Note: Descriptions are shown in the official language in which they were submitted.
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WATER-MODIFIABLE FLUSHABLE POLYOLEFIN-CONTAINING FILM
The application claims priority from the U.S. Provisional Application
60/034,616
filed December 31,1996, the disclosure of which is incorporated herein by
reference.
FIELD OF THE INVENTION
The present invention relates to a flushable polyolefin-containing film. More
particularly, the present invention relates to a flushable polyolefin-
containing film having
greater than about 55 weight percent of a polyolefin and less than about 45
weight
percent of polyethylene oxide).
BACKGROUND OF THE INVENTION
Personal care products, such as diapers, sanitary napkins, adult incontinence
garments, and the like are generally constructed from a number of different
components
and materials. Such articles typically have some portion, usually the backing
layer) liner,
or baffle constructed of a liquid repellent film material. This repellent
material is
appropriately constructed to minimize or prevent the exudation of the absorbed
liquid
from the article and to obtain greater utilization of the absorbent capacity
of the product.
The liquid repellent ~Im commonly used includes plastic materials such as
polyethylene
films and the like.
Although such products are relatively inexpensive) sanitary and easy to use,
disposal of a soiled product is not without its problems. With greater
interest being
placed in protecting the environment today, there is a need to develop
materials that are
more compatible with the existing and developing waste disposal technologies
while still
delivering performance consumers have come to expect. An ideal disposal
alternative
would be to use municipal sewage treatment and private residential septic
systems.
Products suited for disposal in sewage systems can be flushed down a
convenient toilet
and are termed "fiushable." While flushing such articles would be convenient,
the liquid
repellent material which normally does not disintegrate in water tends to plug
toilets and
sewer pipes. It therefore becomes necessary, although undesirable, to separate
the
barrier film material from the absorbent article prior to flushing.
In addition to the article itself, typically the packaging in which the
disposable
article is distributed is also made from a water resistant material. Water
resistivity is
necessary to prevent the degradation of the packaging from environmental
conditions
and to protect the disposable articles therein. Although this packaging may be
safely
stored with other refuse for commercial disposal, and especially in the case
of individual
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packaging of the products, it is often more convenient to dispose of the
packaging in the
toilet with the discarded disposable article. However) in the cases where such
packaging
is composed of a water resistant material, plugging of the drains to the
toilet typically
results.
Desirably, a commercial, flushable product should be relatively responsive to
water and be transportable in a sewer system. Commercially available water
soluble
polymers, such as polyethylene oxide (PEO), polyvinyl alcohol (PVOH),
acrylamide
polymers, acrylic acid-based polymers, and cellulose derivatives, possess the
desired
characteristics for flushability, such as water solubility andlor water
dispersibility.
However, due to their in-use degradability and storage degradation, these
materials
function poorly as components in personal care products. Other disadvantages
are that
these polymers are difficult to process and are substantially more expensive
than
polyolefins.
The requirements for a functional and flushable product provide a substantial
challenge in finding suitable materials with the desired properties. In an
attempt to
overcome the flushability problem of a water resistant film the prior art has
modified the
water resistant polymer. One of the more useful ways of modifying polymers
involves
blending them with other polymers of different structures and properties.
Polymer blends of polyolefins and pofy(ethylene oxide) have been shown to be
water modifiable at expectedly low weight % polyolefin levels. Such blends
would be
anticipated to be flushable when exposed to water in a toilet but do not
possess the dry
mechanical properties required for functionality in use. Moreover, the high
content of
poiy(ethylene oxide) makes such materials prohibitively expensive for use in a
disposable
personal hygiene article such as a sanitary napkin, diaper and the like.
Polymer blends
of polyolefins and polyethylene oxide) containing greater than about 45 weight
percent
of polyolefin are generally water resistant and are not water modifiable.
in view of the problems of the prior art, it remains highly desirable to
provide a
water modifiable film having a substantial portion of thereof composed of a
polyolefin.
More desirably, the water modifiable film should have greater than about 55
weight
percent of a polyolefin. When dry, the film should have the mechanical
properties
necessary for functionality. When wet, the films should lose at least a
portion of its
mechanical properties which would render the film flushable and transportable
in a sewer
system. Such films could be used for making flushable barrier films for
personal care
products.
