Note: Descriptions are shown in the official language in which they were submitted.
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METHOD OF PROCESSING POLYETHYLENE AND
POLYETHYLENE/ELA.STOMER BLENDS
BACKGROUND
Linear polyolefins as well as linear polyethylene blends with elastomers, in
particular, linear polyethylenes and/or elast:omer blends, may be dii~cult to
melt
process. Specifically, due to a low shear sensitivity when compared to highly
branched polyethylenes, the linear polyethylenes and/or elastomer blends can
require more extruder power to pump an equivalent amount of polymer melt. The
1o presence of the elastomer does not necessarily improve the processability
of linear
polyethylenes. As a result, higher extruder head pressures, higher torque,
greater
motor loads, and the like can develop, as compared to the highly branched
materials.
Increases such as higher motor load, head pressure and/or torque can place
undesirable, unacceptable, or unattainable requirements on specific machinery.
As
for instance, a specific extruder having a specific motor power and gearing,
will
reach a maximum of motor load, or head pressure, under certain melt
temperature
conditions for a given polymer being proce sed. If a polymer or polymer blend
is
introduced to such an extruder which has such a higher requirement for power
in at
least one component, such as a polymer having higher molecular weight and/or
narrower molecular weight distribution and,~or lower shear sensitivity, the
extruder
will reach a maximum of one or several of these parameters, and be therefore
limited in its ability to pump/perform at a similar level to the performance
expected/demonstrated with a highly branched or broader molecular weight
distribution polymer such as traditional high pressure low density
polyethylenes. In
the alternative, if melt processing machinery is to be used for certain
production/extrusion, and it is not so limited, the prospect of using more
power or
increasing head pressure for a more difficult to extrude material, while
achievable,
the user of the machinery would prefer to conserve power.
3o Additionally, linear polyethylenes and elastomeric blends thereof may
exhibit other imperfections during extrusion, specifically blown film
extrusion, that
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may be undesirable, such as melt fracture. These imperfections are undesirable
from a quality standpoint. For instance, melt fracture, also known as "shark
skin"
or "orange peel", can lead to poorer optical properties and/or diminished film
physical properties that are generally unacceptable.
The introduction of linear Ziegler-Natta catalyzed polyethyienes in the late
'70s and early '80s and extruder owner's attempts to use these poiyethylenes
in
machines that had been previously used to extrude free radical initiated,
highly
branched, high pressure produced low density polyethylenes provided the early
manifestations of these problems. The advent of metallocene catalyzed linear
1o polyethylenes in the '90s, has continued the trend towards polymers that
when
fabricated into for instance films, offer for example, better physical
properties
and/or manufacturing economics, but have higher power requirements and/or
greater tendency to exhibit melt fracture in the blown film process.
Linear polyethylenes therefore have been the subject of a good deal of
effort to eliminate or reduce such problems. Some of the attempts included
regearing extruders, designing new and more efficient screws and dies,
increasing
the power train, addition of expensive fluoroelastomeric processing aids and
the
like. In nearly every instance, the cost involved has not been
inconsequential, as
well as the inconvenience. But such costs have been born, due to the
desirability of
2o physical properties and/or downgaging possible with the linear
polyethylenes.
GB 1,104,662 suggests addition of the salt of alkyl benzene sulfonic acids
to polyolefins that purportedly gives a beneficial effect on melt extrusion
behavior
of the polyolefin. The purported effect is the reduction of the occurrence of
"shark
skin" or "orange peel". Both alkali and alkaline earth metal salts of alkyl
benzene
sulfonic acids are purported to be effective. The document is devoid of any
identification of the polyethylene, such as molecular weight distribution
(MWD), or
composition distribution breadth index (CDBI).
GB 1,078,738 suggests that addition of an "external lubricant" to high
molecular weight polyolefins can, purportedly, reduce occurrence of melt
fracture.
3o Suggested as external lubricants are salts of monovalent to tetravalent
metals, and
saturated or unsaturated carboxylic acids containing IO to 50 carbon atoms.
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Sulfonates corresponding to the fatty acid salts are also said to be suitable.
However, stearates, palmitates and oleates are exemplified. This document
indicates an equivalence of metal salts of mono to tetra-valent metals.
JP A 59-176339 suggests that when polyolefins are narrowed in MWD or
given higher molecular weight, poor fluidit~r results which in turn gives rise
to melt
fracture. The solution suggested is addition of fluorinated compounds
including
potassium salts of fluoroalkylsulfonic acids. These potassium salts are said
to
exhibit preferable temperature dependence when compared to other cations such
as
sodium, calcium, lithium and ammonium. The polyolefin/salt combination is said
to
to be effective at 230° C or higher.
DE 2823507 suggests molding or calendered objects of ethylene polymers
and propylene polymers containing alkalai or alkaline earth mono sulfonates
from
the group alkyl sulfonates, alkenyl sulfonate;s, alkylaryl sulfonates and
succinic acid
dialkyl ester sulfonates. Sodium or calcium mono sulfonates are preferred. A
suggested benefit is purported to be outstanding separation of the polymer
from
calendering rolls.
JP 58-212429 (60-106846) suggest, polyethylene compositions consisting
of 70-95 weight parts of ethylene homopolymer or ethylene alpha-olefin
copolymer
with a density of at least 0.94 g/cm3; 5-30 weight parts of at least one of
low
2o density polyethylene (high pressure), ethylene vinyl acetate, ionomer, and
ethylene
alpha-olefin copolymer (density not exceeding 0.935 g/cm3); 0.01-5 weight
parts of
magnesium salt or calcium salt of alkylsull:onic acid or alkylbenzenesulfonic
acid;
and 0.05-0.5 weight parts of at least one substance selected from the group
which
includes dibenzylidene sorbitol or its nuclear substituted derivative. The
combination is said to be especially useful in air-cooled inflation film.
US 4,829,116 suggests polyolefin molding compositions purportedly
having no surface defects that includes a fluorine-containing polymer together
with
a wax, preferred polyolefins are said to be ethylene copolymers with 1-olefins
which contains 3-10 carbon atoms. The fluorine containing compounds are
3o preferably copolymers of vinylidene fluoride and hexafluoropropylene or
terpolymers of these monomers with tetra fluoroethylene. Among the suitable
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waxes enu nerated are alkylsulfates or alkyl sulfonates containing straight
chain or
branched ('$ to CZa alkyl radicals and an allt:alai metal ion, preferably a
sodium ion.
Th~;re is a need therefore for a relatively inexpensive, easily implemented
solution tc the processing problems outlined above. Such a solution should
also
include a material that when included in blown film extrusion of linear
polyethyle yes andlor linear polyethylene-elastorner blends, will readily melt
or
incorporate into the melted polyethylene, and not adversely affect physical
properties not be e;ctractable, or negatively impact organoleptics of the
film.
Specifical! ~r, there is a commercial need for a material that may be eaaily
1.o incorpora~. ~ into po!yethylenes and polyethylene elastomer blends, that
will reduce
or elintina to the increased power requirement (e.g. motor load and cr
torque),
increased '.lead pressure, and melt fracture.
St'MM_~ 2Y
'T'1 a present invention is directed to such a material, a certain group of
i5 surfactant s, and methods of their use which when incorporated into a
linear
polyethyl~:.ne or linear polyethylene elastomer blends, can reduce or
eliminate
proeessin; problems such as melt fracture, increased motor load, increased
torque,
and comt~'nations thereof and may thereby iincrease potential production
rates.
