U.S. patent application number 10/693337 was filed with the patent office on 2005-05-12 for articles with radiation cured adhesive as alternative to heat seals.
Invention is credited to Havens, Marvin R., Kyle, David R., Odabashian, Robert A..
Application Number | 20050100251 10/693337 |
Document ID | / |
Family ID | 34549921 |
Filed Date | 2005-05-12 |
United States Patent
Application |
20050100251 |
Kind Code |
A1 |
Havens, Marvin R. ; et
al. |
May 12, 2005 |
Articles with radiation cured adhesive as alternative to heat
seals
Abstract
A bag includes a first and second panel; first and second
layflat side edges; a bottom edge; and a bag mouth; at least one of
the layflat side edges, and the bottom edge, includes a radiation
cured adhesive layer bonding the first and second panels together.
A thermoformed container includes a forming web and a substantially
non-forming web; and a radiation cured adhesive layer disposed
between and bonding at least portions of the forming web and the
substantially non-forming web. A film/foam composite includes a
thermoplastic film and a polymeric foam sheet; and a radiation
cured adhesive layer disposed between and bonding at least portions
of the thermoplastic film and the polymeric foam sheet. An
inflatable packaging cushion includes a plurality of flexible
plastic sheets bonded together in the region of their edges; a
radiation cured adhesive layer bonds at least a portion of the
flexible plastic sheets together.
Inventors: |
Havens, Marvin R.; (Greer,
SC) ; Odabashian, Robert A.; (Greer, SC) ;
Kyle, David R.; (Moore, SC) |
Correspondence
Address: |
CRYOVAC, INC.
SEALED AIR CORP
P.O. BOX 464
DUNCAN
SC
29334
US
|
Family ID: |
34549921 |
Appl. No.: |
10/693337 |
Filed: |
October 23, 2003 |
Current U.S.
Class: |
383/107 |
Current CPC
Class: |
B32B 2439/00 20130101;
B32B 5/18 20130101; B65D 75/44 20130101; B32B 2307/7244 20130101;
B32B 7/05 20190101; B32B 27/065 20130101; B32B 7/12 20130101; B65D
81/052 20130101 |
Class at
Publication: |
383/107 |
International
Class: |
B65D 030/00 |
Claims
What is claimed is:
1. A bag comprising: a) a first panel; b) a second panel; c) first
and second layflat side edges; d) a bottom edge; and e) a bag
mouth; wherein at least one of the first and second layflat side
edges, and the bottom edge, comprises a radiation cured adhesive
layer bonding the first and second panels together.
2. The bag of claim 1 wherein the bag panels each comprise a film
having an oxygen barrier layer, and a bonding layer.
3. The bag of claim 1 wherein the average thickness of the
radiation cured adhesive layer is from 0.1 to 12 micrometers.
4. The bag of claim 1 wherein the radiation cured adhesive forms a
pattern.
5. The bag of claim 1 wherein the radiation cured adhesive forms a
discontinuous layer.
6. A thermoformed container comprising: a) a forming web, the
forming web comprising a polymeric material; b) a substantially
non-forming web comprising a polymeric material; and c) a radiation
cured adhesive layer disposed between and bonding at least portions
of the forming web and the substantially non-forming web.
7. The thermoformed container of claim 6 wherein the forming web
and the substantially non-forming web each comprise a film having
an oxygen barrier layer, and a bonding layer.
8. The thermoformed container of claim 6 wherein the average
thickness of the radiation cured adhesive layer is from 0.1 to 12
micrometers.
9. The thermoformed container of claim 6 wherein the radiation
cured adhesive layer forms a pattern.
10. The thermoformed container of claim 6 wherein the radiation
cured adhesive forms a discontinuous layer.
11. A film/foam composite comprising: a) a thermoplastic film
comprising a polymeric material; b) a polymeric foam sheet; and c)
a radiation cured adhesive layer disposed between and bonding at
least portions of the thermoplastic film and the polymeric foam
sheet.
12. The film/foam composite of claim 11 wherein the thermoplastic
film comprises a layer comprising a polyolefinic material.
13. The film/foam composite of claim 11 wherein the average
thickness of the radiation cured adhesive layer is from 0.1 to 12
micrometers.
14. The film/foam composite of claim 11 wherein the radiation cured
adhesive layer forms a pattern.
15. The film/foam composite of claim 11 wherein the radiation cured
adhesive forms a discontinuous layer.
16. An inflatable packaging cushion comprising a plurality of
flexible plastic sheets bonded together in the region of their
edges, wherein a radiation cured adhesive layer bonds at least a
portion of the flexible plastic sheets together.
17. The inflatable packaging cushion of claim 16 wherein the
flexible plastic sheets each comprise a layer comprising a
polyolefinic material.
18. The inflatable packaging cushion of claim 16 wherein the
average thickness of the radiation cured adhesive is from 0.1 to 12
micrometers.
19. The inflatable packaging cushion of claim 16 wherein the
radiation cured adhesive forms a pattern.
20. The inflatable packaging cushion of claim 16 wherein the
radiation cured adhesive forms a discontinuous pattern.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a container or container
component, e.g. a thermoplastic container or container component,
such as a bag (e.g. for food packaging), including a containers
made from a crosslinked film; a thermoformed container; a film/foam
composite; or an inflatable packaging cushion; in each of which at
least two plies of film, or at least one ply of film and at least
one ply of foam, are joined together by a radiation curable
adhesive.
BACKGROUND OF THE INVENTION
[0002] In many packaging applications, for food and non-food
markets, films and film/foam combinations, such as thermoplastic
films and film/foam combinations, are widely used in making the
packaging or components thereof.
[0003] For example, flexible film bags have been manufactured and
sold for the packaging of a wide variety of products, including
fresh red meat, smoked and processed meat, etc. Examples are shown
in U.S. Pat. No. 6,282,869 (Bullock et al.) incorporated herein by
reference in its entirety. The film for these bags sometimes
comprises a coextruded, totally irradiated and therefore
crosslinked structure, and sometimes an extrusion coated material
with an irradiated, crosslinked substrate and an unirradiated,
uncrosslinked extrusion coating.
[0004] Thermoformed containers likewise are used in packaging many
food and non-food products, and typically include a thermoformed
substrate and a lidding film. Examples are shown in U.S. Pat. No.
4,729,476 (Lulham et al.) incorporated herein by reference in its
entirety.
[0005] Film/foam composites are formed e.g. when a barrier liner is
adhered to a foamed or solid tray, such as a polystyrene,
polycarbonate, or polyolefin tray. Examples are shown in U.S. Pat.
No. 5,952,076 (Foster et al.) incorporated herein by reference in
its entirety.
[0006] Packagers are increasingly using air-inflated cushions
formed from relatively thin films of thermoplastic to protect their
packaged goods within boxes, sleeves, or cases during shipping and
storage. See U.S. Pat. No. 5,803,263 (Pozzo), and U.S. Pat. Nos.
6,276,532 and 6,569,283 (Sperry et al.), all incorporated herein by
reference in their entirety. For example, an inflatable packaging
cushion system that can protect a wide variety of packaged goods is
sold by Sealed Air Corporation under the VISTAFLEX.TM. trademark.
The VISTAFLEX.TM. inflatable packaging cushion includes an
inflation inlet designed for use with an inflation/sealing machine
provided by Sealed Air Corporation under the BT-1.TM. trademark.
The BT-1 inflator/sealer controls both the inflation of the cushion
with compressed air and sealing of the inflated cushion with an
impulse heat sealer. To inflate and seal the VISTAFLEX.TM. cushion,
a user inserts an inflation tube into an inflation inlet of the
cushion. The inflator/sealer inflates the cushion by opening a
valve to allow compressed air to pass through the inflation tube
into the interior of the cushion chamber until the cushion chamber
has been inflated to the desired pressure. At that point, a heat
seal bar compresses the top and bottom sheets of the inlet to
prevent the inflated cushion from deflating. An inflatable
packaging cushion is a useful form of protective packaging for
applications where the cushioning effect of the material offers
protection of a fragile product from physical shock and damage
during shipping of the product. An object to be packaged is, after
inflating the inflatable packaging cushion, intimately wedged
between the internal faces of the cushion which, by its
deformability, adapts to the shape and/or size of the object. Thus,
such a packaging item can be used for packaging articles of various
dimensions and shapes by suitably wedging them each time.
[0007] Common to these packaging formats is a heat-sealing process,
or alternative adhesion techniques such as radio frequency sealing,
gluing, etc. to join films or film plies together, or to join film
or film plies to one or more foam plies. In the case of flexible
bags, a "factory seal" is typically made, referring to any and all
seals necessary to convert a film tubing or flat film into a bag
having an open end. Such seals are usually made at a bag-making
factory, rather than at location at which products are being
packaged.
