
coaxial blowing nozzle a~d produces a laminar flow of
entraining fluid in the area of the forming elongated tube
or cylinder. The fluctuating pressure field has regular
periodic lateral oscillations similar to those of a flag
flapping in a breeze. The continued movement of the
entraining fluid over the elongated cylinder produces
asymmetric fluid drag forces on the cylinder, and at the
thinned walled or weakened portion longitudinally breaks
the cylinder to from a multiplicity of plastic microfilaments,
and detaches the microfilaments from the elvngated cylinder
and from the coaxial blowing nozæle and the de~ached
filaments are carried away from the blowing nozzle. The
surface tension forces of the liquid plastic composition
act on the microfilament and causes the diameter of the
microilament to seek a minimum surface area and to form
a circular cross-section.
The thin walled or weakend section of the elongated
cylinder causes the cylinder to break along its longitudinal
length, The induced fluctuating pressure field causes ~he
elongated cylinder to flap and to quickly enlarge the break
and to form a multiplicity of small diameter microfilaments.
The break proceeds up the length of the elongated cylinder
towards the coaxial nozzle. The continued feeding of
liquid plastic to thP coaxial nozzle stabilizes the break a
short distance below the coaxial nozzle. The micro-
filaments are entrained in the transverse jet entraining
~luid, are stretched, increase in length and pulled and
break away from the portion of the elongated cylinder
attached to the coaxial blowing nozzle.
The means for providing the thinned wall or
weakened por~ion of the forming elongated hollow tu~e or
cylinder may be contained within the coaxial blowing
nozzle in the annular space between ~he outer coaxial nozzle
o and the inner coaxial nozzle. The means provided may take
the form of one or more thickened or enlarged portions o
the inner nozzle disposed lengthwise on the outer surface of
the inner nozzle. The lengthr diameter and height o the
thickened or enlarged portions are such that they cause the
flow of liquid plastic as i~ passes over and around the
thickened or enlarged portions to become thinned and
weakened. The thinned and weakened portion of the liquid
plastic is carried downwardly and outwardly into the forming
elongated hollow cylinder or tube. It is this thinned
or weakened portion of the forming elongated hollow cylinder
or tube that causes the cylinder or tube to break along its
length and form the microfilaments. The thicken~d portion
of the inner nozzle is disposed at or near the outer edge
of the inner nozzle.
The liquid plastic temperature and feed rate, the
transverse jet entraining fluid linear velocity, the blowing
gas pressure and the quench rate at a given coaxial nozzle
gap will to some extent determine the microfilament length
and diameter and size distribution.
A balancing but slightly lower gas pressure than
the blowing gas pressure is pro~ided in the area in which
the elongated cylinder is form~d.
Quench nozzles where the plastic is thermoplastic
and heating nozzles where the plastic is thermosetting
may be disposed below and on either side of the blowing
nozzle to direct cooling or heating fluid at and into
contact with the liquid plastic microfilaments to rapidly
cool or heat and solidify the liquid plastic and form
hardened, smooth microfilaments o rela~ively long length.
Where a thermosetting plas~ic is used, the microfilaments
may be heated and cured and the cured plastic microfilaments
can be subsequently cooled.
THE ADVANTAGES
The present invention overcomes may of the problems
associated with prior at~empts to produce plastic micro-
o filaments and fibers. The process and apparatus of thepresent invention allows the production of plastic micro-
filaments of relatively long leng~h and relatively uniform
diameter such that superior structural materials and
improved filler and reinforcing materials can be designed,
manufactured and tailor made to suit a particular desired
use.
The relatively long plastic microfilaments
produced in accordance with the present invention have the
distinct advantage that due to the method of manufac~ure
microfilaments of small uniform diame~er and relatively
uniform length can be obtained.
The process and appara~us of the present invention
provide a practical means by which relatively long plastic
microfilaments can be made at economic prices and in large
quantities for use as filler and reinforcing materials and
in the manufac~ure of fibers and fabrics.
The microfilaments of the present invention because
of their relatively long length can be spun into fibers and
ropes, and can be woven into fabrics 9 and can be used to
make matted fabrics.
--8~
BRIEF DESCRIPTION OF THE DRAWINGS
The attached drawings illustrate exempl.ary forms
of the method and apparatus of the present invention for
making plastic microilaments.
The Figure 1 of the drawings shows in cross section
an apparatus having mul~iple coaxial blowing nozzle means
for supplying the gaseous material for blowing plastic micro-
filaments J a ~ransverse jet for providing an entrai.ning
fluid to assist in the formati.on and detachment of the
o microfilaments from the blowing nozzles, and means for
supplying a quench or heating fluid to cool or heat the
microfilaments.
Figure 2 of the drawings is an enlarged detailed
cross-section of the nozzle means of apparatus shown in
Figure 1.