Ire certain embodiments of the present invention a method of processing
zo polyethyl~:nes comprising selecting a lines~r polyethylene, from a group
such as
linear loo r density polyethylene (LLDPE), metallocene LLDPE (mLLDPE), high
density p~~lyethylene (HDPE), plastomers, ultra high molecular weight high
density
polyethyl:ne (1;J~F~MW-APE), medium density polyethylenes (MDPE), or
combinations thereof, adding an elastomer~ selected from the group consisting
of
z5 styrene t~.rtadiene styrene (SBS); styrene isoprene styrene (STS); styrene
ethylene
butadiene: styrene (SEBS); styrene ethylene propylene styrene (SEPS); and
combina~ :ans thereof and adding a surfactant. The surfactant being an
aliphatic
sulfonatE~ salt having a cation selected from the group wnsisting of Na, I~,
and Li.
An amo~.~nt of the surfactant should be added that will be sufficient to
improve the
30 melt prc cessability of the polyethylene or polyethylenelelastomer blend.
'The
combinan ion of polyethylenes and
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surfactant or surfactants and optionally an ela~.stomer or elastomers is then
used to
melt proce ~s the combination into a useful article, such as a film. blow
molded part,
and the lik ~.
Th ~ polyethylenes may be conventional Ziegler-Natta (Z-;~ catalyzed
materials ! oat generally have a molecular weight distribution characterized
by the
ratio of w~;ight average molecular weight to the number average molecular
weight
(bi""lM~ , bove about 4, or the polyethylenes may be metallocene catalyzed,
and
will then 1~ 3ve an approximate M"J~f~, of less than 3, preferably less than
2. ~, and a
z-average :molecular weight (M~ divided by R~i", (M~l~l~tW) not exceeding 2.
l0 Al ~o contemplated are compositions of a polyethylene having an Mw~:~in
less than ., and optionally an elastomer or elastomers and an alkali metal
alkyl
sulfonate -~r sulfate wherein the alkyl group has 6-30 carbon atoms. where the
surfactant is present in the polyethylene or polyethylene elastomer blend in a
range
of from 0.')05 to 1 weight percent based on the total weight of the
polyethylene or
is blend. TI'S a surfactant should ideally be substantially non-extractable
from the final
fabricated article.
'TW~se and other features, aspects, and advantages of the present invention
will beca; ne better understood with reference to the following description
and
appended rlaima.
2o DESCRI;'Tr~N
In certain embodiments of the present invention, methods of and
compositi.ms far reducing or eliminating; a) melt fracture; b) torque; c}
increased
head pre:~sure; d) increased motor load, e) combinations thereof, and the
like,
during the; melt processing of polyethyienes, polyethylene elastomer blends
and
25 other pol'. olefins are contemplated. These ernbodiments include both
corwentional
Z-N ancG metallocene catalyzed polyet;hylenes(the latter hereinafter "m-
polyethylc nes), and their combination with certain surfactants and optionally
an
elastomer that when so combined achieve the stated melt processing
improvestuents. The combination of polyethylenes and surfactants are
particularly
3o well suite 3 to melt processing and fabrication. into films, especially
blown films,
blow mol:ed articles, and the like, while reducing or eliminating one or more
of the
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processability problems discussed above and generally without being
extractable
from the final fabricated article.
Following is a detailed description of certain preferred combinations of
polyethylenes and surfactants and optionally an elastomer and methods of using
the
combinations in melt processing into useful articles. Those skilled in the art
will
appreciate that numerous modifications to these preferred embodiments can be
made without departing from the scope of the invention. For example: Although
methods of improving melt processing of m-polyethylenes or m-polyethylene
elastomer blends into films are exemplified, they will have numerous other
uses and
to the films may be formed from other polyolefins or combinations of
polyethylenes.
To the extent this description is specific, it is solely for the purpose of
illustrating
preferred embodiments of the invention and should not be taken as limiting the
present invention to these specific embodiments.
DEFIhTITIONS
torque - horse power/rpm
motor load - amps
head pressure - Kpa (psi)
The Encyclopedia of Polymer Science and Technology, Vol. 8, John Wiley
& Sons, (1968) pp. 573-575 indicates that for a given polymer, processed at a
2o constant melt temperature, there exists a critical shear rate in the melt
fabrication
process. Melt processing of the polymer below this critical shear rate will
result in
a smooth extrudate surface while processing the polymer above it will result
in a
rough extrudate surface. The observed roughness is commonly referred to as
"melt
fracture" but may also be described by other terms such as "sharkskin" or
"orange
peel". For a given polymer, the critical shear rate increases as the melt
processing
temperature of the polymer increases.
The extent of extrudate roughness will vary depending upon the shear rate
at which the polymer is processed. At shear rates just above the critical
value, the
extrudate roughness normally results in a loss of surface gloss and is
typically
called "sharkskin". At higher shear rates, the extrudate exhibits periodic
areas of
roughness followed by areas of smoothness in a more or less regular pattern.
This
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phenomenon is normally described as "cycl.ic melt fracture". At very high
shear
rates, the extrudate may become grossly distorted resulting in a what is
commonly
called "continuous melt fracture".
In general, linear polyethylenes, particularly those with high average
molecular weights and/or narrow molecular weight distributions, tend to be
more
prone to the formation of melt fracture than highly branched polyethyienes,
such as
conventional LDPE made by high pressure polymerization.
The presence of melt fracture in a fabricated article can lead to poorer
optical properties and is generally aesthetically unacceptable. Attempts to
to eliminate melt fracture in articles fabricated from linear polyethylenes by
either
reducing the processing shear rate (reduced production rate) or by increasing
the
processing temperature (increased melt temperature) are generally not
commercially viable. In addition, changes in die design to reduce the shear
rate
(e.g., use of wider die gaps) can result in other problems such as excessive
orientation leading to unbalanced article properties. Although
fluoroelastomeric
processing additives have been used to eliminate sharkskin in linear
polyethylenes
under certain processing conditions, their u:>e is expensive due to the high
cost of
the fluoroelastomer.
2o POLYETHYLENES
The polyethylenes contemplated in certain embodiments of the present
invention, include ethylene alpha-olefin copolymers. By copolymers we intend
combinations of ethylene and one or more. alpha-olefins. In general the alpha-
olefins comonomers can be selected from those having 3 to 20 carbon atoms.
Specifically the combinations may include ethylene 1-butene; ethylene 1-
pentene;
ethylene 4-methyl-I-pentene; ethylene 1-hexene; ethylene 1-octene; ethylene
decene; ethylene dodecene; ethylene, 1-but.ene, 1-hexene; ethylene, 1-butene,
I-
pentene; ethylene, I-butene, 4-methyl-1-p~entene; ethylene, 1-butene, 1-
octene;
ethylene, 1-hexene, 1-pentene; ethylene, 1-hexene, 4-methyl-1-pentene;
ethylene,
1-hexene, 1-octene; ethylene, I-hexene, decene; ethylene, I-hexene, dodecene;
ethylene, propylene, I-octene; ethylene, 1-octene, I-butene; ethylene, I-
octene, 1-
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pentene; ethylene, 1-octene, 4-methyl-1-pentene; ethylene, 1-octene, 1-hexene;
ethylene, 1-octene, decene; ethylene, 1-octene, dodecene; combinations
thereof,
and the like permutations. The comonomer or comonomers will be present in the
copolymers in the range of from about 0.1 to about 40 mole percent. The actual
amount of comonomers will generally define the density range.
