Note: Descriptions are shown in the official language in which they were submitted.
7~
POLYOLEFIN BLENDS CONTAININ~ REACT~V~ AGENTS
The present invention relates to polyolefin
blends and in particular to a physical admixture of a maJor
portion of particles of an ekhylene polymer with a minor
portion o~ particles of a composition oE an ethylene polymer
and an agent that ls capable of reacting with polyoleEins in
the molten state, such reactive agent being a cross-linking
agent and/or a modifying agent and being further defined
hereinbelow.
Polymers oE ethylene, for example, homopolymers
o ethylene and copolymers of ethylene and higher alpha-
olefins, are used in large volumes for a variety of
end-uses, for example, in the form of film, fi~res, moulded
or thermoformed articles, pipe, coatings and the like.
Polyolefin compositions as offered for sale
and/or used in such end-uses often contain reactive and/or
non-reactive agents to modify or stabilize the polymer
during processing or during use of articles fabricated from
the compositions. Typical reactive agents include
cross-linking agents and certain unsaturated compounds.
Typical non-reactive agents include antioxidants and other
stabilizers, nucleation agents and additives that affect the
slip or blocking characteristics of products or the release
of products from moulds used in fabrication processes. It
is important that the incorporation of agents into
polyolefin compositions be carried out so that the resultant
composition has uniEorm properties.
Polymers having properties that are
commercially-acceptable in a variety of end-uses are known.
In addition, improvements in some polymer properties could
lead to improved products and/or use of the polymers in
additional end-uses. For instance, one method of improving
the end-use characteristics of an article rotationaIly
moulded from polymers of ethylene is to incorporate a
cross-linking agent, for example, an organic peroxide, into
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the polymer composition. In the rotational moulding of a
composition containing an organic peroxide, the polymer
flows to coat the inside of the mould and then the
cross-linking agent causes crosslinking of the polymer so as
to increase the molecular welght of the polymer, thereby
improving end-use properties of the resultant article.
Cross-linkable compositions especially adapted for
rotational moulding end-uses are disclosed in European
Patent Publication No. 0 0~7 210 of G. White, published 1983
August 31.
Cross-linkable compositions may also be used in
other end-uses to obtain improvements in product properties;
the cross-linking of the polymer will tend to affect melt
characteristics of the polymer under low shear rate
processing conditions. One example of the use of partial
cross-linking to obtain an improvement in film properties
is disclosed in Canadian Patent No. 1 123 560 of
D.A. Harbourne, which issued 1982 May 18.
Techniques for the incorporation of agents into
polyolefins are well known in the art. Non-reactive agents,
especially stabilizing agents, are frequently incorporated
into molten polymer during the process for the manufactura
of the polymer. Reactive and non-reactive ayents may also
be incorporated into polymers by melt blending techniques in
which the agent is metered into or otherwise added to molten
polymer during extrusion of the polymer into pellets or a
fabricated article.
It is important in the addition of agen-ts that
the agent be uniformly distributed throughout the polymerO
With non-reactive agents, however, the uniormity of the
distribution of the agent is normally less critical than
with reactive agents. F'or example, the re~uirements for a
slip agent or a stabilizer may be less critical than for a
cross-linking agent~ The cross-linking of a polymer
increases the molecular weight of the polymer. Thus, in
order to obtain a product of uniform properties, especially
~z~
-- 3 --
properties clependent on molecular weight, it is important
that the cross-linking of the polymer be carried out in a
uniform manner. I~ the cross-linking is not uniform, the
resultant product may, Eor example, have areas of weakness
due to either insufficient or excessive cross~linking of the
polymer or have gel particles resulting from excessive
cross-linking of the polymer, such gel particles resulting
in unacceptable visual appearance and/or areas of weakness
in the product. Some fabrication processes, for example
blow moulding of bottles and the manufac-ture of sheet and
film, may be more sensitive to non-uniform product
properties than other processes. In order to obtain uniform
product properties, it has been necessary to use expensive
and/or complex processes to incorporate reactive agents into
polymers, including special handling facilities and special
extruder screw designs.
The blending of organic peroxide with molten
polyethylene is disclosed in U.S. Patent 3 182 033 of R~S.
Gregorian, which issued 1965 May 04, and in Canadlan Patent
20 957 473 of H.J. Cook, which issued 1974 November 12. DoA.
Alia disclosed in U.S. Patent 4 197 381, which ~ssued 1980
April 0~, that the blending of crystalline polymers and
amorphous elastomeric polymers aided in the product;on of
cross-linkable polymers having a homogeneous composition.
The blending of reactive agents into polyethylene by means
of a physical blend of polyethylene with a different polymer
containing the reactive agent is disclosed in Canadian
application No. 485 651 of D.W. Boivin and R.A. Zelonka
filed 1986 June 27.
A blend of polyolefins capable of being used to
incorporate reactive agents into polyolefins in a uniform
and more economical manner has now been found.
Accordingly, the present invention provides a
polyolefin blend comprising, in physical admixture, a major
portion of particles of a first polyethylene and a minor
portion of particles of a composition of a second
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polyethylene, in ~h;ch the Eirst polyethylene is selected
Erom the group consisting of homopolymers of ethylene and
copolymers oE e-thylene and at least one C4 - C1o higher
alpha-olefin, said second polyethylene being a copolymer of
ethylene and at least one C4 - Clo higher alpha-oleEin
having a density of at least 0.~90 g/cm3 and a melt index in
the range of 40-200 dg/min., the density of the second
polyethylene being at least about 0.005 g/cm3 lower than
that oE the first polyethylene and the melt index of the
second polyethylene being at least 10 dg/min. higher than
that of the first polyethylene, said composition being a
composition of the second polyethylene and a reactive agent
selected from the group consisting of cross-linking agents
and modifying agents, and mixtures thereof, said reactive
agent being capable of reacting with said polyethylene in a
molten state.
