Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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DISPERSIBLE FILM
TECHNICAL FIELD
This invention relates to a polymer film used to make compounding bags
and rubber bale wrap for rubber mixing, but also extends to polymer films used
to
wrap or contain ingredients for addition to most polymer/additive mixes
requiring a
relatively low process temperature at which temperature the polymer film, bag,
or
over-wrap based on the polymer film must disperse into the mix.
BACKGROUND
In the manufacture of rubber goods, elastomers and additives (generally
compounding ingredients) are combined in a mixer to form a substantially
homogeneous mixture (or rubber compound) which is then formed to the desired
finished product shape. This shaped mixture may then be cured, or cross
linked.
The economics of making rubber induce the manufacturer to make ever more rapid
mixes and ever more rapid cures .in order to remain competitive. Rapid curing
usually implies lower temperature mixing which in turn limits mixing
temperature
because the mix temperature must not exceed the activation temperature of the
curatives. These trends encourage the use of rubber bale wrap and/or
compounding bags using films that melt or soften at ever lower temperatures to
facilitate rapid dispersion of the film in the rubber/additive matrix.
Compounding
bags are used to hold a variety of additives including, but not limited to
curatives
such as sulfur, and primary and secondary accelerators; fillers both
reinforcing and
non-reinforcing; plasticizers such as oil and waxes; tackifiers; and specialty
chemical additives used as coupling agents and stabilizers for heat, ozone, UV
light, and the like. Other polymer mixing and or compounding operations are
analogous to mixing elastomers in the desire to carry bagged compounding
ingredients for addition to a mixing process which requires an easily
dispersed bag.
The use of pre-weighed ingredients has many advantages over the direct
addition by "scoop and shovel," I ) improved housekeeping, 2) improved
industrial
hygiene, 3) loss control, 4) accuracy and consistency for improved quality, S)
reduced labor costs. The actual weighin<r measuring can be done remotely or
very
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near the point of addition to the mixer. It can be a relatively simple manual
operation or a more elaborate automated form-fill-seal operation. In any case,
the
result is a measured quantity of wrapped or bagged material suitable for
direct
addition to the mixer.
Polyethylene film has been used for compounding ingredient bags and/or
rubber bale wraps because of its generally low cost, ability to be formed,
filled and
sealed, and toughness. Very early, the limits of polyethylene became apparent
and
restricted its use. The relatively high melt temperature and Vicat softening
point of
the low density polyethylene restricted it to relatively high temperature
mixes.
Ethylene copolymers having lower melting and Vicat softening points were
introduced such as ethylene vinyl acetate (EVA) copolymers or other low
melting
point ethylene polar comonomer copolymers. More recently metallocene catalyzed
low or very low density polyethylene (generally m-polyethylene) and blends
thereof
have also been used and/or discussed. Additives, such as low melting waxes,
have
also been employed to lower these temperatures. However, these solutions also
encountered limits as the need for ever lower temperatures developed.
Various problems associated with using polyethylene andlor EVA
copolymer films used for bale wrap and compounding bags have been mentioned
here and in US 5,500,260 and incorporated herein by reference for purposes of
US
patent practice. In particular, this patent suggests the need for a film to
have a
Vicat softening point as low as or below 82~ C (also disclosed in US
5,145,747) to
provide adequate dispersion of the film in an elastomer mix.
There is now a need to obtain adequate film dispersion at even lower
temperatures, particularly requiring a film with a melt point as low or lower
than
75~ C for certain rubber mixes (and a Vicat of as low as or lower than 55~ C).
Requirements for even lower Vicat softening points are being developed with
some
industry requirements now as low as 48~ C Vicat softening point.