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SUMMARY OF THE INVENTION
Briefly) the present invention provides for a water-modifiable film or other
thermoplastic article having greater than about 55 weight percent of a
polyolefin and less
than about 45 weight percent of polyethylene oxide). As used herein "water
modifiable"
means that a four mil (one mil equals 0.001 of an inch) thick film, when
immersed in
water for 30 seconds, will have modified by greater than 10~o two or more of
the following
tensile properties: percent strain-to-break, peak stress, energy-to-break and
modulus.
To determine the degree of modification, the 'Snret" values are compared to
the pre-
immersed or "dry" film values.
Another embodiment of the invention is a water-mod~able film having greater
than about 55 weight percent of a modified polyolefin and less than about 45
weight
percent of poly{ethylene oxide). The polyolefin is modified by having from
about 1 weight
percent to about 30 weight percent, based on the total weight of the
polyolefin and
polyethylene oxide), of a monomer grafted onto the polyoiefin backbone.
Preferably the
monomer is 2-hydroxyethyi methacrylate or polyethylene glycol ethyl ether
methacrylate.
Another embodiment of the invention is a water modifiable film having greater
than about 55 weight percent of a modified polyolefin and less than about 45
weight
percent of a modified poly(ethyiene oxide). The polyolefin and polyethylene
oxide) are
modified by having a total of from about 1 weight percent to about 30 weight
percent,
based on the weight of the combined pofyolefin and poiy(ethyfene oxide), of a
monomer
grafted thereto. Preferably the monomer is 2-hydroxyethyl methacrylate or
polyethylene
glycol ethyl ether methacrylate.
It is an object of the invention to provide a polyolefin-containing film that
is water
modifiable. More specifically, it is an object of the invention to provide a
polyolefin-
containing film having greater than about 55 weight percent of a polyolefin
and less than
about 45 weight percent of polyethylene oxide) that is water modifiable.
It is another object of the invention to provide a water modifiable,
polyolefin-
containing film that when immersed in water for about 30 seconds at least two
of the
following tensile properties: percent strain-to-break, peak stress, energy-to-
break and
modutus lose at least 10% of its value relative to the dry film value.
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DETAILED DESCRIPTION OF THE INVENTION
Although the present invention is described with reference to a water
modifiable
film, one skilled in the art would understand the utility of the invention
toward other
thermoplastic articles that can be extruded or injection molded. In one
embodiment of
the invention) the water modifiable film comprises greater than about 55
weight percent
of a polyolefin and less than about 45 weight percent of polyethylene oxide).
Desirably,
the water-modifiable film comprises from about 55 weight percent to about 85
weight
percent of a polyolefin and from about 45 weight percent to about 15 weight
percent of
polyethylene oxide). More desirably, the water-modifiable film comprises from
about 65
weight percent to about 85 weight percent of a polyolefin and from about 35
weight
percent to about 15 weight percent of polyethylene oxide). The polyethylene
oxide)
useful in making the film should have a molecular weight of less than about
200,000 and
more preferably about 700,000.
The saturated ethylene polymers useful in the practice of this invention are
homopolymers or copolymers of ethylene and polypropylene and are essentially
linear in
structure. As used herein, the term "saturated" refers to polymers which are
fully
saturated, but also includes polymers containing up to about 5% unsaturation.
The
homopolymers of ethylene include those prepared under either low pressure,
i.e., linear
low density or high density polyethylene, or high pressure) i.e., branched or
low density
polyethylene. The high density polyethylenes are generally characterized by a
density
that is about equal to or greater than 0.94 grams per cubic centimeter (glcc).
Generally,
the high density potyethylenes useful as the base resin in the present
invention have a
density ranging from about 0.94 g/cc to about 0.97 g/cc. The polyethylenes can
have a
melt index, as measured at 2.16 kg and 190°C, ranging from about 0.005
decigrams per
minute (dg/min) to 100 dg/min. Desirably, the polyethylene has a melt index of
0.01
dglmin to about 50 dglmin and more desirably of 0.05 dg/min to about 25
dg/min.
Alternatively) mixtures of polyethylene can be used as the base resin in
producing the
graft copolymer compositions, and such mixtures can have a melt index greater
than
0.005 dg/min to less than about 100 dglmin.