Density ranges contemplated to be useful include 0.86-0.97 g/cc and all
portions and constituents of the range. Specifically included are the 0.86 -
0.91 S
g/cc (plastomers) 0.916-0.925 (LLDPE), 0.926-0.940 (MDPE), and 0.941-0.970
(HDPE). Melt indices contemplated include 0.001-30, preferably 0.5 to 5.0 for
to blown films, and 0.3-10 for blow molding, and all members of these ranges
(melt
index in dg/min or g/10 minutes).
Polyethylenes that are produced using metallocene catalysts include
ionizing activators as well as alumoxanes.
Included in the embodiments contemplated are those where either m
polyethylenes and Z-N polyethylenes may be blended with each other and/or with
other components such as LDPE, (highly branched, high pressure free radical
polymerized) and other ethylene copolymers such as ethylene vinyl acetate
(EVA),
ethylene n-butyl acrylate (EnBA), ethylene methyl acrylate (EMA}, ethylene
ethyl
acrylate (EEA), ethylene acrylic acid (EAA), ethylene methacrylic acid (EMAA),
2o and ionomers of the acids, terpolymers such as ethylene, vinyl acetate
methyl
acrylate; ethylene, methyl acylate, acrylic acid; ethylene, ethyl acrylate,
acrylic acid;
ethylene, methyl acrylate, methacrylic acid; ethylene, methylacrylate,
methacrylic
acid; and the like.
The polyethylene eiastomer combinations described above, in combination
with the surfactants described below, will be substantially free of propylene
polymers such as polypropylene homopolymers and copolymers. By substantially
free we intend that Less than 5 wt. % of the total polymer will be a propylene
based
polymer, preferably less than 3%, more preferably less than 1%, most
preferably to
totally free of propylene polymers.
3o Also contemplated are mufti-layer blown film extrusions where one or more
of the layers can include a polyethylene/surfactant or
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polyethylec:elelastomersJsurfaetant combination, Such e~ctrusion may inci,rde
a
linear poh~ethylene layer, a heat seal layer, a barrier (gas atidlor vapor)
layer,
rxycle or regind layer or combinations thera~of.
So~~ne of these blend components may affect processing variables in a
s po3itive n~anner, in which case the inven~rion contemplated will include
some
portion of the below discussed surfactants, possibly less than with an
unblended
material.
laic ~st polyethylenes will contain various additives well itnow~n to those of
ordinary s'~:ill in the art, including, but not luruted to slip, anti-block,
anti-oxidants,
~o anti-fogs, acid neutralizers, UV inhibitor.., anti-static agents, pigments,
dyes,
release ag~:mts, fungicides, algecides, bactericides, and the like.
As used in this application, the processing temperature of pr~lyethy~lene in
the blown r~lm process wi31 generally he in the range of 300 - 450° F
(149-232° C),
preferably 35G - 410° C (177-210° C), a point generally above
the melting point of
1s the poly~tliylene and below its degradation ~~r decomposition temperatu:e.
This is
generally the temperature of the melt exiting the die, but may be measured at
any
point doa nstream of the screw elements. The processing temperature will be
understood.' by those of ordinary skill to ~~ary generally by the melt
fabrication
technique, and within a fabrication technique, processing temperature can vary
by
2o the type ~:.:.f processing equipment, or by specific requirements of a
particular
manufactu rer.
SL'RFAC'~~.'ANTS
Tt~ a surfactants contemplated include aliphatic sulfonate salts where the
canon is o~~e of. Li, Na, K Sodium salts being preferred. The surfactants may
also
~5 be describ~;d as alkali metal aliphatic sulfonates where the aliphate group
is a C6 to
C30 alkyl group, preferably C8 to C20, more preferably C12 to C18, The alkyl
group mail be chosen from the group consisting of branched or straight chain
alkenyl, bwanched or straight chain hydroxyl substituted alkyl, and
combinations
thereof ~freferred are combinations of branched or straight chain alkenyls and
3a branched ~ rr straight chain
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hydroxyl s ~bstituted alkyf alkalai metal sulfates or sulfonates, of these the
scdiurrt
combinarc n is most preferred.
On . class of surfactants that arc preferred in this application are a-olefin
suL°onates. As stated in the Kirk-C~thmer Encyclopedia of Chemical T
achnology,
5 Vol. 2?, J~ ~hn W'iley & Sons, (1983), pg. 35:?, a-olefin sulfonates are
produced by
reaction o ' a-oleixn with S03 in air followed by neutralization with a base
to
produce t!1e corresponding salt. The sodium salts are the mast preferred.
Commerci.3 ct-olefin sulfonates are a mi~rnare of alkene suifonates and
hydroxy
allcane sulf mates. The position of the double bond in alkene sulfonates as
well as
to the hydrox v1 group in hydraxy alkane sulfonates varies along the carbon
chain of
the alkyl ~ oup.
Mr-e detailed description of the surfa.otants follows.
Thn surfactant includes those, of the c;eneral formulae:
I,) ~R~ SO~~vh
Ml is selected from the group consisting of~
Li, Na, K,
R1 is selected from the group consisting of
branched or straight chain mono or dl unsaturated alkenyl,
branchad or straight chain hydroxyl substituted alkyl, and
combinations thereof,
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~ ~~herein the carbon number of said R1, ranges from 6 to 30; and
~ herein said surfactant is present in mid combination in a range of up
t ~ 1.0 weight percert, preferably 0,005 to 1.0 weight percent, more
preferably O.OI to 0.5, most preferably 0.03 to 0 35 weight percent
brsed on the total weight of the cornbination.
Or a ~~urfactant represented by one of the formulae:
IL) ~R SO~~M
M1 is selected from the group consisting of
Li, Na, K, and other rations.
R1 is selected from the group consisting of:
branched or straight chain mono or dl unsaturated alkenyl;
branched or straight chain hydroxyl substituted alkyl, arid
combinations thereof,
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12
~Nherein said surfactant is present in said combination up to 1.0 weight
percent, preferably in a range of 0.005 to 1.0 weight percent. more
;preferably 0.01 to 0.5, most pre:Ferably 0.03 to 0.35 weight percent
Sased on the total weight of the combination.
The surfactant or surfactants should he substantially or essentially free of
halogens. By substantially or essentially free of halogens we intend that the
surfactant n olecules will have preferably no h;rlogen.
The surfactants comtemplated, whether a mixture or a single surfactant
should have a melting point less than 240° C. preferably 23a°
C., more preferably
to 220° C., me ~~t preferably 2I0° C.
The surfactants may be present in the polyethylene combination up to 1.0
weight pere~.nt, in the range of from 0.05-1.C~ weight percent, preferably
0.01-0.5,
more prefer ~~bly 0.03- 0.35 weight percent (including all elements in these
ranges}
based on th~:~ total weight of the combination. The amount and type of
surfactant
is present will ietermine the effect on the melt processing characteristics,
for instance
as shown be i ow, smaller amounts at about 0. 3 5 wt% ox below preferably
0.25°~0,
more prefer ably 0.10 wt%, or below, will primarily function to reduce melt
fracture, whi.!e amourrts above that level, up to the indicated higher levels
will begin
to also redm. a head pressures, torque, motor load or combinations thereof.
While
dfl greater amo~..nts than the 0.5 levels may be used, adverse extrusion
effects may
result such a ~ grew slippage.
