Note: Descriptions are shown in the official language in which they were submitted.
217~0~7
Patent
Hindered Amine / Polyolefin Compositions
FIELD OF THE INVENTION
The present invention generally relates to polyolefin blends
suitable for use in extrusion processes. More particularly the present
invention relates to polyolefin compositions suitable for the manufacture of
blown film having a good surface appearance. The invention further
relates to a novel composition of matter consisting of a blend of a
thermoplastic, acrylic-containing polymer and a thermoplastic
fluorocarbon polymer which is useful as an additive for extrudable
polyolefin compositions.
BACKGROUND OF THE INVENTION
In the manufacture of extruded polymers there are a number of
surface defects referred to as sharkskin, snakeskin and orange peel which
all are related to the rheology of the polymer melt and in particular the
melt fracture of the polymer. Melt fracture arises when the shear rate at
the surface of the polymer is sufficiently high that the surface of the
polymer begins to fracture. That is there is a slippage of the surface of
the extruded polymer relative the body of the polymer melt. The surface
generally can't flow fast enough to keep up with the body of the extrudate
and a fracture in the melt occurs generally resulting in a loss of surface
properties for the extrudate.
United States Patent 3,125,547 issued March 17, 1964 assigned to
E.l. DuPont de Nemours and Company discloses blends of polyethylene
and small amounts of elastomeric fluoropolymers to provide a smooth
surface on extrudate at high extrusion speeds.
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Patent
United States patent 4,753,995, assigned to Mobil Oil Corporation,
discloses the use of vinylidene fluoride homopolymer to improve the
extrusion of low density polyethylene.
It is well known to those skilled in the art that the use of hindered
amine light stabilizers ("HALS") has a detrimental effect upon the
effectiveness of fluoropolymers as a polyethylene processing additive. (It
is also known that such fluoropolymers are prone to dehydrofluorination in
the presence of bases - such as amines. Accordingly, a non-binding
theory is that the HALS reacts with the fluoropolymers so as to produce a
reaction product which is a less effective processing additive.)
In U.S. patent 4,963,622, assigned to Union Carbide Corporation, it
is disclosed that the use of an acrylic processing aid improves the
extrusion of high density polyethylene ("HDPE"). However, the use of this
processing aid provides only a marginal improvement in the extrusion of
linear low density polyethylene ("LLDPE") having a narrow molecular
weight distribution.
Acrylic polymers are generally much less expensive than
fluoropolymers. Accordi,)gly, there is an economic incentive to employ
acrylics rather than fluoropolymers as processing additives. However, the
simple addition of an acrylic polymer and a fluoropolymer to a
polyethylene extrusion process has been observed to produce
antagonistic results (i.e. the performance produced by one has been
observed to be adversely affected by the simple addition of the other).
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Patent
We have now surprisingly discovered that a premixed
acrylic/fluoropolymer blend improves the extrusion of a thermoplastic
compound which contains polyolefin, HALS and antiblock agents.
SUMMARY OF THE INVENTION
In one embodiment, the present invention provides:
An extrudable composition comprising:
A) a major component of a thermoplastic polyolefin;
B) less than 1 weight percent, based on the weight of said
thermoplastic polyolefin, of a blend of a fluorocarbon
polymer and an acrylic-containing thermoplastic polymer;
and
C) from 100 to 5000 parts per million, based on the weight of
2 o said thermoplastic polyolefin, of a hindered amine light
stabilizer.
In a pre~lled er"bodi",ent, the composition further contains:
D) from 100 to 5000 parts per million, based on the weight of
said thermoplastic polyolefin, of an inorganic antiblock
agent.
The compositions of this invention are particularly preferred for use
in well known methods to prepare blown film (typically having a thickness
of from 0.2 to 30 mils) and polyolefin-coated wire and cable. The
compositions may also be useful for the extrusion of profiles such as
pipes or tubing and/or the extrusion of thick films (typically greater than
20 mils) such as those used in so-called geomembranes.
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Patent
DETAILED DESCRIPTION
This invention is generally directed towards improvements in the
extrusion of thermoplastic polyolefin compounds (especially those based
on LLDPE) which contain antiblock and UV stabilizers. This improvement
is achieved by the use of a processing additive which is a polymeric blend
of an acrylic-containing ll ,er" ,oplastic and a fluorocarbon polymer.