The Figure 3 of the drawings is an enlarged detailed
cross-section of a modified form of a blowing nozzle in
which the lower end of the nozzle is ~apered inwardly.
The Figure 4A of the drawings is a detailed cross-
section and a top plane view of a coaxial blowing nozzletip of the type shown in Figure 2.
The Figure 4B of the drawings is a detailed cross-
section and top plane view of a coaxial blowing nozzle
. tip of the type illustrated in Figure 3 of the drawings.
The Figure 4C of ~he drawings is a detailed cross-
section and top plane view of a modified form of a coaxial
blowing nozzle.
DETAILED DISCUSSION OF ~IE DRAI~INGS
The invention will be described with reference to
the accompanying Figures of the drawings wherein like
numbers designate like parts ~hroughout the several views.
g
1 Referring to Figures 1 and 2 of the drawings,
there is illustrated a vessel 1, made of suitable con-
tainer material and heated, as necessary, by means not shown
for holding liquid plastic 2. The bottom floor 3 of vessel
1 contains a plurality of openings 4 through which liquid
plastic 2 is fed to coaxial blowing nozzles 5. The
coaxial blowing nozzle 5 can be made separately or can be
formed by a downward extension of the bottom 3 of vessel 1.
The coaxial blowing nozzle 5 consists of an inner nozzle 6
lo having an orifice 6a for a blowing gas or an iner~ blowing
gas and an outer nozzle 7 having an orifice 7a for liquid
plastic. The inner nozzle 6 is disposed within and co-
axial to outer nozzle 7 to form annular space 8 between
nozzles 6 and 7, which annular space provides a flow path
for liquid plastic 2. The orifice 6a of inner nozzle 6
terminates at or a short distance above the plane of ori-
fice 7a of outer nozzle 7.
There is disposed in annular space 8 on the outer
surface of inner nozzle 6 a thickened or enlarged portion
20 means for providing the thinned wall or weakened por-
tion of the elonga~ed hollow plastic tube or cylinder.
The lengthj- diameter and height of the thickened or
enlarged portion 2Q are such tha~ they cause the flow of
liquid plastic as it passes over and around the thickened
or enlarged portion 20 to become thinned and weakened.
The liquid plastic 2 at about atmospheric pressure
or at eleva~ed pressure flows downwardly through annular
space 8 and fills the area ~ between orifice 6a and 7a.
The surface tension forces in liquid ~lastic 2 form a thin
liquid plastic film 9 across orifice 6a and 7a.
A blowing gas 10 which is at or below ambient
temperature or which is heated by means not shown to
about the temperature of the liquid plastic and which
is at a pressure above the liquid plastic pressure at the
0355
-10-
blowing nozzle, is fed through distribution conduit 11
and inner coaxial nozzle 6 and brought into contact
with the inner surf~ce of liquid plastic film 9 The
blowi.ng gas exer~s a positive pressure on the liquid
plastic film to blow and distend the film outwardly to form
the elongated cylinder shaped liquid film 12 of liquid
plastic filled with the blowing gas 10. The elongated
cylinder 12 is initially closed at its outer end and is
connected at its inner end ~o outer nozzle 7 at the
o peripheral edge of orifice 7a. The thinned and weakened
portion of the liquid plastic is carried downwardly and
outwardly to form the elongated hollow plastic tube or
cylinder 12.
The elongated hollow plastic tube or cylinder is
subjected during its formation to an external pulsating or
fluctuating pressure field having periodic oscillations.
The pulsating or fluctuating pressure field produces a
laminar flow of entraining fluid in the vicinity of the
forming elonga~ed hollow plastic tube or cylinder 12.
The thinned wall or weakened portion of the elon-
gated cylinder or tube 12 causes a longitudinal break along
the leng~h of the elongated cylinder 12. The pulsating
or fluctuating pressure field causes the broken elongated
cylinder 12 to flap and to form a multiplicity of small
diameter microfilaments 17. The continued feeding of
liquid plastic 2 to the coaxial nozzle 5 stablizes the
longitudinal break in the elongated cylinder a short
distance below the coaxial nozzle 5. The plastic micro-
filaments, however, remain connected to each other at the
end of the elongated cylinder connected ~o the coaxial
blowing nozzle. The microfilaments 17 are entrained in
the entraining fluid 14, increase in lPngth, are stretched
and-pulled and break away from the portion of the elon-
gated cylinder attached to the coaxial nozzle.
A balancing pressure of a gas or of an inert gas,
i.e. a slightly lower pressure, is provided in the area
of the blowing nozzle into which the elonga~ed tube or
0355
cylinder shaped liquid film is blown. The illustrated
coaxial nozzle can be used to produce plastic micro-
filaments having rela~ively long lengths and relatively
thick uniform diameters and is useful in blowing
plastic microfilaments from low viscosity plastic
material.