Thos: of ordinary skill will appreciate ':hat at higher levels, generally
above
0.1 weight percent, the surfactant or a combination of surfactants will be
ei~'ective
in reducing c' of only melt fracture, but motor Ioad, torque, head pressure
and the
2s like by at leant 5% for one or more ef these variables. Generally at lower
levels
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than 0.1 weight percent the reductions of these motor load, torque and head
pressure parameters will be less, but the :surfactants will be effective in
reducing
melt fracture.
The mechanism of melt fracture reduction is believed to involve the
s formation of a layer of surfactant on the internal metal surfaces of key
components
of the melt processing equipment. This layer effectively increases the
velocity of
molten polymer at the metal interface 'thereby minimizing the polymer flow
distortions that occur as the molten polyn:~er exits the melt processing
equipment
which typically results in melt fracture. The use of a relatively high
concentration
to of surfactant, e.g. 0.5 weight percent, will generally result in a faster
rate of metal
surface coating and, therefore, a more rapid rate of reduction in melt
fracture of the
final fabricated article. At lower surfactant levels, the metal surface
coating rate,
and the corresponding melt fracture reduction rate, will be slower.
It should be noted that when discussing the weight percent of surfactant,
1s we intend that this be based on the total weight of the surfactant and
polyethylene
(or polyethylene blend). If other constituents are included the amount of
surfactant
should be then calculated on a parts per hundred parts of polyethylene basis.
Likewise if a blend constituent (with the linear m-polyethylene) assists in
improving
processability, then the contemplated arr~ount of surfactant will be that
level
2o sufficient to achieve the intended effect, e.g. reduction of one or more of
melt
fracture,. motor load, torque, or head pressure.
For example, blends of one or more of the above surfactants may be used
to achieve the desired results, as well as combinations of polyolefin waxes
and/or
fluoroelastomers and/or fluoropolymers with one or more surfactants. For
instance
2s one or more of the surfactants listed above may be combined with a
polyethylene
wax in ratios from 10-90 and 90-10 and all elements in and between these
ranges,
and a similar combination with fluoroelastomers and/or fluoropolymers is also
contemplated, as well as surfactant/polyethylene wax/fluoroelastomer
combinations.
3o If the polyethylene composition o:r the film made therefrom contain the
optional elastomer or elastomers, the thermoplastic elastomeric films of
certain
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embodiments of the present invention comprise a blend of at least two
copolymers.
One copolymer is an elastomeric block copolymer containing blocks of a
monoalkenyl arene copolymer and a conjugated diene polymer. The second
component is selected from a group of highly amorphous thermoplastic ethylene
copolymers having the primary characteristic of low crystallinity and low
density
(such as m-plastomers and/or m-LLDPE). Optional ingredients which may also be
included in the polymer blends of the present invention include small amounts
of
conventional anti-block concentrates and slip agents, as well as antioxidants
and
stabilizers.
1o THE ELASTOMERIC BLOCK COPOLYMER
The elastomeric block copolymers contemplated for use herein are known
materials having blocks of monoalkenyl arene polymer and blocks of conjugated
diene polymer. The polymer blocks have the general configuration:
A-B-A
and are arranged such that there are at least two monoalkenyl arene polymer
end
blocks A and at a least one elastomeric conjugated dime mid block B. These
polymer blocks may optionally be hydrogenated to eliminate the unsaturation in
the
mid block B. The monoalkenyl arene copolymer blocks comprise from 8% to
about 55% by weight of the block copolymer. The molecular weight of the block
copolymer is such that its melt index is less than about 100 as determined by
ASTM Method D 1238 entitled "Standard Test Method for Flow Rates of
Thermoplastics by Extrusion Plastomer" Condition E.
The term "monoalkenyl arene" includes those particular compounds of the
benzene series such as styrene and its analogues and homologues including o-
methyl styrene and p-methyl styrene, p-tent-butyl styrene, 1,3 dimethyl
styrene, p
methyl styrene in other ring aikylated styrenes, particularly ring methylated
styrenes, and other monoaikenyl polycyciic aromatic compounds such as vinyl
naphthalene, vinyl anthrycene and the like. For the present invention, the
preferred
monoalkenyl arenes are monovinyl, monocyclic arenes such as styrene and p
methyl styrene, styrene being particularly preferred.
CA 02259529 2003-10-27
It is important to embodiments of present invention that the amount of
monoalkenyl scene not exceed an amount of 55%, nor comprise an amount less
than 8% by weight of the copolymer. Preferred amounts of monoalkenyl scene in
the block copolymer are from 25% to 35%. Optionally, the monoalkenyl scene
will
s , be in an amount of about 30%. If a monoalkenyl scene is used in excess of
55
weight percent, the block copolymer is too stiff for the instant blends. The
elastomeric block copolymers are optionally "oil extended" which is the
addition of
a hydrocarbon oil and allows for improved processability and soRer films. The
oils
are optionally added to the commercial elastomeric copolymers in amounts of
10 between 10% t0 40%.
The block B comprises homopoiymers of conjugated diene monomers,
copolymers of two or more conjugated dienes, and copolymers of one or more of
the dienes with a monoalkenyl scene as long as the blocks B are predominantly
conjugated diene units. The conjugated dienes preferably used herein contain
from
15 4 to 8 carbon atoms. Examples of such suitably conjugated diene monomers
include: 1,3 butadiene (butadiene); 2-methyl-1,3 butadiene; isoprene; 2,3
dimethyl-
1,3 butadiene; 1,3 pentadiene (piperylene); 1,3 hexadiene; combinations
thereof,
and the like. Hydrogenation of the unsaturated elastomer (Block B) results in
a
saturated tri-block copolymer (A-B-A).
2o For the instant films, the preferred monoalkenyl scene polymer is
polystyrene; and the preferred conjugated diene polymers are polybutadiene and
polyisoprene, especially preferred being polybutadiene. The preferred
elastomeric
block copolymers are commercially available as linear tri-block copolymers (A-
B-
A) from the Shell Chemical Company, Polymers Division, Houston, Texas, under
the trade name KRATON and from Dexco Polymers of Houston, Texas, under the
family trademark VECTOR. Especially preferred are the linear tri-block
copolymers having polystyrene end blocks and a polybutadiene mid-block (S-B-
S).
Most commercially preferred are oil extended polymers such as ICRATON D 2104
having a melt index of about 7 as determined by ASTM Method D 1238, Condition
E and VECTOR 7400D, having a melt index of about 8.
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16
The thermoplastic elastomeric films of the present invention may contain
from about 20%-70% by weight of the elastomeric block copolymer; preferably
from about 45%-65%; especially preferred being from about 50%-65% based on
the total weight of polyethylene, and elastomer. The percentages herein are
based
on the total weight of the elastomeric film composition. As indicated,
commercial
grades of elastomeric block copolymers can be oil extended and the oil portion
is
not calculated as part of the percentage herein. To firrther enumerate the
elastomer, linear polyethylene (m-plastomer and/or m-LLDPE) the two parts
(polyethylene/elastomer) can be present in a ratio of 1:4-2:1; preferably 1:2-
2:1.
1o The thermoplastic eiastomeric films of the present invention may be used in
a wide variety of applications where thin, elastic material would be useful.
Such
films are particularly useful as low cost elastic members for disposable
wearing
apparel such as diapers; training pants, feminine hygiene devices, medical
gowns,
gathered laminate garments, non-woven head bands, sports apparel, bandages and
protective clothing.
FILM PROPERTIES
Other final product variables or parameters that are included are discussed
below.
The addition of suffcient levels of surfactant to a polyethylene should
2o generally be "property neutral" that is, the surfactant addition should not
substantially diminish any important finished product property such as haze,
impact
resistance, gloss, tear resistance, modulus, and the like.
