U.S. patent application number 09/765679 was filed with the patent office on 2001-09-06 for alloys of immiscible polymers.
Invention is credited to DeLucia, Mary Lucille, Hudson, Robert Leslie, Marmon, Samuel Edward, Ofosu, Simon Kwame.
Application Number | 20010019929 09/765679 |
Document ID | / |
Family ID | 25074201 |
Filed Date | 2001-09-06 |
United States Patent
Application |
20010019929 |
Kind Code |
A1 |
DeLucia, Mary Lucille ; et
al. |
September 6, 2001 |
Alloys of immiscible polymers
Abstract
An extrudable composition is provided which is made from at
least two thermoplastic polymers in a biconstituent construction.
One of the thermoplastic polymers is present as a dominant
continuous phase and the other one or more polymers are present as
a non-continuous phase or phases in an amount of 1.5 weight percent
or less. No compatibilizer is necessary. The polymer of the
non-continuous phase or phases has a polymer melt temperature
higher than 30.degree. C. below the polymer melt temperature of the
continuous phase. The polymer of the dominant phase may be, for
example, polypropylene and the non-continuous phase may be, for
example, polyamide. The extrudable composition may be used to
produce fibers which are generally between about 5 and 50 microns
in diameter. The fibers may be made into nonwoven fabrics.
Inventors: |
DeLucia, Mary Lucille;
(Roswell, GA) ; Hudson, Robert Leslie; (Las Vegas,
NV) ; Marmon, Samuel Edward; (Melbourne, FL) ;
Ofosu, Simon Kwame; (Lilburn, GA) |
Correspondence
Address: |
William W. Letson
Kimberly-Clark Worldwide, Inc.
401 North Lake Street
Neenah
WI
54957-0349
US
|
Family ID: |
25074201 |
Appl. No.: |
09/765679 |
Filed: |
January 19, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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09765679 |
Jan 19, 2001 |
|
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08769820 |
Dec 19, 1996 |
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Current U.S.
Class: |
442/327 ;
428/400; 428/401 |
Current CPC
Class: |
Y10T 442/60 20150401;
Y10T 428/298 20150115; D04H 1/43828 20200501; D04H 1/4383 20200501;
D04H 1/56 20130101; D04H 1/54 20130101; D04H 1/4334 20130101; Y10T
428/2978 20150115; D04H 1/4291 20130101; D04H 1/43825 20200501;
D04H 1/43832 20200501; D01F 6/46 20130101 |
Class at
Publication: |
442/327 ;
428/400; 428/401 |
International
Class: |
D04H 001/00; D04H
003/00; D04H 005/00; D04H 013/00; D02G 003/00 |
Claims
What is claimed is:
1. A nonwoven fabric which is made from fibers extruded from a
composition free of a compatibilizer and comprising at least two
thermoplastic polymers, wherein one of said thermoplastic polymers
is a polyolefin as a dominant continuous phase present in an amount
between 98.5 to 99.9 weight percent, and the other one or more
polymers are polyamides as a non-continuous phase or phases present
in an amount between 0.1 to 1.5 weight percent, and wherein the
polymer of said non-continuous phase or phases has a polymer melt
temperature higher than 30.degree. C. below the polymer melt
temperature of said continuous phase.
2. The fabric of claim 1 which is dyed.
3. The nonwoven fabric of claim 1 which is made from fibers wherein
said continuous phase is at least one polyolefin.
4. The nonwoven fabric of claim 1 which is made from fibers wherein
the non-continuous phase or phases are substantially evenly
distributed throughout said fiber.
5. The nonwoven fabric of claim 1 which is made from fibers wherein
the fibers have diameters of approximately 1 to 50 microns.
6. The nonwoven fabric of claim 1 which is made from fibers which
have been thermally bonded at a temperature between about 93 and
about 163.degree. C.
7. The nonwoven fabric of claim 1 which has a percent elongation of
at least 50% greater than that of nonwoven fabric made from
polypropylene fibers which have been bonded at a similar
temperature.
8. The nonwoven fabric of claim 1 which is made by the process
selected from the group consisting of spunbonding and
meltblowing.
9. The nonwoven fabric of claim 3 which is made from fibers wherein
the polyamides are selected from the group consisting of polyamide
6, polyamide 11, polyamide 12, and copolymers, and blends
thereof.
10. The nonwoven fabric of claim 3 which is made from fibers
wherein said polyolefin is selected from the group consisting of
polyethylene, polypropylene, polybutylenes and copolymers, and
blends thereof, and is present in an amount between 98.5 to 99.9
weight percent, said polyamide is present in an amount between 0.1
to 1.5 weight percent.
11. A personal care product comprising the fabric of claim 1.
12. An infection control product comprising the fabric of claim
1.