However, as the Vicat softening point and melting point of a polyethylene
based film is reduced, the strength properties of films based on such
polyethylenes
or polyethylene blends having such melt/Vicat combinations, generally
decrease,
often dramatically decreasing, creating practical problems with handling,
shipping,
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and storing unused film and bags and then problems with handling film and bags
after filling. A film with such low Vicat softening point as for instance 55~
C
becomes very soft, stretchy, and tacky and will generally have low resistance
to
tearing making it difficult to handle in either wrap or bag making operations
or
further downstream in filling, storage and handling. To compensate for these
low
strength properties, the film and/or bags must be either handled somewhat
delicately to prevent damage or greater thickness of film must be used to
compensate for the low strength. Both of these compensations are commercially
impractical. Greater thickness are both less economical and introduce more
film
into a rubber mix that requires dispersion. Anti-block additives and slip
(generally
erucamide) are used to overcome tack, but especially the slip may make the bag
slippery especially at slip levels high enough to mitigate sticky films
created from
such low melting or softening polyethylenes. Such slippery films are difficult
to
handle. The use of anti-block additives is common in the film industry at
levels as
I S low as 1,000 ppm (0.1 wt%) to levels of as high as 5 wt. %. The use of
calcium
carbonate (CaCO3 ) as a filler in such films is known. However, while CaC03
improves some properties of low melting and/or low Vicat softening point
films,
still more improvement is desired.
A suggested solution to these problems suggested in Patent Number
PCT/L1S94/09988, is the use of polyethylenes that form stronger films to blend
or
co-extrude with these low melt materials. Unfortunately, these polyethylenes
that
form stronger films generally have higher melting points and thus detract from
overall dispersability of films including them.
There is a commercial need therefore for a polyethylene film, preferably a
polyethylene film that has a relatively low melting point as well as a
relatively low
Vicat softening point, that will additionally have physical properties
(strength)
sufficient to allow normal shipping and handling without substantial breakage.
SUMMARY
Embodiments of my invention overcome the generally lower strength of
lower melting point polyethylene films by reinforcing the films with a
suitable filler,
without substantially effecting (raising) the melt point and/or Vicat
softening point.
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Fillers such as talc, more preferably talc with a high aspect ratio, and most
preferred are such fillers or combinations thereof that are surface treated.
Silica,
carbon black and other fillers having a reinforcing effect may also be used.
The use
of a reinforcing filler has several beneficial effects. The fiber or filler
combination
can make the film polyethylene matrix stiffer and tougher as measured by
secant
modulus, puncture and tear resistance of the films. This improved stiffness
and
toughness allows the use of lower thickness film which reduces both the amount
of
the polyethylene added to the intended elastomeric matrix and also reduces the
amount of film material that needs to be dispersed. The reinforcing filler
also
appears to modify the rheoiogy of the polyethylene to make film extrusion more
economical by reducing power requirements and increasing extrusion rate. The
desirable effects of finer depend on the amount of reinforcing filler added as
well as
the type, but the desirable effects generally become effective in the range of
from
5%-50% filler by weight, preferably in the range of from 10-30 percent by
weight
based on the total weight of the polyethylene./filler combination. Such levels
are
above and different from the above mentioned anti-block materials and their
levels.
With embodiments of my invention, I have found that the above-mentioned
disadvantages associated with prior solutions can be minimized or eliminated
by the
use of a film made from at least one filler reinforced low density
polyethylene resin,
where the resin from which the film is made has a Vicat softening point up to
90~ C
and preferably a density up to 0.9I5 g/cm3. In addition, the film (in a
softened or
melted state) is generally compatible with rubber compounds. A film having a
melt
point temperature to achieve such compatibility will generally also allow
shorter
mixing times for the rubber being campounded, therefore providing for greater
productivity. The film's low melting temperature (below 100~ C), substantially
insures fluxing into the rubber compound mix during even abbreviated mixing
cycles. A melted film facilitates dispersion into a rubber mix. Since the
temperature of a particular mix is generally a function of mixing time, a
lower
melting and/or softening film can be dispersed in a shorter time. These lower
melting/softening point films enable the rubber manufacturer to achieve
shorter
mixing times.
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In one aspect of my invention, a polyethylene film, formed from a filler
reinforced ethylene-a-olefin copolymer, is provided wherein such film has:
a) a polyethylene resin density, before reinforcement, and before film
formation, in the range of from 0.85- 0.915 g/cm3;
b) a polyethylene melt index, before reinforcement, in the range from 0.1-
grams per 10 minutes;
c) a reinforcing filler content in the range of from S-50 weight percent
based on the total weight of the polyethylene filler combination;
d) a melting point of the filled reinforced film not exceeding 100~ C.; and
10 e) a Vicat softening point of the filled reinforced film not exceeding 90~
C.