The term thermoplastic polyolefin encompasses a number of widely
used plastics which are prepared by olefin polymerization. Examples of
such thermoplastic polyolefins include polyethylene homopolymer,
polypropylene homopolymer, and copolymers of ethylene with small
amounts of at least one other olefin - such as propylene, butene-1,
hexene-1 or octene-1.
The invention is useful for thermoplastic polyolefins in general but
is particularly well suited for improving the extrusion of linear low density
polyethylene. LLDPE is a copolymer of ethylene with another alpha olefin
(such as the aforementioned butene, hexene or octene) which has a
density of less than 0.940 grams per cubic centimeter. Such LLDPEs are
well known items of commerce and may be prepared by conventional
polymerization processes. The polymerization may be in the gas phase
(that is, at relatively low pressures below 500 psi, prererably below about
250 psi; at te""~eral.lres below about 1 30~C; and using a fluidized bed
catalyst (such as the process patented by Union Carbide Corporation)); in
solution (a process at high temperatures - typically from about 130 to
300~C, by dissolving ethylene and other comonomer(s) in a solvent such
as hexane and in the presence of a coordination catalyst such as those
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~l7~n~7
Patent
disclosed in a number of patents in the name of DuPont) or slurry
polymerization initiated by a coordination catalyst or in the case of high
pressure polymerization by free radicals. The so-called metallocene
catalysts may be used in all of these polymerization processes and the
details of such types of poly",eri~alion are generally well known.
Depending on the type of polymerization, the olefin polymer may
have a molecular weight (weight average - "Mw") from about 10,000 up to
1,000,000, typically from about 100,000 to 350,000. More than one type
of polyolefin may be present in the extrudable compositions. For
example, blends of LLDPE with LDPE are often used to prepare film and
are suitable for use according to this invention.
This invention generally encompasses the use of certain blends of
a fluorocarbon polymer and an acrylic polymer as additives to improve
polyolefin extrusion. The term "acrylic polymer" is widely known but may
mean different things to different people. Accordingly, we have used the
term "acrylic-containing thermoplastic polymer" to describe polymers
which are suitable. As used herein, the "acrylic-containing thermoplastic
polymer", (or "ACTP"), is a polymer which:
(a) is polymeric (i.e. it has a weight average molecular weight of
greater than 500);
(b) is thermoplastic (i.e. it will soften when heated and harden when
cooled and will do so for more than one heaVcool cycle);
(c) is prepared using an "acrylic monomer: (i.e. acrylic acid, or an
ethylenically unsaturated derivative thereof such as methyl
methacrylate, ethyl methacrylate or butyl methacrylate); and
~"J~,dc/9120can.doc - 6 -
2~7~057
Patent
(d) contains at least 20 weight percent of polymer units (or "bound"
units) of the above defined monomer (c).
Thus, the defined term does include the well known polymer methyl
methacrylates (such as those sold under the trademark PLEXIGLAS by
Rohm and Haas); the so-called acrylic process aids which are well known
to those skilled in the art of preparing polyvinyl chloride compounds (such
as those sold under the trademarks PARALOID and/or ACRYLOID by
Rohm and Haas - which PARALOID and ~CRYLOID process aids are
reported to be copolymers of methyl methacrylate, butyl acrylate and
styrene); and the well known styrene/methyl methacrylate copolymers
such as those sold under the trademark NAS by Novacor Chemicals Inc.
of Leominster, MA. However, the term does not include polymers which
contain less than about 15 weight percent of the acrylic monomer - such
as, for example, copolymers of a major portion (typically greater than 90
weight percent) ethylene with a minor amount of a lower alkyl acrylate or
the so-called "carboxylated polyolefins" (which typically contain less than
2 weight percent of an acid or acrylate monomer which is grafted to the
polyolefin). Styrene/methyl methacrylate copolymers having from about
80 to about 45 weight percent bound styrene and from about 20 to about
55 weight percent of bound methyl methacrylate are highly preferred.
The term "fluorocarbon polymer" is meant to convey its
conventional meaning, namely homopolymers and copolymers of the
fluorinated olefins having a fluorine: carbon atom ratio of at least 1:2 and
prereral~ly at least 1:1.
'9120carl.doc - 7 -
2176057 Patent
Suitable homopolymers may be prepared from vinylidene fluoride
or vinyl fluoride. Copolymers may further include a fluorinated olefin
(such as hexafluoropropylene) or a non-fluorinated olefin. This term
includes both elastomeric and thermoplastic polymers.