13. A protective cover comprising the fabric of claim 1.
Description
[0001] This application is a continuation of application Ser. No.
08/769,820 entitled "ALLOYS OF IMMISCIBLE POLYMERS" and filed in
the U.S. Patent and Trademark Office on Dec. 19, 1996. The entirety
of this application is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] Thermoplastic resins have been extruded to form fibers and
webs for a number of years. The common thermoplastics for this
application are polyolefins, particularly polypropylene, and
polyesters. Each material has its characteristic advantages and
disadvantages vis a vis the properties desired in the final product
to be made from such fibers.
[0003] Blends and alloys of two or more polymers are areas of some
interest because of a desire to combine the desirable properties of
such polymers. Dr. Leszek A. Utracki, in his work "Polymer Alloys
and Blends: Thermodynamics and Rheology" (ISBN 0-19-520796-3,
Oxford University Press, New York, N.Y., 1989) discusses the
history of development in this area at some length.
[0004] Examples of alloy or biconstituent fibers may be found in
U.S. Pat. No. 5,108,827 to Gessner which teaches blends wherein the
polymer of the noncontinuous phase (or phases) has a melt
temperature at least 30.degree. C. below the melt temperature of
the continuous phase. Other examples may be found in U.S. Pat. No.
5,534,335 to Everhart et al., commonly assigned, which teaches the
use of a compatibilizer to make polymers miscible.
[0005] There remains a need for an extrudable composition which may
be used for fabric production from fibers where the composition is
an alloy of polymers wherein the polymer melt temperature of the
non-continuous phase is higher than 30.degree. C. below that of the
continuous phase (and may even be higher), which does not use a
compatibilizer and in which desired characteristics are
enhanced.
SUMMARY OF THE INVENTION
[0006] An extrudable composition is provided which is made from at
least two thermoplastic polymers. A compatibilizer is not
necessary. One of the thermoplastic polymers is present as a
dominant continuous phase and the other one or more polymers are
present as a non-continuous phase or phases. The polymer of the
non-continuous phase or phases is present in an amount of 1.5
weight percent or less and has a polymer melt temperature less than
30.degree. C. below the polymer melt temperature of the continuous
phase. The polymer of the non-continuous phase or phases may even
have a polymer melt temperature greater than the polymer melt
temperature of the continuous phase. The extrudable composition may
be extruded into biconstituent fibers which may further be
processed into nonwoven fabrics.
BRIEF DESCRIPTION OF THE FIGURES
[0007] FIG. 1 is a schematic drawing of a process for extruding the
composition of this invention including a main extruder, a side
extruder and a mixer.
[0008] FIG. 2 is a cut-away drawing of a mixer suitable for use in
mixing the extrudable composition of this invention.
[0009] FIG. 3 is a cross-sectional view of a mixer suitable for use
in mixing the extrudable composition of this invention.
DEFINITIONS
[0010] As used herein, the term "nonwoven fabric or web" means a
web having a structure of individual fibers or threads which are
interlaid, but not in an identifiable manner as in a knitted
fabric. Nonwoven fabrics or webs have been formed from many
processes such as for example, meltblowing processes, spunbonding
processes, and bonded carded web processes. The basis weight of
nonwoven fabrics is usually expressed in ounces of material per
square yard (osy) or grams per square meter (gsm) and the fiber
diameters useful are usually expressed in microns. (Note that to
convert from osy to gsm, multiply osy by 33.91).
[0011] As used herein, the term "microfibers" means small diameter
fibers having an average diameter not greater than about 75
microns, for example, having an average diameter of from about 0.5
microns to about 50 microns, or more particularly, microfibers may
have an average diameter of from about 2 microns to about 40
microns. Another frequently used expression of fiber diameter is
denier, which is defined as grams per 9000 meters of a fiber and
may be calculated as fiber diameter in microns squared, multiplied
by the density in grams/cc, multiplied by 0.00707. A lower denier
indicates a finer fiber and a higher denier indicates a thicker or
heavier fiber. For example, the diameter of a polypropylene fiber
given as 15 microns may be converted to denier by squaring,
multiplying the result by 0.89 g/cc and multiplying by 0.00707.
Thus, a 15 micron polypropylene fiber has a denier of about 1.42
(15.sup.2.times.0.89.times.0.00707=1.415). Outside the United
States the unit of measurement is more commonly the "tex", which is
defined as the grams per kilometer of fiber. Tex may be calculated
as denier/9.
[0012] As used herein, the term "spunbonded fibers" refers to small
diameter fibers which are formed by extruding molten thermoplastic
material as filaments from a plurality of fine, usually circular
capillaries of a spinneret with the diameter of the extruded
filaments then being rapidly reduced as by, for example, in U.S.
