U.S. patent application number 10/186863 was filed with the patent office on 2002-12-19 for lidding film for modified atmosphere packaging.
This patent application is currently assigned to Honeywell International Inc.. Invention is credited to Gibboni, David J., Hatley, Earl L., Slotkin, Alan, Ting, Robert R..
Application Number | 20020192446 10/186863 |
Document ID | / |
Family ID | 24304552 |
Filed Date | 2002-12-19 |
United States Patent
Application |
20020192446 |
Kind Code |
A1 |
Hatley, Earl L. ; et
al. |
December 19, 2002 |
Lidding film for modified atmosphere packaging
Abstract
The invention provides improved packaging films, which are
shrinkable, high gas barrier films containing an antifog
composition for modified atmosphere packaging of foods and the
like. The films are useful for producing a modified atmosphere
package useful for the preservation and shelf life extension of
food and non-food oxygen sensitive items.
Inventors: |
Hatley, Earl L.; (Randolph,
NJ) ; Ting, Robert R.; (Plainsboro, NJ) ;
Slotkin, Alan; (Wincote, PA) ; Gibboni, David J.;
(Havertown, PA) |
Correspondence
Address: |
HONEYWELL INTERNATIONAL INC.
101 COLUMBIA ROAD
P O BOX 2245
MORRISTOWN
NJ
07962-2245
US
|
Assignee: |
Honeywell International
Inc.
|
Family ID: |
24304552 |
Appl. No.: |
10/186863 |
Filed: |
July 1, 2002 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10186863 |
Jul 1, 2002 |
|
|
|
09576470 |
May 23, 2000 |
|
|
|
6447892 |
|
|
|
|
Current U.S.
Class: |
428/212 ;
428/195.1; 428/500 |
Current CPC
Class: |
B32B 27/32 20130101;
B32B 27/34 20130101; Y10T 428/31913 20150401; Y10T 428/24942
20150115; B32B 27/30 20130101; Y10T 428/24992 20150115; Y10T
428/24802 20150115; Y10T 428/31855 20150401; Y10T 428/1352
20150115 |
Class at
Publication: |
428/212 ;
428/195; 428/500 |
International
Class: |
B32B 007/02 |
Claims
What is claimed is:
1. A multilayered film which comprises a nylon film attached to a
surface of an ethylene vinyl alcohol film and another nylon film
attached to another surface of the ethylene vinyl alcohol film to
form a composite; a surface of a polyolefin film attached to one of
the nylon films via an intermediate adhesive, and an antifog
composition on another surface of the polyolefin film or
incorporated into the polyolefin film.
2. The multilayered film of claim 1 wherein the composite is
biaxially oriented.
3. The multilayered film of claim 1 wherein the composite is
biaxially oriented from about 1.5 to about 5 times in either or
each of its longitudinal and transverse directions.
4. The multilayered film of claim 1 which is heat shrinkable.
5. The multilayered film of claim 1 which has a length and a width
and which is shrinkable by an amount of from about 2% to about 30%
in its length, or its width or each of its length and width.
6. The multilayered film of claim 1 wherein the nylon films are
attached to the ethylene vinyl alcohol film by coextrusion and the
polyolefin film is attached to one of the nylon films by
lamination.
7. The multilayered film of claim 1 wherein the nylon film
comprises nylon 6, nylon 66, nylon 6/6,6 or combinations
thereof.
8. The multilayered film of claim 1 wherein the nylon film
comprises nylon 6.
9. The multilayered film of claim 1 wherein the ethylene vinyl
alcohol film comprises an ethylene vinyl alcohol polymer having a
degree of hydrolysis of from about 85 to about 99.5 percent and
from about 15 to about 65 mol percent ethylene.
10. The multilayered film of claim 1 wherein each nylon layer has a
thickness of from about 1 .mu.m to about 10 .mu.m; wherein the
ethylene vinyl alcohol film layer has a thickness of from about 1
.mu.m to about 10 .mu.m; and wherein the polyolefin film has a
thickness of from about 3 .mu.m to about 50 .mu.m.
11. The multilayered film of claim 1 wherein the adhesive comprises
a material selected from the group consisting of a polyurethane, an
epoxy, a polyester, an acrylic, an anhydride modified polyolefin
and blends thereof.
12. The multilayered film of claim 1 wherein the adhesive comprises
a colorant, an ultraviolet light absorber or both.
13. The multilayered film of claim 1 wherein the antifog
composition comprises one or more materials selected from the group
consisting of glycerol monoesters of a saturated or unsaturated
fatty acid having from about 8 to about 20 carbon atoms, glycerol
diesters of a saturated or unsaturated fatty acid having from about
8 to about 20 carbon atoms; and ionic surfactants having phosphate,
sulfate or quaternary amine functional end groups.