In another embodiment, a second ethylene copolymer may be added to
improve the melt processability of the first ethylene copolymer. The second
ethylene
copolymer may be a copolymer of ethylene and an ethylinically unsaturated
ester of a
carboxylic acid. The second ethylene copolymer is preferably any polymer with
sufficient branching to contribute to the melt processability of the first
ethylene
copolymer (generally, but not necessarily so called "high-pressure"
polyethylene). In
this embodiment, the first ethylene copolymer, an ethylene a,-olefin
copolymer, is
present in the range of from 75-99 percent by weight of the polyethylene
portion of
the polyethylene/filler blend weight. The second ethylene copolymer is present
in the
range of from 25-1 weight percent based on polyethylene blend weight. By
polyethylene blend weight, I intend that such a polyethylene blend will then
form the
basis for addition of filler, as stated above, accordingly, a polyethylene
blend within
the limits stated above will then have filler added, to form the
polyethylene/filler blend.
DETAILED DESCRIPTION
Certain embodiments of my invention concern certain polyethylene films, their
production and applications based on such films. These films have unique
properties
which make them particularly well suited for use in certain compounding or
mixing
operations. These films have combinations of properties rendering them
superior to
films previously available for many such compounding or manufacturing
operations.
Following is a detailed description of certain preferred films based on
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polyethylene/filler or polyethylene blend filler combinations within the scope
of my
invention, preferred methods of producing these films, and preferred
applications of
these films. 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, though the properties of films based on polyethylene
and/or
polyethylene blend/filler combinations are exemplified in elastomer
compounding
applications, they have numerous other uses such as plastics compounding. To
the
extent my description is specific, this is solely for the purpose of
illustrating preferred
embodiments of our invention and should not be taken as limiting my invention
to
these specific embodiments.
Various Test Methods values given in the text and claims are determined as
follows:
Melt index (MI): ASTM D 1238 Condition E 190~ C, 2.16 kg mass;
expressed in g/10 min.
Vicat softening point: ASTM-1525 with a 1000 g weight. (~ C)
Melting point: Differential Scanning Calorimeter (DSC) second melting curve
melting peak in degrees centigrade. (ASTM D-3417)
STIFFNESS (MODULUS) ASTM D-882 (expressed in pounds per
square inch)
TEAR (ELMENDORF) ASTM D-1922 (expressed in grams or
grams/mil)
The film of the present invention for use as a rubber bale wrap or
compounding bag, has the following properties: good seal strength sufficient
to effect
seals to contain compounding ingredients, a low melting point, good
sealability
including sufFcient hot tack for use in form-fill-and seal applications, a low
Vicat
softening point, improved resistance to tearing and improved stiffness level
as
measured by secant modulus in the filler polyethylene film combinations. The
low
Vicat softening point and the low melting point improve the ability of the
film to be
incorporated into a substantially homogeneous mixture of rubber and/or rubber
compounding ingredients to form generally homogeneous rubber compounds.
The film of the present invention for use as rubber bale wrap and
compounding bags may be made from a single first ethylene a-olefin copolymer
or a
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blend of the first ethylene a-olefin copolymer with one or more other ethylene
a-
olefin copolymers, or with ethylene homopolymers, as long as the Vicat
softening
point is acceptable.
These ethylene a-olefin copolymers or blends thereof are combined with a
reinforcing filler using a means of mixing (well known to those of ordinary
skill) to
provide good filler dispersion resulting in the reinforcement of films based
on this
polymer filler mixture. This means of mixing includes, but is not limited to,
single and
dual screw mixing extruders as well as continuous mixers. Batch mixers would
be
expected to provide appropriate mixing and reinforcement as well.
The film made from the ethylene a-olefin polyethylene/filler mixture has a
Vicat softening point below 90~ C and a melting point below 110~ C.
