U.S. patent application number 09/001525 was filed with the patent office on 2001-10-25 for melt processable poly(ethylene oxide) fibers.
Invention is credited to SCHERTZ, DAVID MICHAEL, WANG, JAMES HONGXUE.
Application Number | 20010033852 09/001525 |
Document ID | / |
Family ID | 21696489 |
Filed Date | 2001-10-25 |
United States Patent
Application |
20010033852 |
Kind Code |
A1 |
WANG, JAMES HONGXUE ; et
al. |
October 25, 2001 |
MELT PROCESSABLE POLY(ETHYLENE OXIDE) FIBERS
Abstract
Melt processable, flushable polymer fibers and methods of making
melt processable, flushable polymer fibers are disclosed. The
fibers comprise poly(ethylene oxide). Preferably, the poly(ethylene
oxide) is modified by grafting polar vinyl monomers, such as
poly(ethylene glycol) methacrylate and 2-hydroxyethyl methacrylate,
onto poly(ethylene oxide). The modified poly(ethylene oxide) has
improved melt processability and can be used to melt process
poly(ethylene oxide) fibers of thinner diameters.
Inventors: |
WANG, JAMES HONGXUE;
(APPLETON, WI) ; SCHERTZ, DAVID MICHAEL; (ROSWELL,
GA) |
Correspondence
Address: |
JOHN S. PRATT
KILPATRICK STOCKTON LLP
1100 PEACHTREE
SUITE 2800
ATLANTA
GA
30309
US
|
Family ID: |
21696489 |
Appl. No.: |
09/001525 |
Filed: |
December 31, 1997 |
Current U.S.
Class: |
424/402 |
Current CPC
Class: |
C08L 71/02 20130101;
C08L 71/02 20130101; C08L 51/08 20130101; Y10T 428/2913 20150115;
Y10T 428/31551 20150401; C08L 2666/04 20130101; Y10T 442/682
20150401; C08F 283/06 20130101; Y10T 442/2738 20150401; Y10T
428/31786 20150401; Y10T 442/681 20150401; Y10T 442/60 20150401;
Y10T 442/696 20150401; D01F 6/66 20130101; Y10T 428/31565 20150401;
Y10T 442/69 20150401; C08G 65/331 20130101 |
Class at
Publication: |
424/402 |
International
Class: |
A01N 025/34 |
Claims
What is claimed is:
1. A fiber comprising poly(ethylene oxide) that is water-soluble
and melt processable.
2. The fiber of claim 1, wherein the fiber diameter has an average
diameter of not greater than about 100 micrometers.
3. The fiber of claim 1, wherein the poly(ethylene oxide) has
sufficient melt strength and sufficient melt elasticity for melt
spinning into fibers.
4. The fiber of claim 3, wherein the poly(ethylene oxide) has an
apparent viscosity of less than 200 Pascal*seconds at shear rates
of not less than 100 second.sup.-1 and not greater than 1,000
second.sup.-1.
5. The fiber of claim 1, wherein the poly(ethylene oxide) has a
molecular weight within the range of about 50,000 g/mol to about
400,000 g/mol.
6. The fiber of claim 3, wherein the fiber consists essentially of
poly(ethylene oxide).
7. A fiber comprising a modified poly(ethylene oxide).
8. The fiber of claim 7, wherein the modified poly(ethylene oxide)
is modified from a poly(ethylene oxide) having an initial molecular
weight before modification within the range of about 50,000 g/mol
to about 400,000 g/mol.
9. The fiber of claim 8, wherein the modified poly(ethylene oxide)
is modified from a poly(ethylene oxide) having an initial molecular
weight before modification within the range of about 50,000 g/mol
to about 200,000 g/mol.
10. The fiber of claim 7, wherein the modified poly(ethylene oxide)
is modified by the addition of an initiator.
11. The fiber of claim 7, wherein the modified poly(ethylene oxide)
is modified by the addition of a monomer and an initiator.
12. The fiber of claim 11, wherein the monomer is a polar vinyl
monomer.
13. The fiber of claim 12, wherein the polar vinyl monomer is
selected from the group consisting of poly(ethylene glycol)
methacrylates and 2-hydroxyethyl methacrylate.
14. The fiber of claim 13, wherein the polar vinyl monomer is a
poly(ethylene glycol) ethyl ether methacrylate and has an average
molecular weight of not greater than about 5,000 grams per mol.
15. The fiber of claim 11, wherein the monomer is added within the
range of about 0.1 to about 20 weight percent relative to the
weight of the poly(ethylene oxide).
16. The fiber of claim 7, wherein the modified poly(ethylene oxide)
is a grafted poly(ethylene oxide).
17. A method for processing poly(ethylene oxide) fibers comprising
the steps of: a) adding a poly(ethylene oxide), a monomer, and an
initiator into a reaction vessel; b) mixing the poly(ethylene
oxide), the monomer and the initiator under conditions sufficient
to graft the polar vinyl monomer onto the poly(ethylene oxide); and
c) drawing fibers from the poly(ethylene oxide).
18. The method of claim 17, wherein the monomer is a polar vinyl
monomer.