The surfactant should have a melting point not generally greater than
30°
C, preferably 25° C, more preferably 20° C, most preferably
15° C above the
processing temperature of the linear polyethylene. The surfactant is generally
and
preferably molten at the processing temperature of the polyethylene. The
processing temperature will be well understood by those of ordinary skill in
the art
and will diffier by melt fabrication technique, e.g. blown film and blow
molding
temperatures will vary. Also the melt processing temperature can be
characterized
3o by the melt temperature itself rather than the extruder zone temperatures.
CA 02259529 2003-10-27
17
EXTR.ACTABILITY
Extractability of the surfactant from the polyethylene-surfactant matrix
should be no more than 7% (wt) of the total surfactant in either water (at
100° C
for 3 hrs.) or 95°/JS% ethanoUwater (at 55° C for 4 hrs.),
preferably not more than
3 5% (wt.), more preferably not more than 4% (wt.), all based on not more than
3
wt. % of surfactant in the polyethylene.
EXAMPLES
E~cam 1R a 1
An antioxidant stabilized metallocene catalyzed linear low density
to polyethylene resin (m-LLDPE), Exceed''" ECD 102 of the following nominal
properties (a 1 melt index, 0.917 gm/cc density, ethylene 1-hexene copolymer
available from Exxon Chemical Co., Houston, TX, USA), is used in this example.
To the ganular m-LLDPE resin (Example 1 ) is added 0.25 wt% BioTerge~ AS-
90B Beads (a sodium C 14-C 16 ~Pha olefin sulfonate available from Stepan Co.,
15 Northfield, IL, USA). A control sample (Comparative example C 1 ) is
prepared by
adding 0.08 wt% Dynamar'''~ FX-9613 (a fluoroelastomeric processing aid
available from 3M Co., St. Paul, MN, USA) to a separate portion of the ganular
m-LLDPE resin. Both portions are compounded and pelletized on a Werner
Pfleiderei twin screw extruder.
2o The two pelletized formulations are extruded into film on a 2.5 inch (6.35
cm) Egari tubular blown film extnader. The extruder has a 24/1 length/diameter
ratio, Sterlex~ barrier LLDPE screw and is equipped with a 6 inch (15.25 cm)
diameter annular die with a 0.030 inch (0.076 cm) die gap. The temperature
profile used ranged from 325 to 410°F ( 162-210° C). Observed
melt temperatures
25 ranged from 432 to 438°F (222-225° C). Extruder screw rpm is
set to achieve
approximately 120 lbs (54.5 kg)/hr of polymer output. Under these conditions,
the
estimated shear rate is approximately 430 sec' 1. The extruded film gauge was
nominally 0.0015 inch (38 microns) with a layflat of approximately 24 inches
(61
cm).
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18
The extrusion sequence for each formulation is as follows. The film line is
purged with an LDPE masterbatch containing approximately 4 wt% diatomaceous
earth antiblock (A1 product from Exxon Chemical Co., Houston, TX, USA).
Next, a portion of the m-LLDPE resin, to which no BioTerge~ AS-90B or
DynamarTM FX-9613 is added, is extruded into film. Samples of the film are
inspected to ensure complete melt fracture. Finally, the test formulation is
extruded into film. Periodic samples of the film are taken and the portions
which
display visible melt fracture, characterized by patterns of irregular flow
known as
sharkskin, are measured in the transverse direction of the film. The % melt
fracture
to is calculated based upon the total layflat width of the film.
The data in Table 1 demonstrates that 0.25 wt% BioTerge~ AS-90B used
in Example 1 substantially eliminates melt fracture in the m-LLDPE film. The
elapsed time for this substantial elimination of melt fracture is nearly the
same
amount of time needed for 0.08 wt% DynamarTM FX-9613 (Comparative example
CI) to eliminate melt fracture. At the end of each run, the extruder rpm is
increased until the motor load limit is reached (93 rpm) and melt fracture-
free film
is maintained for each formulation (680 sec-1 ). A sample with neither FX-9613
nor AS-90B never achieves melt fracture free performances.
This is as expected since extrusion shear under these conditions results in a
rate above the critical shear rate for this m-LLDPE. In the absence of the
surfactant or fluoroelastomer, this will cause melt fracture in the resulting
film.
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WO 98/05711 PCT/US97113856
19
Table 1
Melt Fracture
Elapsed Example Example 1
Time C 1 (w/ 0.25 wt%
(w/ 0.08 AS-90B
wt%
FX-9613
min
0 100 100
94 ---
67 96
7 19
1 I
0 ---
_ 0
=__ ,
5 Table 1A
Example OutputAS-90B FX-961:3Head Die Motor
(lb./hr)Conc. Conc. Pressure PressureLoad
wt%) (wt% si ) si am s
1 120 None None 56?0. 4340. 57.7
1 120 0.25% None 4794. 3670. 45.0
C 1 115 None None 4945. 4008. 54.2
C1 115 None 0.08% ~ 3701. 3098. 46.8
j
In addition, the extruder head pressure, die pressure and motor load
measured during the extrusion of Example I was reduced by approximately 15 to
l0 22 % when compared to the same m-LLDPE resin without BioTerge~ AS-90B.
Comparative example C1 showed reductions in the range of 14 to 25% when
compared to the same m-LLDPE resin without DynamarTM FX-9613.
Based upon this example, 0.25 wt % of the BioTerge~ AS-90B provides
equivalent performance to 0.08 wt % Dynamar~ FX-9613 in reduction of melt
15 fracture, head pressure, die pressure and motor load in Exceed~ ECD102 m-
LLDPE.
Example 2
The m-LLDPE resin used is the same as that of Example 1. The granular
m-LLDPE resin is split into two portions. The first portion, which contained
no
SUEtSTITUTE SHEET (RULE 26;
CA 02259529 1999-O1-04
WO 98/05711 PCT/US97/13856
processing aid previously discussed (e.g. BioTerge~ AS-90B or FX-9613) and
pelletized on a Werner Pfleiderer 57 mm twin screw extruder (Comparative
example C2). To the second portion of m-LLDPE is added 0.06 wt% BioTerge~
AS-90B beads followed by compounding/pelletization on the same twin screw
5 extruder (Example 2).
The two formulations are extruded into film using the same extruder as in
Example 1. The temperature profile used ranged from 325 to 400°F (162-
204° C).
Observed melt temperatures range from 432 to 439°F (222-
226° C). Extruder
screw rpm is held constant at 74 rpm to achieve approximately 140 lbs/hr of
to polymer output. Under these conditions, the estimated shear rate is
approximately
500 sec-l. The extrusion sequence is as follows: A1, Comparative example C2,
Example 2.
The elimination of melt fracture is measured using the same method as in
Example 1. In addition, extruder measurements of head pressure, die pressure
and
15 motor load are taken periodically.
The data in Table 2 demonstrates that 0.06 wt% BioTerge~ AS-90B used
in Example 2 reduces melt fracture in the m-LLDPE film to approximately 1%
within an hour and completely eliminates it within 1.5 hours. As expected, the
rate
of elimination of melt fracture is slower when a lower concentration of
BioTerge~
2o AS-90B is used. By contrast, the m-LLDPE resin which contains no BioTerge~
AS-90B yielded film which was completely melt fractured. Even at this low
concentration, the BioTerge~ AS-90B reduced the extruder head pressure, die
pressure and motor load by 6 - 7%. At the end of the run, the extruder rpm was
increased until the motor load limit was reached (96 rpm) and the Example 2
formulation maintained melt fracture-free film (630 sec-1).