The low density polyethylene has a density of less than 0.94 glcc and are
usually
in the range of 0.91 g/cc to about 0.93 g/cc. The low density polyethylene has
a melt
index ranging from about 0.05 dg/min to about 100 dg/min and desirably from
0.05
dglmin to about 20 dglmin. Ultra low density polyethylene can be used in
accordance
with the present invention. Generally, ultra low density polyethylene has a
density of less
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than 0.s0gicc.
Generally, polypropylene has a semi-crystalline structure having a molecular
weight of about 40,000 or more, a density of about 0.90 g/cc) a melting point
of 168 to
171 °C for isotactic polypropylene and a tensile strength of 5000 psi.
Polypropylene can
also have other tacticities including syndiotactic and atactic.
The above polyolefins can also be manufactured by using the well known
multiple-site Ziegler-Natta catalysts or the more recent single-site
metallocene catalysts.
The metallocene catalyzed polyolefins have better controlled polymer
microstructures
than palyolefins manufactured using Ziegler Natta catalysts) including
narrower molecular
weight distribution, well controlled chemical composition distribution, co-
monomer
sequence length distribution, and stereoregularity. Metallocene catalysts are
known to
polymerize propylene into atactic, isotactic, syndiotactic, isotactio-atactic
stereoblock
copolymer.
Copolymers of ethylene which can be useful in the present invention may
include
copolymers of ethylene with one or more additional polymerizable, unsaturated
monomers. Examples of such copolymers include) but are not limited to,
copolymers of
ethylene and alpha olefins (such as propylene, butane, hexane or octane)
including
linear low density polyethylene, copolymers of ethylene and vinyl esters of
linear or
branched carboxylic acids having 1-24 carbon atoms such as ethylene-vinyl
acetate
copolymers, and copolymers of ethylene and acrylic or methacrylic esters of
linear)
branched or cyclic alkanols having 1-28 carbon atoms. Examples of these latter
copolymers include ethylene-alkyl (meth)acrylate copolymers) such as ethylene-
methyl
acrylate copolymers.
Polyethylene oxide) is available from Union Carbide Corporation under the
trade
name of POLYOX~. Typically, polyethylene oxide) is a dry free flowing white
powder
having a crystalline melting point in the order of about 65°C, above
which polyethylene
oxide) resin becomes thermoplastic and can be formed by molding, extrusion and
other
methods known in the art.
In another embodiment of the invention, the water modifiable film comprises
greater than about 55 weight percent of a modified polyolefin and less than
about 45
weight percent of poly(ethyiene oxide). Desirably, the water modifiable film
comprises
from about 55 weight percent to about 85 weight percent of a modified
polyolefin and
from about 45 weight percent to about 15 weight percent of polyethylene
oxide). More
desirably, the water modifiable ~Im comprises from about 65 weight percent to
about 85
weight percent of a modified polyofe~n and from about 35 weight percent to
about 15
CA 02275669 1999-06-21
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weight percent of polyethylene oxide). The polyolefin is modified by having
grafted
thereto from about 0.1 weight percent to about 30 weight percent, based on the
weight of
the polyolefin and poly(ethyiene oxide), of a monomer. Desirably, the
polyolefin is
modified by having grafted thereto from about 1 weight percent to about 20
weight
percent, and more desirably, from about 1 weight percent to about 10 weight
percent,
based on the weight of the polyolefin and polyethylene oxide)) of a monomer.
Generally, the modified polyolefin is made by feeding to an extruder an amount
of
polyolefin, monomer and a free radical initiator. Preferably the monomer is 2-
hydroxyethyl
methacrylate or polyethylene glycol ethyl ether methacrylate. The modified
polyolefin
and polyethylene oxide) is then melt blended in an extruder to form the water
modifiable
film. The method of making the modified polyolefin is described in greater
detail in
copending U.S. patent application 081733,410 filed October 18,1996 entitled
"METHOD
OF MAKING POLYOLEFINS HAVING GREATER THAN 5 PERCENT 2-
HYDROXYETHYL METHACRYLATE GRAFTED THERETO", the entire disclosure of
which is incorporated herein by reference. In accordance with this embodiment
of the
invention) suitable polyethylene oxide) polymers can have an average molecular
weight
ranging from 100,000 to about 8,000,000.