19. The method of claim 17, wherein the polar vinyl monomer is
selected from the group consisting of poly(ethylene glycol)
methacrylates and 2-hydroxyethyl methacrylate.
20. A fiber produced by the method of claim 17.
Description
FIELD OF THE INVENTION
[0001] The present invention is directed to polymer fibers
comprising poly(ethylene oxide) compositions and methods of making
polymer fibers comprising poly(ethylene oxide). More particularly,
the present invention is directed to fibers comprising grafted
poly(ethylene oxide) compositions.
BACKGROUND OF THE INVENTION
[0002] Disposable personal care products such as pantiliners,
diapers, tampons etc. are a great convenience. Such products
provide the benefit of one time, sanitary use and are convenient
because they are quick and easy to use. However, disposal of many
such products is a concern due to limited landfill space.
Incineration of such products is not desirable because of
increasing concerns about air quality and the costs and difficulty
associated with separating such products from other disposed,
non-incineratable articles. Consequently, there is a need for
disposable products which may be quickly and conveniently disposed
of without dumping or incineration.
[0003] It has been proposed to dispose of such products in
municipal and private sewage systems. Ideally, such products would
be flushable and degradable in conventional sewage systems.
Products suited for disposal in sewage systems and that can be
flushed down conventional toilets are termed "flushable" herein.
Disposal by flushing provides the additional benefit of providing a
simple, convenient and sanitary means of disposal. Personal care
products must have sufficient strength under the environmental
conditions in which they will be used and be able to withstand the
elevated temperature and humidity conditions encountered during use
and storage yet still lose integrity upon contact with water in the
toilet. Therefore, a water-disintegratable material which is
thermally processable into fibers having mechanical integrity when
dry is desirable.
[0004] Due to its unique interaction with water and body fluids,
poly(ethylene oxide) (hereinafter PEO) is currently being
considered as a component material in fibers and flushable
products. PEO,
--(CH.sub.2CH.sub.2O).sub.n--
[0005] is a commercially available water-soluble polymer that can
be produced from the ring opening polymerization of the ethylene
oxide, 1
[0006] Because of its water-soluble properties, PEO is desirable
for flushable applications. However, there is a dilemma in
utilizing PEO in the fiber-making processes. PEO resins of low
molecular weights, for example 200,000 g/mol. have desirable melt
viscosity and melt pressure properties for extrusion processing but
cannot be processed into fibers due to their low melt elasticities
and low melt strengths. PEO resins of higher molecular weights, for
example greater than 1,000,000 g/mol, have melt viscosities that
are too high for fiber-spinning processes. These properties make
conventional PEO difficult to process into fibers using
conventional fiber-making processes.
[0007] PEO melt extruded from spinning plates and fiber spinning
lines resists drawing and is easily broken. PEO resins do not form
fibers using conventional melt fiber-making processes. As used
herein, fibers are defined as filaments or threads or filament-like
or thread-like structures with diameters of about 100 microns and
less. Conventional PEO resins can only be melt processed into
strands with diameters in the range of several millimeters.
Therefore, PEO compositions with appropriate melt viscosities for
processing fibers and with greater melt elasticities and melt
strengths are desired.
[0008] In the personal care industry, flushable melt-spun fibers
are desired for commercial viability and ease of disposal. PEO
fibers have been produced by a solution casting process. However,
it has not been possible to melt process PEO fibers using
conventional fiber making techniques such as melt spinning. Melt
processing techniques are more desirable than solution casting
because melt processing techniques are more efficient and
economical. Melt processing of fibers is needed for commercial
viability. Prior art PEO compositions cannot be extruded into the
melt with adequate melt strength and elasticity to allow
attenuation of fibers. Presently, fibers cannot be produced from
conventional PEO compositions by melting spinning.
[0009] Thus, currently available PEO resins are not practical for
melt extrusion into fibers or for personal care applications. What
is needed in the art, therefore, is a means to overcome the
difficulties in melt processing of PEO resins so that PEO resins
can be formed into fibers for later use as components in flushable,
personal care products.
SUMMARY OF THE INVENTION
[0010] The present invention is directed to polymer fibers
comprising PEO compositions and methods of making polymer fibers
comprising PEO. More particularly, the present invention is
directed to fibers comprising grafted PEO compositions. The
modified PEO compositions have improved melt processability,
allowing fibers to be drawn using conventional fiber-making
techniques and apparatusses. The modification of the PEO resins is
accomplished by grafting a polar vinyl monomer, such as a
poly(ethylene glycol) methacrylate or 2-hydroxyethyl methacrylate,
onto the PEO. The grafting is accomplished by mixing the PEO, the
monomer(s) and a free radical initiator and applying heat. The
resulting grafted PEOs have improved melt processability and may be
used to melt process fibers using conventional fiber processing
techniques.
[0011] To overcome the disadvantages of the prior art, this
invention teaches fibers comprising PEO coplymers comprising
grafted polar functional groups. Such modification of PEO reduces
the melt viscosity and melt pressure of the PEO. The modified PEO
resins can be solidified for later thermal processing into fibers
or processed directly into fibers. The fibers are water soluble and
are useful as components in personal care products.
