U.S. patent application number 10/704655 was filed with the patent office on 2005-05-12 for heat-sealed multi-wall flexible container.
Invention is credited to Norton, Sarilee, Rivlin, Jonathan B..
Application Number | 20050100252 10/704655 |
Document ID | / |
Family ID | 34552175 |
Filed Date | 2005-05-12 |
United States Patent
Application |
20050100252 |
Kind Code |
A1 |
Rivlin, Jonathan B. ; et
al. |
May 12, 2005 |
Heat-sealed multi-wall flexible container
Abstract
The invention relates to a multi-wall flexible container that
includes an outer wall of a laminate of first and second sheets,
and one or more heat sealed or heat sealable joints. The first
sheet is made of a material that is different from that of the
second sheet and the laminate is configured to form a tube with one
of the sheets providing an outer surface of the container. The
container also may include at least one additional wall member
comprising a third sheet material.
Inventors: |
Rivlin, Jonathan B.; (East
Brunswick, NJ) ; Norton, Sarilee; (East Greenwich,
RI) |
Correspondence
Address: |
WINSTON & STRAWN
PATENT DEPARTMENT
1400 L STREET, N.W.
WASHINGTON
DC
20005-3502
US
|
Family ID: |
34552175 |
Appl. No.: |
10/704655 |
Filed: |
November 12, 2003 |
Current U.S.
Class: |
383/116 ;
383/105 |
Current CPC
Class: |
B32B 2037/1276 20130101;
B32B 27/10 20130101; B32B 29/005 20130101; B65D 31/02 20130101;
B32B 2439/00 20130101; B32B 7/12 20130101; B32B 2037/1215 20130101;
B32B 27/08 20130101 |
Class at
Publication: |
383/116 ;
383/105 |
International
Class: |
B65D 033/00 |
Claims
What is claimed is:
1. A multi-wall flexible container comprising: an outer wall member
comprising a laminate of first and second sheets, with the first
sheet made of a material that is different from that of the second
sheet and the laminate configured to form a tube with one of the
sheets providing an outer surface of the container; a first sealed
joint associated with one end of the tube to assist in forming a
bottom portion of the container; and a second sealed joint
associated with the laminate for forming at least one side seam of
the container, wherein one of the first or second sheets comprises
paper while the other comprises a sheet material that is capable of
bonding to paper and that has increased strength or moisture
resistance compared to a paper sheet.
2. The container of claim 1, wherein the first sheet comprises a
polymeric film, a metal foil, or a plastic coated, fiber reinforced
or metallized paper sheet, and the second sheet comprises
paper.
3. The container of claim 2, which further comprises at least one
additional wall member comprising a third sheet material for
providing additional structure to the container.
4. The container of claim 3, wherein the at least one additional
wall member comprises a polymeric film, a metal foil, a fabric, a
netting made of the previously recited materials, a plastic coated,
fiber reinforced or metallized paper sheet, or a cushioning
material comprising a foam or other gas filled cellular
material.
5. The container of claim 3, wherein the additional wall member is
a different material than that of the first sheet.
6. The container of claim 2, wherein the first sheet provides the
outer surface of the container and comprises an oriented polymer
film while the second sheet comprises paper so that the paper may
be viewed through the polymer film while the polymer film protects
the paper from damage during handling of the container.
7. The container of claim 6, which further comprises visual
information comprising one or more ink images provided between the
polymer film and paper sheet.
8. The container of claim 7, wherein the polymer film is adhesively
cold laminated to the paper sheet by a water-based adhesive.
9. The container of claim 8, wherein the water-based adhesive
comprises a vinyl acetate ethylene copolymer.
10. The container of claim 8, wherein the one or more ink images
are resistant to deterioration when in contact with moisture.
11. The container of claim 8, wherein the ink images of the visual
information comprise water-based inks that are applied to the paper
sheet and which include a varnish coating to resist deterioration
when the paper sheet is contacted by the water-based adhesive.
12. The container of claim 9, wherein the ink images of the visual
information comprise organic solvent based inks that are applied to
the polymer film.
13. The container of claim 2, wherein the paper second sheet
provides the outer surface of the container while the first sheet
comprises the polymer film, the metal foil, or the plastic coated
or metallized paper sheet, so that the second paper sheet provides
the outer surface of the container which may be readily printed
while the first sheet provides a moisture resistant interior for
the container.
14. The container of claim 3, wherein the at least one additional
wall member forms a liner that is positioned within the laminate
and configured to form an inner tube to provide additional strength
to and reinforcement of the container and for contacting a product
that is placed in the container, with the first sealed joint
associated with one end of both the laminate and inner tubes to
assist in forming a bottom portion of the container.
