U.S. patent application number 10/000747 was filed with the patent office on 2002-03-28 for shipping container blanks encapsulated in plastic film.
This patent application is currently assigned to Weyerhaeuser Company. Invention is credited to Muise, Herbert D., Neogi, Amar N..
Application Number | 20020036229 10/000747 |
Document ID | / |
Family ID | 23783503 |
Filed Date | 2002-03-28 |
United States Patent
Application |
20020036229 |
Kind Code |
A1 |
Muise, Herbert D. ; et
al. |
March 28, 2002 |
Shipping container blanks encapsulated in plastic film
Abstract
The invention is a shipping container blank whereby all surfaces
and edges are sealed by an overlying a plastic film material. A
container subsequently made from the blank is rendered highly water
resistant. The film material is applied to both sides of the blank
and severed from the supply source. The covered blank is then
heated above the softening point of the film. The film becomes
bonded to the surfaces of the blank and sags around the edges and
into any openings so that the film on the two sides of the blank
come into contact and are sealed to each other. The edges and any
slits and cutouts are then trimmed, as by a die cutter, while
preserving the seals along the edges. Containers made by the
process can generally be recycled, in contrast to wax or resin
impregnated corrugated board.
Inventors: |
Muise, Herbert D.;
(Tumwater, WA) ; Neogi, Amar N.; (Seattle,
WA) |
Correspondence
Address: |
PATENT DEPARTMENT CH2J29
WEYERHAEUSER COMPANY
P.O. BOX 9777
FEDERAL WAY
WA
98063-9777
US
|
Assignee: |
Weyerhaeuser Company
|
Family ID: |
23783503 |
Appl. No.: |
10/000747 |
Filed: |
November 30, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10000747 |
Nov 30, 2001 |
|
|
|
09449259 |
Nov 24, 1999 |
|
|
|
Current U.S.
Class: |
229/5.84 ;
229/939 |
Current CPC
Class: |
B31B 2105/00 20170801;
Y02W 30/80 20150501; B32B 27/32 20130101; B31B 2120/408 20170801;
B32B 29/08 20130101; B65D 65/403 20130101; Y10S 229/939
20130101 |
Class at
Publication: |
229/5.84 ;
229/939 |
International
Class: |
B65D 005/56; B65D
005/62 |
Claims
We claim:
1. A moisture resistant corrugated shipping container blank which
comprises a corrugated paper shipping container blank completely
encapsulated within a thermoplastic film, said blank having slits
for forming the blank into a container and cutouts providing
ventilation for the container contents, the plastic film completely
enclosing all exposed edges of the blank and the edges of the slits
and cutouts in order to prevent moisture entry, the slits and
cutouts being open with the seals around their edges remaining
intact.
2. The shipping container blank of claim 1 in which the
thermoplastic film comprises at least first and second layers, said
layers having a difference in melting points of at least about
15.degree. C., said first layer having the lower melting point and
being located adjacent the shipping container blank
3. The shipping container blank of claim 2 in which the lower
melting point layer has a melting point of at least about
110.degree. C. and the second layer has a melting point of at least
about 130.degree. C.
4. The shipping container blank of claim 1 in which the plastic
film has a thickness of about 0.019-0.075 mm (0.00075-0.003
inches).
5. The shipping container blank of claim 2 in which the plastic
film has a thickness of about 0.019-0.075 mm (0.00075-0.003
inches).
6. The shipping container blank of claim 1 in which the plastic
film is a coextruded multi-layer film having at least one layer of
high density polyethylene and one of low density polyethylene, the
low density layer being located closest to the shipping container
blank.
7. The shipping container blank of claim 2 in which the plastic
film is a coextruded multi-layer film having at least one layer of
high density polyethylene and one of low density polyethylene, the
low density layer being located closest to the shipping container
blank.
8. The shipping container blank of claim 1 in which the film is
pigmented.
9. The shipping container of claim 10 in which the film is printed
before or after application to the shipping container blank.
10. A shipping container formed from the blank of claim 1.
Description
[0001] This application is a continuation of application Ser. No.
09/449,259, filed Nov. 24, 1999, and now U.S. Pat. No.
[0002] The present invention is directed to a method of overlaying
a plastic film material on a shipping container blank, to the
highly water resistant blank formed by the method, and to a
container subsequently formed from the blank.