14. The multilayered film of claim 1 wherein the antifog
composition comprises one or more materials selected from the group
consisting of anionic, cationic, nonionic and amphoteric
surfactants.
15. The multilayered film of claim 1 wherein the antifog
composition comprises glycerol monooleate, glycerol monostearate or
a blend thereof.
16. The multilayered film of claim 1 wherein the antifog
composition is coated on the polyolefin film at a coating weight of
from about 0.2 to about 0.6 g/m.sup.2.
17. The multilayered film of claim 1 wherein the antifog
composition is incorporated into the polyolefin film.
18. The multilayered film of claim 1 wherein the polyolefin film
comprises a homopolymer or copolymer containing a low density
polyethylene, linear low density polyethylene, metallocene
polyethylene or polypropylene.
19. The multilayered film of claim 1 further comprising printed
indicia between the polyolefin film and its attached nylon
film.
20. The multilayered film of claim 1 which has an oxygen
transmission rate of about 0.1 cc/100 in.sup.2/day or less.
21. A process for producing a multilayered film which comprises
coextruding a nylon film to a surface of an ethylene vinyl alcohol
film and another nylon film to another surface of the ethylene
vinyl alcohol film to form a composite; biaxially orienting the
composite; laminating or coextruding a surface of a polyolefin film
to one of the nylon films via an intermediate adhesive; and either
applying an antifog composition onto another surface of the
polyolefin film or incorporating an antifog composition into the
polyolefin film.
22. The process of claim 21 wherein the antifog composition is
applied onto the polyolefin film.
23. The process of claim 21 wherein the antifog composition is
incorporated onto the polyolefin film.
24. The process of claim 21 wherein the composite is biaxially
oriented from about 1.5 to about 5 times in each of the
longitudinal and transverse directions.
25. The process of claim 21 wherein the nylon films are attached to
the ethylene vinyl alcohol film by coextrusion and the polyolefin
film is attached to one of the nylon films by lamination.
26. The process of claim 21 wherein the nylon film comprises nylon
6.
27. The process of claim 21 wherein the adhesive comprises a
material selected from the group consisting of a polyurethane, an
epoxy, a polyester, an acrylic, an anhydride modified polyolefin
and blends thereof.
28. The process of claim 21 wherein the antifog composition
comprises one or more materials selected from the group consisting
of glycerol monoesters of a saturated or unsaturated fatty acid
having from about 8 to about 20 carbon atoms, glycerol diesters of
a saturated or unsaturated fatty acid having from about 8 to about
20 carbon atoms; and ionic surfactants having phosphate, sulfate or
quaternary amine functional end groups.
29. The process of claim 21 wherein the antifog composition
comprises one or more materials selected from the group consisting
of anionic, cationic, nonionic and amphoteric surfactants.
30. The process of claim 21 wherein the antifog composition
comprises glycerol monooleate, glycerol monostearate or a blend
thereof.
31. The process of claim 21 wherein the antifog composition is
coated on the polyolefin film at a coating weight of from about 0.2
to about 0.6 g/m.sup.2.
32. The process of claim 13 wherein the polyolefin film comprises a
homopolymer or copolymer containing a low density polyethylene,
linear low density polyethylene, metallocene polyethylene or
polypropylene.
33. A food package which comprises a container having an open
portion and a multilayered film sealing the open portion; which
multilayered film comprises a nylon film attached to a surface of
an ethylene vinyl alcohol film and another nylon film attached to
another surface of the ethylene vinyl alcohol film to form a
composite; a surface of a polyolefin film attached to one of the
nylon films via an intermediate adhesive, and an antifog
composition on another surface of the polyolefin film or
incorporated into the polyolefin film; the multilayered film being
positioned such that the antifog composition is on the open
portion.
34. A packaged food which comprises the food package of claim 33
and a food product in the food package.
35. The packaged food of claim 34 wherein the food product
comprises a meat.
36. A multilayered film which comprises a shrinkable film attached
to a surface of an oxygen barrier film and another shrinkable film
attached to another surface of the oxygen barrier film to form a
composite; a surface of a polyolefin film attached to one of the
shrinkable films via an intermediate adhesive, and an antifog
composition on another surface of the polyolefin film or
incorporated into the polyolefin film.
37. The multilayered film of claim 36 wherein each shrinkable film
is selected from the group consisting of nylons, polyesters,
oriented polyolefins, and combinations thereof.
38. The multilayered film of claim 36 wherein the oxygen barrier
film comprises ethylene vinyl alcohol.
39. A multilayered film which comprises a shrinkable film coated
with an oxygen barrier coating and another shrinkable film attached
to the oxygen barrier coating to form a composite; a surface of a
polyolefin film attached to one of the shrinkable films via an
intermediate adhesive, and an antifog composition on another
surface of the polyolefin film or incorporated into the polyolefin
film.