15. The container of claim 14, wherein the first sheet provides the
outer surface of the container and comprises an oriented polymer
film while the second sheet comprises paper, and further comprising
visual information comprising one or more ink images provided
between the polymer film and paper sheet, wherein the one or more
ink images are resistant to deterioration when in contact with
moisture so that the visual information may be viewed through the
polymer film and the polymer film protects the visual information
and paper from damage during handling of the container, and the
liner is paper and is spot-adhered to the laminate to hold the
liner material in a desired orientation with regard to the
laminate.
16. The container of claim 6, wherein the first sheet of the
laminate comprises an oriented polymer film that has a surface that
is energized to have increased dynes and an affinity for adhesives,
and wherein the film is laminated to the paper sheet by a
water-based adhesive that contacts the treated surface of the film
and has its water absorbed by the paper sheet to effect lamination
thereof.
17. The container of claim 16, wherein the laminate further
comprises an additional oriented polymer film that has a surface
that is energized to have increased dynes and an affinity for
adhesives, wherein the additional film is laminated to the paper
sheet by a water-based adhesive that contacts the treated surface
of the additional film and has its water absorbed by the paper
sheet to effect lamination thereof and provide an inner surface of
the laminate that provides moisture resistance inside the
container.
18. The container of claim 17, wherein the polymer film of the
outer surface, the inner surface, or both, is polypropylene,
polyethylene, or polyester.
19. The container of claim 18, wherein the film of the outer
protective layer, the inner protective layer, or each layer, is
biaxially oriented.
20. The container of claim 1, wherein the first and second sealed
joints are made by a hot melt adhesive.
21. The container of claim 1, which further comprises a hot melt
adhesive positioned on an open end of the laminate tube to
facilitate formation and sealing of a top portion of the container
after a product is filled therein.
22. In a method of making a multi-wall flexible container that
includes at least two wall members, the improvement which comprises
forming an outer wall member of the container of a laminate of
first and second sheets, with the first sheet made of a material
that is different from that of the second sheet and the laminate
configured to form a tube with one of the sheets providing an outer
surface of the bag, wherein one of the first or second sheets
comprises paper while the other comprises a sheet material that is
capable of bonding to paper and that has increased strength or
moisture resistance compared to paper.
23. A method of forming a multi-wall flexible container for
containing a product therein, which comprises: providing a laminate
comprising a first sheet that will form an outer wall member of the
bag, the first sheet being laminated to a second sheet of a
material that is different from that of the first sheet; folding
the laminate to a tubular shape; providing a first sealed joint on
one end of the laminate and one additional wall member that assists
in forming a bottom portion of the bag; providing a second sealed
joint between side portions of the laminate for forming a side seam
of the bag, with the first and second joints each being provided by
applying and melting a hot melt adhesive that bonds the laminate
ends or portions sheets together to form the joint; and arranging
and configuring the sealed joints to enable the laminate to define
an interior space that is capable of receiving a product therein;
wherein one of the first or second sheets comprises paper while the
other comprises a sheet material that is capable of bonding to
paper and that has increased strength or moisture resistance
compared to paper.
24. The method of claim 23 which further comprises providing-at
least one additional wall member comprising a third sheet material,
wherein folding the laminate and at least one additional wall
member are folded to a tubular shape, and the sealed joints are
arranged and configured to enable the laminate and at least one
additional wall member to define an interior space that is capable
of receiving a product therein.
25. The method of claim 23 which further comprises placing a
product, item, or article in the container, providing a strip of
hot melt adhesive positioned on the laminate tube to facilitate
formation and sealing of a top portion of the container, and
sealing the top portion of the container after the product, item or
article is placed therein to form a sealed container.
26. A multi-wall flexible container produced by the method of claim
23.
27. A sealed and filled multi-wall flexible container produced by
the method of claim 25.
Description
BACKGROUND
[0001] The invention relates to a multi-wall flexible container for
various products and to the laminates and methods used to make the
same.
[0002] A typical flexible container is referred to as a bag. The
prior art is replete with various bag constructions for certain end
uses. Bags made of multiple layers of kraft paper are commonly used
for retaining pellet, granular or particulate products such as
inorganic materials of sand, cement, gypsum or the like, as well as
bulk foods, and in particular, animal or pet foods. The multiple
layers provide additional strength and rigidity to the bag, but the
bags can be damaged due to contact with moisture or sharp objects,
with deterioration or spillage of the bag contents as a result.
