Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1321437
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TITLE
BLEND5 FOR MAKING SKIN PACK~GING FILMS
BACKGROUND OF THE INV:ENTION
This invention relates to blends of
ethylane/carboxylic acid copolymers with high density
polyethylene and inorganic fillers, which blends are
useful ~or making ~ilms for skin packaging
applications.
Skin packaging is a packaging method
involving placing a product on a substrate material,
such as paperboard, and draping heated plastic film
over the product and substrate. A ~acuum is then
applied to draw the film down tightly to the board and
around the product to make a secure and attractive
15 package. One common application for skin packaging is
industrial skin packaging used to protect products in
transit. Products as divergent as computer tapes,
~ lamp;s, service repair kits and table tops may be skin
packaged instead of using die-cut corrugated,
foam-in-place, foam peanuts and other stabilizing or
dunnage materials. Skin packaging offers high
throughputs and full visibility to check for tampering
or missing components and also allows for quick
identi~ication, usually at significant cost
25 reductions.
LGW density polyethylene films are often
used for skin packaging applications, but skin
packaging films of ethylene/acid copolymers have been
found to possess faster cycle times, better board
adhesion, improved draw and better toughness than the
low density polyethylene films. Oddly enough, one
drawback of the ethylene/acid copolymer films is their
- relatively good optical properties since they more
readily show the relatively unattractive packaging
AD-5588 35 board used fvr the skin packaging of industrial items.
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Additivnally, the industrial items themselves are
often relatively unattractive. Thus, a method for
affecting the optical properties of the ethylene/acid
copolymer films, while not adversely affecting the
desirable properties of such films, such as adhesion,
was desired.
E~ 12F ~THE INVENq~ION
A method of modifying ethylene/acid
copolymers by blending them with high density
polyethylene and inorganic fillers has now been found
which sPrves to degrade the optical properties of
films made therefrom without degrading the adhesive
and other dssirable properties of such films.
Surprisingly, this modification o the ethylene/acid
copolymers leads to films which not only retain the
adhesive properties of the unmodified c~polymers, but
in some cases leads to films with adhesive properties
superior to that of the unmodified copolymers.
Specifically, this invention relates to novel blends
comprising:
(a) about 75 to 95.5 % by weight of one or
more ethylene/carboxylic acid copolymers;
(b) about 5 to 20 % by weight of high
density polyethylene; and
25(c) about 0.5 to 5 % by weight of a
particulate inorganic filler,
and to films made there~rom.
DETAILED DESCRIPTION OF THE INVENTION
The ethylene/carboxylic acid copolymers
30 which comprise the greatest part of the blends of this
inven~ion copolymers of ethylene with an alpha,
beta-ethylenically unsaturated carboxylic acid
pre~erably having 3 to 8 carhon atom~. Examples sf
acid monomers include acrylic acid, methacrylic acid,
ethacrylic acid, itaconic acid, maleic acid, fumaric
,
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acid, and monoesters of said dicarboxylic acids, SUC}l
as methyl hydrogen fumarate, ethyl hydrogen fumarate
and maleic anhydride. The concentration of acidic
monomer in the copolymer is generally about 1 to 20
weight %, and preferably rom about 3 to 15 weight %.
Preferr~d copolymers are copolymers of ethylene with
methacrylic acid or acrylic acid, or terpolymers of
ethylene, maleic anhydride and esters of acrylic acid
such as ethyl acrylate. The most preferred copolymer
is a copolymer of ethylene with methacrylic acid,
having an acid content of about 9 weight ~ and a melt
index of about 1.5.
The particulate inorganic fillers useful in
this invention are those ~illers well known in the art
or incorporation into films to improve handling
characteristics. The preferred filler is calcium
carbonate, but examples of other fillers which may be
utilized include, but are not limited to, mica,
aluminum silicate, magnesium silicate, and barium
20 sulfate. Preferably, so as not to adversely affect
the quality of the film, the filler is quite uniform
in size; e.g., for the preferred calcium carbonate
filler, a particle distribution would preferably range
from about 0.3 to 50 microns, and more preferably from
25 about 0.3 to 20 microns. Also, when it is desired to
degrade the optical properties of the film (e.g.,
increase haze or reduce trans~arency), the refracti~e
index of the filler preferably differs from that of
the ethylene/acid copolymer and the high density
30 polyethylene used in the blend.
The preferred high density polyethylene is a
linear ethylene homopolymer of medium molecular weight
distribution having a melt index of about 1.1.
A preferred composition comprises about 82
35 to 94% by weight of ethylene/acid copolymer, about 5
to 15% by weight high density polyethylene, and about
1 to 3 weight % inorganic filler.
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.
The blends of this invention may be made and
extruded into films by methods known in the art. The
following examples illustrate blends and films of this
invention.
Examples
A ~lend was made incorporating the
following:
Component A: 88 % by weight of
ethylene/methacrylic acid copolymer having
9% methacrylic acid, a Melt Index of 1.5
Component B: 10 % by weight of high density
polyethylne having a Melt Index of 1.1
Component C: 2 % by weight calcium
carbonate, 3-5 micron average particle size
15 and extruded into films 4 and 6 mil thick. Control
films extruded from Component A alone and from low
density polyethylene (LDPE) alone were also prepared.
Properties for these films are presented in the
following table. A description of the tests used
20 follows the table.
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Table
Film Properties
BLEND A BLENI) A A LDPE
Film 4 mil 4 mil 6 mil 6 mil 5 mil 5 mil
________..__________________________.__________________
ADH,PP COR (g/in.)
MD 729 681873 736 771 811
TD 629 581718 651 703 694
ADH,UPUP COR
(g/in.) MD 314 308356 363 395 201
TD 333 296364 349 411 218
TEMPERATURE, F 190 230195 198 190 230
HEAT UP, sec. 17 1~16.5 17.5 17.3 30
15 HAZE 71 1.5 - 12.8
GLOSS - - 4 90 - 18
TRANSPARENCY - -0.2 43 0.8
ELMENDORF (g/mil)
MD - -209 224 - 84
TD - - 229 240 - 101
SPENCER IMPACT
~in-lbs/mil) - - 3.1 4.3 - 2
TENSILE (psi)
MD - - 3959 4331 - 2814
TD 3999 4266 - 2947
E~ONGATION (%)
MD - - 512 536 - 540
TD - - 502 574 - 530
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ADH,PP COR - Adh~sion to primed printed corr~gated
board
AD~,UPUP COR - Adhesion to unprimed unprinted
corrugated board
TEMPERATURE - Amount of heat retained in the film as
it contacts the board to activate t.he primer or
adhesive on the ~oard for good adhesion
HEAT UP - The optimum amount of tim~e required to
soften the film ~or skin packaging, i.e., the amount
of time re~uired to "~ouble drape" the ~ilm.
HAZE - ASTM Dl003-61
GLOSS - ASTM D2457-70
TRANSP~ENCY - ~STM D1746-70
ELMENDORF ~ AST~ D1922-67
15 SPENCER IMP~CT - AST~ D3420-85
TENSILE - ASTM D822-83
ELONGATION - ASTM D822-83
MELT INDEX - (Referred to elsewhere in this
specification) - D1238
The data in the Table indicate that the films prepared
from the blends o~ this invention possessed superior
physical properties and better adhesion to unprimed
corrugated ~oard than the film of low density
polyethyl~ne~ ~he films according to ~his invention,
when compared to films prepared from ethylene/acid
copolymer alone (Component A), also possessed a
slight increas~ in adhesion to primed corrugated
board, a reduction in f ilm heat up timet and no
30 adverse reduction in film physical propeties.
.
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