[0012] As used herein, the term "graft copolymer" means a copolymer
produced by the combination of two or more chains of
constitutionally or configurationally different features, one of
which serves as a backbone main chain, and at least one of which is
bonded at some point(s) along the backbone and constitutes a side
chain. As used herein, the term "grafting" means the forming of a
polymer by the bonding of side chains or species at some point(s)
along the backbone of a parent polymer. (See Sperling, L. H.,
Introduction to Physical Polymer Science 1986 pp. 44-47 which is
incorporated by reference herein in its entirety.)
[0013] Modification of PEO in accordance with the invention
improves the melt properties of PEO and allows the thermal
processing of fibers from PEO. The modified PEO compositions have
increased melt strength and increased melt elasticity yet have
reduced melt viscosity. These changes make it possible to produce
PEO fibers using conventional fiber processing methods.
Modification of PEO resins with starting molecular weights of
between about 50,000 g/mol to about 400,000 g/mol allows the PEO
resin to be extruded into thin fibers using conventional melt
spinning processes. Modification of PEO resins with starting
molecular weights of between about 50,000 g/mol to about 300,000
g/mol is desirable and modification of PEO resins with starting
molecular weights of between about 50,000 g/mol to about 200,000
g/mol is most desirable for fiber-making purposes. The modification
of PEO in accordance with this invention improves the melt
properties of the PEO allowing the modified PEO to be melted and
attenuated into fibers. Thus, the modified PEO can be processed
into water-soluble fibers using both meltblown and spunbond
processes which are useful as components in liners, cloth-like
outer covers, etc. in flushable personal care products.
[0014] These and other features and advantages of the present
invention will become apparent after a review of the following
detailed description of the disclosed embodiments.
BRIEF DESCRIPTION OF THE FIGURES
[0015] FIG. 1 is a graph comparing the melt viscosities of an
unmodified 200,000 g/mol molecular weight PEO, Comparative Example
A, versus the melt viscosities of the same PEO resin after
modification, Example 2.
[0016] FIG. 2 is a .sup.13C- Nuclear Magnetic Resonance spectra of
the modified PEO of Example 2.
[0017] FIG. 3 is a .sup.1H- Nuclear Magnetic Resonance spectra of
the modified PEO of Example 2.
DETAILED DESCRIPTION
[0018] Fibers can be made using conventional processing methods
from commercially available PEO resins when modified in accordance
with this invention. The PEO resins useful for modification
include, but are not limited to, PEO resins having initial reported
approximate molecular weights ranging from about 50,000 g/mol to
about 8,000,000 g/mol. Higher molecular weights are desired for
increased mechanical and physical properties and lower molecular
weights are desired for ease of processing. Desirable PEO resins
have molecular weights ranging from about 50,000 to about 400,000
g/mol before modification. More desirable PEO resins have molecular
weights ranging from about 50,000 to about 300,000 g/mol, even more
desirably from about 50,000 to about 200,000 g/mol, before
modification.
[0019] The modified PEO compositions from the above resins provide
a balance between mechanical and physical properties and processing
properties. Two PEO resins within the above desirable ranges are
commercially available from Union Carbide Corporation and are sold
under the trade designations POLYOX.RTM. WSR N-10 and POLYOX.RTM.
WSR N-80. These two resins have reported approximate molecular
weights, as determined by Theological measurements, of about
100,000 g/mol and 200,000 g/mol, respectively.
[0020] Other PEO resins available from Union Carbide Corporation
within the above approximate molecular weight ranges can be used
(See POLYOX.RTM.: Water Soluble Resins, Union Carbide Chemicals
& Plastic Company, Inc., 1991 which is incorporated by
reference herein in its entirety.) as well as other PEO resins
available from other suppliers and manufacturers Both PEO powder
and pellets of PEO can be used in this invention since the physical
form of PEO does not affect its behavior in the melt state for
grafting reactions. This invention has been demonstrated by the use
of several of the aforementioned PEO resins in powder form as
supplied by Union Carbide in and resins in pellet form as supplied
by Planet Polymer Technologies, Inc. of San Diego, Calif. The
initial PEO resin and modified PEO compositions may optionally
contain various additives such as plasticizers, processing aids,
rheology modifiers, antioxidants, UV light stabilizers, pigments,
colorants, slip additives, antiblock agents, etc.
[0021] A variety of polar vinyl monomers may be useful in the
practice of this invention. Monomer(s) as used herein includes
monomers, oligomers, polymers, mixtures of monomers, oligomers
and/or polymers, and any other reactive chemical species which is
capable of covalent bonding with the parent polymer, PEO.