A transverse jet 13 is used to induce the external
pulsating or fluctuating pressure field by directing
an entraining fluid 14 over and around the blowing
o nozzle S at an angle to the axis of the blowing nozzle.
The entraining fluid 14 is heated to about, below or
above the temperature of the liquid plastic 2, by means
not shown. The entraining fluid 14 is fed through distri-
bution conduit 15, nozzle 13 and transverse jet nozzle
orifice 13a and directed at the coaxial blowing nozzle 5.
The transverse jet 13 is aligned to direct the flow of
entraining fluid 14 over and around blowing nozzle 7 in
the microfilament forming region at and behind the
orifice 7a. The entraining fluid as it passes over and
around the blowing nozzle 5 envelo~s and acts on the
liquid plastir as it is being blown to form the elongated
hollow tube or cylinder 12 and ~he microfilaments 1-7
and to detach the microfilaments from the coaxial blowing
nozzle. The surface tension forces of the liquid
plastic act on the diameter of the entrained, falling micro-
filaments 17 and cause the diameter of the microfilaments
to seek a minimum surface area and to form a circular
shaped cross-section area.
Quenc~ or heating noæzles 18 having orifices 18a
are disposed below and on both sides of coaxial blowing
nozzle 5 and direct cooling or heating fluid 19 at and
into contact with the liquid plastic microfilaments 17 to
rapidly cool or heat and cure and solidify the liquid
plastic and form a smooth, hardened ~lastic microfilaments.
The quench or heating fluid 19 also serves to carry the
plastic microfilaments away from the coaxial blowing
nozzle 5. Suffic;ent heating and curing time can be
n~e~
-12-
1 provided by using a heated fluidized bed, heated liquid
carrier or belt carrier system :Eor the thermosetting
plastic microfilaments to cure and harden the micro-
filaments with substantially little or no distortion or
effect on the size of shape of the microfilaments. The
solidified and hardened plastic microfi.laments are
collected by su;table means not shown.
The Figure 3 of the drawings illustrates a Dre-
ferred embodiment of the invention in which the lower por-
lo tion of the outer coaxial nozzle 7 is tapered downwardlyand inwardly at 21. This embodiment as in the previous
embodiment comprises coaxial blowing nozzle 5 which
consists of inner nozzle 6 with orifice 6a and outer
nozzle 7 with orifice 7a. The figure of the drawings
also shows elongated hollow plastic tube or cylinder
shaped liquid film 12 with a plnched portion 16 and
a multiplicity of plastic microfilaments 17. There is
shown disposed in annular space 8 on two opposite sides
of the lower outer surface of inner nozzle 6 two thickened
or enlarged portions 20 means for providing the thinned
wall or weakened portion of the elongated plastic tube or
cylinder 12. The length, diameter and height of the
thickened or enlarged por~ions 20 are such that they
cause the flow of liquid plastic as it passes over and
around the enlarged or thickened portions 20 to become
thinned and weakened.
The use of the .tapered nozzle 21 cons~ruction is
found to substan~ially assist in the formation of a thin
liquid plastic film 9 in the area between orifice 6a of
inner nozzle 6 and orifice 7a of outer nozzle 7. The
inner wall surface 22 of the taper portion 21 of the
outer nozzle 7 when pressure is applied tv liquid plastic
2 forces the liquid plastic 2 to squeeze through a fine
gap fonmed between ~he outer edge of orifice 6a and the
inner surface 22 of form the thin liquid plasitc film 9
across orifice 6a and 7a. Thus, the formation of the liquid
~L2~ )3SS
-13-
1 plastic film Y does not in this embodi.ment rely solely on
the surface tension properties of the liquid plastic. The
illustrated coaxial nozzle can be used to produce plastic
microfilaments having relatively long lengths and allows
making microfilaments of smaller diameter than those made
using the Figure 2 apDaratus and is particularly useful in
blowing high viscosi~y plastic materials and compositions,
The diameter of the microfilaments is determined
in part by the thickness of the wall of the elongated hol-
lo low plastic tube or cylinder which is determined by the gap
formed by the tapered nozzle 21 and the outer edge of the
inner nozzle 6a. This apparatus allows the use of larger
inner diameters of outer nozzle 7 and larger inner
diameters of inner nozzle 6, both of which reduce the
possiblity of plugging of the coaxial nozzles when in
us~ .
The Figure 3 of the drawings also shows an embodi-
ment of the invention in which the outer portion of the
transverse jet 13 is flattened to form a g~nerally
rectangular or oval shaPed orifice opening 13a. The
orifice opening 13a can be disposed at an angle relative
to a line drawn through ~he cen~ral axis of coaxial'
nozzle 5. The preferred angle, however, is that
illustrated in the drawing. That is, at an an,gle of
about 90 to the central axis of the coaxial nozzle 5.