In a preEerred embodiment of the blends of the
presen-t invention, the reactive agent is a cross-linking
agent which is an organic peroxide.
In a further embodiment, the reac-tive agent is a
modifying agent.
In another embodiment, the melt index oE the
second polyethylene is 40-60 dg/min. higher than that of the
first polyethvlene.
The present invent;on also provides a polyolefin
blend comprising, in physical admixture, a major portion of
particles of a first polyethylene and a minor portion of
particles of a composition of a normally solid second
polyethylene, in which the first polyethylene is selected
from the group consisting of homopolymers of ethylene and
copolymers of ethylene and at least one C4 - Cl0 higher
alpha-ole~in, said second polyethylene being a copolymer of
ethylene and at least one C4 - Clo higher alpha-olefin
having a density of at least 0,890 g/cm3 and a melt index oE
at least 40 dg/min., said second polyethylene having a shear
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viscosity that i5 not more than 50% of that of said Eirst
polyethylene when measured at 200C and a shear rate of 400
sec~l, said composition being a composition of the second
polyethylene and a reactive agent selected fro~ the group
consisting of cross-linking agents and modifying agents, and
mixtures thereof, said reactive agent being capable of
reacting with polyethylenes in a molten state.
In a preEerred embodiment, the shear viscosity of
the second polyethylene is not more than about 30 ~ of that
of the first polyethylene.
The present invention further provides a
polyolefin blend comprising, in physical admixture, a major
portion of particles of a first polyolefin and a minor
portion of particles o a composition of a normally solid
second polyolefin, said polyolefins being selected from the
group consisting of homopolymers and copolymers of
hydrocarbon alpha-olefins having 2-lO carbon atoms, said
second polyolefin having a shear viscosi-ty that is not more
than 50% of that of said first polyolefin when measured at
200C and a shear rate o~ 400 sec~l, said composition being
a composition of the second polyolefin and a reactive agent
selected from the group consisting of cross-linking agents
and modifying agents, and mixtures thereof, said reactive
agent being capahle of reacting with said polyolefins in a
molten state.
In addition, the present invention provides a
process or the manufacture of articles from a polyolefin
and a reactive agent capable of reacting with the polyolefin
in a molten state, comprising feeding to melt processing
apparatus a polyolefin blend comprising, in physical
admixture, a major portion of particles of a first
polyolefin and a minor portion of particles of a composition
of a normally solid second polyolefin, said polyolefins
being selected from the group consisting of homopolymers and
copolymers of hydrocarbon alpha-olefins having 2-lO carbon
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atoms, sai~ second polyolefin having a shear viscosity that
i.5 not more than 50% of that of said first polyolefin ~7hen
measured at 200C and a shear rate of 400 sec-l, said
composition being a composition of the second polyolefin and
a reactive agent selected Erom the group consisting o-E
cross-linking agents and modlfying agents, and mixtures
thereof, melting and admixing said blend and forming an
article from the resultant blend. The invention also
provides processes for the manufacture of articles from the
other blends described herein.
The polyolefin of the blends oE the present
invention is particularly described herein with reference to
such polyolefins being a homopolymer of ethylene and/or a
copolymer of ethylene and a minor amount of at least one
C4 - Clo higher alpha-olefin, for example a copolymer of
ethylene and a minor amount of butene-l, hexene-l and/or
octene--l. It is to be understood, however, that the
polyolefins may be broadly defined as being homopolymers or
copolymers of hydrocarbon alpha-olefins having 2-10 carbon
atoms. Techni~ues for the manufacture of such polymers are
~nown in the art.
As noted above, the invention is particularly
defined with reference to the polyolefins being homopolymers
and copolymers of ethylene.
The characteristics of the first polyethylene,
for example, the density and melt index of the polymer, will
depend to a large extent on the intended end-use of the
resultant products but, in embodiments, the density may
range from about 0.890 g/cm3 to about 0.970 g/cm3 and the
melt index, as measured by the method of ASTM D-1238
(condition E), may range up to about 100 dg/min. For
example, polymers intended for film and shee-t end-uses tend
to have melt indices of less than about 10 dg/min whereas
polymers intended for moulding end-uses tend to have higher
values of melt index. The ranges of density and melt index
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of polyoleEins that are useful for various types oE products
are known in the trade.
The characteristics of -the second polyethylene
differ from those described above for the Eirst poly-
ethylene. In one embodiment, the density of the secondpolyethylene is lower than that of the first polyethylene,
being at least 0.890 g/cm3, especially at least 0.910 g/cm3,
but with the proviso that it is at least about 0.005,
especially 0.008 g/cm3 lower than the density of the first
polyethylene. Secondly, the melt index of the second
polyethylene is hi~her than that of the first polyethylene,
being in the range of 40-200, especially 60-150 d~/min., but
with the proviso that it is at leas-t 10 d~/min., preferably
at least 20 dg/min., hi~her than the melt index of the Eirst
polyethylene.