"Fluoroelastomers" may be synthesized, for example by copolymerizing
vinylidene fluoride ("VdF") and hexafluoropropylene ("HFP") so as to
produce a polymer containing about 25 to 50 weight percent of "bound"
hexafluoropropylene. These bound hexafluoropropylene units disrupt the
crystallinity of the polymer and thus help to provide an elastomeric
polymer. Such fluoroelastomers are sold under the trademark VITON by
E.l. DuPont de Nemours and by Minnesota Mining and Manufacturing
("3M") under the trademark DYNAMAR.
2 o It should be further noted that VdF/HFP copolymers which contain
greater than 85 weight percent VdF and less than about 15 weight percent
HFP may be thermoplastic. Elf Atochem of Philadelphia, PA sells different
thermoplastic fluorocarbon polymers under the trademark KYNAR which
include both vinylidene fluoride homopolymers and VdF/HFP copolymers
containing low levels of HFP.
The acrylic-containing thermoplastic polymer and the fluorocarbon
polymer must be blended together prior to the use of the blend to improve
polyolefin extrusion. Accordingly, it is especially preferred to:
(1 ) use an ACTP with good "processibility" (i.e. an ACTP which is
readily melt processed when subjected to heat and shear);
(2) use a combination of an ACTP and fluorocarbon polymer with
similar"processibility" characteristics; and
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~ ~ Patent
(3) in the ideal case, use an ACTP and fluorocarbon polymer which
satisfy the above two criteria and which are at least partly miscible
with each other.
It has been, epo, Led that polymethylmethacrylate ("PMMA") is
miscible with polyvinylidene fluoride (Ref: Kirk-Othmar Encyclopedia of
Chemical Technology, 3rd Edition, Volume 18, p. 464). However, PMMA
can be difficult to melt process.
We have discovered that SMMA may be conveniently blended with
thermoplastic VdF/HFP using conventional polymer mixing equipment and
that it is possible to prepare "homogeneous" blends in this manner.
The term "homogeneous" may mean different things to different
people, but as used herein it refers to a polymer blend which:
(a) has a uniform visual appearance (with respect to a uniform color
and an essential lack of visible physical occlusions); and/or
(b) has a well mixed, "matrix/domain" morphology which is apparent
upon examination by scanning electron microscopy -as evidenced
by the existence of discrete particles having a size of less than
4 microns.
Thus, we have discovered that a "premixed" blend of an ACTP and
fluorocarbon polymer is useful as an additive to improve the extrusion of
polyolefin compounds which contain UV additives and antiblocks. The
weight ratio of ACTP/fluorocarbon polymer may be from 95/5 to 5/95, with
preferred blends having a weight ratio of from 10/90 to 25/75. The most
highly preferred blends contain SMMA and a thermoplastic VdF/HFP
copolymer in these weight ratios.
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2~7~0~7 Patent
The blend is added to the thermoplastic polyolefin in an amount
sufficient to provide from 0.01 weight percent (100 ppm) to 0.2 weight
percent (2000 ppm) of the fluorocarbon polymer, based on the weight of
the thermoplastic polyolefin.
Amounts less than 0.01 weight percent may not provide consistent
improvements in the extrusion of polyolefins. Amounts greater than
0.2 weight percent may be employed but are expensive and wasteful.
The thermoplastic polyolefin-containing compositions of the present
invention contain hindered amine light stabilizers (HALS) and antiblock
agents (such as silica or talc) and may further include fillers, antioxidants
(at least a primary and optionally a secondary antioxidant), pigments,
opacifying agents, static control agents such as glycerol monostearate
2 o and/or low molecular weight polyethylene glycol (e.g. CARBOWAX 3350,
sold by Union Carbide Corporation). The amount of HALS is from 100 to
5000 ppm (preferably 1500 to 3000 ppm) and the amount of antiblock is
from 1000 to 5000 ppm (preferably 1000 to 3000 ppm).
For film applications, prererably no pigment or filler is added and
the film is clear or relatively clear. In other applications such as wire and
cable (electrical or optical) the compound may contain a pigmenVfiller
such as carbon black and other adjuvants (in these types of applications
the unsubstituted olefin polymer may be gldrL6d by extrusion with a
functional ethylenically unsaturated monomer such as maleic anhydride
in the presence of a free radical agent such as a peroxide).