The use of the fla~tened transverse jet entrain-
ing fluid was found, at a given velocity, to.concentrate
the effert of the fluetuating pressure field and to
increase the amplitude of ~he pressure fluctuations
induced in the region of the formation of the elongated
hollow plastic tube or cylinder at the opposite or lee
æide of the blowing nozzle 5.
The Figures 4A, 4B and 4C of the drawings show
detailed cross-sections and top plane views of three
embodiments of the coaxial blowing nozzle tips of the
present invention.
1 In the Figure 4A there is shown disposed in annular
space 8 on the lower outer surface of inner nozzle 6 a
single thickened or enlarged portion 20 for providing
the thinned wall or weakened portion of the elongated
hollow tube or cylinder 12.
In the Figure 4B there is shown disposed in annular
space 8 on opposite sides of the lower ou~er surface of
inner nozzle 6 two thickened or enlarged portions 20 for
providing the thinned wall or weakened portions of the
o elongated hollow ~ube or cylinder 12.
In the Figure 4C there is shown disposed in annu-
lar space 8 equally spaced on the outer surface of inner
nozzle 6 four thickened or enlarged portions 20 for
providing the thinned wall or weakened portions of the
elongated hollow tube or cylinder 12.
.
;~5
--15--
ORGANIC FILM FORMING MATERIAL
AND PLASTIC COMPOSITIONS
-
The organic film forming material and compositions
and particularly the plastic materials and compositions
from which the plastic microfilaments of the present in-
vention are made can be varied to obtain the desired phy-
sical characteristics for blowing and forming, cooling or
heating and curing the microfilaments and the desired stren-
gth characteristics of the plastic microfilaments produced.
o The constltuents of ~he plastic compositions can vary de-
pending on their intended use.
The process and apparatus of the present invention
can be used to blow microfilaments from suitable film forming
plastic materials or compositions having suf~icient vis-
cosity at the temperature at which the microfilaments are
blown to form a stable elongated cylinder shape of the
plastic material being blown and the microfilaments.
The plastic materials to be used to form the micro-
filaments are selected and can be treated and/or mixed with
oth~r materials to adjust their viscosity and surface ten-
sion characteristics such that at the desired blowing tem-
peratures they form stable films and are capable of forming
the elongated hollow plastic ~ubes or cylinders and micro-
filaments of the desired length and diameters.
The plastic compositions that can be used to
form microilaments include thermosetting and thermoplastic
materials such as polyethylene, polypropylene, polystyrene t
polyesters, polyurethanes, polychloro-trifluoro ethylene,
polyvinyl fluoride, polyvinylidene, polymethyl methacrylate
acetyl, phenol-formaldehyde resins and silicone and poly-
carbonate resins. The plastic compositions ~hat can be used
also include cellulose acetate, cellulose acetate-butyrate,
and cellulose acetate~propionate.
~CI Q35S
Thermoplastic resins t~at can be used are polyvinyl
resins such as polyvinyl alcoholl polyvinyl chloride,
copolymers of vinyl chloride and vinyl acetate, polyvinyl
butyral, polystyrene, polyvinylidene chloride, and acrylic
resins such as polymethyl methacrylate, polyallyl, poly-
ethylene, and polyamide (nylon) resins.
Thermosetting resins that can be used include al]cyd,
polysiloxane, phenol-formaldehyde, urea-formaldahyde and
melamine-formaldehyde resins~
The plastic compositions disclosed in applicant's
U.S. Patent 4,303,603, Veatch et al U.S. Patent 2,797,201
and the Moîehouse, Jr. U.S. Patent 3,615,972 can be used
in carrying out the present invention.
There may be added to the plastic compositions chemical
agents or additives which effect the viscosity of the
compositions or of the surface film of the microfilaments
in order to obtain the desired viscosities needed to obtain
a stable film for blowing the hollow elongated tube or
cylinder Suitable chemical agents are materials that act
as solvents for the plastic compositions. The solv~nts
that are used will, of course, depend on the solubility
in the solvent of the plastic composition used. Water,
alcohols, ethers, esters, organic acids, hydrocarbons
and chlorinated hydrocarbons can be used as solvents. To
assist in the blowing and formation of the plastic
microfilaments and to control the surface tension and
viscosity of the elongated cylinder being formed suitable
surface active agents, such as colloidal particles of
insoluble substances and viscosi~y stabilizers can be added
to the plastic composition as additives. These additives
can affect the viscosity of the surface film of the hollow
elongated tube or cylinder to stabilize the film during
cylinder formation.