BACKGROUND OF THE INVENTION
[0003] Water resistant shipping containers are required for
shipping many types of fresh produce. Containers used to date have
principally been prepared by saturating the blank with melted wax
before assembly. Other methods have included impregnation with a
water resistant synthetic resin or coating the container with a
thermoplastic material. In the latter case, forming watertight
seals around the edges and any slits or openings has been a major
problem. In most cases the resulting containers cannot be recycled
and must be disposed of in a landfill.
[0004] One early method of plastic coating is seen in Peters, U.S.
Pat. No. 3,406,052 where plastic material is applied by extruders
depositing a thin film against both faces of a moving box blank.
The extruded film is wider than the blank so that it hangs over all
edges. These are then sealed with a flame. Alternatively, the edges
of the blank may be crushed and sealed with a thermoplastic
mixture. No provision was made for sealing any openings other than
the edges.
[0005] Marshall, in U.S. Pat. No. 3,864,200, describes a box made
using resin impregnated linerboards and a two layer corrugated
medium having an asphalt barrier coating between the layers. All
exposed edges are crushed for a width of about 0.5-1 inch and the
asphalt bleeds through the corrugated medium to provide some
sealing.
[0006] Maughan, in U.S. Pat. No. 3,929,536, shows a moisture
resistant corner post usable in packaging materials. This is made
from multiple layers of corrugated paperboard fully enclosed in a
plastic film. A vacuum former preferably is used to bring the
heated shrink wrap plastic film into conformation. End seals are
made by an undisclosed method.
[0007] Inagaki discloses in U.S. Pat. No. 4,551,123 a tubular paper
container sealed within a thermoplastic film. Edges are either
plastic wrapped or heat sealed.
[0008] Dropsy, in U.S. Pat. No. 4,722,474 shows a package with an
internal thermoformed seam free plastic liner. One embodiment also
shows a plastic coated outer surface with the outer and inner films
being heat sealed along the edges. The plastic coating is
apparently applied after formation of the container. French Patent
No. 2,645,831 is closely related.
[0009] WO 94/02364 describes a container blank formed entirely of a
corrugated of thermoplastic material. Edges and all other openings
are sealed to add strength and prevent entry of liquid.
[0010] WO 90/09927 shows a thermoplastic film encapsulated shipping
container blank similar to one made by the process of the present
invention. A plastic film is applied to both sides of a corrugated
shipping container blank and subsequently heat sealed around all
edges and openings. The document is strangely silent in regard to
any process steps by which the encapsulated container blank is
prepared.
[0011] The present invention describes an efficient process by
which a plastic encapsulated corrugated shipping container blank
may be formed.
SUMMARY OF THE INVENTION
[0012] The present invention is directed to a method of fully
encapsulating corrugated shipping container blanks within a
moisture resistant plastic film. The method requires a source of
thin, thermobondable, thermoplastic film. This is applied to both
sides of a container blank. At a downstream location the film is
heated on both sides of the blank to a sufficient temperature so
that the film bonds to the blank without additional adhesive. The
opposing film layers sag to contact each other along the edges and
over the area of any openings and are thermobonded to form seals.
After a brief cooling period, excess film along the edges and
within any openings is die cut or otherwise removed, leaving the
sealed edges intact.
[0013] Most preferably, the film is applied as a sleeve wrap in
which film supply rolls are located above and below a conveyor
system, the axes of the rolls being transverse to the direction of
travel on the conveyor. The film from each supply roll spans a
planar intermediate space perpendicular to the conveyor travel
direction and is thermally bonded end-to end to form a continuous
sheet. A container blank moving along the conveyor contacts the
film and draws it from the rolls as it travels forward. The film is
directed into contact against the upper and lower faces of the
container blank by rolls or a similar arrangement. When the
container blank has passed the planar intermediate location the
film at the trailing edge of the container blank is pinched
together and thermally bonded. This provides fore and aft seals of
the film wrap. The film at the location of this thermal bond is
severed transversely so that the seal remains intact on both sides
of the severing line. The wrapped container blank continues down
the conveyor line and the film from the supply rolls is again
bonded together end-to-end, ready to be engaged by the following
container blank. A heating station follows in which the film is
bonded to the container blank. At this point the film sags into any
slits and other openings and the upper and lower films are bonded
together where in contact with each other. Some shrinkage of the
film occurs at this time causing the seals to contract tightly
against any exposed edges. A die cutter opens the slits and cutouts
while keeping the seals intact. The container blank is now fully
encapsulated with continuous seals around the peripheral edges and
corner slits or other cutout portions and is ready to be formed
into a moisture resistant shipping container.
[0014] The container when so encapsulated can be readily recycled
since the film is easily removed in a repulper and can be readily
separated from the fiber portion in conventional fiber cleaning
equipment..