Pat. No. 4,340,563 to Appel et al., and U.S. Pat. No. 3,692,618 to
Dorschner et al., U.S. Pat. No. 3,802,817 to Matsuki et al., U.S.
Pat. Nos. 3,338,992 and 3,341,394 to Kinney, U.S. Pat. No.
3,502,763 to Hartman, and U.S. Pat. No. 3,542,615 to Dobo et al.
Spunbond fibers are generally not tacky when they are deposited
onto a collecting surface. Spunbond fibers are generally continuous
and have average diameters (from a sample of at least 10) larger
than 7 microns, more particularly, between about 10 and 20 microns.
The fibers may also have shapes such as those described in U.S.
Pat. No. 5,277,976 to Hogle et al., U.S. Pat. No. 5,466,410 to
Hills and 5,069,970 and U.S. Pat. No. 5,057,368 to Largman et al.,
which describe fibers with unconventional shapes.
[0013] As used herein, the term "meltblown fibers" means fibers
formed by extruding a molten thermoplastic material through a
plurality of fine, usually circular, die capillaries as molten
threads or filaments into converging high velocity, usually hot,
gas (e.g. air) streams which attenuate the filaments of molten
thermoplastic material to reduce their diameter, which may be to
microfiber diameter. Thereafter, the meltblown fibers are carried
by the high velocity gas stream and are deposited on a collecting
surface to form a web of randomly disbursed meltblown fibers. Such
a process is disclosed, for example, in U.S. Pat. No. 3,849,241 to
Butin et al. Meltblown fibers are microfibers which may be
continuous or discontinuous, are generally smaller than 10 microns
in average diameter, and are generally tacky when deposited onto a
collecting surface.
[0014] As used herein, "filament arrays" means substantially
parallel rows of filaments which may be such as those disclosed in
U.S. Pat. Nos. 5,385,775 and 5,366,793.
[0015] As used herein, "multilayer laminate" means a laminate
wherein some of the layers are spunbond and some meltblown such as
a spunbond/meltblown/spunbond (SMS) laminate and others as
disclosed in U.S. Pat. No. 4,041,203 to Brock et al., U.S. Pat. No.
5,169,706 to Collier, et al, U.S. Pat. No. 5,145,727 to Potts et
al., U.S. Pat. No. 5,178,931 to Perkins et al. and U.S. Pat. No.
5,188,885 to Timmons et al. Such a laminate may be made by
sequentially depositing onto a moving forming belt first a spunbond
fabric layer, then a meltblown fabric layer and last another
spunbond layer and then bonding the laminate in a manner described
below. Alternatively, the fabric layers may be made individually,
collected in rolls, and combined in a separate bonding step. Such
fabrics usually have a basis weight of from about 0.1 to 12 osy (6
to 400 gsm), or more particularly from about 0.75 to about 3 osy.
Multilayer laminates may also have various numbers of meltblown
layers or multiple spunbond layers in many different configurations
and may include other materials like films (F) or coform materials,
e.g. SMMS, SM, SFS, etc.
[0016] By the term "similar web" what is meant is a web which uses
essentially the same process conditions and polymers as the
inventive web except those noted. According to Webster's New
Collegiate Dictionary (1980), "similar" means 1) having
characteristics in common; strictly comparable, 2) alike in
substance or essentials; corresponding. Using this commonly
accepted meaning of the word similar, this term means that all
other conditions are essentially the same except for the conditions
mentioned. It should be noted that not all conditions will be
exactly identical between the different polymers since the changes
in the composition itself cause process changes, in for example,
the pressure drop or temperatures needed.
[0017] As used herein, the term "coform" means a process in which
at least one meltblown diehead is arranged near a chute through
which other materials are added to the web while it is formed. Such
other materials may be pulp, superabsorbent particles, cellulose or
staple fibers, for example. Coform processes are shown in commonly
assigned U.S. Pat. No. 4,818,464 to Lau and U.S. Pat. No. 4,100,324
to Anderson et al. Webs produced by the coform process are
generally referred to as coform materials.
[0018] As used herein, the term "polymer" generally includes but is
not limited to, homopolymers, copolymers, such as for example,
block, graft, random and alternating copolymers, terpolymers, etc.
and blends and modifications thereof. Furthermore, unless otherwise
specifically limited, the term "polymer" shall include all possible
geometrical configurations of the molecule. These configurations
include, but are not limited to isotactic, syndiotactic and random
symmetries.
[0019] As used herein, the term "monocomponent" fiber refers to a
fiber formed from one or more extruders using only one polymer.
This is not meant to exclude fibers formed from one polymer to
which small amounts of additives have been added for coloration,
anti-static properties, lubrication, hydrophilicity, etc. These
additives, e.g. titanium dioxide for coloration, are generally
present in an amount less than 5 weight percent and more typically
about 2 weight percent.