40. The multilayered film of claim 39 wherein each shrinkable film
is selected from the group consisting of nylons, polyesters,
oriented polyolefins, and combinations thereof.
41. The multilayered film of claim 39 wherein the oxygen barrier
coating comprises ethylene vinyl alcohol, polyvinyl alcohol,
polyvinylidene chloride or combinations thereof.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to packaging films, or more
particularly to shrinkable, high gas barrier films containing an
antifog composition for modified atmosphere packaging of foods and
the like. The films are useful for producing a modified atmosphere
package useful for the preservation and shelf life extension of
food and non-food oxygen sensitive items.
[0003] 2. Description of the Related Art
[0004] Containers have long been used to store and transfer
perishable food prior to sale at a market where it will be
purchased by the consumer. After perishable foods, such as meats,
fruits, and vegetables, are prepared, they are placed into
containers to preserve those foods for as long as possible.
Maximizing the time in which the food remains preserved in the
containers minimizes the amount of spoilage.
[0005] The environment around which the food is preserved is an
important factor in the preservation process. Not only is
maintaining an adequate temperature important, but the molecular
and chemical content of the gases surrounding the food is
significant as well. By providing an appropriate gas content to the
environment surrounding the food, the food can be better preserved
when maintained at the proper temperature or even when it is
exposed to variations in temperature. This gives the food producer
some assurance that the food will be in an acceptable condition
when it reaches the consumer.
[0006] Preferred modified atmosphere packaging systems for foods,
including raw meats, exposes these foods to extremely low levels of
oxygen because it is well known that the freshness of meat can be
preserved longer under anaerobic conditions than under aerobic
conditions. Maintaining low levels of oxygen minimizes the growth
and multiplication of aerobic bacteria.
[0007] Many multilayered films for modified atmosphere packaging
systems are known. In this regard, U.S. Pat. No. 5,919,547 shows a
laminate which delaminates into a substantially gas-impermeable
portion and a gas-permeable portion. U.S. Pat. No. 6,060,136
teaches a multilayer film having first and second outer layers and
an inner layer. The first and second outer layers comprise a
homogeneous ethylene/alpha-olefin copolymer and the inner layer
comprises a thermoplastic elastomer. This film is not taught to be
heat shrinkable. U.S. Pat. No. 5,766,772 describes multi-layer
heat-shrinkable film endowed with anti-fog properties having a
different structure from this invention.
[0008] It would be advantageous to provide a multilayered packaging
film which is heat shrinkable, sealable to a food container, an
effective gas barrier and has effective antifog properties.
SUMMARY OF THE INVENTION
[0009] The invention provides a multilayered film which comprises a
nylon film attached to a surface of an ethylene vinyl alcohol film
and another nylon film attached to another surface of the ethylene
vinyl alcohol film to form a composite; a surface of a polyolefin
film attached to one of the nylon films via an intermediate
adhesive, and an antifog composition on another surface of the
polyolefin film or incorporated into the polyolefin film.
[0010] The invention also provides a process for producing a
multilayered film which comprises coextruding a nylon film to a
surface of an ethylene vinyl alcohol film and another nylon film to
another surface of the ethylene vinyl alcohol film to form a
composite; biaxially orienting the composite; laminating or
coextruding a surface of a polyolefin film to one of the nylon
films via an intermediate adhesive; and either applying an antifog
composition onto another surface of the polyolefin film or
incorporating an antifog composition into the polyolefin film.
[0011] The invention further provides a food package which
comprises a container having an open portion and a multilayered
film sealing the open portion; which multilayered film comprises a
nylon film attached to a surface of an ethylene vinyl alcohol film
and another nylon film attached to another surface of the ethylene
vinyl alcohol film to form a composite; a surface of a polyolefin
film attached to one of the nylon films via an intermediate
adhesive, and an antifog composition on another surface of the
polyolefin film or incorporated into the polyolefin film; the
multilayered film being positioned such that the antifog
composition is on the open portion.
[0012] The invention still further provides a multilayered film
which comprises a shrinkable film attached to a surface of an
oxygen barrier film and another shrinkable film attached to another
surface of the oxygen barrier film to form a composite; a surface
of a polyolefin film attached to one of the shrinkable films via an
intermediate adhesive, and an antifog composition on another
surface of the polyolefin film or incorporated into the polyolefin
film.
[0013] The invention yet further provides a multilayered film which
comprises a shrinkable film coated with an oxygen barrier coating
and another shrinkable film attached to the oxygen barrier coating
to form a composite; a surface of a polyolefin film attached to one
of the shrinkable films via an intermediate adhesive, and an
antifog composition on another surface of the polyolefin film or
incorporated into the polyolefin film.
