Note: Descriptions are shown in the official language in which they were submitted.
129649~
BICONSTITUENT POLYPROPYLENE/POLYETHYLENE FIBERS
Blends consisting of polypropylene and
polyethylene are spun into fibers having improved
properties.
Polypropylene (PP) fibers and filaments are
5 items of commerce and have been used in making products
such as ropes, non-woven fabrics, and woven fabrics.
U.S. 4,578,414 discloses additives for making
olefin polymer fibers water-wettable, including blends
of polyethylene (PE) and polypropylene (PP).
U.S. 4,518,744 di~closes melt-spinning of
certain polymers and blends of polymers, including
polypropylene (PP). Japanese Kokai 56- 159339 and 56-
15 159340 disclose fibers of mixtures of polyester withminor amounts of polypropylene.
Convenient references relating to fibers and
filaments, including those of man-made thermoplastics,
are, for example:
35,451C-F -1-
.
1~9649~
(a) Encyclopedia of Polymer ~cience and
Technology, Interscience, New York, llol. 6 (1967), pp.
505-555 and Vol. 9 (19~8), pp. 403-440;
(b) Man-Made Fiber and Textile Dictionary,
published by Celanese Corporation;
(c) Fundamentals of Fibre Formation--The
Science of Fibre Spinning and Drawing, by Andrzij
Ziabicki published by John Wiley & Sons, London/New
York, 1976;
(d) Man-Made Fibres, by R. W. Moncrieff,
published by John Wiley & Sons, London/New York, 1975;
(e) Kirk-Othmer Encyclopedia of Chemical
Technology, Vol. 16 for "Olefin Fibers", published by
John Wiley & Sons, New York, 1981, 3rd Edition.
In conformity with commonly accepted vernac-
ular or jargon of the fiber and filament industry, the
following definitions apply to the terms used in this
disclosure:
A "monofilament" (also known as (a.k.a.)
monofil) refers to an individual strand of denier
greater than 15, usually greater than 30;
A "fine denier fiber or filament" refers to a
strand of denier less than 15;
A "multi-filament" (a.k.a. multifil) refers to
simultaneously formed fine denier filaments spun as a
bundle of fibers, generally containing at least 3,
preferably at least 15~100 fibers and can be several
hundred or several thousand;
,
:
35,451C-F -2-
:1296498
"Staple fibers" refer to fine denier strands
which have been formed at, or cut to, staple lengths of
generally 1 to 8 inches (2.5 to 20 cm);
An "extruded strand" refers to an extrudate
formed by passing polymer through a forming-orifice,
such as a die.
A "fibril" refers to a superfine discrete
filament embedded in a more or less continuous matrix.
Whereas it is known that virtually any
thermoplastic polymer can be extruded as a coarse
strand or monofilament, many of these, such as
polyethylene and some ethylene copolymers, have not
generally been found to be suitable for the making of
fine denier fibers or multi-filaments. Practitioners
are aware that it is easier to make a coarse
monofilament yarn of 15 denier than to make a multi-
filament yarn of 15 dénier. It is also recognized that
the mechanical and thermal conditions experienced by a
bundle of filaments, whether in spinning staple fibers
3 or in multi-filaments yarns, are very different to
those in spinning monofilaments. The fact that a given
man-made polymer can be extruded as a monofilament,
does not necessarily herald its use in fine denier or
multi-filament spinning. Whereas an extruded
monofilament which has been cooled can usually be cold-
drawn (stretched) to a finer denier size, even if itdoes not have sufficient melt-strength to be melt-drawn
without breaking, it is apparent that a polymer needs
to have an appreciable melt-strength to be hot-drawn to
fine denier slzes.
35,451C-F -3-
~296498
Low density polyethylene (LDPE) is prepared by
polymerizing ethylene using a free-radical initiator,
e.g. peroxide, at elevated pressures and temperatures,
having densities in the range, generally, of 0.910-
0.935 g/cm3. The LDPE, sometimes called "I.C.I.-type"
polyethylene is a branched (i.e. non-linear) polymer~
due to the presence of short-chains of polymerized
ethylene units pendent from the main polymer backbone.
Some of the older art refers to these as high pressure
polyethylene (HPPE).