[0020] As used herein, the term "conjugate fibers" refers to fibers
which have been formed from at least two polymers extruded from
separate extruders but spun together to form one fiber. Conjugate
fibers are also sometimes referred to as multicomponent or
bicomponent fibers. The polymers are usually different from each
other though conjugate fibers may be monocomponent fibers. The
polymers are arranged in substantially constantly positioned
distinct zones across the cross-section of the conjugate fibers and
extend continuously along the length of the conjugate fibers. The
configuration of such a conjugate fiber may be, for example, a
sheath/core arrangement wherein one polymer is surrounded by
another or may be a side by side arrangement, a pie arrangement or
an "islands-in-the-sea" arrangement. Conjugate fibers are taught in
U.S. Pat. No. 5,108,820 to Kaneko et al., U.S. Pat. No. 4,795,668
to Krueger et al. and U.S. Pat. No. 5,336,552 to Strack et al.
Conjugate fibers are also taught in U.S. Pat. No. 5,382,400 to Pike
et al. and may be used to produce crimp in the fibers by using the
differential rates of expansion and contraction of the two (or
more) polymers. Crimped fibers may also be produced by mechanical
means and by the process of German Patent DT 25 13 251 A1. For two
component fibers, the polymers may be present in ratios of 75/25,
50/50, 25/75 or any other desired ratios. The fibers may also have
shapes such as those described in U.S. Pat. No. 5,277,976 to Hogle
et al., U.S. Pat. No. 5,466,410 to Hills and U.S. Pat. Nos.
5,069,970 and 5,057,368 to Largman et al., which describe fibers
with unconventional shapes.
[0021] As used herein, the term "biconstituent fibers" refers to
fibers which have been formed from at least two polymers extruded
from the same extruder as a blend. The term "blend" is defined
below. Biconstituent fibers do not have the various polymer
components arranged in relatively constantly positioned distinct
zones across the cross-sectional area of the fiber and the various
polymers are usually not continuous along the entire length of the
fiber, instead usually forming fibrils or protofibrils which start
and end at random. Biconstituent fibers are sometimes also referred
to as multiconstituent fibers. Fibers of this general type are
discussed in, for example, U.S. Pat. Nos. 5,108,827 and 5,294,482
to Gessner. Bicomponent and biconstituent fibers are also discussed
in the textbook Polymer Blends and Composites by John A. Manson and
Leslie H. Sperling, copyright 1976 by Plenum Press, a division of
Plenum Publishing Corporation of New York, IBSN 0-306-30831-2, at
pages 273 through 277.
[0022] As used herein, the term "blend" means a combination of two
or more polymers while the term "alloy" means a sub-class of blends
wherein the components are immiscible but have been compatibilized.
"Miscibility" and "immiscibility" are defined as blends having
negative and positive values, respectively, for the free energy of
mixing. Further, "compatibilization" is defined as the process of
modifying the interfacial properties of an immiscible polymer blend
in order to make an alloy.
[0023] As used herein, the term "garment" means any type of
non-medically oriented apparel which may be worn. This includes
industrial work wear and coveralls, undergarments, pants, shirts,
jackets, gloves, socks, and the like.
[0024] As used herein, the term "infection control product" means
medically oriented items such as surgical gowns and drapes, face
masks, head coverings like bouffant caps, surgical caps and hoods,
footwear like shoe coverings, boot covers and slippers, wound
dressings, bandages, sterilization wraps, wipers, garments like lab
coats, coveralls, aprons and jackets, patient bedding, stretcher
and bassinet sheets, and the like.
[0025] As used herein, the term "personal care product" means
diapers, training pants, absorbent underpants, adult incontinence
products, and feminine hygiene products.
[0026] As used herein, the term "protective cover" means a cover
for vehicles such as cars, trucks, boats, airplanes, motorcycles,
bicycles, golf carts, etc., covers for equipment often left
outdoors like grills, yard and garden equipment (mowers,
roto-tillers, etc.) and lawn furniture, as well as floor coverings,
table cloths and picnic area covers.
[0027] As used herein, the term "outdoor fabric" means a fabric
which is primarily, though not exclusively, used outdoors. Outdoor
fabric includes fabric used in protective covers, camper/trailer
fabric, tarpaulins, awnings, canopies, tents, agricultural fabrics
and outdoor apparel such as head coverings, industrial work wear
and coveralls, pants, shirts, jackets, gloves, socks, shoe
coverings, and the like.