Ethylenically unsaturated monomers containing a polar functional
group, such as hydroxyl, carboxyl, amino, carbonyl, halo, thiol,
sulfonic, sulfonate, etc. are appropriate for this invention and
are desrable. Desired ethylenically unsaturated monomers include
acrylates and methacrylates. Particularly desired ethylenically
unsaturated monomers containing a polar functional group are
2-hydroxyethyl methacrylate (hereinafter HEMA) and poly(ethylene
glycol) methacrylates (hereinafter PEG-MA). A particularly desired
poly(ethylene glycol) methacrylate is poly(ethylene glycol) ethyl
ether methacrylate. However, it is expected that a wide range of
polar vinyl monomers would be capable of imparting the same effects
as HEMA and PEG-MA to PEO and would be effective monomers for
grafting. The amount of polar vinyl monomer relative to the amount
of PEO may range from about 0.1 to about 20 weight percent of
monomer to the weight of PEO. Desirably, the amount of monomer
should exceed 0.1 weight percent in order to sufficiently improve
the processability of the PEO. More desirably, the amount of
monomer should be at the lower end of the above disclosed range,
0.1 to 20 weight percent, in order to decrease costs. A range of
grafting levels is demonstrated in the Examples. Typically, the
monomer addition levels were between 2.5 to 15 percent of the
weight of the base PEO resin.
[0022] This invention has been demonstrated in the following
Examples by the use of PEG-MA and HEMA as the polar vinyl monomers.
Both the PEG-MA and HEMA were supplied by Aldrich Chemical Company.
The HEMA used in the Examples was designated Aldrich Catalog number
12,863-5 and the PEG-MA was designated Aldrich Catalog number
40,954-5. The PEG-MA was a poly(ethylene glycol) ethyl ether
methacrylate having a number average molecular weight of
approximately 246 grams per mol. PEG-MA with a number average
molecular weight higher or lower than 246 g/mol are also applicable
for this invention. The molecular weight of the PEG-MA can range up
to 50,000 g/mol. However, lower molecular weights are desirable for
faster grafting reaction rates. The desirable range of the
molecular weight of the monomers is 246 to 5,000 g/mol and the most
desirable range is 246 to 2,000 g/mol. Again, it is expected that a
wide range of polar vinyl monomers as well as a wide range of
molecular weights of monomers would be capable of imparting similar
effects to PEO resins and would be effective monomers for grafting
and modification purposes.
[0023] A variety of initiators may be useful in the practice of
this invention. If grafting is achieved by the application of heat,
as in a reactive-extrusion process, it is desirable that the
initiator generates free radicals with the application of heat.
Such initiators are generally referred to as thermal initiators. In
order for the initiator to function as a useful source of radicals
for grafting, the initiator should be commercially and readily
available, stable at ambient or refrigerated conditions, and
generate radicals at reactive-extrusion temperatures.
[0024] Compounds containing an O--O, S--S, or N.dbd.N bond may be
used as thermal initiators. Compounds containing O--O bonds, such
as peroxides, are commonly used as initiators for polymerization.
Such commonly used peroxide initiators include: alkyl, dialkyl,
diaryl and arylalkyl peroxides such as cumyl peroxide, t-butyl
peroxide, di-t-butyl peroxide, dicumyl peroxide, cumyl butyl
peroxide, 1,1-di-t-butyl peroxy-3,5,5-trimethylcyclohexane,
2,5-dimethyl-2,5-di(t-butylperoxy)hexa- ne,
2,5-dimethyl-2,5-bis(t-butylperoxy)hexyne-3 and bis(a-t-butyl
peroxyisopropylbenzene); acyl peroxides such as acetyl peroxides
and benzoyl peroxides; hydroperoxides such as cumyl hydroperoxide,
t-butyl hydroperoxide, p-methane hydroperoxide, pinane
hydroperoxide and cumene hydroperoxide; peresters or peroxyesters
such as t-butyl peroxypivalate, t-butyl peroctoate, t-butyl
perbenzoate, 2,5-dimethylhexyl-2,5-di(perbenz- oate) and t-butyl
di(perphthalate); alkylsulfonyl peroxides; dialkyl
peroxymonocarbonates; dialkyl peroxydicarbonates; diperoxyketals;
ketone peroxides such as cyclohexanone peroxide and methyl ethyl
ketone peroxide. Additionally, azo compounds such as
2,2'-azobisisobutyronitrile abbreviated as AIBN,
2,2'-azobis(2,4-dimethylpentanenitrile) and
1,1'-azobis(cyclohexanecarbonitrile) may be used as the initiator.
This invention has been demonstrated in the following Examples by
the use of a liquid, organic peroxide initiator available from Elf
Atochem North America, Inc. of 200 Market Street, Philadelphia,
Pa., sold under the trade designation LUPERSOL.RTM. 101.
LUPERSOL.RTM. 101 is a free radical initiator and comprises
2,5-dimethyl-2,5-di(t-butylperoxy)hexane. Other initiators and
other grades of the LUPERSOL.RTM. initiators may also be used, such
as LUPERSOL.RTM. 130.
[0025] A variety of reaction vessels may be useful in the practice
of this invention. The modification of the PEO can be performed in
any vessel as long as the necessary mixing of PEO, the monomer and
the initiator is achieved and enough thermal energy is provided to
effect grafting. Desirably, such vessels include a suitable mixing
device, such as Bradender Plasticorders, Haake extruders, a single
or multiple screw extruders, or any other mechanical mixing devices
which can be used to mix, compound, process or fabricate polymers.