[0008] Heat sealing of certain polymeric materials can be difficult
and relatively slow. In the case of dissimilar materials, heat
sensitive materials (such as some foams), or crosslinked materials,
heat sealing can sometimes become so technically difficult or
impossible as to be commercially unfeasible. Heat can degrade some
foam materials.
[0009] In the case of heat shrinkable films, heat sealing
frequently results in some degree of puckering of the film material
in the area of the heat seal, triggered of course by the
application of heat to the seal area of the package. This
phenomenon can degrade the aesthetics of the package, and in
extreme cases make the package unusable from a commercial
viewpoint.
[0010] Also, where intricate sealing patterns, geometries, or
profiles are desired, or else dictated by the shape of the package,
e.g. in the case of an inflatable packaging cushion, it can be
difficult and expensive to design heat seal tooling that will
adequately and reliably create the patterns.
[0011] In accordance with the present invention, radiation curable
adhesives can be used to bond together films or film and foam, in
the production of a containers or container component, e.g. a
thermoplastic containers or container component, such as a bag
(e.g. for food packaging), including a container made from a
crosslinked film; a thermoformed container; a film/foam composite;
or an inflatable cushioning material; in each of which at least two
plies of film, or at least one ply of film and at least one ply of
foam, are to be joined together.
SUMMARY OF THE INVENTION
[0012] In a first aspect of the invention, a bag comprises a first
panel; a second panel; first and second layflat side edges; a
bottom edge; and a bag mouth; wherein at least one of the first and
second layflat side edges, and the bottom edge, comprises a
radiation cured adhesive layer bonding the first and second panels
together.
[0013] In a second aspect of the invention, a thermoformed
container comprises a forming web, the forming web comprising a
polymeric material; a substantially non-forming web comprising a
polymeric material; and a radiation cured adhesive layer disposed
between and bonding at least portions of the forming web and the
substantially non-forming web.
[0014] In a third aspect of the invention, a film/foam composite
comprises a thermoplastic film comprising a polymeric material; a
polymeric foam sheet; and a radiation cured adhesive layer disposed
between and bonding at least portions of the thermoplastic film and
the polymeric foam sheet.
[0015] In a fourth aspect of the invention, an inflatable packaging
cushion comprises a plurality of flexible plastic sheets bonded
together in the region of their edges, wherein a radiation cured
adhesive layer bonds at least a portion of the flexible plastic
sheets together.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] A detailed description of embodiments of the invention
follows, with reference to the attached drawings, wherein:
[0017] FIG. 1 is a schematic of an end-seal bag in lay-flat
view;
[0018] FIG. 2 is a cross-sectional view through section 2-2 of FIG.
1;
[0019] FIG. 3 is a schematic of a side-seal bag in lay-flat
view;
[0020] FIG. 4 is a cross-sectional view through section 4-4 of FIG.
3;
[0021] FIG. 5 is a fragmentary cross-sectional view through section
5-5 of FIG. 1;
[0022] FIG. 6 is a fragmentary cross-sectional view of an side seal
of FIG. 4;
[0023] FIG. 7 is a schematic of a process and apparatus for making
a film useful in the invention;
[0024] FIG. 8 is a schematic cross-sectional view of a film useful
with the invention;
[0025] FIG. 9 is a schematic cross-sectional view of a film useful
with the invention; FIG. 10 is a plan view of a thermoformed
container of the invention;
[0026] FIG. 11 is a side view of the container of FIG. 10;
[0027] FIG. 12 is a cross-sectional view taken along line XII-XII
of FIG. 10;
[0028] FIG. 13 is an enlarged cross-sectional view of the container
of FIG. 12;
[0029] FIG. 14 is a schematic cross-sectional view of a film/foam
composite of the invention;
[0030] FIG. 15 is a schematic of a process and apparatus for making
a film/foam composite of the invention;
[0031] FIG. 16 is a plan view of a first embodiment of an
inflatable cushion in accordance with the invention, in the
deflated state;
[0032] FIG. 17 is a plan view of the inflatable cushion of FIG. 16,
in the inflated state;
[0033] FIG. 18 is a perspective view of the inflatable cushion of
FIG. 16, in the inflated state;
[0034] FIG. 19 is a plan view of a first alternative embodiment of
the inflatable cushion of FIG. 16, in the deflated state;
[0035] FIG. 20 is a plan view of a second alternative embodiment of
the inflatable cushion of FIG. 16, in the deflated state;
[0036] FIG. 21 is a plan view of an inflatable cushion according to
the invention, in the deflated state, comprising a self-sealing
valve in a corner;
[0037] FIG. 22 is a sectional view along line A-A' of the
self-sealing valve in a corner of the inflatable cushion of FIG.
21;
[0038] FIG. 23 is a detailed view of the self-sealing value in a
corner and of two tabs for guiding the inflatable cushion of FIG.
21;
[0039] FIG. 24 is a sectional view along line B-B' of the valve and
of the two tabs of FIG. 23;
[0040] FIG. 25 is a detailed view of an alternative embodiment of
the self-sealing valve of FIG. 21;
[0041] FIG. 26 is a schematic view of an apparatus and process for
making a bag of the invention;
[0042] FIG. 27 is a plan view of a web printed with a patterned
seal design;
[0043] FIG. 28 is a plan view of the printed web of FIG. 27 after
lamination to a second web; and
[0044] FIG. 29 is a plan view of a waste web resulting from the
process of the invention.
[0045] Definitions
[0046] As used herein, the term:
[0047] "abuse layer" and the like refers to an outer film layer
and/or an inner film layer, so long as the film layer serves to
resist abrasion, puncture, and other potential causes of reduction
of package integrity, as well as potential causes of reduction of
package appearance quality. Abuse layers can comprise any polymer,
so long as the polymer contributes to achieving an integrity goal
and/or an appearance goal; examples include ethylene/alpha-olefin
copolymer having a density of from about 0.85 to 0.95,
propylene/ethylene copolymer, polyamide, ethylene/vinyl acetate
copolymer, ethylene/methyl acrylate copolymer, and ethylene/butyl
acrylate copolymer, etc.
[0048] "barrier" as applied to films and/or film layers, refers to
the ability of a film or film layer to serve as a barrier to one or
more gases. Barrier materials have an oxygen permeability, of the
barrier material, less than 500 cm.sup.3
O.sub.2/m.sup.2.multidot.day.multidot.at- mosphere (tested at 1 mil
thick and at 25.degree. C. according to ASTM D3985), such as less
than 100, less than 50 and less than 25
cm.sup.3O.sub.2/m.sup.2.multidot.day.multidot.atmosphere such as
less than 10, less than 5, and less than 1
cm.sup.3O.sub.2/m.sup.2.multidot.da- y.multidot.atmosphere.
Examples of polymeric materials with low oxygen transmission rates
are ethylene/vinyl alcohol copolymer (EVOH), polyvinylidene
dichloride (PVDC), vinylidene chloride/methyl acrylate copolymer,
polyamide, polyester, metal foil, SiO.sub.x compounds, and
metallized foils such as a sputter coating or other application of
a metal layer to a polymeric substrate such as high density
polyethylene (HDPE), ethylene/vinyl alcohol copolymer (EVOH),
polypropylene (PP), polyethylene terephthalate (PET), polyethylene
naphthalate (PEN), or polyamide (PA). Even a sufficiently thick
layer of a polyolefin such as LLDPE, or PVC (polyvinyl chloride)
can in some instances provide a sufficiently low oxygen
transmission rate for the overall film for its intended function.
The exact oxygen permeability optimally required for a given
application can readily be determined through experimentation by
one skilled in the art.
[0049] "bonding layer" and the like refers to an outermost film
layer (or the single layer of a monolayer film) involved in the
bonding of the film to itself, to another film layer of the same or
another film, and/or another article or container component which
is not a film. can comprise any thermoplastic polymer.
[0050] "bulk layer" refers to any layer of a film which is present
for the purpose of increasing the abuse-resistance, toughness,
modulus, etc., of a multilayer film. Bulk layers can comprise
polymers which are inexpensive relative to other polymers in the
film, and/or which provide some specific purpose unrelated to
abuse-resistance, modulus, etc. Examples include polyolefin;
ethylene/alpha-olefin copolymer, low density polyethylene, and
linear low density polyethylene.