Test Methods
[0028] Cup Crush:
[0029] The softness of a nonwoven fabric may be measured according
to the "cup crush" test. The cup crush test evaluates fabric
stiffness by measuring the peak load (also called the "cup crush
load" or just "cup crush") required for a 4.5 cm diameter
hemispherically shaped foot to crush a 23 cm by 23 cm piece of
fabric shaped into an approximately 6.5 cm diameter by 6.5 cm tall
inverted cup while the cup shaped fabric is surrounded by an
approximately 6.5 cm diameter cylinder to maintain a uniform
deformation of the cup shaped fabric. An average of 10 readings
should be used. The foot and the cup are aligned to avoid contact
between the cup walls and the foot which could affect the readings.
The peak load is measured while the foot is descending at a rate of
about 0.25 inches per second (380 mm per minute) and is measured in
grams. The cup crush test also yields a value for the total energy
required to crush a sample (the "cup crush energy") which is the
energy from the start of the test to the peak load point, i.e. the
area under the curve formed by the load in grams on one axis and
the distance the foot travels in millimeters on the other. Cup
crush energy is therefore reported in gm-mm. Lower cup crush values
indicate a softer laminate. A suitable device for measuring cup
crush is a model FTD-G-500 load cell (500 gram range) available
from the Schaevitz Company, Pennsauken, N.J.
[0030] Melt Flow Rate:
[0031] The melt flow rate (MFR) is a measure of the viscosity of a
polymer. The MFR is expressed as the weight of material which flows
from a capillary of known dimensions under a specified load or
shear rate for a measured period of time and is measured in
grams/10 minutes at a set temperature and load according to, for
example, ASTM test 1238-90b.
[0032] Grab Tensile Test:
[0033] The grab tensile test is a measure of breaking strength and
elongation or strain of a fabric when subjected to unidirectional
stress. This test is known in the art and conforms to the
specifications of Method 5100 of the Federal Test Methods Standard
191 A. The results are expressed in pounds to break and percent
stretch before breakage. Higher numbers indicate a stronger, more
stretchable fabric. The term "load" means the maximum load or
force, expressed in units of weight, required to break or rupture
the specimen in a tensile test. The term "strain" or "total energy"
means the total energy under a load versus elongation curve as
expressed in weight-length units. The term "elongation" means the
increase in length of a specimen during a tensile test. Values for
grab tensile strength and grab elongation are obtained using a
specified width of fabric, usually 4 inches (102 mm), clamp width
and a constant rate of extension. The sample is wider than the
clamp to give results representative of effective strength of
fibers in the clamped width combined with additional strength
contributed by adjacent fibers in the fabric. The specimen is
clamped in, for example, an Instron Model TM, available from the
Instron Corporation, 2500 Washington St., Canton, Mass. 02021, or a
Thwing-Albert Model INTELLECT II available from the Thwing-Albert
Instrument Co., 10960 Dutton Rd., Phila., Pa. 19154, which have 3
inch (76 mm) long parallel clamps. This closely simulates fabric
stress conditions in actual use.
[0034] Trap Tear Test:
[0035] The trapezoid or "trap" tear test is a tension test
applicable to both woven and nonwoven fabrics. The entire width of
the specimen is gripped between clamps, thus the test primarily
measures the bonding or interlocking and strength of individual
fibers directly in the tensile load, rather than the strength of
the composite structure of the fabric as a whole. The procedure is
useful in estimating the relative ease of tearing of a fabric. It
is particularly useful in the determination of any appreciable
difference in strength between the machine and cross direction of
the fabric. In conducting the trap tear test, an outline of a
trapezoid is drawn on a 3 by 6 inch (75 by 152 mm) specimen with
the longer dimension in the direction being tested, and the
specimen is cut in the shape of the trapezoid. The trapezoid has a
4 inch (102 mm) side and a 1 inch (25 mm) side which are parallel
and which are separated by 3 inches (76 mm). A small preliminary
cut of 5/8 inches (15 mm) is made in the middle of the shorter of
the parallel sides. The specimen is clamped in, for example, an
Instron Model TM, available from the Instron Corporation, 2500
Washington St., Canton, Mass. 02021, or a Thwing-Albert Model
INTELLECT II available from the Thwing-Albert Instrument Co., 10960
Dutton Rd., Phila., Pa. 19154, which have 3 inch (76 mm) long
parallel clamps. The specimen is clamped along the non-parallel
sides of the trapezoid so that the fabric on the longer side is
loose and the fabric along the shorter side taut, and with the cut
halfway between the clamps. A continuous load is applied on the
specimen such that the tear propagates across the specimen width.
It should be noted that the longer direction is the direction being
tested even though the tear is perpendicular to the length of the
specimen. The force required to completely tear the specimen is
recorded in pounds with higher numbers indicating a greater
resistance to tearing. The test method used conforms to ASTM
Standard test D1117-14 except that the tearing load is calculated
as the average of the first and highest peaks recorded rather than
the lowest and highest peaks. Five specimens for each sample should
be tested.