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21
Table 2
Example ElapsedAS-90B Head Die Motor Melt
Time Conc. PressurePressureLoad Fracture
min wt% si 'i si am s
C2 94 0 5709 4520 57.4 100
2 0 0.06 5?71 4592 57.5 100
2 30 0.06 5601 4392 55.0 18
2 57 0.06 5462 4338 54.4 1
2 86 0.06 5314 4220 53.6 0
Example 3
The antioxidant stabilized plastomer used in this example was an ExaciTM
3128 (a 1.2 melt index, 0.900 gm/cc density, ethylene 1-butene copolymer
available from Exxon Chemical Co., 1-louston, TX, USA). The pelletized
metallocene plastomer resin was split into two portions. The first portion,
which
contained no processing aid, was tested directly (Comparative example C3). To
the second portion of metallocene plastom~er was added 0.06 wt% BioTerge~ AS
l0 90B beads followed by compounding/pelletization on a Werner Pfleiderer 57
mm
twin screw extruder (Example 3).
The two formulations were extrudc;d into film using the same extruder and
test sequence as Example 2. The temperature profile used ranged from 300 to
395
°F (149-202° C). Observed melt temperatures ranged from 413 to
417°F (212-
16 214° C). Extruder screw rpm was :held constant at 52 rpm to achieve
approximately 120 lbs/hr of polymer output. Under these conditions, the
estimated
shear rate was approximately 430 sec' 1.
The data in Table 3 demonstrates i:hat 0.06 wt% BioTerge~ AS-90B used
in Example 3 completely eliminates melt fracture within 33 minutes. By
contrast,
2o the metallocene plastomer resin which contained no BioTerge~ AS-90B yielded
films which was completely melt fractured. The observed reductions in extruder
head pressure, die pressure and motor load ranged from 10 to 14%. At the end
of
the run, the extruder rpm was increased until the motor load limit was reached
(64
CA 02259529 1999-O1-04
WO 98105711 PCT/US97/13856
22
rpm) and the Example 3 formulation maintained melt fracture-free films (520
sec-
t ).
Table 3
Example ElapsedAS-90B Head Die Motor Melt
Time Conc. PressurePressureLoad Fracture
min wt% si si am s
C3 30 0 6047 4555 62.3 100
C3 56 0 6045 4543 63.0 100
3 0 0.06 5979 4521 60.7 100
3 33 0.06 5503 4131 57.4 0
3 59 0.06 5225 3920 55.9 0
~ ~
Example 4
An antioxidant stabilized Z-N catalyzed linear low density polyethylene
resin (I,LDPE), Escorene~ LL1001 (a 1.0 melt index, 0.918 gm/cc density,
ethylene 1-butene copolymer available from Exxon Chemical Co., Houston, TX,
to USA), is used in this example. The granular LLDPE resin is split into two
portions. The first portion, which contained no processing aid, is pelletized
on a
Weiner Pfleider 57mm twin screw extruder and then tested directly (Comparative
example C4). To the second portion of LLDPE was added 0.06 wt% BioTerge~
AS-90B beads followed by compounding / pelletization on a Werner Pfleiderer 57
mm twin screw extruder (Example 4).
The two formulations were extruded into film using the same extruder and
test sequence as Example 2. The temperature profile used ranged from 233 to
411
°F ( 112-211 ° C). Observed melt temperatures ranged from 434 to
440°F (223-
227° C). Extruder screw rpm was held constant at 69 rpm to achieve
2o approximately 147 Ibs/hr of polymer output. Under these conditions, the
estimated
shear rate was approximately 525 sec-1
The data in Table 4 demonstrates that 0.06 wt% BioTerge~ AS-90B used
in Example 4 reduced melt fracture in the LLDPE film to approximately 24%
within an hour. By contrast, the LLDPE resin which contained no BioTerge~ AS-
90B yielded film which was completely melt fractured. The observed reductions
in
CA 02259529 2003-10-27
23
extruder head pressure, die pressure and motor load ranged from 8 to 15%. Melt
fracture was completely eliminated after 155 minutes. At the end of the run,
the
extruder rpm was increased up to the limit of bubble stability (105 rpm) and
the
Example 4 formulation maintained melt fracture-free film (700 sec-1).
1e 4
Example ElapsedAS-90BB Head Die Motor Melt
Time Conc. PressurePressureLoad Fracture
mlil Wt% St S1 Bin
S
C4 39 0 4877 3724 48.9 100
4 0 0.06 4733 3597 45.3 100
4 41 0.06 4451 3471 41.8 45
4 56 0.06 4419 3423 41.7 24
An antioxidant stabilized metallocene catalyst produced plastomer, Exact~
1o 4049 (a 4.5 melt index, 0.873 g/cc density, ethylene butene copolymer
produced by
Exxon Chemical Co., Houston, Texas, USA) is used in this example. A pelletized
form of the copolymer is introduced into a BrabendeT Plasti-cordec melt mixer
which was heated to 193° C. Typically, 50-60 g of material is
introduced at a
rotation speed of 40 RPM. Upon complete melting, the torque remains
essentially
invariant with time and is used as the base value. Subsequently, a measured
amount of sodium alpha olefin sulfonate (Bio Terge~ AS-90B beads - product of
Stepan Co., Northfield, Illinois, USA) is added. The torque is again measured
at
40 RPM and compared with the base torque value. In this particular example, a
torque reduction (12%) is observed at 0.5 wt% of the Bio Terge~ AS-90B beads.
At higher levels of the Bio Terge~ AS-90B beads, further reductions are noted.
For example, at a 3.0 wt% addition, the torque is reduced by >35%. To insure
that
complete mixing has occurred, the rotation speed is increased to 100 RPM for
five
minutes. The material is dumped from the Brabender, cut into small pieces, and
allowed to cool to room temperature.
The material is foamed in sheets via conventional compression molding
techniques (PHI Co.). 2" x 2" x 0.02" pads are formed using the following
conditions: 2 minute preheat at 193° C, followed by a 3 minute press
cycle at 29
CA 02259529 2003-10-27
24
tons (193° C) and finally a 4 minute cooling to room temperature again
at 29 tons
press~ue.
The tensile properties of all materials are measured on a computer
controlled Instron tensile tester (Model 5565). In most instances, little to
moderate
s improvement in tensile properties are measured.
The films containing Bio Terge°~ AS-90B beads are optically clear
and
homogeneous.
Following the mixing procedure of Example 5 using again the Exact~ 4049
to copolymer, a 3.0 wt% of a calcium alpha olefin sulfonate material (product
of
Stepan Co., Northfield, Illinois, USA) was introduced into the copolymer melt.
In
this particular instance, the torque was not reduced. Expanding the range of
the
calcium-based material from 1.0 to 5.0 wt%, again showed no reduction in
torque.
Compression-molded pads were produced (as in example 5). An
15 examination of the films showed that the calcium alpha olefin sulfonate was
not
mixed and, in fact, a large number of specks, i.e. heterogeneous regions, were
observed, illustrating poor dispersion and mixing.
E 7
Example 5 is repeated using an antioxidant stabilized metallocene catalyst
2o synthesized plastomer, Exact~ 3033 (a 1.2 melt index, 0.900 g/cc density,
ethylene
butene hexene terpoIymer produced by Exxon Chemical Co., Houston, Texas,
USA). Two concentrations (0.5 and 3.0 wt%) of the Bio Terge'~ AS-90B beads
are evaluated. The lower and higher concentrations produced a torque reduction
of 28 and >35%, resp~tively.
