U.S. patent application number 10/748403 was filed with the patent office on 2005-06-30 for plastic packaging for produce products.
Invention is credited to Hatley, Earl L..
Application Number | 20050142310 10/748403 |
Document ID | / |
Family ID | 34700889 |
Filed Date | 2005-06-30 |
United States Patent
Application |
20050142310 |
Kind Code |
A1 |
Hatley, Earl L. |
June 30, 2005 |
Plastic packaging for produce products
Abstract
A packaged produce product formed from at least one polyamide
film. The polyamide film is a coextruded film of at least one layer
of nylon 6 and at least one layer of nylon 6,66. The film is heat
sealed to form a package via the nylon 6,66 layer and produce is
contained within the package. A single polyamide film may be used
and the film is heat sealed to itself. Alternatively, two
overlapped polyamide films are used and the nylon 6,66 layers of
both films are heat sealed together. The package exhibits increased
heat seal strength and improved transmission of gases to provide a
desirable modified atmosphere in the package.
Inventors: |
Hatley, Earl L.; (Randolph,
NJ) |
Correspondence
Address: |
HONEYWELL INTERNATIONAL INC.
101 COLUMBIA ROAD
P O BOX 2245
MORRISTOWN
NJ
07962-2245
US
|
Family ID: |
34700889 |
Appl. No.: |
10/748403 |
Filed: |
December 30, 2003 |
Current U.S.
Class: |
428/35.2 ;
428/35.7 |
Current CPC
Class: |
B32B 38/04 20130101;
B32B 2439/70 20130101; Y10T 428/1334 20150115; B32B 27/34 20130101;
B32B 27/08 20130101; B32B 2307/31 20130101; Y10T 428/1352 20150115;
B32B 27/18 20130101; B32B 2307/724 20130101; B32B 37/153
20130101 |
Class at
Publication: |
428/035.2 ;
428/035.7 |
International
Class: |
B65D 001/00 |
Claims
What is claimed is:
1. A packaged produce product comprising a package formed from at
least one coextruded polyamide film comprising at least one first
layer formed from a polyamide selected from the group consisting of
nylon 6, nylon 66 and blends thereof, and at least one second layer
of nylon 6,66 in contact with said first layer, and produce
contained within said package, said package being formed from at
least one polyamide film being heat sealed via said nylon 6,66
layer.
2. The product of claim 1, wherein said first layer comprises nylon
6.
3. The product of claim 2, wherein said nylon 6 moiety is present
in said nylon 6,66 layer in an amount from about 10 to about 95
weight percent.
4. The product of claim 2, wherein said nylon 6 moiety is present
in said nylon 6,66 layer in an amount from about 55 to about 95
weight percent.
5. The product of claim 2, wherein said nylon 6 moiety is present
in said nylon 6,66 layer in an amount from about 70 to about 90
weight percent.
6. The product of claim 2, wherein the thickness of said polyamide
film ranges from about 1 to about 50 .mu.m.
7. The product of claim 2, wherein the thickness of said polyamide
film ranges from about 5 to about 40 .mu.m.
8. The product of claim 2, wherein the thickness of said polyamide
film ranges from about 10 to about 30 .mu.m.
9. The product of claim 2, wherein said polyamide film is
perforated.
10. The product of claim 2, wherein the heat seal strength of said
polyamide film is at least about 700 grams.
11. The product of claim 1, wherein said package is formed from a
single polyamide film which is heat sealed to itself via said nylon
6,66 layer.
12. The product of claim 1, wherein said package is formed from two
polyamide films which are overlapped, with said nylon 6,66 layer of
both polyamide films being heat sealed together.
13. A packaged produce product comprising a package formed from at
least one coextruded polyamide film comprising at least one layer
of nylon 6, and at least one layer of nylon 6,66 in contact with
said nylon 6 layer, and produce contained within said package, said
package being formed from at least one polyamide film being heat
sealed via said nylon 6,66 layer.
14. The product of claim 13, wherein said nylon 6 moiety is present
in said nylon 6,66 layer in an amount from about 55 to about 95
weight percent.
15. The product of claim 13, wherein said nylon 6 moiety is present
in said nylon 6,66 layer in an amount from about 70 to about 90
weight percent.
16. The product of claim 13, wherein the thickness of said
polyamide film ranges from about 1 to about 50 .mu.m.
17. The product of claim 13, wherein the thickness of said
polyamide film ranges from about 10 to about 30 .mu.m.
18. The product of claim 13, wherein said polyamide film is
perforated.
19. The product of claim 13, wherein the heat seal strength of said
polyamide film is at least about 700 grams.
20. The product of claim 13, wherein said package is formed from a
single polyamide film which is heat sealed to itself via said nylon
6,66 layer.