For a more specific description of the plastic and
resin compositions see Zimmerman and Lavine, "Handbook of
Material Trade Names", Vols. I-IV, 1953-1965.
- 16 -
~'
w~
-17-
The plas~ic compositions of the pr~sent inven-
tion are formulated to have a relatively narrow temperature
difference between the liquid temperature and the plastic
hardening temperature (thermoplastic~ or a relatively
narrow temperature difference between ~he liquid temperature
and the thermosetting and curing temperature. The plastic
compositions are formulated such that they have a high rate
of viscosity increase with the hardening temperature or the
thermosetting temperature such that the microfilaments
will rapidly solidify, harden and streng~hen. That is,
they change from liquid ~o solid within a relative narrowly
defined temperature range and/or cure in a relatively short
time.
BLOWING GAS
The plastic mlcrofilaments can be blown with a gas,
e.g. an inert gas. Suitable blowing gases can be argon,
nitrogen and air. The blowing gases can be selected to
react with the plastic film forming material or composition,
e.g. to assist in the hardening and/or curing of the micro-
filamen~. The blowing gas in reacting with the film forming
material as the -elongated cylinder is being blown and formed,
can to some extent help to stabilize (against break-up)
the film forming plastic material used to form the elongated
cylinder and microfilaments and allow sufficient ~ime for
the microfilaments to form and harden. For certain uses,
oxygen or air can be used as or added to the blowing gas.
The blowing gas can include a catalyst or hardening agent
for the plastic compositions. The addi~ion of a catalyst
or hardening agen~ to ~he blowing gas preven~s contact of
the catalys~ or hardening agent with the plastic composition
until a time just before the hollow elongated tube or
cylinder is formed.
~2~ S
- 1 8 -
1 The entraining fLuid can be a gas at a high or low
temperature and can be selec~ed to reac~ with or be inert
to the plastic composition. Suitable entraining fluids are
ni~rogen, air, steam and argon. A gaseous catalyst for the
plastic can also be included in the entraining fluid.
The quench or heating fluid can be a liquid, a
liquid dispersion or a gas. Suitable ~uench or heating
fluids are steam, a fine water spray, air, nitrogen or
mixtures ~hereof. The selec~ion of a specific quench or
lo heating fluid and quench or heating temperature depends to
some extent on the plastic composition from which the
hollow elongated tube or cylinder is biown.
PROCESS CONDITIONS
-
The organic film forming materials and/or plastic
materials and compositions of the present inventiGn are in a
liquid-fluid form a~ the desired blowing temperature and
during the blowing operation. The liquid plastic composition
can be at a temperature-of about 0G. to about 400C.,
preferably -10DG-. to 300C and more preferably ?0C to 200C.~
depending on the constituents and state of polymerization of,
for example, the plastic composition. The plastic comp-
sition at the blowing temperature is liquid, fluid and flows
easily. The liquid plastic just prior to the blowing oper-
ation can have a viscosi~y of 0.10 to 600 poises, usually
10 to 350 poises and more usually 30 to 200 poises.
The liquid plastic is continuously fed ~o ~he
coaxial blowing nozzle during the blowing operation to pre-
vent premature breaking and detaching of the elongated tube
or cylinder shaped liquid plastic film as it is being formed
by the blowing gas.
The blowing gas or, iner~ blowing gas will be at
about the same temper~ture as the liquid plastic being blown.
The blowing gas temperature can,however, be at a higher temp-
erature than the liquid plastic to assist irl maintaining th~
fluidity of the hollow liquid plastic tube or cylinder during
- 1 9 -
1 the blowing operation or can be at a lower temperature than
the liquid plastic to assist in the solidification and hard-
ening of the plastic microfllame~s as they are formed. The
pressure of the blvwing gas is sufficient to blow the micro-
filamen~s and will be slightly above the pressure of liquid
plastic film at the orifice 7a of the outer nozzle 7. The
blowing gas pressure will also depend on and be slightly
above the ambient pressure external to the blowing nozzle.
The temperatures of the blowing gases will depend
o on the blowing gas used and the viscosi~y-temperature-shear
relationship for the film forming plastic materials used to
make the microfilaments. The ambient pressure ex~ernal to
the blowing nozzle will be such that it substantially
balances, but is slightly less than the blowing gas
pressure.
The transverse jet inert entraining fluid which is
directed over and around the coaxial blowing nozzle to
assist in the formation of the hollow elongated ~ube or
cylinder and detaching of the plastic microfilaments from
the coaxial blowing nozzle can be at about the same temper-
ature as the liquid plastic being blown. The entraining
fluid can, however, be at a higher temperature than the
liquid plastic to assist in maintaining the fluidity of
the hollow elongated tube or cylinder and the microfilaments
during the blowing operation or can be at a lower temper-
a~ure than the liquid plastic to assist in the stabilization
of the forming elongated hollow tube or cylinder film and in
the solidification and hardening of the microfilaments.