Preferably, the
film has a Vicat softening point below 80~ C, more preferably below 70~ C,
most
preferably below 60~ C and a DSC melting point below 100~ C, preferably below
90~
C, more preferably below 80~ C.
In an embodiment of the present invention, a film is made from the mixture of
polyethylene and filler for either bale wrapping or for making compounding
bags. In
either case, the film must have softening and melting characteristics as
described supra
that permit its inclusion into the rubber compounding process, and such
inclusion will
result in a substantially homogeneous compounded elastomer blend.
The Pol.~. ly enes
The films of certain embodiments of my invention may be made from a
reinforced mixture of an ethylene a-olefin copolymer (first ethylene
copolymer). This
first ethylene copolymer has a density in the range of from 0.8S-0.915 g/cm3,
a Vicat
softening point less than 90~ C and a differential scanning calorimeter (DSC)
second
melting point (melting point) not exceeding 100~ C. The a-olefin utilized to
make the
first ethylene copolymer is selected from one or more of propylene, butene-l,
4-
methyl-1-pentene, pentene-1, hexene-1, octene-1 decene-1 and mixtures
thereof.. I
also intend that more than one such ethylene a-olefin copolymer such
combination
include, but are not limited to copolymers such as ethylene propylene;
ethylene,
butene-1; ethylene, hexane-l; ethylene, pentene-1; ethylene 4-methyl-I-
pentene;
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ethylene, octene-1; ethylene, propylene; butene-1; ethylene, propylene, hexene-
I ;
ethylene propylene, pentene-1; ethylene propylene, octene-1; ethylene, and the
like
may be used as the polyethylene portion of the polyethylene/filler blend, as
long as the
melting and/or Vicat softening point remains within the preferred levels
The first ethylene copolymer may be made by a number of processes, including
low pressure, gas phase, fluidized bed, slurry or solution processes. The
catalysts
used for the polymerization are generally of the metallocene-alumoxane,
metallocene-
ionizing activator, or conventional Ziegler-Natta types. Such catalysts are
well
known. Thus, useful catalysts are those disclosed in EP l229368, U. S. Patents
numbers 5,026,798 and 5,198,401 incorporated herein by reference for purposes
of
US patent practice.
Optionally, one or more second ethylene copolymers may be blended into the
first ethylene a-olefin copolymer or copolymers. The second ethylene copolymer
is
preferably not used primarily for depressing either the Vicat softening point
or the
melting point of the first ethylene copolymer, although such use is not
precluded.
Generally, the purpose of the second ethylene copolymer may be to improve melt
processability (higher melt strength) of the polyethylene blend over the
processability
of the first ethylene copolymer alone. The second ethylene copolymer is
generally a
molecule containing branching typical of those produced in high-pressure, free
radical
processes well known to those of ordinary skill. In another embodiment of the
present invention, the second ethylene polymer is a polyethylene homopolymer
or
preferably an ethylene copolymer of ethylene and at least one ethylinically
unsaturated
carboxylic acid ester. Preferred ethylinically unsaturated acrylic acid esters
include,
for example, vinyl acetate, methyl acrylate, butyl acrylate, ethyl acrylate
and
combinations thereof. A preferred ester monomer is vinyl acetate. These
comonomers are present in the second ethylene polymer within a range of from I-
35
weight percent, preferably from 1-30 weight percent of the unsaturated acrylic
acid
ester, based on the total weight of the second ethylene copolymer. Blends of
these
ethylene copolymers can also be used.
The second ethylene copolymers are chosen, in general, primarily based on
their ability to enhance processability of the first ethylene polymer and
their melting
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points and/or Vicat softening points. That is, the melting points and/or Vicat
softening points of such polymers should not have a substantial deleterious
effect on
these same parameters of the first ethylene copolymer, and the film made
therefrom at
the level of inclusion in the blends, but will mitigate processing debits
sometimes
found in the first ethylene copolymers. In general, a 10% improvement in
bubble
stability or neck-in over those of the first ethylene copolymer would be
desirable as a
result of inclusion of the second ethylene copolymer or copolymers. By
substantial
deleterious effect, I intend that inclusion of a second ethylene copolymer or
copolymers would not raise the melting point and/or softening point above the
discussed preferred levels.