The free radical initiators which can be used to graft the monomer onto the
pofyolefin include acyl peroxides such as benzoyl peroxide; dialkyl; diaryl;
or aralkyl
peroxides such as 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)
hexane; 2,5-
dimethyl-2,5-bis {t-butylperoxy) hexyne-3 and bis(a-t-butyl
peroxyisopropylbenzene);
peroxyesters such as t-butyl peroxypivalate; t butyl peroctoate; t-butyl
perbenzoate; 2,5-
dimethylhexyl-2,5-di(perbenzoate); t-butyl di(perphthalate); dialkyl
peroxymonocarbonates and peroxydicarbonates; hydroperoxides such as t-butyl
hydroperoxide, p-methane hydroperoxide, pinane hydroperoxide and cumene
hydroperoxide and ketone peroxides such as cyclohexanone peroxide and methyl
ethyl
ketone peroxide. Azo compounds such as azobisisobutyronitrile may also be
used.
In yet another embodiment of the invention a water modifiable film comprises
greater than about 55 weight percent of a modified polyolefin and less than
about 45
weight percent of modified poly{ethylene oxide). Preferably the water
modifiable film
comprises from about 55 weight percent to about 85 weight percent of a
modified
polyolefin and from about 45 weight percent to about 15 weight percent of
modified
polyethylene oxide). More desirably) the water modifiable film comprises from
about 65
weight percent to about 85 weight percent of a modified polyolefin and from
about 35
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weight percent to about 15 weight percent of modified polyethylene oxide).
Polyethylene oxide) polymers suitable for this embodiment of the present
invention can
have a molecular weight ranging from 100,000 to 8,000,000. The polyolefin and
polyethylene oxide) are modified by grafting thereto a total of from about 0.1
weight
percent to about 30 weight percent, based on the weight of the polyolefin and
polyethylene oxide), of the monomer. Desirably, the polyolefin and
poly(ethyiene oxide)
have a total of from about 1 weight percent to about 20 weight percent of the
monomer
grafted thereto. More desirably) the polyolefin and polyethylene oxide) have a
total of
from about 1 weight percent to about 10 weight percent of the monomer grafted
thereto.
The water modifiable film of the present invention can be made as described in
copending U.S. patent application having U.S. serial no. 081777,226 filed on
December
31) 1996 and entitled "BLENDS OF POLYOLEFIN AND POLYETHYLENE OXIDE) AND
PROCESS FOR MAKING THE BLENDS", the entire disclosure of which is incorporated
herein by reference. Generally, the film is made by melt blending the desired
weight
ratios of a mixture of the polyolefin, polyethylene oxide), the monomer and
the free
radical initiator in an extruder and at a reaction temperature where the
polyolefin and
polyethylene oxide) are converted to a molten state. Preferably) the
polyolefin and
polyethylene oxide) are added at the beginning of the extruder. After melting,
the
monomer is added to the melt blend. Further down the extruder barrel, the free
radical
initiator is fed to the melt blend.
When modifying the polyolefin alone or together with the polyethylene oxide),
the
amount of free radical initiator added to the extruder should be an amount
sufficient to
graft from about 1 percent to 100 percent of the monomer onto the polymer)
i.e., the
polyolefin or polyolefin and polyethylene oxide). This can range from about
0.1 weight
percent to about 2 weight percent of initiator. Preferably, the amount of
initiator added to
the extruder ranges from about 0.1 weight percent to about 1 weight percent
wherein all
such ranges are based on the amount of monomer added to the melt blend.
The water-modifiable polyolefin films of the present invention will, when
immersed
in water for about 30 seconds, have modified at least two of the tensile
properties:
percent stain-to-break, peak stress, energy-to break and modulus by greater
than 10%.
Desirably, at least two of the tensile properties will be reduced greater than
about 25%.
More desirably, at least two of the tensile properties will be reduced from
about 25% to
about 98%, and even more desirably at least two of the tensile properties:
percent stain-
to-break, peak stress, energy-to break and modulus will be reduced from about
30% to
about 80%. The values in determining the extent of the tensile property or
properties
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modification are relative to the dry condition, i.e. pre-immersion value for
that measured
property.
The present invention is illustrated in greater detail by the specific
examples
presented below. It is to be understood that these examples are illustrative
embodiments
and are not intended to be limiting of the invention, but rather are to be
construed broadly
within the scope and content of the appended claims.