The transverse jet en~-raining fluid which assists in
detaching of the plastic microfilaments from ~he coaxial
blowing nozzle can have a linear velocity in the region of
microilament formation of 1 to 120 ft/sec~ usually 5 to
80 f~/sec and more usually 10 to 60 ft/sec.
The leng~h of the plastic microfilaments and ~he
diameter of the plastic microfilaments depends to some extent
on the viscosity of the plastic material and the linear
veloci~y of the ~ransverse jet entraining fluid.
~2~
-20-
1 The quench or heating fluid is at a temperature such
that it rapidly cools or heats the microfilaments to solid-
ify, harden and strengthen the liquid plastic microfilaments.
The quench cooling fluid can be at a temperature of 0 to
200F., usually 40 to 200F. and more usually 50 to 100F.
The heating flllid can be at a temperature of lO0 to 800UF.,
usually 200 to 600F. and more usually 300 to 500F.,
depending on the plastic composition.
The time elapsed from commencement of the blowing
o of the thermoplastic composition to the cooling and initial
hardening of the microfilamen-ts can be .0001 to 60.0 seconds,
preferably .0010 to 30.0 seconds ~nd more preferably 0.10
to 10.0 seconds.
Where a thermosetting plastic composition is used
to form the microfilaments, ~he time elapsed from commence-
ment of thè blowing of the plastic elongated hollow tube
or cylinder to the heating and curing of the microfilaments
can be 0.10 second to 30 minutes, preferably 1 second to
20 minutes and more preferably 10 second to 10 minutes.
03
-21~-
1 APPARATUS
Referring to Figures 1 and 2 of the drawings, the
container vessel is constructed to maintain the liquid
plastic at ~he desired operating temperatures. The liquid
plastic 2 is fed to coaxial blowing nozzle 5. The coaxial
blowing nozzle 5 consists o an inner nozzle 6 having an
outside diameter of 0.32 to 0.010 inch, preferably 0.20 to
0.015 inch and more preferably 0.10 to 0.20 inch and an
outer nozzle 7 having an inside diameter of 0.420 to
o 0.020 inch, preferably 0.260 to 0.025 and more preferably
0.130 to 0.030 inch. The inner nozzle 6 and outer nozzle 7
form annular space 8 which provides a flow path through
which the liquid plastic 2 is extruded. The distance
between the inner noz~le 6 and outer nozzle 7 can be 0.050
to 0.004, preferably 0.030 to 0.005 and more preferably
0.015 to 0.008 inch.
The orifice 6a of inner nozzle 6 ~erminates a short
distance above the plane of orifice 7a of outer nozzle 7.
The orifice 6a can be spaced above orifice 7a at a distance
of 0.001 to 0.125 inch, proferably 0.002 to 0.050 inch
and more preferably 0.003 to 0.025 inch. The liquid
plastir 2 flows downwardly and is extruded through annular
space 8 and-fills the area between orifice 6a and 7a.
The orifices 6a and 7a can be made from stainless steel,
platinum alloys, glass of fused alumina. Stainless steel,
however, is preferred. The surface tension forces in the
liquid plastic 2 form a thin liquid plastic film 9
across orifices 6a and 7a which has abou~ the same or a
smaller thickness as the dis~ancQ of orifice 6a is spaced
above orifice 7a. The liquid plastic film 9 can be 25 to
3175 microns, preferably 50 to 1270 microns and more
preferably 76 to 635 microns thick.
The Figure 2 blowing noz~le can be used to blow
liquid plastic at relatively low viscosi~ies~ for example,
of 10 to 60 posies, and to blow plastic microfilaments of
relatively thick diameter, for example, of 20 to 100
microns or more.
``` ~2~ 5
The transverse jet 13 is used to direct an
entraining fluid 14 through nozzle 13 and transverse jet
nozzle orifice 13a at the coaxial blowing nozxle 5. The
coaxial blowing nozzle 5 has an outer diameter of 0.52
to 0.30 inch,,preferably 0.36 to 0.035 inch and more
preferably 0.140 to 0.040 inch.
The transverse jet 13 is aligned to direct the flow
of entraining fluid 14 over and aro~md outer nozzle 7 in the
hollow elongated tube or cylinder and microfilament forming
o region of the roifice 7a. The orifice 13a of transverse
jet 13 is locatd a distance of 0.5 to 14 times, preferably
1 to 10 times and more preferably 1~5 to 8 times and still
more preferably 1.5 to 4 ~imes the outside diameter of
coaxial blowing nozzle 5 away from ~he point of intersect of
a line drawn along the center axis of transverse jet 13 and
a line drawn along the center axis of coaxial blowing
nozzle 5. The center axis of transverse jet 13 is aligned
at an angle of 15 ~o 85, preferably 25 to 75 and more
preferably 35 to 55 relative to the center axis of the
coaxial blowing nozzle 5. The orifice 13a can be circular
in shape and have an inside diameter o 0.32 to 0.010 inch,
preferably 0.~0 to 0.015 inch and more preferably 0.10 to
O.OZ0 inch.