22. The product of claim 13, wherein said package is formed from
two polyamide films which are overlapped, with said nylon 6,66
layer of both polyamide films being heat sealed together.
23. The product of claim 13, wherein said package comprises a
bag.
24. The product of claim 13, wherein said package comprises a
pouch.
Description
BACKROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to packaged produce products which
are packaged in polyamide films, especially for fruits and
vegetables.
[0003] 2. Description of the Prior Art
[0004] Packaging of fruits and vegetables using plastic packaging
films is well-known in the art. Fresh vegetable and fruit produce
are often packaged at the grower level for shipment to end users.
Such produce needs a moisture permeable packaging material to
permit moisture condensation to escape the sealed package for
extended shelf life, enhanced product maturity, enhanced
appearance, reduced spoilage, as well as increased harvest yield
and to permit better in-transit shipment packaging in cubes. The
produce is sold for food service or institutional uses, as well as
for retail sale and consumer use.
[0005] It has been suggested to perforate the films, such as by
mechanical or laser perforation, in order to permit gases that are
generated by the produce to escape at various rates. This aids in
produce maturity, appearance and extended shelf life. Among the
gases generated by produce in a packaging environment are ethylene,
carbon dioxide and oxygen. As a result, the atmosphere surrounding
the produce in the package is what is referred to as a "modified"
atmosphere.
[0006] U.S. Pat. No. 6,190,710 to Nir et al. discloses a method of
preserving produce by using a polyamide packaging film that has a
certain level of permeability to water vapor, which allows the
packaged produce product to be contained in a specified gaseous
atmosphere. The polyamide film is perforated to a desired extent
such that no or minimal condensation appears on the surface of the
packaging material.
[0007] The Nir et al. patent discloses the use of monolayer
polyamide films for this application, in particular nylon 6, nylon
66, nylon 6,66, nylon 6/12 and blends of the foregoing as well as
blends with other polyamides (e.g., nylon 11, 12 or 6I/6T) or with
other polymers and copolymers. However, the films utilized by Nir
et al. do not have robust strength when they are heat sealed.
Accordingly, it would be desirable to provide a produce package
which is formed from a polyamide film but which has stronger heat
seals such that the package does not split open either in handling
or transit.
[0008] In addition, growers and packagers of fresh fruit and
vegetable produce commonly package with films of polyolefins only,
or blends of polyamides only, or blends of polyolefins and
polyamides, but such films do not adequately permeate enough water
vapor out of the package. This results in interior water
condensation which deteriorates and spoils the produce. It would
also be desirable to provide a produce package formed from
polyamide film which has excellent water vapor permeability, as
well as other desirable gas permeation properties.
SUMMARY OF THE INVENTION
[0009] In accordance with this invention, there is provided a
packaged produce product which comprises a package formed from at
least one coextruded polyamide film comprising at least one first
layer formed from a polyamide selected from the group consisting of
nylon 6, nylon 66 and blends thereof, and at least one second layer
of nylon 6,66 in contact with the first layer, and produce
contained within the package, the film being heat sealed via the
nylon 6,66 layer.
[0010] Also in accordance with this invention, there is provided a
packaged produce product comprising a package formed from at least
one coextruded polyamide film comprising at least one layer of
nylon 6, and at least one layer of nylon 6,66 in contact with the
nylon 6 layer, and produce contained within the package, the
package being formed from at least one polyamide film being heat
sealed via the nylon 6,66 layer.
[0011] The package of this invention exhibits increased heat seal
strength and improved transmission of gases to provide a desirable
modified atmosphere in the package. It has been unexpectedly found
that packages formed from the foregoing coextruded layers exhibit
enhanced moisture permeation. This enables shipment to the consumer
in significantly enhanced product wholesomeness. In addition, using
the coextruded film of this invention results in a package that has
desirable packaging properties and higher heat seal strength than
packages of similar thickness which are formed from a single layer
of nylon 6, for example.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0012] As mentioned above, the use of nylon films in produce
packaging applications is generally disclosed, for example, in U.S.
Pat. No. 6,190,710 to Nir et al., the disclosure of which is
expressly incorporated herein by reference.
[0013] Other examples of plastic packages for fruits and
vegetables, some of which use perforated films, are U.S. Pat. Nos.
4,886,372; 5,492,705; 5,832,699; 6,296,923 and 6,441,340.
[0014] The polyamides useful in the coextruded product of this
invention are film-forming polyamides. Monolayer structures of
nylon 6 film are available from Honeywell International Inc., for
example, under the trademark Capran. Nylon 6 polymers are available
from a number of suppliers, including Honeywell and BASF. Nylon 66
polymers are also available from a number of suppliers, such as Du
Pont.