In an alternate embodiment, the second poly-
ethylene ha~s a density of at least 0.890 ~/cm3, especially
at least 0.910 g/cm3, a melt index of at least 40 dg/min.
and has a lower shear viscosity than the first polyethylene;
in particular the she~r viscosity is not more than 50% of
that of the first polyethylene. Pre~ferably, the shear
viscosity oE the second polyethylene is not more than about
30% of the shear viscosity of the first polyethylene. As
used herein, shear viscosity is determined at 200C at a
shear rate of ~00 sec~l.
In the broader aspects of the invention, the
shear viscosity of the second polyolefin is not more than
50~ of that of the first polyolefin, and especially 5-15% of
that of the first polyolefin.
The second polyolefin is a normally solid polymer
and may include materials frequently referred to as solid
waxes but does not include materials that are liquids at
ambient temperatures and pressures; the blends of the
invention are physical admixtures and are therefore capable
of physical separation into the respective components at
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amblent temperatures.
The second polyethylene contains a reactive agent
selected from the group conslsting of cross-linking agents
and modifying agents, and mixtures thereof. As used herein,
the expression '!reactive agent" refers to an agent that
undergoes a chemical reaction at temperatures at which
polyethylene is in a molten state. It is to be understood,
however, that the rate of chemical reaction may not be
significant until the temperature of the molten polyethylene
is substantially above the melting point of the
polyethylene. For example, it is known that cross-linking
agents for polyethylene are usually selected so that the
cross-linking reaction occurs above the melting point of the
polymer e.g. at or near normal melt processing
temperatures. It is preferred that the reaction temperature
be such that adequate mixing of polymer and reactive agent
may be achieved prior to extensive reaction between polymer
and reactive agent; the half-life of a cross-linking agent
is usually known over a range of temperatures and may be
used to assist in selection of a cross-linking agent
suitable for an intended end-use. It is to be understood
that the reactive agent may be more than one chemical
compound or species and, in that event, part of the
composition of the second polyethylene may contain one
reactive agent and another part of the composition of the
second polyethylene may contain a second reactive agent. It
is to be further understood that if the reactive agent is
more than one chemical compound or species, then each such
reactive agent may be capable of reacting with polyethylene
that is in a molten state and/or one such reactive agent may
be capable of reacting with another such reactive agent.
In the event that the reactive agent is a
cross-linking agent e.g. an organic peroxide, the firs~
polyethylene may, but normally will not, contain organic
peroxide. However, it may under sorne circumstances be
desirable to incorporate portions of the cross-linking
~6~3 ~ ~
formulation into the first polye-thylene. For example, if
the cross-linkable composition is to be comprised of both an
organic peroxide and a co-curing agent, as is disclosed in
the aforementioned publication of G. White, it might be
advantageous to admix the co-curing agent with the Eirst
polyethylene and to admix the organic peroxide with the
second polyethylene. Such an incorporation of the co-curing
agent into the first polyethylene may aid in the fabrication
oE a uniform product. In any event, the first polyethylene
will often contain non-reactive agents known to be
incorporated into polyethylene including antioxidan-ts and
other stabilizers, pigments and the like, it being under-
stood that some so-called non-reactive agents useful in
polyethylene may have detrimental ef~ects on cross-llnking
or other reactive agents useful with polyethylene and as
such will likely not be used in combination with such
cross~linking or other reactive agents.
For blends containing cross-linking agents, the
preferred cross-linking agent is an organic peroxide,
especially a bis(tert. allcyl peroxy alkyl) benzene, dicumyl
peroxide or acetylenic diperoxy compound. Other organic
peroxides are known to those skilled in the art, including
t-butyl hydroperoxide and di-t-butyl peroxide.
2,5-Dimethyl-2,5 bis(-tert~ butyl peroxyisoprop~l)benzene is
the preferred organic peroxide and is available commercially
under the trade mark Vulcup from Hercules Incorporated. ~s
an alternative, the cross-linking agent may be 2,5-dimethyl-
2,5-di(t-butylperoxy)hexyne-3 which is available commercial-
ly under the trade mark Lupersol 130 from Lucidol Division
of Pennwalt Corporation. In an embodiment, the composition
of the second polyethylene may be similar to compositions
disclosed in the aforementloned publication of G. White
except that the polyethylene would be selected so as to meet
the requirements of the present invention. While the amount
of cross-linking agen-t in the second polyethylene may be
varied over a wide ran~e it may be preferable not to have a
~6~:~'79
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high concentration oE cross-linklng agent in the second
polyethylene and to then admix only a small amount o~ the
second polythylene with the first polye-thylene. In that
e~ent, problems may be experienced in mixing the rela-ti~ely
high concentration of cross-linking agent in the second
polyethylene in a uniform manner into the first
polyethylene. If the cross-linking agen-t is an organic
peroxide, it is preferred that less than ~% by weight oE
peroxide be present in the second polyethylene and
preferably 0.05-1.0% by weight of peroxide.
As noted above, a co-curing agent may be
incorporated into the first or second polyethylene i.e.
either separately from or admixed with cross-linking agent.
Examples of co-curing agents include triallyl cyanurate,
triallyl isocyanurate and 1,2-polybutadiene.