[0051] "ethylene/alpha-olefin copolymer" (EAO) refers to copolymers
of ethylene with one or more comonomers selected from C.sub.3 to
C.sub.10 alpha-olefins such as propene, butene-1, hexene-1,
octene-1, etc. in which the molecules of the copolymers comprise
long polymer chains with relatively few side chain branches arising
from the alpha-olefin which was reacted with ethylene. This
molecular structure is to be contrasted with conventional high
pressure low or medium density polyethylenes which are highly
branched with respect to EAOs and which high pressure polyethylenes
contain both long chain and short chain branches. EAO includes such
heterogeneous materials as linear medium density polyethylene
(LMDPE), linear low density polyethylene (LLDPE), and very low and
ultra low density polyethylene (VLDPE and ULDPE), such as
DOWLEX.TM. or ATTANE.TM. resins supplied by Dow, and ESCORENE.TM.
or EXCEED.TM. resins supplied by Exxon; as well as linear
homogeneous ethylene/alpha olefin copolymers (HEAO) such as
TAFMER.TM. resins supplied by Mitsui Petrochemical Corporation,
EXAC.TM. resins supplied by Exxon, or long chain branched (HEAO)
AFFINITY.TM. resins supplied by the Dow Chemical Company, or
ENGAGE.TM. resins supplied by DuPont Dow Elastomers.
[0052] "ethylene homopolymer or copolymer" herein refers to
ethylene homopolymer such as low density polyethylene;
ethylene/alpha olefin copolymer such as those defined herein;
ethylene/vinyl acetate copolymer; ethylene/alkyl acrylate
copolymer; ethylene/(meth)acrylic acid copolymer; or ionomer
resin.
[0053] "film" and the like refers to plastic web, regardless of
whether it is film or sheet. Films used in the present invention
have a thickness of 0.5 to 40 mils.
[0054] "oriented" refers to a polymer-containing material which has
been stretched at an elevated temperature (the orientation
temperature), followed by being "set" in the stretched
configuration by cooling the material while substantially retaining
the stretched dimensions. Upon subsequently heating unrestrained,
unannealed, oriented polymer-containing material to its orientation
temperature, heat shrinkage is produced almost to the original
unstretched, i.e., pre-oriented dimensions. More particularly, the
term "oriented", as used herein, refers to oriented films, wherein
the orientation can be produced in one or more of a variety of
manners.
[0055] "polymer" refers to the product of a polymerization
reaction, and is inclusive of homopolymers, copolymers,
terpolymers, etc.
[0056] "polyolefin" refers to any polymerized olefin, which can be
linear, branched, cyclic, aliphatic, aromatic, substituted, or
unsubstituted. Specific examples include polyethylene homopolymer,
polypropylene homopolymer, polybutene, ethylene/alpha-olefin
copolymer, propylene/alpha-olefin copolymer, butene/alpha-olefin
copolymer, ethylene/vinyl acetate copolymer, ethylene/ethyl
acrylate copolymer, ethylene/butyl acrylate copolymer,
ethylene/methyl acrylate copolymer, ethylene/acrylic acid
copolymer, ethylene/methacrylic acid copolymer, modified polyolefin
resin, ionomer resin, polymethylpentene, etc.
[0057] "tie layer" refers to any internal layer having the primary
purpose of adhering two layers to one another. Tie layers can
comprise any polymer having a polar group grafted thereon, so that
the polymer is capable of covalent bonding to polar polymers such
as polyamide and ethylene/vinyl alcohol copolymer. Tie layers can
comprise polyolefin, modified polyolefin, ethylene/vinyl acetate
copolymer, modified ethylene/vinyl acetate copolymer, and
homogeneous ethylene/alpha-olefin copolymer; anhydride modified
grafted linear low density polyethylene, anhydride grafted low
density polyethylene, homogeneous ethylene/alpha-olefin copolymer,
and anhydride grafted ethylene/vinyl acetate copolymer.
[0058] All compositional percentages used herein are presented on a
"by weight" basis, unless designated otherwise.
DETAILED DESCRIPTION OF THE INVENTION
[0059] Bags: Article
[0060] Film in the form of seamless tubing can be converted into
end-seal bags. FIG. 1 is a lay-flat view of a end-seal bag 10 of
the present invention. End-seal bag 10 is made from seamless
tubular film 12, and has a bag mouth 14, first and second lay-flat
side edges 16 and 18, bottom edge 20, and end-seal 22. FIG. 2
illustrates a cross-sectional view of end-seal bag 10 taken through
section 2--2 of FIG. 1.
[0061] In the end-seal bag, therefore, the side edges of the bag
are actually formed by lay flat folds in the seamless tubing. The
bottom edge of the bag is a cut in the tubing that is closed by the
application of a radiation curable adhesive to the internal surface
of the bottom portion of either or both of first and second panels
(24 and 26) of the bag. The radiation curable adhesive is thus
disposed between the bottom portions of the front and rear panels
(24 and 26) of the bag. The radiation curable adhesive is cured as
disclosed herein to bond together these portions. FIG. 5 shows a
fragmentary enlarged cross sectional view of the end seal 22. A
radiation cured adhesive layer or region 42 bonds together the
internal surfaces of first panel 24 and second panel 26. Although
shown in FIG. 5 as a continuous layer, the radiation cured adhesive
layer can alternatively be discontinuous in nature, disposed in
selected regions but not continuously across the width of the
bottom seal 22 of the bag 10. The radiation cured adhesive layer
can also vary in its vertical extent along the seal (vertical as
viewed in the plan view of FIG. 1). Finally, the thickness or depth
of the radiation cured adhesive layer, although shown in FIG. 5 as
of uniform thickness, can vary in thickness either within one
applied coat of adhesive, or by means of multiple coats of adhesive
in selected regions of the overall seal area.
[0062] Alternatively, film in the form of seamless tubing can be
converted into side-seal bags. FIG. 3 is a lay-flat view of
side-seal bag 30 of the present invention. Side-seal bag 30 is made
from dual-seamed tubular film 32, and has open top 34, first and
second side seals 36 and 38, and bottom edge 40. FIG. 4 is a
cross-sectional view of side-seal bag 30, taken through section 4-4
of FIG. 3.
[0063] In the side-seal bag, therefore, the bottom edge of the bag
is actually formed by a lay flat fold in the seamless tubing. The
side edges of the bag are cuts in the tubing that are closed by the
application of a radiation curable adhesive to the internal surface
of the side edge portions of either or both of front and rear
panels (44 and 46) of the bag. The radiation curable adhesive is
thus disposed between the side edge portions of the front and rear
panels (44 and 46) of the bag. The radiation curable adhesive is
cured as disclosed herein to bond together these portions. FIG. 6
shows a fragmentary enlarged cross sectional view of the side seal
36. A radiation cured adhesive layer or region 48 bonds together
the internal surfaces of first panel 44 and second panel 46.
Although shown in FIG. 6 as a continuous layer, the radiation cured
adhesive layer can alternatively be discontinuous in nature,
disposed in selected regions but not continuously across the length
of the side seal 36 of the bag 30. The radiation cured adhesive
layer can also vary in its lateral extent along the seal (lateral
as viewed in the plan view of FIG. 3). Finally, the thickness or
depth of the radiation cured adhesive layer, although shown in FIG.
6 as of substantially uniform thickness, can vary in thickness
either within one applied coat of adhesive, or by means of multiple
coats of adhesive in selected regions of the overall seal area.
[0064] The teaching herein relating to side seal 36, and
alternative embodiments thereof, apply mutatis mutandis to side
seal 38.
[0065] Bags: Process
[0066] The bags of the invention as described herein are made from
thermoplastic film. Film for the production of the bags as
described herein can be produced by any suitable method, e.g. in
accordance with a process schematically illustrated in FIG. 7. In
the process illustrated in FIG. 7, solid polymer beads (not
illustrated) are fed to one or a plurality of extruders 29 (for
simplicity, only one extruder is illustrated). Inside extruders 29,
the polymer beads are forwarded, melted, and degassed, following
which the resulting bubble-free melt is forwarded into die head 31,
and extruded through an annular die, resulting in tubing 33 which
can be of any suitable thickness, e.g. 5 to 25 mils thick. After
cooling or quenching by water spray from cooling ring 35, tubing 33
is collapsed by pinch rolls 37, and is thereafter fed through
irradiation vault 39 surrounded by shielding 41, where tubing 33 is
irradiated with high energy electrons (i.e., ionizing radiation)
from iron core transformer accelerator 43. Tubing 33 is guided
through irradiation vault 39 on rolls 45. Tubing 33 is irradiated
to a level of e.g. from 10 to 70 kiloGrays. After irradiation,
irradiated tubing 47 is directed through pinch rolls 49, following
which irradiated tubing 47 is slightly inflated, resulting in
trapped bubble 50. However, at trapped bubble 50, the tubing is not
significantly drawn longitudinally, as the surface speed of nip
rolls 52 are about the same speed as nip rolls 49. Furthermore,
irradiated tubing 47 is inflated only enough to provide a
substantially circular tubing without significant transverse
orientation, i.e., without stretching. Slightly inflated,
irradiated tubing 50 is passed through vacuum chamber 54, and
thereafter forwarded through coating die 56. Second tubular film 58
is melt extruded from coating die 56 and coated onto slightly
inflated, irradiated tube 50, to form two-ply tubular film 60.