The line drawn through the center axis of transverse
jet 13 intersects ~he line drawn through the center axis
or cbaxial blowing nozzle S at a point above the orifice
7a of outer nozzle 7 which is .5 times to 4 times,
preferably l.0 to 3.5 times and more preferably 2 to 3 times
the ou~side diameter of the coaxial blowing nozzle 5.
The entraining fluid assists in the formation and
detaching of the plastic microfilaments from the coaxial
blowing nozzle. The use of the transverse jet and entraining
fluid in the manner described also discourages wetting of the
outer wall surface of the coaxial blowing nozzle 5 by
the liquid plastic being blown.
-
~2~Q3~5
. 23-
1 The quench or heating nozzles 18 are disposed below
and on both sides of coaxial blowing nozzle 5 a sufficient
distance apar~ to allow the microfilamen~s 17 to fall
between the quench nozzles 18. The quench nozzles 18 direct
cooling or ~leating fluid 19 at and into contact with the
liquid plastic microfilaments 17 to cool or heat and
solidify the liquid plastic and form hard, smooth, plastic
mîcrofilaments.
The Figure 3 of the drawings illustrates a preferred
o embodiment of the invention. It is found that in blowing
liquid plastic compositions at high viscosities that is is
advantageous to immediately prior to blowing the liquid
plastic to provide by extrusion a very thin liquid plastic
film for blowing into the elongated cylinder shape liquid
film 12. The thin liquid plastic film 9 is provided by
having the lower portion of the outer coaxial nozzle 7
tapered downwardly and inwardly at 21. The tapered portion
21 and inner wall surface 22 thereof can be at an angle of
15 to 75, preferably 30 to 60 and more preferably about
45 rela~ive to the center axis of coaxial blowing nozzle 5.
The orifice 7a can be 0.10 ~o 1.5 times, preferably 0.20
to 1.1 times and more preferably 0.25 ~o .8 times the inner
diameter of orifice 6a of inner nozzle G.
The thickness of ~he liquid plastic film 9 can
be varied by adjusting the distance of orifice 6a of inner
nozzle 6 above orifice 7a of outer nazzle 7 such that the
distance between the peripheral edge of orifice 6a and the
inner wall surface 22 of tapered nozzle 21 can be varied.
By controlling the distance between the peripheral edge of
orifice 6a and the inner wall surface 22 of ~he tapered
nozzle to form a very fine gap and by controlling the
pressure applied ~o feed the liquid plastic 2 through
annular space 8 the liquid plastic 2 can be squeezed or
extruded through the very fine gap to form a relatively
thin liquid plastic film 9.
5S
-24-
1 The proper gap can best be determined by pressing
the inner coaxial nozzle 6 downward w:ith sufficient pressure
to completely block-off the flow of plastic, and ~o then
very slowly raise the inner coaxial nozzle 6 until a
stable system is obtained, i.e. until the hollow elonga~ed
plastic cylinder and the plastic microfilaments are
being formed.
The taperea nozzle construction illustrated in
Figure 3 can be used to blow plastic cornpositions at
o relatively high viscosities as well as to blow plastic
compositions at the relatively low viscosities referred to
with regard to Figure 2 of the drawings. The Figure 3
embodiment of the invention is of particular advantage in
blowing relatively long small diameter microfilaments.
Referring to Figures 4A, 4B and 4C of the drawings
there is shown disposed in annular space 8 on the outer
surface of inner nozzle 6 thickened or enlarged portion 20
means for providing the thinned wall or weakened portion
of the elongated hollow ~ube or cylinder. The lengt'n)
diameter and height of the thickened or enlarged portion
20 are such that they cause the flow of liquid plastic as
it passes over and around the thickened or enlarged portion
20 to become ~hinned and weakened. The thinned and
weakened portion of the liquid plastic is carried down-
wardly and outwardly to form the elongated hollow plastic
tube of cylinder 12, which as a result of the thinned and
weakened por~ion ~reaks up into a multiplicy of relatively
long microfilaments 17.
DESCRIPTION OF THE MICROFILAMENTS
The microfilaments made in accordance with the
present inven~ion can be made from a variety of organic
film forming ma~erials and compositions, particularly
plastic compositions.
~V0355
-25
The plastic microfilaments made in accordance with
the present invention can be made from suitable compositions
selected to have relatively high temperature resistance, be
resistant to chemical a~tack and be resistant to weathering.