The reactive agent may be a modifying agent,
which may be used ei-ther alone or, usually, in combination
with an initiator. Examples of modifying agents include
unsaturated organic acids, and derivatives thereof, e.g.
acrylic acid, methacrylic acid, maleic acid, fumaric acid,
itaconic acid, crotonic acid, maleic anhydrlde,
cross-linkable silane compounds e.g. vinyltrimethoxysilane,
vinyltriethoxysilane, vinyltris(2-methoxyethoxy) silane and
vinylmethyldimethoxysilane, and other compounds capable of
being reacted with molten polyethylene. The use of sulphur
trioxide-trimethylamine complex, as the modifying agent is
described and claimed in the copending patent application of
J.R. Boocock Eiled concurrently herewith. The modifying
agents will usually be used in combination with an initiator
especially a cross-linking agent e.g. an organic peroxide.
With some modifying agents, other initiators are known e.g.
styrene acts as an initiator for maleic anhydride. The
modifying agent and initiator rnay be separately admixed with
the second polyethylene as compositions thereof. Under some
processing conditions, modifying agents may react with
~2~;2~7~
polyethylene in the sub.stantial absence of an added
initiator. For example, it is known to thermally react
maleic anhydride with polyethylene at temperatures of at
least about 375C~
The polyethylenes of the blend may contain a
stabilizing agent e.g. an antioxidant or an ultra violet
stabilizer. Examples of antioxidants are hindered phenolic
antioxidants e.g. octadecyl-3,5-di-tert.butyl-4-hydroxy
cinnamate and tetrakis-methylene-3-(3',5'ditert.butyl-4
hydroxyphenyl) propiona~e methane. Hindered phenolic
antioxidants may be used in combination with a phosphite
antioxidant e.g. di(stearyl)-pentaerythritol diphosphite,
tris di-tert.-butyl phenyl phosphite, dilauryl thiodi-
propionate and bis(2,4-tert.-butylphenyl) pentaerythritol
diphosphite. Examples of ultra violet stabilizers are
2-hydroxy-4-n-octoxybenzophenone, 2-(3'-tert butyl-2'-
hydroxy-5'-methylphenyl)-5-chlorobenzotriazole and
bis-(2,2,6,6,-tetramethyl 4-piperidyl)sebacate. Moreover,
the polyethylenes of the blend may contain sli~ agents,
anti-blocking agents, anti-static agents, mould release
agents, pigments, nucleating or other processing aids or the
like. Examples of slip agents are erucamide and stearamide,
of anti-static agen-ts are bis(hydroxyethyl) tallow amine and
glycerol monooleate, of anti-blocking agents are silica and
mica and of mould release agents are calcium stearate and
zinc stearate. Examples oE nucleating agents or other
processing aids are talc, silica, polyethylene glycol,
fluorinated elastomers and polyolefin waxes, or the like.
As noted above, stabili~ing or other so-called
non-reactive agents may have detrimen~al effects on cross-
linking or other reactive agents and for that reason it may
be preferable not to use certain combinations of agents, as
will be understood by those skilled in the art~
The ratio oE the first polyethylene to the second
polyethylene may be varied over a wide range, particularly
from about 5:1 to about 400:1 and especially about 50:1 to
about 100:1. The ratio selected will depend on a variety of
~6~7~
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factors, includinq the amount oE reactive agent (or o
additiona] reactive agent) to be lncorporated into the
blend, the type(s) of reactive agent, the need for a uniform
product, the type oE processing that the resultant blend is
to be subjected to and the mixing capabilities of apparatus
used therein and the like. With regard to the mixing
capabilities of the apparatus, twin-screw extruders may be
more effective than single screw extruders.
The amount of reactive agent in the blend of the
present invention will depend, in particular, on the type of
reactive a~ent and the intended end-use of the blend. Thus,
the amount could vary, depending on such other factors, from
a few parts per million ~ppm) in the blend to in excess of
one per cent, by weigh-t. ~Such amounts will be understood by
those skilled in the art.
In the event that the reactive agent is a
cross-linking agent, the first and second polyethylenes may
be selected and admixed so that the amount oE cross-linking
agent in the blend is in the range of about 25 ppm to about
1000 ppm by weight of the blend. The amount of
cross-linking agent in the blend will depend primarily on
t~le intended end-use for the blend. Blends intended for the
fabrication of highly cross-linked products will have
relatively high levels of cross-linking agents. On the
other hand, a small amount oE cross-linking agent may be
present in the blend so as to effect only a partial
crosslinking of the resultant product.
The particles of the first and second
polyethylenes may be any convenient shape and size and may
for example be granules, powder, pellets or the like. Such
forms are commercially available forms of polyethylene
and/or may be obtained by known techniques e,g. grinding,
melt pelletization and the like. However, it is preferred
that the particles of the first polyethylene be of
substantially the same size as the particles of the
composition of the second polyethylene. As the diEference
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in size b~atween the particles increases, so does the
possibillty that the two types of particles wlll become
separated ~rom one another during storage, transportation or
other handling of the blend; such differences may be less
cri-tical iE the blend is fed to an extruder shortly after
preparation thereof.
The composition o the second polyethylene may be
produced by techniques known in the art for incorporating
agents into polyethylene. Such methods include melt blend-
ing, coating and extrusion, and injection of the agent intomolten polyethylene. If the reactive agent is a modifying
agent or especially a cross-linking agent, the reactive
agent should be incorporated into the polyethylene ln a
manner that does not result in premature reaction with the
polyethylene, as in known in the art.
The blends of the present invention may be used
for the incorporation of reactive agents into polyethylene,
especially in a versatile and economic manner. The result-
ant blends may be used in a wide variety oE end-uses, as is
known for polyethylene. Such uses include blow-moulding
processes, film and pipe extrusion processes, sheet thermo-
forming processes and rotational moulding processes.