1~ High density polyethylene (HDPE) is prepared
using a coordination catalyst, such as a "Ziegler-type"
or "Natta-type" or a "Phillips-type" chromium oxide
compound. These have densities generally in the range
of 0.94 to 0.98 g/cm3 and are called "linear" polymers
due to the substantial absence of short polymer chains
pendent from the main polymer backbone.
Linear low density polyethylene (LLDPE) is
prepared by copolymerizing ethylene with at least one
a-olefin alkylene of C3-C12, especially at least one of
C4-C8, using a coordination catalyst such as is used in
making HDPE. These LLDPE are "linear", but with alkyl
groups of the a-olefin pendent from the polymer chain.
These pendent alkyl groups cause the density to be in
about the same density range (0.88-0.94 g/cm3) as the
LDPE; thus the name "linear low density polyethylene"
or LLDPE is used in the industry in referring to these
linear low density copolymers of ethylene.
Polypropylene (PP) is known to exist as atactic
(largely amorphous), syndiotactic (largely crystal-
line), and isotactic (also largely crystalline), some
of which can be processed into fi-ne denier fibers. It
35,451C-F -4-
1296498
--5--
is preferable, in the present invention, to use the
largely crystalline types of PP suitable for spinning
fine denier fibers, sometimes referred to as "CR", or
constant rheology, grades.
U.S. 4,181,762, U.S. 4,258,097, and U.S.
4,356,220 contain information about olefin polymer
f~bers, some of which are monofilaments.
U.S. 4,076,698 discloses methods of producing
LLDPE and discloses extrusion of a monofilament.
U.S. 4,584,347 discloses in general terms the
manufacture of xerogel fibers from dilute solutions of
ultra high molecular weight polyethylene or
polypropylene containing a polymeric additive which can
be LDPE, LLDPE or HDPE but there is no exemplification
of a PE/PP mix.
U.S. 4,563,504 discloses the manufacture of
mono-oriented yarns from a mixture of 10-40 weight
percent polypropylene and 60 to 90 weight percent
ethylene a-olefin copolymer. The components can be
mixed in the solid or molten state.
U.S. 4,632,861 discloses that the melt spinning
of LDPE is improved by blending LDPE with polyproplyene
in the amounts of 65-95 weight percent LDPE and 5 to 35
weight percent PP. The resultant fibers have PP
4~ dispersed in a PE continuous phase. Comparative
examples having 40:60 and 20:80 LDPE:PP are given but
the patent teaches that PP content below 35 weight
percent is require for satisfactory spinning.
CA 1199746 discloses mixtures of 40 to 90
weight percent LLDPE to improve the flexibility,
35,451C-F -5_
~296~98
--6--
capacity for hot and cold drawing, and strength of PP
for blow-molding, extrusion drawing or thermoforming.
No reference is made to spinning fibers.
Skoroszewski discloses stretched polypropylene
film fibers containing LDPE and tea~ches that LDPE
contents above 20 weight percent drastically a~fect the
tenacity of the products.
JP 52072744, JP 58011536, JP 58206647 and JP
5904132 disclose moulding compositions comprising
polypropylene and polyethylene but make no reference to
fiber manufacture. JP 52072744 discloses compositions
containing 70 to 98 weight percent polypropylene, 1 to
14 weight percent ethylene/but-1-ene random copolymers
and 1 to 15 weight percent LDPE. JP 58011536 discloses
compositions comprising an ethylene propylene random
copolymer, containing 3 to 9 weight percent ethylene,
and a LLDPE. JP 58206647 discloses a composition
comprising polypropylene, LDPE and LLDPE. JP 59041342
discloses compositions containing 60 to 95 weight
percent LLDPE and 5 to 50 weight percent polypropylene.
It has now been found, unexpectedly, that
improvements are made in polypropylene fibers if the
polypropylene is first blended with 20 percent to 45
percent by weight of a linear low density ethylene
copolymer and the molten mixture intimately mixed
immediately prior to melt spinning.
According to a first aspect, the invention
provides a biconstituent fiber consisting essentially
of polypropylene as a continuous phase, having
distributed therein 20 to 45 percent by weight of
linear low density polyethylene (LLDPE) fibrils as a
35,451C-F -6-
12964~
dispersed phase arrayed in a substantially omni-
directionally splayed manner, said LLDPE having a melt
flow rate (as measured in accordance with ASTMD-1238
(E)) in the range of 12 to 120 g/10 min. The tenacity
and softness of the fibers is improved over that of the
polypropylene or the polyethylene alone.