Also, printing on the bag can be scuffed, scratched or otherwise
damaged during handling or storage of the bag, resulting in a worn
or used appearance which makes the product less desirable for
purchase by consumers. U.S. Pat. Nos. 3,807,626, 3,910,488,
3,945,562, 3,958,749, and 4,515,273 are examples of these type bags
to illustrate their constructions and closures.
[0003] It is also well known to use plastic films for the
construction of bags. Both single and multiple layer plastic films
have been used. These bags have better strength and moisture
resistance than those of paper, but when thicker films or multiple,
layers of film are used, the cost of the bag is increased, with the
additional cost being passed onto the consumers of the bagged
product. These type bags are commonly used for lawn fertilizers or
similar chemicals where containment of the powder or liquid
products therein is an important consideration, thus justifying
their increased cost.
[0004] When a low cost, moisture resistant bag is desired, it is
known to coat paper with a resinous material as disclosed in U.S.
Pat. No. 3,412,771. The coating is sufficient to provide moisture
resistance as well as to allow heat sealed seams to assist in
closure of the bags, while retaining the low cost of the paper
walls. U.S. Pat. No. 3,567,111 discloses a similar bag except that
it includes 2 paper layers and an internal polymer coating. While
such bags are more resistant to moisture from products contained
therein, these have relatively low strength since the bag material
is made from one or two paper plies or layers.
[0005] U.S. Pat. No. 3,184,149 discloses a bag made of a sheet of
flexible material, such as a polymer, cellophane, paper or aluminum
foil, that is folded and joined and sealed along three sides. While
useful for containing lightweight objects or products, the strength
of such bags is suspect since only a single sheet of flexible
material is used and any rip or tear can propagate to complete
failure.
[0006] There are composite multi-wall bag constructions where
multiple layers or sheets of plastic and paper are used, but these
are generally folded upon each other and joined as separate layers,
or are constructed with a "bag in a bag" where a plastic bag is
placed within a paper one or vice versa. U.S. Pat. No. 2,316,385
and U.S. patent application 2003/0035598A1 are examples of bags
that include an inner moisture resistant layer or liner of a
moisture proof material or plastic film. The multiple sheets are
included to combine the desirable properties of each material while
still maintaining a reasonably low cost for the overall bag
construction.
[0007] Bags made by laminating the edges of single or multi-ply
webs of paper cloth, fabric or like webs are known as illustrated
in U.S. Pat. Nos. 2,550,000 and 2,382,930. These bags are lacking
in strength and moisture resistance and the laminated edges are
suspect when different web materials are to be laminated.
[0008] Bags made with multiple layers of plastic that are laminated
together, such as those disclosed in U.S. Pat. No. 3,623,653, are
also known. These bags are more difficult to print and often do not
have sufficient body to facilitate handling during filling of the
bag with product. When heat sealed, these bags can be difficult to
open, as noted by the solution to this problem that is disclosed in
U.S. Pat. No. 3,254,829.
[0009] U.S. Pat. No. 5,244,702 and U.S. patent application
2002/0160216A1 disclose paper-plastic and paper-plastic-paper
laminate sheetings capable of being converted by conventional
equipment into envelopes, grocery bags and other dilatable
container products that initially are in a flat state and are
normally made of paper. The sheeting is composed of a paper facing
sheet cold-laminated by means of a water-based adhesive to a
reinforcing film of synthetic plastic material, such as
polypropylene, polyethylene or polyester. The film is oriented to
impart exceptional tear and burst strength characteristics to the
resultant waterproof product. Since the exterior surfaces of these
container products are formed by the paper facing sheet, they are
readily printable. For some applications, a second paper facing
sheet is cold-laminated to the other side of the film to produce a
three-ply laminate sheeting that has all exposed surfaces readily
printable and able to accept conventional adhesives. While these
laminates are useful for their intended purposes, those documents
explain that the tensile strength of an oriented film is seriously
impaired if heat is applied thereto, because heat acts to relax the
film and cause it to lose its molecular orientation. For this
reason, the use of hot melt adhesives to laminate a reinforcing
film to the paper sheet is interdicted, since this can seriously
diminish the strength and reinforcing characteristics of the
film.
[0010] Despite the existence of these different constructions,
there still remains a need for relatively low cost, durable and
strong flexible container products, and these are now provided by
the present invention.
SUMMARY OF THE INVENTION
[0011] The invention relates to a multi-wall flexible container
comprising an outer wall of a laminate of first and second sheets,
and one or more sealed joints. Generally, the first sheet is made
of a material that is different from that of the second sheet and
the laminate is configured to form a tube with one of the sheets
providing an outer surface of the container. The container may also
include at least one additional wall member comprising a third
sheet material for providing additional structure to the
container.