[0014] The multilayered packaging film of this invention is
preferably heat shrinkable, sealable to a food container, an
effective gas barrier and has effective antifog properties.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0015] In the production of the multilayered film according to the
invention, first a nylon film is attached to a surface of an
ethylene vinyl alcohol film and another nylon film attached to
another surface of the ethylene vinyl alcohol film to form a
composite.
[0016] The preferred nylon is a homopolymer or copolymer is
selected from aliphatic polyamides and aliphatic/aromatic
polyamides having a molecular weight of from about 10,000 to about
100,000. General procedures useful for the preparation of
polyamides are well known to the art. Useful diacids for making
polyamides include dicarboxylic acids which are represented by the
general formula
HOOC--Z--COOH
[0017] wherein Z is representative of a divalent aliphatic radical
containing at least 2 carbon atoms, such as adipic acid, sebacic
acid, octadecanedioic acid, pimelic acid, suberic acid, azelaic
acid, dodecanedioic acid, and glutaric acid. The dicarboxylic acids
may be aliphatic acids, or aromatic acids such as isophthalic acid
and terephthalic acid. Suitable diamines for making polyamides
include those having the formula
H.sub.2N(CH.sub.2).sub.nNH.sub.2
[0018] wherein n has an integer value of 1-16, and includes such
compounds as trimethylenediamine, tetramethylenediamine,
pentamethylenediamine, hexamethylenediamine, octamethylenediamine,
decamethylenediamine, dodecamethylenediamine,
hexadecamethylenediamine, aromatic diamines such as
p-phenylenediamine, 4,4'-diaminodiphenyl ether,
4,4'-diaminodiphenyl sulphone, 4,4'-diaminodiphenylmethane,
alkylated diamines such as 2,2-dimethylpentamethylenediamine,
2,2,4-trimethylhexamethylenediamine, and 2,4,4
trimethylpentamethylenediamine, as well as cycloaliphatic diamines,
such as diaminodicyclohexylmethane, and other compounds. Other
useful diamines include heptamethylenediamine,
nonamethylenediamine, and the like.
[0019] Useful polyamide homopolymers include poly(4-aminobutyric
acid) (nylon 4), poly(6-aminohexanoic acid) (nylon 6, also known as
poly(caprolactam)), poly(7-aminoheptanoic acid) (nylon 7),
poly(8-aminooctanoic acid)(nylon 8), poly(9-aminononanoic acid)
(nylon 9), poly(10-aminodecanoic acid) (nylon 10),
poly(11-aminoundecanoic acid) (nylon 11), poly(12-aminododecanoic
acid) (nylon 12), as well as nylon 46, nylon 66 and nylon 69 and
the like. Useful aliphatic polyamide copolymers include
poly(hexamethylene adipamide) (nylon 6,6), poly(hexamethylene
sebacamide) (nylon 6,10), poly(heptamethylene pimelamide) (nylon
7,7), poly(octamethylene suberamide) (nylon 8,8),
poly(hexamethylene azelamide) (nylon 6,9), poly(nonamethylene
azelamide) (nylon 9,9), poly(decamethylene azelamide) (nylon 10,9),
caprolactam/hexamethylene adipamide copolymer (nylon 6,6/6),
hexatnethylene adipamide/caprolactam copolymer (nylon 6/6,6),
trimethylene adipamide/hexamethylene azelaiamide copolymer (nylon
trimethyl 6,2/6,2), hexamethylene
adipamide-hexamethylene-azelaiamide caprolactam copolymer (nylon
6,6/6,9/6), poly(tetramethylenediamine-co-ox- alic acid) (nylon
4,2), the polyamide of n-dodecanedioic acid and
hexamethylenediamine (nylon 6,12), the polyamide of
dodecamethylenediamine and n-dodecanedioic acid (nylon 12,12), as
well as copolymers thereof and as well as other nylons which are
not particularly delineated here.
[0020] Of these polyamides, preferred polyamides include nylon 6,
nylon 6,6, nylon 6/6,6 as well as mixtures of the same. Of these,
nylon 6 is most preferred.
[0021] Aliphatic polyamides used in the practice of this invention
may be obtained from commercial sources or prepared in accordance
with known preparatory techniques. For example, poly(caprolactam)
can be obtained from Honeywell International Inc., Morristown, N.J.
under the trademark CAPRON.RTM..