Second tubular film 58 can comprise an oxygen-barrier layer, which
does not pass through the ionizing radiation. Further details of
the above-described coating step are generally as set forth in U.S.
Pat. No. 4,278,738, to BRAX et. al., which is hereby incorporated
by reference thereto, in its entirety.
[0067] After irradiation and coating, two-ply tubing film 60 is
wound up onto windup roll 62. Thereafter, windup roll 62 is removed
and installed as unwind roll 64, on a second stage in the process
of making the tubing film as ultimately desired. Two-ply tubular
film 60, from unwind roll 64, is unwound and passed over guide roll
66, after which two-ply tubular film 60 passes into hot water bath
tank 68 containing hot water 70. The now collapsed, irradiated,
coated tubular film 60 is submersed in hot water 70 (having a
temperature of e.g. 185.degree. F.) for a retention time of at
least about 30 seconds, i.e., for a time period in order to bring
the film up to the desired temperature for biaxial orientation.
Thereafter, irradiated tubular film 60 is directed through nip
rolls 72, and bubble 74 is blown, thereby transversely stretching
tubular film 60. Furthermore, while being blown, i.e., transversely
stretched, nip rolls 76 draw tubular film 60 in the longitudinal
direction, as nip rolls 76 have a surface speed higher than the
surface speed of nip rolls 72. As a result of the transverse
stretching and longitudinal drawing, irradiated, coated
biaxially-oriented blown tubing film 78 is produced, this blown
tubing having been both transversely stretched in a ratio of e.g.
from 1:1.5 to 1:6, and drawn longitudinally in a ratio of e.g. from
1:1.5 to 1:6. Alternative ratios are from 1:2 to 1:4 (transverse
direction) and from 1:2 to 1:4 (longitudinal direction).
[0068] While bubble 74 is maintained between pinch rolls 72 and 76,
blown tubing 78 is collapsed by rolls 80, and thereafter conveyed
through pinch rolls 76 and across guide roll 82, and then rolled
onto wind-up roll 84. Roll 86 assures a good wind-up.
[0069] Those skilled in the art will understand that many
variations in the above film making process can offer alternative
processing. For example, a full coextrusion process can be used
instead of an extrusion coating process, particularly where
polymeric materials compatible with the irradiation process are
used, or where the film is not irradiated. Flat cast extrusion can
be used, followed by standard tenterframing techniques to
accomplish orientation of the film. Bags can then be made by back
seaming and end sealing methods well known in the art, but with the
use of radiation curable adhesives in place of heat sealing.
Monoaxial orientation can be employed, or the film can remain
unoriented, that is, not stretch oriented as described above.
Irradiation can alternatively be employed after the film has been
fully coextruded.
[0070] It should also be noted that radiation curable adhesives can
be used to produce one or more seals of a bag with multiple seals,
and heat sealing or another alternative sealing mechanism
(adhesive, glue, radio frequency sealing, ultrasonic sealing, etc.)
can be used to produce one or more of the remaining seals of the
bag.
[0071] End seal and side seal bags can then be made from the
biaxially-oriented blown tubing film.
[0072] Referring to FIGS. 26 through 29, two polymeric film webs
122 and 124 are fed, from feed rolls 126 and 128 respectively into
individual haul off nip rolls 130 and 132 respectively whereby the
film webs are unwound from rolls 126 and 128. Web 126 is advanced
through a printing process 134, whereby the predetermined pattern
135 of the radiation curable adhesive and the seal or weld that
will result therefrom after curing) is printed on a surface of web
126 with a radiation curable adhesive. FIG. 27 is a view of web 126
after printing. The two webs 122 and 124 are then brought together
at the juncture of rolls 136 and 138 (see FIG. 28). Just prior to
that joining, the radiation curable adhesive is exposed to a dose
of ultraviolet light, at station 140, effective to cure the
radiation curable adhesive and thereby bond the two webs together
at points on the respective webs contacted by the pattern 135.
Immediately after the exposure, the two webs are conveyed by a set
of nip rollers 142a and 142b.
[0073] The joined webs are then advanced, e.g. by conveyor, to a
station 146 where the predetermined pattern 135 of each bag is cut.
This can be accomplished by means of an intermittent operation
using a flat steel rule die, or a rotary steel rule die 148 against
a rotary steel anvil 150. The waste web 152 is then conveyed away
(see FIG. 29), while the individual bags are then laid in
imbricated (shingled) fashion on conveyor 156. Waste web 152 in
this embodiment will exhibit patterned holes 153 reflecting the
conformation of the bags cut from the web.
[0074] In an alternative embodiment, a tubular web can be single
edge slit and unfolded to provide one of the webs described
hereinabove with respect to the process of FIG. 26; or the tubular
web can be edge slit and ply separated into two separate flat webs
that can then function as each of the webs disclosed in connection
with FIG. 26.
[0075] Films useful in connection with the invention can be
monolayer films or multilayer films. If multilayer, the film can
have any suitable number of layers, such as a total of from 2 to 20
layers.
[0076] In general, the film can have any total thickness desired,
and each layer can have any thickness desired, so long as the film
provides the desired properties for the particular packaging
operation in which the film is used, e.g. abuse-resistance
(especially puncture-resistance), modulus, optics, oxygen barrier
properties, etc.
[0077] Each layer of the film can be made from any suitable
polymeric material, such as any suitable thermoplastic polymer or
copolymer, such as polyolefin (e.g. ethylene/alpha-olefin
copolymer), ethylene copolymer, polyamide, polyester, polyvinyl
chloride, polypropylene, ethylene/propylene copolymer, homopolymers
of ethylene, ethylene copolymers having at least 50 mole percent of
an ethylene unit and a minor proportion of a monomer
copolymerizable with ethylene, such as vinyl acetate, vinyl
chloride, propylene, butene, hexene, acrylic acid and its esters,
and methacrylic acid and its esters; polybutadiene. Examples of
polyethylenic resins which can be advantageously employed include
the invention are low-, medium- and high-density polyethylenes, and
copolymers thereof.
[0078] FIGS. 2, 4, 5, and 6 depict a monolayer film. This monolayer
film can comprise any suitable polymer, such as those listed above.
Instead of a monolayer film, a multilayer film can be provided to
make bags of the instant invention.
[0079] By way of example, FIG. 3 shows a two layer film 88. Layer
89 is a layer that can be used as the bonding layer, to be joined
to a like layer in a seamless tube, or to another layer of this or
another film. The layers that make up the bonding layers of a bag
of the invention can be the same or different either chemically or
physically. Layer 90 is a second layer. Layers 88 and 89 can also
contain appropriate amounts of other additives, such as slip agents
such as talc, antioxidants, fillers, dyes, pigments and dyes,
radiation stabilizers, antistatic agents, elastomers, and the like
additives known to those of skill in the art of packaging
films.
[0080] A multilayer film of the invention can have one or more
internal or external film layers which have a primary function as
an adhesive or compatibilizer (tie layer) for adhering two layers
to one another; or provide abuse resistance, oxygen barrier, or
other functionality. Usually, the core layer or layers provide the
multilayer film with a desired level of strength, i.e., modulus,
and/or optics, and/or added abuse resistance, and/or specific
impermeability.
[0081] The multilayer films used in the present invention are
optionally irradiated, before bag making and in some cases before
orientation, to induce crosslinking. In the irradiation process,
the film is subjected to an energetic radiation treatment, such as
corona discharge, plasma, flame, ultraviolet, X-ray, gamma ray,
beta ray, and high energy electron treatment, which induces
cross-linking between molecules of the irradiated material. The
irradiation of polymeric films is disclosed in U.S. Pat. No.
4,064,296, to BORNSTEIN, et. al., which is hereby incorporated in
its entirety, by reference thereto. Radiation supplied to cure a
radiation curable adhesive can also function to irradiate the film
layers to induce cross-linking.