When the second ethylene copolymer is included in the manufacture of film
based on the ethylene a-olefin copolymers described above, it is present in
the range
of from 25-1 weight percent based on the total polyethylene weight of the
blend. The
first ethylene a-olefin copolymer is present in the range of from 75- 99
weight
percent, based on the total polymer weight of the blend.
In a preferred embodiment, the first ethylene a-olefin copolymer is present in
the range of from 80-95 weight percent based on the total polymer weight of
the
polymer blend. The second ethylene copolymer is present in the range of from
20-5
weight percent based on the total polymer weight of the polymer blend. More
preferred is a first ethylene a-olefin copolymer of from 85-95 weight percent
and a
second ethylene copolymer from S-15 weight percent. These weight percents are
based on the total weight of the polyethylene portion of the
polyethylene/filler blends.
Additionally, the reinforced film will further exhibit a 1 % secant modulus
machine direction (MD) of greater than 6,000 psi, preferably greater than
7,000 psi,
more preferably greater than 8,000 psi, most preferably greater than l0,000
psi.
Additionally, the film will exhibit a 1 % secant modulus transverse direction
(TD)
greater than 6,000 psi, preferably greater than 7,000 psi, more preferably
greater than
8,000 psi, most preferably greater than 9,000 psi.
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The film will exhibit an Elmendorf tear as follows (g/mil):
MD TD
>1S0 >I40
preferred > I 60 > 160
more preferred >200
most preferred >250
It should be understood that the film produced from either a first ethylene
copolymer, or a blend of at least two different ethylene a-olefin copolymers
(e.g. a
first ethylene a-olefin copolymer and a one or more other ethylene a-olefin
S copolymers) may be reinforced with filler and used for film manufacture
without the
use of the second ethylene copolymer such as an ethylene vinyl acetate
copolymer.
However, in either the case where the first ethylene a-olefin copolymer is
reinforced
and used alone, or in the case where it is blended with at least an other
ethylene a-
olefin copolymer, it is understood that the Vicat softening point of the
resulting film
which may include filler does not exceed 90~ C, and the melting point of the
film does
not exceed 100~ C.
Also contemplated are films made from ethylinically unsaturated carboxylic
acid ester copolymers with the disclosed fillers, in the substantial absence
of an
ethylene a-olefin copolymer. However, it is also contemplated that such films
will
still exhibit the Vicat softening point and melting point upper limits
disclosed, and
preferably one or more of the secant modulus andlor tear strength limits.
Further contemplated are blends of the ethylinically unsaturated carboxylic
acid ester copolymers as the majority component in the polyethylene portion of
the
polyethylene /filler blends used for the films of certain embodiments of the
present
invention.
Accordingly, such embodiments might include the following:
Ethylene ethylinically Ethylene a-olefin
unsaturated carboxylic acid copolymer
ester copolymer
Preferred 75-100 2S-0
More preferred 8S-9S S-15
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The area of blends from 75% weight to 25% weight ethylene oc-olefin
copolymer with the balance as the ethylene ethylinically unsaturated
carboxylic acid
ester copolymer are not excluded.
In all cases the polyethylene portion, whether a blend, or a single
polyethylene,
then makes up the polyethylene portion of the polyethylene/filler mixture. The
mixture, when converted into film should display one or more of the described
Vicat
softening point, melting temperature, I% secant modulus and/or Eimendorf tear.
The Filler/Reinforcement
It should be understood that the reinforcement of the polyethylenes (one or
more of both types of ethylene copolymers disclosed) can be accomplished by
several means. In one case, all ingredients (polymers, fillers, slip agents,
anti-
block, process aids, stabilizers, and the like. ) in the reinforced polymer
can be
mixed together to form a complete polyethylene/filler mixture ready to be
extruded
into film, or alternatively, a "concentrate" of filler and/or additives can be
made in
1 S one or a11 of the copolymers which is then "let down" or diluted with the
balance of
the ingredients and/or polymers to make the same polymer mixture. In the
second
case it is understood that sufficiently intensive mixing will occur in the
film
extruder to provide a homogeneous film.