[0022] Exemplary of aliphatic/aromatic polyamides include
poly(tetramethylenediamine-co-isophthalic acid) (nylon 4,I),
polyhexamethylene isophthalamide (nylon 6,I), hexamethylene
adipamide/hexamethylene-isophthalamide (nylon 6,6/6I),
hexamethylene adipamide/hexamethyleneterephthalamide (nylon
6,6/6T), poly (2,2,2-trimethyl hexamethylene terephthalamide),
poly(m-xylylene adipamide) (MXD6), poly(p-xylylene adipamide),
poly(hexamethylene terephthalanide), poly(dodecamethylene
terephthalamide), polyamide 6T/6I, polyamide 6/MXDT/I, polyamide
MXDI, and the like. Blends of two or more aliphatic/aromatic
polyamides can also be used. Aliphatic/aromatic polyamides can be
prepared by known preparative techniques or can be obtained from
commercial sources. Other suitable polyamides are described in U.S.
Pat. Nos. 4,826,955 and 5,541,267, which are incorporated herein by
reference.
[0023] Ethylene vinyl alcohol compounds are also well known in the
art and readily commercially available. Copolymers of ethylene and
vinyl alcohol suitable for use in the present invention can be
prepared by the methods disclosed in U.S. Pat. Nos. 3,510,464;
3,560,461; 3,847,845; 3,595,740 and 3,585,177. The ethylene vinyl
alcohol copolymer can be a hydrolyzed ethylene vinyl acetate
copolymer. The degree of hydrolysis can range from 85 to 99.5%. The
ethylene vinyl alcohol copolymer preferably contains from 15 to 65
mol percent ethylene and more preferably 25 to 50 mol percent
ethylene. Copolymers of lower than 15 mol percent ethylene tend to
be difficult to extrude while those above 65 mol percent ethylene
have reduced oxygen barrier performance. The term "ethylene/vinyl
alcohol copolymer" or "EVOH" is intended to comprise also the
hydrolyzed or saponified ethylene/vinyl acetate copolymers and
refers to a vinyl alcohol copolymer having an ethylene comonomer,
which may be obtained, for example, by the hydrolysis of an
ethylene/vinyl acetate copolymer or by chemical reaction of
ethylene monomers with vinyl alcohol. Ethylene vinyl alcohol
copolymers are commercially available from a variety of
sources.
[0024] The composite can be formed by any conventional technique
for forming films, including lamination and coextrusion. The
preferred method for making the composite is by coextrusion. For
example, the polymeric material 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. 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.
Alternatively the individual layers may first be formed as separate
layers and then laminated together under heat and pressure with or
without intermediate adhesive layers. Suitable coextrusion
techniques are described in U.S. Pat. Nos. 5,139,878 and 4,677,017.
Composites of nylon and ethylene vinyl alcohol are more fully
described in U.S. Pat. No. 5,055,355 which is incorporated herein
by reference.
[0025] Preferably the composite is then oriented. For the purposes
of the present invention the term draw ratio is an indication of
the increase in the dimension in the direction of draw. Preferably,
in the present invention the film composite is drawn to a draw
ratio of from 1.5:1 to 5:1 uniaxially in at least one direction,
i.e. its longitudinal direction, its transverse direction or
biaxially in each of its longitudinal and transverse directions.
Generally, the film is drawn by passing it over a series of
preheating and heating rolls. The heated film moves through a set
of nip rolls downstream at a faster rate than the film entering the
nip rolls at an upstream location. The change of rate is
compensated for by stretching in the film. This results in dramatic
improvements in barrier properties. Preferably, the composite film
is biaxially oriented and is not heat set so that it is shrinkable
both in its transverse and longitudinal directions.
[0026] In order to form the multilayered film of the invention, a
surface of a polyolefin film is then attached to one of the nylon
films via an intermediate adhesive. An antifog composition is
either applied onto another surface of the polyolefin film or
incorporated into the polyolefin film.
[0027] Suitable polyolefins may be comprised of poly .alpha.-olefin
homopolymers and copolymers and blends thereof, preferably wherein
the .alpha.-olefin monomers have from about 2 to about 10 and
preferably from about 2 to about 6 carbon atoms. Non-limiting
examples of suitable polyolefins are low density polyethylene
(LDPE), linear low density polyethylene (LLDPE), Linear medium
density polyethylene (LMDPE), Linear very-low density polyethylene
(VMDPE), Linear ultra-low density polyethylene (UMDPE), high
density polyethylene (HDPE), polypropylene (PP), syndiotactic
polypropylene (SPP), propylene/ethylene copolymers,
propylene/alpha-olefin copolymers or terpolymers, polyethylene
interpolymers, i.e. copolymers of ethylene with alpha-olefins
characterized by a narrow distribution of the molecular weights and
obtained by means of polymerization with metalocene catalysts (see
U.S. Pat. No. 4,306,041), the copolymers of ethylene with other
monomers, in particular with vinyl acetate, (EVA), wherein the
ethylene units are present in an amount greater than those of vinyl
acetate, and the blends thereof, in any proportion. Polyolefins
also include metallocene polyethylene; polypropylene; polybutylene;
polybutene-1; polypentene-1; poly-3-methylbutene- 1;
poly-4-methylpentene- 1; and polyhexene. Copolymers of olefins and
other polymers include such as polyvinyl chloride, polystyrene and
polyurethane, etc., and mixtures of these. Of these, the preferred
polyolefins are polyethylene and polypropylene.