[0012] Advantageously, a first sealed joint is associated with one
end of the tube to assist in forming a bottom portion of the
container and a second sealed joint is associated with the laminate
for forming at least one side seam of the container. Generally, one
of the first or second sheets comprises paper while the other
comprises a sheet material that is capable of bonding to paper and
that has increased strength and/or moisture resistance compared to
a paper sheet.
[0013] In a preferred embodiment, the first sheet can be any one of
a wide variety of sheet materials, including a polymeric film, a
metal foil, or a plastic coated, fiber reinforced or metallized
paper sheet, and the second sheet comprises paper. The at least one
additional wall member can also be any one of a wide variety of
materials, including a polymeric film, a metal foil, a fabric, a
netting made of the previously recited materials, a plastic coated,
fiber reinforced or metallized paper sheet, or a cushioning
material comprising a foam or other gas filled cellular material.
Generally, the additional wall member comprises a different
material than that of the first sheet.
[0014] In another preferred embodiment, the at least one additional
wall member forms a liner that is positioned within the laminate
and configured to form an inner tube to provide additional strength
to and reinforcement of the container and for contacting a product
that is placed in the container, with the first sealed joint
associated with one end of both the laminate and inner tubes to
assist in forming a bottom portion of the container. Also, the
liner can be spot-adhered to the laminate to hold the liner
material in a desired orientation with regard to the laminate.
[0015] In yet another embodiment, the first sheet of the laminate
provides the outer surface of the container and preferably
comprises an oriented polymer film while the second sheet comprises
the paper sheet. This allows visual information comprising one or
more ink images to be provided between the polymer film and paper
sheet. Preferably, the ink images are resistant to deterioration
when in contact with moisture such as that introduced by a
water-based lamination adhesive so that the visual information may
be viewed through the polymer film while the polymer film protects
the visual information and paper from damage during handling of the
container.
[0016] While methods for manufacturing multi-walled bags are
generally known, the invention relates to an improvement in such
methods which comprises forming the outer wall of the bag of one of
the laminates disclosed herein. The joints of the bags of the
invention typically are made with a hot melt adhesive for optimum
strength and reliability due to the presence of the paper/polymer
film laminate. The method of the invention further comprises
placing a product, item or article in the container, providing a
strip of hot melt adhesive positioned on the laminate tube to
facilitate formation and sealing of a top portion of the container,
and sealing the top portion of the container after the product,
item or article is placed therein to form a sealed container.
[0017] The multi-wall flexible container and the sealed and filled
multi-wall flexible container produced by these methods represent
additional embodiments of this invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0018] The present invention relates to a flexible, multi-wall
container of the type used for transporting, carrying or storing
various products, items or articles. As noted above, it is
advantageous for the outermost wall member of the container to be
made of a laminate of dissimilar sheet materials to provide the
container with enhanced properties.
[0019] One of the sheets of the laminate preferably comprises paper
while the other comprises a sheet material that is capable of
bonding to paper and that has increased strength and/or moisture
resistance compared to paper. The second sheet is usually a paper
sheet to facilitate formation of the laminate. The first sheet then
can be any one of a wide variety of materials that can be laminated
to the paper sheet. These materials include polymeric films, metal
foils, or paper sheets that are treated by the addition of a
plastic coating, fiber reinforcement or metallization. Each of
these materials has enhanced properties compared to paper and this
contributes to the overall improved properties of the
container.
[0020] The polymer films for use as the first sheet can be in the
form of single webs of any type of polymeric or plastic material,
extrusions or coextrusions of different polymers, or multiple
extruded layers of the same or different polymers, and preferably
those that are joined together for dimensional stability. For
example, a single web of a polyolefin or polyester material,
whether oriented or not, is suitable, whether in the form or a film
or foam. Polyesters such as MYLAR and polyamides such as nylon are
preferred, while suitable polyolefins include polypropylene,
polyethylene or copolymers thereof. Polyvinylchlorides or other
thermoplastics can be used when moisture resistance rather than
strength is the primary concern. An extruded multiple layer
laminate of polyethylene and polyester is advantageous when the
combination of properties of those polymers is desired, i.e., one
for strength and temperature resistance and the other for bonding
or heat sealing when forming the container. Similarly, the
combination of a nylon layer and a polyvinyl alcohol layer can be
used when high strength and an oxygen barrier is needed. Also, an
extruded multiple layer laminate of polyethylene and polypropylene
is useful when the combination of a strengthened film and one that
is more easily joined by heat sealing is desired. Three layer
extrusions are also possible, with the inner layer being regrind or
recycle polymer material. These materials are conventionally made
using a multiple head extruder as is known in the polymer art.