It should be further understood that additives often found in films are
contemplated by our invention as well. Such additives will be understood by
those
skilled in the art to include those that will have an effect on surface
characteristics
of films, processability of resins being made into films, thermal stability of
resins or
film and the like. These, and other types of additives, are normally carried
in
polyolefins, but may be added without such polyolefin carriers. The additive
types
mentioned are not meant to be a complete list, but merely illustrative. The
additives included in the film will be understood to be different from the
additives
to be carried in compounding ingredient bags, while they may or may not differ
in
type, their intended use will differ.
The reinforcing fillers can be talc, preferably talc with a high aspect ratio,
with or without surface treatment, or any other type of reinforcing filler
including,
but not limited to, the various forms of silica (fumed, precipitated, and the
like)
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with or without a coupling agent, other mineral type fillers including but not
limited
to other mineral type fillers such as kaolin and other clays, feldspar,
silicas both
natural and synthetic, carbide fillers, metallic oxides, sulfates, silicates
and titanates,
as well as carbon black. Such mineral type fillers may also include surface
S treatment discussed below and/or coupling agents. There are also other
fillers that
may enhance stiffness and tear resistance although the usual primary use of
these
fillers is to impact other properties such as electrical conductivity or flame
retardancy. The surface treatment of talc can be stearic acid or any other
common
treatment intended to increase the affinity of the filler for the
polyethylene. Aspect
ratio of a platy filler such as talc is the platelet effective diameter to
thickness ratio.
CaC03 is efl'ectively a sphere and has an estimated aspect ratio of l, while
the talc
contemplated in certain embodiments of my invention has an aspect ratio
estimated
in the range of 20-50. These filled films provide increased strength
properties and
stiffness which enable easier handling of wrapped/bagged product while still
providing the despersibility of a low melting film structure in a mechanical
(rubber
or elastomer)mixer.
In these preferred embodiments it is preferred that a reinforcing filler such
as
talc, and preferable talc with a high aspect ratio be included in the range of
from S -
50%, and preferably in the range of from 10-40%, more preferably in the range
of 15-
30%, by weight based on the total weight of the polyethylene (or polyethylene
blend)
and the filler. Combinations of fillers are also contemplated. For example,
CaC03
and one or more of the tales or other fillers described above are
contemplated. Such
combinations are part of contemplated embodiments as long as the final
polyethylene/filler combination meets the desired melting, softening, and
physical
properties disclosed herein. The reinforcing filler level (wt%) will be based
on the
total weight of the polyethylene, or polyethylene blend, as well as the weight
of any
and all additives. The reinforcing filler should be present in the ethylene a-
olefin
copolymer (or blends of ethylene a-olef n copolymers) or in a blend of
ethylene a-
olefin copolymers) with at least one ethylene copolymer in an amount effective
to
increase physical properties of the resulting film, while still maintaining a
Vicat
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softening point and DSC melting point within the described limits discussed
earlier.
That is the filler should be present to a level where the following film
properties exists:
Vic~t Melting Point
less tltnn ~C' Icss titan ~(.
90 100
preferred 80 90
more preferred 70 80
most preferred 60
Modulus Tenr
greater greater than
than C C
(K Psi) (g/ml)
MD MD TD
TD
6 6 l50 140
preferred 7 7 160 160
more preferred8 8 200
most preferred10 9 2S0
In the practice of embodiments of this invention, the rubber is generally
compounded utilizing a mechanical mixer. The compounded rubber can include
mixed unvulcanized rubber with the bale wrap and/or a compounding ingredient
bag
film of this invention. The compounded rubber can also include accelerators,
promoters, curing or crosslinking agents, fillers, colorants, anti-oxidants,
and other
adjuvants.