- ~According to a second aspect of the invention,
there is provided a process of preparing a
biconstituent fibers which comprises intimately mixing
molten polypropylene (PP) and molten linear low density
polyethylene (LLDPE), having a melt flow rate (as
measured in accordance with ASTM D-1238 (E)) in the
range 12 to 120 g/10 min in the PP:LLDPE weight ratio
80:20 to 65:45 to disperse the LLDPE ir the PP and
maintaining the dispersion until the mixture, as an
extrudate, is expelled from a spinning die to form a
fiber in which LLDPE fibrils, as a dispersed phase, are
arrayed in a substantially omni-directional splayed
manner.
IN THE DRAWINGS
Figs. 1-4 are provided herewith as visual aids
for relating certain properties of blends described in
this disclosure.
The polyethy~ene for use in this invention is
LLDPE with a molecular weight of the polyethylene in
the moderately high range, as indicated by a melt
index, M.I., (a.k.a. melt flow rate, M.F.R.) value in
the range of from 12 to 120, preferably 20 to 100 g/10
min, especially 50 + 20 g/10 mins, as measured by ASTM
D-1238(E) (190C/2.16 Kg).
35,451C-F -7-
1296~ 64693-4130
It is preferred that the comonomer a-olefin alkylenes in
the LLDPE are, in the C3-C12 range, especially C4 to C8 and
particularly l-octene. Butene (C4) can be used, but l-octene is
preferred. Mlxtures of the alkylene comonomers may be used, such
as butene/octene or hexene/octene in preparing the ethylene/-
alkylene copolymers. The density of the LLDPE is dependent on the
amount of, and the molecular size (i.e. the number of carbons in
the alkylene molecule) of, the alkylene incorporated into the
copolymer. The more alkylene comonomer used, the lower the
density; also, the larger the alkylene comonomer, the lower the
density. Preferably an amount of alkylene comonomer is used which
results in a density in the range of 0.88 to 0.94, most preferably
0.92 to 0.94~ especlally 0.92 to 0.93 g/cm3. Preferably the LLDPE
has an alkylene comonomer content in the range of 3 to 20 percent
by weight of the LLDPE. An ethylene/-octene copolymer having a
density of around 0.925 g/cm3, an octene content in the range of
from 5 to 10 percent and M.F.R. of 50 ~ 20 g/10 min. is very
effective for the purposes of this invention.
In the blend, the weight ratio of PP/PE can range from
80/20 to 55/45, but is preferably in the range of 78/22 to 60/40,
most preferably ln the range of 75/25 to 65/35. An especially
preferred range is 72/28 to 68/32.
The method of melt-mixing is important due to generally
acknowledged immiscibility of the PP and PE. An intensive mixer-
extruder is required which causes, in the blender, on the one
hand, molten PE to be dispersed in the molten PP and the
dispersion maintained until the mixture, as an extrudate, is
expelled from the spinning die.
B
1296~9~
g
The following chart is provided as a means for
describing the results believed to be obtained for the
various ratio ranges of PP/PE, when using PE having an
M.F.R. in the range of 12 to 120 g/10 min., and a
crystalline PP, where the melt viscosity and melt
strength are such that reàsonably good melt-
compatibility and miscibility are achieved by use of
the high-intensity mixer-extruder:
Approx. Range of
Ratio of PE/PP General results one may obtain*
20/80 - 45/55 PE fibrils dispersed in PP
continuous matrix
45/55 - 55/45 co-continuous zones; lamellar
structure
20 55/45 ~ 90/10 PP fibrils dispersed in PE
continuous matrix
*Obviously the results in or around the ratios which
are overlapping at the ends of the middle range are
ambiguous in that some of results obtained from both
~ides of the overlap.