Apparatus used in such processes is referred to herein as
melt processing apparatus. In particularly preferred
embodiments, the blends are used in the manuEacture of film
in a blown film process. As is illustrated hereinafter,
such a use of the blends can result in substantial increases
in the rate of produc-tion of film of acceptable ~uality.
However, for any particular combination of apparatus,
polymer composition and processing conditions, there may be
an optimum level of cross-linking a~ent above which increas-
es in the rate of film production, if any, may be at the
detriment of film quality.
The present invention is illustrated by the
following examples:
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A composi~ion of an ethylene/butene~l copol~mer,
with 0.55% by weight of Vulcup R organic peroxide and 0 55%
by weight of triallyl isocyanurate, was prepared by a melt-
blending technique. The copolymer had a density of 0.950
g/cm3 and a melt index of 50 dg/min~
The composition was admixed with S~LAIR* 58~polyethylene, a copolymer oE ethylene and butene 1 having a
density of 0.955 g/cm3, a melt index of 0.43 dg/min. and a
shear viscosity of 3580 poise, in a ratio of polyethylene:-
composition of 100:1, to give a blend of the present
invention. The resultant blend was fed to a blow moulding
machine equipped with a mould for the fabrication of one
gallon bottles, The bottles obtained were of good quality,
being free of gel particles. Further details are given
below, as Run 1.
As a comparison, the corresponding composition
having an ethylene homopolymer, with a density of 0~960
g/cm3, a melt index of 21 dg/min. and a shear viscosity of
1700 poise, and the organic peroxide and triallyl isocyanu-
rate was preparedO A blend of this composition and SCLAIR58A polyethylene (1:100) was prepared and fed to the blow
moulding machine. It was found that the polymer contained
pellet-sized particles of gel. In addition the polymer melt
failed to fill the bottle cavity and the bottles obtained
were incomplete and full of holes. Further details are
given below as Run 2.
Further details are as follows:
Run No. _ 1 2 _ 3**
30 Diameter swell, %142.3 43.6 ~~
Weight swell, %2 474 394 493
Parison melt strength98 47.6 20.9
sec/lOOg3
1. Defined as (width of parison/0.5 x circumference of die
orifice~-l, expressed as a percentage. Measured at a
shear rate of 9000 sec~l in a blow moulding process
(1.8 litre bottles).
* denotes trade mark
~ ~ '
9~
- 15 -
2. Defined as (actual weight of parison/theoretical weight
of parison~-l, expressed as a percentage. Measured at a
shear rate of 9000 sec~1 as in (1) above. The
theoretical weight of the parison is the weight in the
absence of swell and drawdown.
3. The time in seconds that a parison weighing lOOg will
hang freely from the die of a blow moulding apparatus.
** Comparative data for SCLAIR 5~A polyethylene that does
not contain organic peroxide and triallyl isocyanurate.
Example II
A composition of an ethylene/butene-l copolymer
with 0.25~ by weight of Vulcup R organic peroxlde and 0.25
by weight of triallyl isocyanurate was prepared by a
melt-blending technique. The copolymer had a density oE
0.924 g/cm3, a melt index of 53 dg/min. and a shear
viscosity of 620 poise.
The composition was admixed with SCLAIR 13J4
polyethylene, an ethylene/octene-l copolymer having a
density of 0.926 g/cm3, a melt index of 1.0 dg/min. and a
shear viscosity of 5~40 poise, in a ratio of polyethylene :
composition of 50:1, to give a blend of the present
invention.
The resultant blend was fed to apparatus for the
manufacture of film by a blown film technique. The film had
a thickness of 25 ~m. It was found that a gel-free film
could be produced and that the film has a higher melt
strength than film produced from SCLAIR 13J4 polyethylene
that did not contain the composition of organic peroxidel
The higher mel~ strength permitted an increase in the rate
of production of film of 40%.
Subsequent testing showed that the impact
strength and tensile strength of the film were not adversely
affected by the use of the composition of organic peroxide
and/or the higher production rate.
Example III
Dynamic rheological properties of the ethylene/-
butene-l and ethylene/octene-l copolymers of Example II were
i ,,,~ ~
~6~3'7~
- 16 ~
measured using a Rheometrics* On-Line rheometerO That
rheometer measures the relationship between complex
viscosity and angular frequency which, according to the
Mer~-Cox rule, is equivalent under conditions o~ linear
viscoelas-ticity to the relationship between shear viscosity
and shear ra-te.
The dynamic rheological properties were determin-
ed a~ 200C under conditions that were equivalent to a shear
rate of 400 sec~l. It was found that tne shear viscosities
of the ethylene/butene-l and ethylene/octene-l copolymers
were 980 and 8000 poise respectively.
~ s noted in Example II, film of acceptable
properties could be made according to the present invention
using the above polymers.
Example IV
A granular linear low density polyethylene
identified as ESSO* LL10~1-49, which has a density of 0~918
g/cm3, a melt index of 1.0 dg/min. and a shear viscosity of
6250 poise, was extruded into film using a blown Eilm
process. The film produced had a thickness of 50 ~m/ It
was Eound that the maximum production rate obtainable with
the apparatus and processing conditions being used was 38.
kg/hr. The production rate was limited by, in particular/
s-tability of the bubble in the blown film process and melt
fracture of the polymer at the die lips.
