Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~ i
lO9Z067
.''' . .
.~ ,
.' , . ' , : ~
~ .
C '
. . .
BACKGROUND AND SUMMAl~Y OF Tl~ INV~3NTION
There is a growing tendency to package many articles in ::
. .
plastic filn~ type enclosures rathcr than in cardboard cartons or the like,
particularly when there is a shortage of paper products. For example,
many canned and bottled food pFoducts are now being packaged by
placing them on simple cardboard or plastic trays nd th~n passing
: ' ' ' . ''
,
'
. .......
.
, .:, .
, 1 ; ';
, . . .. . - . . :..,:, ,: . .. . . ... : . -
67
them through conventional heat shrink apparatus in which they
are wrapped in a shrinkable film material, usually polyethylene,
which is then heat shrunk in place. This packaging technique
is used in cases in which it has been conventional in the past.
to use cardboard cartons. These individual packages, which
may consist of twelve or twenty-four cans or bottles of a
product, are then loaded on pallets for shipment. Because
they slide relatively easily with respect to one another they
..
must be anchored to the pallet by some suitable means, It is
common to do this using shrink wrap palletizing techniques,
wherein the pallet and load is enclosed at least in part by a
sheet or sleeve or pre-formed enclosure formed of heat
shrinkable film and then passed through a shrink tunnel where
heat is applied and the film tightly shrunk about the load.
One of the most commonly used heat shrink materials for this
purpose is polyethylene film, however it has been discovered
that when such film is shrunk on loads of indi.vidual packages
where the packages themselves are wrapped in polyethylene
fiIm, the shrinking heat applied in the tunnel causes the outer
polyethylene sleeve or bag to fuse to the individual packages
on:the pallet, thus making it difficult i not impossible to
remove the individual packages intact from the pallet when
they reach their destination.
It is therefore a primary object of the present
invention to provide a packaging system, including method,
film and package, which permits utilization of relatively
inexpensive and readily available polyethylene as the primary
shrink wrap material and which obviates the aforementioned .
disadvantage of known techni~es~. A related object
: 2
bm:
. : . - ,:, - ' : ' ~.,' :.' , , ' ' ,: . . . : . .
1~)9Z06'7
.
resides in the provision of an improved shrink wrap material
having greater toughness and strength than the commonly used
polyethylene film.
In one particular aspect the present invention provides .
a method of utilizing a shrink wrap film to shrink wrap or :
bundle a load of one or more articles where an exposed surface
thereon is formed of the same material as is said film, comprising
the steps of assembling the load to be wrapped, wrapping at least
a portion of the load with a laminate comprising an outer ply
formed of said material and an inner barrier ~ply formed of a
material which will not fuse to said exposed surfaces on said
load when subjected to a film-shrinking heat, and heating the
laminate to shrink same around the load.
In another particular aspect the present invention provides
a packaged load including two layers of heat shrunk fllm
: surrounding said load at least in part and having contiguous
portions in relatively intimate engagement, one of said
layers being a substantially continuous laminate of a heat
shrinkable film of a given material and a barrier film, the
other of said layers being a heat shrinkabls film of the
same general composition as said given material, said laminate
being positioned with said barrier film on the side of said
laminate facing the other of said layers, said barrier film
being formed from a heat shrinkable material which will not
fuse to said given material when in contact therewith and
subjected to film shrinking temperatures
These and other objects of the present invention will
become apparent from the following description and appended
claims, taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a side elevational view of a heat shrinkable
- / -3-
. . . : :
, . .
. . : .
., . ,. : . :
,: . .: . . ... . , .: . .
' . ' ' ' . ': , ' '~ ~ ' '
: . , :
- , .
..
~ ~9;~1)67
film embodying the principles of the present invention and
utilized in the form of a tube or sleeve, shown open;
Figure 2 is a side elevational view of a heat shrinkable
film embodying the principles of the present invention and
utilized in the form of a center-fold bag, shown in collapsed
state;
Figure 3 is a side elevational view of a heat shrinkable -
film embodying the principles of the present invention and
utilized in the form of a gusseted bag, shown in a collapsed
state; ~ . ~
Figure 4 is a sectional view of the laminate construction v
of the heat shrinkable film of the present invention; and
Figure 5 is a perspective view of a pallet load which has
been packaged according to the principles of the present
invention.
DETAILED DESCRIPTIO~ OF THE PREFERRED EMBODIMENT
' The benefits of the present invention are derived from
the u~e of a laminate as the heat shrinkable film material.
.