[0082] Thermoformed Container
[0083] Referring to FIGS. 10 to 13, container 250 has a first web
252 which is a forming web produced by thermoforming or other
suitable techniques well known in the art. Suitable thermoforming
methods, for example, include a vacuum forming or plug-assist
vacuum forming method. In a vacuum forming method, the first web is
heated e.g. by a contact heater and a vacuum is applied beneath the
web causing the web to be pushed by atmospheric pressure down into
a pre-formed mold. In a plug-assist vacuum forming method, after
the first or forming web has been heated and sealed across a mold
cavity, a plug shape similar to the mold shape impinges on the
forming web and, upon the application of vacuum, the forming web
transfers to the mold surface.
[0084] After the first web is in place, a product 254, such as a
smoked sausage or other food or non-food product, is placed, such
as by manual loading, on the first web. Either before, during, or
after the step of placing the product 254 on the first web, a
radiation curable adhesive is applied in either a continuous or
discontinuous fashion in the peripheral area of the first web, on
the surface of the first web that will be subsequently contacted by
the peripheral area of a second web 256. The second, substantially
non-forming web 256 is disposed over the product and the first web
with the radiation curable adhesive disposed on the first web. A
release of vacuum then causes the second web 256 to tack to the
first web 252 so as to enclose the product between the webs and
self-weld the first and second webs at their contiguous
surfaces.
[0085] The radiation curable adhesive forms an intermediate layer
260 in the resulting package. The container is thereafter subjected
to UV, electron beam, or other radiation sufficient to cure the
adhesive and create a bond between the first web 252 and the second
web 256. The radiation curable adhesive layer 260 thus becomes a
bonding layer comprising a radiation cured adhesive.
[0086] Alternatively, the radiation curable adhesive can be applied
in either a continuous or discontinuous fashion in the peripheral
area of the second web (instead of the first web), on the surface
of the second web that will be subsequently contacted by the
peripheral area of the first web 252. In still another alternative,
the radiation curable adhesive can be applied in either a
continuous or discontinuous fashion in the peripheral area of both
the first and second webs.
[0087] After the first and second webs 252 and 256 have been
self-welded, and preferably before the shrinking operation
described above is performed, the peripheral edge of the package is
sealed or bonded by a radiation curable adhesive. This peripheral
seal 260 is located at or near the actual periphery of the
package.
[0088] Although the first and second webs 252 and 256 are depicted
in FIG. 13 as being of monolayer construction, like the films
described herein, these webs can be of multilayer construction,
each layer comprising any suitable polymer such as those disclosed
herein; of any suitable thickness; and made by any suitable
process.
[0089] Film/Foam Composite
[0090] In FIG. 14, a film/foam composite 310 includes bottom film
311 and top foam sheet 312. Bottom film 311 comprises any suitable
polymer such as those disclosed herein. Top foam sheet 312
comprises any suitable foam material, e.g. low density polyethylene
foam having a density of about 2 pcf. In laminate 310, top foam
sheet 312 and bottom film 311 are adhered together by means of a
radiation curable adhesive layer 313. The polyethylene foam can be
extruded in sheet form and then laminated to the polyethylene
film.
[0091] One process of preparing the film/foam composite involves
bringing together a moving continuous web of a thin sheet of
polyethylene foam and a moving continuous web of the bottom film
311, as shown in FIG. 15. A radiation curable adhesive 323 is
stored in a container 322, and applied from a nozzle 321 to one or
both of the facing surfaces of the moving webs at the point of
contact between the moving webs, to form radiation curable adhesive
layer 313. The webs are then brought together by e.g. applying
pressure by two opposing rollers 324 and 325 to the contacting webs
at the point of contact of the moving webs. A radiation curing unit
326, e.g. a UV unit, is positioned downstream on one or both sides
of the composite to achieve bonding of webs 311 and 312 together
and transform radiation curable adhesive layer 313 to radiation
cured adhesive layer 313. Although bottom film 311 is shown as a
monolayer film, it can comprise two or more layers as disclosed
herein.
[0092] The nip pressure applied by the opposed rollers on the
laminate is typically between 0 to 10 pcf and about 150 pcf, e.g.
about 60 pcf.
[0093] The moving continuous web of top foam sheet 312 can be
formed by extrusion, passed through at least one oven, and, while
being at a temperature between 350.degree. F. and 500.degree. F.,
brought into contact with the moving continuous web of bottom film
311. The rollers can be chilling rollers.
[0094] The foam sheet can be that obtained from a third party or
manufactured on site and later used, but in either case the foam
sheet can be reheated just before it is laminated with the
polyethylene film. The lamination can be done using extruded foam
sheet at an elevated temperature immediately after exiting the
oven(s) downstream from the extruder.
[0095] Typically, polyethylene films are 10 mils thick or less, and
polyethylene sheets are greater than 10 mils thick.
[0096] The foam sheet 312 can be formed by means of a conventional
polyethylene foam sheet extrusion process or any other suitable
foam sheet-forming process. The foam sheet can be open or closed
celled.
[0097] The bottom film 311 can be formed by means of a conventional
film extrusion process or any other suitable film-forming
process.
[0098] If the bottom film 311 comprises a heat shrinkable material,
made by orientation techniques well known in the art, and if the
radiation curable adhesive is applied at specific intermittent
points along the interface between the bottom film 311 and top foam
sheet 312, then upon the application of sufficient heat, the
composite will deform to an undulating structure.
[0099] Inflatable Packaging Cushion
[0100] Referring to FIGS. 16, 17 and 18, these show a first
embodiment of an inflatable packaging cushion 100 of the invention,
intended to wedge and to protect one or more objects to be
packaged.
[0101] This inflatable cushion 100 includes an external peripheral
edge 101 which here describes essentially a rectangle and which is
generally adapted to the shape and to the dimension of a packaging
receptacle, for example a box made from rigid cardboard; a trayed
package including a tray, a product disposed in the tray, and a
lidstock sealed to the top of the tray; or the like. This
inflatable cushion 100 includes an internal opening 102, which is
rectangular for example, capable of receiving at least one object
500 to be packaged and a plurality of recesses 103, here four
recesses 103 extending from each of the corners of the rectangular
internal opening 102 towards the peripheral edge 101 of the said
cushion 100 and more precisely in the direction of the corners of
the said peripheral edge 101. As shown in FIGS. 16, 17 and 18, the
inflatable cushion 100 includes two sheets of flexible plastic (of
any suitable polymer or blend of polymers as disclosed herein),
juxtaposed and bonded together in the region of their edges along
the bonding lines LS.
[0102] As seen in FIGS. 17 and 18, the recesses 103 delimit, in
pairs, wedging parts 104, 105, 106, 107, here four wedging parts
capable of coming into contact with the object 500 to be packaged,
by pivoting around preferential pivoting zones 108 defined between
the recesses 103 and the peripheral edge 101.
[0103] The pivoting of the wedging parts 104, 105, 106, 107 around
the preferential pivoting zones 108 enables the size and/or the
shape of the internal opening 102 to be varied in order to adapt it
to objects of various sizes and/or shapes, whilst exerting a
holding pressure on the object or objects to be packaged by virtue
of a return movement which is exerted in the region of the pivoting
zones 108. In this case, the shape of each recess 103 and/or of the
peripheral edge 101 is such that, in this region, two preferential
pivoting zones 108 are located respectively at two locations where
the space between the recess 103 and the external peripheral edge
101 of the cushion 100 is the least. In this example, the
peripheral edge 101 is substantially straight between two corners
and each recess 103 is substantially droplet shaped, that is to say
has a shape constituted by two lines 103b, 103c diverging from a
corner of the internal opening 102 towards the peripheral edge 101
and joined together by a rounded portion 103a in the vicinity of
this edge. In the region of the rounded portion 103a, there are two
locations where the space between the recess 103 and the external
peripheral edge 101 is the least and these two locations define two
preferential pivoting zones 108. The shapes of the recesses 103
and/or of the peripheral edge 101 which are described are not
unique and the person skilled in the art will be able to make
modifications to them, knowing that it suffices to create, between
one recess 103 and the peripheral edge 101, at least one narrowing
so as to define at least one preferential pivoting zone 108.
[0104] The external peripheral edge 101 can have indentations in
the region of each recess 103 in order to define, with the recess,
the preferential pivoting zones 108. As may be better seen in FIG.
18, the shape and the dimension of the recesses 103 and of the
peripheral edge 101 are such that, during the inflating, two
neighboring wedging parts spontaneously pivot in opposite
directions, this spontaneous pivoting being due in particular to
the fact that the inflating of the cushion will generate certain
tensions in its material, especially in the neighboring region of
the recesses, and that these tensions are at a minimum after such a
pivoting has occurred.