DETAILED DESCRIPTION OF THE INVENTION
[0036] The extrudable composition of this invention is an alloy of
at least two immiscible polymers. The alloy of polymers used to
make the composition of this invention is such that the polymer
melt temperature of the non-continuous phase is in the range of
from higher than 30.degree. C. below to any value greater than that
of the continuous phase. The extrudable composition may be extruded
to form fibers which are biconstituent and the fibers may be
further processed into nonwoven fabrics.
[0037] The alloy should be essentially free of any compatibilzer.
Compatibilizers include compounds such as zinc ionomers of
ethylene-methacrylic acid or modified polypropylene with maleic
anhydride and others described in U.S. Pat. No. 5,534,335. It is
believed, though applicants do not wish to be bound by any
particular theory, that a compatibilizer has polar and non-polar
parts and the polar part reacts with or is attracted to a polar
part of one of the polymers to be alloyed. The non-polar part of
the compatibilizer remains available for reaction with or
attraction to the dominant phase polymer and this results in more
intimate mixing. The reduction in the interfacial energy caused by
the compatibilizer allows the size of the discontinuous phase to be
reduced within the continuous phase.
[0038] Another class of compatibilizer is poly(olefin-methacrylic
acid) where the acid groups are partially or fully neutralized by
metal ions.
[0039] Commercial examples of compatibilizers which should be
avoided include Exxelor.RTM. polymer modifier PO1015 or VA1803
available from Exxon Chemical Company, and the family of
Surlyn.RTM. ionomers available from E.I. Dupont de Nemours Inc.,
particularly Surlyn.RTM. 9020 ionomer.
[0040] Exxelor.RTM. polymer modifier P01015 is a proprietary
chemical which has a melt flow rate of 120 g/10 min., a density of
0.91 g/cm.sup.3 and has 0.4 weight percent of grafted maleic
acid/anhydride. Exxelor.RTM. polymer modifier VA1803 has a melt
flow rate of 3 g/10 min., a density of 0.86 g/cm.sup.3 and has 0.7
weight percent of maleic acid/anhydride. Surlyn.RTM. 9020 ionomer
has a melt flow rate of 1.0 g/10 min. and a density of 0.96
g/cm.sup.3. The Surlyn.RTM. ionomer resins are based on ethylene
and methacrylic acid di- and ter- polyers which have been partially
reacted with metallic salts (generally zinc or sodium) to form
ionic crosslinks between the acid groups within a chain or between
neighboring chains.
[0041] Suitable polymer mixtures which may be used in the practice
of this invention include, for example, polyolefins and polyamides,
and polyolefins and polyesters.
[0042] The polyolefin which may be used in the practice of this
invention may be amorphous or crystalline, atactic, isotactic or
sydiotactic. Suitable polyolefins include polyethylene,
polypropylene, polybutylenes and copolymers, blends and mixtures
thereof and are available commercially from a number of suppliers.
The particular properties of polyolefins used in fiber extrusion
and nonwoven fabric production processes such as the spunbonding
and meltblowing processes are known to those skilled in the
art.
[0043] A polyamide which may be used in the practice of this
invention may be any polyamide known to those skilled in the art
including copolymers and mixtures thereof. Examples of polyamides
and their methods of synthesis may be found in "Polymer Resins" by
Don E. Floyd (Library of Congress Catalog number 66-20811, Reinhold
Publishing, NY, 1966). Particularly commercially useful polyamides
are nylon-6, nylon 6,6, nylon-11 and nylon-12. These polyamides are
available from a number of sources such as Emser Industries of
Sumter, S.C. (Grilon.RTM. & Grilamide nylons), Atochem Inc.,
Polymers Division, of Glen Rock, N.J. (Rilsan.RTM. nylons), Nyltech
Industries of Manchester, N.H., among others.
[0044] Modifying the interfacial properties of the immiscible
polymer blend to make an alloy is accomplished through the use of
high shear mixing through the use of for example, a single screw
extruder. Single screw extruders are known in the art as useful in
mixing and have been developed for a number of purposes in polymer
processing such as improvement in physical properties, appearance,
processibility and cost reduction. A detailed description of mixing
and single screw extruders is given in Mixing and Compounding of
Polymers: Theory and Practice, ISBN 1569901562, edited by 1.
Manas-Zloczower and Z. Tadmor, Hanser Publishers, 1994, in chapter
19 (Single Screw Extruders), by Hensen, Imping and Spanknebel.
[0045] Another method of mixing is by using a commercially
available Barmag three dimensional dynamic mixer (3DD). This mixer
is available from Barmag Aktiengelsellschaft, Leverkuser Strase 65,
42897 Remscheid, Germany, or in the U.S. from American Barmag
Corporation, 1101 Westinghouse Boulevard, Charlotte, N.C.
28241.