In the Examples below, the reaction device is a counter-rotating
twin-screw extruder, such as a Haake extruder available from Haake,
53 West Century Road, Paramus, N.J. 07652 or a co-rotating,
twin-screw extruder, such as a ZSK-30 twin-screw, compounding
extruder manufactured by Werner & Pfleiderer Corporation of
Ramsey, N.J. It should be noted that a variety of extruders can be
used to modify the PEO and to produce fibers in accordance with the
invention provided that mixing and heating occur.
[0026] The ZSK-30 extruder allows multiple feeding, has venting
ports and is capable of producing modified PEO at a rate of up to
50 pounds per hour. If a higher rate of production of modified PEO
is desired, a commercial-scale ZSK-58 extruder manufactured by
Werner & Pfleiderer may be used. The ZSK-30 extruder has a pair
of co-rotating screws arranged in parallel with the center to
center distance between the shafts of the two screws at 26.2 mm.
The nominal screw diameters are 30 mm. The actual outer diameters
of the screws are 30 mm and the inner screw diameters are 21.3 mm.
The thread depth is 4.7 mm. The lengths of the screws are 1328 mm
and the total processing section length was 1338 mm. This ZSK-30
extruder had 14 processing barrels, which are numbered
consecutively 1 to 14 from the feed barrel to the die for the
purposes of this disclosure. The first barrel, barrel #1, received
the PEO and was not heated but cooled by water. The die used to
extrude the modified PEO strands has four openings of 3 mm in
diameter which are separated by 7 mm. The modified PEO strands were
extruded onto an air-cooling belt and then pelletized. The extruded
PEO melt strands were cooled by air on a fan-cooled conveyor belt
20 feet in length.
[0027] Another extruder suitable as the reaction device includes a
Haake extruder. The modified PEO compositions of Examples 31, 32
and 33 suitable for fiber-making purposes were modified by a
reactive extrusion process using a Haake extruder. The Haake
extruder that was used was a counter-rotating, twin-screw extruder
that contained a pair of custom-made, counter rotating conical
screws. The Haake extruder had a length of 300 millimeters. Each
conical screw had a diameter of 30 millimeters at the feed port and
a diameter of 20 millimeters at the die. The monomer and the
initiator were added at the feed throat of the Haake extruder
contemporaneously with the PEO resin.
[0028] The Haake extruder comprised six sections as follows:
Section 1 comprised a double-flighted forward pumping section
having a large screw pitch and high helix angle. Section 2
comprised a double-flighted forward pumping section having a
smaller screw pitch than Section 1. Section 3 comprised a
double-flighted forward pumping section having a smaller screw
pitch than Section 2. Section 4 comprised a double-flighted and
notched reverse pumping section where one complete flight was
notched. Section 5 comprised a double-flighted and notched forward
pumping section containing two complete flights. And, Section 6
comprised a double-flighted forward pumping section having a screw
pitch intermediate that of Section 1 and Section 2.
COMPARATIVE EXAMPLE A
[0029] A PEO resin having a molecular weight of about 200,000 g/mol
was processed through the Haake extruder under similar conditions
as the modified examples of the invention for comparative purposes
and to demonstrate that conventional, unmodified PEO resins cannot
be melt processed into fibers. The 200,000 g/mol molecular weight
unmodified PEO resin that was used for this comparative example was
obtained from Planet Polymer Technologies. The resin obtained from
Planet Polymer Technologies was in pellet form and was compounded
from POLYOX.RTM. WSR N-80 PEO resin manufactured by Union Carbide
Corp.
[0030] For processing, the extruder barrel temperatures were set at
170, 180 and 180.degree. C. for the first, second, third heating
zones, respectively, and 190.degree. C. for the die. The screw
speed was set at 150 rpm. The PEO resin was fed into the extruder
at a throughput of about 5 pounds per hour. No monomer or initiator
was added to the PEO resin of Comparative Example A. The unmodified
PEO was extruded under the above conditions, cooled in air and
pelletized for later use. Attempts were made to melt process the
unmodified PEO of Comparative Example A into fibers. Because the
melted PEO of Comparative Example A had too low melt elasticity and
too low melt strength to allow attenuation of the PEO melt, fibers
could not be melt processed using conventional fiber-spinning
techniques, such as Lurgi gun, starter gun and free fall. The PEO
melt extruded from the spinning plate snapped easily and did not
allow the unmodified PEO to be drawn into fibers. Only strands of
about 1 to 2 millimeters in diameter were able to be produced from
the unmodified PEO of Comparative A.
COMPARATIVE EXAMPLE B
[0031] A PEO resin having a molecular weight of about 100,000 g/mol
was processed through the Haake extruder under the same conditions
as above Comparative Example A. The 100,000 g/mol molecular weight
PEO resin that was used for this Comparative Example B was obtained
from Planet Polymer Technologies was in pellet form and was
compounded from POLYOX.RTM. WSR N-10 PEO resin manufactured by
Union Carbide Corp. Attempts were also made to melt process the
unmodified PEO of Comparative Example B into fibers. Fibers of
diameters of less than about 100 micrometers could not be melt
processed from the unmodified 100,000 g/mol molecular weight PEO
resin using conventional fiber-spinning techniques. Even then the
melt could only be drawn very slowly and the melt was easily
broken, making commercial production of fibers from PEO
impractical. Thus, the Comparative Examples A and B demonstrate
that prior art, unmodified PEO resins cannot be melt processed into
fibers.