Polymer blends of PP and PE prepared in such a
mixer are found to be useful, strong, and can be
extruded into products where the immiscibility is not a
problem. As the so-formed extrudate of a mixture which
contains more PP than PE is spun and drawn into fibers,
the molten PE globules become extended into fibrils
within the polypropylene matrix. An important, novel 40 feature of the fibers is that the fibrils of PE are
diverse in their orientation in the PP fiber. A larger
fraction of PE particles is found close to the
periphery of the cross-section of the PP fibers, and
the remaining PE particIes are spread in the inner
portions of the PP fiber. The size of the PE particles
35,451C-F _g_
- l o 1296498
is smallest at the periphery of the fiber's cross-
section and a gradual increase in size is evidenced
toward the center of the fiber. The frequency of small
particles at the periphery is highest, and it decreases
toward the center where the PE particles are largest,
but spread apart more. The PE fibrils near the
periphery Oe the PP fiber's cross-section are diverse
in the direction in which they are oriented or splayea,
whereas close to the center of the PP fiber the
orientation is mostly coaxial with the fiber. For the
purpose of being concise, these fibers will be referred
to herein as blends consisting of PP as a continuous
phase, and containing omni-directionally splayed PE
fibrils as a dispersed phase.
Microscopic examination reveals that the PE
fibrils, when viewed in a cross-section of the bicon-
stituent PP fiber, are more heavily populated near the
outer ~urface than in the middle. The shape of each PE
fibril in the cross-section is dependent on whether one
is viewing a PE fibril sliced at right angles to the
axis of the PE fibril at that point or at a slant to
the axis of the PE fibril at that point. An oval or
elongate shaped section indicates a PE fibril cut at an
angle. An elongate shaped section indicates a PE
fibril which has skewed from axial alignment to a
transverse position.
.
The mixer for preparing the molten blend of
PP/PE is a dynamic high intensity mixer, especially one
which provides 3-dimensional mixing. Insufficient
mixing will cause non-homogeneous dispersion of PE in
PP resulting in fibers of inconsistent properties, and
tenacities lower than that of the corresponding PP
fibers alone. A 3-d1mensional mixer suitable for use
35,451C-F -10-
1296~9~3 `
in the present invention is disclosed in a publication
titled "Polypropylene--Fibers and Filament Yarn With
Higher Tenacity", presented at International Man-Made
Fibres Congress, September 25-27, 1985,
Dornbirn/Austria, by Dr. Ing. Klaus Schafer of Barmag,
Barmer Maschinen-Fab~ik, West Germany.
- The distribution of PE fibrils in a PP matrix
are studied by using the following method: The fibers
are prepared for transverse sectioning by being
attached to strips of adhesive tape and embedded in
epoxy resin. The epoxy blocks are trimmed and faced
with a glass knife on a Sorvall MT-6000 microtome. The
blocks are soaked in a mixture of 0.2 gm ruthenium
chloride dissolved in 10 ml of 5.25 percent by weight
aqueous sodium hypochlorite for 3 hours. This stains
the ends of the fibers with ruthenium to a depth of
about 30 micrometers. The blocks are rinsed well and
remounted on the microtome. Transverse sections of
fibers in epoxy are microtomed using a diamond knife,
floated onto a water trough, and collected onto copper
TEM grids. The grid~ are examined at 100 KV
accelerating voltage on a JEOL 100C transmission
electron microscope (TEM). Sections taken from the
first few micrometers, as well as approximately 20
micrometers from the end are examined in the TEM at
magnifications of 250X to 66,000X. The polyethylene
component in the samples are preferentially stained by
the ruthenium. Fiber sections microtomed near the end
of the epoxy block may be overstained, whereas sections
taken about 20 micrometers away from the end of the
fibers are more likely to be properly stained.
Scratches made by the microtome knife across the face
of the section may also contain artifacts of the stain,
35,451C-F -11_
` -12- 12964~
but a skilled operator can distinguish the artifacts
from the stained PE. The diameter of PE fibrils near
the center of the PP fiber have been found to be,
typically, on the order of about 350 to 500 angstrom
(35 to 50 nm), whereas the diameter of the more
populace fibrils near the periphery edge of the PP --
fiber have been found to be, typically, on the order of
about 100 to 200 angstrom-(10 to 20 nm). This is in
reference to those which appear under high
magnification to be of circular cross-section rather
than oval or elongate.