A pelletized composition of a melt-processing aid
and 1000 ppm of Lupersol 130 organic peroxide in an ethylene/
butene-l copolymer having a density of 0.920 g/cm3, a mel-t
index of 1.40 dg/min. and a shear viscosity of 5250 poise,
was blended into the above linear low density polymer so as
to provide 5~ of the composition in the polymer. When film
was produced using the method described above, the polymer
did not exhibit melt fracture. However, the level of gel in
the film was too high to permit an evaluation of any
increased stability of the bubble.
The above composition was replaced, at a 2%
level, with a pelletized composition of 2500 ppm of Lupersol
* denotes trade mark
3~
~ 17 -
l30 organic peroxide in an ethylene/butene-l copolymer having
a density of 0.92~ g/cm3, a melt index of 53 dy/min. and a
shear viscosity of 620 poise. On extrusion of the blend into
film, it was found that the film obtained was essentially
free of gel and that it was possible to increase the
production rate by 47~, to 56.7 kg/hr.; melt fracture was not
experienced during the trial.
Example V
In a series of runs, ethylene/alpha-olefin
copolymer pellets containing Lupersol 130 organic peroxide
were blended with SCLAIR 13J4 polyethylene, an ethylene/-
octene-l copolymer having a density of 0.925 g/cm3, a melt
index of 1.0 dg/min. and a shear viscosity of 5~0 poise.
The resultant blends were extruded into Eilm in a blown film
process, the apparatus used being equipped with an efficient
mixing screw. Further details of the ethylene/alpha-olefin
copolymer and the results obtained are shown in Table I.
Table I
Shear
Run Copolymer Melt Viscosity Viscosity Film
No,* Comonomer Density Index ~poise)** ~pois0) Quality
1 octene-l 0.9261.0 9000 5440 poor
2 butene-l 0.9245.1 470G 2810 fair
3 butene-l 0.92420.0 1800 1330 good
4 octene-l 0.92~1.0 9000 5440 poor
butene-l 0.9245.1 4700 2~10 poor
6 bu~ene-l 0.92~20.0 1800 1330 good
* In Runs 1 to 3, 1.0% by weight of pellets containing
5000 ppm oE peroxide were used; in the remaining runs, 2~ by
weight of peilets containing 5000 ppm of peroxide were
used.
** Dynamic viscosity measured at 200C, 400
radians/sec.
The results show that when the polymer containing
the peroxide has a melt viscosity that is about the same as
that of major component, film of good quality was not
obtained~ When the melt viscosity of the polymer containing
peroxide was reduced to 50~ of the major polymer component,
as in Runs 2 and 5, film quality was marginal, being
, ~,, ,
~.J,
1~ -
dependent on the amount oE peroxide used. However, when the
melt viscosity of the polymer containing peroxide was only
20% of that of the major polymer component, good quality
~ilm was obtained~
In a related series of runs, attempts were made
to extrude film from a number of blends using apparatus
equipped with a very inefficient mixing screw. It was Eound
that even when the melt viscosity of the polymer containing
peroxide was reduced to 5% of that of the major component,
the peroxide concentration had to be less than 2500 ppm in
order to obtain film of good ~uality. Thus the present
invention will permit the manufacture of film using
apparatus having a very ineEficient mixing screwl although
more efficient mixing screws are preferred.
Example VI
About 1500g of SCLAIR 2114 polyethylene, an
ethylene/butene-l copolymer having a density of 0.924 g/cm3,
a melt index of 53 dg/min. and a shear viscosity of 620
poise, were ground in an Abbe* cut-ter equipped with a 0.48
cm mesh screen. About 45g of sulphur trioxide-trimethyl-
amine complex was dissolved in 600 ml of dis-tilled water at
50C and, with minimal delay, was distributed on the
particles of polyethylene in a Henschel* mixer maintained at
90C. Nitrogen was continuously passed through the mixer
for a period of 20 minutes to remove water vapour. The
resultant coated particles, which were still moist, were
dried overnight in a vacuum oven at 95C.
A masterbatch was prepared by extruding the thus
dried mixture from a lo 90 cm single screw Brabender*
extruder, equipped with a mixing screw, at a melt
temperature of 182C. The extrudate was cooled in a water
bath, cut in a strand cutter and dried overnight under
vacuum. The calculated amount of sulphur trioxide-tri-
methylamine complex in the masterbatch was 2.9% by weight.
A physical admixture of 23g of the masterbatch
and 660g of SCLAIR 13-llE polyethylene, an ethylene/butene-1
* denotes trade mark
,. . . .
~'f~
~,;.. .,~
~2~297~
-- 19 --
copolymer having a density of 0.920 g/cm3, a melt index of
1.40 dg/min. and a shear viscosity of 5250 poise, was
prepared. The admixture was extruded from the Brabender
extruder, now equipped with a venting screw and a breaker
plate, at a melt temperature of 256C, to form cast film
having a width of 13O5 cm and a thickness of 50 ~m. The
hold-up time in the extruder was estimated to be 2.5-5
minutes.
The ~ilm thus obtained was dyeable with basic
dyes, whereas film from either SCLAIR 2114 or SCLAIR 13-llE
polyethylene is not dyeable. In addition, the film did not
show evidence of significant amounts of black specks, which
are produced if a powder of the complex is reacted with
polyethylene.
The sulphonation of polyethylene using sulphur
trioxide-triethylamine complex is the subject of a copending
patent application of J.R.B. Boocock filed concurrently
herewith.