2s The compression-molded films were optically clear and homogeneous,
indicating excellent dispersion and mixing.
E~c~ple 8
Example 7 is repeated substituting the sodium alpha olefin sulfonate with
3.0 wt% calcium alpha olefin sulfonate. No torque reduction is measured. The
3o compression-molded films are heterogeneous with a large number of specks
randomly distributed throughout the film, illustrating poor dispersion and
mixing.
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WO 98/05711 - PCT/US97/13856
Example 9
Example 5 is repeated using an antioxidant stabilized metallocene catalyst
produced plastomer, Exact~ 3028 (a 1.2 melt index, 0.900 g/cc density,
ethylene
butene copolymer produced by Exxon Chemical Co., Houston, Texas, USA.
5 Three concentrations (0.5, 1.0 and 3.0 wt%) of the Bio Terge~ AS-90B beads
are
evaluated. The data in Table 5 demonstrates that as the concentration is
increased
the torque is reduced.
Table 5
Sodium Alpha Olefin Sulfonate Torque Reduction
(wt%) (%)
0.5 21
1.0 27
3.0 35
to Example 10
Example S is repeated using an antioxidant stabilized metaIlocene catalyst
produced plastomer, Exact~ 3025 (a 1.2 melt index, 0.910 g/cc density,
ethylene
butene copolymer produced by Exxon Chemical Co., Houston, Texas, USA). Two
concentrations (0.5 and 3.0 wt%) of the Bio Terge AS-90B beads are evaluated.
15 The date in Table 6 demonstrates that as the concentration is increased the
torque
is reduced.
Table 6
Sodium Alpha Olefin Sulfonate Torque Reduction
__ (wt%) (%)
0.5 25
3.0 30
Example 11
20 Example 5 is repeated using a physical mixture of antioxidant stabilized
metallocene catalyst produced plastomers. In this example, the Exact~ 4049
copolymer and Exact~ 3033 terpolymer are melt mixed in a 93:8 wt ratio and
subsequently, 0.5 wt% of the Bio Terge'~ AS-90B beads were added. A 12%
torque reduction is measured.
CA 02259529 2003-10-27
26
Example 5 procedure is repeated using F.xact~ 4049 and Exact~ 3033
rM
materials with a wide range of fluorocarbon-based materials (Fluorad
Fluorochemical Surfactants produced by 3M, St. Paul, MN, USA). All materials
s used were free of solvents) using comrentional drying procedures prior to
melt
mixing. The data in Table 7 describes the products used in this example as
well as
their chemical structures and the measured torque reductions at 193° C
at a 0.5
wt% concentration. The data demonstrates that no torque reductions are
observed
for both the potassium and ammonium perfluoroallcyl sulfonates. However, a
Io range of torque reductions are observed which is dependent on the specific
fluorocarbon structure.
Table 7
Fluorocarboq-Based Mad
3M. ProductType Description Torque Reduction-Torqnt:.
;. Nutober Euictm 4049 Reduction.-
(%)
- Erict~
.
3033
"/.
'.,
FC-93 AnionicAmmonium 0 0
rlyuoroalkvl
sulfonates
FC-95 AnionicPotassium perfluoroalkyl0 0
and
FC-98 sulfonates. 0 0
FC-99 AnionicAmine pertluoroallryl35 35
sulfonates
FC-100 AmphoterFl~rinated alkyl6 6
is am hoteric mixture
FC-I20 AnionicAmmonium 0 25
rfluoroalkvl
sulfonates
FC-I29 AnionicPotassium fluorinated7 7
alkyl carhoxvlates
FC-135 CatiorueFluorinated alkyl17 58
quaternary ammonium
iodides
FC-143 AnionicAmmonium perfluoralkylI7 34
CaTbOXVlateS
FC-431 NonionicFluorinated alkyl37 30
esters
FC-740 NonionicFluorinated alkyl~ 12 ~ _
esters 8
CA 02259529 2004-09-09
27
Example 5 procedure is repeated using sodium and calcium dodecylbenzene
sulfonate materials. The former material is a product of the Witco Corp.,
Houston,
Texas, USA and the latter material is a product of Stepan Co., North&eld,
Illinois,
USA. The data in Table 8 shows that the calcium-based material provides no
reduction in the torque, while the sodium-based material provides only a
relatively
modest reduction (or no enhancement).
Table 8
DodecylbenzeneProduct DesignationConcentrationTorque
Sulfonate (%) Reduction
(%
Sodium Witconate 90 3.0 11
Sodium Witconate LX 3.0 6
Sodium Witconate SK 3.0 0
Calcium E erimental Product1.0 0
Calcium E erimental Product3.0 0
Calcium Experimental 5.0 J 0
Product ~
1o Examnles 14-18
Table 9 shows the description of samples used in these examples and
summarizes the process data. Examples 14 and 17 are the comparative control
samples . All materials were fabricated on a 3/4" Haake Rheocord extruder,
Model
E in the cast mode. The screw was a 15/5/5, 24:1 L/D with 15° tip. The
polymer
was extruded through a 4" tape die and wound through a stacked calendar
assembly to the winder. All polymers were preblended and compounded on a 1 "
MPM single screw (24:1L/D) compounding extruder at a melt temperature of
-190°C prior to film extrusion. Each example contained 25,000-30,000
ppm silica
antiblock and -2000 ppm erucamide slip. All materials were cast extruded
through
2o a 20 mil die gap at -190°C melt. Materials used consisted of Exact
4049 (4.5 MI;
0.873 density ethylene-butane copolymer), a metallocene plastomer produced by
Exxon Chemical Co., Houston, Texas, USA; Vector 7400 D, an 8.0 MI/0.930
density SBS (31/69/ SB ratio) produced by Dexco Co., Houston, TX USA; and
3.0 wt% of a sodium alpha olefin sulfonate (Bio-Terge~ AS-90B beads produced
CA 02259529 2003-10-27
28
by Stepan Co., Northfield, Illinois, USA as in example 1 ); and 3.0 wt% of
calcium
alpha olefin sulfonate, also produced by Stepan Co.
As can be seen, the sodium alpha olefin sulfonate drastically reduces the
torque requirements when comparing samples 14 and 15 (> 2X). This same trend
~ was also evident when comparing samples 17 and 18, the Exact~ /SBS blends.
In
all fow cases, the film exhibited good melt quality and homogenization. This
was
not the case when comparing sample 15 (calcium alpha olefin sulfonate). The
film
quality was very poor with numerous unmelted gels, even after raising the melt
temperature from 190-240°C. It also did not compare with the sodium
alpha olefin
~o sulfonate concerning torque reductions.
Table l 0 summarizes the test results for examples I4-I 8. Tensile testing
was performed according to ASTM D-882 on a United Six Station tensile tester,
model 7V 1. Tear results were obtained from an Elmendorf tear tester according
to
ASTM D-1922.
The hysteresis testing procedure used-is described as follows. This method
is an Exxon variation of a procedure described by E.L, DuPont and Co. in its
brochure on its polyester urethane elastic product, T-722A. In the variation
used
herein, 1 inch X 6 inch strips are subjected to a strain rate of 150% or 200%
with a
jaw gap separation of 2" and cross head speed of ZO"/min. The hysteresis
stress/-
2o strain curve is plotted on a chart also traveling at 20"/minute. Both the
extension
and retraction cross head speeds (20"/min) were the same and performed on an
Instron model 1123. The film was held for 60 seconds at maximum extension and
then retracted and held for 30 seconds relaxation prior to the next cycle.