COMPARATIVE EXAMPLE A
A 60140 weight percent blend of low density polyethylene {PE) having a melt
index of 1.9 decigrams per minute (dg/min) and a density of 0.917 grams per
cubic
centimeter (g/cc) (Dow 5031; available from Dow Chemical Company, Midland, MI)
and
polyethylene oxide) (PEO) having a molecular weight of 200,000 g/mol (POLYOX~
WSRN-80 available from Union Carbide Corp.) was fed to a Haake counter
rotating twin
screw extruder at a rate of 5 pounds per hour (Iblhr). The extruder had a
length of 300
millimeters. Each conical screw had 30 millimeters diameter at the feed port
and a
diameter of 20 millimeters at the die. The extruder had four heating zones set
at 170,
180, 180 and 190°C. The screw speed of the extruder was 150 rpm.
Film processing of all the blends was performed using a Haake extruder counter-
rotating twin screw extruder as described above with the following
modifications. The
extruder included a 4 inch slit die at a temperature of 195 °C. The
screw speed was at
30 rpm. A chilled wind-up roll was used to collect the film. The chilled roll
was operated
at a speed sufficient to form a film having a thickness of about 4 mils (about
0.004 of an
inch) and was maintained at a temperature of 15-20°C.
Dry tensile tests were performed on a Sintech 1lD tensile tester available
from
MTS Systems Corp., Machesny Park, IL. The film was cut into a type V dogbone
shape
in accordance with ASTM D638. The test was pertormed with a grip separa#ion of
30
millimeters and a crosshead speed of 4 millimeterslsecond.
Wet tensile tests were pertormed on a Vitrodyne V1000 mini-tensile tester
available from Chatillon, Greensboro, NC. The film samples were placed in the
grips and
the testing apparatus was submerged in ambient temperature, non-stirred water
for 30
seconds. The test was then run under the same conditions as the dry tensile
test. Peak
stress, percent strain-to-break, energy-to-break (as area under stress versus
strain curve)
and modulus were calculated using the actual stress versus strain values
recorded from
the tensile tester for each dry or wet tensile test. The peak stress was
recorded as the
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greatest stress value. The percent stain-to-break was recorded as the percent
strain
value at break. The energy-to-break (area under stress versus stain curve) was
calculated by the summation of rectangular slices" under the curve determined
for each
strain value recorded from the tensile test, using the following formula:
((Strain valuex - Strain valuex.,) x (Stress valueX + Stress valuex_~)) / 2
where "x" is the sequential number of the slice. The modulus was calculated by
linear regression of the initial region of the stress versus strain curve.
The dry and wet properties of the ~Im produced from the blend in Comparative
Example A are indicated in Table 1 below.
TABLE 1
Example #- ~ #A
dry wet
Thickness (mil) 4.1 4.2
Strain-to-Break 330 300
Peak Stress - (MPa)16.6 16.2
Energy-break (x10 39.4 38.4
Jlm')
Modulus (MPa) 128.4 103.8
Loss from Dry to ~ #A
Wet
Strain-to-Break 9%
Peak Stress 2~
Energy-to-Break 3%
Modulus 20%
This example shows typical polymer blends in which the volumetric majority of
the
blend is water resistant. The polymer blend was not water modifiable after 30
seconds of
submersion in water.
EXAMPLES 1-3
For Examples 1-3) the low density polyethylene (Dow 5031) was modified by
grafting thereto polyethylene glycol methacrylate (PEG-MA; available from
Aldrich
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Chemical Company, Milwaukee, WI). A Haake extruder as described in Comparative
Example A above was used. The extruder had four heating zones set at 770, 780,
180
and 190°C. The screw speed of the extruder was 150 rpm. The feed to the
extruder
comprised contemporaneously adding, at the extruder feed throat, 5 Iblhr of
polyethylene
and the specified amounts of PEG-MA and free radical initiator ((2,5-dimethyl-
2,5-di(t-
butylperoxy) hexane, supplied by Atochem) 2000 Market St.) Philadelphia, PA
under the
tradename Lupersol 101).