The plastic microfilaments can be made in various
lengths and diameters, depending upon the desired end use
of the microfilaments. The microfilaments can have a length
one half to twelve inches, preferably one to eight inches
and more preferably two ~o six inches. The microfilaments
lo can have a diameter of 0.5 to 40 microns; preferably 1.0
to 30 microns and more preferably 2 to 10 microns.
It is found that for a given set of opera~ing
conditions that the plastic microfilaments that are obtained
have a relatively uniform, narrow diameter size and length
size distribution.
XAMPLES
Example 1
-
A thermoplastic composition comprising polyethylene
polymer is used~to make plastic microfilaments.
A plastic composition is heated to form a fluid
plastic having a viscosity of about 10 to 20 poises at
the blowing nozzle.
Th2 liquid plastic is fed to the apparatus of
Figures 1 and 2 of the drawings. The liquid plastic
passes through annular space 8 of about 0.005 inch, of
blowing nozzle 5 and forms a thin liquid plastic film
across the orifices 6a and 7a. A heated blowing gas
consisting of nitrogen at a positive pressure is applied
to the inner surface of the liquid plastic film causing
30 the film to distend downwardly into a elongated cylinder
shape with its inner end at~ached to the outer edge or
orifice 7a.
S
-~6-
The transverse je~ is used to direct an entraining
fluid which consists of nitrogen heated to about the
temperature of the liquid plastic, at a linear velocity of
20 to 80 feet per second over and around the blowing nozzle
5 which entraining fluid assists in the formation of the
elongated cylinder and of a multiplicity of plastic micro-
filaments and detaching of the plastîc microfilaments from
the elongated cylinder and causing the plastic microfilaments
to be entrained in ~he entraining fluid and carried away from
lo theblowing nozzle 5. The transverse jet is aligned a~ an
angle Gf 35 to 50 relative tD the blowing nozzle.
The entrained plastic microfilaments arP cooled to
about ambient temperature by a cool quench fluid consisting
of a fine water spray which quickly cools~ solidifies
and hardens the plastic microfilaments.
Plastic microfilaments having a diameter of 2 to 6
microns diameter and a one to five inch length ar~e obtained~
Exam~le 2
A thermosetting plastic composition comprising a
mixture of 50~/O by ~e~ght acrylonitrile and 50% by weight
vinylidene chloride and a suitable catalyst is used to make
plas~ic microfilaments.
The plastic compo$ition mix~ure at the blowing
nozzle has a viscosity of about ten poises.
The liquid plastic mixture is heated and is fed to
the apparatus of Figures 1 and 3 of the drawings. The
liquid plastic is passed through annular space 8 of blowing
nozzle 5 and into tapered portion 21 of outer nozæle 7.
The liquid plastic under pressure is squeezed and extruded
through a fine gap formed between the outer edge of
orifice 6a and the inner surface 22 of the tapered portion
21 of outer nozzle 7 and forn~ a thin liquid plastic film
across the oriices 6a and 7a. A heated blowing gas
consisting of nitrogen at a positive pressurP is applied ~o
the inner surface of the liquid plastic film causing the
- 2 7 -
film to distend outwardly in~o an elongated cylinder shape
with its inner end attached to the outer edge of orifice 7a.
The transverse jet is used to direct an entraining
fluid which consists o heated nitrogen at about the
temperature of the liquid plastic at a linear velocity of
20 to 80 feet per second over and around ~he blowing
nozzle 5. The en~raining fluid assists in the forma~ion
of the elongated cylinder and of a multiplicity of plastic
microfilaments and detaching of the plastic microfilaments
o from the elongated cylinder and causes plastic micro-
filaments to be entrained in the fluid and carried away
from the blowing nozzle.
The entrained microfilaments are contacted wi~h a
heating fluid consisting of heated nitrogen which
solidifies, hardens and begins to cure the liquid plastic
microfilaments.
Plas~ic microilaments having a 1 to 5 micron
diameter and having a length of 2 to 10 inches are
obtained.
UTILITY
The plastic microfilaments of the present invention
have many uses including the use of the microfilaments as a
filler or reinforcing material in rubber, cement, plaster
and asphal~ compositions. The plastic microfilaments and
fibers can be ~sed to make tire cords and filter media.
The microfilaments can be spun into fibers and
woven into fabrics or can be used to make ma~ted
fabrics.
The plastic microfilaments can advantageously be
used in plastic or resin boat construc~ion to produce
high strength hulls.
. -2~- .
I 1 These and other uses of the present invention will
become apparent to those skilled in the art from the
foregoing description and the following appended claims.
It will be understood that various changes and
modific2tions may be made in the invention, and that the
scope thereof is not to be limited except as set forth în
the claims.