At less than 20 percent polyethylene in the
polypropylene one obtains better "hand" than with
polypropylene alone, but without obtaining a
significant increase in tenacity and without obtaining
a dimensionally stable fiber. By the term
"dimensionally stable" it is meant that upon storing a
measured fiber for several months and then remeasuring
the tenacity, one does not encounter a significant
change in the tenacity. A change in tenacity indicates
that stress relaxation has occurred and that fiber
shrinkage has taken place. In many applications, such
as in non-woven fabrics, such shrinkage is considered
undesirable.
By using 20 percent to 45 percent polyethylene
in the polypropylene one obtains increased tenacity as-
well as obtaining better "hand" than with polypropylenealone. By using between 25 percent to 35 percent,
especially 28 percent to 32 percent, of polyethylene in
the polypropylene one also obtains a substantially
dimensionally stable fiber. A substantially
dimensionally stable fiber is one which undergoes very
little, if any, change in tenacity during storage. A
35,451C-F -12-
1296498
-13-
ratio of polypropylene/polyethylene of 70/30 is
especially beneficial in obtaining a di~ensionally
~stable fiber. By using 50 percent to 90 percent
polyethylene in the blend, a reduction in tenacity may
be observed, but the "hand" is noticeably softer than
polypropylene alone.
A greater draw ratio gives a higher tenacity
than a lower draw ratio. Thus, for a given PP/PE
ratio, a draw ratio of, say 3.0 may yield a tenacity
greater than PP alone, but a draw ratio of, say 2.0 may
not give a greater tenacity than PP alone.
In order to establish a nominal base point for
making comparisons, several commercially available PP's
are spun into fine denier fibers and the results are
averaged. The average denier size is found to be 2.1,
the average elongation is found to be 208 percent and
the average tenacity at the break point is 2.26
g/denier.
Similarly, to establish a nominal base point,
several LLDPE samples are spun into fine denier fibers
and the results are averaged. The average denier size
is found to be 2.84, the average elongation is found to
be 141 percent, and the average tenacity at the brea~
~ point is 2.23 g/denier.
The following examples illustrate particular
embodiments, but the invention is not limited to these
particular embodiments.
EXAMPLE 1
A blend of 80 percent by weight of PP granules
(M.I., 230C/2.16 kg, about 25 g/10 min. and density of
35,451C-F -13-
1296498
-14-
0.910 g/cc) with 20 percent by weight of LLDPE (1-
octene of from 10 to 15 percent; M.I. of 50 g/10 min.;
density of 0.926 g/cm3) is mechanically mixed and fed
into an extruder maintained at about 245 to 250C where
S the polymers are melted. The molten polymers are
passed through a 3-~imensional dynamic mixer mounted at
the outlet of the extruder. The dynamic mixer is
designed, through a 'combination of shearing and mixing,
to simultaneously divide the melt stream into superfine
layers, and rearrange the layers tangentially,
radially, and axially, thereby effecting good mixing of
the immiscible PP and LLDPE.
The so-mixed melt is transported from the
dynamic mixer,'by a gear pump, through a spinnerent
having 20,500 openings. The formed filaments are
cooled by a side-stream of air, wound on a take-up
roller, stretched over a preheated heptet of Godet
rollers (90 to 140C), run through an air-heated
annealing oven (150 to 170C), followed by another
heptet of Godet rollers (100 to 140C), before crimping
and cutting of the continuous fibers into 38 mm staple
fibers. Appropriate spin-fini~hes are applied to aid
the operatio.n. The stretch ratio is 3.1X.
' Thè resulting fibers have about 20 cpi (crimps
per inch) (2.5 cm) and the titre is in the range of
2.0-2.5 dpf (denier.per filament). The mechanical
properties of the fibers, meas'ured 3 weeks after
production, are as follows (average of 15 randomly
sampled fibers): Titre of 2.14 dpf; tenacity (tensile
at break) of 4.73 g/denier; elongation (at break) of 52
percent. The "hand" (softness) was judged better than
that of similar PP fibers alone.
35,451C-F -14-
1296498
-15-
EXAMPLE 2
This example is like Example 1 above except
that 30 weight percent of the LLDPE and 70 weight
percent of the PP is used.
Results: Titre of 2.66 dpf; tenacity of 3.23
g/den~er; elongation of 61 percent. The hand was
- clearly better than PP alone.