[0105] The four lateral intersecting edges of the object 500 placed
in the inflatable cushion 100 are engaged in the recesses 103; they
are not in contact with the cushion, which minimizes the risk of
wear or of deterioration of the cushion by these intersecting
edges. The recesses constitute, by virtue of their deformability,
preferential impact-damping zones.
[0106] The inflatable cushion 100 shown in FIGS. 16, 17 and 18 has
a self-sealing inflating valve 109 located on one side of the
peripheral edge 101, enabling the cushion to be inflated or
deflated by means of an inflating hose which is inserted into the
valve. This inflating valve 109 can be placed equally on any edge
of the cushion 100 and, for example, on the edge of the internal
opening 102, emerging naturally towards the interior of the
opening. FIG. 19 shows an alternative embodiment of the inflatable
cushion 100 of FIG. 16, which here includes two internal openings
102, 102' of square shape. It comprises eight recesses 103, 103'
which extend from each of the corners of each square internal
opening 102, 102' towards the peripheral edge 101 of the cushion
100. The cushion includes four flats beveled at the four corners.
The internal openings 102, 102' are placed such that each opening
102, 102' comprises two recesses 103, 103' extending in the
direction respectively of two corners of the peripheral edge 101
and two recesses 103, 103' extending respectively towards the
centers of the longitudinal parts 101a, 101b of the peripheral edge
101. The cushion 100 shown in FIG. 19 then comprises eight pivoting
wedging parts 104, 105, 106, 107, 104', 105', 106', 107' each
defined by two successive recesses, the wedging parts being capable
of coming into contact with one or more objects to be packaged.
Moreover, as may be seen in FIG. 19, the cushion 100 comprises a
fixed central wedging part 110 which extends between the openings
102, 102' and which includes a central hole 117, produced by
cutting the two sheets forming the cushion and bonding the cut
edges of the sheets along the line LS. This circularly-shaped
central hole makes it possible to act as an impact-absorbing buffer
when the cushion is placed between the face of a packing box and an
object to be packaged. In addition, this circular hole 117 enables
the thickness of the cushion in the inflated state to be
limited.
[0107] FIG. 20 shows another alternative embodiment of the
inflatable cushion 100 of FIG. 16, which includes two internal
openings 102, 102' each having an essentially straight shape. The
internal openings 102, 102' arranged in parallel have a recess 103,
103' at each end. The cushion 100 then includes four recesses 103,
103', each of the recesses extending in the direction of a corner
of the peripheral edge 101. The cushion 100 comprises three wedging
parts 104, 104', 105. Two of the wedging parts 104, 104' can pivot
and each is delimited by the two recesses 103, 103' extending from
the openings. The third wedging part is a fixed central part 105
lying between the two openings 102, 102'. The cushion 100 includes
at the center of the central wedging part 105, two circular holes
117 which make it possible to limit the thickness of the inflated
cushion and to act as an impact absorber. In the same manner as for
the cushion of FIG. 19, the four corners of this cushion have a
beveled flat area.
[0108] FIG. 21 shows another inflatable cushion 200. Cushion 200 is
designed to be inserted into a packaging item such as a box having
articulated closure flaps adjacent, by one of their edges, to a
corner of the box, as well as an inflatable cushion 100 of the type
shown in FIGS. 16, 17, 18, 19 and 20.
[0109] In FIG. 21, the inflatable cushion 200 comprises two sheets
220 of flexible plastic, bonded together in the region of their
edges along the bonding line LS. As may be seen in FIG. 21, the
inflatable cushion 200 has a rectangular shape adapting to the
shape and to the dimension of a box. This cushion shape is suitable
for packing receptacles have essentially parallelepipedal shapes.
The inflatable cushion 200 can include a self-sealing inflating
valve 210 located in a corner region of the cushion 200. When the
latter is installed in a box, the inflating valve 210 is placed in
the region of a corner of the box, which enables the cushion 200 to
be inflated from outside, after closing the articulated flaps, by
means of an inflating hose 400 inserted into the valve 210. This
inflating characteristic enables a packing box having flaps to be
used without any particular arrangement for allowing the hose to
pass.
[0110] As may be seen in FIGS. 21, 22 and 23, the self-sealing
inflating valve 210 comprises two thin sheets 211 of plastic
juxtaposed and bonded together along two parallel lines so as to
form a passage conduit for the inflating hose 400, open at both
ends. As may be better seen in FIG. 22, the inflating valve 210 is
located between the two sheets 220 forming the cushion 200 in the
corner region of the cushion. Furthermore, the valve, as FIG. 21
shows, extends from a corner of the cushion only along a part of
the length of one diagonal of the cushion, which enables the
cushion to be deflated by inserting the hose 400 into the valve
beyond the free end of the passage conduit.
[0111] According to a variant of the self-sealing inflating valve
210 shown in FIG. 23, the parallel bonding lines of the two thin
sheets 211 move apart locally such that the passage conduit for the
inflating hose created by the lines includes a widening located
some distance from the free end of the conduit placed inside the
cushion 200.
[0112] Thus, when the inflating of the cushion 200 is stopped and
when the hose 400 is still partially engaged in the passage
conduit, the two thin sheets 211 are applied mutually against each
other by virtue of a distortion caused in the vicinity of the free
end of the conduit by the widening, so as immediately to obstruct
the conduit and thus prevent the cushion from partially deflating.
In addition, as FIGS. 21, 23, 24 and 25 show, the sheets 211 are
bonded together at one of their ends and at the two sheets 220
forming the cushion along a bonding line 212a extending along a
beveled flat 212 of the corner of the cushion, thereby leaving a
non-bonded zone in line with an adjacent opening 215 of the conduit
in order to allow the conduit to be open to the outside for
inserting the inflating hose 400.
[0113] In order to facilitate the insertion of the hose into the
conduit, there is provision, as may be seen in FIGS. 21, 23, 24 and
25, for the inflatable cushion to include two flexible guide tabs
213, each of which is constituted by the prolongation, in
superposition, of a sheet 220 of the cushion and of a sheet 211 of
the valve. As shown in FIGS. 23 and 24, a peripheral bond 212b,
separate form the bonding line 212a along the beveled flat 212,
firmly attaches these sheets together and has edges located in the
prolongation of the adjacent edges of the cushion 200. As may be
seen in FIGS. 23, 24 and 25, the end of the inflating valve is
bonded to the cushion along a bonding line 212a, this bond linking,
on the one hand, the two thin sheets 211 and the two sheets 220
constituting the cushion. Alternatively, as shown in FIG. 25, a
single bonding line 212a' can be seen, which extends along the
beveled flat 212 and which makes it possible, on the one hand, to
bond together the sheets forming the self-sealing valve and to bond
them to the sheets forming the cushion, and, on the other hand, to
firmly attach the sheets constituting the guiding tabs to the
cushion. It will be noted that the bonding line 212a' has a width
markedly greater than that of the single bonding line 212a. This
allows the possible inscription, within the bonding line 212a', of
a mark or of any specification relating to the cushion.
[0114] The inflatable cushions 100 shown in FIGS. 16, 17, 18, 19
and 20, can themselves also include, if necessary, a self-sealing
inflating valve in a corner, according to the embodiments shown
more particularly in FIGS. 7, 23, 24 and 25.
[0115] In each instance in the above disclosure, where a bond is
disclosed, this bond can be made using a radiation curable adhesive
(or a blend of radiation curable adhesives) which can be applied by
any suitable means, such as coating, printing, etc., manually or by
machine, in a continuous or discontinuous fashion, randomly or in a
predetermined pattern, geometry, or profile, to one or both of the
relevant surfaces that are to be adhered together.
[0116] Radiation Curable Adhesives
[0117] Radiation curable adhesives useful in place of heat seals
can be selected based on cationic, free radical, and hybrid
chemistries. Radiation curable adhesives offer much faster
production speeds than conventional heat seal processes. They can
be used to construct a variety of adhesive junctions that can
replace heat seals. Because radiation curable adhesives can be
applied via traditional coating processes, the options for specific
shapes or geometries are vast and allow patterns not possible with
heat seals, in a fast, continuous, laminating and curing
process.
[0118] Radiation curable adhesives offer the advantage of bonding
films with controllable bond strengths that can be moderate such as
for tacking or tamper evident applications to very high with
substrate destruction before bond failure. Bond strengths also can
be controlled through formulation and dose from low to high bond
strength.
[0119] Radiation curable pressure sensitive adhesives are available
with controlled tack and bond strength that allow easy removable,
reclosable or permanent bonds along with improved properties such
elevated temperature resistance not possible with thermoplastic
type adhesives.
[0120] The radiation curable adhesive can be applied by
flexographic, rotogravure, rotoscreen, ink jet, roll coating and
other dispensing methods.