[0028] Each of the nylon, ethylene vinyl alcohol film, polyolefin
and adhesive layers may optionally also include one or more
conventional additives whose uses are well known to those skilled
in the art. The use of such additives may be desirable in enhancing
the processing of the compositions as well as improving the
products or articles formed therefrom. Examples of such include:
oxidative and thermal stabilizers, lubricants, release agents,
flame-retarding agents, oxidation inhibitors, dyes, pigments and
other coloring agents, ultraviolet light absorbers and stabilizers,
organic or inorganic fillers including particulate and fibrous
fillers, reinforcing agents, nucleators, plasticizers, as well as
other conventional additives known to the art. Such may be used in
amounts of up to about 10% by weight of the overall composition.
Representative ultraviolet light stabilizers include various
substituted resorcinols, salicylates, benzotriazole, benzophenones,
and the like. Suitable lubricants and release agents include
stearic acid, stearyl alcohol, and stearamides. Exemplary
flame-retardants include organic halogenated compounds, including
decabromodiphenyl ether and the like as well as inorganic
compounds. Suitable coloring agents including dyes and pigments
include cadmium sulfide, cadmium selenide, titanium dioxide,
phthalocyanines, ultramarine blue, nigrosine, carbon black and the
like. Representative oxidative and thermal stabilizers include the
Period Table of Element's Group I metal halides, such as sodium
halides, potassium halides, lithium halides; as well as cuprous
halides; and further, chlorides, bromides, iodides. Also, hindered
phenols, hydroquinones, aromatic amines as well as substituted
members of those above mentioned groups and combinations thereof.
Exemplary plasticizers include lactams such as caprolactam and
lauryl lactam, sulfonamides such as o,p-toluenesulfonamide and
N-ethyl, N-butyl benylnesulfonamide, and combinations of any of the
above, as well as other plasticizers known to the art.
[0029] An antifog composition is formed either on a surface of the
polyolefin film or incorporated into the polyolefin film.
Non-limiting examples of antifog compositions are glycerol
monoesters of a saturated or unsaturated fatty acid having from
about 8 to about 20 carbon atoms, glycerol diesters of a saturated
or unsaturated fatty acid having from about 8 to about 20 carbon
atoms; and anionic, cationic, nonionic and amphoteric surfactants.
Suitable ionic surfactants have phosphate, sulfate or quaternary
amine functional end groups. Other antifog compositions include
sorbitan esters of aliphatic carboxylic acids, glycerol esters of
aliphatic carboxylic acids, esters of other polyhydric alcohols
with aliphatic carboxylic acids, polyoxyethylene compounds, such as
the polyoxyethylene sorbitan esters of aliphatic carboxylic acids
and polyoxyethylene ethers of higher aliphatic alcohols. Preferred
antifog compositions are glycerol monooleate, glycerol monostearate
and blends thereof. When the antifog composition is incorporated
into the polyolefin film, it is blended into the polyolefin film
composition in an amount of from about 0.1 weight percent to about
5 weight percent. When the antifog composition is coated on the
polyolefin film it is preferably applied at a coating weight of
from about 0.2 to about 0.6 g/m.sup.2. Suitable antifog
compositions are described, for example, in U.S. Pat. No.
5,766,772.
[0030] The polyolefin layer is attached to the composite by an
intermediate adhesive or tie layer. Any suitable adhesive may be
employed. Such adhesives include polyurethanes, epoxies,
polyesters, acrylics, anhydride modified polyolefin and blends
thereof. Modified polyolefin compositions have at least one
functional moiety selected from the group consisting of unsaturated
polycarboxylic acids and anhydrides thereof. Such unsaturated
carboxylic acid and anhydrides include maleic acid and anhydride,
fumaric acid and anhydride, crotonic acid and anhydride, citraconic
acid and anhydride, itaconic acid an anhydride and the like.
[0031] The multilayer films of the present invention can be
produced by laminating the polyolefin to the composite by the
intermediate adhesive. Typically, laminating is done by positioning
the individual layers on one another under conditions of sufficient
heat and pressure to cause the layers to combine into a unitary
film. Typically the composite, adhesive, and polyolefin layers are
positioned on one another, and the combination is passed through
the nip of a pair of heated laminating rollers by techniques well
known in the art. Lamination heating may be done at temperatures
ranging from about 120.degree. C. to about 175.degree. C.,
preferably from about 150.degree. C. to about 175.degree. C., at
pressures ranging from about 5 psig (0.034 MPa) to about 100 psig
(0.69 MPa), for from about 5 seconds to about 5 minutes, preferably
from about 30 seconds to about 1 minute.