EXAMPLES
[0032] The 100,000 g/mol POLYOX.RTM. WSR N-10 PEO resin was fed
into the Haake extruder at 5.3 lb/hr along with 0.53 lb/hr of
PEG-MA monomer and 0.026 lb/hr of LUPERSOL.RTM. 101 free radical
initiator, Example 3 of Table 1. The 200,000 g/mol POLYOX.RTM. WSR
N-80 PEO was modified in the same manner with the same monomer and
initiator at the same relative amounts, Example 2 in Table 1. When
monomer and initiator were added to the PEO base resins during
extrusion, the melt elasticities and the melt strengths of the PEO
resins were visibly improved. These modified PEO compositions were
collected in bulk and then ground into a powder for further
processing into fibers.
[0033] The melt viscosities of the PEO resins were observed to have
been substantially reduced by the modification with the monomer and
initiator. The melt viscosity of the unmodified and modified
200,000 g/mol PEO resins were measured at various shear rates and
are presented in FIG. 1. The melt viscosity of the unmodified PEO
resin, WSR N-80, was 319 Pascal*seconds (Pa*s hereinafter) at 1000
second.sup.-1. In contrast, the melt viscosity of the same PEO
resin modified by the addition of monomer and initiator, Example 2,
was reduced to 74 Pa*s at the same shear rate.
[0034] The melt viscosities of Comparative Example A and Example 2
were determined by melt rheology tests performed on a Goettfert
Rheograph 2003 capillary rheometer. The rheometer was operated with
a 30/1 mm length/diameter die at 195.degree. C. The apparent melt
viscosities measured in Pa*s were determined at apparent shear
rates of 50, 100, 200, 500, 1,000 and 2,000 second.sup.-1 in order
to develop rheology curves for each of the PEO compositions. The
rheology curves of the two respective PEO compositions are
presented in FIG. 1. Over the entire range of shear rates tested,
the modified PEO exhibited lower apparent viscosities than the PEO
from which it was modified.
[0035] The modification by grafting of the monomer onto the PEO
brought about a 77 percent drop in melt viscosity. The reduced
viscosity brought about by the modification of the PEO makes
fiber-spinning of the PEO feasible. Fibers of very small diameters,
in the range of 20-30 micrometers, were able to be continuously
drawn from the above modified PEO resins. Fibers within this range
of diameters are useful for making spunbond nonwoven fabrics. PEO
fibers and fabrics are flushable and water-dispersible and can be
used as components in flushable personal care products.
[0036] When the addition of the monomer and initiator was stopped
during the extrusion process, the properties of the PEO resins
reverted to their previous values and fibers could not be drawn
from the unmodified PEO melt. This demonstrates that the
modification does occur and improves the properties of the PEO
which is critical for fiber-making and commercial viability.
[0037] Other examples of modified PEO resins were produced to
further demonstrate the invention. These other examples of modified
PEO resins were produced by varying: the molecular weights, 100,000
and 200,000 g/mol, and the suppliers of the PEO, Union Carbide and
Planet Polymer Technology, Inc. (a compounder, hereinafter
abbreviated PPT); the monomers, 2-hydroxyethyl methacrylate and the
poly(ethylene glycol) ethyl ether methacrylate described above, and
the amount of monomers; the amount of the LUPERSOL.RTM. 101
initiator; and the extruder. The various parameters used in the
various Examples are listed in Table 1 below. The weight
percentages of the components used in the Examples were calculated
relative to the weight of the base resin, PEO, unless otherwise
indicated.
1TABLE 1 Components and Process Conditions of the Examples Ex- am-
Resin Mon- ple Rate omer Initiator Reac- Num- (lb/ Rate Ini- Rate
tion ber Resin hr) Monomer (lb/hr) tiator (lb/hr) Vessel A POLYOX 5
-- 0 -- 0 Haake N-80 B POLYOX 5 -- 0 -- 0 Haake N-10 1 POLYOX 5
PEG-MA 0.26 L101 0.025 Haake N-80 2 POLYOX 5 PEG-MA 0.49 L101 0.026
Haake N-80 3 POLYOX 5 PEG-MA 0.53 L101 0.026 Haake N-10 4 POLYOX 20
PEG-MA 0.30 L101 0.026 ZSK-30 N-80 5 POLYOX 20 PEG-MA 0.58 L101
0.041 ZSK-30 N-80 6 POLYOX 20 HEMA 0.29 L101 0.025 ZSK-30 N-80 7
POLYOX 20 HEMA 0.58 L101 0.045 ZSK-30 N-80
[0038] Examples 1, 2 and 3 were processed in the Haake extruder
under similar conditions as disclosed in the above Comparative
Examples. The same exact extruder design, temperatures and screw
speed were used. However, Examples 1, 2 and 3 included the addition
of monomer and initiator to the PEO resin in order to modify the
PEO resin. The listed amounts of the monomer and the initiator were
added at the feed throat of the Haake extruder contemporaneously
with the PEO resin.