This was
repeated 2 1/2 times. Key pieces of information that are extracted from these
stress/strain plots are the maximum force (modulus) of each cycle, the
residual set
or permanent set (the degree of deformation as measured by the point of stress
divided by total strain/cycle), and the unload force of contractive power as
measured from the last retraction cycle at various elongations. Generally,
five
specimens were tested for each sample, with mean values over these samples
3o developed.
CA 02259529 2004-09-09
29
As can be seen, there are substantially no detrimental effects) to physical
s
properties with the addition of surfactants. In fact, there appears to be
slight
improvement to the elastic properties as compared to the control comparisons
(example 14 and 17).
Table 9
Process Summary
Exam I~ (1) ::14 .15. 16(2)I7 18 r:
Formulation
Exact 4049 100 97 97 30 27
Vector 7400D 70 70
Na oc-olefin Sulfonate 03 03
Ca a-olefin Sulfonate 03
Extruder RPM ~ 32 32 32 32 32
Ext. FidPSI ~ 650 620 560 730 580
Die PSI 100 100 100 100 100
Ext. To ue -G 2600 1200 2100 2300 700
Ext. Melt C 191 193 231 191 193
Gau a mils 2.0 1.9 2.3 2.6 3.6
Line Speed (fpm) - X17- r1' r -15 12
- - 17
~
to (1) % excludes slip and AB addition via masterbatch
(2) Poor extrusion, melt quality. Numerous-unmelted particles.
CA 02259529 2003-10-27
Table 10
1V~D Pronertv Summarv(1)
>Test I4: 15 16 I7 ' I8
Formulation
Exact 4049 100 97 97 30 27
Vector 70 70
Na a-olefin Sulfonate 03 03
Ca a-olefin Sulfonate 03
Tensiles
Yld SI 287 287 233 165 160
Yld Elon % 11.8 11.8 11.5 6.6 6.4
Ult.Tns SI 2780 3260 2740 1900 1520
Brk Elon % 630 670 730 630 660
Tear mil 34.7 33.3 23.2 19.1 26.3
H steresis 150% ext
Set 23.9 21.8 20.0 9.8 7.3
Modulus 1 560 500 460 405 510
Modulus 2 500 440 410 350 450
Unload at 50% 6 10 19 110 150
Unload at 100% (g) 140 i30 130 19~ 260
~ ~ J
(1) MD= Machine Direction
s
Examples 19-26
Table 11 shows the description of samples used in these examples and
summarizes the process data at both standard rates and maximum rates. Examples
19-22 are the control comparatives. Those samples describe a new grade under
to development by Exxon Chemical Co., of Houston, TX, USA referred to as APT-
3.
This is an advanced performance terpolymer having an MI of 2.2 and density of
0.898. Exact 4151 (2.2 MI, 0.896 density, metallocene ethylene, butene
copolymer) is the precursor grade. Advanced Performance Terpolymers are
characterized as having improved processability vs. their precursor
counterpart in
15 the blown film process, i.e. lower motor load and torque requirements and
improved bubble stability attributes. In these embodiments of the present
invention, surfactant addition in the amount of 0.05, 0.1, 0.25 and 0.5 weight
percents are added to APT-3 and compared to the control (APT-3) and base
precursor grade (Exact 4151 ) with and without slip/antibiock addition. The
slip
2o used was Kemamide E erucamide (produced by Witco, Inc., Memphis, TIC, the
CA 02259529 2003-10-27
31
antiblock (AB) was ABT-2500 Talc (produced by Specialty Minerals, Los
Angeles, CA) and the fluoroeiastomeric process aid (PPA) used in some of the
formuiations was Viton A (produced by E.I. Dupont, Wilmington, DE). The
surfactant used is a sodium alpha olefin sulfonate (Bio-Terge~ AS-90B produced
by Stepan Co., Northfield, Illinois USA as in example 1). Prior to film
extnision,
all materials were compounded on a Werner and Pfleiderer ZSK-57 mm twin screw
extruder at a melt temperature between 410-420°F (210-216° C).
The materials
were then fabricated into films on a 2.5" Egan blown film line. This is a 24:1
LID
extruder powered by a 40 HP DC drive. Maximum screw RPM's is 115, thus
to capable of producing a maximum torque of 0.35 HP/Rev. The barrel is liquid
cooled and consists of 3 temperature zones and 5 pressure ports. The screw is
a
24:1 L/D SterleX low work barrier screw having a 0.050" barrier undercut with
a
Maddock mixing device at the end of the screw also having a 0.050" undercut.
The die is a 6" Uniflo lower pressure bottom fed spiral mandrel die with a 60
mil
die gap. The air ring is a 6" dual lip Uniflo design. Screenpack =
20/40/80/20.
Blow up Ratio (BUR) = 2.5. Temperature profile was as follows:
girl Z1 Brl Z2 B Z3 Dies/A~~ters
280° F 375° F 345° F 365° F-~
(138° C) (191° C) (174° C) (185° C)
Each material was extruded at standard rates (~-7 lbs/in die/hr) and
2o maximum rates with all pertinent process data recorded on a data logger.
Each
material was run until lined out as demonstrated via data logger (~1
hr/sampIe).
The maximum rate was defined as either the point of bubble instability (BS)
motor load (ML) or maximum RPM's (RPM). Bubble instability criteria used was
as follows:
~ bubble fluttering
~ gauged ~10%
~ edge wrinkles after adjustments to the collapsing frame.
If any of these criteria was met, the rate was backed off until a stable
condition could be maintained as indicated by the data logger (steady state).
CA 02259529 1999-O1-04
WO 98/05711 PCT/US97/13856
32
As can be seen, surfactant addition has little to no effect on process at low
rates. The real effect occurs between 0.25-0.50 weight percent levels. At 0.5
weight percent level there is an ~20% reduction in motor load compared to APT-
3
and ~30% reduction when compared to the precursor material. Effects on torque
also follow this trend with an ~30 and ~40% reduction, respectively. Low level
surfactant (0.05-0.1 weight %) improves rate production slightly. Between 0.25-
0.5 weight %, the rate is increased substantially due to the reduced motor
load and
lower melt. At 0.5 weight % level, rate production was increased by >25%
compared to APT-3 w/o surfactant and >45% when compared to the precursor.
to No pumping efficiency (lbs/RPM) is lost between 0.05-0.25 weight %.
Between 0.25-0.5 weight % there is a drop off, but this is of little
consequence if
there is available extruder RPM.
Surfactant addition to Exxpol~ metalIocene grades and APT grades can
have a substantial effect on processability especially in monolayer blown film
Z5 production where motor load and torque requirements can be limiting
factors.
These advantages are also seen in conventional Z-N catalyzed LLDPE production.
Table 12 summarizes physical property test results and as can be seen, no
detrimental effects can be attributed to the addition of surfactant. All tests
were
performed according to the appropriate ASTM standard method.
2o Table 13 illustrates no adverse surface sealing effects can be attributed
to
the addition of surfactant. Hot tack comparisons of Exact 4151, APT-3 w/o
surfactant and APT-3 w/surfactant are virtually identical as demonstrated.
In addition, organoleptic testing by a certified odor and taste facility show
no adverse effects for food packaging applications.
CA 02259529 1999-O1-04
WO 98105711 PCT/US97/13856
33
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