Primary and secondary antioxidants may be used in an amount
from about 0.01 to 2, ~ erer~bly 0.01 to about 1 weight %. Fillers may be
~Gfi"~"~c/9120can.doc - 10 -
2~76~57 Patent
incorporated into the compositions of the present invention in amounts up
to about 50%, prererdbly less than about 30%.
Typically, the extrudable polymer compositions of the present
invention will be prepared ("compounded") by melt blending. There are
several methods which could be used to produce the compositions of the
present invention. All the components, including the premixed
o ACTP/fluorocarbon polymer blend, may be dry blended in the requiredweight ratio in a suitable device such as a tumble blender. The resulting
dry blend is then melted in suitable equipment such as an extruder. A
masterbatch could be prepared with some of the polyolefin and the other
ingredients. The masterbatch is then fed to an extruder and melt blended.
In a third method the dry co" IpGi ,ents of the blend may be metered
directly into an extruder.
The extruder may be a twin or single screw extruder. If it is a twin
screw extruder it may be operated in a co-rotaliny mode (i.e. both screws
turning in the same direction) or in a counter rotating mode (i.e. the
screws rotate in opposite directions).
The specific conditions for operation of any extruder will differ from
that of any other extruder. The variations between machines may usually
be resolved by non-inventive testing. Typically, laboratory twin screw
extruders will operate within the following envelope of conditions. The
barrel will be heated to a temperature from about 180 to 210, prererably
from 190 to 200~C. The screw speed will normally be from 50 to 150,
preferably from 100 to 130 RPM's. The back pressure on the extruder will
be from about 1000 to 1300, preferably from 1 100 to 1250 psi. As noted
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~ 2~76~7 Patent
above the specific conditions for the operation of any specific extruder can
readily be determined by one skilled in the art by non-inventive testing in
view of the above envelope of conditions.
The extruder will typically extrude the polymer composition as
strands which are then cooled and cut into pellets for subsequent use,
typically film extrusion.
The film extruder may also be a single or twin screw extruder. The
die may be a slot die or it may be an annular ring die extruding a film of
the polymer blend about a stable bubble of air. The film is collapsed after
passing over or about the bubble.
Example 1
P~ e~aralion of ACTP/Fluorucarl,o, I Polvmer Blend
The ACTP polymer used in this example was a styrene/methyl
methacrylate copolymer sold under the trademark NAS 30 by Novacor
Chemicals Inc. and was reported to contain about 30 weight percent
bound methyl methacrylate and about 70 weight percent bound styrene.
The melt flow rate (as determined by ASTM D1238 at 230~C under a load
of 3.8 kilograms) was reported to have a typical value of 8.6 grams per
10 minutes.
The fluorocarbon polymer used in this example was a thermoplastic
copolymer of vinylidene fluoride and hexafluoropropylene sold in powder
form under the trademark KYNAR 2751 by Elf Atochem of Philadelphia,
PA. Reported (typical) physical properties of KYNAR 2751 are given
below:
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1~ 21760~7 Patent
Melting Point: 135~C
Melt Viscosity at 230~C: 20,000 - 25,000 Poise
Melt Flow Rate:
(ASTM D1238 at 230~C
under 12.5 kg load) 4 - 10 grams / 10 minutes
Two blends of the NAS 30 / KYNAR 2751 were then prepared in a
lab scale Brabender-type ("mixing bowl") polymer mixer under conditions
of heat and shear.
The first blend contained 25 weight percent NAS 30 and 75 weight
percent of KYNAR 2751 (blend "1A").
The second blend contained 10 weight percent NAS 30 and
90 weight percent of KYNAR 2751 (blend "1 B").
Both of the blends appeared homogeneous by visual inspection as
evidenced by uniform color and a lack of occlusions (i.e. no "chunks" or
"specks" were observed).
Example 2
A laboratory scale twin screw extruder was used to prepare
compounds containing LLDPE, conventional stabilizers, other
conventional adjuvants, a process aid consisting of the KYNAR 2751 /
NAS 30 blends from Example 1 plus HALS and antiblock.
A blend made with a fluoroelastomer sold by 3M under the
trademark DYNAMAR FX 9613 (a conventional process aid) was prepared
for a control.
The formulations are shown in Table 10. All figures are shown as
weight percentages.