~ This laminate, shown in cross-section in Figure 4, comprises
a primary ply 12 which is preferably formed of conventionally ~ .
used heat shrinkable polyethylene
' ,' ' ` ~ :' ':.:'
: '
'
:
: .
`:. ' :
~ -;~ -3a- ~ :
. .. . ~. . : : .
, 109206~
film. Layer or ply 12 has laminated thereto a continuous
barrier layer or ply 14 which is formed of a material which (a)
is heat shrinkable to approximately the same extent as
polyethylene under similar heating conditionj, ~b) will heat
seal to itself, (c) will not heat seal or fuse to polyethylene
when subjected to fllm-shrinking temperatures, (d~ is of a
material similar in flexibility to polyethylene, and (e) can
be laminated to polyethylene. One material which has been
found to have these characteristics and provide the
10 ~ ! advantages of the invention, and which is relatively available
and economical is polybutylene, a high molecular weight isotactic
polymer. This material is a polyolefin and is synthesized from
butene-l monomer It is the preferred material. Other
materials which can have these characteristics are polypropylene,
polyvinyl chloride, and Surlyn 1601 resin, the latter being
an ionomer resin manufactured by E. I. DuPont de Nemours and
Co. Polybutylene is preferred over polypropylene because it
is much stronger and tougher and results in a completed wrap
~ of improved toughness and strength, and it is preferred over
polyvinyl chloride and Surlyn 1601 because lt is less
expensive.
The heat shrinkable laminate may be formed in
accordance with known laminating techniques, using standard
~` procedures. For example, the barrier ply may be co-extruded
with the primar~ polyethylene ply in either blown form or
sheet form, it may be coated on the primary ply with a sheet
extruder, or separate film plys may be laminated together using
conventional adhesives or other known lamination techniques.
It is important tha-t the barrier ply be continuous and-~ully
~, . .
r~ 4_
bm:
, . . :` . , .: : ,
.
.:
~1~92~i7
coextensive with the primary ply, not only to provide increased
strength but also to assure that there are no exposed portions
of the primary ply which may fuse to the packages which may
constitute the load. On the other hand, it is preferable to
provide as thin a barrier layer as is possible to minimize the
cost of the laminate, such as when polybutylene is used, In
practice it has been found that a layer as thin as 1/3 of a mil
of polybutylene can be coextruded with polyethylene, Because
the barrier layer contributes to the strength and toughness of
the heat shrunk laminate, less polyethylene may be used.for a
given application than would otherwise be used in the absence
of a tough barrier layer.
The laminate may be used in any conventional form to
accomplish the shrink wrapping or bundling of one or more
articles. For example, the laminate is shown in Figure 1 in the : ~ .
form of a tube or sleeve 10 which is adapted to be dropped over : :
a load and then shrunk in place. Alternatively, it can be in : :
the form of a conventional centerfold bag 16, such as shown in
Fiyure 2, comprising a folded end 18, heat sealed side edges 22 .
~20 and an open bottom 20. Furthermore, if desired it can be ~:
utilized in the form of a conventional gusseted bag~ such as
shown at 2~ in Figure 3, comprising a heat sealed end 26,
integral side gussets 28 and an open bottom 30, Other forms ~ ..
will be apparent to those skilled in the art, such as in sheet :.
form for use in various types of known automatic shrink wrap
equipment. . ~.
In Figure 5 there is illustrated a representative .~ :
load consisting of a plurality of rolls 3~ of polyethylene film
material disposed for shipment on a pallet 32 and heat shrunk
in place on the pallet by means of the.laminate of the presènt
.'; '"' ~. ': . ::
, ' ' . ' ',' . ,',' ,. '.' ' "'. ,: ,': ':', ,' " . :"
l~9ZO~;;7
:
invention utilized in the form of a sleeve or tube. Conventional
heat shrinking procedure~ are used in connection with the
laminate of the present invention~ Because the inner barrier
ply 14 will not fuse to polyethylene, the individual rolls 34
may be easily removed from the pallet after delivery without
the entire shrink wrap being fused thereto, The same is true
in the case of loads consisting of other types of packages
having polyethylene on the outer surface thereof,
Thus, there is disclosed in the above description
and in the drawing several embodiments of the invention which
fully and effectively accomplish the objects thereof, However,
it will be apparent that other variations in the details of
construction may b~ indulged in without departing from the
sphere of the invention herein described, or the scope of
the appended claims.
.
-6-
bm:
.
.
,
'' , ~' ' . ~ : ,
.