[0015] Nylon 6,66 is a copolymer containing caprolactam (nylon 6
monomer) moieties and hexamethylene diamine (nylon 66 precursor)
moieties. The weight ratio of the nylon 6 moiety to the nylon 6,6
moiety in the copolymer may be any desired amount. Preferably, the
weight percent of nylon 6 moiety in the nylon 6,66 copolymer ranges
from about 10 to about 95%, more preferably from about 55 to about
95% and most preferably from about 70 to about 90%. Nylon 6,66
copolymer is available from a nunber of suppliers, including
Honeywell, BASF and Du Pont.
[0016] General procedures for production of the nylons useful in
this invention are well known to the art. The polyamides useful
typically have molecular weights in the range of from about 10,000
to about 100,000.
[0017] The coextruded film useful in this invention can be provided
by any typical coextrusion process. In a typical coextrusion
process, the polymeric materials for the individual layers are fed
into infeed hoppers of a like number of extruders, each extruder
handling the material for one or more of the layers. The melted and
plasticated streams from the individual extruders are fed into a
single manifold co-extrusion die. While in the die, the layers are
juxtaposed and combined, then emerge from the die as a single
multiple layer film of polymeric material. After exiting the die,
the film is cast onto a first controlled temperature casting roll,
passes around the first roll, and then onto a second controlled
temperature roll, which is normally cooler than the first roll. The
controlled temperature rolls largely control the rate of cooling of
the film after it exits the die. Additional rolls may be employed.
In another method, the film-forming apparatus may be one which is
referred to in the art as a blown film apparatus and includes a
multi-manifold circular die head for bubble blown film through
which the plasticized film composition is forced and formed into a
film bubble which may ultimately be collapsed and formed into a
film. Processes of coextrusion to form film and sheet laminates are
generally known in the art. Typical coextrusion techniques are
described, for example, in U.S. Pat. Nos. 5,139,878 and
4,677,017.
[0018] The coextruded film used in this invention may or may not be
oriented. Such orientation includes monoaxial orientation and
biaxial orientation. For purposes of this invention, the terms
"orienting" and "stretching" shall be used interchangeably. The
coextruded may be stretched or oriented in any desired direction
using methods known to those skilled in the art. In such a
stretching operation, the film may be stretched uniaxially in
either the direction coincident with the direction of movement of
the film being withdrawn from the casting roll, also referred to in
the art as the "machine direction", or in as direction which is
perpendicular to the machine direction, and referred to in the art
as the "transverse direction", or biaxially in both the machine
direction and the transverse direction. The coextruded film may be
oriented by the so-called double bubble process.
[0019] As used herein, the term "draw ratio" is an indication of
the increase in the dimension in the direction of draw. Preferred
draw ratios are from about 1.5:1 to 5:1 in at least one direction
and more preferably from about 2:1 to about 3:1 in at least one
direction.
[0020] As mentioned above, the first layer of the film of this
invention is formed from nylon 6, nylon 66 or blends thereof. Nylon
6 is the preferred polymer of the first polyamide layer.
[0021] The coextruded films used in this invention may have any
desirable thickness. Typically, the combined thickness of the
coextruded films ranges from about 1 to about 50 .mu.m, more
preferably from about 5 to about 40 .mu.m and most preferably from
about 10 to about 30 .mu.m. The thicknesses of each individual
layer of the coextruded film may or may not be the same. While the
foregoing thicknesses are referenced, it is to be understood that
other layer thicknesses may be produced to satisfy a particular
need and yet fall within the scope of the present invention. If the
coextruded film is oriented, the thickness of the film before
stretching is selected such that the desired thickness after
stretching is achieved, based on the stretch ratio employed, as is
known in the art.
[0022] The films useful in this invention may include more than one
additional layers. For example, a three layer coextruded film
formed from nylon 6/nylon 6/nylon 6,66 may be employed. However, it
is preferred that the film be formed from a single nylon 6 layer
and a single nylon 6,66 layer.
[0023] Any of the layers of the coextruded film may incorporate
conventional additives. Such additives include, without limitation,
oxidative stabilizers, heat stabilizers, antiblock additives,
lubricants, release agents, oxidation inhibitors, oxygen
scavengers, dyes, pigments other coloring agents, ultraviolet light
absorbers and stabilizers, fillers (organic or inorganic),
nucleating agents, plasticizers, flame retardant agents and other
conventional additives known in the art. Such additives may be
utilized in conventional amounts, typically no more than about 10%
by weight of the individual film layer.
[0024] To enhance the performance of the film in the package, the
film is preferably provided with perforations, such as
microperforations. These perforations may be made by mechanical
means or by a laser. The perforations permit the tailoring of the
modified atmosphere in the package to the particular fruit or
vegetable in the package, as well as its ripeness, etc.