[0046] FIG. 1 shows a system suitable for use in the practice of
this invention. A mixture of polymers in, for example, pellet form,
is introduced to the feed hopper 1. The mixture proceeds into the
main extruder 2 where it is forced through the extruder 2, passing
through five equally sized heating zones. The melted mixture from
the extruder 2 then passes into the 3DD mixer 3 and is ultimately
extruded at the exit 11. Auxiliary mixing can be provided by a side
extruder 9 which receives feed from hopper 8. After exiting the
side extruder 9, the melted mixture is pumped by gear pump 10 into
the main extruder 2 discharge for mixing in the 3DD mixer 3.
Polymers may also be mixed by placing them in separate feed tanks
4, 5, pumping them together through metering pumps 6, 7 and then
into main extruder 2 discharge for mixing in the 3DD mixer 3.
[0047] Yet another method of mixing is by using a cavity transfer
mixer (CTM) by Rapra Corp. which makes available its mixers in the
United States through Davis-Standard of #1 Extrusion Drive,
Pawcatuck, Conn. 06379 which may be used in place of a 3DD mixer. A
CTM mixer is shown in FIG. 2 which shows a central shaft 12 which
is surrounded by a housing 13, 14 divided in two parts for ease of
illustration. The housing 13, 14 is stationary and the shaft 12
rotates in actual use. The rotation of the shaft 12 causes polymer
to be forced into and out of the multitude of depressions 15 on the
shaft 12 and housing 13, 14, causing good mixing. While the
depressions 15 shown in FIG. 2 are circular, many other shapes are
possible. The 3DD mixer uses rectangular, slot-like depressions.
Rhomboid, triangular and any other shape which may be envisioned
may be used. It is also possible to use pins instead of depressions
and to place the pins or depressions at various angles.
[0048] FIG. 3 shows a cross-sectional view of a mixer. The shaft 16
and housing 17 have depressions 18. Polymer may enter at the inlets
19, 20 and move to the discharge 21.
[0049] Distributive and dispersive mixing are essential in any good
mixing or blending. Distributive mixing involves the homogenization
of the dispersed particles in the matrix material. Dispersive
mixing is a mechanism whereby large particles (dispersed phase) are
broken up into finer particles and are evenly distributed
throughout the matrix material. Important parameters for mixing are
constancy of temperature, pressure and above all viscosity. The
viscosity homogeneity gives information about distributive and
dispersive mixing.
[0050] The fibers which may be made from the extrudable composition
of this invention may be produced by the meltblowing or spunbonding
processes which are well known in the art. These processes
generally use an extruder to supply melted polymer to a spinneret
where the polymer is fiberized. The fibers are then drawn, usually
pneumatically, and deposited on a foraminous mat or belt to form
the nonwoven fabric. The fibers produced in the spunbond and
meltblown processes are generally in the range of from about 1 to
about 50 microns in diameter, depending on process conditions and
the desired end use for the fabrics to be produced from such
fibers.
[0051] The fibers may also have other polymers present in a
conjugate structure wherein the biconstituent blend of this
invention makes up one portion of the conjugate fiber, e.g. the
sheath or core, and another polymer or blend makes up the other
portion.
[0052] Fabric made from fibers of the extrudable composition of
this invention may be used in a single layer embodiment or as a
component of a multilayer laminate which may be formed by a number
of different laminating techniques including but not limited to
using adhesive, needle punching, thermal calendering and any other
method known in the art.
[0053] The following examples illustrate particular embodiments of
the invention.
EXAMPLE 1
[0054] The polymer alloys were generally produced by compounding
the ingredients in a cement mixer which should have given a
relatively poorly homogenized mixture. The polyolefin used was
Union Carbide's E5D47 polypropylene, a 38 g/10 min melt flow rate
polymer. The polyamide used was a polyamide 6 sold as Nyltech 2169
by Nyltech Industries.
[0055] The amounts in the initial blends were 2.2 weight percent
polyamide, 2.0 weight percent titanium dioxide pigment and the
balance polypropylene.
[0056] The alloy was melt spun through a standard 600 hole round
pack with a pin density of about 125 holes per inch (hpi), a length
to exit diameter (L/D) of 6 and a 0.6 mm exit diameter. The
extruder and spinpack temperatures were at about 440.degree. F.
(227.degree. C.) and 450.degree. F. (232.degree. C.) respectively
and throughput was typically 0.7 grams/hole/min (ghm). No mixer was
attached to the extruder discharge so the extruded polymer went
directly to the spinpack. The extruded fibers were thermally point
bonded by calendering using an Expanded Hansen Penning bond roll
with a 15% bond area to create a fabric with integrity at a
calender temperature of 283.degree. F. (139.degree. C.) as
indicated in Table 1.