[0121] This approach offers several advantages over the currently
used heat sealing process that includes allowing complex patterns
to be printed on wide web in any desired cushion pattern. The
printing process can allow high throughput of about 200 fpm.
[0122] The adhesive beneficially can rapidly form strong bonds to
the film, web, or other substrate on which it is applied. It is
desirable that the radiation curable adhesive have the following
characteristics as shown in Table 1.
1TABLE 1 Desirable Adhesive Characteristic Radiation Curable
Adhesives No/low volatile organic compounds (VOC's), Typically no
VOC's used. Diluents if used, (no solvents), crosslink into polymer
network Application/printing flexibility Has capability to be
applied by various printing processes such as flexo, gravure, roto-
screen, ink jet and other dispensing methods. Printed adhesive
pattern can be immediately UV adhesives can be immediately
laminated laminated and cured in-line as a rapid continuous and UV
light cured as continuous operation. in-line processes. UV curing
process can often be carried out at 500 to 800 fpm. The curing
equipment has a low foot print and Much lower space requirements
compared to can be retrofitted to existing lamination lines. drying
tunnels. UV light irradiators are available that are less than 12
inches wide. Power supplies also have low space requirements. Rapid
development of full cured properties. Cationic systems reach full
cured properties in hours. Fully cured properties reached in
seconds with radical type system Handling and storage ease.
Typically 1 part thermoset type system and storage stable, even
when left on application equipment. Not distort film Temperature
sensitive substrates can be used with commercially available
systems. Low temperature curing with proper engineering
controls.
[0123] The surface of the film, web, or other substrate on which
the radiation curable adhesive is applied can be corona pre-treated
by standard corona treatment techniques.
[0124] A low adhesive viscosity is beneficial for room temperature
application if a flexographic printing method is employed, but
application of a radiation curable adhesive at elevated
temperatures is also possible. In some cases, matching of the
radiation curable adhesive formulation to the film, web, or other
substrate on which the radiation curable adhesive is to be applied
can be beneficial.
[0125] Film substrates must be at least partially UV light
transparent for free radical type chemistries, where UV light is
used as the radiation type, since the adhesive is cured through the
film, although there are commercial processes based on UV cationic
type chemistry where the adhesive is initiated just before the film
is laminated.
[0126] For example, the adhesive systems are formed or derived from
radiation-curable (i.e., radiation-polymerizable) components. Such
systems have the ability to change from a fluid phase to a highly
cross-linked or polymerized solid phase by means of a chemical
reaction initiated by a radiation energy source, such as
ultra-violet ("UV") light or electron beam ("EB") or other ionizing
radiation. Thus, the reactants of the radiation-curable adhesive
systems are "cured" by forming new chemical bonds under the
influence of radiation.
[0127] Radiation-curable adhesive systems or formulations that are
cured by a free radical mechanism typically include: i) monomers
(e.g., low-viscosity monomers or reactive "diluents") capable of
polymerization by free radical mechanism, ii) oligomers/prepolymers
(e.g., acrylates) capable of polymerization by free radical
mechanism, and optionally iii) other additives, such as
non-reactive plasticizing diluents. Radiation-curable adhesive
systems that are cured by UV light also include one or more
photoinitiators. Radiation-curable radical adhesive systems curable
by electron beam (EB) radiation do not require a photoinitiator,
and may therefore be free of photoinitiator. Together, these
monomers and oligomers/prepolymers may be grouped as
"reactants."
[0128] Reactive (meth)acrylate diluents include, but are not
limited to, trimethylolpropane triacrylate, hexanediol diacrylate,
1,3-butylene glycol diacrylate, diethylene glycol diacrylate,
1,6-hexanediol diacrylate, neopentyl glycol diacrylate,
polyethylene glycol 200 diacrylate, tetraethylene glycol
diacrylate, triethylene glycol diacrylate, pentaerythritol
tetraacrylate, tripropylene glycol diacrylate, ethoxylated
bisphenol-A diacrylate, propylene glycol mono/dimethacrylate,
trimethylolpropane diacrylate, di-trimethylolpropane tetraacrylate,
triacrylate of tris(hydroxyethyl) isocyanurate, dipentaerythritol
hydroxypentaacrylate, pentaerythritol triacrylate, ethoxylated
trimethylolpropane triacrylate, triethylene glycol dimethacrylate,
ethylene glycol dimethacrylate, tetraethylene glycol
dimethacrylate, polyethylene glycol-200 dimethacrylate,
1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate,
polyethylene glycol-600 dimethacrylate, 1,3-butylene glycol
dimethacrylate, ethoxylated bisphenol-A dimethacrylate,
trimethylolpropane trimethacrylate, diethylene glycol
dimethacrylate, 1,4-butanediol diacrylate, diethylene glycol
dimethacrylate, pentaerythritol tetramethacrylate, glycerin
dimethacrylate, trimethylolpropane dimethacrylate, pentaerythritol
trimethacrylate, pentaerythritol dimethacrylate, pentaerythritol
diacrylate, aminoplast (meth)acrylates, and acrylated oils such as
linseed, soya, and castor oils. Other polymerizable compounds that
can be used include (meth)acrylamides, maleimides, vinyl acetate,
vinyl caprolactam, polythiols, vinyl ethers and the like.
Monoacrylates such as cyclohexyl acrylate, isobornyl acrylate,
lauryl acrylate and tetrahydrofurfuryl acrylate and the
corresponding methacrylates are also operable as reactive diluents
as well as (meth)acrylate oligomers such as epoxy acrylates,
urethane acrylates, and polyester or polyether acrylates.
[0129] Useful oligomers/prepolymers include resins having acrylate
functionality, such as epoxy acrylates, polyurethane acrylates, and
polyester acrylates. Exemplary oligomers and prepolymers include
(meth)acrylated epoxies, (meth)acrylated polyesters,
(meth)acrylated urethanes/polyurethanes, (meth)acrylated
polyethers, (meth)acrylated polybutadiene, aromatic acid
(meth)acrylates, and (meth)acrylated acrylic oligomers and the
like.
[0130] If the radiation-curable adhesive are cured by free radical
mechanism and formulated for curing by exposure to UV-light, then
the adhesive includes one or more photoinitiators. Photoinitiators
for free radical curing are well known to those skilled in the art.
Specific examples include, but are not limited to, the benzoin
alkyl ethers, such as benzoin methyl ether, benzoin ethyl ether,
benzoin isopropyl ether and benzoin isobutyl ether. Another class
of photoinitiators are the dialkoxyacetophenones exemplified by
2,2-dimethoxy-2-phenylacetophenone, i.e., IRGACURE.RTM.651
(Ciba-Geigy) and 2,2-diethoxy-2-phenylacetophenone- . Still another
class of photoinitiators are the aldehyde and ketone carbonyl
compounds having at least one aromatic nucleus attached directly to
the carboxyl group. These photoinitiators include, but are not
limited to benzophenone, acetophenone, o-methoxybenzophenone,
acetonaphthalenequinone, methyl ethyl ketone, valerophenone,
hexanophenone, alpha-phenyl-butyrophenone,
p-morpholinopropiophenone, dibenzosuberone,
4-morpholinobenzophenone, 4'-morpholinodeoxybenzoin,
p-diacetylbenzene, 4-aminobenzophenone, 4'-methoxyacetophenone,
benzaldehyde, alpha-tetralone, 9-acetylphenanthrene,
2-acetylphenanthrene, 10-thioxanthenone, 3-acetylphenanthrene,
3-acetylindone, 9-fluorenone, 1-indanone, 1,3,5-triacetylbenzene,
thioxanthen-9-one, xanthene-9-one, 7-H-benz[de]-anthracen-7-one,
1-naphthaldehyde, 4,4'-bis(dimethylamino)-benzophenone,
fluorene-9-one, 1'-acetonaphthone, 2'-acetonaphthone,
2,3-butedione, acetonaphthene, benz[a]anthracene 7.12 diene, etc.
Phosphines such as triphenylphosphine and tri-o-tolylphosphine are
also operable herein as photoinitiators. The photoinitiators or
mixtures thereof are usually added in an amount ranging from 0.01
to 5% by weight of the total composition.