Furthermore, composites of polymer or plastic films and other
materials, with or without fiber or other reinforcement, can be
used for even greater strength or rigidity of the container or
bag.
[0021] Metal foils, such as aluminum or others, can be used as the
first sheet when desired. These materials impart strength, moisture
resistance and a desirable appearance to the laminate. These
materials are easy to laminate to paper and when so laminated are
typically used as the outer surface of the container in order to
take advantage of its desirable appearance. Instead of foil,
metallized paper or polymer films can be used to obtain these
improved appearances. As metallizing techniques are well known in
the art no further mention needs to be made of the processes for
forming these materials.
[0022] Finally, the material to be laminated to paper can be a
paper sheet that is treated by the addition of a plastic coating,
fiber reinforcement or metallization. These treatments enhance the
moisture resistance and/or strength properties of the paper and the
enhancement is then imparted to the laminate and the container.
[0023] The second sheet is made of paper. Any type of paper can be
used, including kraft paper, white paper or even cardboard. These
materials can be of any desired weight for such containers.
[0024] The laminate can be formed in any conventional way. It is
entirely suitable to laminate these materials using a hot melt
adhesive or an reaction cure adhesive provided that care is taken
to assure dimensional stability until the laminate is formed after
those adhesives set and/or cure. For example, when hot melt
adhesives are used, such as conventional heat-meltable polyethylene
adhesives, care must be taken so that the paper and other material
do not slip apart or otherwise move away from each other until the
adhesive cools and sets to form the laminate. The reaction cure
adhesives of the type disclosed in U.S. Pat. No. 5,037,700 can also
be used, but these generally require the addition of heat to
facilitate curing to form the laminate. Again, care must be taken
with such adhesives so that the paper and other material do not
slip apart or otherwise move away from each other until the
adhesive sets and cures to form the laminate.
[0025] As noted, a preferred material for the outer wall member of
the laminate is a polymer film, preferably one that is transparent
and is uniaxially or biaxially-oriented for increased strength.
Film materials suitable for this purpose are polypropylene,
polyethylene, or a polyester such as MYLAR. The tensile strength of
the film is substantially increased by orientation which results in
molecular orientation of the film. In the case of biaxial
orientation, orientation is in both the longitudinal and transverse
directions. This is usually effected by controlled stretching of
the unoriented film. The tensile strength of an oriented film is
seriously impaired, however, if heat is applied thereto, for the
heat acts to relax the film and cause it to lose its molecular
orientation. Thus when oriented films are used, cold lamination is
preferred for forming the laminate. The well known techniques
disclosed in U.S. Pat. No. 5,244,702 and U.S. patent application
2002/0160216A1 are useful for this purpose and the content of each
of those documents is expressly incorporated herein by reference
thereto to the extent necessary to understand these techniques.
[0026] When a transparent outer surface is not needed, the film or
first sheet may be metallized. When a transparent film is to be
metallized, this may be done on the side of the film that is
laminated to the paper so that the metallized surface is protected
against abrasion, wear or damage due to rough handling.
[0027] Preferably, the polymer or plastic film is cold laminated to
the paper sheet under pressure and at ambient temperature (i.e.,
without the intentional addition of heat) by means of a water-based
adhesive. A polyacrylate copolymer adhesive, or by any other
water-based adhesive having similar bonding properties and having
an affinity both for the paper sheet and the polymer or plastic
film or metal foil can be used. Preferably, the water-based
adhesive is a vinyl acetate ethylene copolymer.
[0028] Since paper tends to absorb water in the laminating process,
before the paper sheet and the film are together fed into pressure
rolls and subjected to pressure to effect lamination, a surface of
the film is first coated with the water-based adhesive which does
not encounter the first surface of the paper sheet until these two
surfaces meet in the pressure rolls. In this way, the period during
which absorption of the adhesive into the interior of the paper
sheet can take place is limited. And to render the first surface of
the film more receptive to the water-based adhesive applied
thereto, it is preferably first subjected to ionization to enhance
the dynes on this surface. Hence, when the adhesive-coated film web
and paper web together enter the combining station and are
subjected to pressure by pressure rolls, lamination is effected by
this action. The paper layer absorbs the water from the adhesive so
that a high strength lamination can be rapidly achieved as the
paper and film exit the pressure rollers. These features are
disclosed in the incorporated documents so that they do not require
further explanation herein.
[0029] The cold lamination process enables the present laminate
sheeting to be manufactured at much higher speeds than when other
adhesives, such as hot melt adhesives, are utilized, for example
due to the additional time required for cooling of the hot melt
adhesive before a secure bond is achieved. Another benefit of the
use a water-based adhesive in a cold lamination process is that
this type of adhesive does not require the use of volatile organic
solvents. Thus, adverse health and environmental effects are
avoided because such solvents are not used. Also, additional costs
for recovering or disposing of solvents are not incurred.