[0057] Mechanical data for 2 ounce per square yard (osy) (68 gsm)
spunbond fabrics made from these alloy fibers is shown in the Table
in relation to a control fabric made from fibers of Union Carbide's
E5D47 polypropylene alone, and shows an improvement in properties
of interest.
1TABLE 1 Value Std. of Dev., Value of Std. Dev., Test Units Control
Control Example Example Ratio Basis Wt. Osy 2.05 0.03 2.09 0.07
0.98 Strip Tensile Peak load pounds 11.36 0.29 24.49 0.98 116
Strain percent 27.51 2.99 116.79 16.78 324 Energy in-lb. 8.08 1.66
80.86 14.77 901 Grab Tensile Peak load pounds 12.56 0.97 27.19 2.86
116 Strain percent 68.17 11.01 108.64 13.75 59 Energy in-lb. 16.91
4.42 53.30 12.48 215 Trap Tear 1.sup.st peak pounds 6.21 0.54 14.46
1.71 133 Cup crush Grams 285.02 13.17 262.21 36.28 8 load
[0058] The two fabrics were tested for dyeability by dipping each
for one minute in boiling water containing 1 weight percent of
Dupont Fiber Identification Stain #4. After the minute of boiling,
the fabrics were rinsed in clean water until no dye was visible in
the rinse water, and then dried on blotting paper. The stain is
available from Pylan Products Co. Inc., 1001 Stewart Ave., Garden
City, N.Y. 11530. It was found that the polypropylene fabric did
not accept any stain while the biconstituent fiber accepted the
stain, indicating that polyamide was available at the fiber surface
and not entirely embedded in the polypropylene matrix.
EXAMPLE 2
[0059] A single screw extruder was used having a CTM mixer attached
to its discharge. The screw had a length of 13.5 feet (411.5 cm)
and a diameter of 4.5 inches (11.4 cm) and was charged at a rate of
about 180 pounds/hour with a mixture of Exxon Chemical's
Escorene.RTM. 3445 polypropylene and Nyltech 2169 nylon 6. The
extruder discharge was fed into the CTM which operated at a
temperature of about 460.degree. F. (238.degree. C.). The mixture
was processed into fibers at a rate of 0.70 grams/holelminute (ghm)
with 0.6 mm holes and bonded using an expanded Hansen-Pennings
pattern (EHP). Up to 3 weight percent polyamide was processed using
this configuration.
EXAMPLE 3
[0060] A low shear co-rotation twin screw extruder was used. The
screw was charged with a mixture of Escorene.RTM. 3445
polypropylene and Nyltech 2169 nylon 6. The amounts in the initial
blend were 2 weight percent titanium dioxide pigment and the
balance polypropylene. Trials were conducted at 0 and 1% weight
percent nylon in the polypropylene fibers. The mixture was
processed into fibers through a spinplate having 400 holes and a
length to exit diameter (L/D) of 4 and bonded using an expanded
Hansen-Pennings pattern (EHP). The extruder and spinpack
temperatures were at about 450.degree. F. (232.degree. C.) and
throughput was typically 0.8 grams/hole/min (ghm). No mixer was
attached to the extruder discharge so the extruded polymer went
directly to the spinpack. The extruded fibers were thermally point
bonded by calendering using an Expanded Hansen Penning bond roll
with a 15% bond area to create a fabric with integrity at a
calender temperature of 290.degree. F. (143.degree. C.). Data was
collected for 5 repetitions conducted at each weight percent nylon
used. The results of the trials are summarized in Table 2
below.
2TABLE 2 Grab Tensile Results CD and MD Sample PEAKLOAD PERCENT ID
AVERAGE STD DEV lbs IMPROVEMENT GRAB TENSILE PEAK LOAD CD 100% PP
2137.61 488.02 4.71 -- 1% Nylon 3657.60 1300.30 8.06 71 GRAB
TENSILE PEAK LOAD MD 100% PP 4840.70 657.41 10.67 -- 1% Nylon
8724.89 2536.50 19.23 80
[0061] Although only a few exemplary embodiments of this invention
have been described in detail above, those skilled in the art will
readily appreciate that many modifications are possible in the
exemplary embodiments without materially departing from the novel
teachings and advantages of this invention. Accordingly, all such
modifications are intended to be included within the scope of this
invention as defined in the following claims. In the claims, means
plus function claims are intended to cover the structures described
herein as performing the recited function and not only structural
equivalents but also equivalent structures. Thus although a nail
and a screw may not be structural equivalents in that a nail
employs a cylindrical surface to secure wooden parts together,
whereas a screw employs a helical surface, in the environment of
fastening wooden parts, a nail and a screw may be equivalent
structures.
[0062] It should further be noted that any patents, applications or
publications referred to herein are incorporated by reference in
their entirety.
* * * * *