For Example 1 the PEG-MA feed rate was 0.125 Iblhr and the initiator rate was
0.0125 Ib/hr.
For Example 2 the PEG-MA feed rate was 0.25 Iblhr and the initiator rate was
0.025 Ib/hr.
For Example 3 the PEG-MA feed rate was 0.5 Ib/hr and the initiator rate was
0.025 Ib/hr.
A 60/40 weight percent blend. of polyethylene and polyethylene oxide) was
prepared following the procedure of Comparative Example A, except the modified
polyethylene of each example was substituted for the unmodified polyethylene
of
Comparative Example A.
The dry and wet properties of the film produced from the blends in Examples 1-
3
are indicated in Table 2 below.
TABLE 2
Example #- #1 #2 #3
dry wet dry wet dry wet
Thickness (mil) 4.5 4.5 4.0 4.0 5.0 5.0
Strain-to-Break 330 110 320 70 170 30
Peak Stress - (MPa)13.8 7.0 11.4 4.9 12.2 3.1
Energy-break (x10 32.7 6.7 27.6 2.4 16.5 0.5
J/m )
Modutus (MPa) 117.874.4103.7 56.3119.4 39.4
Loss from Dry to #1 #2 #3
Wet
Strain-to-Break 65% 79% 82%
Peak Stress 49% 57% 75%
Energy-to-Break 80% 91 % 97%
Modulus 37% 46% 33%
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In accordance with the invention, Examples 1-3 illustrate a water modifiable
film
having a modified polyethylene where the polyethylene has PEG-MA grafted
thereto and
unmodified polyethylene oxide). The films were water modifiable after 30
seconds of
submersion in water.
Examples 4-7
A 60/40 weight percent resin blend of tow density polyethylene, Dow 5031, and
polyethylene oxide) having a molecular weight of 200,000 g/mol (POLYOX~ WSRN-
80)
was fed to a Haake extruder as described in Comparative Example A at a rate of
5
pounds per hour (Iblhr). Contemporaneously with the polymer feed to the
extruder,
specified amounts of the monomer, PEG-MA) and free radical initiator (Lupersol
101 }
were added at the feed throat. The extruder had four heating zones set at 170,
180, 180
and 190°C. The screw speed of the extruder was 150 rpm.
For Example 4 the PEG-MA feed rate was 0.125 tb/hr and the initiator rate was
0.0125 Iblhr.
For Example 5 the PEG-MA feed rate was 0.25 Iblhr and the initiator rate was
0.025 Ib/hr.
For Example 6 PEG-MA feed rate was 0.5 Iblhr and the initiator rate was 0.025
Iblhr.
For Example 7 the PEG-MA feed rate was 0.75 Ib/hr and the initiator rate was
0.0375 Ib/hr.
The dry and wet properties of the film produced from the blends in Examples 4-
7
are indicated in Table 3 below.
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TABLE 3
Example #- #4 ~ #6 #7
#5
~
dry wet dry wet dry wet dry wet
Thickness (mil) 4.4 4.4 5.6 5.5 4.2 4.2 4.9 4.6
%Strain 400 70 280 50 590 90 250 50
Peak Stress - (MPa)9.3 3.7 8.3 3.1 9.2 3.5 5.2 1.3
Energy-break (x10 30.61.7 18.1 0.9 46.8 2.0 9.8 0.3
J/m )
Modulus (MPa) 90.141.991.2 32.786.2 38.064.414.5
Loss from Dry to #4 #5 ~ #6 #7
Wet
Strain 83% 83% 85% 81
Peak Stress 60% 63% 62% 75%
Energy-to-Break 94% 95% 96% 97%
Modulus 53% 64% 56% 77%
For Examples 4-7 the amount of monomer grafted to polyethylene was 0.65
weight percent) 1.03 weight percent, 0.51 weight percent and 1.13 weight
percent)
respectively. The weight percent of monomer grafted to the polyethylene was
determined by FT-IR and elemental oxygen content analysis as described in
copending
U.S. patent application 081733,410 filed October 18, 1996. For Example 6 the
amount of
monomer grafted to the polyethylene oxide) was determined to be 9.66 weight
percent
by proton NMR spectroscopy.
In accordance with the invention, Examples 4-7 the water modifiable films were
polymer blends of 60 weight percent of a modified polyethylene and 40 weight
percent a
modified polyethylene oxide) where both the polyethylene and polyethylene
oxide) have
PEG-MA grafted thereto. The films of these polymer blends were water-
modifiable after
30 seconds of submersion in water. A dramatic loss in tensile properties was
observed
for the films from dry to wet.