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2176057
J~ Patent
TABLE 10
Component: Ex. 100 Ex. 200 Ex. 300
LLDPE1 99.305 99.24 99.265
AO-12/AO-23 0.03/0.12 0.03/0.12 0.03/0.12
Zinc Oxide 0.015 0.015 0.15
FE4 0.08 ---
PEG5 0.05 0.06 0.06
Blend 1A6 0.135 ----
Blend 1 B7 ---- ---- 0.11
HALS8 0.15 0.15 0.15
Silica9 0.25 0.25 0.25
Notes:
1. Ethylene-hexene LLDPE having a density of about 0.918 g/cc and
a melt index (ASTM D1238 at 190~C under a load of 2.16 kg) of
about 1.
2. AO-1 = hindered phenol antioxidant (sold under the trademark
IRGANOX 1076 by Ciba Geigy).
3. AO-2 = phosphite antioxidant (sold under the trademark WESTON
339 by General Electric Company).
4. FE = fluoroelastomer sold under the trademark DYNAMAR FX
9613 by 3M.
5. PEG - polyethylene glycol sold under the trademark CARBOWAX
3350 by Union Carbide Corporation.
6. Blend 1A = 25/75 weight ratio blend of NAS 30 / KYNAR 2751 from
Example 1.
7. Blend 1 B = 10/90 weight ratio blend of NAS 30 / KYNAR 2751 from
Example 1.
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2~76~7
Patent
8. HALS = hindered amine light stabilizer (sold under the trademark
CHIMASORB 944)
9. Silica antiblock agent
The amount of blends 1A and 1 B were chosen so as to provide
about 1.0 x 103 ppm of the KYNAR (on an LLDPE basis).
The compounds were mixed in a laboratory extruder under
conventional mixing conditions.
These three compounds were then individually extruded through a
capillary rheometer at 21 0~C. The capillary had a length/diameter ratio of
20/1. The shear rate in the rheometer was adjusted during each test from
a range of less than 100 reciprocal seconds (s~') to a shear rate of about
1 350 s~'.
It will be appreciated by those skilled in the art that this type of
extrusion through a capillary will typically cause surface defects ("melt
fracture") in LLDPE extrudates in the absence of a processing additive at
a shear rate of less than 200 s~'.
The control experiment (Ex. 100 in Table 10; using a conventional
fluoroelastomer as the processing additive) showed some "sharkskin" melt
fracture at a shear rate of about 150 s~' and gross melt fracture (as
3 o evidenced by an extremely rough, distorted extrudate) at a shear rate of about 800 s~'.
The use of blend "1A" (25% SMMA / 75% fluoroplastic; Ex. 200)
provided excellent results, with essentially no "sharkskin" melt fracture at
low shear rates, and with gross melt fracture not occurring until a shear
rate of about 1200 s~'.
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~ ~ Patent
The use of blend 1 B (90% fluoroplastic / 10% SMMA; Ex. 300)
provided another excellent result, with gross melt fracture not occurring
until a shear rate of about 1200 s~'.
Additional data, which illustrate the improved shear viscosity of the
inventive compounds of Ex. 200 and 300 in comparison to the control
compound of Ex. 100, are shown in Table 20.
o TABLE 20
Apparent Shear Viscosity (Pa.s)
Shear Rate (1/s)
Ex.100 Ex. 200 Ex. 300
' 9.2 ~,729.7 ~96 ~.6 ~939.8
38.4 vO 8.8 "1~".5 2165.8
~7.6 Z.~S9.~ ~ 6-v.O ~ 80.6
76.8 2221. ~ ~9 .8 ~ 030 7
96.0 ~ 946.0 ' 222.7 ~ ' 61.4
~ ~ .2 ~ '17.9 ~ 1~ 0.9 ~ 050.3
. ~.4 533.9 ' 0"1.2 972.8
v.6 ",9'.6 9~.7 9' ,.6
9.~.0 9".3 86~.8 82~.9
o.~- ~ 59.7 801-~.4 76
~ 7.2 879.~ 70. .6 679.
_~ 4.U 770.~ 64~.0 ~''2
~0.0 ~92.3 .,90.~ .~'8.
600.0 88.8 20. ~)4
750.0 99.7 ~69.; ~59.~
900.0 ~ 3. 9 ~25.9
1050.0 ---- 38~ .6 387.'
1200.0 ---- 340.7 348.2
3 o 1350.0 ---- 294.0 302.6
Notes:
Ex, 100, the control experiment (using a conventional fluoroelastomer as
the processing additive), began to exhibit sharkskin melt fracture at a
shear rate of about 150 s~'. Gross melt fracture, as evidenced by an
extremely rough, distorted extrudate, was observed to start at a shear rate
of about 800 s~'.