Example VII
In a series of runs, pellets of a polymer were
coated with 2500 ppm of Lupersol 130 organic peroxide
cross-linking agent. The resultant coated pellets were
physically admixed, at a 2% level, with SCLAI~ 13J4
polyethylene, an ethylene/octene-l copolymer having a
density of 0.926 g/cm3, a melt index of 1.0 dg/min. and a
shear viscosity of 5440 poise, to give blends of the present
invention. The resultant blends were fed to -the extruder of
a blown film process; the extruder was equipped with the
most efficient mixing screw that was available.
The film obtained was inspected for quality. The
results obtained are shown in Table II.
i 3
~2~ 7~
- 20 -
Table II
Run Film
NoO Polymer Quality Comments _
l ethylene/butene/- good good melt stren~th
octene
2 HPPE good good melt strength
3 polyethylene wax good good melt strength,
reduoed power consumption
4 polypropylene good good melt strength
white concen~rate good good melt strength
6 black concentra-te good good melt strength
l. (i) ethylene/butene/octene terpolymer, density 0.910
g/cm3, melt index 1.7 dg/min.
(ii) HPPE = high pressure polyethylene, density 0.918
g/cm3, melt index 7.0 dg/min
(iii) polyethylene wax = N-34 Epolene~ polymer, density
0.910 g/cm3, Brookfield viscosity 450 centipoise
at 125C.
(v) polyprop~lene = Shell* 6300, density 0.905 g/cm3,
melt flow index 20.0 dg/min.
~vi) white concentrate = TiO2 in a high pressure
polyethylene.
(vii) black concentrate = carbon black in a linear low
density polyethylene.
Example VIII
~ physical admixture of an ethylene/bu-tene-l
copolymer having a density of 0.920 g/cm3, a melt index of
1.4 dg/min. and a shear viscosity of 5250 poise, a concen-
trate of an organic peroxide cross-linking agent and maleic
anhydride was prepared in a Henschel* mixer such that the
admixture contained 50 ppm of cross-linking agent and 1% by
weight of maleic anhydride. The concentrate of the cross-
linking agent was in the form of pellets of an ethylene/-
butene-l copolymer having a density of 0.924 g/cm3, a melt
index of 53 dg/min. and a shear viscosity of 620 poise,
5i~ * denotes trade mark
!s ~
9~9
21 -
containing Lupersol 130 organic peroxide. The maleic
anhydride was in the Eorm of powder7
The mixture was blended in the Henschel mixer for
five minutes at a maximum temperature of about 70C and then
extruded through a corotating twin screw extruder, the first
two zones of which were at a temperature of 18aC and -the
remaining zones at a temperature of 200C.
A maleic anhydride-grafted polymer containing
0.56~ by weight of maleic anhydride was obtained; the melt
index of the polymer was 0.53.
Films of the grafted polymer were pressed onto
aluminum foil, nylon film and ethylene/vinyl alcohol
copolymer ~ilm at a temperature of about 180C. Good
adhesion of the gra~ted polymer to the foil or film
substrate was observed in each instance.
This example illustrates the use of the present
invention with a modifying agent. The reaction of maleic
anhydride with ethylene/butene~l copolymers is discussed
further in the copending application of C.S. Wong and
R.A. Zelonka filed concurrently herewith.
Example IX
~n e-thylene/butene-l copolymer having a density
of 0.959 g/cm3, a melt index of 85 dg/min. and a shear
viscosity of 3~0 poise, was blended with 2500 ppm of
t-butylhydroperoxide. The resulting blend was physically
admixed with pellets of an ethylene/butene-l copolymer
copolymer having a density of 0.920 g/cm3, a melt index of
5.5 dg/min. and a shear viscosity of 2630 poise, in ratios
of from 3:97 to 6:94.
The admixtures thus obtained were fed to a
process for the extrusion coating of paper. The extruded
admixture had higher melt strength such that the line speed
of the extrusion coating line could be increased from 26
m/minute, in the absence of the peroxide blend, to 46
m/minute.
. . ?
~ 22 ~
Example X
An ethylene/butene-l copolymer having a density
of 0.924 g/cm3, a melt index of 53 dg/min. and a shear
viscosity of 620 poise, was blended with 2500 ppm of
Lupersol 130 organic peroxide. The resulting blend was
physically admixed, at a 4~ and at a 6% level, ~ith SCLAIR
58A ethylene/butene-l copolymer which has a density of 0.955
~/cm3, a melt index of 0.43 dg/min. and a shear viscosity of
3580 poise. The resulting blends were extruded into sheet
having a thickness of 5 mm.
The sheets thus obtained were free of gel, had
higher melt strength than the corresponding sheets formed
from SCLAIR 58A polyethylene and gave improved performance
in the thermoforming process.
Example X_I
Physical admixtures of SCLAIR 13-llE ethylene/-
butene-l copolymer, which has a density of 0~920 g/cm3, a
melt index of 1.4 dg/min. and a shear viscosity of 5250
poise, organic peroxide and maleic anhydride were prepared.
The organic peroxide (Peroxide Concentrate) was
in the form of pellets of a composition of Sclair 2114
polyethylener an ethylene/butene-l copolymer having a
density of 0.924 g/cm3, a melt index of 53 d~/min. and a
shear viscosity of 620 poise, with 4000 ppm of Lupersol 130
or~anic peroxide and 4000 ppm of triallyl isocyanurate. The
maleic anhydride was either in the form of a powder or a
blend in polyethylene, as shown below.