Examples 8-11
For Examples 8-11, a low density polyethylene) Dow 5031, and polyethylene
oxide) (V1ISRN-80) blend was prepared following the procedure of Example 4
having the
respective resin weight ratios, PEG-MA feed rates and initiator rates
indicated.
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For Example 8 the blend was 65/35 PEIPEO, the PEG-MA feed rate was 0.5 Iblhr
and the initiator rate was 0.025 Ib/hr.
For Example 9 the blend was 70/30 PEIPEO, the PEG-MA feed rate was 0.5 Iblhr
and the initiator rate was 0.025 Iblhr.
For Example 10 the blend was 75125 PEIPEO, the PEG-MA feed rate was 0.5
Iblhr and the initiator rate was 0.025 lb/hr.
For Example 11 the blend was 80/20 PEIPEO, the PEG-MA feed rate was 0.5
Iblhr and the initiator rate was 0.025 Iblhr.
The dry and wet properties of the film produced from the btends in 8-11 are
indicated in Table 4 below.
TABLE 4
Exampte #- #8 #9 #10 #11
~~
dry wet dry wet dry wet dry wet
Thickness (mil) 5.0 4.8 5.0 5.1 4.6 4.4 4.4 5.2
%Strain 340 80 300 130 260 220 180 150
Peak Stress - (MPa)7.5 3.6 10.35.8 11.3 10.5 11.4 11.4
Energy-break (x10 21.1 1.6 23.46.2 22.8 16.2 16.8 14.7
J/m)
Modulus {MPa) 91.1 41.090.955.6 119.972.5 138.480.6
Loss from Dry to #8 #9 #10 #11
Wet
Strain 76% 57% 15% 17%
Peak Stress 52% 44% 7% 0%
Energy-to-Break 92% 74% 29% 13%
Modulus 55% 39% 40% 42%
In accordance with the invention, Examples 8-11 were films from polymer blends
having greater than about 60 weight percent of a modified polyethylene and
less than
about 40 weight percent of a modified polyethylene oxide) where both the
polyethylene
and polyethylene oxide) have PEG-MA grafted thereto. The films of these
polymer
blends was water modifiable after 30 seconds of submersion in water. A loss in
tensile
properties was observed for the films from dry to wet.
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Examples 12-15
For Examples 12-15) a 60/40 weight percent resin blend of low density
polyethylene (Dow 5031} and polyethylene oxide) (V1lSRN-80} was prepared
following the
procedure of Example 4) except the monomer used was 2-hydroxyethyl
methacrylate.
The respective monomer feed rates and initiator rates are indicated.
For Example 12 the 2-hydroxyethyl methacrylate feed rate was 0.125 Iblhr and
the initiator rate was 0.0125 Ib/hr.
For Example 13 the 2-hydroxyethyl methacrytate feed rate was 0.25 Ib/hr and
the
initiator rate was 0.025 Ib/hr.
For Example 14 the 2-hydroxyethyl methacrylate feed rate was 0.5 Ib/hr and the
initiator rate was 0.025 Ib/hr.
For Example 15 the 2-hydroxyethy! methacrylate feed rate was 0.75 lblhr and
the
initiator rate was 0.0375 Ib/hr.
The dry and wet properties of the film produced from the blends in 12-15 are
indicated in Table 5 below.
TABLE 5
Example #- #12 #13 #14 #15
dry wet dry wet dry wet dry wet
Thickness (mil) 4.5 4.6 4.2 4.7 4.5 4.5 5.0 4.6
%Strain 350 50 390 40 420 40 350 30
Peak Stress - (MPa)13.33.3 9.0 1.5 10.32.4 8.7 1.9
Energy-break (x10' 33.30.8726.7 0.3632.70.51 23.60.37
J/m)
Modulus (MPa) 107 38.8126 18.499.628.7 109 23.2
Loss from Dry to #12 #13 #14 #15
Wet
Strain 86% 90% 90% 91
Peak Stress 75% 83% 77% 78%
Energy-to-Break 97% 99% 98% 98%
Modulus 64% 85% 71 % 79%
In accordance with this invention) Examples 12-15 were films of polymer blends
having 60 weight percent of a modified polyethylene and 40 weight percent of a
modified
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WO 98129502 PCT/US97J23810
polyethylene oxide) where both the polyethylene and polyethylene oxide) have 2-
hydroxyethyl methacrylate grafted thereto. The dims of these polymer blends
was water-
modifiabte after 30 seconds of submersion in water.