While mono layer extrusion is exemplified, multilayer extrusion is also
contemplated. One or more of the layers would have sufficient filler, to
improve the
physical properties of the resulting films. The base resin (polyethylene) or
polyethylenes for each layer may be the same or dif~'erent. In any case, an
effective
amount of filler must be in one or more layers to achieve improvement in one
or more
of film rnodulus, tear strength and the like.
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Additionally, the polyethylene component of the eventual film may be as stated
supra, a blend or coextrusion of one or more polyethylenes. For instance, a
blend of 2
"ethylene a-olefin copolymers" might include an ethylene, butene-1 copolymer
and
ethylene, octene-I copolymer. Such blends could also include ethylene butene-
1,
ethylene, hexene-1; ethylene, hexene-1, ethylene, octene-1; tri part blends
such as
ethylene, butene 1, ethylene hexene-1, and ethylene octene-1 are also
contemplated.
Further, ~fle so called "second ethylene copolymer" may be one or more
ethylene copolymers such as ethylene vinyl acetate, ethylene methyl acrylate,
ethylene
ethyl acrylate, ethylene n-butyl acrylate, ethylene acrylic acid, ethylene
methacrylic
acid, ionomers of tl~e acid copolymers, terpolymers such as ethylene vinyl
acetate,
metylacrylate; ethylene methyl acrylate, acrylic acid and the like. The second
ethylene
copolymer may be also a blend of two or more such second ethylene copolymers.
The amount of second ethylene copolymer or copolymers blended optionally
with an amount of the first ethylene copolymer or copolymers will be
understood by
those of skill in the art, to be an effective amount to improve the
processability of the
first ethylene copolymer, generally with respect to bubble stability (blown
films) or
neck in (cast films). The use of second ethylene copolymers may also be to add
other
properties to the final film such as lower cost.
It might also be possible to use only the first ethylene copolymer without the
processing benefit of the second ethylene copolymer, especially considering
the
improvement in rheology by the use of fillers.
In any case when speaking of a "polyethylene/filler" blend film or
composition,
it will be understood that I intend the term polyethylene to include any such
blends as
discussed above or such blends that still provide a low melting and/or
softening point.
The amount of filler (e.g. 5-50 weight %) will be based on the total weight of
the
polyethylene or polyethylene blend.
EXAMPLES
Example I
A film was made on a Sterling blown film extrusion line made by having a 1.5
inch diameter, 24:1 L/D screw and a 2 inch diameter die. The resin
(polyethylene)
blend for the film was made by dry blending pellets of 87.5 wt. % Exact~ 4011
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manufactured by Exxon Chemical Co. and 12.5 wt. % of a master batch (a11
ingredients shown below the Exact in the following formulation). This resulted
in a
final blend composition of:
Weight
Exact'' 40l 1 87.50
LD 760.36 10.24
Erucamide 0.375
Stearamide 0.375
Diamataceous Earth 1.500
Dynamar'~' FX 96I3 .009
99.999
The Exact 401 I and LD 7G0.36 are available from Exxon Chemical Company.
Exact 4011 is a butene ethylene copolymer with a nominal density of 0.885 g/cc
and a
2.2 g/10 min. melt index. LD 7G0.36 is an EVA copolymer containing 27.5% vinyl
IS acetate with a 2.3 g/10 min. melt index.
Dynamar'' FX-96l3 is a fluropolymer from 3M Co. used to help eliminate melt
fracture.
Example 2
A film was prepared on the same extrusion line as Example I using a polymer
mixture
reinforced with calcium carbonate, Hi Pflex'' l00, from Specialty Minerals
Corp. This
mixture was prepared on a Werner Pfleider twin screw mixer.
Weight
Exact 40l 1 64.5
LD 760.36 10.0
Erucamide 0.07
Dynamar FX 9613 0.14
Ciba Geigy B-900 0.26
Hi Phlex 100 2S.00
99.97
Example 3
A 10% talc mixture was prepared by dry blending the following and mixing in
the same laboratory extruder as example 1. The 30% UTMT 609BF Concentrate
used here was prepared by Specialty Minerals from 30% UTMT 609BF in Exact 4011
in their laboratory mixer. UTMTG09BF is a treated talc having a high aspect
ratio.