[0030] The paper sheet of the laminate preferably has a thickness
of from about 3 to about 6 mils. The other sheet preferably has a
thickness of from at least about 0.5 to 12 mils, although for the
preferred polymer film it is about 0.5 to 3 mils. The thickness
ratio of paper to other sheet is in the range of between 6:1 to
1:2, and preferably is between 3:1 to 1:1. Other thicknesses for
the first and second sheets and other thickness ratios can be used
if desired depending upon the desired use of the final container or
bag.
[0031] A most preferred embodiment includes a first sheet
comprising a transparent, oriented polymer film which provides the
outer surface of the container while the second sheet comprises
paper so that the paper may be viewed through the polymer film and
the polymer film protects the paper from damage during handling of
the container. In this embodiment, visual information comprising
one or more ink images provided between the polymer film and paper
sheet. These images include colors, printing, symbols or designs,
including trademarks or tradenames and other advertising
information, and the like. The visual information is protected by
the polymer film so that it remains intact as the container is
transported or moved from one location to another and while
displayed in a store or other facility for purchase by
consumers.
[0032] When cold lamination is used to form the laminate, the
second sheet preferably comprises an oriented polymer film that has
a surface that is energized to have increased dynes and an affinity
for adhesives, and the film is laminated to the paper sheet by a
water-based adhesive that contacts the treated surface of the film
and has its water absorbed by the paper sheet to effect lamination
thereof. As water from the water-based adhesive is present during
the lamination, it is preferable for the one or more ink images to
be resistant to deterioration when in contact with this water or
moisture.
[0033] This can be achieved in a number of ways. When the ink
images of the visual information comprise water-based inks that are
conventionally applied to the paper sheet, a varnish coating can be
applied over the inks and paper to resist deterioration from the
moisture of the adhesive when the paper sheet is contacted by the
water-based adhesive. A conventional printing varnish can be used
for this purpose. As this is a standard material that is known to
skilled artisans, there is no need for further detail of it
herein.
[0034] Another way to provide moisture resistant ink images is to
use those that comprise organic solvent based inks and to apply
them to the polymer film. These can be applied by spraying, silk
screening or other conventional ink printing processes. As the inks
contain organic solvents and are hydrophobic, there is no
deterioration when coming in contact with the water of the
adhesive.
[0035] The at least one additional wall member or liner can also be
any one of a wide variety of materials, including all those
mentioned above for the first sheet. In addition, the additional
wall member can be a fabric. The fabric can be knitted, woven or
even braided so long as there is sufficient filaments or fibers for
lamination to the paper sheet. The fibers or filaments in the
fabric can be natural or synthetic with polyester, nylon or KEVLAR
being preferred when reinforcement or high strength is desired.
Alternatively, inorganic materials, such as fiberglass or carbon
fibers, can be used for this purpose.
[0036] Instead of fabrics, nettings or screenings made of any of
the previously recited materials can be used when greater
flexibility of the container is intended. These items are
preferably made of polymers or metal.
[0037] This wall member is generally provided in the form of a
liner that is used to provide additional strength to the container
and protection of its contents. It can be made of a simple material
such as kraft paper, or instead can be made of a foam or celled
material for cushioning, or of a mesh or netting to help retain the
container contents away from the laminate. Generally, the
additional wall member is comprised of a different material than
that of the first sheet of the laminate. To assist in maintaining
the correct portion of the additional wall member in the container,
it can be spot-adhered with adhesive or by spot welding to the
laminate. The skilled artisan can best determine what materials to
select for the first sheet and additional wall member depending
upon the specific products or contents of the container.
[0038] In one particular embodiment of the invention, the container
is in the form of a sealable or sealed bag for containing products
or other merchandise, while in other embodiments, it can be an
sealable envelope or mailing package.
[0039] The bags of the invention can be used to contain a wide
variety of products. In particular, when the inner surface of the
laminate is paper, and the third sheet is paper, the product
normally would be one that does not contain or exude moisture or
liquid. While the outer polymer film of the laminate can contain
such moisture, prolonged storage can affect the paper layer. Dry
products such as animal feed or pet food, rock salt, sand, cement,
gravel, or other inorganic materials, lawn chemicals, or foods such
as beans, corn, wheat, rice, flour, coffee, tea, salt, pepper,
spices or other particulates, potatoes, onions, apples, oranges, or
other fruits or vegetables can be mentioned as typical and
non-limiting examples. The polymer film protects the paper portion
of the laminate and prevents external moisture from entering the
bag to deleteriously affect the product therein.