EXAMPLE 3
This example is like Example 1 above except
that the LLDPE contains 1-butene instead of 1-octene.
It also has M.I. of 50 g/10 min., a density of 0.926 -
g/cm3, and comprises 20 percent by weight of the blend.
Results: Titre of 2.24 dpf; tenacity of 3.93
g/denier; elongation of 48 percent. The hand was
judged better than PP alone.
Table ~ below illustrates the change in
properties when measured about 120 days following the
initial measurements ~hown in Examples 1-3 above.
30 1
TABLE L~ -
DENIER TENACITY ELONGATION
Ratio First Second FirstSecond First Second
Example PP/PE Measure Measure ~leasure easure Measure ~leasure
401 80/20 2.~4 2.81 4.733.41 52 70
2 70/30 2.66 2.69 3.233.37 61 72
3 80/20 2.24 3.00 3.932.99 48 63
35,451C-F _15_
1296498
-16-
The fibers of Examples 1 and 2 were evaluated
again after the exposure to 60C for 42 days plus
balance to 14 months at room temp (25~C), and the
results were obtained as shown in Table IB.
TABLE IB
TENACITY ELONGATION
E ~PLEDENIER (~/denier) (%)
1 3.07 3.42 41.0
2 3.11 3.20 41.6
The 70/30 blend (Example 2) in the tables above
exhibited very little change in tenacity; this is an
25 indication that these particular biconstituent fibers
show unusual permanency of strength, affected very
little by stress relaxation during storage. The 70/30
blend is found to form a high strength non-woven
3 structure (about 2650 gm. force to break a 1 inch (2.5
cm) wide strip) when thermally bonded at about 1 48C
under 700 psi (4.8 MPa) pressure to form a 1 oz./yd2
35 (34 g/m2) fabric.
EXAMPLE 4
Each of the following LLDPE's is blended as in
Example 1 with the PP at ratios of PP/PE as indicated
below, and the blends are all successfully spun as
fibers at two stretch ratios of about 2.0 and about
2.7,
:
35,451C-F -16-
129649?~
LLDPE Ratio of PP/PE
50 MFR, 0.926 density 25/75, 45/55, 65/35, 85/15
(1-octene)
105 MFR, 0.930 density 25/75, 45/55, 65/35
(1-octene)
26 MFR, 0.940 density 25/75, 45/55, 65/35, 85/15
(1-octene) - - -
50 MFR, 0.926 density 25/75, 45/55, 65/35
(1-butene)
EXAMPLE 5
In this set of data, the following described
blends are used, wherein the PP used in each is a
highly crystalline PP having a M.F.R. of 25 g/10
minutes a~ measured by ASTM D-1238 (230C, 2.16 Kg) and
the M.F.R. of the PE's are measured by ASTM D-1238
(190C, 2.16 Kg). All of the PE's are LLDPE's
identified as:
PE-A - LLDPE (1-octene comonomer), 50 M.F.R.,
0.926 density
PE-B - LLDPE (1-octene comonomer), 105 M.F.R.,
0.930 density
PE-C - LLDPE (1-octene comonomer), 26 M.F.R.,
0.940 density
PE-D - LLDPE (1-butene comonomer), 50 M.F.R.,
0.926 density
Blends made of the above described polymers are
made into fibers in the manner described hereinbefore,
the results of which are shown below in Table II.
35,451C-F -17-
~29649
--18--
TABLE I I
Run PE Wt. Ratio Stretch Titer Tenacity 3
No. Used PE/PP Ratio (denier) g/denier Elonq.
-
1 A25/75 2.0 4.15 1.87191
2 A25/75 2.7 2.88 2.6199
3 A45/55 2.0 4.15 1.67217
4 A45/55 2.85 3.27 2.17140
A65/3S 2.0 4.79 1.13298
l 5 6 A65/35 2.7 3.53 1.56208
7 A85/15 2.0 4.27 1.00307
8 A85/15 2.7 3.52 1.21216
9 A85/15 3.0 3.06 1.63150
B25/75 2.0 4.48 1.88243
11 B25/75 3.1 2.88 2.8576
25 12 B45/55 2.0 4.23 1.47225
13 B45/55 3.1 2.85 2.18100
14 B-65/35 2.0 4.17 1.07261
3 15 B65/35 3.1 2.65 1.74113
16 D25/75 2.0 3.87 1.96199
17 D25/75 2.7 2.91 2.8784
35 18 D25/75 3.i 2.51 3.6141
19 D45/55 !2.0 4.15 1.62241
D45/55 2.7 3.07 2.06126
,
,
35,451C-F -18-
12~6~
l g
TABLE II (Continued)
Run PE Wt. Ratio Stretch Titer Tenacity
No,Used PE/PPRatio(denier) g/denier Elong.