[0039] Examples 4, 5, 6 and 7 were modified in the ZSK-30 extruder
detailed above. The fourteen heated barrels of the ZSK-30 extruder
consist of seven heating zones. For the modification of Examples
4-7, the seven zones of the ZSK-30 extruder were all set at
180.degree. C. and the screw speed was set at 300 rpm. The
respective monomer, HEMA or PEG-MA as listed in Table 1, was
injected into barrel #4 and the initiator was injected into barrel
#5. Both the monomer and the initiator were injected via a
pressurized nozzle injector at the listed rate. The order in which
the PEO, monomer and initiator are added to the PEO is not
critical. The initiator and monomer may be added at the same time
or in reverse order. It should be noted that the order used in the
Examples is preferred.
[0040] Although the invention has been demonstrated by the
Examples, it is understood that the PEO, the polar vinyl monomer,
the initiator and the conditions can be varied depending on the
type of modified PEO composition and properties desired.
FIBER-MAKING
[0041] Attempts were made to melt process fibers from the PEO
compositions of Examples 1, 2 and 3 using conventional melt
processing techniques. The modified PEO compositions of Examples 1,
2 and 3 were melt processable into fibers by a research-scale
spunbond process, in contrast to the unmodified PEO compositions of
Comparative Examples A and B which could not be extruded into a
melt with adequate melt strength and elasticity for processing into
fibers. The melt processability of the modified PEO resins was
demonstrated by a conventional spunbond process on an experimental
spinning line comprising a single screw extruder, a melt metering
pump and a spin plate. The spunbond process was used to spin the
fibers but was not used to bind the fibers.
[0042] Freefall fibers and fibers drawn by hand and by a starter
gun on a fiber-spinning line were produced from the modified PEO
composition of Example 1. Freefall fibers and fibers drawn by a
Lurgi gun and by a starter gun on a fiber-spinning line were
produced from the modified PEO composition of Example 2. Freefall
fibers and fibers drawn by a starter gun on a fiber-spinning line
were produced from the modified PEO composition of Example 3.
[0043] Although no attempts have been made to process fibers from
the modified PEO compositions of Examples 4, 5, 6 and 7, the
modified PEO compositions are expected to be melt processable into
fibers. The appearance of the extruded, modified PEO compositions
of Examples 4, 5, 6 and 7 was similar to the appearance of Examples
1, 2 and 3, exhibiting lower viscosities and stickier material.
These reduced melt viscosities make fiber-spinning of the modified
PEO compositions possible and are particularly advantageous for
commercial fiber-making, especially when using methods requiring
melt processing.
[0044] Some of the modified PEO compositions were converted into
meltblown fibers. The fibers retained the same beneficial
water-solubility as unmodified PEO. This property is particularly
desired for flushable applications. The fibers produced by the
spunbond process were also water-soluble and, therefore, are easily
flushable.
[0045] Physical Testing and Characterization of Modified PEO and
Fibers Produced from Modified PEO
[0046] Tensile tests were performed on fibers produced from the
modified PEO compositions of Examples 1, 2 and 3. The tests were
performed using a Sintech 1/D tensile tester available from MTS
Systems Corp., Machesny Park, Ill. The diameter of the fiber was
measured before testing and then the fiber was tested with a grip
separation of one inch and a crosshead speed of 500 mm/min. The
diameters and the tensile properties of the fibers produced from
the modified PEO resins of Examples 1, 2 and 3 were measured and
are reported in Table 2 below. The fibers made from the 200,000
g/mol PEO were significantly more ductile than those made from the
100,000 g/mol. For fibers made from the same molecular weight PEO
base resin, higher PEG-MA additional levels, for example 10 weight
percent, led to significantly increased ductility of the fibers.
The Lurgi gun-drawn PEO fibers at 10% PEG-MA addition had a peak
stress of 7.2 MPa and 648 percent elongation-at-break. These
tensile property values are extremely favorable for PEO derived
fibers considering unmodified PEO is very brittle in nature.
2TABLE 2 Tensile Properties of Fibers Produced from Examples 1, 2
and 3 % Base PEG- Fiber- Fiber Strain Energy Tensile Resin MA Draw-
Diam- Peak to to Modu- MW Added ing eter Stress Break Break lus
(g/mol) (%) Process (.mu.m) (MPa) (%) (in-lb) (MPa) Ex. #1 5 Free
104 11.0 68 0.0108 64.7 200,000 Fall Ex. #1 5 Starter 65 9.7 72
0.0042 127.0 200,000 Gun Ex. #1 5 Hand 214 11.0 236 0.1741 75.8
200,000 Down Ex. #2 10 Free 104 9.1 367 0.0517 49.2 200,000 Fall
Ex. #2 10 Starter 102 8.5 340 0.0430 49.0 200,000 Gun Ex. #2 10
Lurgi 72 7.2 648 0.0336 58.3 200,000 Gun Ex. #3 10 Free 103 2.2 10
0.0003 252.4 100,000 Fall Ex. #3 10 Starter 67 4.1 7.8 0.0001 232.8
100,000 Gun
Chemical Characterization of
[0047] GPC Analysis
[0048] The number-average molecular weight (M.sub.n), the
weight-average molecular weight (M.sub.w), and the z-average
molecular weight (M.sub.z) of Comparative Examples A and B and
Examples 1, 2 and 3 were determined by gel permeation
chromatography (hereinafter GPC). The GPC analysis was conducted by
American Polymer Standards Corporation of Mentor, Ohio. From these
measurements the polydispersity indices (M.sub.w/M.sub.n) of the
respective examples were calculated. The various molecular weights
and the polydispersity of the examples are reported in Table 3
below.