[0131] Radiation-curable adhesive systems or formulations that are
UV cured by cationic mechanism typically include: i) monomers,
oliogomers and/or polymers that are capable of cationic
polymerization such as but not limited to aliphatic and/or
cycloaliphatic epoxides and/or vinyl ethers, many of which are
known to one skilled in the art, ii) one or more cationic
photoinitiators that are known to one skilled in the art as onium
salts, and optionally iii) polyols (organic compounds that contain
hydroxyl functionality that are capable of adding to protonated
epoxide) and other additives, such as non-reactive plasticizing
diluents. There are many epoxides and vinyl ethers that are
suitable. but cycloaliphatic epoxides (containing at least one
epoxide group) are preferred. Examples include but are not limited
to epoxides sold under the CYRACURE.RTM. (Dow Chemical) or
UVACURE.TM. (UCB Chemical) trade names. The cycloaliphatic epoxides
with cationic photoinitiator(s) may be used alone or in combination
with polyols at varying concentrations. Examples of polyols include
polycaprolactone type polyols but other polyols may be used.
[0132] UV cationic onium type photoinitiators useful for UV curable
cationic adhesives are well known by one skilled in the art. U.S.
Pat. Nos. 4,407,759 and 4,417,061, both incorporated herein by
reference in their entirety, are useful for describing onium type
photoinitiators of which there are many types commercially
available. Examples of commercially available onium type
photoinitiators include but are not limited to SarCAT.RTM. CD-1012
and KI-85.TM. from Sartomer.
[0133] Another type of UV adhesive that has found utility are, but
are not limited to, mixtures of free radical UV adhesives and
cationic UV adhesives. They are sometimes called hybrid systems
because they have components that have been previously described as
useful in free radical UV adhesives, and components that have been
previously described as useful in cationic UV adhesives. These
hybrid adhesives cure by free radical and cationic mechanisms when
exposed to light useful for inducing polymerization. Some onium
salt cationic photoinitiators such as iodonium compounds can be
optionally used in combination with free radical type
photoinitiators such as 2-isopropyl thioxanthone to improve the UV
light cationic initiation. An example of this type of mixed UV
cationic photoinitiator system include but not limited to UV 9380
(GE Silicones).
[0134] Although the radiation cured adhesive layer of the various
embodiments is typically shown as extending the full width or
length of a given article, alternatively the radiation curable
adhesive can be applied along a selected region of the article, in
a continuous or discontinuous manner or pattern as desired, in
either the longitudinal direction or with respect to the article
width.
[0135] Other radiation curable adhesives that cure by a free
radical mechanism can be used in connection with the present
invention, of which an example is listed in Table 3, but are not
preferred.
2TABLE 3 Material Material Name Supplier type/function parts TMP-TA
.TM. UCB Chemicals free radical 46.4 Corp crosslinker RICON .TM.
3801 Sartomer acrylated polybutadiene 46.2 crosslinker ODAB .TM.
First Chemical Liquid amine synergist 1.8 Corp. IRGACURE .RTM. 819
Ciba Phosphine oxide 0.4 type free-radical photoinitiator LTX .TM.
First Chemical liquid thioxanthone 0.92 Corp. type free-radical
photoinitiator BD-1 .TM. First Chemical Blend of free-radical 2.78
Corp. photoinitiator
[0136] The ratios and amounts of the components used in E and F can
be varied by one skilled in the art.
[0137] Other cationic photoinitiators can be used as the "E" UV
adhesive (e.g. CD1012).
[0138] Other free radical photoinitiators can be used as the "F"
adhesive.
[0139] The adhesives can be storage stable when properly
stored.
[0140] The adhesives can have viscosities that allow rapid and easy
application at room temperature.
[0141] An electron beam (EB) is one useful form of radiation,
although UV-light radiation can also be used. The radiation source
for an EB system is known as an EB generator.
[0142] Two factors are important in considering the application of
EB radiation: the dose delivered and the beam penetration. The dose
is measured in terms of quantity of energy absorbed per unit mass
of irradiated material; units of measure in general use are the
megarad (Mrad) and kiloGray (kGy). The depth of penetration by an
electron beam is directly proportional to the energy of the
accelerated electrons impinging on the exposed material (expressed
as kiloelectron volts, keV).
[0143] Regardless of the radiation source, the radiation dose will
be sufficient and effective to cure the radiation curable
adhesive.
[0144] Useful radiation dosages can range from e.g. 0.2 to 10
Mrads. Useful energies for the EB can range from 30 to 250 keV.
[0145] Useful EB generation units include those commercially
available from American International Technologies sold under the
trademark MINI-EB.TM. (these units have tube operating voltages
from about 30 to 70 keV) and from Energy Sciences, Inc. sold under
the trademark EZ CURE.TM. (these units have operating voltages from
about 70 to about 110 keV). EB generation units typically require
adequate shielding, vacuum, and inert gassing, as is known in the
art. If the processing techniques employed allow for the use of a
low oxygen environment, the coating and irradiation steps
beneficially occur in such an atmosphere. A standard nitrogen flush
can be used to achieve such an atmosphere.
Radiation Curable Adhesive Thickness
[0146] The radiation curable adhesive is applied in a thickness
that once cured is effective to provide the desired bond strength.
Useful average thicknesses of radiation curable adhesive include,
without limitation, from 0.1 to 12 micrometers. An adhesive
thickness of more than 12 micrometers, at least in parts of the
bond in certain applications, such as the bond around a self
sealing valve (see FIG. 20 to 25) may be beneficial depending on
the total thickness of the valve. In the case of an intermittent,
discontinuous adhesive layer, the average thickness of 0.1 to 12
micrometers is directed to the regions or portions that actually
contain the adhesive. Other average thicknesses that may be useful
depending upon the particular application include from 0.5 to 10
micrometers, such as 1 to 8, 2 to 7 and 3 to 6 micrometers.
[0147] The radiation cured adhesive, once it forms a bonding layer
or region within an article, should be able to withstand normal
packing, distribution, and handling.
[0148] The radiation curable adhesive can be used as a bonding
medium for many different package formats that traditionally rely
on heat sealing or other sealing mechanisms. Examples include VFFS
packages, HFFS packages, lidded trays or cups, pouches, bags, or
other like packages.
[0149] Useful package configurations for use in connection with the
present invention include end-seal bag, a side-seal bag, an L-seal
bag (e.g., sealed across the bottom and along one side with an open
top), or a pouch (e.g., sealed on three sides with an open top).
Such bag configurations are known to those of skill in the art.
See, for example, U.S. Pat. No. 5,846,620 issued Dec. 8, 1998 to
Compton, which is incorporated herein in its entirety by reference.
Additionally, lap seals may be employed, in which the inside region
of the film is bonded to an outside region of the film. In each of
these formats and those disclosed herein, any or all of the seals
traditionally formed by heat or alternative sealing technologies
can be replaced by a radiation cured adhesive bond. Those skilled
in the art will also appreciate that the present invention can be
used in conjunction with traditional heat sealing or other sealing
methods. Thus, e.g. a bag, thermoformed container, film/foam
composite; or inflatable packaging cushion, could have one or more
radiation cured adhesive bonds, as well as one or more heat
seals.
[0150] Suitable food products for packaging by the present method
include fatty foods (e.g., meat products, cheese products), aqueous
foods (e.g., produce and some soups), and dry food (e.g., cereal,
pasta). Examples of meat products that may be packaged include,
poultry (e.g., turkey or chicken breast), bologna, braunschweiger,
beef, pork, lamb, fish, and whole muscle products such as roast
beef, and other red meat products. Examples of produce or
vegetables that may be packaged include cut and uncut lettuce,
carrots, radish, and celery. The food product may be solid, solid
particles, dry, fluid, or a combination thereof.
[0151] A film can also be wrapped around a product and bonded
together as described herein to form a package enclosing the
product. If the film is a heat-shrinkable film, the resulting bag
or other container can be heated to shrink the film around the
product.
[0152] The above descriptions are those of various embodiments and
examples of the invention. Various alterations and changes can be
made without departing from the spirit and broader aspects of the
invention as defined in the claims.
[0153] Any reference to an item in the disclosure or to an element
in the claim in the singular using the articles "a,", "an," "the,"
or "said" is not to be construed as limiting the item or element to
the singular unless expressly so stated.
[0154] Any numerical values recited herein include all values from
the lower value to the upper value in increments of one unit
provided that there is a separation of at least 2 units between any
lower value and any higher value. As an example, if it is stated
that the amount of a component, or a value of a process variable
and the like is, for example, from 1 to 90, such as 20 to 80, such
as 30 to 70, it is intended that values such as 15 to 85, 22 to 68,
43 to 51, 30 to 32 and the like, are expressly enumerated in this
specification. For values which are less than one, one unit is
considered to be 0.0001, 0.001, 0.01 or 0.1 as appropriate. These
are only examples of what is specifically intended and all possible
combinations of numerical values between the lowest value and the
highest value enumerated are to be considered to be expressly
stated in this application in a similar manner.
* * * * *