Example 16
a
For Examples 16, a Wemer & Pfleiderer ZSK-30 extruder (available from Wemer
& Pfleiderer, Ramsey, New Jersey) was used. The extruder had a pair of co-
rotating
screws arranged in parallel. The center distance between the two shafts was
26.2 mm.
The nominal screw diameter was 30 mm. The actual outer screw diameter was 30
mm.
The inner screw diameter was 21.3 mm. The thread depth was 4.7 mm. The
extruder
had 14 processing barrels, with 13 heated ban-els divided into 7 heating
zones. The
overall processing length was 1340 mm.
A 60140 weight percent resin. blend of low density polyethylene (Dow 5031) and
poly(ethytene oxide) having a molecular weight of 100,000 g/mol (POLYOX~ WSRN-
10)
was fed to the ZSK-30 extruder at a rate of 35 Iblhr. The seven heating zones
were all
set at 180 degrees C. The screw speed was 300 rpm.
The dry and wet properties of the film produced from the blend in Example 16
are
indicated in Table 6 below.
TABLE 6
Example #- #16
dry wet
Thickness (mil) 3.2 3.2
~Strain 430 60
Peak Stress - (MPa)11.3 3.6
Energy-break (x10 39.5 1.6
Jlm')
Modulus (MPa) 160 45.3
Loss from Dry to #16
Wet
Strain 86%
' Peak Stress 680
Energy-to-Break 96%
Modulus 72%
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WO 98/29502 PCTIUS97123810
In accordance with the invention, Example 16 was a film of a polymer blend of
60
weight percent of an unmodified polyethylene and 40 weight percent an
unmodified
polyethylene oxide). The film of this polymer blend was water modifiable after
30
seconds of submersion in water.
Examples 17-18
For Examples 17-18, a 60140 weight percent resin blend of low density
polyethylene (Dow 5031) and polyethylene oxide) having a molecular weight of
200,000
glmol (POLYOX~ WSRN-80) was fed to a ZSK-30 extruder as described in Examples
16
at a rate of 34 Ib/hr. The seven heating zones were all set at 180 degrees C.
The screw
speed was 300 rpm. At barrel 4, the monomer (PEG-MA) was added at the
specified
rate. At barrel 5, the free radical initiator (Lupersol 101 ) was added at the
specified rate.
For Example 17, the PEG-MA feed rate was 1.02 Ib/hr and the initiator rate was
0.068 Ib/hr.
For Example 18, the PEG-MA feed rate was 3.06 Ib/hr and the initiator rate was
0.17 Ib/hr.
The dry and wet properties of the film produced from the blends in Examples 17-
18 are indicated in Table 7 below.
TABLE 7
Example #- #17 #18
dry wet dry wet
Thickness (mil) 3.0 4.1 4.2 4.8
%Strain 420 60 310 60
Peak Stress - (MPa)9.4 1.0 9.1 1.0
Energy-break (x10 33.9 0.44 24.5 0.37
JIm3)
Modulus (MPa) 85.1 18.6 86.5 25.8
Loss from Dry to #17 #,18
Wet
Strain 86% 81
Peak Stress 89% 89%
Energy-to-Break 990 98%
Modulus 78% 70%
16 .
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WO 98129502 PCTIUS97123810
In accordance with the invention, Examples 17-18 were films of polymer blends
with 60 weight percent of a modified polyethylene and 40 weight percent of a
modified
polyethylene oxide) where both polyethylene and polyethylene oxide) have PEG-
MA
grafted thereto. The films of these polymer blends was water modifiable after
30
seconds of submersion in water.
While the invention has been described with reference to the preferred
embodiments and illustrated with regard to a range of optional features, those
skilled in
the art will appreciate that various substitutions, omissions, changes and
modifications
may be made without departing from the spirit of the invention. Accordingly,
it is intended
that the foregoing description be deemed merely exemplary of the preferred
scope of the
present invention and not be deemed a limitation thereof.
17