[0032] Although each layer of the multilayer film structure may
have a different thickness, the thickness of each of the nylon
layers of the films in the post-stretched multilayer film structure
is from about 1 .mu.m to about 10 .mu.m, preferably from about 3
.mu.m to about 8 .mu.m, and more preferably from about 4 .mu.m to
about 6 .mu.m. The thickness of the ethylene vinyl alcohol layer in
the post-stretched multilayer films structure is from about 1 .mu.m
to about 10 .mu.m, preferably from about 2 .mu.m to about 8 .mu.m
and more preferably from about 3 .mu.m to about 5 .mu.m. The
thickness of the polyolefin layer in the post-stretched multilayer
films structure is from about 3 .mu.m to about 50 .mu.m, preferably
from about 12 .mu.m to about 30 .mu.m, and more preferably from
about 12 .mu.m to about 20 .mu.m. While such thicknesses are
preferred, it is to be understood that other film thicknesses may
be produced to satisfy a particular need and yet fall within the
scope of the present invention.
[0033] Oxygen transmission rate (OTR) may be determined via the
procedure of ASTM D-3985. In the preferred embodiment, the
multilayered film according to this invention has an OTR of about
0.1 cc/100 in.sup.2/day or less, preferably from about 0.085 cc/100
in.sup.2/day or less and more preferably from about 0.07 cc/100
in.sup.2/day or less at 65% relative humidity at 20.degree. C.
[0034] The multilayered film of the invention is heat shrinkable,
generally by an amount of from about 2% to about 30%, more
preferably from about 10 to about 20% in its length, or its width
or each of its length and width. To provide a tightly adhering lid
for a tray, for example, the film only need to exhibit shrinkage on
the order of about 2 to about 3%. However, in order to have the
film also form (unrestrained) about the side of the tray, higher
shrinkage in the film is desirable. The multilayered film may
further have printed indicia between the polyolefin film and its
attached nylon film. Since such printing is on an internal surface
of the structure, it will not rub off when the surface is
contacted. Optionally, the multilayered film may be uniaxially or
biaxially oriented in a manner and in an amount indicated above for
the composite film and is not heat set so that it is shrinkable
both in its transverse and longitudinal directions. In this case
the composite from which the multilayered film is formed may or may
not have been oriented.
[0035] The film preferably has a puncture resistance of at least
about 1600 grams as measured by ASTM F 1306. Preferably the film
has a haze of about 5% or less as measured by ASTM D1003.
[0036] The multilayered film is useful for forming a food package
including a container, such as a tray, having an open portion and
the multilayered film sealing the open portion. Such a structure is
generally referred to a lidding film. The multilayered film is
positioned such that the antifog composition is adjacent to the
open portion, that is, facing the inside of the container. Such
containers are suitable for packaging a variety of raw meats such
as beef, pork, poultry, and veal, among others. A packaged food may
comprises the food package and a food product such as a meat in the
food package.
[0037] The container may have enclosed side walls, a floor and an
top opening defining a central cavity wherein the open top
optionally has a substantially flat peripheral rim. The
multilayered film surrounds the container and is heat shrunk and
heated sealed to it via the polyolefin film such that the antifog
composition is on the open portion (facing inward). The container
may comprise a material such as cardboard, paperboard, boardstock,
a plastic and combinations thereof. Preferred plastics include any
one of several thermosetting or thermoplastic resins any of which
are capable of sealing to the lidding material. Examples of
materials include acrylonitrile, an acrylic polymer, polyethylene
terephthalate (PET) or copolymers thereof, polyvinyl chloride,
polycarbonate, polystyrene and polypropylene. In use the lidding
film is positioned around the open portion and is caused to shrink,
e.g. by the application of heat, a sufficient amount to seal the
open portion of the container.
[0038] Although in the preferred embodiment the composite is a
three layered structure for subsequent attachment to a polyolefin
layer, e.g. nylon/EVOH/nylon, the invention further contemplates a
composite which has additional layers, for example,
nylon/adhesive/EVOH/adhesive/nylon; nylon/adhesive/oxygen
barrier/adhesive/nylon. Further, the composite may be attached to
the polyolefin layer by coextrusion, lamination, or coating by
extrusion coating of the polyolefin with or without an intermediate
adhesive.