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Weight
Exact 401 1 54.5
30% UTMT 609BF Concentrate 33.0
SSABC0612VA 12.5
S 100.0
This resulted in a film composition as
follows:
We~ht
Exact 40l 1 77.6
UTMT609BF 9.9
LD 760.36 l0.24
Erucamide .3 75
Stearamide .375
Diatomaceous Earth 1.500
Dynmar FX 9613 .009
99.999
Example 4
A 20% talc mixture was prepared in a similar manner as Example 3 from the
same concentrate containing 30% treated talc (30% UTMT-609BF) in Exact 401l,
specially prepared by Specialty Minerals in a laboratory mixer). This dry
blend was let
down in the same laboratory extruder to provide a 20~to overall talc
containing film.
Weight
Exact 401 1 20.5%
30% UTMT 609BF Concentrate 67.0
SSABCOG 12VA 12.5
100
resulting in a film composition of:
Weight
Exact 401 1 G7.4
UTMT 609BF 20. I
LD 760.36 10.24
Erucamide 0.375
Stearamide 0.375
Dia. Earth 1.500
Dynamar FX 9613 .009
99.999
Example 5
A 26% talc mixture was prepared in a similar way by dry blending the following
Weight
30% UTMT 609BF Concentrate 87.5
SSABC0612VA 12.5
100.0%
resulting in:
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Wei_h~t %_
Exact 401 1 61.2
UTMT609BF 26.3
LD 760.36 10.24
Erucamide .375
Stearamide .37S
Diatomaceous. Earth l.500
Dynamar FX 96l3 .009
99.999%
Prospective Examples 6. 7 and 8
Examples 1, 4 and 5 are repeated but the Exact 401 I is replaced
by LD
760.36. It is expected that the inclusiond 25 weight percent talc
of 20 an (Examples 7
and 8) will not raise the Vicat softening
point substantially above the 5 I C
of the resin
itself. Further, at least a 30% improvementin secant modulus (MD
& TD) is
expected as well as a potential improvementimendorf tear.
in E
TABLE 1
Prospective Examples
le 1 2 3 4 5 I 6 7 8
Filler None CaC03 Talc Talc Talc None Talc Talc
Wt% 0 25% 10% 20.1% 26.3% 0 20% 25%
Gauge, mils 1.73 2.I0 2.0 1.9 1.95 2.0 2.0 2.0
Secant Modulus,
psi
MD 6590 8630 8063 12400 13080
TD 3500 4870 9I97 10870 1l870
Elmendorf Tear,
grams
MD 229 356 253 539 337
(g/mil) 132 169.5 l26.5283.6 172.8
TD 218 386 305 607 606
(g/mil) 126 183.8 152.53l9.5 310.7
Power, amps 33 35 30 25 23
Bubble Stabilityleast most
DSC Melting Point,C71.5 72.5 72.7 72.5 73.S
Vicat Softening 56.4 56.4 55.1 53.7 49.4 51 <55 <55
Point,C
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Table 1 shows the unexpected and surprising change in physical properties of
Examples 3 through 5 as reinforcing filler is added. The stiffness and tear
strength of
Example 2 using calcium carbonate is improved over Example 1, while the DSC
melt
point has not been substantially increased, and the Vicat has not changed in
spite of
the significant reinforcement. The use of talc in Examples 3, 4, and 5
surprisingly and
unexpectedly provides even greater reinforcement as shown by the large
increase in
stiffness (secant modulus) and several times increase in tear resistance. In
addition,
the processing characteristics improved as reinforcing filler was added as
shown by a
decrease in power consumption and an improvement in bubble stability. Very
important is the decrease of Vicat softening point temperature as talc content
is
increased indicating an increase in ease of dispersability while increasing
the toughness
of the matrix.
Conclusion
The present invention has been described in considerable detail with
reference to certain preferred versions thereof, other versions are possible.
For
example, while rubber bale wrap and compounding ingredient bag films from
polyethylene talc combinations have been exemplified, other uses are also
contemplated. Therefore, the spirit and scope of the appended claims should
not
be limited to the description of the preferred versions contained herein.