21 D 65/352.0 4.39 1.01 291
22 D 65/352.7 3.08 1.50 145
0 23 C 25/752.0 3.95 2.11 219
24 C 25/753.1 2.66 3.17 80
C 25/753.S 2.36 3.06 91
26 C 25/752.3 2.64 2.73 81
27 C 25/752.3 2.11 2.46 144
28 C 45/552.0 4.01 1.90 266
20 29 C 45/55 3.1 2.72 3.43 76
C 45/55 3.5 2.05 3.64 50
31 C 45/55 2.7 2.a8 3.08 80
25 32 C 65/35 2.0 4.12 1.54 321
33 C 65/35 2.7 3.05 2.19 169
34 C 85/15 2.0 3.94 1.28 351
3 35 C 85/15 2.7 2.84 1.83 194
36 C 85/15 3.1 2.79 2.01 187
Fig. 1 illustrates some of the data for PE-A.
: 4 . Fig. 2 illustrates some of th~e data for PE-B.
Fig. 3 illustrates ~ome of the data far PE-C.
Fig. 4 illustrates some of the data for PE-D.
:: .
Thermal bondability of biconstituent fibers are
demonstrated using a PE/PP blend of 30/70 wherein PE-A
35,451C-F -19-
~;~9649~3
--20--
is employed. After being stored for 150 days after
spinning, thermal bonding is tested by preparing 10
samples oE 1 inch (2.5 cm) wide slivers using a
rotaring device, such as is commonly used in the
5 industry, aiming at 1 oz. per yd2 (34 g/m2) web weight.
Results of the 10 measurements are normalized to 1 oz.
per yd2.(34 g~m2). The pressure between the calanders
10 during the thermal bonding is maintained constant at
700 psig (4.8 MPa) in preparing fabrics. Listed below
are the bonding temperature and corresponding tensile
force, in grams, required to break the fabric.
Bondink TemP~ C Force to
141 1260
144 1250
25 147 2600
149 2750
For comparison with the above, the typical
break force usually obtained for PP based fabrics is
2500~150 grams and the typical range usually obtained
for LLDPE is 1300-1500 grams.
It is noticed that the "drape" and softness of
fabrics made using the PE/PP biconstituent fibers in
spun-bonding is superior to that of PP fibers alone.
In similar manner, fibers are prepared using a
melt temperature in the range of 180 to 260C,
preferably 200 to 250C. Spinning rates of 20 to 150
m/min. ars- preferred. Stretch ratios in the range of
1.5-5X, preferably 2.0-3.0X are preferred. At
35,451C-F -20-
~29649'~
-21-
excessive Godet rolls temperatures, sticking of the
fibers to the rolls may take place. A proper choice of
a spinfinish would tend to aleviate or minimize this,
within a reasonable te~perature range.
Practitioners of the art routinely ~easure the
"hand" (softness) by merely feeling and squeezing a wad
or mat of the fibers being co~mpared.
The diameter of the PE fibrils which are
contained in the fibers are all of sub-micrometer size
and most of them have a diameter of less than about
0.05 micrometers.
Whereas the fibers may be of any denier size,
the preferred denier size is less than 30 and the most
preferred denier size is in the fine denier range of
0.5 to 15, especially in the range of 1 to 5.
The fibers of this invention are useful in a
variety of applications, such as non-wovens, wovens,
yarns, ropes, continuous fibers, and fabrics such as
carpets, upholstery, wearing apparel, tents, and
industrial applications such as filters and me~branes.
The blends over the range of PP/PE ratios of
20/80 to 90/10 exhibit surprisingly good strength
during extrusion and are not subject to the breaking
one normally obtains from blends of incompatible
polymers.
35,451C-F -21-