[0025] The coextruded films may be formed into any suitable package
which contains the produce. For example, a bag may be made from a
single coextruded film which is folded on itself with the nylon
6,66 layer facing inwardly and in which has the sides are heat
sealed together along their perimeter. Once the produce is placed
in the bag (for example, by the grower), the top of the bag may be
heat sealed to itself or merely folded over, depending on the
modified atmosphere desired in the package. The top of the bag may
be twisted together instead. Alternatively, two coextruded films
may be overlapped, with the nylon 6,66 layers facing inwardly, and
the side and bottom edges heat sealed together along their
perimeter to form a bag. The produce is then placed into the bag
and the top heat sealed or not as explained above. In addition to
bags, the packages of this invention may be in the form of pouches,
overwraps, etc. For heat sealing, any conventional device may be
utilized, such as a hot bar, hot wire or thermal impulse.
[0026] The coextruded film package of this invention can contain
any desired fruit or vegetable. Non-limiting examples include
melons, peppers, mangoes, bananas, grapes, strawberries, lettuce,
eggplant, bean sprouts, mushrooms, green beans, cucumbers, carrots,
tomatoes, broccoli, corn, flowers, etc.
[0027] For example, it has been found that a coextruded film of
nylon 6 and nylon 6,66 when employed with a combined thickness of
about 15 to about 25 microns (3.8 to about 6.3 mils) provides a
film structure that permeates from about 8 to about 20 percent more
moisture than polyamide films of similar thickness formed from
monolayer of nylon 6 only, nylon 6,12 only and blends of polyamides
and polyolefins. The heat seal strength between the nylon 6,66
layers of the structure is preferably between at least about 700
grams, more preferably about 1000 to about 1700 grams, for example,
which is stronger than the seal between two nylon 6 layers of
similar thickness.
EXAMPLES
[0028] The following non-limiting examples serve to illustrate the
invention.
Example 1
[0029] A two layer unoriented film is formed by coextruding a nylon
6 layer and nylon 6,66 layer. The melt temperature during extrusion
is between 465 to 544.degree. F. (241 to 284.degree. C.) for the
nylon 6 layer and between 465 to 480.degree. F. (241 to 249.degree.
C.) for the nylon 6,66 layer. The polymers are extruded as a cast
film by a typical cast film extrusion process, with a combined
thickness of 75 mils (19.mu.m).
[0030] The film is tested for its water vapor transmission rate
(WVTR) and its oxygen and carbon dioxide transmission rates, and
such rates are compared with those of a single layer of cast nylon
6 film and a single layer of monoaxially oriented cast nylon 6
film. The results are shown in Table 1.
1TABLE 1 O.sub.2 Trans. Rate O.sub.2 Trans. Rate CO.sub.2 Trans.
Rate WVTR (23 C., 65% RH) (23 C., 90% RH) (23 C., 0% RH) (38 C.,
100% RH) Film (cc/m.sup.2day) (cc/m.sup.2day) (cc/m.sup.2day)
(g-mils)* N 6/6,66 coex 63.23 96.70 439 41 N 6 monolayer 40.36
63.30 319 33-37 N 6 oriented 40.35 49.78 342 -- *normalized to 1
mil
Example 2
[0031] The film of Example 1 is sealed to itself with a pressure of
40 psi (0.28 Mpa) and a 1 second dwell time, at three different
temperatures, with the nylon 6,66 layers being heat sealed
together. As a comparison, a monolayer of nylon 6 is similarly
tested. The results are shown in Table 2.
2 TABLE 2 Seal Strength Seal Strength Seal Strength Film at 400 F.
(g) at 425 F. (g) at 450 F. (g) 6/6,66 coex 732 1650 1453 6
monolayer no seal 450 650
[0032] The coextruded film is formed into a bag by folding over the
film with the nylon 6,66 layer facing inward and heat sealing the
two side edges together. Melons are packaged in the bag.
[0033] As can be seen, coextruded nylon 6/nylon 6,66 films have
higher oxygen, carbon dioxide and water vapor transmission rates
than films of nylon 6 monolayer and monoaxially oriented nylon 6
monolayer. In addition, the heat seal strength of the nylon 6/nylon
6,66 coextruded film is significantly greater than that of
monolayer nylon 6 films. In addition, packages formed from the film
have enhanced moisture permeation which enables shipment to the
consumer of produce with enhanced product wholesomeness. By using
the nylon 6,66 layer to be heat sealed to itself (or to another
nylon 6,66 layer of another coextruded film), lower seal
temperatures can be employed, with stronger seals and a wider
sealing window, in addition to increased permeation of moisture and
gas.
[0034] Having thus described the invention in rather full detail,
it will be understood that such detail need not be strictly adhered
to but that further changes and modifications may suggest
themselves to one skilled in the art, all falling within the scope
of the invention as defined by the subjoined claims.
* * * * *