[0040] Dry materials in pellet or particulate form can be placed in
the bags of the invention. The terms "pellet" and "particulate" are
used to indicate various suitable forms of dry material that can be
contained within the bags of the invention. "Particulates"
generally refers to smaller sized materials, such as those provided
by wheat flour, talcum powder, sand, or rice, while "pellets" refer
to larger size materials, such as beans, peas, coal, gravel, whole
fruit or the like.
[0041] To counter the effects of moisture in the sealed package, an
additional wall member or insert of paper, tissue, cloth or another
absorbent material can be included. When a moist or liquid product
is to be contained, a three-ply laminate of plastic-paper-plastic
can be used. The inner plastic layer would then protect the paper
of the laminate from the deleterious effects of moisture or
liquid.
[0042] The container of the invention may also be used as a mailing
envelope, where the laminate provides the outer wall of the
envelope. When the outermost surface is paper, the envelope can be
printed or otherwise marked with indicia, while when the outermost
surface is a polymer film, a waterproof envelope is provided. The
inner liner can be used to protect the contents of the envelope.
When the envelope is to be used to transport an item that is not
resistant to shock, impact or rough handling, the liner can be made
of a cushioning material comprising a foam or other gas filled cell
material. In particular, when a foam or bubble-wrap material is
used as the liner, the interior of the envelope is well protected
for mailing items such as computer diskettes, glass articles or
other items requiring protection from shock or impact during travel
and transport through the mail.
[0043] Yet another use for the present container is as a package
mailing container. If a moist or wet material is to be mailed, an
inner liner of a water or moisture resistant material with the
plastic/paper laminate forms a mailing package that is internally
resistant to the moist or wet material to be mailed, while the
plastic exterior of the package provides additional moisture
resistance to the package during shipping. As in the envelope
embodiment, a cushioning material can be used as the liner to
protect fragile articles to be shipped.
[0044] In certain embodiments, the paper second sheet is used in
the laminate to provide the outer surface of the container so that
it may be readily printed while first sheet is used to provide a
strength or moisture resistance interior for the container. For
example, when the laminate is one of paper and plastic film, the
film is provided in the interior of the bag to prevent moisture in
the bag from contacting the paper portion of the laminate. When the
surfaces to be joined to form the container are both made of paper,
it is possible to use conventional, commercially available
adhesives for this purpose, rather than the special adhesives that
would be dictated if the surfaces to be sealed together included a
plastic film surface or other surface that is more difficult to
bond. And because these exposed surfaces are paper, they can be
readily printed.
[0045] Alternatively, a paper-polymer film laminate where the
polymer film forms the outer surface of the container can be
further treated to prevent moisture in the container from
contacting and deteriorating the paper sheet of the laminate. One
convenient way to do this is to include a further oriented polymer
film in the laminate. This film can be provided with a surface that
is energized to have increased dynes and an affinity for adhesives,
and then be laminated to the exposed paper surface of the paper
sheet by a water-based adhesive. As above, the water-based adhesive
is applied to the treated surface of the film and has its water
absorbed by the paper sheet to effect lamination thereof and
provide polymer films on both sides of the paper sheet. The second
polymer film forms an inner surface of the laminate that provides
moisture resistance inside the container. Either the film of the
outer protective layer, the inner protective layer, or both are
preferably biaxially oriented when the highest strength is needed
for the container. Polypropylene, polyethylene, or polyester films
are preferably used for this purpose.
[0046] The laminates of the invention can be used to form the
container in exactly the same manner as ordinary paper in a stock
roll for standard equipment adapted to fabricate envelopes, bags or
other dilatable paper products, by slitting, folding and whatever
other operations are dictated by the form of the product.
[0047] The size and shape of the containers of the invention can
vary over a wide range. Also, the manufacturing techniques, which
are already well known for containers made of multiple walls of
paper, can be used with the simple substitution of a laminate for
the outermost paper wall. Preferably, methods of manufacturing
these containers include providing a laminate comprising a first
sheet that will form an outer wall member of the bag, the first
sheet being laminated to a second sheet of a material that is
different from that of the first sheet; providing at least one
additional wall member comprising a third sheet material; folding
the laminate and at least one additional wall member to a tubular
shape; providing a first sealed joint on one end of the laminate
and one additional wall member that assists in forming a bottom
portion of the bag; providing a second sealed joint between side
portions of the laminate for forming a side seam of the bag, with
the first and second joints each being provided by applying and
melting a hot melt adhesive that bonds the laminate ends or
portions sheets together to form the joint; and arranging and
configuring the sealed joints to enable the laminate and at least
one additional wall member to define an interior space that is
capable of receiving a product therein. As noted, one of the first
or second sheets comprises paper while the other comprises a
material that is capable of bonding to paper and that has increased
strength or moisture resistance compared to paper.