[0049] NMR Analysis
[0050] The modified PEO composition of the Examples 1, 2 and 3 were
analyzed NMR spectroscopy. The .sup.13C and .sup.1H NMR spectra of
Example 2 are presented as FIGS. 2 and 3, respectively. The results
of this analyses confirmed that modified PEO contained PEG-MA
units.
[0051] The grafting levels of the modified PEO compositions of
Examples 1, 2 and 3 as measured by NMR analysis are reported as
weight percentages of monomer per weight of PEO base resin that
grafted to the PEO resin and are reported in Table 3. The
percentages of ungrafted monomer of Examples 1, 2 and 3 are
likewise reported in Table 3.
3TABLE 3 Chemical Properties of Comparative Examples A and B and
the Modified PEO Compositions of Examples 1, 2 and 3 Example No. A
B 1 2 3 M.sub.n 12,650 11,050 11,400 11,450 9,450 M.sub.w 148,100
115,900 97,200 109,300 90,600 M.sub.z 840,500 698,400 515,700
541,300 601,500 M.sub.w/M.sub.n 11.71 10.49 8.53 9.53 9.59 % PEG-MA
0 0 4.51 5.08 5.49 grafting level % residual 0 0 0.43 3.41 4.43
ungrafted PEG-MA
[0052] The molecular weights of the modified PEO Examples are
significantly different versus the corresponding unmodified PEO
resin. Significant reductions in molecular weights and the
polydispersity indices were observed after reactive-extrusion of
PEO with the monomer and the initiator compared to the unmodified,
extruded PEO of the Comparative Examples. The weight-average
molecular weight of the N-80 PEO dropped from 148,100 g/mol for the
unmodified, but similarly processed, N-80 PEO of Comparative
Example A to 97,200 g/mol for the 5% grafted N-80 PEO of Example 1
and to 109,300 g/mol for the 10% grafted N-80 PEO of Example 2.
Similarly, the weight-average molecular weight of the N-10 PEO
dropped from 115,900 g/mol for the unmodified N-10 PEO of
Comparative Example B to 90,600 g/mol for the 10% grafted PEO N-10
of Example 3. Thus, the modification of the PEO resins produced a
significant reduction in weight-average molecular weight. However,
the number-average molecular weight was not as greatly affected by
the modification, thereby, producing a significant decrease in the
polydispersity index and, hence, a narrower molecular weight
distribution.
[0053] The fundamental changes in modified PEO brought about by the
chemical grafting have profound and unexpected effects on the
physical properties and melt processability of PEO as demonstrated
herein and discussed above. The narrower molecular weight
distributions of the modified PEO compositions result in improved
melt and solid state properties. Although not wishing to be bound
by the following theory, it is believed that during the
reactive-extrusion processing of PEO resins, the initiator
initiated three competing reactions: 1) grafting of vinyl monomer
onto the PEO, 2) degradation of the PEO, and 3) crosslinking of the
PEO. A novel method of achieving improved properties has been
developed that is contrary to traditional methodology and thinking
in polymer development. The method degrades the polymer into
shorter chains as opposed to only increasing the molecular weight
by grafting and crosslinking. The resulting modified PEO
compositions have improved melt strength and melt elasticity,
overcoming the inherent deficiencies of both low molecular weight
PEO and high molecular weight PEO.
[0054] In the case of grafting, the presence of a sufficient amount
of monomer(s) as demonstrated in the Examples herein, cross-linking
is negligible and does not adversely affect the properties of the
modified PEO. The crosslinking reaction only predominates when
there is little or no monomer present during the modification of
the PEO resin. Therefore, the grafting and the degradation
reactions of the PEO should predominate and are desired to produce
PEO compositions suitable for film and fiber making purposes.
[0055] The modified PEO resins are observed to have improved melt
strengths and melt elasticities, overcoming the inherent
deficiencies of both low molecular weight and high molecular weight
PEO resins. These improved melt properties allow the modified PEO
to be processed into useful fibers with diameters of less than 100
micrometers using conventional fiber drawing techniques.
[0056] The present invention has been illustrated in great detail
by the above specific Examples. It is to be understood that these
Examples are illustrative embodiments and that this invention is
not to be limited by any of the Examples or details in the
Description. Those skilled in the art will recognize that the
present invention is capable of many modifications and variations
without departing from the scope of the invention. Accordingly, the
Detailed Description and Examples are meant to be illustrative and
are not meant to limit in any manner the scope of the invention as
set forth in the following claims. Rather, the claims appended
hereto are to be construed broadly within the scope and spirit of
the invention.
* * * * *