[0015] It is an object of the invention to provide a method for
preparing a highly moisture resistant shipping container.
[0016] It is a further object to prepare a moisture resistant
shipping container that can be readily recycled.
[0017] These and many other objects will become readily apparent
upon reading the following detailed description taken in
conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 shows a plastic encapsulated corrugated paperboard
box blank ready to be formed into a ventilated shipping
container.
[0019] FIG. 2 diagramatically illustrates the process of
encapsulating a container blank within a plastic film
[0020] FIG. 3 is a section through line 3-3 of FIG. 1
[0021] FIG. 4 is a portion in cross section showing greater detail
of the edge seal of the plastic coating.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] The thermoplastic, thermobondable plastic film used in the
present method may be a single layer film but is preferably a
multilayer film comprising at least first and second layers. When a
two layer film is used the layers should have a melting point
difference of at least about 15.degree. C. (25.degree.-30.degree.
F.). Most typically the film will be a coextruded film having an
outer layer of high density polyethylene with a melting point of
about 130.degree. C. (265.degree.-275.degree. F.) and an inner
layer with a melting point of about 110.degree. C.
(230.degree.-240.degree. F.). The inner layer is used adjacent to
and is thermobondable to the corrugated paper shipping container
blank. A most preferred film is a coextruded film as just described
with a third metallocene composition adjacent the low density
polyethylene layer to promote good adhesion to the container blank
surface. A film of this type is available from Golden Eagle
Extrusions Inc., Loveland, Ohio, and from other suppliers. Other
film compositions such as those based on polypropylene, poly(vinyl
chloride), polyesters, or films having one or more layers of one of
these compositions coextruded with one of the other compositions.
Film thickness is not critical but will generally be within the
range of about 0.019-0.075 mm (0.00075-0.003 in). Most typically
the film will be about 0.025 mm (0.001 in) in thickness.
[0023] The film may be applied to each side of the shipping
container blank by any method. Most preferably it is applied by the
sleeve wrap method described earlier.
[0024] In addition to providing a highly water resistant container,
the present method can provide a product that is significantly
superior in appearance to conventional printed containerboard
blanks. This is accomplished by using a pigmented film on at least
the outer surface of the ultimate shipping container. The pigmented
film can be printed before or after application to the container
blank. Image brightness and clarity is outstanding in comparison to
that usually seen on printed containerboard conventionally made
using an outer linerboard ply having an integrally formed thin
white surface layer.
[0025] The method by which the product is prepared is best
understood by reference to the drawings. FIG. 1 represents a
completed containerboard blank 2 having side walls 4, end walls 6,
and top and bottom flaps 8, 10. A single flap 12 is provided to
make the manufacturers joint when the container is assembled.
Cutouts 14, and score lines 15 are provided to facilitate assembly.
The entire upper and lower surfaces are covered with a plastic film
18 with the two layers sealed to each other along the edges and at
all openings.
[0026] A preferred method of forming the product is seen in FIG. 2.
A container blank 20 is fed into a sleeve wrap station where
plastic film is supplied from upper and lower rolls, not shown. The
container blank moves along a conveyer and withdraws the film from
the supply rolls as it moves forward. The film is pressed against
the container blank and then heat sealed and severed at the
trailing edge. Film from the two supply rolls is reunited by the
heat seal and is ready to receive the following container blank. A
heating station 24 bonds the film to the container blank. As shown
here, heated rolls 26 perform this function but other heating
means, such as infra red or a heated press, can be equally
suitable. During heat application at station 24 the film is heated
on both sides so that is softened to the point where it sags into
all openings, such as slits 14 and cutouts 16, and around all of
the peripheral edges. At the sag locations the upper and lower
films contact and bond to each other as is best seen in FIG. 3.
[0027] FIG. 3 shows a cross section along line 3-3 of FIG. 1. The
container blank 20 has upper and lower paper linerboards 40 bonded
to an interior corrugated medium 42. The linerboards are overlaid
with plastic films 44. As shown, the film sags into the score lines
46 and into the cutout openings 48. The two films meet and form
bonds 50 at the edges and 52 at cutout locations 48. FIG. 4 shows
an enlarged view at one of the cutout locations. Here, the film
bridging the cutout serving as a ventilation opening has been
removed by a die cutter leaving the edge bonds 52.
[0028] It will be evident to those skilled in the art that many
variations can be made in the described process without departing
from the spirit of the invention. It is the inventors intent that
these variations should be included within the scope of the
invention if encompassed within the following claims.
* * * * *