[0039] It is within the contemplation of the invention that the
multilayered film may comprise a shrinkable film attached to a
surface of an oxygen barrier film and another shrinkable film
attached to another surface of the oxygen barrier film to form a
composite. Although in the preferred embodiment the composite is a
three layered structure for subsequent attachment to a polyolefin
layer, e.g. shrinkable film/oxygen barrier/shrinkable film, the
invention further contemplates a composite which has additional
layers, for example shrinkable film/adhesive/oxygen
barrier/adhesive/shrinkable film. A polyolefin film is then
attached to one of the shrinkable films by coextrusion, lamination,
extrusion coating or via an intermediate adhesive, wherein an
antifog composition is another surface of the polyolefin film or
incorporated into the polyolefin film. Suitable shrinkable films
include nylons, polyesters, oriented polyolefins, and combinations
thereof. Suitable oxygen barrier films include ethylene vinyl
alcohol, polyvinyl alcohol, polyvinylidine chloride and
combinations thereof.
[0040] It is also within the contemplation of the invention that
the multilayered film comprises a heat shrinkable film coated with
an oxygen barrier coating and another heat shrinkable film attached
to the oxygen barrier coating to form a composite. A polyolefin
film is then attached to one of the heat shrinkable films via an
intermediate adhesive wherein an antifog composition is on another
surface of the polyolefin film or incorporated into the polyolefin
film. Suitable heat shrinkable films are identified above. Suitable
oxygen barrier coatings include ethylene vinyl alcohol, polyvinyl
alcohol, polyvinylidene chloride and combinations thereof.
[0041] The following non-limiting examples serve to illustrate the
invention.
EXAMPLE 1
[0042] A laminate for lidding applications was made by coating a 15
.mu.m biaxially oriented nylon/EVOH/nylon coextruded film (reverse
printed) with a two-component polyether-epoxy adhesive at a coat
rate of 1.95 g/m.sup.2 until substantially dry. The film was then
joined to a 19 .mu.m polyethylene film and laminated through a hot
nip to create the finished laminate. The laminate was coated on the
polyethylene side with an ethyl alcohol solution of an antifog
agent (glycerol monostearate) at a coating weight of 0.36 g/m.sup.2
and passed through an oven until substantially dry.
EXAMPLE 2
[0043] Example 1 was repeated except that the coextruded film was
unprinted, the adhesive was a two-component adhesive consisting of
a polyester polyol substrate and a diisocyanate co-reactant, and
the coating weight of the antifog agent was 0.28 g/m.sup.2 . The
results are shown in Table 1.
EXAMPLE 3
[0044] Example 2 was repeated except that the coextruded film was
reverse printed and the coating weight of the antifog coating was
0.36 g/m.sup.2. The results are shown in Table 1.
EXAMPLE 4
[0045] Example 2 was repeated except that a polypropylene film was
used instead of the polyethylene film and the coating weight of the
antifog agent was 0.33 g/m.sup.2. The results are shown in Table
1.
1 TABLE 1 EXAMPLE Property 2 3 4 Thickness (.mu.m) 35.6 35.6 38.1
Yield (m.sup.2/kg) 26.2 -- 25.8 Tensile Strength TD 77.3 -- 127.0
(MPa) MD 81.0 -- 112.4 Elongation (%) TD 42.81 -- 87.93 MD 66.68 --
94.07 Puncture (kg) (ASTM 1306) 6.25 -- 9.4 Light Transmission (%)
93.2 93.4 94.3 Haze level (%) 6.7 4.1 3.1 Clarity* 87.1 89.9 92.6
Oxygen Transmission Rate (cc/100 in.sup.2/day 65% RH 0.07 0.07 --
and 20.degree. C.) *Using Byk Gardner HazeGard Plus Instrument
EXAMPLE 5
[0046] Films from Example 2 were used as lidding film to seal
polyethylene trays with a meat patty inside. The heat seal
conditions were 250.degree. F. (121.degree. C.) seal temperature
and 350.degree. F. (177.degree. C.) knife temperature. The seal was
good and there was no significant water condensation on the antifog
coating.
EXAMPLE 6
[0047] Example 5 was repeated using films from Example 4 with
polystyrene trays having a polyethylene sealant web, as well as
polypropylene trays. The heat seal conditions were 330.degree. F.
(166.degree. C.) seal temperature and 350.degree. F. (177.degree.
C.) knife temperature. The seal was good and there was no
significant water condensation on the antifog coating.
EXAMPLE 7
[0048] Example 5 was repeated using films made from Example 3 with
polystyrene trays having a polyethylene sealing web. The heat seal
conditions were 275-300.degree. F. (135-149.degree. C.) seal and
300.degree. F. (149.degree. C.) knife. There was no significant
water condensation on the antifog coating after 72 hours.
[0049] While the present invention has been particularly shown and
described with reference to preferred embodiments, it will be
readily appreciated by those of ordinary skill in the art that
various changes and modifications may be made without departing
from the spirit and scope of the invention. It is intended that the
claims be to interpreted to cover the disclosed embodiment, those
alternatives which have been discussed above and all equivalents
thereto.
* * * * *