The physical admixture was fed to a 1.9 cm
Brabender single screw extruder and extruded into a strand
using a melt temperature of 225C.
Adhesion tests were conducted by pressing the
~hopped strand into film between sheets of aluminum at a
temperature of 180C for about 5 seconds.
,'
~26~7~;9
- 23 -
Further details and -the results obtained are as
follows:
Sample A B C
5 SCLAIR 13-llE copolymer (g) 1473 1331 1331
Peroxide Concentrate (g) ].B.75 18.75 18.75
Maleic anhydride*
Powder (g) 7-5
concentra-te #l (g) - 150
concentrate #2 (g) - - 150
Results
_ _ .
Graft (as anhydride plus 0.35 0.31 0.24
acid) (%)
Melt Index (dg/min.) 0.44 0.64 0.72
15 Adhesion** 3 2
* In Sample A, the maleic anhydride was in the Eorm of a
powder; In Sample B, the maleic anhydride was in the
form of maleic anhydride deposited on ground Sclair
2114 polyethylene from -the melt in a rotary
evaporator (Concentrate ~1, which contained about 5%
by we.ight of maleic anhydri.de);
In Sample C, the maleic anhydride was in the form of
maleic anhydride deposited onto ground SCLAIR 2114
polyethylene by evaporation of a solution at 60-65C
in a rotary evaporator followed by application of a
vacuum and cooling to ambient temperature (Concentrate
~2, which contained about 5~ by weight of maleic
anhydride).
** Estimated order of strength of adhesion (1 = bestj.
The adhesion obtained with Sample A was very poor.
23A
SUPPLEMENTAR~ DISCLOSURE
In a preferred embodiment of the process of the
present invention, the blends are used in the manufacture
of film. Such a process for the manufacture of film would
normally be operated so as to produce produc-ts that are
cross-linked to an extent that gel is not formed or that
the shear viscosity of the first polyolefin is increased to
not more than five times its original value. In the
manu~acture of film, it is further preferred that at least
-the polymer of the first polyolefin be at least 70~ by
weight of so-called linear low density polyethylene. In
particular, the polymer should be a copolymer of ethylene
and at least one C4-Clo higher alpha-olefin e.g.
butene-l, hexene-l and/or octene-l, and have a density in
15 the range of 0.910 - 0.930 g/cm3.
It has been disclosed hereinbefore that the
polyethylenes of the blend may contain nucleating agents or
other processing aids, examples of the latter being
fluorina-ted elastomers. Such processing aids are
20 particularly useful in the manufacture of film, especiaily
from linear low density polyethylene, and tend to reduce
any likelihood for melt fracture to occur, as is disclosed
in U~S. Patent 3 125 547 of P.S. Blatz, issued 1964 March
17.
Melt fracture is a phenomenon that may occur
during extrusion of molten polyethylene through a die. At
low rates of extrusion, the extrudate may be smooth but at
some higher rate the extrudate will become rough; the
transition from smooth extrudate to rough extrudate may
30 occur as the result of a relatively small increase in the
rate of extrusion. The phenomenon is well known, being
discussed by for instance J.P. Tordella in SPE Journal,
p 36-40, February 1956. Copolymers of ethylene and
C4-Clo higher alpha-olefins, and especially such
- ~ .
S2~7~
23B
po]ymers of relatively low density, which are now
freguently referred to as linear low density polyethylene,
tend to be particularly susceptible to the occurrence of
melt fracture.
It has been found to be advantageous to
incorporate fluorinated elastomer processing aids into the
blends of the present invention~ especially as part of the
composition of the second polyolefin. Such use of a
fluorinated elastomer is illustrated by the following
example:
Example XII
A linear low density polyethylene, which was an
ethylene/butene-l copolymer having a density of 0.920
g/cm3, a melt index of loO dg/min. and a shear viscosity
of 6000 poise, and containing no additives other than
antioxidant, was extruded through a 6.25 cm extruder
equipped with an annular die havin~ a diameter of 10 cm.
The die gap was 0.75 mm and the melt temperature oE the
polyethylene was 200C. The film blow-up ratio was 2.5:1
and the resultant film had a thickness of 0 1 mm.
Melt fracture was observed in the ex-trusion of the
polyethylene at an extrusion rate of as low as about 7
kg/hour. However, film could still be manufactured at
extrusion rates of up to about 58 kg/hour, at which rate
the film bubble in the blown film extrusion process became
unstable as a result of insufficient melt strength of the
polyethylene.
While continuing to operate the process at the
same extrusion rate, 1.5~ by weight of a concentrate was
fed to the extruder along with the polyethylene. The
concentrate was a linear low density polyethylene, an
ethylene/butene-l copolymer having a density of 0.926
g/cm3~ a melt index of 73 dg/min and a shear viscosity of
7~4
23C
210 poise, and containing 3000 ppm of Lupersol 130 peroxide
and 2.6~ of a fluorinated elastomer processing aid of tAe
type disclosed in the aEorementioned U.S. 3 125 547. After
20 minutes, melt Eracture was no longer observed at the
extrusion rate of 58 kg/hour. Furthermore, the extrusion
rate could be increased by 20% to 71 kg/hour before the
film bubble became unstable. Melt fracture was not
observed at this higher extrusion rate.
The haze and gloss of film produced using the
linear low density polyethylene containing the concentrate
was superior to film produced using the polyethylene
without concentrate, because of the absence of melt
fracture.
.p ~