[0048] In the container of the invention, the first and second
sealed joints are preferably made by a hot melt adhesive, as this
material is the most compatible with the different types of
materials used for the first and second sheets. Even when a
laminate that includes an oriented film is used, the hot melt
adhesive can be used to successfully form the seams and ends of the
container because the amount of heat needed to form the seal is
small compared to the overall size of the laminate, and the
laminate is already formed so that the paper layer acts as a heat
sink for the polymer to avoid a significant loss of strength of the
film.
[0049] Also, a hot melt adhesive is preferably positioned on an
open end of the laminate and additional wall member tubes to
facilitate formation and sealing of a top portion of the container
after a product is filled therein. These hot melt adhesives are
conventional, but a polyamide hot melt adhesive available from
National Starch is preferred.
[0050] Again, while any type of laminate can be used, it is most
preferred to use one that is obtained by cold lamination of the
paper and polymer film in order to obtain optimum strength at a
relatively low cost.
[0051] The multi-wall containers or bags produced by these methods
represent another embodiment of the invention, as do the final
filled and sealed bags that contain one or more products therein.
The most preferred multi-wall container or bag of the present
invention has an outer wall of a polymer film-paper laminate with
the polymer film forming the outer surface of the bag. It also
includes visual information, i.e., printing and coloration, between
the polymer film and paper, and an inner wall of a paper liner.
[0052] The container or bag may be made by cutting the laminate and
additional wall member(s) to the desired size, folding the sides
and bottom edges as desired and joining the folded portions by
placing a strip of solid or liquid hot melt adhesive between the
folded portion followed by heating at least those portions and the
adhesive. As this technique is well known in the art, no further
elaboration is needed herein. After the product is placed in the
bag, the top end can be sealed by folding and heat sealing that
end.
[0053] The bottom of the bag is formed by folding the front and
rear portions of the laminate upon either the front or rear of the
bag, placing the necessary strip(s) of adhesive between the folded
portions and then heat sealing the joint together. For bags that
contain relatively lightweight products, a portion of the end of
the bag, i.e., the front or rear, can be cut away and removed so
that the joint is made with only a single laminate portion that is
folded upon and then joined to the front or rear of the bag. This
alternate construction is preferably used for the top portion of
the bag after filling the bag with the product, since that
simplifies and facilitates the final heat seal closure of the
bag.
[0054] If desired, the laminate can be folded upon itself to form a
continuous tube around an inner tube of the additional wall
member(s) with a portion of the outer wall joined to an overlapping
portion of the inner wall. This can be achieved by placing the hot
melt adhesive strip along the inner or outer layers in the area of
overlapping portions followed by heat sealing together the adhesive
and overlapping portions. Alternatively, the side portions of the
laminate can be folded so that either two outer wall portions or
two inner wall portions face each other in contact with the strip
of hot melt adhesive that is placed between them. The bag can be
made by cutting the tube to the desired length, followed by folding
and heat sealing one of the ends. After filling the bag with the
desired product, the top portion of the bag can be heat sealed and
closed in one of the previously described manners.
EXAMPLE
[0055] A container in the form of a 40 pound multi-wall bag of cat
litter is made in accordance with the invention. As noted herein,
the bag includes a first of a transparent, oriented polypropylene
film which provides the outer surface of the container while the
second sheet comprises paper so that the paper may be viewed
through the film and the film protects the paper from damage during
handling of the container. In this embodiment, visual information
comprising an identification of the product by tradename and in
desired colors are provided on the paper sheet, followed by a
coating of a standard varnish to prevent he water-based inks from
running when contacted by the water-based adhesive that is applied
to the film when the film and paper are joined together during cold
the lamination step. A standard kraft paper is used as an
additional wall member on the interior of the bag, and is used to
retain the pellets of cat litter therein.
[0056] A comparison of the bag of the invention to one made of
multiple layers of paper is summarized in the following details.
The empty bag itself when made according to the invention has a
number of unexpected advantages compared to the paper bag of the
prior art. The inventive bag is lighter and thinner than the paper
bag, and its appearance is shinier and smoother whereas the paper
bag appearance is duller and rougher. In addition, the inventive
bag is tougher and is more scuff resistant that then paper bag.
This enables the present bag to retain its appearance for a longer
time thus increasing its salability in stores.
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