~s~l~"/s~20can.doc - 16 -
2176~7 Patent
Ex. 200 produced no sharkskin melt fracture and began to exhibit gross
melt fracture at a shear rate of about 1200 s~', as compared to about
800 s~' for Ex.100.
Ex. 300 showed similar results with the onset of gross melt fracture also
occurring at a shear rate of about 1200 s~', as compared to about 800 s-'
for Ex.100.
Example 3 (Comparative)
Three different types of vinylidene fluoride-based fluoroplastics
were evaluated as process additives for the extrusion of polyethylene in a
"blown film compound".
The fluoroplastics included a homopolymer vinylidene fluoride (sold
under the trademark KYNAR 721), the KYNAR 2751 (described in
example 1) and another vinylidene fluoride/hexafluoropropylene sold
under the trademark KYNAR 2801.
Each of these three fluoroplastics was used - in the absence of any
acrylic-containing thermoplastic - to prepare compounds with an LLDPE
(similar to the LLDPE used in examples 1 and 2). A total of six
compounds were prepared, (two for each of the three fluoroplastics, with
one blend containing 500 ppm fluoroplastic and the second containing
1000 ppm fluoroplastic on the basis of the LLDPE). The compounds also
contained minor, conventional amounts of other adjuvants including: a slip
agent (750 ppm Erucamide), antioxidant (Irganox 1076 and Weston 399),
an amine (sold under the trademark Kemamine), and zinc stearale
(500 ppm). More significantly, the compounds further contained about
3150 ppm of silica as an antiblock agent.
The six compounds were then used on a commercial-sized blown
film line (operating at a throughput rate of between about 32 and 33 kg
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~ 2~76(~57
Patent
per hour). All six compounds showed unacceptable levels of surface
defects, with between 60 and 100% of the film surface showing melt
fracture defects.
In order to ensure that there was not a machine problem causing
these poor results, a control experiment was performed with a
conventional fluoroelastomer based additive. This control experiment
resulted in the complete elimination of melt fracture at a fluoroelastomer
level of less than 1000 ppm.
These data indicate that silica antiblocks are very antagonistic
towards the e~fectiveness of vinylidene fluoride-containing thermoplastics
in the absence of acrylic-containing thermoplastics.
Example 4 (Com,~ al dli~e)
comPositions Containinq Hindered Amine Li~ht Stabilizers
This example illustrates that hindered amine light stabilizer
additives (also known as "UV" additives) are antagonistic towards
fluorocarbon polymer additives.
A polyethylene compound containing conventional, minor amounts
of adjuvants (including 450 ppm of a fluoroelastomer sold under the
trademark DYNAMAR FX 9613 by 3M) was prepared without a UV
additive. A second blend (otherwise identical to the first blend, except for
the addition of 4000 ppm of a UV additive, believed to be a hindered
amine, sold under the trademark CHIMASORB 944) was also prepared.
No ACTP was present in these compounds.
The two compounds were then extruded through a capillary
rheometer (as described in Example 2).
"~ls120can.d0c - 18-
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~ ~ Patent
Data describing shear viscosity (Pa.s) versus shear rate (s~') are
given in Table 30.
As shown in Table 30, the UV additive-containing compositions
have substantially higher shear viscosities at equivalent shear rates.
More significantly, the blend containing the UV additive
demonstrated onset of melt fracture at a shear rate of about 530 s~'
whereas the blend without the UV additive did not demonstrate onset of
melt fracture until a shear rate of greater than 900 s~'.
TABLE 30
Effect of UV Additive on Shear Viscosity
Shear Rate, s~' Shear Viscosity, Pa.s
No ~ V ~dditive With UV Additive
~7.6 9~7 20~5
6.8 ~'2 7o
9~ 2'8 ~5'0
' 1. ~.'' ' 07~ ~ 383
3~.2 962.1 ' 272
' 5~.7 88~.6 ' ' ~5
9' .8 790.~ ' 0~6
230.3 7''4.~ 9~5.1
v07. 6~,8.- 80n.s
8~.~ 9.6 70 .9
6 . ,: -9. 6_~.0
. . 06.3 . .8
. ~ ,.5 ' 90.2 5 1.7
66 .0 ~5fi.~ 506.4
729.8 ~'' .' ' 72.8
810.8 ~22. ~35.8
848.2 ~ 1~........... 19.4
ps."~ c/9120can.doc - 19 -
